Polyoxometalate Complexes as Precursors to Vanadium‐Doped Molybdenum or Tungsten Oxide Thin Films by Means of Aerosol‐Assisted Chemical Vapour Deposition

Abstract

Aerosol‐assisted chemical vapour deposition of substituted polyoxometalates H4[PMo11VO40], H7[PMo8V4O40], [nBu4N]4[PVW11O40] and [nBu4N]5[PV2W10O40] resulted in the formation of vanadium‐doped metal oxide thin films. Depositions were carried out at 550 °C in methanol or acetonitrile for the POMs that contained molybdenum or tungsten, respectively. The as‐deposited films were X‐ray amorphous and relatively non‐adherent. However, on annealing in air at 600 °C, decolourised translucent films that were more mechanically robust were obtained. Films deposited from H4[PMo11VO40] and H7[PMo8V4O40] consisted of V‐doped MoO3 in the orthorhombic phase and films from [nBu4N]4[PVW11O40] and [nBu4N]5[PV2W10O40] comprised of monoclinic V‐doped WO3. All films were fully characterised by using X‐ray photoelectron spectroscopy, energy‐dispersive X‐ray diffraction, scanning electron microscopy and UV/Vis spectroscopy.

Insertion of VIVIons into the Polyoxotungstate Archetype {As4W40}

“…The spectrum also contains two W 5p 3/2 signals at 41.3 and 39.0 eV, respectively. These binding energies are in good agreement with different measurements of fully oxidized W-containing POMs. − The area ratio of the two tungsten species is 90.9% fully oxidized to 9.1% reduced W atom. This thus corresponds to an atom ratio of 35 fully oxidized to four reduced W atoms.…”

The use of mixed-metal single source precursors for the synthesis of complex metal oxides

“…11,47,48 Mixed-metal SSP compounds are often soluble in organic solvents (and sometimes water), allowing convenient routes to fabricate thin films of CMOs, by straightforward techniques (such as drop-casting and spin-coating), 26,27,35,49,50 spray pyrolysis, 51 sol-gel processes 11,15,52 or (aerosol-assisted) CVD. 53 The use of a single precursor under mild reaction conditions also simplifies CMO synthesis for applications that demand excellent material homogeneity across a large scale. 4,26,42,54 Of course, the advantages of using an SSP may be offset by the challenges and costs of prepraring a specifically designed molecular precursor, which is an important consideration for practical use.…”

“…(x = 0, 1) have been used to make Vdoped α-MoO3 and WO3 via AACVD at 550 ᵒC. 53 Polyoxoniobate clusters have also been used to produce LiNbO3 (Fig. 13), 35 and present a fascinating example of the importance of deposition and drying processes when forming (micro)crystalline films of SSPs prior to calcination.…”

Functionalization of Carbon Surfaces Tunes the Redox Stability of Polyoxometalate@Carbon Electrodes

“…XPS of Vulcan, [O]V, {W 18 }@Vulcan, and {W 18 }@[O]V was performed to probe the concentrations, chemical environ- Deconvolution of the W 4f photoemission signal in the spectrum of {W 18 } reveals a doublet with peaks at 35.6 and 37.7 eV due to the W 4f 7/2 and W 4f 5/2 signals, respectively, as expected for W 6+ . 44 The high-resolution XP spectra of {W 18 }@ Vulcan and {W 18 }@[O]V exhibit peaks centered at 36.2 eV and 38.3 eV, respectively, which is also consistent with the presence of W 6+ in the materials. The O 1s peak for the POMcontaining samples is in the range of 532−533 eV, which is expected for the oxo ligands of the POMs.…”