Cijie Liu1,Dawei Zhang2,Wei Li1,Jamie Trindell3,Keith King3,Sean Bishop3,Joshua Sugar3,Anthony McDaniel3,Andrew Smith3,Perla Salinas3,Eric Coker3,Joerg Neuefeind4,Jian Luo2,Xingbo Liu1
West Virginia University1,University of California San Diego2,Sandia National Laboratories3,Oak Ridge National Laboratory4
Cijie Liu1,Dawei Zhang2,Wei Li1,Jamie Trindell3,Keith King3,Sean Bishop3,Joshua Sugar3,Anthony McDaniel3,Andrew Smith3,Perla Salinas3,Eric Coker3,Joerg Neuefeind4,Jian Luo2,Xingbo Liu1
West Virginia University1,University of California San Diego2,Sandia National Laboratories3,Oak Ridge National Laboratory4
We report a new series of A-site high entropy based on (La<sub>2/3</sub>Sr<sub>1/3</sub>)MnO<sub>3</sub> as the parent perovskite for solar-driven thermochemical hydrogen (STCH), (La<sub>1/6</sub> Pr<sub>1/6</sub> Nd<sub>1/6</sub> Gd<sub>1/6</sub> Sr<sub>1/6</sub> Ba<sub>1/6</sub> )MnO<sub>3</sub> (LPNGSB_Mn), which exhibits favorable thermodynamic and kinetic properties, along with exceptional phase stability and long-lasting cycling durability. Moreover, LPNGSB_Mn shows enhanced hydrogen production (~100 mmol mol oxide<sup>–1</sup> ) compared to the parent perovskite(La<sub>2/3</sub>Sr<sub>1/3</sub>)MnO<sub>3</sub> (~68 mmol mol oxide<sup>–1</sup> ) in a short one-hour redox reaction. 50 cycles redox experiment demonstrates the extraordinary phase stability of LPNGSB_Mn. Notably, LPNGSB_Mn shows an outstanding balance between fast kinetics (7.992×10<sup>–5</sup> cm s <sup>–1</sup> ) and desirable thermodynamics (enthalpy of reduction (ranging between 260 and 286 kJ (mol-O) <sup>−1</sup> );entropy of reduction(ranging between 130 and 164 J (mol-O)<sup>−1</sup> K <sup>–1 </sup>)) along with excellent phase stability during the redox process. Meanwhile, the XPS and in-situ EELS results revealed that Mn is the only redox-active element in this oxide. In addition, the number of A-site elements in the oxide seems to correlate with H<sub>2 </sub>production.