Synthesis of carbon-supported titanium oxynitride nanoparticles as cathode catalyst for polymer electrolyte fuel cells

• Published in: Electrochimica acta 2013-12, Vol.113, p.735-740
• Main Authors: Chisaka, Mitsuharu, Ishihara, Akimitsu, Ota, Ken-ichiro, Muramoto, Hirokazu
• Format: Article
• Language: English
• Subjects: Carbothermal reduction; Catalysts; Cathodes; Heating; Nanoparticles; ORR; Oxynitrides; PEFC; TiO2; Titanium; Titanium dioxide; Titanium oxides; Titanium oxynitride
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2013.06.048

•A sol–gel route for the synthesis of rutile TiO2 was modified to synthesize TiOxNy-C.•N atoms were doped into TiOx nanoparticles solely by the heat-treatment under N2 gas.•The N2-treatment produced sites more active toward ORR compared with NH3-treatment.•TiOx doped with a small amount of N atoms are suggested to be responsible for ORR. For use as the oxygen reduction reaction (ORR) catalyst in polymer electrolyte fuel cell cathodes, carbon-supported titanium oxynitride (TiOxNy-C) nanoparticles with a size of approximately 5nm or less were synthesized without using NH3 gas. A sol–gel route developed for the synthesis of pure rutile TiO2 nanopowders was modified to prepare the carbon-supported titanium oxide nanoparticles (TiOx-C). For the first time, N atoms were doped into TiOx solely by heating TiOx-C under an inexpensive N2 atmosphere at 873K for 3h, which could be due to carbothermal reduction. The TiOx-C powder was also heated under NH3 gas at various temperatures (873–1273K) and durations (3–30h). This step resulted in the formation of a TiN phase irrespective of the heating conditions. Both N2- and NH3-treated TiOxNy-C did not crystallize well; however, the former showed a mass activity more than three times larger than that of the latter at 0.74V versus the standard hydrogen electrode. Thus, titanium oxide nanoparticles doped with a small amount of N atoms are suggested to be responsible for catalyzing ORR in the case of N2-treated TiOxNy-C.