Catalytic Activity In Reaction Research Articles

Cascade Anchoring Strategy for Fabricating High-Loading Pt Single Atoms as Bifunctional Catalysts for Electrocatalytic Hydrogen Evolution and Oxygen Reduction Reactions.

Carbon supports containing single-atomically dispersed metal-Nx (denoted as MSAC-NxCy, x, y: coordination number) have attracted increasing attention due to their superb performance in heterogeneous catalysis. However, large-scale controllable preparation of single-atom catalysts (SACs) with high concentration of supported metal-Nx is still a big challenge because of the metal atom agglomeration during synthesis at high density and temperatures. Herein, we report a stepwise anchoring strategy from a 1,10-o-phenanthroline Pt chelate to an Nx-doped carbon (NxCy) with isolated Pt single-atom catalysts (PtSAC-NxCy) containing Pt loadings up to 5.31 wt % measured via energy-dispersive X-ray spectroscopy (EDS). The results show that 1,10-o-phenanthroline Pt chelate predominantly contributes to the formation of chelate single metal sites that bind tightly to platinum ions to prevent metal atoms from aggregating, resulting in high metal loading. The high-loading PtSAC-NxCy exhibits a low hydrogen evolution (HER) overpotential of 24 mV at 0.010 A cm-2 current density with a relatively small Tafel gradient of 60.25 mV dec-1 and excellent stable performance. In addition, the PtSAC-NxCy catalyst shows excellent oxygen reduction reaction (ORR) catalytic activity with good stability, represented by the fast ORR kinetics under high-potential conditions. Theoretical calculations show that PtSAC-NC3 (x = 1, y = 3) offers a lower H2O activation energy barrier than Pt nanoparticles. The adsorption free energy of a H atom on a Pt single-atom site is lower than that on a Pt cluster, which is easier for H2 desorption. This study provides a potentially powerful cascade anchoring strategy in the design of other stable MSAC-NxCy catalysts with high-density metal-Nx sites for the HER and ORR.

Colossal figure of merit and compelling HER catalytic activity of holey graphyne

Herein, we have conducted a comprehensive study to uncover the thermal transport properties and hydrogen evolution reaction catalytic activity of recently synthesized holey graphyne. Our findings disclose that holey graphyne has a direct bandgap of 1.00 eV using the HSE06 exchange–correlation functional. The absence of imaginary phonon frequencies in the phonon dispersion ensures its dynamic stability. The formation energy of holey graphyne turns out to be − 8.46 eV/atom, comparable to graphene (− 9.22 eV/atom) and h-BN (− 8.80 eV/atom). At 300 K, the Seebeck coefficient is as high as 700 μV/K at a carrier concentration of 1 × 1010 cm-2. The predicted room temperature lattice thermal conductivity (κl) of 29.3 W/mK is substantially lower than graphene (3000 W/mK) and fourfold smaller than C3N (128 W/mK). At around 335 nm thickness, the room temperature κl suppresses by 25%. The calculated p-type figure of merit (ZT) reaches a maximum of 1.50 at 300 K, higher than that of holey graphene (ZT = 1.13), γ-graphyne (ZT = 0.48), and pristine graphene (ZT = 0.55 × 10–3). It further scales up to 3.36 at 600 K. Such colossal ZT values make holey graphyne an appealing p-type thermoelectric material. Besides that, holey graphyne is a potential HER catalyst with a low overpotential of 0.20 eV, which further reduces to 0.03 eV at 2% compressive strain.

Strain engineering of the electrocatalytic activity of nitrogen-rich BeN4 Dirac monolayer for hydrogen evolution reaction

The strong bond energy and short bond length of N≡N triple bond make it a challenging target for synthesizing nitrogen-rich compounds. However, recent research has successfully fabricated atomic-thick BeN4 layers under high pressure (Bykov et al., 2021). Beryllonitrene, a new 2D material, consists of a Be atom and polymeric nitrogen chains and has anisotropic Dirac cones located near the Fermi level. This distinguishes it from graphene, which has isotropic Dirac cones, bulk PtTe2 and 2D borophene, which have Dirac cones located far from the Fermi energy. The anisotropic Dirac cones in beryllonitrene result in ultrahigh carrier mobility and the potential for direction-dependent quantum devices. In this study, we systematically investigated the hydrogen evolution reaction (HER) catalytic activity of nitrogen-rich, non-precious BeN4 monolayer using first-principles DFT calculations. Our results demonstrate that BeN4 monolayer is thermally stable, and Be vacancy is the most energetically favorable site for hydrogen adsorption. We also found the Gibbs free energy (ΔGH∗) of H∗ coverage can be tuned to an optimal value of |ΔGH∗|≤ 0.2 eV through strain engineering, significantly enhancing the HER electrocatalytic activity of BeN4 monolayer. Furthermore, we examined both the homolytic Tafel reaction and heterolytic Heyrovsky reaction for HER mechanism using reaction kinetics and AIMD simulations. These findings can contribute to the development of high-performance, non-precious, and nitrogen-rich 2D catalysts for HER in future research.

Melamine-Ag with dual functions of electrochemiluminescence luminophore and coreactant accelerators: Construction of MIP/M-Ag@MoS2-QDs sensing platform for specific detection of thiabendazole

A novel self-enhancement molecularly imprinted electrochemiluminescence (ECL) sensor (MIP/M-Ag@MoS2-QDs/GCE) was constructed to detect thiabendazole (TBZ) in food. Melamine was used as template to chelate Ag+ to prepare composite nanomaterials (M-Ag). M-Ag possesses both ECL properties and coreactant catalytic properties, which can realize the self-enhancement of ECL luminophore. MoS2-QDs with excellent edge activity and electrochemical reaction catalytic activity were used to accelerate the reaction rate of the microsystem and further enhance the ECL intensity. The specific detection method of TBZ was established by investigating the ECL response mechanism and specific recognition mechanism of MIP/M-Ag@MoS2-QDs/GCE. The ECL intensity was proportioned to the lg C(TBZ) in the linear range 5 × 10−8 mol L−1–5 × 10−5 mol L−1 with a limit detection of 1.42 × 10−8 mol L−1. The satisfactory recovery rate (83.57%–101.03%) was obtained in sample analysis, which was in good agreement with the analysis result of HPLC.

Co3O4 Nanoparticle/F, N‐codoped Graphene for High Efficiency Oxygen Reduction and Zinc‐air Battery

AbstractThe connection between the active components and supports in a catalyst is important for the high activity and long‐term stability during catalysis. Here, Co3O4 nanoparticles embedded in F, N‐doped graphene (Co3O4/F, N‐doped G) are synthesized by silicon‐hydrogen bond reduction. F and N atoms doped graphene interacts with Co3O4 nanoparticles to optimize oxygen reduction reaction (ORR) catalytic activity. The optimal Co3O4/F, N‐doped G‐2 catalyst with Co loading of 3.38 wt% shows a half‐wave potential of 0.852 V vs RHE in 0.1 M KOH solution. Furthermore, Co3O4/F, N‐doped G‐2 catalyst outputs an extremely high open circuit voltage of 1.47 V and an excellent power density of 280 mW cm−2 at current density of 450 mA cm−2 when applied to the primary Zn‐air batteries. Due to the synergetic effects from Co3O4 and supports (F, N‐doped G), Co3O4/F, N‐doped G‐2 catalyst also shows excellent stability and anti‐toxicity, and has good practical application prospects.

Facile preparation of peanut shell derivatives supported MoS2 nanosheets for hydrogen evolution reaction

A facile hydrothermal process was used to prepare peanut shells derivatives (PS)-supported MoS2 nanosheets (PS-MoS2), which showed much better hydrogen evolution reaction (HER) catalytic activity than MoS2. PS-MoS2 displayed excellent catalytic performance with lower onset overpotential (94.5 mV) and good cyclic stability. By analyzing the results of characterization of superficial properties, structure, morphological, and elemental valence state, 11.1%-PS-MoS2 exhibits exceptional catalytic activity due to an effective increase in the amount of exposure of active sites and in the content of lower valence Mo and S with higher HER activity owing to the addition of PS.

External Fields Assisted Highly Efficient Oxygen Evolution Reaction of Confined 1T-VSe2 Ferromagnetic Nanoparticles.

As a clean and effective approach, the introduction of external magnetic fields to improve the performance of catalysts has attracted extensive attention. Owing to its room-temperature ferromagnetism, chemical stability, and earth abundance, VSe2 is expected to be a promising and cost-effective ferromagnetic electrocatalyst for the accomplishment of high-efficient spin-related OER kinetics. In this work, a facile pulsed laser deposition (PLD) method combined with rapid thermal annealing (RTA) treatment is used to successfully confine monodispersed 1T-VSe2 nanoparticles in amorphous carbon matrix. As expected, with external magnetic fields of 800 mT stimulation, the confined 1T-VSe2 nanoparticles exhibit highly efficient oxygen evolution reaction (OER) catalytic activity with an overpotential of 228mV for 10mA cm-2 and remarkable durability without deactivation after >100h OER operation. The experimental results together with theoretical calculations illustrate that magnetic fields can facilitate the surface charge transfer dynamics of 1T-VSe2 , and modify the adsorption-free energy of *OOH, thus finally improving the intrinsic activity of the catalysts. This work realizes the application of ferromagnetic VSe2 electrocatalyst in highly efficient spin-dependent OER kinetics, which is expected to promote the application of transition metal chalcogenides (TMCs) in external magnetic field-assisted electrocatalysis.

M-N4-Gr/MXene Heterojunction Nanosheets as Oxygen Reduction and Evolution Reaction Catalysts: Machine Learning and Density Functional Theory Insights

MXene nanosheet materials with fast charge transfer characteristics and superior electrical conductivity are popular candidates for oxygen electrocatalysts. In this paper, the oxygen reduction and evolution reaction (ORR and OER, respectively) catalytic activities of 78 M-N4-Gr/MXene (Ti2C, Nb2C, and V2C) heterostructure nanosheets were investigated based on density functional theory (DFT) calculations and machine learning (ML) predictions. The random forest regression (RFR) algorithm proved to be the most desirable ML model for the prediction of catalytic activity with ORR/OER root mean square errors of 0.10 and 0.23 V, respectively. The obtained results show that Ni-N4-Gr/Nb2C (η*ORR = 0.31 V) and Ni-N4-Gr/V2C (η*ORR = 0.32 V) are effective ORR catalysts (prediction error of 0.03 V only), Ru-N4-Gr/Nb2C (η*OER = 0.40 V) is a promising OER catalyst, and Co-N4-Gr/V2C (η*ORR = 0.45 V/η*OER = 0.30 V) is an excellent bifunctional catalyst. Through further model analysis, the d band center of the metal active site was determined to be the most effective descriptor and a volcano curve relationship between the intrinsic descriptor and the overpotential was established based on the characteristic importance and Pearson correlation. The research approach adopted in this study may be used to screen and design other MXene heterojunction catalysts and remarkably accelerate catalyst design for many significant reactions.

Direct C–C bond scission of xylitol to ethylene and propylene glycol precursors using single-atom catalysts (SACs) anchored on MgO

Shorter chain alcohols, as opposed to longer ones, are beneficial as biomass feedstock for chemicals and fuels, including hydrogen production. More so, it has been demonstrated that carbon–carbon rather than carbon–oxygen bond-cleaving activity determines the product selectivity of a metal catalyst for higher oxygenates reforming. In this report, we investigate the direct C2–C3 bond-cleaving activity of xylitol via first-principles, periodic density functional theory calculations to identify the differences in activities between single-crystal catalysts (SCCs) and single-atom catalysts (SACs). A comparison of the kinetic barriers revealed that xylitol's C–C bond scission appears to be a near-impossible task on SCCs. However, SACs demonstrated higher performance. For example, Ir1/MgO and Ir1/MgO_Ovac (having surface oxygen vacancy) yielded ∼72% and 54% decrease, respectively, in Gibb’s free activation energy compared to Ir (111) at the xylitol reforming operating temperature of 473 K. Furthermore, electronic structure calculations revealed an up-shift in the DOS for the surface M1 atoms in all investigated SACs compared to the surface atoms of their respective SCCs, resulting in M1 higher d-band center and stronger adsorbate (s) binding. This study highlights the importance of SACs for boosting the atom efficiency of costly metals while also offering a new strategy for tuning the activity of catalytic reactions.

Nanorod Array-Based Hierarchical NiO Microspheres as a Bifunctional Electrocatalyst for a Selective and Corrosion-Resistance Seawater Photo/Electrolysis System

Utilizing earth-abundant seawater over scarce freshwater for hydrogen fuel production via water electrolysis is a promising/sustainable strategy. However, the serious anodic corrosion due to the competing chloride oxidation reaction significantly hampers the overall stability of the electrolyzer. Therefore, it demands an efficient and robust catalyst with high selectivity and corrosion resistance for direct seawater splitting. Here, we present a bifunctional catalyst developed by morphology engineering to form nanorod array-based hierarchical NiO microspheres (NRAHM-NiO) as a three-dimensional (3D) hierarchical oxide/hydroxide urchin-like structure material for highly selective seawater splitting against chloride oxidation. Benefitting from highly intrinsic electroactive sites, good charge transferability, fast-releasing gas bubbles, and corrosion resistance as well as hydrophilic surface, the NRAHM-NiO exhibits outstanding bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic activity toward selective and durable overall seawater splitting. The system requires small cell voltages of 1.66 and 2.01 V to drive current densities of 100 and 500 mA cm–2 at room temperature, respectively. Such catalytic activity is superior compared to the benchmark Pt/C(−)||Pt/C(+) and Pt/C(−)||IrO2(+) pair systems. Importantly, this device demonstrates specific stability as well as selectivity toward the OER in seawater with 99% faradaic efficiency without forming any chlorine species. The experimental results are well supported by density functional theory (DFT) calculations. Powered by a single solar cell, the integrated photolysis system shows 9.9% solar-to-hydrogen (STH) efficiency.

Mechanochemistry-Directed Ligand Design: Development of a High-Performance Phosphine Ligand for Palladium-Catalyzed Mechanochemical Organoboron Cross-Coupling

Mechanochemical synthesis that uses transition-metal catalysts has attracted significant attention due to its numerous advantages, including low solvent waste, short reaction times, and the avoidance of problems associated with the low solubility of starting materials. However, even though the mechanochemical reaction environment is largely different from that of homogeneous solution systems, transition-metal catalysts, which were originally developed for use in solution, have been used directly in mechanochemical reactions without any molecular-level modifications to ensure their suitability for mechanochemistry. Alas, this has limited the development of more efficient mechanochemical cross-coupling processes. Here, we report a conceptually distinct approach, whereby a mechanochemistry-directed design is used to develop ligands for mechanochemical Suzuki-Miyaura cross-coupling reactions. The ligand development was guided by the experimental observation of catalyst deactivation via the aggregation of palladium species, a problem that is particularly prominent in solid-state reactions. By embedding the ligand into a poly(ethylene glycol) (PEG) polymer, we found that phosphine-ligated palladium(0) species could be immobilized in the fluid phase created by the PEG chains, preventing the physical mixing of the catalyst into the crystalline solid phase and thus undesired catalyst deactivation. This catalytic system showed high catalytic activity in reactions of polyaromatic substrates close to room temperature. These substrates usually require elevated temperatures to be reactive in the presence of catalyst systems with conventional ligands such as SPhos. The present study hence provides important insights for the design of high-performance catalysts for solid-state reactions and has the potential to inspire the development of industrially attractive, almost solvent-free mechanochemical cross-coupling technologies.

Through the Self-Optimization process to achieve high OER activity of SAC catalysts within the framework of TMO3@G and TMO4@G: A High-Throughput theoretical study

High-throughput DFT calculations are performed to explore the oxygen evolution reaction (OER) catalytic activity of a series of 2D graphene-based systems with TMO3 or TMO4 functional units. By screening the 3d/4d/5d transition metal (TM) atoms, a total of twelve TMO3@G or TMO4@G systems had extremely low overpotential of 0.33 ∼ 0.59 V, in which the V/Nb/Ta atom in VB group and Ru/Co/Rh/Ir atom in VIII group served as the active sites. The mechanism analysis reveals that the filling of outer electrons of TM atom can play an important role in determining the overpotential value by affecting the ΔGO* value as an effective descriptor. Especially, in addition to the general situation of OER on the clean surface of the systems containing the Rh/Ir metal centers, the self-optimization process of TM-sites was carried out, and it made most of these single-atom catalysts (SAC) systems to have high OER catalytic activity. All these fascinating findings can contribute to an in-depth understanding of the OER catalytic activity and mechanism of the excellent graphene-based SAC systems. This work will facilitate the design and implementation of non-precious and highly efficient OER catalysts in the near future.

Tuning Catalytic Performance of C2N/GaN Heterostructure for Hydrogen Evolution Reaction by Doping

AbstractIn this work, a systematic theoretical study of the hydrogen evolution reaction (HER) catalytic activity of C2N/GaN heterostructure is carried out based on first principles. An indirect bandgap of 1.99 eV and type‐II band alignment are formed in the C2N/GaN heterostructure, which can facilitate the spatially efficient separation of photogenerated carrier pairs, and the band edge position matches the reduction potential of water. The catalytic performance of the HER reaction at the C and N sites is compared and that the N site is better in performance is found, but still requires a potential barrier of 0.60 eV. In order to improve the catalytic performance of the C2N/GaN heterostructure, an N atom is replaced by a P atom to obtain P‐C2N/GaN. The band alignment of the P‐C2N/GaN heterostructure is still type‐II, and the band edges satisfy the reduction potential of water. Fortunately, the P or N sites play a crucial role in the HER process with a relatively low overpotential of 0.38 eV, which suggests that P‐C2N/GaN can improve the catalytic performance of the heterojunction. Overall, the P‐C2N/GaN heterostructure has suitable band gap values and band edges, and efficient charge separation in the heterostructure makes it a promising HER catalyst.

Liquid nitrogen quenching inducing lattice tensile strain to endow nitrogen/fluorine co-doping Fe3O4 nanocubes assembled on porous carbon with optimizing hydrogen evolution reaction

In this work, the lattice tensile strain of nitrogen/fluorine co-doping ferroferric oxide (Fe3O4) nanocubes assembled on chrysanthemum tea-derived porous carbon is induced through a novel liquid nitrogen quenching treatment (named as TS-NF-FO/PCX-Y, TS: Tensile strain, NF: Nitrogen/Fluorine co-doping, FO: Fe3O4, PC: Porous carbon, X: The weight ratio of KOH/carbon, Y: The adding amount of porous carbon). Besides, the electrocatalytic activity influenced by the adding amount of porous carbon, the type of dopant, and the introduction of lattice tensile strain is systematically studied and explored. The interconnected porous carbon could improve electrical conductivity and prevent Fe3O4 nanocubes from aggregating. The induced nitrogen/fluorine could cause extrinsic defects and tailor the intrinsic electron state of the host materials. Lattice tensile strain could tailor the surface electronic structure of Fe3O4 via changing the dispersion of surface atoms and their bond lengths. Impressively, the designed TS-NF-FO/PC5-0.25 delivers a low overpotential of 207.3 ± 0.4 mV at 10 mA/cm2 and demonstrates desirable reaction dynamics. Density functional theory calculations illustrate that the electron structure and hydrogen adsorption free energy (ΔG*H) are optimized by the synergistic effect among porous carbon, nitrogen/fluorine co-doping and lattice tensile strain, thus promoting hydrogen evolution reaction (HER) catalytic activity. Overall, this work paves the way to unravel the enhancement mechanism of HER on transition metal oxide-based materials by electronic structure and phase composition modulation strategy.

Molybdenum-Tungsten carbides based electrocatalysts for hydrogen evolution reaction

ABSTRACT Tungsten carbide-based nano-catalysts (Ni-WC, Co-WC and NiCo-WC) and molybdenum carbide-based nano-catalysts (Ni-MoC, Co-MoC and NiCo-MoC) were synthesised using a carbothermal reduction method. X-ray diffraction, scanning electron microscopy coupled with electron dispersive spectroscopy, x-ray photoelectron spectroscopy and cyclic voltammetry were used to evaluate the prepared electrocatalysts. The cyclic voltammetry results showed that Ni-WC coated electrode displayed the best hydrogen evolution reaction catalytic activity with the lowest overpotential of 1.421 V at a current density of 10 mA cm−2, and a Tafel slope of 135 mV dec−1 which is marginally lower than the benchmark Pt/C coated electrodes. Ni-MoC and Co-MoC coated electrocatalysts also produced current more effectively with a change in potential as compared to the Pt/C coated electrode. The durability test showed Co-WC, NiCo-WC and Ni-MoC coated electrodes to have high stability within a wide range of current densities.

Enhancing the d/p‐Band Center Proximity with Amorphous‐Crystalline Interface Coupling for Boosted pH‐Robust Water Electrolysis

AbstractRationalizing non‐precious pH‐robust electrocatalysts is a crucial priority and required for multi‐scenario hydrogen production customization. Herein, an amorphous–crystalline CoBOx/NiSe heterostructure is theoretically profiled and constructed for efficient and pH‐robust water electrolysis. The crystalline lattice confinement induces a CoCo bond shortening and a B‐site delocalization on amorphous CoBOx, resulting in a decreased d‐p band center difference (Δεd‐p) toward the balanced intermediates adsorption/desorption. Accordingly, the CoBOx/NiSe heterostructure exhibits efficient and robust hydrogen/oxygen evolution reaction (HER/OER) catalytic activity in different electrolytes. Of particular note, it achieves ultralow overpotentials in both the beyond‐Pt HER (14.5 mV) and OER (229.1 mV) at 10 mA cm−2under an alkaline electrolyte, and reaches an industrial‐level OER current density of 2 A cm−2. Water electrolysis is stably delivered with a low η10voltage of 1.48 V. The incorporation of such d‐p orbitals at the amorphous–crystalline interface puts forward new opportunities in rationally designing advanced non‐precious electrocatalysts for water electrolysis.

Ni3S2@MoS2@Ni3Si2 Seaweed‐like Hybrid Structures In‐situ Grown on Ni Foam as Efficient Bifunctional Electrocatalysts

AbstractWater electrolysis is a promising method for sustainable hydrogen production. The exploration of noble metal free bifunctional electrocatalysts with both good hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic activity is crucial for efficient overall water splitting. The design of electrocatalysts to enhance electrocatalytic performance for both HER and OER is still a big challenge. Long Ni3Si2 nanowires have been in‐situ grown on Ni foam by low pressure chemical vapor deposition. A facile hydrothermal method was then adopted to grow Ni3S2@MoS2@Ni3Si2 seaweed‐like structures with high active sites on the Ni3Si2 blades and high charge transport along central stipes. The as‐produced Ni3S2@MoS2@Ni3Si2 seaweed‐like hybrid structures have been demonstrated to have both excellent HER and OER catalytic performance as integrated electrodes. Low overpotentials of 84 mV (η10)/283 mV (η50) and Tafel slopes of 36.0/53.7 mV dec−1 have been achieved for HER/OER, respectively. Excellent long‐term stabilities have been obtained for both HER and OER.

Highly densed BCN nanofiber core with MoS2 shell for enhanced hydrogen evolution reaction and supercapacitance applications

Boron carbon nitrogen (BCN) nanofibers was synthesized using chemical vapor deposition (CVD) followed by depositing molybdenum disulfide (MoS2) forming a core–shell structure. This core–shell nanocomposite was directly grown on carbon paper to form working electrode, where it displayed excellent energy storage ability as well as hydrogen evolution reaction (HER) catalytic activity. We believe that during the shell deposition, it effectively etched the inert basal plane of MoS2, leading to the formation of entrenched valleys and to the further increasing of the active edge sites. Coupled with high surface area and high density BCN nanofibers core, the MoS2/BCN nanofiber catalyst demonstrated a very low overpotential of 85 mV in acidic media at a current density of 10 mA cm−2 for HER. In addition, the optimally tuned MoS2/BCN nanofiber also showed superior electrochemical performance as a supercapacitor with higher specific capacitance of 446.3 A g−1 at current density of 0.25 A g−1. Overall, this excellent catalytic activity is found to be due to their abundant active sites and fast ion transfer capability.

Screening out the Transition Metal Single Atom Supported on Onion-like Carbon (OLC) for the Hydrogen Evolution Reaction

A recent experiment has confirmed that onion-like nanospheres of carbon (OLC) covered with single Pt atoms show comparable hydrogen evolution reaction (HER) catalytic activity to the commercial Pt/C. In this work, we have performed screening calculations on the single transition metal (TM) atom supported on OLC (a total of 26 candidates) using the density functional theory (DFT) to find excellent HER catalysts. Our calculated results indicate that the Nb1/CLO, Mo1/CLO, Ru1/CLO, Rh1/CLO, Pd1/CLO, and Ir1/OLC show high-efficient catalysts performance for the HER, as experimental Pt1/OLC does. We also try to seek an appropriate descriptor relevant to the Gibbs free energies, and the average local ionization energy (ALIE), which is first used to predict HER activity, shows a perfect linear correlation with Gibbs free energy. It is interesting to note that the ALIE descriptor is more successful than the commonly used d-band center.

New horizons of MBenes: highly active catalysts for the CO oxidation reaction.

The search for materials with high intrinsic carbon monoxide oxidation reaction (COOR) catalytic activity is critical for enhancing the efficiency of reducing CO contamination. COOR catalysts, however, have long relied heavily on noble metals and CeO2. Herein, in order to search for non-noble COOR catalysts that are more active than CeO2, 18 oxygen-functionalized MBenes with orthorhombic and hexagonal crystal structures, denoted as orth-M2B2O2 and hex-M2B2O2 (M = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W), were investigated in terms of their COOR catalytic activity by high-throughput first-principles calculations. Hex-Mo2B2O2, orth-Mo2B2O2, hex-V2B2O2 and hex-Cr2B2O2 were found to be more active than CeO2 and possess structural stability below 1000 K, showing the potential to replace CeO2 as the substrates of COOR catalysts. Moreover, orth-Mo2B2O2, hex-V2B2O2 and hex-Cr2B2O2 exhibit even higher COOR catalytic activity than Pt-CeO2 and Au-CeO2, and are expected to be applied as COOR catalysts directly. Further investigations showed that the formation energy of oxygen vacancies could be used as the descriptor of COOR catalytic activity, which would help to reduce the amount of calculations significantly during the catalyst screening process. This work not only reports a series of 2D materials with high COOR catalytic activity and opens up a new application area for MBenes, but also provides a reliable strategy for highly efficient screening for COOR catalysts.