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Shin, Tae Joo
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A General Approach to Preferential Formation of Active Fe-Nx Sites in Fe-N/C Electrocatalysts for Efficient Oxygen Reduction Reaction

Author(s)
Sa, Young JinSeo, Song-JunWoo, JinwooLim, Jung TaeCheon, Jae YeongYang, Seung YongLee, Jae MyeingKang, DongwooShin, Tae JooShin, Hyeon SukJeong, Hu YoungKim, Chul SungKim. Min GyuKim, Tae-YoungJoo, Sang Hoon
Issued Date
2016-11
DOI
10.1021/jacs.6b09470
URI
https://scholarworks.unist.ac.kr/handle/201301/20680
Fulltext
http://pubs.acs.org/doi/abs/10.1021/jacs.6b09470
Citation
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, v.138, no.45, pp.15046 - 15056
Abstract
Iron-nitrogen on carbon (Fe-N/C) catalysts have emerged as promising nonprecious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) in energy conversion and storage devices. It has been widely suggested that an active site structure for Fe-N/C catalysts contains Fe-Nx coordination. However, the preparation of high-performance Fe-N/C catalysts mostly involves a high-temperature pyrolysis step, which generates not only catalytically active Fe-Nx sites, but also less active large iron-based particles. Herein, we report a general “silica-protective-layer-assisted” approach that can preferentially generate the catalytically active Fe-Nx sites in Fe-N/C catalysts while suppressing the formation of large Fe-based particles. The catalyst preparation consisted of an adsorption of iron porphyrin precursor on carbon nanotube (CNT), silica layer overcoating, high-temperature pyrolysis, and silica layer etching, which yielded CNTs coated with thin layer of porphyrinic carbon (CNT/PC) catalysts. Temperature-controlled in situ X-ray absorption spectroscopy during the preparation of CNT/PC catalyst revealed the coordination of silica layer to stabilize the Fe-N4 sites. The CNT/PC catalyst contained higher density of active Fe-Nx sites compared to the CNT/PC prepared without silica coating. The CNT/PC showed very high ORR activity and excellent stability in alkaline media. Importantly, an alkaline anion exchange membrane fuel cell (AEMFC) with a CNT/PC-based cathode exhibited record high current and power densities among NPMC-based AEMFCs. In addition, a CNT/PC-based cathode exhibited a high volumetric current density of 320 A cm-3 in acidic proton exchange membrane fuel cell. We further demonstrated the generality of this synthetic strategy to other carbon supports.
Publisher
AMER CHEMICAL SOC
ISSN
0002-7863
Keyword
HIGH-TEMPERATURENITROGEN-DOPED CARBONHIGH-PERFORMANCE ELECTROCATALYSTSALKALINE FUEL-CELLSFE/N/C-CATALYSTSNONPRECIOUS ELECTROCATALYSTSCOMPOSITE ELECTROCATALYSTCOORDINATION CHEMISTRYMETAL ELECTROCATALYSTORGANIC FRAMEWORK

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