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Non-Equilibrium Crystallization Pathways of Manganese Oxides in Aqueous Solution

preprint
submitted on 22.05.2018 and posted on 22.05.2018 by Wenhao Sun, Daniil A. Kitchaev, Denis Kramer, Gerbrand Ceder

Aqueous precipitation of transition metal oxides often proceeds through non-equilibrium phases, whose appearance cannot be anticipated from traditional phase diagrams. Without a precise understanding of which metastable phases form, or their lifetimes, targeted synthesis of specific metal oxides can become a trial-and-error process. Here, we derive a new thermodynamic potential for the free-energy of a metal oxide in water, which reveals a hidden metastable energy landscape above the equilibrium Pourbaix diagram. By combining this ‘Pourbaix potential’ with classical nucleation theory, we interrogate how solution conditions can influence the multistage oxidation pathways of manganese oxides. We calculate that even within the same phase stability region of a Pourbaix diagram, subtle variations in pH and redox potential can redirect a crystallization pathway through different metastable phases. Our theoretical framework offers a predictive platform to navigate through the thermodynamic and kinetic energy landscape towards the rational synthesis of target metal oxide phases.

Funding

UGA-0-41029-16/ER392000

History

Email Address of Submitting Author

wenhaosun@lbl.gov

Institution

Lawrence Berkeley National Laboratory

Country

United States of America

ORCID For Submitting Author

0000-0002-8416-455X

Declaration of Conflict of Interest

No conflicts of interest

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