Study on Preparation of Ag/AgCl/ZIF-8 Composite and Photocatalytic NO Oxidation Performance

ZIF-8, a subclass of metal-organic frameworks with Zn2+ and 2-methylimidazole, featuring high special surface area and easily adjustable structures have exhibit great application potential in photocatalytic reaction. However, ZIF-8 often suffers from short light harvesting range and rapid recombination of photogenerated carriers, resulting in poorer catalytic activity. Here, ZIF-8 was synthesized by a precipitation method, and then Ag/AgCl nanoparticles were deposited on the surface of ZIF-8 by photo-deposition to obtain Ag/AgCl/ZIF-8 composite. The typical synthesis procedure is as follows: 0.2 g of ZIF-8 powder was dispersed in 50 mL of methanol and sonicated for 30 min to make it uniformly dispersed, then 0.1699 g of AgNO3 (1 mmol) and 0.045 g ZnCl2 were added to the above solution, which was placed on a magnetic stirrer and stirred in the dark for 30 min, followed irradiating it under light for 10 min. The obtained sample was washed several times with methanol and dried under a freeze-drying oven for 12 h. The crystal structure, morphology, specific surface area and light absorption properties were characterized by using X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), specific surface area test method (BET) and UV-Vis diffuse reflection absorption spectra (UV-Vis DRS), respectively. Finally, the photocatalytic oxidation performance of Ag/AgCl/ZIF-8 for NO removal under visible light was systematically studied, and its reaction mechanism was further analyzed. Thus, the resulting Ag/AgCl/ZIF-8 composite showed enhanced NO photocatalytic removal performance, reaching the highest NO removal of 43.5% under 35 min visible light irradiation and better stability compared with the parent ZIF-8. The above results show that: (1) Ag-0 surface plasmon resonance (SPR) effect in Ag/AgCl/ZIF-8 composite enhances the absorption of visible light; (2) ZIF-8 can enrich more oxygen molecules and NO molecules, promoting the formation of superoxide free radicals and NO photocatalytic oxidation performance with a large specific surface area; (3) the photogenerated holes in the composite can be transferred to the surface of AgCl to oxidate Cl- to Cl-0, which possess more strong oxidation ability for improving the photocatalytic oxidation of NO. On the other hand, it effectively inhibits the recombination of photogenerated electrons and holes, which improves the stability of the catalyst.

Automated summary

The Ag/AgCl/ZIF-8 composite material was prepared by depositing Ag/AgCl nanoparticles on the surface of ZIF-8, and its catalytic oxidation performance for NO under visible light was studied. The composite showed enhanced NO removal performance and better stability compared with ZIF-8.