Doping is an important approach to modulate the catalytic properties, for example, the change of the overpotential, of TiO2 semiconductor for water splitting. In this study, by systematically investigating the thermodynamic properties of one-electron water splitting, we found that the required overpotentials can be divided into two groups: one is a high overpotential (similar to 1.0 V) on pristine TNTAs, Pt/TNTAs and N-TNTAs; and the other is a low overpotential (similar to 0.6 V) on F-TNTAs, Pt/N-TNTAs and Pt/F-TNTAs. And two kinds of linear relations between the binding energies of O, HO and HOO intermediates are further identified, which are unambiguously ascribed to the bonding characteristics between the reaction intermediates and the two types of TNTAs with the high and low overpotential, respectively. Therefore, the current work will make a step towards understanding the mechanism of water splitting on various doped TNTAs and designing the superior TiO2-based photoanode materials with lower overpotentials. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.