Interconnected Mn-Doped Ni(OH)2 Nanosheet Layer for Bifunctional Urea Oxidation and Hydrogen Evolution: The Relation between Current Drop and Urea Concentration during the Long-Term

Replacing oxygen evolution reaction with more thermodynamically easy reactions such as urea oxidation reaction (UOR) in water splitting has received increasing attention in recent years. In this study, Mn-doped Ni(OH)(2) is synthesized on carbon paper as a bifunctional electrode for UOR and hydrogen evolution reaction (HER). This novel electrode delivers high activity and durability for both UOR and HER. Moreover, a positive correlation between the current density and urea concentration during the long-term operation is found for the first time, which provides theoretical support to explain the UOR current drops for long-time operation. The full electrolytic cell constructed by Mn-doped Ni(OH)(2) achieves a working potential of 1.407 V at 10 mA cm(-2), which is one of the best UOR-based water splitting systems reported so far. This study brings new knowledge in the mass-transfer controlled anodic reaction process of urea, which promotes the electrolytic systems for both clean energy generation and waste reuse.