Unraveling the role of Mo/Ni synergy in β-Ni(OH)2 for high-performance urea oxidation catalysis

Abstract

Advancing electrocatalytic urea oxidation requires the precise engineering of active sites to enhance efficiency and durability. In this study, the atomic-level synergy between molybdenum (Mo) single atom and β-Ni(OH)2 is explored to develop a highly efficient electrocatalyst for the urea oxidation reaction (UOR). By anchoring Mo atoms onto β-Ni(OH)2, electronic modulation at the Ni sites is induced, optimizing their oxidation state and fostering robust Ni-O-Mo interactions that stabilize catalytic activity. This tailored electronic structure facilitates rapid charge transfer, suppresses undesired phase transitions, and enhances reaction kinetics. The Mo/β-Ni(OH)2 demonstrates exceptional UOR performance, achieving a current density of 10 mA cm-2 at a significantly reduced potential of 1.37 V, which is 220 mV lower than the oxygen evolution reaction. Additionally, it exhibits a remarkably low Tafel slope of 24.4 mV dec-1 and retains 98.6% of its activity after 40 hours of continuous operation. In situ spectroscopic analysis confirms the dynamic structural evolution of Mo/β-Ni(OH)2 during UOR, revealing the stabilization of high-valence Ni species and the suppression of NiOOH formation. Furthermore, it elucidates the electronic reconfiguration at Mo and Ni sites, which play a crucial role in enhancing catalytic performance. The modulation of coordination environments and electronic states significantly lowers the energy barriers along the UOR pathway, as supported by density functional theory calculations. These findings provide fundamental insights into metal-site interactions, offering insights for the design of electrocatalysts with enhanced performance and stability.