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Proton conductors Low-temperature systems

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Presentation on theme: "Proton conductors Low-temperature systems"— Presentation transcript:

1 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

2 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

3 Conductivity of high temperature proton conductors

4 Heteropolyacid with Keggin structure (e.g. H3PO4x12WO3)
Nafion Heteropolyacid with Keggin structure (e.g. H3PO4x12WO3) Poly (2-acrylamido-2-methyl-1-propane sulphonic acid)

5 Organic-inorganic material, synthesised in sol-gel process

6 e.g. poly (acrylic acid), PAMPS
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

7 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

8 Structure of glycidyl methacrylate and products of its reaction with phosphoric acid
G.Zukowska, V. Robertson, M. Marcinek, K.R. Jeffrey, J. R. Stevens J.Phys.Chem. B 10 (2003) 5797

9 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)

10 Proton transport according to Grotthus mechanism
DMF-H3PO4 based gels Protonation of DMF Proton transport according to Grotthus mechanism

11 PC-H3PO4 based gels Auto-dissociation of H3PO4 in PC
Vehicle transport at low acid concentration, Grotthus at high (30-40%) concentration

12 Conductivity isotherms for anhydrous proton conducting gels
 - solvent: DMF  - solvent: PC

13 Conductivity of liquid and gel electrolyes based on PMMA-PC-H3PO4
 - gels  - liquid a)50% mas. H3PO4 b)26% mas. H3PO4 c)19.5% mas. H3PO4

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

15 The coefficients decrease with acid concentration
NMR measurements of the diffusion of deuterons in the DMF/phosphoric acid mixtures and in the PGMA/DMF/H3PO4 gels. K.R. Jeffrey, G.Z. Zukowska, and J.R. Stevens J. Chem. Phys. 119 (2003) 2422 The coefficients decrease with acid concentration and with the introduction of the polymer gel.

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

17 Influence of the type of proton donor on conductivity in electrolytes based on PMMA-PC-DMF (a) and PVdF-DMF (b) (a) (b) - PWA, - diphenyl phosphate, - H3PO4

18 Electrochromic device
Electrochromic layer Transparent conductorprzewodnik Glass Electrolyte Transparent conductor - + ions According to Granqvist

19 Some applications of electrochromic devices

20 Magic ink

21 Modern house

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