Accurate prediction of oxygen vacancy concentration with disordered A-site cations in high-entropy perovskite oxides

Abstract

Entropic stabilized ABO3 perovskite oxides promise many applications, including the two-step solar thermochemical hydrogen (STCH) production. Using binary and quaternary A-site mixed {A}FeO3 as a model system, we reveal that as more cation types, especially above four, are mixed on the A-site, the cell lattice becomes more cubic-like but the local Fe–O octahedrons are more distorted. By comparing four different Density Functional Theory-informed statistical models with experiments, we show that the oxygen vacancy formation energies ($${E}_{V}^{f}$$ E V f ) distribution and the vacancy interactions must be considered to predict the oxygen non-stoichiometry (δ) accurately. For STCH applications, the $${E}_{V}^{f}$$ E V f distribution, including both the average and the spread, can be optimized jointly to improve Δδ (difference of δ between the two-step conditions) in some hydrogen production levels. This model can be used to predict the range of water splitting that can be thermodynamically improved by mixing cations in {A}FeO3 perovskites.

Local Ordering, Distortion, and Redox Activity in (La0.75Sr0.25)(Mn0.25Fe0.25Co0.25Al0.25)O3 Investigated by a Computational Workflow for Compositionally Complex Perovskite Oxides

“…μ O,FERE is the fitted elemental reference energy for oxygen. 47 Using the distribution E v,CCPO f , the oxygen deficiency δ can be predicted as described in the Method Section of Park et al 36 High oxygen vacancy concentrations at the TR conditions can introduce oxygen vacancy interactions, such that the oxygen loss is accompanied by an increase in E v f , as found previously in SrFe 0.75 Mo 0.25 O 3 and SrFeO 3 . Thus, an oxygen vacancy interaction term should be considered (see below).…”

“…In cation-mixed CCPO, it is inevitable that the oxygen vacancy formation energy exhibits a statistical distribution. Given a parent structure, the E v f on different oxygen sites can be sampled to give a distribution, as in many simulation studies. , However, the DFT-MC method will sample the cation configurations around a vacancy; thus, there is no parent structure to define the energy difference. We propose to obtain the oxygen vacancy formation energy distribution based on the sampled bulk and vacancy structure energy distributions.…”

Manganese-based A-site high-entropy perovskite oxide for solar thermochemical hydrogen production

“…Two thermodynamic properties, reduction enthalpy and entropy, are key factors that determine the H 2 production of STCH materials. 81,82 Therefore, we measured the d over a range of P O 2 values and temperatures for LS21_Mn and LPNGSB_Mn through a reported TGA method. [83][84][85] Fig.…”

Lessons Learned from Catalysis to Qubits: General Strategies to Build Accessible and Accurate First-Principles Models of Point Defects

“…The key to performing such simulations is capturing the variable chemical potential at various partial pressures of the reaction precursors. Similar approaches were also recently employed to gain insight into the oxygen vacancy concentrations of high-entropy perovskites . A general framework for capturing a changing μ α in a calculation was recently generalized by Ogawa and co-workers, allowing them to reformulate the traditional constant μ α approach as a constant concentration approach.…”

“…Similar approaches were also recently employed to gain insight into the oxygen vacancy concentrations of high-entropy perovskites. 16 A general framework for capturing a changing μ α in a calculation was recently generalized by Ogawa and coworkers, 17 allowing them to reformulate the traditional constant μ α approach as a constant concentration approach. This extends the usefulness of DFT-derived formation energies because molar ratios are controllable and measurable parameters in experiments.…”