Abstract
In this work, we communicate a facile and low temperature synthesis process for the fabrication of graphene-TiO2 photocatalytic composite thin films. A sol-gel chemical route is used to synthesize TiO2 from the precursor solutions and spin and spray coating are used to deposit the films. Excitation of the wet films during the casting process by ultrasonic vibration favorably influences both the sol-gel route and the deposition process, through the following mechanisms. The ultrasound energy imparted to the wet film breaks down the physical bonds of the gel phase. As a result, only a low-temperature post annealing process is required to eliminate the residues to complete the conversion of precursors to TiO2. In addition, ultrasonic vibration creates a nanoscale agitating motion or microstreaming in the liquid film that facilitates mixing of TiO2 and graphene nanosheets. The films made based on the above-mentioned ultrasonic vibration-assisted method and annealed at 150 °C contain both rutile and anatase phases of TiO2, which is the most favorable configuration for photocatalytic applications. The photoinduced and photocatalytic experiments demonstrate effective photocurrent generation and elimination of pollutants by graphene-TiO2 composite thin films fabricated via scalable spray coating and mild temperature processing, the results of which are comparable with those made using lab-scale and energy-intensive processes.
Highlights
A photocatalyst performs catalytic activity using incident photons as the driving force for a chemical reaction, without being consumed or chemically altered as a result of the reaction.Photocatalysts are low-cost, efficient and environmentally-favored alternatives to commonly used industrial catalysts [1,2,3]
We prepare graphene-TiO2 composite thin films, where both anatase and rutile coexist, using a sol-gel chemical route assisted with ultrasonic vibration, in which we show that vibration significantly reduces the required heat treatment temperature
Graphene-TiO2 photocatalytic thin films were fabricated via the sol-gel method, as the chemical route for the formation of TiO2, and spin and spray coating as the casting methods
Summary
A photocatalyst performs catalytic activity using incident photons as the driving force for a chemical reaction, without being consumed or chemically altered as a result of the reaction.Photocatalysts are low-cost, efficient and environmentally-favored alternatives to commonly used industrial catalysts [1,2,3]. Photocatalyst works based on oxidative surface decomposition of the reactants are typically used for the removal of residual oils and solvents and for inhibiting the growth of microorganisms on the surface [2,3,4]. Some metal oxides, such as TiO2 , with inherent resistance to oxidation and hydration exhibit photocatalytic properties at room temperature [4,5,6]. TiO2 is a large band gap semiconductor that absorbs high energy UV photons to generate electron and hole pairs.
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