Operando study of ethanol oxidation on Pt(111) by infrared spectroscopy at near-ambient pressure

The oxidation of ethanol on the surface of a Pt(1 1 1) single crystal was studied at near-ambient pressures using polarization-modulation reflection absorption infrared spectroscopy (PM-IRRAS). Reaction intermediates adsorbed on the platinum surface as well as ethanol and the main reaction products in the gas phase were followed by PM-IRRAS simultaneously in a batch reactor during stepwise heating from room temperature to 600 K. The experiments were carried out at two different ethanol/oxygen molar ratios, modeling stoichiometric and oxygen-rich conditions. It was shown that the oxidation of ethanol begins already at 330 K. Acetaldehyde, acetic acid, CO2, and water were detected as products in the gas phase. Adsorbed acetaldehyde and ethoxy-groups were distinguished as reaction intermediates on the platinum surface at low temperatures. At higher temperatures between 450 and 600 K, the only surface intermediates were carbonates, indicating their stability and ability to block the catalyst surface. No adsorbed CO was detected in the whole temperature range. The overall mechanism of the oxidation of ethanol on platinum is discussed.