Electrochemical Stability of Metastable Materials

We present a first-principles-based formalism to provide a quantitative measure of the thermodynamic instability and propensity for electrochemical stabilization, passivation, or corrosion of metastable materials in aqueous media. We demonstrate that this formalism can assess the relative Gibbs free energy of candidate materials in aqueous media as well as their decomposition products, combining solid and aqueous phases, as a function of pH and potential. On the basis of benchmarking against 20 stable as well as metastable materials reported in the literature and also our experimental characterization of metastable triclinic-FeVO4, we present quantitative estimates for the relative Gibbs free energy and corresponding aqueous regimes where these materials are most likely to be stable, form inert passivating films, or steadily corrode to aqueous species. Furthermore, we show that the structure and composition of the passivating films formed on triclinic-FeVO4 are also in excellent agreement with the Point Defect Model, as proposed by the corrosion community. An open-source web application based on the formalism is made available at https://materialsproject.org.