2-DIMENSIONAL INFRARED CORRELATION-ANALYSIS OF ELECTROCHEMICAL REACTIONS

Three advanced IR spectroscopy techniques, surface-enhanced IR absorpt ion spectroscopy (SEIRAS), step-scan Fourier-transform interferometry, and two-dimensional (2D) IR correlation analysis, have been applied t o the study of electrochemical reactions. A combined use of SEIRAS and step-scan interferometry enables time-resolved spectral monitoring of electrochemical reactions with time-resolutions ranging from microsec onds to milliseconds. 2D-IR correlation analysis highlights the dynami c information obscured in the time-resolved spectra, The basic concept of 2D-IR is somewhat analogous to that of 2D-NMR, and synchronous and asynchronous 2D spectra defined by two independent wavenumbers are ge nerated by a correlation analysis of dynamic fluctuation of IR signals induced by a potential modulation, The synchronous and asynchronous s pectra characterize the coherence and incoherence respectively of dyna mic fluctuations of IR signals at two different wavenumbers. Bands ari sing from different transient species are clearly differentiated by th eir characteristic time-dependent behavior, The temporal relationship between the intensity fluctuations of different bands also becomes cle ar. From these data, deep insights into reaction processes are gained. The utilities of 2D-IR are demonstrated for the one-electron reductio n of heptylviologen at a silver electrode surface. (C) 1997 Elsevier S cience S.A.