Transcript Conducting Polymer Electrochromic Materials Utilising Room

Forming Conducting Polymers
Utilising Room Temperature Ionic
Liquids
PhD student: Lavinia Astratine
Supervisors:
Dr. Anthony Betts & Prof. John Cassidy (DIT)
Prof. Edmond Magner (MSSI, Limerick)
• 1. Concept
• 2. Objectives
• 3. Lab Work
• 4.Other polymers: polythiophene
& Ionic Liquids
• 5.Future work
1. Concept
• The aim of this project is to use conducting polymers
(CPs), in conjunction with Room Temperature Ionic
Liquids (RTILs), to produce electrochromic films.
• Such films, which change colour in response to
electrical potential changes, could be used in
electronic display devices and in light and energycontrol applications (eg. smart windows which
control light transmittance).
2. Objectives
• Production of improved electrochromic devices,
using a more environmentally-friendly “Green
Chemistry” approach is a desirable goal.
• Conducting polymers (CPs, such as polypyrrole,
polythiophene,
polyaniline
and/or
their
derivatives) have been studied extensively.
A promising CP for electrochromic
applications is polypyrrole
(PPy).
Characteristics of polypyrrole:
• Thin films of polypyrrole are yellow in the undoped
insulating state and black in the doped conductive
state
• Electrochemical degradation has been reported in
many studies
• The electrode potential applied has been found to
influence greatly the degradation process (electrode
potential limit 0.6 V vs. Ag/AgCl)
• Polypyrrole is a quite labile electrode material that
undergoes a relatively fast electrochemical
degradation, at least in aqueous solutions
Electrochimica Acta 52 (2007) 4784–4791
3. Lab Work
Method used: Cyclic Voltammetry
• a) Form PPy films using organic solvents as Electrolyte
Experimental set up
Working Electrode (WE): Pt electrode (diameter 2mm)
Counter Electrode (CE): Silver Wire
Reference Electrode (RE): saturated Ag/AgCl
Pyrrole used for synthesis of PPy films was purified by distillation
and kept refrigerated in the dark.
Monomer solution:
0.1 M Pyrrole and 0.1 M LiClO4 and H2O
Electrolyte solution:
0.1 M LiClO4 and H2O
Results and Discussion
→Potential range:
-1V to +0.8V
→ After 3 sweeps a
yellow film was
deposited on the
electrode surface
• In order to change the
polymer
colour
the
electrode was placed in
electrolyte solution
• Potential range:
-0.4V to +0.5V
• CV in electrolyte for
10 cycles
• The polymer changed
colour to blue
•
b) Form PPy on FTO glass (WE), [0.5cmx3cm]
Monomer solution (deoxygenated
for 10 minutes):
0.1 M Py, 0.1 M LiClO4, H2O
Electrolyte solution:
0.1 M LiClO4, H2O
Potential range: -0.9 V to 1.5 V
Run for 6 sweeps
→ Results in a black oxidized
film, which is unstable
→ Polypyrrole was overoxidized
Observations:
• PPy is oxidizing at ca. 0.6V.
From 0.55V on, the current increases with each potential
sweep.
• No colour change of the polymer was observed on the FTO
glass.
• Probably 1 or 2 scans are enough in the region where the
pyrrole starts to be oxidized (0.95 V).
• The results are better with FTO glass when the monomer
solution is degassed before starting polymer formation.
4.Other polymers: polythiophene
Combines the flexibility, elasticity and malleability
of plastics + electrical conductivity + also often
exhibit colour (polychromism) as electrochromic
materials
Ionic Liquids ‘Green Solvents’
• Ionic liquids (ILs) are room temperature molten
salts, composed mostly of organic ions that can
undergo almost unlimited structural variations
• ILs which function at room temperature, the most
desirable operational temperature range, are
termed “Room Temperature Ionic Liquids”, RTILs
• Examples include 1-butyl-3-methylimidazolium
hexafluorophosphate (BMIM PF6) and its borate
counterpart (BMIM.BF4)
Making polymers in ionic liquids
25cycles
WE: Pt electrode
CE: Pt coil
RE: Pt wire
Monomer Solution:
0.1 M Pyrrole &
BMIM PF6
Polymerization range: -1 V to +1 V
Colours of the film: yellow→orange→red→Black
WE: FTO glass (3cm x 0.5mm)
CE: Pt coil
RE: Pt wire
Monomer Solution:
0.1 M Pyrrole &
BMIM PF6
16 cycles
Polymerization range: -1 V to +1 V
Colours of the film: yellow→light Brown→Brown→Black
5. Future work
• Combine conducting polymers (pyrrole, thiophene) with other
RTILs such as [ChCl][EG], [BMIM][CF3SO3], [Py][CF3SO3] in
order to get different colours during electropolymerization on
optically transparent FTO and Au-sputtered glass substrates.
• Conduct spectroelectrochemical studies of the polymer films,
in order to detect colour changes in situ
• Gain insight into the mechanisms of electrochromism
• Construct simple Proof of Concept Device/Prototype
illustrating potential of technology and transfer technology
Papers
• Electrochimica Acta 52 (2007) 4784–4791, A.Brazier et al.
• Polymer Degradation and Stability 75 (2002) 255–258,
R. Mazeikiene, A. Malinauskas
• Synthetic Metals 157 (2007) 485-491, A. Alumaa et al.
• Electrochimica Acta, Vol.42,No.2,pp. 203-210, 1997,
Yongfang Li
• Journal of Electroanalytical Chemistry 618 (2008) 87–93, by
D. Asil et al.
• Nature Materials, 8, (2009), 621-629, M. Armand, D.R.
MacFarlane, H. Ohno and B. Scrosati
• Polymer 45(2004) 1447-1453, J.M. Pringle et al.
Aknowledgements
- Dr. Anthony Betts & Prof. John Cassidy (DIT)
- Prof. Edmond Magner (MSSI, Limerick)
- Edmond Magner Research Group (MSSI,Limerick)
Thank you
for your attention!