Enhancing ethanol oxidation rate at PtRu electro-catalysts using metal-oxide additives

Metal oxides are investigated, as additives of a PtRu/C catalyst, for enhancing the electro-oxidation of ethanol in acidic solution. High surface area TiO2 and SnO2 additives are synthesized and physico-chemically characterized. These oxides are added to PtRu/C during the catalytic ink preparation to obtain tri-metallic composite electrodes. These composite electro-catalysts are investigated for the ethanol electro-oxidation in half-cell configuration in comparison with additive-free PtRu/C and Pt/C catalysts. The PtRu-based composite catalyst containing SnO2 promoter shows a lower onset potential and larger current density for ethanol oxidation than the additive-free catalyst and that containing TiO2 promoter. The composite catalysts (PtRu/C + metal oxide) are also used in a direct ethanol fuel cell under practical operating conditions and assessed against the benchmark PtRu catalyst. An increase in performance is recorded with the composite tri-metallic electrodes. The analysis of electro-catalytic activity towards ethanol oxidation reaction and ethanolic residues coverage indicates an enhanced capability to activate ethanol chemisorption or a larger electroactive surface area, together with a faster intrinsic activity at lower overpotential, as the reasons for the improved performance with the use of metal oxide additives.