Design aspects of all atomic layer deposited TiO2–Fe2O3 scaffold-absorber photoanodes for water splitting

Iron and titanium oxides have attracted substantial attention in photoelectrochemical water splitting applications. However, both materials suffer from intrinsic limitations that constrain the final device performance. In order to overcome the limitations of the two materials alone, their combinatio...

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Bibliographic Details
Published in:Sustainable energy & fuels 2018, Vol.2 (9), p.2124-2130
Main Authors: Hiltunen, Arto, Tero-Petri Ruoko, Iivonen, Tomi, Lahtonen, Kimmo, Ali-Löytty, Harri, Sarlin, Essi, Valden, Mika, Leskelä, Markku, Tkachenko, Nikolai
Format: Article
Language:English
Subjects:
Absorption spectroscopy
Anatase
Charge transfer
Crystallization
Fabrication
Hematite
Iron
Iron oxides
Oxides
Photoanodes
Photoelectric effect
Photoelectric emission
Rangefinding
Splitting
Titanium
Titanium dioxide
Titanium oxide
Titanium oxides
Ultraviolet radiation
Water splitting
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Summary:Iron and titanium oxides have attracted substantial attention in photoelectrochemical water splitting applications. However, both materials suffer from intrinsic limitations that constrain the final device performance. In order to overcome the limitations of the two materials alone, their combination has been proposed as a solution to the problems. Here we report on the fabrication of an atomic layer deposited (ALD) Fe2O3 coating on porous ALD-TiO2. Our results show that successful implementation requires complete mixing of the TiO2 and Fe2O3 layers via annealing resulting in the formation of a photoactive iron titanium oxide on the surface. Moreover, we found that incomplete mixing leads to crystallization of Fe2O3 to hematite that is detrimental to the photoelectrochemical performance. IPCE and transient photocurrent measurements performed using UV and visible light excitation confirmed that the iron titanium oxide extends the photocurrent generation to the visible range. These measurements were complemented by transient absorption spectroscopy (TAS), which revealed a new band absent in pristine hematite or anatase TiO2 that we assign to charge transfer within the structure. Taken together, these results provide design guidelines to be considered when aiming to combine TiO2 and Fe2O3 for photoelectrochemical applications.
ISSN:2398-4902
DOI:10.1039/c8se00252e