Electrochemical-SERS Investigation on the Decarboxylated Reaction of PMBA in Ionic Liquid and Influence of Interfacial Water

Based on the gas-liquid interface self-assembly method and transfer technology,a glassy carbon electrode loaded with Au nanoparticles monolayer(Au MLF@GC) was prepared,and it was employed to in situ study the interfacial processes of ionic liquid electrochemical systems. The decarboxylation of p-mercaptobenzoic acid(PMBA) catalyzed by surface plasmon resonance(SPR)to phenylthiophenol(TP)as the probe reaction,the electrochemical surface-enhanced Raman spectroscopy(SERS)was developed to investigated the kinetic behaviours of the reaction of PMBA in [BMIm]BF4 systems via the potential-step method. The potential of zero charge(pzc)of the hydrophilic ionic liquid [BMIm]BF4/Au MLF@GC was determined to be -0.95 V by the differential capacitance and i-t measure. ments for electrode immersion. The decarboxylation of PMBA occurred in the positive region of the pzc,and the reaction rate constant was determined based on the second order kinetic reaction and change of the SERS intensities of relevant peaks. The linear relationship between the logarithm of the reaction rate constant and the step potential was resolved. With the addition of extra-water (XW)from 0 to 0.001 and 0.003(molar ratio),the initial step potential was shifted negatively,and the reaction rate constant increased with the addition of water at the same step potential.