(90c) Synthesis of Exsolvable Multi-Metallic Nanoparticles Using the Defect Chemistry of Perovskite Oxides

In-situ exsolution of reducible transition metals from geo-inspired perovskite precursors allows for the synthesis of strongly-adhered nanoparticles that are thermally-stable and homogeneous in size and shape. The perovskite oxides are materials that can reversibly exsolve transition-metal cations as nanoparticles under fluctuating reducing and oxidizing reaction conditions. The exsolution process occurs when the cation dopant diffuses from the bulk of the perovskite and form nanoparticles on the surface under reducing conditions. Earlier work on perovskite oxide precursors has determined that bulk defects can modulate the ionic diffusion of dopant metal monomers. This presentation extends the notion of exploring the rich defect chemistry of geo-inspired perovskite oxides to control the formation and growth of regenerable Ni-Fe nanoparticles from Ni-doped LaFeO₃ perovskite oxide precursors. The Ni-doped lanthanum ferrite perovskite precursors were prepared with varying ratios of the La and Fe in the parent perovskite of either 0.9:1, 1:0.9, and 1:1. The exsolved Ni-Fe nanoparticles exhibited notable ranges in composition, size, and dispersion. The systems were characterized using High-angle annular dark-field imaging scanning transmission electron microcopy (HAADF – STEM), X-ray diffraction and X-ray Absorption Spectroscopy. This presentation will discuss recent work to address the existing materials chemistry challenges for Ni-based bimetallic nanoparticles' controlled formation. These "knobs" include temperature reduction, dopant concentration, and bulk defects that can be used to tailor nanoparticle properties.