Experimental and Theoretical Study on Isotopic Surface-Enhanced Raman Spectroscopy for the Surface Catalytic Coupling Reaction on Silver Electrodes

Surface-enhanced Raman Spectroscopy (SERS) as a unique spectroscopic tool has been broadly used to detect surface reactions, yet normal SERS detection and theoretical simulation cannot satisfy the urgent need of revealing detailed reaction mechanisms. Here, we introduce an isotopic SERS method to demonstrate the occurrence of surface chemical reactions theoretically and experimentally. Isotopic effects on Raman vibrational frequency and intensity due to the change of reduced masses and the vibrational coupling were verified by DFT simulations and its corresponding isotopic SERS measurements. Taking surface catalytic coupling reactions of PATP/PNTP to DMAB on silver surfaces as the modeling system, we first created chemically identical yet vibrationally distinct isotopologues of redox species by artificial isotopic substitution. Our theoretical and experimental results both showed the isotopic effects have obviously different features in the fundamental frequencies and the relative intensities in the Raman spectra of isotope-substituted PATP, PNTP, and DMAB, which can be applied to identify some new surface species on electrode surfaces. The capability of isotopic SERS to investigate the mechanism of surface redox reactions through tracking the signature changes of the species can be significant for revealing the evolution of surface chemical reaction processes.