Visible-light-driven photoelectrochemical water oxidation with Al doped TiO2 nanorod arrays

Doping TiO(2 )with impurity elements is a common strategy to improve its photoelectrochemical water splitting performance, however, it is still challenging to unambiguously illustrate its fundamental effects. In this work, Al doped TiO2 nanorod arrays are grown hydrothermally on fluorine-doped tin oxide substrates and acted as an example system to study the effects of acceptor-type dopant on the photoelectrochemical water oxidation behavior of n-type TiO2, which usually is benefit from donor doping. A strategy that introducing hole scavenger into the electrolyte confirms that the diffusion-controlled charge-transport is the rate-determining step of the photoelectrochemical process. Electronic structure information extracted from electrochemical impedance spectroscopy verifies that Al ions as acceptor compensate for the n-type carrier in the TiO2 and result in the decrease of the donor density, however, the electrochemical impedance measurements also confirm that the charge transport resistance of TiO2 is dramatically decreased after Al doping, which actually plays the decisive role and thereby leading to the significantly enhanced photoelectrochemical water oxidation performance. Such exploration presented in this work is envisioned to provide valuable reference for deep understanding the effects of doping on improving the photocatalytic properties of oxide semiconductors and thus it is helpful for designing and preparing other advanced semiconductor photoelectrodes. (C) 2019 Elsevier B.V. All rights reserved.