Outstanding Oxygen Evolution Reaction Activity Research Articles

Simultaneous Interface Engineering and Phase Tuning of CeO2-Decorated Catalysts for Boosted Oxygen Evolution Reaction.

Heterogeneous catalysts have attracted extensive attention among various emerging catalysts for their exceptional oxygen evolution reaction (OER) capabilities, outperforming their single-component counterparts. Nonetheless, the synthesis of heterogeneous materials with predictable, precise, and facile control remains a formidable challenge. Herein, a novel strategy involving the decoration of catalysts with CeO2 is introduced to concurrently engineer heterogeneous interfaces and adjust phase composition, thereby enhancing OER performance. Theoretical calculations suggest that the presence of ceria reduces the free energy barrier for the conversion of nitrides into metals. Supporting this, the experimental findings reveal that the incorporation of rare earth oxides enables the controlled phase transition from nitride into metal, with the proportion adjustable by varying the amount of added rare earth. Thanks to the role of CeO2 decoration in promoting the reaction kinetics and fostering the formation of the genuine active phase, the optimized Ni3FeN/Ni3Fe/CeO2-5% nanoparticles heterostructure catalyst exhibits outstanding OER activity, achieving an overpotential of just 249mV at 10mAcm-2. This approach offers fresh perspectives for the conception of highly efficient heterogeneous OER catalysts, contributing a strategic avenue for advanced catalytic design in the field of energy conversion.

Hollow-structured cobalt sulfide electrocatalyst for alkaline oxygen evolution reaction: Rational tuning of electronic structure using iron and fluorine dual-doping strategy

Utilizing renewable electricity for water electrolysis offers a promising way for generating high-purity hydrogen gases while mitigating the emission of environmental pollutants. To realize the water electrolysis, it is necessary to develop highly active and precious metal-free electrocatalyst for oxygen evolution reaction (OER) which incurs significant overpotential due to its complicated four-electron transfer mechanism. Hence, we propose a facile preparation method for hollow-structured Fe and F dual-doped CoS2 nanosphere (Fe-CoS2-F) as an efficient OER electrocatalyst. The uniform hollow and porous structure of Fe-CoS2-F enlarge the specific surface area and increase the number of exposed active sites. Furthermore, the Fe and F dual-dopants synergistically contributed to the adjustment of electronic structure, thereby promoting the adsorption/desorption of oxygen-containing reaction intermediates on active sites during the alkaline OER procedure. As a result, the prepared Fe-CoS2-F exhibits outstanding OER activity, characterized by a low overpotential of 298 mV to achieve a current density of 10 mA cm−2 and a Tafel slope as small as 46.0 mV dec−1. Based on computational theoretical calculations, the introduction of the dual-dopants into CoS2 structure reduce the excessively strong adsorption energy of reaction intermediate in the rate determining step, leading to effectively promoted electrocatalytic cycle for OER in alkaline environment. This study presents an effective strategy for preparing noble metal-free OER electrocatalysts with promising potential for large-scale industrial water electrolysis.

Activity trends of Pd clusters supported on C2N for oxygen evolution and reduction reactions

Developing highly efficient electrocatalysts for the oxygen evolution reaction (OER) and reduction reaction (ORR) is crucial for future renewable energy technology. Here, we use first-principles calculations combined with genetic algorithm to determine the structures of various Pd clusters supported on experimentally available C2N monolayer and evaluate the OER and ORR performance. Our findings show that the activity of the supported Pd clusters is closely linked to the local geometrical and electronic structure of the active site. Furthermore, we establish the activity trends of the clusters based on the adsorption free energies of intermediates. In particular, C2N supported Pd7 and Pd8 clusters exhibit outstanding OER activity with low overpotentials. We identify a volcano relation for the OER on the clusters, suggesting that the high activity of the cluster is related to the moderate adsorption strength of intermediates. Mechanistic analysis indicates that the second water formation is the potential-determining step for ORR on the clusters due to the strong adsorption of *OH. Additionally, we identify a linear scaling relationship between the ORR overpotentials and adsorption free energies of *OH, demonstrating that reducing the adsorption strength of reaction intermediates on Pd clusters can improve the activity. This work unravels the activity trends of cluster catalysts and provides strategies for the rational design of highly efficient single-cluster catalysts for OER and ORR.

Superaerophilic/Superaerophobic NiFe-LDHs Electrode for Enhancing Overall Water Splitting in Alkaline Media.

Overall water splitting, as a critical approach to producing green hydrogen, is greatly impeded by the mass transfer of gaseous bubbles and dissolved gas molecules. Herein, a bifunctional superaerophilic/superaerophobic (SAL/SAB) NiFe layered-double-hydroxides (LDHs) electrode has been developed, which can drive H2 and O2 bubbles out of the reaction system by asymmetric Laplace pressure and accelerate dissolved gases diffusion through reducing their diffusion distance. Consequently, the SAL/SAB NiFe-LDHs electrode exhibits excellent HER activity with an overpotential of -76 mV at -10 mA cm-2 and outstanding oxygen evolution reaction activity with an overpotential of 253 mV at 100 mA cm-2. The bifunctional SAL/SAB NiFe-LDHs electrode is further utilized in overall water splitting, which can achieve 10 mA cm-2 with a cell voltage of 1.54 V. This work provides an efficient strategy to improve the efficiency of overall water splitting and can stimulate new electrode design in various gas-involved processes.

A facile synthesis of hierarchical CoFe2O4 nanosheets for efficient oxygen evolution in neutral medium

It is of great significance to develop electrocatalysts that are abundant in Earth's crust, highly efficient, and exceptionally durable for the oxygen evolution reaction (OER), particularly in neutral medium. Herein, the hierarchical CoFe2O4 nanosheets supported on iron foam (CoFe2O4/IF) were prepared by the ambient spontaneous redox reaction between iron foam and Co2+ at room temperature. The chemical composition and structure of as-prepared CoFe2O4/IF nanosheets were characterized by XRD, XPS, SEM and TEM. The CoFe2O4/IF. The as-obtained CoFe2O4/IF electrode presents excellent electrocatalytic OER activity with an overpotential of 429 mV at 10 mA cm−2 and maintains the stability of 50 h in 1 M PBS. The outstanding electrocatalytic OER activity of CoFe2O4/IF can be credited to the decreased transfer resistance and unique structural features. In addition, the CoFe2O4/IF presented here holds promise for noble-metal-free OER electrocatalyst.

Synergistic effect of a bamboo-like Bi2S3 covered Sm2O3 nanocomposite (Bi2S3-Sm2O3) for enhanced alkaline OER.

The availability of hydrogen energy from water splitting through the electrocatalytic route is strongly dependent on the efficiency, durability, and cost of the electrocatalysts. Herein, a novel Bi2S3-covered Sm2O3 (Bi2S3-Sm2O3) nanocomposite electrocatalyst was developed by a hydrothermal route for the oxygen evolution reaction (OER). The electrochemical properties were studied in 1.00 mol KOH solution after coating the target material on the stainless-steel substrate (SS). Physical analysis via XRD, FTIR, IV, TEM/EDX, and XPS revealed that the Bi2S3-Sm2O3 composite possesses metallic surface states, thereby displaying unconventional electron dynamics and purity of phases. The Bi2S3-Sm2O3 composite shows outstanding OER activity with a low overpotential of 197 mV and a Tafel slope of 74 mV dec-1 at a 10 mA cm-2 current density as compared to pure Bi2S3 and Sm2O3. Meanwhile, the composite catalyst retains high stability even after 100 h of the chronoamperometry test. Thus, this work unveils a new avenue for the speedy flow of electrons, which is attributed to the synergetic effect between Bi2S3 and Sm2O3, as well as enriched interfacial defects, which exhibit greater oxygen adsorption capability with improved electronic assemblies in the active interfacial region. In addition, the introduced porous structure in core-shell Bi2S3-Sm2O3 provides extraordinary electrical properties. Thus, this article offers a realistic framework for electrochemical energy generation.

Iron Phosphates as Highly Efficient Precatalysts for Oxygen Evolution Reaction and Their in Situ Electrochemical Conversion

Current energy issues have prompted demand for the innovations in constructing a clean and sustainable energy platforms. One of examples for energy carrier to actualize a zero carbon society is hydrogen, which is a promising carbon-free fuel with an excellent weight energy density. Hydrogen production through alkaline water electrolysis using renewable energy resources (light and wind)-derived electricity is an attractive ecofriendly and cost-effective technology because cheap nonprecious electrocatalysts can be employed in alkaline media. However, oxygen evolution reaction (OER) at the anode side in the water electrolysis is basically slow and prevents the widespread applications of water electrolysis. Thus, highly efficient and cheap electrocatalysts for OER are highly desirable.Iron (Fe)-based compounds have recently received much attention as OER electrocatalysts because Fe is a quite earth-abundant metallic element that is a very cheap and non-toxic. Therefore, Fe is a promising candidate as electrocatalyst for OER. Due to the insufficient OER activity on simple Fe oxides, previous studies have attempted to enhance the activity by incorporating Fe and other metallic elements.[1,2] Recently, we established a novel comprehensive structural descriptor for the OER on Fe-based simple and multimetal oxides;[3] i.e., shorter minimum Fe–O bond length in the crystalline structures led to higher OER activity regardless of elemental composition, Fe–O coordination number, and crystal category. Thus, this descriptor enabled us to quickly develop excellent OER catalyst, Ba0.65Ca0.35Fe12O19, comprising extremely short Fe–O bond lengths.[4] Furthermore, we found that post-spinel CaFe2O4 catalyzes OER via "multi-iron-site mechanism" involving a reaction intermediate with O–O direct formation on multiple Fe atoms, and CaFe2O4 consequently displayed outstanding OER activity despite the long Fe–O bond length.[5] However, we speculate that OER activity of Fe-based oxides cannot be further enhanced based on crystal structures, and it necessitates to employ another type of compounds.In this study, we report the OER performances of Fe-based phosphates in alkaline media. We selected three kinds of Fe-based phosphates with distinct crystal structures: trigonal FePO4, trigonal Fe3O3(PO4), and monoclinic Fe4(P2O7)3. The electrochemical measurements and post-characterizations identified the Fe-based phosphates as efficient precatalysts that can be electrochemically converted into highly active Fe-based compounds. Notably, the OER performances of the electrochemically converted Fe-based compounds overcame those of the above-mentioned most active Fe-based multimetal oxides and any previously reported crystalline OER electrocatalysts. Therefore, the Fe-based phosphates are promising candidates as OER precatalysts, which can be in situ converted into excellent OER electrocatalysts, and have further advantages of low price, environmental friendliness, and easy production.[6] The part of this paper is based on results obtained from a project, JPNP14021, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). This paper was funded in part by the JSPS KAKENHI Grant-in-Aid (18H01786), the JST PRESTO (JPMJPR15S3) and CREST (JPMJCR16P3) programs, the Tokuyama Science Foundation, and the “Creation of Life Innovative Materials for Interdisciplinary and International Researcher Development” program of the MEXT. The authors thank Dr. Takeshi Aihara in Tokyo Institute of Technology for fruitful discussions.

Nest-like NiFe-LDH derived from the ethylene glycol-assisted hydrothermal route: A highly efficient electrocatalyst for water oxidation in neutral solutions

Water oxidation is an optimistic pathway for hydrogen generation with high quality. In this work, nest-like nickel iron-layered double hydroxide (NiFe-LDH) nanomaterials were successfully prepared using the ethylene glycol-assisted hydrothermal strategy. Morphological and structural studies showed that in the assistance of ethylene glycol (EG), morphologies of the NiFe-LDH nanomaterials were modified, and their surface areas were enhanced. The nano nest-like NiFe-LDH-EG3 derived with 3.0 mL of EG exhibited an excellent oxygen evolution reaction (OER) activity with a low overpotential of about 400 mV at a current density of 10 mA/cm2 and a Tafel slope of 79 mV/dec in neutral media, and such an outstanding OER activity was attributed to the modified morphology, good crystallinity, and high surface area of the nest-like NiFe-LDH-EG3.

Metal-organic framework-derived Fe/NiS heterostructure-embedded nanosheets coupled with carbon nanotubes for excellent oxygen evolution reaction

Developing efficient and stable electrocatalysts to speed up the slow kinetics of oxygen evolution reaction (OER) is both an opportunity and a challenge. Herein, we present a metal-organic framework (MOF)-derived highly active OER catalyst (NiFe-MOF-S@CNT) composed of Fe/NiS heterostructure-embedded nanosheets interconnected by carbon nanotubes network via a direct two-step solvothermal method. The optimized NiFe-MOF-S@CNT catalyst demonstrates outstanding OER activity: it requires an ultralow overpotential of 237 mV to deliver a current density of 10 mA/cm2 (η10) with a small Tafel slope of 42.3 mV/dec, surpassing the commercial RuO2 (η10 = 295 mV) and most other transition metal catalysts. Benefiting from the mesoporous structure and large specific surface area, the MOF-derived NiFe-MOF-S@CNT nanosheets facilitate enhancing mass transfer and electrolyte penetration. Additionally, the incorporation of Fe/NiS heterostructures within the nanosheets, along with carbon nanotubes, generates interfacial effects, promoting electronic interactions and exposing more active sites, thus significantly boosting OER activity. The backbone of carbon nanotubes not only enhances conductivity but also prevents agglomeration of the metal phase, ensuring uniform dispersion of active sites. This work offers a cost-effective and green approach for synthesizing highly efficient transition metal-based sulfides and also paves the way for advancing OER electrocatalysis for various energy applications.

Room-Temperature Synthesis of Carbon-Nanotube-Interconnected Amorphous NiFe-Layered Double Hydroxides for Boosting Oxygen Evolution Reaction.

The oxygen evolution reaction (OER) is a key half-reaction in electrocatalytic water splitting. Large-scale water electrolysis is hampered by commercial noble-metal-based OER electrocatalysts owing to their high cost. To address these issues, we present a facile, one-pot, room-temperature co-precipitation approach to quickly synthesize carbon-nanotube-interconnected amorphous NiFe-layered double hydroxides (NiFe-LDH@CNT) as cost-effective, efficient, and stable OER electrocatalysts. The hybrid catalyst NiFe-LDH@CNT delivered outstanding OER activity with a low onset overpotential of 255 mV and a small Tafel slope of 51.36 mV dec-1, as well as outstanding long-term stability. The high catalytic capability of NiFe-LDH@CNT is associated with the synergistic effects of its room-temperature synthesized amorphous structure, bi-metallic modulation, and conductive CNT skeleton. The room-temperature synthesis can not only offer economic feasibility, but can also allow amorphous NiFe-LDH to be obtained without crystalline boundaries, facilitating long-term stability during the OER process. The bi-metallic nature of NiFe-LDH guarantees a modified electronic structure, providing additional catalytic sites. Simultaneously, the highly conductive CNT network fosters a nanoporous structure, facilitating electron transfer and O2 release and enriching catalytic sites. This study introduces an innovative approach to purposefully design nanoarchitecture and easily synthesize amorphous transition-metal-based OER catalysts, ensuring their cost effectiveness, production efficiency, and long-term stability.

Anion/cation-induced strong electronic polarization of N,Fe-CoS2 electrocatalyst to boost efficient oxygen evolution

Designing and developing the high activity and long-term durability electrocatalysts for oxygen evolution reaction (OER) has primary significance for breaking the bottleneck of water electrolysis. Herein, an anion/cation-codoped CoS2 based electrocatalyst, N,Fe-CoS2, for the efficient OER was constructed via two-step electrodeposition and low-temperature calcination. The anion and cation optimized significantly the surface electronic structure of N,Fe-CoS2 and induced synergistically a strong surface electronic polarization along with the generation of abundant Co3+ active sites, which improved considerably the intrinsic catalytic activity. The doping N anion also hindered effectively the catalyst surface oxidation and enhanced the catalytic durability. Benefiting from these, N,Fe-CoS2 exhibited the outstanding OER activity and catalytic durability, and especially at a high current density, acquired its ultra-low OER overpotential of 261 mV at 300 mA∙cm−2 and maintained continuously a stable current density for 80 h without visible attenuation at 100 mA∙cm−2. DFT calculations confirmed the cooperative effect of N anions and Fe cations on improving catalytic activity and unveiled that Fe cations in N,Fe-CoS2 acted a key role in modulating electron densities instead of acting as catalytic sites. This work has an important implication for realizing the synergistic regulation of electron densities of catalytic materials by anions and cations.

High-value utilization of Cr-containing sludge: Eco-friendly and ultra-low-cost electrocatalyst for efficient OER in alkaline media from Cr-containing sludge

Economically sustainable development requires more viable waste recycling solutions. In this context, we address the problem of utilizing chromium-containing sludge, a prevalent and environmentally hazardous waste. Meanwhile, sustainable energy development must develop ecology-friendly and low-cost electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. Herein, we report an ultra-low-cost electrocatalyst from chromium-containing sludge. The optimum preparation conditions are determined by optimizing the calcination temperature and the loading of nickel acetylacetonate. The optimized catalyst delivers excellent stability and outstanding OER activity with overpotentials of 320 mV at 10 mA cm−2 in alkaline media. Density functional theory calculations reveal that the energy barrier of OER is decreased because of the catalyst's heterogeneous structure arrangement and confirm the influence of chromium on performance improvement. The concept of “turning waste into treasure” stimulates the search for methods to process Cr-containing waste and produce low-cost, high-performance electrocatalysts.

Synergistic mechanism of cation-modification and anion-defect dual engineering in FeCo hydroxide/MXene heterostructure for enhanced oxygen evolution

The oxygen evolution reaction (OER) is crucial for electrochemical energy conversion and storage. However, finding OER catalysts that are both effective and durable is still a difficult task. While cation modification and anion-defect engineering are essential for electrocatalysts’ OER activity, MXene-based materials have not been widely studied using these combined strategies. Here, we report a new approach to designing OER catalysts by combining doping and vacancy engineering. We have successfully created Ru-doped FeCo hydroxide nanoarrays with oxygen vacancies on MXene substrates (Ru-FeCo HNs/MXene), significantly enhancing OER kinetics. We use density functional theory (DFT) calculations to demonstrate that the electronic structure is tuned by the combined effects of Ru doping and O vacancy, which lowers the energy barriers for the adsorption/desorption of O-containing intermediates. The optimal Ru-FeCo HNs/MXene achieves outstanding OER activity with a small overpotential of 227 mV at 10 mA cm−2.

A high-entropy and low-cobalt perovskite of La0.7Sr0.3Co0.2Mn0.2Ni0.2Fe0.2Al0.2O3-x for both oxygen evolution and methanol oxidation reactions

The cobalt (Co)-based perovskites as the promising oxygen evolution reaction (OER) catalysts have gained the significant attentions owing to their exceptional intrinsic catalytic activity. However, the major B-site element of Co in these perovskites is high cost and scarcity, which seriously limits their large-scale applications. In this work, we synthesize a high-entropy perovskite (HEP) with the low Co content and high OER catalytic activity. Also, the OER catalytic performances of the perovskites with the different B-site configurational entropies and compositions are systematically investigated. The optimized HEP with the composition of La0.7Sr0.3Co0.2Mn0.2Ni0.2Fe0.2Al0.2O3-x (L5) exhibits the outstanding OER activity with a low overpotential of 339 mV at 10 mA cm−2. Furthermore, no degradation of L5 is observed during long-term OER stability test for 100 h. Interestingly, L5 also shows the superior catalytic activity toward the methanol oxidation reaction (MOR). During the MOR catalytic process, a low overpotential of 219 mV can be achieved at 10 mA cm−2, and the value-added product of formate with the selectivity of ∼70% can be simultaneously obtained. The excellent OER and MOR performances of L5 can be related to the synergistic effects of the major B-site components and configuration entropy effect of HEPs. Our work proposes a promising high-entropy strategy to reduce the Co content in the Co-based perovskites as well as enhance their electrocatalytic activities.

Facilitated catalytic surface engineering of MnCo2O4 electrocatalyst towards enhanced oxygen evolution reaction

The overall conversion efficiency of water electrolysis is primarily restricted by the sluggish kinetics of the oxygen evolution reaction (OER). To overcome the OER bottleneck, fundamental scientific attention is keenly directed toward the development of durable, cost-effective, and highly efficient catalysts, and therefore, the focus of current research. Herein, we report the facile fabrication of promising noble–metal–free oxygen defects engineered MnCo2O4 (Od-MnCo2O4) catalyst as a highly efficient OER water electrocatalyst in an alkaline KOH medium. The MnCo2O4 nanosheet is directly grown on the nickel foam and dramatically changes to a crumpled sphere after NaBH4 treatment, which results in increased oxygen defects (Od). The engineered Od in MnCo2O4 might modify their electronic structure effectively, which results in improved electrical conductivity and a large quantity of electrochemically accessible active surface area. The Od-MnCo2O4 catalyst demonstrates an outstanding OER activity and exhibits a small overpotential of 250 and 316 mV at a current density of 10 and 100 mA cm−2, respectively, with a modest Tafel slope of 64 mV dec–1. The Od-MnCo2O4 catalyst also demonstrates excellent perseverance till 60 h upon continuous chronopotentiometric test even at 100 mA cm−2 and further reveals a static potential response at low and high rates. The excellent OER performance is ascribed to enhanced electrochemically active sites and improved electronic conductivity aroused from the NaBH4 reduction.

Ni0.85Se@CoFe LDH heterostructure nanosheet arrays on Ni foam as efficient electrocatalysts for enhanced oxygen evolution

Exploring high-efficient, earth-abundant and stable electrocatalyst for oxygen evolution reaction (OER) is of vital importance for large-scale implementation of energy converting and storing. Thus, we fabricated a free-standing hierarchical heterostructure electrode of Ni0.85Se@CoFe LDH/NF via a rational combination of hydrothermal, selenization and electrodeposition process, among which the ultrathin CoFe LDH nanosheets intimately assembled onto the vertical aligned Ni0.85Se nanosheets supported on Ni foam. The constructed core-shell nanosheet arrays hold the plentiful hetero-interfaces and intimate interactions through metal-oxygen bonds between two individuals, which guarantee the fast OER kinetic processes. Additionally, CoFe LDH with crystalline/amorphous hybrid structure favors providing more reaction sites. Remarkably, the optimal Ni0.85Se@CoFe LDH/NF binary composites possess outstanding OER activity with a low overpotential of ∼223 and 280 mV at 10 mA cm−2 and 100 mA cm−2 in alkaline solution as well as good durability. This research offers an alternative approach for improving electrocatalytic water splitting through constructing 3D hierarchical heterostructures.

Ultrasmall IrO2 nanoparticles anchored on hollow Co-Mo multi-oxide heterostructure nanocages for efficient oxygen evolution in acid

The application of proton exchange membrane water electrolysis (PEMWE) is largely limited by the sluggish oxygen evolution reaction (OER) kinetics, which usually requires noble metal Ir/Ru-based catalysts. It’s desirable to design low-cost catalysts with less content of Ir/Ru in OER without sacrificing their catalytic performance. Herein, the ultrasmall IrO2 nanoparticles uniformly dispersed on Co3O4-CoMoO4 nanocages (IrO2@Co3O4-CoMoO4) electrocatalyst is demonstrated. Structural characterization indicates that hollow Co3O4-CoMoO4 acts as the effective support to provide abundant anchoring sites and heterogenous interfaces, which enable the catalyst to expose more active sites and accelerate charge transport. As a result, the representative IrO2@Co3O4-CoMoO4 exhibits an outstanding OER activity (η = 236 mV at 10 mA cm−2) with a superior mass activity of 713 A g–1Ir at 1.53 V vs. RHE in 0.5 M H2SO4 that are comparable to most reported catalysts. Theoretical calculations also reveal that the introduction of Mo can effectively modify electronic structure and decrease adsorption energy barriers of oxygen intermediates, and thereby enhancing OER catalytic activity. This work provides a new idea to develop highly efficient low Ir catalysts for OER.

Confinement Accelerates Water Oxidation Catalysis: Evidence from In Situ Studies.

Basic insight into the structural evolution of electrocatalysts under operating conditions is of substantial importance for designing water oxidation catalysts. The first-row transition metal-based catalysts present state-of-the-art oxygen evolution reaction (OER) performance under alkaline conditions. Apparently, confinement has become an exciting strategy to boost the performance of these catalysts. The van der Waals (vdW) gaps of transition metal dichalcogenides are acknowledged to serve as a suitable platform to confine the first-row transition metal catalysts. This study focuses on confining Ni(OH)2 nanoparticle in the vdW gaps of 2D exfoliated SnS2 (Ex-SnS2 ) to accelerate water oxidation and to guarantee long term durability in alkaline solutions. The trends in oxidation states of Ni are probed during OER catalysis. The in situ studies confirm that the confined system produces a favorable environment for accelerated oxygen gas evolution, whereas the un-confined system proceeds with a relatively slower kinetics. The outstanding OER activity and excellent stability, with an overpotential of 300mV at 100mAcm-2 and Tafel slope as low as 93mVdec-1 results from the confinement effect. This study sheds light on the OER mechanism of confined catalysis and opens up a way to develop efficient and low-cost electrocatalysts.

Research advances on electrode materials for solid oxide electrolysis cells

Solid oxide electrolytic cell (SOEC) is an energy conversion device that transfers electrical energy into chemical energy. It has garnered significant attention due to its high efficiency and thick current density. The oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) are two crucial half-reactions of SOEC, while both require excellent electrochemical performance under high-temperature and high-humidity conditions. Therefore, high catalytic activity and good stability of electrode materials are crucial for the practical application of SOEC. The perovskite structure of the oxygen electrodes has outstanding OER activity, while metal ceramic and metal oxide hydrogen electrodes possess good redox properties. This article firstly demonstrates the influence of the physical and electrochemical properties of electrode materials on the performance of SOEC, then illustrates the optimization strategies for electrode materials to improve electrolysis efficiency and extend service life. Finally, the research priorities for the future development of electrode material are summarized.

Synergistic interface engineering and structural optimization over hydroxide-phosphide nanoarray electrocatalysts for efficient alkaline water electrolysis

Developing transitional metal-based electrocatalysts with outstanding oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance is essential for energy-efficiency alkaline water electrolysis. Herein, a group of heterostructured electrocatalysts constructing of nickel-based hydroxide (NiX(OH)x, X = Co, Fe) nanosheets decorated on copper phosphide nanowires arrays，were fabricated. Both of the as-prepared NiCo(OH)x-CuP/CF and NiFe(OH)x-CuP/CF present outstanding HER and OER activity, with the overpotential of 79 and 202 mV to deliver 10 mA cm−2, respectively, along with considerable long-term stability. Encouragingly, the NiCo(OH)x-CuP/CF ǀǀ NiFe(OH)x-CuP/CF couple enables sustainable alkaline water electrolysis and powered by a solar-powered system. In-depth analyses elucidate that owing to the modulated heterogeneous interfacial states, both of the catalytic kinetics can be optimized targeting HER and OER, respectively. More significantly, a regulated electrode-electrolyte microenvironment induced by unique arrays nanostructure efficiently promote the electron-mass transfer capacity, thereby facilitating the catalytic activity expression. This work demonstrates the desirable catalytic performance by rationally designing of hydroxide-phosphide heterostructure, and highlights the structural features on catalytic performance promotion.