Enhancing Mechanism of Visible-light Photocatalytic Activity of Bi2O2CO3

This work studied the effect of oxygen vacancies in the Bi2O22+ and CO32- layers on the crystal structures, electronic and optical properties of Bi2O2CO3 with density functional theory (DFT) methods. The cell parameters and Bi-O bond lengths of Bi2O2CO3 before and after the introduction of oxygen vacancies are similar, so the effect of oxygen vacancies on crystal structures can be ignored. However, oxygen vacancies as electron donor provide electrons for the surrounding atoms, resulting in the change of charge distributions after the introduction of oxygen vacancies. Moreover, oxygen vacancies can reduce the band gap of Bi2O2CO3 and enhance the absorption of visible light. This effect of oxygen vacancies becomes more obvious with the increase of oxygen vacancy concentration. It is notable that the effects of oxygen vacancies in the Bi2O22+ and CO32- layers are different. Once an oxygen vacancy is introduced in the CO32- layer, a defect level appears within the band gap of Bi2O2CO3. The oxygen vacancies in the Bi2O22+ layer are more easily formed in Bi2O2CO3 than in the CO32- layer. Furthermore, the functions of oxygen vacancies in the Bi2O22+ layer for the reduction of band gap and the enhancement of visible light absorption are more effective than that of the oxygen vacancies in the CO32- layer, which is more obvious with the increase of oxygen vacancy concentration. When the concentration of oxygen vacancies in the Bi2O22+ layer reaches to 6.25%, the photoelectric properties of Bi2O2CO3 are the best. The DFT calculation results are consistent with the previous experimental results, and can provide insights into the mechanism for promoting the photoelectric properties of Bi2O2CO3 and other bismuth-based materials. © 2019, Science Press. All right reserved./Copyright