Noble metal-like behavior of plasmonic bi particles as a cocatalyst deposited on (BiO)₂CO₃ microspheres for efficient visible light photocatalysis

Novel plasmonic Bi nanoparticles deposited in situ in (BiO)₂CO₃ microspheres (Bi/BOC) were fabricated via a one-pot hydrothermal treatment of bismuth citrate, sodium carbonate, and thiourea. Different characterization techniques, including XRD, SEM, TEM, XPS, UV–vis DRS, PL, time-resolved fluorescence spectra, and photocurrent generation, were performed to investigate the structural and optical properties of the as-prepared samples. The results indicated that the Bi nanoparticles were generated on the surface of (BiO)₂CO₃ microspheres via the in situ reduction of Bi³⁺ by thiourea. The Bi nanoparticle deposited (BiO)₂CO₃ microspheres were employed for the photocatalytic removal of NO in air under visible light irradiation, and the sample exhibited a drastically enhanced photocatalytic activity and oxidation ability. The highly enhanced activity was attributed to the cooperative contribution of the surface plasmon resonance (SPR) effect, the efficient separation of electron–hole pairs, and the prolonged lifetime of charge carriers by the Bi nanoparticles. The behavior of Bi nanoparticles as a cocatalyst for enhancing photocatalytic activity is similar to that of noble metals in photocatalysis. When the amount of thiourea was controlled at 5%, the corresponding Bi/BOC sample exhibited the highest photocatalytic activity and exceeded those of other types of visible light photocatalysts, such as nonmetal-doped TiO₂, C₃N₄, BiOBr, N-doped (BiO)₂CO₃, and even Ag-deposited (BiO)₂CO₃. The visible light photocatalytic activity of Bi/BOC was also tested at different wavelengths and with different light sources. It was found that the high activity could be well maintained even under a 5 W energy-saving light, demonstrating its great potential in practical applications. On the basis of DMPO-ESR spin trapping, the active species produced from Bi/BOC under visible light were hydroxyl radicals. Bi/BOC could produce more hydroxyl radicals in comparison to BOC due to the SPR effect of Bi, contributing to the enhanced oxidation ability. Furthermore, the Bi/BOC sample displayed a high photochemical stability under repeated irradiation. This work demonstrated the great feasibility of utilizing low-cost Bi nanoparticles as a substitute for noble metals to enhance visible light photocatalysis. © 2014 American Chemical Society.