Flow Field Alkaline Electrolyzer and Method of Manufacture

This application claims the benefit of U.S. Provisional Application No. 63/574,789 filed 4 Apr. 2024, which is incorporated in its entirety by this reference.

This invention relates generally to the electrolysis field, and more specifically to a new and useful system and method in the electrolysis field.

The following description of the embodiments of the invention is not intended to limit the invention to these embodiments, but rather to enable any person skilled in the art to make and use this invention.

As shown in, an electrolyzercan include one or more electrolyzer cellwhere each electrolyzer cell can include an anolyte transport layer, an anode, a cathode, a catholyte transport layer, and a separator. In some variants, one or more of the components of the electrolyzer cell can be integrated into a single component. For example, a membrane electrode assembly can be formed (e.g., an integrated anode, separator, cathode where the separator is between the anode and cathode), the anolyte transport layer and anode and/or catholyte transport layer and cathode can be the same, and/or other suitable combinations of components can be formed. The electrolyzer is preferably an alkaline water electrolyzer (e.g., an electrolyzer where the anolyte and catholyte are water with a pH greater than 11; an electrolyzer where the anolyte and catholyte are water with a hydroxide salt such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, iron (II) hydroxide, aluminium hydroxide, europium (II) hydroxide, thallium (I) hydroxide, etc.; etc.). Additionally or alternatively, an anolyte and/or catholyte can contain carbonate salts such as potassium carbonate, potassium bicarbonate, sodium carbonate, lithium carbonate, sodium acetate, potassium acetate, and/or other suitable basic salt(s) (typically dissolved in water, but potentially using other solvent). In one specific example, the electrolyzer can use a mixed carbonate/hydroxide electrolyte. In other variants, the electrolyzer can be an anion exchange membrane electrolyzer, a Kolbe electrolyzer, and/or other suitable electrolyzer.

In specific examples of the electrolyzer cells at least one of the anolyte transport layer or the catholyte transport layer are preferably a flow cell design. The use of at least one flow cell can result in a significant reduction of applied voltage required to drive the water splitting reaction for a given current density and/or can allow a larger current density (and thus a larger resulting quantity of hydrogen) for a given voltage (see for example). In a first variation (as shown for example inandand also referred to as an ‘asymmetric electrolyzer cell’ design), a flow field designcan be used only as an anolyte transport layer (e.g., the catholyte transport layer can leverage an elastic element). In a second variation (as shown for example inandand also referred to as an ‘asymmetric electrolyzer cell’ design), a flow field designcan be used only a catholyte transport layer (e.g., the anolyte transport layer can leverage an elastic element). In a third variation (as shown for example inandand also referred to as a ‘symmetric electrolyzer cell’ design), both a catholyte transport layer and an anolyte transport layer can have a flow cell design,. In a fourth variation (as shown in. and, and also referred to as a ‘symmetric electrolyzer design’), both a catholyte transport layer and an anolyte transport layer can have elastic elements,. In a fifth variation, an electrolyzer can include a plurality of different electrolyzer cells (e.g., an electrolyzer can include a combination of two or three of the electrolyzer cells of the first, second and/or third preceding variations). However, any suitable electrolyzer and/or electrolyzer cell(s) can be realized.

Variants of the technology can confer one or more advantages over conventional technologies.

First, variants of the technology can enable higher current density alkaline electrolysis performance thereby enhancing the electrolysis reaction (e.g., producing additional hydrogen). For example, variants of the technology can enable current densities exceeding about 0.3 A/cm(e.g., 0.3 A/cm, 0.5 A/cm-, 1 A/cm-, 2 A/cm-, 5 A/cm-, 10 A/cm-, etc.) by reducing the amount of overpotential resulting from bubble formation and/or by enabling increased catalyst site access. In one example, these higher current densities resulted in an electrolyzer with a power density 20 times higher than and 9× more efficient than conventional alkaline electrolyzers. However, other power densities and/or efficiencies can be observed.

Second, variants of the technology can enable the creation of detailed flow structures at low material and/or processing costs. For example, nickel (or other metal) sheets can be hydroformed to generate uniform flow field structures. In this variant, the use of thin metal sheets (e.g. less than 200 microns, less than 500 μm, etc.) can result in cells that are up to 20× (e.g., 2×, 5×, 6×, 8×, 10×, 15×, etc.) thinner than conventional alkaline electrolyzers (and can thereby increase a volumetric power density) and/or can reduce the cost of materials in comparison to traditional bipolar plates.

Third, variants of the technology can design flow fields such that the total energy consumed by the electrolyzer (e.g., electrical energy consumed in electrolysis, hydraulic energy for transporting the electrolyte, etc.) is reduced. For example, parallel flow fields can be used to minimize a pressure drop and thereby reduce hydraulic power required to achieve a high velocity flow. Additionally, variants of the technology can be beneficial for thermal management of the electrolyzer cell (e.g., heat rejection, maintaining a target temperature, etc.).

Fourth, variants of the technology can include inlet and/or outlet features (e.g., into each electrolyte cell, into a subset of electrolyte cells such as alternating electrolyte cells, etc.) which can increase the electrolyte path at the manifolds. In these variants, the increased electrolyte path can provide a technical advantage by increasing electrolyte resistance thereby decreasing shunt currents (i.e., parasitic ionic current traveling from cell to cell through the manifold as opposed to through the electrolyzer cell) and/or otherwise resulting in increased electrolyzer efficiency.

However, further advantages can be provided by the system and method disclosed herein.

As shown in, an electrolyzer can include one or more electrolyzer cell where each electrolyzer cell can include an anode, an anolyte transport layer, a cathode, a catholyte transport layer, and a separator.

In some variants, one or more of the components of the electrolyzer cell can be integrated into a single component. For example, a membrane electrode assembly can be formed (e.g., an integrated anode, separator, cathode where the separator is between the anode and cathode), the anolyte transport layer and anode and/or catholyte transport layer and cathode can be the same,, and/or other suitable combinations of components can be formed.

The electrolyzer is preferably an alkaline water electrolyzer (e.g., an electrolyzer where the anolyte and catholyte are water with a pH greater than 11; an electrolyzer where the anolyte and catholyte are water with a hydroxide salt such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, iron (II) hydroxide, aluminium hydroxide, europium (II) hydroxide, thallium (I) hydroxide, etc.; etc.). Additionally or alternatively, an anolyte and/or catholyte can contain carbonate salts such as potassium carbonate, potassium bicarbonate, sodium carbonate, lithium carbonate, sodium acetate, potassium acetate, and/or other suitable basic salt(s) (typically dissolved in water, but potentially using other solvent). In one specific example, the electrolyzer can use a mixed carbonate/hydroxide electrolyte. In other variants, the electrolyzer can be an anion exchange membrane electrolyzer, a Kolbe electrolyzer, and/or other suitable electrolyzer (e.g., variants of the technology can be applicable to PEM electrolyzers, bipolar electrolyzers, etc.).

The electrolyzer (and/or cells thereof) can be cylindrical, cubic, prismatic, spherical, or any suitable geometry. For example, the inventors have found that a cylindrical electrolyzer can result in uniform flow distributions and electrolyte pressure and can reduce the accumulation of bubbles throughout the electrolyzer or cells thereof. However, other geometries can be used (e.g., to optimize electrolyte contact with the electrode, increase hydrogen production efficiency, for pressure distribution, etc.).

The electrolyzer preferably includes a plurality of electrolyzer cells. The electrolyzer cells are preferably arranged in series (e.g., stacked). However, the electrolyzer cells can be arranged in parallel and/or have any suitable arrangement. For example, an electrolyzer can include 5, 10, 50, 100, 500, 1000, 5000, 10000, and/or any suitable number of electrolyzer cells. Each electrolyzer cell in a stack is preferably substantially the same (e.g., constructed in the same manner but with potential differences in manufacturing, alignment, etc.). However, an electrolyzer can include electrolyzer cells with different constructions (e.g., a combination of symmetric and asymmetric electrolyzer cells can be used within a common electrolyzer stack).

The electrolyzer cells are preferably implemented in a zero-gap configuration (e.g., electrodes in contact with the separator and having the smallest possible distance between them, forming an electrode membrane assembly, etc.). However, the electrodes can have any suitable separation distance between the electrode and the separator.

The electrodes (e.g., anode, cathode) can be made of catalytic material (e.g., made of a material that catalyzes the electrolytic reaction of the respective electrode), include a support material (e.g., disposed with catalytic material such as coated with, containing, alloyed with, etc.), can be layered with (and/or intermixed with) the separator (e.g., catalytic material can be included on, integrated with, etc. the separator such as to form a membrane electrode assembly), and/or can otherwise be designed. For instance, a support material can include a support membrane, a porous material, a support substrate, a foam (e.g., metal foam), a woven material, and/or any suitable support material can be used. The support material can be porous, fibrous, engineered, roughened, mesh, and/or can otherwise achieve a target surface area (e.g., a large specific surface area such as >5 m/g, >10 m/g, >20 m/g, >50 m/g, >100 m/g, >150 m/g, >200 m/g, >500 m/g, >1000 m/g, values or ranges therebetween, etc. as measured using BET or other surface area measurement techniques). Examples of support materials include: steel (e.g., steel mesh, steel fiber, etc.), nickel (e.g., nickel mesh, nickel foam, etc.), carbon fiber (e.g., carbon fiber paper, carbon paper, etc.), titanium (e.g., titanium mesh, titanium foam, etc.), alkaline anion exchange membrane (AAEM), polymers (e.g., a polytetrafluoroethylene (PTFE) frame, mesh, etc.), and/or any suitable materials. In some variations, separate current collectors and gas separators can be used. However, additionally or alternatively, the support material (and/or other suitable component) can function as the spacer and/or membrane. Examples of catalyst materials can include: noble metals and their oxides (e.g. platinum, iridium, ruthenium, etc.), transition metals and their oxides (e.g. nickel, cobalt, iron, copper, etc.), and metal alloys and their oxides (e.g., Ni—Fe alloys, Ni—Mo alloys, Ni—Co alloys, etc.), nickel compounds (e.g., nickel hydroxide, nickel oxyhydride, etc.). The oxide can have any crystal structure (e.g., perovskite, spinel, rutile, etc.). In some variations, the catalyst material can include (e.g., in addition to or as an alternative to the above materials) other non-metal dopants (e.g., lanthanide perovskites) and/or sulfide, carbide, phosphide, boride, chalcogenide, and/or nitride variants of the aforementioned materials. However, any suitable catalyst(s) (with any suitable form factor such as nanoparticles, mesoparticles, microparticles, macroparticles, coating, conformal coating, etc.) can be used. In some variations, water dissociation catalysts (e.g., nickel (II) hydroxide), hydrogen evolution reaction catalysts, and/or oxygen evolution reaction catalysts can be used.

The separator preferably functions to electrically isolate the anode and the cathode, hinder (e.g., minimize, prevent, etc.) gas crossover (e.g., oxygen and hydrogen) between the anode from the cathode, enable (e.g., permit, facilitate, etc.) ionic and/or molecular conduction between the anode and the cathode (e.g., enabling flow of protons, water, etc. between the anode and cathode). However, the separator can otherwise function. The separator is preferably in contact with at least one of the anode and/or the cathode (e.g., forming a membrane electrode assembly, to form a zero gap electrolyzer cell, etc.). However, the separator can be separate from (e.g., with an offset such as maintained by a frame of the electrolyzer and/or electrolyzer cell) the anode and the cathode.

The separator can be made of asbestos, composite (e.g., a polysulfone matrix with zirconium oxide powder such as a Zirfon®, polyphenylene sulfide coated with zirconium oxide such as Ryton, etc.), polymers (e.g., polyantimonic acid, polytetrafluoroethylene, polyquinoxaline, polyphenylquinoxaline, etc.), metal oxides (e.g.,: zirconium oxide, aluminium oxide, nickel oxide, titanium oxide, zinc oxide, iron oxide, tin oxide, chromium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, radium oxide, vanadium oxide, copper oxide, manganese oxide, lead oxide, cerium oxide, beryllium oxide,), ceramics and/or refractory-type materials (e.g., potassium titanate, zirconium silicate, silicon carbide, boron nitride, barium titanate, sodium titanate, etc.), sintered nickel (or other metals, preferably with an oxide coating such as barium titanate, sodium titanate, zirconia, magnesium oxide, titanium oxide, etc.), anion exchange membranes, cation exchange membranes, bipolar membranes, and/or other suitable separator material(s) can be used.

The anolyte transport layer functions to bring anolyte (e.g., alkaline water) into contact with the anode and/or to capture oxidized anolyte (e.g., oxygen) from the anode.

The anolyte transport layer (e.g. elastic element, flow field, etc.) can be characterized by a thickness. This thickness is preferably between 50 microns and 10000 microns (e.g. 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 110 microns, 120 microns, 130 microns, 140 microns, 150 microns, 160 microns, 170 microns, 180 microns, 190 microns, 200 microns, 220 microns, 250 microns, 300 microns, 333 microns, 350 microns, 400 microns, 425 microns, 450 microns, 460 microns, 480 microns, 495 microns, 500 microns, 750 microns, 900 microns, 1000 microns, 1100 microns, 1150 microns, 1175 microns, 1200 microns, 1300 microns, 1500 microns, 1750 microns, 2000 microns, 2235 microns, 2300 microns, 2500 microns, 3000 microns, 3250 microns, 4100 microns, 5000 microns, 6000 microns, 7500 microns, or any value therebetween). Different layers of the anolyte transport layer (e.g., elastic element, flow field, bipolar plate, etc.) can have different thicknesses. In a specific variant, the inventors found that an anolyte transport layer thickness (e.g., a thickness of a bipolar plate defining flow channels of the anolyte transport layer) of approximately 150 microns was suitable for flowing the anolyte across the anode while maintaining reaction efficiency and mechanical robustness. In variants, thinner anolyte transport layers can be used which can reduce cost of material consumption. In other variants, thicker anolyte transport layers can be used for increased mechanical support and can allow for larger flow volumes.

The anolyte transport layer can be circular (example shown in), rectangular (example shown in), square, triangular, polygonal, or any suitable shape (e.g., typically, but not necessarily, matching a shape of the electrolyzer or cell). In a first example, the electrolyzer can be cylindrical and have a circular anolyte transport layer. In another example the electrolyzer can be prismatic and have a rectangular or square anolyte transport layer.

The anolyte transport layer preferably leverages a flow field (e.g., anode flow field or anolyte flow field when used on an anode size of the membrane) which can be beneficial for removing bubbles (e.g., of oxygen formed as the water is oxidized) formed on the anode and thereby reducing an overpotential resulting from bubbles on the anode surface and enabling operation of the electrolyzer cell with greater current density. The flow fields can additionally or alternatively be beneficial for thermal management of the electrolyzer cell (e.g., heat rejection, maintaining a target temperature, etc.) and/or for other purposes. However, the anolyte transport layer can additionally or alternatively include a diffusive transport (e.g., porous, fibrous, elastic etc.) transport layer such as shown inand) and/or other suitable mechanisms for transporting anolyte to the anode.

The flow field structures (e.g., features engineered to generate the flow fields) can be channels in a substrate, protrusions form a substrate, engineered structures (e.g., on an electrode surface), and/or can otherwise be formed. In a specific example, the flow field structures can be engineered in a bipolar plate (e.g., nickel sheet). In one variant, structures can be engineered on a single surface of the bipolar plate. In another variant, structures can be engineered on both surfaces of the bipolar plate (e.g., to enable a flow field on one side toward an anode and on the other side toward a cathode for a subsequent electrolyzer cell within an electrolyzer stack, where the structures are typically identical on opposing surfaces of the bipolar plate). However, the flow field structures can otherwise be engineered.

The flow field structures can include a plurality of parallel flow fields (e.g., parallel straight flow fields), a singular flow field, a tortuous flow field (e.g., serpentine flow field, boustrophedonic flow field, Archimedean spiral flow field, etc.), a plurality of tortuous flow fields (e.g., parallel tortuous flow fields, multipath flow fields, double-armed Archimedean spiral flow field with an example shown in, etc.), pin type flow fields (e.g., mesh flow fields, two-phase flow fields, etc.), and/or other suitable flow fields. Variants that use a plurality of flow fields can be advantageous for minimizing a pressure drop (thereby reducing the amount of hydraulic power required to achieve a high velocity flow). Variants that use a tortuous flow field can be advantageous for reducing a risk of electrode failure resulting from a blockage in the channel (e.g., can have good electrolyte removal properties).

The flow field can be angular, curved, and/or have any suitable structure(s). The flow field shape (e.g., whether angular or curved flow fields are used) can be chosen to match an electrode shape. However, the flow field channel shape can otherwise be selected. In variants that use curved flow fields, each flow field channel typically has a different curvature to optimize for a density of channels achievable on the cell (as shown for example in).

The flow field structures can include (e.g., define) any number of separate flow fields (e.g., any number of channels, grooves, protrusions, etc. creating channels through which the anolyte can pass). In a first variant, the flow field can have a single tortuous (e.g., boustrophedonic as shown in, serpentine as shown in, etc.) flow field channel that spans the area of the anolyte transport layer. In a second variant, the anolyte transport layer can have a plurality of flow field channels (e.g., regions where electrolyte can flow through). The number of channels can be between one channel and hundreds of channels, depending on the geometry of the electrolyzer cell and the channels (e.g., 1 channel, 5 channels, 10 channels, 20 channels, 50 channels, 60 channels, 100 channels, 200 channels, 300 channels, 500 channels, or any number of channels therebetween). For example, a variant of the flow field channels can include a fewer number of wide channels (e.g., 2-10 channels) to achieve a greater volume of electrolyte flow and contact with the electrodes (within each channel). Another variant may include a larger number of thin channels (e.g., 20-80) which can result in high flow rates, minimize formation of and/or retention time on the electrode surface of bubbles, and/or mitigate an impact of clogging within a singular or small number of channels. Any number of channels may be used in order to achieve electrolyzer performance objectives. Typically, in variants with a plurality of flow field channels, the flow field channels will be in parallel (i.e., only fluidly connected at a manifold proximal an inlet and an outlet of the flow field channel). However, in some examples, the flow field channels can be in series (e.g., include bypasses, flow channels, etc. enabling fluid communication directly between channels), which can be beneficial for redistributing flow in the event of a blockage within a given flow field channel.

A flow field channel can have characteristic dimensions. These characteristic dimensions can include depth, width, curvature (e.g., as measured by a radius of curvature), or any other suitable measurement. The depth of the flow channel can be between 0.01 millimeters and 2 cm (e.g., 0.01 mm, 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 1 cm, 2 cm, etc.). The depth of the flow channel can be optimized to control the flow rate, flow characteristics (e.g., laminar vs turbulent flow), and/or other properties of the flow. In a specific example, the inventors have found that a flow channel depth of 0.5 mm was suitable for enabling a flow velocity that readily evacuates bubbles from the electrode surface produced using current densities of interest (e.g., as described above). The width of the flow channel can be between 0.5 mm and 2 cm (e.g., 0.5, 0.8 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 1 cm, 1.1 cm, 1.2 cm, 1.3 cm, 1.4 cm, 1.5, 2 cm, values or ranges therebetween, etc.). Similarly, the width of walls between the flow channels (e.g., structures or regions where electrolyte does not flow) can be between 0.1 mm and 10 cm. However, other channel widths and/or structure widths may work in some variants.

In variants, all channels can have the same characteristic dimensions. In another variant, each channel may have different characteristic dimensions. In other variants, a subset of the channels can share a subset of the same characteristics. For example, a variant of the flow field can include a plurality of channels, each with the same depth and width but with varying curvatures (e.g., length of the flow channel). Additionally or alternatively, the characteristic dimensions can vary across the length of the flow channels. For instance, the channels can be deeper or wider at various positions along the flow path. In one specific example (as shown for instance in), a channel can have a greatest width (and taper therefrom) at the midpoint of the channel along the flow direction. In a second specific example, a channel can have a greatest width at one end of the channel (e.g., inlet or outlet) tapering to a smallest width at the opposing end of the channel (e.g., outlet or inlet respectively). In a third specific example, a channel can have a greatest width at the ends (e.g., inlet and outlet) tapering to a narrowest width in the middle of the flow channel (e.g., leveraging the Venturi effect), example shown in. In other specific examples, a channel can be deepest or shallowest at the midpoint (e.g., middle) of the flow path, examples shown in. However, the channels depth and width can be otherwise varied. This fluctuation in depth and width can be beneficial for controlling the local flow pressure and/or rate throughout the flow path to optimize the electrolyzer performance.

In variants that include a plurality of flow fields and/or channels, another characteristic dimension can include distance between (e.g., wall to wall distance, channel center to channel center distance, etc.) channels or the channel spacing. The channel spacing can vary across the length of the flow path and between individual channels, examples shown in. Spacing of the channels can vary between 0.5 mm and 20 mm (e.g., 0.5 mm, 1 mm, 2, mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or any suitable value). In a specific variant of the flow field that includes a plurality of channels with different curvatures, some adjacent channels near the center of the flow field can have a first spacing while some adjacent channels along the periphery (e.g., outside) of the flow field can have spacings that are up to or greater than 5 times the first spacing (e.g., depending on curvature, variation in the channel characteristic dimensions, size of the electrolyzer cell, etc.), examples shown inand. Spacing of the channel may also be characterized by a ratio between the width of the channel and the spacing. For example, the spacing can be half the channel width (e.g. 1:2) or twice the channel width (e.g. 2:1). Other possible ratios for the spacing and channel width include 1:5, 1:4, 1:3, 1:1, 3:1, 4:1, 5:1, or any other suitable ratio. The spacing between channels can be tuned based on a target flow rate, electrolyte conversion rate, electrolyte distribution, mechanical stability, electrical contact, and/or based on other suitable properties of the electrolyzer or electrolyte. For instance, smaller spacings can result in more contact of the electrolyte to the anode, but can result in decreased mechanical robustness of the anolyte flow layer and/or worse electrical contact between the anolyte flow layer and an electrode.

Each flow field channel can also have different cross-sectional areas orthogonal to the flow direction. The cross-section of the flow channel can be rectangular, rounded, circular, semicircular, triangular, trapezoidal, or otherwise shaped. Different cross-sectional shapes may be used to modify the flow volume, flow pressure, flow rate, and/or other flow properties (e.g., laminar vs turbulent flow). For example, rounded and/or circular cross sections can be used to prevent accumulation of bubbles and/or fluid constriction. The cross-sectional shape can vary across the length of the flow path. For example, in a variant the flow path can transition from having a rectangular cross-section to having a rounded cross-section towards the middle of the flow path. However, the cross-sectional shape can be otherwise varied.

Each flow field channel can also include various geometric features. For example, a flow channel might have grooves, protrusions, dimples, divots, pins, and/or other structural characteristics that line the walls or bed of the channel. These various geometric features can function to alter the flow velocity within each channel and/or mitigate bubbles. Each channel can include any or all of these geometric features, with these geometric features positioned anywhere throughout the flow path. These geometric features can be positioned on key points to control flow, can be spaced evenly or sporadically throughout the flow path, or can be otherwise positioned. In a specific example, dimples or dips can be spaced evenly throughout the flow path, example shown in.

The flow field structures are preferably sized to enable high velocity electrolyte flow at the electrode surface. The high velocity electrolyte flow is preferably at least 0.5 m/s (e.g., 0.46 m/s, 1/s, 1.5 m/s, 2 m/s, 5 m/s, 10 m/s, values or ranges therebetween, etc.). To achieve a target total energy use (e.g., to enable the electrolyzer to operate using renewable energy), the high velocity electrolyte flow is preferably less than a threshold value (e.g., 10 m/s). To achieve the high velocity electrolyte flow, the shape, material, dimensions, and/or other properties of the flow field structures can be tuned. One exemplary embodiment of a flow field structure (as shown for instance in) included channel walls where a channel width was approximately three times a wall thickness and the channel wall height can be about 40% of the wall thickness (e.g., a channel width of about 3.75, a wall width of about 1.25, and a channel wall height of about 0.5). In some variations, a surface roughness of the channel walls can be less than about 0.2 Ra. However, other channel geometries can be realized (e.g., for different materials, for different electrolytes, for different operating temperatures, to achieve a critical flow rate, etc.).

The flow field can optionally include a manifold and/or an inlet and/or outlet structure that modifies the flow pressure before entrance to the functional flow path of the transport layer or after exiting the functional flow path of the transport layer, example shown in. The electrolyzer can have an anolyte inlet manifold, catholyte inlet manifold, an anolyte outlet manifold, and/or a catholyte outlet manifold. The manifold can be configured to maintain and/or control the flow rate and pressure between electrolyzer cells (e.g., to ensure that electrolyte enters each electrolyzer cell at a target pressure and rate). In a specific variant, the manifold can include a separate flow path spanning between 3 mm and hundreds of millimeters (e.g., 3 mm, 5 mm, 10 mm, 25 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1000 mm, or any values therebetween). In another variant, the manifold flow path can have a larger cross sectional area than those of the flow field flow channels to encourage even flow distribution. The flow path of the manifold can form any shape or geometry. The manifold flow path can be straight (example shown in), curved (example shown in), boustrophedonic (example shown in), serpentine, can form a loop (examples shown in), or can be otherwise shaped. The outlet and inlet manifolds can be on opposite sides of the transport plate, on the same side (examples shown inB andC), or otherwise positioned. In variants, the manifold flow path can be in-line and/or on the same plane as the functional flow path. In other variants, the manifold flow path may be misaligned and/or out-of-plane of the functional flow path.

In variants, the inlet manifolds and outlet manifolds can be the same structurally and geometrically. In other variants the outlet manifold can be different from the inlet manifold (e.g., to account for gas flow), examples shown in. For example, in variants the outlet manifold can include a flow path with a larger width or cross-sectional area to account for the produced gas.

A catholyte transport layer preferably functions to transport catholyte (e.g., alkaline water) to the cathode and/or transport reduced catholyte (e.g., hydrogen gas) away from the cathode. In some variants, the catholyte transport layer can be identical to the anolyte transport layer. In other variants, the catholyte transport layer can have a structure as described above for the anolyte transport layer, but the catholyte transport layer and the anolyte transport layer can have different designs (e.g., a boustrophedonic and serpentine flow field respectively, a porous transport layer and a flow field transport layer respectively, similar channel flow paths with different channel depths and widths for each transport layer, etc.).

In variants of the technology that include asymmetric electrolyzer cells, preferably the catholyte transport layer is the non-flow field transport layer (i.e., the anolyte transport layer is a flow field transport layer). However, in these variants, the catholyte transport layer can be the flow field transport layer.

In variants of the technology that include symmetric electrolyzer cells, the flow direction on the anolyte and catholyte are preferably substantially parallel (e.g., electrolyte flows in the same direction, flow paths differ by less than about 50, flow paths overlap spatially over at least 90% of the flow channel width, etc.). However, the flow direction can be antiparallel (e.g., electrolyte flows from top to bottom on one side of the separator and the opposite direction on the opposing side), the flow fields can be substantially perpendicular (e.g., form an angle between 85°-95°), the flow fields can intersect (e.g., at an angle between 5° and 85°), the flow fields can be staggered (e.g., minimally spatially overlap), and/or the flow fields can have any suitable relationship between one another.

In variants of the technology, the electrolyzer can have the same or different anolyte and/or catholyte transport layers for each electrolyzer cell. For example, a variant of the electrolyzer can include a plurality of cells, where each cell has the same anolyte and catholyte transport layer (for a symmetric electrolyzer cell variant). Other variants of the electrolyzer may have a plurality of cells, in which the cells have different anolyte and catholyte transport layers. The anolyte and catholyte transport layers can differ across the stack of cells (e.g., to control and modify the flow rates, flow velocities, flow pressures, etc. across the electrolyzer). For example, an electrolyzer can include cells with transport layers in the middle of the cell stack that reduce the flow velocity compared to cells at an end of the flow stack. In another variant, transport layers optimized to increase flow pressure may be spaced periodically, consistently, sporadically throughout the electrolyzer stack. However, an electrolyzer stack can include other suitable flow structure differences between individual cells.

Components of the electrolyzer (and/or electrolyzer cells thereof) are preferably formed using hydroforming (e.g., hydromechanical deep drawing or ‘hydromec’, aquadraw, bulge forming, explosive forming, explosive hydroforming, rubber pad forming, etc.). In particular, the formation of anolyte and/or catholyte flow fields (e.g., structures for generating flow fields) can be performed using hydroforming as hydroforming enables the reproducible formation of fine details at low material and/or process costs. For example, thin (e.g., <1 mm, <0.5 mm, <0.2 mm, <0.1 mm,,<0.05 mm, etc.) nickel (or other metals such as aluminium, iron, stainless steel, titanium, etc.) can be hydroformed to produce bipolar plates that include flow field structures. Additionally or alternatively, embossing, hollow embossing, hollow embossing rolling, repoussage, coining, casting, drawing, electrohydraulic forming, electromagnetic forming, forging, incremental micro forming, milling, stamping, press hardening, progressive stamping, punching, sinking, spinning, swaging, tube bending, and/or other suitable processes (e.g., depending on materials, sizes, geometries, etc.) can be used to form the components of the electrolyzer.

Components of the electrolyzer (and/or electrolyzer cells thereof) may be coupled together via welding, brazing, soldering, fittings, and/or using other suitable attachment mechanisms. For example, the components or cells can be welded together using steel, aluminum, copper, titanium, and/or any suitable material. In an example, the anolyte transport plate and/or catholyte transport plate can be welded to the anode and cathode with aluminium. However, variants of the technology can use adhesives, screws, or other suitable methods to couple the transport plates to the electrodes or to couple any other components of the electrolyzer.

As shown in, a method of operating an electrolyzer can include: introducing anolyte and catholyte to an alkaline electrolyzer S; oxidizing the anolyte and reducing the catholyte S; and processing the products S. The method is preferably performed using an alkaline water electrolyzer (e.g., as described above). However, the method can be performed using other suitable electrolyzers (e.g., PEM electrolyzer, AEM electrolyzer, etc.). The method preferably functions to produce hydrogen using an alkaline water electrolyzer. At the anode of the electrolyzer, the chemical reaction, 2OH→HO+½O+2e, can be performed. At the cathode of the electrolyzer, the chemical reaction, 2 HO+2 e→H+2OH, can be performed. The method can result in the overall reaction: HO→H+½O.

Introducing anolyte and catholyte to an alkaline electrolyzer Sfunctions to pass electrolyte through the alkaline electrolyzer to react electrochemically. Scan be performed continuously, periodically, in batches, and/or with any other timing. Scan be performed by using pumps to introduce the anolyte and catholyte to the alkaline electrolyzer.

The anolyte and catholyte are preferably water with a pH greater than about 11. For example, the anolyte and catholyte can be water with a hydroxide salt such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, iron (II) hydroxide, aluminium hydroxide, europium (II) hydroxide, thallium (I) hydroxide, and/or any other hydroxide salt (or other basic salt). However, in variants the anolyte and/or catholyte can contain carbonate salts such as potassium carbonate, potassium bicarbonate, sodium carbonate, carbonic acid, lithium carbonate, and/or other suitable basic salt(s). In other variants, the electrolyte can be mixed carbonate/hydroxide electrolytes.

The introduction of electrolyte (e.g., anolyte, catholyte, etc.) to the electrolyzer can be controlled based on various parameters. For example, the electrolyte can be introduced at a flow rate between 0.1 liters per minute per cell and 300 liters per minute per cell (e.g. 0.1 L/min/cell, 0.2 L/min/cell, 0.5 L/min/cell, 0.6 L/min/cell, 0.8 L/min/cell, 1 L/min/cell, 1.5 L/min/cell, 2 L/min/cell, 2.1 L/min/cell, 2.3 L/min/cell, 2.4 L/min/cell, 2.5 L/min/cell, 2.6 L/min/cell, 2.7 L/min/cell, 2.8 L/min/cell, 2.9 L/min/cell, 3 L/min/cell, 3.1 L/min/cell, 3.2 L/min/cell, 3.3 L/min/cell, 3.4 L/min/cell, 3.5 L/min/cell, 3.6 L/min/cell, 3.7 L/min/cell, 3.8 L/min/cell, 3.9 L/min/cell, 4 L/min/cell, 5 L/min/cell, 10 L/min/cell, 20 L/min/cell, 30 L/min/cell, 50 L/min, 75 L/min, 100 L/min, 125 L/min, 150 L/min, 200 L/min, 250 L/min, values or ranges therebetween, etc.). The flow rate can alternatively be greater than 30 liters per minute per cell (e.g., to increase hydrogen production, to further facilitate bubble desorption from electrode surface, etc.). In variants, local mass flow rates (e.g., amount of electrolyte entering a cell, amount of electrolyte leaving a cell, amount of electrolyte entering a flow channel, amount of electrolyte exiting a flow channel, etc.) can be monitored (e.g., to ensure equal pressure balance between electrolyzer cells).

Within an electrolysis cell (e.g., within flow channels thereof), the electrolyte (e.g., anolyte, catholyte, etc.) can have a flow velocity between 0.01 and 2 meters per second or any range or value therebetween (e.g., 0.01 m/s, 0.05 m/s, 0.1 m/s, 0.2 m/s. 0.3 m/s, 0.4 m/s, 0.5 m/s, 0.6 m/s, 0.7 m/s, 0.8 m/s, 0.9 m/s, 1 m/s, 1.5 m/s, 2 m/s, etc.). In variants, higher flow velocities can be used to encourage evacuation of bubbles from the electrode surface. In a specific example, the inventors found that a flow velocity of 0.2 meters per second was sufficient for evacuating bubbles efficiently from the electrodes. The flow velocity can be consistent throughout the electrolyzer (e.g. all channels have the same flow velocity, all cells have the same flow velocity, etc.), can be variable throughout the cell or electrolyzer (e.g. different flow velocities in different channels or different electrolyzer cells, etc.), or can be otherwise controlled. In variants, local flow velocities (e.g. flow velocity at specific cells, channels, etc.) can be monitored to assess flow distribution.

In variants, the introduction of electrolyte (e.g., anolyte, catholyte, etc.) to the system can also be characterized by flow mass rate, flow pressure, or any other suitable metric. For example, the electrolyte can be introduced at a mass flow rate between 0.1 kg of electrolyte per minute per cell and 300 kg per minute per cell (e.g. 0.1 kg/min/cell, 0.2 kg/min/cell, 0.5 kg/min/cell, 0.6 kg/min/cell, 0.8 kg/min/cell, 1 kg/min/cell, 1.5 kg/min/cell, 2 kg/min/cell, 2.1 kg/min/cell, 2.3 kg/min/cell, 2.4 kg/min/cell, 2.5 kg/min/cell, 2.6 kg/min/cell, 2.7 kg/min/cell, 2.8 kg/min/cell, 2.9 kg/min/cell, 3 kg/min/cell, 3.1 kg/min/cell, 3.2 kg/min/cell, 3.3 kg/min/cell, 3.4 kg/min/cell, 3.5 kg/min/cell, 3.6 kg/min/cell, 3.7 kg/min/cell, 3.8 kg/min/cell, 3.9 kg/min/cell, 4 kg/min/cell, 5 kg/min/cell, 10 kg/min/cell, 20 kg/min/cell, 30 kg/min/cell, 50 kg/min, 75 kg/min, 100 kg/min, 125 kg/min, 150 kg/min, 200 kg/min, 250 kg/min, etc. or any values or ranges therebetween, etc.).

However, introducing anolyte and catholyte to an alkaline electrolyzer Scan be otherwise performed.

Oxidizing the anolyte and reducing the catholyte Sfunctions to electrochemically convert water into Oand H. Scan be performed continuously, periodically, and/or any other timing. Scan require energy provided by an external power source, such as a battery, solar panel, electrical grid, or any suitable electricity source.