Patent Publication Number: US-2010112391-A1

Title: Counter-flow membraneless fuel cell

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     This application claims the benefit of priority from U.S. Provisional Patent Application No. 61/193,157, filed Oct. 31, 2008, the entire content of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION  
     The present application relates to a fuel cell, and more particularly a membraneless fuel cell wherein a flow of reductant and oxidant are provided to a transport zone in which ions are exchanged and the reductant and oxidant undergo oxidation and reduction, respectively. 
     BACKGROUND OF THE INVENTION 
     If fuel cells are to become viable portable power sources in the future, solutions to a number of difficult, persistent technical problems are needed. Many of these problems are associated with the presence of the proton exchange membrane, which is highly sensitive to various factors, such as operating temperatures and membrane humidity. Efforts in portable applications have largely focused on reducing the size of proton exchange membrane (PEM) fuel cells. By portable power sources, this is generally referring to substitutes for batteries that power portable electronic devices. This approach carries all the cost and efficiency issues associated with larger scale PEM fuel cells. Moreover, the reduction in size exaggerates some of these problems, and introduces even further problems that require resolution for a commercially viable product. 
     One approach has been to deliver parallel co-laminar flows of oxidizer and fuel saturated electrolytes into a single channel with a cathode on one side and an anode on another. See, e.g., Membraneless Vanadium Redox Fuel Cell Using Laminar Flow, Ferrigno et al., J. Amer. Chem. Soc. 2002, 124, 12930-12931; Fabrication and Preliminary Testing of a Planar Membraneless Microchannel Fuel Cell, Cohen et al., J. Power Sources, 139, 96-105; and Air-Breathing Laminar Flow-Based Microfluidic Fuel Cell, Jayashree et al., J. Am. Chem. Soc., 2005, 127, 16758-16759. See also, U.S. Pat. Nos. 7,252,898 and 6,713,206. Each of these is incorporated into the present application by reference in their entirety for background teachings. 
     This approach has various shortcomings. First, the fuel and oxidizer will mix downstream of the entry point, wasting the majority of the fuel. Second, the diffusivity of many oxidizers leads to mixed potentials at the anode due to oxidizer cross-over to the anode. This takes energy away from the circuit and also leads to inefficiency of the overall cell. Third, a mass transport boundary layer builds up on the electrodes which generates mass transport losses in the fuel cell and decreases performance. Fourth, the architecture of the cell is restricted to the geometries, length scales, and electrolytes where laminar flow is ensured. 
     U.S. Patent Publication Nos. 2003/0165727 and 2004/0058203 disclose mixed reactant fuel cells where the fuel, oxidant and electrolyte are mixed together and then flow through the anode and cathode. These publications are incorporated herein by reference. According to these publications, the anode is allegedly selective for fuel oxidation and the cathode is allegedly selective for oxidizer reduction. The designs in these publications have significant shortcomings. First, the amount of some oxidizers that can be typically carried by an electrolyte is relatively low (e.g., the oxygen solubility in an electrolyte is typically quite low relative to fuel solubility). This means that a relatively high flow rate is required for the mixed reactants to ensure that an ample amount of oxidizer is flowing through the cell. That is, a relatively high flow rate is required to maximize oxidizer exposure and reaction at the cathode. But increasing the flow rate requires increased work, thus detracting from the overall power efficiency of the cell. Increasing the flow rate also advects the reactants downstream before they can fully react, resulting wasted reactants. Moreover, electrodes that are selective by virtue of their material properties tend to have lower reaction activity rates than non-selective electrodes. Because the designs in these two publications rely primarily on the use of selective electrodes for both the cathode and anode, this further detracts from the efficiency of the cell. 
     The present application addresses the aforementioned challenges without a proton exchange membrane. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, there is provided a method for generating electrical current using a fuel cell comprising an anode, a cathode, a first flow channel associated with the anode, a second flow channel associated with the cathode, and a plurality of spaced apart exchange zones wherein the first and second flow channels are open to one another. The method includes flowing a first flow comprising a fuel and a first electrolyte through the first channel. The fuel is oxidized at the anode to generate electrons for conduction to a load and oxidation products in the first flow. The method includes flowing a second flow that includes an oxidizer and a second electrolyte through the second channel. The cathode receives electrons from the load and the oxidation products, and the oxidizer forms reduction products to complete an electrochemical circuit. The plurality of exchange zones are positioned and the flows are oriented within their respective first and second channels such that the first and second flows contact one another intermittently at the exchange zones to enable transport of the reduction and oxidation products to the anode and the cathode. 
     According to an aspect of the invention, there is provided a fuel cell that includes an anode configured to be connected to a load, a cathode configured to be connected to the load; and a first flow channel associated with the anode, and configured to receive a flow of a fuel and a first electrolyte so that, in use, the fuel is oxidized by the anode to generate electrons for conduction to the load and oxidation products in the first electrolyte. The fuel cell also includes a second flow channel associated with the cathode, and configured to receive a flow of an oxidizer and a second electrolyte so that, in use, the oxidizer is reduced by its reaction with the oxidation products and incoming flux of electrons from the load to form reduction products, and a plurality of spaced apart exchange zones wherein the first and second flow channels are open to one another. The first and second flow channels are oriented such that the flow of the fuel and first electrolyte and the flow of the oxidizer and the second electrolyte within their respective first and second channels contact one another intermittently. 
     Other aspects, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which: 
         FIG. 1  is a schematic view of a fuel cell in accordance with an embodiment of the present invention; 
         FIG. 2  is a schematic view of a fuel cell in accordance with an embodiment of the present invention; 
         FIG. 3  is a schematic view of Detail A of  FIG. 1 ; 
         FIG. 4  is a schematic view of Detail B of  FIG. 2 ; 
         FIG. 5  is a schematic view of an embodiment of a portions of the fuel cell of  FIG. 2 ; 
         FIG. 6  is a schematic cross-sectional view of a fuel cell according to an embodiment of the present invention; 
         FIG. 7  is a schematic cross-sectional view of the fuel cell of  FIG. 6 , with the cross-section being taken about 90° relative to the cross-section of  FIG. 6 ; 
         FIG. 8  is a top perspective view of a portion of the fuel cell of  FIGS. 6 and 7 ; 
         FIG. 9  is a schematic view of the flow of anode reactants and cathode reactants through the fuel cell of  FIGS. 6 and 7 ; and 
         FIG. 10  is a schematic cross-sectional view of a fuel cell according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION  
     The Figures illustrate several embodiments of various aspects of the inventions claimed. These embodiments are in no way intended to be limiting, and are intended only as an example for facilitating an understanding of the principles of the claimed inventions. In some instances, various components are illustrated schematically, as it is understood many different structures may be used. 
     In the illustrated embodiment of  FIG. 1 , a fuel cell system is generally indicated at  10 . The fuel cell system  10  has an anode  12  and a cathode  14  that are each connected to a load L. The anode  12  and the cathode  14  may be solid in embodiments where the respective fluids flow across or along the anode and the cathode, or may be wholly or partially porous in embodiments where the respective fluid flow through the anode and the cathode, as discussed in further detail below. The system  10  also includes a fuel source  16  configured to supply a fuel, which may be mixed with an electrolyte, an oxidizer source  18  configured to supply an oxidizer, which may be mixed with an electrolyte. 
     The fuel source  16  is connected to a first fluid passageway  22  and is configured to supply the fuel to the first fluid passageway  22 . The fuel may be fed to the first fluid passageway  22  by gravity, surface forces, such as surface tension or electroosmotic flow, or a fuel flow generator, such as a pump, may be used to generate flow of the fuel through the first fluid passageway  22 . 
     Similarly, the oxidizer source  18  is connected to a second fluid passageway  26  and is configured to supply the oxidizer to the second fluid passageway  26 . The oxidizer may be fed to the second fluid passageway  26  by gravity, surface forces, such as surface tension or electroosmotic flow, or an oxidizer flow generator, such as a pump, may be used to generate flow of the oxidizer through the first fluid passageway  26 . 
     The first fluid passageway  22  may be defined by a channel or conduit that is in contact with or defines the anode  12 . The anode  12  may comprise a catalyst that is configured to catalyze the fuel so that the fuel is oxidized into at least oxidized fuel ions and electrons for conduction by the anode  14  to the load L. An oxidation product is an ionic or molecular byproduct of the fuel&#39;s oxidation that has donated at least one electron. An oxidation product may also be referred to as a cation because the loss of an electron may result in a positive charge. However, the cations may be supported in the electrolyte by negative ions. Non-limiting examples of catalysts that may be used include platinum, ruthenium, palladium, nickel, gold, and carbon or alloys of the aforementioned. The first fluid passageway  22  is preferably designed so that the flow of the fuel and electrolyte, which may be referred to as an anolyte, in the passageway  22  is a laminar flow. 
     Similarly, the second fluid passageway  26  may be defined by a channel or conduit that is in contact with or defines the cathode  14 . The cathode  14  receives electrons from the load L and may comprise a catalyst that is configured to catalyze the oxidizer so that the oxidizer is reduced into at least reduced products. A reduced product is an ionic or molecular byproduct of the oxidizer that has gained at least one electron. A reduced product may also be referred to as an anion because the gain of an electron may result in a negative charge. However, the anions may be supported in the electrolyte by positive ions. Non-limiting examples of catalysts that may be used include platinum, ruthenium, palladium, nickel, gold, and carbon or alloys of the aforementioned. Like the first fluid passageway  22 , the second fluid passageway  26  is preferably designed so that the flow of the oxidizer and electrolyte, which may be referred to as a catholyte, in the passageway  26  is a laminar flow. The fuel cell  10  also includes an insulator  28 , as schematically shown in  FIG. 3 , that is located between the anode  12  and the cathode  14 . The insulator  28  is configured to prevent a short-circuit between the anode  12  and the cathode, i.e., prevent the anode  12  and the cathode  14  from directly conducting electrons between each other, so that the electrons can only be conducted through the load L, while still allowing for ionic or molecular exchange. 
     As illustrated in  FIG. 1 , the fuel cell system  10  also includes an intersection  30  that connects the first fluid passageway  22  with the second fluid passageway  26 . A more detailed view of the intersection  30  is shown in  FIG. 3 . The intersection  30  is arranged so that the anolyte flow containing the oxidation products in the first fluid passageway  22  contacts the catholyte flow containing the reduction products in the second fluid passageway  26  to enable the necessary ionic or molecular exchange between the two flows to complete the reaction. Thus, the overall fuel cell reaction may be characterized by (a) the oxidation of fuel to generate oxidation products and electrons for conduction to the load L, (b) the reduction of the oxidizer supported by receiving electrons from the load L, and (c) the exchange of the oxidized and reduced products at, for example, the intersection  30  to complete the overall reaction. The intersection  30  may also be called an exchange zone because the intersection  30  is the location at which, for example in an acidic fuel cell, the ions are exchanged between the fuel and the oxidizer, although reactions do not necessarily have to occur at the intersection. In embodiments in which ions are exchanged in the exchange zone, the exchange zone may be called an ion exchange zone, although such a term is not intended to be limiting in any way. By-products that are generated may be neutral, but they do not have to be neutral. Although the fluid will be “net-neutral,” the individual species may have charges. 
     The exchange zone may have a relatively large area to facilitate reaction of the ions so that the resistance of the electrochemical circuit may be reduced, which may maximize potential at each electrode (i.e., at the anode  12  and the cathode  14 ). Having an area that is too high, however, may result in more diffusive mixing at the intersection  30 , as well as flow instabilities, which may disrupt the laminar flows within the first and second fluid passageways  22 ,  26  or allow cross-over of the reactants. 
     As illustrated in  FIG. 1 , the first fluid passageway  22  extends past the intersection  30  such that part of the flow of the anolyte, which includes oxidation products, does not contact the flow of the catholyte, which includes reduction products, and the second fluid passageway  26  extends past the intersection such that part of the flow of the catholyte does not contact the flow of the anolyte. As illustrated, the first fluid passageway  22  and the second fluid passageway  26  intersect again at a further intersection  32  that defines a further exchange zone. 
     In the illustrated embodiment, six intersections or exchange zones are provided. Of course, more or less intersections may be provided, depending on the application. The intersections or exchanges zones are arranged so that there is intermittent contact between the respective flows within the first and second fluid passageways  22 ,  26 . By arranging the first fluid passageway  22  and the second fluid passageway  26  in this way, the contact area between the two streams (i.e., of anolyte and catholyte) flowing through the passageways  22 ,  26  may be minimized, but the instances or frequency of contact between the two streams may be increased. This may reduce the overall diffusive mixing effects, maintain a stable flow pattern in each of the passageways  22 ,  26 , and allow for an overall large area for ion exchange. This arrangement may also allow essentially no cross-over of un-reacted fuel and oxidizer from one fluid passageway to the other fluid passageway. 
     In the embodiment illustrated in  FIG. 2 , the flow of the anolyte in the first fluid passageway  22  is counter to the flow of the catholyte in the second fluid passageway  26 . As shown in  FIG. 4 , which is a detailed view of an intersection  34  or exchange zone, this configuration may allow the flows in the first fluid passageway  22  and the second fluid passageway  26  to create a small vortex or recirculation zone  36  within the exchange zone. Such a vortex may create a “virtual membrane” for ion transport between the two flows, without allowing depletion of the reactants as a result of substantial cross-over. 
     In an embodiment, the fuel may be hydrogen saturated sulfuric acid and the oxidant may be oxygen saturated sulfuric acid. For an acidic cell using such reactants, oxidation of the fuel at the anode  12  may be generally represented by the following equation: 
       H 2 →2H + +2 e   −   (1) 
     and reduction of the oxidant (oxidizer) at the cathode  14  may be represented by the following equation: 
       0.5O 2 +2 e   − +2H 1 →H 2 O   (2) 
     and the net reaction of the system is: 
       H 2 +0.5O 2 →H 2 O   (3) 
     Thus, the byproduct of these reactions is water. 
     For an alkaline fuel cell, oxidation of the fuel at the anode  12  may be generally represented by the following equation: 
       H 2 +2OH − →2H 2 O+2 e   −   (4) 
     and reduction of the oxidant (oxidizer) at the cathode  14  may be represented by the following equation: 
       O 2 +2H 2 O+4 e   − →4OH −   (5) 
     and the net reaction of the system is: 
       H 2 +0.5O 2 →H 2 O   (6) 
     which is the same net reaction described above in reference to an acidic fuel cell in equation (3). 
     For either type of fuel cell (i.e., acidic or alkaline), other possible reactions may occur, including various intermediary reactions, or different reactions when different reactants are used. The system generates an open circuit voltage based on the potentials of its respective half cell reactions. When current is drawn through the load L, this voltage will generally decrease in value to zero, the point of maximum extractable current, or short circuit voltage. 
       FIG. 5  illustrates an embodiment in which a flow of a supporting electrolyte is provided to the intersection  34 . As illustrated, the flow of the supporting electrolyte is provided substantially perpendicular to the flows of the catholyte and anolyte. The supporting electrolyte may be selected to carry any by-product of the reaction of the oxidation products and the reduction products, such as the H 2 O of equation (3) above, away from the flow passageways  22 ,  26  and out of the fuel cell. The supporting electrolyte also replenishes the electrolyte in the exchange zone, which may increase the local conductivity and further reduce Ohmic voltage losses in the cell. Such an embodiment may be particularly useful in a three-dimensional microfluidic fuel cell that includes several layers of flow passageways. 
       FIGS. 6 and 7  illustrate cross-sectional views of an embodiment of a fuel cell  100 . The cross-sectional view of  FIG. 7  is about 90° from the cross-sectional view of  FIG. 6 , as will become more apparent below. The fuel cell  100  includes a plurality of plate-like structures that may be stacked together to form the fuel cell  100 . The plate-like structures include a cathode  102 , a catholyte flow guide  104  configured to guide a catholyte  105  across the cathode  102 , and an anolyte flow guide  106  configured to guide an anolyte  107  across an anode  108 . As illustrated, current collectors  110 ,  112  are placed in contact with the cathode  102  and anode  108 , respectively, and are connectable to a load L. The current collectors  110 ,  112  may also be in the form of plate-like structures, or may have any other suitable structure that allows the current flow between the cathode  102  and the load L, as well as the anode  108  and the load L. These individual fuel cell layers can be stacked offering a compact form factor for increasing power density. A more detailed view of an embodiment of the flow guides  104 ,  106  is illustrated in  FIG. 8  and discussed below. 
     As shown in  FIGS. 6 and 7 , the catholyte  105  and the anolyte  107  come into contact with each other at a plurality of discrete locations, i.e., intersections  134 .  FIG. 7  schematically illustrates the flow of the catholyte  105  and the anolyte  107  within the respective guides  104 ,  106 . The intersections  134  indicate locations at which the catholyte  105  and anolyte  107  are exposed to each other such that ion transport may take place, as discussed above, without the catholyte  105  and anolyte  107  substantially mixing with each other. As such, the intersections  134  may also be referred to as ion transport zones, or ion exchanges zones, because such locations are where the oxidation products and the reduction products react or transport to complete the fuel cell reaction discussed above. 
       FIG. 8  illustrates an embodiment of the flow guides  104 ,  106  that may be used to guide flows of the catholyte  105  and anolyte  107 , respectively, so that the oxidant and the fuel come into contact at the intersections  114 . The flow guides  104 ,  106  are desirably electrochemically inert and non-conductive so that they may contact each other without contributing to the electrochemical reaction that takes place in the fuel cell  100  or causing any short-circuits within the fuel cell  100 . As shown in  FIG. 8 , the catholyte flow guide  104  may be a plate-like structure that is provided with a plurality of generally parallel slots  116  that are oriented in a first direction  117 . As shown in  FIG. 9 , the anolyte flow guide  106  may also be a plate-like structure that is provided with a plurality of generally parallel slots  118  that are oriented in a second direction  119 . In the illustrated embodiment, the first direction  117  and the second direction  119  are substantially perpendicular to each other so that an angle between the first direction and the second direction is about 90°. In other embodiments, the angle defined by the first direction and the second direction may be less than about 90°. For example, in an embodiment, the angle may be between about 5° and about 90°, or about 30° and 60° or about 45°. When one of the flow guides  104  is placed on top of the other flow guide  106 , as show in  FIG. 8 , a plurality of openings  120  are created, which define the intersections  114  illustrated in  FIGS. 6 and 7 . 
     The slots  116 ,  118  of the flow guides  104 ,  106  create flow channels when the fuel cell is assembled, and may be configured to allow the catholyte  105  and the anolyte  107 , respectively, to flow from one end of the slot  116 ,  118  to the other end of the slot  116 ,  118  in such a manner that the flows are laminar. In other embodiments, instead of having unitary plate-like structures or grids for the flow guides  104 ,  106 , the slots  116 ,  118  could be defined by individual members positioned in spaced apart relation. 
     As illustrated in  FIG. 9 , a delivery manifold  122  may be connected to each slot  116  in the catholyte flow guide  104  so that the oxidizer may be delivered to each slot  116 . The manifold  122  may have any suitable configuration and preferably provides the oxidizer to the slots  116  in such a way that the flow rate in each slot  116  is substantially the same. A flow generator may be connected to the manifold  124  as well as a source of oxidizer and electrolyte to generate the flow rate of the catholyte discussed above. An exit manifold  124  may also be connected to an opposite end of each slot  116  that is connected to the delivery manifold  122 . The exit manifold  124  may be connected to a return system (not shown) that is configured to direct the electrolyte to a collector or separator that allows any undesirable by-products to be removed from the electrolyte and any oxidizer or reduced oxidizer to be returned to the delivery manifold  122 . 
     Similarly, a delivery manifold  130 , also shown schematically in  FIG. 9 , may be connected to each slot  118  in the anolyte flow guide  106  so that the fuel may be delivered to each slot  118 . The manifold  130  may have any suitable configuration and preferably provides the fuel to the slots  118  in such a way that the flow rate in each slot  118  is substantially the same. A flow generator may be connected to the manifold  130  as well as a source of fuel and electrolyte to generate the flow rate of the anolyte discussed above. An exit manifold  132  may also be connected to an opposite end of each slot  116  that is connected to the delivery manifold  130 . The exit manifold  132  may be connected to a return system (not shown) that is configured to direct the electrolyte to a collector or separator that allows any undesirable by-products to be removed from the electrolyte and any unused fuel or oxidant to be returned to the delivery manifold  130 . 
     In the embodiment illustrated in  FIG. 9 , the direction of the flows of the catholyte and the anolyte may create a small vortex or circulation zone  136  within the ion exchange zone of the intersection  134 . As discussed above with respect to  FIG. 4 , such a vortex may create a virtual membrane for ion or molecular transport between the two flows, without allowing depletion of the reactants by substantial cross-over. 
     The flow channels created by the slots  116 ,  118  may span the microfluidic to millifluidic range, i.e., the smallest dimension, such as the depth of the channel, may be in the range of about 1 μm to about 10 mm. The lengths of the channels may be designed so that the most efficient reactant utilization may be achieved, and may depend on the concentrations of the particular reactants in the catholyte and the anolyte. In an embodiment, the length of the channels may be selected within an aspect ratio that is based upon the Peclet number (Pe), as specified by equation (4) below: 
         Pc=UH/D    (4) 
     where U is the average velocity of the catholyte or anolyte in the channel, which may be controlled by the flow rate, H is the characteristic dimension of the channel (such as the width or height), and D is the diffusion coefficient of the catholyte or anolyte that is flowing in the channel. Preferably, the channel geometry and flow rates are selected so that a high Peclet number, such as greater than 10 is achieved, so as to substantially prevent intermixing of the catholyte and the anolyte at the intersection points, (contact zones). 
     The cathode  102  may be made out of a catalyst material so that when the cathode  102  is connected to the anode  108  via the load L, the cathode reduces the oxidizer. In an embodiment, the cathode  102  may include a catalyst material that is only on the portions of the surface of the cathode  102  that form walls of the channels defined by the slots  116  and come into contact with the oxidizer and electrolyte (catholyte). Similarly, the anode  108  may be made out of a suitable catalyst material so that when the anode  108  is connected to the cathode  102  via the load L and is in contact with the fuel and electrolyte, the anode  108  oxidizes the fuel. In an embodiment, the anode  108  may include a catalyst material that is only on portions of the surface of the anode  108  that form walls of the channels defined by the slots  118  and come into contact with the fuel and the electrolyte (anolyte). 
       FIG. 10  illustrates an embodiment of a fuel cell  200  in which a cathode  202  and an anode  204  are porous such that a catholyte  203  and an anolyte  205  may flow through the cathode  202  and the anode  204 , respectively. In the illustrated embodiment, the cathode  202  and the anode  204  are spaced from each other by a small gap  206 , which may serve as an insulator. In an embodiment, the gap  206  may be filled with an electrically insulating, yet ion exchanging medium. Gap  206  may be a porous material or a gap filled with fluid. 
     The electrodes (i.e., anode and cathode) can be made up of any electrically conductive material that is coated with a suitable catalyst. In an embodiment, each electrode comprises a porous material that is the catalyst itself, including but not limited to a catalyst coated carbon cloth, a porous foam, a packed bed of catalyst particles, and/or colloidal crystals. 
     In addition to any fuel, oxidant, electrolyte or catalyst material mentioned above, any of the following in various combinations may be used in any of the embodiments described above, as well as in any other embodiment within the scope of any aspect of the invention. 
     Electrodes/Catalysts: Platinum, Platinum black, Platinized metal (any), Nickel, Nickel Hydroxide, Manganese, Manganese Oxides (all states), Palladium, Platinum Ruthenium alloys, Nickel Zinc alloys, Nickel Copper alloys, Gold, Platinum black supported on metal oxides, Platinum Molybdenum alloys, Platinum Chromium alloys, Platinum Nickel alloys, Platinum Cobalt alloys, Platinum Titanium alloys, Platinum Copper alloys, Platinum Selenium alloys, Platinum Iron alloys, Platinum Manganese alloys, Platinum Tin alloys, Platinum Tantalum alloys, Platinum Vanadium alloys, Platinum Tungsten alloys, Platinum Zinc alloys, Platinum Zirconium alloys, Silver, Silver/Tungsten Carbide, Iron tetramethoxyphenyl porphorin, Carbon or Carbon Black. 
     Fuels: Formic acid, Methanol, Ethanol, 1-proponal, 2-proponal, Cyclobutanol, Cyclopentanol, Cyclohexanol, Benzyl alcohol, Lithium, Zinc, Aluminum, Magnesium, Iron, Cadmium, Lead, Acetaldehyde, Propionaldehyde, Benzaldehyde, Ethylene glycol, Glyoxal, Glycolic acid, Glyoxylic acid, Oxalic acid, 1,2-propanediol, 1,3-propanediol, Glycerol, Hydrogen, Vandium(II)/Vanadium(III), Carbon Monoxide, Sodium Borohydride, Other Borohydrides (e.g. Potassium), and other metal redox systems e.g.: Iron/chromium, Nickel/cadmium. 
     Oxidants: Air, Oxygen gas, Dissolved Oxygen, Hydrogen Peroxide, Potassium Permanganate, Vanadium(IV)/Vanadium(V) and Manganese Oxide. 
     Electrolytes: Potassium Hydroxide, Sodium Hydroxide, Sulfuric acid, Nitric acid, Formic acid, Phosphoric acid, Trifluoromethanesulfonic acid (TFMSA), Ionic liquids (all types), Acetimide, Fluoroalcohol emulsions, and Perflourocarbon emulsions (e.g. Flourinert®). 
     The foregoing illustrated embodiment(s) have been provided solely for illustrating the structural and functional principles of the present invention and are not intended to be limiting. To the contrary, the present invention is intended to encompass all modifications, substitutions, alterations, and equivalents within the spirit and scope of the following appended claims.