Reduction Thermodynamics of Sr1-xCexMnO3 and CexSr2-xMnO4 Perovskites for Solar Thermochemical Hydrogen Production

Herein, the compositional families Sr1-xCexMnO3 (SCMX, X = 100x, x = 0.10, 0.20, and 0.30) and CexSr(2-x)MnO(4) (CSMX, X = 100x, x = 0.10, 0.20, and 0.30) are studied to determine the effects of perovskite structure and cerium content on thermal reduction thermodynamics and the resulting impact on solar thermochemical hydrogen production (STCH). Relying on thermogravimetric results from oxygen nonstoichiometry experiments, fits for various thermodynamic quantities are produced, including defect-reaction specific enthalpy (Delta H degrees) and entropy (Delta S degrees), as well as the d- dependent standard partial molar enthalpy, Delta(h) over bar degrees O, and entropy Delta(s) over bar degrees O, of oxygen as a function of composition within these two perovskite families. The results of this thermodynamic study are also discussed in the context of structure and cerium dopant level. Experimental hydrogen production results show that the SCM family produces slightly larger amounts of hydrogen per mole of oxide compared with the CSM family under similar reduction and oxidation temperature conditions, however, a direct correlation between structure, cerium content, and water-splitting capacity could not be discerned.