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

The two-electron CO reduction reaction (2e-CORR) is the most promising process for realizing industrial utilization of CO, but it is hindered by the competitive hydrogen evolution reaction (HER) because of the comparable equilibrium potential. Strategies to enhance 2e-CORR 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 CORR against HER. By means of constant-potential calculations and constrained ab initio molecular dynamics simulations, we demonstrate the good stability and high CORR 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 CORR 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-CORR.