Preparation Of Functionalized Nickel Vanadium Metal Composite And Electrocatalytic Performance For Hydrogen Evolution

Hydrogen,as a clean and reproducible energy source,has been extensively considered for use as sustainable energy.To produce hydrogen at a large-scale,electrochemical splitting of water is the best option and has been researched widely.To date,Pt-based catalysts has been identified as benchmark hydrogen evolution reaction（HER）electrocatalysts.However,the cost and scarcity immensely restrict their widespread application.Consequently,it is urgently required to develop an efficient and nonprecious electrocatalyst based on earth abundant elements.Transition metal-based compounds hold a promising status to substitute for noble metal catalysts.Among multiple methods,it has been proved that hierarchical heterostructure can enhance the interaction of different components and promote the charge transfer,which can effectively improve the catalytic performance.Hence,this paper has carried out the following two aspects of research:The study of Ni outward diffusion during the pyrolysis process can result in the formation of unique structure with the oxygen vacancies.Heterogeneous Ni/V-Mo O₂nanocomposites were prepared by vanadium doping whose nanoparticles adhere to the surface of nanorods.（1）We report a facile route to synthesize hierarchical nickel vanadium nanohybrid（Ni@V₂O₃/NF）with strong electron transfer through calcining Ni₃V₂O₈/NF under reductive atmosphere.The oxygen vacancies present in V₂O₃can efficiently donate electron to the Ni nanoparticles,which accordingly regulate the electronic structure and improve the electrocatalytic activity of materials.Meanwhile,the appropriate Ni outward diffusion during the pyrolysis process can result in the formation of unique structure in form of Ni nanoparticles encased by V₂O₃,which favors the interaction between two components,generates numerous active sites and benefits the enhancement of HER performance.Thus,the as-fabricated Ni@V₂O₃/NF behaves with an overpotential of 19mV at 10 m A·cm^-2,a small Tafel slope value of 48.5 mV/dec and good stability.（2）Heterogeneous Ni/V-Mo O₂nanocomposites were synthesized by hydrothermal method and calcination in hydrogen reduction atmosphere.Doping vanadium can not only adjust the structure of the catalyst,but also increase the content of oxygen vacancies and accelerate the electron transfer.During the pyrolysis process,the outward diffusion of Ni forms the unique structure:Ni nanoparticles attached to the nanorods,which helps to strengthen the interaction between the two components,accelerate the electron transfer,and form abundant active sites to improve the hydrogen evolution performance.Therefore,the as prepared Ni/V-Mo O₂/NF has a small overpotential(16 mV at 10 m A·cm^-2)and Tafel slope（39.2 mV/dec）.