Heterojunction And Spatially Separated Dual Cocatalysts For Synergistic Enhancement Of Photocatalytic Performance Of TiO₂ Hollow Nanosphere

Solar photocatalytic degradation of organic pollutants in wastewater is one of the effective ways for wastewater treatment,and the key is the development of high-performance photocatalytic materials.TiO₂ has attracted extensive attention due to its excellent anti-photocorrosion stability,abundant raw material,and low cost.However,the photocatalytic applications of TiO₂ nanomaterials are limited by the following two key factors:（1）large band gap（3.0-3.2 e V）and narrow spectral response region;（2）rapid recombination of photogenerated electrons and holes.Therefore,it is of great significance for constructing high-performance photocatalysts that how to broaden the absorption range of TiO₂ photocatalytic materials and achieve effective separation of photogenerated charges.In this work,TiO₂@WO₃ photocatalysts with red blood cell structure and hollow nanosphere structure was synthesized by template method and water bath method.WO₃ was directly grown on the surface of TiO₂,and then it was calcined to form a tight interface to improve the transfer and separation of charge carriers.Based on this work,hydrothermal and photoreduction methods were used to decorated spatially separated the dual cocatalyst MnO_x and Au nanoparticles on the inner and outer surface of the hollow structure TiO₂@WO₃ heterojunction.On the one hand,the plasmon resonance absorption（480-650 nm）of Au nanoparticles and optical absorption（<480 nm）of WO₃ are not overlap and the loaded Au nanoparticles can further broaden the solar absorption ability of TiO₂/WO₃ hollow microspheres.On the other hand,the spatially separated dual cocatalysts can drive the electrons and holes near the surface to flow in opposite directions,inhibiting the recombination of photogenerated carriers,improving the separation efficiency of photogenerated carriers,and further enhancing the photocatalytic performance of TiO₂@WO₃.In addition,it was investigated that the mechanism of synergistic enhancement of photocatalytic performance by heterojunction hollow microspheres and the spatially separated double cocatalysts.The main research content is as follows:（1）TiO₂@WO₃ photocatalysts with red blood cell and hollow nanosphere structure was synthesized by using tetrabutyl titanate and Na₂WO₄·2H₂O as precursors,and WO₃ was directly grown on the surface of the TiO₂ by water bath method.A series of TiO₂@WO₃ composites were obtained by regulating the ratio of precursors,and the obtained TiO₂@WO₃ products were used to degrade methyl orange（MO）and phenol under xenon lamp irradiation.When the W/Ti atom ratio was 10%(TW_0.1),the degradation performance was the most outstanding,and 98%methyl orange could be degraded within 25 min,which was 18.4 times and40.9 times higher than that of pure TiO₂ and WO₃,respectively.70%phenol could be degraded within 100min,which was 6.14 times and 7.44 times higher than that of pure TiO₂ and WO₃,respectively.Furthermore,it has excellent photocatalytic cycle stability.（2）Based on the previous work,the hydrothermal method and the photoreduction method were used to construct MnO_x@TiO₂@WO₃@Au hollow nanospheres photocatalysts by loading the cocatalysts MnO_x and Au nanoparticles on the inner and outer surfaces of TiO₂@WO₃ hollow nanospheres,respectively.In he obtained photocatalysts,Au nanoparticles not only broaden the visible light absorption of TiO₂@WO₃,but also enhance the transfer of photogenerated electrons and holes in the opposite direction with the spatially separated MnO_x cocatalyst.Compared with TiO₂@WO₃,MnO_x@TiO₂@WO₃ and TiO₂@WO₃@Au and pure TiO₂ and WO₃,MnO_x@TiO₂@WO₃@Au hollow nanospheres decorated with dual cocatalysts exhibited the best photocatalytic activity of the degradation of phenol and 98%of phenol was degraded within 100 min.This work has fully demonstrated that the combination of spatially separated cocatalysts and heterostructures is one of the effective strategies to obtain high-performance photocatalysts.