Photoelectrochemical properties of electrospun titania nanofibers - comparison with nanoparticles
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Photoelectrochemical properties of electrospun titania nanofibers - comparison with nanoparticles Jan M. Macak,1 Jaromir Pytel,1 Jesus Rodriguez Ruiz,2 and Radim Beranek3 1 Research and Development, Elmarco, Ltd., Svarovska 621, 460 10 Liberec 9, Czech Republic 2 Dip. Ingegneria Chimica e Materiali - Università degli Studi di Cagliari - Piazza D'Armi, s.n. 09123 Cagliari, Italy 3 Department of Chemistry & Pharmacy, University of Erlangen-Nuremberg, Egerlandstr. 1, D91058 Erlangen, Germany ABSTRACT Photoelectrochemical properties of photoelectrodes consisting of pressed layers of electrospun TiO2 nanofibers were investigated by wavelength-resolved photocurrent measurements in LiClO4 (0.1 M) aqueous electrolyte with or without addition of KI as an additional hole scavenger. The photocurrents on nanofiber electrodes were three-times lower as compared to electrodes based on Hombikat nanocrystalline particles. The calcination of electrodes was necessary to observe enhanced efficiencies in the presence of iodide. The most striking difference between nanofiber and particulate electrodes was found in the effect of calcination on the efficiency of water photooxidation. INTRODUCTION In recent years we have witnessed enhanced interest in fabrication of artificial photochemical systems and devices capable of harnessing solar energy to produce electricity (solar cells) or chemical fuels (e.g., hydrogen) [1-3]. This is motivated by the need for development of low-cost and easily processed alternatives to conventional solar energy converting systems which often suffer from high costs of materials and manufacturing methods. In this context, one of the major strategies consists in utilizing cheap semiconductors that enable both light-induced generation and separation of electrical charges which can subsequently undergo redox reactions with substrates or induce a photocurrent [4,5]. One of the most promising semiconductors for such applications is titanium dioxide, particularly due to its low cost, non-toxicity, and stability against photocorrosion [6-9]. The scope of its possible applications is very wide and ranges from photocatalytic systems utilizing neat titania to photovoltaic applications in which titania serves as an electron collector covered by visible light absorbing chromophores like organic dyes [10,11] or quantum dots [12-14]. Notably, control of materials morphology on the micro- and nanometer length scale is often crucial for efficient utilization of the light energy. This can be exemplified by enhanced photoconversion efficiencies achieved by using semiconductor nanocrystals [10], nanotubes [15,16] or nanowires [17,18]. Herein we present our studies of photoelectrodes based on titania nanofibers prepared by largescale electrospinning technology. We examine their optical and photoelectrochemical properties, and compare them with conventional nanocrystalline layer electrodes.
EXPERIMENTAL TiO2 nanofibers were prepared by electrospinning (Nanospiderâ„¢) from ethanolic solution of polyvinylpyrrolidone contai
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