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标题：Direct in situ observations of single Fe atom catalytic processes and anomalous diffusion at graphene edges
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作者：Jiong Zhao ; Qingming Deng ; Stanislav M. Avdoshenko 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2014
卷号：111
期号：44
页码：15641-15646
DOI：10.1073/pnas.1412962111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe single metal atom has been proposed to be a catalyst during the growth of carbon nanotubes; however, this hypothesis is still not confirmed. Our direct in situ transmission EM observation of the restructuring of the graphene edges interacting with an Fe atom directly revealed the intermediate states: pentagon and hexagon structures. In particular, our experiments and simulations show that the single Fe atom behaves differently on the graphene zigzag and armchair edges, giving insights to the growth mechanisms of various sp2 carbon structures. Single-atom catalysts are of great interest because of their high efficiency. In the case of chemically deposited sp2 carbon, the implementation of a single transition metal atom for growth can provide crucial insight into the formation mechanisms of graphene and carbon nanotubes. This knowledge is particularly important if we are to overcome fabrication difficulties in these materials and fully take advantage of their distinct band structures and physical properties. In this work, we present atomically resolved transmission EM in situ investigations of single Fe atoms at graphene edges. Our in situ observations show individual iron atoms diffusing along an edge either removing or adding carbon atoms (viz., catalytic action). The experimental observations of the catalytic behavior of a single Fe atom are in excellent agreement with supporting theoretical studies. In addition, the kinetics of Fe atoms at graphene edges are shown to exhibit anomalous diffusion, which again, is in agreement with our theoretical investigations.
关键词：graphene edge ; single Fe atom ; catalytic ; anomalous diffusion ; TEM