The Roles of Graphene and Ag in the Hybrid Ag@Ag2O-Graphene for Sulfamethoxazole Degradation

Li Zhou,Huiping Deng,Guoyan Zou

doi:10.3390/catal8070272

Abstract

Ag@Ag2O-graphene (Ag@Ag2O-G) with different concentrations of graphene was synthesized using a facile in situ precipitation method. The photocatalysts were characterized by field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS). The antibioticsulfamethoxazole (SMX) degradationunder simulated solar light and visible light irradiationwas investigated to evaluate photocatalytic performance. The composite photocatalyst Ag@Ag2O-G with 2.5 wt% graphene presented the highest activity among all the prepared composite photocatalysts. The coupling of graphene and Ag0 increased the photocatalyticactivity and stability of pure Ag2O. Under higher SMX concentrations, the adsorption, not the photocatalytic ability, playeda crucial role during the SMX removal process. On the basis of the characterization and reactive oxygen species (ROS) scavenging experiments, a separation and transfer mechanism of photogenerated carriers was proposed. In the photocatalytic degradation of SMX, the major active species wereidentified as photogenerated holes; photogenerated electrons in the conduction band (CB) of Ag2O could not transfer to graphene through Ag0due to the more negative reduction potential of graphene. This is an important result regardinggraphene and Ag0 roles which isdifferent from that for the photocatalytic degradation of dyes. This researchmay provide new insights into photocatalytic processes for the degradation of non-dye pollutants bycomposite materials to guidethe design of highly efficient reaction systems.

Highlights

Semiconductor photocatalysis, one of the most promising technologies for solar energy utilization and environmental remediation, has attracted tremendous attention since the semiconductor TiO2 was applied to the decomposition of organic contaminants [1,2]
Ag@Ag2 O, AgBr/Ag2 O, Ag2 O/TiO2 heterostructure were introduced to decompose methyl orange (MO), and such attempts have exhibited high efficiency and stability [7,8,9]. These results indicate that Ag2 O-based materials have greater potential as stable and highly efficient photocatalysts than pure Ag2 O for photocatalytic decomposition of organic contaminants under visible light irradiation
It can be clearly seen that the Ag2 O nanoparticles were close to spherical in shape with an average diameter of approximately 100 nm and covered by graphene with a folder surface

Summary

Introduction

Semiconductor photocatalysis, one of the most promising technologies for solar energy utilization and environmental remediation, has attracted tremendous attention since the semiconductor TiO2 was applied to the decomposition of organic contaminants [1,2]. Pure Ag2 O has been rarely used as a visible light-driven photocatalyst because of its high photosensitivity and low-stability properties under light irradiation. There have been a few attempts to use Ag2 O-based materials as a photocatalyst under visible light irradiation. Ag@Ag2 O, AgBr/Ag2 O, Ag2 O/TiO2 heterostructure were introduced to decompose methyl orange (MO), and such attempts have exhibited high efficiency and stability [7,8,9]. These results indicate that Ag2 O-based materials have greater potential as stable and highly efficient photocatalysts than pure Ag2 O for photocatalytic decomposition of organic contaminants under visible light irradiation

Methods

Results

Conclusion