METAL-ELECTRODES BONDED ON SOLID POLYMER ELECTROLYTE MEMBRANE (SPE) .6. METHANOL OXIDATION ON MOLYBDENUM MODIFIED PT-SPE ELECTRODE

The methanol gas phase oxidation on Pt-SPE electrode is enhanced by molybdenum modification. The Tafel plot is divided into three regions: region I with an extremely low polarization, around ca 0.1 V (25°C); region II around 0.2-0.25 V (25°C), ca 0.15 V lower than that on the unmodified Pt-SPE electrode; and region III with a polarization above ca 0.4 V (25°C) where the modification effect disappeared. The catalytic effect of the molybdenum species is enhanced further at higher temperatures, > 102 times larger current in region II at 80°C than at 25°C. The modification conditions were examined in detail. The methanol pressure dependence with a fractional reaction order of 0.3 and the different activation energy between modified and unmodified Pt-SPE electrode, 12 and 24 kcal mol-1, are briefly discussed. The oxidation products are CO2 and HCOOCH3. The water supply affects both the oxidation current and the product distribution. © 1990.