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

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 °C was modified using H₃PO₄, Fenton-like reaction, (NH₄)₂S₂O₈ 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)₂S₂O₈ 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.