With a band gap of 2.2 eV and good chemical stability in water, α-Fe₂O₃is almost an ideal material for photoelectrochemical water splitting. Recently, it was shown that Fe₂O₃ dendrite nanostructures can split water with an efficiency (solar-to-hydrogen) of 3.2% [1]. Despite this encouraging breakthrough, two major challenges remain. First, more insights into the materials properties are required to improve the efficiency to the theoretical value of 12.9%. Second, alternative synthesis methods are needed for practical application, and these methods should have good reproducibility and should be easy to scale up.

In this work, a novel process called EDOX (ElectroDeposition and thermal OXidation) was developed for the fabrication of Fe₂O₃ photoelectrodes. During the process, Fe films are first synthesized by electrodeposition on a conductive substrate, after which the metal films are oxidized under controlled atmosphere to form α-Fe2O3 films. While the Fe₂O₃ nanowire arrays are reported to grow during oxidation of iron [2], we will show that this is not trivial and depends strongly on the nature of the metallic iron substrate and the oxidation conditions.
The viability of the technique will be demonstrated by some first results on Ti-doped α-Fe₂O₃ films (~200nm thick) deposited on the TCO substrate. These films show a photocurrent of 0.33 mA/cm2 at a bias of 1.23 V vs. RHE under illumination with AM1.5 simulated sunlight.

References
[1] A. Kay, I. Cesar, and M. Grätzel, J.Am.Chem.Soc, 128, 15714, 2006.
[2] T. Yu, Y. Zhu, X. Xu, et. al, Small, 2, 80, 2006.