Exsolution of Embedded Ni–Fe–Co Nanoparticles: Implications for Dry Reforming of Methane

As a promising robust and thermally stable dry methane reforming (DRM) catalyst, perovskite precursors for the controlled nucleation and growth of NiFeCo nanoparticles from La(Fe,Ni,Co)O3 precursor structures have been explored in this work. We study the structure–reactivity relationship of the formed NiFeCo nanoparticles as a function of the reduction temperature, reaction environment, and bulk point defects. We closely examine different levers that can control the size, composition, and reactivity of NiFeCo nanoparticles. The material properties are investigated by a combination of characterization techniques such as X-ray diffraction, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and energy-dispersive X-ray spectroscopy. Dry reforming of methane (DRM) reaction testing and temperature-programmed surface reaction (TPSR) experiments are used to probe the catalyst performance and regenerability of the multimetallic nanoparticles. NiFeCo nanoparticles formed from perovskite oxide precursors show a greater propensity to form alloys or aggregates than the conventional wet coimpregnation method. HAADF-STEM and TPSR experiments suggest that the NiFeCo nanoparticles formed are initially Fe-rich but become Ni- and Co-rich in the reactive atmosphere after aging for 24 h. This works provides insight into relevant factors that can control the properties of multimetallic nanoparticles formed from perovskite oxide precursors.