Fabrication And Electrochemical Properties Of Sulfide Semiconductors

Sulfide semiconductor materials have great application prospects in the field of electrochemical hydrogen evolution due to their excellent physical,chemical properties and abundant reserves.However,the poor conductivity and low catalytic activity of sulfide semiconductor materials constrain its development in the field of catalysis.In this paper,we focus on the defects of sulfide semiconductor materials in catalytic hydrogen evolution,and different sulfide semiconductor materials were prepared by simple and easy preparation method,regulate the morphology and size of materials,thereby improving the catalytic hydrogen evolution performance of sulfide semiconductor materials.The main results are as follows:Hierarchical MoS₂ nanosheets/polypyrrole nanofibers（MoS₂ NSs@PPy NFs）core/shell nanostructures were successfully fabricated through a simple and environmentally friendly method by using PPy nanofibers as the core and MoS₂ NSs as the shell.The as-fabricated three dimensional MoS₂ NSs@PPy NFs proved to be the effective hydrogen evolution reaction（HER）catalyst,which only needed 60 and 196 mV overpotential to approach 10 and100 mA cm^-2,respectively.Furthermore,a small Tafel slope of 33 mV dec^-1 and low onset overpotential of 20 mV were achieved,which were smaller than the previously reported values.The MoS₂ NSs@PPy NFs catalyst may hold great potential for practical applications.Self-assembled ultrathin Ni-Co-S nanomaterials were grown on nickel foam and served as an excellent electrocatalyst for hydrogen evolution reaction（HER）in alkaline solution with high activity and stability.The results showed that during the sulfidation process,the Ni-Co-S nanomaterials undergone a complex chemical reaction.As the increasing of sulfidation time,the nanoflakes structure of the Ni-Co-S material experienced the evolution process from the collapse to vertical growth to collapse again.The electrochemical hydrogen evolution performance of the catalytic material achieved the best overall for sulfidation time of 10 h,which possesses the onset potential of 42 mV and it can maintain its hydrogen evolution performance after 35,000 cycles of CV cycles with negligible losses.The ultrathin and porous structure can provide a huge number of exposed active sites.The highly-conductive Ni foam can promote the electron transfer process,and the three dimensional（3D）networked structure can facilitate the diffusion and penetration of electrolyte.Theα-manganese dioxide（α-MnO₂）nanotube material was prepared by a simple hydrothermal method,and the manganese-sulfide（MnS）nanometer was obtained by calcining theα-MnO₂ nanotube material in a tube furnace（sulfur source:sublimed sulfur）.The MnS/ZIF-67 core-shell micro/nano composites were prepared by coating ZIF-67 on MnS nanofibers,which showed relatively good electrocatalytic hydrogen evolution performance in alkaline electrolyte environment.The onset overpotential is 311 mV,and the Tafel slope is225.2 mV dec^-1.Studies have found that improved manganese materials can be tried to conduct electrocatalytic hydrogen evolution properties.