Improving the catalytic activity of Pt-Rh/C towards ethanol oxidation through the addition of Pb

Abstract

This paper describes the effect of composition on the catalytic activity of carbon-supported Pt-Pb, Pt-Rh, and Pt-Rh-Pb catalysts towards ethanol oxidation in acid media. The catalysts were synthesised by a polyol reduction method and characterised using several experimental techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption near edge structure, and X-ray energy dispersive spectroscopy. The catalytic activity towards ethanol oxidation was evaluated by cyclic voltammetry, chronoamperometry, and in situ Fourier transform infrared spectroscopy (FTIR) experiments. XRD data indicate the presence of Pb in both alloyed and oxide forms. TEM images reveal nanoparticles well-dispersed on the carbon support, with spherical shapes and particle sizes around 2.0–6.5 nm. The Pt3RhPb/C catalyst showed the highest catalytic activity for ethanol oxidation, reaching current densities 6.0 times higher than the commercial Pt/C catalyst. The trimetallic catalyst showed the highest CO2 and acetic acid formation, explaining the higher current densities presented during cyclic voltammetry and chronoamperometry. Additionally, since the oxidation appears to follow a non-selective path, the role of Pb in the trimetallic catalyst is not related to driving the reaction towards the production of CO2. The improvement in catalytic activity occurred due to the synergy between the metals.