This study addresses the synthesis, characterization, and thermochemical redox performance evaluation of perovskites and parent structures (Ruddlesden–Popper phases) as a class of oxygen-exchange materials for hydrogen generation via solar two-step water splitting. The investigated materials are La x Sr1–x MO3 (M = Mn, Co, Fe), Ba x Sr1–x (Co,Fe)O3, LaSrCoO4, and LaSrFeO4, also used as mixed ionic-electronic conductors in fuel cells. Temperature-programmed reduction, powder X-ray diffraction, and thermogravimetric analysis were used to obtain a preliminary assessment of these materials performances. Most of the perovskites studied here stand out by larger thermal reduction capabilities and oxygen vacancies formation at modest temperatures in the range 1000–1400 °C when compared with reference nonstoichiometric compounds such as spinel ferrites or fluorite-structured ceria-based materials. In addition, these materials offer noticeable access to metallic valence transitions during reoxidation in steam atmosphere that are not available in stoichiometric oxides. The promising behaviors characterized here are discussed in regard to the crystal chemistry of the perovskite and parent phases.

A-site and B-site substituted lanthanum manganite perovskites were synthesized and characterized for application in two-step metal oxide redox cycles for thermochemical splitting of CO2.

The design of complex inorganic materials is a challenge because of the diversity of their potential structures. We present a method for the computational identification of materials containing multiple atom types in multiple geometries by ranking candidate structures assembled from extended modules containing chemically realistic atomic environments. Many existing functional materials can be described in this way, and their properties are often determined by the chemistry and electronic structure of their constituent modules. To demonstrate the approach, we isolated the oxide Y(2.24)Ba(2.28)Ca(3.48)Fe(7.44)Cu(0.56)O21, with a largest unit cell dimension of over 60 angstroms and 148 atoms in the unit cell, by using a combination of this method and experimental work and show that it has the properties necessary to function as a solid oxide fuel-cell cathode.