Influence of Pd-Au/MWCNTs surface treatment on catalytic activity in the formic acid electrooxidation
Influence of Pd-Au/MWCNTs surface treatment on catalytic activity in the formic acid electrooxidation
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DOI：
10.1002/pssc.201100215
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发表时间：
2011-11
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通讯作者：
A. Małolepszy;M. Mazurkiewicz;Anna Mikolajczuk;L. Stobiński;A. Borodziński;B. Mierzwa;B. Lesiak;J. Zemek;P. Jiříček
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作者：
A. Małolepszy;M. Mazurkiewicz;Anna Mikolajczuk;L. Stobiński;A. Borodziński;B. Mierzwa;B. Lesiak;J. Zemek;P. Jiříček
采用改进的多元醇微波辅助法制备了Pd-Au/MWCNTs，考察了不同处理方式对其形貌和甲酸电氧化催化活性的影响。用下列标准处理方法从制备后的催化剂上吸附乙二醇所形成的碳质沉积物中提纯金属颗粒表面：1.在300℃空气中热处理，2.在300℃空气中退火，然后在200℃下用5%H2/Ar还原，3.在200℃下用5%H2/Ar还原。令人惊讶的是，催化活性最高的样品是没有额外净化处理的样品。用透射电子显微镜、X射线衍射仪和电子能谱等方法对催化剂进行了表征。所有催化剂中均存在两种PdX AU1-x相。处理1和处理2导致：1.部分去除金属表面的碳化物；2.增大金属颗粒尺寸；3.减少富Pd相含量；4.增加催化剂表面层中的Au/Pd比。处理4对样品的形貌没有明显影响，但降低了其在甲酸燃料电池中的催化活性。这可能是在还原(H2)气氛下的热处理过程中碳沉积的适当齐聚(©2011 Wiley-VCH Verlag GmbH&Co.KGaA，Weinheim)
Influence of different treatments of Pd-Au/MWCNTs prepared by a modified polyol microwave-assisted method on the morphology and the catalytic activity in the formic acid electrooxidation was investigated. The following standard treatments were applied to purify the metal particles surface from the carbonaceous deposits formed from ethyl glycol adsorbed on the catalyst after the preparation: 1. annealing in air at 300 °C, 2. annealing in air at 300 °C and then reduction in 5%H2/Ar at 200 °C, 3. reduction in 5%H2/Ar at 200 °C. Surprisingly, the most catalytically active sample was that without additional purification treatments. The TEM, XRD and electron spectroscopy methods were applied to characterise the catalysts. Two Pdx Au1–x phases are present in all catalysts. The treatment number 1 and 2 caused: 1. partial removing of the carbonaceous deposits from the metal surface, 2. increases metal particle sizes, 3. decreases of Pd rich phase content, 4. increases ratio of Au to Pd in the catalyst surface layer. Treatment number 4 did not change significantly the sample morphology but decreased its catalytic activity in formic acid fuel cell. It can be due oligomerization of carbon deposits during thermal treatment in reducing (H2) atmosphere (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)