Improved fuel cell with selectively conductive anode

Abstract

A solid-polymer electrolyte fuel cell comprising a solid-polymer electrolyte, a cathode, and anode components connected electrically in series, wherein: i) the anode components comprise an anode, an anodic gas diffusion layer, and a selectively conductive component, the gas diffusion layer being separated from the anode by the selectively conductive component; ii) the selectively conductive component comprises a mixture layer in contact with the side of the anode facing the solid-polymer electrolyte, the mixture layer comprising a mixture of a selectively conductive material and carbon; iii) the electrical resistance of the selectively conductive component in the presence of hydrogen is more than 100 times lower than the electrical resistance in the presence of air, and the mixture layer comprises 6% to 14% by weight of carbon.

Description

BackgroundField of the InventionThe present invention relates to solid polymer electrolyte fuel cells that selectively include conductive anodes that improve durability, and methods and constructions for obtaining desirable performance and tolerance to polarity reversal.Description of Related ArtA continuing effort in research and development with respect to fuel cells continues because of the energy efficiency and environmental advantages that they may potentially offer. Solid polymer electrolyte fuel cells are particularly suitable for being considered as power supplies in transportation applications, for example, automotive applications. However, improving the durability of such cells with respect to repeated load by running up and running down remains a challenge, especially for automotive applications.Unacceptably high degradation rates of performance can occur in solid polymer electrolyte fuel cells that are repeatedly subjected to start-up and shut-down cycles. Degradation can be further exacerbated when low catalyst loadings are used in the electrodes for cost savings. Often, there is a trade-off between the durability and the cost in the fuel cell. During start-up and shut-down of fuel cell systems, corrosion promoting events may occur. In particular, at such times, air may be present at the anode (either intentionally or as a result of leakage) and it is known that the transition between air and fuel in the anode causes transient high potentials at the cathode, resulting in corrosion of carbon and dissolution of the platinum catalyst. Such transient high potentials at the cathode may result in significant degradation of performance over time. It has been observed that the lower the catalyst loading, the faster the degradation of performance. The industry must therefore find means to address degradation of performance.A number of approaches to solve the degradation problem occurring during start-up and shutdown have been proposed in the prior art. For example, the problem has been addressed by employing higher catalyst loadings or valves around the stack to avoid the entry of air into the anode during storage and by using carefully designed shutdown strategies. Some proposed systems involve inert nitrogen purging and nitrogen / oxygen purging to prevent damaging gas combinations from being present during these transitions. See, for example, U.S. Pat. Nos. 5,013,617 and 5,045,414.Some other concepts include fuel cell stack start-up strategies that include fast flows to minimize potential spikes. For example, U.S. Pat. No. 6,858,336 B2 and U.S. Pat. No. 6,887,599 B2 disclose disconnecting a fuel cell system from its primary load and rapidly purging the anode with air at startup and, correspondingly, with hydrogen gas at startup to reduce degradation that may otherwise occur. While this may eliminate the need to purge with an inert gas, the disclosed methods still include additional steps in power down and power up, which could potentially cause complications. The shutdown and startup can thus require additional time, and separate equipment is required to perform these methods.More recently, in commonly owned PCT application Serial No. 2011 / 076,396 A1, which is hereby incorporated by reference in its entirety, it has been disclosed that degradation of a solid polymer fuel cell during start-up and shut-down can be reduced by electrically introducing a suitable selectively conductive component into the fuel cell in series with the anode components. The component is characterized by a low electrical resistance in the presence of hydrogen or fuel and a high resistance in the presence of air (for example, more than 100 times lower in the presence of hydrogen than in the presence of air).However, it was mentioned in WO 2011 / 076 396 A1 that the presence of a selectively conductive component or layer could possibly lead to a loss of the performance of the cell (due to an increase in the internal resistance) and also could reduce the tolerance of the fuel cell to polarity reversals. However, a reasonable choice of components (e.g., such as those illustrated in the examples) may be effective in improving durability with only a minimal, acceptable impact on performance. And, a remedy for reducing the tolerance to polarity reversal has been proposed. Instead of extending the layer of selectively conductive material over the entire active surface of the anode, some areas could be provided in which the layer is not present to allow for dissipation of currents during polarity reversal and / or to provide a sacrificial area in the case of cell polarity reversal. Furthermore, it has been mentioned that it may be advantageous to keep the selectively conductive layer separate from the anodic catalyst. For example, an intermediate carbon layer may be interposed between the two for this purpose. Although this may also provide a possible solution to the tolerance to polarity reversal, this may adversely affect performance.It has thus been found that it is difficult to simultaneously achieve an economically preferred tolerance to polarity reversal and an economically preferred performance as well as durability during start-up / shutdown. However, in the later patent application US 2014 / 0 030 625 A1, an improved approach has been disclosed to address the problem of lower tolerance to polarity reversal when a selectively conductive anode component is used in such cells. Fuel cells exhibiting acceptable performance in all respects could be obtained by incorporating a carbon interlayer which is in contact with the side of the anode opposite to the solid polymer electrolyte and by suitably selecting the selectively conductive material and the carbon interlayer such that the voltage of the fuel cell is greater than about 0.5 V when operated at 1.5 A / cm 2. However, although this was acceptable, cells containing such interlayers did not perform as well as cells without such interlayers.US 2012 / 0 328 967 A1 relates to a fuel cell with a selectively conductive anode component, in which, by installing a selectively conductive component in electrical series with the anode components in a solid polymer fuel cell, degradation during the switching on and off can be reduced, as a result of which the switching on and off processes can be simplified, so that it is possible to dispense with certain system devices, the anode does not have to be flushed quickly with hydrogen during switching on and not with air during switching off, and in addition the auxiliary load normally used in such flushing processes is dispensed with.Further prior art is disclosed in the publications US 2004 / 0 121 122 A1 and US 2009 / 0 075 155 A1.There remains a desire to improve in fuel cells that selectively include conductive anodes, and specifically to improve performance and tolerance to polarity reversal. The present invention fulfills this and other needs.SummaryThe use of a selectively conductive component in the anode of a solid polymer electrolyte fuel cell desirably improves start-up / shut-down durability. However, it has been found that it is difficult to simultaneously achieve an economically acceptable tolerance to polarity reversal and an economically acceptable performance as well as durability during start-up / shutdown in this way. The present invention addresses these problems by interposing an intermediate layer comprising a mixture of a selectively conductive material and carbon between the anode and the anodic gas diffusion layer of the cell. Surprisingly, this approach can provide desirable tolerance to polarity reversal and improved cell performance.Specifically, the improved solid polymer electrolyte fuel cell includes a solid polymer electrolyte, a cathode, and anode components electrically connected in series, the anode components including an anode, an anodic gas diffusion layer, and a selectively conductive component, the gas diffusion layer being separated from the anode by the selectively conductive component. The selectively conductive component is either the aforementioned mixture layer or comprises the mixture layer in its structure. The mixture layer in the selectively conductive component comprises a mixture of a selectively conductive material and carbon and is disposed in contact with the side of the anode opposite to the solid polymer electrolyte. As in WO 2011 / 076 396 A1, the electrical resistance of the selectively conductive component in the presence of hydrogen is more than 100 times lower and preferably more than 1000 times lower than the electrical resistance in the presence of air.A suitable selectively conductive material comprises a noble metal such as platinum deposited on a metal oxide such as tin oxide. An example selectively conductive material comprises SnO 2. A suitable carbon for the mixture layer is a synthetic graphite.The mixture layer comprises from about 6 weight percent to about 14 weight percent carbon. The thickness of the mixture layer may be in the range of about 6 to about 12 micrometers.The selectively conductive component may consist solely of the mixture layer, or alternatively may comprise the mixture layer and a separate selectively conductive layer. In such a dual layer embodiment, the separate selectively conductive layer is disposed in contact with the side of the mixture layer opposite the solid polymer electrolyte. The selectively conductive layer may consist essentially of the selectively conductive material and binder.In exemplary fuel cells using such dual layer embodiments, the mixture layer may comprise from about 13 weight percent to about 50 weight percent carbon. The thickness of the mixture layer may be in the range of about 2 to about 4 micrometers. And the thickness of the selectively conductive layer may be in the range of about 2 to about 8 micrometers.As in the aforementioned US 2014 / 0 030 625 A1, it may be desirable to select the properties of the selectively conductive material, the carbon and the mixture layer such that the voltage of the fuel cell is greater than about 0.5 V when operated at 1.5 A / cm 2.By being directed in part to tolerance to polarity reversal, the invention is particularly intended for fuel cell stacks and particularly for those in fuel cell systems which are subject to numerous sequences of start-up and shut-down (for example over 1000) over the life of the system, because the cumulative effects of degradation will be much more significant. For example, the invention is particularly suitable for automotive applications in which the fuel cell system is the power supply for a propulsion for the vehicle.Brief Description of the DrawingsFIG. 1 is an exploded schematic view of the various components forming a unit solid polymer electrolyte fuel cell for a fuel cell stack. FIG. 2 compares plots of voltage versus time during the polarity reversal test for representative cells of the invention comprising a mixture layer (of selectively conductive oxide and carbon) with plots for comparative cells from the examples. Figure 3 compares polarization plots for representative cells of the invention comprising a mixture layer with plots for comparative cells from the examples. FIG. 4 compares plots of the output voltage at 1.5 A / cm 2 versus the number of startup / shutdown cycles for representative stacks of the invention that include a blend layer with plots for comparative conventional stacks of the examples. Figure 5 compares plots of voltage versus time during the polarity reversal test for representative cells of the invention comprising a bilayer (a mixture layer combined with a selectively conductive layer) with plots for comparative cells of the Examples. Figure 6 compares polarization plots for representative cells of the invention comprising a bilayer with plots for comparative cells from the examples. FIG. 7 compares plots of output voltage at 1.5 A / cm 2 versus number of cycles of ramp-up / ramp-down for a representative stack of the invention comprising a bilayer with a plot for a comparative conventional stack of the examples.DETAILED DESCRIPTIONHere, in a quantitative context, the term "about" should be construed as being in the range up to plus 10% and down to minus 10%.An improved solid polymer electrolyte fuel cell of the invention comprises a selectively conductive anode component comprising a mixture layer of a selectively conductive material and electrically conductive carbon in contact with the side of the anode opposite the solid polymer electrolyte. The selectively conductive anode component provides improved durability during start-up and shut-down. The use of the mixture layer alleviates related losses of the tolerance to polarity reversal and the performance of the cell (i.e., output voltage vs. current density performance).Apart from the selectively conductive anode component, the construction of the fuel cell and stacks thereof may be any of the conventional constructions known to those skilled in the art. FIG. 1 is an exploded schematic view of the various components forming a unit solid polymer electrolyte fuel cell for use in a fuel cell stack. The unit cell 1 comprises a solid polymer electrolyte 2, a cathode 3 and an anode 4. An anodic GDL 7 is associated with (but separated from) an anodic electrode 4. Adjacent to these two GDLs are a cathodic flow field plate 8 and an anodic flow field plate 9. The selectively conductive component 5 is electrically inserted in series with the other anode components.As shown in FIG. 1, the selectively conductive component 5 includes a mixture layer 10 disposed on the side of the anode 4 opposite to the solid polymer electrolyte 2. The selectively conductive component 5 may also optionally comprise an additional selectively conductive layer 11 on the side of the mixture layer 10 opposite the solid polymer electrolyte 2.As per the teachings in WO 2011 / 076 396 A1, the selectively conductive component 5 is overall constructed such that its electrical resistance in the presence of hydrogen is more than 100 times lower and preferably more than 1000 times lower than the electrical resistance in the presence of air. This provides a desired durability for repeated cycles of start-up and shut-down.A noble metal deposited on a metal oxide is suitable for use as the selectively conductive material used in the selectively conductive component 5, the mixture layer 10, and optionally in the selectively conductive layer 11. For example, platinum deposited on tin oxide is suitable. And in particular, as illustrated in the examples below, the selectively conductive material may be SnO 2.The mixture layer 10 comprises a carbon and a selectively conductive material. A variety of carbon powders may be suitable for use. For example, synthetic graphite is suitable. The mixture layer 10 may also comprise a binder, as typically used in the art. Pore forming materials may also be used in the mixture layer 10 during manufacture (also as known in the art).The structure of the mixture layer 10 is selected to provide improved tolerance to polarity reversal and fuel cell performance. As will be appreciated by those skilled in the art, the most suitable types and amounts of materials used in the mixture layer 10 will vary along with their thickness and porosity depending upon other characteristics of the construction of the cell. However, an orientation for such appropriate selection of the construction can be obtained from the examples below. It can be expected by the skilled person to make suitable modifications according to the different peculiarities of the construction of the cell. For example, suitable amounts of carbon in the mixture layer 10 may range from about 6 weight percent to about 14 weight percent. And suitable thicknesses for the mixture layer may range from about 6 to about 12 micrometers. Qualitatively, larger amounts of carbon can be expected to improve performance and tolerance to polarity while compromising durability. Likewise, thinner selectively conductive components may be expected to improve performance and tolerance to polarity reversal while compromising durability. Thus, it will be appreciated that modifications may be required to obtain the most suitable balance between these properties.As illustrated in the examples below, the use of the optional selectively conductive layer 11 in conjunction with the blend layer 10 (a "dual layer" construction) can provide for greater improvement in certain embodiments. The optional selectively conductive layer 11 is preferably made substantially of selectively conductive material and a binder, and does not contain carbon powder. However, pore-forming materials can also be used therein again during production.As with the mixture layer 10 above, the most suitable types and amounts of materials used in the optional selectively conductive layer 11 will vary along with those of the mixture layer 10 used in combination therewith and along with their respective thicknesses and porosities depending on other characteristics of the construction of the cell. And again, orientation for selection of construction herein can be obtained from the examples below. For example, in such a dual layer embodiment, suitable amounts of carbon in the associated mixture layer 10 may now range from about 13 weight percent to about 50 weight percent carbon. And suitable thicknesses for an associated mixture layer 10 may range from about 2 to about 4 micrometers. In such a dual layer embodiment, the thickness of the selectively conductive layer 11 may be in the range of about 2 to about 8 micrometers. For improved cell performance, the various selections are made such that the voltage of the fuel cell is greater than about 0.5 V when operated at 1.5 A / cm 2.Methods for the incorporation of noble metals onto a metal oxide, methods for the preparation of suitable dispersions for the coating of the selectively conductive layers and for the execution of the coating, and other considerations regarding the construction are discussed in detail in WO 2011 / 076 396 A1 and can be considered here for use. Various other methods for forming and depositing layers such as the mixture layer 10 and the optional selectively conductive layer 11 are also known in the art and may be used herein.The use of a selectively conductive component in the anode of the fuel cell provides the advantage of improved durability during start-up / shut-down. And the incorporation of this mixture layer according to the invention additionally provides greater advantages with respect to the tolerance to polarity reversal and the performance of the cell. Furthermore, the thickness of the membrane electrode arrangement can be reduced compared to the approach of introducing a carbon layer as in accordance with the aforementioned US 2014 / 0 030 625 A1.The following examples were included to illustrate certain aspects of the invention, but should not be construed as limiting in any way.ExamplesVarious test fuel cells and stacks were prepared and subjected to start-up / shut-down cycle tests, polarity tolerance tests, and performance tests to compare these properties. The rows included comparative fuel cells (with and without select conductive layers inserted) as well as fuel cells comprising different variations of the invention (with blend layers alone and with blend layers combined with an optional selectively conductive layer).The cells all comprised catalyst coated membrane electrolytes (CCMs) disposed between anodic and cathodic gas diffusion layers (GDLs) comprising commercial carbon fiber paper from Freudenberg. (In many cases, complete GDLs were obtained commercially from Freudenberg.) The CCMs all had membrane electrolytes formed from a 14 to 18 micrometer thick perfluorosulfonic acid ionomer coated on opposite sides with the desired anodic and cathodic catalyst layers. The catalyst used in the conventional carbon supported platinum (Pt / C) catalyst layers of the cathode and anode was a commercial product comprising about 46 weight percent Pt. The coated catalyst layer in the cathodes and anodes comprised about 0.3 to 0.4 and about 0.1 mg / cm 2 of Pt, respectively.The selectively conductive layers and mixture layers used in the experimental cells comprised a distinct SnO 2- composition obtained from a commercial supplier. The mixture layers also comprised various amounts of synthetic graphite (KS4 from Timcal). As indicated, these layers were provided as coatings on the anodic GDL and were applied using a solid-liquid ink dispersion comprising a mixture of the SnO 2, optionally synthetic graphite, METHOCEL™ methyl cellulose polymer, distilled water and isopropyl alcohol. PTFE was incorporated into the dispersions as a binder. The dispersions were then applied, dried and sintered as described in the aforementioned PCT patent application WO 2011 / 076 396 A1.Assemblies comprising the appropriate CCMs, the selectively conductive layers and / or mixture layers, and anodic and cathodic GDLs were then bonded together under elevated temperature and pressure and placed between appropriate cathodic and anodic flow field plates to complete the test fuel cell designs.The cells were then conditioned by operating at a current density of 1.5 A / cm 2 with hydrogen and oxygen as feed reactants at 100% RH and at a temperature of 60°C for at least 16 hours.The performance characteristics of the individual cells were determined by measuring the output voltage as a function of the applied current density and, on the other hand, under the same conditions as above. The current density was varied from 0 to over 2 A / cm 2 and voltage versus current density plots (polarization plots) were generated.The polarity reversal study involved operating individual cells first at a lower current density of 1 A / cm 2 for 2 hours, then turning off the current, switching the feeding of the reactant to the anode from hydrogen instead to nitrogen, and then forcing 0.2 A / cm 2 from the cell, thereby subjecting the cells to conditions of polarity reversal. Typically, the cell voltage would plateau roughly at a value between 0 and about -3 volts for a variable time period and then suddenly drop to a value much less than -5 volts at which point the investigation ended. The length of time to this sudden point of decay is indicative of the ability of the cells to tolerate polarity reversal and will be referred to hereafter as the reverse time.For the start-up / shut-down study, stacks of many cells were operated at a current density of 1.5 A / cm 2 using hydrogen and air as reactants at 60°C and 70% RH, and they were periodically subjected to start-up / shut-down cycles designed to promote degradation. Cycling included removing the electrical load while maintaining the flow of reactants for 10 seconds, applying a load for 5 seconds to draw 0.7 A / cm 2, increasing the load for 30 seconds to draw 1.5 A / cm 2 removing the load for 5 seconds while maintaining the flow of reactants, purging the anode with air for 15 seconds, and repeating. The average output voltage of each cell was recorded after each cycle of power up / power down. In addition, polarization properties (voltage as a function of current density) properties for the stacks were obtained throughout the power-up / power-down cycle test.Table 1 provides a brief description of the selectively conductive anode components used in each individual cell tested. The selectively conductive components in the cells of the present invention were arranged as shown in Fig. 1. Table 1. Table 1.C. Cnone; comparative cellSCSelective conductive layer only; thickness 10 microns; comparative cellM(6%C)Blend layer with 6 weight percent KS4; thickness 10 micronsM(8%C)Blend layer with 8 weight percent KS4; thickness 10 micronsM (9.5%C)Mixture layer containing 9.5 weight percent KS4; thickness 9 micronsM(11.3%C)Mixture layer containing 11.3 percent by weight KS4; thickness 11 micrometersM(13%C)Mixture layer with 13 percent by weight KS4; thickness 9 micrometersB(50%C)7μDual layer construction; blend layer with 50 weight percent KS4, thickness 3 microns; & selective conductive layer, thickness 7 micronsB(50%C)2μDual layer construction; blend layer with 50 weight percent KS4, thickness 3 microns; & selective conductive layer, thickness 2 micronsTable 2 provides a brief description of the selectively conductive anode components used in the stacks tested. Again, the selectively conductive components were arranged as shown in Figure 1. Table 2. Table 2.C1*none; comparative cell stacksC2*none; comparative cell stacksM*(6%C)7μBlend layer with 6 weight percent KS4; thickness7 micronsM*(6%C)11μBlend layer with 6 weight percent KS4; thickness11 micrometersB*(50%C)2μDual layer construction; blend layer with 50 weight percent KS4, thickness 3 microns; & selective conductive layer, thickness 2 micronsThe experimental cells were then operated and tested as described above. Figure 2 compares plots of voltage versus time during the polarity reversal study for the cells of the invention which comprise only one mixture layer (i.e., no optional selectively conductive layer present) with plots for the comparative cells C and SC. Comparative cell C does not have a selectively conductive layer which is present at all and works very well in the reverse with a reverse time of about 75 minutes. The comparative cell SC has a selectively conductive layer but no mixture layer and also no carbon interlayer in order to improve the tolerance to polarity reversal. It operates very poorly and has a reversal time of less than one minute. The various cells of the invention having present admixture layers operate increasingly well in reversal with an increased amount of carbon present in the admixture layer.FIG. 3 compares graphic representations of the polarization for cells according to the invention, which comprise only one mixture layer, with graphic representations for the comparative cell C and also for the cells B12 and B13 which were reproduced and added from the above-mentioned US 2014 / 0 030 625 A1. As can be seen in Figure 3, the cells of the invention exhibit a modest loss in performance compared to cell C with no selectively conductive component. However, the cells of the present invention perform significantly better than cells B12 and B13 which used an intermediate carbon layer. Cells B12 and B13 were the best working cells in the examples of US 2014 / 0 030 625 A1, which provided improved tolerance to polarity reversal.FIG. 4 compares plots of the average output voltage at 1.5 A / cm 2 versus the number of start-up / shut-down cycles for the inventive stacks having only one blend layer with the plot for the comparative conventional stack C1*. The performance of the stack of the present invention is significantly better than that of the conventional stack.Figure 5 compares plots of voltage versus time during the polarity reversal study for the cells of the invention comprising a bilayer (a mixture layer combined with a selectively conductive layer) with plots for the comparative cells C and SC. As in Fig. 2, comparative cell C operated very well in the reverse, while comparative cell SC operated very poorly. The double layer cells of the invention worked well in this study.Figure 6 compares the polarization plots for the cells of the invention comprising a bilayer with the plots for the comparative cells. The cell B(50%C)2μhaving the thinner selective conductive layer performed better than the cell B(50%C)7μhaving the thicker selective conductive layer. The former cell showed the best performance with respect to polarization of all cells examined.FIG. 7 compares plots of the average output voltages at 1.5 A / cm 2 versus the number of cycles of ramp-up / ramp-down for the dual layer stack of the present invention with a plot for the comparative conventional stack C2*. The performance of the stack of the present invention is better than that of the conventional stack.The above examples show that cells or stacks comprising a mixture layer of selectively conductive material and carbon have significantly improved performance while maintaining tolerance to polarity reversal and durability during start-up / shut-down. Furthermore, in certain embodiments, cells comprising a bilayer exhibit even greater improvement.All of the aforementioned U.S. Patents, publications of U.S. Patent Applications, U.S. Patent Applications, foreign patents, foreign patent applications, and non-patent related publications referred to in this specification are hereby incorporated by reference in their entirety.Although particular elements, embodiments, and applications of the present invention have been shown and described, it is, of course, understood that the invention is not limited thereto, as modifications may be made by those skilled in the art without departing from the spirit and scope of the present disclosure, particularly in light of the above teachings. For example, the invention is limited not only to fuel cells operated with pure hydrogen as a fuel, but also to fuel cells operated with any hydrogen-containing fuel or fuels having hydrogen and various impurities such as reformate containing CO and methanol. Such modifications are to be considered within the scope and spirit of the following claims.

Claims

A solid polymer electrolyte fuel cell comprising a solid polymer electrolyte, a cathode, and anode components electrically connected in series, wherein: i) the anode components comprise an anode, an anodic gas diffusion layer, and a selectively conductive component, wherein the gas diffusion layer is separated from the anode by the selectively conductive component; ii) the selectively conductive component comprises a mixture layer contacting the side of the anode opposite the solid polymer electrolyte, wherein the mixture layer comprises a mixture of a selectively conductive material and carbon; iii) the electrical resistance of the selectively conductive component in the presence of hydrogen is greater than 100 times lower than the electrical resistance in the presence of air, and the mixture layer comprises from 6 weight percent to 14 weight percent carbon.The fuel cell of claim 1, wherein the electrical resistance of the selectively conductive component in the presence of hydrogen is more than 1000 times lower than the electrical resistance in the presence of air.The fuel cell of claim 1, wherein the selectively conductive material comprises a noble metal deposited on a metal oxide.The fuel cell of claim 3, wherein the selectively conductive material comprises platinum deposited on tin oxide.The fuel cell of claim 4, wherein the selectively conductive material comprises SnO 2.The fuel cell of claim 1, wherein the carbon is a synthetic graphite.The fuel cell of claim 1, wherein the thickness of the mixture layer is in a range of 6 to 12 micrometers.The fuel cell of claim 1, wherein the selectively conductive component comprises a selectively conductive layer in contact with the side of the mixture layer opposite the solid polymer electrolyte, the selectively conductive layer consisting essentially of the selectively conductive material and binder.The fuel cell of claim 8, wherein the thickness of the mixture layer is in the range of 2 to 4 micrometers.The fuel cell of claim 8, wherein the thickness of the selectively conductive layer is in the range of 2 to 8 micrometers.The fuel cell of claim 1, wherein the characteristics of the selectively conductive material, the carbon, and the mixture layer are selected such that the voltage of the fuel cell is greater than 0.5 V when operated at 1.5 A / cm 2.A method for increasing the polarity tolerance of a solid polymer electrolyte fuel cell, the solid polymer electrolyte fuel cell comprising a solid polymer electrolyte, a cathode, and anode components electrically connected in series, wherein: i) the anode components comprise an anode, a gas diffusion layer, and a selectively conductive component, wherein the gas diffusion layer is separated from the anode by the selectively conductive component; ii) the selectively conductive component comprises a layer in contact with the side of the anode opposite the solid polymer electrolyte, wherein the layer comprises a selectively conductive material; iii) the electrical resistance of the selectively conductive component in the presence of hydrogen is greater than 100 times less than the electrical resistance in the presence of air; and wherein the method comprises: mixing carbon into the layer in contact with the side of the anode opposite the solid polymer electrolyte, thereby forming a mixture layer comprising a mixture of the selectively conductive material and carbon, wherein the mixture layer comprises from 6 weight percent to 14 weight percent carbon.The method of claim 12 comprising incorporating a selectively conductive layer in contact with the side of the mixture layer opposite the solid polymer electrolyte, wherein the selectively conductive layer consists essentially of the selectively conductive material and binder.A fuel cell stack comprising the fuel cell according to claim 1.A vehicle comprising a power supply for a drive comprising the fuel cell stack of claim 14.

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