Selective CO₂ Reduction over γ-Graphyne Supported Single-Atom Catalysts: Crucial Role of Strain Regulation

The two-electron CO₂ reduction reaction (2e-CO₂RR) is the most promising process for realizing industrial utilization of CO₂, but it is hindered by the competitive hydrogen evolution reaction (HER) because of the comparable equilibrium potential. Strategies to enhance 2e-CO₂RR activity and selectivity by suppressing HER are highly demanded. Inspired by the low in-plane Young's modulus of the recently synthesized γ-graphyne (GY), we propose tensile-strain regulation as an effective method to improve the selectivity of the CO₂RR against HER. By means of constant-potential calculations and constrained ab initio molecular dynamics simulations, we demonstrate the good stability and high CO₂RR activity of GY-supported Co (Co-GY) single-atom catalysts (SACs). The change in potential of zero charges of *COOH is revealed to be more sensitive to tensile strain than that of *H species on Co-GY SACs, resulting in a slower change of its adsorption energy than that of *H species under working potentials and consequently enhanced CO₂RR selectivity toward CO production. Besides, the strain-dependent regulation mechanism also applies to other M-GY SACs, demonstrating strain regulation as an effective strategy for designing and manipulating SACs for the selective 2e-CO₂RR.