Oxygen Evolution Reaction Overpotential Research Articles

Interconnected nickel cobalt vanadate quasi-spheres as an efficient and stable oxygen evolution electrocatalyst in alkaline media

The present work reports the one-step hydrothermal fabrication of carbon fiber paper (CFP) supported interconnected nickel cobalt vanadate (Ni3-xCoxV2O8) microparticles. The CFP substrate was selected for its conductive support and strong adhesion to materials, thereby improving durability. Crystal structure analysis confirmed the successful incorporation of Co into the Ni3V2O8 lattice, resulting in a single orthorhombic phase of Ni3-xCoxV2O8 without altering the crystal structure. Compositional tuning was achieved by varying Ni/Co molar feeding ratios to optimize electrocatalytic oxygen evolution reaction (OER) performance in 1 M KOH. The compositionally tuned interconnected NiCo2V2O8 microspheres exhibited improved OER activity compared to its individual counterparts and other compositions. It exhibited a low OER overpotential of ∼ 351 mV to reach a current density of 50 mA cm−2 and good long-term stability for 20 h, without any performance decay. These results suggest that the NiCo2V2O8 could serve as a cost-effective alternative to valuable electrocatalysts for the alkaline OER.

A comprehensive study of parasitic gas evolution reactions in a vanadium redox flow battery

The gas evolution reactions (GERs) in a vanadium redox flow battery (VRFB) are dangerous and can cause a series of issues such as an imbalance in the state of charge (SOC) and electrode degradation, among others. To gain a deeper understanding of parasitic GERs in VRFBs, a transient multidimensional multiphysics VRFB model was developed by coupling the transport of multiphase species and electrochemical reactions. First, it was predicted that the hydrogen evolution reaction (HER) occurs during the whole charge-discharge process due to the negative activation overpotential of the HER whereas the oxygen evolution reaction (OER) occurs only at the end of the charging process. Second, the charging current has a strong effect on the HER in the region near the bipolar plate. Third, it was found that the HER increases almost seven times (from 163.3 A m−3 to 1167.1 A m−3) when the operating temperature increases from 298.15 K to 313.15 K. The temperature has a more significant effect on the activation overpotential of OER than that of HER. Furthermore, the increasing HER with the increasing SOC results in an SOC imbalance of 0.54% after 10 charge-discharge cycles, which accounts for 11% of the overall capacity loss.

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.

Pyrochlore@PBA derived electrocatalyst containing Ru nanoparticle and NiFe alloy for the oxygen evolution and reduction reactions

Developing enhanced electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is essential for commercializing green energy technologies, such as Zn–air batteries. In this study, a uniquely designed metal catalyst–support material composite was synthesized using a Prussian blue analogue (PBA) and Y2Ru2O7 (YRO) pyrochlore for Zn-air battery. P–S-doped Ru nanoparticles and PBA-derived NiFe alloys anchored on the YRO pyrochlore (YRO@NiFe/Ru-PS) were synthesized in one pyrolysis process via in situ exsolution. The electronic structure of the Ru and NiFe particles was tailored by the pyrochlore support and P–S dual doping, which decreased the energy barrier for the catalytic reaction. YRO@NiFe/Ru-PS exhibited outstanding OER (overpotential = 241 mA/cm2; Tafel slope = 36 mV/dec) and ORR (half-wave potential = 0.83 V; Tafel slope = 65 mV/dec) performances. Furthermore, it also exhibited high performance in Zn–air battery applications (power density = 112 mW/cm2). This paper proposes an efficient and unique design strategy for developing OER/ORR bifunctional electrocatalysts.

Synergistic two-dimensional metal sulfide heterostructures from ZIF-67: A promising catalyst for efficient overall water splitting

The morphology of nanomaterials plays a significant role in electrocatalytic water splitting. Metal–organic frameworks (MOFs) offer several advantages, including high porosity, large specific surface area, adjustable structure and various morphologies. Among the various MOFs, zeolitic imidazolate framework-67 (ZIF-67) is a cobalt-based MOF that can produce carbon-containing metal sulfides through appropriate sulfurization and annealing processes. Since the control of the morphology of nanostructured electrocatalysts plays a crucial role in optimizing catalytic activity, in this study, we synthesized rhombic dodecahedral, cubic, and plate-shaped ZIF-67 nanocrystals and utilized them as templates to fabricate Co3S4@CoMoS3 nanomaterials with various morphologies. These materials were characterized and subjected to electrochemical tests to evaluate their performance in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and electrocatalytic water splitting. The electrochemical measurements revealed that the plate-shaped Co3S4@CoMoS3–P exhibited the low overpotential for OER at 20 mA cm−2, with a value of 200 mV and a Tafel slope of 173 mV dec−1. Similarly, for HER at 10 mA cm−2, it showed an overpotential of 240 mV and a Tafel slope of 93 mV dec−1. Moreover, in the water splitting setup employing a dual electrode configuration, the plate-shaped Co3S4@CoMoS3–P achieved a voltage of 1.61 V at 20 mA cm−2, outperforming a commercial electrode combination (10% Pt/C//RuO2) in terms of water-splitting efficiency.

In situ construction of S-doped NiFe-layered double hydroxide nanoarrays on porous reduced graphene oxide as efficient oxygen evolution electrocatalysts for electrolytic cells

The application of NiFe-layered double hydroxide (NiFe-LDH) as electrocatalysts for oxygen evolution reaction (OER) is seriously limited owing to low conductivity, insufficient active sites and self-aggregation. The construction of anion-doped NiFe-LDH nanoarray structures with ideal electrochemical activity is an effective strategy. Herein, we report a facile solvothermal approach for the synthesis of S-doped NiFe-LDH nanosheets loaded in situ on porous reduced graphene oxide (rGO) to form a composite with nanosheet array structure (S-NiFe-LDH/rGO) for OER. The S-NiFe-LDH/rGO nanosheet array ensures a large specific surface area, abundant accessible active sites and high stability. The moderate S doping in NiFe-LDH can tune the local electronic structures of Ni and Fe to optimize the binding of metal sites with reaction intermediates, thus enhancing the OER activity. The S-NiFe-LDH/rGO electrocatalyst shows the small OER overpotential of 264 mV at 10 mA cm−2 and the low Tafel slope of 55 mV dec−1. Moreover, S-NiFe-LDH/rGO displays good durability and structural stability due to the strong anchoring effect. The assembled two-electrode S-NiFe-LDH/rGO||Pt electrolytic cell exhibits a low cell voltage of 1.53 V at 10 mA cm−2, which is superior to the RuO2||Pt benchmark cell (1.60 V), indicating the practical feasibility for water electrolysis. This design strategy provides a promising insight into the fabrication of advanced OER non-noble metal electrocatalysts.

An efficient cerium dioxide incorporated nickel cobalt phosphide complex as electrocatalyst for All-pH hydrogen evolution reaction and overall water splitting

Transition metal phosphides (TMPs) have been considered as potential electrocatalysts with adjustable valence states, metal characteristics, and phase diversity. However, it is necessary but remains a major challenge to obtain efficient and durable TMPs catalysts, which can realize efficiently for not only all-pH hydrogen evolution reaction (HER), but also oxygen evolution reaction (OER). Hence, cerium dioxide incorporated nickel cobalt phosphide growth on nickel foam (CeO2/NiCoP) is fabricated by hydrothermal and phosphating reaction. CeO2/NiCoP shows excellent activity for all-pH HER (overpotentials of 48, 58 and 72 mV in alkaline, neutral and acidic solution at the current density of 10 mA cm−2), and has a small OER overpotential (231 mV @ 10 mA cm−2). Moreover, the voltage of overall water splitting in alkaline solution and simulated seawater electrolyte is only 1.46 and 1.41 V (10 mA cm−2), respectively, coupled with outstanding operational stability and corrosion resistance. Further mechanism research shows that CeO2/NiCoP possesses rich heterointerfaces, which serves more exposed active sites and possesses a promising superhydrophilic and superaerophobic surface. Density functional theory calculations manifest that CeO2/NiCoP has appropriate energy for intermediates of reactions. This work provides a deep insight into the CeO2/NiCoP catalyst for high-performance water/seawater electrolysis.

Enhancing Oxygen Evolution Reaction by Simultaneously Triggering Metal and Lattice Oxygen Redox Pair in Iridium Loading on Ni‐Doped Co3O4

AbstractSince the active sites in catalytic systems are either metal sites or lattice oxygen, simultaneously triggering metal and lattice oxygen redox pair with low energy barriers is expected to provide diversified and efficient sites to accelerate oxygen evolution reaction (OER) kinetics, but this is a great challenge. Herein, Ir species (Ir clusters and Ir single atoms) loaded on Ni‐doped Co3O4 is designed (Ir/Ni‐Co3O4), where metallic Ir clusters downsize to spread into high‐density Ir single atoms to load on reconstruction‐derived Ni‐doped CoOOH. In situ spectroscopy, isotope‐labeled, and chemical probe experiments demonstrate that metal site and lattice oxygen are simultaneously activated to participate in the OER. Further theoretical studies demonstrate that the Co site is the most favorable site to promote the OER through an adsorbate evolution mechanism with a low energy barrier of 1.69 eV. The Ni cooperating with Ir atoms synergistically upshifts energy positions of the O p band centers. Thus, the lattice O that bridges Ni and Ir atoms is activated to participate in the OER via coupling with adsorbed O on the Ir site to fulfill O─O bond formation. Benefiting from the conjoint participation of the metal and lattice oxygen redox pair, Ir/Ni‐Co3O4 affords extremely low OER overpotentials of 177 and 263 mV at corresponding 10 and 500 mA cm−2.

Advanced Mott-Schottky heterojunction of semi-conductive MoS2 nanoparticles/metallic CoS2 nanotubes as an efficient multifunctional catalyst for urea-water electrolysis

Metallic CoS2 has attracted considerable interest for the catalysis of electrochemical reactions; however, its catalytic activity is still lower than that of commercial novel metal-based catalysts. Semiconductive 2H-MoS2 also holds a high capability for catalysis. In this work, a rationally designed Mott-Schottky heterojunction of ultrasmall MoS2 nanoparticles/CoS2 nanotube arrays is constructed via an effective synthetic protocol. Because of the difference in the Fermi level of the metallic CoS2 and semiconducting MoS2, strong Mott-Schottky interaction occurs at their heterointerface to gain equalization, resulting in the optimization of intermediates adsorption energies, thereby favoring the reaction kinetics of hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and urea oxidation reaction (UOR). Consequently, the proposed catalyst yields high current densities at small HER and OER overpotentials or low UOR potentials, small Tafel slopes, and desirable stability, confirming its excellent electrocatalytic activities for these key half-reactions toward significantly boosting water and urea electrolysis.

Synergistic reaction kinetics of Pt single atoms/MoS2 and nanoparticles for energy-saving hydrogen production assisted by green electrosynthesis of azotetrazolate compound

Overall water splitting (OWS) involves two important half-reactions, namely hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, due to the high theoretical overpotential of OER, OWS needs to be realized with high energy consumption. Using anodic oxidation reaction with lower theoretical potential to replace oxygen evolution reaction (OER) can effectively reduce the energy consumption of overall water splitting (OWS) for hydrogen production. Here, we introduce a new oxidation reaction of green electrosynthesis of energetic materials (EMs) and coupled with OWS. The catalyst was prepared by electrodepositing Pt nanoparticles (Pt NPs) and Pt single atoms (Pt SAs) on MoS2 nanosheets, which drives highly-efficient hydrogen production of 35.6 mV to drive 10 mA cm−2. DFT calculations reveal the synergistic mechanism of Pt NPs and Pt SA/MoS2 substrate for promoting hydrogen production, is that the energy barrier of water dissociation was reduced on the Pt NC sites and the produced H* migrated to the adjacent S sites for Heyrovsky step, while the Pt SA sites served as electron regulator for more thermoneutral H* adsorption on S sites, realizing the synergistic reaction kinetics in MoS2/Pt for promoting alkaline HER. Importantly, by integrating the OWS and electrosynthesis of 5,5′-azotetrazole (ZT) EMs, the cell voltage can be significantly reduced to 1.29 V at 10 mA cm−2, realizing low-energy-consumption for hydrogen production. Meanwhile, the green electrosynthesis of ZT is achieved to avoid the hazardous process of traditional preparation methods. This study presents a new strategy for green electrosynthesis of EMs and low-energy-consumption hydrogen production.

Engineering hexagonal-silicon monolayer for high-performance water splitting electrocatalysts

We report on the performance of hexagonal silicon (hSi)-based electrocatalysts with lattice substitution using a single Ge (Ge/hSi) and a single Ti (Ti/hSi) in promoting the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) via the water splitting process. All data provided in this work is generated using density functional theory (DFT)- based total energy calculations. Based on the results, we conclude that both Ge/hSi and Ti/hSi surfaces have the potential to be developed as HER and OER electrocatalysts. The Ti/hSi electrocatalyst outperforms Ge/hSi in terms of performance in decomposing H2O molecules and promoting OER due to its twice lower overpotential than the OER overpotential on the Ge/hSi surface. However, in comparison to H bonding to the Ti/hSi surface, Ge/hSi is somewhat weaker at binding H∗, making Ge/hSi slightly easier to induce HER compared to Ti/hSi. These findings will have a considerable impact on the development of new non-Pt group metal (non-PGM) catalysts.

Two-dimensional phthalocyanine-based covalent organic frameworks as high-performance electrocatalysts for oxygen reduction and oxygen evolution

It is crucial to use efficient catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in energy conversion devices, aiming to mitigate energy crises. The catalytic activity of MPc-PI-COF-1 and MPc-PI-COF-2 (M = Mn, Fe, Co) towards ORR and OER is investigated systematically based on DFT methods. Different M-N4 sites can adjust the binding strength of oxygen-containing intermediates to effect catalysis activity, while the different linkers have only a minor effect. FePc-PI-COF-1 and MnPc-based COFs have low ORR overpotential (ηORR) values, even lower than Pt(111). For OER, CoPc-based COFs have comparable OER overpotential (ηOER) values to that on RuO2(110). To sum up, MnPc-based COFs are efficient ORR catalysts, and CoPc-based COFs have high OER activity. FePc-PI-COF-1 could be served as an effective bifunctional catalyst with a ηORR value of 0.38 V and ηOER value of 0.56 V. Moreover, FePc-PI-COF-1 exhibits exceptional resistance to various impurity gases, indicating its strong tolerance against poisoning. These study offer valuable insights for the rational discovery of reticular materials as highly efficient electrocatalysts.

Regulating Lattice Oxygen of Co3O4/CeO2 Heterojunction Nanonetworks for Enhanced Oxygen Evolution

Developing efficient and cost‐effective electrocatalysts as substitutes for noble metals remains a big challenge, which demands significant advancements in both material designing and mechanistic understanding. Herein, Co3O4/CeO2 heterojunction nanonetworks are successfully synthesized through metal organic framework precursor. Notably, Co3O4/CeO2 heterojunctions can effectively regulate electronic structure of Co3O4, thus inducing oxygen atom from Co3O4 lattice to participating in oxygen evolution reaction (OER) via lattice oxygen‐mediated mechanism, which reduces reaction overpotential. Additionally, the porous network structure can facilitate electrolyte transfer and provide more active sites for electrocatalytic reactions. Consequently, Co3O4/CeO2 heterojunction nanonetworks exhibit great electrocatalytic performance and high durability, requiring only an OER overpotential of 259 mV at current density of 100 mA cm−2 in 1 M KOH, markedly outperforming Co3O4 nanocatalysts (309 mV) and showing promising potential as substitutable non‐noble OER catalysts.

Continuous medium approach to approximate the high concentrated aqueous electrolyte with different types of electrochemical structure.

Superconcentrated aqueous electrolytes have recently emerged as a new class of electrolytes, called water-in-salt electrolytes. They are distinguished, in both weight and volume, by a quantity of salt greater than water. Currently, these electrolytes are attracting major interest, particularly for application in aqueous rechargeable batteries. These electrolytes have only a small amount of free water due to an ultrahigh salt concentration. Consequently, the electrochemical stability window of water is wider than the predicted thermodynamic value of 1.23V. Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been shown to be shifted to more negative and positive potentials, respectively. The decrease in free water population is recognized as being involved in the increase in the electrochemical stability window of water. Here, we study the quantitative contribution of the decrease in the free water molecule concentration to the permittivity of the solution and of the activity of water to the OER and HER overpotentials when the salt concentration increases. We compare our model with that of Kornyshev and get three types of electrolyte structures: diluted, gradient of water contents, and aggregation. The theoretical calculation of the redox potentials of the OER and HER is compared with the experimentally determined electrochemical properties of aqueous LiTFSI electrolytes.

Highly mixed high-energy d-orbital states enhance oxygen evolution reactions in spinel catalysts

Design, synthesis, and engineering of electrocatalysts for the oxygen evolution reaction (OER) are essential for attaining desirable electrocatalytic performance towards practical implementation. Emerging spinel-type OER catalysts have not reached the desirable activity and durability, thus demanding critical research to advance the field. To achieve enhanced OER performance for spinel-type OER catalysts, we present an efficient strategy of electronic structure modulation of central metal atoms. Modulation of the electronic properties of the Zn and Co atoms through the counter anionic components (O, S, and Se) regulates the adsorption of oxygen intermediates and thus enhances OER activity, which is systematically demonstrated using Density Functional Theory (DFT) calculation. Although the zinc cobalt selenide catalyst showed the less pronounced trigonal distortion, the mixing of eg orbitals with selenium accounts for the experimentally observed enhancement in OER activity. The result is, in contrast to the benchmark catalyst made of RuO2, ZnCo2Se4@rGO demonstrated lower OER overpotential (η10 = 302 mV) and Tafel slope (58 mV dec−1) as well as greater durability at 10 mA cm−2 for 50 h. The implementation of this strategy in several spinel-type catalysts could improve their electrocatalytic performance.

In situ lithiation modulation of LiNi0.8Co0.1Mn0.1O2 as bifunctional electrocatalysts for highly efficient overall water splitting

LiNi0.8Co0.1Mn0.1O2 (NCM811) is a common cathode material in lithium-ion batteries (LIBs), and the ever-increasing consumption of large quantities of LIBs raises critical concerns about their recycling. Herein, we propose an in-situ lithiation route to tune the structure and electrocatalytic properties of NCM811 by Li+ intercalation and exfoliation in LIBs. In this strategy, the morphology and microstructure of the lithiated NCM811 can be controlled by a specified discharge voltage. The lithiation modulation effectively converted the large NCM811 particles into many flower-like nanosheets. The resulting nanosheets are interconnected and have a rich porous structure, which is conducive to the complete penetration and diffusion of electrolytes and accelerating the charge transfer rate. Moreover, oxygen vacancies and amorphous regions were induced in the nanosheets to provide more active sites. The novel lithiation-modulated nanosheets demonstrate high activity and bifunctional characteristics for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Specifically, the lithiated NCM811 nanosheets demonstrate a low HER overpotential of 58 mV@10 mA cm−2 and OER overpotential of 222@10 mA cm−2. The assembled electrolytic cell for overall water-splitting requires only 1.74 V to reach 100 mA cm−2 with outstanding durability. This work provides a unique strategy for structural modulation of NCM811 cathode in LIBs as high-performance electrocatalysts for water splitting, and demonstrates a high-value recycle of spent LIB electrodes.

Spin-State Modulation on Metal-Organic Frameworks for Electrocatalytic Oxygen Evolution.

Electrochemical oxygen evolution reaction (OER) kinetics are heavily correlated with hybridization of the transition metal d-orbital and oxygen intermediate p-orbital, which dictates the barriers of intermediate adsorption/desorption on the active sites of catalysts. Herein, a strategy is developed involving strain engineering and coordination regulation to enhance the hybridization of Ni 3d and O 2p orbitals, and the as-synthesized Ni-2,6-naphthalenedicarboxylic acid metal-organic framework (DD-Ni-NDA) nanosheets deliver a low OER overpotential of 260mV to reach 10mAcm-2 . By integrating an alkaline anion exchange membrane electrolyzer and Pt/C electrode, 200 and 500mAcm-2 current densities are reached with cell voltages of 1.6 and 2.1V, respectively. When loaded on a BiVO4 photoanode, the nanosheet enables highly active solar-driven water oxygen. Structural characterizations together with theoretical calculations reveal that the spin state of the centre Ni atoms is regulated by the tensile strain and unsaturated coordination defects in DD-Ni-NDA, and such spin regulation facilitates spin-dependent charge transfer of the OER. Molecular orbital hybridization analysis reveals the mechanism of OH* and OOH* adsorption energy regulation by changes in the DD-Ni-NDA spin state, which provides a deeper understanding of the electronic structure design of catalysts for the OER.

Combining First-Principles Modeling and Symbolic Regression for Designing Efficient Single-Atom Catalysts in the Oxygen Evolution Reaction on Mo2CO2 MXenes.

In this study, we address the significant challenge of overcoming limitations in the catalytic efficiency for the oxygen evolution reaction (OER). The current linear scaling relationships hinder the optimization of the electrocatalytic performance. To tackle this issue, we investigate the potential of designing single-atom catalysts (SACs) on Mo2CO2 MXenes for electrochemical OER using first-principles modeling simulations. By employing the Electrochemical Step Symmetry Index (ESSI) method, we assess OER intermediates to fine-tune the activity and identify the optimal SAC for Mo2CO2 MXenes. Our findings reveal that both Ag and Cu exhibit effectiveness as single atoms for enhancing OER activity on Mo2CO2 MXenes. However, among the 21 chosen transition metals (TMs) in this study, Cu stands out as the best catalyst for tweaking the overpotential (ηOER). This is due to Cu's lowest overpotential compared to other TMs, which makes it more favorable for the OER performance. On the other hand, Ag is closely aligned with ESSI = ηOER, making the tuning of its overpotential more challenging. Furthermore, we employ symbolic regression analysis to identify the significant factors that exhibit a correlation with the OER overpotential. By utilizing this approach, we derive mathematical formulas for the overpotential and identify key descriptors that affect the catalytic efficiency in the electrochemical OER on Mo2CO2 MXenes. This comprehensive investigation not only sheds light on the potential of MXenes in advanced electrocatalytic processes but also highlights the prospect of improved activity and selectivity in OER applications.

Transition metal doped WSi2N4 monolayer for water splitting electrocatalysts: a first-principles study

High-performance water splitting electrocatalysts are urgently needed in the face of the environmental degradation and energy crisis. The first principles method was used in this study to systematically examine the electronic characteristics of transition metal (Sc, Ti, V, Cr, Mn, Fe, and Ru) doped WSi2N4 (TM@WSi2N4) and its potential as oxygen evolution reaction (OER) catalysts. Our study shows that the doping of TM atoms significantly improves the catalytic performance of TM@WSi2N4, especially Fe@WSi2N4 shows a low overpotential (η OER = 470 mV). Interestingly, we found that integrated-crystal orbital Hamilton population and d-band center can be used as descriptors to explain the high catalytic activity of Fe@WSi2N4. Subsequently, Fe@WSi2N4 exhibits the best hydrogen evolution reaction (HER) activity with a universal overpotential of 47 mV on N1 sites. According to our research, Fe@WSi2N4 offers a promising substitute for precious metals as a catalyst for overall water splitting with low OER and HER overpotentials.

Establishing theoretical landscapes for identifying basal plane active sites in MBene toward multifunctional HER, OER, and ORR catalysts

Exploring multifunctional electrocatalysts to realize efficient hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is urgently desired for developing novel renewable energy storage and conversion technologies. However, integrating these three merits in one single catalyst remains a big challenge due to the difficulty in balancing the adsorption strengths of multiple reaction intermediates. Herein, through first-principles calculations, we systematically investigated the electrocatalytic activity of M2B2, M3B4, and M4B6 type MBenes (M = Cr, Mn, Fe, Co, and Ni) for multifunctional HER, OER, and ORR. The results indicate that most of the investigated MBenes show outstanding catalytic activity for HER with hydrogen adsorption Gibbs free energy close to the optimal value (0 eV). Thereinto, Ni2B2 and Co3B4 MBenes can be promising multifunctional HER/OER/ORR electrocatalysts, and Fe3B4 MBene is expected to be a promising bifunctional electrocatalyst for HER/ORR. Especially, Ni2B2 MBene is even better than the benchmark RuO2 catalyst with ultralow low overpotentials of 0.26 and 0.30 V for OER and ORR, respectively. Then, we proposed that the overpotentials of OER/ORR can be well described by the varied ΔGOH* on MBene, which has been further illuminated through the d-band center and charge transfer analysis. Importantly, new scaling relations between the adsorption energies of OOH* and O* on MBenes have been established, where ΔGOOH* and ΔGO* possess different slopes versus ΔGOH*, allowing the significantly lower overpotentials of OER and ORR to be achieved. This work provides not only promising multifunctional HER/OER/ORR electrocatalysts but also new scaling relations to achieve the rational design of MBene-based electrocatalysts.