EIS and relaxation times study for CO adsorbed on bimetallic Pt-Mo catalysts during the methanol oxidation reaction

Both Pt/C and PtMo/C catalysts were synthesized by Platinum and Molybdenum phases with Vulcan Carbon as support. The behavior of Pt-based catalysts in electrolytic media was analyzed and its Electrochemical Impedance Spectroscopy (EIS) was fitted as electric circuits to elucidate mechanisms such as adsorption, desorption and oxidation that developed during the methanol oxidation reaction through Direct Methanol Fuel Cells (DMFC). Special attention was paid to the carbon monoxide oxidation reaction on the catalyst surfaces to detect the CO poisoning effect. EIS data were used to propose the modified Randles electric circuits, which consisted of a Constant Phase Element (CPE) connected in parallel with the series of Charge Transfer Resistance (RCT) and a Finite Diffusion Warburg Element (ZW), aimed at identifying the mass transfer process. Distribution of Relaxation Times analysis (DRT) was estimated to identify other characteristics of the individual processes for both catalysts and to detect the poisoning effect of the species adsorbed on the catalyst surface.