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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
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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
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Conductivity of high temperature proton conductors
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Heteropolyacid with Keggin structure (e.g. H3PO4x12WO3)
Nafion Heteropolyacid with Keggin structure (e.g. H3PO4x12WO3) Poly (2-acrylamido-2-methyl-1-propane sulphonic acid)
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Organic-inorganic material, synthesised in sol-gel process
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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
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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
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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
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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)
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Proton transport according to Grotthus mechanism
DMF-H3PO4 based gels Protonation of DMF Proton transport according to Grotthus mechanism
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PC-H3PO4 based gels Auto-dissociation of H3PO4 in PC
Vehicle transport at low acid concentration, Grotthus at high (30-40%) concentration
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Conductivity isotherms for anhydrous proton conducting gels
- solvent: DMF - solvent: PC
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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
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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
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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.
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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.
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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
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Electrochromic device
Electrochromic layer Transparent conductorprzewodnik Glass Electrolyte Transparent conductor - + ions According to Granqvist
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Some applications of electrochromic devices
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Magic ink
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Modern house
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