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

Abstract

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.