Photocatalytic Performance of Zinc Oxide and Metal-Doped Zinc Oxide for Various Organic Pollutants

Zinc oxide (ZnO) has a high photocatalytic potential to decompose volatile organic pollutants into CO2 and H2O which depend on their physical properties, such as particle shape and size, band gap, type of dopant, and optical and structural properties. Using 93 references listed in this review, the relationship between metal dopant and synthesis methods to the efficiency of ZnO and composite ZnO-metal in degrading pollutants for photocatalyst applications is studied. The basic principles of the photocatalyst process is described when the electrons at the valence band of ZnO get the energy from solar spectrum, generate the charge (electron and hole), and then continue to react with superoxide and water, resulting in radical atoms which break the bonds of organic pollutants. Rare earth dopants have the highest efficiency up to 100 % at 15 min irradiation. Conclusions and future prospects of ZnO and metal-doped ZnO are also discussed. Perspectives and challenges of the future development of ZnO-based photocatalysts are evaluated.