Preparation And Properties Of WS₂/Co₉S₈ Core-shell Nanocrystals@hollow-porous Carbon Fiber（HCF） For Water Electrolysis

With the petroleum consumption and environmental pollution aggravation,an efficient approach to renew energy sources for human society i5 of high demand.Electrocatalytic production of hydrogen and oxygen from water electrolysis has been proposed and developed as an effective way to reduce our heavy reliance upon traditional fossil fuels.Noble metals and their oxides remain being regarded as the most important state-of-the-art catalysts for water electrolysis while the scarcity and high-cost extremely hinder their large-scale practical applications.To overcome these disadvantages,the design of cost-efficient and alternative earth-abundant materials with high electrocatalytic performance for water electrolysis is highly imperative.Recett years,a variety of materials have been widely investigated as HER and OER catalysts,such as transition metalsand their carbides,oxides,sulfides phosphides and selenides,since their abundant sources,low cost,easy preparation,potential stability as well as excellent electrocatalytic activity.Furthermore,bimetal and bimetallic compound(such as WS2 and Co9S8)display tunable and unique properties,providing superior electrochemical performance due to its modulation on the absorption energy of the reaction intermediates.However,they were still facing the problem of poor conductivity.As a solution in present research,we utilized the carbon basis materials to promote their electric conductivity and their electrochemical performances were systematically investigated.The main conclusions in this thesis can be summatized as:(1)Firstly,the PAN/PS fibers were carefully designed by tuning the concentration of PAN/PS in DMF.Then,by regulating the the molar ratios(W6+:Co3+)in the PAN/PS solution,the AMT and(or)Co(acac)3 loaded PAN/PS micro-nanofibers were fabricated.Moreover,the morphologies,composition,element distribution,through-pore size as well as through-pore size distribution of these fibers were systematically investigated.The results showed that the AMT and(or)Co(acac)3 loaded PAN/PS significantly enhanced the through-pore size of relevant fiber membranees.(2)We synthesized WS2,Co9S8 and WS2/Co9S8 nanocrystals with different diamension,structure and morphology grown on hollow-porous carbon fibers via calcination and S vapor inducing reaction treatment as bifunctional catalysts for water electrolysis.(3)Finally,the effects of structure and morphology on the water electrolysis of WS2 and(or)Co9S8@hollow-porous carbon fibers were investigated.The catalyst W1Co1S@HCF with W/Co molar ratio of 1:1 presented excellent HER activity for 228±8.38 mV overpotential at a current density of 10 mA/cm2 with the Tafel slope of 111 mV/dec.More importantly,the W:Co1S@HCF had superior stability in acidic electrolyte solution.The catalyst W.Co3S@HCF with W/Co molar ratio of 1:3 gained excellent OER activity for 437±19.47 mV overpotential at a current density of 10 mA/cm2 with the Tafel slope of 99 mV/dec.