Facile Preparation of ZnO Nanoparticles and Ag/ZnO Nanocomposite and Their Photocatalytic Activities under Visible Light

Thi Anh Tuyet Pham,Van Anh Tran,Minh Viet Nguyen,Van Duong Le,Duc Duc Truong,Xuan Truong Do,Anh-Tuan Vu,Hao Li

doi:10.1155/2020/8897667

Abstract

Zinc oxide (ZnO) has been known as an excellent photocatalyst for the degradation of a variety of organic pollutants under UV irradiation. This work describes a synthesis of ZnO nanoparticles via a facile precipitation method, and Ag was doped into Ag/ZnO nanocomposite to improve the photocatalytic degradation of BPA under visible light irradiation. The obtained ZnO nanoparticles were 20 nm in size and had a relatively high surface area and pore volume, 26.2 m2/g and 0.48 cm3/g, respectively. The deposition of Ag led to a decrease in the surface area, pore volume, and band gap energy ( E g ) of ZnO nanoparticles. However, the photocatalytic activity of Ag/ZnO composite in the case increased. The performance of ZnO was compared with Ag/ZnO composites at the different molar ratios, and the kinetic reaction of BPA in these catalysts was investigated by the first-order kinetic model. The sample of Ag/ZnO-10 composite had the highest catalytic activity and showed the degradation efficiency, reaction rate, and degradation capacity of 100% in 120 min, 0.014 min-1, and 40 mg/g, respectively. In comparison, the effects of Ag/ZnO molar ratio, catalyst dosage, solution pH, and concentration of BPA on photocatalytic degradation were investigated. Additionally, the photocatalytic performance of Ag/ZnO-10 composite was evaluated by the degradation of other persistent organic compounds such as phenol, tartrazine, and methylene blue and compared to other catalysts in literature.

Highlights

Today, significant development of inorganic nanoparticles has been their potential application in the environment, biology, electronics, optics, transport, and information technology [1]
The band gap energy of Zinc oxide (ZnO) was 3.220 eV. This was lower than that of Ag/ZnO-2 composite (3.230 eV) but larger than that of other composites; the band gap energies were 3.205, 3.125, and 3.181 eV for Ag/ZnO-5, Ag/ZnO-10, and Ag/ZnO-15, respectively. These results indicated that the doping of Ag into composite at the higher molar ratio than 2 reduced the band gap energy; it could increase the photocatalytic activity of composite under visible light
When Ag was doped into composites at the molar ratio of Ag/ZnO larger than 2, the band gap energy of composite was decreased, and the degradation efficiency and the reaction rate increase

Summary

Introduction

Significant development of inorganic nanoparticles has been their potential application in the environment, biology, electronics, optics, transport, and information technology [1]. Besides the advantages of this material due to the high electron aperture rate and low charge separation efficiency [11], the pure ZnO often exhibits relatively low photocatalytic activity under visible light irradiation, and ZnO does not meet the requirements of a photocatalyst when applied to practical processes [3, 12, 13]. That is why the enhanced catalytic activity of ZnO in visible light by doping other elements is a great concern to scientists To this moment, the ZnO nanomaterials with different shapes and sizes have been prepared by many methods such. Among the various noble metal-semiconductor photocatalysts, Ag/ZnO can generate an effective Schottky barrier at the junction interface, supporting electron capture, thereby increasing the separation efficiency of electron-hole pairs and boost visible light harvesting capability. The optimal reaction conditions and the photocatalytic performance of Ag/ZnO-10 composite were evaluated by degradation of other persistent organic compounds such as phenol, tartrazine (TA), and methylene blue (MB)

Materials and Methods

Results and Discussion

Photodegradation of BPA

Conclusion