Interactions of SO2 and H2S with amorphous carbon films

There is significant interest in development of efficient catalyst-sorbents for the capture and conversion of sulfur-compounds such as H2S and SO2. In this work, ultra-high vacuum (UHV) techniques have been used to carefully prepare and thoroughly characterize amorphous carbon (a-C) thin films as models of activated carbon sorbents. Films with modified surface chemistries were prepared by oxidation of a sputter deposited carbon film (a-COx) and by sputter depositing carbon in the presence of N2 (a-CNx) or methane (a-CHx). Temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) were used to study H2S and SO2 surface chemistry on these films and on a highly oriented pyrolytic graphite (HOPG) reference-surface. The modification of the carbons with different heteroatoms influences both the strength of their interactions with SO2 and H2S and their capacities for sulfur-compound adsorption.

The microstructure and chemical composition of carbonaceous materials dictate their interactions with sulfur dioxide and hydrogen sulfide. For example, sulfur dioxide desorbs from amorphous carbon thin films with first-order kinetics and desorption energies (Edes) that decrease with increasing exposure (L) (at ∼100 K), suggesting interaction with heterogeneous edge defects on the carbon matrix.Figure optionsDownload as PowerPoint slide