Research Progress on ZnO Based Nano-photocatalysts
When the photon energy is greater than or equal to the band gap width of the semiconductor material,the electrons absorb the photon energy,jump to the conduction band,and leave holes in the valence band.At this time,part of the electrons and holes migrate to the surface of the catalyst,react with oxygen or water to generate free radicals,and conduct redox reaction with pollutants,thus degrading pollutants.The common photocatalytic materials are ZnO and rare-earth doped ZnO nanomaterials.The common preparation methods include precipitation,hydrothermal,sol-gel and so on.The introduction of rare earth ions will form a large number of defect levels and impurity levels in the band gap of ZnO.The existence of these levels promotes the multi-photon process,which promotes the absorption of visible light by the ZnO lattice,promotes the separation of electron holes,and promotes the improvement of photocatalytic ability.
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