中文摘要：

将含氮聚合物聚苯胺（PANI）均匀地担载到具有大比表面积、多级孔结构和高导电性的3D碳纳米笼（CNC）表面,再热解PANI制得了N掺杂位富集于表面、且具有优良导电性的碳基纳米材料.通过改变热解温度和前驱物中PANI的含量,对热解产物的表面N含量和导电性进行了调控.优化得到的NCNC-2-900催化剂具有优异的氧还原反应（ORR）催化性能,其起始电位高（-46 m V vs Ag/Ag Cl）,明显优于体相N掺杂的CNC（-105 m V）,且稳定性好（运行10 h后仍保留96%活性）.该结果表明在保持良好导电性的同时增加表面N掺杂位是提高碳基材料ORR活性的有效途径.

英文摘要：

Fuel cells can efficiently convert chemical energy of fuels into electrical energy in a green manner, representing one of the most promising movable power sources. The main bottleneck for the wide application of fuel cells is the sluggish oxygen reduction reaction（ORR） which is usually catalyzed by expensive and unstable Pt catalysts. Hence, the exploration of cost-efficient and long-life ORR electrocatalysts is of great significance. Recently carbon-based metal-free ORR electrocatalysts have attracted much interest due to their superior activity and stability as well as the abundance and low cost. It is generally accepted that nitrogen doping of carbon materials boost the ORR activity by breaking the electroneutrality of carbon layer and activating π electrons. Considering that the embedded N doping sites are useless for ORR but significantly affect electron conduction, the carbon materials with N-enriched surface of high activity and pristine carbon bulk of high conductivity should present better ORR performance than the bulk N-doped counterpart. In this contribution, we report an efficient strategy for the synthesis of ORR electrocatalysts with surface enriched N doping and high conductive bulk by dispersing polyaniline（PANI） on the surface of 3D hierarchical carbon nanocages（CNC）, followed by heat treatment in Ar. The N content and conductivity of the pyrolyzed products are regulated by changing the pyrolysis temperature and the weight ratio of PANI/CNC composite. The optimized electrocatalyst with the N content of 2.21 at% and the conductivity of 203 S·m-1 exhibits excellent ORR catalytic performance with high onset potential of-46 m V vs Ag/Ag Cl, obvious superior to the bulk N-doped CNC（-105 m V）. This catalyst also possesses high stability（96% activity retention after 10 h continuous tests） and dominated 2-electron pathway for ORR with transferred electron number of 2.8. This result suggests an efficient route to improve the ORR activity of carbon-based materials by increasing the N