Detailed Interface Composition of Graphitized Soot and Carbon T900: Reference Material for Atmospheric Studies investigated by a flowing gas experiment

Two graphitized thermal soot samples (GTS6, GTS80) and graphitized soot with a deposited overlayer of organic carboxylic acid (GTS80 impregnated with 1,2,4-benzenetricarboxylic acid (4.88 % (w/w) 1,2,4 BTCA)) have been investigated in a flowing gas experiment under molecular flow conditions using a Knudsen flow reactor. As a comparison, a typical commercial amorphous carbon T900 has a significantly larger coverage of surface functional groups (SFG's) than both processed carbons GTS6 and GTS80 probed by NO2, O3, NH2OH, CF3COOH, HCl and N(CH3)3. Despite the high temperature processing, the interface of GTS6 and GTS80 still retains a significant coverage of reduced sites using O3 as a probe gas, namely approximately 10 and 1 % of a monolayer (ML), respectively, compared to 46 % for T900. Using N(CH3)3 as a probe gas we established that the tailor-made BTCA-covered GTS80 sample is highly acidic as expected having a -COOH group coverage of 51.7 ± 10.5 % of a molecular layer (ML). The corresponding initial uptake probability of most probe gases on T900 are significantly larger than for both GTS carbons, in line with the trends in coverage after saturating adsorption of probe gases.