Water oxidation promoted synergistically by CeO₂-shell on CoNiO₂-core

Rare-earth based transition metal oxides have proved to be the most promising candidates in the exploration of non-precious oxygen evolution reaction (OER) catalysts. However, the knowledge regarding their active sites and electrocatalytic mechanism is very limited due to their different crystallization behaviors and there are still big challenges in the efficient coupling of transition and rare-earth metals with full utilization of active sites. To improve and stabilize OER catalysis, we developed the core–shell CeO₂@CoNiO₂ nanoplates (NPLs) for enhanced and stable OER catalysis. Surprisingly, CeO₂ shell regulates the electronic structure of CoNiO₂ core and increases the number of active sites and oxygen vacancies to achieve high electrochemical performance in a three-electrode system. Compared with CoNiO₂ nanoparticles, the developed core–shell NPLs exhibit favorable performance with an overpotential of only 206 mV at 10 mA/cm² and robust electrochemical stability of 500 h at 10 mA/cm² and 300 h at 50 mA/cm². In situ Raman spectroscopy unveils that CeO₂@CoNiO₂ is structurally more stable than CoNiO₂, which is consistent with its performance persistence. Besides, theoretical calculations confirm that the Ce shell serves as the active centers for OER, and the formed core–shell metal oxides NPLs promote the adsorption and dissociation of water, thus causing the fast generation of O₂. This work provides a new perspective for designing highly active core–shell structure of mixed metal oxides of transition and rare-earth metals for OER.