A defective bismuth-indium catalyst promotes water dissociation for selective carbon dioxide electroreduction to HCOOH

Electroreduction of CO2 to formic acid (HCOOH) is promising for CO2 utilization but remains a substantial challenge due to the lack of high-efficiency electrocatalysts. Herein, the defective BiIn bimetallic catalyst derived from a P-doped BiIn pre-catalyst is developed, which enables CO2 conversion to HCOOH with high activity and selectivity. Mechanistic investigations demonstrate that: (i) the interaction between Bi and In orbitals optimizes the adsorption strength of the key intermediate *OCHO; and (ii) the P leakage could induce the generation of defective BiIn during the self-reconstruction process, which strengthens *OH adsorption, resulting in an accelerated water dissociation and promoted CO2 reduction. The defective BiIn@P catalyst exhibits a 97.3% faradaic efficiency at a current density of 500 mA cm-2 in alkaline electrolytes. This work deepens our understanding of the CO2 reduction mechanism on a BiIn-based catalyst, guiding in the design of advanced CO2R catalysts. A defective BiIn bimetallic catalyst derived from a P-doped BiIn pre-catalyst is developed, which enables CO2 conversion to HCOOH with high activity and selectivity.