Publication date: 15th December 2014
Barium tantalum compounds are well-known photocatalysts for water splitting.[1,2] Interestingly, also the gray mixed-valance compound Ba3TaV4TaIVO15 showed significant photocatalytic activity.[3]
One approach to optimize the activity is band-gap narrowing by exchange of oxide with nitride ions and simultaneous oxidation of the tantalum(IV) ions. We successfully synthesized light yellow Ba3Ta5O14N (tantalum(V) only!) as phase-pure material crystallizing isostructurally to the known mixed-valence oxide Ba3Ta5O15 (Rietveld refinement using X-ray powder data).
The electronic structure of Ba3Ta5O14N was studied theoretically with a hybrid Hartree–Fock-DFT method. Successively, two nitride ions were placed on two of the Wyckoff positions 2d, 4h, 8i, and 8j. The most stable structure was obtained when they were placed at 4h sites having fourfold coordination.
By incorporating nitride, the band gap decreases to 2.9 eV, giving rise to an absorption band well in the visible-light region. The results of our photocatalytical investigations on Ba3Ta5O14N will be presented.
References
[1] R. Marschall, J. Soldat, M. Wark, Photochem. Photobiol. Sci. 2013, 12, 671–677.
[2] J. Soldat, M. Wark, R. Marschall, Chem. Sci. 2014, DOI: 10.1039/c4sc01127a.
[3] C. Feger, R. Ziebarth, Chem. Mater. 1995, 7, 373–378.
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