Monday, March 23, 2009

J. Phys Chem B and C, vol. 113, Issue 12

Nothing from J Phys Chem B this time around.

Diffusion in Confined Dimensions: Li+ Transport in Mixed Conducting TiO2−B Nanowires
Martin Wilkening*, Christopher Lyness, A. Robert Armstrong and Peter G. Bruce§

J. Phys. Chem. C, 2009, 113 (12), pp 4741–4744
DOI: 10.1021/jp8107792
Copyright © 2009 American Chemical Society
Abstract: The precise determination of diffusion parameters plays a key role in Li battery research and is a rather complex problem when electrode materials, i.e., mixed conductors, have to be investigated. In the present contribution, we show how stimulated echo nuclear magnetic resonance (NMR) can be used to go beyond the limits of standard NMR methods for the characterization of dynamic properties of one of the most promising new electrode materials viz. Li intercalated TiO2−B nanowires. It turned out that Li self-diffusion is very slow with an activation energy of 0.48(1) eV. Obviously, the shorter diffusion length compensates for this low mobility so that, nonetheless, facile incorporation and removal of Li is possible when the nanowires are used in an ion battery.

Probing the Incorporation of Ti(IV) into the BEA Zeolite Framework by XRD, FTIR, NMR, and DR UV−jp810722bis

Jean-Philippe Nogier, Yannick Millot, Pascal P. Man, Tetsuya Shishido§, Michel Che# and Stanislaw Dzwigaj*
J. Phys. Chem. C, 2009, 113 (12), pp 4885–4889
DOI: 10.1021/jp8099829
Copyright © 2009 American Chemical Society
Abstract: The method (Dzwigaj, S., et al. Chem. Commun. 1998, 87) proposed earlier to incorporate V(V) ions into the BEA zeolite framework at the solid−liquid interface from V precursors in aqueous solution has been successfully extended to the solid−gas interface and titanium, with TiCl4 vapor as the precursor. The use of TiCl4 vapor has the advantage to restrict the speciation of titanium to this single species and to lead to a significant amount of Ti (5 Ti wt %) determined by chemical analysis. The incorporation of Ti into the SiBEA zeolite framework is evidenced by XRD. The reaction of TiCl4 vapor with H-bonded and terminal SiO−H groups of vacant T-atom sites is monitored by FTIR, 29Si MAS NMR, 1H−29Si CP MAS NMR and 1H MAS NMR. The presence of tetrahedral Ti(IV) as the main titanium species is evidenced by diffuse reflectance UV−vis. A possible pathway for the formation of framework tetrahedral Ti(IV) in TiSiBEA is proposed.

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