Oxygen Evolution Reaction Performance Research Articles

Elevated Water Oxidation by Cation Leaching Enabled Tunable Surface Reconstruction.

Water electrolysis is one promising and eco-friendly technique for energy storage, yet its overall efficiency is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Therefore, developing strategies to boost OER catalyst performance is crucial. With the advances in characterization techniques, an extensive phenomenon of surface structure evolution into an active amorphous layer was uncovered. Surface reconstruction in a controlled fashion was then proposed as an emerging strategy to elevate water oxidation efficiency. In this work, Cr substitution induces the reconstruction of NiFexCr2-xO4 during cyclic voltammetry (CV) conditioning by Cr leaching, which leads to a superior OER performance. The best-performed NiFe0.25Cr1.75O4 shows a ~1500 % current density promotion at overpotential η=300 mV, which outperforms many advanced NiFe-based OER catalysts. It is also found that their OER activities are mainly determined by Ni : Fe ratio rather than considering the contribution of Cr. Meanwhile, the turnover frequency (TOF) values based on redox peak and total mass were obtained and analysed, and their possible limitations in the case of NiFexCr2-xO4 are discussed. Additionally, the high activity and durability were further verified in a membrane electrode assembly (MEA) cell, highlighting its potential for practical large-scale and sustainable hydrogen gas generation.

Elevated Water Oxidation by Cation Leaching Enabled Tunable Surface Reconstruction

AbstractWater electrolysis is one promising and eco‐friendly technique for energy storage, yet its overall efficiency is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Therefore, developing strategies to boost OER catalyst performance is crucial. With the advances in characterization techniques, an extensive phenomenon of surface structure evolution into an active amorphous layer was uncovered. Surface reconstruction in a controlled fashion was then proposed as an emerging strategy to elevate water oxidation efficiency. In this work, Cr substitution induces the reconstruction of NiFexCr2‐xO4 during cyclic voltammetry (CV) conditioning by Cr leaching, which leads to a superior OER performance. The best‐performed NiFe0.25Cr1.75O4 shows a ~1500 % current density promotion at overpotential η=300 mV, which outperforms many advanced NiFe‐based OER catalysts. It is also found that their OER activities are mainly determined by Ni : Fe ratio rather than considering the contribution of Cr. Meanwhile, the turnover frequency (TOF) values based on redox peak and total mass were obtained and analysed, and their possible limitations in the case of NiFexCr2‐xO4 are discussed. Additionally, the high activity and durability were further verified in a membrane electrode assembly (MEA) cell, highlighting its potential for practical large‐scale and sustainable hydrogen gas generation.

Cerium-doped Nickel SulfideNanospheres as EfficientCatalysts for Overall Water Splitting.

The development of non-precious metal electrocatalysts with excellent activity and durability for electrochemical water splitting has always been a goal. Transition metal sulfides are attractive electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction(OER). In this article, we designed and constructed efficient catalysts with multiple synergistic interactions and synthesized Ce-NiS2@NFnanosphere using a solvothermal method. Ce-NiS2@NF exhibits excellent HER performance, OER performance, and overall water splitting capability in alkaline electrolytes, demonstrating good stability. The addition of Ce influences the activity of the catalysts, attributed to the synergistic interactions creating more active sites and higher intrinsic activity through the introduction of Ce heteroatoms. Additionally, the self-supported conductive substrate promotes electron transfer, enhancing the intrinsic activity and active site density of the catalyst.This study provides an in-depth investigation into structural design and performance enhancement, offering ideas for designing efficient catalysts for overall water electrolysis. This work provides an in-depth study in terms of structural design performance enhancement and provides ideas for designing efficient alkaline bifunctional catalysts. Valuable insights have been provided in elucidating the intrinsic mechanism of the catalytic activity of cerium-doped nickel sulfidenanospheres,thus providing new guidance in the field of energy conversion technology.

Enhancing the acidic oxygen evolution reaction performance of RuO2-TiO2 by a reduction-oxidation process

As a promising alternative to Ir based acidic oxygen evolution reaction (OER) catalysts, Ru suffers from severe fading issues. Supporting it on robust oxides such as TiO2 is a simple and effective way to enhance its lifetime. Here, we find that a simple reduction-oxidation process can further improve both activity and stability of RuO2-TiO2 composites at high potentials. In this process, the degree of oxidation was carefully controlled to form Ru/RuO2 heterostructure to improve OER activity. Moreover, due to the oxophilicity difference of Ru and Ti, the structure of catalysts was changed from supported to embedded, which enhanced the protective effect of TiO2 and mitigated the dissolution of Ru element in acidic electrolyte, making as-prepared Ru/RuO2-TiO2 with better durability at all tested potentials.

Unveiling the potential of a g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction photocatalyst for rechargeable zinc-air battery: Visible-light-driven photo-assisted charging for bifunctional ORR and OER at the air cathode

Advancements in solar-driven energy storage technology have been achieved for rechargeable zinc-air batteries (RZABs), facilitating accelerated kinetic responses in both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, we successfully synthesized a novel g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction through a facile hydrothermal process, demonstrating its efficacy as a bifunctional photocatalyst. Upon exposure to LED irradiation, this heterojunction triggers an effective separation of the photogenerated electron-hole pairs, resulting in enhanced oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance by 46.19 % and 65.69 % respectively, compared to non-LED conditions. Interestingly, the reduction in the potential gap under LED irradiation (0.06 V), correlating with a significant 2.71 % increase in round-trip efficiency (RTE), is observed. In addition, the optimized band alignment derived from g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction for photo-assisted charging rechargeable zinc-air batteries is proposed. Insightfully, photo-enhanced charging in RZABs mechanism during the charge/discharge process through in-situ X-ray absorption spectroscopy (XAS) is monitored, confirming the large interaction between O2 adsorption and Bi 6d orbitals of g-C3N4/BiOBr/Bi2O2CO3 in the presence of LED. In conclusion, our innovative g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction underscores the significant role that visible-light-driven photocatalysts can play in enhancing the efficiency of rechargeable zinc-air batteries.

Enhanced Oxygen Evolution and Zinc-Air Battery Performance via Electronic Spin Modulation in Heterostructured Catalysts.

Beyond optimizing electronic energy levels, the modulation of the electronic spin configuration is an effective strategy, often overlooked, to boost activity and selectivity in a range of catalytic reactions, including the oxygen evolution reaction (OER). This electronic spin modulation is frequently accomplished using external magnetic fields, which makes it impractical for real applications. Herein, spin modulation is achieved by engineering Ni/MnFe2O4 heterojunctions, whose surface is reconstructed into NiOOH/MnFeOOH during the OER. NiOOH/MnFeOOH shows a high spin state of Ni, which regulates the OH- and O2 adsorption energy and enables spin alignment of oxygen intermediates. As a result, NiOOH/MnFeOOH electrocatalysts provide excellent OER performance with an overpotential of 261 mV at 10 mA cm-2. Besides, rechargeable zinc-air batteries based on Ni/MnFe2O4 show a high open circuit potential of 1.56 V and excellent stability for more than 1000 cycles. This outstanding performance is rationalized using density functional theory calculations, which show that the optimal spin state of both Ni active sites and oxygen intermediates facilitates spin-selected charge transport, optimizes the reaction kinetics, and decreases the energy barrier to the evolution of oxygen. This study provides valuable insight into spin polarization modulation by heterojunctions enabling the design of next-generation OER catalysts with boosted performance.

Enhancing oxygen evolution reaction through self-reconstruction of 2D nanoarrays on nickel foam

The synthesis of nanostructured transition metal compounds with adjustable components are often challenging due to the involvement of multiple synthetic procedures or complex manipulations. In this work, a one-step self-regulating acid-etching strategy is employed for nickel iron-layered double hydroxide (NiFe LDH). A two-dimensional (2D) NiFe LDH nanosheet is speedy and efficiently formed. This as-prepared NiFe LDH exhibits electrocatalytic activity for oxygen evolution reaction (OER). This approach avoids numerous structural design challenges and provides highly active sites and a robust interface between catalyst and support. As a result, 2D NiFe LDH electrodes demonstrate highly efficient OER performance with a low overpotential of 300 mV and a Tafel slope of 70.6 mV dec−1 at a current density of 100 mA cm−2.

Metal vacancies and self-reconstruction of high entropy metal borates to boost the oxygen evolution reaction

Exploring highly efficient oxygen evolution reaction (OER) electrocatalysts is important for industrial water electrolysis. Herein, a new high entropy material was reported, i.e., an amorphous high entropy metal borate (CrMnCoNiFe)0.2BOx was synthesized by a new simple solvothermal method. The key of this new synthesis method was to obtain (CrMnCoNiFe)0.2BOx with a high specific surface area (446 m2/g) and porous structure, being expected to promote OER reaction. (CrMnCoNiFe)0.2BOx provided a low overpotential of 236 mV at 10 mA cm−2, a reduced Tafel slope of 64 mV dec–1, and good stability. The outstanding OER performance of (CrMnCoNiFe)0.2BOx was attributed to the high entropy structure, generation of metal vacancies, and self-reconstruction during OER. The Cr vacancies generated during the OER process have been demonstrated by Cr 2P XPS and EPR experiments. Various in situ and Ex-situ analyses such as In situ Raman, XPS, and TEM were used to investigate the self-reconstruction of the (CrMnCoNiFe)0.2BOx during the OER. The resulting metal (oxy)hydroxide was believed to be the true active center for OER. The DFT calculation showed the high entropy structure can reduce the adsorption and conversion energy barriers of oxygen-containing intermediates, matching well with the catalytic performance results. This study provided a new simple strategy to construct high entropy metal borate (CrMnCoNiFe)0.2BOx and would inspire the design of high-performance OER catalysts.

Activating MnO2 nanosheet arrays for accelerated water oxidation through the synergic effect of Ni loading and O vacancies

Birnessite (δ-MnO2), inspired by biological photosynthesis, holds promise as oxygen evolution reaction (OER) catalysts in water electrolysis for clean energy. Given that Mn3+ serves as the active sites, various strategies have been employed to increase the Mn3+ content to boost the OER activity. To surpass the limitations of the traditional adsorbate evolution mechanism (AEM), we have adopted an electrochemical reduction method to introduce metallic Ni and enrich oxygen vacancies onto δ-MnO2 nanosheets. The resulting Ni/MnO2v/CC exhibits exceptional OER performance, with a reduction in overpotential by 190 mV (from 478 mV to 289 mV) at 10 mA cm−2 and a Tafel slope as low as 45 mV dec-1, indicating accelerated catalytic activity. Experimental and theoretical analyses attribute this enhancement to a transition from the traditional AEM to lattice oxygen mechanism (LOM) mechanism. Moreover, the dual modification also enhances electronic conductivity, electrochemical surface area, and charge transfer ability of δ-MnO2. Our work offers a pathway to overcome conventional limitations in OER electrocatalysts, applicable not only to Mn-based catalysts but also to a range of other transition metal oxides.

Spectroscopic Investigations of Complex Electronic Interactions by Elemental Doping and Material Compositing of Cobalt Oxide for Enhanced Oxygen Evolution Reaction Activity

AbstractDoping and compositing are two universal design strategies used to engineer the electronic state of a material and mitigate its disadvantages. These two strategies are extensively applied to design efficient electrocatalysts for water splitting. Using cobalt oxide (CoO) as a model catalyst, it is proven that the oxygen evolution reaction (OER) performance can be progressively improved, first by Fe‐doping to form Fe‐CoO solid solution, and further by the addition of CeO2 to produce a Fe‐CoO/CeO2 composite. X‐ray absorption spectroscopy (XAS) reveals that distinct electronic interactions are induced by the processes of doping and compositing. Fe‐doping of CoO can break down the structural symmetry, changing the electronic structure of both Co and O species at the surface and decreasing the flat‐band potential (Vfb). In comparison, subsequent compositing of Fe‐CoO with CeO2 induces negligible electronic changes in the Fe‐CoO (as seen in ex situ characterizations), but significantly modifies the oxidative transformations of both Co and Fe under OER conditions. The spectroscopic investigations reveal that Fe‐doping and CeO2 compositing play different roles in modifying the electronic properties of CoO in its pristine state and during OER catalysis, in return, providing useful guidance for the design of more efficient electrocatalysts using these two strategies.

Ce-4f as an electron-modulation reservoir weakening Fe-O bond to induce iron vacancies in CeFevNi hydroxide for enhancing oxygen evolution reaction

Designing novel rare-earth-transition metal composites is at the forefront of electrocatalyst research. However, the modulation of transition metal electronic structures by rare earths to induce vacancy defects and enhance electrochemical performance has rarely been reported. In this study, we systematically investigate the mechanism by which Ce-4f electron modulation weakens the Fe-O bond, thereby altering the electronic structure in CeFevNi hydroxide to improve oxygen evolution reaction (OER) performance. Theoretical calculations and experimental characterizations reveal that Ce-4f orbitals function as electron-modulation reservoirs, capable not only of retaining or donating electrons but also of influencing the material's electronic structure. Moreover, Ce-4f bands optimize the Fe lower Hubbard bands (LHB) and O-2p bands, leading to weakened Fe-O bonds and the formation of cationic vacancies. This change results in the upshift of the d-band center at the active sites, favoring the reaction energy barrier for oxygen intermediates in the OER process. The synthesized catalyst demonstrated an overpotential of 201 mV at 10 mA cm−2 and a lifetime exceeding 200 h at 100 mA cm−2 under alkaline conditions. This work offers a proof-of-concept for the application of the mechanism of rare earth-induced transition metal vacancy defects, providing a general guideline for the design and development of novel highly efficient catalysts.

Cost-efficient sunlight-driven thermoelectric electrolysis over Mo-doped Ni5P4 nanosheets for highly efficient alkaline water/seawater splitting

Thermoelectric water spitting to hydrogen systems has great potential in the production of environment-friendly fuel using renewable solar energy in the future. In this work, we prepared porous nanosheet Mo doping Ni5P4 catalysts on nickel foam with efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in alkaline media. Density Functional Theory (DFT) calculations and experimental studies have shown that Mo doping deadeneds the interaction between H and O atomic orbitals of transition state water molecules, effectively weakening the activation energy of H2O dissociation. Therefore, Mo doping is favorable for enhancing HER activity with overpotential at 10 mA cm–2 of 93 mV and Tafel slope of 40.1 mV dec–1 in 1 M KOH. Besides, it exhibits high alkaline OER activity with an ultra-low overpotential of 200 mV at 10 mA cm–2. Moreover, this catalyst only needs 1.537 V in a dual-electrode configuration of the electrolytic cell, which is much lower than the commercial Pt/C-RuO2 couple (1.614 V). In addition, we have developed and constructed a solar thermoelectric generator (TEG) that is capable of floating on water. This TEG has a continuous power output and an exceptionally long lifespan, providing a stable power supply to the synthesized catalyst electrolyzer. It can produce a maximum power output of over 90 mW, meeting the requirement of converting solar radiation heat into usable electricity. As a result, the system achieves productivity of 0.11 mL min–1 H2. This solar thermal energy conversion technology shows the possibility of large-scale industrial production of H2 and provides a new idea for exploring heat source utilization.

Helium plasma irradiation on Nickel: Nanostructure formation and electrochemical characteristics

Nanotechnology offers new avenues for the design, fabrication, and application of novel materials. Helium plasma exposure is a technique that can be used to fabricate self-supported metallic nanostructures. In this work, we explore the plasma irradiation conditions for fabricating various morphologies on planar nickel surfaces, and evaluate the electrochemical performance of these surfaces for oxygen evolution reaction (OER) in alkaline media. The preferential growth towards certain morphologies such as nano-pillars, nano-blocks, and micro-structures, is found to be primarily influenced by the applied plasma conditions and two counteracting processes of sputtering and annealing. The plasma treatment increased the electrochemical surface area of the modified samples by approximately 3 to 4 times as compared to the planar/unmodified surfaces, along with an increase in the OER performance for all morphologies. However, in addition to the increased surface area, the electrochemical performance was found to be dependent on the shape, size and thickness of the nano/micro-features. Moving ahead, the ability of this technique to achieve control over the feature size along with its effectiveness for a broad range of metals offers new routes for nanostructuring and functionalization of emerging materials.

Nanoengineered Cobalt Electrocatalyst for Alkaline Oxygen Evolution Reaction.

The alkaline oxygen evolution reaction (OER) remains a bottleneck in green hydrogen production owing to its slow reaction kinetics and low catalytic efficiencies of earth abundant electrocatalysts in the alkaline OER reaction. This study investigates the OER performance of hierarchically porous cobalt electrocatalysts synthesized using the dynamic hydrogen bubble templating (DHBT) method. Characterization studies revealed that electrocatalysts synthesized under optimized conditions using the DHBT method consisted of cobalt nanosheets, and hierarchical porosity with macropores distributed in a honeycomb network and mesopores distributed between cobalt nanosheets. Moreover, X-ray photoelectron spectroscopy studies revealed the presence of Co(OH)2 as the predominant surface cobalt species while Raman studies revealed the presence of the cubic Co3O4 phase in the synthesized electrocatalysts. The best performing electrocatalyst required only 360 mV of overpotential to initiate a current density of 10 mA cm-2, exhibited a Tafel slope of 37 mV dec-1, and stable OER activity over 24 h. The DHBT method offers a facile, low cost and rapid synthesis approach for preparation for highly efficient cobalt electrocatalysts.

Lattice Oxygen Activation through Deep Oxidation of Co4N by Jahn-Teller-active Dopants for Improved Electrocatalytic Oxygen Evolution.

Triggering the lattice oxygen oxidation mechanism is crucial for improving oxygen evolution reaction (OER) performance, because it could bypass the scaling relation limitation associated with the conventional adsorbate evolution mechanism through the directly formation of oxygen-oxygen bond. High-valence transition metal sites are favorable for activating the lattice oxygen, but the deep oxidation of pre-catalysts suffers from a high thermodynamic barrier. Here, taking advantage of the Jahn-Teller (J-T) distortion induced structural instability, we incorporate high-spin Mn3+ (t2g3eg1) dopant into Co4N. Mn dopants enable a surface structural transformation from Co4N to CoOOH, and finally to CoO2, as observed by various in-situ spectroscopic investigations. Furthermore, the reconstructed surface on Mn doped Co4N triggers the lattice oxygen activation, as evidenced experimentally by pH-dependent OER, tetramethylammonium cation adsorption and on-line electrochemical mass spectrometry measurements of 18O-labelled catalysts. In general, this work not only offers the introducing J-T effect approach to regulate the structural transition, but also provides an understanding about the influence of catalyst's electronic configuration on determining the reaction route, which may inspire the design of more efficient catalysts with activated lattice oxygen.

Promotion of the oxygen evolution reaction by introducing MoS2 into CoFe LDH via improved charge transfer and electrocatalytical activity

It is of great significance to investigate economical and efficient non-noble metal electrocatalysts for improving the kinetics of slow oxygen evolution reaction (OER). This study presents a hydrothermal method employed for the synthesis of MoS2@CoFe LDH/NF (NF: nickel foam) electrocatalysts. The layered structure of CoFe LDH offers abundant active sites for OER. The combined effects of MoS2 nanoparticles and LDH structure elevate the catalytic performance of OER. When the current density of 10 mA cm−2, the overpotential and Tafel slope were measured to be 234 mV and 87.68 mV dec-1. Moreover, the current density remained at 90 % of its initial value for 18 h in an alkaline solution, demonstrating excellent stability. Consequently, this study provides valuable insights for designing nanoparticle-LDH heterostructures to achieve resultful OER in practical applications.

Enhanced OER performance by varying Al-WO3 electrocatalyst thickness: Process optimization

Oxygen evolution reactions (OER) are highly significant and play a critical role in the advancement of fuel cells, electrolyzers, chemicals, and solar energy conversion devices. The challenge in the quest is attributed to the absence of an efficient electrocatalyst assembly that functions optimally. A simple method of electrodeposition of Al:WO3 on a fluorinated tin oxide (FTO) electrode was used to investigate the OER in this study. The electrodepositions were achieved by employing a three-electrode cell at various scan rates ranging from 10 to 100 mV/s. During this investigation, the influence of the scan rate on electrocatalyst loadings and the impact of electrocatalyst layer thickness on the OER were examined. The electrodepositions of Al:WO3@FTO were analyzed using a range of optical, chemical, and physical techniques such as SEM, XRD, FT-IR, Raman spectroscopy, EDX, EDS mapping, and electrochemical tests. The FTIR and Raman analysis confirmed the synthesis of AL:WO3 while the peaks detected at angles 38.7° and 43° by XRD with planes (111) and (200), served as a distinctive characteristic for identifying aluminum (Al). The peaks observed at angles of 27.8°, 30.7°, 33°, 50.45°, and 58° correspond to WO3 material. The characterization techniques also confirmed that the synthesized material is highly crystalline in nature. The OER potential using Al:WO3@FTO electrodes with different electrocatalyst thicknesses, ranging from 8 nm to 31 nm was investigated by studying various electrochemical techniques such as CV, LSV, CPE, Tafel slope, HP2P splitting, EIS, TOF, short and long-term electrode stability, and double layer capacitance. The linear regression coefficient (R2) was also calculated to measure the relationship between the electrocatalyst's thickness and each electrochemical test. The findings indicated that increasing the scan rates resulted in thinner and denser electrodepositions on the FTO substrate as the thinnest film was formed at 100 mV/s. An inverse relationship between electrocatalyst layer thickness and OER activity was observed. The electrode with the thinnest and most compact electrocatalyst layer, specifically ED Al:WO3@FTO08, exhibited the lowest onset potential of 1.48 V and a maximum current of 84 mA/cm2 at 1.76 V. It also demonstrated superior reaction kinetics, as evidenced by its lower Tafel slope value of 49 mV/dec, which is the lowest among all the electrodes that were prepared. In particular, the electrode with a thin and compact electrocatalyst layer worked better in OER operations than the other five electrodes that had higher amounts of Al:WO3.

Facile fabrication of nickel-cobalt oxide for efficient oxygen evolution reaction from ammonia leaching solution of spent lithium-ion batteries

Ammonia leaching has been gained considerable attention for its ability to selectively extract nickel and cobalt from spent ternary cathode material. Despite its efficacy, the subsequent recovery of ammonia leachate remains challenging. Herein, a short-process and sustainable method for the synthesis of nickel-cobalt oxide via ammonia evaporation of ammonia leachate and heat treatment of the resultant precursor has been proposed. The ammonia evaporation process, conducted at an evaporation temperature of 130 °C with hydrazine hydrate as a reducing agent, facilitated the precipitation of ∼95% Ni and ∼99% Co as a precursor. Subsequently, the effect of precursor roasting temperature on electrode material synthesis was systematically studied. The precursor was roasted at 300 °C to successfully synthesize nickel-cobalt oxide. Physical and electrochemical characterizations revealed that the nickel-cobalt oxide possesses a significant specific surface area of 161.150 m2/g, and exhibits excellent oxygen evolution reaction performance, evidenced by an overpotential of 350.7 mV at 10 mA/cm2 and a Tafel slope of 159.8 mV/dec. Overall, the proposed method not only promotes the recycling and utilization of ammonia reagents and mother liquor, but also introduces an innovative approach for the synthesis of nickel-cobalt oxide as an electrode material.

Iron, Tungsten Dual-Doped Nickel Sulfide as Efficient Bifunctional Catalyst for Overall Water Splitting.

Developing low-cost and highly efficient bifunctional catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is a challenging problem in electrochemical overall water splitting. Here, iron, tungsten dual-doped nickel sulfide catalyst (Fe/W-Ni3S2) is synthesized on the nickel foam, and it exhibits excellent OER and HER performance. As a result, the water electrolyze based on Fe/W-Ni3S2 bifunctional catalyst illustrates 10mAcm-2 at 1.69V (without iR-compensation) and highly durable overall water splitting over 100h tested under 500mAcm-2. Experimental results and DFT calculations indicate that the synergistic interaction between Fe doping and Ni vacancy induced by W leaching during the in situ oxidation process can maximize exposed OER active sites on the reconstructed NiOOH species for accelerating OER kinetics, while the Fe/W dual-doping optimizes the electronic structure of Fe/W-Ni3S2 and the binding strength of intermediates for boosting HER. This study unlocks the different promoting mechanisms of incorporating Fe and W for boosting the OER and HER activity of Ni3S2 for water splitting, which provides significant guidance for designing high-performance bifunctional catalysts for overall water splitting.

FeCo‐oxalate Organic Framework as an Efficient Electrocatalyst for Oxygen Evolution Reaction

Developing nonprecious metallic electrocatalysts for water splitting is of vital importance for sustainable environment and energy technologies. As for oxygen evolution reaction (OER), FeCo‐based bimetallic catalysts have been found to act as promising candidates owing to their high intrinsic activity. Herein, a novel FeCo‐oxalate organic framework was grown on nickel foam (FeCo‐OA@NF) under mild conditions. The optimized electrocatalyst shows good OER performance with a low overpotential of 275 mV at the current density of 100 mA cm−2 in alkaline environment, comparable to that of commercial Ru‐based catalyst. Moreover, the quantification of produced oxygen by both gas chromatography and drainage method demonstrates nearly 100% Faradaic efficiency. Except for the contribution of Fe and Co species for the excellent OER catalytic activity, in‐situ Raman spectroscopy reveals that the positive effect of oxalate coordination also makes a difference, which can possibly reduce electron transport resistance and provide more active sites. This work provides a promising approach for the preparation of alkaline oxygen evolution electrocatalysts with low‐cost and high performance.