Halide-Mediated\nPhase Control of Fe<sub><i>x</i></sub>Co<sub>1–<i>x</i></sub>C<sub><i>y</i></sub> Nanoparticles

The ability to control the compositional phase in first\nrow transition\nmetal bimetallic carbides as well as systematically controlling the\nmetal ratio is complicated by the rich phase diagram, differences\nin metal reactivity, and differences in carbon solubility in the first-row\nmetal carbides. Prussian blue analogues (PBAs) have been shown to\nact as a single source precursor for the formation of nanocrystal\nmetal carbides with maintenance of their metal. An investigation of\ncrystal phase control in the ternary (Fe<sub><i>x</i></sub>Co<sub>1–<i>x</i></sub>)<sub><i>y</i></sub>C<sub><i>z</i></sub> formed by PBA collapse is yet to be\nexplored. In this study, we demonstrate the ability to tune phase\n(from most carbon rich to least carbon rich) M<sub>2</sub>C, M<sub>5</sub>C<sub>2</sub>, M<sub>7</sub>C<sub>3</sub>, and M<sub>3</sub>C, as well as the bimetallic alloy (M) in bimetallic FeCo nanocarbides\nthrough a strategy that pairs synthetic and density functional theory\napproaches to enable future targeted structure–function research\non intriguing catalytic, therapeutic, and magnetic applications.