Investigation of Perovskite Structures as Oxygen-Exchange Redox Materials for Hydrogen Production from Thermochemical Two-Step Water-Splitting Cycles

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 LaxSr1–xMO3 (M = Mn, Co, Fe), BaxSr1–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 ...