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Oxygen Reduction Reaction in a Droplet on Graphite: Direct Evidence that the Edge Is More Active than the Basal Plane
Author(s) -
Shen Anli,
Zou Yuqin,
Wang Qiang,
Dryfe Robert A. W.,
Huang Xiaobing,
Dou Shuo,
Dai Liming,
Wang Shuangyin
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201406695
Subject(s) - electrocatalyst , carbon fibers , electrolyte , catalysis , pyrolytic carbon , graphite , electrochemistry , chemistry , highly oriented pyrolytic graphite , platinum , metal , chemical engineering , oxygen reduction reaction , oxygen , carbon nanotube , inorganic chemistry , materials science , nanotechnology , electrode , organic chemistry , composite material , pyrolysis , composite number , engineering
Carbon‐based metal‐free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline medium have been extensively investigated with the aim of replacing the commercially available, but precious platinum‐based catalysts. For the proper design of carbon‐based metal‐free electrocatalysts for the ORR, it would be interesting to identify the active sites of the electrocatalyst. The ORR was now studied with an air‐saturated electrolyte solution droplet (diameter ca. 15 μm), which was deposited at a specified position either on the edge or on the basal plane of highly oriented pyrolytic graphite. Electrochemical measurements suggest that the edge carbon atoms are more active than the basal‐plane ones for the ORR. This provides a direct way to identify the active sites of carbon materials for the ORR. Ball‐milled graphite and carbon nanotubes with more exposed edges were also prepared and showed significantly enhanced ORR activity. DFT calculations elucidated the mechanism by which the charged edge carbon atoms result in the higher ORR activity.