Efficient visible light photocatalytic activity and enhanced stability of BiOBr/Cd(OH)2 heterostructures

Abstract

Novel BiOBr/Cd(OH)₂ heterostructures were synthesized by a facile chemical bath method under ambient conditions. A series of BiOBr/Cd(OH)₂ heterostructures were obtained by tuning the Bi/Cd molar ratios. The obtained heterostructures were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Optical properties were studied by UV-visible spectroscopy, diffuse reflectance spectroscopy and photoluminescence (PL). Photocatalytic studies on rhodamine B (RhB) under visible light irradiation showed that the heterostructures are very efficient photocatalysts in mild basic medium. Scavenger test studies confirmed that the photogenerated holes and superoxide radicals (O₂˙⁻) are the main active species responsible for RhB degradation. Comparison of photoluminescence (PL) intensity suggested that an inhibited charge recombination is crucial for the degradation process over these photocatalysts. Moreover, relative positioning of the valence and conduction band edges of the semiconductors, O₂/O₂˙⁻ and ˙OH/H₂O redox potentials and HOMO–LUMO levels of RhB appear to be responsible for the hole-specificity of degradation. Photocatalytic recycling experiments indicated the high stability of the catalysts in the reaction medium without any significant loss of activity. This study hence concludes that the heterojunction constructed between Cd(OH)₂ and BiOBr interfaces play a crucial role in influencing the charge carrier dynamics and subsequent photocatalytic activity.