Ionic liquid assisted combustion synthesis of ZnO and its modification by AuSn bimetallic nanoparticles: An efficient photocatalyst for degradation of organic contaminants

Highlights: • AuSn incorporated in ZnO which was prepared by ionic liquid assisted SCS method. • Catalytic efficiency was studied towards the degradation of organic contaminants. • 3Au1Sn/ZnO showed much higher efficiency with respect to other nanocatalyst. • Well-dispersed and intimate connected AuSn can improve catalytic performance. • Enhanced light absorption and higher surface area plays major role in the activity. -- Abstract: AuSn/ZnO nanocatalyst was synthesized by a two-step synthetic approach in which AuSn alloy bimetallic nanoparticles (NPs) were incorporated into presynthesized ZnO in 1-butyl 3-methylimidazolium (BMIMBF₄) ionic liquid (IL) via combustion route. The structure, morphology, and optical properties of the above synthesized material were analysed by using various analytical techniques, including X-Ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive Spectroscopy Mapping (EDS), UV–vis Spectroscopy, Photoluminescence, Nitrogen Adsorption–Desorption, photoelectrochemical measurements and X-Ray Photoelectron Spectroscopy (XPS). The average particle size and the homogeneous distribution of AuSn nanoparticle over the surface of ZnO was analyzed by using TEM. XPS analysis provides information regarding the elemental structure of individual species as well as the possible electronic interaction between the nanoparticles. The photocatalytic activity of the nanocatalyst was studied towards the degradation of organic contaminants such as rhodamine B dye, 2-chlorophenol, phenol, 2,4- dichlorophenol and 2,4-dinitrophenol. After 90 min the complete degradation of Rhodamine B (95%) and phenol (94%) and its derivatives was achieved under visible irradiation. The high photoactivity of 3Au1Sn/ZnO can be attributed to the combined effect of enhanced light absorption intensity, longer lifetime of electron-hole pair, lower electron-hole recombination rate, increased stability, higher surface area and the synergistic effect between the metal nanoparticles and support material. It is expected that our current work could open promising prospects for the utilization of Sn-based bimetallic system as a potential visible light photocatalyst for environmental applications.