Research Papers

Partially Oxidized Tantalum Carbonitride as New Cathodes Without Platinum Group Metals for Polymer Electrolyte Fuel Cell

[+] Author and Article Information
Akimitsu Ishihara

Chemical Energy Laboratory, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama-shi, Kanagawa 240-8501, Japana-ishi@ynu.ac.jp

Motoko Tamura, Koichi Matsuzawa, Shigenori Mitsushima, Ken-ichiro Ota

Chemical Energy Laboratory, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama-shi, Kanagawa 240-8501, Japan

J. Fuel Cell Sci. Technol 8(3), 031005 (Feb 18, 2011) (6 pages) doi:10.1115/1.4003161 History: Received March 15, 2010; Revised July 15, 2010; Published February 18, 2011; Online February 18, 2011

A partially oxidized TaC0.58N0.42 has been investigated as a new cathode for polymer electrolyte fuel cells. The catalytic activity for oxygen reduction reaction (ORR) significantly depended on an oxidation state of the TaC0.58N0.42. TaC0.58N0.42 and Ta2O5 had a poor catalytic activity for the ORR. The onset potential on the partially oxidized TaC0.58N0.42 for the ORR had a maximum value of 0.9 V versus reversible hydrogen electrode in 0.1moldm3H2SO4 at 30°C, which indicated that the partially oxidized TaC0.58N0.42 had definite catalytic activity for the ORR. Hard X-ray photoelectron spectroscopy and X-ray diffraction analyses revealed that the surfaces of the partially oxidized TaC0.58N0.42 were oxidized, although the inner parts of the partially oxidized TaC0.58N0.42 remained tantalum carbonitride. These results suggested that an appropriate oxidation of the TaC0.58N0.42 was essential to enhance the catalytic activity for the ORR.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

XRD patterns of the powder specimens with different holding times of heat treatment. The holding time of the upper specimen was longer, and the lowest specimen was the starting material, TaC0.58N0.42.

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Figure 2

Effect of the mixture of the partial oxidized TaC0.58N0.42(DOO=0.43) with carbon black on the potential–current curves under N2 and O2 in 0.1 mol dm−3H2SO4 at 30°C with a scan rate of 5 mV s−1. (a) No addition of carbon black and (b) mixture with carbon black (5 wt %).

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Figure 3

Dependence of the onset potential EORR on the carbon content in the powder catalyst

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Figure 4

Effect of the DOO on the iORR at 0.8 V versus RHE using the mixture of the partially oxidized TaC0.58N0.42 with the carbon black (7 wt %) catalysts

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Figure 5

Relationship between the DOO and the EORR

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Figure 6

XPS of (a) Ta 4f, (b) O 1s, and (c) N 1s

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Figure 7

Relationship between the square root of the photoelectric quantum yield Y1/2 and the photon energy

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Figure 8

Relationship between the DOO and the ionization potential

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Figure 9

Relationship between the ionization potential and the onset potential of the ORR

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Figure 10

Onset potential for oxygen reduction reaction of nonprecious metal oxide-based cathodes developed at Yokohama National University (0.1 mol dm−3H2SO4, 30°C)



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