Photo-induced dissolution of Bi2O3 during photocatalysis reactions: Mechanisms and inhibition method

Photo-induced dissolution greatly limits the application of Bi2O3 photocatalyst in water treatment. In this study, mechanisms for the photo-induced dissolution of Bi2O3 were proposed. (1) Under UV light, h+ forms and diffuses through Bi2O3. (2) The h+, which reaches the surface of Bi2O3 and can be regarded as a monatomic oxygen ion (OS-), is weakly bonded to the crystal lattice. (3) Two OS- combine and the generated (O-O)2- ionic group is oxidized by h+, resulting in the release of O2 and dissolution of Bi2O3. However, modification of Bi2O3 using polyaniline (PANI) greatly inhibits Bi2O3 dissolution under UV. Under the PANI to Bi2O3 mass ratio of 1.5%, the concentration of produced Bi3+ significantly decreased from 2.02 to 0.27 mg/m2 with a high methylene blue (MB) degradation efficiency of 98.3%, thanks to the separation of h+ from VB-Bi2O3 to HOMO-PANI. This study provided the theoretical foundation for the modification and application of Bi2O3 in water treatment.