Hierarchical ZnO nanorod-array films with enhanced photocatalytic performance

Hierarchical thin-film photocatalysts exhibiting surface roughness at two length scales were prepared by the consecutive formation of ZnO microstripes and ZnO nanorod-array. ZnO stripes with microscale roughness were fabricated after removing the ink-jet printed ribs. Then, nanoscale roughness was achieved by the growth of ZnO nanorods on the surface. The surface morphology and structural and optical properties were characterized by FESEM, X-ray diffraction, XPS, photoluminescence and UV-vis spectroscopy. The photocurrents of selectively grown ZnO nanorods under UV or visible light irradiation were investigated by scanning electrochemical microscopy with a scanning optical fiber. The surface comprising hierarchical microstructures and nanostructures not only increases the surface area of the photocatalyst but also helps the diffusion of organic dye during the photodegradation test. The photodegradation efficiency of the hierarchical thin-film photocatalyst was improved compared with the ZnO nanorod photocatalyst. Photocatalytic performance was further enhanced when Ag nanoparticles were deposited on the hierarchical photocatalyst.