| AVS 57th International Symposium & Exhibition | |
| Late Breaking Session | Wednesday Sessions |
| Session LB-WeA |
| Session: | Late Breaking Session Featuring Talks on Energy, Graphene and Atom-Probe Tomography |
| Presenter: | C.A. Wolden, Colorado School of Mines |
| Authors: | R. Moorish, Colorado School of Mines M. Rahman, University College Dublin, Ireland D. MacElroy, University College Dublin, Ireland C.A. Wolden, Colorado School of Mines |
| Correspondent: | Click to Email |
Hematite (α-Fe2O3) is a promising material for sustainable generation of H2 due to its low cost, widespread availability, chemical stability, and ability to absorb a significant fraction of visible light. However numerous challenges remain in order for this material to approach its theoretical potential of 15% solar to hydrogen efficiency. The two most important metrics for photocurrent are its onset potential and the current plateau. The latter is a measure of the fraction of photo-generated carriers that are extracted to perform water splitting. In this work we address this challenge through the production of oriented nanorod arrays on fluorine-doped tin oxide (FTO) coated glass using the approach developed by Vayssieres and coworkers.[1] This simple aqueous solution method is scalable and employs low cost precursors. In previous studies well-developed arrays of vertical nanorods were formed, by unfortunately such structures yielded poor photoelectrochemical performance (<5 µA/cm2).[2] In this paper it is shown that the temperature used for post-deposition calcination has a profound impact on material properties and performance. The critical temperature is found to be ~725 ºC. Films calcined below this temperature displayed negligible photocurrent, while samples treated at above had dramatic improvement in photocurrent density. The enhanced performance is correlated with increased optical absorption and improved crystallinity, which are thought to enhance carrier generation and transport, respectively. Electron microscopy and energy dispersive spectroscopy suggests that significant diffusion of tin from the FTO into the Fe2O3 matrix occurs during high temperature annealing process. The benefits of this process may include enhanced conductivity as well as improvement of the FTO/ Fe2O3 interface. Initial testing of these films under simulated sunlight produced photocurrent densities >300 µA/cm2 at 1.23 V versus the reversible hydrogen electrode, a 100-fold increase over previous reports. In this presentation we will discuss the sensitivity to process conditions, and update further improvements achieved to the system.
References
[1] L. Vayssieres, N. Beermann, S. E. Lindquist, and A. Hagfeldt, "Controlled aqueous chemical growth of oriented three-dimensional crystalline nanorod arrays: Application to iron(III) oxides," , 233-235, (2001).
[2] N. Beermann, L. Vayssieres, S.-E. Lindquist, and A. Hagfeldt, "Photoelectrochemical Studies of Oriented Nanorod Thin Films of Hematite," , 2456-2461, (2000).