Construction And Hydrogen Evolution Properties Research Of Bimetallic Sulfides Derived From Polyoxometalates

Transition metal dichalcogenides are stable and easily obtained at a low price,which are the efficient catalysts to replace Pt in the field of electrocatalysis for hydrogen.However,this kind of materials have poor intrinsic conductivity and less active sites,leading to low HER catalytic activity.By introducing secondary metal sources to construct bimetallic sulfides,the intrinsic electronic structure of sulfides can be regulated,the number of active sites can be increased,so the HER performance can be improved.However,it is still difficult to accurately control the metal proportion in bimetallic sulfides.A variety of bimetallic sulfides were prepared by calcination using POMs.We can accurately regulate the metal proportion in sulfide products by taking advantage of easily modified and adjustable molecular structure of POMs.In addition,the selected POMs can give play to the advantages of the two metals at the same time,compared with two POMs containing single metal component,the cost is saved and the process is simplified.Different properties of carbon substrates were introduced into the system to further enhance the electrical conductivity of bimetallic sulfides and accelerate the electron transport rate at the catalysts interface.Results presented as follows:1.Using Keplerate-type {Mo72M30}(M=Fe,V)as the precursors,{Mo72M30} was uniformly loaded on the conductive substrate through the redox polymerization process of {Mo72M30} and pyrrole monomer(Py),and a series of Mo-based bimetallic sulfides with controlled metal ratios were prepared by calcination((Fe0.3Mo0.7)S2,(Fe0.3Mo0.7)S2@C,(V0.34M00.66)S2 and(V0.34Mo0.66)S2@C).Among them,(Fe0.3Mo0.7)S2@C shows the best HER electrocatalytic activity in 1 M KOH,the overpotential is 132 mV with a current density of 10 mA cm-2.2.In order to further regulate the HER properties of bimetallic sulfides with other metal ratios,Finke-type[M4(H2O)2(PW9O34)2]10-(M=Co,Ni)were used as metal sources,by means of electrostatic interaction between POMs and carbon substrate(rGO),the POMs were uniformly loaded on the carbon substrate as precursors,a series of W-based bimetallic sulfides((Co0.27W0.73)S2/rGO,(Ni0.32W0.68)S2/rGO)with controllable metal ratios were prepared by calcination.The results showed that(Co0.27W0.73)S2/rGO has the outstanding HER performance under alkaline conditions,with an overpotential of 153 mV when the current density is 10 mA cm-2.