CeO_x Promoted Electrocatalytic CO₂ Reduction to Formate by Assisting in the Critical Hydrogenation Step

Bismuth oxide is one of the best-known formate production catalysts from electrocatalytic reduction of CO2. It came as a surprise here that its hybridization with CeOx drastically boosted the catalytic activity and stability on CO2 reduction toward formate formation. Specifically, the formate faradaic efficiency of Bi2O3–CeOx exceeds 85% starting from −0.3 V vs reversible hydrogen electrode (RHE) and remains above 90% from −0.5 V to −1.1 V vs RHE, outperforming the pure Bi2O3 and most other reported formate catalysts. Experimental and computational results suggest that the significantly enhanced catalytic activity arises from the electronic synergy between Bi2O3 and CeOx. The electronic synergy results in abundant defects in CeOx favorable for CO2 activation and adsorption. Moreover, CeOx promotes water dissociation to form H* but with a large energy barrier to H2, which can easily react with CO2 and accelerate the rate-determining step of hydrogenation step. The generality of the CeOx-promoted catalysis for CO2 reduction to formate is also demonstrated for In2O3. This work opens up a new avenue for the design of efficient CO2RR electrocatalysts.