Inhibition Effect of Surface Oxygenated Species on Ammonia Oxidation Reaction

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• 作者：Wei Peng ; Li Xiao ; Bing Huang ; Lin Zhuang ; Juntao Lu
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：November 24, 2011
• 年：2011
• 卷：115
• 期：46
• 页码：23050-23056
• 全文大小：994K
• 年卷期：v.115,no.46(November 24, 2011)
• ISSN：1932-7455

文摘

The ammonia oxidation reaction (AOR) cannot proceed on Pt surface at potentials corresponding to the formation of surface oxygenated species (O_ads and OH_ads), it is thus suspicious that, in addition to the N_ads, the surface oxygenated species may also play an inhibitive role. Yet this is difficult to be proven in aqueous media where the AOR is always accompanied with the water oxidation reaction. In the present work, we carry out differential electrochemical mass spectroscopy (DEMS) studies of the AOR in nonaqueous media where no surface oxygenated species is involved, and the results turn out be remarkably different from those obtained in KOH solution. It is evident that, without the blocking of oxygenated species, the Pt surface can remain continuously active for AOR, and N₂ is the dominant product. More strikingly, Pd becomes highly active for the AOR in nonaqueous media, a result enormously different from that in KOH solution where Pd exhibits a very low catalytic activity because of severer surface passivation by oxygenated species. This work provides compelling evidence for the inhibition effect of surface oxygenated species on the AOR, and illuminates our understanding of relevant reaction mechanisms.