Synthesis & Characterization of TiO2 & doped TiO2 Nanostructures for application in Dye Sensitized Solar Cell

Project Guide Project Student Dr.Tom Mathews Jose Martina PScientific Officer (G) 13PGN02SND Internal Project GuideIGCAR- Kalpakkam Dr.V. Sri Devi Co-ordinator Center for NanoScience Lady Doak College Madurai

Outline of the work

• Synthesis of TiO2 nanotube powders by Electrochemical

anodization Technique

• Modification of the synthesized TiO2 by Nitrogen doping

• Characterization of the synthesized TiO2 using XRD, HRTEM,

FESEM and DRS

IntroductionTitania is a wide band gap semiconductor metal oxide.

Nano structures of this material has widespread application

in solar energy conversion .

Electrochemical anodization was found to be the easiest and

cost effective method for the synthesis of TiO2 nanotubes

By this technique powder nanotubes of TiO2 were

synthesized

The bandgap was modified by N-doping

Biological and chemical inertnessNon-toxicityLow costAvailabilityLong term stability against photo and chemical corrosion

Advantages Titania

Applications

Photocatalysis (hydrogen generation and organic

destruction)

Sensors

Self cleaning properties

Antibacterial action

Photovoltaic devices

Motivation

To synthesize TiO2 nanotubes by electrochemical anodization technique and to study the crystalline and morphological stability for Dye Sensitized Solar Cell application

What is Solar Energy?

Energy produced by the sun

Clean, renewable source of energy

Harnessed by solar collection

methods such as solar cells

Converted into usable energy such as

electricity

• 26,126 kWh/CapitaEnergy

Generation

• 183,161 TWh/CapitaEnergy

Consumption

Energy Demand

To overcome the demand solar cell is used

Photovoltaic Solar Cells

Generate electricity directly from sunlight2 Main types:

Single-crystal silicon (traditional)• Widespread• Expensive to manufacture

Dye-sensitized (“nano”)• Newer, less proven• Inexpensive to manufacture• Flexible• High power conversion

efficiencies 

Silicon-based solar cell

Dye-sensitized solar cell

Synthesis of one dimensional TiO2 architectures

Nano architectures – Nanotubes, rods and wires more active due to

directionality and large surface area. Hence nanotubular Architectures of

TiO2 were preferred

Nanotubular architectures

Nanotube powders

Electrochemical Anodization

Nanotube arrays

Rapid Breakdown anodization

Advantages of Electro chemical anodization

Cost effective

Simplest of all techniques

Aspect ratio tuning by changing the electrochemical

parameters

Chemical reaction involved…..2Ti + 2H2O 2TiO2 + 4e + 4H+

Working Electrode: Ti foil

Counter Electrode: Platinum foil Electrolyte : 0.1M

perchloric acid Applied voltage :11V

White powders of Titania ……

Synthesis of TiO2 powder nanotubes

Technique used … Rapid break down anodization

Synthesis of TiO2 nanotube arrays

Working Electrode: Ti foil

Counter Electrode: Platinum foil Electrolyte : 97 g of

ethylene glycol +0.5 g ammonium fluoride +2.5 g of DI water

Applied voltage :40V

Technique

used …

Electrochem

ical

Anodization

TiO2 Doping Dopants :Urea,

Hydrazine, Ammonia with different

concentrations….Voltage applied:

40 V

To overcome the disadvantage of tio2 dopants are usedDopants modify nano-TiO2’seffective range of light sensitivity

from the ultra-violet (UV) region to the visible light region due to band gap tuning

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1. Photovoltaic StudiesSolar Cell Fabrication and testing of DSSC fabricated using TiO2 nanotube arrays on

Ti foils and FTO coated glasses

Dye loaded TiO2 on FTO glass

Pt electrode

DSSC ready!!!!!!!

Taken for solar cell performance studies

•Dye-0.5mM N 719 dye in acetonitrile•Electrolyte- solaronix Iodolyte

Schematic of DSSCA sandwitch structure made of two conducting electrodes with a redox electrode filling the inter layer separation. Exposure of light - excitation of the dye - injects electrons to the CB of the oxide layerElectron hope through the semiconductor and collected at the collector electrode.Electrons flow through the external circuit and reach to the counter electrodeReduce the oxidized form of the electrolyte.

DSSC MECHANISM

S + hν → S∗ (1)S∗ → S+ + e− (TiO2)

3I- →I3- + 2e−

S+ + e− → S I3

− + 2 e− → 3 I−

RBA Electrochemical synthesis routes provide an attractive alternative to the standard methods of synthesizingnanomaterials. Electrochemical anodic oxidation has been widely used to synthesize TiO2 nanotubes ontitanium metal surface. Recently, an anodization of Ti foil in an electrolyte containing chloride or perchlorateions can produce high aspect ratio TiO2 NTs in very short time (~ 50 µm in < 1 min), which the mainadvantage of this kind of anodization that known as “rapid breakdown anodization”

TiO2 Nanostructures – Energy Related Applications

Dye Sensitized Solar Cell Hydrogen Generation by water splitting

Counter Electrode Working electrode

Pt – Optimization

Electrochemical Characterization

Ammonia annealing

Electrochemical anodization

Electrochemical impedance spectroscopy

Mott Schotky plot Studies

Synthesis of 1. TiO2 nanotube powders2. N-doped TiO2 nanotube

powders3. TiO2 nanotube arrays4. N-doped TiO2 nanotube

arrays

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Scanning Electron MicroscopyTransmission Electron MicroscopyX ray DiffractionRaman SpectroscopyFourier Transform Infra Red Spectroscopy

X-ray Photoelectron Spectroscopy- compositional analysis

PhotoluminescenceUltraviolet and Visible Absorption Spectroscopy

Temperature Programmed Desorption Reduction OxidationBrunauer Emmet Teller adsorption methodApplication:Field EmissionContact AnglePhotocatalytic Hydrogen GenerationSolar Cell Fabrication and testing

Morphology and structural characterization

Optical characterization

Chemi & Physisorption surface area measurement

Characterization

Experimental Details

Synthesis of TiO2 nanotubes by electrochemical

anodization.

Annealing of the anodized samples at different

temperatures.

Characterization by FESEM and XRD

Surface wettability by studies by contact angle

measurements.

Conclusions

Self aligned TiO2 nanotube arrays were synthesized on Ti

substrates by electrochemical anodization technique.

The potentiostatic transients qualitatively revealed the

mechanism of nanotube formation

Structural and morphological stability were revealed from

XRD and FESEM analysis.

Shows very good surface wettability with solar cell indicates

its potential application in Dye sensitized solar cell.

Ongoing studies & Future plans……

Characterization of TNTA on Ti substrates, TNTA on FTO

coated glasses and N doped TNTA using FESEM, TEM, XRD,

XPS, Micro Raman, DRS, FTIR,UV visible spectroscopy

To investigate the DSSC performance of the synthesized TiO2

nanotube arrays photocat h2 gen by water splitting

Study the effect of crystallinity on the solar cell performance of

the material