Remarkably fast and reusable photocatalysis by UV annealed Cu 2 O-SnO 2 p-n heterojunction.

Powdered micro- or nano-particles photocatalyst has separation and recovery challenges, which may create a second pollution to environment and harmful to animals. To address those issues, SnO2 , Cu2 O and Cu2 O-SnO2 p-n heterojunction thin films are formed on glass substrates using efficient co-sputtering method that is commonly employed for large-area high-definition display panel. Using first-order kinetics, 100 °C ultraviolet (UV) annealed Cu2 O-SnO2 p-n heterojunction shows the superb fast degradation rate constant of 0.21 and 0.16 min-1 for methylene blue (MB) and methyl orange (MO) organic dyes, respectively, as photogenerated electron-hole pairs is increased. Record best degradation rate constants of 0.15 and 0.08 min-1 for respective MB and MO are still achieved even after four repeated cycles. The 100 °C UV annealed Cu2 O-SnO2 film catalyst displays greater degradation efficiency in both dyes, reaching 100% degradation at room temperature after 30 and 35 min of illumination for MB and MO respectively. The scavenger experiments show that hydroxyl (· OH) and superoxide radicals (· O2 - ) are the major active species in the degradation of dye. The 100 °C UV annealed Cu2 O-SnO2 film catalyst showed stability as well as reusability towards the dye degradation. As a result, the present work delivers an effective way to enhance the photocatalytic performance and also an easy recovery of the catalyst, which can be explored for various emerging pollutants.