Construction of Ag nanosphere-decorated ZnO composite films and Ag’s crucial role in boosting photocatalytic performance

ZnO films immobilized on SUS316L wire mesh are prepared by a conventional low-temperature hydrothermal method. To improve their photocatalytic activity, we decorate the films with Ag nanospheres using the impregnating photoreduction treatment. The prepared films are characterized using a series of advanced analytical methods. The SEM and EDS results show that continuous films consisting of ZnO nanorods shaped as six-prism cones are formed in the hydrothermal process. Ag 0 nanospheres with the dimension from a few to several hundred nanometers decorate the ZnO nanorods. Compared to the individual ZnO film, Ag–ZnO heterojunction improves the absorption of UV and visible light, decreases the bandgap value, and shifts the band position toward more positive potentials. It also inhibits the recombination of photo-inspired electrons and holes, thereby improving the photodegradation ability. The photocatalytic performance of Ag–ZnO composite films increases at most 5.6-fold compared to the bare ZnO film. Active holes (h + ), superoxide ( \(\bullet {\text{O}}_{2}^{ - }\) ), and hydroxyl ( \(\bullet {\text{OH}}\) ) species play significant roles in organic dye RhB photodegradation under simulated sunlight irradiation.