W₂O₃I₄ and WO₂I₂: metallic phases in the chemical transport reaction of tungsten

Abstract

WO2I2, a compound important in the chemical transport reaction of elemental tungsten and the hitherto unknown W2O3I4 are reported with their layered structures. Increasing iodine content increases the metallicity of the compounds.

Benchmarking the Stability of Hole-Transport Materials for p–i–n Perovskite Solar Cells: The Importance of Interfacial Reactions

“…The obtained results are quite surprising since Mo 6+ , V 5+ , and W 6+ , mostly representing the corresponding oxides, are known to be powerful oxidants and should be able to oxidize easily iodide anions I – to molecular iodine I 2 . − However, both WO 3 and MoO 3 were reported to be the least efficient with respect to the photocatalytic oxidation of I – to I 2 among a big series of studied oxides. , Furthermore, I – was reported to be able to intercalate into WO 3 structure (presumably replacing some of the O atoms) without oxidation to I 2 . Finally, even though binary iodides of Mo 6+ , V 5+ , and W 6+ are not known, these elements form stable oxyiodides MO 2 I 2 (W, Mo) and VOI 3 . − WO 2 I 2 has been characterized by X-ray single crystal diffraction, revealing both oxygen and iodide anions incorporated in the lattice . On the contrary to Mo 6+ , V 5+ , and W 6+ , there are no stable iodides or oxyiodides known for Cu 2+ , which partially explains why CuO x so aggressively reacts with MAPbI 3 forming CuI and I 2 among other products.…”

“…55−58 WO 2 I 2 has been characterized by Xray single crystal diffraction, revealing both oxygen and iodide anions incorporated in the lattice. 59 On the contrary to Mo 6+ , V 5+ , and W 6+ , there are no stable iodides or oxyiodides known for Cu 2+ , which partially explains why CuO x so aggressively reacts with MAPbI 3 forming CuI and I 2 among other products.…”