Large-scale Hydrogen Production Research Articles

Cascade Reaction Enables Heterointerfaces-Enriched Nanoarrays for Ampere-Level Hydrogen Production.

Designing high-performance electrocatalysts with superior catalytic activity and stability is essential for large-scale hydrogen production via water electrolysis. Heterostructure nanoarrays are promising candidates, though achieving both high activity and stability simultaneously, especially under high current densities, remains challenging. To this end, we have developed a cascade reaction process that constructs a series of heterostructure nanoarrays with rich heterointerfaces. This process involves treating nickel foam (NF) with molten KSCN and transition metal salts. Initially, NF reacts with KSCN to form Ni9S8 nanoarrays and S2- ions, which are subsequently captured by transition metal ions to form sulfides that are directly integrated onto the nanoarrays, resulting in abundant heterointerfaces. Both experimental and theoretical results indicate that these rich heterointerfaces significantly enhance the interfacial interaction between Ni9S8 and RuS2 within the nanoarrays (termed RH-Ni9S8/RuS2), markedly improving both the intrinsic activity and stability for the hydrogen evolution reaction (HER). Impressively, the RH-Ni9S8/RuS2 demonstrates exceptional HER performance, achieving a low overpotential of just 180 mV at 1000 mA cm-2 and maintaining stability for up to 500 h under such high-current-density conditions. This innovative approach paves the way for the interfacial design and synthesis of high-performance catalysts for ampere-level hydrogen production.

Construction of δ-FeOOH/NiMn2S4 heterointerface for efficient alkaline oxygen evolution reaction

Alkaline water electrolysis driven by sustainable energy is a viable approach for large-scale green hydrogen production. The development of non-precious metal-based electrocatalysts that combine high activity and stability for the alkaline oxygen evolution reaction (OER) is of great importance. In this work, we design and construct a δ-FeOOH/NiMn2S4/NF heterointerface using a solvothermal/calcination process followed by a facile successive ionic layer adsorption reaction (SILAR) treatment. Experimental tests indicate that the formation of the heterogeneous interface between the δ-FeOOH and the NiMn2S4 creates a good electron transport channel for an efficient electrocatalytic process and improves the charge transfer kinetics. As a result, the prepared δ-FeOOH/NiMn2S4/NF exhibits a low overpotential of 210 mV at 10 mA cm−2 and a low Tafel slope value of 46.6 mV dec−1, and satisfactory stability with a 92.9 % retention after 72 h of OER operation at around 100 mA cm−2. In situ Raman and in-situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) tests show that the introduction of δ-FeOOH inhibits the oxidation of Ni2+ to Ni3+ and stabilizes the Ni-S bond to prevent its auto-oxidation, leads to an increase in the electrocatalytic OER activity.

Dynamic hydrogen bubble template electrodeposition of a self-supported Co-P electrocatalyst for efficient alkaline oxygen evolution reaction

The development of efficient, inexpensive, and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) represents a significant challenge for the large-scale production of hydrogen. The primary obstacle to the advancement of OER is the necessity for a considerably higher overpotential than the theoretical oxygen evolution potential, due to the sluggish kinetics of the electron transfer reaction, which involves a large amount of thermodynamic energy. In this article, amorphous and cauliflower-like Co-P electrocatalysts were in situ grown on nickel foam by dynamic hydrogen bubble template (DHBT) electrodeposition method. The Co-P electrocatalyst with Co/P ratio optimal presented excellent electrocatalytic activities with a low overpotential of 239 mV for OER at 10 mA·cm−2 and long-term stability in 1.0 M KOH. The outstanding OER performance of the catalyst is mainly attributed the synergistic effect of amorphous and cauliflower-like structure, superhydrophilicity surface, and the electronic regulation by adjusting the atomic ratio of Co to P. This research will bring fresh ideas and strategies for developing novel simple, affordable, and efficient electrocatalysts to boost OER kinetics.

Enhanced NiO-CaO-based multifunctional material pellets with Ce and La oxides on aluminosilicate support for sorption-enhanced chemical looping steam reforming of glycerol

Multifunctional materials in pellet form composed of NiO-CaO-based aluminosilicate support have been developed for hydrogen (H2) production via sorption-enhanced chemical looping steam glycerol reforming (SE-CL-SGR). The effect of CaO content (50–70 wt%) and an addition of promoter (CeO2 and La2O3) on material properties and H2 production performances were investigated. A good H2 production of 90 %v/v purity for 75 mins has been achieved from 15 wt% NiO, 70 wt% CaO, and 30 wt% aluminosilicate support (15Ni(70Ca.30S)) pellets. However, it totally showed a loss of CO2 adsorption ability by the 5th cycle as a formation of carbon caused the pellet cracking. Rare-earth oxides such as CeO2 and La2O3 have been incorporated into the structure to improve the mechanical properties. An addition of 5 wt% La2O3 (5La-15Ni(70Ca.30S)) provides superior H2 production performance to that with CeO2 and without rare-earth as 95 %v/v H2 purity can be constantly produced for 60 mins throughout five testing cycles. These enhancements indicate that the CeO2 and La2O3 modifications effectively improve the multifunctional material pellet performance and stability, making it suitable for large-scale hydrogen production applications.

Photothermal Synergistic Hydrogen Production via a Fly-Ash-made Interfacial Vaporific System.

Employing UV-vis spectrum for hydrogen generation and vis-IR spectrum to elevate reaction temperatures and induce phase transitions effectively enhances yield and purifies water, demonstrating a judicious strategy for solar energy utilization. This study presents an interfacial photothermal water splitting system that utilizes all-inorganic, economical industrial by-products known as fly ash cenospheres (FAC) for solar-driven hydrogen generation. In this system, the yield reaches 254.8µmol h-1cm-1, representing an 89% augmentation compared to that of the three-phase system. In situ experiments, combined with theoretical calculation, reveal the system's robust light absorption capacity, facilitating rapid gas separation, thus improves the solar-to-hydrogen (STH) efficiency. Furthermore, the system demonstrates strong performance in turbid water and scalability for expansive applications, achieving a hydrogen yield exceeding 50 L h-1 m-2 from various water sources. Facilitating large-scale hydrogen production and water purification, it thereby establishing its potential as a viable solution for sustainable energy generation.

Thermal design and analysis of a fully solar-driven copper-chlorine cycle for hydrogen production

Solar copper-chlorine (Cu-Cl) thermochemical cycle is a clean, efficient and large-scale hydrogen production technology. However, when the Cu-Cl cycle is driven by solar energy, large amounts of flows with various heat-absorption and release characters at different temperatures from 25°C to 500°C, resulting in a complex internal heat exchanger network (HEN). The feasible HEN design, the heat transfer losses, and the improvement direction of the system are still unclear. Therefore, a fully solar-driven Cu-Cl cycle for hydrogen production is proposed, in which a 100 MW solar tower and an S-CO2 cycle are utilized to supply heat and electricity. A feasible HEN and possible pinch points are obtained considering energy cascade utilization. Comprehensive energy and exergy conditions are presented and the effects of direct normal irradiance (DNI), recuperative ratio (RR) and maximum temperature (Tm) are assessed. The results show that the receiver has the highest energy efficiency but the lowest exergy efficiency, and the overall system energy and exergy efficiencies are 15.93% and 16.64%. Pinch points of heating the Cu-Cl cycle and S-CO2 cycle lead to limitations of heat transfer. Furthermore, positive effects of increasing RR and Tm are significantly weakened and even turn into negative effects for increasing Tm.

Polyhydroxykanoate-Assisted Photocatalytic TiO2 Films for Hydrogen Production.

The photocatalytic production of hydrogen using biopolymer-immobilized titanium dioxide (TiO2) is an innovative and sustainable approach to renewable energy generation. TiO2, a well-known photocatalyst, benefits from immobilization on biopolymers due to its environmental friendliness, abundance, and biodegradability. In another way, to boost the efficiency of TiO2, its surface properties can be modified by incorporating co-catalysts like platinum (Pt) to improve charge separation. In this work, the surface of commercial TiO2 PC500 was modified with Pt nanoparticles (Pt1%@PC500) and then immobilized on glass surfaces using polyhydroxyalkanoate biopolymer poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBH). The as-prepared immobilized Pt-modified TiO2 photocatalysts were fully characterized using various physicochemical techniques. The photocatalytic activity of the photocatalyst film was investigated for photocatalytic hydrogen production through water reduction using ethanol as a sacrificial donor. The impact of the film preparation conditions, e.g., PHBH concentration, PHBH:catalyst ratio, and temperature, on activity and stability was studied in detail. The application of biopolymer PHBH as a binder provides a green alternative to conventional immobilization methods, and with the application of PHBH, a stable and active photocatalyst film that showed lower activity compared to that of the suspended photocatalyst but good recyclability in six runs was prepared. A long-term photocatalytic hydrogen production experiment was carried out. In 98 h of operation, 12 mmol of hydrogen was produced in three consecutive runs with a PHBH/Pt1%@PC500 film having an area of ∼5.3 cm2. A significantly lower hydrogen productivity was observed after the first run, possibly due to a change in film structure, but thereafter, the productivity remained almost constant for the second and third runs. Hydrogen was the main product in the gas phase (90%), but carbon dioxide (4-5%) and methane (4-5%) were obtained as important byproducts. The byproducts are a consequence of the use of the sacrificial reagent ethanol. The results of the film performance are very promising, with regard to large-scale continuous hydrogen production.

Dual chalcogenide coordination engineering on a self-supported alloy electrode for enhanced hydrogen evolution reaction.

The electrochemical hydrogen evolution reaction (HER) holds substantial promise for large-scale green hydrogen production due to its cost-effectiveness, high performance, and scalability for repeated implementation. A promising strategy that involves a novel transition-metal chalcogenide with a self-supported framework can improve the reaction kinetics in the HER. We synthesize a nano three-dimensional self-supported HER catalyst via a straightforward one-step chemical vapor deposition process. This method incorporates a dual co-reaction with sulfur (S) and selenium (Se) onto a commercially available Monel alloy (CNSSe). The dynamics ion exchange redox reactions promote the formation of heterogeneous catalyst structures. Density functional theory (DFT) calculations indicate that the CNSSe catalyst exhibits low hydrogen coverage, as evidenced by a thermoneutral free energy of adsorbed hydrogen (ΔGH*) of 0.105 eV, which can be attributed to the dual introduction of S and Se. Consequently, the optimized CNSSe electrocatalyst achieves an enhancement in HER performance exceeding 100% compared to catalysts introduced exclusively with either S or Se. These results underscore the substantial potential of the optimized CNSSe electrocatalyst to improve both the performance and economic feasibility of HER technologies in alkaline water electrolysis.

Regulation of Oxide Pathway Mechanism for Sustainable Acidic Water Oxidation.

The advancement of acid-stable oxygen evolution reaction (OER) electrocatalysts is crucial for efficient hydrogen production through proton exchange membrane (PEM) water electrolysis. Unfortunately, the activity of electrocatalysts is constrained by a linear scaling relationship in the adsorbed evolution mechanism, while the lattice-oxygen-mediated mechanism undermines stability. Here, we propose a heterogeneous dual-site oxide pathway mechanism (OPM) that avoids these limitations through direct dioxygen radical coupling. A combination of Lewis acid (Cr) and Ru to form solid solution oxides (CrxRu1-xO2) promotes OH adsorption and shortens the dual-site distance, which facilitates the formation of *O radical and promotes the coupling of dioxygen radical, thereby altering the OER mechanism to a Cr-Ru dual-site OPM. The Cr0.6Ru0.4O2 catalyst demonstrates a lower overpotential than that of RuO2 and maintains stable operation for over 350 h in a PEM water electrolyzer at 300 mA cm-2. This mechanism regulation strategy paves the way for an optimal catalytic pathway, essential for large-scale green hydrogen production.

Contribution of Copper Slag to Water Treatment and Hydrogen Production by Photocatalytic Mechanisms in Aqueous Solutions: A Mini Review.

Hydrogen has emerged as a promising energy carrier, offering a viable solution to meet our current global energy demands. Solar energy is recognised as a primary source of renewable power, capable of producing hydrogen using solar cells. The pursuit of efficient, durable, and cost-effective photocatalysts is essential for the advancement of solar-driven hydrogen generation. Copper slag, a by-product of copper smelting and refining processes, primarily consists of metal oxides such as hematite, silica, and alumina. This composition makes it an attractive secondary resource for use as a photocatalyst, thereby diverting copper slag from landfills and generating 0.113 μmol/g h of hydrogen, as noted by Montoya. This review aims to thoroughly examine copper slag as a photocatalytic material, exploring its chemical, physical, photocatalytic, and electrochemical properties. Additionally, it evaluates its suitability for water treatment and its potential as an emerging material for large-scale solar hydrogen production.

The role of FexCu(1‒x) electrodeposits from a deep eutectic solvent in promoting the hydrogen evolution reaction

Hydrogen from water splitting is more powerful, clean, and more energy-efficient than fossil fuels. Since the electrode material influences the performance and operating cost of industrial electrolyzers, this work induces technological innovation through FexCu(1−x) alloys with electrocatalytic action toward the hydrogen evolution reaction (HER). The materials were galvanostatically deposited on 1020 carbon steel. It was used electrolytes formulated with deep eutectic solvents (DES) and aqueous solvents (AQS) were used to verify their influence on the coatings' composition, morphology, and electrocatalytic activity. The results proved that even after fixing the operating conditions (electrochemical potential, current density, and deposition time), the alloys produced in DES are richer in Fe (≅ 77-85%, w/w). For comparison, those obtained from AQS have greater proportion of Cu (≅ 65%, w/w). Stoichiometry changes also alter the topography, surface area, and electrocatalytic activity of FexCu(1−x) alloys for hydrogen production. The electrochemical studies carried out also revealed that the association between Fe and Cu as alloying elements has a positive synergistic effect of reducing the HER overpotential by around 125 mV, using 1 mol L−1 KOH at 296 K. Considering stability and resistance to corrosion, FexCu(1−x) alloys produced in DES stood out as the most promising for possible adaptation in electrolyzers developed for large-scale hydrogen production.

Boosted Hydrogen evolution reaction based on synergistic effect of graphene, MoS2 and RuO2 ternary electrocatalyst

Hydrogen holds the promise of replacing fossil fuels and offers a sustainable pathway for energy generation. However, the large-scale production of hydrogen via the environment friendly electrocatalytic process relies heavily on the performance of electrocatalysts. In this study, we investigate the electrocatalytic performance of graphene nanosheets (GNS), molybdenum disulfide (MoS2), ruthenium dioxide (RuO2), and their composites for hydrogen evolution reaction (HER), a novel combination that has not been explored in previous literature. We synthesize the materials using Liquid Phase Exfoliation at 500 and 1000 RPMs for GNS and MoS2 and via hydrothermal methods for RuO2 nanosheets and nanoparticles, aiming to exploit synergistic effects for enhanced activity and stability. The synthesized GNS-1000/MoS2-1000/RuO2-NSs composite demonstrates promising HER results, showcasing a low overpotential of 63 mV and a reduced Tafel slope of 59 mV/dec. This improvement indicates enhanced electron transfer, improved active site dispersion, and increased surface area due to the synergistic effects, which also aids in long-term electrochemical stability. Our study underlines the potential of GNS/MoS2/RuO2 composites, particularly the GNS-1000/MoS2-1000/RuO2-NSs, in transforming hydrogen production methods and promoting efficient, sustainable energy solutions. The implications of our findings extend the boundaries of materials engineering, edging us closer to a sustainable energy future.

Numerical investigation of hydrogen vapor cloud explosion from a conceptual offshore hydrogen production platform

Offshore hydrogen production platforms have the potential to become significant components in the upcoming large-scale offshore hydrogen production, contributing to the global commitment to carbon neutrality. However, the risk of hydrogen leaks is inherent, and the ignition of released flammable mixture can lead to catastrophic explosion, endangering both structures and nearby personnel. This study aims to numerically investigate the hydrogen vapor cloud explosion from offshore hydrogen production platform. The solvers published within the OpenFOAM framework are validated against two public tests involving hydrogen gas explosions within obstacles. A numerical model of the hydrogen vapor cloud explosion from a conceptual offshore hydrogen production platform is then constructed. The effect of offshore facility layout configuration on flame propagation mechanism and overpressure characteristics is analyzed. Results indicate that the presence of compressor equipment and cylindrical hydrogen storage tank leads to accelerated flame propagation and higher overpressure peaks. By reducing the cross-sectional area of the compressor equipment by 68% perpendicular to the flame propagation direction, the maximum flame propagation speed and overpressure are reduced by 88.6% and 94.2%, respectively. With an appropriate layout that maintains a cross-sectional area of 0.008, the presence of compressor equipment may not exacerbate the consequences compared to scenarios without any compressor equipment. This study provides a foundational basis for the safety design of offshore hydrogen production platforms, aiming to mitigate potential hydrogen explosion hazards.

Sustained hydrogen production through alkaline water electrolysis using Bridgman–Stockbarger derived indium-impregnated copper chromium selenospinel

The depletion of conventional fossil fuels necessitates the development of sustainable energy alternatives, with electrochemical water splitting for hydrogen (H2) production being a promising solution. However, large-scale hydrogen generation is hindered by the scarcity of cost-effective electrocatalysts to replace noble metals such as Pt and RuO2 in the Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER). In this study, we report the synthesis of CuCr2-xInxSe4 (x = 0, 0.2, 0.4) using a dual approach combining the Bridgman-Stockbarger method and ball milling. Among the synthesized materials, CuCr1.8In0.2Se4 demonstrates outstanding HER activity in 1.0 M KOH, achieving a potential of −0.16 V vs. RHE at a current density of 10 mA cm−2. Moreover, the material shows remarkable durability during a three-electrode accelerated degradation test in an alkaline medium, maintaining its performance over 24 h at a constant current density of −200 mA cm−2, with a stable potential of −0.57 V vs. RHE. Additionally, CuCr1.8In0.2Se4 was tested in a two-electrode configuration alongside CoFe LDH, achieving a benchmark of 1.7 V for overall water splitting. It sustained a current density of 400 mA cm−2 for 24 h in an accelerated degradation test, exhibiting a minimal loss of 0.1 V after the testing period. These results highlight CuCr1.8In0.2Se4 as a promising non-noble metal catalyst for HER, demonstrating its potential to reduce reliance on noble materials for large-scale hydrogen production.

Rational Design of Ultrahigh-Loading Ir Single Atoms on Reconstructed Mn─NiOOH for Enhanced Catalytic Performance in Urea-Water Electrolysis.

Investigating advanced electrocatalysts is crucial for improving the efficacy of water splitting to generate environmentally friendly fuel. The discovery of highly effective electrocatalysts, capable of driving oxygen evolution reaction (OER) and urea oxidation reaction (UOR) in urea-alkaline environments, is pivotal for advancing large-scale hydrogen production. This study aims to introduce a new method that involves creating nanosheets of high-loading iridium single atoms embedded in a manganese-containing nickel oxyhydroxide matrix (Ir@Mn─NiOOH). These nanostructures are derived from self-supported hydrate pre-catalyst nanosheets grown on nickel foam and then activated through electrochemical etching pretreatment. The Ir@Mn─NiOOH nanoarchitecture displays outstanding electrocatalytic activity, having a low overpotential of just 258mV and a potential of 1.319V (at 10mAcm-2) for OER and UOR, respectively. Such extraordinary catalytic characteristics of Ir@Mn─NiOOH is mainly owing to the strong synthetic electronic interaction between Ir single atoms and Mn─NiOOH, which can change its electronic characteristics and boost electrochemical catalytic sites. This research presents a new way to produce exceptionally efficient catalysts by adding a synergistic effect to complex multi-electron processes.

Electronic Structure Engineering of Single-Atom Tungsten on Vacancy-enriched V3S4 Nanosheets for Efficient Hydrogen Evolution.

Constructing single-atom catalysts (SACs) and optimizing the electronic structure between metal atoms and support interactions is deemed one of the most effective strategies for boosting the catalytic kinetics of the hydrogen evolution reaction (HER). Herein, a sulfur vacancy defect trapping strategy is developed to anchor tungsten single atoms onto ultrathin V3S4 nanosheets with a high loading of 25.1wt.%. The obtained W-V3S4 catalyst exhibits a low overpotential of 54mV at 10mA cm-2 and excellent long-term stability in alkaline electrolytes. Density functional theory calculations reveal that the in situ anchoring of W single atoms triggers the delocalization and redistribution of electron density, which effectively accelerates water dissociation and facilitates hydrogen adsorption/desorption, thus enhancing HER activity. This work provides valuable insights into understanding highly active single-atom catalysts for large-scale hydrogen production.

Interfacial Electronic Structure Engineering of NiCo2Se4 and NiTe2 Nanorods for Enhanced Hydrogen Evolution Reaction.

Finding the best candidates with outstanding electrocatalytic capabilities for the hydrogen evolution reaction is essential for realizing large-scale hydrogen production through electrolysis. In this study, we synthesized NiCo2Se4 (NCS) and NiTe2 (NT) nanorod arrays using a hydrothermal method. The confirmation of catalyst formation was achieved through X-ray diffraction analysis, electron microscopy imaging, and X-ray photoelectron spectroscopy. Leveraging the plentiful heterointerfaces and synergistic effects arising from the incorporation of bimetallic components, the NCS/NT electrocatalyst demonstrates remarkable efficacy in catalyzing the hydrogen evolution reaction. It achieves a minimal overpotential of 163 mV to attain a current density of 50 mA cm-2, showcasing exceptional catalytic activity. Further exploration has revealed that the engineering of heterogeneous interfaces and the morphology of nanorods not only guarantee the exposure of numerous active sites and expedite electron-mass transfer but also trigger electron modulation. Such modulation serves to fine-tune the adsorptive and desorptive dynamics of reaction intermediates, culminating in an enhancement of the catalyst's inherent activity. This study illuminates the novel composite electrocatalyst with robust synergy, highlighting the pivotal role of their unique nanostructures in achieving high-efficiency hydrogen production via electrolysis.

A gradient porous transport layer enabling a high-performance proton-exchange membrane electrolysis cell

Large-scale green hydrogen production through proton-exchange membrane electrolysis cells (PEMECs) is constrained by high costs. Operating PEMECs at high current densities while minimizing overpotentials, particularly the mass transport overpotential due to intense water-oxygen two-phase flow, is crucial. The porous transport layer (PTL) plays a key role in facilitating water-oxygen two-phase flow and affecting ohmic resistance and catalyst utilization. In this study, a gradient PTL has been developed by introducing titanium mesh with tunable pores between the titanium felt and the flow field. The woven mesh structure with large pores facilitates water transport under the ribs, while the titanium felt reduces ohmic resistance and improves catalyst utilization. Experimental results demonstrate that the gradient PTL with a single layer of titanium mesh (pore size: 0.6 mm) can reduce the mass transport overpotential from 0.478 V to 0.206 V at 5 A/cm2 and maintain low ohmic and activation overpotentials compared with the conventional PTLs. Additionally, the gradient PTL with two titanium mesh layers (pore sizes: 0.6 mm and 0.28 mm) can further facilitate water transport, reducing mass transport overpotential to 0.149 V at 5 A/cm2. Numerical simulations reveal that the developed gradient PTL increases the volume fraction of liquid water and ensures uniform water distribution in the catalyst layer. The combined results indicate that the gradient PTL design is promising for enhancing mass transport performance while maintaining low ohmic resistance and high catalyst utilization, making PEMECs more viable for large-scale hydrogen production.

Amorphous/crystalline Ni-Fe based electrodes with rich oxygen vacancies enable highly active oxygen evolution in seawater electrolysis

To realize large-scale production of hydrogen through seawater electrolysis, it is highly crucial to engineer high-activity and robustly stable catalytic materials for oxygen evolution reaction (OER). Here, a facile etching growth strategy based on Ni foam (NF) is employed to fabricate an amorphous/crystalline Ni-Fe based electrode with rich oxygen vacancies as a promising OER electrocatalyst (a/c-NiFeOxHy@NF). Of note, the introduction of Fe induces the generation of plentiful Ni(Fe)OOH species, which can contribute to the remarkable OER behavior. Profiting from the favorable geometric microstructure of ultrathin nanosheets coupled with 3D open-pore architecture and regulated electronic state by increased oxygen vacancies and abundant crystalline-amorphous boundaries, the resulting a/c-NiFeOxHy@NF displays prominent electrocatalytic OER activity in pure alkaline solution and seawater, achieving impressive overpotentials of only 219 and 233 mV to reach 100 mA cm−2, respectively. More significantly, the electrode can keep stable operation without obvious attenuation for over 1200 h at 100 mA cm−2, demonstrating its exceptional corrosion resistance. Such robustness of this electrode surpasses those of almost all reported OER electrocatalysts. Furthermore, in a self-assembled seawater electrolyzer with a/c-NiFeOxHy@NF as the anode and l-RuP@NF as the cathode, a large current density of 500 mA cm−2 is easily achieved at the voltage of 1.795 V at 65 °C. The work offers a novel paradigm for constructing low-cost, high-efficiency, and ultra-stable OER catalysts, which shows huge promise for industrial seawater electrolysis applications.

Selenate oxyanion-intercalated NiFeOOH for stable water oxidation via lattice oxygen oxidation mechanism

Transition metal-based compounds can serve as pre-catalysts to obtain genuine oxygen evolution reaction (OER) electrocatalysts in the form of oxyhydroxides through electrochemical activation. However, the role and existence form of leached oxygen anions are still controversial. Herein, we selected iron selenite-wrapped hydrated nickel molybdate (denoted as NiMoO/FeSeO) as a pre-catalyst to study the oxyanion effect. It is surprising to find that SeO42− exists in the catalyst in the form of intercalation, which is different from previous studies that suggest that anions are doped with residual elements after electrochemical activation, or adsorbed on the catalyst surface. The experiment and theoretical calculations show that the existence of SeO42− intercalation effectively adjusts the electronic structure of NiFeOOH, promotes intramolecular electron transfer and O–O release, and thus lowers the reaction energy barrier. As expected, the synthesized NiFeOOH-SeO only needs 202 and 285 mV to attain 100 and 1000 mA cm−2 in 1 M KOH. Further, the anion exchange membrane water electrolyzer (AEMWE) consisting of NiFeOOH-SeO anode and Pt/C cathode can reach 1 A cm−2 at 1.70 V and no significant attenuation within 300 h. Our findings provide insights into the mechanism, by which the intercalated oxyanions enhance the OER performance of NiFeOOH, thereby facilitating large-scale hydrogen production through AEMWE.