Oxide-Based Electrocatalysts as Precious Metal and Carbon Free Cathodes for PEFC

Abstract

Development of non-platinum electrocatalysts for oxygen reduction reaction (ORR) is required for real commercialization of polymer electrolyte fuel cells. We focused on high stability of group 4 and 5 metal oxide-based compounds in acidic media. In this study, in order to demonstrate superior durability of oxide-based cathodes, we prepared all oxide-based cathodes which were composed of magneli phase titanium oxide (Ti4O7) as electric conductive and Ti-Nb complex oxide with oxygen vacancies as active sites (Ti4O7-TixNbyOz). The ORR activity of the Ti4O7+TixNbyOz was higher than that of the Ti4O7, indicating that the active sites might be oxygen vacancies on the TixNbyOz. The onset potential of the Ti4O7+TixNbyOz was over 1.0 V vs RHE. No degradation of the ORR performance of the Ti4O7+TixNbyOz was observed during potential cycling from 1.0 to 1.5 V as degradation test. Therefore, we successfully demonstrated that the all oxide-based (carbon free) cathodes had high durability in high potential region.