Lanthanum Manganite Perovskites with Ca/Sr A-site and Al B-site Doping as Effective Oxygen Exchange Materials for Solar Thermochemical Fuel Production

Perovskite oxides have recently been proposed as promising redox intermediates for solar thermochemical splitting of H2O and CO2, offering the benefit of significantly reduced operating temperatures. We present a systematic experimental screening of doped lanthanum manganites within the composition space La1-x(Ca,Sr)(x)Mn1-yAlyO3 and identify several promising redox materials. In particular, La0.6Sr0.4Mn0.6Al0.4O3 and La0.6Ca0.4Mn0.6Al0.4O3 boast a five- to thirteen-fold improvement in the reduction extent compared to the state-of-the-art material CeO2 in the temperature range 1200-1400 degrees C. The materials are shown to be capable of splitting CO2 into CO fuel when isothermally cycled between low-pO(2) and high-pCO(2) environments at 1240 degrees C and to approach full reoxidation in CO2 with temperature swings as low as 200 degrees C, with mass-specific fuel yields up to tentimes that of CeO2. The underlying material thermodynamics are investigated and used to explain the favorable redox behavior.