Preparation And Photocatalytic Performance Study Of G-C₃N₄/BiOBr Composite Materials

As an abundant carbon based material,g-C₃N₄ becomes more and more concerned because its chemical and thermal stable,nontoxic,visible light responsive,metal-free polymer.It is widely used in energy and environment fields.At present,g-C₃N₄ as a semiconductor photocatalyst with outstanding advantages still has some problems.Such as the small specific surface area of bulk g-C3N4?Bg-C3N4?,the limited reactants for adsorption,poor dispersibility and easy agglomeration,thus reduce the photocatalytic performance.The high recombination rate of electron and hole results in low quantum efficiency and poor photocatalytic activity,poor conductivity and reduced carrier migration rate.To solve these problems,a lot of research has been carried out about g-C₃N₄ to improve its photocatalytic properties.This paper proposes that Pg-C3N4 nanosheets obtained by HCl protonation and ultrasonic increase its specific surface area and solution stability.The BiOBr nanoplatelets grow in situ on Pg-C₃N₄ to form Pg-C₃N₄/BiOBr heterojunction nanosheets to separate photogenerated electrons and holes.?1?The bulk g-C₃N₄ is successfully prepared by using urea and melamine as precursors at different temperatures.U1-C₃N₄ prepared by treatment at 520?for 4hours with urea as precursor has better crystallinity and the surface morphology is favorable for photocatalytic reaction.The Eg-C3N4 nanosheets have no obvious agglomeration,good morphology and maximum specific surface area when exfoliated for 10 hours.Pg-C3N4 nanosheets have the best stability after HCl protonated for 9hours.Based on the surface treatment of Bg-C₃N₄,the prepared Eg-C₃N₄ nanosheets and Pg-C3N4 nanosheets have successfully improved the specific surface area and dispersion properties of materials.At the same time improved the optical properties of Bg-C3N4,resulting in improved visible light photocatalytic degradation of organic dyes.?2?To separate photogenerated electrons and holes,a unique two-dimensional?2D?heterojunction was constructed,in which BiOBr nanosheets are grown on the surface of Pg-C3N4 nanosheets by in-situ deposition.The photocatalytic activity of the samples was evaluated by the degradation of rhodamine B under visible light irradiation.The results reveal that BiOBr is coupled with Pg-C₃N₄ via the interaction between O atoms in BiOBr nanosheets and?-electrons in CN heterocycles by XRD,FESEM,FTIR,HRTEM and XPS.In comparison with the pure Pg-C3N4,the photocatalytic activity of Pg-C3N4/BiOBr is improved 4 times.The enhanced photocatalytic activity can be mainly ascribed to more efficient interfacial charge transfer and separation of photogenerated charge carriers due to the larger specific surface areas,increased contact surface,and well-aligned straddling band-structures.