IN-SITU FTIR STUDY OF THE ELECTROCATALYTIC OXIDATION OF ETHANOL AT IRIDIUM AND RHODIUM ELECTRODES

In-situ Fourier transform IR (FTIR) reflectance spectroscopy has been used to study the electroadsorption and oxidation of ethanol at polycrystalline Ir and Rh electrodes in HClO4 solutions. The formation of surface and solution species has been followed optically during slow voltammetric scans. Ethanol electroadsorption leads to the formation of linearly bonded and bridge-bonded CO on Rh surfaces but only to linearly bonded CO on Ir. In the oxidation potential region, Ir electrodes show different catalytic properties from Rh electrodes, with Ir being a more selective catalyst than Rh. Oxidized states at early potentials play an activating role in ethanol electro-oxidation. Acetaldehyde is probably an intermediate product, but the major product on Ir electrodes is acetic acid whereas CO2 is the main product at Rh electrodes.