Immobilization of zinc oxide-based photocatalysts for organic pollutant degradation: A review

Immobilization of ZnO-based photocatalyst on supportive substrates has gained attention expeditiously in the last decade in the field of organic pollutant removal. In this review, recent development of supportive substrates along with immobilization methods and photocatalytic performances of the immobilized system were discussed. Until now, glass substrate was the most commonly reported, while polymeric materials that offer stretchability, handling flexibility and low fabrication cost appeared to be the promising substrates. Hydrothermal method was favourable for the immobilization of ZnO-based photocatalysts. This was attributed to its ability to control size and morphology of ZnO nanostructures. The ZnO-based photocatalysts worked satisfactorily in solutions with pH range of 6.5–8. Future development of the immobilized ZnO-based photocatalysts shall address issues including flexible supporting substrates, specific surface area increment for both photocatalysts and supportive substrates, lifespan of photogenerated charge carriers, stability, and applicability to industrial-scale operations.