Publication date: 21st July 2025
Exsolution of transition-metal cations from perovskite-oxide hosts has emerged as an outstanding route for producing oxide-supported metal nanoparticles: Various transition-metal cations can be incorporated into the host lattice under oxidising conditions at sintering temperatures and exsolved as metallic nanoclusters after a reducing treatment at much lower temperatures. Despite extensive investigations over the past decade, there is no consistent, comprehensive and fundamental description of why exsolution occurs. Furthermore, it is unclear how the exsolving cations can be sufficiently mobile within a perovskite lattice at temperatures well below those used for sintering.
In this study we used hybrid Density-Functional-Theory (DFT) calculations to examine these two central issues: why exsolution occurs and how it occurs. From our results we proposed a single model that explains diverse experimental observations; why transition-metal cations (but not host cations) exsolve from perovskite lattices upon reduction; why different transition-metal cations exsolve under different conditions; why the metal nanoparticles are embedded at the surface; why the oxide’s surface orientation affect behaviour; why exsolution occurs surprisingly rapidly at relatively low temperatures; and why the re-incorporation of exsolved species involves far longer times and much higher temperatures. Our model’s foundation is that the transition-metal cations are completely reduced to metal atoms within the perovskite lattice as the Fermi level is shifted upwards within the bandgap. This understanding of the exsolution phenomenon provides the basis for a facilitated optimisation of current exsolution systems and for the accelerated development of new exsolution systems.
Bonkowski, A., Wolf, M.J., Wu, J., Parker, S.C., Klein, A. and De Souza, R.A., A single model for the thermodynamics and kinetics of metal exsolution from perovskite oxides. J. Am. Chem. Soc. 2024, 146, 23012-23021.
This project has received funding: from the European Union’s Horizon 2020 research and innovation program under grant agreement no 101017709 (EPISTORE); from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)─463184206 (SFB 1548, FLAIR: Fermi Level Engineering Applied to Oxide Electroceramics); and from EPSRC under grant EP/R023603/1.
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