Structural, Morphological and Photoelectrochemical Behavior of Hematite Modified by 120 MeV Ag 9+ Ions Aadesh P. Singh 1 , Saroj Kumari 1 , Rohit Shrivastav 2 , Sahab Dass 2 , Vibha R. Satsangi 1* 1 Department of Physics & Computer Science 2 Department of Chemistry Dayalbagh Educational Institute, Dayalbagh, Agra-282005, India * E-mail: vibhasatsangi@gmail.com ABSTRACT Nanostructured hematite thin film for photoelectrochemical (PEC) splitting of water has great potential in the design of low-cost, environmental friendly solar-hydrogen production. Presently, solar-to-hydrogen conversion efficiency of PEC cell using iron oxide is limited by its poor charge transport due to high recombination losses and mismatch of band edges position with the redox level of water. High energy heavy ion irradiation provides the researchers a new dimension to introduce the desired changes in the behaviour of the material, which largely influence their properties. In order to get efficient PEC system, spray-pyrolytically deposited nanostructured hematite thin films were modified by irradiating the samples with 120 MeV Ag 9+ ions with fluences ranging from 5x10 11 to 1x10 13 ions/cm 2 . Irradiated samples exhibited a partial transition from the hematite to the magnetite phase and reduction in particle size as indicated by XRD and Raman analysis. SEM picture showed a decrease the thickness and porosity of the films after irradiation. These irradiated films, when used in PEC cell showed significantly higher photocurrent density than unirradiated α-Fe 2 O 3 . INTRODUCTION Swift heavy ion (SHI) irradiation can have a significant effect on the structural, morphological, optical, electrical and photoelectrochemical properties of the metal oxide [1-2]. High energy ions lose their energy in the target mainly via inelastic collisions leading to the excitation of the target electrons, which is associated with modification in the various properties of the material [3-4]. In the present study, effect of high energy ion irradiation on iron oxide (α-Fe 2 O 3 ) thin films have been presented with respect to photoelectrochemical splitting of water using solar energy for the production of hydrogen. For efficient photoelectrochemical water splitting, the material should have strong optical absorption of visible and ultraviolet radiation [5], efficient charge transfer properties between the semiconductor and the electrolyte [6], an energy band-gap of around 2.0 eV with conduction and valence band edges optimally placed with respect to the water redox potentials and should be stable in electrolyte. Iron oxide with a bandgap of ~2.0 eV [7], allows the utilization of a large fraction of the solar spectrum (~40%), but its energy conversion efficiency is limited by poor charge transport due to high recombination losses and mismatch of band edges with the redox level of water [8]. Photoelectrochemical response and the dynamics of the photogenerated charge carriers in hematite has been the subject of several studies [9-10]. In this study, 120 MeV Ag 9+ ion was used as an effective tool for creation of suitable modification in the thin films of nanostructured hematite for photoelectrochemical production of hydrogen via splitting of water. Mater. Res. Soc. Symp. Proc. Vol. 1217 © 2010 Materials Research Society 1217-Y03-60