Fabrication of wire mesh–supported ZnO photocatalysts protected against photocorrosion

In this work a catalyst consisting of high surface area ZnO nanoflowers supported on a stainless steel wire mesh was synthesized by hydrothermal growth, and tested for the catalytic photodegradation of methylene blue under UV irradiation. The stability of the photocatalyst was evaluated by assessing the evolution over several reaction stages of catalytic activity and ZnO loss. The initial high activity of this catalyst was followed by a significant decrease after successive reaction cycles due to the dissolution of the ZnO as a consequence of photocorrosion. Impregnation of the catalyst with small amounts of silver enhanced its initial catalytic activity, but failed to produce the photostabilisation of the catalyst that has been reported in the literature. Dip-coating the photocatalyst (either undoped or silver doped) with a diluted polysiloxane solution produced a transparent polysiloxane coating that completely prevented photocorrosion and allowed a stable catalytic activity to be maintained over 8 reaction stages at values higher than those obtained with uncoated catalysts after just 2-3 reactions stages with negligible loss of ZnO.