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.

The view that the theoretical capacity of spinel Li4Ti5O12 is limited by the number of available octahedral sites to accommodate lithium ions is debated. Combining the electrochemical and XRD results with the crystal structure of Li4Ti5O12, we demonstrate the corresponding reaction mechanism of the low-potential intercalation behavior of Li4Ti5O12 and modify the classical viewpoint on the theoretical capacity of Li4Ti5O12. The theoretical capacity of Li4Ti5O12 is limited by the number of tetravalent titanium ions, but not the octahedral or tetrahedral sites to accommodate lithium ions in the voltage range of 2.5 to 0.01 V, corresponding to 293 mAhg−1, but not 175 mAhg−1.

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