Effect of Ti- or Si-doping on nanostructure and photo-electro-chemical activity of electro-spun iron oxide fibres

Pure and titanium- or silicon-doped iron oxide fibres are synthesised by electro-spinning over conductive fluorine doped tin oxide (FTO)/glass substrates, and the effect of the type of dopant on the morphology of the fibres and the crystalline phase of the oxide is investigated by means of several complementary characterisation techniques. Results show that in the absence of dopant, highly porous fibres, consisting of interconnected polycrystalline hematite grains, are obtained. Doping with titanium does not influence the crystalline phase of the oxide, but the better packed structure of the fibres causes them to detach from the support. Silicon-doping results in a different phase of the host oxide (maghemite) and good adhesion of the fibres to the FTO/glass support. Very preliminary tests to evaluate the photo-electrochemical activity of the samples demonstrate that the photocurrent measured with Si-doped maghemite fibres is 53% higher with respect to that obtained with pure hematite fibres, as an effect of the nearly threefold increase in the donor concentration brought about by doping. This, in turn, improves the charge transfer at the interface, leading to a higher charge injection from the electrode to the electrolyte and, thus, to a greater photo-oxidation efficiency.