Interaction of sulfur dioxide with titanium–carbide nanoparticles and surfaces: A density functional study

Abstract

In the control of environmental pollution, metal carbides are potentially useful for trapping and destroying sulfur dioxide (SO2). In the present study, the density functional theory was employed to study the surface structures and electronic properties of the adsorbed SO2 on titanium carbides: metcar Ti8C12, nanocrystal Ti14C13, and a bulk TiC(001) surface. The geometries and orientations of SO2 were fully optimized on all these substrates. Our calculations show that, in spite of the high C/Ti ratio and C2 groups, metcar Ti8C12 exhibits extremely high activity towards SO2. The S–O bonds of SO2 spontaneously break on Ti8C12. The products of the decomposition reaction (S, O) interact simultaneously with Ti and C sites. The C atoms are not simple spectators, and their participation in the dissociation of SO2 is a key element for the energetics of this process. Nanocrystal Ti14C13 also displays a strong interaction with SO2. Although the dissociation of SO2 on Ti14C13 cannot proceed as easily as that on Ti8C12, it could occur by thermal activation even at very low temperature. SO2 is weakly bonded with the bulk TiC(001) surface. By thermal activation the dissociation of SO2 on a TiC(001) surface may also take place but it should be much more difficult than that on Ti14C13. Therefore, we suggest that the carbide nanoparticles (Ti8C12 and Ti14C13) should have special chemical activity towards SO2 removal associated with their “magic” structures.