Theoretical Investigations On The Highly Efficient And Nonprecious WP-based Catalysts For Hydrogen Evolution Reaction And The Correlative Catalytic Mechanism

The excessive consumption of fossil fuels and the continuous deterioration of the environment have driven us to search for clean and sustainable energy sources.As a primary energy carrier,hydrogen has become our first choice to replace fossil fuels because of its many virtues including high energy density,abundance and environmental friendliness.One of the important topics in the development of hydrogen energy is to reduce the energy consumption in the electrolysis process by reducing the hydrogen evolution overpotential.Therefore,high-efficient hydrogen evolution catalyst has attracted extensive attention.In this thesis,we make WP as the focus of our research,through density functional theory（DFT）calculations,we have detailedly investigated the structures and the catalytic activities for hydrogen evolution reaction（HER）of pristine and monovacancy defected WP systems.Initially,through the Bravais–Friedel–Donnay–Harker（BFDH）crystal morphology algorithm prediction,the most probable exposed facets of bulk WP is estimated to the（101）surface.And then the surface energy computation is used to determine the atomic arrangement of the most stable surface.Based on the（101）surface with the most stable termination,we explore the HER activity of WP by computing the adsorption free energy values of H*(ΔG_H*).The calculatedΔG_H*results reveal that the（101）surface can exhibit the good HER catalytic activity,where the top site over W atoms can serve as the most active site for HER(theΔG_H*results above the two W atoms on the surface are-0.114 eV and-0.095 eV,respectively).This is mainly due to the fact that when adsorbing H*at the correlative W-sites,the existence of antibonding characteristic can effectively weaken the interaction between the hydrogen atom and the adsorption site.In addition,we have also proposed an effective strategy through introducing the monovacancy on the（101）surface to further improve the HER catalytic activity of WP system.Through calculation,we find that the existence of monovacancy defects,especially the formation of W-monovacancy,can improve the HER catalytic activity on the（101）surface.This is mainly due to the appearance of monovacancy make the decreased coordination number of correlative atoms,bringing some new active sites around the defect.Subsequently,we compute theΔG_H*values as a function of varying hydrogen coverage(θ_H*)for the four defective（101）surfaces.The computed results reveal that all these defective（101）surfaces can still exhibit high HER activity in a wide hydrogen coverage.Particularly,the formation of a W-monovacancy can significantly improve HER activity over a wider range of H coverage.Therefore,we can draw the conclusion that the existence of monovacancy defects can effectively improve the hydrogen evolution catalytic activity of the surface,especially the formation of W-monovacancy.Clearly,all these fascinating findings at the atomic level can be beneficial for realizing the high-efficient nonprecious HER electrocatalysts based on the tungsten phosphide and even other transition metal phosphides in the near future.