Presentation on theme: "Proton conductors Low-temperature systems"— Presentation transcript:
1 Proton conductors Low-temperature systems water containing systems. e.g. Nafion, heteropolyacidsoxoacids 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 systemsoxides, 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) NafionHeteropolyacid 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 electrolytesAcidic groups (-COOH, -SO3H) in side or main chain (part of the polymer bachbone),e.g. poly (acrylic acid), PAMPSComplexes of polymer with salt or acid: polymer with basic sites in a chain is a solvent for the dopantPolymer gels- three component systems, combining polymer matrix swollen with dopant solution in an an apropriate solventPolymers 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 electrolytesPolymers:Acrylic and methacrylic polymers (PMMA, PAN,PGMA,PAAM), poly (vinylidene fluoride), poly (vinyl chloride), PEOSolvents:Propylene carbonate, ethylene carbonate, N, N-dimethylformamide, glymes, N-vinylpyrrolidoneAcids: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. StevensJ.Phys.Chem. B 10 (2003) 5797
9 Mechanism of proton transport in polymer electrolytes GrotthusFast exchange of protons („hoping”) between neighbouring moleculesVehicleTransport of a proton as a part of a bigger species (e.g. anion)
10 Proton transport according to Grotthus mechanism DMF-H3PO4 based gelsProtonation of DMFProton 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 - liquida)50% mas. H3PO4b)26% mas. H3PO4c)19.5% mas. H3PO4
14 Conductivity of liquid and gel electrolytes based on PGMA-DMF-H3PO4 - gels - liquida)50% mas. H3PO4b)44% mas. H3PO4c)38% mas. H3PO4d)26% mas. H3PO4e)8% mas. H3PO4e*)5% mas. H3PO4GMA (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. StevensJ. Chem. Phys. 119 (2003) 2422The coefficients decrease with acid concentrationand 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 matrixThe 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 layerTransparent conductorprzewodnikGlassElectrolyteTransparent conductor-+ionsAccording to Granqvist
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