DEVELOPMENT OF PHOTOCATALYTIC MATERIALS FOR SOLAR LIGHT CONVERSION INTO FUELS

Solar light possesses a large amount of energy. The sun provides to our planet an intense flux of high energetic photons capable to promote extremely up-hill reactions, such as the photosynthetic fixation of CO2 in biological systems. This energy flow drives life on Earth. My PhD thesis is focused on solar driven conversion processes. While in the first year I principally investigated the photocatalytic reduction of CO2 with TiO2-based materials. In the second year I started to explore new promising visible light harvesting materials and in particular I worked on CdSe quantum dots synthesis and on their use as photocatalysts for hydrogen production under visible light, with special interest on the size dependent recombination of the photogenerated. Finally, during my stage by Professor Kamat’s laboratory at Notre Dame University (Indiana, US), I started to work on the use of WO3/BiVO4 heterojunction photoanodes, for photoelectrocatalytic applications, and especially on charge carriers dynamics through transient absorption spectroscopy measurements. A short overview of the main themes treated during my PhD is outlined below. 1st year 1. Photocatalytic tests on TiO2 based materials in the photoassisted reactions of CO2 reduction and steam reforming of methanol, as a part of the research project FotoRiduCO2 PON01_02257. 2nd year 2. Synthesis and characterization of CdSe quantum dots with different size and their application in photocatalytic H2 production under visible light irradiation. 3. Preparation of WO3, BiVO4 and WO3/BiVO4 photoanodes for photoelectrochemical water splitting application and their study with transient absorption techniques. 3rd year 4. Preparation and characterization through femtosecond transient absorption spectroscopy of BiVO4 and WO3/BiVO4 films with variable BiVO4 thickness. The use of different pump energy allowed to suggest a new optical transition model that accounts for the electron transfer paths between the two oxides. Photoelectrochemical experiments validate the proposed model.