One-step electrodeposition of ligand-free PdPt alloy nanoparticles from water droplets: Controlling size, coverage, and elemental stoichiometry

We present a robust and facile method to produce metal nanoparticle (NP) alloys in a one-step synthesis using direct electrodeposition onto highly oriented pyrolytic graphite (HOPG). Precursor salts, H2PtCl6 and Pd(NO3)(2), were dissolved in a 1 mM sodium dodecylsulfate (SDS) water droplet with 1 x phosphate buffered saline solution and suspended in a dichloroethane (DCE) continuous phase. Tetrabutylammonium perchlorate was added to the DCE continuous phase to maintain charge balance during electrodeposition. NP fabrication via electrodeposition was driven by droplet collisions onto HOPG, which was biased at a potential where the metal precursor salts would reduce to their respective zero-valent atoms. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) were used to study the size, coverage, and morphology of the NPs as well as the atomic stoichiometry. EDX mapping indicated homogeneous distribution of Pd and Pt at the single NP level. Homogeneously alloyed PdPt NPs were realized from this study with demonstrated control over metal composition, surface coverage, and NP size.