Determination of the Surface Oxidation Degree of the Carbonaceous Materials by Quantitative TG-MS Analysis

摘要

The developed quantitative TG-MS analysis was used for the determination of the surface oxidation degree of activated carbon cryogels. The surface chemistry of a prepared carbon cryogels pyrolyzed at 400 and 500 degrees C was modified using H3PO4, Fenton-like reaction, (NH4)(2)S2O8 with H2SO4 and HNO3 with H2O2 into a different surface oxidation degree. The influence of activation method and the amount of oxygen surface groups were characterized by elemental analysis, immersion calorimetry, water vapor adsorption, and Boehm titration. The obtained results from these methods were compared with the amount of surface oxygen determined by TG-MS. It was found out, that with the more intensive oxidation method (Fenton < (NH4)(2)S2O8 with H2SO4 < HNO3 with H2O2) the concentration of oxygen-containing surface groups increases, which lead to considerably higher parameters of immersion heat, amount of adsorbed water and acidity of the sample surface. The H3PO4 treatment of carbon cryogels causes no significant changes in the surface chemistry. The results obtained from the TG-MS analysis imply the good agreement with the results obtained from other used methods. It was proved that the quantitative TG-MS analysis could be a useful tool for the characterization of the surface of the carbonaceous materials.