Spindle Nanorods of CeO2 and NiS Heterointerface Coated by the NC Layer: A High-Performance Bifunctional Electrocatalyst for Water Splitting

Currently, nickel sulfides are widely employed in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), thanks to the narrow electronegativity difference of only 0.67 eV between nickel and sulfur. Among them, NiS stands out in terms of the OER performance; however, its HER performance and stability remain somewhat inadequate. The construction of heterogeneous interfaces can efficiently improve the HER performance and regulate the electronic structure of the NiS catalyst. CeO₂ has been discovered to possess exceptional electronic modulation capabilities, which may lead to the effective enhancement of both HER and OER of the NiS catalyst. As a result, a nitrogen-doped carbon-coated CeO₂-NiS heterogeneous interface catalyst (NC/NiS-CeO₂) is designed as a bifunctional electrocatalyst for HER and OER with high performance. The NC/NiS-CeO₂ catalyst demonstrates excellent HER (47 mV at 10 mA cm^-2) and OER (92 mV at 10 mA cm^-2) performances in a 1 M KOH alkaline solution. Characterization analysis reveals that the coupling of the heterostructure interface, which consists of CeO₂ and NiS, significantly enhances electron conduction, the synergistic effect, and the electrocatalytic activity of the electrode. This study demonstrates that the HER and OER activity can be effectively improved by constructing a rational heterogeneous interface.