Hybrid catalyst layer for electrolyzers

Abstract

This invention describes systems, methods, and apparatus for enhancing the performance of catalyst layers in electrolyzers. The enhanced catalyst layer comprises a catalyst mixture containing catalyst particles and corrosion-resistant conductive nanoparticles to optimize interfacial contact and reduce in-plane discontinuities, even with low areal loadings of the catalyst particles. For example, the catalyst layer comprises a matrix containing a homogeneous mixture of catalyst particles and corrosion-resistant conductive nanoparticles. The catalyst particles are configured to facilitate water electrolysis. The catalyst particles contain iridium and have a high surface area. The corrosion-resistant conductive nanoparticles are configured to resist oxidation, reduce packing discontinuities in the catalyst particles, and provide conductive bridges between the catalyst particles. The matrix is ​​configured to support the catalyst particles and the corrosion-resistant conductive nanoparticles.

Description

Technical Field

[0001] This invention relates to the field of electrolysis, and more specifically, to systems and methods for enhancing the performance of catalyst layers. Background Technology

[0002] In electrolysis systems, electrocatalysts are commonly used to accelerate half-cell reactions. Iridium, as the active component in electrocatalysts, enables efficient and robust oxygen evolution reactions. However, iridium is relatively abundant. Therefore, a lower iridium areal loading is desirable.

[0003] Iridium oxide-based catalysts are the preferred catalysts for promoting the oxygen evolution reaction in polymer electrolyte membrane water electrolyzers. Iridium oxides have a relatively high density (e.g., 11.66 g / cm³). Therefore, iridium oxides form compact electrode structures even with low areal loadings.

[0004] According to Tafel kinetics, the voltage loss resulting from using a small iridium oxide areal loading in a membrane electrode assembly, or the voltage loss of a given membrane electrode assembly due to iridium dissolution and aggregation during operation, is theoretically very low. However, significant voltage losses have been observed in actual tests. For example, an iridium oxide areal loading of 0.1 mg / cm² or less will result in a catalyst layer with a thickness of less than 1 μm. Furthermore, the catalyst layer will have a relatively irregular interfacial surface to contact adjacent porous transport layers. Summary of the Invention

[0005] The observed voltage drop is attributed to the reduced catalyst layer thickness and the increased contact resistance and in-plane resistance. The irregular interfacial surface reduces the contact between the catalyst layer and the adjacent porous transport layer. Furthermore, the low areal loading in the thin film leads to in-plane discontinuities, resulting in in-plane contact resistance, which in turn increases the cell voltage drop. This in-plane contact resistance may exist in the initial stages due to the non-uniform dispersion of catalyst particles within the film, and / or may arise during operation due to iridium dissolution.

[0006] The system, method, and apparatus according to the present invention provide a catalyst mixture comprising catalyst particles and corrosion-resistant conductive nanoparticles.

[0007] Advantageously, even with low areal loadings of catalyst particles, the catalyst mixtures described herein can optimize, for example, interfacial contact and reduce in-plane discontinuities during the initial stages and throughout operation.

[0008] The catalyst layer is formed from a catalyst mixture comprising catalyst particles within a binder and corrosion-resistant conductive nanoparticles. The corrosion-resistant conductive nanoparticles are configured to increase the continuity of the catalyst layer and optimize the interfacial contact. The size of the corrosion-resistant conductive nanoparticles can be designed to bridge the filling discontinuities between the catalyst particles.

[0009] Furthermore, the interfacial contact of the catalyst layer can be optimized by adjusting its thickness to produce a uniform interfacial surface. The optimal thickness can be determined based on the size of the catalyst particles and the corrosion-resistant conductive nanoparticles. For example, in some aspects, corrosion-resistant conductive nanoparticles are used to reduce durability losses associated with contact resistance by producing a mixed oxide catalyst layer with an optimized thickness at low iridium loading values. For instance, the thickness of the mixed oxide catalyst layer can be at least 2 micrometers, at least 4 micrometers, or even thicker when the iridium oxide areal loading is 0.1 mg / cm².

[0010] According to various aspects of the invention, the catalyst layer comprises a matrix containing a homogeneous mixture of catalyst particles and corrosion-resistant conductive nanoparticles. The catalyst particles are configured to facilitate water electrolysis. The catalyst particles comprise iridium and have a high surface area. The corrosion-resistant conductive nanoparticles are configured to resist oxidation, reduce discontinuities in the catalyst particle packing, and provide electrically conductive bridges between the catalyst particles. The matrix is ​​configured to support the catalyst particles and the corrosion-resistant conductive nanoparticles.

[0011] According to another aspect of the invention, the catalyst particles are selected from the group consisting of iridium oxide particles or iridium oxide-containing particles.

[0012] According to another aspect of the present invention, the corrosion-resistant conductive nanoparticles are selected from the group consisting of Magnéli phase titanium oxide (Ti4O7), platinum-coated titanium dioxide (Pt / TiO2), platinum-coated niobium oxide (Pt / Nb2O5), platinum-coated zirconium oxide (Pt / ZrO2), and platinum-coated tantalum oxide (Pt / Ta2O5).

[0013] According to another aspect of the present invention, the corrosion-resistant conductive nanoparticles are selected from the group consisting of platinum-coated titanium dioxide (Pt / TiO2), gold-coated titanium dioxide (Au / TiO2), and iridium-coated titanium dioxide (Ir / TiO2).

[0014] According to another aspect of the invention, the corrosion-resistant conductive nanoparticles are platinum-coated particles, wherein the platinum content is 40% to 80% by weight, based on the weight of the corrosion-resistant conductive nanoparticles.

[0015] According to another aspect of the present invention, the average size of the corrosion-resistant conductive nanoparticles is 20 nanometers to 300 nanometers.

[0016] According to another aspect of the present invention, the weight ratio of corrosion-resistant conductive nanoparticles to catalyst particles is 0.5:1 to 8:1.

[0017] According to another aspect of the invention, the thickness of the catalyst layer is greater than 4 micrometers, and the packing density of iridium oxide is less than 0.25 mg / cm³.

[0018] According to another aspect of the invention, the thickness of the catalyst layer is greater than 2 micrometers, and the packing density of iridium oxide is less than 0.5 mg / cm³.

[0019] According to various aspects of the present invention, a membrane electrode assembly includes an anode, a cathode, and a membrane disposed between the anode and the cathode. The anode has a catalyst layer comprising a matrix containing a homogeneous mixture of catalyst particles and corrosion-resistant conductive nanoparticles. The catalyst particles are configured to facilitate water electrolysis. The catalyst particles comprise iridium and have a high surface area. The corrosion-resistant conductive nanoparticles are configured to resist oxidation, reduce packing discontinuities in the catalyst particles, and provide conductive bridges between the catalyst particles. The matrix is ​​configured to support the catalyst particles and the corrosion-resistant conductive nanoparticles.

[0020] According to another aspect of the invention, the catalyst particles are selected from the group consisting of iridium oxide particles or iridium oxide-containing particles.

[0021] According to another aspect of the present invention, the corrosion-resistant conductive nanoparticles are selected from the group consisting of Magnéli phase titanium oxide (Ti4O7), platinum-coated titanium dioxide (Pt / TiO2), platinum-coated niobium oxide (Pt / Nb2O5), platinum-coated zirconium oxide (Pt / ZrO2), and platinum-coated tantalum oxide (Pt / Ta2O5).

[0022] According to another aspect of the invention, the corrosion-resistant conductive nanoparticles are platinum-coated particles, wherein the platinum content is 50% to 80% by weight, based on the weight of the corrosion-resistant conductive nanoparticles.

[0023] According to another aspect of the present invention, the average size of the corrosion-resistant conductive nanoparticles is 20 nanometers to 300 nanometers.

[0024] According to another aspect of the present invention, the weight ratio of corrosion-resistant conductive nanoparticles to catalyst particles is 0.5:1 to 8:1.

[0025] According to another aspect of the invention, the thickness of the catalyst layer is greater than 4 micrometers, and the packing density of iridium oxide is less than 0.25 mg / cm³.

[0026] According to various aspects of the invention, an electrolyzer includes a membrane electrode assembly and a pair of polar plates adjacent to opposite sides of the membrane electrode assembly. The membrane electrode assembly includes an anode, a cathode, and a membrane located between the anode and cathode. The anode has a catalyst layer comprising a matrix containing a homogeneous mixture of catalyst particles and corrosion-resistant conductive nanoparticles. The catalyst particles are configured to facilitate water electrolysis. The catalyst particles comprise iridium and have a high surface area. The corrosion-resistant conductive nanoparticles are configured to resist oxidation, reduce packing discontinuities of the catalyst particles, and provide conductive bridges between the catalyst particles. The matrix is ​​configured to support the catalyst particles and the corrosion-resistant conductive nanoparticles. Each of the pair of polar plates is electrically connected to and fluidly connected to the corresponding anode and cathode.

[0027] According to another aspect of the present invention, the corrosion-resistant conductive nanoparticles are selected from the group consisting of Magnéli phase titanium oxide (Ti4O7), platinum-coated titanium dioxide (Pt / TiO2), platinum-coated niobium oxide (Pt / Nb2O5), platinum-coated zirconium oxide (Pt / ZrO2), and platinum-coated tantalum oxide (Pt / Ta2O5).

[0028] According to another aspect of the invention, the corrosion-resistant conductive nanoparticles are platinum-coated particles, wherein the platinum content is 40% to 80% by weight, based on the weight of the corrosion-resistant conductive nanoparticles.

[0029] According to another aspect of the invention, the weight ratio of corrosion-resistant conductive nanoparticles to catalyst particles is from 0.5:1 to 8:1.

[0030] The above-described features and advantages of the invention, as well as other features and advantages, will become apparent from the following detailed description of the best mode for carrying out the invention, taken in conjunction with the accompanying drawings. Attached Figure Description

[0031] The accompanying drawings are illustrative and not intended to limit the scope of the claims. Exemplary aspects are discussed in the following detailed description and are shown in the drawings, wherein:

[0032] Figure 1 An electrolysis environment according to various aspects of the present invention is shown;

[0033] Figure 2 It shows Figure 1 Electrolysis systems within an electrolysis environment;

[0034] Figure 3 It shows Figure 2 A partial exploded view of the electrolytic-cell stack within the electrolysis system;

[0035] Figure 4 It shows Figure 3 A side view of the anodes within the stack of the electrolytic cell; and

[0036] Figure 5 A side view of a contrast anode formed without the use of corrosion-resistant conductive nanoparticles is shown. Detailed Implementation

[0037] The following detailed description is merely exemplary and is not intended to limit application or use. Furthermore, it is not intended to be limited by the explicit or implicit theories presented in the foregoing description of the technical field, background art, invention summary, or accompanying drawings, or the following detailed description.

[0038] Figure 1 An electrolysis environment 10 according to various aspects of the present invention is shown. The electrolysis environment 10 includes a power source 20, a fluid supply device 30, an electrolysis system 40, and one or more product outlets 50.

[0039] Power source 20 is configured to supply power to electrolysis system 40. Power source 20 can provide power generated off-site and / or on-site. Off-site power source can be, for example, a power grid connected to electrolysis system 40. On-site power source can be, for example, renewable energy sources, including solar panels, wind collectors, hydrogen batteries (e.g., hydrogen fuel cells and hydrogen storage devices), or combinations thereof.

[0040] The fluid supply device 30 is configured to supply reactants to the electrolysis system 40. The reactants are configured to be broken down into their components by the electrolysis system 40. The reactants may be, for example, water, such that the electrolysis system 40 outputs diatomic hydrogen and diatomic oxygen. The fluid supply device 30 may also include one or more additives or mechanisms configured to facilitate the decomposition of reactants within the electrolysis system 40.

[0041] Electrolysis system 40 (refer to below) Figure 2 (In more detail) The system is configured to receive fluid from fluid supply device 30 and decompose reactants using electricity received from power source 20. The decomposition products are then supplied from electrolysis system 40 to product outlet 50.

[0042] Product outlet 50 is configured to store and / or transfer products generated by electrolysis system 40 to other parts of electrolysis environment 10. These products may be stored for on-site use, stored for off-site bulk transfer, transferred off-site via infrastructure, or a combination of the above. In some aspects, on-site use includes, for example, producing energy via fuel cells, generating heat through combustion, or a combination thereof. In some aspects, bulk transfer is carried out by supplying products to container vehicles, product-consuming vehicles (e.g., hydrogen-powered vehicles), or combinations thereof. In some aspects, electrolysis environment 10 includes at least one product infrastructure, and one or more products are supplied to the respective product infrastructure.

[0043] Figure 2 An example electrolysis system 40 for electrolysis environment 10 is shown. In the illustrated embodiment, the electrolysis system 40 is located within a container 90. Advantageously, the container 90 allows the electrolysis system 40 to be transported between different locations and deployed for temporary or indefinite use. The electrolysis system 40 includes a fluid input stream 42, a power input device 44, an electrolysis cell stack 100, and one or more output streams 46, 48.

[0044] Fluid input flow 42 is configured to store and / or deliver fluid to the electrolyzer stack. Fluid input flow 42 may include a fluid receiving element 42a, a fluid storage device 42b, and a stack inlet 42c.

[0045] The fluid receiving element 42a is configured to be connected to and receive reactants from the fluid supply device 30. The fluid can be received continuously or in batches.

[0046] The fluid storage device 42b is configured to store and / or buffer reactants input to the electrolytic cell stack 100. The fluid storage device 42b may be, for example, a fluid storage container and may store reactants at a predetermined pressure. The predetermined pressure may be, for example, atmospheric pressure, above atmospheric pressure, or below atmospheric pressure. In some aspects, the fluid storage device 42b is not included within the electrolysis system 40.

[0047] Stack inlet 42c is configured to deliver reactants from an upstream portion of fluid input stream 42 to the electrolyzer stack. Stack inlet 42c may include one or more mechanisms configured to regulate the products for the electrolyzer stack. For example, stack inlet 42c may include a plurality of valves and / or pumps configured to maintain and / or regulate the pressure and flow rate of reactants entering the electrolyzer stack 100.

[0048] The power input device 44 is configured to store and / or supply power used by the electrolytic cell stack. The power input device 44 may include a power receiving element 44a and a power storage device 44b. The power receiving element 44a is configured to be connected to and receive power from the power source 20. The power storage device 44b is configured to store and / or buffer the power input to the electrolytic cell stack 100. The power storage device 44b may be, for example, a battery or a capacitor.

[0049] Electrolytic cell stack 100 (see below) Figure 3 (To be described in further detail) It is configured to use electricity received from power input device 44 to decompose the reactants into a variety of products.

[0050] Each output stream 46, 48 is configured to deliver one or more corresponding products from the electrolyzer stack to the product outlet 50 of the electrolysis environment 10. Output streams 46, 48 may include a hydrogen output stream 46 and an oxygen output stream 48.

[0051] Hydrogen output stream 46 is configured to deliver hydrogen produced by the electrolyzer stack to one or more corresponding product outlets 50. Hydrogen output stream 46 may include, for example, a hydrogen storage device 46a and a hydrogen output element 46b.

[0052] Hydrogen storage device 46a is configured to store and / or buffer hydrogen produced by the electrolyzer stack 100. Hydrogen storage device 46a may, for example, be a hydrogen storage device configured to store hydrogen in a predetermined form. This predetermined form may be, for example, storing hydrogen under pressure or converting hydrogen into hydrogen complexes or hydrogen-containing molecules. Hydrogen complexes or hydrogen-containing molecules may be configured to store and release hydrogen based on changes in one or more physical properties of the hydrogen storage device. In some aspects, hydrogen storage device 46a is not included within the electrolysis system 40.

[0053] Hydrogen output element 46b is configured to connect to one or more corresponding product outlets 50 and deliver hydrogen produced by the electrolyzer stack 100 to these outlets. The hydrogen can be transferred continuously or in batches.

[0054] Oxygen output stream 48 is configured to deliver oxygen generated by electrolyzer stack 100 to one or more corresponding product outlets 50. Oxygen output stream 48 may include, for example, an oxygen storage device 48a and an oxygen output element 48b.

[0055] Oxygen storage device 48a is configured to store and / or buffer oxygen produced by the electrolyzer stack 100. Oxygen storage device 48a may be, for example, an oxygen storage container configured to store pressurized oxygen. In some aspects, oxygen storage device 48a is not included within the electrolysis system 40.

[0056] Oxygen output element 48b is configured to connect to one or more corresponding product outlets 50 and deliver oxygen generated by the electrolyzer stack 100 to these outlets. The oxygen can be transferred continuously or in batches.

[0057] The output stream may also include several optional components. For example, the output stream may include one or more by-product output streams, one or more flow separation elements, one or more flow conditioning elements, and a recirculation stream.

[0058] The by-product output stream is configured to transfer one or more by-products generated during decomposition within the electrolytic cell stack 100 to one or more output devices of the electrolytic environment 10.

[0059] Stream separation elements are configured to separate a portion of a received stream into one or more outputs. For example, a stream separation element may be or include elements configured to separate hydrogen from water, oxygen from water, reactants from products, reactants from contaminants, or combinations thereof.

[0060] Flow control elements are configured to regulate a given flow to provide the desired composition or physical state. For example, flow control elements can be configured to change the temperature of the flow, the pressure of the flow, humidify the flow, dehumidify the flow, or combinations thereof.

[0061] The recirculation flow is configured to receive reactant material recovered through, for example, a flow separation element, and to deliver the reactant material to the fluid input flow 42.

[0062] Figure 3 A partial exploded view of an electrolytic cell stack 100 according to various aspects of the present invention is shown. The electrolytic cell stack 100 includes one or more electrolytic cells 102. Each electrolytic cell 102 includes a membrane electrode assembly 104 between a pair of polarization plates 106.

[0063] The membrane electrode assembly 104 includes an anode 108 and a cathode 110 electrically isolated by a membrane layer 112. The anode 108 is configured to decompose reactants into their constituent components. For example, the anode 108 is configured to decompose water into molecular oxygen, protons, and electrons via the oxygen evolution reaction. The anode 108 environment includes a high potential that readily oxidizes certain materials, such as carbon materials.

[0064] The cathode 110 is configured to precipitate products by combining one or more decomposition products with provided electrons. For example, the half-reaction of the cathode 110 can be the hydrogen evolution reaction, which produces gaseous hydrogen by combining protons received from the membrane with an equal number of electrons.

[0065] Membrane 112 is configured to transport ions from anode 108 to cathode 110 while inhibiting electron transfer therethrough. Membrane 112 can also be configured to inhibit the transfer of reactants, certain decomposition products, and / or decomposition byproducts therethrough. For example, membrane 112 may allow or facilitate proton transfer while inhibiting or preventing the transfer of water and molecular oxygen therethrough. In some aspects, the membrane is a proton exchange membrane configured to transfer protons therethrough. The proton exchange membrane can be, for example, a NAFION. TM .

[0066] The membrane electrode assembly 104 can have suitable designs, such as a three-layer design, a five-layer design, a seven-layer design, etc. Although the designs shown and described below are symmetrical in terms of the number of layers and the size of each corresponding layer, asymmetrical designs with different numbers of layers, different layer thicknesses, and / or different layer sizes on the anode and cathode sides are conceivable.

[0067] In the three-layer design (or “catalyst-coated film”), both the anode 108 and the cathode 110 include a catalyst layer 114. The anode-side catalyst layer 114 includes anode-side catalyst particles 202 (e.g., reference...). Figure 4 Further discussion concerns iridium oxide particles 202, configured to promote decomposition reactions while resisting degradation under the operating conditions of the electrolyzer 102. For example, the anode-side catalyst particles 202 are configured to resist oxidation while oxidizing water in the high-potential environment of the anode 108, and to maintain structural integrity at the operating temperature of the anode 108. For instance, if the anode-side catalyst particles 202 provide higher oxidation resistance in an oxidizing environment, anode-side catalyst particles 202 with lower activity for the oxygen evolution reaction may be preferred over particles with higher activity. The anode-side catalyst layer 114 can also be configured to promote the transfer of hydrated protons to the membrane. The anode-side catalyst particles 202 can be, for example, iridium oxide particles, iridium-containing particles, iridium oxide-coated particles, etc.

[0068] The anode-side catalyst layer 114 also includes corrosion-resistant conductive nanoparticles 204 (reference). Figure 4 (To be further discussed), it is configured to enhance the performance of the anode-side catalyst layer 114. For example, corrosion-resistant conductive nanoparticles 204 are configured to optimize interfacial contact and reduce in-plane discontinuities in the anode-side catalyst layer 114.

[0069] Anode-side catalyst particles 202 and corrosion-resistant conductive nanoparticles 204 are incorporated into a matrix. This matrix can be, for example, an ionomer.

[0070] The cathode-side catalyst layer 114 includes catalyst particles configured to promote the reduction of protons to gaseous hydrogen. The cathode-side catalyst particles can be, for example, platinum particles, platinum-containing particles, platinum-coated particles, or combinations thereof. The cathode-side catalyst particles are bonded to the matrix, for example, by an ionomer.

[0071] In the five-layer design, the anode 108 and cathode 110 include a catalyst layer 114 and a diffusion layer 116. In other words, the five-layer design is a three-layer design with a diffusion layer 116 on each side of the catalyst coating film.

[0072] The anode-side diffusion layer 116 can be, for example, a porous transport layer. The porous transport layer is configured to transport reactants from the outer surface of the membrane electrode assembly 104 to the anode-side catalyst layer 114 for reaction, transport evolved molecular oxygen from the catalyst layer 114 to the outer surface of the membrane electrode assembly 104, and transport released electrons from the catalyst layer 114 to the outer surface of the membrane electrode assembly 104. The porous transport layer is formed of a porous, conductive material that is oxidation-resistant in the high potential and oxygen-rich environment of the anode 108 and has a robust structure under the stacking compression and operating temperatures of the electrolyzer 102. The porous transport layer can be formed of, for example, titanium.

[0073] The cathode-side diffusion layer 116 can be, for example, a gas diffusion layer. The gas diffusion layer is configured to transport the evolved products (e.g., gaseous hydrogen) from the cathode-side catalyst layer 114 to the outer surface of the membrane electrode assembly 104, and to transport supplied electrons from the outer surface of the membrane electrode assembly 104 to the catalyst layer 114. The gas diffusion layer is formed of a porous, conductive material that has a robust structure under the stacking compression and operating temperature of the electrolyzer 102. The gas diffusion layer can be formed of, for example, carbon fibers, carbon particles, carbon nanoparticles, binder materials, or combinations thereof.

[0074] In the seven-layer design, the anode 108 and cathode 110 include a catalyst layer 114 and a diffusion medium. In other words, the seven-layer design is a three-layer design with a diffusion medium on each side of the catalyst coating film. The diffusion medium includes at least a first layer and a second layer.

[0075] The first layer is disposed adjacent to the catalyst layer 114. The first layer is configured to enhance the performance of the catalyst layer 114. For example, the first layer may be configured to inhibit the permeation of ionic polymers and / or catalyst particles from the catalyst layer 114 into the diffusion medium. In a further example, the first layer may be configured to inhibit excess mass flow of reactants into the catalyst layer 114. In an even further example, the first layer may be configured to facilitate the transfer of reaction byproducts or by-products from the catalyst layer 114 to the diffusion medium. In yet another further example, the first layer may facilitate electron transfer between the catalyst layer 114 and the diffusion medium by increasing the contact area with the catalyst particles (more than the contact area of ​​a separate second layer). In some aspects, the first layer is a microporous layer.

[0076] The second layer is located on the outer surface of the membrane electrode assembly 104. The second layer is configured to facilitate mass transfer and electron transfer between the catalyst layer 114 and the outer surface of the membrane electrode assembly 104. For example, the second layer may be configured to facilitate mass transfer of water between the outer surface of the membrane electrode assembly 104 and the catalyst layer 114. In a further example, the second layer may be configured to facilitate mass transfer of gaseous hydrogen or molecular oxygen from the catalyst layer 114 to the outer surface of the membrane electrode assembly 104. In some aspects, the second layer is a diffusion layer 116, such as a gas diffusion layer or a porous transport layer.

[0077] In some aspects, the anode-side diffusion medium is a porous transport medium. A porous transport medium may, for example, include a microporous layer as a first layer and a porous transport layer as a second layer.

[0078] The anode-side microporous layer can be configured to optimize the function of the electrolyzer 102 by, for example, increasing interfacial contact with the catalyst layer 114, preventing the migration of ionic polymers or catalyst particles into the porous transport layer, optimizing interfacial contact resistance, optimizing mass transfer or combinations thereof by reducing capillary pressure, etc. The microporous layer can be formed of a suitable material, such as titanium with the desired pore size and density.

[0079] The anode-side diffusion layer 116 can be, for example, a porous transport layer. The porous transport layer is configured to transport reactants from the outer surface of the membrane electrode assembly 104 to the anode-side catalyst layer 114 for reaction, transport evolved molecular oxygen from the catalyst layer 114 to the outer surface of the membrane electrode assembly 104, and transport released electrons from the catalyst layer 114 to the outer surface of the membrane electrode assembly 104. The porous transport layer is formed of a porous, conductive material that is oxidation-resistant in the high potential and oxygen-rich environment of the anode 108 and has a robust structure under the stacking compression and operating temperatures of the electrolyzer 102. The porous transport layer can be formed of, for example, titanium.

[0080] In some aspects, the cathode-side diffusion medium is a gas diffusion medium. The gas diffusion medium may include, for example, a microporous layer as a first layer and a gas diffusion layer as a second layer.

[0081] The cathode-side microporous layer can be configured to optimize the function of the electrolyzer 102 by, for example, increasing interfacial contact with the catalyst layer 114, preventing the migration of ionic polymers or catalyst particles into the porous transport layer, optimizing interfacial contact resistance, and enhancing the hydrophilicity of the cathode-side diffusion medium, thereby suppressing the back diffusion of hydrogen through the membrane. The cathode-side microporous layer can be formed of, for example, a conductive material and a polymer binder material. The conductive material can be, for example, conductive particles formed from one or more carbon materials. The polymer material can be, for example, a hydrophilic or hydrophobic polymer. In some aspects, the polymer binder material is a polymer matrix that suspends the conductive particles in a loading sufficient to provide the desired conductivity.

[0082] The cathode-side diffusion layer 116 can be, for example, a gas diffusion layer. The gas diffusion layer is configured to transport the evolved products (e.g., gaseous hydrogen) from the cathode-side catalyst layer 114 to the outer surface of the membrane electrode assembly 104, and to transport supplied electrons from the outer surface of the membrane electrode assembly 104 to the catalyst layer 114. The gas diffusion layer is formed of a porous, conductive material that has a robust structure under the stacking compression and operating temperature of the electrolyzer 102. The gas diffusion layer can be formed of, for example, carbon fibers, carbon particles, carbon nanoparticles, binder materials, or combinations thereof.

[0083] The polarization plate 106 is configured to transfer charge from an adjacent cathode 110 or anode 108. Each side of the polarization plate 106 includes a flow field configured to transport fluid through it. The fluid in each flow field can be, for example, one or more reactants, one or more products, or a coolant. The polarization plate 106 can have low electrical resistance, high mechanical stability, and high chemical stability. The polarization plate 106 can also have high thermal conductivity.

[0084] Each anode-side polarization plate 106 is electrically connected to at least one other anode-side polarization plate 106, and each cathode-side polarization plate 106 is electrically connected to at least one other cathode-side polarization plate 106. The anode-side polarization plate 106 is electrically isolated from the cathode-side polarization plate 106. Each polarization plate 106 is disposed adjacent to at least one electrolytic cell 102, and may be a single polarization plate or a dual polarization plate.

[0085] Each single-polarization plate is disposed adjacent to a single electrolytic cell 102 and includes a first surface opposite to the second surface. The first surface of the single-polarization plate includes a flow field, for example, for one or more reactants or one or more products. Whether the flow field transports reactants or products depends on whether the single-polarization plate is adjacent to the anode 108 or the cathode 110. The second surface of the single-polarization plate may include a flow field configured to transport coolant therethrough.

[0086] Each dual-polarized plate is located between a pair of electrolytic cells 102. The dual-polarized plate will be adjacent to the anode 108 or cathode 110 of the pair of electrolytic cells 102. Each dual-polarized plate includes a first surface opposite to the second surface and a body between the first and second surfaces. Both the first and second surfaces of the dual-polarized plate include flow fields to transport one or more reactants or one or more products. Whether the flow fields transport reactants or products depends on whether the single-polarized plate is adjacent to the anode 108 or the cathode 110. The body may include flow fields configured to transport coolant therethrough. The dual-polarized plate can be formed, for example, by placing two single-polarized plates back to back and bonding them together.

[0087] Electrolyzer 102 also includes a gasket 120, for example, disposed around one or more of the catalyst layer 114, diffusion layer 116, and diffusion medium. The gasket 120 is configured to reduce and / or balance the compressive forces applied to an effective portion of the membrane electrode assembly 104. The gasket 120 is also configured to provide a fluid seal between the plate and the membrane layer 112.

[0088] The electrolytic cell stack 100 also includes end plates 118. End plates 118 are located at the top and bottom of the electrolytic cell stack 100. End plates 118 include multiple port groups. Each port group includes an inlet port and an outlet port. Each port group is fluidly connected to one or more channels of a flow field within the electrolytic cell stack 100 to form a fluid loop. For example, a fluid loop may deliver a corresponding fluid from the inlet port to the inlet of the flow field through, for example, a first set of through-holes in the plates and gaskets 120. The corresponding fluid may then be delivered through the corresponding flow field to the outlet of the flow field. After leaving the flow field, the corresponding fluid may be delivered through, for example, a second set of through-holes in the plates and gaskets 120 to the outlet port. As used herein, “fluid” can refer to reactants, products, coolants, or any combination thereof, depending on the context. For example, “fluid inlet” may refer to any one or all of a reactant inlet, an oxidant inlet, or a coolant inlet, depending on the context, while “product channel” may refer to a channel for delivering desired products and / or byproducts, depending on the context. It is conceivable that one or more port groups may include a fluid inlet or fluid outlet on one end plate 118, while the remaining fluid outlets or fluid inlets are located on opposite end plates 118, such that the corresponding fluid loops extend longitudinally through the electrolyzer stack 100.

[0089] End plate 118 is also configured to engage a compression member, which is configured to apply a compressive force to the electrolytic cell stack 100 along the stacking direction. The compressive force is configured to hold the components of the electrolytic cell stack 100 in place through contact pressure between adjacent components. In some aspects, the compression member includes a plurality of threaded rods that structurally engage with the end plate 118. The threaded rods can be tightened to increase the compressive force to a desired magnitude along the stacking direction, resulting in a contact pressure distribution along the interface between longitudinally adjacent components.

[0090] Figure 4 This is a side view of the anode 108 of the membrane electrode assembly 104, including a membrane layer 112, an anode-side catalyst layer 114, and a porous transport layer. The anode-side catalyst layer 114 is formed of a mixture of anode-side catalyst particles 202 and corrosion-resistant conductive nanoparticles 204 within a binder (not shown).

[0091] The anode-side catalyst particles 202 are configured to promote the decomposition reaction while resisting degradation under the high potential and high temperature conditions of the electrolyzer 102. For example, the anode-side catalyst particles 202 are configured to oxidize water while resisting oxidation in the high potential environment of the anode 108 and maintaining structural integrity under the high temperature conditions present in the anode 108. In the illustrated embodiment, the anode-side catalyst particles 202 are made of iridium oxide (IrO). x The catalyst particles 202 on the anode side can be formed. It is conceivable that they may include other materials or may be support particles coated with iridium oxide.

[0092] The anode-side catalyst particles 202 have a high surface area to optimize contact with reactants while reducing the loading value. For example, the anode-side catalyst particles 202 can achieve a high surface area using a porous structure. For example, the surface area measured by the Brunauer-Emmett-Teller (“BET”) method can be approximately 20 m². 2 / g to approximately 300m 2 / g.

[0093] In some aspects, the anode-side catalyst particles 202 may have an average diameter D50 of about 2 nanometers to about 250 nanometers. More specifically, the average diameter of the anode-side catalyst particles 202 may be about 10 nanometers to about 50 nanometers. The catalyst particles 202 can be selected to provide the desired unmixed packing density. The unmixed packing density can be measured by forming a coating that does not contain any corrosion-resistant conductive nanoparticles 204. In some aspects, the unmixed packing density of the anode-side catalyst particles 202 is about 1 g / cm³ to about 3 g / cm³. More ideally, the unmixed packing density of the anode-side catalyst particles 202 is about 1.2 g / cm³ to about 2.5 g / cm³. Those skilled in the art will recognize that the packing density of the catalyst particles 202 in the mixed catalyst layer 114 will be lower than the unmixed packing density of the catalyst particles 202.

[0094] The corrosion-resistant conductive nanoparticles 204 are configured to optimize the performance of the electrolyzer 102 while reducing the catalyst loading. The packing density of the corrosion-resistant conductive nanoparticles 204 is also lower than the packing density of the anode-side catalyst particles 202. The corrosion-resistant conductive nanoparticles 204 may have specific sizes and / or shapes to provide the desired unmixed packing density. The unmixed packing density can be measured by forming a coating free of any anode-side catalyst particles 202. In some aspects, the unmixed packing density of the corrosion-resistant conductive nanoparticles 204 is from about 0.5 g / cm³ to about 2.5 g / cm³. More ideally, the unmixed packing density of the corrosion-resistant conductive nanoparticles 204 is from about 1 g / cm³ to about 2 g / cm³. Those skilled in the art will recognize that the packing density of the corrosion-resistant conductive nanoparticles 204 in the mixed catalyst layer 114 will be lower than the unmixed packing density of the corrosion-resistant conductive nanoparticles 204.

[0095] Advantageously, the corrosion-resistant conductive nanoparticles 204 suppress voltage loss when the iridium loading decreases by providing conductive bridges between the anode-side catalyst particles 202 (otherwise, the anode-side catalyst particles 202 would be disconnected from each other). Furthermore, the corrosion-resistant conductive nanoparticles 204 can also dilute the anode-side catalyst particles 202, thereby producing a thicker catalyst layer 114 with the same catalyst loading. The thicker catalyst layer 114 with optimized thickness reduces contact resistance and increases interfacial contact between layers.

[0096] The optimal thickness of catalyst layer 114 depends on the surface characteristics of the layers adjacent to catalyst layer 114. For example, if the adjacent layer has a rough surface (e.g., a porous transport layer), the catalyst layer can have an optimal thickness of at least about 4 micrometers. In a further example, if the adjacent layer has a smooth surface (e.g., a microporous layer of a porous transport medium), the catalyst layer can have an optimal thickness of at least about 2 micrometers.

[0097] The corrosion-resistant conductive nanoparticles 204 may include one or more suitable materials, such that the corrosion-resistant conductive nanoparticles 204 are corrosion-resistant under the high potential and oxygen-rich conditions of the anode 108, can withstand the operating temperature of the anode 108, and can withstand the compression of the electrolytic cell stack 100.

[0098] The corrosion-resistant conductive nanoparticles 204 can be a homogeneous material or coated particles. The coated corrosion-resistant conductive nanoparticles 204 include a support and a coating. The support is configured to provide a structure and compatible surface to receive the coating thereon and withstand the temperature of the anode 108. Advantageously, the support provides space-filling alternatives for more valuable elements and compounds without reducing the effectiveness of the corrosion-resistant conductive nanoparticles 204. The support can be formed from, for example, titanium oxides (e.g., TiO2, Ti4O7), niobium oxides (e.g., Nb2O5), zirconium oxides (e.g., ZrO2), tantalum oxides (e.g., Ta2O5), or combinations thereof.

[0099] The coating is configured to withstand the high potential and oxygen-rich environment of the anode 108. The coating can be, for example, iridium, platinum, noble metals, their oxides, or combinations thereof. More specifically, the coating can be selected from the group consisting of iridium, platinum, and gold.

[0100] The coating is applied to the support in an amount sufficient to protect it from environmental impacts. In some embodiments, the coating is a continuous layer to form a core-shell structure. In some embodiments, the coating is discontinuous and applied in an amount sufficient to achieve the conductivity required across the corrosion-resistant conductive nanoparticles 204 and through the catalyst layer 114. In some embodiments, the platinum content in the coating is from about 40% to about 80% by weight, based on the weight of the particles.

[0101] In some aspects, the corrosion-resistant conductive nanoparticles 204 can be formed from one or more titanium oxides (e.g., TiO2, Ti4O7), iridium-coated oxides, noble metal oxides, noble metal-coated oxides, or combinations thereof. Iridium-coated oxides can be, for example, iridium-coated titanium oxides (e.g., Ir / TiO2), iridium-coated niobium oxides (e.g., Ir / Nb2O5), iridium-coated zirconium oxides (e.g., Ir / ZrO2), iridium-coated tantalum oxides (e.g., Ir / Ta2O5), or combinations thereof.

[0102] The noble metal oxide particles can be, for example, gold oxides and platinum oxides. The noble metal-coated oxides can be, for example, platinum-coated oxides and gold-coated oxides. Platinum-coated oxides can be, for example, platinum-coated titanium oxides (e.g., Pt / TiO2), platinum-coated niobium oxides (e.g., Pt / Nb2O5), platinum-coated zirconium oxides (e.g., Pt / ZrO2), platinum-coated tantalum oxides (e.g., Pt / Ta2O5), or combinations thereof. Gold-coated oxides can be, for example, gold-coated titanium oxides (e.g., Au / TiO2), gold-coated niobium oxides (e.g., Au / Nb2O5), gold-coated zirconium oxides (e.g., Au / ZrO2), gold-coated tantalum oxides (e.g., Au / Ta2O5), or combinations thereof.

[0103] Preferably, the corrosion-resistant conductive nanoparticles 204 are selected from the group consisting of Magnéli phase titanium oxide (Ti4O7), platinum-coated titanium dioxide (Pt / TiO2), platinum-coated niobium oxide (Pt / Nb2O5), platinum-coated zirconium oxide (Pt / ZrO2), and platinum-coated tantalum oxide (Pt / Ta2O5). In a further preferred example, the corrosion-resistant conductive nanoparticles 204 are selected from the group consisting of platinum-coated titanium dioxide (Pt / TiO2), gold-coated titanium dioxide (Au / TiO2), and iridium-coated titanium dioxide (Ir / TiO2). More preferably, the corrosion-resistant conductive nanoparticles 204 are platinum-coated titanium dioxide (Pt / TiO2). In an alternative, even more preferred aspect, the corrosion-resistant conductive nanoparticles 204 are iridium-coated titanium oxide (Ir / TiO2). Although not explicitly stated, the iridium-coated titanium oxide coating may be partially or completely oxidized before being incorporated into the catalyst layer 114.

[0104] The corrosion-resistant conductive nanoparticles 204 can have a particle size of about 2 nanometers to about 300 nanometers. The average particle size based on D50 is 10 nanometers to 150 nanometers. Advantageously, the size in this range enhances the electrical continuity between the catalyst particles 202 on the anode side and enhances the contact between the catalyst layer 114 and adjacent layers (e.g., porous transport layers).

[0105] The binder is configured to form a matrix to maintain the particle distribution in the catalyst layer 114. The binder may be, for example, an ionomer configured to provide ion transport to and / or from the anode-side catalyst particles 202.

[0106] The catalyst layer 114 comprises iridium oxide anode-side catalyst particles 202 and corrosion-resistant conductive nanoparticles 204 in a desired loading ratio. In some aspects, the weight ratio of corrosion-resistant conductive nanoparticles 204 to iridium oxide particles 202 is from about 0.5:1 to about 8:1. The desired iridium oxide loading and the desired layer thickness can be selected before choosing the weight ratio of iridium oxide to corrosion-resistant conductive nanoparticles 204. For example, if the adjacent layer has a rough surface (e.g., a porous transport layer) and the desired iridium oxide areal loading is about 0.1 mg / cm², the weight ratio of corrosion-resistant conductive nanoparticles 204 to iridium oxide particles 202 is selected from a value from about 0.5:1 to about 8:1, resulting in a catalyst layer with an optimized thickness of 4 micrometers. In a further example, if the adjacent layer has a smooth surface (e.g., a microporous layer of a porous transport medium), and the desired iridium oxide areal loading is approximately 0.1 mg / cm², the weight ratio of corrosion-resistant conductive nanoparticles 204 to iridium oxide particles 202 is selected from a value between approximately 0.5:1 and approximately 8:1, resulting in a catalyst layer with an optimized thickness of 2 μm. It can be seen that if a larger desired thickness of the resulting catalyst layer is desired, the selected weight ratio of corrosion-resistant conductive nanoparticles 204 to iridium oxide particles 202 can be increased to provide a catalyst layer 114 with a larger thickness at the same iridium oxide areal loading. Similarly, if a reduced iridium oxide are desired, the selected weight ratio of corrosion-resistant conductive nanoparticles 204 to iridium oxide particles 202 can be increased to provide a catalyst layer 114 with the same thickness.

[0107] Specifically, if the thickness of the mixed oxide catalyst layer 114 is 2 micrometers and the iridium oxide areal loading is 0.1 mg / cm², then the weight ratio of the selected corrosion-resistant conductive nanoparticles 204 to iridium oxide particles 202 is 3:1 to provide an iridium oxide packing density of 0.5 g / cm³. Similarly, if the thickness of the mixed oxide catalyst layer 114 is 4 micrometers and the iridium oxide areal loading is 0.1 mg / cm², then the weight ratio of the selected corrosion-resistant conductive nanoparticles 204 to iridium oxide particles 202 is 7:1 to provide an iridium oxide packing density of 0.25 g / cm³.

[0108] Figure 5This is a side view of the anode 308 of an example membrane electrode assembly, including a membrane layer 112, an anode-side catalyst layer 314, and a porous transport layer. The anode-side catalyst layer 314 is formed of the same number and amount of anode-side catalyst particles 202 as the membrane electrode assembly 104.

[0109] It can be seen that, although the loading weight of the anode-side catalyst particles 202 is the same, the anode-side catalyst layer 314 is thinner than the anode-side catalyst layer 114 of the electrolyzer stack 100. Furthermore, it can be seen that, despite the same loading weight of the anode-side catalyst particles 202, there is a significant electrical discontinuity between the anode-side catalyst particles 202. This discontinuity increases the voltage drop of the anode 308.

[0110] Those skilled in the art will understand that the present invention is readily adaptable to various modifications and alternatives, and that some representative embodiments have been illustrated by way of example in the accompanying drawings and described in detail above. However, it should be understood that the novel aspects of the invention are not limited to the specific forms shown in the drawings. Rather, the invention is intended to cover all modifications, equivalents, combinations, sub-combinations, arrangements, groupings, and alternatives that fall within the scope and spirit of the invention and are defined by the appended claims.

[0111] As used herein, unless the context clearly indicates otherwise: the words “and” and “or” should indicate both a parallel and a choice relationship, unless the context clearly indicates otherwise; the word “all” means “any and all”; the word “any” means “any and all”; the word “including” means “including but not limited to”; the singular forms “a”, “a” and “the” include the plural, and vice versa.

[0112] All numerical values ​​of parameters (e.g., quantities or conditions) in this specification, unless explicitly stated or clearly indicated by the context (including the appended claims), shall be understood to be modified by the term "about" in all cases, regardless of whether "about" actually precedes the numerical value. The numerical parameters listed herein and in the appended claims are approximate values ​​and may vary according to the desired characteristics obtained according to the invention. At least, no attempt is made to limit the application of the doctrine of equivalents to the scope of the claims; each numerical parameter should be interpreted at least according to the number of significant figures reported and the application of ordinary rounding techniques.

[0113] Approximate terms, such as “approximately,” “about,” “generally,” etc., may be used in this text with meanings such as “in, near, or almost in,” “within 0-10%,” or “within acceptable manufacturing tolerances,” or logical combinations thereof.

[0114] While those skilled in the art will readily understand the limits and scope of the term "about," the term "about" implies that the stated numerical value or property allows for imprecision. If the imprecision provided by "about" is not understood in its usual sense in the art, then "about" at least indicates a variation that may arise from the usual methods of measuring and using these parameters. For example, if there is no other understanding in the art, the term "about" means within 10% (e.g., ±10%) of the stated value.

[0115] While those skilled in the art will readily understand the limits and scope of the term "substantially," the term "substantially" implies that a certain degree of imprecision is permissible for the stated value or property. If the imprecision implied by "substantially" cannot be otherwise understood in the art for its usual meaning, then "substantially" at least indicates variation that may arise from manufacturing processes and the measurement of such parameters. For example, if there is no other understanding in the art, the term "substantially" means within 5% (e.g., ±5%) of the stated value.

[0116] While those skilled in the art will readily understand the limits and scope of the term "essentially," the term "essentially" implies that some slight inaccuracies are permissible in the stated numerical value or property. If the inaccuracy implied by "essentially" cannot be otherwise understood in the art for its usual meaning, then "essentially" means that variations in the desired parameter are at least negligible and likely insurmountable. For example, if there is no other understanding in the art, the term "essentially" refers to within 1% (e.g., ±1%) of the stated value.

[0117] While those skilled in the art will readily understand the boundaries and scope of the term "pure," it implies that a compound may contain very trace amounts of other materials. If the imprecision provided by "pure" is not understood in its usual sense within the art, then "pure" at least indicates variations that may arise from separation processes and measurements of such parameters. For example, unless otherwise understood in the art, the term "pure" refers to a purity greater than 99.9% of the material.

[0118] It should be understood that the ranges provided herein include the range, subranges within the range, and each value within the range. For example, the range of 5% to 20% should be interpreted as including not only the explicitly listed limit of about 5% to about 20%, but also individual values ​​such as 5%, 7%, 9%, 13%, etc., and subranges such as about 5% to about 9%, about 7% to about 10%, etc.

[0119] Although the best mode of carrying out the invention has been described in detail, those skilled in the art will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.

Claims

1. A catalyst layer, comprising: A homogeneous mixture of the following substances: Catalyst particles configured to promote water electrolysis, the catalyst particles comprising iridium and having a high surface area; as well as Corrosion-resistant conductive nanoparticles, configured to resist oxidation, reduce packing discontinuities of the catalyst particles, and provide conductive bridges between the catalyst particles; as well as A matrix configured to support the catalyst particles and the corrosion-resistant conductive nanoparticles.

2. The catalyst layer according to claim 1, wherein the catalyst particles are selected from the group consisting of iridium oxide particles or iridium oxide-containing particles.

3. The catalyst layer according to claim 1, wherein the corrosion-resistant conductive nanoparticles are selected from the group consisting of platinum-coated titanium dioxide (Pt / TiO2), gold-coated titanium dioxide (Au / TiO2), and iridium-coated titanium dioxide (Ir / TiO2).

4. The catalyst layer according to claim 1, wherein the corrosion-resistant conductive nanoparticles are platinum-coated particles, and the platinum content is 40% to 80% by weight based on the weight of the corrosion-resistant conductive nanoparticles.

5. The catalyst layer according to claim 1, wherein the average size of the corrosion-resistant conductive nanoparticles is 20 nanometers to 300 nanometers.

6. The catalyst layer according to claim 1, wherein the weight ratio of the corrosion-resistant conductive nanoparticles to the catalyst particles is 0.5:1 to 8:

1.

7. The catalyst layer according to claim 1, wherein the thickness of the catalyst layer is greater than 4 micrometers and the packing density of iridium oxide is less than 0.25 mg / cm³.

8. A membrane electrode assembly, comprising: Anode, the anode having a catalyst layer, the catalyst layer comprising: A homogeneous mixture of the following substances: Catalyst particles configured to promote water electrolysis, the catalyst particles comprising iridium and having a high surface area; and Corrosion-resistant conductive nanoparticles, configured to resist oxidation, reduce packing discontinuities in the catalyst particles, and provide conductive bridges between the catalyst particles; and A matrix configured to support the catalyst particles and the corrosion-resistant conductive nanoparticles; cathode; and A membrane located between the anode and the cathode.

9. An electrolytic cell, comprising: A membrane electrode assembly, comprising a membrane disposed between an anode and a cathode, wherein the anode has a catalyst layer comprising: A homogeneous mixture of the following substances: Catalyst particles configured to promote water electrolysis, the catalyst particles comprising iridium and having a high surface area; and Corrosion-resistant conductive nanoparticles, configured to resist oxidation, reduce packing discontinuities in the catalyst particles, and provide conductive bridges between the catalyst particles; and The matrix is ​​configured to support the catalyst particles and the corrosion-resistant conductive nanoparticles; and a pair of polarization plates are adjacent to opposite sides of the membrane electrode assembly, each of the polarization plates being electrically connected to and fluidly connected to the corresponding anode and cathode.

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