Recent Advances of Urea-Oxidation Coupled Hydrogen Generation on Cobalt-Based Electrocatalysts

Electrochemical water splitting is a promising approach to produce green hydrogen, while its efficiency is determined by the sluggish oxygen evolution reaction (OER) occurring on the anode due to its high overpotential. The urea oxidation reaction (UOR) has emerged as a highly promising alternative to the conventional OER, resulting from its low overpotential in various electrolytes. Numerous electrocatalysts have been further synthesized to achieve an even lower overpotential of the UOR. Among the investigated materials, cobalt-based electrocatalysts are particularly promising for urea-assisted hydrogen generation because of their tunable electronic structures, multiple oxidation states, structural versatility, and relatively low cost. These features promote efficient UOR and HER kinetics, enabling bifunctional catalysts to replace the sluggish OER and reduce the energy requirement for hydrogen production while offering the additional benefit of urea-rich wastewater treatment. This review thus elaborates on the progress and advances of the coupled UOR with the HER on various cobalt-based electrocatalysts. It highlights key parameters that govern the HER/UOR performance on electrocatalysts, followed by various modification strategies for cobalt-based electrocatalysts. The catalytic performance of diverse cobalt-based materials is then systematically evaluated. This article ends with an overview of current challenges and future prospects for the development of cobalt-based electrocatalysts in sustainable hydrogen production and environmental applications.