Fuel cell and electrolyte electrode comprising non-ionomer binder

Abstract

The invention relates to fuel cells and electrolyzer electrodes comprising non-ionomer binders. An electrode of an electrochemical device includes a carbon-based support structure, an ion conducting material dispersed on and within the support structure, a catalyst dispersed on and within the support structure, and a non-ionomer hydrocarbon-based binder dispersed on the support structure. The ion conducting material enables proton transport across the electrode, the catalyst promotes a chemical reaction of the fuel received at the electrode, and the binder holds the electrode. The electrode may be included in an electrochemical device, such as a fuel cell.

Description

TECHNICAL FIELD

[0001] The information provided in this section is for the purpose of generally presenting the context of the disclosure. The work of the presently named inventors, to the extent the work is described in this section, as well as aspects of the description that can not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the disclosure.

[0002] The present disclosure relates generally to electrodes of electrochemical devices, such as fuel cells configured to power vehicles. Typically, electrodes of fuel cells include ionomers, such as perfluorosulfonic acid (PFSA)-based ionomers, to act as a physical binder for carbon-supported or dispersed catalyst nanoparticles and to maintain the mechanical integrity of the electrode. Such ionomers also enable proton transport across the catalyst layer of the electrode. BACKGROUND

[0003] However, PFSA ionomers act to suppress or reduce the kinetic activity of catalyst layers, such as platinum, over the useful life of the electrochemical device. As such, PFSA ionomers reduce efficiency and block active sites of the catalyst, requiring higher catalyst concentrations at the electrode. Further, PFSA ionomers are typically applied at a high PFSA ionomer ratio relative to the mass of carbon in the substrate, such as at a ratio of approximately 1.0 or greater. Further, PFSA ionomers slowly degrade over time when handled and, as such, pose an environmental hazard. SUMMARY

[0004] One aspect of the present disclosure provides an electrode of an electrochemical device. The electrode includes a carbon-based support structure, an ionically conductive material dispersed on and within the support structure, a catalyst dispersed on and within the support structure, and a non-ionomer hydrocarbon-based binder dispersed on the support structure. The ionically conductive material enables proton transport across the electrode. The catalyst facilitates a chemical reaction of a fuel received at the electrode. The binder maintains the electrode.

[0005] Embodiments of the present disclosure can include one or more of the following optional features. In some examples, the ionically conductive material includes a sulfate salt.

[0006] In some embodiments, the catalyst includes at least one from the group consisting of (i) platinum and (ii) a platinum alloy.

[0007] In some further embodiments, a ratio of platinum to the mass of carbon in the support structure is less than or equal to 0.6.

[0008] In some aspects, the binder includes at least one of the group consisting of (i) carboxymethyl cellulose, (ii) polyninylidene fluoride, and (iii) styrene butadiene rubber.

[0009] In some further aspects, a ratio of a mass of the carboxymethyl cellulose in the binder to a mass of the carbon in the support structure is less than or equal to 0.2.

[0010] In some still further aspects, a ratio of a mass of the polyninylidene fluoride in the binder to a mass of the carbon in the support structure is less than or equal to 0.2.

[0011] In some constructions, the catalyst and the binder are combined with a solvent to be dispersed on the support structure as a catalyst dispersion ink.

[0012] In some further constructions, the solvent is free of alcohol.

[0013] In some examples, a thickness of the catalyst dispersed on the support structure is less than or equal to 20 microns.

[0014] Another aspect of the disclosure provides an electrochemical device. The electrochemical device includes an electrode. The electrode includes a carbon-based support structure, an ionically conductive material including a sulfate salt and dispersed on and within the support structure, a catalyst including platinum and dispersed on and within the support structure, and a non-ionomeric hydrocarbon-based binder dispersed on the support structure. The ionically conductive material enables transport of protons across the electrode. The catalyst facilitates a chemical reaction of a fuel received at the electrode, the catalyst including a ratio of a mass of the platinum to a mass of the carbon in the support structure less than or equal to 0.6. The binder holds the electrode, the binder including at least one of the group consisting of (i) carboxymethyl cellulose, (ii) polyninylidene fluoride, and (iii) styrene butadiene rubber.

[0015] Implementations of this aspect of the disclosure can include one or more of the following optional features. In some aspects, a ratio of a mass of the carboxymethyl cellulose in the binder to a mass of the carbon in the support structure is less than or equal to 0.2.

[0016] In some implementations, a ratio of a mass of the polyninylidene fluoride in the binder to a mass of the carbon in the support structure is less than or equal to 0.2.

[0017] In some aspects, the catalyst and the binder are combined with a solvent and dispersed on the support structure as a catalyst dispersion ink.

[0018] In some additional aspects, the solvent is free of alcohol.

[0019] In some constructions, a thickness of the catalyst dispersed on the support structure is less than or equal to 20 microns.

[0020] Yet another aspect of the disclosure provides a vehicle. The vehicle includes a fuel cell, and the fuel cell includes an electrode. The electrode includes a carbon-based support structure, an ionically conductive material including a sulfate salt and dispersed on and within the support structure, a catalyst including platinum and dispersed on and within the support structure, and a non-ionomeric hydrocarbon-based binder dispersed on the support structure. The ionically conductive material enables transport of protons across the electrode. The catalyst facilitates chemical reactions of a fuel received at the electrode, the catalyst including a mass ratio of platinum to carbon in the support structure that is less than or equal to 0.6. The binder holds the electrode, the binder including at least one of the group consisting of (i) carboxymethyl cellulose, (ii) polyvinylidene fluoride, and (iii) styrene butadiene rubber.

[0021] Implementations of this aspect of the disclosure can include one or more of the following optional features. In some aspects, a mass ratio of the carboxymethyl cellulose in the binder to carbon in the support structure is less than or equal to 0.2.

[0022] In some implementations, a mass ratio of the polyvinylidene fluoride in the binder to carbon in the support structure is less than or equal to 0.2.

[0023] In some aspects, the catalyst and the binder are combined with a solvent and dispersed on a substrate as a catalyst dispersion ink, wherein a thickness of the catalyst dispersed on the substrate is greater than or equal to 10 microns.

[0024] The disclosure also includes the following technical solutions:

[0025] Scheme 1. An electrode of an electrochemical device, the electrode comprising:

[0026] a carbon-based support structure;

[0027] an ionically conductive material dispersed on and within the support structure, the ionically conductive material enabling transport of protons across the electrode;

[0028] a catalyst dispersed on and within the support structure, the catalyst facilitating chemical reactions of a fuel received at the electrode; and

[0029] a non-ionomeric hydrocarbon-based binder dispersed on the support structure, the binder holding the electrode.

[0030] Scheme 2. The electrode of Scheme 1, wherein the ion-conducting material comprises a sulfate salt.

[0031] Scheme 3. The electrode of Scheme 1, wherein the catalyst comprises at least one from the group consisting of (i) platinum and (ii) a platinum alloy.

[0032] Scheme 4. The electrode of Scheme 3, wherein a mass ratio of platinum to carbon in the support structure is less than or equal to 0.6.

[0033] Scheme 5. The electrode of Scheme 1, wherein the binder comprises at least one from the group consisting of (i) carboxymethyl cellulose, (ii) polyvinylidene fluoride, and (iii) styrene butadiene rubber.

[0034] Scheme 6. The electrode of Scheme 5, wherein a mass ratio of carboxymethyl cellulose in the binder to carbon in the support structure is less than or equal to 0.2.

[0035] Scheme 7. The electrode of Scheme 5, wherein a mass ratio of polyvinylidene fluoride in the binder to carbon in the support structure is less than or equal to 0.2.

[0036] Scheme 8. The electrode of Scheme 1, wherein the catalyst and the binder are combined with a solvent as a catalyst dispersion ink dispersed on the support structure.

[0037] Scheme 9. The electrode of Scheme 8, wherein the solvent is free of alcohol.

[0038] Scheme 10. The electrode of Scheme 1, wherein a thickness of the catalyst dispersed on the support structure is less than or equal to 20 microns.

[0039] Scheme 11. An electrochemical device comprising:

[0040] an electrode comprising:

[0041] a carbon-based support structure;

[0042] an ion-conducting material comprising a sulfate salt and dispersed on and within the support structure, the ion-conducting material enabling transport of protons across the electrode;

[0043] a catalyst comprising platinum and dispersed on and within the support structure, the catalyst facilitating a chemical reaction of a fuel received at the electrode, and the catalyst comprising a mass ratio of platinum to carbon in the support structure less than or equal to 0.6; and

[0044] a non-ionomeric hydrocarbon-based binder dispersed on the support structure, the binder holding the electrode, and the binder comprising at least one of the group consisting of (i) carboxymethyl cellulose, (ii) polyvinylidene fluoride, and (iii) styrene butadiene rubber.

[0045] Scheme 12. The electrochemical device of Scheme 11, wherein a mass ratio of carboxymethyl cellulose in the binder to carbon in the support structure is less than or equal to 0.2.

[0046] Scheme 13. The electrochemical device of Scheme 11, wherein a mass ratio of polyvinylidene fluoride in the binder to carbon in the support structure is less than or equal to 0.2.

[0047] Scheme 14. The electrochemical device of Scheme 11, wherein the catalyst and the binder are combined with a solvent as a catalyst dispersion ink dispersed on the support structure.

[0048] Scheme 15. The electrochemical device of Scheme 14, wherein the solvent is free of alcohol.

[0049] Scheme 16. The electrochemical device of Scheme 11, wherein a thickness of the catalyst dispersed on the support structure is less than or equal to 20 microns.

[0050] Scheme 17. A vehicle comprising:

[0051] a fuel cell comprising:

[0052] an electrode comprising:

[0053] a carbon-based support structure;

[0054] an ionically conductive material comprising a sulfate and dispersed on and within the support structure, the ionically conductive material enabling transport of protons across the electrode;

[0055] a catalyst comprising platinum and dispersed on and within the support structure, the catalyst facilitating a chemical reaction of a fuel received at the electrode, and the catalyst comprising a mass ratio of platinum to carbon in the support structure less than or equal to 0.6; and

[0056] a non- ionomeric hydrocarbon-based binder dispersed on the support structure, the binder holding the electrode, and the binder including at least one of the group consisting of (i) carboxymethyl cellulose, (ii) polyvinylidene fluoride, and (iii) styrene butadiene rubber.

[0057] Scheme 18. The vehicle of Scheme 17, wherein the ratio of the mass of carboxymethyl cellulose in the binder to the carbon in the support structure is less than or equal to 0.2.

[0058] Scheme 19. The vehicle of Scheme 17, wherein the ratio of the mass of polyvinylidene fluoride in the binder to the carbon in the support structure is less than or equal to 0.2.

[0059] Scheme 20. The vehicle of Scheme 17, wherein the catalyst and the binder are combined with a solvent as a catalyst dispersion ink dispersed on a substrate, wherein the thickness of the catalyst dispersed on the substrate is less than or equal to 20 microns. BRIEF DESCRIPTION OF DRAWINGS

[0060] The drawings described herein are for illustrative purposes only of selected arrangements and are not intended to limit the scope of the present disclosure.

[0061] Figure 1 is a perspective view of a vehicle including an electrochemical device.

[0062] Figure 2 is a rendering of a non-ionomeric electrode of an electrochemical device.

[0063] Figure 3 is a diagram showing the flow of fuel, oxygen or air, electrons, and protons during operation of an electrochemical device.

[0064] Figure 4 is a line graph comparing hydrogen-air polarization curves during operation of an electrochemical device having an electrode with PFSA-based ionomer to an electrochemical device having a non-ionomeric electrode.

[0065] Figure 5 is a bar graph comparing electrochemical surface area (ECSA) before and after the operational life cycle of an electrochemical device having an electrode with PFSA-based ionomer to an electrochemical device having a non-ionomeric electrode.

[0066] Figure 6 is a line graph comparing the electrode proton transport resistance versus relative humidity of an electrochemical device having an electrode with PFSA-based ionomer to an electrochemical device having a non-ionomeric electrode.

[0067] Throughout the drawings, corresponding reference numerals indicate corresponding parts. DETAILED DESCRIPTION

[0068] Example configurations will now be described more fully with reference to the accompanying drawings. Example configurations are provided by way of non-limiting examples so as to provide an thorough description of the disclosure. Various configurations can be provided and the example configurations can be implemented in many different ways, with specific configurations being provided as examples. Specific examples of components, devices, and methods are described below to provide a thorough understanding of the example configurations. These examples may

[0069] The terminology used herein is for the purpose of describing particular example configurations only and is not intended to be limiting. As used herein, the singular forms "a," "an," and "the" can be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having," are inclusive and therefore specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order in which they are described unless explicitly identified as an order dependent step. Additional or alternative steps can be employed.

[0070] When an element or layer is referred to as being "on," "engaged to," "connected to," "attached to," or "coupled to" another element or layer, it can be directly on, engaged, connected, attached, or coupled to the other element or layer, or one or more intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," "directly attached to," or "directly coupled to" another element or layer, there are no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0071] The terms "first," "second," "third," etc. can be used herein to describe various elements, components, regions, layers and / or sections. Such elements, components, regions, layers and / or sections should not be limited by such terms. These terms can be used only to distinguish one element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numeric terms do not imply a sequence or order to the contributed by the terms. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example configurations.

[0072] In this application, including the definitions below, the term "module" can be replaced with the term "circuit." The term "module" can refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; a memory (shared, dedicated, or group) that stores code for execution by a processor (shared, dedicated, or group); other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

[0073] The term "code," as used in this application, can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, and / or objects. The term "shared processor" encompasses a single processor that executes some or all code from multiple modules. The term "group processor" encompasses a processor that, in combination with additional processors, executes some or all code from one or more modules. The term "shared memory" encompasses a single memory that stores some or all code from multiple modules. The term "group memory" encompasses a memory that, in combination with additional memory, stores some or all code from one or more modules. The term "memory" can be a subset of the term "computer-readable medium." The term "computer-readable medium" does not encompass transitory propagating signals and thus can be considered tangible and non-transitory. Non-limiting examples of non-transitory computer-readable media include nonvolatile memory, magnetic storage, and optical storage.

[0074] The apparatus and methods described in this application can be partially or entirely implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions stored on at least one non-transitory, tangible computer-readable medium. The computer programs can also include and / or rely on stored data.

[0075] A software application (i.e., a software resource) can refer to computer software that causes a computing device to perform a task. In some examples, a software application can be referred to as an "application," an "app," or a "program." Exemplary applications include, without limitation, system diagnostic applications, system management applications, system maintenance applications, word processing applications, spreadsheet applications, messaging applications, media streaming applications, social networking applications, and gaming applications.

[0076] A non-transitory memory can be a physical device that is used to temporarily or permanently store a program (e.g., a sequence of instructions) or data (e.g., program state information) for use by a computing device. A non-transitory memory can be a volatile and / or non-volatile addressable semiconductor memory. Examples of non-volatile memory include, but are not limited to, flash memory and read-only memory (ROM) / programmable read-only memory (PROM) / erasable programmable read-only memory (EPROM) / electrically erasable programmable read-only memory (EEPROM) (e.g., commonly used for firmware such as a boot program). Examples of volatile memory include, but are not limited to, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), phase change memory (PCM), and magnetic or optical disks.

[0077] These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and / or object-oriented programming language, and / or in assembly / machine language. As used herein, the terms “machine-readable medium” and “computer-readable medium” refer to any computer program product, non-transitory computer readable medium, devices and / or means used to provide machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and / or data to a programmable processor.

[0078] Various implementations of the systems and techniques described herein can be realized in digital electronic and / or optical circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and / or interpretable on a programmable system including at least one programmable processor, which can be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.

[0079] The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0080] To provide for interaction with a user, one or more aspects of the disclosure can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube), LCD (liquid crystal display), or touch screen, for displaying information to the user and optionally a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device used by the user; for example, by sending web pages to a web browser on a user's client device in response to requests received from the web browser.

[0081] Electrodes used in fuel cells are responsible for conducting electrons and catalyzing the chemical energy conversion to electrical energy. This electrical energy is ultimately used to power a machine in which the fuel cell is disposed, such as a vehicle. The electrodes do not contain perfluorosulfonic acid (PFSA) based ionomers, but rather, the electrodes use carbon-supported structures with sulfate functionality to transport protons across the electrode, which enables the chemical energy conversion to electrical energy. Additionally, non-ionomeric binders are used to provide structural integrity to the electrodes, as well as to bind catalyst to the electrodes. The catalyst can include platinum and is responsible for supporting the reaction between hydrogen and oxygen in the fuel cell, which also enables the chemical energy conversion to electrical energy. The binders can include carboxymethyl cellulose (CMC), polyvinylidene fluoride, and / or a combination of both CMC and polyvinylidene fluoride.

[0082] Reference Figures 1-3 The vehicle 10 includes an electrochemical device 12, such as a fuel cell system having a plurality of fuel cells 12a arranged as a fuel cell stack, which generates power for driving a propulsion system of the vehicle 10. In order to provide power from the electrochemical device 12 to the vehicle 10, a conversion of chemical energy to electrical energy occurs within each fuel cell 12a, and the generated electrical energy powers and enables operation of the vehicle 10. Each fuel cell 12a includes a pair of electrodes 14, such as an anode 14a and a cathode 14b. The anode 14a is negatively charged, and the cathode 14b is positively charged. The anode 14a and the cathode 14b are separated by an electrolyte 16 of the fuel cell 12a.

[0083] During operation of the electrochemical device 12, hydrogen 18 is fed to the anode 14a of the fuel cell 12a, and the anode 14a enables the hydrogen 18 to separate into protons 20 and electrons 22. Any excess hydrogen 18 that does not separate into protons 20 and electrons 22 is either exhausted from the fuel cell 12a or recycled into the fuel cell 12. The protons 20 flow through the electrolyte 16, while the electrons 22 flow through an external circuit 24, where an electrical charge 26 is generated. It is this electrical charge 26 that provides power to the vehicle 10. As the electrons 22 travel through the external circuit 24 and the protons 20 travel through the electrolyte 16, both the electrons 22 and the protons 20 eventually enter the cathode 14b. Air or oxygen 28 is fed to the cathode 14b of the fuel cell 12a, and the cathode 14b causes the electrons 22 and the protons 20 to combine with the oxygen 28 to generate water 32. The water 32 is exhausted from the fuel cell 12a as waste, or can be recycled back into the fuel cell 12a. Additionally, any excess oxygen 28 that does not combine with the electrons 22 and the protons 20 is exhausted from the fuel cell 12a or recycled back into the fuel cell 12a. The composition of the electrodes 14 provides structural integrity and allows for certain actions to occur at both the anode 14a and the cathode 14b, such as separating and combining protons 20, oxygen 28, and electrons 22, as well as facilitating the flow of protons 20 across the electrodes 14.

[0084] The electrode 14 includes a carbon-based support structure 34 that serves as a container or body of the electrode 14. To enable the transport of the protons 20 across the electrode 14, an ionically conductive material 36 is dispersed on and / or at least partially within the support structure 34 of the electrode 14. For example, the ionically conductive material 36 can include a sulfate salt. Further, the electrode 14 includes a catalyst 38 dispersed on and / or at least partially within the support structure 34. In the illustrated example, the catalyst 38 includes platinum as platinum can be an effective element that sufficiently facilitates the splitting of the hydrogen 18 into the protons 20 and the electrons 22 at the anode 14a or the recombination of the oxygen 28 with the protons 20 and the electrons 22 to form the water 32 at the cathode 14b. Further, the electrode includes a binder 40 that helps physically hold the carbon-based support structure 34, the ionically conductive material 36, and the catalyst 38 together and / or at a base 41 of the electrode 14. As discussed further below, the binder 40 is a non-ionomer and hydrocarbon-based binder that has a reduced or negligible or non-existent impact on the kinetic activity of the catalyst 38 and has a reduced or negligible or non-existent environmental impact as compared to a PFSA ionomer-based binder.

[0085] In some applications, the binder 40 includes carboxymethyl cellulose (CMC), while in other applications, the binder 40 used includes polyvinylidene fluoride (PVDF) or styrene butadiene rubber (SBR). In some other applications, the binder 40 used includes a combination of CMC and / or PVDF and / or SBR in adjustable ratios. Thus, the binder 40 maintains the physical integrity and operational efficiency of the electrode 14.

[0086] As the non-ionomer binder 40 of the electrode 14 has a negligible or non-existent impact on the kinetic activity of the platinum-based catalyst 38 over the life cycle of the electrode 14, the mass ratio of platinum to carbon in the support structure 34 can be reduced without impacting the operational efficiency of the fuel cell 12a. For example, the mass ratio of platinum to carbon in the support structure 34 can be less than or equal to 0.6. This ratio allows the catalyst 38 to effectively facilitate the splitting of the hydrogen 18 into the protons 20 and the electrons 22 or the recombination of the oxygen 28 into the water 32. Further, the catalyst 38 can have a reduced thickness when dispersed on the support structure 34, such as a thickness between approximately five (5) microns and twenty (20) microns. As the electrode 14 includes the non-ionomer binder 40, the platinum catalyst 38 will experience reduced or negligible or non-existent degradation over the life of the electrochemical device 12. Thus, a reduced amount of the conductive material 36 can be used in the formation of the electrode 14 while still allowing the electrode 14 to maintain its operational efficiency.

[0087] The formation of the electrode 14 includes dispersing a known amount of the catalyst 38 into the binder 40 in the solvent 43, thereby creating a catalyst dispersion ink 45. Further, the binder 40 can include CMC and / or PVDF. The catalyst dispersion ink 45 can then be applied to the substrate 41, and thus the catalyst 38 and the binder 40 can be dispersed across the support structure 34. As described below, the catalyst dispersion ink 45 can be milled in the presence of Zr02beads prior to coating the support structure 34 and / or the substrate 41 with the catalyst dispersion ink 45.

[0088] The ratio of the CMC to the mass of carbon in the support structure 34 as the binder 40 can be less than or equal to approximately 0.2. Additionally, the dispersion of the catalyst dispersion ink 45 and the concentration of the catalyst 38 in the catalyst dispersion ink 45 is configured to achieve a thickness of the catalyst 38 on the support structure 34 of greater than or equal to approximately five (5) microns, such as a thickness between approximately five (5) microns and twenty (20) microns. In some cases, the solvent 43 can include an alcohol, such as propanol. In these cases, the alcohol can enhance the ability of the binder 40 to disperse uniformly on the support structure 34. The mass ratio of the alcohol to water in the solvent 43 can be between approximately 1.0 and 3.0. In some examples, the solvent 43 can be free of alcohol.

[0089] The catalyst dispersion ink 45 can be milled in the presence of a milling media, such as zirconium oxide (Zr02) beads, prior to applying the catalyst dispersion ink 45 to the substrate 41 to achieve a sufficient particle size throughout the catalyst dispersion ink 45. For example, the catalyst dispersion ink 45 can be milled overnight, or for a period of eight (8) hours or more, ten (10) hours or more, twelve (12) hours or more, etc. After the catalyst dispersion ink 45 is milled, it can be applied to the substrate 41 to form the electrode 14.

[0090] In some examples, the formation of the electrode 14 includes dispersing a known amount of the catalyst 38 into the binder 40 in the solvent 43, where the binder 40 includes a combination of CMC and PVDF or another suitable insoluble latex material. The catalyst dispersion ink 45 can then be applied to the substrate 41, and thus the catalyst 38 and the binder 40 can be dispersed across the substrate 41.

[0091] The ratio of the mass of CMC as the binder 40 to the carbon in the support structure 34 can be less than or equal to approximately 0.2, and the ratio of the mass of PVDF in the binder 40 to the carbon in the support structure 34 can be less than or equal to approximately 0.2. Additionally, the concentration of the catalyst 38 in the dispersion and solvent 43 of the catalyst dispersion ink 45 is configured to achieve a thickness of the catalyst 38 on the support structure 34 of greater than or equal to approximately five (5) microns, such as a thickness between approximately five (5) microns and approximately twenty (20) microns. In some cases, the solvent 43 can include an alcohol, or the solvent 43 can be free of an alcohol. Moreover, the PVDF of the binder 40 helps to facilitate adhesion of the binder to the support structure 34, as the PVDF is a relatively soft and water insoluble latex that allows it to easily conform to the geometry of the support structure 34 and provide additional adhesion strength.

[0092] Referring to Figure 4 , the graph 400 compares hydrogen-air polarization curves during operation of an electrochemical device with electrodes having PFSA-based ionomer to an electrochemical device 12 with electrodes 14 free of ionomer, where the first line 42 represents operation of an electrochemical device with PFSA-based ionomer at the beginning of its life cycle, and the third line 46 represents operation of an electrochemical device with PFSA near the end of its life cycle. The second line 44 represents operation of an electrochemical device free of ionomer at the beginning of its life cycle, and the fourth line 48 represents operation of an electrochemical device free of ionomer near the end of its life cycle. As shown, the graph 400 maps the voltage produced by the electrochemical devices at different current densities.

[0093] As shown, while the second line 44 represents a slightly lesser voltage capability of the electrochemical device 12 free of ionomer than the electrochemical device with PFSA represented by the first line 42, the voltage capability provided by the electrochemical device 12 represented by the second line 44 is still viable for adequate fuel cell operation.

[0094] Moreover, the comparison of the third line 46 to the fourth line 48 shows that the electrochemical device 12 free of ionomer can degrade to a less severe extent than the electrochemical device with PFSA, particularly at higher current densities, when the respective electrochemical devices are near the end of their life cycles.

[0095] Referring to Figure 5electrochemical device 12 with electrodes 14 without ionomer. The ECSA is defined by the effective surface area of the catalyst 38 in the form of fine platinum nanoparticles on the support structure 34. The greater the effective surface area of the nanoparticles, the more efficient the catalyst 38 can split hydrogen 18 into protons 20 and electrons 22 or recombine oxygen 28 into water 32, which means that the electrochemical device 12 can operate more efficiently. Over time as the electrochemical device 12 is used, the platinum can inherently degrade, becoming less and less efficient. Ionomer increases the rate of degradation of the platinum. The first bar 50 represents the total effective surface area of the platinum catalyst 38 nanoparticles at the beginning of the life of the electrochemical device 12 with electrodes 14 without ionomer. The second bar 52 represents the total effective surface area of the platinum catalyst nanoparticles at the beginning of the life of the fuel cell with electrodes including ionomer. The third bar 54 represents the total effective surface area of the platinum catalyst 38 nanoparticles near the end of the life of the electrochemical device 12 with electrodes 14 without ionomer. The fourth bar 56 represents the total effective surface area of the platinum catalyst nanoparticles near the end of the life of the fuel cell with electrodes including ionomer. The reduction in effective surface area of the platinum catalyst 38 is shown from the first bar 50 to the third bar 54 is not as great as the reduction in effective surface area of the platinum catalyst from the second bar 52 to the fourth bar 56. Thus, the electrodes 14 without ionomer can not degrade the catalyst 38 as quickly or significantly as the electrodes including ionomer.

[0096] Referring to Figure 6 The line graph 600 includes two electrode-proton transport curves that compare the electrode proton transport resistance versus relative humidity for an electrochemical device with electrodes with PFSA-based ionomer to an electrochemical device 12 with electrodes 14 without ionomer. Determining the resistance of proton transport involves measuring the resistance of the electrode 14 as a function of relative humidity in the cathode 14b. Generally, the greater the relative humidity, the lower the resistance of the electrode 14. The first line 58 represents the resistance of the electrodes 14 without ionomer, while the second line 60 represents the resistance of the electrodes with PFSA. Both the first line 58 and the second line 60 show that as the relative humidity in the cathode 14b increases, the resistance decreases. As shown, the level of resistance during operation of the electrochemical device 12 with electrodes 14 without ionomer is substantially similar or slightly higher than the level of resistance during operation of the electrochemical device with PFSA-based ionomer.

[0097] A number of implementations have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of this disclosure. Accordingly, other implementations are within the scope of the following claims.

[0098] The foregoing description is provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Various elements or features of a specific structure are generally not limited to the particular structure disclosed, but are meant to be interchangeable and can be used in other suitable structures, as applicable, even if not specifically shown or described. These may be changed by variations in the steps or parts illustrated or described, as well as alternatives, now known or later developed, that would perform similar functions. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. An electrode for an electrochemical device, the electrode comprising: Carbon-based support structure; An ion-conducting material dispersed on and within the support structure, the ion-conducting material enabling protons to be transported across the electrodes; A catalyst dispersed on and within the support structure, the catalyst promoting the chemical reaction of the fuel received at the electrode; as well as A non-ionomer hydrocarbon-based binder dispersed on the support structure, the binder holding the electrode.

2. The electrode according to claim 1, wherein, The ion-conducting material includes sulfates.

3. The electrode according to claim 1, wherein, The catalyst comprises at least one from the group consisting of (i) platinum and (ii) platinum alloys.

4. The electrode according to claim 3, wherein, The mass ratio of platinum to carbon in the supporting structure is less than or equal to 0.

6.

5. The electrode according to claim 1, wherein, The adhesive comprises at least one of the group consisting of (i) carboxymethyl cellulose, (ii) polyvinylidene fluoride and (iii) styrene-butadiene rubber.

6. The electrode according to claim 5, wherein, The mass ratio of carboxymethyl cellulose in the binder to carbon in the support structure is less than or equal to 0.

2.

7. The electrode according to claim 5, wherein, The mass ratio of polyvinylidene fluoride in the adhesive to carbon in the support structure is less than or equal to 0.

2.

8. The electrode according to claim 1, wherein, The catalyst and the binder are combined with the solvent and dispersed on the support structure as catalyst dispersion ink.

9. The electrode according to claim 8, wherein, The solvent does not contain alcohol.

10. The electrode according to claim 1, wherein, The thickness of the catalyst dispersed on the support structure is less than or equal to 20 micrometers.

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