The photocatalytic activity of graphene oxide/Ag₃PO₄ nano-composite: Loading effect

Abstract

Graphene oxide (GO)/Ag₃PO₄ nano-composite was successfully prepared by wet chemical technique. Samples were synthesized with three different concentrations of the GO. The structural studies such as grain size, dislocation density and lattice strain were performed by using X-ray diffraction (XRD) technique. The surface chemical state and doping process has been investigated by X-ray photoelectron spectroscopy (XPS). The evaluation of conduction band (CB), valance band (VB), direct and indirect band gap was performed through diffused reflectance spectroscopy (DRS). Surface morphology was observed through the field emission scanning electron microscope (FESEM). The obtained characterization results confirmed the formation of GO/Ag₃PO₄ composite with slight decrease in the band gap based on the amount of GO incorporated inside the GO/Ag₃PO₄ nano-composites. The photocatalytic performance of the prepared materials was evaluated in the decolourization reaction of methyl orange dye under the illumination of visible light radiation. The obtained photocatalytic results indicated that the addition of GO to Ag₃PO₄ has improved its photocatalytic performance. The sample with small GO loading exhibited remarkable photocatalytic performance than the neat Ag₃PO₄, i.e. the rate constant was almost 3.5 times higher.

Introduction

Graphene oxide (GO) belongs to carbon family. However, it attracts more research attention than the other family members in terms of thermal and mechanical properties [1]. It is well established that the properties of GO are highly depend on the oxidation state and hydroxyl groups [2], [3], [4]. GO has attract a lot of interest in photocatalysis because of its high electron absorption affinity and hence, an overall improvement in the electron-hole separation [5], [6]. The metal/metal oxide coated GO nano-composite are in practices to remove the pollutant [7], [8] and antibacterial activities [9].

Ag₃PO₄ is a promising photocatalyst compared to other classical semiconductor metal oxides such as TiO₂ and ZnO₂ under visible light illumination. However, in spite of its high photocatalytic efficiency, it has very limited environmental applications because of its low structural stability [10]. GO has been suggested as an attractive candidate to overcome stability problem and to improve the photo-degradation process [11]. Chen and coworkers [12] evaluated the performance of GO/Ag₃PO₄ composite for photocatalytic degradation of rhodamine B (RhB) and methyl orange (MO) under visible-light illumination. On the other hand, Wang and coworkers [13] found that GO/Ag₃PO₄/g-C₃N₄ composite has higher photocatalytic efficiency under the visible light than GO/Ag₃PO₄. Furthermore, Dong and coworkers [14] fabricated reduced GO/Ag₃PO₄ sheets via chemical route and reported a remarkable Ag₃PO₄ stability during the photo-degradation process. Bai and coworkers [15] have investigated the GO/Ag₃PO₄ nano-sheets for photocatalytic degradation reaction.

In the current study, GO/Ag₃PO₄ composite was prepared with different concentrations of GO. The prepared materials were characterized by several techniques to understand more about the nature of the composite. The photocatalytic activity of the prepared materials was evaluated in the decolourization of methyl orange and it was compared with that of neat Ag₃PO₄. The possible reasons for the higher photocatalytic activity are discussed and the proposed mechanism is suggested for this reactions.