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 (SnMN 6 /G). Formation energy calculations are conducted to evaluate the stability of the studied catalyst. The calculated results demonstrate that SnMN 6 /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 CO 2 hydrogenation. Based on the analysis, the optimal path of HCOOH synthesis is CO 2 * → HCOO* → HCOOH* on SnMN 6 /G. In addition, the rate-determining step of the reaction CO 2 → HCOOH is CO 2 * → HCOO* on all SnMN 6 /G. Furthermore, the catalytic activity of SnMN 6 /G is ranked in the following order: SnZnN 6 /G > SnNiN 6 /G > SnCoN 6 /G > SnCuN 6 /G > SnFeN 6 /G. Moreover, the activity origin of the catalyst is explored through Mulliken charge analysis, which SnZnN 6 /G exhibits stronger charge fluctuation during the reaction process, which may be the source of its high activity. This work clarifies that SnZnN 6 /G is a highly active dual-atom catalyst for HCOOH synthesis.