Composition-Dependent NiS-Enriched FeNi₂S₄/ZnCr₂O₄ Catalyst for Electrochemical Oxygen Evolution Reaction

Transition metal sulfide and oxide nanomaterials are gaining popularity as catalysts for electrochemical water splitting because of their cost effectiveness, durability, and stability without using noble metals. Our study focuses on a hybrid electrocatalyst, NiS-enriched FeNi2S4/ZnCr2O4, which is synthesized in two steps by sol-gel followed through thermal decomposition in an aqueous solution by a hydrothermal process. We investigated its potential application in the electrochemical oxygen evolution reaction (OER). Powder X-ray diffraction and X-ray photoelectron spectroscopy analyses were used to determine the chemical composition and structure. The results showed that the FeNi2S4 structure has an enriched NiS phase. Additionally, the morphology of the synthesized FeNi2S4/ZnCr2O4 was revealed by field emission scanning electron microscopy (FE-SEM). Under alkaline (1 M KOH) conditions, the FeNi2S4/ZnCr2O4 hybrid nanostructure showed a low overpotential value of 295 mV (Tafel slope, 59 mV dec(-1)) for OER activities due to the synergistic effects of FeNi2S4 and ZnCr2O4. Furthermore, the hybrid nanostructure demonstrated its long-term stability and efficiency as an electrocatalyst for OER activities, surpassing previously reported superior electrocatalysts and state-of-the-art materials.