EXAFS Studies on the Formation of MoS2 Nanowires

Probing the Active Sites of MoS2 Based Hydrotreating Catalysts Using Modulation Excitation Spectroscopy

“…Structural parameters determined from fitting the Mo K-edge EXAFS spectra of the sulfided catalysts at 400 °C and the reference MoS 2 are given in Supporting Information, Tables S2–S4. For all the catalysts, Mo–S contribution at 2.40–2.41 Å with a coordination number (CN) of 4.1–4.8,which is 6 in bulk phase, indicates the presence of MoS 2 phase with sulfur deficient Mo sites, which is in accordance with earlier studies. − Mo–Mo coordination at 3.16–3.17 Å is also in agreement with earlier reported values; , however, the values of CN = 0.26–0.43 are too low. Note that these in situ EXAFS measurements were conducted at high temperature, which corresponds to the large Debye–Waller factor (thermal disorder) making EXAFS oscillations weaker and affecting the corresponding CNs .…”

“…Structural parameters determined from fitting the Mo K-edge EXAFS spectra of the sulfided catalysts at 400 °C and the reference MoS2 are given in Tables S2-S4. For all the catalysts, Mo-S coordination at 2.40-2.41 Å with a CN of 4.1-4.8 (which is 6 in bulk phase) indicates presence of MoS2 phase with sulfur deficient Mo sites which is in accordance with earlier studies [67][68][69][70] . Mo-Mo coordination at 3.16-3.17 Å is also in agreement with earlier reported values [67][68] , however the values of CN=0.26-0.43 is too low.…”

Influence of H 2 O and H 2 S on the composition, activity, and stability of sulfided Mo, CoMo, and NiMo supported on MgAl 2 O 4 for hydrodeoxygenation of ethylene glycol

“…But with an average Mo-Mo CN < 1from EXAFS, the majority of the particles were too small (< 2 nm) to detect with TEM at the applied resolution. These results are in line with the findings of Seo and Lee[94], who showed that the formation of MoS2 particles can take place through the initial formation of nanoparticles of ≤ 1 nm at mild sulfidation conditions. No Mo-Mo backscattering at 3.16 Å was detected for these particles indicating a very low coordination number, but at the same time, a Mo-S signal at 2.4 Å with a CN of 3.6 was reported, and the elemental S/Mo ratio was 1.3[94].…”

“…These results are in line with the findings of Seo and Lee[94], who showed that the formation of MoS2 particles can take place through the initial formation of nanoparticles of ≤ 1 nm at mild sulfidation conditions. No Mo-Mo backscattering at 3.16 Å was detected for these particles indicating a very low coordination number, but at the same time, a Mo-S signal at 2.4 Å with a CN of 3.6 was reported, and the elemental S/Mo ratio was 1.3[94]. As the sulfidation temperature was increased, they showed (TEM and EXAFS) that the nanoparticles merged to form the well-known MoS2 slab structures giving stronger Mo-Mo backscattering.…”