Preparation, Characterization And Electrochemical Properties Of Nitrogen-doped Ordered Mesoporous Carbons

During the past several years, porous carbon materials attracted particular attentions due to their large surface area, tailorable textural properies, high conductivities and highly chemical stability. These structural properties make carbon materials exhibit potential applications in fuel cell, catalysis, hydrogen storage adsorption and seperation. Among all the properties investigated, the surface modifications of porous carbons remain a particularly interesting topic in materials sciences.In this work, nitrogen-doped ordered mesoporous carbons (NOMCs) were successfully nanocasted from hexagonally ordered mesoporous SBA-15, using polyaniline as carbon precursor. The structural parameters of NOMCs were systematically investigated using powder X-ray diffraction (XRD), N2 adsorption, thermogravimetic analysis (TGA), transmission electron microscopy (TEM), elemental analysis and X-ray photoelectron spectroscopy (XPS). It was found that the obtained NOMC featured typical CMK-3 mesoporous carbon despite the pyrolysis temperature varied from 600 to 950°C. The resulting NOMC charactistic of CMK-3 exhibited high surface area (988-1166 m2/g) and narrow pore size (2.7-3.3 nm). XPS showed that nitrogen atoms were incorporated in graphitic sheets as quaternary nitrogen and pyridine-like nitrogen. Also there existed a strong interaction between nitrogen atoms and Pt nanoparticles. Moreover, the N/C molar ratio in the framework of mesoporous carbon reduced from 9.5% to 4.8% as the synthesis temperature increased from 600 to 950°C.The obtained carbon materials (NOMCs) were applied as catalyst support for platinum loading. The activities of methanol oxidation on Pt/NOMCs were investigated by cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS). It was found that the presence of surface nitrogen functional groups was critical to the high disperse of Pt catalysts on the carbon materials. Doping of nitrogen atoms in the carbon materials could effectively improve the dispersion of platinum nanoparticles and the CO tolerance of Pt catalyst. The Pt/NOMCs showed higher activity than Pt/XC-72 under the identical condition in term to methanol oxidation.NOMC were also applied as adsorbents for Cr6+ removal. All the NOMCs exhibited the fast adsorption rate and the excellent adsorption capacity for Cr6+. The adsorption equilibrium can quickly achieve within several minutes. For the initial concentration of Cr6+ of 5×10-4 mol/L, 38% to 74% Cr6+ can be effectively adsorbed on the NOMC with 10 min. Nitrogen functional group on carbon as well as the large surface area may be responsible for the observed high adsorption capacity, although detailed experiments are still required to perform.