Developing high-efficiency and affordable electro-catalysts remains a crucial bottleneck on the way to the practical applications of the electrochemical urea oxidation reaction (UOR) scenarios. In recent years, Ni-based materials have proven to be excellent electrocatalysts for the UOR in alkaline medium. Understanding the characteristics that affect UOR activity and determining the mechanism are of vital importance for the development of UOR electro-catalysts. Therefore, in situ characterization techniques performed under UOR conditions are urgently needed to monitor the key intermediates together with identifying the UOR active centers and phases. Herein, recent advances regarding in situ techniques for the characterization of Ni-based electrocatalysts are summarized, including Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy. The results from these in situ measurements not only reveal the structural transformation of the catalytic species under UOR conditions, but also disclose the crucial role of NiOOH during the UOR. The evidence displayed by identified intermediate product information helps scientists better understand the UOR path and find solutions. Furthermore, those knowledge will provide helpful inspiration and guidance for the further development of high-efficiency UOR catalysts.
Keywords in situ techniques, urea oxidation reaction, active phases, reaction species