In situstudies of energy-related electrochemical reactions using Raman and X-ray absorption spectroscopy

Electrochemical energy conversion technologies involving processes such as water splitting and O2/CO2reduction, provide promising solutions for addressing global energy scarcity and minimizing adverse environmental impact. However, due to a lack of an in-depth understanding of the reaction mechanisms and the nature of the active sites, further advancement of these techniques has been limited by the development of efficient and robust catalysts. Therefore, in situcharacterization of these electrocatalytic processes under working conditions is essential. In this review, recent applications of in situRaman spectroscopy and X-ray absorption spectroscopy for various nano- and single-atom catalysts in energy-related reactions are summarized. Notable cases are highlighted, including the capture of oxygen-containing intermediate species formed during the reduction of oxygen and oxidation of hydrogen, and the detection of catalyst structural transformations occurring with the change in potential during the evolution of oxygen and reduction of CO2. Finally, the challenges and outlook for advancing in situspectroscopic technologies to gain a deeper fundamental understanding of these energy-related electrocatalytic processes are discussed.