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AssigneeCabot Corporation
InventorsMark J. Hampden-Smith, Toivo Kodas, Paolina Atanassova, Paul Napolitano, Rimple Bhatia, James H. Brewster
Estimating the term…
Electrocatalyst powders and energy devices fabricated using electrocatalyst powders and methods for making energy devices. The energy devices, such as fuel cells, have improved performance over a range of operating conditions.
A membrane electrode assembly comprising at least an anode, a cathode and a membrane separating said anode and said cathode, wherein at least one of said anode and said cathode comprises electrocatalyst particles fabricated by heating suspended droplets of an electrocatalyst precursor composition while said droplets are suspended in a gas.
A membrane electrode assembly comprising at least an anode, a cathode and a membrane separating said anode and cathode, wherein at least one of said anode and cathode comprises composite electrocatalyst aggregates having an active species dispersed on a support phase wherein said aggregates are substantially spherical and wherein the volume average size of said aggregates is not greater than about 100 μm.
A membrane electrode assembly comprising at least an anode, a cathode and a membrane separating said anode and said cathode, wherein at least one of said anode and said cathode comprises an electrocatalyst layer and said electrocatalyst layer comprises substantially spherical electrocatalyst particles.
A liquid vehicle comprising catalyst particles, said liquid vehicle being adapted to be deposited using a direct-write tool to form a catalyst layer, wherein said liquid vehicle comprises a liquid carrier and catalyst particles having a volume average particle size of not greater than about 20 μm dispersed in said liquid carrier.
A method for the deposition of an electrocatalyst layer, comprising the steps of:
A membrane electrode assembly comprising at least an anode, a cathode and a membrane separating said anode and said cathode, wherein at least one of said anode and said cathode comprises electrocatalyst aggregates, said electrocatalyst aggregates comprising an active species phase dispersed on a porous support phase and a polymer phase intimately mixed within the structure of said aggregates.
A membrane electrode assembly comprising at least an anode, a cathode and a membrane separating said anode and said cathode, wherein at least one of said anode and said cathode comprises electrocatalyst particles consisting of an active species phase dispersed on a support phase and wherein said electrocatalyst particles have an average internal pore size of not greater than about 20 nanometers.
A membrane electrode assembly comprising an electrocatalyst layer, wherein said layer comprises 20 to 40 volume percent electrocatalyst, 20 to 40 volume percent proton conducting polymer and at least about 30 volume percent porosity.
A membrane electrode assembly comprising an anode, a cathode and a membrane separating said anode and said cathode, wherein said cathode comprises an electrocatalyst layer having a supported active species loading of not greater than about 0.2 mg/cm2, and wherein the cell voltage of said membrane electrode assembly is at least about 0.6 V at a constant current density of about 600 mA/cm2 at 50° C. and atmospheric pressure, using a feed gas of pure air to said cathode and pure hydrogen to said anode at a substantially constant flow rate and with external humidification.
A membrane electrode assembly comprising an anode, a cathode and a membrane separating said anode and said cathode, wherein said cathode comprises an electrocatalyst layer having a supported active species loading of not greater than about 0.1 mg/cm2, wherein said membrane electrode assembly has a cell voltage of at least about 0.7 V at a current density of at least about 150 mA/cm2 at 50° C. and atmospheric pressure, using a feed gas of pure air to said cathode and pure hydrogen to said anode at a substantially constant flow rate and with external humidification.
A membrane electrode assembly comprising an anode, a cathode and a membrane separating said anode and said cathode, wherein said cathode comprises an electrocatalyst layer having a supported active species loading of not greater than about 0.2 mg/cm2, and wherein said membrane electrode assembly has a cell voltage of at least about 0.6 V at a current density of at least about 550 mA/cm2 at 50° C. and atmospheric pressure, using a feed gas of pure air to said cathode and pure hydrogen to said anode at a substantially constant flow rate and with external humidification.
A membrane electrode assembly comprising an anode, a cathode, and a membrane separating said anode and said cathode, wherein said cathode comprises an electrocatalyst layer having a supported active species loading of not greater than about 0.4 mg/cm2, and wherein said membrane electrode assembly has a cell voltage of at least about 0.5 V at a current density of at least about 800 mA/cm2 at 50° C. and atmospheric pressure, using a feed gas of pure air to said cathode and pure hydrogen to said anode at a substantially constant flow rate and with external humidification.
A membrane electrode assembly comprising an anode, a cathode, and a membrane separating said anode and said cathode, wherein said cathode comprises an electrocatalyst layer having a supported active species loading of not greater than about 0.5 mg/cm2, and wherein said membrane electrode assembly has a cell voltage of at least about 0.5 V at a current density of at least about 800 mA/cm2 at 50° C. and atmospheric pressure, using a feed gas of pure air to said cathode and pure hydrogen to said anode at a substantially constant flow rate and with external humidification.
A membrane electrode assembly comprising an anode, a cathode, and a membrane separating said anode and said cathode, wherein said cathode comprises an electrocatalyst layer having a supported active species loading of not greater than about 0.1 mg/cm2 and has a delta E value of not greater than about 50 millivolts at 200 mA/cm2 and not greater than about 100 millivolts at 400 mA/cm2 and not greater than about 175 millivolts at 600 mA/cm2, when measured at 50° C. and atmospheric pressure, using a feed gas of pure hydrogen to said anode at a substantially constant flow rate and with external humidification.
A membrane electrode assembly comprising an anode, a cathode, and a membrane separating said anode and said cathode, wherein said cathode comprises an electrocatalyst layer having a supported active species loading of not greater than about 0.2 mg/cm2 and has a delta E value of not greater than about 50 millivolts at 200 mA/cm2 and not greater than about 100 millivolts at 600 mA/cm2 and not greater than about 170 millivolts at 1000 mA/cm2, when measured at 50° C. and atmospheric pressure,using a feed gas of pure hydrogen to said anode at a substantially constant flow rate and with external humidification.
A membrane electrode assembly comprising an anode, a cathode, and a membrane separating said anode and said cathode, wherein said cathode comprises an electrocatalyst layer having a supported active species loading of not greater than about 0.4 mg/cm2 and has a delta E value of not greater than about 50 millivolts at 200 mA/cm2, not greater than about 100 millivolts at 600 mA/cm2 and not greater than about 250 millivolts at 1000 mA/cm2, when measured at 50° C. and atmospheric pressure, using a feed gas of pure hydrogen to said anode at a substantially constant flow rate and with external humidification.
A membrane electrode assembly comprising an anode, a cathode, and a membrane separating said anode and said cathode, wherein said cathode comprises an electrocatalyst layer having a supported active species loading of not greater than about 0.6 mg/cm2 and has a delta E value of not greater than about 80 millivolts at 200 mA/cm2, not greater than about 150 millivolts at 600 mA/cm2 and not greater than about 200 millivolts at 1000 mA/cm2, when measured at 50° C. and atmospheric pressure, using a feed gas of pure hydrogen to said anode at a substantially constant flow rate and with external humidification.
Dependencies are inferred from the claim text.
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Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium: carbon
Manganese, technetium or rhenium: manganese
Of noble metals: of the platinum group metals
Characterised by their physical properties: electric or magnetic properties
Term end not estimated
1. Field of the Invention
The present invention relates to particulate materials such as electrocatalyst particles and complex multi-component particles for the fabrication of energy devices such as fuel cells. The present invention also relates to improved energy devices incorporating the particulate materials.
2. Description of Related Art
FIG. 1 illustrates the structure of aggregate electrocatalyst particles according to the present invention.
FIG. 2 illustrates the formation steps of a supported electrocatalyst formation according to an embodiment of the present invention.
FIG. 3 illustrates a two-fluid nozzle that is useful for the production of electrocatalyst powders according to the present invention.
The present invention is generally directed to powders useful in the construction of energy devices, such as electrocatalyst powders useful in fuel cells, and to methods for producing the powders. One preferred embodiment of the present invention is directed to composite electrocatalyst powders that are useful in fuel cells for catalyzing chemical reactions. The present invention is also directed to novel structures and devices fabricated using the powders. One example is a fuel cell, such as a PEM fuel cell composed of a number of MEAs. The materials according to the present invention can advantageously be formed into thin layers using direct write deposition and similar techniques to form unique structures.
As used herein, the term electrocatalyst particles or powders refers to aggregate particles that include one or more highly dispersed phases, typically metal or metal oxide clusters or crystallites, with dimensions on the order of about 1 nanometers to 10 nanometers that are dispersed over the surface of the support particles. Support particles can be chosen from a metal oxide (e.g., RuO2, In2O3, ZnO, IrO2, SiO2, Al2O3, CeO2, TiO2 or SnO2), aerogels, xerogels, carbon or a combination of the foregoing. In the following discussion, carbon is used as an example. The carbon support particles typically have sizes in the range of about 10 nanometers to 5 μm, depending on the nature of the carbon material. However, carbon particulates having sizes up to 25 μm can be used as well. The individual carbon particles supporting the dispersed active species phase typically do not exist as discrete particles but tend to associate to form structures that contain a number of discrete particles. Throughout the present application, the larger structures formed from the association of these discrete carbon particles supporting the dispersed phase are referred to as aggregates or aggregate particles, and typically have a size in the range from 0.5 to 25 μm. In contrast, conventional methods for producing electrocatalyst powders form aggregates that can range in size from two or more carbon particles supporting the discrete metal phase to millimeter sized aggregates. In addition, the aggregates can further associate into larger “agglomerates”. The aggregate morphology, aggregate size, size distribution and surface area of the electrocatalyst powders are characteristics that have a critical impact on the performance of the catalyst. The aggregate morphology, aggregate size and size distribution determines the packing density and the surface area determines the type and number of surface adsorption centers where the active species are formed during synthesis of the electrocatalyst. The inability to control the fundamental electrocatalyst powder characteristics is a major obstacle for the future development of energy storage and production devices. One of the major advantages of the electrocatalyst powders described here is that that morphology (spherical), aggregate size and aggregate size distribution is controlled by the droplet size and size distribution during powder production.
FIG. 1 illustrates the morphology and structure of the electrocataylst powders according to the present invention. FIG. 1(a) illustrates a plurality of the aggregate electrocataylst particles in a powder batch. FIG. 1(b) illustrates one electrocatalyst particle having a size of about 1.2 μm. FIG. 1(c) illustrates the structure of the particle of FIG. 1(b) in greater detail, wherein the individual support particles can be seen. FIGS. 1(d) and 1(e) illustrated the active species dispersed on the support phase of the aggregate particle. Thus, the electrocatalyst powders of the present invention are not mere physical admixtures of different particles, but are comprised of support phase particles that include a dispersed phase of an active species. The compositions and ratios of the aggregate particle components can be varied independently and various combinations of carbons, metals, metal alloys, metal oxides, mixed metal oxides, organometallic compounds and their partial pyrolysis products can be produced. One embodiment of the present invention is directed to electrocatalyst particles with two or more different materials as the dispersed active species. As an example, combinations of Ag and MnOx dispersed on carbon can be useful for some electrocatalytic applications. Other examples of multiple active species are mixtures of porphyrins, partially decomposed porphyrins, Co and CoO. Although carbon is a preferred material for the support phase, other materials such as metal oxides can also be useful for some electrocatalytic applications, as is discussed above.