A hierarchical NiFeOOH@CeO_2−x nanosheets array boosts electrocatalytic activity and durability at high current densities for water oxidation

The oxygen evolution reaction (OER) reaction kinetics of nickel-iron (oxy)hydroxides (NiFeOOH) is limited by their weak adsorption of OER intermediates. Herein, a hierarchical NiFeOOH@CeO_2−x nanosheets array was in situ grown on a nickel foam by a facile laser direct writing method, which exhibits superior OER activity and durability at high current densities in alkaline electrolytes. The hierarchical nanosheets array exposes abundant catalytic active sites, which greatly promote OER reaction rate. The strong electronic interaction at the NiFeOOH/CeO_2−x interface leads to favorable electron transfer from Ni²⁺/³⁺ and Fe³⁺ to Ce³⁺/⁴⁺. The Ni sites with high valences show enhanced OH⁻ adsorption and also promote the formation of *OOH intermediate, thereby greatly improving OER intrinsic activity. The oxygen deficient CeO_2−x primary sheets guarantee good electrical conductivity. Such a well-designed catalytic electrode requires overpotentials of only 229 and 287 mV to achieve current densities of 50 and 500 mA·cm⁻², respectively, and sustains superior stability at 500 mA·cm⁻² and 1 A·cm⁻².