Electrochemical Surface-Enhanced Raman Spectroscopy for Energy Modulation of Surface Plasmon-Mediated Photoelectrochemical Reactions of para-Aminothiophenol on Silver Nanoparticle-Modified Electrodes

Surface plasmon resonance (SPR) of noble metal nanoparticles (NPs) provides a pathway to efficiently absorb and confine light to nanoscale surface electrons, thereby bridging photonics and photoelectrochemistry. In this article, SPR-enhanced photoelectrochemical synergistic reactions are studied by surface-enhanced Raman spectroscopy (SERS) to improve the chemical reaction activity and examine changes in the reaction selectivity. We first demonstrate that hot holes arising from SPR decay contribute to the surface catalytic coupling reaction of PATP on a silver NP electrode. Then, by using potential step electrochemical SERS, we further inspect the kinetics of the surface catalytic coupling reaction by monitoring the time-dependent SERS intensity of the characteristic band at 1436 cm(-1), which can be attributed to the stretching vibration of the N= N double bond. When synergistically combined with other external field factors, such as the applied potential and pH at electrochemical interfaces, SPR-enhanced photoelectrochemical reactions can be further tuned to gain reaction efficiency and selectivity for the formation of p,p'-dimercaptoazobenzene (DMAB) at relatively high potentials and 4 '-mercapto-N-phenylquinone diimine (MPQDI) at even higher potentials with a high pH. The simulated Raman spectra from the density functional theoretical calculations also support these results. The latter product for the first time demonstrates that dual reaction pathways occur for PATP adsorbed on the silver NP electrodes. The SPR effect provides a viable approach for studying the photoelectrochemistry at the interface of nanoparticle-modified metal electrodes and electrolytes.