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

摘要

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.