Solar Thermochemical Redox Cycling Using Ga- and Al-Doped LSM Perovskites for Renewable Hydrogen Production

Solar thermochemical hydrogen production using redox-active metal oxides is a promising pathway for the production of green hydrogen and synthetic fuel precursors. Herein, the perovskite material (La0.6Sr0.4)0.95Mn0.8Ga0.2O3−δ (LSMG6482) is identified as a promising metal oxide for thermochemical water splitting. LSMG6482, along with more-established water splitters ceria and (La0.6Sr0.4)0.95MnxAl1–xO3−δ (LSMA) perovskites, is experimentally characterized via thermogravimetric (TGA) analysis and high-temperature water splitting in a reactor simulating solar concentrating conditions. TGA analysis demonstrated that LSMG6482 has high and stable oxygen exchange capacity under controlled pO2 redox cycling, demonstrated by large changes in oxygen nonstoichiometry (δ) relative to ceria. Water splitting experiments using laser heating (Tred = 1400 °C, Tox = 1200 °C) resulted in H2 yields of 165.1 μmol g–1 for the candidate LSMG6482 composition, exceeding that of all benchmark materials tested. Under high conversion oxidation conditions, where H2 is cointroduced with H2O (150 ≤ nH2O/nH2 ≤ 500), H2 yields were greatest for LSMG6482 and LSMA6482, up to four times that of ceria at the highest nH2O/nH2 conditions. Crystallographic analysis showed that over the course of experimentation, there is some secondary phase growth for all perovskite compositions, except for LSMA6482, but there was no observable degradation in H2 yields.