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Abstract
Shell-core nanostructured carbon materials with a nitrogen-doped graphitic layer as
a shell and pristine carbon black particle as a core were synthesized by carbonizing
the hybrid materials containing in situ polymerized aniline onto carbon black. In
an N-doped carbon layer, the nitrogen atoms substitute carbon atoms at the edge and
interior of the graphene structure to form pyridinic N and quaternary N structures,
respectively. As a result, the carbon structure becomes more compact, showing curvatures
and disorder in the graphene stacking. In comparison with nondoped carbon, the N-doped
one was proved to be a suitable supporting material to synthesize high-loading Pt
catalysts (up to 60 wt %) with a more uniform size distribution and stronger metal-support
interactions due to its high electrochemically accessible surface area, richness of
disorder and defects, and high electron density. Moreover, the more rapid charge-transfer
rates over the N-doped carbon material are evidenced by the high crystallinity of
the graphitic shell layer with nitrogen doping as well as the low charge-transfer
resistance at the electrolyte/electrode interface. Beneficial roles of nitrogen doping
can be found to enhance the CO tolerance of Pt catalysts. Accordingly, an improved
performance in methanol oxidation was achieved on a high-loading Pt catalyst supported
by N-doped carbon. The enhanced catalytic properties were extensively discussed based
on mass activity (Pt utilization) and intrinsic activity (charge-transfer rate). Therefore,
N-doped carbon layers present many advantages over nondoped ones and would emerge
as an interesting supporting carbon material for fuel cell electrocatalysts.