Manganese-based A-site high-entropy perovskite oxide for solar thermochemical hydrogen production

Non-stoichiometric perovskite oxides have been studied as a new family of redox oxides for solar thermochemical hydrogen (STCH) production owing to their favourable thermodynamic properties. However, conventional perovskite oxides suffer from limited phase stability and kinetic properties, and poor cyclability. Here, we report a strategy of introducing A-site multi-principal-component mixing to develop a high-entropy perovskite oxide, (La1/6Pr1/6Nd1/6Gd1/6Sr1/6Ba1/6)MnO3 (LPNGSB_Mn), which shows desirable thermodynamic and kinetics properties as well as excellent phase stability and cycling durability. LPNGSB_Mn exhibits enhanced hydrogen production (similar to 77.5 mmol moloxide-1) compared to (La2/3Sr1/3)MnO3 (similar to 53.5 mmol moloxide-1) in a short 1 hour redox duration and high STCH and phase stability for 50 cycles. LPNGSB_Mn possesses a moderate enthalpy of reduction (252.51-296.32 kJ (mol O)-1), a high entropy of reduction (126.95-168.85 J (mol O)-1 K-1), and fast surface oxygen exchange kinetics. All A-site cations do not show observable valence changes during the reduction and oxidation processes. This research preliminarily explores the use of one A-site high-entropy perovskite oxide for STCH. The A-site high-entropy perovskite oxide (La1/6Pr1/6Nd1/6Gd1/6Sr1/6Ba1/6)MnO3 with enhanced hydrogen production, phase stability, and surface oxygen exchange kinetics, offering the potential for tailoring properties in the STCH application.