High-purity Hydrogen Production Research Articles

Dynamic Fe-O-Cu induced electronic structure modulation on CuOx electrode for selective electrocatalytic oxidation of glycerol

Electrocatalytic glycerol oxidation reaction to produce high-value organic chemicals has research significance for managing the overproduction of glycerol and handling the energy crisis. Herein, a copper-based self-supporting catalytic electrode with a dynamic Fe-O-Cu optimized coordination (Fe-CuOx/CF) was prepared. The oxygen-bridged asymmetric coordination structure (Fe-O-Cu) optimized the electronic configuration and promoted the formation of the crucial intermediate species. After Fe was embedded in the lattice of copper oxides, a remarkable enhancement in the adsorption capacity of OH- and glycerol was confirmed. As a result, Fe-CuOx/CF exhibited an excellent production capacity of formate, with high faradaic efficiency and selectivity values of 93.65 % and 95.10 %. Concurrent production of formate and high purity hydrogen was achieved in the double-electrode flow electrolyzer. This work provides guiding significance for the optimization of the catalytic coordination and the design of high-efficiency transition metal-based catalysts for electrooxidation of biomass platform molecules.

Computational Fluid Dynamics Modelling of Hydrogen Production via Water Splitting in Oxygen Membrane Reactors.

The utilization of oxygen transport membranes enables the production of high-purity hydrogen by the thermal decomposition of water below 1000 °C. This process is based on a chemical potential gradient across the membrane, which is usually achieved by introducing a reducing gas. Computational fluid dynamics (CFD) can be used to model reactors based on this concept. In this study, a modelling approach for water splitting is presented in which oxygen transport through the membrane acts as the rate-determining process for the overall reaction. This transport step is implemented in the CFD simulation. Both gas compartments are modelled in the simulations. Hydrogen and methane are used as reducing gases. The model is validated using experimental data from the literature and compared with a simplified perfect mixing modelling approach. Although the main focus of this work is to propose an approach to implement the water splitting in CFD simulations, a simulation study was conducted to exemplify how CFD modelling can be utilized in design optimization. Simplified 2-dimensional and rotational symmetric reactor geometries were compared. This study shows that a parallel overflow of the membrane in an elongated reactor is advantageous, as this reduces the back diffusion of the reaction products, which increases the mean driving force for oxygen transport through the membrane.

Boosting the Production of Hydrogen from an Overall Urea Splitting Reaction Using a Tri-Functional Scandium-Cobalt Electrocatalyst.

The creation of highly efficient and economical electrocatalysts is essential to the massive electrolysis of water to produce clean energy. The ability to use urea reaction of oxidation (UOR) in place of the oxygen/hydrogen evolution process (OER/HER) during water splitting is a significant step toward the production of high-purity hydrogen with less energy usage. Empirical evidence suggests that the UOR process consists of two stages. First, the metal sites undergo an electrochemical pre-oxidation reaction, and then the urea molecules on the high-valence metal sites are chemically oxidized. Here, the use of scandium-doped CoTe supported on carbon nanotubes called Sc@CoTe/CNT is reported and CoTe/CNT as a composite to efficiently promote hydrogen generation from highly durable and active electrocatalysts for the OER/UOR/HER in urea and alkali solutions. Electrochemical impedance spectroscopy indicates that the UOR facilitates charge transfer across the interface. Furthermore, the Sc@CoTe/CNT nanocatalyst has high performance in KOH and KOH-containing urea solutions as demonstrated by the HER, OER, and UOR (215mV, 1.59, and 1.31V, respectively, at 10mA cm-2 in 1m KOH) and CoTe/CNT shows 195 mV, 1.61 and 1.3V, respectively. Consequently, the total urea splitting system achieves 1.29V, whereas the overall water splitting device obtaines 1.49V of Sc@CoTe/CNT and CoTe/CNT shows 1.54, 1.48 V, respectively. This work presents a viable method of combining HER with UOR for maximally effective hydrogen production.

Effect of Cu doping on morphology and properties of calcium ferrite and its application as oxygen carrier in chemical looping hydrogen production

Chemical looping hydrogen production with inherent CO2 capture has been widely recognized as a clean and efficient approach to high-purity hydrogen production because of the ultra-pure H2 product without any purification facilities. It is crucial to develop oxygen carriers with better performance to improve fuel conversion and hydrogen production efficiency. The potential of Ca2Fe2O5 in steam converting has been confirmed. However, its lower oxygen transfer capacity, that is, it tends to produce lower fuel conversion in fuel reactors, which will limit its practical application. Here, we report the development of Cu-doped Ca2Fe2O5-based oxygen carriers using sol-gel technology. The effects of B-site substitution of Cu element on the morphological properties and redox properties of Ca2Fe2-xCuxO5 (x = 0, 0.1, 0.25, 0.5, 1) oxygen carriers were evaluated based on experiments and density functional theory calculations. The results show that Cu doping not only elevated the surface oxygen content and enhanced the oxygen activity of the oxygen carriers, but also increased the Fe3+ at the B-site, thus enhanced their binding ability with oxygen molecules. Vacancy formation was a rate-determining step in the chemical looping hydrogen production (CLH), and Cu-doped Ca2Fe2O5 reduced the energy of oxygen vacancy formation. In the CLH process, the doping of Cu significantly improved the hydrogen productivity and fuel conversion rate. The fuel conversion rate was positively correlated with the doping amount of Cu. When x = 1, Ca2Fe2-xCuxO5 had the maximum fuel conversion rate, and its average conversion was 54.2% more than that of undoped Ca2Fe2O5. Ca2Fe2-xCuxO5 with x = 0.25 was the most suitable for CLH with the highest H2 yield, which was 20.3% more than that of Ca2Fe2O5. Moreover, its properties remained stable over multiple redox cycles with high activity and stability for CO-CLH.

The Dependence of NiMo/Cu Catalyst Composition on Its Catalytic Activity in Sodium Borohydride Hydrolysis Reactions.

The production of high-purity hydrogen from hydrogen storage materials with further direct use of generated hydrogen in fuel cells is still a relevant research field. For this purpose, nickel-molybdenum-plated copper catalysts (NiMo/Cu), comprising between 1 and 20 wt.% molybdenum, as catalytic materials for hydrogen generation, were prepared using a low-cost, straightforward electroless metal deposition method by using citrate plating baths containing Ni2+-Mo6+ ions as a metal source and morpholine borane as a reducing agent. The catalytic activity of the prepared NiMo/Cu catalysts toward alkaline sodium borohydride (NaBH4) hydrolysis increased with the increase in the content of molybdenum present in the catalysts. The hydrogen generation rate of 6.48 L min-1 gcat-1 was achieved by employing NiMo/Cu comprising 20 wt.% at a temperature of 343 K and a calculated activation energy of 60.49 kJ mol-1 with remarkable stability, retaining 94% of its initial catalytic activity for NaBH4 hydrolysis following the completion of the fifth cycle. The synergetic effect between nickel and molybdenum, in addition to the formation of solid-state solutions between metals, promoted the hydrogen generation reaction.

Feasibility Study on Production of Slush Hydrogen Based on Liquid and Solid Phase for Long Term Storage

To achieve net-zero objectives, the expansion of renewable energy sources is anticipated to be accompanied by an increased use of carbon-free fuels, such as hydrogen. Internationally, there are proposals for transporting hydrogen by synthesizing it into carriers like ammonia or Liquid Organic Hydrogen Carriers (LOHCs). However, considering the energy consumption required for hydrogenation and dehydrogenation processes and the need for high-purity hydrogen production, the development of liquid hydrogen transportation technologies is becoming increasingly important. Liquid hydrogen, with a density approximately one-sixth that of liquid natural gas and a boiling point roughly 90 K lower, poses significant challenges in suppressing and managing boil-off gas during transportation. Slush hydrogen, a mixture of liquid and solid phases, offers potential benefits. with an approximate 15% increase in density and an 18% increase in thermal capacity compared to liquid hydrogen. The latent heat of fusion of solid hydrogen effectively suppresses boil-off gas (BOG), and the increased density can reduce transportation costs. This study experimentally validated the long-duration storage and transportation concept of slush hydrogen by adapting NASA’s (National Aeronautics and Space Administration) proposed IRAS (Integrated Refrigeration and Storage) technology for compact and mobile tanks. Slush hydrogen was successfully produced by reaching the triple point of hydrogen, resulting in a composition of 47% solid and 53% liquid, with a density of approximately 80.9 kg/m3. Most importantly, methodologies were presented to observe and measure whether the hydrogen was indeed in the slush state and to determine its density. Additionally, CFD (Computational Fluid Dynamics) analysis was performed using solid hydrogen properties, and the results were compared with experimental values. Notably, this analytical technique can be utilized in designing large-capacity tanks for storing slush hydrogen.

Performance prediction of experimental PEM electrolyzer using machine learning algorithms

Proton exchange membrane water electrolyzer (PEMWE) is a sustainable energy conversion device that uses electrical energy to oxidize water and convert it into chemical energy (hydrogen and oxygen) and heat. Despite their numerous advantages, such as high current density, efficiency, high-purity hydrogen production, compatibility with renewable energy sources, and compact design, they have not yet matured due to durability, cost, and electrochemical performance deficiencies. Effective assessment of performance and durability is crucial for electrolyzer design and optimization. This study analyzes the electrochemical performance of PEMWE with artificial intelligence approaches using experimental data. Three different machine learning (ML) techniques − Multilayer Perceptron (MLP), Support Vector Machine (SVM), and Random Forest (RF) were trained and tested for predicting the hydrogen flowrate and current density for PEMWE using different input parameters. These input parameters include cell voltage, temperature, torque, and water flowrate. SVM was detected to be the best technique in predicting all output parameters with a Mean Absolute Error (MAE) of 0.0317 and 0.0671 for current density and hydrogen flowrate predictions in the test set, respectively. The study results show that machine-learning algorithms can optimize operational parameters in electrolyzer control systems.

Influence of Different Operating Conditions on Iridium Dissolution in a Proton Exchange Membrane Water Electrolyzer

Polymer electrolyte membrane (PEM) water electrolysis plays a key role in the global decarbonization scheme by coupling the intermittent renewable energy sources to the production of high-purity hydrogen. Its deployment onto a GW scale, however, is hindered by the cost and availability of the precious metal catalysts utilized in today’s commercial systems, primarily by that of Ir used as the anode catalyst for the oxygen evolution reaction (OER). With the continuous increase in the demand for carbon-free hydrogen, drastic reductions from the current Ir loading of 1 – 2 mgIr cm-2 by at least an order of magnitude, without compromising the overall electrolyzer performance, are of crucial importance.1 In the recent years, significant efforts have been focused on understanding PEM electrolyzer degradation mechanisms and developing the necessary mitigation strategies, with a special focus being placed on the anode catalyst layer (CL).2-4 Recent results from our group showed that there are two main pathways for Ir to be removed from the anode CL: dissolution into the anode water line and transport through the membrane and the cathode CL.5 In the present work, we aim to shed light onto the effects influencing Ir dissolution under intermittent operation by quantitative analysis of the main Ir sinks within an electrolyzer and the determination of the charge of the dissolved Ir species.5, 6 Various accelerated stress tests with square-wave configuration aimed at accelerating Ir-based anode CL degradation were performed and the results were compared to those obtained during steady-state operation of the electrolyzer cell, which was used as a reference point. The influence of electro-diffusion, electroosmotic drag and Ir redeposition back to the ACL onto Ir dissolution were analyzed in detail to obtain deeper understanding on the Ir degradation processes. M. Clapp, C. M. Zalitis, M. Ryan, Perspectives on current and future iridium demand and iridium oxide catalysts for PEM water electrolysis. Catal Today 420, (2023). S. M. Alia et al., Electrolyzer Performance Loss from Accelerated Stress Tests and Corresponding Changes to Catalyst Layers and Interfaces. J Electrochem Soc 169, (2022). Z. Q. Zeng et al., Degradation Mechanisms in Advanced MEAs for PEM Water Electrolyzers Fabricated by Reactive Spray Deposition Technology. J Electrochem Soc 169, (2022). A. Weiss et al., Impact of Intermittent Operation on Lifetime and Performance of a PEM Water Electrolyzer. J Electrochem Soc 166, F487-F497 (2019). M. Milosevic et al., In Search of Lost Iridium: Quantification of Anode Catalyst Layer Dissolution in Proton Exchange Membrane Water Electrolyzers. Acs Energy Lett 8, 2682-2688 (2023). A. P. Dam, B. Y. A. Abuthaher, G. Papakonstantinou, K. Sundmacher, Insights into the Path-Dependent Charge of Iridium Dissolution Products and Stability of Electrocatalytic Water Splitting. J Electrochem Soc 170, (2023).

Activated Migration of Hydroxide Ion in Anolyte for Enhancing Performance of Scaled-up Non-Noble Catalysts in Pure Water-Fed Anion Exchange Membrane Water Electrolysis

The continuous advancement in water electrolysis technologies has illuminated the potential of sustainable energy sources, particularly in the realm of green hydrogen production. Anion exchange membrane water electrolysis (AEMWE) stands out as a promising technology capable of theoretically yielding high-purity hydrogen. However, the commercialization of AEMWE faces challenges arising from the inherent discord between high performance and the elevated costs associated with noble metal catalysts, such as platinum and iridium. Moreover, prevalent studies often focus on a limited electrode area of less than 4 cm2, thereby restricting the exploitation of the high purity hydrogen production capabilities inherent in AEMWE. This research prioritizes the enhancement of performance through a meticulously crafted membrane-electrode assembly (MEA) employing a 25 cm2 Ni-frame caged NiMoO4 catalyst for cathode synthesis. The observed performance improvement is attributed to the augmented active site of the catalyst, consisting of NiMoO4 entrapped in the Ni substrate during the compression process of the electrode. Additionally, the increase in local pH at the interfacial between electrode and bulk electrolyte is facilitated by the capillary phenomenon resulting from the space between the Ni substrate and the NiMoO4 catalyst layer, leading to enhanced migration of the electrolyte containing hydroxide ions. Acknowledgements This research was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resources from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040590).

Development of Bifunctional Electrocatalyst for Overall Water Electrolysis: Vanadium and Phosphorus Dual-Doping Strategy on Ni3S2 Nanoneedle

Along with the rapid consumption of fossil fuels and serious environmental pollution, the development of renewable and clean energy has been receiving a lot of attention recently. Among the various renewable energy sources, hydrogen (H2) is considered as most promising substance in future energy society owing to its high gravimetric energy density and environmental friendliness. Electrochemical water electrolysis system is powerful strategy for high-purity hydrogen production without emission of any pollutants. It consists of two electrocatalytic reactions: oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, the practical efficiency of water electrolysis is limited due to the intrinsically sluggish reaction kinetics of OER and HER. To date, the precious metal-based electrocatalysts such as RuO2 and Pt/C for OER and HER, respectively, were employed as state-of-the-art electrocatalyst to enhance the performance of water electrolysis. However, due to the high expense, mono-functionality, and unsatisfactory stability of the precious metal-based materials, research on bifunctional electrocatalysts with low cost and high activity has become an urgent topic. To date, numerous scientific endeavors have been dedicated to the advancement of highly efficient non-noble metal-based bifunctional electrocatalysts such as transition metal oxides, hydroxides, sulfides, carbides, nitrides, and phosphides. Among these, Ni3S2 has emerged as a particularly promising electrocatalyst for water splitting, garnering substantial attention owing to its high electric conductivity, rich redox property, abundance in the Earth's crust, and environmentally friendly characteristics. Nevertheless, the electrocatalytic activity of Ni3S2 lags behind that of noble metal counterparts. Therefore, elaborate modification of Ni3S2 catalyst should be conducted to further improve its intrinsic activity toward OER and HER. Among the various strategies, heteroatom doping into Ni3S2 structure could be adopted as powerful technique for enhancement of electrocatalytic performance. The homogeneously incorporated dopants not only generate lattice disorders but elaborately modulate the surface electronic property. Specifically, high-valent cation dopants such as vanadium and molybdenum can effectively mediate the change of chemical states of Ni active sites during the step-wise electrocatalytic procedure. Meanwhile, additionally introduced anion dopants, which have lower electronegativity compared with sulfur, can reduce the electron trapping phenomenon induced by excessive electron transfer from nickel to sulfur. Inspired by above features, we synthesized V and P co-doped Ni3S2 nanoneedles directly grown on nickel foam (V-Ni3S2-P/NF) through facile two-step preparation method. First, V doped Ni3S2 nanoneedles were homogeneously grown on NF (V-Ni3S2/NF) by hydrothermal process without use of nickel precursor. The vanadium ions promote the nucleation of Ni3S2 species and lead the preferential growth toward 1D direction during the hydrothermal reaction. After that, the V-Ni3S2/NF was annealed in the tube furnace with the NaH2PO2 as a phosphorus precursor under the Ar flow. Under the mild annealing condition, the PH3 gases generated from thermal decomposition of NaH2PO2 reacted with the V-Ni3S2 species. Consequently, the V-Ni3S2 was partially phosphidated into V-Ni3S2-P throughout anion exchange process. As a result, the V-Ni3S2-P/NF electrocatalyst exhibited excellent bifunctional activity toward both OER and HER compared with mono-doped and un-doped counterparts and precious metal-based electrocatalysts. Furthermore, the outstanding electrocatalytic performance of V-Ni3S2-P/NF was well-maintained over the 100 h of continuous operation under alkaline condition. This study will contribute to the development of efficient and cost-effective electrocatalysts for future energy conversion and storage technologies.

Unlocking Efficient Hydrogen Production: Nucleophilic Oxidation Reactions Coupled with Water Splitting.

Electrocatalytic water splitting driven by sustainable energy is a clean and promising water-chemical fuel conversion technology for the production of high-purity green hydrogen. However, the sluggish kinetics of anodic oxygen evolution reaction (OER) pose challenges for large-scale hydrogen production, limiting its efficiency and safety. Recently, the anodic OER has been replaced by a nucleophilic oxidation reaction (NOR) with biomass as the substrate and coupled with a hydrogen evolution reaction (HER), which has attracted great interest. Anode NOR offers faster kinetics, generates high-value products, and reduces energy consumption. By coupling NOR with hydrogen evolution reaction, hydrogen production efficiency can be enhanced while yielding high-value oxidation products or degrading pollutants. Therefore, NOR-coupled HER hydrogen production is another new green electrolytic hydrogen production strategy after electrolytic water hydrogen production, which is of great significance for realizing sustainable energy development and global decarbonization. This review explores the potential of nucleophilic oxidation reactions as an alternative to OER and delves into NOR mechanisms, guiding future research in NOR-coupled hydrogen production. It assesses different NOR-coupled production methods, analyzing reaction pathways and catalyst effects. Furthermore, it evaluates the role of electrolyzers in industrialized NOR-coupled hydrogen production and discusses future prospects and challenges. This comprehensive review aims to advance efficient and economical large-scale hydrogen production.

Copper hydride species activated hypophosphite hydrolysis towards litre-level and high-purity hydrogen production

Large-scale generation of high-purity hydrogen (H2) from simple hydrolysis strategy is vital, but the traditional technologies remain problems of economy and efficiency. Herein, a new and low-cost technical route is highlighted to realize the litre-level and efficient production of high-purity H2 from sodium hypophosphite (NaH2PO2) hydrolysis at room temperature. The formation and stabilization of CuH species on the designed Cu–Cu2O/CuH catalyst plays a key role in stimulating a continuous reversible NaH2PO2 hydrolysis cycle for H2. Impressively, this new technology achieves the high generated rate of 3.3 L h−1•cm−2 for H2 in alkaline media, which outperforms the other existing hydrolysis technologies. The proposed catalytic mechanism involves renewable CuH active species catalyzing the spontaneous reaction of NaH2PO2 and H2O to form H2 gas and phosphate. From the view of practical application, the developed coupling catalytic system also operates efficiently in deionized water, seawater and tap water solutions, shows unique interference immunity and high stability of convenient H2 generation.

Highly durable and efficient anion exchange membrane water electrolyzer using one-step fabrication of the integrated electrode by the hot-press process

Herein, we develop a commercial-scale anion exchange membrane (AEM) water electrolyzer with exceptional durability that employs a Co oxide anode and commercial Pt/C cathode. The anode of the AEM water electrolyzer was developed using a simplified one-step hot-pressing process utilizing a single-phase Co oxide to achieve a uniform electrode surface and simplify the fabrication process. The Co oxide electrode obtained at the optimal hot-pressing temperature of 250 °C, exhibited excellent durability and catalytic activity compared to electrodes synthesized at other temperatures. This can be attributed to its spinel structure and the presence of Co3+ as the primary active site for the oxygen evolution reaction. The AEM water electrolyzer demonstrated remarkable performance, with a high hydrogen production efficiency of 79.46% and ultra-low degradation rate of only 2 mV kh−1 during a long-term durability test of 1000 h at 50 °C. These results indicate the exceptional potential of the AEM water electrolyzer comprising a Co oxide anode as a promising technology for efficient and sustainable production of high-purity hydrogen.

The hybrid Pt nanoclusters/Ru nanowires catalysts accelerating alkaline hydrogen evolution reaction

Water electrolysis via alkaline hydrogen evolution reaction (HER) is a promising approach for large-scale production of high-purity hydrogen at a low cost, utilizing renewable and clean energy. However, the sluggish kinetics derived from the high energy barrier of water dissociation impedes seriously its practical application. Herein, a series of hybrid Pt nanoclusters/Ru nanowires (Pt/Ru NWs) catalysts are demonstrated to accelerate alkaline HER. And the optimized Pt/Ru NWs (10 ​% wt Pt) exhibits exceptional performance with an ultralow overpotential (24 ​mV at 10 ​mA ​cm−2), a small Tafel slope (26.3 ​mV dec−1), and long-term stability, outperforming the benchmark commercial Pt/C-JM-20 ​% wt catalyst. This amazing performance also occurred in the alkaline anion-exchange membrane water electrolysis devices, where it delivered a cell voltage of about 1.9 ​V at 1 ​A ​cm−2 and an outstanding stability (more than 100 ​h). The calculations have revealed such a superior performance exhibited by Pt/Ru NWs stems from the formed heterointerfaces, which significantly reduce the energy barrier of the decisive rate step of water dissociation via cooperative-action between Pt cluster and Ru substance. This work provides valuable perspectives for designing advanced materials toward alkaline HER and beyond.

Rechargeable zinc-water battery for sustainable hydrogen generation

Metal-water primary batteries hold promise for distributed hydrogen production but suffer from limited renewability of metal electrodes in aqueous electrolytes. Here, we introduce a novel concept of a rechargeable zinc-water battery featuring a reversible zinc anode paired with a bifunctional water electrolysis electrode, realized in a specially designed aqueous electrolyte-a mild zinc triflate aqueous electrolyte with the addition of ethylenediaminetetraacetic acid disodium (EDTANa2). The system enables high-purity hydrogen production during discharge and high-purity oxygen production during charge in a membrane-free setup. In the zinc-water battery, EDTANa2 enhances the water-splitting electrode's performance by replacing hydrophobic OTF- anions, ensuring optimal water activity. Additionally, EDTANa2 enhances Zn electrode reversibility by chelating Zn2+, preventing solvated water decomposition during zinc deposition. This integrated battery continuously undergoes charge-discharge cycles for over 55 h at a current density of 6 mA cm-2. Moreover, it achieves a high hydrogen evolution rate of 12.5 mL cm-2 h-1, enabling cost-effective, high-purity hydrogen production without expensive membranes. These findings open new avenues for sustainable hydrogen generation and energy storage in nano energy systems.

Mechanisms of formation and shape control of pentagonal Pd-nanostars and their unique properties in electrocatalytic methanol oxidation and membrane separation of high-purity hydrogen

Membranes on palladium alloy basis with surface modified by nanoparticles with high catalytic activity are useful in deep hydrogen purification and single-stage process of high-purity hydrogen production. This paper reports the development and improvement of methods for synthesis of Pd-based pentatwinned nanoparticles of strictly specified morphology with certain shapes, facets and composition. The competing effect of surfactants and optimization of the halide ions ratio in solution make it possible to direct a particle growth towards formation of pentatwinned Pd-nanostars. Pd–23%Ag coatings synthesized on the surface showed uniquely high peak current density of up to 238 mA cm−2 in alkaline methanol oxidation reaction. This is due to both increased surface area and greater catalytic activity of nanostars’ facets. A record increase in hydrogen permeability of up to 12.5 mmol s−1 m−2 at 100 °C has been achieved for palladium-silver membranes with modified surface. This indicates an acceleration of sorption/desorption stages. The developed method for controlling morphology of nanoscale coatings opens the way to the production of membrane hydrogen filters, which operate at room temperature.

Vacuum pressure swing adsorption intensification by machine learning: Hydrogen production from coke oven gas

Hydrogen is a vital resource in the fight against climate change, and it has the potential to revolutionize the energy sector. Our research focused on optimizing the production of high-purity hydrogen using coke oven gas (COG), a valuable hydrogen source in the steel industry. By leveraging advanced artificial neural networks (ANNs), we can predict the performance and exergy efficiency of a 6-bed 12-step vacuum pressure swing adsorption (VPSA) process accurately and efficiently. The Pareto fronts were addressed by combining the evolutionary algorithm with ANNs, and the effects of operating parameters were discussed in detail. Importantly, we found that our VPSA process can achieve a hydrogen purity of 99.99% with 45.2% exergy efficiency. We also demonstrated that using ANNs can significantly enhance VPSA process optimization, making it a valuable tool for extracting high-purity hydrogen from COG.

Synergistic etching of nickel foam by Fe3+ and Cl− ions to synthesize nickel-iron-layered double hydroxide nanolayers with abundant oxygen vacancies for superior urea oxidation

Urea electrolysis is an appealing topic for hydrogen production due to its ability to extract hydrogen at a lower potential. However, it is plagued by sluggish kinetics and noble-metal catalyst requirements. Herein, we developed nickel-iron-layered double hydroxide (NiFe-LDH) nanolayers with abundant oxygen vacancies (OV) via synergistically etching nickel foam with Fe3+ and Cl- ions, enabling the efficient conversion of urea into H2 and N2. The synthesized OV-NiFe-LDH exhibits a lower potential (1.30 vs. reversible hydrogen electrode, RHE) for achieving 10 mA cm−2 in the urea oxidation reaction (UOR), surpassing most recently reported Ni-based electrodes. OV provides favorable conductivity and a large surface area, which results in a 4.1-fold in electron transport and a 5.1-fold increase in catalyst reactive sites. Density Functional Theory (DFT) calculations indicate that OV can lower the adsorption energy of urea, and enhance the bonding strength of *CONHNH, giving rise to improved UOR. This study provides a viable path toward economical and efficient production of high-purity hydrogen.

Ni-CaO-CaZrO3 bi-functional materials for high purity hydrogen production via sorption enhanced steam reforming of ethanol

Ethanol is an ideal hydrogen carrier, which can be converted to hydrogen-rich syn-gas via the steam reforming reaction. Sorption-enhanced steam reforming is a promising approach to produce high-purity hydrogen by mixing the sorbent and catalyst particles. The idea of bi-functional materials, loading both sorption and catalytic site in a single particle, could transform the inter-particle heat-mass transfer to intra-particle heat-mass transfer. This work studied the sorption-enhanced steam reforming of ethanol (SESRE) over Ni-CaO-CaZrO3 bi-functional catalysts containing sorption and catalytic sites. Bi-functional Ni-CaO-CaZrO3 catalysts were synthesized using a simple sol-gel technique. The influence of operating conditions including temperature, steam-to-carbon ratio (S/C) and weight hourly space velocity (WHSV) on Ni10-Ca90Zr10 bi-functional materials were discussed. The operating condition with a temperature of 600 °C, weight hourly space velocity of 0.34 h−1 and steam-to-carbon ratio of 3 was the most suitable reaction condition for hydrogen production in this study. Over the optimized operation conditions, the influence of Ni loadings on hydrogen production performance was further studied. The result indicated that 10 wt% is the best Ni loading in this study for Ni-CaO-CaZrO3, which enables >95% hydrogen purity in the gaseous product in the pre-breakthrough stage, with the longest breakthrough time (90 min). Furthermore, under the best operation conditions, the Ni10-Ca90Zr10 displayed excellent stability over 10 cyclic tests. In the 10th cycle, about 90% hydrogen purity was constantly obtained for at least 60 min during the pre-breakthrough stages. This study demonstrated that the Ni10-Ca90Zr10 bi-functional material is effective and stable for producing hydrogen from ethanol and has the potential to establish a method of generating clean energy with minimal carbon emission.

Численное моделирование водородопроницаемости с концентрационной зависимостью коэффициента диффузии

The paper presents a nonlinear mathematical model of alloys hydrogen permeability for membrane technologies of high-purity hydrogen production. Diffusion processes in the material bulk are taken into account as well as physical and chemical phenomena at the surface: adsorption, desorption and relatively fast dissolution. The iterative computational algorithm and software in Scilab have been developed to model the hydrogen permeability with dynamic boundary conditions and concentration-dependent diffusion coefficient.