International Journal of Hydrogen Energy, Vol.44, No.30, 15892-15906, 2019
Study of oxidation states of Fe- and Co-doped TiO2 photocatalytic energy materials and their visible-light-driven photocatalytic behavior
In this work we propose a study to determine the structure of Fe and Co doped TiO2 by using the Fe K-edge, Co K-edge and Ti K- edge X-ray absorption near edge spectroscopy. The detailed analysis of Fe and Co-doped TiO2 before and after Methylene blue (MB) treatment was examined under the irradiation of 35 W xenon arc lamp for 3 h. The materials treated with MB were studied by X-ray absorption spectroscopy, EPR and FT-IR which revealed that the oxidation state of Co2+ was photo-oxidized to Co3+ and Fe3+ was photo-reduced to Fe2+ or less. Thermodynamic, kinetic properties were studied at different reaction temperature and the activation energy (E-a), enthalpy (Delta H), entropy (Delta S) and free energy (Delta G) of activation were calculated for the reaction. The activation energy has been found for TiO2, Fe-TiO2 and Co-TiO2 as 24.771, 11.413 and 15.801 kJ mol(-1) respectively. The structure, morphology and optical properties were studied by XRD, UV-diffuse reflectance spectra, FESEM, TEM and PL. Moreover, electrochemical studies were carried out to demonstrate the oxygen evolution reaction (OER) activity on TiO2, Fe-TiO2 and Co-TiO2 in 1 M of H2SO4 electrolyte, with a scan rate of 50 mV s(-1) and the as-prepared photocatalysts could act as the promising electrode materials for water splitting. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.