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

Partially oxidized TaC 0.58 N 0.42 has been investigated as a cathode for polymer electrolyte fuel cells ͑PEFCs͒.Catalytic activity for the oxygen reduction reaction ͑ORR͒ significantly depends on the oxidation state of TaC 0.58 N 0.42 .TaC 0.58 N 0.42 and Ta 2 O 5 had a poor catalytic activity for the ORR.The onset potential on the partially oxidized TaC 0.58 N 0.42 for the ORR had a maximum value of 0.83 V vs a reversible hydrogen electrode in 0.1 mol dm -3 H 2 SO 4 at 30°C.X-ray diffraction analysis showed that the specimens, which had a definite catalytic activity for the ORR, had both TaC x N y and Ta 2 O 5 peaks.This result indicated that an appropriate oxidation of the TaC 0.58 N 0.42 was essential to enhance the catalytic activity for the ORR.