Unlocking new crossing field: In situ surface-enhanced Raman spectroscopy analyzing the alternating current catalytic...

This study investigates the integration of in situ surface-enhanced Raman spectroscopy (SERS) for monitoring alternating current (AC) electrocatalytic degradation processes. A custom-built device was employed to ensure electric field distributions comparable to those in typical electrolytic cells. AC-driven degradation using a Au/TiO2 substrate, with methylene blue (MB) as a probe, was conducted therein. In situ Raman data were analyzed to reveal key reaction indicators, including spectral intensity variations, relative peak intensity ratios, and charge transfer efficiencies throughout the degradation process of varying field frequencies and photoillumination conditions. Two distinct degradation mechanisms were identified for the AC electrocatalytic degradation: reactive oxygen species (ROS)-driven degradation and direct charge transfer from the electrode surface. Furthermore, investigation of the combined AC electrocatalytic and photocatalytic processes revealed that energy injection from AC electric fields and photoillumination can be stored in substrate electrons for up to several tens of seconds, with cumulative effects even when the two energy inputs are not synchronized. These mechanistic findings provide fundamental insights into AC electric field-assisted processes and offer a foundation for the rational utilization of green and widely available energy sources of AC electric fields and photoenergy.