Boosting Electrochemical CO ₂ Reduction to Formate over La-Doped SnO ₂ via Pinning Effect and Water Activation

Abstract

Electrochemical reduction of CO 2 to formate over Sn-based catalysts offers an effective carbon-neutral approach for chemical production and renewable energy storage. However, poor selectivity under high current densities persists, primarily due to the instability of Sn–O active sites and slow water dissociation. In this work, a La-doped SnO 2 catalyst is synthesized for efficient CO 2 conversion to formate. Detailed in situ experimental and theoretical studies reveal that La doping induces a pinning effect that effectively stabilizes the Sn–O structure, decreasing the energy barrier for *OCHO conversion. Meanwhile, La species accelerate water activation to provide *H species, and then the moderate *H coverage promotes formate production. As a result, the La-doped SnO 2 exhibits high formate selectivity over a broad potential window from −0.8 to −1.2 V vs reversible hydrogen electrode (RHE), achieving a formate Faradaic efficiency of up to 93.2% with a partial current density of −315.4 mA cm –2 at −1.0 V vs RHE. This work may provide insights into the pinning effect and encourage more design strategies to explore lanthanide element doping for efficient CO 2 electroreduction catalysts.