Photoelectrochemical response of Fe 2 O 3 films reinforced with BiFeO 3 nanofibers
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Research Letter
Photoelectrochemical response of Fe2O3 films reinforced with BiFeO3 nanofibers Albert Queraltó and Sanjay Mathur, Institute of Inorganic Chemistry, University of Cologne, Greinstrasse 6, 50939 Cologne, Germany Address all correspondence to Prof. Dr. Sanjay Mathur at [email protected] (Received 25 April 2018; accepted 22 May 2018)
Abstract BiFeO3 (BFO) p-type semiconducting nanofibers were deposited on fluorine-doped SnO2 substrates by a combination of electrospinning (BiFeO3) and spin-coating (Fe2O3) procedures. Photocurrent density values of BFO nanofibers which increased with the annealing temperature to values six times larger were obtained. Different amounts of BFO nanofibers (5, 10, and 25 wt%) were also integrated into α-Fe2O3 films. The photocurrent density of the α-Fe2O3/BFO nanofiber films had the highest value for a 10 wt% BFO nanofibers. The anisotropy in charge transport due to the underlying nanofibrous pathways which prevented the charge carrier recombination was the main cause for the enhancement of the photocurrent density.
Introduction Photoelectrochemical (PEC) water splitting is noticeably one of the superior methods for a clean and sustainable production of energy. The use of solar energy in the production of hydrogen from water is one of the promising alternatives that could potentially provide a clean and cost-effective solution to fossil fuels.[1,2] Solar water splitting is based on immersing a semiconducting electrode into an electrolyte and harvest sunlight to break down water into its constituents for converting solar energy into chemical energy. Prerequisites for an efficient water splitting system include that the photoanode material should be able to generate a voltage higher or equivalent to the water splitting potential (1.23 V) and its band gap should allow absorption of a broad range of the solar spectrum, as well as the band edges must be compatible with hydrogen and oxygen redox potentials.[1] Moreover, long-term stability against photocorrosion, long carrier diffusion lengths, and efficient charge transport are key criteria for efficient photoelectrocatalysts. In the context of large surface area materials, electrospinning is a cost-effective net-shaping methodology that allows the fabrication of nanofiber-based photoelectrodes with large surface areas and porosity.[3] Electrospinning has been employed to fabricate a wide range of oxide materials, such as TiO2, Fe2O3, CuO, NiO, BiFeO3, LaFeO3, LaNiO3, and BaTiO3, used in photocatalysis, water splitting, magnetism, multiferroics, piezoelectricity, supercapacitors, and gas sensing applications.[4–8] TiO2 is one of the most investigated materials for water splitting due to its very high photocatalytic efficiency, non-toxicity, and stability.[9] Nevertheless, its large band gap (3.2 eV) only allows the absorption in the UV range that
restricts the overall PEC efficiency. Thus, alternative transition oxide materials have been investigated in order to achieve visible-light-driven water splitting. Particularly, bismuth ferrit
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