Facile fabrication of CeO₂–TiO₂ thin films via solution based CVD and their photoelectrochemical studies

Present work reports a single step deposition protocol for the growth of robust, durable and homogenous CeO₂–TiO₂ composite thin films for the investigation of their photoelectrochemical (PEC) properties. The transparent methanol solution of triacetatocerium (III) hydrate and of tetraisopropoxytitanium (IV) precursors in 1:1 mol ratio was employed in aerosol assisted chemical vapor deposition (AACVD) on FTO substrates at temperatures of 550 and 600 °C in the ambient air. These precursors were converted into their trifluroacetates in situ, under these deposition conditions, for their compatibility in the AACVD procedure. XRD, SEM, EDX and XPS analyses verified the formation of uniformly dispersed crystalline CeO₂ and TiO₂ phases in spherical shaped morphologies and a direct bandgap of 2.6 eV was measured from the UV–Visible spectrophotometry. PEC studies of the composite films revealed that the heterojunction developed between n-type CeO₂ and n-type TiO₂ facilitated the separation and transportation of electrons and holes, leading to a promising photocurrent density of about 1.0 mA cm^{− 2} and prolonged photo stability measured under one-sun illumination (100 mW cm^{− 2}) which is up to 60 min at 0.7 V versus Ag/AgCl. This behavior was further confirmed from electrochemical impedance spectroscopy and Bode phase angle measurements. It was also shown that the films fabricated at 550 °C has higher porosity leading to larger interface contacts and thus was able to generate higher photo activity.