Space-confined preparation of high surface area tungsten oxide and tungsten nitride inside the pores of mesoporous silica SBA-15

Tungsten-Based Catalysts for Environmental Applications

“…Though W dispersion is not easily obtained on amorphous silica, recent developments of mesostructured silicas (MCM 41 [67,68], KIT-5 and KIT-6 [69,70], SBA-15 and SBA-16 [71][72][73]) has allowed inserting significant amounts of tungsten while limiting the It should be noted that WO 3 clusters (crystallized or not) may contain Zr atoms from the support (Figure 9a). Tungstate species depicted in Figure 9 are in agreement with the model of growth mode of W species when the surface density exceeds 5 W nm −2 [65].…”

“…Though W dispersion is not easily obtained on amorphous silica, recent developments of mesostructured silicas (MCM 41 [67,68], KIT-5 and KIT-6 [69,70], SBA-15 and SBA-16 [71][72][73]) has allowed inserting significant amounts of tungsten while limiting the formation of WO 3 nanocrystals. This technique has been extended to spongelike silicate TUD-1 discovered at Delft University [74].…”

Porous WS 2 and W 2 N powders by hard templating with colloidal silica

“…According to the reactions (1) and ( 2), the theoretical weights changes (gain or loss) were calculated as equal to +7.0% and -17.7 %, respectively, suggesting a partial conversion of the oxide to the sulfide (95% yield) and to the nitride (90% yield). This discrepancy could also be related to the experimental uncertainty coupled to a surface oxidation of the non-oxide phases by air (after the synthesis) and in the case of the nitridation to the formation of an amorphous phase, that is not detected by XRD [13,26].…”

“…Moreover, these two approaches are more energy-and time-consuming (ball-milling of 24h, silica template synthesis) than our investigated route. Regarding the tungsten nitride material, the amplitude of variation of the specific surface area value is narrower since values of 17 m 2 /g to 79 m 2 /g were reported [9,19,26,7,20,13,18,22]. The nitrogen-based ceramic materials with the highest surface properties are essentially prepared from tungstic acid (WO 3 .xH 2 O) as tungsten precursor.…”

“…Others authors substituted solid reactants containing nitrogen and sulfur by gaseous reagents such as ammonia (NH 3 ) and hydrogen sulfide (H 2 S), respectively, for an enhancement of the interfacial reactivity between the components [18][19][20][21][22][23][24]. With the use of a hard-template that is supposed to control the size and shape of the porosity, the fabrication of tailored tungsten-based inorganic compounds were performed by means of silica mesoporous templates (SBA- [6,25] and W 2 N [26] materials (after template removal), respectively. As expected, this last approach leads to the fabrication of promising highly ordered mesoporous tungsten nitride and suphide materials, with among the highest specific surfaces areas and best controlled pore sizes ever reported.…”