Hydrothermal synthesis of BiOBr and BiOBr/CNT composites, their photocatalytic activity and the importance of early Bi6O6(OH)3(NO3)3•1.5H2O formation

Bismuth oxybromide (BiOBr) is a novel visible light photocatalyst and when combined with multiwalled carbon nanotubes (CNT), it could lead to low electron/hole recombination rates, thus enhancing its photocatalytic activity. In this work, hierarchal BiOBr and BiOBr/CNT composites were successfully synthesized via hydrothermal method. The samples prepared were characterized for structural, morphological and optical properties via XRD, SEM, TEM and DRS. The influence of carbon nanotubes on various properties of BiOBr were studied and correlated. The impact of synthesis parameters (time and temperature) on structural properties was also studied. The photocatalytic degradation of phenol as model pollutant was carried out under visible light source to determine its photocatalytic activity. It was found that the presence of CNTs induced a growth in the crystallite size of the particles, which somewhat lowered the photocatalytic activity. As the CNT content increased in the sample so does the activity, due to the CNTs' visible light absorption capacity. Furthermore, a crystal orientation changes (crystallographic plane of (003)) were induced by varying several parameters, which were found to be influencing the activity as well, while the formation of Bi6O6(OH)(3)(NO3)(3)center dot 1.5H(2)O was also observed. Its presence enhanced the photocatalytic activity but induced an instability problem.