Controllable nitrogen introduction into porous carbon with porosity retaining for investigating nitrogen doping effect on SO2 adsorption

Abstract

Chemical doping of nitrogen into carbon framework has been demonstrated effective for gas molecules (e.g. CO2, SO2, NOx) adsorption. Here we report a series of nitrogen-doped porous carbons with controllable doping level (4.25–10.23%) and consistent pore structure (surface area around 1000m2/g) by a co-assembly method. Based on the unique structure, SO2 was used as probe molecule to independently study the N doping effect on the SO2–carbon surface interactions from both experimental and calculation aspects. The results indicate that SO2 adsorption capacities are proportional to the nitrogen contents and the sample with 10.2% nitrogen content gives the highest SO2 adsorption capacity of 48.3mg/g, 2.95 times higher than non-doped carbon. Moreover, combining the literature data with our studies indicates that both pore structure and N species play a contribution in SO2 adsorption process. For the NPC materials with similar pore structure, the increase of N contents improves the SO2 adsorption area in pores of N doped carbon mainly by enhancing the physisorption on various locations of carbon surface including basal plane and edge positions. Density functional theory (DFT) calculations indicate that nitrogen atom itself cannot serve as active site for SO2 adsorption. The role of nitrogen doping is to remodel the local electronic density, the polarity of carbon atoms as well as charge distribution of carbon surface, which induces the enhanced SO2 adsorption.