Study of the Electrocatalytic Properties of Electrodes for Water Electrolysis

Abstract

In this study, pristine ZnS, ZnFe₂O₄, and their composite ZnS/ZnFe₂O₄ heterostructure were successfully synthesized via a simple electrodeposition method and comprehensively characterized using structural, optical, and electrochemical techniques. X-ray diffraction (XRD) confirmed the crystalline nature and successful formation of as-prepared electrode. UV–Vis spectroscopy and Tauc analysis revealed a shift in the absorption edge of the heterojunction, resulting in a novel band gap of 2.80 eV, enabling visible-light excitation. Mott–Schottky analysis demonstrated the formation of a p–n heterojunction with enhanced charge carrier concentration and a favorable flat-band potential shift, promoting efficient interfacial charge separation. Electrochemical investigation showed superior hydrogen evolution reaction (HER) acti vity for the ZnS/ZnFe₂O₄ electrode in alkaline media, delivering a low overpotential of 261 mV at −10 mA•cm⁻² and a Tafel slope of 122 mV•dec⁻¹, indicating Volmer-step-dominated kinetics. Electrochemical impedance spectroscopy (EIS) revealed the lowest charge-transfer resistance (2.13 Ω) and the highest electrochemically active surface area (ECSA = 30.25 cm²), suggesting rapid electron transport and abundant active sites. The composite electrode also demonstrated excellent durability, maintaining stable performance after 1500 LSV cycles and 3 hours of continuous operation at −100 mA•cm⁻². Notably, under visible-light irradiation, HER activity was further enhanced due to improved electrical conductivity and efficient charge separation at the ZnS/ZnFe₂O₄ interface. The formation of the p–n heterojunction effectively reduces charge recombination and creates new active sites, significantly enhancing hydrogen production. These findings highlight the potential of heterojunction engineering and establish ZnS/ZnFe₂O₄ as a cost-effective and durable photo and electrocatalyst for sustainable hydrogen generation in alkaline media.