Polyol-assisted coprecipitation synthesis of BiOI photocatalyst and its activity to remove NOx

BiOI samples were synthesized by coprecipitation method in glycerol medium at 100 degrees C followed by a thermal treatment of the precursor powders at 250 degrees C. Additionally, the polyols mannitol and sorbitol were incorporated in order to revise the effect of -OH groups in the physicochemical properties of the final product. Through X-ray powder diffraction, scanning and transmission electron microscopy studies revealed that the addition of mannitol resulted in the formation of BiOI nanosheets with specific anisotropic growth along (102) crystal orientation. XPS analysis showed differences in the organic material adsorbed on the surface of samples that justified the high NO conversion degree (96%). The analysis by N-2 adsorption-desorption isotherms by BET protocol revealed specific surface areas around 40 m(2) g(-1). The addition of mannitol reduced the time of reaction from 48 to 12 h for the formation of BiOI, which was able to act as photocatalyst with a NO conversion degree of 96% (BiOI-M12C). The selectivity of the complete oxidation reaction to the formation of NO3- ions was confirmed by colorimetric analysis revealing a value of 97% and discarding the formation of NO2 as main product of photocatalytic reaction. Electron paramagnetic resonance (EPR) revealed that the main radical in the mechanism of photooxidation of NO was the superoxide ion (O-center dot(2)-).

Automated summary

BiOI samples were synthesized using coprecipitation method and the addition of mannitol resulted in the formation of BiOI nanosheets with specific anisotropic growth. The different adsorbed organic materials on the sample surface justified the high NO conversion degree.