A DFT study on benzene adsorption over tungsten sulfides: surface model and adsorption geometries

Abstract

Benzene adsorption on a WS 2 (100) surface was studied by ab initio periodic DFT computations. Benzene adsorption is facile on the bridge site of the bare W edge via g 2 or g 3 coordination. Taking into account the stable configuration at the W edge under typical hydrotreating reaction conditions (623 K, H 2 S/H 2 = 0.01), benzene adsorption is found to be difficult, even when defective bridge sites are created.

A DFT study on benzene adsorption over a corner site of tungsten sulfides

“…This corresponds to sulfur coverage of 50% at the W edge and 83% at the S edge. This result is very similar to our previous work on the W and S edges in WS 2 (1 0 0), which resulted in sulfur coverages of 50% at the W edge and 87.5% at the S edge [18]. We conclude that surface stability of the normal edge plane for alternating W and S edge in the WS 2 slab is maintained even around the corner of the hexagonal structure between W and S edge.…”

“…Logadóttir et al established that benzene adsorption may take place on a fivefold coordinated Mo atom in the Mo edge of MoS 2 [11]. We have also reported benzene adsorption over the defective W edge with benzene adsorbed to the bridging site between two 5-fold coordinated W atoms [18]. Similarly, Cristol et al described thiophene derivatives adsorbed on the defective bridging site between two 5-fold coordinated Mo atoms in Mo edge of MoS 2 [10].…”

“…Sun et al have studied the stable configuration of WS 2 , Ni-WS 2 and Co-WS 2 surfaces [17]. We have recently studied the adsorption of benzene on a WS 2 slab [18]. Benzene only adsorbed to a bare W edge, whereas no benzene adsorption sites were identified on sulfur-containing tungsten and sulfur edges of WS 2 representative for typical hydrotreating reaction conditions.…”

Density functional study of the adsorption and van der Waals binding of aromatic and conjugated compounds on the basal plane of MoS2

“…This is of significant importance, since molecules such as thiophene and dibenzoethiophene have been found to make weak chemical bonds with the equilibrium edge structures and single vacancies on the equilibrium edges. 2,5,10,14,15 The linear correlation found in Fig. 4 could be used to estimate the vdW contribution for larger molecules such as dibenzothiophene and could therefore prove to be useful in the development of reaction path diagrams including vdW forces.…”

“…[2][3][4][5][7][8][9][10][11][12][13][14][15] In calculating accurate chemisorption energies of molecules on surfaces, the DFT has a well-proven record. 16 The calculation of physisorption energies has been much more of a challenge, however, due to the absence of the ubiquitous van der Waals ͑vdW͒ forces in the most widely used implementations of DFT.…”