More reactive oxygen species generation facilitated by highly dispersed bimodal gold nanoparticle on the surface of Bi2WO6 for enhanced photocatalytic degradation of ofloxacin in water.

An essential strategy to eliminate emerging contamination in water is to initiate more reactive oxygen species (ROS) in the catalytic systems. 0.14 wt.% Au loaded Bi2WO6 (Bi2WO6/Au-400 °C) was fabricated after 400 °C annealing with the assistance of glutathione for Au atom anchoring and stabilization on Bi2WO6 surface. Bimodal Au size distribution of highly dispersed small size clusters (0.5 ± 0.1 nm) and large size nanoparticles (6.3 ± 1.0 nm) simultaneously existed on Bi2WO6 nanosheets in Bi2WO6/Au-400 °C, which were verified through high resolution transmission electron microscopy (HR-TEM). 95% of ofloxacin (OFX) was degraded over Bi2WO6/Au-400 °C in 180 min under visible light irradiation with a reaction constant of 24.5 × 10-3 min-1, which showed 3.0 and 2.5-fold enhancement compared with bare Bi2WO6 and unimodal Bi2WO6/Au-500 °C (annealed at 500 °C, Au NPs (8.6 ± 1.0 nm)), respectively. The enhanced catalytic activity originated from the additional ROS production that initiated by photo-induced electron transported from small Au clusters to large Au NPs through the conduction band of Bi2WO6. Moreover, it still maintained a good stability after five cycling performance and the total cost of 10 g Bi2WO6/Au-400 °C was estimated to be 6.78 $. Lower-content of bimodal Au NPs decorated Bi2WO6 catalyst possesses high efficiency to degrade pollutant and lower cost, which provides a promising alternative in practical environmental remediation by photocatalysis.