Silver nanoparticles-promoted bismuth titanate perovskite nanosheets photocatalyst for water purification

Photocatalysis is a recognized approach in the detoxification of pollutants and in water splitting. Such process is more appealing when it is driven by visible or solar light. In this context, we synthesized bismuth titanate perovskite oxide (Bi 4 Ti 3 O 12 , BTO) photocatalyst by sol–gel hydrothermal process. The resulting BTO materials was affected by the titania source and by the synthesis medium pH parameter. Titanium butoxide [Ti( n - BuO) 4 ] was much better than titanium isopropoxide [Ti( i - PrO) 4 ] in producing regular nanosheets with higher surface area, while 75 ml of 5.0  M sodium hydroxide was the optimum concentration for the synthesis of regular, thin, porous, almost equal size nanosheets. The photocatalytic activity of BTO was improved by loading silver nanoparticles (AgNPs) by photo-assisted reduction. The optimum weight percent of loading AgNPs was found to be 1.5 % because it led to the highest light absorbance, the smallest band gap energy, the minimum rate of electron-hole recombination. The photocatalytic degradation efficiency of 1.5 wt% Ag/BTO reached as high as 99.0 % of rhodamine B (RhB, 100 ml, 6 ppm of initial concentration) under 70 min of irradiating visible light (>420 nm). Moreover, pH had a strong influence on the photocatalytic activity of 1.5 wt% Ag/BTO, with pH=3.0 was the optimum, owing to its impact on the interaction between the positively-charged photocatalyst surface and the negatively-charged RhB molecules. It was found that superoxide radicals played key role in the photocatalytic activity.