Surface Reconstruction of La₂CuO₄ during the Electrochemical Reduction of Carbon Dioxide to Ethylene and Its Benefits for Enhanced Performance

Electrochemical reduction (ECR) of CO₂ to C₂H₄ has a potential key role in realizing the carbon neutral future, which ultimately relies on the availability of an efficient electrocatalyst that can exhibit a high Faradaic efficiency (FE) for C₂H₄ production and robust, long-term operational stability. Here, for the first time, we report that upon applying reductive potential and electrolyte to the benchmark La₂CuO₄ catalyst, surface reconstruction occurred, i.e., the appearance of a distinctive phase evolution process over time, which was successfully monitored using ex situ powder XRD and operando Mott-Schottky (M-S) measurements of La₂CuO₄ samples that were soaked into the electrolyte and subjected to CO₂-ECR for different durations. At the end of such a reconstruction process, an outermost layer consisting of lanthanum carbonate, a thin outer layer made of an amorphous Cu⁺ material formed over the core bulk La₂CuO₄, as confirmed by various characterization techniques, which resulted in the redistribution of interfacial electrons and subsequent formation of electron-rich and electron-deficient interfaces. This contributed to the enhancement in FE for C₂H₄, reaching as much as 58.7%. Such surface reconstruction-induced electronic structure tuning gives new explanations for the superior catalytic performance of La₂CuO₄ perovskite and also provides a new pathway to advance CO₂-ECR technology.