Zinc oxide (ZnO) has, in the past, been successfully applied as a photocatalyst to oxidise a wide range of organic compounds. Currently, powder is widely used, but is difficult to handle and reuse. ZnO can been immobilised on rigid supports to overcome these problems, however this can lower the surface area and photocatalytic activity. Consequently, in this work different ZnO thin films nanostructures have been studied, to systematically correlate surface morphology to photocatalytic activity, to find the optimal ZnO nanostructured thin film as a photocatalyst for industrial wastewaters.

Three different nanostructured films were compared to ZnO powder: vertically aligned nanorods, and two different woven structures – one formed by solution-precipitation on a clean glass support and the other by solution-precipitation on a magnetron-sputtered ZnO templated support. Azure B was as the model compound and the degradation rate was measured and compared with and without oxygen. The stability of each thin film to reuse was also determined.
It was found that the nanorod morphology had the highest reaction rate of the three nanostructures with k(1st order)=0.0012/min. This was only 26% of the reaction rate of the powder ZnO, where k(1st order)=0.0046/min. Using 5mL/s oxygen as additional oxidant only affected the rate for the nanorod morphology, increasing it by 33%. Unfortunately, all films had poor durability, SEM images showing morphological changes after only three uses for all films and chemisorption deactivation for the nanorod films. Future work is therefore concentrated on increasing the durability and activity of the nanorod structures.