Enhanced electrochemical hydrogen evolution performance of WS₂ nanosheets by Te doping

Hydrogen evolution reaction (HER) activities of WS₂ can be improved by doping exotic atom to increase active sites on base plane and narrow the bandgap. However, most of these catalysts of exotic atom doped WS₂ are composed of semiconductor and the electronegativity between atoms is similar, which do harm to tuning bandgap with a wide range and decreasing the value of free Gibbs energy (ΔG_H) for hydrogen adsorption. Given that Te can tune bandgap with a wide range and the electronegativity between S and Te differ greatly, a vertically arranged WS₂ nanoelectrode is prepared by doping Te on WS₂. According to experimental studies and the density functional theory calculations (DFT), the bandgap of WS₂ nanosheets is successfully narrowed after doping Te. This lowers the Schottky barrier which benefits the transfer of charges and improves electrocatalytic performance in turn. Meanwhile, the presence of Te atoms with much lower electronegativity than S increases the electron density of the adjacent region, thereby the S edges of basal plane around Te atoms and hollow sites of WS₂ nanosheet become active to drive HER, which has been verified by the reduced ΔG_H of S edges of basal plane from 2.27 to 2.08 eV and hollow sites from 2.28 to 1.85 eV after the doping in DFT. Te-doped WS₂ nanosheets used as excellent HER catalysts with an overpotential of 213 mV to drive a current density of 10 mA/cm², a small Tafel slope of 94 mV/dec, along with a superior stability in acid media.