Strain Relaxation in Metal Alloy Catalysts Steers the Product Selectivity of Electrocatalytic CO 2 Reduction.

Strain engineering in bimetallic alloy structures is of great interest in electrochemical CO 2 reduction reactions (CO 2 RR), in which it simultaneously improves electrocatalytic activity and product selectivity by optimizing the binding properties of intermediates. However, a reliable synthetic strategy and systematic understanding of the strain effects in the CO 2 RR are still lacking. Herein, we report a strain relaxation strategy used to determine lattice strains in bimetal MNi alloys (M = Pd, Ag, and Au) and realize an outstanding CO 2 -to-CO Faradaic efficiency of 96.6% and show the outstanding activity and durability toward a Zn-CO 2 battery. Molecular dynamics (MD) simulations predict that the relaxation of strained PdNi alloys (s-PdNi) is correlated with increases in synthesis temperature, and the high temperature activation energy drives complete atomic mixing of multiple metal atoms to allow for regulation of lattice strains. Density functional theory (DFT) calculations reveal that strain relaxation effectively improves CO 2 RR activity and selectivity by optimizing the formation energies of *COOH and *CO intermediates on s-PdNi alloy surfaces, as also verified by in situ spectroscopic investigations. This approach provides a promising approach for catalyst design, enabling independent optimization of formation energies of reaction intermediates to improve catalytic activity and selectivity simultaneously.