Construction Of Bi₂₄O₃₁Br₁₀-based Composite Photocatalysts For Degradation Of Organic Pollutants

As a new photocatalyst,Bi₂₄O₃₁Br₁₀,excellent two-dimensional layered structure,suitable band gap energy and good stability,has attracted extensive attention in the field of photocatalysis.However,the photocatalytic performance of Bi₂₄O₃₁Br₁₀ is weakened due to its low efficiency of photoelectron-hole separation and low utilization of visible light.Consequently,construction of Bi₂₄O₃₁Br₁₀-based heterojunction compound photocatalysts were designed by the method of solvothermal and room temperature chemical deposition.The morphologies,compositions and photochemical properties of the as-prepared composite photocatalysts were studied by a variety of characterization methods.The photocatalytic degradation of pollutants of efficiency and cycling stability were analyzed,and the mechanism of the enhancement of photocatalytic degradation activity was investigated by free radicals trapping experiment.The main research contents of this paper are as follows:（1）Preparation of AgI/Bi₂₄O₃₁Br₁₀ 0D/2D composite photocatalyst and its photocatalytic performance for degradation of rhodamine B（Rh B）.The Bi₂₄O₃₁Br₁₀ nanosheets were synthesized by solvothermal method,and then AgI nanoparticles（30-40 nm）were loaded onto Bi₂₄O₃₁Br₁₀ nanosheets by precipitation to construct the 0D/2D composite structure Specifically,AB-30（mass fraction of AgI,30%）composite exhibited remarkable photocatalytic activity of 97.6%towards Rh B degradation under 120 min of simulated sunlight irradiation,and the degradation rate constant（k）of Rh B was approximately 20.7 and 2.9 times higher than that of pure Bi₂₄O₃₁Br₁₀ and AgI,respectively.The improvement of photocatalytic performance of as-prepared AgI/Bi₂₄O₃₁Br₁₀ heterojunction composites was ascribed to the synergistic effect of wide visible-light harvest capacity and the rapid transfer and separation efficiency of charge carriers.DRS analysis validated that the introduction of AgI could broaden the visible-light absorption of AgI/Bi₂₄O₃₁Br₁₀ composite.The results of EIS,PL and photocurrent response tests showed that AgI/Bi₂₄O₃₁Br₁₀ composite possessed fast the efficient separation and migration of photogenerated charge carriers.Based on capture experiments,DRS and Mott-Schottky experiments,a probable photocatalytic mechanism of Z-scheme heterojunction between Bi₂₄O₃₁Br₁₀ and AgI was proposed.In addition,the results of the cycle experiment and fresh and used of XRD and SEM analysis of the photocatalyst showed that the AgI/Bi₂₄O₃₁Br₁₀ composite photocatalyst had good photocatalytic stability and structural stability.（2）Fabrication of AgI/Bi₂₄O₃₁Br₁₀/RGO 0D/2D ternary composite photocatalyst for degradation of tetracycline（TC）and Rh B.The Bi₂₄O₃₁Br₁₀/r GO binary composite was prepared by one-pot solvothermal method.And then AgI nanoparticles were deposited on Bi₂₄O₃₁Br₁₀/r GO nanosheets to fabricate AgI/Bi₂₄O₃₁Br₁₀/r GO 0D/2D ternary composite photocatalyst by deposition method.The results illustrated that the AgI/Bi₂₄O₃₁Br₁₀ ternary composite photocatalyst modified by RGO had higher specific surface area and more efficient carrier separation efficiency,and the visible light absorption capacity is significantly improved between500 nm and 800 nm.The catalytic performance of the samples was evaluated by degradation of TC and Rh B.The AgI/Bi₂₄O₃₁Br₁₀/RGO ternary composite catalyst exhibited remarkable photocatalytic activity,which 92.1%of TC was degraded within80 min under simulated sunlight irradiation,And the degradation rate constant is 0.024min^-1.In addition,the AgI/Bi₂₄O₃₁Br₁₀/RGO compound degraded 97.1%of Rh B within75 min,and the degradation rate constant(0.041 min^-1)was 13.2 and 4.2 times than that of pure Bi₂₄O₃₁Br₁₀ and AgI,respectively.The enhancement of photocatalytic performance of as-prepared AgI/Bi₂₄O₃₁Br₁₀/RGO compound was attributed to the synergy effect of Bi₂₄O₃₁Br₁₀,AgI and RGO:on the one hand,the formation ofⅡheterojunction promoted separation of photo-induced electronic and holes;on the other hand,RGO as an electron acceptor and with good electrical conductivity,which promotes the transfer of photo-induced electron between AgI and Bi₂₄O₃₁Br₁₀,and improves the specific surface area and the absorption capacity of visible light.