Electrochemical Kinetics and X-ray Absorption Spectroscopic Investigations of Oxygen Reduction on Chalcogen-Modified Ruthenium Catalysts in Alkaline Media
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- 作者：Nagappan Ramaswamy ; Robert J. Allen ; Sanjeev Mukerjee
- 刊名：Journal of Physical Chemistry C
- 出版年：2011
- 出版时间：June 30, 2011
- 年：2011
- 卷：115
- 期：25
- 页码：12650-12664
- 全文大小：1557K
- 年卷期：v.115,no.25(June 30, 2011)
- ISSN：1932-7455
文摘
The oxygen reduction reaction (ORR) in alkaline media has been investigated on chalcogen-modified ruthenium nanoparticles (Ru/C, Se/Ru/C, Se/RuMo/C, S/Ru/C, S/RuMo/C) synthesized in-house via aqueous routes. In acidic medium, it is well known that modification by a chalcogen prevents the oxidation of the underlying transition-metal (Ru) surface, thereby promoting direct molecular O2 adsorption on the Ru metal. On an unmodified Ru catalyst in alkaline media, the surface oxides on Ru mediate the 2e鈥?/sup> reduction of molecular O2 to a stable peroxide anion (HO2鈥?/sup>) intermediate via an outer-sphere electron-transfer mechanism. This increases the activity of HO2鈥?/sup> near the electrode surface and decreases the overpotential for ORR by effectively carrying out the reduction of HO2̅鈥?/sup> to OH鈥?/sup> at the oxide-free ruthenium metal site. An increase in ORR activity of Ru is observed by modification with a chalcogen; however, the increase is not as significant as observed in acidic media. Ternary additives, such as Mo, were found to significantly improve the stability of the chalcogen-modified catalysts. Detailed investigations of the ORR activity of this class of catalyst have been carried out in alkaline media along with comparisons to acidic media wherever necessary. A combination of electrochemical and X-ray absorption spectroscopic (EXAFS, XANES, 螖渭) studies has been performed in order to understand the structure/property relationships of these catalysts within the context of ORR in alkaline electrolytes.