High Surface Area Anode Catalyst for Aem Electrolyzers

This application claims the benefit of Chinese Patent Application No. 202410702859.0, filed on May 31, 2024. The entire disclosure of the above application is incorporated herein by reference.

The present technology relates to advancements in electrochemical systems for efficient hydrogen and oxygen production within Anion Exchange Membrane (AEM) electrolyzers and, more specifically, catalyst layer compositions for use within AEM electrolyzers.

This section provides background information related to the present disclosure which is not necessarily prior art.

The field of electrochemical systems for hydrogen and oxygen production has been a subject of extensive research and development due to the growing demand for clean and sustainable energy sources. Anion Exchange Membrane (AEM) electrolyzers, which facilitate the electrolysis process to generate these gases, are critical components in this domain.

The reliance on precious metals such as platinum (Pt), iridium (Ir), and ruthenium (Ru) as catalysts in AEM electrolyzers has been a significant impediment to cost-effective hydrogen and oxygen production. Despite their catalytic prowess, the exorbitant cost of these materials contributes to the high capital expenditure of electrolyzer systems. This reliance on expensive catalysts renders the production of hydrogen and oxygen via electrolysis economically unviable when compared to conventional energy sources, thus stalling the potential for widespread adoption of this clean technology.

The integration of less-conductive catalysts within electrolytic cells has also presented a considerable challenge. Catalytic nanoparticles, known for their high surface area and potential for high reactivity, are rendered less effective without a mechanism for efficient electron transfer. This inefficiency in electron conduction hampers the overall performance of electrolyzers, creating a critical barrier to their efficacy and broader industrial application.

The use of high concentration alkaline solutions in AEM electrolyzers further compounds the challenges faced in the field. While these solutions facilitate the electrolysis process, they introduce maintenance and operational (M&O) complexities. The corrosive nature of these solutions necessitates robust safety measures, specialized handling, and the use of materials capable of withstanding such caustic environments. The additional requirements for managing these solutions not only increase the operational costs but also impose stringent safety protocols, further complicating the deployment of electrolytic technology.

There is a continuing need for a catalyst layer composition and an associated AEM electrolyzer structure that can efficiently incorporate less-conductive catalysts to provide an alternative to precious metal catalysts, thereby minimizing or eliminating the use of precious metals in the AEM electrolyzer and optimize electron transfer processes in operation. Desirably, the catalyst layer composition and an associated AEM electrolyzer structure reduce the need for caustic alkaline solutions by permitting for operation of the AEM electrolyzer without high concentration alkaline solutions, for enhanced efficiency, safety, and cost-effectiveness of the AEM electrolyzer.

In concordance with the instant disclosure, a catalyst layer composition and an associated AEM electrolyzer structure that can efficiently incorporate less-conductive catalysts to provide an alternative to precious metal catalysts, thereby minimizing or eliminating the use of precious metals in the AEM electrolyzer, optimize electron transfer processes in operation, and which reduce the need for caustic alkaline solutions by permitting for operation of the AEM electrolyzer without high concentration alkaline solutions, for enhanced efficiency, safety, and cost-effectiveness of the AEM electrolyzer, has surprisingly been discovered.

The present technology includes articles of manufacture, systems, and processes that relate to electrochemical systems and methods for hydrogen and oxygen generation, particularly to the development of catalyst layer compositions and AEM electrolyzers. More specifically, the technology pertains to the design and manufacturing of catalyst layers that provide a high surface area and conductive support in the form of meso porous particles with open pores, combined with less-conductive catalysts that are either grown on the surface of these particles through various deposition methods or mixed and adsorbed by the meso porous particles. The present disclosure further encompasses AEM electrolyzer structures that incorporate these catalyst layers, as well as methods for manufacturing such structures using spraying and decal processes. The technology aims to enhance the efficiency and safety of AEM electrolyzers by improving the surface area and conductive support for the anode catalyst, thereby facilitating the electrochemical reactions within the AEM electrolyzers necessary for the production of hydrogen and oxygen gases.

In one embodiment, a conductive meso porous catalyst layer for an AEM electrolyzer is disclosed, which includes a catalyst composition comprising meso porous particles with open pores, such as Raney nickel with diameters ranging from 5 to 100 micrometers, and a less-conductive catalyst such as nickel iron oxide (e.g., NiFeO). The less-conductive catalyst is either grown on the surface of the meso porous particles through a growth process or admixed with the meso porous particles. The growth process includes at least one of chemical deposition, electro-chemical deposition, hydrothermal deposition, and an etching of a surface of the meso porous particles, as non-limiting examples. The meso porous particles and the less-conductive catalyst are then either bonded by a thermal process or held together by a binder, providing a cohesive and functional catalyst layer for efficient operation of the AEM electrolyzer, and ensuring efficient electron transfer and enhancing the overall performance of the AEM electrolyzer.

In another embodiment, the present disclosure features an AEM electrolyzer structure that incorporates the aforementioned catalyst layer composition. This structure comprises a cathode side equipped with a bipolar plate or half plate, a porous transport layer, and a catalyst layer. On the anode side, the structure includes a similar bipolar plate or half plate, a porous transport layer, and a meso porous layer formed from the catalyst composition. The meso porous layer is a high surface area and conductive support layer. An anion exchange membrane separates the cathode and anode sides, ensuring efficient ion transfer and electrolysis process within the system.

In a further embodiment, the present disclosure describes a method for manufacturing an AEM electrolyzer structure. This method involves providing the catalyst layer composition as detailed above, applying it to a porous transport layer through a spraying process, and then assembling the AEM electrolyzer structure with the applied catalyst layer composition. The spraying process may utilize a nitrogen airbrush to ensure even distribution and adherence of the catalyst composition to the transport layer.

In yet another embodiment, the present disclosure outlines an alternative method for manufacturing an AEM electrolyzer structure. This method also starts with the provision of the catalyst layer composition. However, in this case, the composition is applied to the porous transport layer using a decal process. This involves casting the catalyst ink having the catalyst layer composition onto a substrate and then transferring the dried ink to the porous transport layer. The AEM electrolyzer structure is then assembled with the applied catalyst layer composition, ensuring a robust and efficient electrolysis system.

In a particular embodiment, a catalyst layer system is affixed to the surface of a porous transport layer (PTL) for an anode side of an electrolyzer. This system is composed of a blend of non-conductive catalytic nanoparticles, such as nickel iron oxide (NiFeO), and conductive meso-particles made from non-precious materials, such as a nickel alloy, with a high surface area. These components are cohesively bound using a polymeric binder, specifically polytetrafluoroethylene (PTFE), for example, at a concentration of 5-10% by weight, creating a unified layer where the less-conductive catalyst is intimately integrated with the conductive framework provided by the meso-particles.

The layer system is characterized by the dispersion of non-conductive catalytic particles throughout the conductive matrix of metallic meso-particles, such as a nickel alloy. This strategic distribution facilitates a substantial improvement in electron transfer capabilities, thereby enhancing the operational efficiency of the electrolyzer. The result is a system that performs electrolysis more effectively due to the optimized electron pathways within the catalyst layer.

The production of the meso-particles for this catalyst layer system is achieved through methods such as spraying or mechanical transfer processes, followed by thermal post-treatment. This manufacturing approach is notably simpler and more user-friendly compared to traditional methods that require the construction of multiple catalytic and conductive layers or employ complex techniques like electrospinning under high-voltage fields (e.g., electrospinning on 10-30 kV field strength) to produce nanofibers.

By applying precise compression to the PTL during the assembly of the electrolytic cell, the resulting catalyst layer is further rendered more compact and is positioned in closer proximity to the membrane. This arrangement significantly reduces the distance hydroxide ions must travel to reach the membrane, leading to improved electrolyzer performance. Consequently, there is no longer a need for high concentration alkaline solutions or precious metal particles to facilitate electron conduction within the electrolyzer, resulting in a more cost-effective and economically advantageous system.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

The following description of technology is merely exemplary in nature of the subject matter, manufacture and use of one or more inventions, and is not intended to limit the scope, application, or uses of any specific invention claimed in this application or in such other applications as may be filed claiming priority to this application, or patents issuing therefrom. Regarding methods disclosed, the order of the steps presented is exemplary in nature, and thus, the order of the steps can be different in various embodiments, including where certain steps can be simultaneously performed, unless expressly stated otherwise. “A” and “an” as used herein indicate “at least one” of the item is present; a plurality of such items may be present, when possible. Except where otherwise expressly indicated, all numerical quantities in this description are to be understood as modified by the word “about” and all geometric and spatial descriptors are to be understood as modified by the word “substantially” in describing the broadest scope of the technology. “About” when applied to numerical values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by “about” and/or “substantially” is not otherwise understood in the art with this ordinary meaning, then “about” and/or “substantially” as used herein indicates at least variations that may arise from ordinary methods of measuring or using such parameters.

All documents, including patents, patent applications, and scientific literature cited in this detailed description are incorporated herein by reference, unless otherwise expressly indicated. Where any conflict or ambiguity may exist between a document incorporated by reference and this detailed description, the present detailed description controls.

Although the open-ended term “comprising,” as a synonym of non-restrictive terms such as including, containing, or having, is used herein to describe and claim embodiments of the present technology, embodiments may alternatively be described using more limiting terms such as “consisting of” or “consisting essentially of.” Thus, for any given embodiment reciting materials, components, or process steps, the present technology also specifically includes embodiments consisting of, or consisting essentially of, such materials, components, or process steps excluding additional materials, components or processes (for consisting of) and excluding additional materials, components or processes affecting the significant properties of the embodiment (for consisting essentially of), even though such additional materials, components or processes are not explicitly recited in this application. For example, recitation of a composition or process reciting elements A, B and C specifically envisions embodiments consisting of, and consisting essentially of, A, B and C, excluding an element D that may be recited in the art, even though element D is not explicitly described as being excluded herein.

As referred to herein, all compositional percentages are by weight of the total composition, unless otherwise specified. Disclosures of ranges are, unless specified otherwise, inclusive of endpoints and include all distinct values and further divided ranges within the entire range. Thus, for example, a range of “from A to B” or “from about A to about B” is inclusive of A and of B. Disclosure of values and ranges of values for specific parameters (such as amounts, weight percentages, etc.) are not exclusive of other values and ranges of values useful herein. It is envisioned that two or more specific exemplified values for a given parameter may define endpoints for a range of values that may be claimed for the parameter. For example, if Parameter X is exemplified herein to have value A and also exemplified to have value Z, it is envisioned that Parameter X may have a range of values from about A to about Z. Similarly, it is envisioned that disclosure of two or more ranges of values for a parameter (whether such ranges are nested, overlapping or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges. For example, if Parameter X is exemplified herein to have values in the range of 1-10, or 2-9, or 3-8, it is also envisioned that Parameter X may have other ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3, 3-10, 3-9, and so on.

When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be 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.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. 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 embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below”, or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The present technology improves the efficiency and safety of electrolytic cells by introducing a meso porous layer composed of meso porous particles with open pores, which significantly enhances catalytic activity. This innovative approach allows for the use of lower KOH solution concentrations, contributing to a safer maintenance and operational environment, and eliminates the need for precious metals, thus reducing costs. The manufacturing process is simplified, resulting in a more user-friendly and cost-effective production, while also achieving lower catalyst loading without compromising the high performance, stability, and durability of the electrolyzer.

illustrates a meso porous catalyst layerformed from a catalyst composition, which is a critical component of the AEM electrolyzer. The catalyst compositionwithin this layer includes meso porous particles, characterized by open poresthat facilitate catalytic reactions. The meso porous particlesmay be Raney nickel as a non-limiting example. One of ordinary skill in the art may also select other suitable materials for the meso porous particleswithin the scope of the present disclosure.

The open poresof the present disclosure may be provided by certain activation processes, for example. Activation process within the scope of this disclosure will include, in order, first, providing the alloy without pores, and then providing the less-conductive catalyst, and then forming the pores in the alloy by leaching out the aluminum, and then, finally, application of the less-conductive catalyst. It should be appreciated that the application of the less-conductive catalyst may be completed substantially simultaneously with the formation of the pores, for example, by a leaching process, as described further herein. The employment of pre-activated particles, or the employment of other suitable activation process, are also contemplated and considered to be within the scope of the present disclosure.

In particular, where the meso porous particlesinclude the Raney nickel, the Raney nickel may be manufactured through the activation process, which involves the selective leaching of aluminum from NiAl alloy particles using strong alkaline chemicals such as KOH. This activation process creates a high surface area material that is highly reactive. As used herein, the term “high surface area” means a surface area of a particle that is a typical high range would be around 100 m/g or more. One of ordinary skill in the art may also select other suitably high surface area parameters for the meso porous particles, as desired.

Due to its reactivity, activated Raney nickel must be carefully stored under specific conditions to maintain its structural integrity. If exposed to air while dry, the material can spontaneously ignite, resulting in the loss of its high surface area. Consequently, activated Raney nickel is typically preserved in water or diluted KOH solution to prevent such occurrences. Handling activated Raney nickel presents challenges, particularly during processes such as spraying, drying of catalyst layers, and any form of heat treatment. Therefore, to mitigate the risk of combustion, these procedures are conducted under an inert atmosphere such as Argon, as a non-limiting example.

An alternative approach to circumvent this issue involves forming the catalyst layer using NiAl alloy and subsequently initiating the activation process. This method allows for the creation of the mesoporous structure after the catalyst layer has been established. At least some of the ‘less conductive’ catalyst will adhere to the newly formed mesoporous surface during activation, and at least a portion may be washed away. To address this challenge, one potential solution is to synthesize the less-conductive catalyst directly within or on the surface of the preformed catalyst layer.

The less-conductive catalyst, is strategically integrated with the meso porous particles, either through a deposition process or by being admixed and adsorbed. This integration is necessary for the performance of the catalyst, as it ensures a high degree of contact between the catalyst and reactants. When the less-conductive catalystis introduced to activated Raney nickel, the risk of ignition is reduced, yet the potential for combustion remains a concern, and the use of an inert gas environment such as Argon, for example, is advised during handling. The less-conductive catalystmay be at least one of nickel iron oxide (NiFeO), Fe-LDH (i.e., layered double hydroxide), high entropy multi-metal LDH like FeNiCoMnCr-LDH, and NiFeCoO, as particular non-liming examples. A skilled artisan may also select other suitable materials for the less-conductive catalystconsistent with the present disclosure, as desired.

It should be appreciated that conductivity is the inverse of resistance. Conductivity quantifies how well a material conducts electricity. Higher conductivity values mean better electrical flow. In view of this understanding, as used herein, the term “less-conductive”pertains to a catalyst, designated as, which exhibits at least the following characteristics.

In the event that the catalystis provided in a powdered state, the catalystis required to be compacted between a pair of gold-coated copper plates for testing to determine that the catalystis sufficiently “less-conductive,” resulting in a compressed layer with a thickness of 0.1 millimeters. The compression must be executed at a pressure of 1 Megapascal (MPa). The resistance specific to the area, ascertained between the gold-coated copper plates, must exceed 100 milliohm-square centimeters (mOhm cm). This measurement of resistance must be conducted while maintaining the pressure at 1 MPa.

In the event that the catalystis synthesized atop mesoporous particles, the catalystmust be detached to yield a powdered form for such testing. In situations where detachment is not feasible, the catalystshould be cultivated on an alternative substrate that permits its subsequent removal for testing to determine that the catalystis sufficiently “less-conductive.”

One skilled in the art may also select other suitable testing parameters for determining whether or not the catalystis sufficiently “less-conductive” within the meaning of the present disclosure, as desired.

The meso porous particlesand the less-conductive catalystare one of bonded by a thermal process, and held together by the binder. It should be appreciated that the meso porous particlesare what are bonded or held by the binder, and not necessarily the less-conductive catalyst, when the binderis employed. As a non-limiting example, the thermal process can be a plasma spraying process. One of ordinary skill in the art may also select other suitable thermal processes for the bonding of the meso porous particlesand the less-conductive catalystwithin the scope of the present disclosure.

Where the binderis used, the bindercan be a polytetrafluoroethylene (PTFE) dispersion as one non-limiting example, serves to maintain the structural integrity of the catalyst composition by holding the meso porous particlesand the less-conductive catalysttogether. It should be appreciated that one skilled in the field may also select other suitable materials for the binderunder the teachings of the present disclosure.

The open poresof the meso porous particlesmay be selected with sizes ranging from 2 nanometers to 5 micrometers, more particularly from 5 nanometers to 1 micrometer, and most particularly between 20 nm and 500 nm in diameter. In a most particular embodiment, the open pores may have a size ranging from 10 nanometers to 5 micrometers. The open poresmay provide an optimized structure for enhanced catalytic reactions within the AEM electrolyzer. A skilled artisan may select other suitable ranges of size for the open poresunder the present disclosure, as desired.

The meso porous particles, which may be the Raney nickel as a non-limiting example, are a significant portion of the catalyst composition, and may make up 60-95% by weight, for example. The precise size range of the open pores, between 10 nm and 50 nm in diameter, may be selected to maximize the surface area available for catalysis while maintaining structural stability. The less-conductive catalyst, which may be nickel iron oxide (NiFeO) as a non-limiting example, is carefully chosen for its catalytic properties. The less-conductive catalystmay constitute 1-20% by weight of the catalyst composition. The binder, which may be a PTFE dispersion, may be present at a concentration of 3-15% by weight within the catalyst composition, ensuring that the catalyst particles are adequately bonded to the support structure. Other suitable concentrations for the meso porous particles, the less-conductive catalyst, and the bindermay also be employed, as desired.

The meso porous layer is affixed to an additional conductive support layer, known as a porous transport layer (PTL), which is shown asin. The PTL may feature additional open pores up to 1 millimeter in size, for example. The PTL is essential for facilitating effective mass transport and electron flow within the electrolyzer, contributing to the overall efficiency of the system.

The catalyst particles may be strategically grown or deposited as well onto the surface areas of the conductive support (e.g., the meso porous layer) to enhance electrochemical reactions, particularly within the open pores, to maximize the active surface area available for electrolytic reactions. This design consideration may be employed for enhancing the electron transfer efficiency, which directly impacts the performance and stability of the AEM electrolyzer.

Typically, the microporous layer is added on top of the additional conductive support. However, where the additional conductive support is metal foam with the additional open pores, the microporous layer may alternatively engineered to ensure that the catalyst particles are either distributed on an outer surface of the metal foam or uniformly distributed within the additional open pores of the metal foam. This uniform distribution may be desired for optimizing the utilization of the catalyst and promoting uniform reaction rates across the electrolyzer. Additionally, in certain examples, the conductive support may undergo a surface modification process to increase the affinity of the catalyst particles to the support, ensuring a strong bond and high durability of the meso porous catalyst layer.

The conductive support with open pores may be seamlessly integrated into the AEM electrolyzer, forming an interface with adjacent layers that minimizes potential barriers to ion and electron transport. This integration is optimized for operation in specific ranges of pH, temperature, and electrolyte concentration, making the system suitable for a wide variety of electrolysis applications. The design also allows for compatibility with various types of less-conductive catalysts, providing flexibility in catalyst selection based on desired electrolysis performance characteristics.

Referring now toan AEM electrolyzer systemis depicted, which includes an anion exchange membrane, a cathode side, and an anode side. The cathode sidecomprises a bipolar plate, a porous transport layer, and a catalyst layer. The anode sideincludes a bipolar plate, a porous transport layer, and a meso porous catalyst layerderived from the catalyst composition. The meso porous catalyst layeron the anode side is specifically configured to enhance electron transfer, which may provide for efficient hydrogen generation.

With reference toa flowchart describing a method for manufacturing an AEM electrolyzer system is presented, and which encompasses stepsto, and particularly involving a spraying procedure. The method may include a stepof providing the catalyst composition as described herein. A stepmay include applying a meso porous catalyst layer to a porous transport layer by a spraying process that incorporates the catalyst composition. The method may also include a stepthat involves assembling the AEM electrolyzer structure with the meso porous catalyst layer applied to the porous transport layer. The spraying process may utilize a nitrogen airbrush, which may be selected for its ability to provide a uniform and fine distribution of the catalyst composition onto the porous transport layer.

outlines a method for manufacturing an AEM electrolyzer structure, and which includes stepsto. A stepinvolves providing the catalyst composition as described herein. A stepincludes applying a meso porous catalyst layer to a porous transport layer by a decal process. A stepas shown ininvolves assembling the AEM electrolyzer structure with the meso porous catalyst layer applied to the porous transport layer. The decal process may involve casting a catalyst ink that includes the catalyst composition onto a substrate and transferring the catalyst ink after drying to the porous transport layer. This decal process may be chosen for its precision and ability to create a uniform catalyst layer with controlled thickness.

illustrates a method for manufacturing an AEM electrolyzer system, and which includes stepsto, and particularly involving a decal procedure. A stepinvolves preparing the catalyst composition as described herein. A stepas shown inincludes applying the meso porous catalyst layer to a porous transport layer for placement on an anode side of an anion exchange membrane. A stepinvolves assembling the AEM electrolyzer system with a cathode side and anode side separated by the anion exchange membrane.

The method may also include a step of activating the meso porous particles to enhance catalytic activity. The assembling step may include aligning bipolar plates or half plates with the anion exchange membrane to form an integrated cell structure. The method may also include a step of conditioning the anion exchange membrane in alkali-ion form prior to assembly. The applying step may further include a thermal treatment to sinter the catalyst layer composition onto the porous transport layers, in certain examples.