Hierarchically porous tungsten oxidenanotubes with crystalline walls made of the metastable orthorhombic polymorph

Abstract

A simple route towards highly crystalline and hierarchically porous tungsten oxide nanotubes is presented.Interestingly, due to the limited wall thickness, the metastable orthorhombic high-temperature polymorph could be stabilized for the first time at room temperature without doping. In brief, ammonium metatungstate (AMT) is grafted over core-crosslinked poly(butadiene)-block-poly(2-vinylpyridine) (PB-b-P2VP) nanorods at pH 3. Coulomb interactions between protonated PB-b-P2VP nanorods (pK a 4.5) and metatungstate anions promote hybrid formation. Subsequent calcination of the PB-b-P2VP-AMT hybrid material at 490 C results in a non-woven structure of hierarchically porous and crystalline, orthorhombic tungsten oxide nanotubes as confirmed by electron microscopy, X-ray diffraction, and nitrogen physisorption.

Selective Template Removal by Thermal Depolymerization to Obtain Mesostructured Molybdenum Oxycarbide

“…Separation and purification of the hybrid material was carried out as published. [10] Removal of P2VP-b-PAMA Template and Carburization: The removal of PAMA core was carried out by calcination under vacuum (10 -3 mbar) in a closed tube furnace at 320°C (ramping rate 3°C·min -1 ) for 2 h. The resulting material was black. Carburization was accomplished by heating the calcined composite material in an argon atmosphere to 700°C (ramping rate 3°C·min -1 ) for 2 h.…”

“…[10] Hybrid materials were synthesized by dropwise addition of 500 mL of a dispersion of 200 mg P2VP-b-PAMA in aqueous HCl (0.001 m) to a solution of APM [400 mg, (NH 4 ) 6 Mo 7 O 24 ] (Alfa Aesar) in aqueous HCl (500 mL, 0.001 m) under vigorous stirring. Separation and purification of the hybrid material was carried out as published.…”

“…Ammonium paramolybdate [APM: (NH 4 ) 6 Mo 7 O 24 ] was used as molybdenum precursor together with rigid, tailor-made poly(2-vinylpyridine)-block-poly(allyl methacrylate) P2VP-b-PAMA diblock copolymer cylindrical brushes as structure-directing agent. Coulomb interactions between the protonated P2VP brush [10] and the isopolyoxomolybdate lead to robust hybrid formation (Scheme 1D). The PAMA core of this diblock copolymer allows on one hand for crosslinking of the formed hexagonal microphase (Scheme 1B) to obtain rigid nanowires to be applied as template (Scheme 1C).…”

High-power positive electrode based on synergistic effect of N- and WO3 -decorated carbon felt for vanadium redox flow batteries

“…Inside of this wide peak, can be differenced two peaks, which is attributed to two different crystallinity of tungsten oxide in sample [24]. All samples show a weak peak at 3745 cm -1 as an indicator for hydroxide groups.…”

Template Removal via Boudouard Equilibrium Allows for Synthesis of Mesostructured Molybdenum Compounds

“…[9,15] Details on the synthesis and characterization are given in the supporting information and recent reports, respectively. [11,21,22] [a]…”