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Uncovering fast solid-acid proton conductors based on dynamics of polyanion groups and proton bonding strength
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DOI：10.1039/d4ee01219d.png)
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Abstract
En 中文
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. Cation lattice flexibility and covalent bond lengths serve as good physical descriptors of proton conduction in solid acids and enable the discovery of promising proton conductors beyond traditional chemistries.
Keywords:
HIGH-TEMPERATURE PHASE
CERAMIC FUEL-CELLS
SUPERPROTONIC CONDUCTIVITY
HIGH-PERFORMANCE
POWER-DENSITY
HYDROGEN-BOND
TRANSITIONS
CRYSTALS
CSH2PO4
THERMODYNAMICS
Journal
IF:
30.8
Papers:
6.9K
Citations:
12.4W