Single metal atoms supported on N-doped 2D M2C MXenes: an efficient electrocatalyst for overall water splitting

Abstract

Single-atom catalysts (SACs) are widely used as catalysts for overall water splitting due to their maximum utilization of surface active sites. However, until now, efficient SACs for water splitting are still lacking. Herein, a systematic screening of the overall water splitting performance of Fe, Co, and Ni atoms anchored on M₂C, nitrogen modified M₂C, and Fe and N co-modification M₂C MXenes is performed by using first-principles calculations. The results show that Fe/Mo₂C exhibits better hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances among the studied TM/Mo₂C structures, with the corresponding value of ΔG_H* and η_OER being 0.03 eV and 0.66 V, respectively. In addition, there is an obvious volcanic curve relationship between the d-band center (ε_d) of TM/M₂C and the overpotential of the OER (η_OER). Low N doping concentrations (25%) can also adjust the HER and OER activity of M₂C. Interestingly, N doping and Fe loading co-modification Mo₂C (Fe/N-Mo₂C) shows the best HER and OER properties among the studied TM/N-Mo₂C structures, with the corresponding ΔG_H* and η_OER being 0.01 eV and 0.39 V, respectively. The thermodynamics binding energy and dynamics simulation results reveal that TM/M₂C and TM/N-M₂C are dynamically stable at the reaction temperature. This work shows that Fe/N-Mo₂C can be a potential catalyst for overall water splitting.