Kinetics of Toluene Electrohydrogenation on Pt/C Catalyst
Résumé
The kinetics of the toluene (TL) electrohydrogenation on a carbon-supported platinum catalyst (Pt/C) have been investigated as a fundamental study of the cathode reaction in an electrolyzer with water decomposition. Since the TL electrohydrogenation on a Pt wire and Pt/C catalyst is a fast kinetic reaction with a low solubility, and slow mass transfer in an aqueous electrolyte, a potential step sequence was employed to determine its kinetic performance. Based on this method, a non-faradic current and faradic current could be identified and thereafter separated by a capacitance simulation. This experiment was performed in a TL-saturated sulfuric acid electrolyte to minimize the effect of the TL mass transfer. Based on the mass transfer-free TL electrohydrogenation experimental results, the exchange current densities of the TL electrohydrogenation on the Pt/C were 0.48, 0.49, 0.72, and 0.8mAcm(-2) at 25, 40, 50, and 60 degrees C, respectively. We found that the carbon support has a high impact towards the TL electrohydrogenation on the Pt-supported material. The carbon material works as a sponge by absorbing TL from the solution, and providing a large TL coverage for the Pt surface. Finally, a Tafel plot of the TL electrohydrogenation on the Pt/C catalyst was obtained and the kinetic performance was determined. The apparent active energy of the TL electrohydrogenation on the Pt/C was then calculated as 13.1kJmol(-1).