Synergistic Tuning of Diffusion Enables Surface-Passivation-Directed Electrodeposition of Shaped Bimetallic Nanoparticles

Many applications for shape-controlled metal nanoparticles require their immobilization on a surface, creating a need for development of direct substrate-based synthesis routes for increasingly complex materials. Colloidal chemical syntheses for shape-controlled nanoparticles are common, but transferring insight from synthesis in solution to growth on a substrate requires accounting for significant differences in reagent diffusion between these two growth environments─a nontrivial challenge. In the present work, we establish fundamental principles for rationally adapting reaction parameters from colloidal syntheses to electrodeposition such that the growth of nanoparticles on the electrode proceeds under comparable reagent diffusion conditions to those that drive shape direction during colloidal growth. To demonstrate these principles, we successfully translate reaction conditions from colloidal synthesis to electrodeposition for a series of dilute bimetallic (silver) gold nanoparticles whose shapes are controlled by surface deposition of silver: concave cubes, octahedra, rhombic dodecahedra, truncated ditetragonal prisms, and tetrahexahedra. By comparing open-circuit potential measurements of the colloidal syntheses with chronopotentiometry measurements from galvanostatic electrodeposition, we determine the adjustments required to establish ideal growth kinetics for each electrodeposition. We identify specific synthetic handles─mode of mass transport, surfactant concentration, applied current density, and secondary metal concentration─required to modulate reagent transport to the electrode surface, as well as the direction they must be modified so that the relative rates of silver and gold ion reduction mimic colloidal growth. These generalizable synthetic parameters for controlling reagent diffusion and concentrations near the electrode surface open possibilities for the electrodeposition of complex multimetallic and shaped nanomaterials.