▎ 摘　　要

As an essential component of single-atom catalysts, support materials determine the dispersion, utilization, and stability of single metal atoms. Here, we reported the potential of defective and doped graphene as a single-atom catalyst (SAC) support for CO2 conversion to formic acid by hydrogenation. The support effect was screened based on the stability of a single-metal atom. Our calculation revealed that Cu, Pd, and Ru supported on defective graphene with monovacancy (m-VacG) have higher adsorption energy than the cohesive energy of their bulk counterparts; therefore we selected Cu, Pd, and Ru supported on m-VacG as potential SACs to examine the catalytic reaction. The stability and reactivity of SACs/ m-VacG were uncovered by molecular dynamics (MD) simulations, migration barrier calculation, and electronic structure analysis. The reaction of CO2 hydrogenation proceeds through two pathways starting from different initial states, i.e., the coadsorption of H-2 and CO2 on SACs/m-VacG (path A) and H-2 adsorption on SACs/m-VacG (path B). From the reaction pathways analysis, it is found that path B dominates the entire reaction thermodynamically with lower energy barrier compared with path A. Moreover, Pd supported on m-VacG is predicted to be the highest active SAC with the lowest energy barrier along the reaction path.