Improving natural sunlight photocatalytic efficiency of ZnO nanowires decorated by iron oxide cocatalyst via a simple drop method

Abstract

In this study, iron oxide cocatalysts were deposited on the surface of ZnO nanostructures by a simple “drop, evaporation, calcination” method. Different deposition concentrations were studied, allowing to extend the photocatalyst absorption spectral range from UV to visible light, improving the photocatalytic efficiency under natural sunlight. An optimal deposition concentration of 0.06% molar percentage of iron against zinc led to improve by 11% the Methyl Orange (MO) photocatalytic degradation after 5 h under natural sunlight. No iron leaching was detected by ICP-MS analysis after the water purification by photocatalysis. By studying the lifetime stability of the optimal sample under a powerful UV light source, no losses of photocatalytic efficiency were recorded after several degradation cycles. Nevertheless, under this powerful light source, photocorrosion damages were observed with two antagonistic effects: (1) no photocorrosion effect for the ZnO regions covered by iron oxide and (2) ZnO photocorrosion and an acceleration of the dissolution of the ZnO nanostructures in uncovered regions. Thus, we assume the electron/hole delocalisation, which is responsible of the photocatalytic activity improvement, is also the reason justifying the ZnO photocorrosion acceleration of uncovered part. The photocorrosion phenomena was observed only under the powerful UV light source, not under natural sunlight.