Reduced Graphene Oxide–P25 Nanocomposites as Efficient Photocatalysts for Degradation of Bisphenol A in Water

Abstract

Reduced graphene oxide-titanium dioxide photocatalyst (rGO-TiO 2 ) was successfully synthesized by the hydrothermal method. The rGO-TiO 2 was used as photocatalyst for the degradation of bisphenol A (BPA), which is a typical endocrine disruptor of the environment. Characterization of photocatalysts and photocatalytic experiments under different conditions were performed for studying the structure and properties of photocatalysts. The characterization results showed that part of the anatase type TiO 2 was converted into rutile type TiO 2 after hydrothermal treatment and 1% rGO-P25 had the largest specific surface area (52.174 m 2 /g). Photocatalytic experiments indicated that 1% rGO-P25 had the best catalytic effect, and the most suitable concentration was 0.5 g/L. When the solution pH was 5.98, the catalyst was the most active. Under visible light, the three photocatalytic mechanisms were ranked as follows:1% rGO-P25 also had strong photocatalytic activity in the photocatalytic degradation of BPA under sunlight irradiation. 1% rGO-P25 with 0.5 g/L may be a very promising photocatalyst with a variety of light sources, especially under sunlight for practical applications.Catalysts 2019, 9, 607 2 of 15 out under normal temperature and pressure [10]; modern production cleaning process, where the energy source of this process is solar energy that cannot cause secondary pollution, and organic matter can be mineralized into clean energy such as H 2 O and CO 2 [11]; fast reaction rate, where organic pollutants can be destroyed completely within minutes to hours [12]. However, some drawbacks limit the practical application of TiO 2 . For instance, fast h + /e − recombination [13]; the large bandgap energy of 3.2 eV can only be excited by ultraviolet light (UV) with a wavelength less than 387 nm [3,6,[14][15][16][17]. In recent years, scientists have advanced many strategies in order to further improve the photocatalytic performance of TiO 2 , such as doping with non-metallic elements, combining with metal ions, depositing noble metals, and creating heterojunctions with other semiconductors [12,[18][19][20][21][22]. More recently, in contrast to other materials, graphene, graphene oxide (GO), and the graphene monolith formed by the stripping of GO, reduced graphene oxide (rGO) used in this experiment received wider attention because of its good mechanical strength, high electron mobility, chemical stability, optical properties, and high surface area [23][24][25][26][27]. Among them, rGO is a derivative of graphene and has a unique sp 2 hybrid carbon network [28]. The surface of the relatively inert graphene becomes extremely active due to the introduction of a large number of oxygen-containing functional groups such as hydroxyl group, epoxy group, carbonyl group, and a carboxyl group [29,30]. Therefore, the surface of graphene can also be connected to specific functions such as biomolecules, polymers, and inorganic particles [31]. The photocatalytic enhancement of rGO-TiO 2 composites can be attributed to three aspects: fi...

Sunlight Driven Photocatalytic Degradation of 2-Chlorophenol by Polypyrrole/Graphene Oxide Composites

“…Meanwhile, the image of GO in Figure 6b represents layers of flaky shapes (Deng et al, 2011). This is a similar observation reported by Yu et al, (2019) as seen in Figure 6c revealing PPy/GO films with a non-uniform surface with flaky lumps morphology and half embedded onto the polymer matrix. This indicates the incorporation of GO sheets is formed due to the unevenness of the PPy films (Molina et al, 2015).…”

“…Figure 6 displays the SEM images of PPy, GO, and PPy/GO composite (1:1). The images of PPy (Figure 6a) exhibits a hemispherical and cauliflower-like structure (Yu et al, 2019). Meanwhile, the image of GO in Figure 6b represents layers of flaky shapes (Deng et al, 2011).…”

“…Besides that, the existence of hydroxyl groups in the GO shows photocatalytic properties as shown by water splitting and hydrogen production (Munawaroh et al, 2018). The presence of hydroxyl, epoxy, carbonyl, and carboxyl groups on GO's surface with high negative charge makes it extremely active (Yu et al, 2019). This shows that the surface of GO can be fabricated with a specific functional group such as inorganic particles, polymers, or biomolecules to improve its performance as photocatalyst.…”

Adsorption and photocatalytic degradation of gas-phase UDMH under simulated sunlight by AgBr/TiO2/rGA

“…6 Furthermore, graphene can also serve as the electron transport medium in the photocatalytic reaction for high electron mobility. [7][8][9] In practice, the synergistic effect of adsorption and photocatalysis should be emphasized to obtain high gas degradation efficiency. TiO 2 , as an efficient photocatalyst, is widely used in environmental applications because of its wide bandgap, low cost, high chemical stability, and non-toxic properties.…”

Understanding the Role of Silver Nanostructures and Graphene Oxide Applied as Surface Modification of TiO2 in Photocatalytic Transformations of Rhodamine B under UV and Vis Irradiation

“…For example, extensive surface coverage with silver nanoparticles can negatively affect the photocatalytic activity of decorated semiconductor, due to the possibility of nanoparticles acting as the recombination centers [ 18 , 19 ]. Furthermore, excess of reduced graphene oxide loaded in composite with TiO 2 can limit photocatalyst activity through the occurrence of a shielding effect [ 20 ]. Some reports indicate that GO under photocatalytic process conditions undergoes reduction and degradation [ 21 , 22 ].…”