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We identified the perovskite oxides LaMn0.5Ni0.5O3 (L2MN), Gd0.5La0.5Mn0.5Ni0.5O3 (GLMN), and GdMn0.5Ni0.5O3 (G2MN) as candidate solar thermal chemical hydrogen (STCH) redox mediators from their density functional theory (DFT)-computed electronic and oxygen vacancy properties following a high-throughput computational screening of AA′BB′O6 compositions that are likely to form as perovskites and split water. At a thermal reduction temperature of 1350 °C and a water splitting temperature of 850 °C, the L2MN and GLMN perovskites produced ∼65 μmol g–1 of hydrogen per cycle with no phase degradation over three redox cycles at 40 mol % steam, while the G2MN perovskite did not produce STCH under these conditions. When reoxidized by exposure to a gas flow with a H2O:H2 molar ratio of 1333:1, which represents operating conditions where the thermodynamic driving force of water splitting is lowered by orders of magnitude relative to 40 mol % steam, the L2MN and GLMN perovskites each produced ∼35 μmol g–1 of hydrogen per cycle. Guided by DFT, we propose that L2MN and GLMN’s STCH activities arise from B-site cation antisite defects that facilitate oxygen vacancy formation and thus redox cycling, whereas the synthesized G2MN has few antisite defects and is therefore inactive for STCH. 

Abstract Perovskite oxides (ternary chemical formula ABO₃) are a diverse class of materials with applications including heterogeneous catalysis, solid-oxide fuel cells, thermochemical conversion, and oxygen transport membranes. However, their multicomponent (chemical formula$${A}_{x}{A}_{1-x}^{\text{'}}{B}_{y}{B}_{1-y}^{\text{'}}{O}_{3}$$ $A_x{A}_{1-x}^{\text{'}}{B}_y{B}_{1-y}^{\text{'}}{O}_3$) chemical space is underexplored due to the immense number of possible compositions. To expand the number of computed$${A}_{x}{A}_{1-x}^{{\prime} }{B}_{y}{B}_{1-y}^{{\prime} }{O}_{3}$$ $A_x{A}_{1-x}^{\prime }{B}_y{B}_{1-y}^{\prime }{O}_3$compounds we report a dataset of 66,516 theoretical multinary oxides, 59,708 of which are perovskites. First, 69,407$${A}_{0.5}{A}_{0.5}^{{\prime} }{B}_{0.5}{B}_{0.5}^{{\prime} }{O}_{3}$$ $A_{0.5}{A}_{0.5}^{\prime }{B}_{0.5}{B}_{0.5}^{\prime }{O}_3$compositions were generated in thea⁻b⁺a⁻Glazer tilting mode using the computationally-inexpensive Structure Prediction and Diagnostic Software (SPuDS) program. Next, we optimized these structures with density functional theory (DFT) using parameters compatible with the Materials Project (MP) database. Our dataset contains these optimized structures and their formation (ΔH_f) and decomposition enthalpies (ΔH_d) computed relative to MP tabulated elemental references and competing phases, respectively. This dataset can be mined, used to train machine learning models, and rapidly and systematically expanded by optimizing more SPuDS-generated$${A}_{0.5}{A}_{0.5}^{{\prime} }{B}_{0.5}{B}_{0.5}^{{\prime} }{O}_{3}$$ $A_{0.5}{A}_{0.5}^{\prime }{B}_{0.5}{B}_{0.5}^{\prime }{O}_3$perovskite structures using MP-compatible DFT calculations. 

Abstract A high‐throughput computational framework to identify novel multinary perovskite redox mediators is presented, and this framework is applied to discover the Gd‐containing perovskite oxide compositions Gd₂BB′O_6,GdA′B₂O₆, and GdA′BB′O₆that split water. The computational scheme uses a sequence of empirical approaches to evaluate the stabilities, electronic properties, and oxygen vacancy thermodynamics of these materials, including contributions to the enthalpies and entropies of reduction, ΔH_TRand ΔS_TR. This scheme uses the machine‐learned descriptor τ to identify compositions that are likely stable as perovskites, the bond valence method to estimate the magnitude and phase of BO₆octahedral tilting and provide accurate initial estimates of perovskite geometries, and density functional theory including magnetic‐ and defect‐sampling to predict STCH‐relevant properties. Eighty‐three promising STCH candidate perovskite oxides down‐selected from 4392 Gd‐containing compositions are reported, three of which are referred to experimental collaborators for characterization and exhibit STCH activity. The results demonstrate that the high‐throughput computational scheme described herein—which is used to evaluate Gd‐containing compositions but can be applied to any multinary perovskite oxide compositional space(s) of interest—accelerates the discovery of novel STCH active redox mediators with reasonable computational expense.