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

Electrochemical reduction of CO₂ 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 SnO₂ catalyst is synthesized for efficient CO₂ 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 SnO₂ 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 CO₂ electroreduction catalysts.