STUDY OF METHANOL ELECTROOXIDATION ON RH-SN OXIDE, PT-SN OXIDE, AND IR-SN OXIDE IN COMPARISON WITH THAT ON THE PT METALS

Catalytic activities of Rh-Sn oxide, Ir Sn oxide. and Pt-Sn oxide were studied with respect to their tin oxide effect in comparison with those of the Pt metals and each other. Surface chemical states were observed using XPS for the Rh-Sn and Pt Sn oxides. Electrochemical and XPS results were compared to each other. Tin oxide showed a pronounced enhancement of the catalytic activity toward methanol electrooxidation on Pt Sn oxide with respect to Pt itself in acidic solutions, but not in alkaline solutions. In the case of Rh-Sn oxide, tin oxide had a negative catalytic activity effect, with respect to Rh, and had no effect in the case of Ir-Sn oxide, with respect to Ir. This difference was considered to be correlated to the presence or the absence of redox coupling of the respective Pt group metal species. Formaldehyde electrooxidation was also studied on Pt Sn oxide in acidic solution. In alkaline solution, Pt Sn oxide was also used for not only formaldehyde. but also formate electrooxidations and its catalytic activity was discussed in comparison with Pt itself.