Tracking structural evolution: operando regenerative CeOx/Bi interface structure for high-performance CO2 electroreduction

Unveiling the structural evolution and working mechanism of catalysts under realistic operating conditions is crucial for the design of efficient electrocatalysts for CO₂ electroreduction, yet remains highly challenging. Here, by virtue of operando structural measurements at multiscale levels, it is identified under CO₂ electroreduction conditions that an as-prepared CeO₂/BiOCl precatalyst gradually evolves into CeO_x/Bi interface structure with enriched Ce³⁺ species, which serves as the real catalytically active phase. The derived CeO_x/Bi interface structure compared to pure Bi counterpart delivers substantially enhanced performance with a formate Faradaic efficiency approaching 90% for 24 hours in a wide potential window. The formate Faradaic efficiency can be further increased by using isotope D₂O instead of H₂O. Density functional theory calculations suggest that the regenerative CeO_x/Bi interfacial sites can not only promote water activation to increase local ^*H species for CO₂ protonation appropriately, but also stabilize the key intermediate ^*OCHO in formate pathway.