Interface Engineering Overall Seawater Splitting of Self-Supporting CeO@NiCo₂O₄ Arrays

Exploring advanced electrocatalysts for overall seawater splitting is of great significance for large-scale green hydrogen production in which interface engineering has been considered as an effective strategy to enhance the intrinsic activities of the electrocatalysts. In this work, CeO-modified NiCo₂O₄ nanoneedle arrays are designed and constructed in situ grown on Ni foam (NF) through a facile two-step synthesis method. Density functional theory calculations reveal that the strong interaction between CeO and NiCo₂O₄ can regulate the electronic states of metal surfaces and optimize the electronic structures of the materials, essentially improving the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) properties. Specifically, in alkaline electrolytes, CeO@NiCo₂O₄/NF exhibits superior electrocatalytic activities and stabilities, requiring overpotentials of 238 mV for the OER and 144 mV for the HER to achieve a current density of 10 mA cm^-2. When applied to a simulated seawater splitting device, the CeO@NiCo₂O₄/NF also maintains a battery voltage of 1.66 V to reach 10 mA cm^-2 and exhibits good stability for over 60 h, with high faradic efficiencies (FEs) close to 100% for both the OER and HER.