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 XANES region of the Pt L 3 edge by the -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 -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.