Abstract: Systems and methods for growth of multi-component single crystals are described. A first solution is flowed over a surface of a seed crystal coupled to a nozzle such that a plurality of first ions solvated in the first solution and a plurality of second ions in a second solution combine on the surface of the seed crystal to grow the single-crystal thereon. The first solution and the second solution are immiscible. A feed tank is fluidly coupled to the at least one nozzle and includes the first solution. In some aspects, the nozzle is configured to flow both the first solution and the second solution over the seed crystal.

Abstract: A method of making a fuel cell including the following steps: comprising: (a) mixing carbon nanotubes (CNT) with an initial dispersion, wherein the initial dispersion includes an ionomer; (b) heating and stirring the initial dispersion to form a CNT-ionomer composite suspension; (c) after forming the CNT-ionomer composite suspension, mixing the CNT-ionomer composite suspension with an electrode catalyst solution to form an electrode ink, wherein the electrode catalyst solution includes a carbon black powder and a catalyst supported by the carbon black powder; and (d) coating a proton exchange membrane with the electrode ink to form the fuel cell electrode.

Abstract: A method of making a fuel cell including the following steps: comprising: (a) mixing carbon nanotubes (CNT) with an initial dispersion, wherein the initial dispersion includes an ionomer; (b) heating and stirring the initial dispersion to form a CNT-ionomer composite suspension; (c) after forming the CNT-ionomer composite suspension, mixing the CNT-ionomer composite suspension with an electrode catalyst solution to form an electrode ink, wherein the electrode catalyst solution includes a carbon black powder and a catalyst supported by the carbon black powder; and (d) coating a proton exchange membrane with the electrode ink to form the fuel cell electrode.

Abstract: A method for forming a carbon supported catalyst includes a step of providing a first carbon supported catalyst having a platinum-group metal supported on a first carbon support. Characteristically, the first carbon support has a first average micropore diameter and a first average carbon surface area. The first carbon supported catalyst is contacted with an oxygen-containing gas at a temperature less than about 450° C. for a predetermined period of time to form a second carbon supported catalyst, wherein the first carbon support or the second carbon supported catalyst is acid leached.

Abstract: A method for making tungsten-alloy nanoparticles that are useful for fuel cell applications includes a step of combining a solvent system and a surfactant to form a first mixture. A tungsten precursor is introduced into the first mixture to form a tungsten precursor suspension. The tungsten precursor suspension is heated to form tungsten nanoparticles. The tungsten nanoparticles are combined with carbon particles to form carbon-nanoparticle composite particles. The carbon-nanoparticle composite particles are combined with a metal salt to form carbon-nanoparticle composite particles with adhered metal salt, the metal salt including a metal other than tungsten. The third solvent system is then removed. A two-stage heat treatment is applied to the carbon-nanoparticle composite particles with adhered metal salt to form carbon supported tungsten-alloy nanoparticles. A method for making carbon supported tungsten alloys by reducing a tungsten salt and a metal salt is also provided.

Abstract: A positive electrode includes a sulfur-based active material, a binder, a conductive filler, and porous, one-dimensional metal oxide nanorods. The one-dimensional metal oxide nanorods are mixed, as an additive, throughout the positive electrode with the sulfur-based active material, the binder, and the conductive filler. The positive electrode with the porous, one-dimensional metal oxide nanorods may be incorporated into any sulfur-based battery.

Abstract: In an example method, a transition metal precursor is selected so its transition metal has a diffusion rate that is slower than a diffusion rate of silicon. An aqueous mixture is formed by dissolving the precursor in an aqueous medium, and adding silicon particles to the medium. The mixture is exposed to a hydroxide, which forms a product including the silicon particles and a transition metal hydroxide precipitate. The product is dried. In an inert or reducing environment, silicon atoms of the silicon particles in the dried product are caused to diffuse out of, and form voids in and/or at a surface of, the particles. At least some silicon atoms react with the transition metal hydroxide in the dried product to form i) a SiOx (0<x?2) coating on the silicon particles and ii) the transition metal, which reacts with other silicon atoms to form silicides.

Abstract: A positive electrode includes a sulfur-based active material, a binder, a conductive filler, and porous, one-dimensional metal oxide nanorods. The one-dimensional metal oxide nanorods are mixed, as an additive, throughout the positive electrode with the sulfur-based active material, the binder, and the conductive filler. The positive electrode with the porous, one-dimensional metal oxide nanorods may be incorporated into any sulfur-based battery.

Abstract: In an example of a method for making a hollow carbon material, a carbon black particle is obtained. The carbon black particle has a concentric crystallite structure with an at least partially amorphous carbon core and a graphitic carbon shell surrounding the at least partially amorphous carbon core. The carbon black particle is exposed to any of a heat treatment, a chemical treatment, or an electrochemical treatment which removes the at least partially amorphous carbon core to form the hollow carbon material.

Abstract: Methods of synthesizing platinum-nickel-alloy nanoparticles and supported catalysts comprising the nanoparticles are provided. The methods may comprise forming a reaction mixture in a reaction vessel; heating the reaction mixture sealed in the reaction vessel to a reaction temperature; maintaining the temperature of the reaction vessel for a period of time; cooling the reaction vessel; and removing platinum-alloy nanoparticles from the reaction vessel. The reaction mixture may comprise a platinum precursor, a nickel precursor, a formamide reducing solvent, and optionally a cobalt precursor. In some embodiments the reaction temperature is at or below the boiling point of the formamide reducing solvent, such as from about 120° C. to about 150° C., for example. The platinum-alloy nanoparticles provide favorable electrocatalytic activity when supported on a catalyst support material.

Abstract: In an example method, a transition metal precursor is selected so its transition metal has a diffusion rate that is slower than a diffusion rate of silicon. An aqueous mixture is formed by dissolving the precursor in an aqueous medium, and adding silicon particles to the medium. The mixture is exposed to a hydroxide, which forms a product including the silicon particles and a transition metal hydroxide precipitate. The product is dried. In an inert or reducing environment, silicon atoms of the silicon particles in the dried product are caused to diffuse out of, and form voids in and/or at a surface of, the particles. At least some silicon atoms react with the transition metal hydroxide in the dried product to form i) a SiOx (0<x?2) coating on the silicon particles and ii) the transition metal, which reacts with other silicon atoms to form silicides.

Abstract: In an example of a method for making a hollow carbon material, a carbon black particle is obtained. The carbon black particle has a concentric crystallite structure with an at least partially amorphous carbon core and a graphitic carbon shell surrounding the at least partially amorphous carbon core. The carbon black particle is exposed to any of a heat treatment, a chemical treatment, or an electrochemical treatment which removes the at least partially amorphous carbon core to form the hollow carbon material.

Abstract: Methods of synthesizing platinum-alloy nanoparticles, supported catalysts comprising the nanoparticles, and further methods of forming supported catalysts comprising Pt3(Ni,Co) nanoparticles having (111)-oriented faces or facets are disclosed. The methods may comprise forming a reaction mixture in a reaction vessel; sealing the reaction vessel; heating the reaction mixture sealed in the reaction vessel to a reaction temperature; maintaining the temperature of the reaction vessel for a period of time; cooling the reaction vessel; and removing platinum-alloy nanoparticles from the reaction vessel. The reaction mixture may comprise a platinum precursor, a nickel precursor, a formamide reducing solvent, and an optional capping agent. The platinum-alloy nanoparticles provide favorable electrocatalytic activity when supported on a catalyst support material.

Abstract: An electrocatalyst is described. The electrocatalyst includes a core of a non-noble metal or non-noble metal alloy; and a continuous shell of a noble metal or noble metal alloy on the core, the continuous shell being at least two monolayers of the noble metal or noble metal alloy. Methods for making the electrocatalyst are also described.

Abstract: The durability of a fuel cell having a polymer electrolyte membrane with an anode on one surface and an oxygen-reducing cathode on the other surface is improved by replacing conductive carbon matrix materials in an electrode with a matrix of electrically conductive metal compound particles. The electrode includes a catalyst supported on a nanosize metal oxides and electrically conductive nanosize matrix particles of a metal compound. One or more metal compounds such as a boride, carbide, nitride, silicide, carbonitride, oxyboride, oxycarbide, or oxynitride of a metal such as cobalt, chromium, nickel, molybdenum, neodymium niobium, tantalum, titanium, tungsten, vanadium, and zirconium is suitable. For example, the combination of platinum particles deposited on titanium dioxide support particles mixed in a conductive matrix of titanium carbide particles provides an electrode with good oxygen reduction capability and corrosion resistance in an acid environment.

Abstract: An electrocatalyst is described. The electrocatalyst includes a core of a non-noble metal or non-noble metal alloy; and a continuous shell of a noble metal or noble metal alloy on the core, the continuous shell being at least two monolayers of the noble metal or noble metal alloy. Methods for making the electrocatalyst are also described.

Abstract: The durability of a fuel cell having a polymer electrolyte membrane with an anode on one surface and an oxygen-reducing cathode on the other surface is improved by substituting electrically conductive titanium carbide or titanium nitride particles for carbon particles as oxygen-reducing and hydrogen-oxidizing catalyst supports. For example nanosize platinum particles deposited on nanosize titanium carbide or titanium nitride support particles provide good oxygen reduction capability and are corrosion resistant in an acid environment. It is preferred that the catalyst-on-titanium carbide (nitride) particles be mixed with non-catalyst-bearing carbon in the electrode material for improved electrode performance.

Abstract: A precursor halide compound is reduced to a predetermined product at substantially ambient conditions. The halide is added to an anhydrous liquid reaction medium containing one or more alkali metals or alkaline earth metals as reductants. The metal reductants are dispersed as very small globules in the liquid by cavitation of the liquid, such as by application of high intensity ultrasonic vibrations or high-shear mixing to the reaction vessel. Continued cavitation of the liquid medium affects low temperature reduction of the precursor halide(s) to produce a metal, metal alloy, metal compound, ceramic material, metal matrix-ceramic composite material, or the like. The practice may be applied, for example, to titanium tetrachloride, alone or with other chlorides, to produce titanium metal, titanium alloys (for example Ti-6Al-4V), and titanium compounds (TiSi2).

Abstract: A precursor halide compound is reduced to a predetermined product at substantially ambient conditions. The halide is added to an anhydrous liquid reaction medium containing one or more alkali metals or alkaline earth metals as reductants. The metal reductants are dispersed as very small globules in the liquid by cavitation of the liquid, such as by application of high intensity ultrasonic vibrations or high-shear mixing to the reaction vessel. Continued cavitation of the liquid medium affects low temperature reduction of the precursor halide(s) to produce a metal, metal alloy, metal compound, ceramic material, metal matrix-ceramic composite material, or the like. The practice may be applied, for example, to titanium tetrachloride, alone or with other chlorides, to produce titanium metal, titanium alloys (for example Ti-6Al-4V), and titanium compounds (TiSi2).

Abstract: Nanometer to micrometer sized particles containing platinum and having selected morphologies are prepared by a sonochemical process. A compound of platinum is dissolved, suspended, or diluted in a suitable liquid medium at a predetermined concentration and the liquid is maintained at a predetermined temperature from sub-ambient temperatures to above ambient temperatures. A reducing gas is bubbled through the liquid as it is subjected to cavitation at a controlled power to affect the reductive decomposition of the platinum compound. The morphology of the precipitated platinum particles can be varied widely by varying the described concentration, temperature and power parameters.