Photo-excited electrochemical surface-enhanced Raman spectroscopy: in situ/operando insights into photoelectrocatalytic interfaces

Photoelectrocatalysis plays a vital role in sustainable energy conversion technologies. However, the understanding of these reaction mechanisms remains incomplete because of the complexity of photoelectrochemical interfaces and the trace amounts of interfacial substances. Introducing photoexcitation into electrochemical surface-enhanced Raman spectroscopy (EC-SERS) enables monitoring reaction processes of photoelectrocatalysis by the integration of photo/electrochemical characterization and Raman spectroscopy. In this review, we classify this methodology as photo-excited EC-SERS. We first introduce the fundamental aspects of photo-excited EC-SERS, covering principles, substrate materials, and experimental setups. Then, the applications of photo-excited EC-SERS in key photoelectrocatalytic reactions, such as water splitting, CO₂ reduction, and organic oxidation, are discussed. Combined with practical cases, the values of photo-excited EC-SERS in photoelectrocatalytic processes are discussed, including: (1) understanding charge transfer interfacial processes; (2) capturing transient intermediates in the vibration fingerprints; and (3) analyzing the mechanism and pathway of photoelectrocatalytic reactions. In addition, we examine the application of photo-excited EC-SERS in biosensors. Finally, we point out the challenges of photo-excited EC-SERS in monitoring photoelectrocatalytic reactions, which we believe will motivate researchers to take advantage of the technology's versatility and applicability to help sustainable energy development.