Mitsuharu Chisaka

Oxygen Reduction Reaction Activity of Vulcan XC-72 Doped with Nitrogen under NH3 Gas in Acid Media

We doped Vulcan XC-72 (VXC-72) with nitrogen by heating it under flowing NH 3 gas in various conditions and investigated its oxygen reduction reaction (ORR) activity in 0.1 M H 2 SO 4 . The cyclic voltammograms, X-ray photoelectron spectra, and Brunauer-Emmett-Teller analyses indicated that the heating temperature greatly influenced ORR activity, nitrogen content, and surface area of VXC-72. Furthermore, the heating time also influenced the ORR activity. Therefore, the rate of cooling as well as that of heating at above 773 K was found to be fixed to evaluate ORR activity. Under controlled heating/cooling conditions, the maximum onset potential for ORR was 0.70 V vs normal hydrogen electrode when VXC-72 was heated at 1223 K for 24 h under NH 3 gas (200 mL min -1 ).

Activity and durability of the oxygen reduction reaction in a nitrogen-doped rutile-shell on TiN-core nanocatalysts synthesised via solution-phase combustion

Core–shell-structured titanium oxynitride nanocatalysts were synthesised on carbon black via an inexpensive solution-phase combustion route. The synthesis conditions were systematically optimised to exhibit the highest oxygen reduction reaction (ORR) activity at 0.9 V versus the reversible hydrogen electrode in 0.1 mol dm−3 H2SO4. The nitrogen-doped rutile TiO2 shell successfully protected the TiN core without altering the ORR mechanism after 20 000 potential cycles between 0.6 and 1.0 V.

Effect of Organic Solvents on the Pore Structure of Catalyst Layers in Polymer Electrolyte Membrane Fuel Cells

The effect of organic solvents in catalyst inks on the pore structure of catalyst layers (CLs) in polymer electrolyte membrane fuel cells was investigated. The pore size distribution of CLs fabricated from catalyst inks containing either ethylene glycol (EG) (CL EG ), propylene glycol (PG) (CL PG ), or 1,3-propanediol (PDO) (CL PDO ) was measured. The dielectric constants of these three organic solvents were > 10, and perfluorosulfonate ionomer was dissolved in the catalyst inks. The pore volume (v) of CL PDO , CL EG , and CL PG increased in this order: v PDO < v EG < v PG , suggesting that the pore structure of the CLs depended on the solvent evaporation process.

Nano-TaOxNy particles synthesized from oxy-tantalum phthalocyanine: how to prepare precursors to enhance the oxygen reduction reaction activity after ammonia pyrolysis?

Nano-TaOxNy oxygen reduction reaction (ORR) catalysts were supported on multi-walled carbon nanotubes (MWCNTs) using two-step pyrolysis of oxy-tantalum phthalocyanine (TaOPc). For the first time, slightly oxidized Ta3N5 has been experimentally proposed to be ORR active in acidic media.

Zirconium Oxynitride-Catalyzed Oxygen Reduction Reaction at Polymer Electrolyte Fuel Cell Cathodes

Most nonplatinum group metal (non-PGM) catalysts for polymer electrolyte fuel cell cathodes have so far been limited to iron(cobalt)/nitrogen/carbon [Fe(Co)/N/C] composites owing to their high activity in both half-cell and single-cell cathode processes. Group IV and V metal oxides, another class of non-PGM catalysts, are stable in acidic media; however, their activities have been mostly evaluated for half-cells, with no single-cell performances comparable to those of Fe/N/C composites reported to date. Herein, we report successful syntheses of zirconium oxynitride catalysts on multiwalled carbon nanotubes, which show the highest oxygen reduction reaction activity among oxide-based catalysts. The single-cell performance of these catalysts reached 10 mA cm–2 at 0.9 V, being comparable to that of state-of-the-art Fe/N/C catalysts. This new record opens up a new pathway for reaching the year 2020 target set by the U.S. Department of Energy, that is, 44 mA cm–2 at 0.9 V.