One-step formation of synergistic ZnO/SnO2 composite nanostructures derived from annealing of crystalline ZnSn(OH)6 nanocubes for enhanced catalytic degradation of organic pollutants

Abstract

Binary metal oxides/hydroxides derived primary metal oxide composites have a pivotal role in diverse applications because of the beneficial interfacial contact, good synergism, high porous nature, and high stability. The current work deals with the derived ZnO/SnO2 composite nanostructures from post-annealing crystalline ZnSn(OH)6 (ZTO-RT) nanocubes, initially synthesized via a single-step hydrothermal synthesis method. First, the pristine ZTO-RT is synthesized @ 180 °C in a hydrothermal autoclave. Further, the transformation of ZTO-RT to ZnO/SnO2 composite nanostructures is performed at two different annealing temperatures of 500 °C (ZTO-DV-500) and 750 °C (ZTO-DV-750) in the vacuum. The respective samples' physical characterization was studied and compared using various analytical techniques. The X-ray diffraction analysis affirms the amorphous nature of ZTO-DV-500 and the poly-crystalline nature of ZTO-DV-750. The nanocube morphologies of the samples are retained even at high-temperature sintering. The existence of metal-oxygen bonds on the surface of the ZnO/SnO2 composite is sustained by X-ray photoelectron spectroscopy. ZTO-DV-750 has larger pores (pore volume - 0.091 cm3 g−1) than the ZTO-DV-500 (0.051 cm3 g−1). In the presence of NaBH4 aqueous solution, the enhanced rhodamine B dye degradations of ZTO-DV-750 are observed. At low RhB concentrations (5 mg L−1), the ZTO-DV-500 and ZTO-DV-750 rate constants are determined to be 0.099 and 0.156 min−1, respectively, while at high concentration (10 mg L−1), these values are 0.043, and 0.091 min−1. Therefore, the ZTO-DV-750 composite has shown potent catalytic activity with NaBH4 over ZTO-DV-500 to decolourise organic dyes.