Issue 15, 2024

Uncovering fast solid-acid proton conductors based on dynamics of polyanion groups and proton bonding strength

Abstract

Achieving high proton conductivity in inorganic solids is key for advancing many electrochemical technologies, including low-energy nano-electronics and energy-efficient fuel cells and electrolyzers. A quantitative understanding of the physical traits of a material that regulate proton diffusion is necessary for accelerating the discovery of fast proton conductors. In this work, we have mapped the structural, chemical and dynamic properties of solid acids to the elementary steps of the Grotthuss mechanism of proton diffusion. Our approach combines ab initio molecular dynamics simulations, analysis of phonon spectra and atomic structure calculations. We have identified the donor–hydrogen bond lengths and the acidity of polyanion groups as key descriptors of local proton transfer and the vibrational frequencies of the cation framework as the key descriptor of lattice flexibility. The latter facilitates rotations of polyanion groups and long-range proton migration in solid acid proton conductors. The calculated lattice flexibility also correlates with the experimentally reported superprotonic transition temperatures. Using these descriptors, we have screened the Materials Project database and identified potential solid acid proton conductors with monovalent, divalent and trivalent cations, including Ag+, Sr2+, Ba2+ and Er3+ cations, which go beyond the traditionally considered monovalent alkali cations (Cs+, Rb+, K+, and NH4+) in solid acids.

Graphical abstract: Uncovering fast solid-acid proton conductors based on dynamics of polyanion groups and proton bonding strength

Supplementary files

Article information

Article type
Paper
Submitted
18 Mar 2024
Accepted
18 Jun 2024
First published
19 Jun 2024
This article is Open Access
Creative Commons BY-NC license

Energy Environ. Sci., 2024,17, 5730-5742

Uncovering fast solid-acid proton conductors based on dynamics of polyanion groups and proton bonding strength

P. Žguns, K. Klyukin, L. S. Wang, G. Xiong, J. Li, S. M. Haile and B. Yildiz, Energy Environ. Sci., 2024, 17, 5730 DOI: 10.1039/D4EE01219D

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