to enhance the activity of several semiconductors. In this book chapter, several types
of graphene/semiconductor composites have been discussed for environmental
remediation application. We have selectively discussed the fundamentals, basic
principles, and mechanism of semiconductor photocatalysts. In addition, the preparation, properties, characterization techniques, and applications of graphene-based
materials in water purification have also been emphasized. The photocatalytic
performance toward the removal of heavy metal ions and degradation of contaminants was synergistically improved when graphene was coupled with semiconductors. The size-dependent properties of semiconductors together with the unique
properties of graphene induce further functionalities, such as the prolonged visible
light absorption edge, enhanced charge separation properties, high adsorption capacity, and stability of the composites.
We have illustrated how theoretical studies have used to explain the
photocatalytic behavior of semiconductor. Electronic structure calculations have
shown how interface is significant to determine the photocatalytic activity and
adsorption behavior of semiconductor photocatalyst materials. This book chapter
mentions how first-principle studies can be applied routinely to study charge transfer
and electronic properties of materials, which are often challenging to study
experimentally.
Several fabrication methods have developed for both in situ and ex situ
processing of semiconductor nanoparticles on the graphene sheet; however, some
pressing issues must be addressed before large-scale application of these
nanocomposites can be effectively achieved. Thus, the technology for fabricating
high-quality graphene is still at the fundamental stage; further improvements are
needed since the accurate control of the final product in terms of defect sites,
reaggregation, purity, the number of layers, and control of defects is yet to be
established. Moreover, large surface area architectures (graphene-based xerogels
and aerogels) must be applied for heavy metal ions removal using the adsorption
technique because the high surface area, nanoporosity, and microstructures of
graphene show excellent adsorption capabilities of pollutants and heavy metal ions.
The design and fabrication of novel photocatalyst materials are one of the key
research goals. The existing photocatalytic materials have several drawbacks, such
as high cost, large band gaps, low active surface area, etc. It is of great significance to
find cost-effective and advanced materials to prepare composite photocatalysts for
practical applications. A perfect material for engineering composites should fulfill
several requirements, such as visible light activity, high solar conversion efficiency,
proper band-gap structure for redox reactions, high photostability for long-term
applications, and scalability for commercialization.
Currently, the hybrid HSE06 functionals, which can precisely describe the
electronic structures, cannot clearly offer a solution to the long-range van der
Waals interaction in graphene-based composite materials. Thus, new functionals
and codes, which can precisely address both the van der Waals interactions and
electron correlation effects, are significant. This will become a key tool for hastening
the design of advanced materials for water purification.
24
F. Opoku et al.
of graphene/semiconductor composites have been discussed for environmental
remediation application. We have selectively discussed the fundamentals, basic
principles, and mechanism of semiconductor photocatalysts. In addition, the preparation, properties, characterization techniques, and applications of graphene-based
materials in water purification have also been emphasized. The photocatalytic
performance toward the removal of heavy metal ions and degradation of contaminants was synergistically improved when graphene was coupled with semiconductors. The size-dependent properties of semiconductors together with the unique
properties of graphene induce further functionalities, such as the prolonged visible
light absorption edge, enhanced charge separation properties, high adsorption capacity, and stability of the composites.
We have illustrated how theoretical studies have used to explain the
photocatalytic behavior of semiconductor. Electronic structure calculations have
shown how interface is significant to determine the photocatalytic activity and
adsorption behavior of semiconductor photocatalyst materials. This book chapter
mentions how first-principle studies can be applied routinely to study charge transfer
and electronic properties of materials, which are often challenging to study
experimentally.
Several fabrication methods have developed for both in situ and ex situ
processing of semiconductor nanoparticles on the graphene sheet; however, some
pressing issues must be addressed before large-scale application of these
nanocomposites can be effectively achieved. Thus, the technology for fabricating
high-quality graphene is still at the fundamental stage; further improvements are
needed since the accurate control of the final product in terms of defect sites,
reaggregation, purity, the number of layers, and control of defects is yet to be
established. Moreover, large surface area architectures (graphene-based xerogels
and aerogels) must be applied for heavy metal ions removal using the adsorption
technique because the high surface area, nanoporosity, and microstructures of
graphene show excellent adsorption capabilities of pollutants and heavy metal ions.
The design and fabrication of novel photocatalyst materials are one of the key
research goals. The existing photocatalytic materials have several drawbacks, such
as high cost, large band gaps, low active surface area, etc. It is of great significance to
find cost-effective and advanced materials to prepare composite photocatalysts for
practical applications. A perfect material for engineering composites should fulfill
several requirements, such as visible light activity, high solar conversion efficiency,
proper band-gap structure for redox reactions, high photostability for long-term
applications, and scalability for commercialization.
Currently, the hybrid HSE06 functionals, which can precisely describe the
electronic structures, cannot clearly offer a solution to the long-range van der
Waals interaction in graphene-based composite materials. Thus, new functionals
and codes, which can precisely address both the van der Waals interactions and
electron correlation effects, are significant. This will become a key tool for hastening
the design of advanced materials for water purification.
24
F. Opoku et al.