Photoanodes with Fully Controllable Texture: The Enhanced Water Splitting Efficiency of Thin Hematite Films Exhibiting Solely (110) Crystal Orientation

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• 作者：Stepan Kment ; Patrik Schmuki ; Zdenek Hubicka ; Libor Machala ; Robin Kirchgeorg ; Ning Liu ; Lei Wang ; Kiyoung Lee ; Jiri Olejnicek ; Martin Cada ; Ivan Gregora ; Radek Zboril
• 刊名：ACS Nano
• 出版年：2015
• 出版时间：July 28, 2015
• 年：2015
• 卷：9
• 期：7
• 页码：7113-7123
• 全文大小：700K
• ISSN：1936-086X

文摘

Hematite, 伪-Fe₂O₃, is considered as one of the most promising materials for sustainable hydrogen production via photoelectrochemical water splitting with a theoretical solar-to-hydrogen efficiency of 17%. However, the poor electrical conductivity of hematite is a substantial limitation reducing its efficiency in real experimental conditions. Despite of computing models suggesting that the electrical conductivity is extremely anisotropic, revealing up to 4 orders of magnitude higher electron transport with conduction along the (110) hematite crystal plane, synthetic approaches allowing the sole growth in that direction have not been reported yet. Here, we present a strategy for controlling the crystal orientation of very thin hematite films by adjusting energy of ion flux during advanced pulsed reactive magnetron sputtering technique. The texture and effect of the deposition mode on the film properties were monitored by XRD, conversion electron M枚ssbauer spectroscopy, XPS, SEM, AFM, PEC water splitting, IPCE, transient photocurrent measurements, and Mott鈥揝chottky analysis. The precise control of the synthetic conditions allowed to fabricate hematite photoanodes exhibiting fully textured structures along (110) and (104) crystal planes with huge differences in photocurrents of 0.65 and 0.02 mA cm^鈥? (both at 1.55 V versus RHE), respectively. The photocurrent registered for fully textured (110) film is among record values reported for thin planar films. Moreover, the developed fine-tuning of crystal orientation having a huge impact on the photoefficiency would induce further improvement of thin hematite films mainly if cation doping will be combined with the controllable texture.