Partially Oxidized Tantalum Carbonitrides as a New Nonplatinum Cathode for PEFC–1–

Partially oxidized has been investigated as a cathode for polymer electrolyte fuel cells (PEFCs). Catalytic activity for the oxygen reduction reaction (ORR) significantly depends on the oxidation state of . and had a poor catalytic activity for the ORR. The onset potential on the partially oxidized for the ORR had a maximum value of 0.83 V vs a reversible hydrogen electrode in at . X-ray diffraction analysis showed that the specimens, which had a definite catalytic activity for the ORR, had both and peaks. This result indicated that an appropriate oxidation of the was essential to enhance the catalytic activity for the ORR.