Emulsions are critical across a broad spectrum of industries. Unfortunately, emulsification requires a significant driving force for droplet dispersion. Here, we demonstrate a mechanism of spontaneous droplet formation (emulsification), where the interfacial solute flux promotes droplet formation at the liquid-liquid interface when a phase transfer agent is present. We have termed this phenomenon fluxification. For example, when HAuCl4 is dissolved in an aqueous phase and [NBu4][ClO4] is dissolved in an oil phase, emulsion droplets (both water-in-oil and oil-in-water) can be observed at the interface for various oil phases (1,2-dichloroethane, dichloromethane, chloroform, and nitrobenzene). Emulsification occurs when AuCl4– interacts with NBu4+, a well-known phase-transfer agent, and transfers into the oil phase while ClO4– transfers into the aqueous phase to maintain electroneutrality. The phase transfer of SCN– and Fe(CN)63– also produce droplets. We propose a microscopic mechanism of droplet formation and discuss design principles by tuning experimental parameters.

Carbon-supported Ag−Pd bimetallic nanocatalysts were successfully synthesized via the rotating disk slurry electrode (RoDSE) technique in a nominal precursor solution as a cost-effective means to improve oxygen reduction reaction (ORR) performance in fuel cell (FC) applications. Silver and palladium have both individually shown good catalytic activity. The work presented here compares three different electrodeposition methods using RoDSE, a robust electrodeposition method that allows the synthesis of highly dispersed Ag/Pd nanoparticles on Vulcan XC-72R, minimizing the catalyst preparation time. The electrochemical methods consist of (1) alternated, (2) sequential, and (3) simultaneous Ag and Pd electrodeposition on unsupported Vulcan XC-72R. Different characterization techniques such as TEM, XRD, ICP, and Raman spectroscopy were used to confirm the presence of Ag and Pd on the carbon substrate. The Ag/Pd face centered cubic crystal facets were determined by XRD with an approximate particle diameter of 23 nm for each electrochemical method. Performance of the catalysts was assessed for the ORR using cyclic voltammetry and rotating disk electrode techniques. Herein, we demonstrate that among the three methods of bimetallic Ag/Pd electrodeposition, an alternated approach yielded the best performance, measured using onset potential (E onset ), peak current density, and electron transfer in an alkaline media, in O 2saturated 0.1 M KOH.

Nanodroplet-mediated electrodeposition is a reliable method for electrodepositing nanoparticles by confining a small amount of metal-salt precursor in water nanodroplets (radius ∼400 nm) suspended in an oil continuous phase.

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Nature builds multiphase environments to drive specific reactivity across boundaries. Multiphase systems present an opportunity to drive reactions that would otherwise not occur in bulk, continuous phases. Here, we demonstrate preferential nucleation near the three-phase boundary as a function of its geometry. A submicroliter water droplet deposited on an electrode immersed in a continuous 1,2-dichloroethane (DCE) phase is used to fabricate a three-phase junction (water|DCE|electrode). Adjusting the angle of the three-phase junction by changing the hydrophilicity of the electrode can lead to precipitation of ferrocenemethanol (FcMeOH) at the three-phase boundary only. Analysis by cyclic voltammetry coupled to numerical simulations provides insight into the physicochemical origin of the precipitation depending on the three-phase boundary angle. This finding offers a convenient means to control the local reactivity at three-phase boundaries.