Atomic‐Level Elucidation of Lattice‐Hydrogens in Copper Catalysts for Selective CO ₂ Electrochemical Conversion toward C ₂ Products

Abstract Copper is the most efficient and practical electrocatalyst for the electrochemical reduction of carbon dioxide (ECR) to give multicarbon (C 2+ ) products, but the mechanism by which such products are formed – though known to involve lattice‐hydrogens – remains elusive, and the selectivity of the reaction is poor. Herein, we report the synthesis of [AuCu 24 (dppp) 6 H 22 ] + , a copper hydride nanocluster bearing exposed Cu 3 H 3 units in specific surface cavities, and our use of it to study the mechansim and selectivity of the reduction of CO 2 to C 2+ products. Results of in situ infrared spectroscopy and theoretical calculations showed that these Cu 3 H 3 units can effectively lower the energy barrier to the formation of the *COCOH intermediate, which allowed the competition between the C 1 and C 2 pathways to be elucidated. Isotope labeling experiments and catalyst recrystallization studies corroborated the theoretical simulations, identifying the lattice‐hydrogen (H − ) in the Cu 3 H 3 active unit as being indispensable for the formation of C 2 H 4 . The molecular design guidelines which this work has facilitated constitute a new approach towards the of copper‐based catalysts that convert CO 2 to C 2+ products based on lattice‐hydrogen engineering.