PbO2 decorated ZnO-TiO2 core-shell nanoflower structures by zinc anodising for photo- and anodic degradation of Reactive Black-5 dye

Christian Harito, Syed Z.J. Zaidi, Dmitry V. Bavykin, Alysson S. Martins, Brian Yuliarto, Frank C. Walsh and Carlos Ponce de León

Abstract

This work shows that metallic zinc can be used as a low-cost substrate or electrode for photocatalyst and electrocatalyst use by anodising in mild bicarbonate solution. Electrochemical anodising was used to produce ZnO nanowires by controlling operational conditions and dip-coating the anodised surface with TiO₂ to produce a core-shell coating with photocatalytic properties. The PbO_2, which is known as good electrocatalyst, was electrodeposited over the ZnO-TiO₂ core-shell structure to alter its surface for electrocatalytic degradation of dye. The electrochemical and photocatalytic behaviours of the coatings were analysed for the removal of RB-5 dye as model pollutant. For the ZnO-TiO₂ core-shell, the photocatalytic removal mechanism was driven by the heterojunction photocatalytic effect of photocatalytically active anatase TiO₂ and wurtzite ZnO. Photocatalysis was switched to electrocatalytic behaviour after incorporation of PbO_2. Although the UV light might be blocked by PbO₂, the electrochemical degradation was enhanced due to the creation of OH free radicals over the PbO₂ particles decorating a ZnO-TiO₂ core-shell composite coating.