Electrooxidation of ethanol at polycrystalline and platinum stepped single crystals: A study by differential electrochemical mass spectrometry

The electrooxidation of adsorbed and bulk solution of 10−2 M ethanol and D6-ethanol at polycrystalline platinum, smooth, roughened and Ru modified Pt(3 3 2), Pt(3 3 1) and Pt(1 1 1) electrodes was studied by on-line differential electrochemical mass spectroscopy (DEMS) using a dual thin layer flow through cell. On polycrystalline Pt, the main (or even single) product is acetaldehyde; due to the flow through conditions the amount of acetaldehyde further oxidized to acetic acid is negligible. At stepped single crystals with (1 1 1) terraces (Pt(s)[n(1 1 1) × (1 1 1)], acetic acid is produced at a lower potential than acetaldehyde. This demonstrates that in addition to the reaction path involving C–C bond splitting leading to CO2 (via adsorbed CO and CHx) and the reaction path leading to acetaldehyde there is a third, direct reaction path leading to the formation of acetic acid. Step decoration by Ru does not lead to an increased reactivity. This is different from the strong cocatalytic effect of Ru at step sites on the oxidation of CO. Furthermore, Ru does not influence the relative amount of acetaldehyde formed.