In situ/operando vibrational spectroscopy for the investigation of advanced nanostructured electrocatalysts

Electrochemical energy conversion via electrocatalysis offers promising solutions to tackle problems of global energy crisis and environmental issues. The rational design of efficient electrocatalysts requires an in-depth understanding of the underlying mechanism and the structure-activity relationship of key electrocatalytic processes such as oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR). To gain a comprehensive understanding of these electrochemical systems, in situ characterization techniques capable of determining catalyst states as well as important reaction intermediates under operando conditions are necessary. Vibrational spectroscopic methods, including Raman and FTIR-based techniques, are powerful tools to monitor surface transformation, active sites, and interfacial intermediates under reaction conditions. Here, recent developments of in situ/operando vibrational spectroscopic techniques in the probing of various electrochemical reactions and processes are described and summarized. The outlook for future research directions in this field is also discussed. The aim is to attract increasing attention of the wider community to in situ/operando characterization techniques and promote the fundamental understanding of reaction mechanisms and structure-activity relationships in electrocatalytic energy conversion systems.