Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9617678 | Microporous and Mesoporous Materials | 2005 | 8 Pages |
Abstract
A series of activated carbons having from 0.8 to 7.2 wt.% of nitrogen substituted for carbon in graphene layer was prepared by steam activation of chars derived from polyacrylonitrile (PAN), oxidized form of polyvinylpyridine (PVPox) and their blends with coal-tar pitch (CTP). Porosity development at 50 wt.% burn-off was monitored using N2 adsorption at â196 °C and the surface chemistry was characterized by elemental analysis, X-ray photoelectron spectroscopy, pH of the point zero charge pHPZC and acid/base titration. Activated carbons from PAN and CTP/PAN blends show a similar moderate porosity development (SBET â¼Â 800 m2 gâ1). PVPox gives most microporous carbons (SBET â¼Â 1400 m2 gâ1) but the porosity diminishes with pitch contribution to blend. Substitutional nitrogen effectively enhances the basicity of the carbon surface. pHPZC increases proportionally to nitrogen content and reaches a maximum over 10 for PAN derived carbon of N/C ratio 0.07. Conversely, the maximum number of basic sites from titration with HCl, â¼2 mmol gâ1, is found for PVPox carbon with a moderate nitrogen proportion (N/C = 0.025), however, with a superior porosity development. Introduction of nitrogen does not affect the number and distribution of acidic oxygen groups of activated carbon.
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Authors
J. Machnikowski, B. Grzyb, H. Machnikowska, J.V. Weber,