| Metal-air batteries and electrochemical overall water splitting have been identified asgreen and renewable energy conversion and storage.However,the high energy barriers and sluggish kinetics of electrochemical hydrogen evolution reaction（HER）,oxygen reduction and evolution reactions（ORR and OER）lead to low energy utilization and disappointed output power.Despite the high activity of noble-metal-based electrocatalysts for HER（Pt）,ORR（Pt）or OER（Ir/RuOx）,the weak durability and high cost impede their practical application in industrial level.Therefore,developing low cost,highly efficient and robust electrocatalysts based on earth-abundant non-noble metals is imperative.To promote their electrocatalytic activities,substantial approaches have been carried out,including the heteroatom doping,hetero-structural design,and the atomic metal-active site construction,etc.In this work,a series of W-and-Mo based electrocatalysts were prepared by interface engineering and defect engineering.The performance and structure-activity reaction were also performed to replace the nobel metal catalyst and promote the industrial application of the non-noble metal electrocatalyst..More specific key point from our study are:1.Hierarchical WO3“nanowire-array-on-nanosheet-array”（WO3NWA-NSA）structure on nickel（Ni）foam via a facile hydrothermal method,which could be used as a device directly.The obtained WO3 NWA-NSA structurespossess high specific surface area（SSA）and abundant pore structure,which could provide more active sites for OER.As a catalyst for OER,the WO3 NWA-NSA catalysts reached 10 mA/cm2 with an extremely low overpotential of 200 m V in alkaline solution.Besides,the Tafel slope was only 30 m V dec-1,which was lower than most reported precious metal oxide catalysts.Through the theoretical calculations,the oxygen-defective WO3 not only promoted the conductivity of WO3,but also changed its electronic structure.Our research shows that WO3 is a promising OER and HER catalyst.2.Here the WO3 powders from Part 1 as the raw material,a facile solid-state synthesis strategy to construct the interface engineering of W2N/WC heterostructures were reported,in which abundant interfaces are formed.The as-prepared W2N/WC heterostructures electrocatalyst delivers an efficient and stable electrocatalyticfor ORR,OER and HER.Furthermore,such W2N/WC heterostructures electrocatalyst also exhibits remarkable performance for Zn-air batteries and overall water splitting.Density functional theory（DFT）computations reveal that W2N/WC interfaces synergistically facilitate transport and separation of charge,thus accelerating the electrochemical ORR,OER and HER.This work paves a new way for constructing efficient and low-cost electrocatalyst in electrochemical energy devices.3.Interfaces between metal and same-metal based compounds are known to form an ohmic junction with very low resistance,resulting in band bending and electronsflow from the metal element to the conduction band of metal-based compoundsto lower their energies until their Fermienergy levels reach the same value.Mo modified MoC1-x nanorods structure for HER were prepared via a wet-chemical route and a subsequent annealing treatment,in which Mo accelerate the charge transfer and MoC1-x-x provide active sites.The electrons can be quickly transferred at the interfaces between Mo and MoC1-x.Owing to the synergistic effect of Mo and MoC1-x,the as-obtained Mo/α-MoC1-x-x exhibited excellent HER activity with a low onset potential of-120 mV.4.Hierarchical Mo2Cx N1-x-x Nanosheets Supported on Ni foam electrocatalyst toward overall water splitting was successfully obtained via hydrothermal and facile pyrolysis under inert flow.Mo2CxN1-x-x achieves excellent overall water splitting performance with a cell potential as low as 1.56 V reaching a current density of 10 mA·cm-22 and keeps the excellent stability.The strategy for preparing such nanostructures may open up opportunities for exploring low-cost highperformance electrocatalysts for various applications. |
