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We summarize the current knowledge on crystal structures, synthesis, applications, and Raman spectroscopy of Wadsley phases of vanadium oxide, including VO2 (B), V6O13, V4O9, V3O7, and V2O5. While these oxides have garnered significant attention for potential energy storage applications and have been studied for decades, there remains inconsistency in data regarding their characteristic Raman spectra. To address this, we synthesized a series of Wadsley phases by physical vapor deposition of amorphous vanadium oxide films and subsequent annealing in a controlled environment. X‐ray diffraction studies confirmed the formation of VO2 (B), V6O13, V4O9, and V3O7. We meticulously measured the room‐temperature Raman spectra of these phases, offering robust reference data for the easy identification of vanadium oxides in unknown samples. Finally, we studied low‐temperature phase transitions in VO2 (B) and V6O13. [ABSTRACT FROM AUTHOR]

Single-phase three-dimensional vanadium oxide (V 4 O 9 ) was synthesized by reduction of V 2 O 5 using a gas stream of ammonia/argon (NH 3 /Ar). The as-synthesized oxide, prepared by this simple gas reduction method was subsequently electrochemically transformed into a disordered rock salt type-"Li3.7V4O9" phase while cycling over the voltage window 3.5 to 1.8 V versus Li. The Li-deficient phase delivers an initial reversible capacity of ∼260 mAhg -1 at an average voltage of 2.5 V vs. Li + /Li 0 . Further cycling to 50 cycles yields a steady 225 mAhg -1 . Ex situ X-ray diffraction studies confirmed that (de) intercalation phenomena follows a solid-solution electrochemical reaction mechanism. As demonstrated, the reversibility and capacity utilization of this V 4 O 9 is found to be superior to battery grade, micron-sized V 2 O 5 cathodes in lithium cells., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Senguttuvan, Lee, Key and Johnson.)

Abstract: V4O9: A missing link of Wadsley phases has been successfully synthesized by using sulfur as a reducing agent at a low temperature and its structure has been determined by combining electron, X-ray and neutron diffractions. V4O9 has an orthorhombic Cmcm structure and the lattice parameters are a=10.356(2)Å, b=8.174(1)Å and c=16.559(3)Å at room temperature. The structure is composed of shared edges and corners of three types of polyhedra; a VO6 distorted octahedron, a VO5 pyramid and a VO4 tetrahedron. The structure of V4O9 is very similar to that of vanadyl pyrophosphate (VO)2P2O7 which has PO4 tetrahedra instead of VO4 tetrahedra. This indicates that V4O9 is a salt of pyro-ion [V2O7]4-; (VO)2V2O7. The magnetic properties of V4O9 have been investigated by magnetic susceptibility, high-field magnetization and inelastic neutron scattering measurements. V4O9 is a quantum spin system with a spin-gapped ground state. The excitation gap between the singlet ground state and the excited triplet state is approximately 73K. The magnetic susceptibility behavior suggests that V4O9 is a spin-1/2 dimer system with significant interdimer interactions, as opposed to (VO)2P2O7, which is an alternating spin-1/2 chain system. This difference is thought to be due to the fact that VO4-mediated interactions are considerably weaker than PO4-mediated interactions. [Copyright &y& Elsevier]

Abstract: Vanadium oxide supported on mesoporous zirconium phosphate catalysts has been synthesized, characterized and tested in the selective oxidation of H2S to sulfur. The nature of the vanadium species depends on the V-loading of catalyst. Catalysts with a V-content lower than 4wt% present both isolated vanadium species and V2O5 crystallites. However, V2O5 crystallites have been mainly observed in catalysts with higher V-content, although the presence of isolated V-species on the surface of the metal oxide support cannot be completely ruled out. The catalytic behaviour also depends on V-loading of catalysts. Thus, while the catalytic activity of catalysts can be related to the number of V-sites, the catalyst decay is clearly observed in samples with low V-loading. The characterization of catalysts after the catalytic tests indicates the presence of sulfur on the catalyst, which is favoured on catalysts with low V-loading. However, a clear transformation of V2O5 to V4O9 can be proposed according to XRD and Raman results of used catalysts with high V-loading. The importance of V5+–O–V4+ pairs in activity and selectivity is also discussed. [Copyright &y& Elsevier]