| The formation of aniline derivatives from nitrobenzene derivatives is a complicated reaction,which involves multiple electrons,protons,and intermediates.It is difficult to systematically characterize the transformation process at the molecular level with conventional electrochemical methods.However,the EC-SERS,which combines the electrochemical(EC)and the surface-enhanced Raman spectroscopy(SERS),can dynamically detect the fingerprint information of the molecules and give a better description of the redox process in the interface.In this paper,para-Nitrothiophenol(PNTP)was selected as the model molecule.The mechanism and kinetics of the photoelectrochemical reduction reaction of PNTP on AuNPs@Au electrode were systematically studied.This paper was mainly divided into the following two parts:(1)Cyclic voltammetry and EC-SERS methods were used to study the adsorption and the reaction process of PNTP on the electrode surface.First,the real surface area and surface roughness of the electrode surface were determined by applying a cyclic voltammetry scan on a smooth gold electrode.Secondly,the surface adsorption capacity,reaction mechanism and reaction efficiency of PNTP were studied after the adsorption of PNTP molecules on the smooth gold electrode.Thirdly,the gold electrode surface was modified with gold nanoparticles(AuNPs)to construct AuNPs@Au electrode.Combined with the theoretical calculations,the photoelectrochemical reduction reaction mechanism of PNTP was studied by the EC-SERS method.Thus,the nitro radical anion or hydrogenated p-nitrothiophenol was proved as the first intermediate in PNTP electron transfer.Finally,by changing the pH of the solution,the effect of pH on the photoelectrochemical reduction of PNTP was studied.(2)The photoelectrochemical reduction kinetics of PNTP on AuNPs@Au electrode was systematically studied.First,the Fermi energy level of the electrode,which is dependent on the potential of the gold electrode,could be changed in the EC-SERS experiment.In this case,the hot electron energy generated by SPR relaxation could be matched with the lowest unoccupied molecular orbital energy level of the molecule.With the investigation of the effect of potential on photoelectrochemistry reduction,we can succeed in controlling the reaction model.Secondly,the kinetic information of the photochemical and the photoelectric reduction of PNTP was studied by the EC-SERS,respectively,in which time-resolved detection could be realized.Finally,according to the mechanism of the photoelectrochemical reduction of PNTP on AuNPs@Au electrode,the kinetic model of the reaction was constructed after simplified and approximated. |
