Rational design of Co4S3/Ni9S8 heterostructure on nickel foam for efficient bifunctional oxygen and urea oxidation reactions

Abstract

The development of bifunctional catalysts capable of adapting to complex reaction environments in real time for OER and UOR poses a major challenge during the electrolysis of industrial wastewater, where the concentration of urea is constantly changing. In this work, a series of heterostructured electrocatalysts are synthesized on nickel foam through controlled hydrothermal sulfidation, achieving synergistic enhancement in both oxygen evolution reaction (OER) and UOR. The optimized catalyst, Co₄S₃/Ni₉S₈/NF, delivers a current density of 100 mA cm⁻² at an ultralow potential of 1.571 V for OER and 1.328 V for UOR, with corresponding Tafel slope of 53.74 mV dec⁻¹ and 3.91 mV dec⁻¹, respectively. Furthermore, the Co₄S₃/Ni₉S₈/NF exhibits robust durability across 36 h of continuous operation in a 0.2 M Urea-containing alkaline electrolyte. The excellent activity of Co₄S₃/Ni₉S₈/NF can be attributed to its heterostructure, which features vertically growing nanoparticle clusters that enhance electrolyte permeability and active site exposure, as well as interfacial charge redistribution at the heterojunction, thereby optimizing the *OOH adsorption for OER and the urea dehydrogenation kinetics for UOR.