In situ characterization techniques: main tools for revealing OER/ORR catalytic mechanism and reaction dynamics

The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are some of the most important reactions in electrochemical energy technologies such as fuel cells and metal–air cells. However, the lack of in-depth understanding of reaction mechanisms and clear identification of catalytic active sites hinders the development of high-performance and durable electrocatalysts for the OER and ORR. In situ characterization techniques enable on-site monitoring of the surface oxidation state and local atomic structural transitions, facilitating the identification of active sites and enhancing our fundamental understanding of reaction mechanisms in these systems. This article reviews the main progress in the OER/ORR process using various in situ techniques. By utilizing in situ characterization techniques, the factors affecting catalyst catalytic performance are revealed from a direct or indirect perspective. Finally, the main challenges and prospects of in situ characterization techniques in ORR/OER research are discussed.