Efficient Pourbaix diagrams of many-element compounds

Abstract

Pourbaix diagrams are an invaluable tool for exploring the corrosion profiles of materials as a function of ambient pH and electrochemical potential. 1 In recent years, high-throughput computational materials science efforts like those from the Materials Project 2,3 have enabled more comprehensive Pourbaix diagrams to be constructed and disseminated from computational data. 4,5 These analyses have informed a number of computational studies of materials for electrochemical applications, aqueous electrocatalysis 6-9 and photoelectrocatalysis, 10? ,11 non-equilibrium crystallization, 12,13 and corrosion-resistant alloy design. 14,15 In these, pourbaix analysis of multi-element systems is particularly valuable, as finding elusive materials like acid-stable oxygen evolution catalysts, 7 earth-abundant hydrogen evolution catalysts, 16 and selective CO 2 reduction catalysts 17 has and will likely continue to require exploration and optimization in multi-element spaces. However, Pourbaix analysis of phase stability on these resources have been limited to 3 or fewer elements, largely because computing the electrochemical phase stability of higher composition spaces has proven inefficient with existing 1 arXiv:1909.00035v1 [cond-mat.mtrl-sci]

Acid-Stable Oxides for Oxygen Electrocatalysis

“…The aqueous stability was evaluated by computing Pourbaix diagram of each material using the Materials Project methods. [8][9][10] Here, we briefly summarize the basic ideas and details are directed to the cited references. In the Pourbaix diagram, the stable domains are determined based on the knowledge of all possible equilibrium redox reactions in the chemical composition of interest.…”

“…In this work, building on the extensive works constructing computational Pourbaix diagrams, [7][8][9] we evaluated the aqueous stability of 47,814 oxides under typical ORR/OER potentials in strong acid based on the data in the Materials Project. 10 Based on a set of stability criteria, we identified 68 acid-stable ternary and quaternary oxides. We further constructed an acid-stable periodic table based on a statistical analysis of compositions of these 68 acid-stable oxides and find that oxides containing the elements of Sb/Ti/Sn/Ge/Mo/W tend to have high corrosion resistance in an acidic and oxidative environment.…”

“…We began our search among the 47,814 oxides included in the Materials Project database. 10 The aqueous stability of these materials is then computed in the potential range of 0.6 -1.0 V (vs. SHE) and 1.2 -2.0 V (vs. SHE) for ORR and OER, respectively, at pH = 0. We note that, in the literature the high-throughput screenings [11][12][13] based on aqueous stability often only evaluate the materials' stability at a given potential, which may be insufficient to identify a "truly" stable candidate, since in experiment the catalyst is often cycled over a range of operating potentials at certain pH.…”

“…The phase diagram was constructed using the energies of relevant compounds obtained from the Materials Project. 10,15,16 By applying the aqueous stability criterion of ∆G pbx < 0.5 eV/atom on the 47,814 oxides, we obtained 68 non-binary acid-stable oxides, shown in Table 1 and Table S1. (Table was separated based on the band gap of 1.0 eV due to page limit.)…”

Metastability at Defective Metal Oxide Interfaces and Nanoconfined Structures

“…[83] Additionally, there are cases where the stabilization of metastable structures and interfaces is linked with the electrochemical environment, as demonstrated for BaTiO3, for which the bare surfaces have been calculated unstable. [84] In the most simple way, computational Pourbaix diagrams can be constructed to estimate the electrochemical stability [85][86][87] and metastability [88] of the solid/liquid(water) interface at the atomistic and bulk level and to design novel materials [89][90][91] . This methodology combines computational (bulk) information on solid phases (total energies) and experimental data for dissolved species (dissolution energies).…”