Electrodeposition Synthesis Of Molybdenum (Tungsten) Sulfide Nanostructures And Their Electrocatalytic Property For Hydrogen Evolution Reaction

Hydrogen?H₂?,as a clean and renewable energy carrier can be an ideal alternative for fossil fuels.Water electrolysis is a desired technique to produce H₂.But it is necessary to use highly active electrocatalysts to lower the overpotentials and reduce energy consumption for hydrogen evolution reaction?HER?.Up to now,the most active electrocatalyst for HER is Pt-based noble metals.But their large application in industry is restricted by its high cost and low reservation.Thus,it is necessary to find the cheap and highly active HER electrocatalyst to alter Pt-based materials,especially based on the earth-abundant elements.It has been demonstrated that molybdenum sulfide?MoS_x?is a potential highly active HER electrocatalyst through both the theory and experiments.The active sites of MoS_x are located on the edge.Thus,in order to enhance HER activity,it becomes a main strategy to produce MoS_x with more edge sites.To date,the synthetic methods of MoS_x are hydrothermal,vapor deposition,high temperature sulfidation,restacking and so on.But either harsh conditions,such as,high temperature,high pressure and high vacuum,or complicated synthetic process is involved in these processes.Thus,it is desirable to find a mild and simple method to prepare MoS_x with high activity.Electrodeposition is an ideal way to prepare MoS_x owing to its advantages of simple,mild,easy to control and low cost.In this thesis,we synthesized the highly active electrocatalysts MoS_x with different structures by the facile electrodeposition method,mainly focus on the three aspects as follows:the increase of edge sites,improvement of conductivity and the change of surface structure.We investigated the inner link among the electrodeposition conditions,catalytic properties and morphology structure in detail.At last,we preliminary investigated the HER activity and electrodeposition synthesis of WS_x,which has the similar structure with MoS_x.?1?In order to increase the edge sites,we electrodeposited MoS_x island structures in the mixed solvent of H₂O and DMF.We also investigated the effect of the ratio of V_DMF:V_H2O on the morphology,structure and the HER electrocatalytic properties;?2?In order to enhance the conductivity,we electrodeposited the Ni-P/MoS_x composites with a higher HER activity.And we also investigated the mechanism of the improved MoS_x HER activity by the incorporation of Ni-P with high conductivity;?3?Based on the change of surface structure and the increase of unsaturated S atoms,we electrodeposited the uniform and homogeneous distribution MoS_x nanoparticles.The obtained MoS_x exhibits excellent electrocatalytic HER property,with an overpotential very closely to Pt/C.But its stability and current density are remained to be improved;?4?We investigated the HER activity of WS_x based on liquid exfoliation.And we preliminary investigated the inner links between HER activity and the electrodeposition conditions of WS_x.