Electrochemical reduction and evolution of oxygen are two critical reactions, which almost determine the performance and efficiency of clean-energy devices due to their sluggish reaction kinetics and large overpotential. Apart from the oxygen reduction/evolution reaction (ORR/OER), the importance of the hydrogen evolution/oxidation reaction (HER/HOR) cannot be ignored either, as hydrogen can work as the powerful fuel with water as the only product.
The core of accelerating the interfacial electrochemical reaction is the exploration of efficient and robust electrochemical catalysts, which relies on the in-depth understanding of reaction mechanism and intermediate process, especially at the molecular, or even atomic level.
Recently, a research team reviewed the recent applications of in situ Raman spectroscopy and X-ray absorption spectroscopy (XAS) in various energy-related reactions including ORR, OER, HER/HOR, and CO2RR occurring on nano- and single-atom catalysts. Using these techniques, the oxygen-containing intermediate species were captured during the reduction of oxygen and the oxidation of hydrogen, and the structural transformation of catalysts with the change of potentials was detected during the evolution of oxygen and reduction of CO2.