Facile Synthesis of a Composite Comprising Multiwalled Carbon Nanotubes with a <i>p</i>–<i>n</i> Heterojunction of Zinc Oxide and Silver Oxide: Applications to Efficient Photocatalytic Decomposition of Emerging Hazardous Pollutants Under Sunlight

Bisphenol A (BPA) is a ubiquitous chemical in our daily lives, and its production and use are rapidly increasing, with a high risk of exposure to the environment and living organisms through water pollution. Therefore, we have developed efficient semiconductor-based photocatalysts coupled with multiwalled carbon nanotubes (MWCNTs) to treat and detoxify BPA-containing wastewater in the solar light spectrum. Specifically, to reduce the problems of a binary composite (ZAO) of zinc oxide nanoparticles and silver oxide nanoparticles, MWCNTs were integrated through a wet chemical, cocrystallization, and sealed-state high-pressure annealing process. Morphological investigations revealed that MWCNTs successfully formed a composite with ZAO, a p–n heterojunction, creating a ternary composite (ZnO–Ag2O@MWCNTs, ZAMC). Results showed that exciton recombination was substantially reduced. During 50 min of simulated sunlight exposure, ZAMC demonstrated superior photocatalytic performance, achieving 92.4% photodegradation of BPA. Similarly, the composite further demonstrated robust photocatalytic performance, resulting 96.1%, 92.0%, and 90.9% degradation of a cation dye, methylene blue, and pharmaceuticals, tetracycline and ibuprofen. A recyclability test showed only a 7.7% decrease in performance after five cycles. Similarly, ZAMC showed maximal photocatalytic activity at pH 12. The overall improved performance of ZAMC is credited to a well-developed heterojunction formation that leads to a reduced bandgap, a greater surface area, a greater abundance of active sites, and prolonged retention of the photogenerated excitons.