Abstract
The electrooxidation of methanol was enhanced on PtSn-SPE, PtRu-SPE and PtIr-SPE in sulfuric acid solution, when compared with the activity of Pt-SPE, which has already been shown to have a higher activity than a Pt electrode. SPE is an abbreviation for Nafion, a solid polymer electrolyte. It is suggested that this dual enhancement of the oxidation rate for PtSn-SPE and PtRu-SPE catalysts is due to the modification of the oxidation state of Pt by Sn and Ru and to the presence of H2O and CH3OH, both modified by the SPE matrix. This modification appears to weaken their hydrogen bonds in solution. Both Pt and Ir have catalytic properties for methanol oxidation, but a PtIr-SPE catalyst showed a more enhanced catalytic activity than either of them. This will be discussed in terms of Ir, oxidized at relatively low positive potentials, assisting the redox process of Pt0/Pt2+ or Pt2+/Pt4+ in the SPE matrix, where CH3OH and H2O are present in modified forms. For comparison, IrPd-SPE was also used as an electrode and showed a higher activity than Ir alone, although Pd did not have any activity toward methanol oxidation in sulfuric acid solution. Irrespective of the kind of Pt-SPEs, the Tafel slope was approximately 120 mV; the CH3OH concentration dependence was of the order of 0.2–0.6. The pH dependence was nearly 0.5 against NHE. The activation energy of the Pt-SPEs for the reaction ranged between 20 and 33 kJ mol−1.
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Aramata, A., Kodera, T. & Masuda, M. Electrooxidation of methanol on platinum bonded to the solid polymer electrolyte, Nafion. J Appl Electrochem 18, 577–582 (1988). https://doi.org/10.1007/BF01022253
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DOI: https://doi.org/10.1007/BF01022253