Catalytic Activity For Hydrogen Evolution Reaction Research Articles

HER catalytic activity and regulation of a transition metal atom-anchored BC3 monolayer: a first-principles study.

An atomic-level understanding of the hydrogen evolution reaction (HER) on a transition metal (TM) atom-anchored 2D monolayer is vital to explore highly efficient catalysts for hydrogen production. Here, the catalytic activities and modulation of TM atom (Ti, Fe, Cu, Zn, Mo, Ag, Au)-doped BC3 monolayers are investigated by first-principles calculations. Au@BC3 and Fe@BC3 are proven to be potentially excellent HER catalysts. Partial oxidation engineering on Zn@BC3 could improve its performance. Au@BC3 and Ti, Cu and Mo-anchored BC3 with the support of a NbB2 (0001) surface are expected to replace Pt due to the Gibbs free energy changes extremely close to zero. It is revealed that the catalytic activity of the adsorption site is highly related to the degree of charge transfer between the adsorption site and substrate.

Insights of the efficient hydrogen evolution reaction performance in bimetallic Au4Cu2 nanoclusters.

The design of efficient electrocatalysts for improving hydrogen evolution reaction (HER) performance using atomically precise metal nanoclusters (NCs) is an emerging area of research. Here, we have studied the HER electrocatalytic performance of monometallic Cu6 and Au6 nanoclusters and bimetallic Au4Cu2 nanoclusters. A bimetallic Au4Cu2/MoS2 composite exhibits excellent HER catalytic activity with an overpotential (η10) of 155 mV vs. reversible hydrogen electrode observed at 10 mA cm-2 current density. The improved HER performance in Au4Cu2 is due to the increased electrochemically active surface area (ECSA), and Au4Cu2 NCs exhibits better stability than Cu6 and Au6 systems and bare MoS2. This augmentation offers a greater number of active sites for the favorable adsorption of reaction intermediates. Furthermore, by employing X-ray photoelectron spectroscopy (XPS) and Raman analysis, the kinetics of HER in the Au4Cu2/MoS2 composite were elucidated, attributing the favorable performance to better electronic interactions occurring at the interface between Au4Cu2 NCs and the MoS2 substrate. Theoretical analysis reveals that the inherent catalytic enhancement in Au4Cu2/MoS2 is due to favorable H atom adsorption over it and the smallest ΔGH* value. The downshift in the d-band of the Au4Cu2/MoS2 composite influences the binding energy of intermediate catalytic species. This new catalyst sheds light on the structure-property relationship for improving electrocatalytic performance at the atomic level.

Theoretical design of active Ga2O3 monolayer-based catalysts for electrocatalytic HER.

Electrocatalytic hydrogen evolution reaction (HER) offers a sustainable and clean route for hydrogen production. Developing a high-efficiency HER catalyst is extremely essential toward meeting future energy needs. Herein, the Sn-doped Ga2O3 monolayer, O-defected Ga2O3 monolayer, and Ru-adsorbed Ga2O3 monolayer with high electrocatalytic performances toward HER are reported (their H adsorption free energies are 0.169, 0.126 and 0.065 eV, respectively). The Sn-doped Ga2O3 monolayer follows the Volmer-Heyrovsky mechanism, and the O-defected Ga2O3 monolayer and Ru-adsorbed Ga2O3 monolayer are suitable for Volmer-Tafel mechanisms. The strain from -4% to 4% in the X- or Y-direction could linearly modulate the HER activities of the Sn-doped Ga2O3 monolayer and O-defected Ga2O3 monolayer. The Sn-doped Ga2O3 monolayer, O-defected Ga2O3 monolayer, and Ru-adsorbed Ga2O3 monolayer only manifest high HER catalytic activities in the strong acidic media. These phenomena can provide a rational approach to enhance the HER activity for Ga2O3 monolayer-based materials.

Rational design of pt-decorated nickel phosphide for boosting the catalytic activity toward alkaline water splitting

Designing efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential to upgrade the existing energy structure. Pt-based catalysts have extraordinary catalytic activity for HER, but they are limited by high costs and low reserves. Herein, we report that the combination of Pt and nickel phosphides can effectively reduce the amount of Pt and improve the catalytic activity. The synthesized Pt/Ni-P/NF catalyst exhibits excellent HER activity which requires only 86 mV overpotential at a current density of 10 mA cm−2, together with a Tafel slope of 66.6 mV dec−1, and also exhibits high stability for 100 h at a current density of 100 mA cm−2 with small decay. When Pt/Ni-P/NF and Ni-P/NF were used as the cathode and anode of an alkaline electrolytic cell (Pt/Ni-P/NF || Ni-P/NF), the cell voltage was only 1.59 V at a current density of 10 mA cm−2. This work provides a new method for designing high-activity and high-stability catalysts for industrial water splitting.

Operando XAS Investigation of Bimetallic Iron−Molybdenum Sulfide Electrocatalysts for the Hydrogen Evolution Reaction

Nowadays green hydrogen production has been seen as a key element for the future development and large-scale implementation of fuel cell technology, while electrolyzer technologies represent the most advanced methods for producing pure hydrogen from water. The preparation of efficient, cost-effective, and stable noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) at the cathode of proton exchange membrane electrolyzers (PEMEL) remains one of the main issues that need to be solved to allow the widespread use of hydrogen as an energy carrier.Molybdenum sulfide (MoSx) is a well-known material showing promising HER catalytic activity, especially in its amorphous state and when doped with other transition metals1. The successful implementation of a bimetallic iron-molybdenum sulfide electrocatalyst for HER into a PEM electrolyzer has been recently reported2. However, the structure of their active sites requires a more elaborate investigation. In this study, we employed operando X-ray absorption spectroscopy to identify potential-induced structural and electronic changes in FeMoSmw bimetallic iron−molybdenum sulfides and MoSmw obtained by a microwave irradiation synthetic approach 2. Extended X-ray absorption fine structure (EXAFS) spectra at Mo and Fe K-edges under operando conditions provided us with accurate structural characterization of the catalytic active sites: while an amorphous MoS3 phase is detected and retained in both MoSmw and FeMoSmw at low potential, a FeS phase is observed at the Fe K-edge, likely explaining the better performance of the bimetallic iron-molybdenum sulfides electrocatalysts compared to iron-free molybdenum sulfides.

Immobilizing Bimetallic RuCo Nanoalloys on Few-Layered MXene as a Robust Bifunctional Electrocatalyst for Overall Water Splitting.

Doping Co atoms into Ru lattices can tune the electronic structure of active sites, and the conductive MXene can adjust the electrical conductivity of catalysts, which are both favorable for improving the electrocatalytic activity of the catalyst for water splitting. Here, ruthenium-cobalt bimetallic nanoalloys coupled with exfoliated Ti3 C2 Tx MXene (RuCo-Ti3 C2 Tx ) have been constructed by ice-templated and thermal activation. Due to the strong interaction between the RuCo nanoalloys and conductive MXene, RuCo-Ti3 C2 Tx not only exhibits an excellent hydrogen evolution reaction (HER) performance with a low overpotential and Tafel slope (60 mV, 34.8 mV dec-1 in 0.5 M H2 SO4 and 52 mV, 38.7 mV dec-1 in 1 M KOH), but also good oxygen evolution reaction (OER) performance in an alkaline electrolyte (266 mV, 111.1 mV dec-1 in 1 M KOH). The assembled RuCo-Ti3 C2 Tx ||RuCo-Ti3 C2 Tx electrolyzer requires a lower potential (1.56 V) than does the Pt/C||RuO2 electrolyzer at 10 mA cm-2 . A boosted catalytic HER activity from immobilizing the RuCo nanoalloys on MXene was unveiled by density functional theory calculations. This study provides a feasible and efficient strategy for developing MXene-based catalysts for overall water splitting.

2H-2M Phase Control of WSe2 Nanosheets by Se Enrichment Toward Enhanced Electrocatalytic Hydrogen Evolution Reaction.

The phase control of transition metal dichalcogenides (TMDs) is an intriguing approach for tuning the electronic structure toward extensive applications. In this study, WSe2 nanosheets synthesized via a colloidal reaction exhibit a phase conversion from semiconducting 2H to metallic 2M under Se-rich growth conditions (i.e., increasing the concentration of Se precursor or lowering the growth temperature). High-resolution scanning transmission electron microscopy images are used to identify the stacking sequence of the 2M phase, which is distinctive from that of the 1T' phase. First-principles calculations employing various Se-rich models (intercalation and substitution) indicated that Se enrichment induces conversion to the 2M phase. The 2M phase WSe2 nanosheets with the Se excess exhibited enhanced electrocatalytic performance in the hydrogen evolution reaction (HER). In situ X-ray absorption fine structure studies suggested that the excess Se atoms in the 2M phase WSe2 enhanced the HER catalytic activity, which is supported by the Gibbs free energy (ΔGH* ) of H adsorption and the Fermi abundance function. These results provide an appealing strategy for phase control of TMD catalysts.

First principles study on high-efficient overall water splitting by anchoring cobalt boride with transition metal atoms

Developing efficient, low-cost electrocatalysts is of great significance for improving the efficiency of water electrolysis. In this work, the structure, electronic properties, hydrogen evolution reaction (HER), and oxygen evolution reaction (OER) activity of transition metal-doped cobalt boride (TM@CoB) were thoroughly investigated using density functional theory. Ni@CoB and Cu@CoB exhibited excellent catalytic activity for HER. Specifically, Ni@CoB demonstrated a ΔGH* value of 0.0537 eV, surpassing the most commonly used Pt catalyst. The reaction mechanism followed the Heyrovsky mechanism, and it also showed good OER activity, making it a potential candidate for OER electrocatalysts. Compared to the original CoB, Ni@CoB showed a 70 % improvement in HER activity and a 65 % improvement in OER activity. The Ni@CoB catalyst was synthesized, and its catalytic performance was experimentally validated. This work offers a new perspective and guidance for the development of bifunctional electrocatalysts.

Atomic-level polarization in electric fields of defects for electrocatalysis

The thriving field of atomic defect engineering towards advanced electrocatalysis relies on the critical role of electric field polarization at the atomic scale. While this is proposed theoretically, the spatial configuration, orientation, and correlation with specific catalytic properties of materials are yet to be understood. Here, by targeting monolayer MoS2 rich in atomic defects, we pioneer the direct visualization of electric field polarization of such atomic defects by combining advanced electron microscopy with differential phase contrast technology. It is revealed that the asymmetric charge distribution caused by the polarization facilitates the adsorption of H*, which originally activates the atomic defect sites for catalytic hydrogen evolution reaction (HER). Then, it has been experimentally proven that atomic-level polarization in electric fields can enhance catalytic HER activity. This work bridges the long-existing gap between the atomic defects and advanced electrocatalysis by directly revealing the angstrom-scale electric field polarization and correlating it with the as-tuned catalytic properties of materials; the methodology proposed here could also inspire future studies focusing on catalytic mechanism understanding and structure-property-performance relationship.

Enhanced interfacial charge transfer by oxygen vacancies in ZnCdS/NiCo-LDH heterojunction for efficient H2 evolution

The elaborate modulation of charge transfer in Z-scheme heterojunctions is of significant importance yet poses a formidable challenge for achieving efficient photocatalytic hydrogen production. The present study reports the fabrication of ZnCdS nanoparticle wrapped by NiCo-layered double hydroxide with enriched oxygen vacancies (ZCS@LDH-Ov) was fabricated, which exhibits enhanced interfacial binding and internal electric field (IEF) in comparison to ZCS@LDH. Under visible-light irradiation, the as-prepared ZCS@LDH-Ov exhibits a superior photocatalytic H2 production rate of up to 2.68 mmol·g−1·h−1, which is approximately 9.24-fold and 2.68-fold of the pristine ZnCdS and ZCS@LDH, respectively. The stability of the photocatalyst after 5 cycles is obviously enhanced, with ZCS@LDH exhibiting a remaining hydrogen evolution reaction (HER) rate of 52.7 % and ZCS@LDH-Ov demonstrating an impressive remaining rate of 98.2 %. The Z-scheme facilitates rapid charge transfer and efficient separation, thereby enhancing the catalytic activity for HER. The excellent recyclability of ZCS@LDH-Ov is primarily attributed to enhanced photo-corrosion resistance of ZnCdS, which can be ascribed to the efficient transfer of photo-generated holes through a rapid interfacial charge pathway.

High-Performance Hydrogen Evolution Reaction Catalysts in Two-Dimensional Nodal Line Semimetals.

The discipline of topological quantum catalysts (TQCs) is developing due to the emergence of exotic quantum materials and their corresponding catalysts. Although a series of 3D TQCs with different topological signatures are proposed, the emergence of 2D TQCs in 2D topological semimetals is still rarely touched by others. As a typical example, we proposed that the 2D nodal line semimetal Cu2Si monolayer is a superior TQC for hydrogen evolution reaction (HER). Using first-principles calculations, we find that the Cu2Si monolayer exhibits two Γ-centered nodal lines (L1 and L2) in the kz = 0 plane. The Gibbs free energy (ΔGH*) of Cu2Si is as low as 0.195 eV, comparable to that of Pt, and better than other conventional catalysts. Moreover, it is found that changing the position of nodal lines (relative to the Fermi level) under different electron/hole conditions can effectively affect the catalytic activity of HER. Besides Cu2Si, the emergence of high HER performance in other 2D nodal line semimetals, Ti3C2, Cr2S3, ScCl, and CuSe, is also theoretically determined. These results highlight the critical role of nodal lines in studying electrocatalytic mechanisms for TQCs and benefit the seeking of high-performance HER catalysts without noble metals on a 2D scale.

Ligand Modulation of Active Sites to Promote Cobalt-Doped 1T-MoS2 Electrocatalytic Hydrogen Evolution in Alkaline Media.

Highly efficient hydrogen evolution reaction (HER) electrocatalyst will determine the mass distributions of hydrogen-powered clean technologies, while still faces grand challenges. In this work, a synergistic ligand modulation plus Co doping strategy is applied to 1T-MoS2 catalyst via CoMo-metal-organic frameworks precursors, boosting the HER catalytic activity and durability of 1T-MoS2 . Confirmed by Cs corrected transmission electron microscope and X-ray absorption spectroscopy, the polydentate 1,2-bis(4-pyridyl)ethane ligand can stably link with two-dimensional 1T-MoS2 layers through cobalt sites to expand interlayer spacing of MoS2 (Co-1T-MoS2 -bpe), which promotes active site exposure, accelerates water dissociation, and optimizes the adsorption and desorption of H in alkaline HER processes. Theoretical calculations indicate the promotions in the electronic structure of 1T-MoS2 originate in the formation of three-dimensional metal-organic constructs by linking π-conjugated ligand, which weakens the hybridization between Mo-3d and S-2p orbitals, and in turn makes S-2p orbital more suitable for hybridization with H-1s orbital. Therefore, Co-1T-MoS2 -bpe exhibits excellent stability and exceedingly low overpotential for alkaline HER (118 mV at 10 mA cm-2 ). In addition, integrated into an anion-exchange membrane water electrolyzer, Co-1T-MoS2 -bpe is much superior to the Pt/C catalyst at the large current densities. This study provides a feasible ligand modulation strategy for designs of two-dimensional catalysts.

Ligand Modulation of Active Sites to Promote Cobalt‐Doped 1T‐MoS2 Electrocatalytic Hydrogen Evolution in Alkaline Media

AbstractHighly efficient hydrogen evolution reaction (HER) electrocatalyst will determine the mass distributions of hydrogen‐powered clean technologies, while still faces grand challenges. In this work, a synergistic ligand modulation plus Co doping strategy is applied to 1T−MoS2 catalyst via CoMo‐metal‐organic frameworks precursors, boosting the HER catalytic activity and durability of 1T−MoS2. Confirmed by Cs corrected transmission electron microscope and X‐ray absorption spectroscopy, the polydentate 1,2‐bis(4‐pyridyl)ethane ligand can stably link with two‐dimensional 1T−MoS2 layers through cobalt sites to expand interlayer spacing of MoS2 (Co−1T−MoS2‐bpe), which promotes active site exposure, accelerates water dissociation, and optimizes the adsorption and desorption of H in alkaline HER processes. Theoretical calculations indicate the promotions in the electronic structure of 1T−MoS2 originate in the formation of three‐dimensional metal‐organic constructs by linking π‐conjugated ligand, which weakens the hybridization between Mo‐3d and S‐2p orbitals, and in turn makes S‐2p orbital more suitable for hybridization with H‐1s orbital. Therefore, Co−1T−MoS2‐bpe exhibits excellent stability and exceedingly low overpotential for alkaline HER (118 mV at 10 mA cm−2). In addition, integrated into an anion‐exchange membrane water electrolyzer, Co−1T−MoS2‐bpe is much superior to the Pt/C catalyst at the large current densities. This study provides a feasible ligand modulation strategy for designs of two‐dimensional catalysts.

Ammonium ions intercalated 1T/2H-MoS2 with increased interlayer spacing for high-efficient electrocatalytic hydrogen evolution reaction

As an effective catalyst for the hydrogen evolution reaction (HER), the catalytic performance of MoS2 is largely depends on its conductivity and active sites. Herein, we design and prepare a 1T/2H-MoS2 material with increased interlayer spacing for accelerating HER catalytic activity. The increased interlayer spacing can expose more active sites and also endow large channels for ion transport. Meanwhile, the effective combination of conductive 1T and 2H phase MoS2, and the presence of phase boundaries further improve the catalytic activity. Accordingly, the prepared catalyst delivers superior HER performance of a low overpotential (159.9 mV@10 mA cm−2) and a low Tafel slope (55.5 mV dec-1). Furthermore, it also exhibits a remarkable electrochemical stability under acidic condition. This work may provide a reasonable strategy for the preparation of highly active MoS2 based catalysts with increased interlayer spacing.

Synthesis of NiBTC metal-organic framework thin layers on nickel foam by different electrochemical methods: A comparative study for hydrogen evolution reaction

In this study, for the first time two electrochemical synthesis techniques including cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used for MOF synthesis. The Ni3(BTC)2 electrocatalyst was synthesized and deposited without any binder, for a short time and at ambient temperature on the nickel foam substrate. Morphology studies showed that the LSV method leads to preserving the 3D structure of nickel foam which promotes the catalytic activity. It should be noted that two parameters, such as voltage range and scan rate, were optimized during the LSV method. Moreover, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to confirm the MOF's structural integrity. Furthermore, the Brunauer-Emmett-Teller (BET) method verified the porous structure of NiBTC MOF. Additionally, the performance of bare and modified nickel foams was also examined for the hydrogen evolution reaction (HER) which demonstrated the tremendous potential of NiBTC/Ni foam in HER catalytic activity.

Amorphous MoS2 Decorated Ni3 S2 with a Core-shell Structure of Urchin-Like on Nickel-Foam Efficient Hydrogen Evolution in Acidic and Alkaline Media.

The large-scale commercialization of the hydrogen evolution reaction (HER) necessitates the development of cost-effective and highly efficient electrocatalysts. Although transition metal sulfides, such as MoS2 and Ni3 S2 , hold great potential in the field of HER, their catalytic performance has been unsatisfactory due to incomplete exposure of active sites and poor electrical conductivity. In this work, via a simple hydrothermal strategy, amorphous MoS2 nanoshells in the form of urchin-like MoS2 -Ni3 S2 core-shell heterogeneous structure is realized and in situ loaded on nickel foam (A-MoS2 -Ni3 S2 -NF). In particular, XPS analysis results show that the coupling of amorphous MoS2 and Ni3 S2 makes the electrode surface exhibit electron-abundant property, which will have a positive impact on HER catalytic activity. In addition, the fully exposed active site of amorphous MoS2 is another crucial factor contributing to its high catalytic performance of A-MoS2 -Ni3 S2 -NF electrode. In particular, at a current density of 10mA cm⁻2 , the overpotential of electrode is 95mV (1.0m KOH) and 145mV (0.5m H2 SO4 ). This work highlights the importance of amorphous MoS2 and MoS2 -Ni3 S2 of sea-urchin core-shell structure in optimizing HER performance, which provides an important reference for HER research.

Size and Synergy Effects of Ultrafine 2.6 nm CoNi Nanoparticles Within 3D Crisscross N‐Doped Porous Carbon Nanosheets for Efficient Water Splitting

AbstractA non‐precious metal‐based catalyst for water electrolysis provides great promise for cost‐effective and highly efficient sustainable hydrogen production. It herein rationally synthesizes uniform superminiature CoNi nanoparticles (2.6 nm) embedded in 3D N‐doped randomly oriented and erected porous carbon nanosheets (CoNi@N‐PCNS). Taking advantage of the large specific surface area, expedited intermediate transport, and effectively exposed active sites of the hierarchical architecture, located CoNi nanoparticles yield a high atom utilization efficiency. Density functional theory calculations indicate that synergetic and cooperative interactions inside CoNi alloy modulate the d‐band center, leading to a moderate adsorption and desorption energy of reaction intermediates, further accelerating both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. Accordingly, the as‐synthesized CoNi@N‐PCNS catalyst establishes superb catalytic activities for HER and OER, revealing overpotentials of 71.2 and 263.8 mV at 10 mA cm−2, respectively. Remarkably, when assembled as a two‐electrode electrolyzer, a satisfying cell voltage of 1.59 V at 10 mA cm−2, and superior stability are demonstrated, highlighting great promise toward water electrolysis.

MoS2 catalysts with adjustable size and layer structure derived from polyoxometalates-ionic liquids complexes for hydrogen production and hydrogenation

In the period of energy conversion, the effective utilization of fossil fuels and the development of new energy sources are becoming extremely imperative. MoS2 have excellent catalytic activity for fuel hydrogenation and hydrogen production. However, the synthesis of highly dispersed MoS2 that can expose more active sites has been challenging. Herein, (DODA)6Mo7O24 with organic–inorganic core–shell structure was prepared by POMs-ILs (polyoxometalates-ionic liquids) self-assembly. MoS2 with adjustable size and layer structure derived from (DODA)6Mo7O24 by controllable confined-sulfidation effect for hydrogenation and hydrogen evolution reaction (HER). Among them, MoS2 (T280S1:4t30) has the lowest overpotential, and only 200 mV is needed to reach the current density of 10 mA·cm−2. At the same time, it has the optimal hydrogenation performance with the highest selectivity for octahydroanthracene and perhydroanthracene, along with a hydrogenation percentage of 48.04 % in the process of anthracene hydrogenation. Density functional theory demonstrated that the monolayer MoS2 was more favorable for water molecule dissociation and hydrogen molecule activation, which proves that the MoS2 has excellent catalytic activity for HER and hydrogenation simultaneously. This work is instructive for the synthesis of MoS2 and its application in HER and hydrogenation.

Mo2C nanocrystalline coupling with Ni encapsulated in N-doped fibrous carbon network as bifunctional catalysts towards advanced anion exchange membrane electrolyzers

Anion exchange membrane water electrolysis (AEMWE) has been considered to be the promising approach for cost-effective hydrogen production. However, the noble metal catalysts of AEM enable it still under the early stage of development. Herein, Mo2C nanocrystalline coupling with Ni have been successfully encapsulated into robust carbonaceous network (Mo2C/NC@0.5Ni) as inexpensive transition metal catalysts for AEM electrolyzers. The Mo2C nanocrystals are uniformly confined in N doped porous carbon network which is derived from the decomposition of PVP and urea during carbonation process. Importantly, rational designed Ni layers are also coated on the surface of the network structure. When utilized as bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), the Mo2C/NC@ 0.5Ni can achieve desirable overpotentials of 103 mV and 307 mV at a current density of 10 mA cm−2 in 1 M KOH, respectively. Furthermore, the Mo2C/NC@ 0.5Ni‖Mo2C/NC@ 0.5Ni AEM electrolyzers requires only a voltage of 1.9 V to reach a current density of 110.5 mA cm−2 with remarkable durability over 50 h. Numerous interconnected porous structure and defects caused by N doping can provide abundant active sites, facilitate electrons transportations and suppress the aggregation of inner Mo2C. Particularly, the conductive Ni layers could effectively improve the structural strength and induce the synergistic effect with Mo2C component, thereby, improving the catalytic activity and stability. In addition, the DFT calculation results indicate that the Mo2C/NC@ 0.5Ni catalyst has a lower Gibbs free energy of hydrogen adsorption (ΔGH*=−0.21 eV), which is beneficial to its HER catalytic activity. This work provides an insight in developing advanced AEMWE for high efficient and green hydrogen production.

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.