Iron doped nanostructured TiO 2 for photoelectrochemical generation of hydrogen Aadesh P. Singh a , Saroj Kumari a , Rohit Shrivastav b , Sahab Dass b , Vibha R. Satsangi a, * a Department of Physics & Computer Science, Faculty of Science, Dayalbagh Educational Institute, Dayalbagh, Agra 5, India b Department of Chemistry, Faculty of Science, Dayalbagh Educational Institute, Dayalbagh, Agra 5, India article info Article history: Received 4 April 2008 Received in revised form 14 July 2008 Accepted 14 July 2008 Available online 20 September 2008 Keywords: Photoelectrochemical Hydrogen Iron doping TiO 2 Sol-gel abstract This paper describes the photoelectrochemical studies on nanostructured iron doped tita- nium dioxide (TiO 2 ) thin films prepared by sol-gel spin coating method. Thin films were characterized by X-ray diffraction, Raman spectroscopy, spectral absorbance, atomic force microscopy and photoelectrochemical (PEC) measurements. XRD study shows that the films were polycrystalline with the photoactive anatase phase of TiO 2 . Doping of Fe in TiO 2 resulted in a shift of absorption edge towards the visible region of solar spectrum. The observed bandgap energy decreased from 3.3 to 2.89 eV on increasing the doping concentration upto 0.2 at.% Fe. 0.2 at.% Fe doped TiO 2 exhibited the highest photocurrent density, w0.92 mA/cm 2 at zero external bias. Flatband potential and donor density determined from the Mott– Schottky plots were found to vary with doping concentration from 0.54 to 0.92 V/SCE and 1.7  10 19 to 4.3  10 19 cm 3 , respectively. ª 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. 1. Introduction Titanium dioxide (TiO 2 ) is one of the most favoured metal oxide semiconductor for its use as photoanode in photo- electrochemical (PEC) splitting of water into hydrogen and oxygen, due to its band edges matching with the redox level of the water, relatively low cost, chemical stability, and photostability [1,2]. However, the low efficiency of hydrogen production with TiO 2 is mainly due to its large bandgap (w3.2 eV) lying in the UV region of solar radiation, which accounts only for 4% of the incoming solar energy [3,4], rendering the overall process impractical. Another difficulty with TiO 2 is the high recombination rate of the photoexcited electron–hole pairs [5]. Thus, for efficient production of hydrogen, it is necessary to not only extend the absorbance of TiO 2 into visible regions but also reduce the recombina- tion of photo-generated electrons and holes. This paper is an effort in this direction to improve the PEC behaviour of TiO 2 . Recently many studies have been carried out to change the bandgap and thereby electronic properties of TiO 2 by doping it with transition metal ions such as Fe, Nb, Mn, Co, Sn, Cd and Ni [6–9]. Presence of metal ion in quantum sized TiO 2 is also reported [10] to influence the photoreactivity, charge carrier recombination rates and interfacial electron transfer rates in TiO 2 . Among the various dopants, substitution of iron (III) ions in the titania lattice is most favoured [11] due to similar size of Fe 3þ and Ti 4þ ions. Many methods such as sol-gel [12], hydrothermal [13], wet impregnation [14], ion-implantation [15], and metal organic chemical vapor deposition (MOCVD) [16] have been reported for the preparation of Fe doped nanostructured TiO 2 catalysts. Most of these papers deal with photocatalytic application [6,13,17–19]. In the present study * Corresponding author: Tel.: þ91 9319104320; fax: þ91 562 2801226. E-mail address: vibhasatsangi@rediffmail.com (V.R. Satsangi). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he 0360-3199/$ – see front matter ª 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2008.07.041 international journal of hydrogen energy 33 (2008) 5363–5368