P-band center theory guided activation of MoS_(2) basal S sites for pHuniversal hydrogen evolution

The edge S sites of thermodynamically stable 2H MoS_(2)are active for hydrogen evolution reaction(HER)but the active sites are scarce.Despite the dominance of the basal S sites,they are generally inert to HER because of the low p-band center.Herein,we reported a synergistic combination of phase engineering and NH_(4)^(+) intercalation to promote the HER performance of MoS_(2).The rational combination of 1T and 2H phases raises the p-band center of the basal S sites while the intercalated NH4+ions further optimize and stabilize the electronic band of these sites.The S sites with regulated band structures afford moderate hydrogen adsorption,thus contributing to excellent HER performance over a wide pH range.In an acid medium,this catalyst exhibits a low overpotential of 169 mV at 10 mA·cm^(−2)and Tafel slope of 39 mV·dec^(−1)with robust stability,superior to most of recently reported MoS_(2)-based non-noble catalysts.The combined use of in/ex-situ characterizations ravels that the appearance of more unpaired electrons at the Mo 4d-orbital reduces the d-band center which upshifts the p-band center of the adjacent S for essentially improved HER performance.This work provides guidelines for the future development of layered transition-metal-dichalcogenide catalysts.