Efficient water oxidation using α-Fe2O3 thin films conformally coated on vertically aligned titania nanotube arrays by atomic layer deposition

Thin alpha-Fe2O3 films have been grown on vertically aligned titania nanotube (VA-TNT) arrays through atomic layer deposition to effectively collect charge carriers and meanwhile to enhance light absorption when used as photoanodes for photoelectrochemical water splitting. Extensive electron microscopy analyses reveal that alpha-Fe2O3 was conformally deposited on both the inner and outer walls of the TNTs, forming a sandwich structure. Impedance spectroscopy measurement shows that the series resistance and interface resistance between titania and alpha-Fe2O3 are small, only ca. 1.2 and 20.8 Omega cm(-2), respectively. Consequently, the VA-TNT array attached to the titanium substrate can serve as an efficient current collector to promote the separation of photo-generated carriers. A photocurrent of ca. 1 mA cm(-2) at 1.23 V versus RHE and a hole density of ca. 2.3 x 10(19) cm(-3) have been observed under 100 mW cm(-2) illumination. (C) 2015 Elsevier B.V. All rights reserved.