In situ rapid-scan time-resolved microscope FTIR spectroelectrochemistry: study of the dynamic processes of methanol oxidation on a nanostructured Pt electrode

In this paper we report the development of an electrochemical in situ rapid-scan time-resolved microscope infrared reflection spectroscopy (RS-TR-MFTIRS), which consists of a FTIR spectrometer with rapid-scan facility, an infrared microscope in combination with a nanostructured Pt microelectrode, and a versatile external reflection (or thin-layer) spectroelectrochemical flow cell. It has been demonstrated that the RS-TR-MFTIRS can successfully overcome the disadvantages in mass transport, transient response and uniformity of current flow that arise from a conventional external reflection infrared cell. The dynamic process of methanol oxidation on a nanostructured platinum microelectrode in alkaline solution was employed as a test reaction to characterize the performance of the newly developed technique. The results illustrate that cyclic voltammograms (CVs) and infrared spectra within a potential interval of 2.6 mV can be simultaneously recorded at a potential scan rate up to 200 mV s−1. The dynamic processes of the poisoning intermediate (adsorbed CO species) and reactive intermediate (formate ions) involved in methanol oxidation in alkaline solutions were studied intensively. It has been revealed that the bridge-bonded CO (COB) species and formate ions are generated preferentially at the onset potential (−0.54 V vs SCE) of methanol oxidation, while the linearly bonded CO (COL) species originate at more positive potentials that are close to the anodic current peak potential (−0.17 V vs SCE) of methanol oxidation.