Preparation of N-doped microporous carbon nanospheres by direct carbonization of as-prepared mesoporous silica nanospheres containing cetylpyridinium bromide template

Abstract

N-doped microporous carbon nanospheres (MCNs) are prepared directly from the as-prepared mesoporous silica nanospheres (MSNs) with a disordered pore structure by a new, simple and direct carbonization method. The as-prepared MSNs containing cetylpyridinium bromide (CTPB) template are effective for direct carbonization. Neither MSN with a two-dimensional hexagonal pore symmetry nor MSN with cetyltrimethylammonium bromide (CTAB) template is effective for this new method. Thus, this method is very cost-effective and environmentally benign. Furthermore, N-doping into the carbon matrix naturally occurrs during the carbonization process, because of the presence of pyridinium N atoms in the CTPB template. The N-doped MCN material is a good sorbent material for CO2 adsorption owing to the Lewis basic sites of N atoms as well as good microporosity. The low surface coverage isosteirc heat of CO2 adsorption (Qst) is calculated by the Clausius–Clapeyron equation using the data obtained at 273 and 298 K, and the calculated value of Qst is 58.4 kJ mol−1. This value is relatively very high compared to the other N-doped porous carbon materials. Both the Lewis basic sites of N atoms and uniform microporosity in the N-doped MCNs are responsible for this high value.