A novel mixed zirconium phosphate/phosphonate based on glyphosine, of formula Zr2(PO4)H5(L)2·H2O [L = (O3PCH2)2NCH2COO], was synthesized in mild conditions. The compound has a layered structure that was solved ab initio from laboratory PXRD data. It crystallizes in the monoclinic C2/c space group with the following cell parameters: a = 29.925(3), b = 8.4225(5), c = 9.0985(4) Å, and β = 98.474(6)°. Phosphate groups are placed inside the sheets and connect the zirconium atoms in a tetradentate fashion, while uncoordinated carboxylate and P−OH phosphonate groups are exposed on the layer surface. Due to the presence of these acidic groups, the compound showed remarkable proton conductivity properties, which were studied in a wide range of temperature and relative humidity (RH). The conductivity is strongly dependent on RH and reaches 1 × 10−3 S cm−1 at 140 °C and 95% RH. At this RH, the activation energy of conduction is 0.15 eV in the temperature range 80−140 °C. The similarities of this structure with related structures already reported in the literature were also discussed.

A Layered Mixed Zirconium Phosphate/Phosphonate with Exposed Carboxylic and Phosphonic Groups: X‑ray Powder Structure and Proton Conductivity Properties

DONNADIO, Anna;NOCCHETTI, Morena;COSTANTINO, FERDINANDO;TADDEI, MARCO;CASCIOLA, Mario;VIVANI, Riccardo
2014

Abstract

A novel mixed zirconium phosphate/phosphonate based on glyphosine, of formula Zr2(PO4)H5(L)2·H2O [L = (O3PCH2)2NCH2COO], was synthesized in mild conditions. The compound has a layered structure that was solved ab initio from laboratory PXRD data. It crystallizes in the monoclinic C2/c space group with the following cell parameters: a = 29.925(3), b = 8.4225(5), c = 9.0985(4) Å, and β = 98.474(6)°. Phosphate groups are placed inside the sheets and connect the zirconium atoms in a tetradentate fashion, while uncoordinated carboxylate and P−OH phosphonate groups are exposed on the layer surface. Due to the presence of these acidic groups, the compound showed remarkable proton conductivity properties, which were studied in a wide range of temperature and relative humidity (RH). The conductivity is strongly dependent on RH and reaches 1 × 10−3 S cm−1 at 140 °C and 95% RH. At this RH, the activation energy of conduction is 0.15 eV in the temperature range 80−140 °C. The similarities of this structure with related structures already reported in the literature were also discussed.
2014
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11391/1303497
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