In situ decoration of plasmonic Ag nanocrystals on the surface of (BiO)2CO3 hierarchical microspheres for enhanced visible light photocatalysis

Abstract

Novel plasmonic 0D Ag nanocrystal decorated 3D (BiO)₂CO₃ hierarchical microspheres were fabricated with a one-pot hydrothermal method. The as-prepared samples were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N₂ adsorption–desorption isotherms, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, photoluminescence spectra, ns-level time-resolved fluorescence spectra, photocurrent generation and EIS measurement. The results indicated that the 0D Ag nanoparticles were deposited on the surface of 3D (BiO)₂CO₃ hierarchical microspheres. The deposited Ag nanoparticles were reduced from Ag⁺ by the citrate ions from bismuth citrate. The photocatalytic activity of the as-prepared samples was evaluated towards the degradation of NO at ppb-level under visible light irradiation. The intermediate NO₂ was monitored on-line during the photocatalytic reaction. The pure (BiO)₂CO₃ microspheres exhibited decent visible light photocatalytic activity because of the surface scattering and reflecting (SSR effect) resulting from the special 3D hierarchical architecture. The Ag-decorated (BiO)₂CO₃ microspheres (Ag/BOC) exhibited greatly enhanced photocatalytic activity, photocurrent generation and promoted NO₂ oxidation compared to the pure (BiO)₂CO₃ microspheres. The enhanced photocatalytic activity and photocurrent generation of Ag/BOC was ascribed to the cooperative contribution of the surface plasmon resonance (SPR effect), efficient separation of electron–hole pairs and prolonged lifetime of charge carriers induced by Ag nanoparticles. The photocatalytic performance of Ag/BOC was dependent on the content of Ag loading. When the amount of Ag is controlled at 5%, the highest photocatalytic performance can be achieved. Further increasing the Ag loading content promotes aggregation of the Ag particles and transforms the uniform microspheres into non-uniform microspheres, which is not beneficial to improving the activity. Importantly, the as-prepared Ag/BOC composites exhibited high photochemical stability after multiple reaction runs. The concepts of enhancing the activity through the SSR and SPR effects provide a new avenue for the development of efficient noble metal/bismuth-based plasmonic photocatalysts with attractive nano/micro architectures for efficient visible light photocatalytic activity.