Study On Modification And Photocatalytic Performance Of Bismuth-based Semiconductor Photocatalyst

As human society continues to develop,the energy crisis and environmental pollution problems are becoming more and more serious.The photocatalytic and piezoelectric catalytic technologies of semiconductor materials are playing an increasingly important role in solving these problems.This paper mainly studies two kinds of semiconductor catalysts,which are a basic salt of bismuth[Bi₆O₆?OH?₃]?NO₃?₃·1.5H₂O and bismuth titanate(Bi₄Ti₃O₁₂).Both materials have poor photocatalytic performance due to their inherent properties.In this paper,different modification methods were used to effectively enhance their catalytic activity under visible light.At the same time,the potential of Bi₄Ti₃O₁₂ as a ferroelectric material in the field of piezoelectric catalysis was further explored through modification.The main research results are as follows:?1?Using glucose as carbon source,carbon-doped[Bi₆O₆?OH?₃]?NO₃?₃·1.5H₂O was prepared by hydrothermal method,and then Bi nanoparticles were reduced in situ by Na BH₄.The impurity level introduced by carbon doping reduces the band gap of the basic salt,and the plasmon resonance effect?SPR?of Bi nanoparticles effectively enhances the absorption of visible light.The synergy of the two significantly enhances the catalytic activity of the composite photocatalyst.The rate of degradation for rhodamine B?Rh B?of composite photocatalysts under visible light is 1.89 times and 10.41 times that of carbon-doped basic salt and original basic salt,respectively.?2?Lanthanum-doped bismuth titanate nanosheets(Bi_3.25La_0.75Ti₃O₁₂)were prepared by hydrothermal method,and then a large amount of surface oxygen vacancies were introduced into it by simple and economic vacuum heat treatment.By adjusting the temperature and time of vacuum activation,the ratio of oxygen vacancies on the surface of the nanosheet can be controlled,which in turn affects its catalytic activity under visible light.Samples activated for3h at a temperature of 330?have the best catalytic activity,and the degradation efficiency of hexavalent chromium Cr?VI?or methyl orange?MO?under visible light is significantly improved.Moreover,the synergistic catalysis existing between the two pollutants makes simultaneous photocatalytic degradation of Cr?VI?and MO more efficient than single component degradation.?3?Lanthanum-doped bismuth titanate nanosheets were prepared by molten salt method.And as the doping amount of lanthanum increases,the thickness of nanosheets continues to decrease,and the rate of piezoelectric catalytic degradation of Rh B under dark field ultrasound exhibits a law of increasing first and then decreasing.Sample Bi_2.5La_1.5Ti₃O₁₂ showed the best catalytic activity.Under 60 minutes ultrasonic treatment,Rh B was basically degraded completely,and its rate was 6.63 times that of the original bismuth titanate.Lanthanum doping enhances the polarization electric field strength of bismuth titanate,under ultrasonic conditions,the free charge is effectively separated,and the redox reaction with H₂O and dye molecules occurs,thus enhancing the catalytic activity.