ABSTRACT. Citrus residues (CR) have a high content of water and organic matter, which makes them suitable substrates for hydrogen production. Some studies have been reported on this, most with a focus on the evaluation of optimal and nutritional conditions (Rocha et al., 2023) (Rocha et al., 2023), as well as on the use of physicochemical pretreatments (Saadatinavaz et al., 2021) to increase production efficiency. However, this field of research has not yet been widely explored. Biological treatment with fungi has proven to be a promising technique for increasing biogas production efficiency due to the degradation of lignin by enzyme action, which increases the availability of the substrate for fermentation processes (Liang et al., 2024). Therefore, the objective of the present study was to evaluate the effect of fungal hydrolysis by Fusarium oxysporum, Phytophthora sp., Colletotrichum gloeosporioides, and Alternaria alternata individually on lemon peels for their subsequent fermentation and increased hydrogen production. For the fungal hydrolysis test, an inoculum was prepared for each of the strains, one cm3 of fungal culture grown on PDA agar was placed in 150 mL of medium (2 % w/v glucose and 1 % w/v yeast extract), the culture was incubated at 30°C for 7 days, after inoculum growth, 15 mL of the inoculum was then removed and placed in flasks containing 100 g of lemon peel, this was carried out for a period of 7 days, during which time samples were taken daily for carbohydrate analysis and limonene concentration, which has been described as an inhibitor of hydrogen production. Hydrogen production was carried out in batch tests, using a useful volume of 360 mL. A hydrolyzed substrate concentration of 10 g VS/L and an initial pH adjusted to 7 were used. Heat-treated granular anaerobic sludge (105°C) was used as inoculum, maintaining a substrate/inoculum ratio of 2.7. A micronutrient solution was also added. All assays were performed in triplicate for statistical analysis. Volatile fatty acids (VFAs) were determined by high-performance liquid chromatography (HPLC). Among the results, it was observed that the fungi influenced the lemon peels, as an increase in the concentration of soluble carbohydrates was detected, indicating greater substrate availability for subsequent fermentation. Regarding hydrogen production, the effect of biological pretreatment with fungi was significant compared to the control, i.e., the non-hydrolyzed substrate.

ABSTRACT. Orange peel waste has been classified as inefficient for biogas production due to the inhibitory effect of limonene present in these residues (Forgács et al., 2012). A similar inhibitory effect is also expected to impact hydrogen production through dark fermentation. One strategy to overcome this limitation is co-digestion, a technique in which two or more organic wastes are combined to balance nutrient content and mitigate the adverse effects of inhibitors present in the substrates, thereby enhancing biogas production, chemical yields, and process stability (Vázquez-López & Moreno-Andrade, 2025). The objective of this study was to evaluate hydrogen production from the co-digestion of fruit and vegetable waste (FVW) and orange peels (OP) to assess potential inhibition by limonene present in OP. Batch experiments were conducted using AMPTS equipment. The FVW mixture had a total solids (TS) content of 122.19 g/kg and total volatile solids (TVS) content of 109.24 g/kg. The TS and TVS contents for OP were 241.18 g/kg and 229.72 g/kg, respectively. Mono-digestion (controls) and co-digestion experiments were performed at the following FVW:OP (w/w) ratios: 0:100, 100:0, 75:25, 50:50, 25:75, and 0:0, maintaining an organic matter concentration of 10 g VS/L. A micronutrient solution was added, and the initial pH was adjusted to 7.5, following the protocol described by Carrillo-Reyes et al., (2020). Anaerobic granular sludge thermally pretreated at 105 °C was used as inoculum, with a TVS content of 656 g/kg, and a substrate-to-inoculum ratio of 2.7 was maintained. Each treatment was performed in quadruplicate for statistical analysis. Limonene content, total carbohydrates, volatile fatty acids, and biogas composition were measured. Significant differences were observed between treatments. The highest hydrogen production was achieved with the 25:75 FVW/OP ratio, reaching a cumulative volume of 233.82 mL H₂. In contrast, the lowest production (93.45 mL H₂) was recorded in the FVW mono-digestion (100:0). According to the results, OP has the potential for hydrogen production independently, as no inhibitory effect attributable to limonene was detected. Furthermore, co-digestion with FVW enhanced hydrogen production by 150% compared to the assay with FVW alone.

ABSTRACT. La creciente necesidad de alternativas energéticas sostenibles ha impulsado el desarrollo de sistemas capaces de generar hidrógeno en condiciones ambientales moderadas. Entre ellos, la biofotólisis con microalgas fotosintéticas emerge como una estrategia prometedora. En este proceso, la energía solar activa los fotosistemas I y II, provocando la ruptura de la molécula de agua en oxígeno, protones y electrones; estos últimos son utilizados por la enzima hidrogenasa para la producción de hidrógeno molecular. Este estudio hace énfasis en la cinética de crecimiento de Chlamydomonas reinhardtii estructurando su modelo microalgal a partir de agua de una laguna interdunaria como sustrato, para ello, se realizó la recolección de muestras en un sitio de alta influencia antropogénica, seguido de la identificación morfológica mediante observación óptica, aplicando claves taxonómicas del Standard Methods for the Examination of Water and Wastewater. Se determinó el pH conforme a la NMX-AA-008-SCFI-2016 con promedio inicial de 7.5, y se evaluaron los sólidos totales y sólidos volátiles siguiendo la NMX-AA-034-SCFI-2015 con una concentración de sólidos totales de 2.153 g/L y de sólidos volátiles de 1.08 g/L, indicando una alta disponibilidad de materia orgánica y algal. Posteriormente, se prepara el medio de cultivo TAP (Tri-acetato-fosfato) debido a su alta fuente de carbono y nutrientes para el crecimiento micro algal para ser inoculado en cajas petri con condiciones estériles, seguido, es sembrado en cultivos de proporciones TAP/sustrato de 90/10, 80/20 y 75/25, bajo iluminación controlada de 150 µmol m⁻² s⁻¹ en una incubadora con 200 rpm, con una temperatura de 30 °C. El crecimiento celular fue monitoreado mediante conteo directo en cámara de Neubauer, cuantificándose las células en tres intervalos temporales: días 0 a 1, días 2 a 4 y días 5 a 7. Durante los días 0 a 1, se registraron concentraciones iniciales de 2.0 × 10⁴ cel/mL para la proporción 90/10, 3.0 × 10⁴ cel/mL para 80/20 y 2.8 × 10⁴ cel/mL para 75/25, indicando la fase de adaptación celular al medio de cultivo. Posteriormente, entre los días 2-4, se observó un incremento considerable en la densidad celular, alcanzando valores de 6.5 × 10⁴ cel/mL para 90/10, 7.5 × 10⁴ cel/mL para 80/20 y 8.2 × 10⁴ cel/mL para 75/25, correspondientes a la fase exponencial de crecimiento. Finalmente, en el periodo de días 5 a 7, se detectó el mayor aumento en la concentración celular, con 1.5 × 10⁵ cel/mL en la condición 90/10, 1.8 × 10⁵ cel/mL en 80/20, y alcanzando un máximo de 2.0 × 10⁵ cel/mL en 75/25, lo que evidencia un crecimiento continuo de las microalgas en cultivo batch. Estos resultados concluyen que la concentración 75/25 contribuye a un entorno metabólicamente más activo, lo cual resulta óptimo para la formación de biomasa más eficiente bajo un fotoperiodo constante, siendo el nutriente que acelera el crecimiento celular más exponencial, alcanzando la mayor densidad al séptimo día de cultivo. Estos elementos, considerados de forma integrada, fortalecen la viabilidad técnica del sistema y permiten avanzar hacia su implementación en escenarios energéticos, posicionando a la biofotólisis como una plataforma con alto potencial dentro de la biotecnología ambiental.

ABSTRACT. The presence of lactic acid bacteria (LAB) in hydrogen (H2)-producing microbial communities has been identified as a factor contributing to low H2 yields and instability during long-term reactor operation. This is attributed to the secretion of antimicrobial compounds, such as bacteriocins (low molecular weight peptides), and the production of high concentrations of lactic acid by LAB during fermentation. However, this negative role of LAB as microorganisms producing antimicrobial compounds during H2 production has been scarcely explored. This study evaluated the influence of antimicrobial compounds secreted by LAB on fermentative H2 production during the self-fermentation of the organic fraction of municipal solid waste (OFMSW). LAB strains were isolated from digestate obtained from a lactic acid-producing bioreactor fed with a mixture of food waste and corn industry wastewater, taking the sample at 25 days of operation. The isolated strains were screened for inhibitory activity against Pseudomonas putida (indicator bacterium) using well-diffusion assays. Strains exhibiting inhibitory activity were molecularly identified throughout amplifications of the 16S rRNA gene. The selected strains were cultivated for 24 h in MRS broth and then centrifuged. Two types of cell-free supernatants were prepared to test their effect on H2 production: (1) neutralized supernatants, containing organic acids, proteinaceous, and non-proteinaceous compounds, and (2) ammonium sulfate-precipitated supernatants, mainly containing proteinaceous compounds. Then, batch fermentations were conducted using OFMSW at a concentration of 10.0 g of volatile solids/L and the substrate´s native microbiota as inoculum. Supernatants were added at a concentration of 10.0 g/L of protein. The pH was adjusted to 6.5 and reactors were incubated at 37 °C for 6 days. Eighteen bacterial strains were isolated, of which 5 showed inhibitory activity against P. putida. The strains were molecularly identified as Lactobacillus gasseri LB11, and Lactobacillus plantarum LB13, LB15, LB17, and LB18. The addition of supernatants had a significant effect on H2 from OFMSW (p<0.05), with different behavior depending on the type of supernatant. Precipitated supernatants exhibited an inhibitory effect, decreasing H2 production by 5.0-30.0% compared to the control (without supernatants), with L. plantarum LB17 showing the highest inhibition. In contrast, neutralized supernatants promoted H2 production, increasing yields by 2.1 and 2.6 times with L. plantarum LB17 and L. plantarum LB18. These results suggested both negative and positive effects of LAB supernatants on H2 production. The inhibitory effect could be attributed to peptides (likely bacteriocins) present in the precipitated supernatants (possibly bacteriocins), while the enhancement in H2 production might be due to lactic acid in the neutralized supernatants serving as an additional substrate. In conclusion, it was demonstrated that LAB isolated in this study secrete organic acids and proteinaceous compounds that significantly impact H2 production from OFMSW.

ABSTRACT. Hydrogen production by water electrolysis is a key technology for the energy transition. Hydrogen is an energy vector with a calorific value of 145 MJ/kg in its pure state, a very high value compared to that of natural gas (48MJ/kg) or gasoline (46MJ/kg) when burned completely. It is also a very valuable reagent in many biorefining processes, as it improves the quality of biofuels and facilitates the synthesis of chemical products, contributing to the development of sustainable industry. Water is the compound that contains the greatest amount of hydrogen on Earth, which is why hydrogen can be obtained from its electrolytic separation, to facilitate this separation it is necessary to acidify or alkalinize it. During the biodiesel production process, in the final washing stage, alkaline water with sodium hydroxide is generated as waste, which is proposed to be used as raw material to generate green hydrogen. This technology uses electricity, generated by renewable sources such as wind, solar or biomass, to separate the water molecule into oxygen and hydrogen. The energy is stored as chemical energy in the hydrogen molecule, which can be used as renewable energy. The electrolysis is done in a simple way using elctrolithrolytes as they function as agents that change the electrical conductivity and pH which facilitates the reaction because it is more reactive, this solution is placed in an electrolytic cell with an electrode and an anode which when applying the potential difference between the electrodes, the water decomposes to produce hydrogen at the cathode and oxygen at the anode, plus different charge carrier ions: H +, OH-, O- and free electrons. The current challenges of alkaline water electrolyzers are the integration of renewable energy sources to operate, due to their low current densities and slow kinetics. Therefore, this research establishes the configuration of the operating variables and proposes their integration in the design of the equipment, increasing the efficiency and performance in the production of green hydrogen from alkaline water. To reduce the energy required for this process, a nickel catalyst supported on SBA-15 was used, which acts as a facilitator in the reduction of hydrogen. The factors taken into account were: alkalinity of the solution, temperature, catalyst concentration and voltage (at low levels emulating the energy obtained by green electricity generators).

ABSTRACT. The rising global demand for clean and renewable energy has intensified research efforts toward innovative technologies capable of addressing both energy production and environmental sustainability. Hydrogen, recognized as a clean fuel due to its high energy density and pollution-free combustion, has gained significant attention as a potential alternative to fossil fuels. Among the various hydrogen production methods, photocatalytic water splitting driven by solar irradiation offers a sustainable and low-energy pathway to generate hydrogen without carbon emissions. While freshwater has traditionally been used in photocatalytic hydrogen evolution studies, its limited availability worldwide poses sustainability concerns. In contrast, seawater represents a vast and readily accessible resource that could enable large-scale hydrogen production. However, the complex ionic composition of seawater, including ions such as Na⁺, Mg²⁺, Ca²⁺, and Cl⁻,introduces significant challenges such as competitive side reactions, catalyst corrosion, and surface deactivation, all of which must be addressed to develop efficient photocatalytic systems. This study focuses on the perovskite oxide SrTiO₃, a material of interest due to its favorable electronic band structure aligned with the hydrogen and oxygen evolution reactions, chemical stability under photocorrosion conditions, and potential resistance in harsh environments such as seawater. SrTiO₃ was synthesized via the sol-gel method, chosen for its ability to produce homogeneous and crystalline materials with controlled morphology. Comprehensive structural and morphological characterizations were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) surface area analysis, complemented by optical property assessment through UV-Vis spectroscopy. Photocatalytic hydrogen production was evaluated under simulated solar irradiation using two aqueous media: pure water and simulated seawater. Triethanolamine (5% v/v) served as a sacrificial electron donor to facilitate charge separation and enhance hydrogen evolution. Hydrogen generation was monitored by gas chromatography. This study aims to assess the potential of SrTiO₃ as a photocatalyst for hydrogen production in different aqueous environments and to identify the factors influencing its activity in complex ionic media, providing a foundation for future material optimization.

ABSTRACT. H2 plants supplied by renewable energy have to adapt their production depending on the renewable energy availability. Varying renewable power generation requires varying load situations of H2 plant. Poor control of input voltage for an electrolyser plant causes more losses, higher harmonic emissions and require more reactive power compensation. A combination of well-designed harmonic filter and reactive power compensation systems (hereafter power quality solution) interacting with an intelligent on-load-tap-changer (OLTC), makes the usage of thyristor technology for H2 plants highly cost efficient and increases overall electrolyser efficiency and lifespan. Such a coordination between power quality solution and OLTC can only be defined based on intensive network simulation analysis. Hence, such a simulation analysis shall be carried out during an early stage of project planning and design finalization of H2 electrolyser plant. This paper focuses on how an accurately designed power quality solution in conjunction with suitable OLTC tap positions facilitates in reduction of not only overall capital expenditure by significantly reducing the power quality system requirements but also reduces operational expenditure during changing requirements within H2 cells lifetime (which is begin of life and end of life operation).

ABSTRACT. ​​To promote hydrogen as a key solution for decarbonizing sectors such as industry and power generation, fostering scientific literacy around hydrogen technologies is essential for driving systemic change, beginning in secondary and higher education. In 2022, a low-cost, easy-to-use alkaline wet-cell electrolyzer was developed for educational purposes using recycled materials—including a glass coffee jar and stainless steel electrodes made from bolts, nuts, and washers—based on educational content sourced from YouTube. Despite its accessibility, this early prototype experienced over 10 explosions during a year and a half of use due to empirical operation and structural limitations. Its efficiency was measured at 29.99% at 10 Amps, revealing a need for design improvements. This study focuses on redesigning the electrolyzer to create a safer and more efficient educational system. Key improvements include the use of parallel plate electrodes with increased active areas (97.84 cm² for the cathode and 103.5 cm² for the anode), electrodeposition of nickel on the anode, and replacement of the fragile glass container with a polypropylene vessel resistant to alkaline conditions. The lid was also upgraded to a threaded polypropylene design with two ¾" NPT connections—one sealed and the other connected to a gas outlet and purification filter. The updated system was tested using a 4% w NaOH solution and a GCCSJ DC power source (10 A–30 V). Polarization curves were generated using three-minute current pulses ranging from 1 A to 10 A, measuring voltage and gas volume at each step. The redesigned electrolyzer achieved a 12.62% increase in efficiency compared to the original model. This project highlights the importance of integrating safety, efficiency, and student engagement in the design of educational electrolyzers, offering a practical foundation for understanding hydrogen technologies and cultivating a new generation of young innovators in the field.

ABSTRACT. The search for alternative energy sources to fossil fuels is one of the most relevant topics today due to their ecological impact on the environment. In recent years, multiple options have emerged, one of them is hydrogen, a fuel with significant potential and a host of challenges to be solved, ranging from gas production to its transportation and application. Green hydrogen is typically produced through the hydrolysis of alkaline water using equipment called electrolyzers. A challenge that these devices often present is the interaction of corrosive agents that affect various components, such as the electrodes themselves. A commonly used solution is to replace materials with others with greater chemical stability in a particular environment, which translates into greater corrosion resistance. Among these materials, we can mention titanium, a metal known for its high corrosion resistance and its hydrogen production reaction that is currently being investigated. In order to enhance the catalytic behavior of titanium electrodes, in this present work were used zirconia coating and electrochemically characterized. The use of coatings made from sol-gel processes such as zirconia, can be a solution to enhance the catalytic behavior of the base material, improving the hydrogen evolution reaction while increasing the electrode's corrosion resistance, since zirconia acts as a physical barrier between the base material and the environment to prevent corrosion. The aim of this project is to evaluate the corrosion resistance, and the catalytic behavior of the base titanium electrode compared with a zirconia coating electrode. The preliminary results indicate that both properties were improved by the interaction of the zirconia coating with the dissolution, specifically, zirconia roughness and its barrier effect.

ABSTRACT. Alkaline water electrolysis is considered as the most favorable method for cost-effective production of green hydrogen using renewable energy. In this context, developing efficient and scalable alkaline electrolyzers is essential for meeting global hydrogen needs. In the present study, an advanced zero gap bipolar electrolyzer of 5 kW has been developed, modeled and experimental characterized under different operating conditions. A mathematical semi-empirical model is utilized to describe the behavior of alkaline electrolyzer under real operating conditions investigating the influence of key design parameters, including electrode thickness and spacing. Polarization experiments and electrochemical independence spectroscopy tests were carried out to investigating the influence of various operating parameters such as temperature, density current, electrolyte flow on hydrogen production, ohmic resistance, cell voltage and global efficiency. The model parameters and computations done with the model were adjusted and validated with experimental data taken from in situ experimental characterization. The results highlight the critical role porous electrode thickness on the global cell resistance and cell performance, emphasizing the need for accurate modeling based on cell and electrode design. These aspects are crucial when designing alkaline electrolyzers since the process efficiency is found to be very sensitive to them. The experimental analysis suggests that operation mode (dynamic or stationary) impacts the performance of the electrolyzer. The performance of the cell grows with the increase of the thickness of the porous electrode at low current densities (< 0.6 A cm-2); however, the bubble removal capacity decreases as the thickness of the electrode increases and increases current density. Thinner porous electrodes exhibit high area resistance at higher current densities decreasing cell efficiency and increasing energy consumption. Experimental results allow identifying the optimal operation point in the electrolyzer, at temperature of 70 °C is obtained a global efficiency of 53.2 % for energy consumption of 6 kWh Nm-3H2 to a current density of 0.5 A cm-2. The results obtained carry crucial implications for the design of more efficient and cost-effective electrolyzers for industrial hydrogen production.

ABSTRACT. The growing demand for clean and sustainable energy sources has driven research into the efficient production of hydrogen. Water electrolysis is a promising route, but its application in saline environments, such as seawater, poses significant challenges. The high corrosiveness of the saline medium and the potential competition of electrochemical reactions, such as chlorine evolution, require the development of robust, selective and efficient electrocatalysts. In this context, titanium (Ti) and its widely used alloy Ti6Al4V are characterized by their recognized exceptional corrosion resistance in chloride-containing environments. This research focuses on a comprehensive comparison of the catalytic effect of pure titanium and the Ti6Al4V alloy on the hydrogen evolution reaction (HER) in synthetic salt water solutions to identify the better performing material for electrolysis applications in marine and coastal environments. For this comparative study, electrodes were fabricated from pure commercial titanium and from a Ti6Al4V alloy. Prior to the electrochemical tests, the electrodes were subjected to metallographic surface preparation by roughening. The electrochemical characterization was performed with a CorrTest CS350 potentiostat/galvanostat system. Cyclic voltammetry was used to evaluate the overall electrochemical behavior of the materials in the potential range for HER in salt water. Tafel polarization curves were recorded to determine the kinetic parameters of the reaction. Electrochemical impedance spectroscopy (EIS) was used to analyze the charge transfer resistance at the electrode-electrolyte interface and the double layer capacitance in order to observe the mechanism of the reaction kinetics and the properties of the active surface. The experiments were carried out in synthetic salt solutions with a 3.5% NaCl concentration to simulate typical seawater conditions. The results showed remarkable differences in the electrocatalytic activity for HER between pure titanium and the Ti6Al4V alloy in the salt water medium. While both materials proved capable of catalyzing proton reduction to produce hydrogen, significant differences were found in the overpotential required to achieve the catalytic current densities relevant to practical applications. The Ti6Al4V alloy exhibited a slightly lower overpotential compared to pure titanium, suggesting more favorable reaction kinetics. A detailed analysis of the Tafel curves for both materials indicated notable differences in the predominant reaction mechanism on the respective surfaces in the saline environment. The EIS data complemented these results and showed differences in charge transfer resistance, suggesting an influence of alloy composition on the ease with which electrons are transferred to active sites for the hydrogen evolution reaction. In addition, long-term stability tests were performed under conditions of sustained cathodic polarization to evaluate the durability of both materials as electrocatalysts in a saltwater environment. The evolution of overpotential and current density was monitored over time to detect signs of deactivation or corrosion. This comparative study provides valuable and detailed information for the selection of the optimal material, between pure titanium and Ti6Al4V alloy, as electrocatalyst for the hydrogen evolution reaction in salt water electrolysis applications. The results contribute significantly to the fundamental knowledge of electrocatalysis in saline media and provide information for the development of more efficient, economical and durable hydrogen generation systems for coastal areas and other applications where salt water is an abundant and accessible source. Identifying the differences in catalytic performance and stability between these two widely used materials provides the basis for future research on surface modification or alloying with other elements to further improve the efficiency and selectivity of titanium-based electrocatalysts for saltwater HER, minimize competition from the chlorine evolution reaction, and maximize the production of clean hydrogen.

ABSTRACT. High-strength low-alloy (HSLA) steels are used in high-pressure hydrogen transport applications but can be affected by embrittlement phenomena induced by the presence of hydrogen. This type of steel has a microstructure predominantly composed of ferrite and pearlite, along with the presence of carbides, mainly niobium (Nb) and titanium (Ti), which promote both precipitation and solid solution strengthening. Hydrogen in steels can cause cracking, reduction in mechanical properties, blistering, and brittle fracture, potentially leading to catastrophic failure. Therefore, it is important to determine the conditions under which susceptibility to hydrogen embrittlement increases. In this research work, the influence of cathodic hydrogen charging on the tensile mechanical properties and its effects on the fracture surface were evaluated. The main objective was to assess the impact on mechanical strength, elongation percentage, reduction of area percentage, and to determine embrittlement indices and fracture mechanisms in a high-strength low-alloy steel. The steel was subjected to a cathodic hydrogen charging process for one hour in a 0.5 M sulfuric acid (H₂SO₄) solution, in order to introduce hydrogen into the steel’s microstructure and simulate critical service conditions. After the hydrogen charging, tensile tests were conducted to study the material’s behavior under mechanical loading through the analysis of stress-strain curves. The results showed that the steel exhibited a reduction in ultimate tensile strength and yield strength, as well as an increase in the embrittlement index. On the other hand, fractographic analyses indicated the formation of cleavage zones and the presence of cavities related to hydrogen accumulation. These findings suggest a degradation in mechanical properties attributable to the effect of high hydrogen concentration in the steel matrix. These results were consistent with the outcomes of the permeability tests, which showed a high hydrogen concentration and a low diffusion coefficient.

ABSTRACT. The conversion of poultry litter into biochar represents a viable strategy for sustainable waste management and energy generation. This study investigates the production of biochar via pyrolysis at 700 °C under a nitrogen atmosphere, followed by chemical activation with potassium hydroxide (KOH) and nitrogen doping through thermal treatment with urea. The resulting material exhibited a high surface area of 2607 m² g⁻¹, enhancing its properties for energy and electrocatalytic applications.

Additionally, platinum nanoparticles (PtNPs) were synthesized via a green synthesis approach using sargassum extract and subsequently supported on the nitrogen-doped biochar. Structural and compositional characterization was conducted using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), BET surface area analysis, and CHNS elemental analysis.

The electrochemical performance of the materials was evaluated using cyclic and linear voltammetry in 0.1 M KOH solution, employing a rotating ring-disk electrode at a scan rate of 20 mV s⁻¹. The 5%Pt-BC and 10%Pt-BC electrocatalysts exhibited an onset potential of 0.904 V versus the reversible hydrogen electrode (RHE), indicating high catalytic activity towards the oxygen reduction reaction (ORR), a key process in fuel cell technology. Furthermore, the voltammetric curves displayed a semi-rectangular shape, suggesting behavior dominated by electrochemical double-layer capacitance at the electrode-electrolyte interface. These findings highlight poultry litter-derived biochar as a multifunctional material with potential applications in energy storage and catalysis, contributing to sustainable waste valorization strategies.

ABSTRACT. Nonrenewable energy sources such as hydrocarbons have been widely used by humanity in the last century, but their use is limited by their finite nature. The growing energy demand and the dramatic rise in greenhouse gas emissions mostly in the recent decades have generated the need to implement new sustainable energy generation methods. Green hydrogen has emerged as a potential alternative as an energy carrier for electricity production, which can be used directly in electrochemical reactions present in fuel cells, or as a fuel blended with natural gas for use in conventional power plant combustion systems based on gas turbines, thereby reducing greenhouse gas emissions and providing future energy security. The transition from fossil fuels to hydrogen-based systems presents a significant technological and economic challenge, since most of the energy generation systems were originally designed to operate with nonrenewable fuels. A gradual transition can be achieved, using existing combustion systems and progressively incorporating small fractions of hydrogen. This work presents a stoichiometric analysis of the combustion process of hydrogen-natural gas mixtures at different hydrogen fractions. The behavior of the stoichiometric coefficients of the reactants and products, varying the hydrogen content from 0 to 100%, as well as the theoretical air required to decrease the equivalence ratio from 1 to 0.5, was analyzed by developing a mathematical model. Subsequently, the model was implemented in the Engineering Equation Solver (EES) software, generating an interface to modify the combustion parameters and evaluate the system’s behavior as hydrogen is added. The key combustion parameters analyzed were the adiabatic flame temperature, air-fuel ratio, and Wobbe index. The results indicate, firstly, an increase of up to 8.1% in the adiabatic flame temperature when complete combustion with 100% theoretical air takes place. Second, the results indicate that it is possible to use small percentages of hydrogen, up to 18% blended with natural gas, in existing equipment without requiring significant modifications to current natural gas-based combustion systems, while also achieving a reduction of up to 8.26% in greenhouse gas emissions.

ABSTRACT. In the context of the ongoing energy transition and economic decarbonization, renewable energy sources and hydrogen-based technologies are emerging as key alternatives to reduce fossil fuel dependence and mitigate greenhouse gas emissions. Among the various hydrogen production and utilization technologies, proton exchange membrane electrolyzers (PEMEL) and proton exchange membrane fuel cells (PEMFC) stand out for their versatility and low environmental impact, making them suitable for a range of applications, including the residential sector. The scientific literature suggests that conventional electric and thermal energy supply systems can be replaced by alternative energy schemes based on photovoltaic energy integrated with hydrogen production, storage, and utilization. This study presents sizing calculations and a cost analysis of components for an off-grid residential micro-cogeneration system according to three alternatives: (i) a baseline system using photovoltaic panels and a solar water heater, (ii) a system with a PEMFC fuel cell and hydrogen storage in pressurized tanks with external hydrogen supply and use of residual heat for water heating, and (iii) a system integrating an electrolyzer and a PEMFC fuel cell for producing, storing and utilize hydrogen internally also with heat recovery for water heating . The first step was to build a power load profile for a high-income household located in a city of central Mexico. The load profile was constructed by itemizing the electrical appliances with the rated power and the expected hours of operation. Afterwards, energy models were developed for the sizing process, based on data from scientific literature and technical datasheets of the components available in the energy market. Finally, an economic model was then developed and implemented to estimate the cost of energy (COE) for each system, considering current capital costs, market prices for electricity and hydrogen, and the operational lifespan of system components. The results indicate that the capital cost for the baseline systems is US$8760 with a COE of US$1.51, the system with PEMFC with external hydrogen supply has a capital cost of US$51,990 and a COE of US$ 0.9005 and the third alternative having an estimation of US$254,743 for capital cost and cost of energy of US$2.463. Among the three alternatives analyzed, the second configuration featuring a PEMFC fuel cell with hydrogen storage in pressurized tanks offers the greatest economic viability.

ABSTRACT. Biomethane is a biofuel under development and shows excellent potential for production and application in the industry. Previous works have shown that biogas can be enriched using hydrogenotrophy and green hydrogen sources. In addition to this, it is known that with mesophilic and thermophilic temperatures, the best productivities of this gas are obtained. Operating at low-mesophilic temperatures could help to require less energy and lower costs for methane enrichment at high temperatures; however, few studies have addressed the comparison in terms of methane concentration and productivity with an inoculum acclimatized to the lower operational temperature. Therefore, the main objective of this work was to acclimate an anaerobic sludge to hydrogenotrophy at 25 °C. The acclimatization was performed by two incubation cycles using a mixture of 70% H2 and 30% CO2 as substrate. The total and working volumes of the batch reactors were 1125 mL and 400 mL. The reactors were incubated at 100 kPa pressure and an initial pH of 7.0. Units with inoculum incubated at 35ºC were used as controls. The inoculum was incubated at each temperature without organic matter addition for 45 days to allow organic matter consumption before the hydrogenotrophy acclimatization. During 77 days of incubation of the reactors, two cycles of substrate addition were applied. In cycle 1, it was producing 1.33 ± 0.50 and 1.62 ± 0.58 L of CH4/Lreactor at 25 °C and 35 °C, respectively. The same trend was observed in cycle 2, having 1.26 ± 0.45 and 1.32 ± 0.48 L of CH4/Lreactor, respectively. Comparing the biomethane productivity at a temperature of 25 °C in cycle 1 and cycle 2, a decrease of 5.1 % was observed. Similarly, with the temperature of 35 °C, the productivity decreased by 18.42%; despite this, the stability of the systems improved in cycle 2. The methane concentration obtained was >90% at both temperatures. The results suggest that the hydrogenotrophy performance between these temperatures is similar. This work demonstrated the potential of upgrading systems operated at low-mesophilic temperatures, such as 25ºC.

ABSTRACT. Design of an integrated hybrid system to supply electricity to rural communities using sodium batteries to reduce environmental impact and help low-income communities.

ABSTRACT. Electrocatalysis plays a central role in the design and economic viability of direct alcohol fuel cells, with ethanol being a particularly attractive fuel due to its high energy density, availability, and low environmental impact. However, the electrochemical oxidation of ethanol in acidic or alkaline media is a highly complex process, characterized by multiple reaction pathways and the formation of more than forty intermediate species, including acetaldehyde, acetic acid, and various carbonaceous fragments. These intermediates can strongly adsorb onto the catalyst surface, leading to partial deactivation and limiting the overall conversion efficiency. To quantitatively describe these phenomena, a microkinetic model is developed that integrates the dynamics of adsorption-desorption processes, elementary surface reactions, and mass and charge transport phenomena in the porous electrode. The model explicitly considers the applied potential, the surface coverages of adsorbed species, the activation energy barriers, and electron transfer rates, using generalized Butler-Volmer equations to describe the electrochemical steps. The system of nonlinear differential equations is solved using robust numerical methods. The model allows the prediction of the evolution of surface coverages, current–potential (polarization) curves, and selectivity toward final products under various operating conditions, including temperature, ethanol concentration, current density, and catalyst composition. The results show that the efficiency of complete oxidation to carbon dioxide strongly depends on the catalyst surface structure and the availability of active sites for the adsorption of oxygenated species. Additionally, the accumulation of inhibiting intermediates such as adsorbed CO can be mitigated by employing bifunctional material designs or applying potential pulses. The model constitutes a fundamental predictive tool for the rational development of new catalysts and operational strategies to enhance the performance of direct alcohol fuel cells.

ABSTRACT. This study presents a comprehensive numerical and experimental investigation of catalyst layers (CLs) employed in hydrogen electrochemical compressors (EHCs). Three catalyst layers were fabricated using the electro-spray deposition technique. The catalyst ink was prepared by mixing 10 mg of Vulcan Carbon with 20 wt% platinum, 216 µL of Nafion® solution, and 648 µL of isopropyl alcohol per square centimeter of electrode surface. Scanning Electron Microscopy (SEM) was used to capture micrographs of the electrodes, both from the surface and cross-sections, at various magnifications. From these micrographs, the electrode thickness was measured at multiple locations, resulting in an average thickness of 0.002323 cm.

To accurately quantify the porosity of the CLs, the SEM images were processed through binarization using a Support Vector Machine (SVM) classification algorithm, effectively distinguishing between solid agglomerates and pores. Following this, the linear path and two-point correlation methods were applied to determine an average porosity of 0.22, with the remaining 0.78 corresponding to the agglomerated solid fraction. Based on the material densities and manufacturing ratios, a platinum-to-carbon weight ratio of 0.25 and an ionomer-to-total CL weight ratio of 0.52 were established.

Synthetic microstructures were generated according to these parameters on a 350×350 pixel grid, where each pixel represented a distinct phase of the material. Two primary distributions were designed: one with vertically aligned random phases (representing isotropy (Ixy) 0.0) and another with fully random phase distributions (representing Ixy 1.0). Intermediate microstructures with Ixy values ranging from 0.1 to 0.9 were reconstructed using a simulated annealing method (SA), progressively increasing disorder and randomness in the phase distributions.

Finite Volume Method (FVM) combined with the Tri-Diagonal Matrix Algorithm (TDMA) was utilized to solve the governing transport equations. Effective transport coefficients (ETCs) for electrons, protons, and gas diffusion were determined for each microstructure. Additionally, the effective platinum surface area was calculated based on the connectivity and phase distribution of neighboring nodes. Using the parameter of conduction and diffusion parameters for each node, electrode dimensions, and typical operational conditions, polarization curves were generated through overpotential models for each Ixy state. The results indicated that improving the alignment of the CL structure (i.e., reducing Ixy) significantly enhanced performance. Transitioning from Ixy 1.0 to 0.9 increased the power density by 86.66%, while transitioning to 0.7 Ixy increased it by 101.20%.

Moreover, SEM micrographs at 9,000× magnification (25×25 µm²) were analyzed by extracting 350×350 pixel regions equivalent to 14×14 µm². These images were processed and evaluated similarly to the synthetic structures. When using ETCs corresponding to Ixy 0.0, the polarization behavior of real microstructures exhibited an 80% similarity to synthetic structures with Ixy 0.3. Under ETCs for Ixy 1.0, the similarity increased to 95% when compared to Ixy 1.0 synthetic structures. Relative standard deviations across current density and potential curves ranged from 4.17% to 13.7%, with an average of 10.97%.

These results demonstrate that microstructural alignment and phase distribution significantly influence the electrochemical performance of CLs, offering valuable insights for the design and optimization of high-efficiency hydrogen electrochemical compressors.

ABSTRACT. This work shows the development and evaluation of a power electronics device for water electrolysis in a low-power Hydrogen Generation prototype. The presented design covers the analysis and evaluation of a single-stage two-pulse thyristor controlled rectifier to provide a suitable electric current for water electrolysis, and a data-acquisition-system (DAS) software for continuously monitoring key parameters as current, voltage, and temperature of the electrolyzer. Experimental results show the developed electronic device, the current-voltage curve of a 40 watts three series connected monocells electrolyzer, and the galvanostatic and potentiostatic efficiencies instead of hydrogen generation rate. The developed electronic system may be adapted to electrolyzers with different power specifications in hydrogen production systems.

ABSTRACT. As a result of the development of a Python code and a graphical user interface, a software application for the control, monitoring, and data acquisition of an alkaline electrolysis test bench has been produced. This system is responsible for managing the operating sequence of the process, user administration, experiment configuration and parameters, and data storage of the test procedures. Furthermore, during experimentation, system parameters and graphical outputs are displayed in real time. For the interface, object-oriented programming has been employed, utilizing the PyQt6 library to manage human-machine interface components, the SQLite3 library for database creation, manipulation, and access, and the PyVISA library to handle communication with the power supply. Digital filters have been implemented in the data acquisition process in order to discard inconsistent data. Moreover, the algorithm applied prevents the software from failing due to erroneous input values. The software consists of several windows. The first is a login window, which requires a username and password to ensure data security and protect access to the test bench. Subsequently, the main window is displayed, containing a menu divided into four sections (users, administrators, completed experiments, and experimentation). In the completed experiments window, a table presents the key data of all previous tests. When a specific test is selected, the full dataset is retrieved from the database. At this stage, it is possible to generate and save plots based on the collected information, including the characteristics of the electrolyzer used, the parameters obtained in each test, and operating conditions such as temperature, voltage, current, acquisition time, and test type. In the experimentation window, the test type (e.g., polarization curves, resistance tests) and operating conditions are entered. Two widgets are provided to display flow and current graphs as a function of time. Additionally, several labels are used to present parameters (such as mass flow, voltage, power, etc.), and buttons (start, stop, set) are used to manage the process. Once the experiment is initiated, real-time data visualization is enabled. Serial communication using the RS232 protocol has been adopted, allowing data transmission and reception between the system and both the direct current power supply and the flow meter. In order to ensure efficient operation, parallel processes have been implemented to avoid delays in data acquisition and processing. This project is currently in an early stage of development and is expected to serve as the foundation for future integration of artificial intelligence and advanced modeling. Therefore, it is anticipated that the potential of this development will be significantly leveraged.

ABSTRACT. To address the dual challenge of reducing greenhouse gas emissions and meeting growing energy demand, the Power-to-X concept has emerged as a key strategy. This approach involves producing synthetic fuels and chemicals from renewable energy sources, contributing to a more sustainable energy transition. This study focuses on simulating the production of synthetic fuels via the Fischer–Tropsch process, which converts green hydrogen and CO₂—captured from fossil fuel plants—into long-chain hydrocarbons similar to conventional fuels, but with lower environmental impact. The research represents the initial phase of a project aimed at identifying feasible technological pathways for Mexico’s energy transition. It includes preliminary assessments of economic viability, environmental impact, and inherent safety to support informed decision-making. Baja California is chosen as the case study due to its strong solar and wind potential, making it ideal for Power-to-X implementation. Using Aspen Plus V14, 1,000 scenarios are simulated to reflect variations in renewable energy input. Each scenario is evaluated using the Total Annual Cost (TAC), ECO-99, and Process Risk Index (PRI) to assess economic, environmental, and safety performance. The simulations yield products such as light gases, synthetic gasoline, jet fuel, and green diesel, with production levels dependent on the energy supplied. Results show that electrolyzers consume about 79% of the total system power, while the rest is used mainly by compressors. This work contributes to the identification of Power-to-X technologies that align with Mexico’s renewable energy potential, infrastructure, and sustainability goals.

ABSTRACT. Green hydrogen, produced through alkaline water electrolysis using renewable energy, is emerging as a key solution for decarbonizing sectors such as transportation and industry. The electrode material selection is an important factor; the platinum group elements have the most catalytic properties, but the high cost makes it difficult to use them. Nevertheless, improving the catalytic efficiency of the electrodes is crucial to carrying out the hydrogen evolution reaction (HER) and reducing the costs of this technology. The present investigation aims to evaluate the HER in electrodes with zirconia coating. The coating on 316 stainless steel was obtained by a colloidal electrophoretic deposition method, followed by a heat treatment to generate a crystalline zirconia structure on the substrate. The microstructural characterization of the ZrO2/316 electrode was made by field emission scanning electron microscopy (FESEM). The electrochemical tests were carried out in a three-electrode cell using an alkaline medium. The potentiodynamic curve shows that the effect of the zirconia coating is slight at the cathodic branch. However, the electrode with zirconia shows a passivation zone compared to the substrate, which indicates corrosive protection against the corrosive condition of the alkaline medium. Additionally, electrochemical impedance spectroscopy (EIS) was made at different cathodic overpotentials (20, 40, 60, 80, and 100 mV). The results were fitting and adjusting equivalent electrical circuit (EEC) with two constants time in parallel to the ZrO2/316 electrode, characteristic of coating electrodes. The value of the capacitance of the double electrochemical layer was obtained, and the roughness factor (Rf) was calculated, which indicated that the ZrO2/316 electrode showed four times more than the substrate. The surface morphology of the electrode is different from that of the substrate, as micrographs show an increase in surface roughness according to the Rf values. The addition of zirconia coating increases the electrochemical area, and even though the overpotential at a current of 10 mA/cm² does not change significantly, the presence of a passivation zone at coating electrodes suggests the improvement of corrosion resistance, maintaining the catalytic capacity.

ABSTRACT. The objective of this research work is to evaluate the influence of chromium content on the kinetics of the hydrogen evolution reaction (HER) on porous Ni and Ni–Cr alloy electrodes during alkaline electrolysis. The porous electrodes were fabricated using the powder metallurgy process, employing Ni–Cr compositions with 5, 10, 15, and 20 wt% chromium (referred to as Ni–Cr5, Ni–Cr10, Ni–Cr15, and Ni–Cr20, respectively). The powders used to fabricate the porous electrodes underwent a preliminary mechanical milling treatment for 10 hours before being compacted and sintered. In order to assess the solubility of chromium in the nickel matrix, an X-ray diffraction (XRD) analysis was conducted. The results showed that as the Cr concentration increases, additional intermetallic phases are formed, which may positively contribute to the enhancement of the hydrogen evolution reaction (HER). For the electrocatalytic evaluation of the Ni and Ni–Cr systems, electrochemical impedance spectroscopy (EIS) tests were conducted at different cathodic overpotentials relative to the reference electrode, using an AC amplitude of 10 mV and a frequency range from 100,000 Hz to 0.01 Hz. A 1.5 M NaOH solution at room temperature was used as the electrolyte. In the Nyquist plots, it can be observed that as the cathodic overpotential becomes more negative during the EIS evaluation, the semicircles become more clearly defined, indicating an increase in the double-layer capacitance and a decrease in the charge transfer resistance. The experimental data was fitted using an electrochemical equivalent circuit to model the electrochemical behavior at the electrode-electrolyte interface. The model that best describes the system corresponds to a series circuit, consisting of a solution resistance (Rs) in series with two constant phase element (CPE) components. In parallel with each CPE, a resistance to the pores (Rp) and another resistance to charge transfer (Rct) are considered during the electrocatalytic reaction. The use of CPEs instead of ideal capacitances reflects the surface heterogeneity of the electrodes. The decrease in Rct in the Ni–Cr porous electrodes at higher overpotentials confirms the improvement in the electrocatalytic activity of the electrodes under alkaline electrolysis conditions.

ABSTRACT. The advancement of low-platinum nanocatalysts for acidic water electrolysis is essential for reducing the cost of hydrogen production while maintaining high efficiency and durability. This work presents a detailed study of Pt–La1-xSrxCoO3/C nanocomposites (x = 0, 0.1, 0.3, 0.5) supported on Vulcan XC-72. These materials contain only 10 wt. % Pt—half the content in commercial Pt/C—offering a significant reduction in noble metal usage without sacrificing catalytic performance. X-ray diffraction (XRD) confirmed successful Sr incorporation into the LaCoO3 lattice, producing a phase transition from rhombohedral to cubic symmetry with increasing Sr content. FTIR analysis revealed key functional groups (Pt–O, Co–O, La(Sr)–O, O–Co–O), while SEM coupled with elemental mapping showed homogeneously dispersed Vulcan support with localized perovskite clusters and distinct Pt phases. Electrochemical performance was evaluated in a three-electrode half-cell using 0.1 M HClO4. The catalyst with x = 0.5 demonstrated superior hydrogen evolution reaction (HER) activity, reaching 10 mA cm-2 at an overpotential of –11.51 mV vs RHE, outperforming commercial Pt/C (–12.90 mV). After 3000 accelerated degradation cycles, this catalyst retained significant activity (–14.79 mV), confirming excellent durability despite reduced Pt content. For the oxygen evolution reaction (OER), the x = 0.1 composition exhibited comparable activity to Pt/C, with a +30 mV overpotential increase and similar long-term stability. To evaluate device-level performance, we propose an asymmetric PEM electrolyzer configuration using x = 0.5 at the cathode (HER) and x = 0.1 at the anode (OER). This cell will be benchmarked against a Pt/C–Ru/C system to assess its overall activity and stability. These findings underscore the potential of Pt–La1-xSrxCoO3/C nanocatalysts as bifunctional, low-platinum materials for sustainable hydrogen production in acidic media.

ABSTRACT. There are three main water electrolysis processes: alkaline, proton exchange membrane (PEM), and anion exchange membrane (AEM) electrolysis. PEM water electrolyzers use membranes such as Nafion™ due to their high conductivity, reliability, and superior performance. Alkaline water electrolyzers, on the other hand, use less expensive catalysts compared to PEM systems and offer a longer operational lifespan, making alkaline electrolysis a more cost-effective option for hydrogen production in fuel enrichment and combustion applications. Currently, AEM technology is under development. This emerging approach, which combines features of both alkaline and PEM electrolyzers, has not yet been industrialized but offers greater flexibility and does not require the use of noble metals. This project explores the use of nickel-based catalysts, which are inexpensive and abundant. Moreover, nickel can be alloyed with iron and copper to enhance performance in green hydrogen production, a sustainable energy alternative aimed at reducing greenhouse gas emissions. The metal catalysts were synthesized by chemical reduction and were physicochemically characterized using SEM-EDS (to observe different surfaces and morphologies), XRD (to analyze crystalline phases), and electrochemical techniques such as cyclic voltammetry (CV) and linear sweep voltammetry (LSV) to evaluate catalytic activity and determine the Tafel slope. These electrochemical measurements were carried out in a three-electrode cell connected to an AUTOLAB potentiostat, using a 1 M KOH solution as the electrolyte. The synthesized catalysts were deposited onto the working electrode to analyze the hydrogen evolution reaction (HER) and calculate the Tafel slope. The catalyst that demonstrated the best performance was the NiCu alloy, with a Tafel slope of 79 mV·dec⁻¹ at an overpotential of 0.15 V, this is attributed to the large surface area of the material and the synergy between the Ni and Cu atoms.

ABSTRACT. Energy plays a critical role in national development. In 2023, 77% of Mexico’s electricity was generated from fossil sources, and the transport sector emitted approximately 487,000 kt of CO₂. This dependency contrasts with international commitments, such as the Paris Agreement, which mandate a transition towards clean energy. Despite Mexico’s high renewable potential, its adoption remains limited, hindering decarbonization objectives.

Hydrogen has emerged as a high-impact energy alternative, owing to its physicochemical properties and its capability to integrate into high-demand applications. This work presents the development of a purification system for diaphragm-free alkaline electrolyzers, specifically designed to eliminate potassium hydroxide (KOH) carryover during oxyhydrogen (HHO) gas production for dual-fuel engines. The gas generated carries electrolyte vapor, which induces corrosion in metallic components of the electrolysis system, contaminates lubricating oil, and reduces engine lifespan. Therefore, a phase separation and vapor condensation system were designed and implemented to minimize the presence of impurities.

The design process involved modeling with Solid Edge software and computational fluid dynamics (CFD) simulations in ANSYS, complemented by the Advanced Product Quality Planning (APQP) methodology to prevent early failures and ensure quality from the outset. The manufacturing process included a two-stage vertical phase separator, constructed from materials resistant to alkaline media and optimized to operate with 30% KOH within a temperature range of 75–80 °C. Additionally, a condenser was integrated to maximize heat transfer without inducing pressure losses.

The system was validated in a 5 kW pilot plant, operating at 0.5 A/cm² and producing an average of 7 L/min of HHO gas over 100 hours of experimentation. A 48% reduction in KOH carryover was recorded compared to conventional systems. The purification efficiency was evaluated through electrical conductivity tests in deionized water, yielding post-operation values of 32 μS/cm, within acceptable limits for engine applications. The demonstrated thermal stability, separation, and purification efficiency position this development as a viable solution for high-purity HHO generation, contributing to the energy transition and decarbonization of industrial and transportation sectors.

ABSTRACT. In hydrogen economy, some advantages are observed, such as energy security, the use of biomass as a renewable energy source, and lower pollution. The production of hydrogen from the reforming of glycerol with water vapor is thermodynamically feasible and can be calculated according to the minimization of total Gibbs free energy using Aspen Plus software. For the simulation, the reactor was selected and different temperatures from 300 to 1000 degrees were studied, and the pressure was varied from 1 to 20 atmospheres. It was found that the best equilibrium yields of H2, CH4, CO, and CO2 are achieved at 700°C. By increasing the total pressure, it was found that the yield of H2 decreases; conversely, if the pressure decreases, good yields about are obtained at 1 atm at temperatures between 600-700 °C. An increase in the water/glycerol 1:10 in the feed stream favors the production of H2, decreases the production of CO as well as CH4 across the entire temperature range. A good water/glycerol ratio between 10 and 15 was found for the production of H2, minimizing the production of CO2 with a maximum at 823 K (550°C). A low carbon yield was also found when the temperature was below 823 K (550°C) and the water/glycerol ratio was greater than 3. The experimental analysis of the glycerol reforming reaction was carried out using Ni-Co/Ex-Hydrotalcite sweeping temperatures from 300 to 700 degrees, finding greater hydrogen production at 600°C and comparing the results obtained in the Aspen Plus simulation with the experimental reaction. Also by XRD and scanning electron microscopy analysis were performed for the Ni/Co hydrotalcite catalyst, a hydrotalcite-type structure was found. These catalysts were used for this reaction because they were previously studied in the steam reforming of ethanol , finding high selectivities for hydrogen. In a next stage, the products obtained from the reaction steam reforming glycerol were passed to a methanation reactor. For this experimental reaction the Ni/CeO2 catalyst (chosen from the literature) was evaluated . This catalyst was used because high CO2 conversions and high selectivities towards CH4 are reported in the literature. Finally, the results obtained in the ethanol and glycerol reforming reaction are compared.

ABSTRACT. Green hydrogen production research with alternative methods has increased to achieve competitive costs and viable production rates. Aluminum corrosion in aqueous acid solution has proven to be a promising method. Variables such as initial temperature and pressure conditions, shape and size of the metal, presence of promoters, HCl concentration, among others can be studied in order to make the hydrogen production process more efficient. In this research, a shrinking core model was modified to describe kinetic behaviors and evaluate the feasibility of hydrogen production reactions by aluminum corrosion in aqueous solutions by varying HCl concentration (1.125 to 1.75 M) in the presence of Na2MoO4 nanoparticles as a promoter. The experiments were evaluated on a pilot-scale, the zero-reaction time was taken when aluminum was added in the reactor. Pressure and temperature variations were monitored during reaction to quantify the H2 production rates. At low HCl concentrations, the diffusion of ion species/water molecules through the AlOOH layer to the Al surface controls throughout reaction. Although, for high HCl concentrations, a sequence of two controlling stages was required: the diffusion of ion species/water molecules through the AlOOH layer to the aluminum surface, followed by the chemical reaction on the Al surface. This kinetic study provides important reactor design criteria for continuous hydrogen production.

ABSTRACT. The global energy transition requires technological solutions that enable the efficient and sustainable production of green hydrogen. Although alkaline electrolyzers are a mature and economically accessible technology, they have limitations in terms of energy efficiency, which typically ranges between 40% and 50%. This low efficiency is a critical obstacle to their large-scale adoption, due to high operating costs and the difficulty of integrating them into smart energy systems. In view of this, we present a perspective on the integration of deep learning techniques to model and predict the behavior of the electrochemical system, through real-time monitoring using a robust data acquisition system. This system will allow the adjustment of key operating parameters, such as voltage, current, temperature, and pressure. These parameters will form the structure of a robust database that will be used to train different algorithms that are part of machine learning models capable of predicting energy efficiency under different operating conditions. This proposal aims to lay the foundations for the development of an intelligent system for the analysis and optimization of operating variables in an alkaline electrolyzer, using deep learning techniques. The design of a methodological framework is proposed that encompasses the collection of experimental data and the validation of predictive models under real operating conditions. This research seeks to lay the foundations for future implementations of artificial intelligence in alkaline electrolysis systems, with the aim of maximizing overall efficiency and enabling their integration into larger-scale energy schemes. The proposed approach will not only contribute to improving the energy performance of the system, but also to reducing electricity consumption per cubic meter of hydrogen produced, extending the useful life of components, and reducing operating costs. The study case is a 10 kW Alkaline Electrolyser. Furthermore, this line of research represents a significant contribution to the field of electrochemical and applied artificial intelligence, in line with strategic objectives related to energy transition, climate change mitigation, and the adoption of clean technologies at the national and international levels.

ABSTRACT. The development of green hydrogen technologies requires not only high-efficiency energy conversion systems but also adaptive control strategies that are able to address the intermittency of renewable sources. This work presents a novel method to optimize the operation of Proton Exchange Membrane (PEM) electrolyzers powered by photovoltaic (PV) arrays, through the integration of an embedded neural network into a DC-DC buck converter. The system leverages real-time sensor data (voltage, current, stack temperature, and gas flow rates) to estimate the Faradaic efficiency—defined as the ratio of actual hydrogen production to the theoretical maximum dictated by the electrical input—and dynamically adjusts the power delivery via an offline-trained neural network, ensuring electrochemical optimality under fluctuating irradiance and load conditions. Unlike conventional MPPT algorithms that prioritize power extraction, our control paradigm subordinates power electronics to the electrolyzer’s electrochemical state, maximizing hydrogen production efficiency. The prototype’s modular and cost-effective architecture (e.g., STM32-based) enables scalable deployment, bridging academic research with industrial applications. The expected outcome is a deeper integration of real-time intelligence in power electronics applied to green hydrogen production, contributing both to the academic understanding of system dynamics and to the practical deployment of smarter renewable energy infrastructures.

ABSTRACT. Advanced high-strength steels (AHSS) have gained significant importance in structural applications, particularly in the automotive industry, due to their excellent combination of mechanical strength and ductility. In this context, medium manganese steels (4–12 wt.%) belonging to the third generation have stood out for their ability to activate plasticity mechanisms during its deformation, such as twinning-induced plasticity (TWIP) and/or transformation-induced plasticity (TRIP), which optimize stress distribution and energy absorption under mechanical load. However, their behavior in the presence of hydrogen remains a challenge for their use in critical environments, making it essential to study its effects. In this research, the effect of intercritical annealing temperature on hydrogen permeability was evaluated in a medium-Mn AHSS. The material was initially processed by hot rolling, followed by intercritical annealing heat treatments at three temperatures: 670, 680, and 690 °C, with a constant soaking time of 10 minutes. The hydrogen permeability was assessed through electrochemical tests using a Devanathan-Stachurski double-cell setup, aimed at determining parameters such as the steady-state flux and the breakthrough time of hydrogen at the detection cell. The results showed that the annealing temperature significantly altered the fraction and stability of retained austenite, as well as the ferrite content, producing variations in hydrogen diffusivity. At lower temperatures, finer microstructures with lower retained austenite content were observed, which correlated with reduced hydrogen permeability, suggesting a higher degree of trapping and lower diffusible hydrogen mobility. In contrast, higher annealing temperatures favored hydrogen mobility, reflecting a lower trapping capability. These findings establish clear relationships between thermal treatment, resulting microstructure, and resistance to hydrogen, which is essential for designing steels with improved resistance to hydrogen embrittlement without compromising their mechanical properties.

ABSTRACT. The transition from polluting energy sources to renewable, efficient, and economically viable alternatives has become imperative due to growing concerns about climate change and the depletion of non-renewable energy resources. In this context, hydrogen production via heterogeneous photocatalysis has been widely investigated to contribute to the world’s energetic crisis. However, there are diverse obstacles that need to be addressed; the most important is to increase the efficiency of the reaction; different solutions have been proposed, such as photocatalysts with appropriate band gap, morphology controlled, noble metal doping, or heterojunctions. Among the different photocatalysts that have been studied, graphitic carbon nitride nanosheets (g-C3N4) are one of the most promising photocatalysts due to their physicochemical stability, appropriated band gap (2.7 eV), and facile synthesis. On the other hand, more recently, In2O3 nanocubes have been studied as photocatalysts due to their stability, band gap (2.6 eV), oxygen vacancies, and favored {001} facets, underlining the significance of morphology control. Nevertheless, these two photocatalysts on their own have not reached the desired performance. Thence, looking to improve the reaction yield, we used different percentages (0.5, 1, 1.75, 2.5, and 5 wt.%) of indium trioxide (In2O3) nanocubes to synthesize a series of heterojunctions. Additionally, heterojunctions were co-catalyzed with 1 wt.% of palladium (Pd), a strategy that remains scarcely explored in literature. The novelty of this work lies in the use of well-defined In2O3 nanocubes to construct heterojunctions with g-C3N4 decorated with Pd, offering a promising approach to enhance photocatalytic hydrogen evolution through synergistic electronic and structural effects. The catalysts were characterized using X-ray diffraction, UV-visible spectroscopy, photoluminescence spectroscopy, nitrogen physisorption, and transmission electron microscopy. Such characterization showed that g-C3N4 nanosheets and In2O3 nanocubes were correctly synthesized and mixed to form different heterojunctions decorated with dispersed Pd nanoparticles. The heterojunctions were evaluated in the photo-production of hydrogen from methanol-water mixtures under UV and visible illumination conditions. The results indicate that all the heterojunctions had a better performance than the g-C3N4 just decorated with Pd, highlighting the key role of In2O3 nanocubes. Also, optimum performance was obtained with the 1%- In2O3 heterojunction, indicating counterproductive effects from higher concentrations of In2O3; this information was supported by photoluminescence spectra analysis. Results point out the critical role of the control of morphology for the two photocatalysts and the synergies obtained by mixing them and adding a noble metal like Pd. Acknowledgements. We are thankful to PAPIIT-UNAM, Mexico for supporting the work carried out through the projects: IN116424, and IV100124. The authors thank Pedro Casillas and Josue Romero for technical assistance.

ABSTRACT. The rising demand for sustainable energy sources has propelled advancements in hydrogen-based technologies, such as electrolyzers, which require highly efficient electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). In this study, we present the synthesis and characterization of synergistic nickel-molybdenum electrocatalysts with four distinct morphologies: nanorods, nanocuboids, nanosheets, and hollow nanospheres. These materials were synthesized via controlled hydrothermal reactions and directly grown on a conductive three-dimensional nickel foam substrate, followed by thermal treatment under a reductive Ar/H₂ (7%/93%) atmosphere. Electrochemical evaluations were conducted in alkaline media using a conventional three-electrode configuration. Linear sweep voltammetry curves were recorded for both the HER and the OER, Tafel slopes were calculated, and the electrical double-layer capacitance (CDL) was analyzed. Complementary characterizations included scanning electron microscopy (SEM) imaging and X-ray diffraction (XRD) analysis. For the HER, the nanosheets demonstrated superior performance, achieving a current density of 10 mA/cm² at an overpotential of only 164 mV. Performance rankings were as follows: nanocuboids (207 mV), nanorods (213 mV), and hollow nanospheres (217 mV). Corresponding Tafel slopes aligned with these findings, with values of 54.4 mV/dec for nanosheets, 104.4 mV/dec for nanocuboids, 100.6 mV/dec for nanorods, and 101.3 mV/dec for hollow nanospheres, suggesting more favorable kinetics in sheet-like structures. For the OER, the nanocuboids exhibited optimal performance, requiring an overpotential of 297 mV to achieve a current density of 10 mA/cm², followed by nanorods (326 mV), nanosheets (392 mV), and hollow nanospheres (430 mV). The Tafel slopes mirrored this trend, with values of 50.1 mV/dec for nanocuboids, 63.7 mV/dec for nanorods, 86.9 mV/dec for nanosheets, and 95.7 mV/dec for hollow nanospheres, indicating more favorable kinetics in compact structures. The findings highlight the significant impact of morphology on catalytic performance. Direct growth on nickel foam ensured efficient electrical conductivity, eliminating the need for binders that often hinder electrocatalytic activity. This approach supports the rational design of cost-effective, high-performance electrocatalysts tailored for hydrogen production technologies.

ABSTRACT. Hydrogen technologies, including fuel cells and water electrolysis, are becoming increasingly significant as society endeavors to mitigate the harmful environmental impacts of fossil fuels. These technologies play a pivotal role in decarbonizing multiple sectors-most notably transportation, industry, and power generation-by offering cleaner and more sustainable alternatives to conventional energy sources. A key component in hydrogen technologies is the catalyst used as the anode or cathode, which directly influences the efficiency and overall performance of the system, depending on the intrinsic properties of the active material.

Platinum group metals (PGMs) have long been recognized for their exceptional catalytic performance. This advantage stems from their optimal binding energy between M-H (M= metal), which facilitates efficient hydrogen adsorption and desorption mechanisms. These characteristics make PGMs highly effective for critical electrochemical reactions, such as the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR). However, their widespread application faces limitations due to the scarcity and high cost of PGMs. Consequently, growing interest is focused on developing alternative catalysts that can either reduce PGM content or eliminate their use altogether, while maintaining competitive performance.

In this study, nanomaterials based on NixMo100-x-CK were synthesized using incipient wetness impregnation followed by thermal reduction at varying molar ratios. The objective was to explore the effect of metal proportion on catalytic performance and determine the optimal composition for a PGM-free NiMo-based catalyst. After identifying the optimal catalyst, low Pt loads were incorporated into the NiMo system to create a bimetallic catalyst with enhanced activity. The resulting material was evaluated for its efficacy in both HER and HOR.

Half-cell studies demonstrated that the 3% Pt/Ni90Mo10 -CK catalyst exhibited remarkable catalytic activity. For HER, it achieved a current density of 10 mA/cm² at an overpotential (η10) of only 65.2 mV, with a Tafel slope of 41.6 mV dec⁻¹, indicating favorable kinetics. For HOR, the catalyst exhibited a Tafel slope of 32.9 mV dec⁻¹ and an impressive exchange current density (Jo) of 1.03 mA/cm². These results underscore the potential of the NiMo-based catalyst with minimal Pt loading as a cost-effective and competitive alternative to traditional PGM-heavy systems, such as 20% Pt-C, in HER and HOR applications.

Overall, this work highlights the critical role of NiMo molar ratio in determining catalytic performance and demonstrates the significant improvement achieved by incorporating small amounts of Pt into the system. By optimizing the bimetallic composition, this work opens new avenues for the development of high-performance, low-cost catalysts that align with sustainability and energy transition goals, contributing to the broader adoption of hydrogen technologies in a decarbonized future.

ABSTRACT. Se preparó un catalizador de alta resistencia a la compresión hecho de Ni-Co/Al2O3-SiO2 en forma de esferas. El precursor de alúmina fue un gel de bohemita obtenido por precipitación y el gel de sílice se obtuvo a partir de un ácido silícico, que se mezclaron a diferentes concentraciones, para obtener cuatro muestras diferentes. Las esferas se obtuvieron por mezcla mecánica usando un granulador de tambor. Las esferas se secaron a 110°C y se calcinaron a 550 ° C. Las técnicas de caracterización incluyeron: resistencia mecánica, área y textura BET, adsorción de agua, MEB, EDS, TGA y acidez IR de piridina adsorbida. Las esferas mostraron alta resistencia a la compresión y se observó que a medida que aumenta el contenido de silicio, tanto el área superficial como la resistencia mecánica aumentaban. El catalizador con Ni (10% en peso) Co (4,5%) soportado en Al2O3-SiO2 evaluado a 540ºC mostró una conversión de etanol del 80% y selectividades de: 71% de H2, 19% de CH4 y 10% de CO2 y no se observó CO Las evaluaciones catalíticas se realizaron en un reactor integral (30 g, d partícula = 1/8 pulg.).

ABSTRACT. Hydrogen storage remains a major challenge for its use as an energy carrier, due to the limitations of current technologies in terms of safety, efficiency, and cost. The nitrogen reduction reaction (NRR) represents a viable alternative for storing and transporting hydrogen, since it promotes the reduction of atmospheric nitrogen to ammonia, a compound that can safely and efficiently store and release the gas. Recent studies suggest that coordination complexes based on transition metals such as copper (Cu) combined with the use of carbon nanostructures are a promising option for the design of efficient bimetallic nanocatalysts for NRR. However, there is a need to develop selective nanocatalysts with low noble metals content, such as platinum (Pt). This study reports the synthesis of bimetallic nanocatalysts supported on carbon nanotubes (CNTs) and graphene (G) functionalized with the [(C6H5N3) Cu)]n (Cu-BTA) coordination complex. The methodology includes the synthesis of Cu-BTA via the Schlenk technique, functionalizing CNTs and G under reflux conditions, and synthesizing Pt-based nanocatalysts using the BAE method. The Pt content in the nanocatalysts is restricted to 5 wt.%, labeled as Pt/CNT, Pt/CNTCu-BTA, Pt/G, and Pt/GCu-BTA. Characterization using 1H-NMR and FTIR confirms the formation of the Cu-BTA complex. XRD analysis identifies reflections associated with Cu-BTA and Cu oxides in CNTCu-BTA and GCu-BTA. The EDS analysis of Pt/CNTCu-BTA and Pt/GCu-BTA shows that the Pt and Cu content is approximately 5 wt. % in each one. The XRD patterns show reflections that suggest the formation of Pt-Cu alloyed phases in such nanocatalysts. Their electrochemical characterization by cyclic voltammetry shows an increase in current density (j) after chronopotentiometry test, suggesting an activation of sites on the nanocatalyst. On the other hand, the ammonia production performance of Pt/CNTCu-BTA (1.3 mg h¹ mg¹cat) and Pt/GCu-BTA (7.3 mg h¹ mg¹cat) at 0.9 V, is close and even superior to that obtained with commercial 20% Pt/C (1.6 mg h¹ mg¹cat). This behavior is attributed to the positive effect of support functionalization with Cu, which allows a better conversion of N2 to ammonia.

ABSTRACT. This study addresses key challenges in hydrogen storage and compression for sustainable energy systems by evaluating the performance of a prototype Electrochemical Hydrogen Compressor (EHC). Experimental characterization was carried out using chronoamperometry and polarization curves across a range of applied voltages and pressures. The results were integrated with a theoretical model to establish predictive correlations between cathode pressure, applied voltage, and time. From this, an empirical equation was derived to estimate compression behavior and optimize tank sizing. The EHC prototype achieved a cathode pressure of 100 psi in 194 seconds at 2.0 V (7.2 A), demonstrating stable and efficient operation under all test conditions. Further analysis included volumetric flow rate, energy efficiency, and compression dynamics, providing a comprehensive performance assessment. The results underscore the potential of EHCs as compact, silent, and energy-efficient alternatives to mechanical compressors, particularly for applications in hydrogen storage and renewable energy systems. This work contributes to the development of predictive tools for EHC design and supports the advancement of scalable hydrogen compression solutions suitable for integration into industrial and distributed energy infrastructures.

ABSTRACT. The global transition toward a low-carbon economy requires the development of clean energy carriers and robust infrastructure. Among the hydrogen carriers under consideration, anhydrous ammonia is gaining increasing attention due to its high hydrogen density, ease of storage and transport, and relatively low cost compared to other options such as liquid hydrogen or organic hydrides. However, its corrosive nature, especially when contaminated—presents significant challenges to the integrity of metallic components in pipelines and valve systems. This study evaluates the suitability of industrial ball valves for anhydrous ammonia service, taking as a reference an existing, certified ball valve design originally developed for hydrogen applications. Building on this foundation, a new preliminary prototype design for an ammonia ball valve has been developed. The main objective is to assess the technical adaptations required for safe and cost-effective use with ammonia, while minimizing the reliance on stainless steel due to its high material and fabrication costs. The research integrates thermodynamic modeling, regulatory review, and engineering analysis to propose design improvements aligned with industrial certification requirements. Thermodynamic behavior of ammonia is analyzed through simulations conducted using the CoolProps open-source thermophysical property library. These simulations focus on phase behavior and pressure variations inside the valve chamber under various thermal conditions, providing essential input for mechanical design considerations and safety margins. The results help define critical pressure thresholds and operating ranges that influence valve performance, especially under conditions where the valve remains closed or partially open. The certification framework is based on an in-depth review of European and international standards applicable to ammonia-handling components. In particular, the study focuses on the requirements defined by DIN EN 378, which governs safety and environmental aspects of refrigeration systems, and DIN EN ISO 21922, which establishes design and performance criteria for valves and devices used with toxic and corrosive refrigerant gases such as ammonia. These standards are used to establish a baseline for design, material selection, tightness testing, and pressure resistance. Although experimental testing has not yet been completed, field trials will involve exposing the designed prototype valve to ammonia under controlled temperature and pressure conditions. These tests aim to validate the simulation outcomes and confirm the mechanical and chemical performance of the selected materials. This work contributes to the development of safer, more affordable valve technologies for ammonia-based hydrogen infrastructure. It supports the broader goals of the hydrogen economy by facilitating the integration of ammonia into pipeline networks and promoting standardized approaches to component certification. The findings are especially relevant for manufacturers, engineers, and policymakers engaged in the deployment of next-generation hydrogen and ammonia infrastructure.