TY - JOUR

T1 - Improved charge carrier separation in barium tantalate composites investigated by laser flash photolysis

AU - Schneider, J.

AU - Nikitin, K.

AU - Wark, M.

AU - Bahnemann, D.W.

AU - Marschall, R.

N1 - Funding information: We thank Julia Soldat, Ruhr-University Bochum, for providing the two samples. D. W. B. and R. M. acknowledge financial support from the BMBF (Bundesministerium fur Bildung und Forschung), research project DuaSol (03SF0482C and 03SF0482D). R. M. gratefully acknowledges funding from the Emmy-Noether program (MA 5392/3-1) of the German Research Foundation DFG. M. W. acknowledges financial support from the DFG (WA 1116/28). The work carried out in Hannover (Germany) was supported by the Global Research Laboratory (GRL) Program (NRF-2014K1A1A2041044) funded by the Korea government (MSIP) through NSF. The present study was performed within the Project Establishment of the Laboratory Photoactive Nanocomposite Materials no. 14.Z50.31.0016 supported by a Mega-grant of the Government of the Russian Federation.

PY - 2016/4/28

Y1 - 2016/4/28

N2 - Charge carrier dynamics in phase pure Ba 5Ta 4O 15 and in a Ba 5Ta 4O 15-Ba 3Ta 5O 15 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 Ba 5Ta 4O 15 the recombination of the charge carriers could not be prevented and the trapped electrons also recombine with the CH 2OH radical formed via the methanol oxidation by the trapped holes. However, in the composite, the electron can be stored in the system, the CH 2OH radical injects an electron into the conduction band of the second component of the composite, i.e., Ba 3Ta 5O 15. Thus, the electrons are available for an extended period to induce reduction reactions.

AB - Charge carrier dynamics in phase pure Ba 5Ta 4O 15 and in a Ba 5Ta 4O 15-Ba 3Ta 5O 15 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 Ba 5Ta 4O 15 the recombination of the charge carriers could not be prevented and the trapped electrons also recombine with the CH 2OH radical formed via the methanol oxidation by the trapped holes. However, in the composite, the electron can be stored in the system, the CH 2OH radical injects an electron into the conduction band of the second component of the composite, i.e., Ba 3Ta 5O 15. Thus, the electrons are available for an extended period to induce reduction reactions.

UR - http://www.scopus.com/inward/record.url?scp=84966326695&partnerID=8YFLogxK

U2 - 10.1039/c5cp07115a

DO - 10.1039/c5cp07115a

M3 - Article

VL - 18

SP - 10719

EP - 10726

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 16

ER -