CeO2‐Accelerated Surface Reconstruction of CoSe2 Nanoneedle Forms Active CeO2@CoOOH Interface to Boost Oxygen Evolution Reaction for Water Splitting

Interface engineering is an efficient strategy to create high‐performance electrocatalysts for water splitting. In the present work, CeO2@CoSe2 nanoneedle on carbon cloth (CeO2@CoSe2/CC) demonstrates high efficiency for oxygen evolution reaction (OER) and water splitting. CeO2 with abundant O vacancies facilitates the adsorption of OH− and boosts the reconstruction of CoSe2 into CoOOH at lower potentials. The in situ generated active CeO2@CoOOH heterointerface upshifts the d‐band center of Co site, thereby decreasing the free energy of rate‐determining step (RDS) (*O to *OOH) during the OER process. It delivers a low OER overpotential of 245 mV at 10 mA cm−2. CeO2@CoSe2/CC is also found to be active for hydrogen evolution reaction (HER, 138 mV overpotential at 10 mA cm−2), profiting from CeO2‐facilitated *H2O dissociation and *H adsorption on CoSe2. The overall water splitting is achieved over the CeO2@CoSe2/CC bifunctional electrode with a low electrolysis voltage of 1.54 V at 10 mA cm−2. This work offers valuable insights into CeO2‐assisted surface reconstruction as well as provides water electrolysis catalysts through interface engineering.