Theoretical Investigation of Graphene Supported Sn–M (M = Fe, Co, Ni, Cu, Zn) Dual-Atom Catalysts for CO2 Hydrogenation to HCOOH

This work selects a series of transition metals (Fe, Co, Ni, Cu, and Zn) and Sn metal to construct a series of Sn–M dual-atom catalysts (SnMN6/G). Formation energy calculations are conducted to evaluate the stability of the studied catalyst. The calculated results demonstrate that SnMN6/G (M = Fe, Co, Ni, Cu, Zn) dual-atom catalysts exhibit high structural stability. From the calculated electrostatic potential and Fukui(−) index, it is determined that the Sn atom is the main reaction site for CO2 hydrogenation. Based on the analysis, the optimal path of HCOOH synthesis is CO2* → HCOO* → HCOOH* on SnMN6/G. In addition, the rate-determining step of the reaction CO2 → HCOOH is CO2* → HCOO* on all SnMN6/G. Furthermore, the catalytic activity of SnMN6/G is ranked in the following order: SnZnN6/G > SnNiN6/G > SnCoN6/G > SnCuN6/G > SnFeN6/G. Moreover, the activity origin of the catalyst is explored through Mulliken charge analysis, which SnZnN6/G exhibits stronger charge fluctuation during the reaction process, which may be the source of its high activity. This work clarifies that SnZnN6/G is a highly active dual-atom catalyst for HCOOH synthesis.