Modified nanostructured Bismuth Ferrite thin films for application in photoelectrocatalysis

Abstract

The thesis project is focused on the synthesis and characterization of nanostructured bismuth ferrite, BiFeO3 (BFO), thin films with enhanced photoelectrocatalytic properties. Photoelectrocatalytic materials are semiconductors that are able to catalyze water splitting processes or other reactions under sunlight irradiation. They can, through the absorption of photons, create electron/hole pairs which can be exploited to carry out electrochemical reactions. BFO is a very promising perovskite-type material with an optical band gap that fits well with the sunlight irradiation in the visible region. Since most of the conventional photocatalyst like TiO2 is limited by a wide band gap and a UV light absorption, the BFO material is an interesting visible light driven photoactive material for solar energy conversion. The main disadvantages of such material are poor efficiency and high variability in the photoelectrocatalytic performance. BFO’s performance depends on structure, defects, phase, electronic properties, which are directly connected with the synthetic methodology. In this thesis a sol-gel synthesis has been optimized in order to prepare highly reproducible thin films, that could be directly applied to a device, with modified structure and improved photoelectrocatalytic performance. Moreover, in order to achieve sensitization in the Near Infrared Region where pure BFO is not active, a composite nanomaterial has been developed. Previously prepared nanoparticles with peculiar optical properties have been dispersed in a BFO matrix and the optical and structural characterization have been carried out to correlate the enhancement of photoelectrocatalytic properties with the modification caused by the nanoparticles doping.