Revealing Adsorption Conformation and Electro-oxidation Mechanism of Urea on the Ni Film Catalyst by In Situ ATR-SEIRAS

The electrochemical urea oxidation reaction (UOR) is considered as a promising alternative to the oxygen evolution reaction due to its lower thermodynamic equilibrium potential (0.37 V). Nickel (Ni)-based catalysts have been universally used for UOR due to their lower cost and higher catalytic activity. However, the lack of mechanistic clarity has limited the study of catalyst constructional relationship. Herein, electrochemical in situ attenuated total reflection-surface-enhanced infrared spectroscopy was utilized to investigate the adsorption conformation and the reaction mechanism of UOR on the Ni-based catalyst. Combining CO(15NH2)2 isotopic experiments and polarization spectra method, the O-terminal adsorbed structure of urea, *O═C(NH2)2, was unveiled as a reaction precursor. Moreover, with the potential increasing, *O═C(NH2)2 was converted to the N-terminal adsorbed structure, *NHCONH2, which was oxidized to generate CO2 and N2 by undergoing dehydrogenation. The finding could promote the knowledge of the reaction mechanism of UOR on Ni-based catalysts, which is conducive to the further design of high-performance catalysts for urea oxidation.