A novel high-entropy perovskite oxide of Ca0.2Gd0.2La0.2Pr0.2Sr0.2Mn0.6Al0.4O3 for high-performance thermochemical fuel production

Perovskite oxides have been reported as promising catalysts for thermochemically splitting H 2 O/CO 2 into fuels with only heat energy input (e.g., solar thermochemical H 2 ) for over a decade. However, they still suffer from low fuel productivity, low H 2 O/CO 2 conversion rates, and poor catalyst stability. This work discovered a new high entropy perovskite oxide catalyst of Ca 0.2 Gd 0.2 La 0.2 Pr 0.2 Sr 0.2 Mn 0.6 Al 0.4 O 3 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 H 2 O splitting at 1000 °C under 40 % H 2 O), this as-synthesized catalyst demonstrated over 10 stable redox cycles with an average H 2 productivity of 320 μmol H 2 per gram catalyst, around 1.4, 2.2, and 6.0 times those of Sr 0.4 La 0.6 Mn 0.6 Al 0.4 O 3 , BaCe 0.25 Mn 0.75 O 3 , and CeO 2 , the state-of-the-art catalysts. It is also approximately 1.65 times the recently reported meta-high-entropy perovskite oxide catalyst of La 0.8 Sr 0.2 Mn 0.2 Fe 0.2 Co 0.4 Al 0.2 O 3 . The H 2 productivity of 207 μmol H 2 per gram catalyst under a high conversion condition (e.g., H 2 production under 5 % H 2 O) reached 2 times that of BaCe 0.25 Mn 0.75 O 3 . While replacing 40 % H 2 O with 40 % CO 2 , 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 0.4 La 0.6 Mn 0.6 Al 0.4 O 3 . The fully thermal reduction and CO 2 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. • A novel phase-pure high-entropy perovskite oxide was discovered. • The equimolar doping on the A-site to form perovskites can help stabilize the structural stability. • The oxide can serve as an excellent thermochemical redox catalyst for high-performance H 2 and CO production. • The catalyst demonstrated hydrogen production performance higher than some state-of-the-art materials.