Probing the origin of group VB transition metal monocarbides for high-efficiency hydrogen evolution reaction: A DFT study

Abstract

Transition metal carbides have received increasing attention for the application in hydrogen evolution reaction (HER), especially the group VB transition metal monocarbides (GVB-MCs). GVB-MCs display excellent HER activity in electrochemical water splitting which can even be favorably comparable with Pt in acidic condition, whereas it still remains as a challenge to illustrate their inherent catalytic mechanism. Herein, we use first-principle study to get insight into the HER activity of GVB-MCs and ascertain their catalytic mechanism. The resultant density functional theory (DFT) calculations suggest that the (110) surfaces of GVB-MCs have high stability and good conductivity. More importantly, we discover the highly active sites of the metal–metal bridge for the first time, which play an important role in guaranteeing the excellent HER activity on the (110) surfaces of GVB-MCs. Specifically, the Gibbs free energy of hydrogen adsorption (ΔGH*) of VC (110) surface (0.011 eV) is superior to that of precious metal Pt, and the calculated activation energy (0.667 eV) for the Tafel reaction on VC (110) surface is only slightly lower than that on the Pt (111) surface. Therefore, this work emphasizes the importance of active sites and provides reliable DFT guidelines for the further design of effective GVB-MCs electrocatalysts.