Ammonia-treated carbon-supported cobalt tungsten as fuel cell cathode catalyst

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• 作者：Tomoyuki Ando ; Shamsul Izhar ; Hiroyuki Tominaga ; Masatoshi Nagai
• 关键词：Non-Pt electrocatalyst ; ORR ; Cobalt tungsten nitrides ; N-containing carbon ; XRD ; TPR ; XPS
• 刊名：Electrochimica Acta
• 出版年：2010
• 出版时间：1 March 2010
• 年：2010
• 卷：55
• 期：8
• 页码：2614-2621
• 全文大小：1071 K

文摘

The ammonia-treated carbon-supported cobalt tungsten (Co–W/C) was prepared by a reaction employing a temperature program in a stream of NH₃ between 773 and 1073 K. The effects of the NH₃ heat-treatment temperature, Co–W ratio and the preparation method were investigated. The activity of Co–W/C for the oxygen reduction reaction (ORR) was evaluated using a rotating disc electrode and single fuel cell measurements. The Co–W/C prepared by the impregnation method with the same atomic ratio of Co and W, and NH₃ heat treated at 823 K, exhibited the highest ORR activity with an onset potential of 0.74 V (vs. RHE at 5 μA cm⁻²). The XRD and temperature-programmed measurements revealed that the catalyst active species were ascribed to the presence of CoW oxynitride and Co nitride. The catalyst surface was characterized as nitrided metal (accommodation of the N-atom in the host Co–W lattice resulting from a sufficient distance between the Co–W atoms and N) and N-containing carbon (Co surrounded by N-atoms and attached to the C support) by X-ray photoelectron spectroscopy. The Co–W oxynitrides, Co nitride and pyrrolic-type nitrogen of the N-containing carbons are likely responsible for the good ORR activity.