Two commercial soot samples are analysed by temperature programmed desorption mass spectroscopy (TPD-MS) in order to
determine the functional groups at their surface. A systematic approach has been developed, which assures that all functional groups
decomposing between 100 °C and 900 °C can be distinguished and assigned. For the understanding of the mechanism of the reaction
between soot and NO2 diffuse reﬂectance infrared Fourier transform spectroscopy (DRIFTS) and TPD-MS are applied. Both spectroscopic
techniques monitor the formation of new species. The reaction with NO2 results in the formation of an acidic functional
group, which decomposes into CO2 and NO at 140 °C. It is proven that NO2 reacts directly with the carbon surface. Pre-existing
functional groups do not interfere. From these results the reaction sequence has been concluded.