Interface Engineering and External Stimuli-Driven Enhancement of Metal/Oxide Catalysts for Urea Oxidation Reaction

Abstract

The urea oxidation reaction (UOR) is a promising alternative to the oxygen evolution reaction for reducing the energy demand of electrochemical hydrogen production while simultaneously treating urea-containing wastewater. However, its practical application remains limited by sluggish multielectron-transfer kinetics, inefficient interfacial charge transport, catalyst deactivation, and the accumulation of strongly adsorbed intermediates. This dissertation investigates interface engineering and external-stimulus-assisted strategies to improve UOR activity by regulating electronic junctions, charge redistribution, carrier transport, and the local catalytic environment. First, Ga-doped ZnO-supported Ni catalysts were investigated to determine how Schottky and Ohmic junction behavior affects metal/oxide electrocatalysis. Appropriate Ga doping promoted low-resistance interfacial charge transfer, favorable metal–support interactions, and improved UOR activity and stability. Second, a Ni/CoO/g-C3N4 ternary heterostructure was developed for sonication-assisted UOR. Acoustic stimulation enhanced mass transport and interfacial charge transfer, while the mechanically responsive g-C3N4 component contributed to dynamic charge redistribution within the composite. Photon-assisted UOR was subsequently investigated using a Co3O4/g-C3N4 heterostructure. Interfacial electronic coupling and direct Z-scheme charge transfer improved the separation and utilization of photogenerated carriers, resulting in enhanced catalytic kinetics under illumination. Finally, a CuS/WO3 heterostructure was developed to combine photoinduced charge separation with photothermal activation. Light irradiation and the resulting thermal enhancement accelerated interfacial reaction kinetics and reduced the electrical potential required for UOR. Collectively, these studies demonstrate that catalyst interfaces act as electronically active regions that govern charge transport, active-state accessibility, and the utilization of externally supplied energy. The integration of junction engineering with acoustic, optical, and photothermal stimulation provides a versatile strategy for improving UOR and advancing energy-efficient hydrogen production coupled with wastewater remediation.