Leveraging Bismuth Immiscibility to Create Highly Concave Noble Metal Nanoparticles

The nanoscale integration of metals with differences in structure and electronics, while important for manipulating surface adsorption, does not typically yield structures with well-defined morphologies in colloidal synthesis. To create structures with unusually undercoordinated surfaces, we leverage the immiscibility of face-centered cubic noble metals with rhombohedral Bi to synthesize well-defined nanostructures with controllable concavity. With Au, three distinct morphologies can be achieved: concave tetrahedra, stella octangula (dual tetrahedron), and concave stella octangula. With Pd, we synthesize concave tetrahedra. Structural and compositional analysis shows that only ~ 6 x10 -6 moles of surface Bi are needed to realize these morphologies. Electrocatalytic experiments and simulations reveal that the concave Au architectures are highly active toward alcohol oxidation compared to non-Bi-directed concave nanoparticles and that surface Bi is critical for adsorption. This integration of immiscible elements provides a powerful strategy for creating highly active nanoparticles with precision.