Interfacial La Diffusion in the CeO₂/LaFeO₃ Hybrid for Enhanced Oxygen Evolution Activity

The electrochemical oxygen evolution reaction (OER) is of great significance for energy conversion and storage. The hybrid strategy is attracting increasing interest for the development of highly active OER electrocatalysts. Regarding the activity enhancement mechanism, electron coupling between two phases in hybrids has been widely reported, but the interfacial elemental redistribution is rarely investigated. Herein, we developed a CeO2/LaFeO3 hybrid electrocatalyst for enhanced OER activity. Interestingly, a selective interfacial La diffusion from LaFeO3 to CeO2 was demonstrated by the electron energy loss spectra and elemental mapping. This redistribution of cations triggers the change of the chemical environment of interface elements for charge compensation because of the electroneutrality principle, which results in increased oxygen vacancies and high-valent Fe species that promote the OER electrocatalysis. This mechanism might be extended to other hybrid systems and inspire the design of more efficient electrocatalysts.