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Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties

[Image: see text] Transition-metal phosphates show a wide range of chemical compositions, variations of the valence states, and crystal structures. They are commercially used as solid-state catalysts, cathode materials in rechargeable batteries, or potential candidates for proton-exchange membranes...

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Autores principales: Petersen, Hilke, Stegmann, Niklas, Fischer, Michael, Zibrowius, Bodo, Radev, Ivan, Philippi, Wladimir, Schmidt, Wolfgang, Weidenthaler, Claudia
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2021
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8826274/
https://www.ncbi.nlm.nih.gov/pubmed/34807595
http://dx.doi.org/10.1021/acs.inorgchem.1c02613
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author Petersen, Hilke
Stegmann, Niklas
Fischer, Michael
Zibrowius, Bodo
Radev, Ivan
Philippi, Wladimir
Schmidt, Wolfgang
Weidenthaler, Claudia
author_facet Petersen, Hilke
Stegmann, Niklas
Fischer, Michael
Zibrowius, Bodo
Radev, Ivan
Philippi, Wladimir
Schmidt, Wolfgang
Weidenthaler, Claudia
author_sort Petersen, Hilke
collection PubMed
description [Image: see text] Transition-metal phosphates show a wide range of chemical compositions, variations of the valence states, and crystal structures. They are commercially used as solid-state catalysts, cathode materials in rechargeable batteries, or potential candidates for proton-exchange membranes in fuel cells. Here, we report on the successful ab initio structure determination of two novel titanium pyrophosphates, Ti(III)p and Ti(IV)p, from powder X-ray diffraction (PXRD) data. The low-symmetry space groups P2(1)/c for Ti(III)p and P1̅ for Ti(IV)p required the combination of spectroscopic and diffraction techniques for structure determination. In Ti(III)p, trivalent titanium ions occupy the center of TiO(6) polyhedra, coordinated by five pyrophosphate groups, one of them as a bidentate ligand. This secondary coordination causes the formation of one-dimensional six-membered ring channels with a diameter d(max) of 3.93(2) Å, which is stabilized by NH(4)(+) ions. Annealing Ti(III)p in inert atmospheres results in the formation of a new compound, denoted as Ti(IV)p. The structure of this compound shows a similar three-dimensional framework consisting of [PO(4)](3–) tetrahedra and Ti(IV+)O(6) octahedra and an empty one-dimensional channel with a diameter d(max) of 5.07(1) Å. The in situ PXRD of the transformation of Ti(III)p to Ti(IV)p reveals a two-step mechanism, i.e., the decomposition of NH(4)(+) ions in a first step and subsequent structure relaxation. The specific proton conductivity and activation energy of the proton migration of Ti(III)p, governed by the Grotthus mechanism, belong to the highest and lowest, respectively, ever reported for this class of materials, which reveals its potential application in electrochemical devices like fuel cells and water electrolyzers in the intermediate temperature range.
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spelling pubmed-88262742022-02-10 Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties Petersen, Hilke Stegmann, Niklas Fischer, Michael Zibrowius, Bodo Radev, Ivan Philippi, Wladimir Schmidt, Wolfgang Weidenthaler, Claudia Inorg Chem [Image: see text] Transition-metal phosphates show a wide range of chemical compositions, variations of the valence states, and crystal structures. They are commercially used as solid-state catalysts, cathode materials in rechargeable batteries, or potential candidates for proton-exchange membranes in fuel cells. Here, we report on the successful ab initio structure determination of two novel titanium pyrophosphates, Ti(III)p and Ti(IV)p, from powder X-ray diffraction (PXRD) data. The low-symmetry space groups P2(1)/c for Ti(III)p and P1̅ for Ti(IV)p required the combination of spectroscopic and diffraction techniques for structure determination. In Ti(III)p, trivalent titanium ions occupy the center of TiO(6) polyhedra, coordinated by five pyrophosphate groups, one of them as a bidentate ligand. This secondary coordination causes the formation of one-dimensional six-membered ring channels with a diameter d(max) of 3.93(2) Å, which is stabilized by NH(4)(+) ions. Annealing Ti(III)p in inert atmospheres results in the formation of a new compound, denoted as Ti(IV)p. The structure of this compound shows a similar three-dimensional framework consisting of [PO(4)](3–) tetrahedra and Ti(IV+)O(6) octahedra and an empty one-dimensional channel with a diameter d(max) of 5.07(1) Å. The in situ PXRD of the transformation of Ti(III)p to Ti(IV)p reveals a two-step mechanism, i.e., the decomposition of NH(4)(+) ions in a first step and subsequent structure relaxation. The specific proton conductivity and activation energy of the proton migration of Ti(III)p, governed by the Grotthus mechanism, belong to the highest and lowest, respectively, ever reported for this class of materials, which reveals its potential application in electrochemical devices like fuel cells and water electrolyzers in the intermediate temperature range. American Chemical Society 2021-11-22 2022-02-07 /pmc/articles/PMC8826274/ /pubmed/34807595 http://dx.doi.org/10.1021/acs.inorgchem.1c02613 Text en © 2021 The Authors. Published by American Chemical Society https://creativecommons.org/licenses/by/4.0/Permits the broadest form of re-use including for commercial purposes, provided that author attribution and integrity are maintained (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Petersen, Hilke
Stegmann, Niklas
Fischer, Michael
Zibrowius, Bodo
Radev, Ivan
Philippi, Wladimir
Schmidt, Wolfgang
Weidenthaler, Claudia
Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties
title Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties
title_full Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties
title_fullStr Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties
title_full_unstemmed Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties
title_short Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties
title_sort crystal structures of two titanium phosphate-based proton conductors: ab initio structure solution and materials properties
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8826274/
https://www.ncbi.nlm.nih.gov/pubmed/34807595
http://dx.doi.org/10.1021/acs.inorgchem.1c02613
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