Physical Properties of 6R-TaS2

Microwave‐Induced Structural Engineering and Pt Trapping in 6R‐TaS2 for the Hydrogen Evolution Reaction

“…Figure 1b shows the crystal structure of the 6R-TaS 2 , consisting in a stack of layers alternating trigonal prismatic (1H) and octahedral (1T) Ta coordination. [33,34,36] The as-produced 6R-TaS 2 crystals were further characterized by scanning electron microscopy (SEM) coupled with energydispersive X-ray spectroscopy (EDS) (Figure 1c-e; Figure S2 and Table S1, Supporting Information), showing a S:Ta atomic ratio of 1.9 ± 0.2, which is in agreement with previous studies on TaS 2 using similar synthesis processes. [25,39,41] Noteworthy, the exceeding Ta may intercalate between the TaS 2 layers, partially eliminating van der Waals gaps, similarly to non-layered (3D) polytypes of group-5 TMDs (e.g., Nb 1+x S 2 , x = 0.35).…”

“…[ 39 ] We point out that when the material is prepared from Ta foil or wire, 2H ‐TaS 2 is typically obtained. [ 33,36 ] Differently, when (partially oxidized) Ta powder is used as a starting material, 6R ‐TaS 2 is synthesized instead of 2H ‐TaS 2 (which, however, marginally contributed to the final crystal composition). [ 36 ] Generally, at the synthesis temperature used in our case, 2H ‐TaS 2 is promoted in the presence of highly hydrogenated Ta, while a decrease of its hydrogenation level can result in the production of the 6R polytype (or even 1T polytype for dehydrogenated Ta).…”

“…[ 32 ] However, these two phases of TaS 2 significantly differ from each other. In fact, the 2H polytype is made of layers with trigonal prismatic Ta coordination (similarly to the 3R ‐TaS 2 ), [ 33–35 ] while the 6R polytype alternates layers with trigonal prismatic and octahedral Ta coordination [ 36 ] (similarly to 4H b ‐TaS 2 ). [ 37 ] Therefore, these mixed coordinated polytypes can show properties resembling to those exhibited by either trigonal prismatic ( 2H or 3R ) or octahedral ( 1T ) phases, [ 38 ] stressing the need for multiple, careful material characterizations for the correct assignment of their phase.…”

Single‐Step Synthesis and Surface‐Assisted Growth of Superconducting TaS2 Nanowires

“…[16] Bulk 6R-TaS 2 has been reported to exhibit superconductivity, with T c = 2.3 K at ambient pressure and T c > 4 K at 17.3 kbar. [21] As discussed with respect to 6R-TaS 2 nanobelts [16] based on the arguments of by Friend and Yoffe, [22] the increased transition temperatures of the nanomaterials, relative to that of the bulk material, could originate from a suppression of the periodic lattice distortion that drives charge density wave formation. A similar mechanism leads to an enhancement of the transition temperature of bulk 2H-TaS 2 following intercalation (T c = 2-5.5 K) or the application of pressure.…”

Single‐Step Synthesis and Surface‐Assisted Growth of Superconducting TaS2 Nanowires

“…Further, the transition temperature of the 2H‐TaS 2 nanowires is higher than that reported for the 6R‐TaS 2 nanobelts ( T c =2.7 K) 16. Bulk 6R‐TaS 2 has been reported to exhibit superconductivity, with T c =2.3 K at ambient pressure and T c >4 K at 17.3 kbar 21. As discussed with respect to 6R‐TaS 2 nanobelts16 based on the arguments of by Friend and Yoffe,22 the increased transition temperatures of the nanomaterials, relative to that of the bulk material, could originate from a suppression of the periodic lattice distortion that drives charge density wave formation.…”