Elucidating Oxygen Reduction Active Sites in Pyrolyzed Metal鈥揘itrogen Coordinated Non-Precious-Metal Electrocatalyst Systems

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• 作者：Urszula Tylus ; Qingying Jia ; Kara Strickland ; Nagappan Ramaswamy ; Alexey Serov ; Plamen Atanassov ; Sanjeev Mukerjee
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：May 1, 2014
• 年：2014
• 卷：118
• 期：17
• 页码：8999-9008
• 全文大小：533K
• 年卷期：v.118,no.17(May 1, 2014)
• ISSN：1932-7455

文摘

Detailed understanding of the nature of the active centers in non-precious-metal-based electrocatalyst, and their role in oxygen reduction reaction (ORR) mechanistic pathways will have a profound effect on successful commercialization of emission-free energy devices such as fuel cells. Recently, using pyrolyzed model structures of iron porphyrins, we have demonstrated that a covalent integration of the Fe鈥揘_x sites into 蟺-conjugated carbon basal plane modifies electron donating/withdrawing capability of the carbonaceous ligand, consequently improving ORR activity. Here, we employ a combination of in situ X-ray spectroscopy and electrochemical methods to identify the various structural and functional forms of the active centers in non-heme Fe/N/C catalysts. Both methods corroboratively confirm the single site 2e^{鈥?/sup> 脳 2e鈥?/sup> mechanism in alkaline media on the primary Fe2+鈥揘₄ centers and the dual-site 2e鈥?/sup> 脳 2e鈥?/sup> mechanism in acid media with the significant role of the surface bound coexisting Fe/Fe_xO_y nanoparticles (NPs) as the secondary active sites.}