Preparation of MgO-Templated N-Doped Mesoporous Carbons from Polyvinylpyrrolidone: Effect of Heating Temperature on Pore Size Distribution

Tomoya Takada,Mayu Kurihara

doi:10.3390/c5020015

Abstract

Magnesium oxide (MgO)-templated nitrogen (N)-doped mesoporous carbons were prepared by using polyvinylpyrrolidone (PVP) as a raw material and magnesium lactate (Mglac) as a precursor for the MgO template to examine the influence of heating temperature and MgO precursor (magnesium acetate was used in similar previous studies) on the pore size and nitrogen content. The MgO-templated carbon was obtained by heating the PVP/Mglac mixture in an inert atmosphere followed by an acid treatment for MgO removal. The mesopore size of the carbons was approximately 4 nm regardless of heating temperature, corresponding to the crystallite size of the MgO template estimated via X-ray diffraction. This indicates that the mesopore of approximately 4 nm was generated using the MgO template. However, larger pores were also found to exist. This result indicates that the larger pores generated through processes other than the MgO templating, likely the thermal decomposition of PVP, are contained in the templated carbon. The volume of the larger pores and the specific surface area increased with increasing heating temperature. The nitrogen content of the carbon decreased as the heating temperature was increased, but it was found to be irrelevant to the MgO precursor.

Highlights

N-doped mesoporous carbons were derived from PVP/magnesium lactate (Mglac) mixtures
N-doped carbon possessing a unique peak pore width (4 nm) was prepared by using Mglac, indicating that the pore size distribution can be controlled by choosing the Magnesium oxide (MgO) source in the case of N-doped mesoporous carbon
This peak mesopore size did not depend on the heating temperature and was comparable to the MgO crystallite size for all samples prepared at 800–1000 ◦ C

Summary

Introduction

Nitrogen (N)-doped carbon has been extensively studied from various technological viewpoints [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]. Doping carbon materials with N has been known to increase their electrostatic capacitance. This effect is usually explained by the introduction of surface functional groups containing nitrogen; such functional groups act as sites for electron-donating and accepting (redox) reactions [14]. These redox reactions contribute to the increased electrostatic capacitance, the improvement of pore wettability is another important effect of N-doping that can lead to increased capacitance.

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Conclusion