Titanium-Niobium Oxides Mixed with Ti4O7 as Precious-Metal- and Carbon-Free Cathodes for Polymer Electrolyte Fuel Cells

Abstract

The development of non-platinum electrocatalysts for oxygen reduction reactions (ORR) is required for the commercialization of polymer electrolyte fuel cells. We focused on highly stable group 4 and 5 metal oxide-based compounds in acidic media. In this study, we proposed precious-metal- and carbon-free cathodes based on oxides and demonstrated the superior durability of oxide-based cathodes by preparing titanium-niobium oxides mixed with Ti4O7 (TixNbyOz + Ti4O7). The ORR activity of the TixNbyOz + Ti4O7 is higher than that of the Ti4O7, indicating that the TixNbyOz might have active sites for the ORR. The highest onset potential of the TixNbyOz + Ti4O7 was ca. 1.1 V with respect to reversible hydrogen electrode. No degradation of the ORR performance of TixNbyOz + Ti4O7 was observed during both start-stop and load cycle tests. Therefore, we successfully demonstrated that the precious-metal- and carbon-free oxide-based cathodes had superior durability under the cathode conditions of a polymer electrolyte fuel cell.