The Preparation And Visible-light Performance Of Bismuth Ferrite Photocatalyst

Photocatalytic degradation of organic pollutants and hydrogen generation from photolytic water splitting on semiconductor has received considerable attentions. Recently, bismuth ferrite has attracted a great of interests for solar applications due to its narrow band gap and the bulk photovoltaic effect. Comparing with TiO2-based photocatalysts, BiFeO3 has a narrower band gap of 2.1-2.5 eV, which allows the photocatalytic activity under visible light to become prominent. However, it is generally known that single-phase BiFeO3 is difficult to synthesis. Thus, in this thesis, the main study is focused on the synthesis of single-phase BiFeO3 by different methods; exploration of the effects of preparation conditions on bismuth ferrite and its photocatalytic performance. Then, the mechanism of photocatalysis was proposed. The main results are as follows:1. Hydrothermal method:The single-phase cubic BiFeO3 powders with -2 um particle size were successfully synthesized with PVP as the dispersant. It was found that the PVP not only changes the dispersion and morphology of BiFeO3, can also promote crystallization of synthesized BiFeO3; among all the prepared samples, dispersed cubic BiFeO3 particles could be achieved highest activity on photodegrading MO under visible light; the photocatalytic efficiency should be driven by the morphology rather than particle size.2. Sol-gel method:Well-dispersed BiFeO3 nanoparticle can be prepared without using any complex or dispersant at a relative low temperature (500℃). It is found that the precursor concentration have significant influences on the impurity of synthesized BiFeO3; the particle size increased with the increase of precursor concentration at same annealing temperature; compared with the visible-light response of BiFeO3, the particle size of BiFeO3 may be the main factor influencing the photocatalytic efficiency3. Microwave method:Under the same conditions, the reaction time for the synthesis of single-phase bismuth ferrite by microwave hydrothermal method was shorter than hydrothermal method and the dispersion of synthesized BiFeO3 was better. It is found that the phase purity of the product was dependent on the microwave time and phase of BFO transformed during the microwave heating process; the particle size increased with the increase of reaction time.