TY - JOUR

T1 - Influence of the Dopant Concentration on the Photoelectrochemical Behavior of Al-Doped TiO2

AU - Murashkina, A.A.

AU - Rudakova, A.V.

AU - Ryabchuk, V.K.

AU - Nikitin, K.V.

AU - Mikhailov, R.V.

AU - Emeline, A.V.

AU - Bahnemann, D.W.

N1 - Funding information: 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. We are also grateful to the RC “Nanophotonics”, RC “Nanotechnology”, RC “Chemical Analysis and Materials Research Centre”, RC “XRD Studies”, and RC “Optical and Laser Materials Research” of the Research Park at the Saint Petersburg State University for helpful assistance in conducting the synthesis and the characterization of the samples.

PY - 2018/4/12

Y1 - 2018/4/12

N2 - In the present study, we explored the effect of Al-dopant concentration within the range of <1.1 wt % on the photoelectrochemical (PEC) activity of an Al-doped TiO 2 photoanode. The experimental dependencies of PEC efficiency on Al-dopant concentration indicate that there is an optimal Al concentration of 0.5 wt % corresponding to the highest photoactivity. The analysis of the spectral dependencies of the photocurrent confirms that 0.5 wt % Al provides the highest activity at photoexcitation in both intrinsic and extrinsic absorption spectral range. It was also shown that Al doping does not affect the optical band gap of TiO 2. The dependence of PEC activity on Al concentration correlates with the corresponding dependencies of the flat-band potential and work function, indicating the Fermi-level shift toward the conduction band for the Al concentration <0.5 wt % and toward the valence band for the Al concentration >0.5 wt %. Such alteration of the Fermi-level position is explained in terms of alteration of the type of major compensating intrinsic defects from [Vo••-TiTi′] for the Al concentration <0.5 wt % acting as shallow traps to [AlTi′-Vo••-AlTi′]× for the Al concentration >0.5 wt % acting as deep traps. Transformation of compensating defects from shallow traps, which are ineffective in charge recombination processes, to deep traps, which act as effective recombination centers, is responsible for the optimal dopant concentration, 0.5 wt %, to achieve the higher PEC activity of Al-doped TiO 2.

AB - In the present study, we explored the effect of Al-dopant concentration within the range of <1.1 wt % on the photoelectrochemical (PEC) activity of an Al-doped TiO 2 photoanode. The experimental dependencies of PEC efficiency on Al-dopant concentration indicate that there is an optimal Al concentration of 0.5 wt % corresponding to the highest photoactivity. The analysis of the spectral dependencies of the photocurrent confirms that 0.5 wt % Al provides the highest activity at photoexcitation in both intrinsic and extrinsic absorption spectral range. It was also shown that Al doping does not affect the optical band gap of TiO 2. The dependence of PEC activity on Al concentration correlates with the corresponding dependencies of the flat-band potential and work function, indicating the Fermi-level shift toward the conduction band for the Al concentration <0.5 wt % and toward the valence band for the Al concentration >0.5 wt %. Such alteration of the Fermi-level position is explained in terms of alteration of the type of major compensating intrinsic defects from [Vo••-TiTi′] for the Al concentration <0.5 wt % acting as shallow traps to [AlTi′-Vo••-AlTi′]× for the Al concentration >0.5 wt % acting as deep traps. Transformation of compensating defects from shallow traps, which are ineffective in charge recombination processes, to deep traps, which act as effective recombination centers, is responsible for the optimal dopant concentration, 0.5 wt %, to achieve the higher PEC activity of Al-doped TiO 2.

UR - http://www.scopus.com/inward/record.url?scp=85045376059&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcc.7b12840

DO - 10.1021/acs.jpcc.7b12840

M3 - Article

VL - 122

SP - 7975

EP - 7981

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 14

ER -