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

• Thin α-Fe2O3 films are conformally grown on vertically aligned titania nanotube arrays.
• Titania nanotube arrays serve as efficient current collector facilitating the separation of photo-generated carriers.
• A photocurrent of 1.05 mA cm−2 at 1.23 V is achieved.

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 20.8 Ω 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. 2.3×1019 cm−3 have been observed under 100 mW cm−2 illumination.