Photocatalytic Performance Of SnO₂QDs/BiVO₄ Heterojunction Photocatalysts

Photocatalysis is an important technology to solve environmental pollution,among which photocatalyst is the most important part of photocatalytic technology.SnO₂ is a typical semiconductor photocatalyst.In practical application,the wide band gap and high recombination rate of photogenerated charge of SnO₂ are not conducive to the photocatalytic reaction.Therefore,the photocatalysis performance of SnO₂ based photocatalyst materials is improved by morphology regulation,heterojunction and noble metal loading.The optical absorption capacity,carrier separation ability and photocatalytic enhancement mechanism of SnO₂ based photocatalyst materials are studied.The main contents are summarized as follows:1.SnO₂ QDs and BiVO₄ photocatalysts with particle size of 2-5 nm were synthesized by hydrothermal method,and SnO₂ QDs/BiVO₄ heterojunction with excellent photocatalytic performance was synthesized by wet impregnation method.After 120 min of simulated solar irradiation,the heterojunction（S7B3）with the mass ratio of SnO₂ QDs and BiVO₄ of 7:3 has the best photocatalytic activity.After 120 min of simulated solar irradiation,the degradation efficiency of S7B3 heterojunction for Rh B reached 83%,and the photocatalytic reaction rate was k=0.017 min^-1,which was 22.1 times and 37.8 times of SnO₂ QDs and BiVO₄,respectively.2.Under simulated sunlight,SnO₂ QDs/BiVO₄ photocatalyst follows a direct Z-type charge transfer mechanism.The electrons in the conduction band of SnO₂ QDs can migrate to the valence band of BiVO₄,and the separation of photogenerated electron holes is realized.On the conduction band of BiVO₄,the electrons react with O₂ to form·O₂^-.The holes remaining in the valence band of SnO₂ QDs react with H₂O to form·OH,which plays an important role in photocatalysis.In BiVO₄,the conduction band reacts with O₂ to form·O₂^-.The h⁺in the valence band reacts directly with Rh B.The hole in SnO₂ QDs valence band reacts with H₂O to form·OH.·O₂^-and h⁺play an important role in photocatalysis.3.Ag@SnO₂ QDs/BiVO₄ photocatalyst was synthesized by photo induced method.After 120 min of solar irradiation,the degradation efficiency of Rh B reached 93%,and the reaction rate was 0.0235 min^-1,which was 30 times and 1.28 times of SnO₂ QDs and SnO₂QDs/BiVO₄,respectively.At the same time,the cycling experiment also shows that Ag@SnO₂ QDs/BiVO₄ heterojunction has excellent stability.4.The mechanism of enhanced photocatalytic performance of Ag@SnO₂ QDs/BiVO₄indirect Z-type heterojunction under simulated sunlight was discussed.The SPR effect of Ag enhances the optical absorption of the heterojunction,and the Ag@SnO₂ QDs/BiVO₄meets the indirect Z-type heterojunction.The electrons in the conduction band of SnO₂QDs migrate to the Ag surface to form a Schottky barrier.At the same time,the photogenerated holes in the valence band of BiVO₄ are attracted to the Ag surface to combine with the photogenerated electrons and promote the separation of photogenerated charges.