Facile in-situ construction of granular–polyhedral Ag2O–Ag2CO3/lamellar Bi2O2CO3–Bi2MoO6 spherical heterojunction with enhanced photocatalytic activity towards pollutants

Abstract Using Bi2MoO6 hollow spheres as precursors, NaOH as etchant and atmospheric CO2 as carbon source, a granular–polyhedral Ag2O–Ag2CO3/lamellar Bi2O2CO3–Bi2MoO6 spherical heterojunction material with full–spectrum photocatalytic properties was gained through a one step in-situ precipitation approach. Granular Ag2O, polyhedral Ag2CO3 and lamellar Bi2O2CO3 were deposited in-situ on the interior and exterior surfaces of Bi2MoO6 hollow spheres to form nanospheres with a diameter of about 2.8 µm. Using methylene blue (MB) as a model molecule, the effect of NaOH concentration and silver oxide loading on the catalyst activity was investigated to screen out the best catalyst. The results showed that the degradation rate of Ag2O–Ag2CO3/Bi2O2CO3–Bi2MoO6-1/2-0.1 M was 3.45 and 2.71 times greater than those of Ag2O–Ag2CO3 and Bi2O2CO3–Bi2MoO6-0.1 M, respectively. Meanwhile, the visible light photocatalytic performance of Ag2O–Ag2CO3/Bi2O2CO3–Bi2MoO6 toward MB and antibiotics (tetracycline hydrochloride (TC), chlorotetracycline hydrochloride (CTC)) were also examined. Results confirm that the heterogeneous materials displayed the boosted photocatalytic activity for MB, TC and CTC. The boosted activity of the composite Ag2O–Ag2CO3/Bi2O2CO3–Bi2MoO6 is attributed to improved the utilization of light, increased surface active sites, and formation effective heterojunction between Ag2O–Ag2CO3 and Bi2O2CO3–Bi2MoO6. Capture experiments have shown the major active species in the photocatalytic degradation system, and a plausible photocatalytic mechanism has been postulated in conjunction with photoelectrochemical experiments.