Improved electrocatalytic stability in ethanoloxidation by microwave-assisted selective deposition of SnO2 and Pt onto carbon

Abstract

Pt/SnO₂/C nanostructures with SnO₂/Pt molar ratios ranging from 2.5 to 0.6 were synthesized by simple and fast microwave-assisted routes. The materials are composed of 3–5 nm SnO₂ and Pt nanoparticles dispersed on the carbon support, with the morphology of the coating depending on the SnO₂/Pt ratio: a homogenous layer of nanoparticles coating the carbon surface is obtained for SnO₂/Pt of 2.5, whereas small Pt–SnO₂ clusters are formed for lower ratios. The electrocatalytic activity of the composites on the ethanol oxidation reaction (EOR) was studied by cyclic voltammetry and chronoamperometry. All the binary catalysts exhibited lower onset potentials for the EOR and slower decay of the current density with time than a commercial Pt/C catalyst. However, improved peak current densities were only observed for the composites with ratios 1.6, 1.0 and 0.6, indicating that the formation of metal and metal oxide nanoparticles clusters is favorable for the EOR. This morphology facilitates the hydroxyl groups transfer from the metal oxide to the platinum at low potentials and also the electron transfer between carbon and platinum. The best overall performance was found for the catalyst with SnO₂/Pt = 1, on which the number of three-phase boundaries is maximized. Moreover, the catalyst with SnO₂/Pt = 1 continued to exhibit significantly better catalytic performance on the EOR than the commercial catalyst after potential cycling.