The electrochemical oxidation of ethanol on platinum, rhodium, and platinum−rhodium electrodes is studied
using on-line differential electrochemical mass spectrometry (DEMS) and in-situ infrared spectroscopy (FTIR).
The data were normalized using the oxidation of a CO monolayer in order to compare the activity of the
different electrodes. Three products have been detected, namely CO2 and acetaldehyde (detected by DEMS)
and acetic acid (detected by in-situ FTIR, since acetic acid is not volatile enough to be detected by DEMS).
It is found that rhodium is the far less active electrocatalyst for ethanol electrochemical oxidation. Pure platinum
and Pt90Rh10 present similar overall normalized current density, but Pt90Rh10 presents a better CO2 yield than
pure platinum. The best CO2 yield is found for the Pt73Rh27 electrodes. The acetaldehyde yield decreases as
rhodium is added to the electrode. The ratio CO2/CH3CH2O increases when rhodium is added to the electrode.
The possible reasons for the different reactivity for the studied electrodes is discussed in terms of C−H bond
activation and C−O bond coupling on the different surfaces.
In situ Fourier Transform Infrared Spectroscopy is used to study the catalytic properties of a Pt/Ru alloy as compared to pure platinum. Spectra taken at different potentials show the different behaviour of both metals with respect to methanol adsorption and oxidation. In the potential region below 700 mV the presence of Ru atoms increases the electrocatalytic activity of platinum. In the case of the alloy the poisoning adsorbate COad is adsorbed to a less extent and its seems to be weaker bonded to the Pt/Ru than to the Pt surface.
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