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

•The EIS experiments have shown that the Molybdenum aggregation allows the organic species oxidation at low potentials than Pt/C catalyst.•The PtMo/C surface has shown stability at a wide potential range during the organic species oxidation like methanol and CO.•DRT results demonstrate that the PtMo/C surface recovers its catalytic capability faster than Pt/C surface, even at COads presence.•DRT results demonstrate that Molybdenum increases the catalytic activity of PtMo/C surface, playing a role avoid poisoning by CO. 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.