Tungsten dioxide: structure refinement by powder neutron diffraction

Palmer, D. Jason; Dickens, P.G.

doi:10.1107/s0567740879008785

Cited by 48 publications

(35 citation statements)

References 6 publications

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“…Electron, neutron, and x-ray diffraction experiments have detected a large number of transition-metal dioxides to possess very stable ␤Ј rutile crystal phases. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In addition, some theoretical studies, at different levels of theory, have confirmed the structural results of the experiments, showing enhanced stability of the rutile phase for most metal dioxides. [20][21][22][23] Rutile oxides are interesting in connection with electrochemical and photoelectrochemical water splitting, [24][25][26][27] and recently the surface redox processes on, e.g., RuO 2 and TiO 2 have been treated using density functional theory ͑DFT͒.…”

Section: Introductionmentioning

confidence: 95%

Formation energies of rutile metal dioxides using density functional theory

et al. 2009

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We apply standard density functional theory at the generalized gradient approximation ͑GGA͒ level to study the stability of rutile metal oxides. It is well known that standard GGA exchange and correlation in some cases is not sufficient to address reduction and oxidation reactions. Especially the formation energy of the oxygen molecule and the electron self-interaction for localized d and f electrons are known shortcomings. In this paper we show that despite the known problems, it is possible to calculate the stability of a wide range of rutile oxides MO 2 , with M being Pt, Ru, Ir, Os, Pb, Re, Mn, Se, Ge, Ti, Cr, Nb, W, Mo, and V, using the electrochemical series as reference. The mean absolute error of the formation energy is 0.29 eV using the revised Perdew-Burke-Ernzerhof ͑PBE͒ GGA functional. We believe that the reason for the success is due to the reference level being H 2 and H 2 O and not O 2 and due to a more accurate description of exchange for this particular GGA functional compared to PBE. Furthermore, we would expect the self-interaction problem to be largest for the most localized d orbitals; that means the late 3d metals and since Co, Fe, Ni, and Cu do not form rutile oxides they are not included in this study. We show that the variations in formation energy can be understood in terms of a previously suggested model separating the formation energy into a metal deformation contribution and an oxygen binding contribution. The latter is found to scale with the filling of the d band.

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Section: Introductionmentioning

confidence: 95%

Formation energies of rutile metal dioxides using density functional theory

et al. 2009

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“…The lattice parameters of pure TiO 2 are a = 4.593 Å, c = 2.956 Å, with Z = 2 and vol. = 62.42 Å 3 (Cromer & Herrington 1955), while WO 2 has a distorted rutile structure (monoclinic) that shows pronounced W-W pair formation with a volume of 65.43 Å 3 for two formula units (Palmer & Dickens 1979). The lattice parameters vary linearly with x: the a-axis expands while the c-axis contracts due to W-W pair formation that occurs even in the doped TiO 2 (Aryanpour et al 2009).…”

Section: Characterizationmentioning

confidence: 99%

Catalyst supports for polymer electrolyte fuel cells

Subban

Zhou

Leonard

et al. 2010

Phil. Trans. R. Soc. A.

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A major challenge in obtaining long-term durability in fuel cells is to discover catalyst supports that do not corrode, or corrode much more slowly than the current carbon blacks used in today's polymer electrolyte membrane fuel cells. Such materials must be sufficiently stable at low pH (acidic conditions) and high potential, in contact with the polymer membrane and under exposure to hydrogen gas and oxygen at temperatures up to perhaps 120• C. Here, we report the initial discovery of a promising class of doped oxide materials for this purpose: Ti 1−x M x O 2 , where M = a variety of transition metals. Specifically, we show that Ti 0.7 W 0.3 O 2 is electrochemically inert over the appropriate potential range. Although the process is not yet optimized, when Pt nanoparticles are deposited on this oxide, electrochemical experiments show that hydrogen is oxidized and oxygen reduced at rates comparable to those seen using a commercial Pt on carbon black support.

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“…Für M 0 2 mit M = V, Mo, W, Tc und Re wurden jedoch charakteristische Abweichun gen von der Rutilstruktur beobachtet [1,2]. Diese betreffen insbesondere die Anordnung der Katio nen in den kantenverknüpften MOö -Oktaederketten.…”

Section: Introductionunclassified