Bimetallic Cu-Bi catalysts for efficient electroreduction of CO₂ to formate

Electrochemical CO₂ reduction offers an effective means to store renewable electricity in value-added chemical feedstocks. Much effort has been made to develop catalysts that achieve high Faradaic efficiency toward Formate production, but the catalysts still need high operating potentials to drive the CO₂-to-formate reduction. Here we report physical vapor deposition to fabricate homogeneously alloyed, compositionally controlled Cu Bi bimetallic catalysts over a large area with excellent electrical conductivity. Operating electrochemical studies in Ar-saturated and CO₂-saturated electrolytes identified that Cu-Bi catalysts notably suppress the competing H₂ evolution reaction and enhance CO₂-to-formate selectivity. We reported a formate Faradaic efficiency of >95% at an improved cathodic potential of ∼-0.72 V vs. RHE and a high formate cathodic energy efficiency of ∼70%. The electrochemical reaction is stable over 24 h at a current density of 200 mA cm^-2. The work shows the advantages of bimetallic catalysts over single metal catalysts for increased reaction activity and selectivity.