Synthesis And Performance Of Tungsten Selenide And Its Composites

Hydrogen is a promising candidate for the development of new,clean,and efficient energy carriers due to its high-energy density.Although platinum?Pt?has been demonstrated to be an efficient electrocatalyst for the hydrogen evolution reaction?HER?,the scarcity and high cost hinder its practical application.Hence,the development of inexpensive,highly active,acid-stable HER catalysts becomes the international research frontiers and hot spots.Recently,two-dimensional transition metal dichalcogenides?MX₂?,have attracted considerable attention as electrocatalysts.In this thesis,the synthesis and modification of new WSe₂ HER catalyst are investigated.Firstly,the synthesis and HER performance of WSe₂ were studied;then,the synthesis and HER performance of WSe₂/CNTs composite have been further investigated;finally,the synthesis and HER performance of RGO/WSe₂ composite were investigated.The main research contents and results are as follows.?1?The flowerlike and graphene-like few-layered WSe₂ have been synthesized through a facile one-pot solvothermal method respectively.The HER performances of both electrocatalysts have been investigated.The results show that compared with flowerlike WSe₂ with a low HER performance,the graphene-like WSe₂ exhibits excellent HER performance with a small Tafel slope of 78 mV dec-1,a low onset overpotential of ¹50 mV and a very long-term stability.The remarkable enhancement in catalytic performance of graphene-like WSe₂ is attributed to its unique porous nanostructure and abundant active reaction sites.?2?For the first time,a WSe₂/CNTs hybrid network?WCHN?composed of fewlayered WSe₂ nanosheets interwoven with carbon nanotubes?CNTs?has been synthesized through a facile one-pot solvothermal method.Compared with bare WSe₂ with relatively poor performance for HER,the WCHN exhibits superior HER performance with a small Tafel slope of 59.7 mV/decade,a remarkably low onset overpotential of ¹20 mV,a high current density and excellent long-term stability.The significant enhancement in HER performance of the WCHN is attributed to the unique network structure produced by twodimensional WSe₂ nanosheets interwoven with one-dimensional highly conductive CNTs,which not only provides abundant active reaction sites,but also guarantees robust contact between the WSe₂ nanosheets and the CNTs.?3?For the first time,a RGO/WSe₂ hybrid network constructed with few-layered WSe₂ nanoflowers anchored on graphene nanosheets has been synthesized through a facile one-pot solvothermal method.Compared with bare WSe₂,the RGO/WSe₂ hybrid demonstrates a highly effective and stable electrocatalytic performance: it delivers a small Tafel slope of 57.6 mV dec-1,a remarkably low onset overpotential of 150 mV,a high current density of 38.43 mA cm-2 at-300 mV vs RHE and excellent long-term stability.The superior HER performance of RGO/WSe₂ hybrid is attributed to the unique WSe₂-anchored-on-graphene structure,which ensures the robust contact between the few layered WSe₂-nanoflowers catalyst and the highly conductive graphene matrix,leading to enhance the charge transfer kinetics between the catalytic edge sites and the graphene nanosheets.