Transcript Slajd 1 - Polymer Ionics Research Group

Proton conductors
Low-temperature systems
•water containing systems. e.g. Nafion, heteropolyacids
•oxoacids and their salts, which show proton conductivity
even in the absence of water due to their self-dissociation,
e.g. CsHSO4 (s=10-3 S cm-1 above 412 K)
•blends of organic compounds exhibiting basic sites with
acids, e.g. H3PO4 or H2SO4.
•Xerogels- amorphous materials obtained by drying of the
inorganic gels synthesised using sol-gel route.
High temperature systems
•oxides, hydroxides and apatites
Proton conductivity of some water containing compounds
200 100
0
T / oC
4
log (s T)/ S cm-1 K
2
0
1 M HCl
Nafion
H4SiW12O40 x 28 H2O
(fully hydrated)
(heteropolyacid)
SnO2 x n H2O
(particle hydrate)
-2
Zirconium phosphonate
containing -SO3H x 5.9 H2O
-4
H3UO2AsO4 x H2O
-6
+
H3O --alumina
-8
ice
-10
2
3
4
1000 T-1/ K-1
5
6
The loss of water, which in most cases takes place at
temperatures close to the boiling point of water, results in a
decrease in conductivity
Conductivity of high temperature proton conductors
T / oC
400
200
100
1M NaOH
2
log (s T)/ S cm-1 K
0
-2
0
Y2O3
(undoped)
Y: SrZrO3
(single crystal)
Nd: BaCO3
-4
Ni:KTaO3
-6
Y:SrCeO3
-8
-10
Fe:LiNbO3
1
2
3
-1
-1
1000 T / K
4
CF2 CF2
Nafion
CF2 CF
OCF2
CF
OCF2CF2 SO3Na
m
n
CF3
m = 0, 1, 2 ;
n
= 1-5
Heteropolyacid with Keggin structure
(e.g. H3PO4x12WO3)
Poly (2-acrylamido-2-methyl1-propane sulphonic acid)
R
CH2 CH
C
R
n
O
HN
H3C
C
CH3
H2C
O
S
OH
O
O
Si
O
Si
R'
Organic-inorganic
material, synthesised in
sol-gel process
Organically
modified
silicate
O
Si
R'
R'
O
Si
Si
Inorganic
organic
polymer
(ORMOCER)
P
P
P
Si
R''Y
P= polymerisable ligand
R'=(CH2 )3NH2 , C6 H5
R"=ionic ligand
Y= ions
Polymer electrolytes
•Acidic groups (-COOH, -SO3H) in side or main chain (part of the
polymer bachbone),
e.g. poly (acrylic acid), PAMPS
•Complexes of polymer with salt or acid: polymer with basic sites in a
chain is a solvent for the dopant
•Polymer gels- three component systems, combining polymer matrix
swollen with dopant solution in an an apropriate solvent
Polymers which may be applied in proton conducting systems should fulfil some
requirements, such as:
- chemical and thermodynamic stability
- specific protonic conductivity
- conductivity range depending on the perspective application, i.e. 10-1- 10-3 S cm-1
for fuel cells and 10-5- 10-7 S cm-1 for sensors or electrochromic devices
- properties independent of the humidity level
- thin film configuration.
The use in electrochromic devices requires also high transparency of membranes
Gel electrolytes
Polymers:
Acrylic and methacrylic polymers (PMMA, PAN,PGMA,PAAM),
poly (vinylidene fluoride), poly (vinyl chloride), PEO
Solvents:
Propylene carbonate, ethylene carbonate, N, Ndimethylformamide, glymes, N-vinylpyrrolidone
Acids:
Phosphoric acid and its acidic esters, sulfuric acid, sulphonic
acids, phosphonic acids, heteropolyacids
Structure of glycidyl methacrylate and products of its reaction with
phosphoric acid
b CH3
CH2
C
C
d e
c
CH2 CH CH2
O
a
GMA
O
+
HO
O
O
P
OH
OH
b CH3
H2O
b CH3
C
CH2 C
a
O
(2b)
CH2
d e
c
CH2 CH CH2
a
HO
b CH3
OH
(2a) CH2
GMA
b CH
3
CH2 C
a
C
O
O
O
O
P
(3)
O
O
CH2
e'
d'
CH
OH
C
O
CH2
c'
C
P
OH
O
d
e
CH2 CH CH2 O
c
C
O
O
OH
CH3 b'
c
d e
CH2 CH CH2
O
C
a
e
O
O
H2O
P
O
d
CH2 CH CH2 OH
O
O
O
O
(1)
c
C
C
O
P
OH
O
GMA
CH2
a'
CH2
a
CH3 b
C
C
O
O
O
b' CH3 O
(4)
e
c
d
CH2 CH CH2 O
CH2 C
a'
C
O
P
OH
O
e' CH
2
d' CH OH
O
CH2
c'
G.Zukowska, V. Robertson, M. Marcinek, K.R. Jeffrey, J. R. Stevens
J.Phys.Chem. B 10 (2003) 5797
Mechanism of proton transport in polymer electrolytes
Grotthus
Fast exchange of protons („hoping”) between neighbouring molecules
Vehicle
Transport of a proton as a part of a bigger species (e.g. anion)
DMF-H3PO4 based gels
Protonation of DMF
CH3
HC
N
O
CH3
HC
+ H3PO4
N
+
CH3
OH
CH3
+
HC
CH3
N
OH
+ H2PO4-
CH3
Proton transport according to Grotthus mechanism
(DMF)H+ (DMF)
(DMF)H+ (DMF)
(DMF)H+ (DMF)
(DMF)
H+(DMF)
(DMF)
H+(DMF)
(DMF)
H+(DMF)
(DMF)
(DMF)H+
(DMF)
(DMF)H+
(DMF)
(DMF)H+
PC-H3PO4 based gels
H4PO4+
H3PO4
H2PO4-
Auto-dissociation of H3PO4 in PC
Vehicle transport at low acid concentration,
Grotthus at high (30-40%) concentration
5 H3PO4
16.815
mol/ l at 311 K
2 H4PO4+ + H2PO4- + H3O+ + H2P2O720.89
0.42
0.461
0.461
Conductivity isotherms for anhydrous
proton conducting gels
-1
log (s/ S cm )
-3.2
-3.6
-4.0
-4.4
10
20
30
% mas. H3PO4
40
50
 - solvent: DMF
 - solvent: PC
Conductivity of liquid and gel electrolyes
based on PMMA-PC-H3PO4
(c)
(b)
(a) -2
-3
-1
log (s/ cm )
-4
-5
-6
-7
-8
-9
2.5
3.0
3.5
4.0
1000 T-1/ K-1
4.5
5.0
 - gels
 - liquid
a)50% mas. H3PO4
b)26% mas. H3PO4
c)19.5% mas. H3PO4
Conductivity of liquid and gel electrolytes
based on PGMA-DMF-H3PO4
 - gels
 - liquid
a)50% mas. H3PO4
b)44% mas. H3PO4
c)38% mas. H3PO4
d)26% mas. H3PO4
e)8% mas. H3PO4
e*)5% mas. H3PO4
(e)
(d)
(c)
(b)
(a)
-2
-3
GMA (glycidyl
methacrylate) reacts with
phosphoric acid with
formation of acidic
phosphates (stronger acids
than H3PO4) which results
in increase in conductivity
log(s/Scm-1)
-4
-5
-6
-7
-8
-9
2.5
3.0
3.5
4.0
1000/ T
4.5
5.0
NMR measurements of the diffusion of deuterons in the DMF/phosphoric acid
mixtures and in the PGMA/DMF/H3PO4 gels.
-9
2 -1
Diffusion Coefficient (x 10 m s )
10
1
0.1
0.01
DMF/D3PO4 40%
DMF/D3PO4 20%
DMF/D3PO4 7%
PGMA/DMF/D3PO4 40%
PGMA/DMF/D3PO4 20%
0.001
2.5
2.7
2.9
3.3
3.1
3.5
-1
1000/Temperature (K )
K.R. Jeffrey, G.Z. Zukowska, and J.R. Stevens
J. Chem. Phys. 119 (2003) 2422
A comparison of the diffusion coefficients for the deuterons and phosphorus in
the samples containing 40% phosphoric acid with and without the polymer
matrix
0.1
31
P DMF/D3PO4 40%
2
H DMF/D3PO4 40%
31
P PGMA/DMF/D3PO4 40%
-9
2 -1
Diffusion Coefficient (x 10 m s )
2
H PGMA/DMF/D3PO4 40%
The measurements were made using
the static magnetic field gradient
NMR technique. The diffusion
coefficients for the deuterons are
about a factor of three greater than
that for phosphorus in comparable
samples. The influence of the gel is to
reduce the diffusion coefficient.
0.01
0.001
2.6
2.8
3.0
3.2
3.4
-1
1000/Temperature (K )
3.6
Influence of the type of proton donor on
conductivity in electrolytes based on PMMA-PCDMF (a) and PVdF-DMF (b)
(a)
(b)
-2.50
-3.00
-3.50
-1
log (s/ S cm )
-1
log (s / S cm )
-3.00
-4.00
-4.50
-5.00
-3.50
-4.00
-4.50
-5.00
-5.50
-5.50
-6.00
3.0
3.5
4.0
4.5
-1
-1
1000 T / K
5.0
3.0
3.5
4.0
4.5
-1
-1
1000 T / K
- PWA, - diphenyl phosphate, - H3PO4
5.0
Electrochromic device
-
+
+
+
+
+
ions
According to Granqvist
Some applications of electrochromic devices
Magic ink
Modern house