Construction Of Multilvel MoS₂-based Materials For Electrochemical Water Splitting

In this paper,the electronic structure of MoS₂-based materials are modulated by regulating its size,geometric configuration,defects and vacancies,doping,and phase to build highly active catalytic surfaces,thereby accelerating the kinetic process of water electrolysis and promoting the hydrogen evolution and oxygen evolution reaction.The specific contents are as follows:（1）Oxygen doped hollow MoS₂（H-O-MoS₂）nanospheres were synthesized by oil-water two-phase method and anion exchange reaction.When the current density is 10 m A cm^-2,the overpotential is 207 m V and the corresponding Tafel slope is 65 m V dec^-1.Density functional theory（DFT）calculations show that oxygen doping can modulate the electronic structure of MoS₂,which leads to the high activation of the catalytic inert surface and the great increase of the conductivity,thus increasing the rate of hydrogen adsorption and desorption in the process of hydrogen production from electrolytic water.（2）In this work,monodisperse,uniform yolk-shell O-MoS₂ microspheres were synthesized through oil-water microemulsion method.The sulfur vacancoies were induced by oxygen doping guides Pt nanoparticles（ca.10.9 nm）anchored on the shell of O-MoS₂microspheres to generate O-MoS₂@Pt nanoreactor.EPR,XPS,and XAFS were used to study the anchoring mechanism of Pt.The O-MoS₂@Pt nanoreactor showed 244 m V overpotential(10 m A cm^-2)and 53 m V dec^-1 Tafel slope in alkaline medium,which was superior to commercial Ir O₂ and most of the reported MoS₂ based catalysts.Meanwhile,the catalyst showed excellent cycle durability within 24 hours.（3）The hollow MoO₂/MoS₂/C nanoreactor with a clear three layer"conductor/catalyst/protective layer"was successfully synthesized by the oil water microemulsion method,which effectively catalyzed hydrogen evolution over all pH values.The overpotential of the optimized MoO₂/MoS₂/C nanoreactor is 77 m V,91 m V,and 97 m V(10 m A cm^-2)in acidic,alkaline and neutral media,respectively,and the Tafel slope is 41 m V,49 m V,and 53 m V dec^-1,respectively,which is superior to most MoS₂ based electrocatalysts reported so far.The defect carbon shell（2～3 nm）produced in situ prevented the corrosion of the electrocatalyst in acidic and alkaline media.The stability of the structure and composition of the electrocatalyst was verified by in-situ Raman and XRD characterization.