Theoretical Investigation of Single-Atom Catalysts for Hydrogen Evolution Reaction Based on Two-Dimensional Tetragonal V2C2 and V3C3

Developing stable and effective catalysts for the hydrogen evolution reaction (HER) has been a long-standing pursuit. In this work, we propose a series of single-atom catalysts (SACs) by importing transition-metal atoms into the carbon and vanadium vacancies of tetragonal V2C2 and V3C3 slabs, where the transition-metal atoms refer to Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. By means of first-principles computations, the possibility of applying these SACs in HER catalysis was investigated. All the SACs are conductive, which is favorable to charge transfer during HER. The Gibbs free energy change (Delta GH*) during hydrogen adsorption was adopted to assess their catalytic ability. For the V2C2-based SACs with V, Cr, Mn, Fe, Ni, and Cu located at the carbon vacancy, excellent HER catalytic performance was achieved, with a |Delta GH*| smaller than 0.2 eV. Among the V3C3-based SACs, apart from the SAC with Mn located at the carbon vacancy, all the SACs can act as outstanding HER catalysts. According to the Delta GH*, these excellent V2C2- and V3C3-based SACs are comparable to the best-known Pt-based HER catalysts. However, it should be noted that the V2C2 and V3C3 slabs have not been successfully synthesized in the laboratory, leading to a pure investigation without practical application in this work.