Facile fabrication of Bi2GeO5/Ag@Ag3PO4 for efficient photocatalytic RhB degradation

Abstract

In this study, Bi 2 GeO 5 /Ag 3 PO 4 nano-composites were synthesized by simple two-step approach. Then, Bi 2 GeO 5 /Ag@Ag 3 PO 4 Z-scheme heterojunction was assembled by subsequent photocatalytic processes. It was characterized using XRD, SEM, TEM, HR-TEM, EDX, SAED, XPS, PL, UV–Vis DRS, photoelectrochemical and photodegradation experiments. Results illustrated that the catalytic activity of Bi 2 GeO 5 /Ag 3 PO 4 nano-composites is remarkably superior to those of Bi 2 GeO 5 and Ag 3 PO 4 . The influence of Bi 2 GeO 5 amount on the performance of the composites was also studied. Results showed that 0.1Bi 2 GeO 5 /Ag 3 PO 4 composite exhibited the best photocatalytic efficiency for rhodamine B (RhB) degradation, and gave rise to a 96% degradation of RhB after 30 ​min visible-light irradiation. In the degradation of RhB, the apparent rate constant of 0.1Bi 2 GeO 5 /Ag 3 PO 4 is the largest, which is 0.06836min −1 . After 4 cycles, RhB degradation by 0.1Bi 2 GeO 5 /Ag 3 PO 4 still maintained 84%, equivalent to 1.7-fold higher than that of Ag 3 PO 4 . The trapping experiments revealed that holes (h + ) and superoxide anions (O- 2 · ) were the primary species responsible for the decomposition of RhB in 0.1Bi 2 GeO 5 /Ag 3 PO 4 . Furthermore, the mechanism of improving photocatalytic activity was proposed relied on the experiments and characterization results. The formation of Bi 2 GeO 5 /Ag@Ag 3 PO 4 Z-scheme heterojunction by photocatalytic processes dramatically increased its photocatalytic activity and stability. Based on the aforesaid analysis, a Z-scheme reaction mechanism was proposed for the Bi 2 GeO 5 /Ag 3 PO 4 photocatalytic degradation process. • Bi 2 GeO 5 /Ag@Ag 3 PO 4 Z-scheme heterojunction was assembled by photocatalytic processes. • The formation of Ag particles during photocatalysis enhances the catalytic activity. • The formation of Z-scheme heterojunction can be extended to other catalysts.