In situ electrochemically etching-derived ZnO nanotube arrays for highly efficient and facilely recyclable photocatalyst

A facile two-step electrochemical method was for the first time presented to achieve ZnO nanotube (ZNT) arrays via in situ electrochemically etching electrodeposited ZnO nanorod (ZNR) arrays. The novel two-step synthesis strategy simultaneously considered the recyclability and high surface-to-volume (S/V) ratio of ZNT arrays used as the photocatalyst. Thus, the ZNT photocatalyst in the form of immobilized films was facilely reusable with little loss in degradation of methyl orange (MO). Further investigation on surface nanofeature and surface defect of as-synthesized ZNT arrays indicated that in comparison with the ZNR arrays, the higher photocatalytic activity of the ZNT arrays could not only be ascribed to a larger S/V ratio that allowed more organic substances to adsorbed to the surfaces of the catalyst, but also be related to the larger content of surface oxygen defects as revealed by photoluminescence (PL) spectra that may act as the active centers of the catalysts and capture the photogenerated electrons or holes, decreasing the recombination of the photogenerated electrons and holes. Our synthesis strategy highly paid attention to both the recyclability and biology safety issue that was induced by the discharge of nanoscale materials to natural environment.