With high redox ability of electrons and holes, Z-scheme heterojunction is a promising composite structure in the photocatalysis. However, it is challenging to inhibit the recombination of carriers by Z-scheme transfer. Herein, a novel Ag 3 PO 4 /AgBr/Ti 3 C 2 Tx hybrid with dual channel carrier transfer structure was fabricated. Ti 3 C 2 Tx not only serves as a template for growth of Z-scheme Ag 3 PO 4 /AgBr, but also can be used to accommodate holes transferred from Ag 3 PO 4 and AgBr. The first channel is consisted of Z-scheme transfer of carriers in Ag 3 PO 4 /AgBr. And the hole transfer from the AgBr valence band to Ti 3 C 2 Tx constitutes the second channel, which avoids directly carrier recombination in AgBr valence band. Dual channel carrier transfer pathway was proved by in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS). After Ti 3 C 2 Tx was introduced, the quantum efficiency of Ag 3 PO 4 /AgBr increased from 10.59% to 12.50% with reducing Cr(VI), indicating an increase in carrier utilization. The improvement of the degradation efficiency of rhodamine B from 80.77% to 94.72% is benefited from the enhanced quantum efficiency. The dual channel carrier transfer heterojunctions design provides a new idea for constructing an efficient composite photocatalytic structure.
Zhuanni Yu,Mengmeng Xu,Qiang Wang,Xiaowei Sun,Jing Lan
An efficient semiconductor composite, silver/silver orthophosphate/silver bromide, was successfully synthesized by a facile one-step reduction and ion exchange process. Its crystal structure, morphology, optical property, surface element composition were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible diffuse reflectance spectrometer and X-ray photoelectron spectrometer. The effects of composite proportion and synthesis duration on performances of as-prepared photocatalysts were investigated, and the results showed that Br/P molar ratio of 3 and the synthesis duration of 4 h were the optimum conditions. The radical scavenging experiments indicated that the hole and superoxide radical were the main active species in this reaction system. The Ag/Ag 3 PO 4 /AgBr-3 presented excellent stability and recyclability, maintaining 92% of degradation efficiency after 5 cycles. The good photocatalysis performance could be attributed to the formation of the heterojunction between Ag and Ag 3 PO 4 /AgBr.
Hongbin Yu,Danyang Wang,Bin Zhao,Ying Lu,Xinhong Wang,Suiyi Zhu,Weichao Qin,Mingxin Huo
A ternary dual Z-scheme heterojunction photocatalyst composed of Ag 3 PO 4 , AgBr and g-C 3 N 4 was prepared by a facile chemical deposition method. Scanning electron microscope equipped with energy-dispersive X-ray, X-ray diffraction, diffusive reflective spectrophotometry and X-ray photoelectron spectroscopy were carried out to characterize the morphology, element and structure properties of the photocatalysts. The photocatalytic activity was evaluated by the photoelectrochemical tests and the degradation of tetracycline (TC). The results indicated that the composite Ag 3 PO 4 /AgBr-20%g-C 3 N 4 exhibited the best photocatalytic activity in terms of the photocurrent response and the degradation of TC under visible light irradiation. The degradation rate of TC over the ternary photocatalyst was 0.12 min −1 , which was 2.55 and 3.24 times faster than that over Ag 3 PO 4 /AgBr and Ag 3 PO 4 , respectively. During photocatalysis, metallic Ag could be formed and served as the electron transfer mediator to build the dual Z-scheme heterojunction by bridging the recombination of electrons and holes. By this manner, more efficient separation of photo-generated carriers and better redox ability could be obtained, consequently promoting the photocatalytic activity. Additionally, the trapping experiments verified that O 2 − and h + played prominent roles in the photocatalytic processes, while the impact of OH on the removal efficiency was relatively small.
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