Discovery of Novel Ferrites for Thermochemical H₂ Production Cycle via High-Throughput Thermodynamic Screening

This study highlights the discovery of the (MgMnCo)_1-xFe_xO_y system, identified through a high-throughput thermodynamic screening utilizing the CALPHAD methodology, as a highly efficient material system for two-step thermochemical water splitting under mitigated redox reaction conditions. The screening focuses on a wide range of ferrite systems (M_1-xFe_xO_y, M═Mn, Al, Mg, Co, Ni, 0.05< x< 0.95) and particularly underscores the (MgMnCo)_1-xFe_xO_y system for its high oxygen capacity during redox cycles. Remarkably, (MgMnCo)_0.65Fe_0.35O_y achieves state-of-the-art turnover number and a higher theoretical solar-to-fuel efficiency of 43.6% compared to benchmark ceria at 17.4%. CALPHAD-based thermodynamic analysis and spectroscopic electronic structure analysis reveal that the excellent redox performance of this material is attributed to the simultaneous contributions of Fe and Mn cations. This dual active feature is discovered for the first time in any ferrite cycles to the best of available knowledge, offering significant opportunities to explore new multi-cation ferrite systems in the related research field. In addition, the screening methodology employed here can potentially be extended to other thermochemical processes.