Preparation And Performance Of Transition Metal Phosphides And Nickel Heterojunctions As An Efficient Hydrogen Evolution Catalyst

The excessive use of fossil energy has caused some pressure on the environment,and hydrogen energy is gradually gaining attention as a green and clean energy source because the product of hydrogen combustion is only water.Hydrogen can be effectively produced by electrochemical water splitting,However,the phenomenon of polarization during water electrolysis significantly hinders the rate of hydrogen production,so efficient hydrogen evolution catalysts need to be prepared to reduce the overpotential in the electrochemical water splitting.Precious metal catalysts like platinum have shown the ability to significantly decrease the overpotential,but the scarcity of precious metal reserves and high prices limit the large-scale use of precious metal catalysts.As a result,it has become crucial to develop inexpensive and efficient non-noble metal electrocatalysts for electrochemical water splitting.In this paper,Cu₃P@Ni and Co P@Ni heterojunction arrays were rationally constructed as catalysts for hydrogen evolution reaction（HER）by modulating the morphological structure and electronic structure of the materials with non-noble metal nickel as the active sites.In Chapter 3 of this paper,Cu₃P nanowire arrays were successfully prepared on copper foam by anodic oxidation-thermal phosphidation,and a layer of metallic Ni was uniformly deposited on the surface of Cu₃P nanowire arrays by electrodeposition to form the core-shell Cu₃P@Ni structure,and the coupling of metallic Ni and Cu₃P could lead to a rapid charge transfer for the optimized band structure.Cu₃P@Ni was evaluated for HER activity in a 1 M KOH solution,the overpotential to reach the current density of 10 m A cm^-2was only 42 m V,with a low Tafel slope of 41 m V dec^-1.After a long-term stability test,the HER activity of Cu₃P@Ni remained excellent,indicating that Cu₃P@Ni can serve as an efficient and stable catalyst for HER.According to DFT theoretical calculations,the Cu₃P@Ni heterojunction demonstrated suitable adsorption free energy compared to its single component counterparts,indicating higher intrinsic HER catalytic activity.In Chapter 4 of this paper,Co P nanowire arrays were successfully fabricated on carbon cloth via a hydrothermal and phosphidation process,A layer of metallic Ni was successfully deposited onto the surface of Co P nanowire arrays by electrodeposition.The electrochemical performance of Co P@Ni was tested in 1 M KOH solution,and the overpotential to reach the current density of 10 m A cm^-2was only 71 m V,with a low Tafel slope of 66 m V dec^-1.After a long-term stability test,the Co P@Ni electrocatalyst retained its high performance in HER,demonstrating its potential for practical applications as an efficient and stable electrocatalyst.According to DFT theoretical calculations,the Co P@Ni heterojunction demonstrated suitable adsorption free energy compared to its single component counterparts,indicating higher intrinsic HER catalytic activity.The successful synthesis of Cu₃P@Ni and Co P@Ni has shown that the electronic structure and active sites can be tuned by constructing heterojunction structures to design efficient electrocatalysts for HER.