Nb-doped TiO2 cathode catalysts for oxygen reduction reaction of polymer electrolyte fuel cells

Nb-doped TiO2 particles were studied as electrocatalysts for the oxygen reduction reaction (ORR) under acidic conditions. The Nb-doped TiN nanoparticles were first synthesized by meso-porous C3N4 and then fully oxidized to Nb-doped TiO2 by immersing in 0.1 M H 2SO4 at 353 K for 24 h. Although the ORR activity of the as-obtained sample was low, a H2 treatment at relatively high temperature (1173 K) dramatically improved the ORR performance. An onset potential as high as 0.82 VRHE was measured. No degradation of the catalysts was observed during the oxidation-reduction cycles under the ORR condition for over 127 h. H2 treatment at temperatures above 1173 K caused the formation of a Ti4O7 phase, resulting in a decrease in ORR current. Elemental analysis indicated that the Nb-doped TiO 2 contained 25 wt% residual carbon. Calcination in air at 673 or 973 K eliminated the residual carbon in the catalyst, which was accompanied by a dramatic decrease in ORR activity. This post-calcination process may reduce the conductivity of the sample by filling the oxygen vacancies, and the carbon residue in the particle aggregates may enhance the electrocatalytic activity for ORR. The feasibility of using conductive oxide materials as electrocatalysts is discussed. © 2013 Elsevier B.V.

Arashi, T., Seo, J., Takanabe, K., Kubota, J., & Domen, K. (2014). Nb-doped TiO2 cathode catalysts for oxygen reduction reaction of polymer electrolyte fuel cells. Catalysis Today, 233, 181–186. doi:10.1016/j.cattod.2013.12.009

This work was supported in part by the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) of the Cabinet Office of Japan, the International Exchange Program of the A3 Foresight Program of the Japan Society for the Promotion of Science (JSPS), and the "Elements Strategy Initiative to Form Core Research Center" (since 2012), of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. One of authors, Seo, appreciates the support of the Global Centers of Excellence (GCOE) Program of JSPS for her work at the University of Tokyo.

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