Letter pubs.acs.org/NanoLett
Facile Solution Synthesis of α-FeF3 ·3H2O Nanowires and Their Conversion to α-Fe2O3 Nanowires for Photoelectrochemical Application Linsen Li,† Yanghai Yu,† Fei Meng, Yizheng Tan, Robert J. Hamers, and Song Jin* Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States S Supporting Information *
ABSTRACT: We report for the first time the facile solution growth of α-FeF3·3H2O nanowires (NWs) in large quantity at a low supersaturation level and their scalable conversion to porous semiconducting α-Fe2O3 (hematite) NWs of high aspect ratio via a simple thermal treatment in air. The structural characterization by transmission electron microscopy shows that thin α-FeF3·3H2O NWs (typically 100 nm in diameter) become polycrystalline porous α-Fe2O3 NWs. We further demonstrated the photoelectrochemical (PEC) application of the nanostructured photoelectrodes prepared from these converted hematite NWs. The optimized photoelectrode with a ∼400 nm thick hematite NW film yielded a photocurrent density of 0.54 mA/cm2 at 1.23 V vs reversible hydrogen electrode potential after modification with cobalt catalyst under standard conditions (AM 1.5 G, 100 mW/cm2, pH = 13.6, 1 M NaOH). The low cost, large quantity, and high aspect ratio of the converted hematite NWs, together with the resulting simpler photoelectrode preparation, can be of great benefit for hematitebased PEC water splitting. Furthermore, the ease and scalability of the conversion from hydrated fluoride NWs to oxide NWs suggest a potentially versatile and low-cost strategy to make NWs of other useful iron-based compounds that may enable their large-scale renewable energy applications. KEYWORDS: Nanowire, α-FeF3·3H2O, α-Fe2O3, conversion, photoelectrochemical water splitting, nanostructured hematite photoelectrodes
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dimensions may circumvent their shortcomings or make them much more tolerable for applications.4,8−11 In particular, nanostructures of hematite have been exploited in the past few years to significantly enhance its photoelectrochemical (PEC) water oxidation performance for solar water splitting.4,5,12−18 Despite having the advantages of favorable bandgap, excellent stability, abundance, and low cost,4 hematite has poor absorptivity near the bandgap (α−1 ∼ 0.12 μm at λ = 550 nm),19 low mobility (
