Electrode design, synthesis of, and methods of use

Abstract

Methods of manufacturing a multi-layered electrode having at least one nanostructured interlayer for use in an electrochemical cell for the treatment of fluids are provided. The methods comprise the steps of providing at least one conductive substrate, performing at least one interlayer formation step to the at least conductive substrate to synthesize the at least one nanostructured interlayer on the at least one conductive substrate, performing at least one modification step configured to alter the electronic, chemical, or structural properties of the at least one nanostructured interlayer, and performing at least one coating step for depositing at least one coating to the nanostructured interlayer, creating at least one conductive and electrochemically active layer.

Description

ELECTRODE DESIGN, SYNTHESIS OF, AND METHODS OF USECROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 712,735 filed October 28, 2024, entitled “ELECTRODE DESIGN, SYNTHESIS OF, AND METHODS OF USE”, which is specifically incorporated by reference herein for all that it discloses or teaches.FIELD

[0002] Embodiments herein are generally related to improved methods of manufacturing electrodes for use in electrochemical cells, such electrodes being applicable in a wide range of systems including the treatment of fluids, energy storage, and conversion systems (e.g., batteries, supercapacitors, fuel cells), sensors, corrosion protection, catalysis, water splitting, and electroplating, as well as electrochemical advanced oxidation processes (AOPs), activation of peroxymonosulfate and / or peroxydisulfate, electro-Fenton reactions including in situ hydrogen peroxide (H2O2) generation, electrosynthesis, and electroreduction of contaminants.

[0003] Electrodes for electrochemical oxidation are commonly fabricated using catalytic materials such as mixed metal oxides, doped metal oxides, metal carbides and metal nitrides. These electrodes often employ coatings applied directly onto a conductive substrate to provide the necessary catalytic activity. While such approaches can achieve reasonable electrochemical performance, they frequentlysuffer from challenges of limited adhesion, high fabrication cost, and reduced lifetime in aggressive environments such as chloride-rich or high-COD wastewater.

[0004] Various strategies have been investigated to improve electrode performance, including doping, defect engineering, noble-metal mixed metal oxides (e.g., lrO2- / RuO2-based and Sb-doped SnO2systems), boron-doped diamond films, Magneli- phase titanium sub-oxides (e.g., Ti4O7), and more recently perovskite / spinel oxides, transition-metal carbides and nitrides and more. Although such methods may enhance catalytic activity, they generally focus only on the composition of the active layer and do not adequately address interfacial stability or structural integration. As a result, electrodes prepared by these methods are prone to delamination, progressive performance decay, and inefficient charge transfer across interfaces. In addition, many state-of-the-art electrodes rely on noble-metal dopants or advanced deposition techniques such as CVD or PVD, which increase fabrication cost and limit scalability.

[0005] Multi-layered electrode architectures have been developed to provide a balance of catalytic activity, conductivity, and durability. These typically comprise a conductive substrate, an interlayer, and a final active coating. A properly engineered interlayer can improve adhesion, provide mechanical and chemical stability, and facilitate charge transfer, while the active coating contributes sustained catalytic activity. Such combined structural and compositional approaches offer the potential to address the cost, durability, and efficiency limitations of current electrode technologies.

[0006] In multilayered electrode architectures, the interlayer is critical for promoting adhesion between the active coating and the substrate, facilitating charge transfer, and increasing surface area for electrochemical reactions. A range of methods and dopants have been explored to enhance conductivity and stability; however, current interlayers still face major challenges. Many show insufficient long-term adhesion, leading to delamination, or limited conductivity across the interface, reducing efficiency. Prolonged exposure to chloride-rich or oxidizing environments can further degrade the interlayer or coating, reducing electrode activity and shortening service life.

[0007] Accordingly, there remains a need for improved electrodes that combine strong interlayer adhesion, high conductivity, and stability in aggressive electrolytes, while also reducing reliance on costly materials. It is desirable that such electrodes operate reliably under harsh electrochemical conditions and maintain activity over extended periods, particularly for the treatment of fluids such as grey water, industrial effluents, or saline waste streams.SUMMARY

[0008] According to embodiments, methods of manufacturing a multi-layered electrode having at least one nanostructured interlayer are provided, the multi-layered electrode for use in an electrochemical cell for the treatment of fluids. In some embodiments, the methods comprise providing at least one conductive substrate, performing at least one interlayer formation step to the at least conductive substrate to synthesize the at least one nanostructured interlayer on the at least one conductive substrate, performing at least one modification step configured to alter the electronic,chemical, or structural properties of the at least one nanostructured interlayer, and performing at least one coating step for depositing at least one coating to the nanostructured interlayer, creating at least one conductive and electrochemically active layer.

[0009] In some embodiments, the at least one interlayer formation step may be selected from a multi-step anodization process, a multi-pass deposition process, a sequential thermal conversion process, or a combination thereof. In some embodiments, the at least one interlayer formation step may comprise performing one or more of a chemical vapor deposition, physical vapor deposition, atomic layer deposition, electrophoretic deposition, sol-gel processing, thermal treatment, spark plasma sintering, plasma spraying, cold spraying, or additive manufacturing techniques.

[0010] In some embodiments, the at least one modification step may be selected from at least one of doping the at least one nanostructured interlayer with a dopant species, introducing controlled defects in the at least one nanostructured interlayer, or a combination thereof. In some embodiments, the at least one doping step may include hydrothermal treatment, spray pyrolysis, chemical vapor deposition, physical vapor deposition, electrodeposition, dip coating and thermal decomposition of precursor salts, solid-state diffusion, plasma treatment, or combinations thereof. In some embodiments, the at least one dopant species comprises an anionic, a cationic, or a mixed-valence species.

[0011] In some embodiments, the introduction of controlled defects may comprise introducing oxygen or nitrogen vacancies.

[0012] In some embodiments, the at least one coating may comprise metal oxides, nitrides, carbides, borides, silicides, perovskite oxides, diamond-based films, MXenes, conductive polymers, Magneli phases, and combinations thereof.

[0013] In some embodiments, the methods may further comprise performing one or more post-processing treatments under controlled atmospheres. In some embodiments, the one or more post-processing treatments may be performed sequentially or in combination with the at least one interlayer formation and the at least one modification steps.

[0014] In some embodiments, the conductive interlayer may form an electrochemically active surface layer for enhancing electrooxidation of the fluids by the electrochemical cell.

[0015] According to embodiments, a multi-layered electrode having at least one nanostructured interlayer for use in an electrochemical cell for the treatment of fluids is provided. In some embodiments, the electrode may comprise at least one first layer formed from a conductive substrate, at least one nanostructured interlayer disposed on the conductive substrate, the nanostructured interlayer having at least one ordered nanotube formed from at least one interlayer formation step, the nanostructured interlayer modified by the deposition of at least one dopant species, the introduction of at least one defect, or a combination thereof, and at least one coating disposed on the at least one nanostructured interlayer, to form a conductive and electrochemically active layer.

[0016] In some embodiments, the conductive substrate may be one or more of a metal, metal alloy, metal composite, conductive ceramic, carbon-based material,conductive polymers, or combination thereof. In some embodiments, the conductive substrate may be a metal oxide.

[0017] In some embodiments, the at least one dopant species may comprise an anionic, a cationic, or a mixed-valence species. In some embodiments, the at least one defect may comprise an oxygen or nitrogen vacancy.

[0018] In some embodiments, the at least one coating may comprise metal oxides, nitrides, carbides, borides, silicides, perovskite oxides, diamond-based films, MXenes, conductive polymers, Magneli phases, and combinations thereof.

[0019] In some embodiments, the at least one coating may comprise a multilayer stack including at least one barrier layer, at least one catalytic layer, and at least one protective outer layer.

[0020] In some embodiments, the electrode may be subjected to one or more posttreatments under controlled atmospheres selected from vacuum, argon, nitrogen, oxygen, air, forming gas, or carbon-rich proximity to tailor structural, electrical, or chemical properties.

[0021] In some embodiments, the at least one ordered nanostructure may comprise a nanotube array, nanowire, nanoporous or mesoporous film, foam, nanolaminate stack, or combination thereof.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures.

[0023] Figure 1 shows a schematic representation of an example multilayered electrode system, according to embodiments;

[0024] Figure 2 shows a schematic flow chart depicting an embodiment of example steps taken to manufacture the multilayered electrode system showing FIG. 1 , according to embodiments;

[0025] Figure 3A shows a scanning electron microscopy image of TiO2 nanotube bottoms following a one-step anodization steps, according to embodiments;

[0026] Figure 3B shows a scanning electron microscopy image of TiO2 nanotube bottoms following the multi-step interlayer formation step shown in FIG.2, according to embodiments;

[0027] Figure 4A shows a scanning electron microscopy image of an example nanostructured interlayer depicted in FIG. 1 , according to embodiments;

[0028] Figure 4B shows a scanning electron microscopy image of a doped and coated interlayer depicted in FIG. 1 , according to embodiments; and

[0029] Figure 5 shows a scanning electron microscopy image of least one doped electrode of FIG. 1 , as manufactured using the steps shown in FIG. 2, according to embodiments.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] According to embodiments, improved apparatus and methods of manufacturing improved multi-layered electrodes for use in electrochemical cells operative for the treatment of fluids are provided. Broadly, the present electrodes may comprise at least one first layer formed from a conductive substrate, at least one nanostructured interlayer disposed on the conductive substrate, and at least one conductive and electrochemically active layer disposed on the nanostructured interlayer. Broadly, the present methods may comprise synthesizing the multi-layered electrode byperforming at least one inter-layer formation step (e.g., anodization, deposition, or thermal conversion), at least one doping and / or defect-engineering step, and at least one coating step.

[0031] In some embodiments, without limitation, the present apparatus and methods may comprise developing at least one nanostructured interlayer using one or more interlayer formation steps. In some embodiments, the at least one interlayer formation step may comprise, without limitation, a multi-step anodization process, a multi-pass deposition process, a sequential thermal conversion process, or a combination thereof.

[0032] In some embodiments, the methods may further comprise at least one modification step configured to alter the electronic, chemical, or structural properties of the synthesized at least one nanostructured interlayer. For example, in some embodiments, the modification step may be selected from at least one of a doping step for doping the at least one nanostructured interlayer with a dopant species, a defect-engineering step for introducing controlled defects in the at least one nanostructured interlayer, or a combination thereof.

[0033] In some embodiments, the at least one doping step may include one or more of hydrothermal treatment, spray pyrolysis, chemical vapor deposition (CVD), physical vapor deposition (PVD), electrodeposition, or dip coating and thermal decomposition of precursor salts. In some embodiments, the at least one doping step may comprise doping the at least one interlayer with at least one dopant species (e.g., cationic, anionic, or mixed-valence).

[0034] In some embodiments, the defect-engineering step may comprise introducing controlled defects, such as oxygen vacancies.

[0035] In some embodiments, the methods may comprise performing at least one coating step for depositing at least one conductive and electrochemically active coating on the at least one nanostructured interlayer.

[0036] Without being limited to theory, it has been discerned that multi-step formation processes may be used to reinforce nanotubular or nanoporous architectures, preventing delamination and damage thereof. The generation of at least one ordered nanostructure using the presently improved methods may serve to improve chemical stability and charge injection.

[0037] Moreover, it has been discerned that modifying the at least one interlayer with a suitable dopant species and / or at least one defect profile (e.g., introducing titanium- based dopants and partial reduction to generate Ti3+centers, Co, Mn, Ni, B, Nb, Sr; rare-earth elements, and combinations thereof), as well as employing co-doping, gradient doping, or defect engineering, can enhance conductivity and tune catalytic behaviour. Additionally, introducing optional barrier and / or adhesion layers between the at least one conductive substrate and the at least one active coating layer, and employing outer coatings selected from metal oxides, nitrides, carbides, borides, silicides, perovskite oxides, diamond-based films (e.g., boron-doped diamond (BDD) and diamond-like carbon (DLC)), MXenes (e.g., Ti3C2Tx), conductive polymers, Magneli phases, and combinations thereof, may serve to increase chemical stability and corrosion resistance while providing high oxidation or reduction headroom and desired electrochemical selectivity.

[0038] Herein, advantageously, the presently improved methods may be used to extend the life of the at least one electrode, resulting in outperformance of known mixed oxide / doped electrodes, and serving to enhance the mechanical and chemical stability, conductivity, and prolonged service life for advanced electrochemical applications. The presently improved methods serve to synthesize at least one robust, efficient multi-layered electrode, manufactured from material having enhanced stability, conductivity, and degradation capabilities for advanced electrooxidation in the treatment of fluid applications, i.e., water treatment applications and the degradation of dissolved organic matter therein.

[0039] Herein, advantageously, the presently improved methods may at least be used to generate an interlayer providing a stable foundation for the formulated corrosion- resistant active top layer, such as mixed metal oxides, nitrides, or carbides, enhancing the stability and catalytic activity. The presently improved methods aim to overcome limitations of known doped electrodes, which lack long-term stability and well- structured interlayers for charge injection and durability. The presently improved methods provide an interlayer serving to improve adhesion, prevent oxygen from reaching the substrate (avoiding oxide formation and resistance), and increase surface area for reactions, promoting active oxidants and extending the electrode's lifespan. Without limitation, the presently described apparatus and methods of use offer improved performance and durability in electrooxidation processes.

[0040] The improved multilayered electrode system and methods of manufacture will now be described in more detail having regard to FIGS. 1 - 5.

[0041] According to embodiments, having regard to FIG. 1 , at least one embodiment of the presently improved multi-layered electrode 10 is provided. Generally, as will be described, electrode 10 may be configured to provide at least one conductive substrate (base) layer 12, and at least one conductive and electrochemically active coating (top) layer 18, and at least one nanostructured interlayer positioned therebetween 14, such configuration optimizing electrode 10 for electrooxidation processes.

[0042] In some embodiments, electrode 10 may comprise at least one first layer formed from a conductive substrate 12. For example, conductive substrate 12 may comprise, without limitation, metals, metal alloys, metal composites, conductive ceramics (e.g., Magneli phases), carbon-based materials (e.g., graphite, glassy carbon, carbon composites), conductive polymers, or combinations thereof.

[0043] In some embodiments, conductive substrate 12 may support formation of one or more nanostructured interlayer 14 having an ordered morphology (e.g., nanotube arrays, nanowires, nanoporous or mesoporous films, foams, nanolaminate stacks, 16). As will be described, such interlayer 14 may comprise at least one dopant species 19 and / or the introduction of at least one controlled defect. Such interlayer 14 may be electrochemically active, and may optionally be configured in combination with barrier layers, adhesion layers, or graded compositions.

[0044] In certain embodiments, the at least one nanostructured interlayer 14 may further provide a high-surface-area base for attachment of at least one conductive and electrochemically active coating 18 (e.g., metal oxide coating), optimized for electrooxidation processes for treating fluid in an electrochemical cell.

[0045] According to embodiments, having regard to FIG. 2, methods of manufacturing the multi-layered electrode 10 are provided.

[0046] In some embodiments, the methods of manufacture may comprise at least the steps of providing at least one conductive substrate 12 and performing at least one interlayer-formation step 20 to the at least one conductive substrate 12 to synthesize the at least one nanostructured interlayer 14.

[0047] In some embodiments, having regard to FIG. 2, the at least one interlayerformation step 20 may comprise at least one anodization step, such as a multi-pass anodization step. In other embodiments, anodization may be omitted, and the interlayer-formation step 20 may comprise performing one or more of chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), electrophoretic deposition (EPD), sol-gel processing, thermal oxidation or conversion, spark plasma sintering (SPS), plasma spraying, cold spraying, or additive manufacturing techniques.

[0048] Without limitation, it is contemplated that the at least one interlayer-formation step 20 may serve to reinforce the nanostructured interlayer 14, thereby preventing delamination or damage and improving its mechanical stability. In addition, the at least one interlayer-formation step 20 may enhance chemical stability and promote efficient charge injection.

[0049] In some embodiments, by way of example, surface preparation of the at least one conductive substrate 12 can include polishing, cleaning, and / or electrolytic or plasma treatments, or other suitable surface modification techniques. For example, the at least one substrate 12 may be polished with progressively finer emery papers,rinsed, dried, electrolytically polished in a sulfuric and phosphoric acid solution, and ultrasonically cleaned in a series of solvents, ensuring the removal of impurities.

[0050] In embodiments employing anodization, the prepared conductive substrate 12 may be introduced to suitable electrolytes and biased under controlled waveforms to form ordered nanostructures 16. For example, without limitation, a range of electrolytes (aqueous or non-aqueous, including fluoride-containing systems), voltages, temperatures, and durations may be used to tailor feature size and adhesion.

[0051] By way of non-limiting example, the at least one anodization step may be conducted in ethylene glycol or other solvents (e.g., glycerol, dimethyl sulfoxide (DMSO), or water-based systems) with fluoride sources at voltages selected to achieve a desired morphology over suitable durations (e.g., at a voltage range of approximately 40 - 60 V for a period ranging from approximately one to three hours in an ethylene glycol electrolyte with 0.1 - 0.6 wt% NF F and distilled water, using a titanium anode). Pulsed or bipolar waveforms and temperature control may also be employed. It should be appreciated that such values are illustrative only and may be varied according to the materials used and the geometry of the substrate.

[0052] In some embodiments, the at least one anodization step 20 may serve to form at least one nanostructured interlayer 14, such as a titanium dioxide (TiO2) nanotube array. For example, FIG. 3A shows scanning electron microscopy image of TiO2nanotube bottoms following a one-step anodization step, while FIG. 3B shows an image of TiO2nanotube bottoms following the presently described multi-stepanodization process (where a visible bonding layer is observed). Without limitation, it is contemplated that the present at least one anodization step 20 may serve to reinforce the structural integrity of nanostructured features such as nanotubes 16, preventing delamination or damage. Equivalent interfacial strengthening may also be achieved by alternative routes, including atomic layer deposition (ALD)-derived nanolaminates, TiN / TiC barrier layers, interfacial carbides or nitrides, or plasma- sprayed underlayers.

[0053] According to embodiments, the methods may further comprise performing at least modification step configured to alter the electronic, chemical, or structural properties of the at least one nanostructured interlayer 14.

[0054] In some embodiments, the at least one modification step may comprise at least one doping step 30 for doping the at least one nanostructured interlayer 14 with at least one dopant species 19 (e.g., cationic, anionic, or mixed-valence), the introduction of controlled engineering defects, or a combination thereof.

[0055] In some embodiments, suitable dopant species may include, without limitation, titanium-based dopants (including partial reduction to introduce Ti3+centers), cobalt, manganese, nickel, boron, nitrogen, fluorine, niobium, strontium, and rare-earth elements such as lanthanum and cerium, as well as combinations thereof. In some embodiments, co-doping strategies, gradient doping, defect engineering (e.g., oxygen vacancies), or nitrogenation may be employed. Without limitation, it is contemplated that the at least one doping step 30 may serve to optimize the conductivity, stability, and catalytic activity of the nanostructured interlayer 14.

[0056] In some embodiments, by way of example, the at least one doping step 30 may comprise hydrothermal treatment, spray pyrolysis, chemical vapor deposition, physical vapor deposition, atomic layer deposition, electrodeposition, or dip-coating followed by thermal decomposition of precursor salts, solid-state diffusion, plasma treatment, or combinations thereof, or other suitable doping techniques.

[0057] In some embodiments, for example, the methods may further comprise performing at least one post-processing treatments 32 under controlled atmospheres (e.g., vacuum, argon, nitrogen, air, oxygen, forming gas, or carbon-rich proximity for partial reduction) with selected ramp and dwell profiles to promote incorporation of dopant species, defect formation, and desired phase evolution. Such post-processing treatments 32 may be conducted over a non-limiting temperature range of approximately 300 °C to 1300 °C and may enhance structural, electrical, and chemical properties of electrode 10 (e.g., improving charge transfer ability, electrooxidation performance, and mitigating conductivity limitations). In some embodiments, the posttreatments 32 may be applied sequentially or in combination with deposition or interlayer-formation steps (e.g., annealing following atomic layer deposition, sol-gel processing, or anodization) to further optimize electrode performance. Coating 18 thickness, porosity, and microstructure (e.g., amorphous or crystalline; single-phase or multiphase) may be selected to balance activity, transport, and durability. Other suitable annealing conditions and structural configurations may likewise be employed.

[0058] In some embodiments, the methods may further comprise performing at least one coating step 40 for depositing at least one conductive and electrochemically active coating 18 on the nanostructured interlayer 14. Suitable coating families may include,without limitation, metal oxides, nitrides, carbides, borides, silicides, perovskite oxides (e.g., LaMnO3, LaNiO3, LaZnO3, LaFeO3, LaCoO3, NaTiO3, BaZnO3, and doped variants), diamond-based films (e.g., boron-doped diamond (BDD) and diamond-like carbon (DLC)), MXenes (e.g., Ti3C2Tx), Magneli phases (TinO2n-i), conductive polymers, and combinations thereof. For example, by way of illustrative example, the at least one coating may include lrO2-SnO2, Sb2O5, RuO2, TiN, ZrN, TiC, NbC, and perovskite compounds such as La-based oxides.

[0059] In some embodiments, the one or more coating layers 18 may be configured as multilayer stacks, for example comprising barrier layers, catalytic layers, and / or protective outer layers. In certain embodiments, the stacks may be designed to optimize adhesion, conductivity, durability, anticorrosion protection, oxidation state flexibility, high electronic and ionic conductivity, enhanced oxidant production, and high oxygen evolution potential (OEP).

[0060] Without limitation, it is contemplated that the one or more coating layers 18 may enhance stability and OEP, thereby aiding in the degradation of pollutants during the treatment of fluids. Moreover, the composition and processing of the coatings 18 may be tailored to desired performance characteristics, allowing for customized properties in both mixed and solid-solution forms.

[0061] In some embodiments, the at least one coating step 40 may be carried out using known techniques such as sol-gel, spin or spray coating, chemical bath or hydrothermal synthesis, chemical vapor deposition, physical vapor deposition, atomic layer deposition, electrophoretic deposition, electrodeposition, spray pyrolysis,thermal spraying (plasma or cold), screen printing, inkjet printing, aerosol jet printing, or combinations thereof, optionally followed by one or more thermal treatments 32 under selected atmospheres. For example, as above, the at least one electrode 10 may undergo a post-processing process, such as an annealing process 32 at a high temperature, such as between approximately 350°C - 550°C. FIG. 4A shows an anatase TiO2 nanotube array 16 post annealing at 450°C, and FIG. 4B shows a doped TiO2 nanotube array 16 after applying the at least one coating step 40.

[0062] According to embodiments, the present methods may further comprise formulating precursor solutions to synthesize mixed-oxide coatings such as lrO2 / Sb2O5-doped SnO2, or other coating families disclosed herein (e.g., metal oxides, nitrides, carbides, borides, perovskite oxides, diamond-based films such as BDD or DLC, MXenes, or conductive polymers), applicable to a range of substrates and interlayers. In some embodiments, subsequent thermal processes 32 (e.g., annealing under controlled atmospheres, rapid thermal processing, or spark plasma sintering) may be employed to crystallize the coating layer 18, ensuring the desired morphological and functional properties of the electrode 10. In some embodiments, such thermal processes 32 may be applied sequentially or in combination with interlayer formation 20 or deposition steps 30 to further optimize coating 18 performance.

[0063] In some embodiments, the engineered composition and thickness of the coating of mixed oxide, or carbide, and nitride may be selected based on desired properties such as electrochemical activity, the ability to produce active oxidants, chemical stability at different pH levels, availability of higher oxidation states, andconductivity. Without limitation, the appropriate materials and the composition may be chosen to improve performance and longevity of electrode 10.

[0064] Herein, having regard to FIG. 5, the presently improved methods of manufacture may be used to synthesize at least one electrode 10 having enhanced stability, conductivity, and degradation capabilities for advanced electrooxidation in water treatment applications, i.e. , degradation of the dissolved organic matter in water. As above, the presently improved at least one electrode 10 may serve to enhance OEP (e.g., high OEP of 2.41 ), demonstrating enhanced efficiency in generating active oxidants and facilitating the electrooxidation degradation of organic contaminants and aiding pollutant degradation. The presently described improved multi-layer composite electrode 10 design aids in enhancing the lift of the at least one electrode 10, surpassing the capabilities of known mixed oxide / doped electrodes.

[0065] Without limitation, the presently improved methods of manufacture may serve to produce an ordered, self-supported nanostructured interlayer 14 operative to serve as a proper base for the attachment of conductive coatings 18, as well as improving charge injection by providing more surface area. For example, modifying interlayer 14 with at least one dopant species 19 (e.g., transition metals, main-group elements, or rare-earths) and / or through defect engineering (e.g., oxygen or nitrogen vacancies), including the use of co-doping or gradient doping processes, may enhance interlayer 14 conductivity, catalytic activity, stability, selectivity, or other desired electrochemical properties.

[0066] Although a few embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications can bemade to these embodiments without changing or departing from their scope, intent or functionality. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and the described portions thereof.

Claims

WE CLAIM:

1. A method of manufacturing a multi-layered electrode having at least one nanostructured interlayer, the multi-layered electrode for use in an electrochemical cell for the treatment of fluids, the method comprising: providing at least one conductive substrate, performing at least one interlayer formation step to the at least conductive substrate to synthesize the at least one nanostructured interlayer on the at least one conductive substrate, performing at least one modification step configured to alter the electronic, chemical, or structural properties of the at least one nanostructured interlayer, and performing at least one coating step for depositing at least one coating to the nanostructured interlayer, creating at least one conductive and electrochemically active layer.

2. The method of claim 1 , wherein the at least one interlayer formation step is selected a multi-step anodization process, a multi-pass deposition process, a sequential thermal conversion process, or a combination thereof.

3. The method of claim 2, wherein the at least one interlayer formation step comprises performing one or more of a chemical vapor deposition, physical vapor deposition, atomic layer deposition, electrophoretic deposition, sol-gel processing, thermal oxidation or conversion, spark plasma sintering, plasma spraying, cold spraying, or additive manufacturing techniques.

4. The method of claim 1 , wherein the modification step is selected from at least one of doping the at least one nanostructured interlayer with a dopant species, introducing controlled defects in the at least one nanostructured interlayer, or a combination thereof.

5. The method of claim 4, wherein the at least one doping step includes hydrothermal treatment, spray pyrolysis, chemical vapor deposition, physical vapor deposition, electrodeposition, dip coating and thermal decomposition of precursor salts, solid- state diffusion, plasma treatment, or combinations thereof.

6. The method of claim 4, wherein the at least one dopant species comprises an anionic, a cationic, or a mixed-valence species.

7. The method of claim 4, wherein the introduction of controlled defects comprises introducing oxygen or nitrogen vacancies.

8. The method of claim 1 , wherein the at least one coating comprise metal oxides, nitrides, carbides, borides, silicides, perovskite oxides, diamond-based films, MXenes, conductive polymers, Magneli phases, and combinations thereof.

9. The method of claim 1 , wherein, the method further comprises performing one or more post-processing treatments under controlled atmospheres.

10. The method of claim 9, wherein the one or more post-processing treatment are performed sequentially or in combination with the at least one interlayer formation and at least one modification steps.

11. The method of claim 1 , wherein the conductive interlayer forms an electrochemically active surface layer for enhancing electrooxidation of the fluids by the electrochemical cell.

12. A multi-layered electrode having at least one nanostructured interlayer for use in an electrochemical cell for the treatment of fluids, the electrode comprising: at least one first layer formed from a conductive substrate, at least one nanostructured interlayer disposed on the conductive substrate, the nanostructured interlayer having at least one ordered nanotube formed from at least one interlayer formation step, the nanostructured interlayer modified by the deposition of at least one dopant species, the introduction of at least one defect, or a combination thereof, and at least one coating disposed on the at least one nanostructured interlayer, to form a conductive and electrochemically active layer.

13. The electrode of claim 12, wherein the conductive substrate is one or more of a metal, metal alloy, metal composite, conductive ceramic, carbon-based material, conductive polymers, or combination thereof.

14. The electrode of claim 13 wherein the conductive substrate is a metal oxide.

15. The electrode of claim 12, wherein the at least one dopant species comprises an anionic, a cationic, or a mixed-valence species.

16. The electrode of claim 12, wherein the at least one defect comprises an oxygen or nitrogen vacancy.

17. The electrode of claim 12, wherein the at least one coating comprises metal oxides, nitrides, carbides, borides, silicides, perovskite oxides, diamond-based films, MXenes, conductive polymers, Magneli phases, and combinations thereof.

18. The electrode of claim 12, wherein the at least one coating comprises a multilayer stack including at least one barrier layer, at least one catalytic layer, and at least one protective outer layer.

19. The electrode of claim 12, wherein the electrode is subjected to one or more posttreatments under controlled atmospheres selected from vacuum, argon, nitrogen, oxygen, air, forming gas, or carbon-rich proximity to tailor structural, electrical, or chemical properties.

20. The electrode of claim 12, wherein the at least one ordered nanotube comprises a nanotube array, nanowire, nanoporous or mesoporous film, foam, nanolaminate stack, or combination thereof.

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