Probing the Intermediate in the Electrochemical Reduction of Nitrobenzene Derivative by EC-TERS

Identification of the molecular structure of intermediates during the electrochemical reaction systems is vitally important for clarifying reaction paths and mechanisms, which requires in situ spectroscopic techniques that could provide chemical fingerprint information and high detection sensitivity. Electrochemical tip-enhanced Raman spectroscopy (EC-TERS) offers rich fingerprint information, single-molecule sensitivity, and high spatial resolution to probe intermediates in electrochemical reactions. Here we employed EC-TERS to monitor the electrochemical reduction process of a nitrobenzene derivative, 4-nitrophenyl isocyanide (4-NPIC), on a well-defined Pd/Au(111) single crystal surface. By leveraging the benefits of the well-defined configuration in EC-TERS, we were able to identify the molecular structure of the negatively charged intermediate during the reaction in neutral solution, which cannot be clearly identified by electrochemical surface-enhanced Raman spectroscopy (EC-SERS). The present work demonstrates the advantage of EC-TERS in capturing the fine structure of immediate species during electrochemical reactions and paves the way for utilizing EC-TERS for in situ and nanoscale analysis of reaction intermediates in important electrochemical systems.