slide viva april 2016

1

VIVA VOCEAPRIL 2016

Title:Improvement of Formation of Carbon Doped Titanium Dioxide (TiO2) Particles via

Electrospraying Technique

Name:Siti Umairah bt Halimi

2012326965Supervisors:

Dr Noor Fitrah Abu BakarSiti Norazian Ismail

Page 2 2

Titanium Dioxide (TiO2)

• Molecular structure

• Major drawback and improvement

Page 3 3

Doping TiO2

Intentionally introducing an impurity element (N,C,S etc.) into TiO2 latice in order to alter its properties.

3 mechanism of modification on doped TiO2

or

Narrowing band gap energy by substituting O in TiO2 (R. Asahi, 2011),

Introduce an impurity energy level above valence band (Hiroshi Irie, 2003)

Form oxygen vacancy site near conduction band (Aziz A. A, 2012)

Page 4 4

Previous Method of Producing Doped TiO2 Chemical precipitation

Advantages- Simple method - Time efficient

Disadvantages - Heating - Highly aggregates - Particles properties affected by heating

Sol gel process

Advantages- Simple method - Produce large quantity of sample

Disadvantages - Crucial control of condensation- Few stages of drying- Particles properties affected by phase transformation

2

Page 5 5

Problem Statement Objectives

High band gap energy (~3.2 eV).activate under UV light irradiation(λ<387 nm)

Large and wide distribution ofdoped TiO2 particles size

Common synthesis methodrequires calcination at high temperature

To investigate the potential of using electrospraying tehnique towards formation of small size of C-doped TiO2 droplets

To characterize chemical andphysical properties of electrosprayed C-doped TiO2particles

To evaluate the performance of electrosprayed C-doped TiO2 indegradation of phenol as model pollutant under visibe light radiation

Page 6 6

Electrospraying Technique Technique that uses an electric field to disperse a liquid jet into fine charged

droplets through Coulomb Fission of charges.

Advantages

- High stability of TiO2 particles in suspension

- Produce dried TiO2 particles without calcination

- Dried TiO2 particles with fine and narrow size distribution

Page 7 7

Scope Carbon dopant precursor

Zeta potential and particles distribution of C-doped TiO2 suspension

Coulomb fission behaviour during electrospraying to produce small C-doped TiO2 particles

Degradation of phenol under visible light radiation using electrosprayed C-doped TiO2

Limitation Concentration of carbon dopant

precursor used (0.25 M - 1.0 M)

pH value of C-doped TiO2 suspension (pH 2 - 13)

Voltage applied during electrospraying (1.8-2.3 kV)

C-doped TiO2 suspension was electrosprayed at working distance 10-20 cm

Characterization using Nano-Zetasizer, FESEM, UV-Vis, XPS, FTIR and XRD

Research Methodology

3

Page 9 9

Preparation of C-doped TiO2 Suspension

7 mL TTIP

50 mL H2O

50 mL Ethanol

10 mL Acetic Acid

Solution A Solution B

Dopant precursor0.25 M, 0.5 M, 0.75 M, 1.0 M

1 hour, 500 rpm 30 min, 50 kHz

Page 10 10

(a) (b)

(c)(d)

Electrospraying Technique

Dripping Pulsating

Taylor Cone jet Multi jet

Most desired spraying mode to produce fine and narrow distribution of particles

Page 11 11

Estimation of Primary Charged Droplet - Scaling Laws Suspension parameter

Scaling laws

)16(3 6/1

KQd o

d

Parameter Value Liquid density,ρ (kg/m3) 1000

Electrical permittivity of vacuum,εo (C2/Nm) 8.85 x 10-12

Liquid flow rate,Q (m2/s) 5.56 x 10-10

Surface tension,γ (N/m) 43.44 x 10-3

Conductivity of liquid,K (S/m) 0.8Relative permittivity,εr 88

)()66.1(3/1

6/1

KQ

d orrd

)(3/1

2164.1K

Qd ord

(R.P.A Hartman, 2001) (F.De La Mora, 2012) (Ganan-Calvo, 2011)

3/1dp dd

Theoretical dried droplet size

Number of fission events = dd dp

Page 12 12

Characterization of Electrosprayed C-doped TiO2

Nano-Zetasizer : Zeta potential value and particles size distribution of C-doped TiO2 partciles in suspension

FESEM : Morphology and droplets size of electrosprayed C-doped TiO2

UV-Vis Spectroscopy : Absorption wavelength on electrosprayed C-doped samples and un-doped sampleXPS : Detect the presence of carbon element in electrosprayed C-doped TiO2 sample

FTIR : To study the changes in functional group for electrosprayed C-doped TiO2 and un-doped TiO2 sample

XRD : To determine the crystal phase of electrosprayed C-doped TiO2

4

Page 13 13

Degradation of Phenol Under Visible Light

Absorbance at wavelength 319 nm

– A = εCd

– where: A = absorbance

ε = molar absorption coeffcient of phenol

C = concentration

d = cuvette length

Set up experiment

Phenol sample was taken every 1 hour for 4 hours degradation time

15 cmLamp

Hot plate

Results and Discussions

Page 15 15

Zeta Potential and C-doped TiO2 Particles Distribution in Suspension

Zeta potential, pH 2 = 27.98 mV

Particles size in suspension, pH 2 = 249 nm

IEP = pH 4.3

Suspension was stabilized at pH 2 because it is close to the suspension initial condition after hydrolysis. Too much electrolytes can cause destabilization (Lizhu Zhang, 2012) Page 16 16

Scaling Laws and FESEM Results of Droplets Size Distribution a) 10 cm working distance

b) 15 cm working distance

c) 20 cm working distance

Average droplets size = 163.2 ±157.4 nm



Increasing WD produced fine size of C-doped TiO2 particles with narrow size distribution of dropets

5

Page 17 17

Scaling laws, theoretical dried droplet size and number of fission events

*Hartman model **Fernandez de la Mora model ***Ganan-Calvo model

Model

Primary droplet size, dd (nm)

Theoretical dried droplet size, dp (nm)

Average deposited droplet size (FESEM) (nm)

Theoretical number of fission events

Hartman 2755 1164.40 - 2F.D.L Mora 641.46 271.11 - 2G.Calvo 991.32 418.98 - 2FESEM

1. 10 cm - - 163.2 ± 157.4 -2. 15 cm - - 162.8 ± 179.9 -3. 20 cm - - 147.5 ± 173.5 -

Experimental number of fission events

---

17*17*19*

4** 6***4** 6***4** 7***

)16(3 6/1

KQd o

d

)()66.1(

3/16/1

KQ

d orrd

)(3/1

2164.1K

Qd ord

3/1dp dd

Theoretical dried droplet size

Page 18 18

UV-Vis Analysis and Calculation of Band Gap Energy

chJE )(

Conversion factor, 1eV = 1.6 x 10-19 J

Sample Cut off wavelength (nm) Band gap energy (J) Band gap energy (eV)

(a) un-doped 4.13 x 10-7 4.81 x 10-19 3.0

(b) 0.25 M C-doped 4.2 x 10-7 4.73 x 10-19 2.96

(c) 0.5 M C-doped 5.06 x 10-7 3.93 x 10-19 2.46

(d) 0.75 M C-doped 4.93 x 10-7 4.03 x 10-19 2.52

(e) 1.0 M C-doped 4.4 x 10-7 4.52 x 10-19 2.83

(f) unelectrosprayed 0.5 M C-doped 4.3 x 10-7 4.62 x 10-19 2.89

Page 19 19

XPS Analysis of Chemical Element Present in 0.5 M C-doped TiO2

a) Wide scan of elemental species b) Binding energy of single element Ti

c) Binding energy of single element C d) Binding energy of single element O

C-O

458 eV (lit.review)

456 eV-Ti-C

Page 20 20

FTIR analysis of functional groups in C-doped and un-doped TiO2

Electrosprayed un-doped TiO2

Electrosprayed 0.25 M C-doped TiO2




Un-electrosprayed 0.50 M C-doped TiO2

6

Page 21 21

XRD analysis of crytal phase of C-doped and un-doped TiO2

Electrosprayed un-doped TiO2





Un-electrosprayed 0.50 M C-doped TiO2

Page 22 22

Degradation of Phenol Using 0.5 M C-doped TiO2Electrosprayed 0.5 M C-doped TiO2 Unelectrosprayed 0.5 M C-doped TiO2

Degradation time (min) Absorbance Concentration

(mg/L) Absorbance Concentration (mg/L)

0 1.879 2.08 1.986 2.20

60 0.427 0.47 0.762 0.84

120 0.305 0.33 0.469 0.52

180 0.232 0.25 0.244 0.27

240 0.032 0.03 0.103 0.11

Conclusions

Page 24 24

Conclusions

From mechanism of droplet fission and Scaling laws, the primary droplet undergo fission and the deposited C-doped TiO2 produced from electropraying technique has fine and narrow distribution of droplets size

The C-doped TiO2 suspension were stabilized at pH 2 with high zeta potential value and small perticles size in suspension which is +27.98 mV and 249.12 nm respectively.

Since carbon element was introduced in TiO2, TiO2 properties were enhanced. The produced C-doped TiO2 particles has desired anatase phase, low band gap energy and active under visible light radiation.

The C-doped TiO2 paticles was effective as catalyst for degradation of pollutant under visible light radiation .

7

Page 25 25

Recommendations

Further explore on fission behavior and other parameters such as viscosity and conductivity that can affect the electrospraying technique.

Doping with other elements in addition to carbon element as per discussed in this study .

slide viva april 2016

Documents