Bimetallic Nanoparticles Supported on Cr2O3 Microspheres As Heterogeneous Photocatalysts for Light-Induced Alcohol Oxidation

Abstract

The development of environmentally benign photocatalytic processes with high reaction rate and high selectivity has always been a significant challenge. Plasmonic metal nanoparticles have been promising light-driven photocatalysts in chemical transformations due to their localized surface plasmon resonance (LSPR). In this study, bimetallic catalysts with various loadings and Ag/Au ratios supported on Cr2O3 microspheres were synthesized and evaluated as heterogeneous photocatalysts for benzyl alcohol oxidation under monochromatic 532 nm laser irradiation. Au and Ag nanoparticles were uniformly decorated on Cr2O3 microspheres by deposition precipitation and wet impregnation method respectively. The optical and physical properties of the as-prepared photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-Ray spectroscopy (EDX), diffuse reflectance spectroscopy (DRS), X-Ray diffraction (XRD) and RAMAN spectroscopy. The bimetallic Ag-Au-Cr2O3 catalysts presented an enhanced photocatalytic activity compared to monometallic catalysts. It should be noted that the enhanced photocatalytic activity was dependent on Ag-Au ratio. Specifically, 0.5 wt.% Ag - 3 wt.% Au /Cr2O3 photocatalyst showed the highest photocatalytic activity, achieving up to 91.2% conversion and 98.5 % selectivity of the targeted benzaldehyde. The remarkable photocatalytic performance over bimetallic nanoparticles can be ascribed to the synergistic effect of Ag-Au alloy nanoparticles under visible light irradiation. Phototelectrochemical tests were performed to further evaluate the role of plasmon mediated charge transfer in the activity of bimetallic nanoparticles.