New hematite heterostructures for solar fuels
Morgan Stefik a, Maurin Cornuz a, Michael Grätzel a
Oral, Morgan Stefik, presentation 015
Publication date: 31st March 2013


Hematite (α-Fe2O3) is a promising photoanode material for photoelectrochemical (PEC) water splitting due to its abundance, low-cost, stability, and substantial sun light absorption with a bandgap of 2.1 eV.  Since the first hematite PEC water splitting demonstration in 1976(1), there have been numerous advancements, particularly through interface engineering, doping, and nanostructuring of hematite (2). One of the fundamental challenges to using hematite to achieve water splitting with high external quantum efficiency (EQE) is the disparity between the long photon absorption length (hundreds of nm) and the short hole diffusion length (2-4 nm). There are many examples of nanostructure approaches that have had some success at improving this situation by decreasing the necessary diffusion length for holes to reach the semiconductor-liquid junction (SCLJ). We recently reported a nanocomposite approach that combines a high surface area transparent, conducting oxide support with thin films of hematite, each having high internal quantum efficiency (3).  This design enables hematite to have both short hole diffusion lengths to the SCLJ as well as short electron paths to the conducting support.  Here we present our latest results expanding upon this work with hematite heterostructures that lead to significant performance improvements.  In addition we will present our newly developed support materials and improved solution processable hematite. 

(1) Hardee, KL.; Bard, AJ. Application of Chemically Vapor-Deposited Iron-Oxide Films to Photosensitized Electrolysis. J. Electrochem. Soc. 1976, 123.7, 1024-1026. (2) Sivula, K.; Le Formal, F.; Grätzel, M. Solar Water Splitting: Progress Using Hematite Photoelectrodes. Chem. Sus. Chem. 2011, 4, 432-449. (3) Stefik, M.; Cornuz, M.; Mathews, N.; Hisatomi, T.; Mhaisalkar, S.; Grätzel, M., Transparent, Conducting Nb:SnO2 for Host-Guest Photoelectrochemistry. Nano Letters 2012, 12, 5431-5435.
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