Fabrication of High-Crystallinity ZnO Nanorods for Photocatalytic Application

ZnO nanorods were synthesized on AZO substrates by chemical bath deposition, and were subsequently annealed under an air and vacuum ambient. Both annealing processes could improve the crystallinities of ZnO nanorods. The air-annealed ZnO nanorods showed higher crystallinity and partial reduction of oxygen-vacancy-related defects. The air-annealed ZnO nanorods exhibited a much higher photodegradation efficiency of 70% degradation for methyl red. In addition, as-grown ZnO nanorods were coated with undoped and Al-doped ZnO by mist chemical vapor deposition. Both coated thin layers modified the surface of ZnO nanorods, while the AZO-coated ZnO nanorods showed higher crystallinity and light absorption which resulted in the improvement in the photodegradation rate of methyl red. These findings demonstrate that appropriate annealing treatment and AZO surface engineering for ZnO nanorods are effective approaches for improving crystallinity, which leads to improvement of the photocatalytic efficiency of ZnO-based materials.