Nitrogen doping is an effective method for modulating the electronic states and properties of graphene. In particular, chemical vapor deposition using nitrogen-containing organic molecules such as pyridine has been expected to be a facile way to control the doping site and amount of nitrogen. However, the atomic structure of nitrogen-doped graphene (NG) synthesized from such molecules has not been investigated. Furthermore, the nitrogen doping sites of NG synthesized at a high temperature of more than 1000 K have also not been measured. In this study, we carried out Scanning Tunneling Microscopy (STM) measurements on the structure of NG synthesized from pyridine, and elucidated the doping sites. Furthermore, we investigated how the doping of nitrogen atoms affects the reactivity with oxygen molecules to reveal the active site of a carbon alloy catalyst. We found that NG synthesized at 1150 K has nitrogen atoms doped into the pyridinic site, and these pyridinic sites enhance the reactivity to oxygen when comparing the defects with/without nitrogen. These findings will help with the synthesis of NG when controlling the doping sites and the development of a catalyst with high efficiency.
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