Photoelectrochemical water splitting at nanostructured ZnFe2O4 electrodes

Semiconducting nanocrystalline ZnFe2O4 thin films were deposited by aerosol-assisted chemical vapour deposition (AACVD) for photoelectrochemical (PEC) water splitting. The effect of deposition parameters such as solvent type, temperature and deposition time on PEC properties has been investigated. The SEM analysis illustrated that the morphology of the films changes significantly with the change of solvent. The films deposited from ethanolic precursor solution have a morphology consisting of interconnected cactus-like ZnFe2O4 structure growing vertically from the FTO substrate. The current-voltage characterization proved that the nanocrystalline ZnFe2O4 electrodes exhibit n-type semiconducting behaviour and the photocurrent was found strongly dependent on the deposition solvent, deposition temperature and deposition time. The maximum photocurrent density of 350 mu A/cm(2) at 0.23 V vs. Ag/AgCl/3 M KCl (similar to 1.23V vs. RHE) was obtained for the ZnFe2O4 electrode synthesized using the optimum deposition temperature of 450 degrees C, the deposition time of 35 min, and 0.1 M solution of (1) in ethanol. The electrode gave an incident photon to electron conversion efficiency of 13.5% at an applied potential of 0.23 V vs. Ag/AgCl/3 M KCl at 350 nm. The donor density of the ZnFe2O4 was 3.24 x 10(24) M-3 and the flatband potential is approximately -0.17 V, which remarkably agrees with the photocurrent onset potential of -0.18 V vs. Ag/AgCl/3 M KCl. (C) 2010 Elsevier B.V. All rights reserved.