Dimethyl ether (DME) is a clean-burning alternative to diesel fuel that meets strict emissions standards in combustion engines. DME is currently derived from natural gas but can also be synthesized from biomass on-site and is thus a sustainable and highly distributed energy source. DME has properties similar to propane and can utilize established fueling infrastructure and handling procedures. In addition to its use in internal combustion engines, the convenience of DME generation and transport can be exploited to overcome the high-pressure infrastructure requirements of hydrogen fuel in more efficient electrochemical fuel cells.
We here describe the synthesis of monodisperse spherical Pt2Bi alloy nanoparticles ca. 5 nm as well as larger non-uniform Pt2Bi alloy nanoplatelets in electrostatically stabilized aqueous suspensions for use in direct-DME fuel cells. Synthesis involves the use of stannous chloride as an inorganic autocatalytic reducing and stabilizing agent and is unique to nanoparticle (NP) synthesis. The method avoids the problems of system contamination due to in-situ electrochemical reduction as well as the unsustainable use of organic solvents and hazardous reducing agents. Furthermore, a stable Pt2Bi alloy (confirmed through HAADF-STEM, XRD, XAS, and EDS) is obtained without the need for subsequent high temperature annealing in reducing environments. The dealloyed nanoparticles exhibit substantial enhancement in dimethyl ether (DME) electro-oxidation activity relative to Pt-C with minimal surface poisoning. ECSA peak deconvolution assisted by Bi and Ge adatom analyses indicate the proportion of Pt(100) to Pt(110) facets on the dealloyed Pt2Binanoplatelets is substantially greater than on Pt-C. These changes in surface atom coordination are consistent in the substantial reduction of poisoning by adsorbed intermediates observed on the dealloyed PtBi2 nanoparticles versus Pt-C, as predicted by theoretical analyses and single crystal studies with pure Pt.