Defect Formation in Pr₃ZrO₈ for Thermochemical Oxygen and Hydrogen Production  

Developing clean and scalable O₂ and H₂ production technologies is vital for a sustainable energy future. Our recent experiment identified Pr₃ZrO₈ (PZO) as a promising redox-active oxide achieving high O₂ and H₂ yields at intermediate temperature (500-900^oC). While defects govern redox capacity, electronic and ionic transport, their formation and behavior in PZO remain unexplored. Here we investigate intrinsic defect formation in PZO using hybrid density functional theory with spin-orbit coupling, which is essential for capturing its magnetic ground state and electronic structure.  Entropy is found to be crucial for phase stability of PZO. Our results show that oxygen vacancy exhibits remarkably low formation energies even at O-rich condition, consistent with the high oxygen deficiency observed experimentally, whereas Pr vacancies are energetically unfavorable. The Pr-on-Zr antisite defect also shows relatively low formation energy in its neutral charge state. These findings elucidate the microscopic origins of its oxygen off-stoichiometry, phase stability, and redox activity.