HEMATITE PHOTOANODES MODIFIED WITH AN IRON(III) WATER OXIDATION CATALYST Nicola Dalle Carbonare(a), Roberto Argazzi(b), Stefano Caramori(a), Carlo Alberto Bignozzi(a) (a) Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 17-27 44121 Ferrara, Italy, [email protected] (b) CNR/ISOF c/o Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 17-27 44121 Ferrara, Italy. Photo driven water splitting using semiconductor electrodes may play an important role in the production of hydrogen, converting the solar radiation into useful chemical vectors. Besides attaining proper energy efficiencies, one goal should also be the utilization of cheap and harmless materials for the easy fabrication of stable devices. In this context, hematite (α-Fe2O3) is an interesting material to produce water splitting photoanodes based on very abundant elements, due to its band gap of ca. 2 eV, a correct position of the Valence Band with respect to O 2/H2O couple and a great stability in basic aqueous solution. Several methods have been explored to produce high porous doped nanostructured electrodes (e.g., APCVD,[1] spray pyrolysis[2]) in order to maximize the minority carriers transport and transfer from hematite to the electrolyte. Moreover, post-synthesis functionalization with water oxidation catalysts (i.e., Co-Pi,[3] IrO2[4]) is necessary due to an incorrect matching between charge recombination and charge transfer kinetics. Driven by previous results obtained from our group in efficient hydrogen production with 3J cells modified with Fe(III) compounds,[5] we have performed an exhaustive investigation of hematite photoanodes produced with a simple hydrothermal method [7] and functionalized with an amorphous Iron(III) water oxidation catalyst by SILAR method (Successive Ionic Layer Adsorption and Reaction).[6] The DC photoelectrochemical characterization revealed an evident improvement in the photoanodic activity of electrodes in the presence of the catalyst (Fe-OEC) and Electronic Impedance Spectroscopy (EIS) gave us key information about the dynamics of charge transfer at the interface between the solution and the modified hematite surface. [1] A. Kay, I. Cesar, M. Grätzel, J. Am. Chem. Soc. 128 (2006) 15714. [2] A. Duret, M. Grätzel, J. Phys. Chem. B 109 ( 2005) 17184. [3] M. Barroso, A. J. Cowan, S. R. Pendlebury, M. Grätzel, D. R. Klug, J. R. Durrant, J. Am. Chem. Soc. 133 ( 2001) 14868. [4] S. D. Tilley, M. Cornuz, K. Sivula, M. Grätzel, Angew. Chem., Int. Ed. 49 (2010) 6405. [5] V. Cristino, S. Berardi, S. Caramori, R. Argazzi, S. Carli, L. Meda, A. Tacca, C. A. Bignozzi, Phys. Chem. Chem. Phys. 15 (2013) 13083. [6] N. Dalle Carbonare, V. Cristino, S. Berardi, S. Carli, S. Caramori, R. Argazzi, A. Tacca, L. Meda, C. A. Bignozzi, Phys. Chem. Chem. Phys. (2014) accepted article. ise141607