Study On The Electrocatalytic Hydrogen Production Of Low-dimensional Layered Molybdenum Disulfide-based Nanosheets

In today’s society,energy crisis and environmental problems are increasingly serious,and it is urgent to find a renewable clean energy source.Hydrogen is a kind of ideal energy carrier with no pollution and high energy density.Electrocatalytic（EC）hydrogen evolution reaction（HER）is an efficient and sustainable hydrogen production technology.Until now,noble platinum（Pt）group metals have been the most efficient HER electrocatalysts,but their scarcity and high cost hinder their practical applications for large-scale hydrogen production.Therefore,it is the key to explore high-activity,low-cost,and earth-abundant electrocatalysts to replace noble Pt group-based catalysts.Recently,two-dimensional transition-metal-dichalcogenide nanosheets,especially molybdenum disulfide（MoS₂）nanosheets（NSs）,have received significant attention for HER owing to their superior edge active sites,low cost and abundant resources.MoS₂ NSs with exposed preferentially edge active sites have been extensively studied for the HER application.But,the basal surface of MoS₂ is catalytically inert,and moreover its activity is also limited by the low intrinsic conductivity.In addition,two-dimensional（2D）NSs are easy to agglomerate and difficult to assembly into well-defined macroscopic electrodes.Herein,based on chemical vapor deposition（CVD）and hydrothermal methods,we successfully fabricated the MoS₂ NS arrays（NSAs）on three-dimensional（3D）conductive carbon fiber cloth（CFC）substrates to be used as EC HER electrodes.Then the strategies of microstructure regulation and surface modification were employed to boost the HER performance.1.The MoS₂ NSs synthesized by CVD and hydrothermal methods were compared to identify the relationships between their microstructure features and EC HER activities.The MoS₂ NSs prepared via CVD route can preferentially expose edge active sites and have relatively high conductivity due to their high crystallinity.But the HER activity only arise from the edge sites while the defect-free basal surface is catalytically inert,thus exhibiting a relatively poor HER activity.For the MoS₂ NSs prepared via hydrothermal rout,the quasi-amorphous texture creates the abundant defects on their basal surfaces,which may bring up new active sites on the basal plane,but simultaneously hinder electron transmission,then leading to the contradictory situation for overall HER performance.These understandings provide scientific guidance for designing MoS₂-based HER catalysts.2.A controllable Pt decoration strategy on MoS₂ NSs anchored on 3D conductive CFC substrates was employed to enhance electrocatalytic HER activity to an upper level comparable to commercial Pt foil catalysts in acidic media,with a low overpotential of 70 mV and a Tafel slope of 36 mV per decade as well as a large exchange current density of 0.43 mA cm^-2.The results show that laden Pt makes the inert basal surface of MoS₂ an attractive platform steering three electron channels toward two types of active sites,that is,electron transfer from CFC to MoS₂ edge sites and surface Pt sites,as well as photo-excited electron injection from MoS₂ domains to adjacent Pt sites,promising an excellent HER performance.This study presents a feasible approach to boost the HER activity of MoS₂ through surface decoration activating the inert basal surface and provides deep insights for designing MoS₂-based HER catalysts.