Ordering of a Nanoconfined Water Network around Zinc Ions Induces High Proton Conductivity in Layered Titanate

Abstract

We demonstrated that the chemical intercalation of Zn2+ ions within the interlayer space of the structure of a disordered layered titanate results in a drastic increase of the room-temperature bulk proton conductivity from 8.11 × 10–5 S m–1 for the pristine to 3.7 × 10–2 S m–1 for Zn-titanate. Because of the crystallographic disordered nature of these compounds, we combined different techniques to establish the structural-transport relationships. The pair distribution function revealed that upon chemical insertion of Zn2+, the local lepidocrocite arrangement is maintained, providing a suitable model to investigate the effect of chemically intercalated ions on the transport properties and dynamics within the interlayer space. Broadband dielectric spectroscopy (50 to 1010 Hz) enabled establishing that Zn2+ inclusion promotes proton-hopping by self-dissociation of H2O molecules yielding high proton mobility. Using Zn–K edge extended X-ray absorption fine structure and chemical analyses (EDX, TGA, 1H NMR), Zn2+ ions were shown to be stabilized by ZnCl2(H2O) complexes within the interlayer space. Such complexes induce an increase of the H-bonding strength as evidenced by 1H NMR, yielding a fast proton motion. Molecular dynamics simulations highlighted proton transfer between water molecules from the structural interlayer and bonded to Zn2+ ions. The increasing interactions between these water molecules favor proton transfer at the origin of the fast bulk proton conductivity, which was assigned to a Grotthuss-type mechanism taking place at a long-range order. This work provides a better understanding of how ion–water interactions mediated ionic transport and opens perspectives into the design of ionic conductors that can be used in energy-storage applications.

Synthesis, crystal structure and 19F NMR parameters modelling of CaTiF6(H2O)2 yielding to a revision of the bond-valence parameters for the Ti4+/F− ion pair

“…Because, for each sample, the recycle delays were chosen to ensure that the amount of signal detected is maximum (20 s for adamantane), we assume that the integrated This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=4253528 P r e p r i n t n o t p e e r r e v i e w e d intensities are proportional to the number of scans and the molar quantity of H atoms in the rotor [23].…”

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“…Water dynamics in hydrous TMOs are affected by other species in the interlayer, such as cations, which provides a further mechanism to tune structural water properties. For example, chemical intercalation of Zn 2+ into a hydrous layered titanate increased the proton conductivity by three orders of magnitude (35). The interlayer Zn 2+ ions are proposed to increase the self-dissociation of H 2 O molecules and enhance proton transport via a Grotthuss-type mechanism.…”

Single-Atom Sn-Loaded Exfoliated Layered Titanate Revealing Enhanced Photocatalytic Activity in Hydrogen Generation

“…LTs consisting of TiO 6 -interconnected layers can be found in different chemical compositions in which there is a strong electrostatic interaction among the layers. These LTs usually accompany an alkali metal counterion and, consequently, distinctly differ in their features and activities, but their large bandgaps are a feature in common. , However, exchanging these alkali metals with other species can generate a significant change in the physicochemical activity of LTs. − Therefore, the investigations of the photocatalytic activities of cation-exchanged LTs may bring serendipity features that require to be undertaken.…”