RENEWABLE FUELS BY PHOTOCATALYTIC
REACTIONPRESENTED BY:
SAAD ARIF MM-26
DANIYAL AHMED MM-33
MOIZ ULLAH BAIG MM-36
SURFACE COATING | MATERIALS ENGINEERING DEPARTMENT | NEDUET
INTRODUCTION
• Conversion of solar energy into chemical energy
• Promising technology to solve energy shortage problems
• Photocatalytic processes
2
• The photogenerated electron-
hole pairs separate from each
other and vigorously migrate to
active sites at semiconductor
surface where they reduce the
electron acceptors or oxidize the
donor species.
3
• Electron-hole pairs may recombine. PROBLEM!!
• For an efficient photocatalytic activity;
1) The electron hole pairs separate effectively
2) The photocatalyst offers more sites 4
ENHANCEMENT OF PHOTOCATALYTIC ACTIVITY
• Graphene has been used as a support for fabricating various
nanohybrids with semiconductors such as TiO2.
• The hybrid solves the problem
• Graphene, a good electron collector and transporter, hinders
recombination.
• The hybrid increases the absorption of light intensity, hence
efficient solar energy utilization.
• The large surface area of graphene supplies more active sites.5
SYNTHESIS OF GRAPHENE-BASED PHOTOCATALYSTS
• Solution mixing
• In-Situ Growth
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SOLUTION MIXING
• GO-TiO2 nanocomposite prepared
by colloidal blending method
• Chemical interaction take place
between functional groups of GO &
TiO2.
• Two phase method was proposed
• PMMA beads as sacrificial templates
• Microwave radiations
simultaneously remove the template
and reduce GO into graphene 7
Polyethyleneimine: adhesives, ability to modify the surface, used as flocculating agent with sols
IN-SITU GROWTH
• To fabricate 2D sandwich-like graphene-TiO 2 hybrid
nanosheets, in situ simultaneous reduction-
hydrolysis technique (SRH) was exploited
• Ethylenediamine reduces GO to Graphene
• while TiO2 formed by hydrolysis of Titanium
(IV)bis(ammonium lactato)dihydroxide
• graphene serves as a two-dimensional “mat” well to
anchor the forming TiO 2 nanoparticles
• TiO 2 hinders the restacking of sheets of graphene
• High-quality nano-sized ultrathin TiO2 grown on
graphene nanosheets by solvothermal synthetic route
8
Titanium (IV)bis(ammonium lactato)dihydroxide
APPLICATION OF GRAPHENE BASEDPHOTOCATALYST
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PHOTOCATALYTIC CONVERSION OF CO2 TO RENEWABLE FUELS
• The basic process can be summarized into three steps:
1. generation of charge carriers (electron–hole pairs) upon absorption of
photons with suitable energy from light irradiation,
2. charge carrier separation and transportation,
3. chemical reactions between surface species and charge carriers
• Conversion of CO2 to valuable hydrocarbons is one of the best solutions to
both the global warming and the energy shortage problems.
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CO2 REDUCTION
• Photocatalytic CO2 conversion is a
complicated combination of
photophysical and photochemical
processes.
• The reaction is initiated by
photoexcitation
• They can travel to the surface
• React with surface adsorbed species
(CO2 in this case)
• In order to reduce CO2 into
hydrocarbons, electrons in the
semiconductor are required to have
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RENEWABLE FUELS PRODUCTION
• The graphene-TiO2 hybrid prepared with the SRH
route shows high photocatalytic activity toward
conversion of CO2 to CH4 and C2H6 in the
presence of water vapor
• The synergistic effect of the surface-Ti 3 + sites
through reduction of Ti 4 + caused by reducing
agent Ethylenediamine and graphene favors the
generation of C2H6
• The electron-rich graphene may help stabilize
the ·CH 3 species, which restrains combination
of ·CH3 with H+ and e−1 into CH4 12
CONCLUSION
• The improved electrical mobility of the less defective graphene allows
photoexcited electrons to more effectively diffuse to reactive sites,
facilitating photoreduction reactions.
• graphene-based photocatalysts represent a new class of promising
materials in the field of photo-driven chemical conversion using
abundant solar energy.
• The principal challenge to facilitate the development of graphene-
based photocatalysts lies in understanding reciprocity of graphene
and semiconductor after hybridization.13
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