Indium–Oxygen Integrative Catalytic Pairs for Boosting Asymmetric C–C Coupling in Electrochemical Formic Acid Reduction Reaction

Abstract Electrocatalytic upgrading of C1 molecules into value-added C2 oxygenates, especially acetaldehyde and ethanol, offers a promising route for environmentally friendly chemical synthesis. Herein, we report a theory-guided experimental discovery of an indium–oxygen integrative catalytic pairs (ICPs) that enables efficient asymmetric C–C coupling in electrochemical formic acid reduction reaction (FRR). Grand-canonical constant-potential and constrained ab initio molecular dynamics (AIMD) simulations show that the In–O ICPs on a carbon support exhibit structural flexibility, which provide dual active sites for formic acid adsorption and activation. The resulting electronically asymmetric dual active sites lead to inequivalent hydrogenated intermediates (*CH2 and *CHO), followed by low-energy-barrier asymmetric *CH2–*CHO coupling, ultimately producing ethanol and acetaldehyde. The underlying reaction mechanisms are investigated via comprehensive structural and electronic analyses. Leveraging the theoretical predictions, experimental results validate the feasibility of the In–O ICPs for enabling formic acid-to-C2 oxygenates conversion, particularly acetaldehyde formation. Beyond identifying an effective electrocatalytic platform, this joint theoretical-experimental study reveals a mechanism of asymmetric dual-site activation and C–C coupling, offering a conceptual framework for designing ICP-based catalysts for multi-intermediate electrocatalysis.