When nitrogen is doped in graphite carbon, and pyridine-type N cites are formed, redox function, similar to Pt, appears. Such nitrogen-doped carbon material can be used as electrode materials of fuel cells for saving the Pt usage.
We have successfully synthesized nitrogen-doped CNTs, which have rich pyridine N cites and show a good redox property. The N-doped CNTs have a unique structure; the outer shape is very similar normal CNTs, but inner hollows are not straw-like hollows but room-like voids connected in a column along with the tube. In such structure, many corners are generated, in which nitrogen atoms are suggested to be doped and occupied.
With the cooperation of WAKI laboratory of the Tokyo Institute of Technology, we have checked the redox properties of the N-doped CNTs by using electrochemical characterization methods. The results are shown below.