Mechanism of phase transition in proton-conductive inorganic solid acid salts studied by solid-state NMR

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K05405
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Physical chemistry
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: HAYASHI Shigenobu 国立研究開発法人産業技術総合研究所, 計量標準総合センター, 招聘研究員 (00344185)
• Research Collaborator: JIMURA Keiko
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 固体ＮＭＲ / プロトン伝導 / 無機固体酸塩 / 相転移 / 水素結合

Outline of Final Research Achievements

Inorganic solid acid salt Cs2(HSO4)(H2PO4) showed high proton conductivity in the superprotonic phase above 370 K, and the phase was retained on cooling even at room temperature for a long period. These characteristic properties should correlate to the hydrogen bond network connecting the SO4 and PO4 groups. In the present work, the structures of the hydrogen bond network were studied by solid state NMR. We measured 31P, 1H and 133Cs magic-angle-spinning (MAS) NMR spectra, 31P static NMR spectra, 31P{1H} dipolar dephasing experiment, and 1H{31P} rotational-echo double resonance (REDOR). The 31P NMR spectra indicate that all the P sites are crystallographically equivalent. The 31P{1H} dipolar dephasing experiment strongly supports that the number of hydrogen bonds around the PO4 tetrahedron is four. The 1H and 133Cs MAS NMR spectra show that a part of the hydrogen bond network is disordered. Based on those NMR results, we proposed a model structure of the hydrogen bond network.

Free Research Field

化学