To study the mechanism of the photo-thermochemical cycle (PTC), titanium dioxide (TiO2) and Fe-doped TiO2 films were produced using a sol-gel method and applied in the PTC for water splitting. A comparison of H-2 production shows that Fe-doped TiO2 performed better than undoped TiO2. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) were used to assess the crystal structure and morphology of the films. UV-vis diffuse reflectance spectra (UV-vis DRS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) analyses were also conducted to investigate the charge transfer and reaction mechanisms on the TiO2 surface. Density functional theory (DFT) calculations related to the anatase (101) surface of TiO2 and Fe-doped TiO2 were performed to verify and provide guidance for enhancing the PTC mechanism. As a result, several key factors of the mechanism have been clarified and a reaction mechanism has been proposed for the whole cycle. (C) 2016 Elsevier B.V. All rights reserved.