CA2934237A1 - Anode for improved reversal tolerance in fuel cell stack - Google Patents
Anode for improved reversal tolerance in fuel cell stack Download PDFInfo
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- CA2934237A1 CA2934237A1 CA2934237A CA2934237A CA2934237A1 CA 2934237 A1 CA2934237 A1 CA 2934237A1 CA 2934237 A CA2934237 A CA 2934237A CA 2934237 A CA2934237 A CA 2934237A CA 2934237 A1 CA2934237 A1 CA 2934237A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/92—Metals of platinum group
- H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
- H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/8605—Porous electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
- H01M8/04238—Depolarisation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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Abstract
A method is disclosed for improving the voltage reversal tolerance of a solid polymer electrolyte fuel cell whose anode comprises a mixture of a supported hydrogen oxidation reaction catalyst (e.g.
carbon supported Pt) and oxygen evolution reaction (OER) catalyst (e.g. Ir oxide). The method comprises decreasing the amount of catalyst support relative to the amount of OER catalyst in the anode. The resulting anode is both thinner and has a higher volumetric density of OER catalyst, and the voltage reversal tolerance of the cell.
carbon supported Pt) and oxygen evolution reaction (OER) catalyst (e.g. Ir oxide). The method comprises decreasing the amount of catalyst support relative to the amount of OER catalyst in the anode. The resulting anode is both thinner and has a higher volumetric density of OER catalyst, and the voltage reversal tolerance of the cell.
Description
Docket No.: P830851/CA/1 ANODE FOR IMPROVED REVERSAL TOLERANCE IN FUEL CELL STACK
BACKGROUND
Field of the Invention The present invention relates to designs of the anode for solid polymer electrolyte fuel cells and particularly to fuel cells intended for use in stacks for automotive applications. The anode designs improve the voltage reversal tolerance of the fuel cells.
Description of the Related Art Solid polymer electrolyte fuel cells electrochemically convert fuel and oxidant reactants, such as hydrogen and oxygen or air respectively, to generate electric power. These cells generally employ a proton conducting, solid polymer membrane electrolyte between cathode and anode electrodes. Gas diffusion layers are typically employed adjacent each of the cathode and the anode electrodes to improve the distribution of gases to and from the electrodes. In a typical fuel cell, flow field plates comprising numerous fluid distribution channels for the reactants are provided adjacent the gas diffusion layers to distribute fuel and oxidant to the respective electrodes and to remove by-products of the electrochemical reactions taking place within the fuel cell. Water is the primary by-product in a cell operating on hydrogen and air reactants. Because the output voltage of a single cell is of order of 1 V, a plurality of cells is usually stacked together in series for commercial applications. Fuel cell stacks can be further connected in arrays of interconnected stacks in series and/or parallel for use in automotive applications and the like.
If for some reason a cell (or cells) in a series stack is not capable of delivering the same current being delivered by the other cells in the stack, that cell or cells may undergo voltage reversal. Depending on the severity and duration of the voltage reversal, the cell may be irreversibly damaged and there may be an associated loss in cell and stack performance. Thus, it can be very important in practical applications for the cells in large series stacks to either be protected against voltage reversal or alternatively to have a high tolerance to voltage reversal.
The application of fuel cell technology in the automotive industry has accelerated in recent years.
Many car makers have recently launched or will start mass production of fuel cell cars in the near future. The success of these activities will strongly depend on the technical progress with regards to fuel cell performance, durability and cost reduction. Several technical hurdles remain challenging.
Docket No.: P830851/CA/1 One of these pertains to the possibility for the occurrence of a fuel starvation condition on the anode (i.e. where the anode receives insufficient fuel for intended operation). A
fuel starvation condition can happen during start up from below freezing temperatures as a result of ice blockages in the anode, or during operation at normal operating temperatures as a result of anode "flooding" (where liquid water blocks passageways in the anode). It is well recognized that anode fuel starvation conditions can lead to cell voltage reversal due to the associated rise of anode potential, and further can lead to corrosion of the carbon supports which are typically used to support the anode catalyst (typically platinum). As a consequence of this corrosion, a loss in effective platinum surface area occurs at the anode and cell function is degraded. Therefore, a voltage reversal tolerant anode is a critical design requirement for the anodes in commercial fuel cell stacks.
There are several ways to improve fuel cell anodes for purposes of voltage reversal tolerance. For example, material approaches were described in US6517962 and US6936370 in which voltage reversal tolerance was improved by incorporating materials, namely catalysts for promoting the oxygen evolution reaction (OER) such as ruthenium, iridium, and/or their oxides into the anode. An approach involving a structural change was also described by US6517962 in which the anode porosity and/or the anode water intake was modified appropriately by employing a hydrophobic layer (e.g. a polytetrafluoroethylene layer) between the anode and an adjacent anode gas diffusion layer.
There remains a desire for improvement in fuel cells with regards to tolerance to voltage reversal.
The present invention fulfills this and other needs.
SUMMARY
The present invention relates to solid polymer electrolyte fuel cells and particularly to anode designs for such cells. Such fuel cells comprise a cathode, a solid polymer electrolyte, and an anode, and the anode comprises a mixture of an amount of hydrogen oxidation reaction (HOR) catalyst supported on an amount of catalyst support and an amount of an oxygen evolution reaction (OER) catalyst. The anode also typically comprises ionomer and other optional additives.
Surprisingly it has been found that the voltage reversal tolerance of such fuel cells can be improved by decreasing the amount of catalyst support relative to the amount of OER catalyst. This results in an anode which is both thinner and in which the volumetric density of the OER catalyst is increased.
Depending on the approach used, the amount of HOR catalyst in the anode may remain unchanged or may be varied.
The HOR catalyst typically may be Pt catalyst but is not limited thereto. The catalyst support may be carbon. The OER catalyst may be iridium, ruthenium, oxides thereof and may be supported or non-
BACKGROUND
Field of the Invention The present invention relates to designs of the anode for solid polymer electrolyte fuel cells and particularly to fuel cells intended for use in stacks for automotive applications. The anode designs improve the voltage reversal tolerance of the fuel cells.
Description of the Related Art Solid polymer electrolyte fuel cells electrochemically convert fuel and oxidant reactants, such as hydrogen and oxygen or air respectively, to generate electric power. These cells generally employ a proton conducting, solid polymer membrane electrolyte between cathode and anode electrodes. Gas diffusion layers are typically employed adjacent each of the cathode and the anode electrodes to improve the distribution of gases to and from the electrodes. In a typical fuel cell, flow field plates comprising numerous fluid distribution channels for the reactants are provided adjacent the gas diffusion layers to distribute fuel and oxidant to the respective electrodes and to remove by-products of the electrochemical reactions taking place within the fuel cell. Water is the primary by-product in a cell operating on hydrogen and air reactants. Because the output voltage of a single cell is of order of 1 V, a plurality of cells is usually stacked together in series for commercial applications. Fuel cell stacks can be further connected in arrays of interconnected stacks in series and/or parallel for use in automotive applications and the like.
If for some reason a cell (or cells) in a series stack is not capable of delivering the same current being delivered by the other cells in the stack, that cell or cells may undergo voltage reversal. Depending on the severity and duration of the voltage reversal, the cell may be irreversibly damaged and there may be an associated loss in cell and stack performance. Thus, it can be very important in practical applications for the cells in large series stacks to either be protected against voltage reversal or alternatively to have a high tolerance to voltage reversal.
The application of fuel cell technology in the automotive industry has accelerated in recent years.
Many car makers have recently launched or will start mass production of fuel cell cars in the near future. The success of these activities will strongly depend on the technical progress with regards to fuel cell performance, durability and cost reduction. Several technical hurdles remain challenging.
Docket No.: P830851/CA/1 One of these pertains to the possibility for the occurrence of a fuel starvation condition on the anode (i.e. where the anode receives insufficient fuel for intended operation). A
fuel starvation condition can happen during start up from below freezing temperatures as a result of ice blockages in the anode, or during operation at normal operating temperatures as a result of anode "flooding" (where liquid water blocks passageways in the anode). It is well recognized that anode fuel starvation conditions can lead to cell voltage reversal due to the associated rise of anode potential, and further can lead to corrosion of the carbon supports which are typically used to support the anode catalyst (typically platinum). As a consequence of this corrosion, a loss in effective platinum surface area occurs at the anode and cell function is degraded. Therefore, a voltage reversal tolerant anode is a critical design requirement for the anodes in commercial fuel cell stacks.
There are several ways to improve fuel cell anodes for purposes of voltage reversal tolerance. For example, material approaches were described in US6517962 and US6936370 in which voltage reversal tolerance was improved by incorporating materials, namely catalysts for promoting the oxygen evolution reaction (OER) such as ruthenium, iridium, and/or their oxides into the anode. An approach involving a structural change was also described by US6517962 in which the anode porosity and/or the anode water intake was modified appropriately by employing a hydrophobic layer (e.g. a polytetrafluoroethylene layer) between the anode and an adjacent anode gas diffusion layer.
There remains a desire for improvement in fuel cells with regards to tolerance to voltage reversal.
The present invention fulfills this and other needs.
SUMMARY
The present invention relates to solid polymer electrolyte fuel cells and particularly to anode designs for such cells. Such fuel cells comprise a cathode, a solid polymer electrolyte, and an anode, and the anode comprises a mixture of an amount of hydrogen oxidation reaction (HOR) catalyst supported on an amount of catalyst support and an amount of an oxygen evolution reaction (OER) catalyst. The anode also typically comprises ionomer and other optional additives.
Surprisingly it has been found that the voltage reversal tolerance of such fuel cells can be improved by decreasing the amount of catalyst support relative to the amount of OER catalyst. This results in an anode which is both thinner and in which the volumetric density of the OER catalyst is increased.
Depending on the approach used, the amount of HOR catalyst in the anode may remain unchanged or may be varied.
The HOR catalyst typically may be Pt catalyst but is not limited thereto. The catalyst support may be carbon. The OER catalyst may be iridium, ruthenium, oxides thereof and may be supported or non-
2 Docket No.: P830851/CA/1 supported. An exemplary anode of the invention comprises a mixture of carbon supported Pt and iridium oxide.
In one approach, the decreasing step is accomplished by increasing the loading of hydrogen oxidation reaction catalyst on the catalyst support. In this way, the total amount of catalyst support in the anode can be reduced while keeping the amount of hydrogen oxidation reaction catalyst in the anode essentially constant.
In another approach, the decreasing step is accomplished simply by using less of the same supported HOR catalyst in the anode. That is, the loading of hydrogen oxidation reaction catalyst on the catalyst support is kept essentially constant and less of this supported HOR catalyst is used in the anode. Both the amount of catalyst support and the amount of hydrogen oxidation reaction catalyst are reduced in this approach. This approach may be adopted if the expected reduction in performance and durability is not too significant and is considered acceptable. An advantage of this approach is that the cost of the HOR catalyst used is reduced accordingly.
Desirably, the method of the invention results in an anode which is thinner and in which the volumetric density of the OER catalyst is increased. The anode thickness can be further controlled to a certain extent not only by the material amounts, but also by the specific materials chosen and their associated properties (e.g. particle shape). Further, anode thickness can also be controlled by the processes used to produce it (including catalyst ink mixing and coating processes).
BRIEF DESCRIPTION OF THE DRAWINGS
Figures la and lb show schematics of fuel cell anodes comprising mixtures of supported HOR
catalyst and OER catalyst in which the volumetric density of the OER catalyst is relatively dilute and relatively dense respectively.
Figures 2a and 2b show SEM images of fuel cell anodes in the Examples in which the volumetric density of the OER catalyst is relatively dilute and relatively dense respectively. In these Figures, the white areas are OER catalyst.
Figure 3 plots reversal tolerance time versus Ir02/carbon support weight ratio for cells tested in the Examples and illustrates the effect of decreasing the amount of carbon support relative to OER
catalyst.
In one approach, the decreasing step is accomplished by increasing the loading of hydrogen oxidation reaction catalyst on the catalyst support. In this way, the total amount of catalyst support in the anode can be reduced while keeping the amount of hydrogen oxidation reaction catalyst in the anode essentially constant.
In another approach, the decreasing step is accomplished simply by using less of the same supported HOR catalyst in the anode. That is, the loading of hydrogen oxidation reaction catalyst on the catalyst support is kept essentially constant and less of this supported HOR catalyst is used in the anode. Both the amount of catalyst support and the amount of hydrogen oxidation reaction catalyst are reduced in this approach. This approach may be adopted if the expected reduction in performance and durability is not too significant and is considered acceptable. An advantage of this approach is that the cost of the HOR catalyst used is reduced accordingly.
Desirably, the method of the invention results in an anode which is thinner and in which the volumetric density of the OER catalyst is increased. The anode thickness can be further controlled to a certain extent not only by the material amounts, but also by the specific materials chosen and their associated properties (e.g. particle shape). Further, anode thickness can also be controlled by the processes used to produce it (including catalyst ink mixing and coating processes).
BRIEF DESCRIPTION OF THE DRAWINGS
Figures la and lb show schematics of fuel cell anodes comprising mixtures of supported HOR
catalyst and OER catalyst in which the volumetric density of the OER catalyst is relatively dilute and relatively dense respectively.
Figures 2a and 2b show SEM images of fuel cell anodes in the Examples in which the volumetric density of the OER catalyst is relatively dilute and relatively dense respectively. In these Figures, the white areas are OER catalyst.
Figure 3 plots reversal tolerance time versus Ir02/carbon support weight ratio for cells tested in the Examples and illustrates the effect of decreasing the amount of carbon support relative to OER
catalyst.
3 Docket No.: P83085 I /CA/1 Figure 4 plots reversal tolerance time versus amount of Pt loading in the anode for cells tested in the Examples. The amount of C support here was proportional to the amount of Pt.
Figure 5 compares reversal tolerance time versus amount of Ir02 in the anode for cells tested in the Examples where the anodes comprised carbon supported Pt catalysts with two different Pt loadings on the supports.
Figure 6 plots reversal tolerance time versus 1r02/carbon support weight ratio for cells tested in the Examples where the anodes comprised carbon supported Pt catalysts with two different Pt loadings on the supports.
DETAILED DESCRIPTION
It is well known that corrosion of the typical carbon supports used in fuel cell anodes occurs when the anode is exposed to the high potentials experienced (e.g. >1.6V) during a voltage reversal event. The carbon corrosion will lead to decreased electrical conductivity in the anode and eventually the OER
reaction will be inhibited when electron transport becomes more difficult.
Therefore, if the anode can be made in such a way that electron transport is less affected by the structural changes experienced during voltage reversal (e.g. due to carbon corrosion), the OER reaction can be extended and the length of time that the fuel cell can be exposed to reversal can be substantially increased before failure.
The present invention is applicable to solid polymer electrolyte fuel cells whose anodes comprise a mixture of supported HOR catalysts and OER catalysts. Applicable HOR catalysts include platinum and other noble metals and alloys. Catalyst supports for these HOR catalysts are typically high surface area materials and include high surface area carbons but also other materials such as niobium oxide, tungsten oxide, titanium oxide, and combinations thereof. Applicable OER
catalysts include but are not limited to Ir02 supported on Ti02. An exemplary anode of the invention comprises a mixture of carbon supported Pt and iridium oxide.
In the present invention, the voltage reversal tolerance of the fuel cells is improved by decreasing the amount of catalyst support relative to the amount of OER catalyst. This desirably results in an anode which is both thinner and in which the volumetric density of the OER catalyst is increased.
In a preferred embodiment, the ratio between the amount or loading of the OER
catalyst to the thickness of the anode is greater than 20 fig/cm3. Such a ratio can be achieved by increasing OER
catalyst loading. Alternatively such a ratio can be achieved by reducing the amount of supported
Figure 5 compares reversal tolerance time versus amount of Ir02 in the anode for cells tested in the Examples where the anodes comprised carbon supported Pt catalysts with two different Pt loadings on the supports.
Figure 6 plots reversal tolerance time versus 1r02/carbon support weight ratio for cells tested in the Examples where the anodes comprised carbon supported Pt catalysts with two different Pt loadings on the supports.
DETAILED DESCRIPTION
It is well known that corrosion of the typical carbon supports used in fuel cell anodes occurs when the anode is exposed to the high potentials experienced (e.g. >1.6V) during a voltage reversal event. The carbon corrosion will lead to decreased electrical conductivity in the anode and eventually the OER
reaction will be inhibited when electron transport becomes more difficult.
Therefore, if the anode can be made in such a way that electron transport is less affected by the structural changes experienced during voltage reversal (e.g. due to carbon corrosion), the OER reaction can be extended and the length of time that the fuel cell can be exposed to reversal can be substantially increased before failure.
The present invention is applicable to solid polymer electrolyte fuel cells whose anodes comprise a mixture of supported HOR catalysts and OER catalysts. Applicable HOR catalysts include platinum and other noble metals and alloys. Catalyst supports for these HOR catalysts are typically high surface area materials and include high surface area carbons but also other materials such as niobium oxide, tungsten oxide, titanium oxide, and combinations thereof. Applicable OER
catalysts include but are not limited to Ir02 supported on Ti02. An exemplary anode of the invention comprises a mixture of carbon supported Pt and iridium oxide.
In the present invention, the voltage reversal tolerance of the fuel cells is improved by decreasing the amount of catalyst support relative to the amount of OER catalyst. This desirably results in an anode which is both thinner and in which the volumetric density of the OER catalyst is increased.
In a preferred embodiment, the ratio between the amount or loading of the OER
catalyst to the thickness of the anode is greater than 20 fig/cm3. Such a ratio can be achieved by increasing OER
catalyst loading. Alternatively such a ratio can be achieved by reducing the amount of supported
4 Docket No.: P830851/CA/1 HOR catalyst in the anode. In a yet further alternative, a different supported HOR catalyst material can be used which has a different (e.g. greater) loading of HOR catalyst on the support. In this case, the higher loaded, supported HOR catalyst can allow for a thinner catalyst layer to be produced with the same total amount of HOR catalyst present.
Without being bound by theory, it is believed that the present method results in an anode with a denser OER catalyst structure in which there is improved electrical contact between the OER and HOR catalyst materials. The improved electrical contact renders the anode less susceptible to the adverse effects of corrosion of the catalyst support which can occur during reversal events. Figures la and lb illustrate the expected structural effects resulting from the inventive method. Figures la and lb show schematics of fuel cell anodes comprising mixtures of supported HOR
catalyst and OER
catalyst in which the volumetric density of the OER catalyst is relatively dilute and relatively dense respectively.
The following Examples have been included to illustrate certain aspects of the invention but should not be construed as limiting in any way.
EXAMPLES
In the following, various experimental fuel cell anodes were prepared. Where indicated, experimental fuel cells were prepared with these anodes and their voltage reversal tolerance was determined at their beginning of life.
Anodes were made using the same iridium (Ir) oxide powder as the OER catalyst in all cases. Two supported HOR catalysts were used in the experimental anodes. Both were carbon black supported Pt catalyst powders but comprised different Pt loading on the carbon black supports, namely 50 and 30 weight %.
Using these materials, fuel cell anodes having different total amounts of OER
catalyst, HOR catalyst, and carbon black supports, and having certain different ratios of OER
catalyst/C support were prepared.
Experimental fuel cells using these anodes were also made in a conventional manner. The cells were then conditioned by operating at a current density of 1.5 A/cm2, with hydrogen and air as the supplied reactants at 100 %RH, and at a temperature of 60 C for at least 16 hours to obtain a stable steady-state performance. Voltage reversal testing was then carried out which involved operating the cells at
Without being bound by theory, it is believed that the present method results in an anode with a denser OER catalyst structure in which there is improved electrical contact between the OER and HOR catalyst materials. The improved electrical contact renders the anode less susceptible to the adverse effects of corrosion of the catalyst support which can occur during reversal events. Figures la and lb illustrate the expected structural effects resulting from the inventive method. Figures la and lb show schematics of fuel cell anodes comprising mixtures of supported HOR
catalyst and OER
catalyst in which the volumetric density of the OER catalyst is relatively dilute and relatively dense respectively.
The following Examples have been included to illustrate certain aspects of the invention but should not be construed as limiting in any way.
EXAMPLES
In the following, various experimental fuel cell anodes were prepared. Where indicated, experimental fuel cells were prepared with these anodes and their voltage reversal tolerance was determined at their beginning of life.
Anodes were made using the same iridium (Ir) oxide powder as the OER catalyst in all cases. Two supported HOR catalysts were used in the experimental anodes. Both were carbon black supported Pt catalyst powders but comprised different Pt loading on the carbon black supports, namely 50 and 30 weight %.
Using these materials, fuel cell anodes having different total amounts of OER
catalyst, HOR catalyst, and carbon black supports, and having certain different ratios of OER
catalyst/C support were prepared.
Experimental fuel cells using these anodes were also made in a conventional manner. The cells were then conditioned by operating at a current density of 1.5 A/cm2, with hydrogen and air as the supplied reactants at 100 %RH, and at a temperature of 60 C for at least 16 hours to obtain a stable steady-state performance. Voltage reversal testing was then carried out which involved operating the cells at
5 Docket No.: P830851/CA/1 a current density of 0.2 A/cm2 with nitrogen on the anode and air on the cathode. Typically, the cell voltage would roughly plateau at a value between 0 and about ¨ 1.5V for a variable amount of time and then drop off suddenly to a value much less than ¨2.5V, at which point testing ended. The length of time to this sudden drop off point is representative of the cell's ability to tolerate voltage reversal and is denoted in the following as the reversal tolerance time.
Table 1 below summarizes the structure and certain properties of each of the anodes made using the catalyst with 50 wt% Pt loading on the carbon black supports (denoted as HOR
Pt 50 wt%), and also tabulates the reversal time for each at the beginning of life (BOL) for the experimental fuel cells made with these anodes.
In a like manner, Table 2 below summarizes the structure and certain properties of each of the anodes made using the catalyst with 30 wt% Pt loading on the carbon black supports (denoted as HOR Pt 30 wt%), and also tabulates the reversal time for each at the beginning of life (BOL) for the experimental fuel cells made with these anodes.
Table 1. HOR Pt 50 wt% anode properties and cell results Anode # Pt loading OER loading Reversal tolerance 0ER/carbon ( g/cm 2) (pg/cm 2) time (min) i 30 15 0.5 137 ii 30 50 1.7 543 iii 30 85 2.8 1342 iv 65 15 0.2 95 v 65 50 0.8 341 vi 65 85 1.3 552 vii 100 15 0.2 97 viii 100 50 0.5 271 ix 100 85 0.9 505 x 65 50 0.8 284 xi 65 50 0.8 350 xii 50 50 1.0 394 xiii 40 50 1.3 463
Table 1 below summarizes the structure and certain properties of each of the anodes made using the catalyst with 50 wt% Pt loading on the carbon black supports (denoted as HOR
Pt 50 wt%), and also tabulates the reversal time for each at the beginning of life (BOL) for the experimental fuel cells made with these anodes.
In a like manner, Table 2 below summarizes the structure and certain properties of each of the anodes made using the catalyst with 30 wt% Pt loading on the carbon black supports (denoted as HOR Pt 30 wt%), and also tabulates the reversal time for each at the beginning of life (BOL) for the experimental fuel cells made with these anodes.
Table 1. HOR Pt 50 wt% anode properties and cell results Anode # Pt loading OER loading Reversal tolerance 0ER/carbon ( g/cm 2) (pg/cm 2) time (min) i 30 15 0.5 137 ii 30 50 1.7 543 iii 30 85 2.8 1342 iv 65 15 0.2 95 v 65 50 0.8 341 vi 65 85 1.3 552 vii 100 15 0.2 97 viii 100 50 0.5 271 ix 100 85 0.9 505 x 65 50 0.8 284 xi 65 50 0.8 350 xii 50 50 1.0 394 xiii 40 50 1.3 463
6 Docket No.: P830851/CA/1 Table 2. HOR Pt 30 wt% anode properties and cell results Anode # Pt loading OER loading Reversal tolerance OER/carbon (ftg/cm 2) (ftg/cm 2) time (mm) xiv 30 15 0.2 104 xv 30 50 0.7 324 xvi 30 85 1.2 676 As is evident from the data in the tables above, for each OER loading, the thinner the anode is, the longer the reversal time.
Figures 2a and 2b show SEM images of fuel cell anode #s iv and vi respectively in which the volumetric density of the OER catalyst is relatively dilute and relatively dense respectively. In these Figures, the white areas are OER catalyst. The anode of Figure 2b appears to have a denser OER
structure and much better electrical connectivity of OER catalyst throughout than that of Figure 2a.
Therefore, it is expected that the anode of Figure 2b will have a more stable electrical conductivity than that of Figure 2a during voltage reversal.
Figure 3 plots reversal tolerance time versus 1i-02/carbon support weight ratio for the anodes and associated cells in Table I. Figure 3 illustrates the effect of decreasing the amount of carbon support relative to OER catalyst. As shown here, the reversal time increases as the 1r02/carbon support ratio increases.
Figure 4 plots reversal tolerance time in selected cells from Table 1 which had the same amount of Ir02 in the anodes (i.e. 50 tig/cm2) but where the amount of C supported catalyst was varied. Here, reversal tolerance time is plotted versus amount of Pt loading in the anodes.
The amount of C support here was proportional to the amount of Pt. The results here suggest that reversal tolerance can be improved by decreasing the relative amount of carbon supported Pt catalyst relative to a fixed amount of OER catalyst in the anode.
The results obtained in cells using the two different C supported Pt catalyst materials (i.e. the HOR Pt wt% and the HOR Pt 50 wt%) are compared in Figures 5 and 6 for three different OER loadings (i.e. 15, 50, and 85 p,g/cm2). Figure 5 compares reversal tolerance time versus amount of Ir02 in the anode. In cells having greater amounts of Ir02, the results for reversal tolerance time were quite different even though the amount of Ir02 present in the anodes was the same.
On the other hand, 30 Figure 6 compares reversal tolerance time versus 1r02/carbon support weight ratio. The reversal tolerance times here are quite similar as long as the 1r02/carbon support weight ratio is the same.
Figures 2a and 2b show SEM images of fuel cell anode #s iv and vi respectively in which the volumetric density of the OER catalyst is relatively dilute and relatively dense respectively. In these Figures, the white areas are OER catalyst. The anode of Figure 2b appears to have a denser OER
structure and much better electrical connectivity of OER catalyst throughout than that of Figure 2a.
Therefore, it is expected that the anode of Figure 2b will have a more stable electrical conductivity than that of Figure 2a during voltage reversal.
Figure 3 plots reversal tolerance time versus 1i-02/carbon support weight ratio for the anodes and associated cells in Table I. Figure 3 illustrates the effect of decreasing the amount of carbon support relative to OER catalyst. As shown here, the reversal time increases as the 1r02/carbon support ratio increases.
Figure 4 plots reversal tolerance time in selected cells from Table 1 which had the same amount of Ir02 in the anodes (i.e. 50 tig/cm2) but where the amount of C supported catalyst was varied. Here, reversal tolerance time is plotted versus amount of Pt loading in the anodes.
The amount of C support here was proportional to the amount of Pt. The results here suggest that reversal tolerance can be improved by decreasing the relative amount of carbon supported Pt catalyst relative to a fixed amount of OER catalyst in the anode.
The results obtained in cells using the two different C supported Pt catalyst materials (i.e. the HOR Pt wt% and the HOR Pt 50 wt%) are compared in Figures 5 and 6 for three different OER loadings (i.e. 15, 50, and 85 p,g/cm2). Figure 5 compares reversal tolerance time versus amount of Ir02 in the anode. In cells having greater amounts of Ir02, the results for reversal tolerance time were quite different even though the amount of Ir02 present in the anodes was the same.
On the other hand, 30 Figure 6 compares reversal tolerance time versus 1r02/carbon support weight ratio. The reversal tolerance times here are quite similar as long as the 1r02/carbon support weight ratio is the same.
7 Docket No.: P830851/CA/1 All of the above U.S. patents, U.S. patent application publications, U.S.
patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification, are incorporated herein by reference in their entirety.
While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since 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 foregoing teachings. Such modifications are to be considered within the purview and scope of the claims appended hereto.
patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification, are incorporated herein by reference in their entirety.
While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since 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 foregoing teachings. Such modifications are to be considered within the purview and scope of the claims appended hereto.
8
Claims (6)
1. A method for improving the voltage reversal tolerance of a solid polymer electrolyte fuel cell, the fuel cell comprising a cathode, a solid polymer electrolyte, and an anode, and the anode comprising a mixture of an amount of hydrogen oxidation reaction catalyst supported on an amount of catalyst support and an amount of an oxygen evolution reaction catalyst, the method comprising:
decreasing the amount of support relative to the amount of oxygen evolution reaction catalyst.
decreasing the amount of support relative to the amount of oxygen evolution reaction catalyst.
2. The method of claim 1 wherein the hydrogen oxidation reaction catalyst is platinum.
3. The method of claim 1 wherein the catalyst support is carbon.
4. The method of claim 1 wherein the oxygen evolution reaction catalyst is iridium oxide.
5. The method of claim 1 wherein the decreasing step comprises:
increasing the loading of hydrogen oxidation reaction catalyst on the catalyst support; and keeping the amount of hydrogen oxidation reaction catalyst in the anode essentially constant.
increasing the loading of hydrogen oxidation reaction catalyst on the catalyst support; and keeping the amount of hydrogen oxidation reaction catalyst in the anode essentially constant.
6. The method of claim 1 wherein the decreasing step comprises:
keeping the loading of hydrogen oxidation reaction catalyst on the catalyst support essentially constant; and reducing the amount of hydrogen oxidation reaction catalyst in the anode.
keeping the loading of hydrogen oxidation reaction catalyst on the catalyst support essentially constant; and reducing the amount of hydrogen oxidation reaction catalyst in the anode.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2934237A CA2934237A1 (en) | 2016-06-28 | 2016-06-28 | Anode for improved reversal tolerance in fuel cell stack |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2934237A CA2934237A1 (en) | 2016-06-28 | 2016-06-28 | Anode for improved reversal tolerance in fuel cell stack |
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| CA2934237A1 true CA2934237A1 (en) | 2016-08-31 |
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| Application Number | Title | Priority Date | Filing Date |
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| CA2934237A Abandoned CA2934237A1 (en) | 2016-06-28 | 2016-06-28 | Anode for improved reversal tolerance in fuel cell stack |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109792066A (en) * | 2016-09-08 | 2019-05-21 | 戴姆勒股份公司 | The method in starting below freezing for fuel cell system |
| CN112534613A (en) * | 2019-11-27 | 2021-03-19 | 苏州擎动动力科技有限公司 | Membrane electrode, preparation method thereof and fuel cell |
| CN112599796A (en) * | 2020-12-14 | 2021-04-02 | 中国科学院大连化学物理研究所 | Batch production method and equipment for high-yield and antipole-resistant catalytic electrode of fuel cell |
| CN113677431A (en) * | 2019-04-12 | 2021-11-19 | 株式会社古屋金属 | Water electrolysis catalyst for fuel cell anode, anode catalyst composition, and membrane electrode assembly |
-
2016
- 2016-06-28 CA CA2934237A patent/CA2934237A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109792066A (en) * | 2016-09-08 | 2019-05-21 | 戴姆勒股份公司 | The method in starting below freezing for fuel cell system |
| CN109792066B (en) * | 2016-09-08 | 2022-06-24 | 燃料电池中心两合股份有限公司 | Method for subfreezing start-up of a fuel cell system |
| CN113677431A (en) * | 2019-04-12 | 2021-11-19 | 株式会社古屋金属 | Water electrolysis catalyst for fuel cell anode, anode catalyst composition, and membrane electrode assembly |
| CN112534613A (en) * | 2019-11-27 | 2021-03-19 | 苏州擎动动力科技有限公司 | Membrane electrode, preparation method thereof and fuel cell |
| WO2021102739A1 (en) * | 2019-11-27 | 2021-06-03 | 苏州擎动动力科技有限公司 | Membrane electrode and manufacturing method thereof, and fuel cell |
| CN112599796A (en) * | 2020-12-14 | 2021-04-02 | 中国科学院大连化学物理研究所 | Batch production method and equipment for high-yield and antipole-resistant catalytic electrode of fuel cell |
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