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

Abstract

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)xMn1−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 °C. The materials are shown to be capable of splitting CO2 into CO fuel when isothermally cycled between low-pO2 and high-pCO2 environments at 1240 °C and to approach full reoxidation in CO2 with temperature swings as low as 200 °C, with mass-specific fuel yields up to ten times that of CeO2. The underlying material thermodynamics are investigated and used to explain the favorable redox behavior.