Estudo eletroquímico da reação de oxidação da mistura metanol-etanol

Abstract

The world is undergoing a transition in its energy system. Hydrogen-based systems, namely fuel cells that convert hydrogen into electricity, have been widely investigated. However, limitations related to hydrogen gas availability as a fuel in fuel cells have driven research toward the use of alcohols such as ethanol and methanol. In an effort to improve the performance of the alcohol electro-oxidation process investigated in this study, PtRu/C, PtSn/C, and Pt/C electrocatalysts were employed for comparison, all prepared by the Formic Acid Method (FAM). This work involved the synthesis of the electrocatalysts, physical characterization by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and electrochemical characterization through cyclic voltammetry and chronoamperometric measurements in acidic media. The physical characterization results of the PtRu/C and PtSn/C electrocatalysts revealed important features related to their performance. X-ray diffraction analysis indicated the formation of binary alloys in PtRu/C and PtSn/C, suggested by the absence of distinct diffraction peaks corresponding to the alloying metals and by their low degree of crystallinity. Furthermore, SEM analysis showed that the materials exhibit a morphology composed of nanoparticle agglomerates dispersed on a carbon support, with particle sizes ranging from 10 to 50 nm. Electrochemical characterization demonstrated that PtRu/C and PtSn/C exhibited satisfactory electrocatalytic activity for the electro-oxidation of methanol, ethanol, and methanol–ethanol mixtures when compared to Pt/C. The electrochemical data indicated that PtRu/C showed higher activity for oxidation at methanol–ethanol ratios of 30:70 and 50:50, standing out in the oxidation of the mixture. Chronoamperometric profiles at the 50:50 ratio further revealed enhanced catalytic activity for methanol–ethanol mixture electro-oxidation, as evidenced by the current density decay over time. The 10:90 ratio exhibited a response for methanol–ethanol mixture electro-oxidation on the PtSn/C electrocatalyst, followed by chronoamperometric voltammograms at 10:90 and 30:70 ratios, which showed significant catalytic activity for mixture oxidation at a fixed potential of 0.6 V. Based on these results, the use of binary catalysts is relevant for understanding the electro-oxidation performance of methanol–ethanol mixtures. The findings indicate that higher ethanol proportions in the alcohol mixture favor electro-oxidation on PtSn/C electrocatalysts, whereas higher methanol proportions enhance electro-oxidation activity on PtRu/C electrocatalysts.