In situ step-scan time-resolved microscope FTIR spectroscopy applied in irreversible electrochemical reactions

Abstract

We demonstrated in the present paper, for the first time, the application of step-scan time-resolved FTIR external reflection spectroscopy in studies of irreversible electrochemical reactions. Through combination of a particularly designed flow thin layer IR cell and a nanostructured microelectrode, the solution in the thin layer between IR window and microelectrode as well as adsorbates on electrode surface can be rapidly renewed, which allows irreversible reactions to be repeated quickly. Electrooxidation of CO adsorbed on a nanostructured platinum microelectrode (nm-PtME) in H 2SO 4 solutions was employed as a test reaction to illustrate the performance of the newly developed technology. It has confirmed that to regenerate a CO adlayer on the nm-PtME after stripping completely CO adsorbates may take about 6 s in CO-saturated solution (CO concentration ∼1.0 mM) at a flow rate of 20 ml min −1, which satisfies the requirement of the repeatability in step-scan FTIR data collection. Time-resolved FTIR spectra for CO irreversible oxidation have been recorded at a time resolution of 250 μs. It has been revealed that the IR band center of CO slightly decreases with time within initial 4 ms and then maintains a constant value in the evolvement of the oxidation. Such variation demonstrates that CO oxidation on nm-PtME is mainly occurred in through a nucleation and growth mechanism. The present study has thrown light on investigation of fast dynamic processes and kinetics of irreversible electrochemical reactions by using in situ step-scan time-resolved FTIR spectroscopy.