A novel high-entropy perovskite oxide of Ca_0.2Gd_0.2La_0.2Pr_0.2Sr_0.2Mn_0.6Al_0.4O₃ for high-performance thermochemical fuel production

Perovskite oxides have been reported as promising catalysts for thermochemically splitting H₂O/CO₂ into fuels with only heat energy input (e.g., solar thermochemical H₂) for over a decade. However, they still suffer from low fuel productivity, low H₂O/CO₂ conversion rates, and poor catalyst stability. This work discovered a new high entropy perovskite oxide catalyst of Ca_0.2Gd_0.2La_0.2Pr_0.2Sr_0.2Mn_0.6Al_0.4O₃ by equimolarly doping the A-site of Sr and Al-doped lanthanum manganates. Under common thermochemical redox cycle conditions (i.e., thermal reduction at 1350 °C under Ar and H₂O splitting at 1000 °C under 40 % H₂O), this as-synthesized catalyst demonstrated over 10 stable redox cycles with an average H₂ productivity of 320 μmol H₂ per gram catalyst, around 1.4, 2.2, and 6.0 times those of Sr_0.4La_0.6Mn_0.6Al_0.4O₃, BaCe_0.25Mn_0.75O₃, and CeO₂, the state-of-the-art catalysts. It is also approximately 1.65 times the recently reported meta-high-entropy perovskite oxide catalyst of La_0.8Sr_0.2Mn_0.2Fe_0.2Co_0.4Al_0.2O₃. The H₂ productivity of 207 μmol H₂ per gram catalyst under a high conversion condition (e.g., H₂ production under 5 % H₂O) reached 2 times that of BaCe_0.25Mn_0.75O₃. While replacing 40 % H₂O with 40 % CO₂, our catalyst demonstrated excellent stability (10 stable redox cycles) and an average CO productivity of ∼420 μmol CO per gram of catalyst, which is three times that of Sr_0.4La_0.6Mn_0.6Al_0.4O₃. The fully thermal reduction and CO₂ splitting took less than 30 min, proving fast redox kinetics. The excellent catalyst stability was ascribed to stable crystal structures under severe reduction/oxidation conditions. This work has opened a promising avenue for discovering new catalysts for thermochemical redox cycle fuel production from heat only.