Abstract
In the pursuit towards the use of sunlight as a sustainable source for energy generation and environmental remediation, photocatalytic water splitting and photocatalytic pollutant degradation have recently gained significant importance. Research in this field is aimed at solving the global energy crisis and environmental issues in an ecologically-friendly way by using two of the most abundant natural resources, namely sunlight and water. Over the past few years, carbon-based nanocomposites, particularly graphene and graphitic carbon nitride, have attracted much attention as interesting materials in this field. Due to their unique chemical and physical properties, carbon-based nanocomposites have made a substantial contribution towards the generation of clean, renewable and viable forms of energy from light-based water splitting and pollutant removal. This review article provides a comprehensive overview of the recent research progress in the field of energy generation and environmental remediation using two-dimensional carbon-based nanocomposites. It begins with a brief introduction to the field, basic principles of photocatalytic water splitting for energy generation and environmental remediation, followed by the properties of carbon-based nanocomposites. Then, the development of various graphene-based nanocomposites for the above-mentioned applications is presented, wherein graphene plays different roles, including electron acceptor/transporter, cocatalyst, photocatalyst and photosensitizer. Subsequently, the development of different graphitic carbon nitride-based nanocomposites as photocatalysts for energy and environmental applications is discussed in detail. This review concludes by highlighting the advantages and challenges involved in the use of two-dimensional carbon-based nanocomposites for photocatalysis. Finally, the future perspectives of research in this field are also briefly mentioned.
Highlights
The problems of global energy shortage and environmental pollution are continuously increasing and various research groups are working to develop an alternative for the depleting fossil fuel reserves to effectively address the energy crisis and other environmental issues [1,2]
The results indicate about 99% degradation occurred within 60 min of visible-light irradiation for nanocomposites optimized at 0.5 wt % reduced graphene oxide (RGO) in the photocatalyst
The decrease in the band gap energy of the nanocomposite was ascribed to the covalent bond formation of C–O–C between g-C3N4 and RGO, which has been confirmed by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS)
Summary
On the basis of all the above-mentioned reports, it can be concluded that besides acting as an electron reservoir to capture and shuttle the electrons, graphene act as a photosensitizer and transform the UV-active semiconductors into visible light responsive materials This photosensitization by graphene has opened many new paths in fabricating novel graphene–semiconductor-based nanocomposites for various photocatalytic applications. G-C3N4 was first investigated as a photocatalyst by Wang et al [64] in 2009 for visible-light-based water splitting reactions to generate clean, renewable energy in the form of H2 They found and explained the appropriate band gap structure of g-C3N4 to absorb visible light and evolve H2 and O2 by reduction and oxidation reactions during the photocatalytic process.
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