CeOx 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 CO 2 . It came as a surprise here that its hybridization with CeO x drastically boosted the catalytic activity and stability on CO 2 reduction toward formate formation. Specifically, the formate faradaic efficiency of Bi 2 O 3 –CeO x 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 Bi 2 O 3 and most other reported formate catalysts. Experimental and computational results suggest that the significantly enhanced catalytic activity arises from the electronic synergy between Bi 2 O 3 and CeO x . The electronic synergy results in abundant defects in CeO x favorable for CO 2 activation and adsorption. Moreover, CeO x promotes water dissociation to form H* but with a large energy barrier to H 2, which can easily react with CO 2 and accelerate the rate-determining step of hydrogenation step. The generality of the CeO x -promoted catalysis for CO 2 reduction to formate is also demonstrated for In 2 O 3 . This work opens up a new avenue for the design of efficient CO 2 RR electrocatalysts.