A novel CeO2-xSnO(2)/Ce2Sn2O7 pyrochlore stoichiometric redox cycle with superior H-2 production capacities is identified and corroborated for two-step solar thermochemical water splitting (STWS). During the first thermal reduction step (1400 degrees C), a reaction between CeO2 and SnO2 occurred for all the CeO2-xSnO(2) (x = 0.05-0.20) solid compounds, forming thermodynamically stable Ce2Sn2O7 pyrochlore rather than metastable CeO2-delta. Consequently, substantially higher reduction extents were achieved owing to the reduction of Ce-IV to Ce-III. Moreover, in the subsequent reoxidation with H2O (800 degrees C), H-2 production capacities increased by a factor of 3.8 as compared to the current benchmark material ceria when x = 0.15, with the regeneration of CeO2 and SnO2 and the concomitant reoxidation of Ce-III to Ce-IV. The H2O-splitting performance for CeO2-0.15SnO(2) was reproducible over seven consecutive redox cycles, indicating the material was also robust. (C) 2017 American Institute of Chemical Engineers