Reliable electrochemical phase diagrams of magnetic transition metals and related compounds from high-throughput ab initio calculations

摘要

Magnetic transition metals (mTM = Cr, Mn, Fe, Co, and Ni) and their complex compounds (oxides, hydroxides, and oxyhydroxides)are highly important material platforms for diverse technologies, where electrochemical phase diagrams with respect to electrodepotential and solution pH can be used to effectively understand their corrosion and oxidation behaviors in relevant aqueousenvironments. Many previous decades-old mTM–Pourbaix diagrams are inconsistent with various direct electrochemicalobservations, because experimental complexities associated with extracting reliable free energies of formation (ΔfG) lead toinaccuracies in the data used for modeling. Here, we develop a high-throughput simulation approach based on density-functionaltheory (DFT), which quickly screens structures and compounds using efficient DFT methods and calculates accurate ΔfG values,using high-level exchange-correlation functions to obtain ab initio Pourbaix diagrams in comprehensive and close agreement withvarious important electrochemical, geological, and biomagnetic observations reported over the last few decades. We also analyzethe microscopic mechanisms governing the chemical trends among the ΔfG values and Pourbaix diagrams to further understandthe electrochemical behaviors of mTM-based materials. Last, we provide probability profiles at variable electrode potential andsolution pH to show quantitatively the likely coexistence of multiple-phase areas and diffuse phase boundaries.