Preparation And Characterization Of Yttrium,Indium Doping And G-C₃N₄ Composite Metastable Phase Bismuth Oxide

Because of the degradation of photocatalyst in organic,printing and dyeing wastewater,it was received extensively attention.Developing high-efficiency photo-responsive photocatalysts has become a hot topic in the world.Bismuth oxide has shown wide application in many fields such as electronic ceramics,optoelectronic devices,high temperature superconductors and catalysts due to chemical stability,non-toxicity and unique optical properties.In this paper,three Bi₂O₃ with different space groups were prepared by co-precipitation method,using lanthanum nitrate pentahydrate and sodium hydroxide as raw material and precipitant.Its photocatalytic performance was improved by bismuth sites doping and heterojunction recombination strategies.Moreover,the corresponding energy band and density of states were obtained by the first-principle calculations.?-,?-,and?-type Bi₂O₃ were all polycrystalline pure phase powders using X-ray diffraction analysis.The corresponding morphologies were composed of long strips,irregular shapes with spikes on the surface and regular tetrahedron by scanning electron microscopy characterization.The precipitation reaction time shortened with increment of temperature for metastable phase synthesis.After photodegrading rhodamine B with 10 mg?L^-1,the photocatalytic performance of?phase was better than that of?and?phase.Based on the first-principle calculation,three crystal phases were indirect,direct,and indirect bandgap semiconductors,respectively.Moreover,the valence band and the conduction band were mainly composed of O 2p and Bi 6p states.Compared to pure gamma phase structure,the crystal structure remained the cubic phase after introducing yttrium or indium element into bismuth sites.When the impurity content was increased,the particles size on the tetrahedron surface gradually increased.Different morphology configurations resulted into acceleration of photocatalytic degradation rate for Rhodamine B dye.Yttrium and indium doping induced the band gap width change using ultraviolet-visible diffuse reflectance spectroscopy analysis and the first-principle calculation.Graphite phase carbon nitride?g-C₃N₄?was synthesized by calcining melamine in solid state reaction.The g-C₃N₄/?-Bi₂O₃ composite was prepared by mixing g-C₃N₄ with the?phase with certain mass ratio.When the mass of g-C₃N₄ increased,the peak width at diffraction angle28.5^o enlarged and the morphology inclined to thick sheet configuration of pure g-C₃N₄.Thus the g-C₃N₄/?-Bi₂O₃ heterojunction was formed.Compared with other mass ratios of g-C₃N₄/?-Bi₂O₃,the sample with 1:1 possessed the smallest band gap width.This advantage enhanced the light response of the sample,inducing improvement of the photocatalytic performance.