Operando infrared spectroscopic insights into the dynamic evolution of liquid-solid (photo)electrochemical interfaces

The scaling up of hydrogen energy system depends on the development of robust and efficient catalysts for water splitting and the reverse reactions. Operando infrared (IR) spectroscopy is one of the key methods to provide intuitive insights for hydrogen/oxygen-based intermediates to accelerate the screening process of catalysts. Unfortunately, the application of operando IR spectroscopy in the liquid-solid catalytic system is strongly impeded by the dramatic absorption of water and weak signals of photo/electrochemical reaction intermediates. In this review, we scrutinize the system-level strategies of operando IR measurement for (photo)electrolytic liquid-solid interfaces, including the light sources, optical pathway and reaction cell design. Particularly, operando synchrotron radiation IR measurement recently developed in our group is emphasized for its ability to study diluted catalytic site systems, such as metal-organic framework (MOF) and single-atom catalysts. A series of in-depth investigations of transient M–O–O, M–O–O–H and M–O bonds in OER and ORR processes is presented as the vital contributions of operando IR measurement to monitor the evolution of intermediate structures.