Proton conductorsProton conductorsLow-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 (=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

1000 T-1/ K-12 3 4 5 6

log

( T

)/ S

cm

-1 K

-10

-8

-6

-4

-2

0

2

4

H3O+--alumina

ice

H3UO2AsO4 x H2O

1 M HClNafion

(fully hydrated) H4SiW12O40 x 28 H2O

(heteropolyacid)

Zirconium phosphonatecontaining -SO3H x 5.9 H2O

SnO2 x n H2O

(particle hydrate)

200 100 0 T / oC

Proton conductivity of some water containing compounds

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 conductorsConductivity of high temperature proton conductors

1000 T-1/ K-11 2 3 4

log

( T

)/ S

cm

-1 K

-10

-8

-6

-4

-2

0

2

Fe:LiNbO3

1M NaOH

Y:SrCeO3

Ni:KTaO3

Y2O3

(undoped)

Nd: BaCO3

200 100 0T / oC

Y: SrZrO3

(single crystal)

400

Heteropolyacid with Keggin structure (e.g. H3PO4x12WO3)

CF2 CF2 CF2

OCF2

CF

CF3

CF OCF2CF2 SO3Na

m n

m = 0, 1, 2 ; n = 1-5

Nafion

CH2 CH

C

R R

O

NH

C CH3

CH2

CH3

S OO

OH

n

Poly (2-acrylamido-2-methyl-1-propane sulphonic acid)

O

O R'

O

OR' R'

R''Y

SiSi

Si

P P P

Si

Si

Si

P= polymerisable ligand

R'=(CH2)3NH2, C6H5

R"=ionic ligand

Y= ions

Organically modified silicate

Inorganic organic polymer

(ORMOCER)

Organic-inorganic material, synthesised in sol-gel process

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, N-dimethylformamide, 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 Structure of glycidyl methacrylate and products of its reaction with phosphoric acidphosphoric acid

CH2 C C O CH2 CH

CH3

O O

CH2

CH2 C C O CH2 CH

CH3

O OH

CH2P

O

O OH

O

P

O

OH OH

O

CH2 C C O CH2 CH

CH3

O

CH2 OH

PO

OH

O

O

CH2 C C O CH2 CH

CH3

O

CH2

P

OH

OH OH

O

PO

O

O

O

CH2 C C O CH2 CH

CH3

O

CH2

CH2 CH CH2

OH

O

C CO

CH3

CH2

CH2 C C O CH2 CH

CH3

O O

CH2P

O

O OH

O

CH2

CH

CH2

OH

OC

O

C

CH3

CH2

+

(1)

(2a)

(2b)

GMA

(4)

a

a

a

a

a

a'

b

b

b

b

b

b'

b'

c

c

c

c

c'

c'

a'

c

d

d

d

d

d

a

bc

d

e

e

e

e

e

e

e'

e'

d'

d'

(3)

H2O

H2O

GMA

GMA

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 Mechanism of proton transport in polymer electrolyteselectrolytes

GrotthusFast exchange of protons („hoping”) between neighbouring molecules

VehicleTransport of a proton as a part of a bigger species (e.g. anion)

DMF-HDMF-H33POPO4 4 based gelsbased gels

(D M F )(D M F )H + (D M F )(D M F ) (D M F )H + (D M F )H +

(D M F )H + (D M F )(D M F ) (D M F ) H + (D M F ) H + (D M F )

(D M F ) (D M F )H +(D M F )(D M F ) (D M F )H + (D M F )H +

Protonation of DMF

Proton transport according to Grotthus mechanism

NCH

O

CH3

CH3

NCH

OH+

CH3

CH3

N+CH

OH

CH3

CH3

+ H 3 P O 4 + H 2 P O 4-

PC-HPC-H33POPO44 based gels based gels

Auto-dissociation of H3PO4 in PCVehicle transport at low acid concentration,

Grotthus at high (30-40%) concentration

H3PO4 H2PO4-H4PO4

+

5 H3PO4 2 H4PO4+

+ H2PO4- + H3O

+ + H2P2O72-

16.815mol/ l at 311 K

0.89 0.42 0.461 0.461

Conductivity isotherms for anhydrous proton conducting

gels

- solvent: DMF - solvent: PC % mas. H3PO4

10 20 30 40 50

log

(/ S

cm

-1)

-4.4

-4.0

-3.6

-3.2

Conductivity of liquid and gel Conductivity of liquid and gel electrolyes based on PMMA-electrolyes based on PMMA-

PC-HPC-H33POPO44

- gels - liquida)50% mas. H3PO4

b)26% mas. H3PO4

c)19.5% mas. H3PO4

1000 T-1/ K-1

2.5 3.0 3.5 4.0 4.5 5.0

log

(/ c

m-1

)

-9

-8

-7

-6

-5

-4

-3

-2(a)

(b)

(c)

Conductivity of liquid and gel Conductivity of liquid and gel electrolytes based on PGMA-electrolytes based on PGMA-

DMF-HDMF-H33POPO44 - gels - liquida)50% mas. H3PO4

b)44% mas. H3PO4

c)38% mas. H3PO4

d)26% mas. H3PO4

e)8% mas. H3PO4

e*)5% mas. H3PO4

1000/ T

2.5 3.0 3.5 4.0 4.5 5.0

log(

/S

cm-1

)

-9

-8

-7

-6

-5

-4

-3

-2(a)

(b)

(c)

(d)

(e)

GMA (glycidyl methacrylate) reacts with phosphoric acid with formation of acidic phosphates (stronger acids than H3PO4) which results in increase in conductivity

NMR measurements of the diffusion of deuterons in the DMF/phosphoric acid NMR measurements of the diffusion of deuterons in the DMF/phosphoric acid

mixtures and in the PGMA/DMF/Hmixtures and in the PGMA/DMF/H33POPO44 gels. gels.

1000/Temperature (K-1)

2.5 2.7 2.9 3.1 3.3 3.5

Dif

fusi

on C

oeff

icie

nt (

x 10

-9 m

2 s-1)

0.001

0.01

0.1

1

10

DMF/D3PO4 40%

DMF/D3PO4 20%

DMF/D3PO4 7%

PGMA/DMF/D3PO4 40%

PGMA/DMF/D3PO4 20%

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 A comparison of the diffusion coefficients for the deuterons and phosphorus in the samples containing 40% phosphoric acid with and without the polymer the samples containing 40% phosphoric acid with and without the polymer

matrixmatrix

1000/Temperature (K-1)

2.6 2.8 3.0 3.2 3.4 3.6

Dif

fusi

on C

oeff

icie

nt (

x 10

-9 m

2 s-1)

0.001

0.01

0.131P DMF/D3PO4 40%2H DMF/D3PO4 40%31P PGMA/DMF/D3PO4 40%2H 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.

- PWA, - diphenyl phosphate, - H3PO4

Influence of the type of proton donor on conductivity in electrolytes based on PMMA-PC-

DMF (a) and PVdF-DMF (b)

1000 T-1/ K-1

3.0 3.5 4.0 4.5 5.0

log

( /

S cm

-1)

-5.50

-5.00

-4.50

-4.00

-3.50

-3.00 (a)

1000 T-1/ K-13.0 3.5 4.0 4.5 5.0

log

( /

S cm

-1)

-6.00

-5.50

-5.00

-4.50

-4.00

-3.50

-3.00

-2.50 (b)

Electrochromic deviceElectrochromic device

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