Design,Synthesis And Electrocatalytic Performance Of Nicke-Vanadium-Based Heterostructure Electrocatalysts For Hydrogrn Production

Hydrogen fuel is a clean and renewable resource that is expected to play an important role in future energy supply.The electrochemical water splitting technology coupled with renewable energy is a sustainable way of producing hydrogen.However,the large-scale industrial application of this reaction is severely restricted by its sluggish kinetics in both two half-reactions,namely,oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）.On the other hand,due to the scarcity of freshwater resources,seawater with rich reserves is considered a suitable raw material for industrial hydrogen production.But under seawater conditions,competitive chlorine evolution reaction（Cl ER）often occur with OER,and the resulting highly corrosive hypochlorite byproducts can easily lead to electrode corrosion.It is generally believed that using a low theoretical potential hydrazine hydrate oxidation reaction（Hz OR）to replace the high theoretical potential anode OER is an optimized way to avoid Cl ER and achieve efficient and low-cost industrial hydrogen production.At present,precious metal catalysts platinum and ruthenium-based oxides are efficient HER and Hz OR electrocatalysts,but their high cost and scarcity hinder their industrial application.Therefore,developing cheap and efficient transition metal-based HER and Hz OR electrocatalysts is of great significance.This article mainly studies the low-cost nickel vanadium complex,especially the high active and stable electric catalyst for basic HER and Hz OR,and the intrinsic correlation of electrocatalysts composition-structure-catalytic properties.The main research progress is as follows:（1）Ni₂P/V₂O_3-x/NF heterojunction nanosheet electrocatalysts supported on nickel foam（NF）with high HER activity and stability were prepared by a simple hydrothermal and phosphating annealing method.Experimental studies and density functional theory（DFT）calculations show that the composition phases(Ni₂P and V₂O_3-x)optimized by interface coupling and defect-induced double effects synergistically catalyze alkaline HER,effectively improving the intrinsic activity of the catalyst.The introduction of abundant oxygen defects in V₂O_3-xcan further improve its conductivity,and its close contact with metal-like Ni₂P gives the catalyst high charge transfer ability.In addition,the constructed superhydrophilic nanostructures can ensure the maximum utilization of active sites.Based on the above factors,the prepared Ni₂P/V₂O_3-x/NF heterojunction electrocatalyst exhibits good alkaline HER catalytic activity and stability.This work highlights the potential of rational combination of defect-rich metal oxides and transition metal phosphides to construct efficient heterostructure electrocatalysts and illustrates the feasibility of designing a simple synthesis strategy to solve the problems of intrinsic activity,conductivity and number of active sites that plague the catalyst at one time.（2）Based on the previous work,the hydrothermal sample was treated with heat nitriding.The nanosheet structure Ni₃N/V₂O_3-x/NF heterojunction electrocatalyst was constructed with high catalytic activity and stability.Experiments and DFT calculations show that the construction of Ni₃N/V₂O_3-xheterojunction can induce charge rearrangement,thereby optimizing the active site of the catalyst and reducing the reaction kinetic energy barrier.The resulting catalyst exhibits excellent HER and Hz OR activities in both alkaline traditional electrolytes and hydrazine-mixed alkaline seawater electrolytes.Since its excellent dual-function electrocatalytic activity,it can be used as both cathode and anode electrodes.Benefiting from the excellent bifunctional electrocatalytic activity,the obtained catalyst can be used as both cathode and anode electrodes in the hydrazine oxidation-assisted alkaline seawater hydrogen production system to achieve a high current density of 1000 m A cm^-2 at a cell voltage of1.4 V,and it has good stability.This work reveals the potential of nitride/metal oxide heterojunction composite electrocatalysts as bifunctional electrocatalysts for hydrazine hydrate oxidation assisted alkaline seawater electrolysis.