Improved charge carrier separation in barium tantalate composites investigated by laser flash photolysis.

Title Improved charge carrier separation in barium tantalate composites investigated by laser flash photolysis.
Authors J. Schneider; K. Nikitin; M. Wark; D.W. Bahnemann; R. Marschall
Journal Phys Chem Chem Phys
DOI 10.1039/c5cp07115a
Abstract

Charge carrier dynamics in phase pure Ba5Ta4O15 and in a Ba5Ta4O15-Ba3Ta5O15 composite have been studied by means of diffuse reflectance laser flash photolysis spectroscopy in the presence and absence of an electron donor, in order to reveal the reason for the improved photocatalytic performance of the latter. For the first time the transient absorption of trapped electrons with a maximum at around 650 nm and of trapped holes with a transient absorption maximum at around 310 nm is reported for tantalates. The decay kinetics of the photogenerated charge carriers could be fitted by second order reaction kinetics, and the direct recombination of the trapped electrons with the trapped holes was proven. In the absence of an electron donor, no difference in the decay behavior between the phase pure material and the composite material is found. In the presence of methanol, for the pure phase Ba5Ta4O15 the recombination of the charge carriers could not be prevented and the trapped electrons also recombine with the ?CH2OH radical formed via the methanol oxidation by the trapped holes. However, in the composite, the electron can be stored in the system, the ?CH2OH radical injects an electron into the conduction band of the second component of the composite, i.e., Ba3Ta5O15. Thus, the electrons are available for an extended period to induce reduction reactions.

Citation J. Schneider; K. Nikitin; M. Wark; D.W. Bahnemann; R. Marschall.Improved charge carrier separation in barium tantalate composites investigated by laser flash photolysis.. Phys Chem Chem Phys. 2016;18(16):1071926. doi:10.1039/c5cp07115a

Related Elements

Tantalum

See more Tantalum products. Tantalum (atomic symbol: Ta, atomic number: 73) is a Block D, Group 5, Period 6 element with an atomic weight of 180.94788. Tantalum Bohr ModelThe number of electrons in each of tantalum's shells is [2, 8, 18, 32, 11, 2] and its electron configuration is [Xe] 4f14 5d3 6s2. The tantalum atom has a radius of 146 pm and a Van der Waals radius of 217 pm. High Purity (99.999%) Tantalum (Ta) MetalTantalum was first discovered by Anders G. Ekeberg in 1802 in Uppsala, Sweden however, it was not until 1844 when Heinrich Rose first recognized it as a distinct element. In its elemental form, tantalum has a grayish blue appearance. Tantalum is found in the minerals tantalite, microlite, wodginite, euxenite, and polycrase. Due to the close relation of tantalum to niobium in the periodic table, Tantalum's name originates from the Greek word Tantalos meaning Father of Niobe in Greek mythology.

Barium

See more Barium products. Barium (atomic symbol: Ba, atomic number: 56) is a Block S, Group 2, Period 6 element with an atomic weight of 137.27. The number of electrons in each of barium's shells is [2, 8, 18, 18, 8, 2] and its electron configuration is [Xe] 6s2. Barium Bohr ModelBarium is a member of the alkaline-earth metals. The barium atom has a radius of 222 pm and a Van der Waals radius of 268 pm. Barium was discovered by Carl Wilhelm Scheele in 1772 and first isolated by Humphry Davy in 1808. Elemental BariumIn its elemental form, barium is a soft, silvery-gray metal. Industrial applications for barium include acting as a "getter," or unwanted gas remover, for vacuum tubes, and as an additive to steel and cast iron. Barium is also alloyed with silicon and aluminum in load-bearing alloys. The main commercial source of barium is the mineral barite (BaSO4); it does not occur naturally as a free element . The name barium is derived from the Greek word "barys," meaning heavy.

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