Journal
SCIENCE CHINA-CHEMISTRY
Volume 62, Issue 4, Pages 515-520Publisher
SCIENCE PRESS
DOI: 10.1007/s11426-018-9423-8
Keywords
concentrated solutions; ion dynamics; ion volume effect; chemical affinity; ion-vacancy couple
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Funding
- National Natural Science Foundation of China [21673163, 21832004, 21802170]
- Central South University [502045001, 20180020050002]
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We present a conceptual framework for understanding and formulating ion transport in concentrated solutions, which pictures the ion transport as an ion-vacancy coupled charge transfer reaction. A key element in this picture is that the transport of an ion from an occupied to unoccupied site involves a transition state which exerts double volume exclusion. An ab initio random walk model is proposed to describe this process. Subsequent coarse-graining results in a continuum formula as a function of chemical potentials of the constituents, which are further derived from a lattice-gas model. The subtlety here is that what has been taken to be the chemical potential of the ion in the past is actually that of the ion-vacancy couple. By aid of this new concept, the driving force of ion transport is essentially the chemical affinity of the ion-vacancy coupled charge transfer reaction, which is a useful concept to unify transport and reaction, two fundamental processes in electrochemistry. This phenomenological model is parameterized for a specific material by the aid of first-principles calculations. Moreover, its extension to multiple-component systems is discussed.
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