Surface chemistry of carbon: activation of molecular oxygen

Three different industrial carbon blacks were characterized in their surface chemistry with respect to their relative abilities to activate molecular oxygen. A variety of techniques was used including x-ray diffraction, gasification experiments, electron spectroscopy as XPS and UPS, helium ion scattering spectroscopy, thermal desorption spectroscopy and the catalytic oxidation of aqueous SO2 as a “chemical probe” for activated oxygen. The activation properties for molecular oxygen at high temperatures were probed by analysing the gasification characteristics in 5 vol % oxygen-inert gas mixtures; at low temperatures the activity in the oxidation of SO2 to sulfuric acid with molecular oxygen was taken as indicator. For this reaction the carbons had to be activated by ammonia treatment at elevated temperatures. Thermal desorption spectroscopy and valence band photoemission provided data for the identification of reaction intermediates in the activation process of oxygen. The important role of surface chemica...