Oxygen-functionalized highly mesoporous carbon xerogel based catalysts for direct methanol fuel cell anodes

Abstract

PtRu catalysts were prepared using a highly mesoporous carbon xerogel submitted to different oxygen functionalization treatments: diluted and concentrated nitric acid as well as gas-phase 5% O2−N2 oxidation. Catalysts with 20 wt % loading and equimolar Pt:Ru metallic phase were prepared using an impregnation procedure involving chemical reduction with formic acid. The so-obtained carbon materials, as well as the different catalysts synthesized, were characterized by means of N2 physisorption, temperature-programmed desorption (TPD), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry and chronoamperometry were performed to study their activity toward carbon monoxide and methanol oxidation. Functionalization of the carbon support was found to play a definitive role in the interaction between carbon material and the active phase, determining metallic dispersion, alloying degree, and reduction extent. The activity of the catalysts in methanol electro-oxidation was directly related to the metal oxidation state and alloying degree.