Facile and inexpensive synthesis of Ag doped ZnO/CNTs composite: Study on the efficient photocatalytic activity and photocatalytic mechanism

Abstract

In present study, an effective photocatalytic activity for Reactive Black GR and metronidazole degradation was evaluated using microwave-assisted prepared Ag doped ZnO, ZnO/CNTs and Ag doped ZnO/CNTs composites as photocatalyst under visible and sunlight irradiation. The photocatalysts were extensively characterized using a variety of standard tools. The results of XRD and XPS analysis identified the presence of Ag in synthesized composites. The introduction of Ag into the lattice of ZnO deteriorated crystal growth with the reduction of crystallites size, suppressed electron-hole pair's rate and shift in the optical absorption response from UV to visible region due to its surface plasmon resonance effect. The presence of CNTs enhanced the specific surface area of the composites meanwhile content of hydroxyl oxygen at the surface reduced concurrently, that increased the surface hydroxyl groups in the framework of ZnO. Moreover, CNTs acted as electron sink to significantly reduce the photocorrosion of ZnO, consequently improving the photostability of the synthesized samples. An appropriate amount of Ag (2 wt%) and CNTs (2 wt%) (AZC1 composite) was measured to be an optimized composition in accordance with the highest efficiency of the photocatalytic activity. The photocatalytic activity of AZC1 composite for the degradation of Reactive Black GR was measured to be 100% within just 30 min of solar light irradiation and 120 min of visible light illumination, while the corresponding metronidazole degradation was achieved within 40 min of solar light irradiation and 120 min of visible light illumination. A photocatalytic mechanism was proposed to explain the increased photocatalytic performance of the synthesized photocatalysts. This work represents an effective strategy to enhance the photocatalytic activity of ZnO and provides information to synthesize facile, inexpensive and eco-friendly Ag doped ZnO/CNTs photocatalysts.