Microwave-assisted polyol synthesis of carbon-supported platinum-based bimetallic catalysts for ethanol oxidation

Abstract

High surface area carbon-supported Pt, PtRh, and PtSn catalysts were synthesized by microwave-assisted polyol procedure and tested for ethanol oxidation in perchloric acid. The catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning tunnelling microscopy (STM), TEM, and EDX techniques. STM analysis of unsupported catalysts shows that small particles (similar to 2 nm) with a narrow size distribution are obtained. TEM and XRD examinations of supported catalysts revealed an increase in particle size upon deposition on carbon support (diameter similar to aEuro parts per thousand 3 nm). The diffraction peaks of the bimetallic catalysts in X-ray diffraction patterns are slightly shifted to lower (PtSn/C) or higher (PtRh/C) 2 theta values with respect to the corresponding peaks at Pt/C catalyst as a consequence of alloy formation. Oxidation of ethanol is significantly improved at PtSn/C with the onset potential shifted for similar to aEuro parts per thousand 150 mV to more negative values and the increase of activity for approximately three times in comparison to Pt/C catalyst. This is the lowest onset potential found for ethanol oxidation at PtSn catalysts with a similar composition. Chronoamperometric measurements confirmed that PtSn/C is notably less poisoned than Pt/C catalyst. PtRh/C catalyst exhibited mild enhancement of overall electrochemical reaction in comparison to Pt/C.