Electrolyzer system repair and revive techniques

Abstract

A method for repairing, rejuvenating or reviving at least one aging, or degraded, or underperforming electrolyzer cell, including an oxygen electrode and a hydrogen electrode in to improve, or to enhance electrolysis efficiency and / or to extend the service lifetime of the electrolyzer cell. The method includes providing one or more activation solutions to the electrolyzer cell. The method also includes providing one or more deposition solutions including one or more metal ions to deposit the one or more metals onto at least one of the oxygen electrode and hydrogen electrode after providing the one or more activation solutions. Further, the method includes forming an oxygen evolution reaction (OER) electrocatalyst onto the oxygen electrode using an OER precursor solution, a hydrogen evolution reaction (HER) electrocatalyst onto the hydrogen electrode using a HER precursor solution, or both, after providing the one or more deposition solutions.

Description

IS24.1057-WO-PCTELECTROLYZER SYSTEM REPAIR AND REVIVE TECHNIQUESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 703,320, filed October 4, 2024 which is incorporated herein by reference in its entirety.BACKGROUND

[0002] The present disclosure generally relates to techniques for repairing and rejuvenating electrolyzer stack and cells. More specifically, the present disclosure relates to techniques for repairing anodes, cathodes, and electrocatalysts in electrolyzer cells.

[0003] Electrolysis of water is utilized for the production of hydrogen (H2) to be used as an alternative energy source and green hydrogen for hard-to-abate heavy industries such as chemical and steel industries. Electrolysis of water utilizes water as a feed material and converts, using an electrochemical cell, water into H2 and oxygen (O2) via a redox reaction by applying an external electrical power to the cell. Electrolysis of water is generally implemented by an electrolyzer system that includes one or more stacks of electrochemical cells (e.g., electrolyzer cells). Electrolyzer cells make use of an electrochemical reaction in a cell that comprises an anode, a cathode, electrocatalysts, gas distribution fields, and an electrolyte. A conventional electrolyzer, such as liquid alkaline electrolyzer, have a limited lifetime (e.g., less than about 10 years). The limited lifetime may be due to deterioration of the electrocatalysts and / or metal bi-polar electrodes used in the electrolyzer cells.SUMMARY

[0004] A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

[0005] In one embodiment, the present disclosure relates to a method for repairing, rejuvenating or reviving at least one aging, or degraded, or underperforming electrolyzer cell,IS24.1057-WO-PCT including an oxygen electrode and a hydrogen electrode in to improve, or to enhance electrolysis efficiency and / or to extend the service lifetime of the electrolyzer cell. The method includes providing one or more activation solutions to the electrolyzer cell. The method also includes providing one or more deposition solutions including one or more metal ions to deposit the one or more metals onto at least one of the oxygen electrode and hydrogen electrode after providing the one or more activation solutions. Further the method includes forming an oxygen evolution reaction (OER) electrocatalyst onto the oxygen electrode using an OER precursor solution, a hydrogen evolution reaction (HER) electrocatalyst onto the hydrogen electrode using a HER precursor solution, or both, after providing the one or more deposition solutions.

[0006] In one embodiment, the present disclosure relates to a system. The system includes one or more electrolyzer cells including at least one set of an oxygen electrode, a hydrogen electrode, an oxygen evolution reaction (OER) catalyst, and a hydrogen evolution reaction (HER) catalyst. The system also includes one or more fluid conduits fluidly coupling the one or more electrolyzer cells to one or more fluid vessels. Further, the system includes a controller configured to: provide one or more activation solutions to the one or more electrolyzer cells along the one or more fluid conduits; and provide one or more deposition solutions including one or more metal ions to the one or more electrolyzer cells to deposit the one or more metals onto at least one of the oxygen and hydrogen electrode after providing the one or more activation solutions along the one or more fluid conduits; and provide an OER precursor solution and / or HER precursor solution to form an OER electrocatalyst onto the oxygen electrode and / or an HER electrocatalyst onto the hydrogen electrode to the one or more electrolyzer cells after providing the one or more deposition solutions along the one or more fluid conduits.

[0007] In one embodiment, the present disclosure relates to a method. The method includes controlling the one or more flow control devices to provide one or more surface activation solutions to activate one or more surfaces of one or more electrolyzer cells. The method also includes controlling the one or more flow control devices to provide a remediation solution to deposit metal ions onto at least an electrode of the one or more electrolyzer cells after providing the surface activation solution. Further, the method includesIS24.1057-WO-PCT controlling the one or more flow control devices to provide one or more metal salt solutions to rejuvenate a hydrogen evolution reaction (HER) catalyst and an oxygen evolution reaction (OER) catalyst of the one or more electrolyzer cells after providing the remediation solution.

[0008] The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0010] FIG. 1 is a schematic diagram of a first example of an embodiment of an electrolyzer system, in accordance with aspects of the present disclosure;

[0011] FIG. 2 is a schematic diagram of a second example of an embodiment of an electrolyzer system, in accordance with aspects of the present disclosure;

[0012] FIG. 3 is a schematic diagram of an electrolyzer subsystem that may be utilized in the electrolyzer system of FIG. 1, in accordance with aspects of the present disclosure;

[0013] FIG. 4 is a flow diagram of a first example of a process for repairing, rejuvenating, or otherwise maintaining one or more electrolyzer cells, in accordance with aspects of the present disclosure;

[0014] FIG. 5 is a flow diagram of a second example of a process for repairing, rejuvenating, or otherwise maintaining one or more electrolyzer cells, in accordance with aspects of the present disclosure;

[0015] FIG. 6 is a flow diagram of an example process for electrolyzer stack or cell cleaning process, in accordance with aspects of the present disclosure;

[0016] FIG. 7 is a flow diagram of an example process for activating one or more surfaces of the electrolyzer cells, in accordance with aspects of the present disclosure;IS24.1057-WO-PCT

[0017] FIG. 8 is a flow diagram of an example process for reestablishing one or more surfaces of the electrolyzer cells, in accordance with aspects of the present disclosure;

[0018] FIG. 9 is a flow diagram of an example process for oxygen evolution reaction (OER) catalyst rejuvenation, in accordance with aspects of the present disclosure; and

[0019] FIG. 10 is a flow diagram of an example process for hydrogen evolution reaction (HER) catalyst rejuvenation, in accordance with aspects of the present disclosure.DETAILED DESCRIPTION

[0020] Certain embodiments commensurate in scope with the present disclosure are summarized below. These embodiments are not intended to limit the scope of the disclosure, but rather these embodiments are intended only to provide a brief summary of certain disclosed embodiments. Indeed, the present disclosure may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0021] As used herein, the term “coupled” or “coupled to” may indicate establishing either a direct or indirect connection (e.g., where the connection may not include or include intermediate or intervening components between those coupled), and is not limited to either unless expressly referenced as such. The term “set” may refer to one or more items. Wherever possible, like or identical reference numerals are used in the figures to identify common or the same elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale for purposes of clarification.

[0022] As used herein, the terms “inner” and “outer”; “up” and “down”; “upper” and “lower”; “upward” and “downward”; “above” and “below”; “inward” and “outward”; and other like terms as used herein refer to relative positions to one another and are not intended to denote a particular direction or spatial orientation. The terms “couple,” “coupled,” “connect,” “connection,” “connected,” “in connection with,” and “connecting” refer to “in direct connection with” or “in connection with via one or more intermediate elements or members.”IS24.1057-WO-PCT

[0023] Furthermore, when introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment,” “an embodiment,” or “some embodiments” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, the phrase A “based on” B is intended to mean that A is at least partially based on B. Moreover, unless expressly stated otherwise, the term “or” is intended to be inclusive (e.g., logical OR) and not exclusive (e.g., logical XOR). In other words, the phrase A “or” B is intended to mean A, B, or both A and B.

[0024] As discussed above, certain electrolyzer system (e.g., one or more electrolyzer stacks (e.g., including multiple electrolyzer cells) or cells), may have a relatively short lifetime due to deterioration of one or more catalysts (e.g. electrocatalysts such as oxygen evolution reaction (OER) catalysts and / or hydrogen evolution reaction (HER) catalysts). For example, the one or more catalysts may include a nickel-based catalyst such as Raney Nickel. Raney Nickel is an alloy, which may be used for OER and / or HER catalyst in alkaline (ALK) electrolysis. It is composed of nickel and aluminum, processed through specific chemical methods to create a porous catalyst structure. The preparation of Raney nickel may involve mixing nickel and aluminum in a certain ratio, forming an alloy, and then obtaining fine particles through quenching and crushing. At least in some instances, 80 / 20 Raney nickel is used, which means 80% nickel and 20% aluminum. The alloy may be thermally sprayed onto a Ni mesh or Ni foam substrate to form mechanical and metallurgical bonds with the nickel substrate. After spraying Raney nickel onto the nickel mesh, the relatively high nickel (e g., greater than or equal to about 50%, 60%, 70%, or 80%) content and low aluminum content (e.g., less than or equal to about 30%, 20%, 15%, 10%) may provide that the nickel in the molten Raney nickel can effectively bond with the mesh. It made be advantageous to activate the sprayed nickel mesh using a basic solution, such as sodium hydroxide solution. The Raney nickel may be “activated” by reacting away the aluminum in the Raney nickel. As the aluminum in the coating is reacted away, the surface of the coating will become pitted,IS24.1057-WO-PCT significantly increasing the electrode’s specific surface area and thereby improving electrolysis efficiency. However, the catalyst may degrade due to, as a non-limiting example, electrolyte aging due to the impurity increases, as of the results of the corrosion of metal components in the stack or one or more individual electrolyzer cells as well as in the BOP (Balance of Plant) systems, which also contribute to the impurity of the potassium hydroxide (KOH) electrolyte.

[0025] Accordingly, the present disclosure relates to techniques for repairing or rejuvenating the one or more catalysts (e.g., the OER catalyst, the HER catalyst, or both) of electrolyzer systems. The disclosed techniques include providing an acidic solution (e.g. a mild acidic solution) to wash and / or remove poison catalyst from the one or more catalysts. The disclosed techniques also include performing one or more electroplating processes (e.g., a first electroplating, a second electroplating, a third electroplating, and so on) to repair, rejuvenate, or otherwise modify a condition of components (e.g., anode(s), cathode(s), OER catalyst(s), HER catalyst(s), or a combination thereof) of an electrolyzer system. Further, the disclosed techniques may include cleaning, activating, and other processes discussed herein that may be used to, for example, remove poisoned catalysts and reactivate oxidized surfaces, or otherwise repair the components of the electrolyzer system. These operations (e.g., cleaning, activating, electroplating, and the like) may be at least partially automated and / or implemented using flow conduits coupled to the electrolyzer system so that the operations may be performed efficiently and prevent the electrolyzer system from being disassembled for maintenance.

[0026] With the preceding in mind, turning now to the figures, FIG. 1 shows a first example of an electrolyzer system 10 in accordance with the present disclosure, such as a liquid alkaline electrolyzer system. As shown, the electrolyzer system 10 includes one or more fluid vessels 12 (e.g., external fluid vessels), an electrolyzer cells subsystem 14 (e.g., an electrolyzer stack subsystem comprising one or more cells), a fluid supply conduit 16 (e.g., one or more fluid supply conduits), and a fluid circulating conduit 18 (e.g., one or more fluid circulating conduits). The cells are not shown in details but they contain two compartments each including an electrode (oxygen and hydrogen electrode), and a membrane separating the two compartments. Such membrane allows liquid to flow through it and between the twoIS24.1057-WO-PCT compartments. Additionally, the electrolyzer system 10 includes a pump 20 and a filter 22. In operation, the pump 20 may provide a fluid flow 24 of one or more solutions or fluids stored in the one or more fluid vessels 12 to one or more electrolyzer cells 26 of the electrolyzer cells subsystem 14. As described in more detail herein, the one or more fluid vessels 12 may store an acid wash solution, a surface activation solution (e.g., activation solution), a deionized water solution, an electroplating mitigation solution, a rejuvenation solution, or a combination thereof. The one or more electrolyzer cells 26 include inlet conduits 28 and outlet conduits 30. The inlet conduits 28 provide the fluid flow 24 of the one or more solutions stored in the one or more fluid vessels 12, which may be used to wash, activate, rinse, electroplate, rejuvenate, and perform other operations described herein with respect to repairing the electrolyzer system 10. The inlet conduits 28 and the outlet conduits 30 may or may not each include valves that selectively couple a subset of the electrolyzer cells 26 to the fluid supply conduit 16 and the circulating return conduit 18. As shown, the inlet conduit 28 is a single inlet conduit that is coupled to the fluid supply conduit 16, and the single inlet conduit 28 splits into two inlets to provide the fluid flow 24 to the electrolyzer cells 26. However, it should be noted that other configurations of inlet conduits 28 may be used, such as a single inlet conduit 28 that couples the fluid supply conduit 16 and an electrolyzer cell 26, two inlet conduits 28 that coupled the fluid supply conduit 16 and the electrolyzer cell 26, or more than two inlet conduits 28. Without wishing to be bound by theory, it is believed that using multiple inlet conduits 28 (e.g., two inlet conduits for one electrolyzer cell 26) may provide more uniform flow. Accordingly, the fluid flow 24 may be provided on a first side of the electrolyzer cell 26 (e.g., proximate to a first side) and / or a second side of the electrolyzer cell 26 (e.g., proximate to a second side).

[0027] In some embodiments, the one or more fluid vessels may contain the electrolyte that is circulated to the electrolyzer, when the electrolyzer is in operation and the other fluids as described above when the electrolyzer is in maintenance, wherein the rejuvenation occurs. Therefore, rejuvenation and / or repair process may be performed in situ, without using a specific equipment, allowing a faster and more economical maintenance.

[0028] In some embodiments, the electrolyzer system 10 may separately provide each fluid from the fluid vessels through the fluid supply conduit 16 and the circulating returnIS24.1057-WO-PCT conduit 18. In this way, a controller 29 (e.g., processor-based controller) may be used to wash, activate, or rejuvenate at least a subset or all of the electrolyzer cells 26 (e.g., at least one, at least two, at least three, and so on), or perform other operations described herein. It should be noted that although the electrolyzer cells subsystem 14 of the electrolyzer system 10 of FIG. 1 shows four electrolyzer cells 26, the electrolyzer cells subsystem 14 may include any number of electrolyzer cells (e.g. one, two, three, four, five, six, or more than six electrolyzer cells 26). To perform the operations described herein, the electrolyzer system 10 may include a controller 29 (e.g., control system).

[0029] The controller 29 may include a processor 31, which may execute instructions stored in memory 32, a power supply 33, and / or storage 34. As such, the memory 32 and / or the storage 34 of the controller 29 may be any suitable article of manufacture that can store the instructions. The memory 32 and / or the storage 34 may be ROM memory, random-access memory (RAM), flash memory, an optical storage medium, or a hard disk drive, to name a few examples. A display 36, which may be any suitable electronic display, may provide a visualization, a data log, or other indication of properties of the one or more electrolyzer cells 26. The controller 29 may be capable of adjusting (e.g., modifying) operation of the pump 20 to increase or decrease a flow rate of the fluid flow 24. The controller 29 may also be capable of receiving electrical measurements indicating an amount of current supplied to the one or more electrolyzer cells 26 of the electrolyzer system 10. In some instances, the controller 29 may be capable of receiving other types of sensor measurements and may be used to determine a condition (e.g. a maintenance condition) of the one or more electrolyzer cells 26, such as temperature measurements, concentrations of certain elements (e.g., Ni, Ti, V, others discussed herein), concentrations or certain ions, and so on. As one non-limiting example, the controller 29 may receive sensor measurements indicating a concentration of certain ions and / or a presence of certain ions in the rejuvenation solution over a time period. The controller 29 may determine a condition of the one or more electrolyzer cells 26 (e.g., or the electrolyzer cell subsystem 14) based on the change of the concentration over the time period, which may indicate a progress of the rejuvenation of the one or more electrolyzer cells. The controller 29 may decrease the flow rate of the fluid flow 24 (e.g., stop the fluid flow) based on the condition of the one or more electrolyzer cells 26. In this way, theIS24.1057-WO-PCT disclosed techniques may provide at least a semi-automated process for rejuvenating the one or more electrolyzer cells 26.

[0030] Further, the controller 29 may be capable of controlling operation of one or more valves 37 (if any) of the electrolyzer system 10 and / or additional parameters such as the flow of the fluid in the electrolyzer stack subsystem 14 (e.g., the stack). The illustrated embodiment of FIG. 1 shows several exemplary positions of valves 37. However, it should be noted that the electrolyzer system 10 may include fewer valves 37 or more valves 37 in other positions other than those shown in FIG. 1. The valves 37 and / or pump 20 may be referred to herein as “flow control devices”. In general, the controller 29 may control one or more of the flow control devices to perform the operations described herein. The controller 29 may be also used to control electrical power supply to the entire stack subsystem 14 or partial sub-stack of the 14 during electrochemical processes of rejuvenation. The controller 29 and the associated power supply can provide the controlled constant current or constant voltage to the entire stack of 26 for all cells’ repairing / rejuvenation or to the certain section of the stack for the specific cells within the stack.

[0031] FIG. 2 shows a second example of the electrolyzer system 10. As shown, the electrolyzer system 10 of FIG. 2 includes one or more fluid vessels 12, an electrolyzer cells subsystem 14, a fluid supply conduit 16, and a fluid circulating return conduit 18. Additionally, the electrolyzer system 10 includes a pump 20 and a filter 22. The electrolyzer system 10 of FIG. 2 may also be controlled by the controller 29 in a generally similar manner as described above with reference to FIG. 1. The pump 20 provides a fluid flow 24 via the inlet conduits 28 and the fluid flow 24 exits the electrolyzer cells 26 via the outlet conduits 30. The illustrated embodiment of FIG. 2 also includes an electrochemical regeneration unit 42. The electrochemical regeneration unit 42 may receive fluids from the fluid circulating return conduit 18 that exited the electrolyzer cells 26 via the outlet conduits 30. The electrochemical regeneration unit 42 may include a cathode and anode that may be used to apply a voltage to fluids to oxidize or reduce chemical components (e.g., ions) in the fluids that were previously used for operations described herein with respect to repairing the electrolyzer system 10. The fluids containing the chemical components oxidized or reduced by the electrochemical regeneration unit 42 (e.g., thereby regenerating the chemicalIS24.1057-WO-PCT components) may be recycled into the one or more fluid vessels 12 for further continuous uses. In some embodiments, the regenerated chemical(s) (e.g., regenerated protective additives or other chemicals or solutions described herein) are pumped to one or more fluid vessels 12 when the one or more fluid vessels 12 store the original solution (e.g., the solutions previously used for operations described herein with respect to repairing the electrolyzer system 10.

[0032] As described above, the fluid flow 24 from the one or more fluid vessels 12 may be used to wash, activate, rinse, electroplate, rejuvenate, and perform other operations described herein with respect to repairing the electrolyzer system 10. In FIGS. 1 and 2, the operations may be performed for the anode, the cathode, or both but in a predetermined order (e g., the anode and then the cathode or vice versa). In some embodiments, the electrolyzer system 10 may include suitable features for selectively providing the fluid flow 24 to either the anode or the cathode. An example of this implementation is shown in FIG. 3.

[0033] As shown in more details on FIG. 3, the electrolyzer system 10 includes an anode portion 44 and a cathode portion 46 separated by a membrane 47 selective to certain ions that allows passage of certain ions but not fluid between the anode portion 44 and cathode portion 46. Such electrolyzer may for instance be an Anion Exchange Membrane electrolyzer system. The electrolyzer of FIG. 3 includes one or more fluid vessels 12, an electrolyzer cells subsystem 14, a fluid supply conduit 16, and a fluid circulating return conduit 18. Additionally, the electrolyzer system 10 includes a pump 20 and a filter 22. The electrolyzer system 10 of FIG. 3 may also be controlled by the controller 29 in a generally similar manner as described above with reference to FIG. 1. As shown, the fluid supply conduit 16 is coupled to the anode portion 44 of the electrolyzer cells subsystem 14 via the inlet conduits 28a and the outlet conduits 30a. Accordingly, the fluid flow 24 may be provided to the anode portion 44 as opposed to the cathode portion 46. In this way, the anode portion 44 may be selectively washed, activated, rinsed, chemical plated, rejuvenated, and so on. Further, the supply fluid conduit 16 may alternatively couple to the cathode portion 46 of the electrolyzer cells subsystem 14 via the cathode inlet conduits 28b and the cathode outlet conduits 30b. Accordingly, the fluid flow 24 may be provided to the cathode portion 46 as opposed to theIS24.1057-WO-PCT anode portion 44. In this way, the cathode portion 46 may be selectively washed, activated, rinsed, chemical plated, rejuvenated, and so on.

[0034] As described herein, repairing the electrolyzer cells 26 of the electrolyzer system 10 may include operations such as providing solutions for washing, activating, rinsing, electroplating, chemical deposition, rejuvenating, or a combination thereof. FIG. 4 shows an example method 50 for repairing, rejuvenating, or otherwise maintaining the electrolyzer system 10. Although described in a particular order, it should be noted that the method 50 may be performed in any order and certain steps may be omitted and or repeated. For instance, the block 58 may be performed before the block 56. In some embodiments, the method 50 may be controlled by the controller 29 (the processor 31 of the controller 29), or any other suitable processing device.

[0035] At block 52, the process 50 includes providing one or more activation solutions to the electrolyzer system 10. In some embodiments, the one or more activation solutions may include an acidic solution. The acidic solution may be used to clean or remove contaminants within the electrolyzer cells 26 before electroplating or chemical deposition. In some embodiments, the acidic solution may be a mild acidic solution (e.g., having a pH greater than or equal to three, four, five, or six, less than seven, and around pH 7). In some embodiments, providing acidic solution may include the processor controlling operation of the pump 20 and / or one or more valves 37 to provide a mild acidic solution stored or otherwise contained in the one or more fluid vessels 12. For pH of 7 washing, it’s actually the de-ionized water rinsing for remove any residual chemical during the previous operations.

[0036] At block 54, the process 50 includes providing one or more deposition solutions (e.g., chemical deposition solutions, electrochemical deposition solutions, or a combination thereof). In some embodiments, block 54 may include providing one or more deposition solutions to the one or more electrolyzer cells 26, and depositing the one or more metal ions on the electrode using the deposition solutions. In some embodiments, block 54 includes chemical deposition). In such embodiments, the deposition may occur spontaneously, or otherwise in the absence of an applied voltage using the power supply 33. The deposition solutions may include solutions with nickel-containing materials and / or other 3d transitionIS24.1057-WO-PCT metal ions, such as cobalt salt, iron salt, or other salts as understood by one of ordinary skill in the art. In other embodiments, the depositing via the deposition solutions may include applying a voltage using power supply connected to the entire stack or to certain subset of the stack (e.g., electrodeposition or electroplating). Tables 1-3 below shows example half reactions corresponding to metal salts or other compositions that may be utilized for relatively low pH processes that may be performed in the absence of an applied voltage or by applying a voltage for Ni plating on the degraded electrodes.

[0037] Tables 4 and 5 shows example half reactions corresponding to metal salts or other compositions that may be utilized for relatively high pH processes may be performed in the absences of an applied voltage or by applying a voltage for Ni plating on the degraded electrodes.IS24.1057-WO-PCTTable 1- Half reactions corresponding to example chemical compositions that may be used to re-establish a damaged surface of the cathode portion to reduce catalyst agglomeration and to regain surface area for relatively low pHs.Table 2- Half reactions corresponding to example chemical compositions that may be used to re-establish a damaged surface of the anode portion to reduce catalyst agglomeration and to regain surface area for relatively low pHs by applying a potential.IS24.1057-WO-PCTTable 3- Half reactions corresponding to example chemical compositions that may be used to re-establish a damaged surface of the cathode portion to reduce catalyst agglomeration and to regain surface area for relatively low pHs by applying a potential.Table 4- Half reactions corresponding to example chemical compositions that may be used to re-establish a damaged surface of the anode portion to reduce catalyst agglomeration and to regain surface area for relatively high pHs.Table 5- Half reactions corresponding to example chemical compositions that may be used to re-establish a damaged surface of the cathode portion to reduce catalyst agglomeration and to regain surface area for relatively high pHs.IS24.1057-WO-PCT

[0038] At block 56, the process 50 includes forming an HER electrocatalyst onto the hydrogen electrode using a HER precursor solution. In some embodiments, forming the HER electrocatalyst may include electroplating on the HER electrocatalyst, (e.g., by applying a current between the hydrogen and oxygen electrodes). For example, the controller 29 may activate the pump 20 that causes HER precursor solution (e.g., a metal salt solution) to flow into the electrolyzer cells 26 (e.g., a cathode portion 46, an anode portion 44, or both). As such, fresh Ni, NiMo alloy, or other metals (e.g., platinum group metals) may be deposited, optionally electroplated, onto the HER catalyst. At block 58, the process 50 includes forming an OER electrocatalyst onto the oxygen electrode using a OER precursor solution. In some embodiments, forming the OER electrocatalyst may include electroplating on the OER electrocatalyst, (e.g., by applying a current between the hydrogen and oxygen electrodes). As described herein, the OER catalyst may include NiO / (Ni(OH)2. As such, depositing, optionally electroplating, on the OER catalyst may include providing a nickel-containing salt solution, and electrodepositing fresh Ni onto the OER catalyst. Then, the fresh Ni may be oxidized, thereby forming Ni0 / (Ni(0H)2. As described herein, it should be noted that the disclosed techniques may be utilized for individual electrolyzer cells, multiple electrolyzer cells (e.g., subcells, or sub-stacks), or the entire electrolyzer system 10.

[0039] In some embodiments, depositing the OER and / or HER electrocatalyst may include forming nanoparticle OER and / or HER electrocatalysts. For example, the one or more HER precursor or OER precursor solution may include a metal salt, a reducing agent, and one or more surfactants. As one non-limiting example, the controller 29 may control operation of the pump 20 to provide a HER precursor solution that includes metal salt (e.g., a Nickel salt) and one or more surfactants or co-precipitation solution may be added to the cathode portion (ie hydrogen electrode). Then, the controller 29 may control operation of the pump 20 to provide a second chemical deposition solution that includes a suitable reducing agent (e.g., sodium borohydride, hydrazine, and others understood by one of ordinary skill in the art). In this way, the OER and / or HER electrocatalyst may be provided with a high surface area-to volume ratio, that may improve performance of the OER and / or HER electrocatalyst as compared to other techniques that may not result in nanoparticle or nanoscale feature formation.IS24.1057-WO-PCT

[0040] In some embodiments, forming the OER and / or HER electrocatalyst may include providing non-precipitation ions for the counter electrode. Such ions may be part of the precursor solution for the particular electrode. For example, to re-establish Ni on the hydrogen electrode (i.e., electrodeposition on the hydrogen electrode), Ti2+ions can be added to the HER precursor solution. During Ni electroplating on the hydrogen electrode, Ti2+is oxidized to Ti3+without sacrificing the Ni on the oxygen electrode.

[0041] FIG. 5 shows a non-limiting example of a method 60 repairing, rejuvenating, or otherwise maintaining the electrolyzer system 10. Although described in a particular order, it should be noted that the method 60 may be performed in any order and certain steps may be omitted and / or repeated. In some embodiments, the method 60 may be controlled by the controller 29 (the processor 31 of the controller 29), or any other suitable processing device.

[0042] At block 64, the process 60 includes cleaning electrolyzer stack or electrolyzer cells 26. At block 66, the process 60 includes activating surfaces of the electrodes (e.g., the cathode portion 46 and or the anode portion 44) or the electrocatalyst. A block 68, the process 60 includes reestablishing the surface of the bipolar electrodes. At block 70, the process 60 includes rejuvenating the OER catalyst. At block 72, the process 60 includes rejuvenating the HER catalysts. Each of these steps are discussed in more detail herein, with respect to FIGS. 6-10.

[0043] One non-limiting example of block 64 described with respect to the process 60 is illustrated in FIG. 6. Although described in a particular order, it should be noted that the method of block 64 may be performed in any order and certain steps may be omitted and or repeated. In some embodiments, the method of block 64 may be controlled by the controller 29 (the processor 31 of the controller 29), or any other suitable processing device.

[0044] At block 80, the method of block 64 includes draining any existing solution (especially electrolyte) from the one or more electrolyzer cells 26 (e.g., the electrolyzer stack). At block 82, the method of block 64 includes flushing and rinsing the one or more electrolyzer cells 26 with deionized water. In some embodiments, blocks 80 and / or 82 may be performed multiple times to remove any residual contaminants. For thorough cleaning, elevated temperature and or pressurized rinsing may be applicable.IS24.1057-WO-PCT

[0045] It is presently recognized that is may be advantageous to perform block 64 before applying the remediation methods described herein. For example, it may be desirable to clean the electrolyzer cells 26 for the rejuvenation operations.

[0046] One non-limiting example of block 66 described with respect to the process 60 of FIG. 5 is illustrated in FIG. 7. Although described in a particular order, it should be noted that the method of block 66 may be performed in any order and certain steps may be omitted and / or repeated. In some embodiments, the method of block 66 may be controlled by the controller 29 (the processor 31 of the controller 29), or any other suitable processing device.

[0047] At block 90, the method of block 66 may include filling (e.g., providing) one or more of the electrolyzer cells 26 with a surface activation solution such as a caustic or basic solution (e.g., at a temperature, T and pressure, P). For example, the surface activation solutions may include a sodium hydroxide solution. At block 92, the method of block 66 may include draining (e.g., completely draining) the surface activation solution from the one or more electrolyzer cells 26. In some embodiments, block 64 as described above with reference to FIG. 5 may be performed after block 92. At block 94, the method of block 66 may include filling (e.g., providing) the one or more electrolyzer cells 26 with an additional surface activation solution. In some embodiments the additional surface activation solution may include a mild acidic solution. At block 96, the method of block 66 may include draining (e.g., completely draining) the additional surface activation solution from the one or more electrolyzer cells 26. In some embodiments, block 64 as described above with reference to FIG. 5 may be performed after block 94.

[0048] Accordingly, the method of block 66 may be utilized to remove the contaminated surface of electrode and electrocatalyst. For example, for the organic contamination either by grease or organics leaching from elastomer or from diaphragm, a mild sodium hydroxide (NaOH) could be applied. For carbonates clogging or HER Ni catalyst oxidation layer, a mild acid such as hydrochloric acid (HC1) could be applied to remove the contamination. A specific, non-limiting example is described below.

[0049] During long durations of operation of the electrolyzer system 10, the catalyst may lose surface area, resulting in higher specific current density for a certain geometric cell sizeIS24.1057-WO-PCT and thus higher overpotential. Further, the catalyst might experience agglomeration due to crystalline migration or particle losses into the electrolyte via convective liquid flow as well as stripping by gas evolution. To re-establish the lost surface area and / or regain catalyst loading, chemical or electrochemical deposition of Ni can be applied to hydrogen or oxygen electrodes, and / or both electrodes. To illustrate this, one non-limiting example of block 68 described with respect to the process 60 of FIG. 5 is illustrated in FIG. 8.

[0050] At block 100, the method of block 68 includes filling the one or more electrolyzer cells 26 with a remediation solution. At block 102, the method of block 68 includes providing an acidic solution (e.g., at a predetermined temperature, T, over a time interval, f) to at least one side of the electrode (e.g., the anode portion 44 or the cathode portion 46 as described above with reference to FIG. 3). At block 104, the method of block 68 includes reversing polarity for the opposite electrode using a current, I. In some embodiments, block 64 as described above with reference to FIG. 5 may be performed after block 104. Alternatively the method of block 68 may proceed with block 106 instead of block 102. At block 106, the method of block 68 includes performing an alkaline solution plating at a predetermined temperature (e.g., T that may be the same or different than the T discussed at block 102) over a time interval (e.g., t that may be the same or different than the t discussed at block 102). on at least one side of the electrode. In some embodiments, block 64 as described above with reference to FIG. 5 may be performed after block 106. In any case after performing block 104 or block 106, and optionally performing block 64, the method of block 68 may include, at block 108 providing or admitting pitting corrosion agents to rough the surface. In some embodiments, block 64 as described above with reference to FIG. 5 may be performed after block 106.

[0051] A non-limiting example of blocks 102 and 104 is described below. The electrolyzer cells 26 may be filled with Ni salts electrolyte, such as Ni(NOs)2, NiCLz, and NiSC . The plating electrolyte may also contain other additives, including non-precipitation ions for the counter electrode reaction. For example, to re-establish Ni on the hydrogen electrode (i.e., electrodeposition on the hydrogen electrode), Ti2+ions can be added to the electroplating solution. During Ni electroplating on the hydrogen electrode, Ti2+is oxidized to Ti3+without sacrificing the Ni on the oxygen electrode. After completing the plating jobIS24.1057-WO-PCT on one electrode, plating on the opposite electrode can be done by reversing the power source polarity.

[0052] A non-limiting example of block 106 is described below. Another method of Ni plating involves an alkaline Ni plating solution with a pH range between 8 and 11. In an alkaline environment, the Ni counter electrode tends to become passivated, favoring the water oxidation reaction that produces O2 gas rather than Ni oxidation. This electroplating bath can be applied to oxygen electrodes, as well as the positive side of bipolar plates within the electrolysis stack. After completing the plating job on one electrode, plating on the opposite electrode can be done by reversing the power source polarity.

[0053] In any case, after completion of hydrogen electrode Ni-plating, the polarity can be reversed to plating Ni on oxygen electrode. This operation is preferred for the low pH electroplating solution. During Ni electroplating, the plating solution can be operated as a flowing fluid to maintain stable Ni salts and additives concentration. Alternatively, the plating solution can remain in a steady state, as long as the concentration is sufficient to supply the necessary Ni plating on the working electrode. After completing both hydrogen and oxygen electrode plating and the DI water washing / rinsing, introducing pitting corrosion agents into the stack creates pits on the newly plated Ni surface.

[0054] Drying the newly plated Ni electrodes and / or newly plated bipolar plates might be necessary. This process helps maintain good adhesion of the coating and ensures proper surface finishing. Drying can be achieved by flowing inert gases through the entire stack. The inert gases used can be N2, Ar, H2, or even under vacuum pumping for a certain period of time.

[0055] After fresh Ni is plated on both hydrogen and oxygen electrode, to improve OER electrocatalyst performance, Ni0 / Ni(0H)2 electrocatalysts can be formed on the oxygen electrode. Example electroplating solutions are discussed herein. In general, depending on the pH range of the plating solution, different additives may to be added to protect the counter electrodes (now hydrogen electrode) from Ni electrooxidation and its dissolving / leaching into the solution. As referred to herein, “electroplating protection solutions” refer to solutions that include chemical compositions that may protect the counter electrode from NiIS24.1057-WO-PCT electrooxidation, dissolving, and / or leaching. Such electroplating protection solutions may include, but are not limited to, ions such as V2+, NH , H3PO3, Eu2+, Ti2+, In+, IICO3', (EbPCh) , [Cr(edta)(H2O)]2(e.g., Cr ion coordinated with ethylenediaminetetraacetic acid and water molecule), Cr(CN)4, 2NH3O . One non-limiting example of block 70 described with respect to the process 60 of FIG. 5 is illustrated in FIG. 9. Although described in a particular order, it should be noted that the method of block 70 may be performed in any order and certain steps may be omitted and or repeated. In some embodiments, the method of block 70 may be controlled by the controller 29 (the processor 31 of the controller 29), or any other suitable processing device.

[0056] At block 110, the process 70 includes fding high pH plating agents into one or more electrolyzer cells 26. For example, the controller 29 may activate the pump to cause high pH plating agents which may include chemical components shown in Tables 4 or 5. At block 112, the process 70 includes applying a positive potential on the O2 electrode and a negative potential on the H2 electrode. In some embodiments, block 64 as described above with reference to FIG. 5 may be performed after block 112.

[0057] One example of OER catalyst rejuvenation involves maintaining the solution fluid at high pH (>9). The oxygen electrode and hydrogen electrode are connected to positive and negative terminals of a power source, respectively. The Ni on the oxygen electrode undergoes oxidation, forming NiO / Ni(OH)2, while Ni is plated onto the hydrogen electrode.

[0058] To further improve HER electrocatalyst performance, advanced electrocatalysts, such as NiMo alloy and even PGM (Pt), can be plated on the hydrogen electrode. The electroplating solutions used for this embodiment are discussed herein. In general, depending on the pH range of the plating solution, different additives may to be added to protect the counter electrodes (oxygen electrode) from Ni electrooxidation and its dissolving / leaching to the solution. One non-limiting example of block 72 described with respect to the process 60 of FIG. 5 is illustrated in FIG. 10. Although described in a particular order, it should be noted that the method of block 72 may be performed in any order and certain steps may be omitted and or repeated. In some embodiments, the method of block 72 may be controlled by the controller 29 (the processor 31 of the controller 29), or any other suitable processing device.IS24.1057-WO-PCT

[0059] At block 120, the process 72 includes filing the remediation solution to the one or more electrolyzer cells 26. At block 122, the process 72 includes providing a high pH Ni / Mo solution to the H2 electrode. At block 124, the process 72 includes applying a negative voltage on the H2 electrode, controlling temperature and current. At block 126, the process 72 includes providing a low pH Pt solution or Ni / Mo solution to the H2 electrode. At block 128, the process 72 includes applying a negative voltage on the H2 electrode in the presence of an oxidation agent, such as V2+. In some embodiments, block 64 as described above with reference to FIG. 5 may be performed after block 124 or block 128.

[0060] An alternative method for rejuvenating OER / HER electrodes (e.g., blocks 70 and 72 described in FIGS. 5, 9, and 10) may include chemical deposition or co-deposition of Ni or Ni alloy for the electro-catalysts. This process does not utilize an electrical power source, but instead pumping and circulation of chemicals into the stack. To precipitate or coprecipitate Ni or Ni alloy catalysts, Ni ion-bearing salts such as Ni(NC>3)2, and / or other 3d transition metal ions like cobalt salt (Co(NO3)2) and iron salt (FeSCh), are dissolved in deionized water at certain concentration either simultaneously or individually but mixed together in the following step before pumping in to the electrolyzer stack. These salts can also be dissolved in organic solvents such as isopropanol. Metal or metal alloy nucleation can be formed on the Ni substrate by introducing chemical reduction agents at a certain temperature (room temperature or elevated temperature but not exceeding to 80 °C) for a specified period. After formation of certain catalyst loading (0.1 to 1 mg / cm2), the solution is pumped out for future uses or treatments for continuous usages. The electrolyte stack is to be washed / rinsed by de-ionized water multiple times followed by drying operations.

[0061] In some instances, the electrolyzer stack may experience non-uniform degradation, with more severe degradation in certain cells (e.g., those close to both end plates due to extensive electrolyte erosion). Therefore, optimized operation of individual cells or sub-stacks can be achieved by applying electroplating voltage selectively across chosen cells or sub-stacks. The electroplating solution can flow through the entire stack without altering the fluid pipeline. Alternatively, the electro-processing solution can be directed through specific sections of the stack by disconnecting or blocking non-repairing areas. In the first case, the impact of the solution on non-repairing sections should be minimal, as no electricalIS24.1057-WO-PCT voltage is applied to these areas, preventing electrochemical reactions on the electrodes. However, water cleaning and rinsing are necessary for the entire stack to remove residual solution.

[0062] During blocks 68, 70, and 72, the electro-cathodic reduction of Ni2+deposits Ni on the electrodes. As a result, the concentration of nickel ions (Ni2+) gradually decreases. To maintain a constant concentration for satisfactory Ni plating quality and quantity, it becomes necessary to continuously monitor and replenish nickel ions in the solution. Ni salts can be added by dosing the consumed amount into an external solution reservoir (such as electrolyte), which is then pumped and circulated through the cells / stack. Similarly, water replenishment should be considered due to water splintering into O2 at the anode and H2 at the cathode. This is particularly important for high pH rejuvenation solutions where Ni0 / Ni(0H)2 forms on the anode. To maintain water balance, a small amount of water may be added to the reservoir. For low pH rejuvenation solutions, the electro-oxidation reaction of metal ions (e.g., Ti2+to Ti3+) occurs at the anode. To replenish Ti2+, an external electrochemical reactor is to be implemented to reduce Ti3+back to Ti2+. The balanced Ti2+ / Ti3+solution is then fed back into the external reservoir, which connects to the electrolyzer stack.

[0063] With reference to blocks 68, 70, and 72, the regeneration / rejuvenation service can alternatively be performed in phased steps for the anode, then the cathode, or vice versa, or for only the selected electrode. This can be done by injecting the desired treatment solutions (such as Ni salts and additives) into the desired electrode cambers and electrolyte / gas channel. Phased or specifically selected regeneration would simplify the process and target the regeneration electrodes.

[0064] Technical effects of the disclose embodiments provide repairing or rejuvenating the one or more catalysts (e.g., the OER catalyst, the HER catalyst, or both) of electrolyzer systems. The disclosed techniques (e.g., cleaning, activating, electroplating, and the like) may be at least partially automated and / or implemented using flow conduits coupled to the electrolyzer system so that the techniques may be performed efficiently and prevent the electrolyzer system from being disassembled for maintenance.IS24.1057-WO-PCT

[0065] The subject matter described in detail above may be defined by one or more clauses, as set forth below.

[0066] A method for repairing, rejuvenating or reviving at least one aging, or degraded, or underperforming electrolyzer cell, including an oxygen electrode and a hydrogen electrode in to improve, or to enhance electrolysis efficiency and / or to extend the service lifetime of the electrolyzer cell. The method includes providing one or more activation solutions to the electrolyzer cell. The method also includes providing one or more deposition solutions including one or more metal ions to deposit the one or more metals onto at least one of the oxygen electrode and hydrogen electrode after providing the one or more activation solutions. Further the method includes forming an oxygen evolution reaction (OER) electrocatalyst onto the oxygen electrode using an OER precursor solution, a hydrogen evolution reaction (HER) electrocatalyst onto the hydrogen electrode using a HER precursor solution, or both, after providing the one or more deposition solutions.

[0067] The method of any preceding clause, including applying a current across the oxygen electrode and the hydrogen electrode of the electrolyzer cell to facilitate deposition of the one or more metals onto the at least one of the oxygen electrode and the hydrogen electrode using the one or more deposition solutions.

[0068] The method of any preceding clause, including depositing the one or more metals onto a first electrode among the hydrogen electrode and the oxygen electrode by applying a current circulating from a second electrode among the hydrogen electrode and oxygen electrode, distinct from the first electrode, to the first electrode.

[0069] The method of any preceding clause, after having deposited the one or more metals to the first electrode, applying a current circulate from the first electrode to the second electrode to deposit the one or more metals onto the second electrode.

[0070] The method of any preceding clause, further including providing one or more protection additives in the deposition solutions, in the HER precursor solution or in the OER precursor solution, wherein the protecting additives are optionally oxidized while the metal ions are reduced.IS24.1057-WO-PCT

[0071] The method of any preceding clause, wherein the one or more protection additives includes one or more of V2+, NI L , H3PO3, Eu2+, Ti2+, In+, HCCh', (FbPCh [Cr(edta)(H2O)]2, Cr(CN)4, NH3OH1, H2(gas), or HCOOH.

[0072] The method of any preceding clause, wherein the one or more activation solutions include a sodium hydroxide solution and / or a hydrochloric acid solution.

[0073] The method of any preceding clause, wherein providing one or more activation solutions includes providing a caustic solution followed by an acidic solution.

[0074] The method of any preceding clause, wherein the one or more deposition solutions includes a 3d transition metal solution.

[0075] The method of any preceding clause, wherein the one or more deposition solutions includes a nickel-salt solution, such as a nickel nitrate solution, a nickel chloride solution or a nickel sulfate solution.

[0076] The method of any preceding clause, wherein providing the one or more activation solutions includes: at least partially filling the one or more electrolyzer cells with the one or more activation solutions; draining the one or more activation solutions from the at least partially filled one or more electrolyzer cells; and flushing and rinsing the one or more electrolyzer cells with deionized water.

[0077] The method of any preceding clause, further including draining an electrolyte solution from the one or more electrolyzer cells; and flushing and rinsing the one or more drained electrolyzer cells using deionized water; and providing the one or more activation solutions to one or more electrolyzer cells after flushing and rinsing the one or more drained electrolyzer cells.

[0078] The method of any preceding clause, wherein the one or more activation solutions include a mild acidic solution.

[0079] The method of any preceding clause, including applying a current across the oxygen and hydrogen electrodes to facilitate deposition of the HER electrocatalyst onto the hydrogen electrode using the HER precursor solution and / or an OER electrocatalyst onto the oxygen electrode using the OER precursor solution.IS24.1057-WO-PCT

[0080] The method of any preceding clause, wherein the OER electrocatalyst includes one or more of NiO and Ni(0H)2.

[0081] The method of any preceding clause, wherein the HER electrocatalyst includes one or more of NiMo or Pt.

[0082] The method of any preceding clause, wherein the electrolyzer cell include all or a selected subset of electrolyzer cells of an electrolyzer stack system.

[0083] The method of any preceding clause, including controlling one or more fluid distribution devices of a stack to circulate the activation solutions, deposition solutions, OER precursor solution and / or HER precursor solution into the selected subset of electrolyzer cells.

[0084] A system includes one or more electrolyzer cells including at least one set of an oxygen electrode, a hydrogen electrode, an oxygen evolution reaction (OER) catalyst, and a hydrogen evolution reaction (HER) catalyst. The system also includes one or more fluid conduits fluidly coupling the one or more electrolyzer cells to one or more fluid vessels. Further, the system includes a controller configured to: provide one or more activation solutions to the one or more electrolyzer cells along the one or more fluid conduits; and provide one or more deposition solutions including one or more metal ions to the one or more electrolyzer cells to deposit the one or more metals onto at least one of the oxygen and hydrogen electrode after providing the one or more activation solutions along the one or more fluid conduits; and provide an OER precursor solution and / or HER precursor solution to form an OER electrocatalyst onto the oxygen electrode and / or an HER electrocatalyst onto the hydrogen electrode to the one or more electrolyzer cells after providing the one or more deposition solutions along the one or more fluid conduits.

[0085] The system of any preceding clause, further including an electric external power supply system to provide DC electricity for deposition of the one or more metals and electrocatalyst formation

[0086] The system of any preceding clause, including a pump communicatively coupled to the controller.IS24.1057-WO-PCT

[0087] The system of any preceding clause, wherein the controller is configured to provide one or more protection solutions while providing the one or more deposition solutions, HER precursor solution or OER precursor solution, wherein the one or more protection solutions include one or more chemical species that are oxidized while the one or more metal ions are reduced.

[0088] The system of any preceding clause, including one or more external chemical vessels configured to provide the one or more activation solutions, the one or more deposition solutions, the OER precursor and / or HER precursor solutions, or a combination thereof, before pumping them in to an electrolyzer stack or one or more electrolyzer cells.

[0089] The system of any preceding clause, including one or more external electrochemical cells configured to regenerate or electrochemically reduce consumed or oxidized protection additives after they are used to deposit the one or more metals in the one or more electrolyzer cells.

[0090] The system of any preceding clause, wherein the regenerated protective additives are pumped to one or more external chemical vessels configured to provide the deposition solution, the HER precursor solution, the OER precursor solution, or a combination thereof, before pumping them in to an electrolyte stack or one or more electrolyte cells

[0091] The system of any preceding clause, wherein the regenerated protected additives are recirculated to the electrolyte stack or one or more electrolyte cells for continuous uses and rejuvenation operations.

[0092] The system of any preceding clause, where the operation can be on-site in the field for an electrolyzer stack with minimum interruption of daily operations and without disassembling the electrolyzer stack nor interrupting shipping of equipment.

[0093] A method includes controlling the one or more flow control devices to provide one or more surface activation solutions to activate one or more surfaces of one or more electrolyzer cells; controlling the one or more flow control devices to provide a remediation solution to deposit metal ions onto at least an electrode of the one or more electrolyzer cells after providing the surface activation solution; and controlling the one or more flow control devices to provide one or more metal salt solutions to rejuvenate a hydrogen evolutionIS24.1057-WO-PCT reaction (HER) catalyst and an oxygen evolution reaction (OER) catalyst of the one or more electrolyzer cells after providing the remediation solution.

[0094] The method of any preceding clause, wherein controlling the one or more flow control devices to provide the remediation solution includes: providing the remediation solution to an anode portion of the one or more electrolyzer cells; and providing an additional remediation solution to a cathode portion of the one or more electrolyzer cells after providing the remediation solution to the anode portion.

[0095] The method of any preceding clause, wherein the one or more metal salt solutions include a Pt ion-containing solution, such as but not limited to PtC142-, Pt(OH)4 (aq.).

[0096] The method of any preceding clause, wherein the one or more metal salt solutions include a Ni / Mo-containing solution.

[0097] The method of any preceding clause, comprising performing the method on-site in the field for an electrolyzer stack with minimum interruption of daily operations and without disassembling the electrolyzer stack nor interrupting shipping of equipment.

[0098] The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. Moreover, the order in which the elements of the methods described herein are illustrated and described may be re-arranged, and / or two or more elements may occur simultaneously. The embodiments were chosen and described in order to best explain the principals of the disclosure and its practical applications, to thereby enable others skilled in the art to best utilize the disclosure and various embodiments with various modifications as are suited to the particular use contemplated.

[0099] Finally, the techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function]...” or “step for [perform]ing [aIS24.1057-WO-PCT function]...”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Claims

IS24.1057-WO-PCTCLAIMS1. A method for repairing, rejuvenating or reviving at least one aging, or degraded, or underperforming electrolyzer cell, including an oxygen electrode and a hydrogen electrode in to improve, or to enhance electrolysis efficiency and / or to extend the service lifetime of the electrolyzer cell, comprising: providing one or more activation solutions to the electrolyzer cell; providing one or more deposition solutions including one or more metal ions to deposit the one or more metals onto at least one of the oxygen electrode and hydrogen electrode after providing the one or more activation solutions; and forming an oxygen evolution reaction (OER) electrocatalyst onto the oxygen electrode using an OER precursor solution, a hydrogen evolution reaction (HER) electrocatalyst onto the hydrogen electrode using a HER precursor solution, or both, after providing the one or more deposition solutions.

2. The method of claim 1, including applying a current across the oxygen electrode and the hydrogen electrode of the electrolyzer cell to facilitate deposition of the one or more metals onto the at least one of the oxygen electrode and the hydrogen electrode using the one or more deposition solutions.

3. The method of claims 1 or 2, including depositing the one or more metals onto a first electrode among the hydrogen electrode and the oxygen electrode by applying a current circulating from a second electrode among the hydrogen electrode and oxygen electrode, distinct from the first electrode, to the first electrode.

4. The method of claim 3, after having deposited the one or more metals to the first electrode, applying a current circulate from the first electrode to the second electrode to deposit the one or more metals onto the second electrode.

5. The method of claims 1-4, further comprising:IS24.1057-WO-PCT providing one or more protection additives in the deposition solutions, in the HER precursor solution or in the OER precursor solution, wherein the protecting additives are optionally oxidized while the metal ions are reduced.

6. The method of claim 5, wherein the one or more protection additives includes one or more of V2+, NH4+, H3PO3, Eu2+, Ti2+, In+, HCO3; (H2PO.I)2, [Cr(edta)(H2O)J2, Cr(CN)4, NH3OH+ H2(gas), or HCOOH.

7. The method of claims 1 -6, wherein the one or more activation solutions comprise a sodium hydroxide solution and / or a hydrochloric acid solution.

8. The method of claims 1 -7, wherein providing one or more activation solutions includes providing a caustic solution followed by an acidic solution.

9. The method of claims 1-8, wherein the one or more deposition solutions comprises a 3d transition metal solution.

10. The method of claims 1-9, wherein the one or more deposition solutions comprises a nickel-salt solution, such as a nickel nitrate solution, a nickel chloride solution or a nickel sulfate solution.

11. The method of claims 1-10, wherein providing the one or more activation solutions comprises: at least partially filling the one or more electrolyzer cells with the one or more activation solutions; draining the one or more activation solutions from the at least partially filled one or more electrolyzer cells; and flushing and rinsing the one or more electrolyzer cells with deionized water.

12. The method of claims 1-11, further comprisingIS24.1057-WO-PCT draining an electrolyte solution from the one or more electrolyzer cells; flushing and rinsing the one or more drained electrolyzer cells using deionized water; and providing the one or more activation solutions to one or more electrolyzer cells after flushing and rinsing the one or more drained electrolyzer cells.

13. The method of claim 1, wherein the one or more activation solutions comprise a mild acidic solution.

14. The method of claim 13, including applying a current across the oxygen and hydrogen electrodes to facilitate deposition of the HER electrocatalyst onto the hydrogen electrode using the HER precursor solution and / or an OER electrocatalyst onto the oxygen electrode using the OER precursor solution.

15. The method of claims 1-14, wherein the OER electrocatalyst includes one or more of NiO and Ni(0H)2.

16. The method of claims 1-15, wherein the HER electrocatalyst includes one or more of NiMo or Pt.

17. The method of claims 1-16, wherein the electrolyzer cell include all or a selected subset of electrolyzer cells of an electrolyzer stack system.

18. The method of claim 17, comprising controlling one or more fluid distribution devices of a stack to circulate the activation solutions, deposition solutions, OER precursor solution and / or HER precursor solution into the selected subset of electrolyzer cells.

19. A system, comprising:IS24.1057-WO-PCT one or more electrolyzer cells comprising at least one set of an oxygen electrode, a hydrogen electrode, an oxygen evolution reaction (OER) catalyst, and a hydrogen evolution reaction (HER) catalyst; one or more fluid conduits fluidly coupling the one or more electrolyzer cells to one or more fluid vessels; and a controller configured to: provide one or more activation solutions to the one or more electrolyzer cells along the one or more fluid conduits; provide one or more deposition solutions including one or more metal ions to the one or more electrolyzer cells to deposit the one or more metals onto at least one of the oxygen and hydrogen electrode after providing the one or more activation solutions along the one or more fluid conduits; and provide an OER precursor solution and / or HER precursor solution to form an OER electrocatalyst onto the oxygen electrode and / or an HER electrocatalyst onto the hydrogen electrode to the one or more electrolyzer cells after providing the one or more deposition solutions along the one or more fluid conduits.

20. The system of claim 19, further comprising an electric external power supply system to provide DC electricity for deposition of the one or more metals and electrocatalyst formation21. The system of claims 19 or 20, comprising a pump communicatively coupled to the controller.

22. The system of claims 19-21, wherein the controller is configured to provide one or more protection solutions while providing the one or more deposition solutions, HER precursor solution or OER precursor solution, wherein the one or more protection solutions comprise one or more chemical species that are oxidized while the one or more metal ions are reduced.IS24.1057-WO-PCT23. The system of claims 19-22 comprising one or more external chemical vessels configured to provide the one or more activation solutions, the one or more deposition solutions, the OER precursor and / or HER precursor solutions, or a combination thereof, before pumping them in to an electrolyzer stack or one or more electrolyzer cells.

24. The system of claims 19-23, comprising one or more external electrochemical cells configured to regenerate or electrochemically reduce consumed or oxidized protection additives after they are used to deposit the one or more metals in the one or more electrolyzer cells.

25. The system of claim 24, wherein the regenerated protection additives are pumped to one or more external chemical vessels configured to provide the deposition solution, the HER precursor solution, the OER precursor solution, or a combination thereof, before pumping them in to an electrolyte stack or one or more electrolyte cells26. The system of claim 25, wherein the regenerated protection additives are recirculated to the electrolyte stack or one or more electrolyte cells for continuous uses and rejuvenation operations.

27. The system of claims 19-26, where the operation can be on-site in a field for an electrolyzer stack with minimum interruption of daily operations and without disassembling the electrolyzer stack nor interrupting shipping of equipment.

28. A method comprising: controlling one or more flow control devices to provide one or more surface activation solutions to activate one or more surfaces of one or more electrolyzer cells;IS24.1057-WO-PCT controlling the one or more flow control devices to provide a remediation solution to deposit metal ions onto at least an electrode of the one or more electrolyzer cells after providing the surface activation solution; and controlling the one or more flow control devices to provide one or more metal salt solutions to rejuvenate a hydrogen evolution reaction (HER) catalyst and an oxygen evolution reaction (OER) catalyst of the one or more electrolyzer cells after providing the remediation solution.

29. The method of claim 28, wherein controlling the one or more flow control devices to provide the remediation solution comprises: providing the remediation solution to an anode portion of the one or more electrolyzer cells; and providing an additional remediation solution to a cathode portion of the one or more electrolyzer cells after providing the remediation solution to the anode portion.

30. The method of claim 28 or 29, wherein the one or more metal salt solutions comprise a Pt ion-containing solution, such as but not limited to PtCh2’, Pt(OH)4 (aq.).

31. The method of claims 28-30, wherein the one or more metal salt solutions comprise a Ni / Mo-containing solution.

32. The method of claims 28-31, comprising performing the method on-site in a field for an electrolyzer stack with minimum interruption of daily operations and without disassembling the electrolyzer stack nor interrupting shipping of equipment.

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