期刊
NANO-MICRO LETTERS
卷 10, 期 1, 页码 -出版社
SHANGHAI JIAO TONG UNIV PRESS
DOI: 10.1007/s40820-017-0157-1
关键词
Hierarchical pores; Hollow cores; N doping; Electrocatalysis; Oxygen reduction reaction
资金
- National Key Research and Development Program of China [2016YFB0700204]
- NSFC [51502327, 51602332]
- Science and Technology Commission of Shanghai Municipality [15520720400, 15YF1413800, 14DZ2261203, 16DZ2260603]
- Key Project for Young Researcher of State Key Laboratory of High Performance Ceramics and Superfine Microstructure
- Chinese Academy of Sciences
A series of triple hierarchical micro-mesomacroporous N-doped carbon shells with hollow cores have been successfully prepared via etching N-doped hollow carbon spheres with CO2 at high temperatures. The surface areas, total pore volumes and micropore percentages of the CO2-activated samples evidently increase with increasing activation temperature from 800 to 950 degrees C, while the N contents show a contrary trend from 7.6 to 3.8 at%. The pyridinic and graphitic nitrogen groups are dominant among various N-containing groups in the samples. The 950 degrees C-activated sample (CANHCS-950) has the largest surface area (2072 m(2) g(-1)), pore volume (1.96 cm(3) g(-1)), hierarchical micro-mesopore distributions (1.2, 2.6 and 6.2 nm), hollow macropore cores (similar to 91 nm) and highest relative content of pyridinic and graphitic N groups. This triple micro-meso-macropore system could synergistically enhance the activity because macropores could store up the reactant, mesopores could reduce the transport resistance of the reactants to the active sites, and micropores could be in favor of the accumulation of ions. Therefore, the CANHCS-950 with optimized structure shows the optimal and comparable oxygen reduction reaction (ORR) activity but superior methanol tolerance and long-term durability to commercial Pt/C with a 4e(-)-dominant transfer pathway in alkaline media. These excellent properties in combination with good stability and recyclability make CANHCSs among the most promising metal-free ORR electrocatalysts reported so far in practical applications. [GRAPHICS]
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