The photocatalytic activity of graphene oxide/Ag3PO4 nano-composite: Loading effect
Graphical abstract
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.
Section snippets
Synthesis of graphene oxide (GO)
GO has been synthesized using graphite powder (Sigma-Aldrich 99.99% purity) according to Hummers method [16].The graphite powder were treated by 5% hydrochloric acid (HCl), filtered, washed with deionized water (DI) and dried for 24 h at 110 °C.Afterthat, 5 gm of the treated graphite powder were mixed with 108 ml of sulfuric acid (H2SO4) at 0 °C and stirred for 10 min in an ice bath. Then, 15 g of potassium permanganate (KMnO4) was slowly added to the solution with continuing stirring. The
Structure analysisof GO/Ag3PO4 nano-composites
The X-rays diffraction (XRD) patterns of the pure Ag3PO4 and graphene oxide (GO) nano-composites of differentconcentration of GO are shown in Fig. 1. The structure of pure and GO/Ag3PO4 were found as a body-centered cubic according to (JCDPS card No. 01-075-6002) The diffraction planes (hkl planes) are documented in Table 1. It has been noticed that there are no indication of GO diffraction plane in XRD pattern. The possibility regarding the absence of GO plane in the Ag3PO4 that GO has
Conclusions
GO/Ag3PO4 nano-composite exhibited the enhanced photocatalytic activity as compared to the neat Ag3PO4. The maximum photo-degradation was observed at 50 ml of graphene oxide loading. The direct band gap was noticed from 2.51 eV to 2.38 eV while the indirect band gap was found 2.40 eV to 2.23 eV at different concentration of graphene oxide. Consequently, the variation in the valance band and conduction band was also monitored. The grain size was affected by the graphene oxide and varies from 58.59 nm
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