In situ spectroscopy studies for elucidating mechanistic insights into the electrocatalytic oxygen evolution reaction

The oxygen evolution reaction (OER) is a pivotal step in a wide range of energy conversion and storage systems. However, its intrinsically high overpotential and the involvement of complex reaction pathways comprising multiple proton-electron coupled transfer steps lead to sluggish reaction kinetics, thereby severely limiting the overall energy conversion efficiency. Conventional electrochemical characterization techniques are somewhat inadequate for directly capturing information regarding the real-time evolution of catalyst surfaces and interfacial structures during the OER. To elucidate the dynamic reaction behavior of the OER, in situ spectroscopic techniques have emerged as powerful tools by enabling real-time monitoring of molecular vibrational signatures or electronic structure variations under electrochemical working conditions. These techniques provide direct insights into the formation of adsorbed species, key reaction intermediates, and catalytically active states at the catalyst-electrolyte interface, and clarify their intrinsic correlations with reaction kinetics. Consequently, in situ spectroscopy offers a solid experimental foundation for constructing a comprehensive OER reaction mechanism and for guiding the rational design of highly efficient electrocatalysts. This review systematically summarizes the advances on in situ infrared reflection spectroscopy, in situ Raman spectroscopy, in situ sum-frequency generation vibrational spectroscopy, in situ fluorescence spectroscopy, and in situ UV-visible spectroscopy, compares their respective advantages and limitations, and provides perspectives on their future development and application prospects.