Bixbyite-type V2O3--a metastable polymorph of vanadium sesquioxide

A metastable polymorph of vanadium sesquioxide was prepared by the reaction of vanadium trifluoride with a water-saturated gaseous mixture of 10 vol % hydrogen in argon. The new polymorph crystallizes in the bixbyite-type structure. At temperatures around 823 K a transformation to the well-known corundum-type phase is observed. Quantum-chemical calculations show that the bixbyite-type structure is about 9 kJ/mol less stable than the known corundum-based one. This result, in combination with the absence of imaginary modes in the phonon density of states, supports the classification of the bixbyite-type phase as a metastable V(2)O(3) polymorph. At ~50 K a paramagnetic to canted antiferromagnetic transition is detected.     

Understanding the Role of Gold Nanoparticles in Enhancing the Catalytic Activity of Manganese Oxides in Water Oxidation Reactions

The Earth‐abundant and inexpensive manganese oxides (MnO_x) have emerged as an intriguing type of catalysts for the water oxidation reaction. However, the overall turnover frequencies of MnO_x catalysts are still much lower than that of nanostructured IrO₂ and RuO₂ catalysts. Herein, we demonstrate that doping MnO_x polymorphs with gold nanoparticles (AuNPs) can result in a strong enhancement of catalytic activity for the water oxidation reaction. It is observed that, for the first time, the catalytic activity of MnO_x/AuNPs catalysts correlates strongly with the initial valence of the Mn centers. By promoting the formation of Mn³⁺ species, a small amount of AuNPs (<5 %) in α‐MnO₂/AuNP catalysts significantly improved the catalytic activity up to 8.2 times in the photochemical and 6 times in the electrochemical system, compared with the activity of pure α‐MnO₂.     

ChemInform Abstract: Anosovite‐Type V3O5: A New Binary Oxide of Vanadium.

The new anosovite‐type polymorph of the title compound is synthesized by reaction of either V₂F₆·4H₂O or a mixture of 60 wt.% VF₂·4H₂O and 40 wt.% VF₃·3H₂O with a flowing water‐saturated gaseous mixture of 15—20 vol% H₂ in argon (588 K, 14—18 h).     

The crystal structure of δ-VOPO4 and its relationship to ω-VOPO4

The crystal structure of δ-VOPO₄ was determined from powder X-ray diffraction data in the tetragonal space group P4₂/mbc (No. 135) with a = 9.0547(7) Å and c = 8.6080(8) Å. The structure is found to be closely related to that of ω-VOPO₄, thus disproving two traditional structure hypotheses commonly found in the literature. The structural relationship between the two phases is discussed in the light of a recently observed fast phase transition from ω- to δ-VOPO₄.     

New results on proton emission from odd-odd nuclei

⁷⁸Kr beams were used to bombard ⁵⁸Ni, ⁹²Mo and ⁹⁶Ru, producing three new, odd-odd, proton-emitting isotopes, ¹³⁰Eu, ^164mIr and ¹⁷⁰Au. Preliminary experimental and theoretical results will be presented in this paper. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: mahmud@ph.ed.ac.uk