Cutting-Edge Optimization Strategies and In Situ Characterization Techniques for Urea Oxidation Reaction Catalysts: A Comprehensive Review

Urea electrolysis presents an eco-friendly, cost-effective method for hydrogen (H₂) production and pollution control. However, its efficiency is limited by a slow 6-electron transfer process, necessitating advanced electrocatalysts to accelerate the urea oxidation reaction (UOR) and moderate overpotential, thereby cutting energy losses. Developing efficient, affordable electrocatalysts is vital for practical urea electrolysis (UE) and improving UOR kinetics. Optimizing UOR electrocatalysts requires creating highly active sites, enhancing electrical conductivity, and manipulating electronic structures for improved electron transfer and intermediate binding affinities. This review explores recent advances in UOR catalyst design, focusing on transition metal-based catalysts, including nanostructures, phases, defects, heterostructures, alloys, and composites. It underscores the importance of understanding structure-performance relationships, surface reconstruction phenomena, and mechanisms through in situ characterization. Additionally, it critically assesses the challenges in UOR catalysis and provides insights for developing high-performance electrocatalysts. The review finishes with perspectives on future research directions for green hydrogen generation via urea electrolysis.