Atomic nickel cluster decorated defect-rich copper for enhanced C2 product selectivity in electrocatalytic CO2 reduction

[Display omitted] •A coordination enabled galvanic replacement method was developed.•This method was used to decorate defect-rich copper with atomic nickel clusters.•The catalyst was used for electrochemical reduction of CO2.•Multi-carbon product selectivity was significantly enhanced.•The reaction mechanism was revealed by detailed DFT calculations. This work describes a coordination enabled galvanic replacement method to decorate atomic Ni clusters on defect-rich Cu surface to provide the first Ni/Cu bimetallic system that significantly enhances the production of C2 products from electrocatalytic CO2 reduction. Specifically, with a surface Ni/Cu ratio of 0.82 %, a 7-fold increase in the selectivity for C2 products was found in comparison with pristine Cu. Density functional theory calculations reveal that the rate determining step for *CO formation changes from the formation of *COOH on copper to the chemisorption of CO2 on Ni decorated surfaces. An alteration of binding sites from Ni-Ni bridge for *CO2 and *COOH to Ni-Cu bridge for *CO is discovered and is proposed to favor the key CC coupling step. The catalytic mechanism demonstrated in the Cu-Ni system points to the new directions for the development of advanced bimetallic electrocatalysts for producing multi-carbon materials from CO2 reduction.