Thermodynamics has strong predictive power for materials synthesis by identifying the stability region of target phases, but does not give explicit information about the relative competitiveness of undesired byproduct phases in synthesis. In this work, we propose a quantitative and computable measure to guide the selection of synthesis conditions. Defining thermodynamic competition as the difference in driving force between a target phase and its competing phases, we hypothesize that phase-pure synthesis becomes more likely when this thermodynamic competition is minimized. We systematically validate this hypothesis with two approaches: (1) we analyze large-scale solution synthesis procedures as text-mined from the literature, and show that experimentally-optimized synthesis conditions are near the predicted thermodynamic optimum point, and (2) direct experimental evaluation of synthesis in LiIn(IO3)4 and LiFePO4, which show that phase-pure synthesis occurs only when thermodynamic competition is minimized. Our work demonstrates that a quantitative assessment of thermodynamic competition is an effective descriptor for synthesis optimization and a promising tool for optimizing aqueous solution-based experimental synthesis conditions.

Searching for a material that simultaneously satisfies highly conductive and corrosion-stable properties is crucial for various energy conversion applications, particularly for catalyst-supporting materials in polymer electrolyte membrane fuel cells (PEMFC). Here, we suggest the Mg-Ti-O chemical space as promising ternary compounds with high electrical conductivity and corrosion stability in acidic conditions to be potentially used in such applications. A high electrical conductivity (6.09 × 10-1 S/cm) and a good corrosion stability (1.2 × 10-4 mA cm-2 at pH = 1) are achieved at room temperature, by tuning the chemical compositions of Mg1-x Ti2+x O5 (MTO). We found that the corrosion stability of suggested MTO is two orders of magnitude higher than that of conventional carbon supporters used for PEMFC while providing high electrical conductivity. Furthermore, our combined computational and experimental works elucidate that the reducing gas environment during the solid-state synthesis ensures the higher Ti solubility in MTO, i.e., a reduced valence state of Ti, thus promoted the electrical conduction.

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