Doping with tetravalent titanium cation impurities is an effective means to enhance the performance of hematite (alpha-Fe2O3) photoanodes. These nevertheless face problems of inefficient activation of impurity donors, which thereby impairs the photoelectrochemical water oxidation property of hematite. Herein, we propose a simple method to activate Ti4+ dopants in spray-pyrolyzed hematite thin films via a rapid thermal annealing (RTA) treatment. The donor carrier density of Ti-doped Fe2O3 thin films (doping level, i.e., Ti/Fe: 0.5-10%) is significantly increased by RTA at 700 degrees C for 30 s, for instance, ca. 1.35 x 10(19) cm(-3) at the doping level of 5% (5%-Ti:Fe2O3-700). This is 19.3 times as high as those treated by traditional annealing in a muffle furnace at 500 degrees C for 1800 s (5%-Ti:Fe2O3-500). A photocurrent density of 5%-Ti:Fe2O3-700 for water oxidation reaches 0.91 mA cm(-2) at 1.23 V vs. RHE. This is ca. 6-fold higher than 5%-Ti:Fe2O3-500. Electrochemical impedance spectroscopy, XRD, Raman spectroscopy, and scanning probe microscopy measurements suggest that RTA performs more efficiently than traditional annealing for promoting the substitutional incorporation of Ti4+ cations into the hematite lattice. This simple RTA treatment for donor-activation should be applicable to other semiconductor-dopant combinations-thin films or nanostructures, for the development of high-performance photoanodes for water oxidation. (C) 2019 Elsevier Ltd. All rights reserved.