[Investigation of electrocatalytic reduction of oxalic acid on Pb electrode through in situ FTIR reflection spectroscopy].

Electrochemical in situ Fourier transform infrared reflection spectroscopy was used in the investigation of electrocatalytic reduction of oxalic acid on Pb electrode. The multi-step potential FTIRS and time-resolved FTIRS procedures were used in the present study. The results of MSFTIRS demonstrate that glyoxylic acid could be detected below -0.70 V. The quantity of glyoxylic acid cumulated on Pb electrode surface reaches a maximum at -0.85 V, then it decreases as electrode potential is further decreased. Meanwhile the C-O stretching vibration of -CH2OH group at around 1 093 cm(-1) could be detected at -0.95 V. It was revealed that all the produced glyoxylic acid may be reduced further into glycolic acid at potentials below -1.50 V. Furthermore, none of other new substances could be detected at more negative potentials, which indicated that glycolic acid could not be further reduced. The results of time resolved Fourier transform infrared reflection spectroscopy at -0.75 V indicate that the integrated intensity of the IR band at about 1 750 cm(-1) for the stretching vibration of C=O (-CHO) linearly increases with the reaction time. The TRFTIR spectra at -1.60 V show that not only the IR absorption of C=O (HOOC-CHO) stretching is observed, but also that of C-O (-CH2OH) stretching at about 1 093 cm(-1) can be seen. The current study demonstrated that electrochemical in situ Fourier transform infrared reflection spectroscopy is a powerful tool for the study of electrosynthesis processes, and for the detection of each species involved in the reaction at molecular level. The results are of significance to understand the reaction mechanism of electrocatalytic reduction of oxalic acid.