Electrooxidation of Ethanol on Pt. An in Situ and Time-Resolved XANES Study

The ethanol oxidation reaction is studied using X-ray absorption spectroscopy during chronoamperometric cell operation with a carbon-supported Pt catalyst. The analysis of the MANES region of the Pt L-3 edge by the Delta mu-technique allows the coverage of the Pt surface with OH-, n-fold O-, and C-species to be determined. The current voltage characteristics and the coverage is modeled by means of a multistep reaction mechanism based on a modified Butler-Volmer approach that additionally includes adsorbate adsorbate lateral interactions. The model is validated against experimental current and surface coverage data over time. With the model, the importance of acetaldehyde formation via initial C-alpha-H vs O-H bond cleavage is examined, the latter dominating at higher potentials on vacant sites remaining in the oxygen coverage coming from water activation.