Self-Supported NiCo₂S₄@Ce-NiFe LDH/CeO₂ Nanoarrays for Electrochemical Water Splitting

Abstract

The design of high-performance OER catalysts is crucial for efficient electrochemical water splitting (EWS). Herein, a NiCo₂S₄@Ce-NiFe LDH/CeO₂ heterostructure nanoarray electrocatalyst with abundant oxygen defect sites is reported. The introduction of Ce species activates the lattice oxygen in the oxyhydroxides, inducing the transformation of the catalytic mechanism toward the lattice oxygen oxidation mechanism (LOM) pathway, bypassing the thermodynamic limitation of the adsorbate evolution mechanism (AEM), and strengthening the intrinsic activity of the material. Moreover, the reversible transitions between different oxidation states of Ce species and the high oxygen storage capacity of CeO₂ regulate the adsorption behavior of the reaction intermediates, allowing it to be easier for the material to enrich the oxygen-containing intermediates, thereby improving the adsorption kinetics. Accordingly, NiCo₂S₄@Ce-NiFe LDH/CeO₂ exhibits remarkable OER performance (η₅₀ = 226 mV, η₁₀₀ = 244 mV) and brilliant stability. Additionally, the presence of the CeO₂ protective layer inhibits the impact of Cl^- and other pollutants in seawater, which enables NiCo₂S₄@Ce-NiFe LDH/CeO₂ to perform satisfactorily in seawater electrolysis, as well. This study offers a fresh perspective on the design of defect-rich OER catalysts.