In situ spectroelectrochemical measurements during the electro-oxidation of ethanol on WC-supported Pt-black, based on sum-frequency generation spectroscopy

In this paper we report in situ sum-frequency generation (SFG) spectroscopy experiments, carried out during the electro-oxidation of ethanol on Pt-black supported on tungsten carbide (WC). Well-defined SFG resonances were measured in the 1320-1350 cm−1 spectral range with the VIS beam set at 523.5 nm. The assignment of SFG bands was carried out with the aid of vibrational spectra calculated in the framework of Density Functional Theory (DFT). The spectra recorded in situ showed various kinds of changes in terms of spectral patterns and peak intensities, as a function of the applied potential and of the oxidation time, yielding information on the modification of the catalyst-adsorbate structure. To the best of the authors' knowledge, this is the first in situ electrochemical SFG work carried out in this particular wavelength range - specially diagnostic for electrocatalysis and made accessible by use of the CLIO IR free-electron laser - and with an electrode functionalised with a real catalyst, in powder form.