Synergetic Photocatalytic Nanostructures Based on Au/TiO₂/Reduced Graphene Oxide for Efficient Degradation of Organic Pollutants

Abstract

Recently, there is crucial interest in the design and fabrication of nanocatalysts for efficient decomposition of organic pollutants in wastewater using visible light. This work reports the assembling fabrication of synergetic photocatalytic Au/TiO2/RGO nanostructures by utilizing the reduced graphene oxide (RGO) as substrate material and efficient separator for electrons and holes. The Au/TiO2 nanostructures with a ≈7 nm TiO2 particles size are dispersed uniformly on RGO nanosheets. UV–vis diffuse reflectance spectroscopy verifies that Au/TiO2/RGO nanocomposites show strong absorption of visible light. The degradation efficiency after 1 h for hydroquinone under visible light and UV light is ≈77% and ≈90%, respectively. Under visible light, the calculated apparent rates (k) of the Au/TiO2/RGO nanocomposites are 0.0112 and 0.0174 min−1 for decomposition of methylene blue and hydroquinone. That are five times greater than that of bare TiO2. The high photocatalytic activity is mainly attributed to the synergy between RGO and Au/TiO2 nanostructure. The strategy of composite nanostructures assembling on RGO is ensured to have a great practicable potential for the designing of high efficient multielement composite nanoparticles catalysts.

Dual Cocatalysts in TiO2 Photocatalysis

“…Graphene have several major functions ( Figure ): i)The large theoretical specific surface area of graphene provides more surface active sites for adsorption and catalysis of reactant molecules (such as dye molecules and CO 2 molecules) ii)Graphene can act as a scaffold to prevent the nanocatalysts from aggregation and increase the specific area of hybrid photocatalysts iii)The dark color of graphene is beneficial for promoting the light absorption of photocatalysts …”

“…The hot electrons generated from Au NPs are first injected to TiO 2 , and the electrons further transfer to graphene. This hot‐electron injection charge transfer mechanism is commonly used in Au–rGO–TiO 2 ternary photocatalytic system . Sequential interfacial charge transfer effectively restrains the recombination and prolongs the lifetime of photogenerated charge carriers.…”

“…Graphene can also serve as a supporting material to restrict the aggregation of NPs. Zhao et al reported an Au/TiO 2 /RGO nanostructure with RGO as a host. The reduced graphene oxide nanosheets directed the uniform distribution of Au/TiO 2 NPs on RGO surface and prevented the aggregation.…”

2D/2D Graphitic Carbon Nitride (g-C3N4) Heterojunction Nanocomposites for Photocatalysis: Why Does Face-to-Face Interface Matter?

“…By harvesting solar energy as the source of renewable energy, photocatalysis will make significant impacts in the areas of (1) light-driven water splitting to hydrogen (H2) and oxygen (O2) (Chen et al, 2010;Bai et al, 2016;Wei et al, 2016;Putri et al, 2017;Yubin et al, 2017), (2) conversion of carbon dioxide (CO2) to energy bearing fuels (Ong et al, , 2014cTan et al, 2014Tan et al, , 2016Tan et al, , 2017Gui et al, 2015;Guo et al, 2016a;Zhang et al, 2016c), (3) mineralization of waste and pollutants (Ong et al, 2014d,e;Fang et al, 2016;Liu et al, 2016c;Topcu et al, 2016;Zhao et al, 2016b), (4) selective organic transformations (Liu et al, 2014;Zhao et al, 2016a), and (5) disinfection of bacteria (Keane et al, 2014;Bing et al, 2015) (Figure 1). Very recently, two-dimensional (2D) semiconductor photocatalysts have triggered a renaissance of interest in the field of energy, and environmental-related applications thank to the high ratio of surface-to-volume and unprecedented electronic and optical characteristics (Ong et al, 2014b;Bai et al, 2015;Liang et al, 2015d;Fang et al, 2016;Kalantar-zadeh et al, 2016;She et al, 2017;Xueting et al, 2017).…”

Synthesis of hybrid nanosheets of graphene oxide, titania and gold and palladium nanoparticles for catalytic applications

“…30 For instance, the combination of an electron donor or electron acceptor material with a plasmonic nanoparticle (forming a nanoparticle-based hybrid, for example) enables the tuning of charge states in a metal. 14,15,19,35,36 This, in turn, affects the population and separation of SPR excited hot-electrons and holes that can drive reduction or oxidation processes. Therefore, the immobilization of plasmonic nanoparticles onto supports presenting electronic properties that enable the modulation of nanoscale charge transfer processes opens the possibility for the control of plasmonic catalytic properties in addition to providing a facile strategy to improve stability.…”