STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

[0001] The U .S. Government has a paid-up license in this invention and has the right in limited circumstances to require the patent owner to license others on reasonable terms as provided by the terms of Contract No. N00014-08-C-0104, awarded by the Office of Naval Research.

TECHNICAL FIELD

[0002] This invention is related to a catalyzed carbon, a method of making the catalyzed carbon, and a catalytic electrode in which the catalyzed electrode is used, particularly for an electrochemical battery cell or fuel cell.

BACKGROUND

[0003] The applications for high power and light weight electrochemical cells can have enormous impacts on various programs for mobile electronic equipment for both commercial and military applications. Fuel cells and metal-air cells (such as Zn-air ₍ Li-air) have an apparent advantage over Li-ion cells and other electrochemical cells due to their extremely high specific capacity. This feature results from the fact that active materials for one or both electrodes do not have to be stored in the inside of cell, and thus significantly reduces the total battery weight and volume, For example, metal-air cells and some types of fuel cells use oxygen from the surrounding air as the active material of the positive electrode (cathode), at which oxygen is reduced via an Oxygen Reduction Reaction (ORR). The ORR is catalyzed by a catalyst in the cathode,

[0004] For cells to support high rate and high power discharge, the catalytic electrode must be capable of catalyzing the electrode reaction at a sufficiently high rate, A variety of ORR catalysts are known. Many of these materials are expensive. To provide a battery at an acceptable cost, catalysts with a reduced catalytic activity are often used, especially in lower cost batteries, including metal-air cells. However, the power densities of such cells are usually low, which limits the applications for which they can be used. The critical challenge for improving these cells is improving the catalytic electrode without adding too much cost.

[0005] At relatively low rates, the reaction can proceed to a high depth of discharge, but at higher rates the polarization in the catalytic electrode can limit cell performance. To reduce polarization and improve cell performance at high rates, the catalytic reaction kinetics need to be improved, and the amount of reactant made available to the reaction sites in the catalytic electrode should be increased. Due to these facts, it is of critical importance to develop a cost effective and efficient catalyst with high catalytic activity, and an efficient way to disperse this catalyst within the electrode.

[0006] Metal oxides are less expensive alternatives to catalysts such as platinum and palladium. Manganese oxides (MnO _x ) are popular catalysts in commercialized zinc-air batteries and have attracted much attention, not only because of their wide structural diversity, considerable ORR catalytic activity, and low cost, but also because they are relatively environmentally friendly. To better utilize the electrocatalyst in the catalytic electrode and improve its high rate performance, a nanoparticle catalyst is preferred. The catalyst is often dispersed on a suitable support structure. Carbon particles are a popular support structure, especially in metal-air cell electrodes. However, it is a challenge to homogeneously mix nano-sized metal oxide catalysts with micro-sized carbon particles during electrode fabrication due to the tremendous difference of particle sizes, density and surface properties between the metal oxide and carbon and, the tendency of agglomeration of catalyst nanoparticles during handling and processing. Sonication has been used to disperse catalyst materials, as disclosed in patent publication numbers US2008/0096061A1,

US6428931B1, US7259126B2 and WO2008/025751A1 for example. A typical ultrasonic mixture of MnO _x particles with carbon particles is unable to effectively eliminate the agglomeration of the MnO _x particles and causes a non-uniform distribution of MnO _x particles and fewer electrocatalytic active sites for the electrode reaction.

[0007] Therefore, a more effective way to uniformly apply nanoparticle metal oxide catalyst onto the surface of carbon support material is needed.

SUMMARY

[0008] A first aspect of the invention is a catalyzed carbon including a carbon supported metal oxide catalyst. The carbon supported metal oxide catalyst has a plurality of catalytic structures, and the catalytic structures including a metal oxide film on a surface of carbon particles and nano-metal oxide particles attached to the carbon particles. Embodiments can include one or more of the following features:

• the metal of the metal oxide comprises manganese; the metal oxide can include both manganese dioxide and manganese (II) oxide; a ratio of the manganese dioxide to the manganese (II) oxide can be from 0.5: 1 to 4: 1 ; the ratio of the manganese dioxide to the manganese (II) oxide can be at least 1: 1 ; the ratio of the manganese dioxide to the manganese (II) oxide can be less than or equal to 3: 1; the ratio of the manganese dioxide to the manganese (II) oxide can be approximately 2: 1 ;

• the plurality of catalytic structures includes a plurality of carbon particle types; more than one of the carbon particle types can include a film of metal oxide on the carbon particles and nano-metal oxide particles attached to the carbon particles;

• the metal oxide film is no more than 8 nm thick and discontinuous;

• the metal oxide film is nanoporous;

• the nano-metal oxide particles include crystalline particles; and

• the carbon particles include active carbon particles;

• the carbon particles include a carbon particle type having an average BET surface area in the range of 800 to 900 m ² /g;

• the carbon particles include a carbon particle type having an average BET surface area in the range of 1600 to 1750 m ² /g;

• the carbon supported metal oxide catalysts are doped with a metal-containing dopant; the dopant can include gold.

[0009] A second aspect of the invention is an electrochemical. The cell includes a housing and a plurality of electrodes, one of the plurality of electrodes including a catalyzed carbon. The catalyzed carbon includes a carbon supported metal oxide catalyst. The carbon supported metal oxide catalyst includes a plurality of catalytic structures, and the catalytic structures include a metal oxide film on a surface of carbon particles and nano-metal oxide particles attached to a surface of the carbon particles. Embodiments can include one or more of the following features:

• the cell is a metal-air cell; the cell can be a zinc-air cell; the cell can be a lithium-air cell;

• the metal of the metal oxide comprises manganese; the metal oxide can include both manganese dioxide and manganese (II) oxide; a ratio of the manganese dioxide to the manganese (II) oxide can be from 0.5: 1 to 4: 1; the ratio of the manganese dioxide to the manganese (II) oxide can be at least 1: 1 ; the ratio of the manganese dioxide to the manganese (II) oxide can be less than or equal to 3: 1; the ratio of the manganese dioxide to the manganese (II) oxide can be approximately 2: 1 ;

• the plurality of catalytic structures includes a plurality of carbon particle types; more than one of the carbon particle types can include a film of metal oxide on the carbon particles and nano-metal oxide particles attached to the carbon particles;

• the metal oxide film is no more than 8 nm thick and discontinuous; • the metal oxide film is nanoporous;

• the nano-metal oxide particles include crystalline particles; and

• the carbon particles include active carbon particles;

• the carbon particles include a carbon particle type having an average BET surface area in the range of 800 to 900 m ² /g;

• the carbon particles include a carbon particle type having an average BET surface area in the range of 1600 to 1750 m ² /g;

• the carbon supported metal oxide catalysts are doped with a metal-containing dopant; the dopant can include gold.

[0010] A third aspect of the invention is a method for producing a catalyzed carbon. The method includes synthesizing a metal oxide on a surface of carbon particles to form a carbon supported metal oxide catalyst with a plurality of catalytic structures including a film of metal oxide on the carbon particles and nano-metal oxide particles attached to the carbon particles. Embodiments can include one or more of the following features:

• the synthesizing step includes dissolving the metal oxide in solution;

• the synthesizing step includes mixing the carbon particles with the metal oxide;

• the synthesizing step includes sonication; the sonication can be performed for more than a half hour; the sonication can be performed for approximately an hour;

• a suspension containing the carbon supported metal oxide catalysts is filtered, washed, and then dried;

• the metal of the metal oxide comprises manganese; the metal oxide can include both manganese dioxide and manganese (II) oxide; a ratio of the manganese dioxide to the manganese (II) oxide can be from 0.5: 1 to 4: 1; the ratio of the manganese dioxide to the manganese (II) oxide can be at least 1: 1 ; the ratio of the manganese dioxide to the manganese (II) oxide can be less than or equal to 3: 1; the ratio of the manganese dioxide to the manganese (II) oxide can be approximately 2: 1 ;

• the plurality of catalytic structures includes a plurality of carbon particle types; more than one of the carbon particle types can include a film of metal oxide on the carbon particles and nano-metal oxide particles attached to the carbon particles;

• the metal oxide film is no more than 8 nm thick and discontinuous;

• the metal oxide film is nanoporous;

• the nano-metal oxide particles include crystalline particles; and

• the carbon particles include active carbon particles; • the carbon particles include a carbon particle type having an average BET surface area in the range of 800 to 900 m ² /g;

• the carbon particles include a carbon particle type having an average BET surface area in the range of 1600 to 1750 m ² /g;

• the carbon supported metal oxide catalysts are doped with a metal-containing dopant; the dopant can include gold.

[0011] A fourth aspect of the invention is an electrochemical cell prepared by a process including synthesizing a metal oxide on a surface of carbon particles to form a carbon supported metal oxide catalyst. The carbon supported metal oxide catalyst having a plurality of catalytic structures including a metal oxide film of particles of the carbon supported metal oxide catalyst and nano-metal oxide particles attached to a surface of the particles of carbon supported metal oxide catalyst. Embodiments can include one or more of the following features:

• the cell is a metal-air cell; the cell can b a zinc-air cell; the cell can be a lithium-air cell;

• the metal in the metal oxide used in the synthesis step includes manganese.

• the metal of the metal oxide comprises manganese; the metal oxide can include both manganese dioxide and manganese (II) oxide; a ratio of the manganese dioxide to the manganese (II) oxide can be from 0.5: 1 to 4: 1; the ratio of the manganese dioxide to the manganese (II) oxide can be at least 1: 1 ; the ratio of the manganese dioxide to the manganese (II) oxide can be less than or equal to 3: 1; the ratio of the manganese dioxide to the manganese (II) oxide can be approximately 2: 1 ;

• the plurality of catalytic structures includes a plurality of carbon particle types; more than one of the carbon particle types can include a film of metal oxide on the carbon particles and nano-metal oxide particles attached to the carbon particles;

• the metal oxide film is no more than 8 nm thick and discontinuous;

• the metal oxide film is nanoporous;

• the nano-metal oxide particles include crystalline particles; and

• the carbon particles include active carbon particles;

• the carbon particles include a carbon particle type having an average BET surface area in the range of 800 to 900 m ² /g;

• the carbon particles include a carbon particle type having an average BET surface area in the range of 1600 to 1750 m ² /g; • the carbon supported metal oxide catalysts are doped with a metal-containing dopant; the dopant can include gold.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the drawings:

FIG. 1 is an elevational view, in cross-section, of a prismatic shaped metal-air cell with a catalytic electrode;

FIG. 2 is an elevational view, in cross-section, of a button-shaped metal-air cell with a catalytic electrode;

FIG. 3 is a schematic representation of a carbon particle with an amorphous metal oxide film and metal oxide nano-crystalline particles on the surface of the carbon particle;

FIGs. 4A and 4B are tables showing characteristics of a number of different carbons;

FIG. 5 is a graph showing the catalytic activity of various materials on a peroxide decomposition test;

FIG. 6 is a graph showing the catalytic activity of various manganese oxide/carbon composites on a peroxide decomposition test;

FIG. 7 is a chart showing the power capability of electrodes containing various manganese oxide/carbon composites on a half cell limiting current test;

FIG. 8 is a chart showing the power capability of full cells with electrodes containing various manganese oxide/carbon composites on a limiting current test;

FIG. 9 is a graph of the results for various materials on a Rotating Disc Electrode test: and FIG. 10 is a chart showing the catalytic activity for various materials on a limiting current test.

DETAILED DESCRIPTION

[0013] The embodiments of the present inventions described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present inventions.

[0014] All publications and patents mentioned herein are incorporated herein by reference in their respective entireties for the purpose of describing and disclosing, for example, the constructs and methodologies that are described in the publications which might be used in connection with the presently described invention. The publications discussed above and throughout the text are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventor is not entitled to antedate such disclosure by virtue of prior invention.

[0015] For purposes of description herein, the terms "upper," "lower," "right," "left," "rear," "front," "vertical," "horizontal," and derivatives thereof shall relate to the invention as oriented in the Figures. However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific parts, devices and processes illustrated and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

[0016] Unless otherwise specified, the following definitions and methods are used herein:

• "catalyzed carbon" means carbon catalyzed with a metal oxide including the MnO _x /C nanocomposites;

• "MnO _x /C nanocomposites" means carbon with a metal oxide film with nano-metal oxide particles attached to the carbon;

• "crystalline" means having a regular three-dimensional molecular structure;

• "nanoporous" means a regular framework supporting a regular, porous structure with pores roughly in the nanometer range (from 1x10 ⁷ m to 0.2x10 ⁹ m);

• "sonication" means the act of applying sound energy, such as ultrasound energy, to

agitate particles;

• "sonochemical process" means the application of ultrasound to chemical reactions and processes;

• "specific surface area" is measured using the Brunauer, Emmet, and Teller (BET)

method, using nitrogen;

• "oxide" means any oxide of the metal, including one or more oxygen atoms attached to one or more of the metal atoms;

• "nanoparticle", as generally used herein refers to particle or a structure in the nanometer (nm) range, typically from about 0.1 nm to about 1000 nm in diameter;

• "catalyst" as generally used herein refers to any chemical which enhances the rate and/or efficiency of molecular dissociation compared with the rate and/or efficiency of dissociation in the absence of the catalyst; and • "vertically aligned carbon nanothubes are nanotubes extending from and generally normal to a substrate, surface or plane, preferably at an angle of no greater than 30 degrees, and more preferably at an angle of no greater than 15 degrees, from perpendicular to the substrate, surface or plane.

[0017] Unless otherwise specified herein, all disclosed characteristics, values and ranges are as determined at room temperature (20-25°C).

[0018] To provide a more effective catalyst, a metal oxide that is effective as a catalyst is distributed uniformly on the surface of carbons. This can be accomplished using a sonochemical process (i.e., an sonically assisted chemical process) for synthesizing a metal oxide in the presence of the carbon, to form the metal oxide on surfaces of the carbon. The carbons can be in any particulate form, including powders, flakes, fibers, graphene nanopellets, nanotubes and combinations thereof, with carbon powders and nanotubes being preferred. The composite catalyst (one or more metal oxides disposed on surfaces of the carbon) includes a metal oxide film and nano-metal oxide particles (metal oxide particles with 80 percent of the particles having a dimension less than 200 nm) covering at least a portion of the carbon structures (particles, nanotubes, etc.). The metal oxide film is preferably a substantially amorphous metal oxide film.

[0019] A preferred carbon powder is an activated carbon powder, such as steam activated carbon powder. An activated carbon is a carbon with a specific surface area (BET method using nitrogen) of at least about 500 m ² /g, with 1500 m ² being achievable. Examples of steam activated carbon powders are Type PWA carbon (Calgon Carbon Corp., Pittsburgh, Pa., USA), NORIT® Supra DLC30 carbon, NORIT® Super carbon and DARCO® G-60 carbon (all from American NORIT Co., Inc., Marshall, Tex., USA). Use of DARCO® G60 and/or NORIT® DLC30 carbon, or similar carbons, is preferred. Details of the BET surface area, pore size, pore volume distribution, and surface area distribution data for these and other carbons is shown in FIGs. 4A and 4B. DARCO® G-60 carbon is a steam activated carbon. Other properties of DARCO® G-60 carbon include: carbon particles pass through a No. 100 sieve but do not pass through a No. 325 sieve (US Standard Series sieves per ASTM E-l 1); a particle size distribution with a dso of about 34 μηι, a ds of about 5.5 μηι and a dgs of about 125 μιη; a specific surface area (BET method using nitrogen) from about 600 to about 1000 m ² /g; a pore volume of about 0.0.741 ml/g, dry basis; a bulk density (tamped) of about 0.40 g/ml; and an iron content of the carbon no greater than 200 parts per million (ppm). Surpra DLC 30 carbon is an activated carbon with a particle size distribution having a dso of about 20 μπι, a dio of about 4 μπι and a d9o of about 100 μπι; a specific surface area (BET method using nitrogen) of about 1700 m ² /g; a pore volume of about 0.710 ml/g; and a tap density of about 0.275 g/ml.

[0020] Carbon nanotubes (CNTs) are especially advantageous because they have a high surface area and unique structure. CNTs have a hollow cylindrical nanostructure, the walls of which have one or more layers of graphene (i.e., they can be single walled or multi- walled). Vertically aligned carbon nanotubes (VACNTs) are especially preferred. Vertically aligned carbon nanotube arrays (VACNTAs) can be formed on a substrate, with

approximately parallel CNTs projecting from the substrate. VACNTAs can be made using a suitable method; examples include:

• Xiong et al., J ^w. Chem. Soc. 2010, 132, 15839-15841;

• Fan et al., Science, Vol. 283, 22 January 1999, 512-514;

• Turano et al., J. Electronic Materials, Vol. 35, No. 2, 192-194;

• de Villoria et al., Nanotechnology, 20 (2009), 40561 1 (8 pages);

• Wendy Beckman, "UC Researchers Shatter World Records with Length of Carbon

Nanotube Arrays," http://www.uc. edu/news/NR.aspx?id=5700, April 27, 2007; and

• Mohamed et al., J. Applied Sciences , 11 (8), 2011, 1341-1345.

VACNTAs are also available commercially, such as from NanoLab, Inc., Newton, MA, USA.

[0021] CNTs are suitably in a range from about 1 nm to about 150 nm. In general, the smaller the diameter the greater the external surface area, as long as the inside diameters of the tubes are large enough for molecules of the cell electrolyte to pass through. For example, a preferred outside diameter range for use with an aqueous potassium hydroxide electrolyte is from 10 nm to about 120 nm. Preferably the outside diameter is at least about 15 nm.

Preferably the outside diameter is no greater than about 100 nm. The length of the CNTs is suitably within the range from about 15 μηι to about 500 μηι. Preferably the length is at least about 30 μπι, and more preferably at least about 50 μπι. Preferably the length is no more than about 400 μηι, and more preferably no more than about 250 μιη. The site density of the CNTs in a VACNTA is suitably from 10 ⁷ to 10 ¹¹ CNTs per cm ² , preferably from 10 ⁸ to 10 ¹¹ CNTs per cm ² , and more preferably from 10 ⁹ to 10 ¹⁰ CNTs per cm ² . The spacing of the CNTs in a VACNTA can be defined by the weight percent of the maximum theoretical density of the carbon material from which the CNTs are made, which is suitably at least about 25 weight percent to about 55 weight percent. Preferably the spacing will provide at least about 30 weight percent of the maximum theoretical density. Preferably the spacing will provide up to about 48 weight percent, and more preferably up to about 45 weight percent of the maximum theoretical density.

[0022] Suitable metal oxides include those of transition metals, particularly those transition metal oxides with good catalytic activity. Suitable metals are generally contained within groups 3 to 11, preferably groups 4 to 10, of the Periodic Table of the Elements plus the lanthanide and actinide series (IUPAC Nomenclature of Inorganic Chemistry,

Recommendations 2005). Manganese, cobalt, nickel, ruthenium and iridium are preferred transition metals. Copper, silver and gold are not preferred transition metals because gold and silver oxides are expensive, and copper oxides may not have the desired stability in the cell environment. The metal oxide can contain a single type of cation (e.g., with a formula AO _x , where A is a metal cation such as manganese or cobalt), or more than one type of cation (i.e., in a mixed metal oxide). Examples of mixed metal oxides include binary metal oxides (with a formula A _x B _y O _z , where A and B are different metal cations, such as N1C0 ₂ O ₄ and Mn _x Co ₃ - _x 0 ₄ ).

[0023] Metal oxide catalysts are synthesized in situ on the surface of the carbon structures to form carbon supported nano-metal oxide catalysts (nanocomposites). These carbon supported metal oxide catalysts have at least two different structures accompanied by two different morphologies simultaneously - a film and nano-crystalline particles. As illustrated by the model shown in FIG. 3, a carbon-supported nano-metal oxide catalyst 50 includes a metal oxide film 54 on the surface of a carbon particle 52. In addition, a relatively uniform distribution of nano-crystalline manganese oxide particles 56 is on the surface of the carbon particle 52. The metal oxide film is preferably substantially amorphous. It can be thin (i.e, no greater than about 8 nm thick, preferably about 1-8 nm thick, and more preferably about 3-6 nm thick). It is preferably a discontinuous and/or a nanoporous film. While it may be discontinuous and/or nanoporous, the film is preferably uniformly distributed. The nanocomposite with such structures may be synthesized by a sonochemical assisted reduction reaction. No reducing agents are used, and the use of surfactants is optional. These nanocomposites demonstrate a higher ORR catalytic activity and better air electrode service.

[0024] In the sonochemical process for synthesizing the metal oxide on the surface of the carbon structures, the carbon is immersed in a precursor solution containing one or more soluble precursors. The precursors generally include the desired cation(s), with a valence higher than desired in the final nanocomposite. The solution is subjected to sonication, such as with an ultrasonic processor, for a period of time to reduce the precursors and deposit the metal oxide on the carbon. Examples of metal oxides and precursors that may be suitable include: one or more soluble Mn ⁷⁺ compounds (e.g., sodium permanganate, potassium permanganate, calcium permanganate, ammonium permanganate, silver permanganate) to produce manganese oxide.

[0025] Additional benefits can also be obtained when the metal oxides are doped with another metal. The metals that may be used as dopants include Au, Cu, Ir, La, Ag, Ni, Pt, Ru, and combinations thereof. Preferably, Au, Pt and/or Ni are used. The metal dopants do not have to be in pure form, can include alloys, can be metal compounds (e.g., oxidized), or can be in any other catalytically active form or combination.

[0026] Gold and gold-based alloy nanoparticles have a high ORR activity. The high cost of gold, however, prohibits wide use in commercial applications. Gold can be used as a doping element to co-deposit with metal oxide nanoparticles onto the carbon surface during sonochemical synthesis to further improve its catalytic activity while keeping the cost reasonable.

[0027] A preferred metal oxide catalyst is MnO _x . The permanganate compound used can affect the structure of the MnO _x deposited on the CNTs. For example, using NaMn0 ₄ tends to result in more amorphous MnO _x , while using KMn0 ₄ tends to result in more crystalline MnO _x . Mixtures of NaMn0 ₄ and KMn0 ₄ in varying ratios can be used to adjust the overall structure of the MnO _x . The quantities of carbon and solution, permanganate concentration, temperature, ultrasonic energy applied and time can all affect the rate at which the MnO _x is deposited, and each of these parameters can be adjusted to provide the desired quantity of MnO _x deposited, the time required and the efficiency of the process. It is also possible to dope the MnO _x /carbon nanocomposite with one or more metals, such as Au, Cu, Ir, La, Ag, Ni, Pt and Ru, or oxides thereof, to improve the catalytic activity. This can be accomplished by adding cations of the desired metal to the permanganate solution for example. This process can also be modified to decorate VANCTAs with other catalysts besides MnO _x , such as for use in other battery systems besides aqueous alkaline systems.

[0028] In one embodiment, the overall composition of the manganese oxide can be characterized as MnO _x , where x is from about 1 to about 2, preferably from about 1.2 to about 2.0, more preferably from about 1.6 to 1.8, and most preferably approximately 1.7. The ratio of Mn0 ₂ to MnO, two of the potential manganese compounds in the mixture, can be 0.5: 1 to 4: 1, preferably at least 1 : 1, preferably less than or equal to 3: 1, and more preferably approximately 2: 1. The carbon can be a carbon powder with primary particles that are generally sphere-like in shape, typically with a maximum dimension of about 20 to 30 μπι in size, with some smaller particles, down to 10 μηι or less. The primary manganese oxide particles are alternatively generally rod-like in shape and typically about 20 nm in width and about 50 to 200 nm long.

[0029] Electrochemical cells according to the invention can be metal-air, hydrogen generating or oxygen generating cells, or fuel cells for example. The invention is exemplified by metal-air battery cells as described below. Metal-air battery cells can be made in a variety of shapes and sizes, including button cells, cylindrical cells and prismatic cells as disclosed in U.S. Publication No. 2008/0160413, which is incorporated herein by reference. Metal-air battery cells can include various metals (e.g., zinc, aluminum, magnesium or lithium) as the negative electrode (anode) active material.

[0030] Examples of prismatic and button metal-air cells are shown in FIGs. 1 and 2, respectively. An embodiment of a button cell 10 is illustrated in FIG. 2. Cell 10 is an air cell that includes a cup-shaped anode casing 26 (referred to as a cup) and a cathode casing 12 (referred to as a can) that is cup-shaped and has a relatively flat central region 14 which is continuous with and surrounded by an upstanding wall 16 of uniform height. Alternatively, in one embodiment the central region 14 of the can bottom may protrude outward from the peripheral part of the can bottom. At least one hole 18 is present in the bottom of cathode can 12 to act as an air entry port. The casings 12, 26 can include single or multiple steps if desired.

[0031] An embodiment of a prismatic cell 110 is shown in FIG. 1. The cell 110 illustrated is an air cell that includes cathode casing (can) 112 and an anode casing (cup) 126. Anode casing 126 and cathode casing 112 are generally prismatic -shaped, and preferably rectangular, with each casing 126, 1 12 defining four linear or nonlinear sidewalls connected to a base or central region, preferably planar. Alternatively, cathode casing 112 can have a base with an area that protrudes outward from the peripheral part of the casing base. At least one hole 118 is present in the bottom of cathode can 112 to act as an air entry port. The casings 1 12, 126, can include single or multiple steps if desired.

[0032] Referring to FIGs. 1 and 2, a catalytic positive electrode, such as air electrode 20, 120 is disposed near the bottom of the cathode casing 12, 1 12. As shown in greater detail in FIG. 1, the air electrode 120 can include a catalytic layer containing the carbon supported catalysts described above with a binder. Air electrode 20, 120 also preferably has a hydrophobic layer 22, 122, such as a hydrophobic membrane or film, laminated thereon. The hydrophobic layer 22, 122 is laminated on the side of the air electrode closest to the bottom of the cell when oriented as shown in FIG. 1. Air electrode 20, 120 also preferably contains an electrically conductive current collector 123 (FIG. 1), typically a metal screen or expanded metal, such as nickel or a nickel plated or clad iron or steel, embedded therein, preferably on the side of the electrode opposite the hydrophobic layer 22, 122. The air electrode may also optionally contain a barrier membrane 137, such as a PTFE film, between the laminated hydrophobic layer 22, 122 and flat central region 14, 114 of the bottom of the casing 12, 112.

[0033] In a preferred embodiment, the catalytic layer 121 contains a catalytic composition that includes carbon particles with a substantially amorphous metal oxide film and nano-crystalline metal oxide particles attached to the carbon particles.

[0034] The catalytic composition can include a binder for binding the particles of carbon together. The binder can be a fluorocarbon material, such as polytetrafluoroethylene (PTFE) or fluorinated ethylene propylene (FEP). Suitable PTFE materials that can be used to make the catalytic layer composition include TEFLON® materials (available from E.I. duPont de Nemours & Co., Polymer Products Div., Wilmington, Del., USA), including powders such as TEFLON® 7C and, preferably, dispersions such as TEFLON® T30B, T30N, TE3857, TE3859 and modifications thereof. More preferably the PTFE material is T30B or a modification of TE3859 (e.g., TE3859 fluorocarbon resin plus 2 percent TRITON™ X-100 octylphenol ethoxylate nonionic surfactant (Dow Chemical Company, Midland, Mich., USA) based on the weight of the TE3859). The fluorocarbon binder can be fibrillated in the catalytic material mixing process.

[0035] In a preferred embodiment, the catalytic layer 121 of the electrode 120 contains oxidized nano-manganese and activated carbon in a ratio of from about 0.01/1 to about 0.10/1 by weight and from 1-25 weight percent PTFE binder (the minimum amount is more preferably at least 2, even more preferably at least 5 and most preferably at least 7 weight percent; the maximum amount is more preferably no greater than 15 and most preferably no greater than 12 weight percent).

[0036] The hydrophobic layer 22, 122 is hydrophobic material that has a low enough surface tension to be resistant to wetting by the electrolyte, yet porous enough to allow the required gas (e.g., oxygen in the air for a metal-air cell) to enter the electrode at a rate sufficient to support the desired cell reaction rate. Fluorocarbon membranes such as polytetrafluoroethylene (PTFE) can be used for the hydrophobic layer. A preferred PTFE material is a high permeability material with an air permeability value of from 1 to 300 seconds. A preferred PTFE material has an apparent density from about 1.5 to 1.7 g/cm ² . Examples of preferred materials are unsintered natural PTFE film, such as 0.10 mm (0.004 inch) thick PTFE membrane, product number N6389A (from Performance Plastics Product (3P), Houston, Tex., USA) with an air permeability value of about 100-200 seconds and an apparent density of about 1.60+-0.5 g/cm ² ; and expanded TEFLON® film, such as 0.076 mm (0.003 inch) thick expanded film sample number 12850830.1 (from W.L. Gore & Associates, Inc., Elkton, Md., USA). The air permeability value is the time required for 2.5 cm ³ of air under a constant pressure of 30.94 g/cm ³ (12.2 inches of water, or 0.44 pounds/in ² ) to pass through an area of 0.645 cm (0.1 in ² ) and can be measured with a Gurley Densometer, Model 4150, for example.

[0037] At least one layer of separator 24, 124 is positioned on the side of the air electrode 20, 120 facing the anode 28, 128. The separator 24, 124 is ionically conductive and electrically nonconductive. The total thickness of the separator 24, 124 is preferably thin to minimize its volume, but must be thick enough to prevent short circuits between the anode 28, 128 and air electrode 20, 120. While there are advantages to a single layer, two (or more) layers may be needed to prevent short circuits through a single pore, hole or tear in the material. For aqueous alkaline metal-air cells, cellulosic materials such as rayon, cotton and wood fiber (e.g., paper) and combinations thereof are preferred. An example of a preferred separator is a combination of a layer of water- wettable nonwoven polypropylene membrane treated with surfactant (adjacent to the anode 28, 128) and a layer of hydrophobic polypropylene membrane (adjacent to the air electrode 20,120), such as CELGARD® 5550 and CELGARD® 3501 separators, respectively, both from Celgard, Inc., Charlotte, N.C., USA. Another example of a preferred separator material is rayon bound with polyacrylic acid (e.g., FS22824AB grade separator from Carl Freudenberg KG, Weinheim, Germany, and BVA 02530 grade separator from Hollingsworth & Vose, East Walpole, Mass., USA). The separator 24, 124 is preferably adhered to the entire surface of the air electrode 20, 120 to provide the best ion transport between the electrodes and to prevent the formation of air pockets between the air electrode 20, 120 and the separator 24, 124. Similarly, adjacent layers of the separator 24, 124 are adhered to each other.

[0038] A layer of porous material 138 can be positioned between air electrode 20, 120 and the bottom of casing 12, 112 to evenly distribute air to electrode 20, 120. A sealant 129 such as a thermoplastic hot melt adhesive, for example SWIFT® 82996 (from Forbo Adhesives, LLC of Research Triangle Park, N.C., USA) can be used to bond portions of the cathode to cathode casing 112.

[0039] Cell 10, 110 also includes anode casing 26, 126 which forms the top of the cell. The anode casing 126 in FIG. 1 has a rim 135 is flared outward at its open end. The anode casing 26 in FIG. 2 has essentially straight side walls and that has a rim 35 with little or no outward flare. Alternatively, a cell can have a refold anode casing in which the rim is folded outward and back along the side wall to form a substantially U-shaped side wall with a rounded edge at the open end of the casing.

[0040] The anode casing 26, 126 can be formed from a substrate including a material having a sufficient mechanical strength for the intended use. The anode casing 26, 126 can be a single layer of material such as stainless steel, mild steel, cold rolled steel, aluminum, titanium or copper. Preferably the anode casing includes one or more additional layers of material to provide good electrical contact to the exterior surface of the anode casing 26, 126, resistance of the external surface to corrosion, and resistance to internal cell gassing where the internal surface of the anode casing 26, 126 comes in contact with the anode 28, 128 or electrolyte. Each additional layer can be a metal such as nickel, tin, copper, or indium, or a combination or alloy thereof, and layers can be of the same or different metals or alloys. Examples of plated substrates include nickel plated steel, nickel plated mild steel and nickel plated stainless steel. Examples of clad materials (i.e., laminar materials with at least one layer of metal bonded to another layer of metal) include, as listed in order from an outer layer to an inner layer, two-layered (biclad) materials such as stainless steel/copper, three-layered (triclad) materials such as nickel/stainless steel/copper and nickel/mild steel/nickel, and materials with more than three clad layers.

[0041] The anode casing 26, 126 can include a layer that is post-plated (i.e., plated after forming the anode casing into its desired shape). The post-plated layer is preferably a layer of metal with a high hydrogen overvoltage to minimize hydrogen gassing within the cell 10, 110. Examples of such metals are copper, tin, zinc, indium and alloys thereof. A preferred metal is tin, and a preferred alloy is one comprising copper, tin and zinc.

[0042] The material of the anode casing 126 in FIG. 1 can have a substrate having a steel layer pre-plated with a layer of nickel on each side, as well as a post-plated layer of tin or a copper-tin-zinc alloy for example. The anode casing 126 in this embodiment can also be provided with a strike layer between the substrate and the post-plated layer. A preferred strike layer s a post-plated layer of copper which promotes adhesion between the substrate and the final post-plated layer.

[0043] In the embodiment shown in FIG. 2, anode casing 26 is made from a nickel- stainless steel-copper triclad material, with the copper layer on the inside, post-plated with tin or an alloy of copper, tin and zinc. The preferred composition of a layer of an alloy of copper, tin and zinc includes 50 to 70 weight percent copper, 26 to 42 weight percent tin, and 3 to 9 weight percent zinc. A strike layer of copper can be post-plated onto the anode casing 26 prior to the final post-plated layer to improve its adhesion to the triclad substrate material. The copper-tin-zinc alloy can be applied in multiple layers with the under layer(s) having a higher copper content than the surface layer, as described in detail in U.S. patent application Ser. No. 11/933,552, filed Nov. 1, 2007, which is hereby incorporated by reference.

[0044] The anode casing 26, 126 can be formed using any suitable process. An example is a stamping process. A button cell anode casing 26 is preferably formed using three or more progressively sized stamping dies, after which the casing 26 is punched out of the coil of triclad strip.

[0045] During manufacture of the cell, anode casing 26, 126 can be inverted, and then a negative electrode composition or anode mixture 28, 128 and electrolyte put into anode casing 26, 126. The anode mixture insertion can be a two step process wherein dry anode mixture materials are dispensed first into the anode casing 26 followed by KOH solution dispensing. In a prismatic cell, the wet and dry components of the anode mixture are preferably blended beforehand and then dispensed in one step into the anode casing 126. Electrolyte can creep or wick along the inner surface 36, 136 of the anode casing 26, 126, carrying with it materials contained in anode mixture 28, 128 and/or the electrolyte.

[0046] An example of an anode mixture 28, for a button cell comprises a mixture of zinc, electrolyte, and organic compounds. The anode mixture 28 preferably includes zinc powder, a binder such as SANFRESH™ DK-500 MPS, CARBOPOL® 940 or CARBOPOL® 934, and a gassing inhibitor such as indium hydroxide (In(OH)3) in amounts of about 99.7 weight percent zinc, about 0.25 weight percent binder, and about 0.045 weight percent indium hydroxide. SANFRESH(TM) DK-500 MPS is a crosslinked sodium polyacrylate from Tomen America Inc. of New York, N.Y., and CARBOPOL® 934 and CARBOPOL® 940 are acrylic acid polymers in the 100% acid form and are available from Noveon Inc. of

Cleveland, Ohio.

[0047] The electrolyte composition for a button cell can be a mixture of about 97 weight percent potassium hydroxide (KOH) solution where the potassium hydroxide solution is 28- 40 weight percent, preferably 30-35 weight percent, and more preferably about 33 weight percent aqueous KOH solution, about 3.00 weight percent zinc oxide (ZnO), and a very small amount of CARBOWAX® 550, which is a polyethylene glycol based compound available from Union Carbide Corp., preferably in an amount of about 10 to 500 ppm, more preferably about 30 to 100 ppm, based on the weight of zinc composition in the anode.

[0048] An anode mixture 128, for a prismatic cell can include a mixture of zinc, electrolyte, and organic compounds. The anode mixture 128 preferably includes zinc powder, electrolyte solution, a binder such as CARBOPOL® 940, and gassing inhibitor(s) such as indium hydroxide (Tn(OH)3) and DISPERBYK® D 190 in amounts of about 60 to about 80 weight percent zinc, about 20 to about 40 weight percent electrolyte solution, about 0.25 to about 0.50 weight percent binder, about 0.045 weight percent indium hydroxide and a small amount of DISPERBYK® D190, preferably in an amount of about 10 to 500 ppm, more preferably about 100 ppm, based on the weight of zinc. DISPERBYK® D 190 is an anionic polymer and is available from Byk Chemie of Wallingford, Conn.

[0049] The electrolyte composition for a prismatic cell can be a mixture of about 97 weight percent potassium hydroxide (KOH) solution where the potassium hydroxide solution is about 28 to about 40 weight percent, preferably about 30 to about 35 weight percent, and more preferably about 33 weight percent aqueous KOH solution, and about 1.00 weight percent zinc oxide (ZnO).

[0050] Preferred zinc powders are low-gassing zinc compositions suitable for use in alkaline cells with no added mercury. Examples are disclosed in U.S. Pat. No. 6,602,629 (Guo et al.), U.S. Pat. No. 5,464,709 (Getz et al.) and U.S. Pat. No. 5,312,476 (Uemura et al.), which are hereby incorporated by reference.

[0051] One example of a low-gassing zinc is ZCA grade 1230 zinc powder from Zinc Corporation of America, Monaca, Pa., USA, which is a zinc alloy containing about 400 to about 550 parts per million (ppm) of lead. The zinc powder preferably contains a maximum of 1.5 (more preferably a maximum of 0.5) weight percent zinc oxide (ZnO). Furthermore, the zinc powder may have certain impurities. The impurities of chromium, iron, molybdenum, arsenic, antimony, and vanadium preferably total 25 ppm maximum based on the weight of zinc. Also, the impurities of chromium, iron, molybdenum, arsenic, antimony, vanadium, cadmium, copper, nickel, tin, and aluminum preferably total no more than 68 ppm of the zinc powder composition by weight. More preferably, the zinc powder contains no more than the following amounts of iron, cadmium, copper, tin, chromium, nickel, molybdenum, arsenic, vanadium, aluminum, and germanium, based on/the weight of zinc: Fe-3.5 ppm, Cd-8 ppm, Cu-8 ppm, Sn-5 ppm, Cr-3 ppm, Ni-6 ppm, Mo-0.25 ppm, As-0.1 ppm, Sb-0.25 ppm, V-2 ppm, Al-3 ppm, and Ge-0.06 ppm.

[0052] In another embodiment, the zinc powder preferably is a zinc alloy composition containing bismuth, indium and aluminum. The zinc alloy preferably contains about 100 ppm of bismuth, 200 ppm of indium, and 100 ppm of aluminum. The zinc alloy preferably contains a low level of lead, such as about 35 ppm or less. In a preferred embodiment, the average particle size (D50) is about 90 to about 120 microns. Examples of suitable zinc alloys include product grades NGBIA 100, NGBIA 115, and BIA available from N.V. Umicore, S.A., Brussels, Belgium.

[0053] Cell 10, 110 also includes a gasket 30, 130 made from an elastomeric material which serves as the seal. The bottom edge of the gasket 30, 130 has been formed to create an inwardly facing lip 32, 132, which abuts the rim of anode casing 26, 126. Optionally, a sealant may be applied to the sealing surface of the gasket, cathode casing and/or anode casing. Suitable sealant materials will be recognized by one skilled in the art. Examples include asphalt, either alone or with elastomeric materials or ethylene vinyl acetate, aliphatic or fatty polyamides, and thermoplastic elastomers such as polyolefins, polyamine, polyethylene, polypropylene and polyisobutene. A preferred sealant is SWIFT® 82996, described hereinabove.

[0054] The cathode casing 12, 112 can be made of nickel plated steel. The cathode casing 12, 112, including the inserted air electrode 20, 120 and associated membranes can be inverted and pressed against the anode cup/gasket assembly, which can be preassembled with the casing inverted so the rim of the casing faces upward. While inverted, the edge of the cathode casing 12, 112 can be deformed inwardly, so the rim 34, 134 of the cathode casing 12, 1 12 is compressed against the elastomeric gasket 30, 130, which is between the cathode casing 12, 112 and the anode casing 26, 126, thereby forming a seal and an electrical barrier between the anode casing 26, 126 and the cathode casing 12, 112.

[0055] Any suitable method may be used to deform the edge of the cathode casing 12, 112 inward to seal the cell, including crimping, colleting, swaging, redrawing, and combinations thereof as appropriate. Preferably the button cell 10 is sealed by crimping or colleting with a segmented die so that the cell can be easily removed from the die while a better seal is produced. As used herein, a segmented die is a die whose forming surfaces comprise segments that may be spread apart to enlarge the opening into/from which the cell being closed is inserted and removed. Preferably portions of the segments are joined or held together so they are not free floating, in order to prevent individual segments from moving independently and either damaging the cell or interfering with its insertion or removal. Preferred crimping mechanisms and processes are disclosed in commonly owned U.S. Pat. No. 6,256,853, which is hereby incorporated by reference. Preferably a prismatic cell 110 is sealed by crimping.

[0056] A suitable tab (not shown) can be placed over the opening 18, 1 18 until the cell 10, 1 10 is ready for use to keep air from entering the cell 10, 110 before use. [0057] A catalytic composition for the active layer of a catalytic electrode can be made from a catalytic mix using the aforementioned catalyzed carbon powders. Oxidation of the nano-catalyst particles or formation of oxidized nano-catalyst particles from a precursor can take place before or during the mixing process. The degree of oxidation can be controlled. The oxide can provide one or more functions, such as aiding the catalytic reaction, imparting stability, and/or reducing agglomeration of the nanoparticles.

EXAMPLE 1

[0058] 1.20 g of NaMn04'xH ₂ 0 (Aldrich, >97%) was dissolved in 750 ml of deionized water in a 1000 ml beaker; 13 g DARCO® G60 carbon was added to the solution while stirring with a magnetic stirrer and sonicating with a Hielscher USP400 lab ultrasonic processor (24kHz) with H22 horn, at constant power, 100% amplitude. After 1 hour of sonication, the suspension was filtered and washed several times using deionized water, and then dried at 120 F in air for 5 hours.

[0059] The synthesized material was characterized by Scanning Electron

Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM/EDS), Transmission Electron Microscopy/Selected Area Electron Diffraction (TEM/SAED) and X-Ray Photoelectron Spectroscopy (XPS). Numerous tiny MnO _x particles were deposited on the surfaces of the carbon particles by the sonochemical reduction process. Although the distribution of the MnO _x on the carbon surface was discontinuous, it was fairly uniform. Inductively Coupled Plasma/Mass Spectroscopy (ICP/MS) analysis indicated approximately 5 weight percent of MnO _x in the MnO _x /C composite. The oxidation state of Mn in the MnO _x /C composite was identified as approximately 3.4, by a peroxidation method, which means the MnO _x in the composite was approximately MnOi.7. The size of the MnO _x particles decorated on the carbon surface was too small to be determined by SEM. EDS analysis showed that all of the attached nanoparticles were deposited MnO _x , and the presence of apparent Mn peaks in areas where there were no observable MnO _x nanoparticles is consistent with a very thin film of MnO _x coated on the carbon particle surface in addition to nanoparticles of MnO _x observed in SEM and TEM. High Resolution TEM (HRTEM) analysis on the edge of a carbon particle verified that the carbon particle is covered by a thin film of MnO _x with a thickness of about 3 nm to 6 nm. TEM/SAED analysis showed the MnO _x nanoparticles had a crystalline structure, while the MnO _x thin film had a substantially amorphous structure. FIG. 3 is a schematic representation of a MnO _x /C composite particle 40, includes a carbon particle 42, with both a thin film 44 as well as nanoparticles 46 of MnO _x on the surface of the carbon particle 42.

EXAMPLE 2

[0060] A peroxide decomposition test was used to compare the catalytic activity of the MnCVcarbon composite from Example 1 to that of three other materials. One was a blend of MnO _x and carbon, made by adding a dispersion of commercially available MnO _x nanoparticles (from Quantum Sphere Inc.) in deionized water (a surfactant and ultrasonic agitation were used to aid in making the dispersion) to G60 activated carbon/water slurry, mixing in a high sheer mixer with ultrasonic agitation, filtering, washing and drying. The second was a MnCVcarbon composite having a thin film coating of MnO _x on the carbon, made by a thermal conversion of a manganese nitride precursor in the presence of G60 activated carbon under argon. The third was G60 activated carbon with no MnO _x catalyst. Each of the MnO _x /carbon materials contained 5 weight percent MnO _x .

[0061] The peroxide decomposition test was conducted in a 100 ml three -neck round-bottom reaction flask with the center neck connected to a gas-volume measuring device and the other two necks covered by rubber septums and glass stoppers. A 0.1030 gram sample of the material to be tested was placed into the flask, followed by (in order) 1.0 niL of 33 weight percent KOH solution, 1.0 mL of 99.6 weight percent isopropanol solution, and 0.2 mL of 33 to 50 weight percent hydrogen peroxide solution. The volume of gas generated, which is directly related to the catalytic activity of the test material, was recorded over time (e.g., at 10, 20, 30 and 60 seconds). The chart in FIG. 5 summarizes the results of the peroxide decomposition test. The Mn _0x /C nanocomposite from Example 1 (line 58) had the highest catalytic activity. Line 52 represents the activated carbon with no catalyst, line 54 represents the Mn _0x /carbon composite made by thermal conversion of manganese nitride in the presence of activated carbon, and line 56 represents the blend of commercially available Mn _0x nanoparticles and carbon.

EXAMPLE 3

[0062] 1.20 g of NaMn04-xH20 (Fisher Scientific) was dissolved in 750ml of 18 Mohm deionized water; 7.5 g DA CO® G60 activated carbon and 5.5 g NORIT® Supra 30 (DLC30) activated carbon was added to the solution and stirred using a magnetic stirrer. USP400 lab ultrasonic processor (24k Hz) with H22 horn placed at optimal depth and away from vortex, constant power and 100% amplitude. After 60 minutes sonication, the suspension was filtered and washed thoroughly using 18 Mohm deionized water; rinsed with ample 18 Mohm deionized water, and then dried at about 120°F in air over 48 hours.

[0063] MnO _x /C composites were also made using 100 percent G60 and 100 percent DLC30 carbons, with various sonication times. All of the composites had a substantially amorphous MnO _x film and nano-crystalline MnO _x particles on the carbon surfaces. The composites were compared on the peroxide decomposition test and limiting current tests on both half cells and full cells, as described above.

[0064] Each of the materials was tested on the peroxide decomposition test described above. FIG. 6 is a graph showing the results. The dotted lines represent G60 carbon with different sonication (line 61 for 15 minutes, line 62 for 30 minutes, line 63 for 45 minutes and line 64 for 60 minutes), the dashed lines represent the DLC30 carbon (lines 65, 66, 67 and 68 sonicated for 15, 30, 45 and 60 minutes, respectively), and the solid line (69) represents a blend of 40 percent G60 and 60 percent DLC30 sonicated for 60 minutes. In general, the composites made with DLC30 carbon had higher catalytic activity than the corresponding composites with G60 carbon, the composite with a blend of G60 and DLC30 carbons performed better than the composites with G60 or DLC30 carbons alone, and longer sonication times tended to produce composites with higher catalytic activity.

[0065] Each of the materials was tested on a limiting current test, in both half cells and full cells. A composite made by a thermal conversion of G60 carbon, as described in Example 2, was also tested as a control. The limiting current test was performed on electrodes from each of the three carbon composite lots using a potentiodynamic scanning technique. A three-electrode system was used as the electrochemical cell for a catalytic air electrode half-cell testing. Pt and Zn wires were used as the counter electrode and reference electrode, respectively, and the electrolyte was 33% KOH. The scan was run from open circuit voltage to 1.05V (vs. Zn) at lmV/sec. The current recorded at 1.05V (vs. Zn) is defined as the limiting current, which is a measure of catalytic electrode's rate capability. FIG. 7 illustrates the air electrode power capability for several of the composites on the half cell LC test, and FIG. 8 shows power capability on full cells. L455 was the control lot, L456 through L459 contained DLC30 carbon sonicated for 15 minutes, 30 minutes,45 minutes and 60 minutes, respectively; and L460 contained the blend of G60 and DLC30 carbons. Power capabilities of the sonochemically produced composites were similar to the power capability of the composite made by thermal conversion, but the composite made by the sonochemical process using a blend of G60 and DLC30 carbons preformed better than the other composites. EXAMPLE 4

[0066] Gold doped MnO _x /C nanocomposites (MnO _x (Au)/C nanocomposites) were made by adding Au ³⁺ in suspension during the sonochemical synthesis and co-deposited onto the carbon surface by the sonochemical reduction reactions without introducing any reducing agents. In various samples, up to l.Og AuC¾ was dissolved in 750ml of deionized water, and then 4.8 g of KMnCvxffiO was added while stirring; stirring was continued until the AuC¾ was dissolved. Then 52 g of Darco G60 activated carbon was slowly added, stirring until no dry carbon was observed. Sonication was performed using a Hielscher USP400 lab ultrasonic processor (24 kHz) with H22 horn placed away from vortex, at constant power and 100% amplitude, while stirring the solution. After 45 to 90 minutes sonication, the suspension was filtered, washed thoroughly using the deionized water, then dried at 110°F for 72 hours.

[0067] Surface morphology and element mapping of MnO _x (Au)/C nanocomposites were evaluated using SEM and EDS. The EDS results revealed that both MnO _x and gold nanoparticles were coated onto carbon surface with a fairly uniform distribution. Most of the deposited gold tends to stay in or around the MnO _x particles at the carbon surface. XRD results indicate that the nanoparticles deposited on the carbon surface consist of MnO _x and gold. No gold alloys/compounds were detected in any of the MnO _x (Au)/C nanocomposites with gold doping from 6 ppm to 38 ppm, which suggests that the nanoparticle catalyst formed on the carbon surface is a mechanical mixture of Μ¾θ4 and gold.

[0068] Doped and undoped nanocomposite samples were tested on the peroxide decomposition test, which showed that doping increased, with a correlation of the gold doping level and the cumulative oxygen produced during the first 10 seconds of the peroxide decomposition test.

EXAMPLE 5

[0069] Four lots of composite MnO _x /carbon materials were made, using different types of carbon and different methods of depositing MnO _x type catalyst on the surfaces of three carbons were used: DARCO® G60 activated carbon from American Norit Co., Inc., and NPL330 and NPL328 grades of VACNTAs from NanoLab, Inc. Characteristics of the VACNTAs are summarized in Table 1 : Table 1

[0070] The PECVD growth method includes coating the substrate with an adhesion layer (titanium or chromium), overcoating with a nickel catalyst, and then growing the CNTs on the coated substrate in a chemical vapor deposition (CVD) chamber. The method of nickel nanoparticle deposition defines the nanotube site density. Standard aligned VACNT forests are produced from a sputtered nickel catalyst film on the substrate, while forests with a lower density of NCTs on the substrate are produced by electrodeposition of nanoparticles of the nickel catalyst onto the substrate.

[0071] The carbons were decorated with catalyst, depositing catalyst on the surface of the carbon particles/nanotubes using one of several processes: (1) a thermal conversion process in which the carbon powder is heated in a manganese nitrate solution, (2) a sonochemical process; and (3) a chemical process in which sonication was not used. In the sonochemical process used, 750 ml of a solution containing 0.08 weight percent NaMn04 and 0.08 weight percent KMn04 was put into a reaction vessel with a magnetic stirbar in an ultrasonic processor. Approximately 13 grams of carbon (G60 powder or a sheet of VACNT A) was immersed in the solution, and an H22 ultrasonic horn was placed into the solution. The ultrasonic processor was operated at 24 kHz and 100 percent amplitude, sonicating the contents for 45 minutes. The resultant MnOx/C nanocomposite material was removed from the processor, rinsed and dried. In the chemical process, the carbon material was immersed in a NaMn04/ KMn04 solution (same concentration and period of time as for the sonochemical process), the solution was heated at 70°C without sonication, and the resultant composite material was rinsed and dried in the same manner as in the sonochemical process.

[0072] Physical characterization was done to confirm desired composition of the decorated carbon materials: Scanning Electron Microscopy (SEM) elemental mapping confirmed the presence of nano-sized MnOx on the surfaces of the G60 and CNTs. Energy Dispersive X-ray Spectroscopy (EDS) analysis was used to quantify the amounts of manganese, which are summarized in Table 2. X-ray diffraction (XRD) was used to determine the crystalline structure of the deposited MnOx. As in Example 1 , no XRD peaks characteristic of crystalline MnOx were identified, indicating that the MnOx was

substantially amorphous, nanocrystallme, or a combination of amorphous and nanocrystallme in each of the lots. Based on testing in the previous examples, it was believed that the composite structure included both a substantially amorphous MnOx film and nanocrystallme MnOx particles on the surface of the carbon.

Table 2

[0073] A Rotating Disc Electrode (RDE) test was used to determine the catalytic activity of the materials in Lots 1 to 7. The disk electrodes for lots 1 to 4 were prepared by dispersing 0.200 g of the carbon-catalyst mix in 20 mL of solution (75 mL of 95+ weight percent isopropyl alcohol, 75 mL of 18 Mohm deionized water, and 3 mL of 5 weight percent Nafion solution (from Sigma-Aldrich)); sonicating for 20 minute; dispensing 5 of the dispersion onto the glassy carbon disk of a Pine Instrument AFE6R1PT RRDE Assembly, being sure not to let the droplet wet the Teflon surrounding the disk, and ensuring that no air bubbles are present on the droplet; covering the electrode with a dust cover; and allowing the electrode to air dry. The disk electrodes for Lots 5 and 6 were prepared by removing 6 μg catalyzed VACNTA from its original growth substrate with a sharp razor, carefully transferring it onto the surface of a rotating disk electrode, and adhering it to the rotating disk electrode with 5 of solution (75 mL of 95+ weight percent isopropyl alcohol, 75 mL of 18 Mohm deionized water, and 3 mL of 5 weight percent Nafion solution). Testing was conducted in 1M KOH with saturated oxygen using a Pine MSRX rotator and a Bipotentiostat, with a scan rate of 20 mV/sec, a ring potential of 500 mV, and a Hg/HgO (lM NaOH) reference electrode. [0074] The results for raw G60 carbon (no catalyst) (Lot 1) as well as MnO _x /carbon composites in Lots 2 to 7 are plotted in FIG. 9, in which potential vs. Hg/HgO is on the x-axis and current in amps is on the y-axis. Lots 1 to 7 are represented by lines 91 to 97, respectively. High onset potential and high current are both desirable. FIG. 9 shows that the catalytic activity of the VACNTA composites was better than the catalytic activity of the G60 composites, regardless of the method of catalyst deposition, and the sonochemical method was the best method of depositing the catalyst on the VACNTAs.

EXAMPLE 6

[0075] Air electrodes were made and testing using the materials from Lots 1, 2, 3, 4 and 5 in Example 5. There was insufficient VACNTA material from Lot 6 to make electrodes. For each of Lots 1 to 4, the material was mixed with about 7 weight percent

polytetrafluoroethylene (PTFE) and pressed into a catalytic sheet. A gold-plated nickel screen current collector was pressed into one surface of the catalytic sheet, and a PTFE film was pressure laminated to the surface of the catalytic sheet opposite the current collector to form an electrode sheet. For each of Lots 5 and 7, a 1 cm x 1 cm section of the

MnO _x /VACNTA composite was removed from its quartz substrate with a razor blade to form a catalytic sheet. Each catalytic sheet was made into an electrode sheet by pasting onto a gold plated nickel mesh current collector using a solution consisting of 35 weight percent graphite, 23 weight percent isopropyl alcohol, and 42 weight percent PTFE emulsion; drying at 110°C overnight; and pressing a PTFE air diffusion layer onto the surface of the catalytic sheet opposite the current collector.

[0076] Limiting current half cell testing as described in Example 3 was done on electrodes made with the materials from Lots 1 to 5 and 7. The electrode with the Lot 7 carbon composite failed on the limiting current test due to electrolyte flooding. This may have been due to the CNTs being too short and/or thin. The results for the carbon composite electrodes from Lots 1 to 5 are summarized in FIG. 10. These results show that not only did the NPL 330 VACNTA decorated sonochemically with MnO _x have superior catalytic activity, but provided current rate capability superior to those of the G60 composite material.

[0077] The above description is considered that of the preferred embodiments only. Modifications of the invention will occur to those skilled in the art and to those who make or use the invention.