Bismuth is an abundant earth metal whose low environmental and human toxicity has made it an alternative to lead in solder. Bi is also a fairly noble element in that it is stable in water across a wide pH range. These characteristics make Bi an ideal candidate for use as an abundant, inexpensive, and durable support in highly dispersed nanoparticle (NP) systems exposed to hot, aqueous conditions; as is the case with proton exchange membrane fuel cells (PEMFC) electrocatalysts. The dissolution of base metal cores of Ni, Fe, and Co in such environments has impeded commercialization of novel core-shell NP architectures that attempt to minimize the use the precious metals such as Pt and Ru by confining them as a shell or monolayer on the surface of the NP. Unfortunately, Bi NP formation is currently based on unsustainable methods employing organic solvents, organic precursors, and dangerous reducing agents such as hydrazine that frequently yield highly non-uniform structures.We here investigate a sustainable, one beaker, all-aqueous synthesis processes to produce monodisperse pure Bi and Bi-Pt alloy NPs. The method involves use of SnCl2 as both reducing and stabilizing agent. Bi reduction proceeds according to: 2BiCl4� + 3Sn2+ = 2Bi0 + 3Sn4+ + 8Cl�. To our knowledge, adsorption and complexation of Sn ligands on Bi NP surfaces for reduction and stabilization during growth has not been previously reported. While Bi reduction by Sn has been previously shown, NP formation using a Group V element with SnCl3� is unexpected. We present ex-situ, time-resolved, 119Sn M�ssbauer spectroscopic analyses of Sn ligand surface shell evolution from the initial ionic complexes to the reduced Bi metal and Bi-Pt alloy NPs. Electrochemical data is also presented that demonstrates unprecedented oxygen reduction reaction (ORR) mass and specific activity enhancement relative to pure Pt.

Use SnCl<sub>3</sub><sup>-</sup> surface ligand as bismuth reducing agent for sustainable nanoparticle synthesis

246th National Meeting (2013)

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Use SnCl3- surface ligand as bismuth reducing agent for sustainable nanoparticle synthesis

Use SnCl₃^- surface ligand as bismuth reducing agent for sustainable nanoparticle synthesis