Active plane modulation of Bi₂O₃ nanosheets via Zn substitution for efficient electrocatalytic CO₂ reduction to formic acid

Formic acid is considered one of the most economically viable products for electrocatalytic CO₂ reduction reaction (CO₂RR). However, developing highly active and selective electrocatalysts for effective CO₂ conversion remains a grand challenge. Herein, we report that structural modulation of the bismuth oxide nanosheet via Zn²⁺ cooperation has a profound positive effect on exposure of the active plane, thereby contributing to high electrocatalytic CO₂RR performance. The obtained Zn-Bi₂O₃ catalyst demonstrates superior selectivity towards formate generation in a wide potential range; a high Faradaic efficiency of 95% and a desirable partial current density of around 20 mA·cm⁻² are obtained at −0.9 V (vs. reversible hydrogen electrode (RHE)). As proposed by density functional theory calculations, Zn substitution is the most energetically feasible for forming and stabilizing the key OCHO* intermediate among the used metal ions. Moreover, the more negative adsorption energy of OCHO* and the relatively low energy barrier for the desorption of HCOOH* are responsible for the enhanced activity and selectivity.