Boosting proton reduction via isolated Cu atoms in Bi lattice for efficient electroreduction of CO2 to formate

Abstract Current Bi-based catalysts suffer from low current density for electroreduction of CO2 to formate due to the high energy barrier of H+ reduction to *H on Bi sites. Here we report a unique BiCu single-atom alloy catalyst (SAAC) that can deliver a ultrahigh formate partial current density (jformate) of 434 mA cm–2, the highest among the reported Bi-based electrocatalysts to date, with a formate Faradaic efficiency (FEformate) of 96.5% at –0.55 V (vs. RHE) in a flow cell, while BiCu alloy catalyst containing Cu nanoclusters can only deliver a jformate of 48.5 mA cm–2 with a FEformate of 37.3% under an identical condition. Mechanism investigations reveal that the isolated single-atom Cu in BiCu SAAC can dramatically reduce the energy barrier of H+ reduction to *H on Cu site for boosting the reduction of CO2 to formate. Our work provides a new strategy for engineering unfavourable energy barrier of electrocatalysts to promote CO2 reduction.