Electrooxidation of acetaldehyde on a carbon supported Pt catalyst at elevated temperature/pressure: An on-line differential electrochemical mass spectrometry study

摘要

The electrooxidation of acetaldehyde on a Pt/Vulcan catalyst was investigated over a wide range of temperatures (23-100 ℃) in a flow cell under controlled transport conditions, employing high temperature/high pressure (3 bar overpressure) on-line differential electrochemical mass spectrometry (DEMS). Potentiodynamic and potentiostatic measurements of the Faradaic current and of the CO_2 formation rate reveal that complete oxidation to CO_2 prevails only at higher temperatures and lower potentials, with ～80%/40% current efficiency for CO_2 formation at 0.5 V/0.6Vin0.1 M solution and at 100 ℃, in contrast to a few percent at room temperature. Oxidation to acetic increases at higher potential. The increase of the CO_2 current efficiency with temperature is reflected by a higher apparent activation barrier for complete oxidation to CO_2 (39 ± 2 kJ mol~(-1) at 0.6 V, 0.1 M) compared to that of the overall acetaldehyde oxidation reaction given by the Faradaic current (32±2kJ mol~(-1)) and that for oxidation to acetic acid (27 ± 3 kJ mol~(-1)). Analogous measurements on the electrooxidation of acetic acid show very low reactivities even at 100 C, and a high apparent activation energy (173 ±6kJ mol~(-1)). The importance of fuel cell relevant reaction and mass transport conditions in model studies is discussed.