Fabrication of flexible sheets of Cu/CuO/Cu₂O heterojunction nanodisks: A dominant performance of multiple photocatalytic sheets under natural sunlight

Development of immobilized photocatalyst on a flexible sheet is an urgent need for wastewater treatment in industry. A facile method is established to fabricate flexible Cu/CuO/Cu₂O heterojunction nanodisks. The existence of both phases of CuO and Cu₂O are identified by XRD, XPS and Raman spectroscopy. The combined CuO and Cu₂O phases having different bandgaps are responsible for an improved photodegradation due to increased charge separation efficiency and an extended range of photoexcitation while decreasing recombination of photogenerated electrons and holes. For the first time, a single to several sheets of Cu/CuO/Cu₂O heterojunction nanodisk are introduced to investigate the performance of photodegradation and continued to maximum of eight sheets. The superior photocatalytic performance of Cu/CuO/Cu₂O heterojunction on rhodamine dye solution is observed and compared with recent reports related to the similar architecture. It is identified that the part of photoexcited electrons are consumed to oxidizes O₂ to generate superoxide radicals due to the closer oxidation potential between O₂/•O₂⁻ and Cu₂O, besides the transfer to the conduction band of CuO. Hence, the proposed flexible photocatalytic sheet benefits for the stable and continuous usage in a large-scale process to degrade toxic pollutants without sacrificing their photocatalytic activity.