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

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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

THANK YOU