Nitrogen-enriched ordered mesoporous carbons through direct pyrolysis in ammonia with enhanced capacitive performance
By Wang, Xiqing; Liu, Chen-Guang; Neff, David; Fulvio, Pasquale F.; Mayes, Richard T.; Zhamu, Aruna; Fang, Qing; Chen, Guorong; Meyer, Harry M.; Jang, Bor Z. & Dai, Sheng
Published in J. Mater. Chem. A
The Royal Society of Chemistry
2013
Abstract
Self-assembly of phenolic resins and a Pluronic block copolymer via the soft-template method enables the formation of well-organized polymeric mesostructures, providing an easy way for preparation of ordered mesoporous carbons (OMCs). However, direct synthesis of OMCs with high nitrogen content remains a significant challenge due to the limited availability of nitrogen precursors capable of co-polymerizing with phenolic resins without deterioration of the order of mesostructural arrangement and significant diminishment of nitrogen content during carbonization. In this work, we demonstrate pyrolysis of the soft-templated polymeric composites in ammonia as a direct, facile way towards nitrogen-enriched OMCs (N-OMCs). This approach does not require any nitrogen-containing carbon precursors or post-treatment, but takes advantage of the preferential reaction and/or replacement of oxygen with nitrogen species, generated by decomposition of ammonia at elevated temperatures, in oxygen-rich polymers during pyrolysis. It combines carbonization, nitrogen functionalization, and activation into one simple process, generating N-OMCs with a uniform pore size, large surface area (up to 1400 m2 g-1), and high nitrogen content (up to 9.3 at%). More importantly, the ordering of the meso-structure is well-maintained as long as the heating temperature does not exceed 800 [degree]C, above which (e.g., 850 [degree]C) a slight structural degradation is observed. When being used as electrode materials for symmetric electric double layer capacitors, N-OMCs demonstrate enhanced capacitance (6.8 [small mu ]F cm-2vs. 3.2 [small mu ]F cm-2) and reduced ion diffusion resistance compared to the non-NH3-treated sample.