| Molybdenum disulfide（Mo S2）,as a typical transition metal disulfide,has attracted extensive attention in the fields of catalysis,lithium-ion batteries and supercapacitors due to its layered structure,adjustable configuration and composition,excellent chemical stability.However,the basal plane of Mo S2 is not fully utilized in the catalytic reaction.The low atomic utilization of Mo S2 limits its electrochemical activity.The sulfide Mo edge and unsaturated S atom are the active centers in the catalytic reaction.Defect engineering is an effective strategy to activate Mo S2 basal plane.The preparation and performance of Mo S2 are affected by defects.This paper aims to understand the influence of defect structure on the electrochemical properties of Mo S2.The influence of different defect shape and defect concentration were studied for their electrochemical properties.The possible mechanisms were elaborated based on density functional theory.The influence of surface defect of Mo S2 was studied via calculating their electronic structure,surface charge distribution and catalytic activity.The specific research contents are as follows:（1）The research of defect types on electrochemical properties of Mo S2 regulation mechanism:N was selected as the electronic modulator.A series of pore defects were designed by changing their defect types and pore shapes.Based on density functional theory,the related parameters were calculated,including band structure,thermal forming energy,Gibbs free energy and water decomposition energy barrier.Those parameters were used to explore the impact of pore defect types on electrochemical performance of N-Mo S2 system.The theoretical results show that nitrogen doping regulates the electronic structure and base plane catalytic activity of Mo S2.The pore defects changed the active edge perimeter and atomic ratio of the catalytic activity.It is more beneficial to control the active edge perimeter of pore defects within a certain range for HER catalytic reaction.N-doped Mo S2 was synthesized by hydrothermal calcination.The structural characteristics were characterized by instruments,including X-ray powder diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,transmission electron microscopy,scanning electron microscopy and automatic specific surface area and aperture testing.The prepared materials were assembled into a testable three-electrode system.The electrochemical catalytic performance was conducted in electrochemical workstation to compare catalytic activity,including linear scanning,Tafel slope,cyclic voltammetry,electrochemical impedance and stability.Pore defect-rich Mo S2 was prepared and exhibited an enhanced electrocatalytic activity（145 m V at 10 m A/cm2）.The experimental results show that N-Mo S2 with pore defects possess improved electrocatalytic activity.（2）The research of defect concentrations on electrochemical properties of Mo S2 regulation mechanism:A series of P-doped Mo S2 was constructed using P as the electronic modulator.Based on the first principle,the related parameters were calculated,including the state density,free energy of hydrogen evolution and surface charge distribution.Those parameters were used to explore the influence of defect concentration on electrochemical performance of Mo S2.The theoretical results show that the surface catalytic capacity and conductivity of Mo S2 are improved with P doping.The charge redistribution between P,Mo and S atoms increases the surface activity.The enhanced conductivity could be confirmed by increased electrons near Fermi level and accelerated electron transfer process.The synergistic effect between surface activity and conductivity ensures the efficiency and catalytic activity of HER.Mo S2 with different P doping amounts were synthesized by one-step hydrothermal method.The structural characteristics were characterized by XRD,SEM,TEM,XPS and other characterization techniques.The electrochemical behaviors of P-Mo S2 were tested,including LSV,Tafel,CV,EIS and I-t curves.The hydrogen evolution reaction can achieve a low overpotential of 152 m V at 1 m A cm-2 and a continuous 30 h operation.The experimental results show that P-Mo S2doped with medium concentration has better electrocatalytic activity and stability. |
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