Continuous Hydrogen Production Research Articles

Hydrogen and syngas production through dynamic chemical looping reforming-decomposition of methane

This work introduces CeZr0.5GdO4 spinel particles as novel oxygen carriers for use in the reforming and decomposition of methane into H2 and CO via the chemical looping technique. These particles were prepared by a modified sol-gel combustion method to increase their reactivity by increasing the surface area and consequently more accessibility of the gas feed to the solid phase. The performance of the synthesized materials was dynamically evaluated in terms of activity and stability at different operating temperatures (800–900 °C). The air used in the oxidation step eliminates almost all of the deposited solid carbon and converts it to CO, while providing the oxygen consumed in the reduction step. Oxygen carrier particles showed a conversion of more than 90% in all cycles after about 30 min of reduction operations. By the optimal operating path proposed in this research, more than 90% of the reactor exhaust gas is allocated to the production of H2 and CO with almost complete elimination of CO2 and H2O in a shorter period of time. This will also reduce the time required for coke gasification and lattice oxygen replenishment of the spinel. Finally, the CeZr0.5GdO4 proved to be a successful oxygen carrier for the continuous production of hydrogen and carbon monoxide with almost no remarkable reduction in activity during successive redox cycles.

A freestanding nanoporous NiCoFeMoMn high-entropy alloy as an efficient electrocatalyst for rapid water splitting

The development of low-cost non-noble-metal-based electrocatalysts that can work stably at high current densities is crucial to apply a hydrogen evolution reaction (HER) and an oxygen evolution reaction (OER) in electrolyzed water. This study developed a freestanding nanoporous high-entropy alloy foil as a dual-functional electrocatalyst. The proposed electrocatalyst combines dealloying and polarization and shows excellent electrocatalytic activity in an alkaline electrolyte. It has an extremely small overpotential of 150 mV at 1,000 mA cm−2 for the HER and a low Tafel slope of 29 mV dec−1. At the same current density, the overpotential of the OER is only 350 mV. The alkaline electrolyzer using the electrocatalyst as both anode and cathode requires a cell voltage of only 1.47 V to output a stable current density of 10 mA cm−2. This enables it to be an efficient bifunctional electrocatalyst for alkaline overall water splitting and better stability for more than 375 h of continuous hydrogen production while providing substantial material cost savings relative to platinum. Density functional theory calculations indicate that the ultrahigh HER activity of the catalyst originates from the synergetic effect of optimized hydrogen adsorption in the segregation area and enhanced H2O adsorption in the un-segregation area produced by spinodal decomposition.

Modeling of continuous dark fermentative hydrogen production in an anaerobic up-flow column bioreactor

Dark fermentation (DF) of several types of wastes is a promising process to alleviate environmental pollution as it leads to the production of valuable hydrogen (H2) gas and high added value products, such as volatile fatty acids (VFAs). In this study a kinetic model for fermentative H2 production in an Up-flow column reactor (UFCR) is presented. Τhe model structure includes seven biochemical reactions taking place in a two-phase biofilm-liquid system. The observed difference in the overall stoichiometry of the bioconversion process for different hydraulic retention times (HRTs) is predicted by this model as it is attributed to the difference in the extent of individual bioconversion steps, each of which has a constant stoichiometry but a different rate depending on the HRT. The respective kinetic parameters were estimated through model fitting to the experimental results of the UFCR, which operated at different HRTs (12–2 h) and fed with the soluble fraction of a food industry waste (FIW). A good agreement of the experimental and predicted values of soluble metabolic products and H2 production was obtained, rendering this model as a useful tool for further investigation and prediction of the characteristics of the DF process in attached-biomass growth systems.

Experimental validation of a dynamic modelling of a Reversible Solid Oxide Cells (rSOCs)

The integration of Hydrogen technologies in different end-uses such as transport, electric microgrids, residential and industrial applications, will increase exponentially soon. Hydrogen as energy carrier allows more favourable energy conversion than other conventional systems and is crucial in worldwide decarbonize end uses. The production of green hydrogen, using RES, is a key area for the evolution of this technology. In this context, SWITCH is a Horizon 2020 European Project that aims to design, build and test an in-situ fully integrated and continuous multisource hydrogen production system, based on solid oxide cell technology. Reversible Solid Oxide Cell (rSOCs) technologies allow to convert renewable energy as hydrogen in the power-to-gas application (P2G) and in reversible mode is able to produce electricity from hydrogen stored, power-to-power application (P2P). rSOCs are really interesting to stabilize the random nature of RES because a combined electrolysis and fuel cell system should be able to switch between the two modes as quickly as possible in order to optimize the integration and the use of RES. However, rSOCs need a complex BoP from the thermal point of view, able to guarantee high efficiency even at partial load mode as well as easy start-up and shutdown procedures. In this work, a Stack Box Module dynamic model was developed in Modelica environment as a dynamic tool for the definition and optimization of BoP requirements. Stack model was validated in SOFC (Solid Oxide Fuel Cell) and SOE (Solid Oxide Electrolyser). The results of the simulation provide verification of the technical/thermodynamic behaviour and flexibility of a stack box of 70 cells. Dynamic modelling allows to evaluate the effect of the reagent inlet temperatures on the operation and hydrogen production/consumption in terms of yield as well as the transients between the different operative modes. Model has been validated by experimental measurements performed in the laboratory. In particular, the kinetics of the reactions governing steam methane reforming (SMR) was considered from data found in the literature, while the ASR (Area Specific Resistance) value was calibrated according to experimental data. The results of the dynamic model show as model can be a useful design and optimization tool for the SOCs technology.

Hydrogen production from the steam reforming of bioethanol over novel supported Ca/Ni-hierarchical Beta zeolite catalysts

This paper studies the H2 production via the steam reforming of a bioresource-derived ethanol mixture over supported Ca-modified Ni-hierarchical Beta zeolite catalysts. The results showed that the hierarchical Beta zeolite with rich pore structure could be synthesized in one step by using the new quaternary ammonium gemini cationic surfactant. The zeolite had bigger BET area and pore volume than the traditional Beta zeolite. The support plays a key role for the improve of catalytic behavior. The internal structure of the catalyst can be changed by introducing calcium and nickel ions into the synthesized zeolite at the same time through ion exchange. The interaction between active metal and the support would increase, so the dispersion of the active metal can be improved. The intermediate CO2 was efficiently absorbed by Ca in situ, which is an exothermic reaction and also help to provide the heat for the reactor. The adsorption of СО2 in situ transmitting the reversible reforming and water gas shift reactions to the products outside their conventional thermodynamic restrictions, which enhanced H2 production and permits high conversion to be attained. By using the method of gradient distribution of active metal in the support, the repeated catalytic effect similar to that of a hierarchical reactor was constructed, which showed excellent catalytic effect in low and medium high temperature bioethanol reforming to hydrogen. The experimental results show that when the reaction temperature is 350 °C, the 10Ni-MBeta(DI) catalyst maintains stable catalytic efficiency for continuous hydrogen production of 50 h via ESR, high hydrogen production and good stability.

Status of Stack & System Development at Sunfire and Industrial Outlook

Introduction Sunfire develops and produces high-temperature fuel cell (SOFC), electrolyzer (SOEC) and co-electrolysis (Co-SOEC) systems. SOFCs convert fuels and gases into electricity and heat for residential, commercial and industrial applications. SOECs and Co-SOECs convert water and/or CO2 with preferably renewable electricity into hydrogen or syngas. With these technologies, Sunfire addresses a multitude of challenges in our energy systems. Development and industrial outlook Sunfire continuously improves its technology on stack as well as at system integration level. For the stack technology, a decrease of the combined life cycle costs (€ kW-1 h-1) is the key driver for development. Recent improvements in this KPI as well as updates to our long-term stack tests in SOFC (~25kh), SOEC (~10kh) and Co-SOEC (~5kh) will be shown and discussed.Furthermore, updates on production scaling will be shown. This includes improvement of various processes as well as buying and commissioning new equipment for automated production.Sunfire’s products are also continuously being improved. Our existing micro-CHP solution (Sunfire-Home) offers a rated electrical output of 750 W and a thermal output of 1,300 W. In addition to reducing emissions, the advantages of Sunfire-Home include high efficiency, fully automatic operation with remote access and simple integration with modern building technology. Updates on the running units within the scope of the PACE-project and next steps will be shown.With Sunfire-Remote, we provide a compact SOFC-system for self-sufficient and off-grid power supply from pipeline gas and Propane. The units are battery chargers primarily and provide continuous power for a wide range of applications with an average power consumption up to 400 W. Flexibility in the kilowatt range can be covered by batteries that has to be selected according to the needed capacities and specific requirements. Also here, updates of the market status will be given.Furthermore, Sunfire is the leading provider of SOEC systems worldwide, quickly moving into the multi-megawatt market for industrial applications. By focusing on the utilization of industrial off-heat to maximize overall electrical efficiency, the operational cost for continuous hydrogen production can be kept at a minimum. Sunfire units are therefore specifically suited for brown-field industrial applications, as demonstrated at the steel plant of Salzgitter. There, a 730 kWelAC SOEC system was installed in 2020 within the GrInHy2.0 project, after successfully operating a 150 kWelAC rSOC system since 2017.(1) The electrolyzer is expected to be in operation for at least 13,000 hours by the end of 2022, while producing at least 100 tons of green hydrogen from renewable electricity. Additionally, a 2,6MW SOEC System for the operation at a refinery of Neste in Rotterdam is currently being planned within the framework of the MULTIPHLY project as will be shown.In addition to pure hydrogen electrolysis (HyLink), Sunfire is also developing the Co-SOEC (SynLink) providing renewable syngas, a mixture of H2 and CO, for chemical applications and Power-to-Liquid processes. The operation with Sunfires technology has been successfully demonstrated within the Kopernikus PtX project and the next step will be the supply of a 1 MW Co-SOEC unit within MegaSyn. References (1)Schwarze, O. Posdziech, J. Mermelstein, S. Kroop, Fuel Cells, (2019).

Dynamic membrane bioreactor for high rate continuous biohydrogen production from algal biomass

This study aimed to achieve continuous biohydrogen production from red algal biomass using a dynamic membrane bioreactor (DMBR). The DMBR was continuously fed with pretreated Echeuma spinosum containing 20 g/L hexose. The highest average hydrogen production rate (HPR) of 21.58 ± 1.59 L/L-d was observed at HRT 3 h, which was higher than previous reports for continuous H2 production from biomass feedstock. Metabolic flux analysis revealed that butyric acid and propionic acid were the major by-products of the H2-producing and H2-consuming pathways, respectively, of the algal biomass fermentation. Hydrogen consumption by propionic acid pathway could not be prevented completely by heat treatment. PICRUSt2 analysis predicted that Clostridium sp., Anaerostipes sp., and Caproiciproducens sp. might significantly contribute to the expression of both ferredoxin hydrogenase and propionate CoA-transferase. This study would provide the design and operational information on high-rate bioreactor for continuous hydrogen production using biomass.

Introduction of loop operating system to improve the stability of continuous hydrogen production for the thermochemical water-splitting iodine–sulfur process

The thermochemical water-splitting iodine–sulfur process facilitates hydrogen production. This study proposes a new loop operation by subdividing the process configuration into four sections before transferring the continuous operation. The loop operation should define the section affecting the fluctuations to easily stabilize the system. The proposed loop operation was validated by analyzing the material and heat balances using a process simulator. The calculated results showed that the material balances of the respective loop sections were closed without component discharge to outside sections. The loop operation would transfer to the continuous operation by connecting all sections. Considering the switching of operation modes, the material and heat balance showed no or little difference, indicating that two operation modes can only be changed by switching the pipelines. Thus, the loop sections can be operated individually to stabilize the IS process system, and the loop operation can be transferred smoothly to the continuous operation.

Advances in Hydrogen Production from Natural Gas Reforming

Steam natural gas reforming is the preferred technique presently used to produce hydrogen. Proposed in 1932, the technique is very well established but still subjected to perfections. Herein, first, the improvements being sought in catalysts and processes are reviewed, and then the advantage of replacing the energy supply from burning fuels with concentrated solar energy is discussed. It is especially this advance that may drastically reduce the economic and environmental cost of hydrogen production. Steam reforming can be easily integrated into concentrated solar with thermal storage for continuous hydrogen production.

Concentrated Solar Energy with Thermal Energy Storage for Hydrogen Production by Three-Step Thermochemical Water-Splitting Cycles

The high-temperature thermochemical water splitting (TWS) cycles utilizing concentrated solar energy (CSE) and water are the most promising alternatives to produce renewable hydrogen. Here we couple CSE with thermal energy storage (TES) and TWS cycles to best levelize the cost of hydrogen by 2030, due to the synergies with concentrated solar power (CSP), the high technology-readiness-level (TRL) for the upstream thermal energy production and storage, and the medium TRL for the downstream TWS cycles. A similar design of the solar field and tower and TES for CSP advanced ultrasupercritical (AUSC) or supercritical CO2 (sCO2) power cycles for 100 MW of continuous production of electricity, permit the continuous production of hydrogen at ∼2,750 kg/h a day. The predicted cost is 1.058 to 1.197 $/kg H2 by 2030.

Continuous hydrogen production and microbial community profile in the dark fermentation of tequila vinasse: Response to increasing loading rates and immobilization of biomass

Dark fermentation of concentrated and undiluted tequila vinasse, without extra nutrients, in a CSTR was the objective of this study. Organic loading rates (OLR) from 40 to 160 gCOD/L-d and influence of presence of biomass carriers were assessed. With suspended biomass, a stable hydrogen production rate (HPR) of 1.1 L H2/L-d was obtained at an OLR of 80 gCOD/L-d. Adding biomass carriers in the CSTR increased the stable HPR from 0.3 to 0.7 L H2/L-d when an OLR of 120 gCOD/L-d and 6%–20%-diluted vinasse were used. Influent formic, and valeric acids were consumed consistently, while lactic, butyric and acetic acids were produced suggesting that carboxylic acids metabolism, besides sugar fermentation, contributed to hydrogen production. Clostridium predominance over Sporolactobacillus changed after a 160 gCOD/L-d shock load, however correlation analyses showed that the original COD content of vinasse, rather than the OLR, influenced HPR, carboxylic acids profile and bacterial population.

Saccharification of agave bagasse with Cellulase 50 XL is an effective alternative to highly specialized lignocellulosic enzymes for continuous hydrogen production

Agave bagasse is the lignocellulosic residue of the tequila industry and a potential feedstock for hydrogen production (H2) via dark fermentation after proper saccharification. Highly specialized enzymes for hydrolysis of lignocellulosic biomass are costly, hindering their application in continuous processes. This work investigated the use of a generic cellulase (Cellulase 50 XL), to prepare the hydrolysates from agave bagasse, either alone or combined with a highly specialized hemicellulase (Viscozyme L). The combination of Cellulase 50 XL and Viscozyme L increased the release of both total carbohydrates and chemical oxygen demand (COD) in 28.5% and 22.2%, respectively compared with Cellulase 50 XL. Conversely, the maximum volumetric H2 production rate (VHPR, 9.9 L H2/L-d) reached with the Cellulase 50 XL hydrolysates in continuous stirred tank reactors at an organic loading rate of 100 g COD/L-d, is the highest VHPR reported so far with enzymatic agave bagasse hydrolysates obtained with non-specialized enzyme. The estimated cost of H2 production using Cellulase 50 XL at lab-scale was 0.7 USD/L H2. From a systematic comparison of H2 productivities and lab-scale costs with similar studies it was concluded that: i) the composition, and not only the concentration of total carbohydrates plays a critical role in the performance of H2 production, ii) Cellulase 50 XL was one of the best cost-effective alternatives despite being designed for food sectors and not for the hydrolysis of lignocellulosic biomass. Overall, considering H2 productivities and cost of H2 production, Cellulase 50 XL hydrolysates resulted an appropriate option for cost-effective continuous H2 production.

Hydrogen production from herbal wastewater via anaerobic fermentation with diatomite‐immobilized sludge

AbstractThe feasibility and performance of continuous hydrogen production from herbal wastewater via anaerobic fermentation was investigated at different organic loading rates (OLRs) (from 12 to 96 kg chemical oxygen demand [COD]·L−1·day−1) in diatomite‐immobilized sludge reactor and suspended sludge reactor. Results indicated that the diatomite‐immobilized sludge reactor presented more efficient and stable performance than suspended sludge reactor in terms of hydrogen production rate. In diatomite‐immobilized sludge reactor, the highest hydrogen production rate of 11.17 ± 0.45 mmol·L−1·h−1 was achieved at the optimum OLR of 72‐kg COD·L−1·day−1. The metabolic route of acetate acid and butyrate acid production at low OLR (from 12‐ to 40‐kg COD·L−1·day−1) was modified to be ethanol production by an increase in OLR to 56 and 72‐kg COD·L−1·day−1, which was reflected by the distribution of bacterial community. The maximum energy recovery efficiency by dual production of hydrogen and ethanol was determined to be 31.2 kJ·L−1·h−1 at OLR of 72‐kg COD·L−1·day−1.

Integration of Earth‐Abundant Catalysts on Si Solar Cells for Overall Solar Hydrogen Production

Development of low‐cost and earth‐abundant metal catalysts, as alternative to noble metals, is a promising approach for direct hydrogen production from solar light with integrated photoelectrochemical devices. Herein, a mild electrochemical method is used to directly synthesize two earth‐abundant catalysts, namely, CoP and CoSe, on planar‐junction p+nn+‐Si solar cells. It is observed that the CoP–Si photocathodes achieve the best performance with ≈12 h of stability, a photocurrent density of up to 38 mA cm−2 at 0 V versus the reversible hydrogen electrode (RHE), and an onset potential of 488 mV versus RHE, and one of the most efficient solar‐driven hydrogen generation from earth‐abundant systems to date. Overall solar water splitting is also demonstrated in a tandem device configuration with a top TiO2 nanorod arrays photoanode achieving more than 5 h continuous hydrogen production. These results demonstrate the feasibility of using low‐cost earth‐abundant materials and the established Si solar cells technology for direct water splitting powered from sunlight.

Scaling-up up-flow microbial electrolysis cells with a compact electrode configuration for continuous hydrogen production

Maintaining high current densities is a key challenge in scaling-up microbial electrolysis cell (MEC) reactors. In this study, a novel 10 L MEC reactor with a total electrode surface area greater than 1 m2 was designed and evaluated to maximize the current density and H2 recovery. Performances of the reactor suggest that the longitudinal structure with parallel vertical orientation of the electrodes encouraged high fluid mixing and the sheet metal electrode frames provided distributed electrical connection. Results also demonstrated that the electrode pairs located next to reactor walls decreased current density, as did separating the electrodes with separators. High volumetric H2 production rate of 5.9 L/L/d was achieved at a volumetric current density of 970 A/m3 (34 A/m2). Moreover, the observed current densities of the large reactor were accurately predicted based on the internal resistance analysis of small scale MECs (0.15 L), demonstrating the scalability of the single chamber MEC design.

Supported polyoxometalates as emerging nanohybrid materials for photochemical and photoelectrochemical water splitting

Abstract Sunlight and water are among the most plentiful and sustainable resources of energy. Natural photosystem II in the plants uses these resources in ecofriendly manner for the production of atmospheric oxygen and energy. Inspired by this natural process, the development of artificial catalytic system to facilitate the solar-induced water splitting for the continuous production of hydrogen is the holy grail of the chemist and energy experts to meet the future energy demand at minimal environmental cost. Despite considerable research efforts dedicated to this area in the last decade, the development of highly efficient, stable and economic photocatalysts remain a challenging task for the large scale H2 production from water. Polyoxometalates (POMs)-based materials are emerging photo/photoelectrocatalysts in this quest owing to their multi-electron redox potential and fast reversible charge transfer properties, which are the essential requirements of photo-assisted water splitting catalysis. They are generally soluble in aqueous medium and thus their inherent catalytic/co-catalytic properties can be better exploited by incorporating/immobilizing them over suitable support materials. Therefore, exploration of discrete POM units over the support materials possessing high surface area, functionalizable architecture, flexible pore size and good light harvesting ability is an attractive area of research that has resulted in the generation of a strong library of heterocatalysts. The underlying support not only offers stability and recyclability attributes to the POM units but also provides decent dispersion, easy/maximum accessibility to the active sites, enhanced absorption capability, and synergistically enhances the activity by transfer of electrons and efficient charge/carriers separation by creating POM-support junctions. This mini-review emphasizes on the strategies for the incorporation of POMs on various porous supports like metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), oxide-based semiconductors, carbonaceous materials, etc., and their applications as effective photo/photoelectrocatalysts for water splitting. In addition, the mechanistic study, comparative analysis and the future potential of these novel nanoscale materials is also highlighted. We believe that this review article will provide a new direction and scientific interest at the boundary of materials engineering, and solar-driven chemistry for the sustainable energy conversion/storage processes.

Intensification and optimization of continuous hydrogen production by dark fermentation in a new design liquid/gas hollow fiber membrane bioreactor

A liquid/gas membrane bioreactor (L/G MBR) was developed to intensify the dark fermentation process. A hollow fiber membrane module was used to combine biohydrogen production, in situ liquid–gas separation and hydrogen producing bacteria retention in a single unit. The L/G MBR was seeded once and did not require further microbial input, as consistent average hydrogen yield of 0.97 ± 0.09 mol-H2/added mol-glucose and hydrogen production rate of 106.5 ± 10.6 mL-H2/L-medium/h were reached over a year. Different biogas extraction strategies showed that efficient in situ H2 extraction is possible without sweeping gas in the lumen of the fibers, thus facilitating H2 purification in an industrial setting. Modelling predicted an optimal hydrogen yield of 1.2 mol/mol-glucose added for a glucose concentration in the feed of 13.1 g/L, close to experimental hydraulic retention time of 8–10 h with an organic loading rate of 1.4 g-glucose/L-medium/h. No washout of hydrogen-producing bacteria was observed at low HRT (2 h), suggesting the possibility of further hydrogen production rate enhancement using an optimized organic loading rate. Acetate and butyrate were the main metabolites identified. Clostridium and Enterobacter dominated in the liquid outlet. The relative abundance of Clostridium pasteurianum increased with glucose concentration in the bioreactor, as opposed to Clostridium beijerinckii which was more abundant at low glucose concentration. The original hollow fiber L/G MBR configuration enabled the testing and selection of fermentation strategies that greatly simplified the implementation of the dark fermentation process by addressing its key operational bottlenecks. Indeed, the L/G membrane surface served as a support and reservoir for the hydrogen producing bacteria across a wide range of HRT conditions.

One-dimensional CO9S8-V3S4 heterojunctions as bifunctional electrocatalysts for highly efficient overall water splitting

Development of cost-effective, active and durable electrocatalysts for overall water splitting is still a huge challenge. Herein, we have constructed one-dimensional (1D) cobalt sulfide and vanadium sulfide heterojunction nanowires arranged on carbon cloth (Co9S8-V3S4/CC) as bifunctional electrocatalysts for the efficient overall water splitting. The 1D wire-structured Co9S8-V3S4 heterojunctions possess large surface area, plentiful active sites and rapid transport of electrons/reactants and the release of gas. Importantly, the electron transfer from Co9S8 to V3S4 occurs at the interface due to the strong electronic coupling effect in Co9S8-V3S4 heterojunction, in which the electron-attracting V3S4 (V2+) optimizes the adsorption of H* active species for hydrogen evolution reaction (HER), while the electron-losing Co9S8 (Co3+) responds to the enhancement of oxygen evolution reaction (OER) activity. Co9S8-V3S4/CC exhibits low overpotentials of 85 and 232 mV at 10 mA cm−2 and small Tafel slopes of 51 and 59 mV dec−1 for HER and OER, respectively. Especially, the electrolyzer with Co9S8 V3S4/CC as both the anode and cathode requires low onset voltage of 1.35 V and cell voltage of 1.53 V at 10 mA cm−2 and exhibits high Faradaic efficiencies and robust stability. It can be driven by a solar cell (1.53 V) for continuous production of hydrogen and oxygen. This study highlights the design of 1D sulfide heterojunction in pursuit of highly efficient electrocatalysts for overall water splitting.

One-step synthesis of amorphous nickel iron phosphide hierarchical nanostructures for water electrolysis with superb stability at high current density.

The development of noble-metal-free high-performance bifunctional catalysts for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential but challenging for hydrogen production from water electrolysis. Herein, amorphous bimetallic nickel-iron phosphide hierarchical nanostructures enrooted on nickel-iron alloy foam (NiFeP/NFF) are facilely fabricated via direct phosphidation of NFF at low temperature and developed as an efficient self-supporting bifunctional electrocatalyst to catalyze both the OER and HER with high activity, fast kinetics and excellent stability. Moreover, an alkaline water electrolyzer simultaneously utilizing NiFeP/NFF as the cathode and anode only needs a cell voltage of 1.58 V to afford a current density of 10 mA cm-2, overpassing most of the reported bifunctional electrocatalysts and comparable to noble metal-based ones. Impressively, the NiFeP/NFF-based symmetric electrolyzer can work well without appreciable performance degradation at a high current density of 500 mA cm-2 for over 1000 h for continuous hydrogen production with 100% faradaic efficiency, showing superb durability and great promise for industrial application.

An economically sustainable bifunctional Ni@C catalyst in a solar-to-hydrogen device employing a CIGS submodule

In this work, Ni@C was successfully fabricated using a one-step metal wire explosion method and employed as a bifunctional catalyst material for electrodes in an electrolyzer connected to a CIGS-sub module for continuous hydrogen production.