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

Abstract

Thin α-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 α-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 α-Fe2O3 are small, only ca. 1.2 and 20.8Ωcm−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. 1mAcm−2 at 1.23V versus RHE and a hole density of ca. 2.3×1019cm−3 have been observed under 100mWcm−2 illumination.