Synthesis Of Bi₂O2?OH??NO₃? Based Two-dimensional Heterojunctions And Their Visible Light Photocatalytic Activity

In recent years,the environmental pollution has become more and more serious,it is imperative and urgent to find a treatment of environmental pollution which is efficient and environmental friendly.The typical[Bi₂O₂]²⁺layered structure catalysts enables the possibility for synthesis of ultrathin nanosheets.Herein,the ultrathin two-dimensional Bi₂O₂?OH??NO₃?/BiOBr?donated as BION/BiOBr?heterojunctions and Bi₂O₂?OH??NO₃?/Bi₂MoO₆?donated as BION/BMO?composites were prepared by hydrothermal method and ultrasonic stripping method.Meanwhile,we analyzed their photocatalytic properties and photocatalytic mechanism.The main research work is as follows:?1?Ultrathin two-dimensional BION/BiOBr heterojunctions were synthesized by hydrothermal method using Bi?NO₃?₃·5H₂O and CTAB as raw materials.The ultrathin two-dimensional composite materials were prepared by ultrasonic method using the mixture of ethanol and water as the solvent.The structure,morphology,exposed crystal surface and light absorption properties of ultrathin two-dimensional BION/BiOBr heterojunctions were characterized by XRD,SEM,HRTEM,UV-Vis DRS analysis.The results showed that the thickness values of the small-sized and large-sized for BION/BiOBr ultrathin nanosheets were 1.725nm and 3.213nm respectively.The band gaps of BION and BiOBr were 3.4eV and 2.81eV,and the exposed crystal planes were{001}planes.?2?We discussed the photocatalytic performance of the as-obtained ultrathin two-dimensional BION/BiOBr heterojunctions by degrading tetracycline?TC?,Rhodamine B?RhB?and formaldehyde.Comparing with the pure BION and BiOBr,the ultrathin two-dimensional Bi₂O₂?OH??NO₃?/BiOBr heterojunctions had a better visible light photocatalytic performance.The stablity of the samples were evaluated by recycling degradation experiments and XRD spetra after degradation.The results showed that the ultrathin two-dimensional BION/BiOBr heterojunctions exhibited excellent repetitive stability.In addition,the samples were characterized by ESR,photocurrent,electrical impedance and photoluminescence spectra.It confirmed that the BION/BiOBr ultrathin photocatalyst had lower recombination rate and the main active radicals were superoxide radicals.?3?The composite material of BION/Bi₂MoO₆ was synthesized by one-pot hydrothermal method.The as-prepared samples were characterized by XRD,SEM,UV-Vis DRS and PL.The results indicated that the composites of BION and Bi2MoO6?donated as BMO?were successfully synthesized,meanwhile the crystal structure did not change.As for the composites,red shift to the optical absorption edge of BMO was observed and the photoresponse range became larger.Tetracycline was used as modern pollutant to investigate the photocatalytic performance and mechanism of BION/BMO composites.Compared with pristine BION and BMO,the BION/BMO composites possessed higher photodegradation efficiency.The optimum ratio of BION to BMO was determined to be 1:1;also it can be seen that the emission intensity of it was lower than those of pure BiOBr and other composites,suggesting that the recombination of photo-induced electron–hole pairs was hampered.The trapping experiment results suggested that the O₂^-?was the main active radicals.The synthesized BION/BiOBr two-dimensional ultrathin heterojunctions and BION/BMO composites have potential applications in photocatalytic degradation of tetracycline.Moreover,the stripping method of BION/BiOBr two-dimensional ultrathin heterojunctions used in this study has certain reference significance for the synthesis of Bi-based two-dimensional ultrathin materials.