Fabrication And Visible-light Photocatalytic Performance Of Bismuth Titanate-based Nanocomposites

Photocatalysis,as a green technology with potential applications,has become one of the research focuses since the energy and environment problems become increasingly prominent in recent years.The research of high-efficient visible-light photocatalysts is of the top priority to realize the extensive application of photocatalytic technology.Bismuth titanate Bi₁₂TiO₂₀,a new-type visible-light photocatalytic material,has been widely studied because of its unique and diverse crystal and electronic structure.However,there are two problems including narrow visible light response and high recombination rate of photo-generated electrons and holes for it.Therefore,two Bi₁₂TiO₂₀-based nanocomposite photocatalysts were synthesized by adopting two modified methods simultaneously to enhance the photocatalytic performance in this study.A novel nanoplate-like Bi₁₂TiO₂₀/g-C₃N₄ heterojunction was fabricated by a facile hydrothermal-annealing method,and its morphology,structure,optical property and visible-light photocatalytic property were characterized.The heterojunction presents the nanoplate morphology about 40 nm in thickness and several hundreds of nanometers in size.The g-C₃N₄ nanosheet with rough surface binds tightly on the smooth surface of Bi₁₂TiO₂₀ through the heterojunction structure,which is proved by the existence of C-O bond.The absorption edge wavelength of the heterojunction composite has a red shift compared with pure Bi₁₂TiO₂₀ and its recombination rate of photo-generated charge carriers decreases significantly compared with pure g-C₃N₄.The Bi₁₂TiO₂₀/g-C₃N₄ heterojunctions display higher photocatalytic performance for Rhodamine B degradation than pure Bi₁₂TiO₂₀ and g-C₃N₄ and among them,the Bi₁₂TiO₂₀/g-C₃N₄-3 sample is the highest one.This phenomenon can be primarily attributed to the energy band match and the heterojunction structure.Furthermore,their synergistic effect greatly improves the photocatalytic property of the heterojunction composite.The Bi₁₂TiO₂₀/C₆₀ nanocomposite microsphere was fabricated by a solvothermal-annealing method,and its morphology,structure,optical property and visible-light photocatalytic property for Rhodamine B degradation were evaluated.The composite material displays the microspheric morphology,about 200-300 nm in diameter.There are mesoporous structure on the surface and inside channels of the microspheres after calcination,which can increase the specific surface area.The formability,crystallinity and optical absorption property of the sample are the best when the solvothermal temperature is 150 ^oC.The optimal additive amount of C₆₀ is 2 wt%and this sample has the highest photocatalytic performance.Moderate C₆₀ amount can provide the transfer channel for electrons,thus accelerating the separation of photo-generated charge carriers.However,excessive C₆₀ amount may cover on the surface of microspheres and become new recombination center,which would reduce the photocatalytic performance.