Thermodecomposition synthesis of porous beta-Bi2O3/Bi2O2CO3 heterostructured photocatalysts with improved visible light photocatalytic activity

Novel porous beta-Bi2O3/Bi2O2CO3 p-n heterostructures were synthesized by partially decomposing porous Bi2O2CO3 at 300-375 degrees C. The structures, morphologies, optical properties, and specific surface areas of the as-synthesized samples were characterized by means of thermogravimetry and differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, UV-Vis spectroscopy, and N-2 gas adsorption. Two types of dyes, methyl orange (MO) and methylene blue (MB), were chosen as model organic pollutants to evaluate the photocatalytic activity of the as-synthesized samples. The porous beta-Bi2O3/Bi2O2CO3 p-n heterostructures exhibited much higher photocatalytic activity than beta-Bi2O3 and Bi2O2CO3 and MO and MB could be completely degraded within 24 and 50 min, respectively. In addition, phenol as a colorless organic pollutant was also chosen to further study the photocatalytic activity of Bi2O2CO3, beta-Bi2O3 and beta-Bi2O3/Bi2O2CO3. The beta-Bi2O3/Bi2O2CO3 heterostructures also showed much higher photocatalytic activity for the photodegradation of phenol than beta-Bi2O3 and Bi2O2CO3. The obtained results indicated that the formed p-n heterojunction in the porous beta-Bi2O3/Bi2O2CO3 composite significantly contributed to the improvement of electron-hole separation and the enhancement of photocatalytic activity. The mechanisms for the enhanced photodegradation of selected organic pollutants over the beta-Bi2O3/Bi2O2CO3 composite are discussed in this study.