Electrochemical In Situ Fast Time-Resolved Microscope FTIR Reflection Spectroscopy And Its Applications In The Studies Of Surface Dynamic Processes On Nanostructured Pt Electrodes

Electrochemical in situ infrared reflection spectroscopy, on the basis of its fingerprint and surface selection rules, can identify the nature of adsorbates and their surface bonding and orientation in electrode/electrolyte interfaces. The time-resolved and space-resolved spectroscopy have become currently two main directions of the development of electrochemical in situ IR spectroscopy. The former is unique in probing short lifetime intermediates, tracking reaction processes and providing dynamic information at molecule level in electrochemistry.In this thesis, we have established an electrochemical in situ step-scan time-resolved microscope FTIR external reflection spectroscopy (in situ SSTR-MFTIRS). The setup consists of an infrared microscope working with microelectrodes, and a home-designed and fabricated signal synchronizer. The time resolution of in situ spectra can reach up to 10s. Abnormal infrared effects (AIREs) of the nanostructured Pt microelectrode was used to improve significantly the IR determination sensitivity. The fast time-resolved FTIRS carried out in a thin-layer IR cell extended the possibility of using in situ SSTR-MFTIRS to study a wide variety of electrochemical reactions. It has been demonstrated that the SSTR-MFTIRS is a promising tool to be used in studies of kinetics and surface processes of fast reactions.The studies include: (1) the dynamic processes of site conversion between bridge bonded CO (COB) and linear bonded CO (COO on a nanostructured Pt microelectrode. Based on the determination of intermediate CO species in the site conversion processes and the acquisition of quantitative data of concerning the kinetics, a model of site conversion of adsorbed CO was suggested; (2) A novel spectroelectrochemical flow cell and a microelectrode possessing fastmass transfer were specially designed and fabricated, which allow irreversible electrochemical reactions to be studied by SSTR-MFTIRS. It has illustrated that the irreversible oxidation of CO adsorbed on nanostructured Pt microelectrode occurred according a nucleation and growth mechanism; (3) The potential induced orientation conversion of SCN" adsorbed on nanostructured Pt microelectrode was also investigated by using the SSTR-MFTIRS. It was found that the conversion rate from S-bonded SCN" to N-bonded SCN" is considerably slower than that of the reverse reaction.Through a home-developed software to realize the synchronization between 263A potentiostat (EG&G) and FTIR spectrometer, we have developed an electrochemical in situ rapid-scan time-resolved microscope FTIR reflection spectroscopy (RSTR-FTIRS), by which the collection of infrared spectra with an interval 2.6mV and the acquisition of cyclic voltammograms at a scan rate as large as 200mVs-1 can be done simultaneously. By using the RSTR-FTIRS, new information on the kinetics of methanol electrocatalytic oxidation in alkaline media was obtained.The establishment of the two types of electrochemical in situ fast time-resolved microscope FTIR reflection spectroscopy have progressed substantially the technique of electrochemical in situ external reflection infrared spectroscopy. The results concerning surface dynamic processes and kinetics obtaining in the present study have thrown a light in understanding at the molecular level the principle of electrode kinetics, and to develop the theory of electrocatalysis and relevant disciplines.