Synergistic effect of a cobalt dopant and Au nanoparticles on the photocatalytic activity of ZnO nanorods

The photocatalytic performance of zinc oxide nanorods (ZnO NRs) still needs improvement. In this regard, the addition of noble-metal nanoparticles (NPs) and doping with transition metals can be employed. In this study, nanocomposites of ZnO NR/Au and Co-doped ZnO NR/Au NPs were synthesized by ultrasonic spray pyrolysis and hydrothermal method and subsequently used as photocatalysts for the degradation of methylene blue. Results revealed that pure ZnO NRs exhibit a degradation rate of only 28.8%, while ZnO NR/Au NPs exhibit a degradation rate of 37.3%, and Co-doped ZnO NR/Au NPs exhibit the highest degradation rate of up to 46.5%. Based on these results, the presence of Au on the ZnO NR surface can enhance the photocatalytic activity due to its key role as an electron sink, which reduces the recombination rate of electrons and holes, while the incorporation of Co into ZnO NRs can also enhance the number of crystal defects, which can widen the visible-light absorption spectrum. (paper)