Tuning the catalytic property of TiO2 nanotube arrays for water splitting

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 (∼1.0 V) on pristine TNTAs, Pt/TNTAs and N-TNTAs; and the other is a low overpotential (∼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.

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► Doping reduces the overpotential for water splitting on TNTAs.
► Two groups of overpotentials are found: high (∼1.0 V)and low (∼0.6 V).
► Two kinds of adsorption energies linear relations are identified.