Development of microstructured coating with flexible chemical composition adjustment for electrocatalytic application

Abstract

The current invention relates to a method for producing a nickel-based electrocatalyst for a urea oxidation reaction, wherein the method comprises electrodepositing nickel or an alloy thereof, thereby obtaining an electrodeposited coating, optionally further modifying said electrodeposited coating thereby obtaining a nickel-based electrocatalyst, wherein the nickel-based electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus. The inventions also relate to a nickel-based electrocatalyst for a urea oxidation reaction, wherein the nickel-based electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus.

Description

[0001] DEVELOPMENT OF MICROSTRUCTURED COATING WITH FLEXIBLE CHEMICAL COMPOSITION ADJUSTMENT FOR ELECTROCATALYTIC APPLICATION

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method for producing a nickel-based electrocatalyst for a urea oxidation reaction (UOR). In a second aspect, the present invention also relates to a nickel-based electrocatalyst for a UOR. In another aspect, the present invention also relates to a use of the method or the nickel-based electrocatalyst.

[0004] BACKGROUND

[0005] The production of hydrogen as a clean and sustainable energy carrier has gained significant attention in recent years. Hydrogen has emerged as a highly promising energy carrier due to its exceptional mass energy density. With three times more energy than diesel and 2.5 times more than natural gas, hydrogen presents a compelling alternative for a greener future.

[0006] However, the current methods of hydrogen production pose significant challenges in terms of cost and environmental impact. The most common technique, steam reforming of hydrocarbons, generates substantial CO? emissions, contributing to climate change and environmental degradation. To address these concerns, researchers have turned to electrolysis of water as a zero-carbon alternative for hydrogen production.

[0007] By passing an electric current through water, the process splits water molecules into hydrogen and oxygen. However, water is a highly stable molecule, requiring a considerable amount of energy to break its bonds. The electrocatalytic process of water splitting comprises two half reactions: the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. However, it is the OER that significantly limits water splitting for hydrogen generation. This reaction involves a complex proton-coupled electron transfer process, requiring a substantial overpotential to overcome the formidable energy barrier. As a result, the OER stands as the key obstacle preventing large-scale commercial application of water electrolysis.

[0008] The high energy requirements and associated costs pose significant obstacles to widespread adoption of water electrolysis for hydrogen production. Therefore, there is a pressing need to develop cost-effective and environmentally friendly approaches that can reduce the thermodynamics and cell voltage required for water electrolysis, particularly by addressing the challenges posed by the OER.

[0009] The present invention and embodiments thereof serve to provide a solution to one or more of above-mentioned disadvantages. To this end, the present invention relates to the development of an improved catalyst for catalyzing the OER.

[0010] SUMMARY OF THE INVENTION

[0011] In a first aspect, the present invention relates to a method according to claim 1. Preferred embodiments of the method are shown in any of the claims 2 to 12.

[0012] The present invention relates to a method for producing an enhanced nickel-based electrocatalyst for the urea oxidation reaction. The method of the preferred embodiment involves electrodeposition, alloying, and functional post-treatments processes. By electrodepositing nickel or a nickel alloy, an electrodeposited coating is obtained, which can be further modified to enhance its catalytic properties. Specifically, the modification includes the incorporation of a nickel-based electrocatalyst comprising nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus. This results in a highly active and stable electrocatalyst with improved performance, stability, and selectivity for urea oxidation and hydrogen production.

[0013] A particularly preferred embodiment is shown in claim 3. This claims a nickel-based electrocatalyst comprising nickel and at least two metallic elements from the list of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium; further comprising a non-metallic element chosen from: boron, nitrogen, sulfur, phosphorus, carbon and silicium; and oxygen. This results in a highly active and stable electrocatalyst with improved performance, stability, and selectivity, non-corrosion for urea oxidation, hydrogen production, carbonates and bicarbonates in particular when the medium is basic.

[0014] The preferred embodiments of the method, as described in the patent claims, provide additional details and variations of the method steps. These include techniques such as dynamic hydrogen bubble template electrodeposition, pulse plating, ion beam implantation, and co-deposition with ceramic microparticles. Each technique offers specific advantages in terms of controlled morphology, improved catalytic activity, stability, and tailored surface properties of the electrocatalyst. Furthermore, the method encompasses the use of magnetron sputtering techniques, such as high-power impulse magnetron sputtering or bipolar high voltage, to coat various surfaces (2D, powders ...) with clusters / nanoparticles (decoration) with high specific surface or a uniform and denser layer (core-shell types) with metals and their sub-stoichiometric oxides, hydroxides nitrides and sulfides. Aerosol-assisted chemical vapor deposition or spray pyrolysis can also be utilized to obtain metallic oxides, nitrides, and phosphides. These techniques enhance the performance, stability, and catalytic activity of the electrodeposited coating, making it suitable for various applications in fields such as electrocatalysis, energy conversion, and sensor technologies.

[0015] Overall, the method described in the patent application offers a comprehensive approach to produce an improved nickel-based electrocatalyst for efficient urea oxidation reactions. The incorporation of various techniques and modifications allows for precise control, customization, and optimization of the electrocatalyst's composition and characteristics, leading to enhanced catalytic properties and addressing the challenges associated with urea oxidation and hydrogen production.

[0016] In a second aspect, the present invention relates to a method / use according to claim 13. A preferred embodiment of the nickel-based electrocatalyst is shown in claim 14.

[0017] The developed nickel-based electrocatalyst comprises nickel and other carefully selected elements, exhibits outstanding catalytic activity, enhanced efficiency, durability, selectivity, and cost-effectiveness in the urea oxidation reaction. These remarkable advantages position it as a highly promising electrocatalyst for various applications, spanning energy conversion and storage systems, as well as environmental and industrial processes involving the oxygen evolution reaction (OER).

[0018] In a third aspect the present invention relates to a use according to claim 15.

[0019] The use as described herein provides an advantageous effect, enabling the efficient, sustainable, and scalable generation of hydrogen from urea. Embracing this approach drives the transition towards a cleaner and more sustainable energy landscape, effectively addressing concerns related to climate change and fostering a greener future. Furthermore, in a further or alternative embodiment of the invention, the method's significance can be extended to the relevance of the urea oxidation reaction in various fields, such as fuel cells and wastewater treatment. Developing an efficient electrocatalyst for this reaction contributes to technological advancement and addresses environmental challenges associated with urea-containing waste streams.

[0020] DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention relates to a method for producing a nickel-based electrocatalyst for a urea oxidation reaction (UOR) and the resulting electrocatalyst. More specifically, the invention pertains to a method involving electrodepositing nickel or a nickel alloy, optionally modifying the electrodeposited coating, and obtaining an electrocatalyst comprising nickel and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus. The resulting electrocatalyst demonstrates enhanced activity and efficiency in the urea oxidation reaction, thereby finding utility in various applications including hydrogen production.

[0022] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0023] As used herein, the following terms have the following meanings:

[0024] "A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.

[0025] "About" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / - 20% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1% or less, and still more preferably + / -0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.

[0026] "Comprise", "comprising", and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein. Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0027] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints.

[0028] Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members.

[0029] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.

[0030] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0031] In a first aspect, the invention provides a method for producing a nickel-based electrocatalyst, wherein the method comprises electrodepositing nickel or an alloy thereof, thereby obtaining an electrodeposited coating, optionally further modifying said electrodeposited coating thereby obtaining a nickel-based electrocatalyst, wherein the nickel-based electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus. In a preferred embodiment, the nickel-based electrocatalyst is particularly suited for a urea oxidation reaction (UOR). The inventors have surprisingly found that the combination of nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus, result in a stable, effective electrocatalyst for the urea oxidation reaction.

[0032] In a preferred embodiment, the invention provides a method for producing a nickel- based electrocatalyst for a urea oxidation reaction (UOR), wherein the method comprises electrodepositing nickel or an alloy thereof, thereby obtaining an electrodeposited coating, optionally further modifying said electrodeposited coating thereby obtaining a nickel-based electrocatalyst, wherein the nickel-based electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus.

[0033] In a preferred embodiment, the urea oxidation reaction is used to produce hydrogen. This offers notable advantages, especially in the processing of wastewater that contains urea. By employing the urea oxidation reaction, the wastewater can be effectively converted into a high-value commodity, namely hydrogen. Despite its potential as a zero-carbon alternative for hydrogen generation, the electrolysis of water demands significant energy input due to the inherent stability of water molecules. Water splitting involves two half reactions: the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. The OER, in particular, poses challenges as it requires high overpotentials to overcome the energy barriers involved in the multi-step proton-coupled electron transfer process. This limitation hinders the large-scale commercial application of water electrolysis.

[0034] To reduce the thermodynamic constraints, one approach is to add urea to the electrolyte. Urea electrolysis under standard conditions requires only a cell potential of approximately 0.37 V, significantly lower than the roughly 1.23 V required for water electrolysis. This reduction in cell voltage can lead to hydrogen production at a 70% lower cost. The electrochemical decomposition of urea-containing water, preferably waste such as urine, offers several benefits. For example, the electrolysis of urea enables the generation of hydrogen and nitrogen without CO? emissions, as it is mineralized and precipitated in the liquid phase. This creates a virtuous cycle for sustainable hydrogen production. The use of electrocatalysts is crucial to maintain low reaction potentials. Efficient catalysts exhibit high current density at low overpotentials without performance degradation over time. Urea oxidation can contribute to the removal of contaminants or the production of valuable co-products, such as polysaccharides and proteins, adding environmental value to the process.

[0035] However, catalyzing the urea oxidation reaction efficiently is a challenge. Platinum is known for its catalytic behavior towards urea but suffers from limited energy yield due to high overpotentials, slow reaction kinetics, and catalyst poisoning.

[0036] To this end, the present invention provides a solution wherein the method presented offers a highly advantageous approach to produce a nickel-based electrocatalyst suitable for the urea oxidation reaction (UOR). Nickel offers better electrocatalytic performance than platinum and is more economically viable. Improving the catalytic behavior of nickel-based materials can be achieved by modifying the specific surface area through different forms of nickel and by forming nickel alloys with varying chemical compositions.

[0037] This method involves the electrodepositing of nickel or a nickel alloy to obtain an electrodeposited coating, which can be further modified to yield a nickel-based electrocatalyst. The resulting electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus. The utilization of electrodeposition enables precise control over the deposition process, ensuring uniform coating and efficient utilization of materials. Electrodeposition is advantageous for its scalability, ease of operation, and compatibility with various electrode surface materials including nickel and nickel alloys.

[0038] Moreover, the method allows for the customization of the electrodeposited coating, facilitating the production of a nickel-based electrocatalyst with tailored properties. By introducing additional elements selected from the aforementioned group, the composition and characteristics of the electrocatalyst can be finely adjusted to optimize its performance in the urea oxidation reaction.

[0039] The inclusion of multiple elements in the electrocatalyst can induce synergistic effects, leading to improved catalytic activity, stability, and selectivity. The composition of the nickel-based electrocatalyst offers enhanced performance specifically tailored for the urea oxidation reaction. Furthermore, nickel itself possesses excellent catalytic properties, including high electrical conductivity, good corrosion resistance, and catalytic activity towards various reactions. By alloying nickel with other elements, the overall catalytic performance of the electrocatalyst can be further enhanced, making it a suitable base material for this application. Lastly, the method offers versatility in the selection of alloying elements. There can be different combinations be selected of cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus based on specific requirements and objectives, allowing for optimization of the electrocatalyst's performance for different applications.

[0040] In an embodiment of the invention the nickel-based electrocatalyst comprises at least one element selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium and at least one element selected from the group of: boron, nitrogen, oxygen, sulfur, phosphorus.

[0041] The electrocatalyst comprises nickel as the primary component. To enhance its catalytic performance, it is preferred to introduce other non-metallic elements, such as sulfur, nitrogen, and oxygen, phosphorus in the form of metallic sulfides, nitrides, phosphides and oxides. These elements can be incorporated either during the production of catalytic powders or through post-treatment of catalysts. This introduction serves multiple purposes, including activating the substrate, producing coatings, and modifying the surface energy. Such modifications have a positive effect on improving the contact between the electrolyte and the catalyst, leading to a reduction in overvoltage at the electrode, particularly beneficial for electrochemical reactions.

[0042] Regarding bimetallic transition metal alloys, the present invention conducted highlights the necessity of favoring other transition metals over platinum (Pt), which is less effective and more expensive. In particular, the Ni-Fe bimetallic alloy shows promise as it outperforms pure nickel, demonstrating stability even at high current density. Among the other metals, molybdenum has been identified, particularly in the form of sulfides and various oxides, often combined with a NiCo alloy. Alternatively, the combination of nickel and nickel-iron alloy has surprising advantages in terms of chemical and mechanical stability, with the oxide of this alloy remaining conductive. Furthermore, adding tungsten (W) to the nickel alloy results in coatings that resist corrosion better both at room temperature (lasting longer) and at high temperatures without causing issues with the electrode's performance.

[0043] Additionally, La-doped Zr, Cu, and Ni mixed oxide perovskites have shown effectiveness as catalysts in other NH3 / urea conversion technologies, such as photocatalysis, solid oxide fuel cells and solid oxide electrolysis cells.

[0044] In a preferred embodiment of the invention, the method comprises electroplating as a deposition technique.

[0045] The term "electrodeposition" is a general term that encompasses the broader range of processes involving the deposition of materials through electrochemical means. It refers to the process of depositing a material onto a surface by utilizing an electrochemical reaction. It involves the application of an electric current to facilitate the migration of charged particles from an electrolyte solution to a substrate or electrode surface. While electrodeposition is often associated with depositing metals, it can also include the deposition of other materials like ceramics, polymers, composites, or even multi-layered structures.

[0046] The term "electroplating" is a process of depositing a thin layer of metal onto a surface through an electrochemical reaction. It specifically refers to the process of depositing a metal coating onto a substrate or electrode surface through the use of an electric current. Electroplating typically involves immersing the substrate into an electrolyte solution containing metal ions of the desired coating material. The substrate serves as the cathode, and a metal anode is also present in the solution. When an electric current is applied, metal ions from the electrolyte are reduced at the cathode surface, resulting in the deposition of a metal layer.

[0047] Electrodeposition is a broader term encompassing various deposition techniques, including electroplating. Electroplating specifically refers to the process of depositing a thin layer of metal onto a substrate's surface.

[0048] In a preferred embodiment of the invention, the electrodepositing comprises dynamic hydrogen bubble template (DHBT) electrodepositing to obtain a structured material, preferably to create structured morphologies such as foam-shaped or pyramid-shaped structures. DHBT electrodepositing provides a unique and controlled approach to fabricate structured morphologies within the electrocatalyst material. By introducing hydrogen gas bubbles during the deposition process, the resulting electrocatalyst can exhibit distinct structural features such as foam-shaped or pyramid-shaped architectures.

[0049] This controlled structuring has profound effects on the electrocatalytic properties and performance. It significantly increases the surface area of the electrocatalyst. The foam-shaped or pyramid-shaped structures generated through DHBT electrodepositing offer a highly porous and interconnected network. This enlarged surface area provides a larger active area for catalytic reactions, allowing for enhanced electrocatalytic activity and improved overall performance in the UOR. The increased surface area also promotes efficient mass transport and accessibility of reactants to active sites, leading to enhanced reaction kinetics.

[0050] DHBT electrodepositing promotes uniformity and controllability of the electrocatalyst's morphology. By manipulating the deposition parameters and hydrogen bubble dynamics, it becomes possible to precisely engineer the desired foam-shaped or pyramid-shaped structures within the electrocatalyst material. This level of control ensures consistent and reproducible morphologies, which is crucial for obtaining reliable and predictable electrocatalytic performance.

[0051] The structured morphologies obtained through DHBT electrodepositing also enhance the stability and durability of the electrocatalyst. The interconnected foam-shaped or pyramid-shaped structures offer improved mechanical integrity, preventing aggregation or detachment of active sites during the UOR. This structural stability ensures sustained catalytic performance over prolonged operation times, making the electrocatalyst more robust and long-lasting.

[0052] In a preferred embodiment of the invention, the electrodepositing comprises pulse plating. Pulse plating refers to a specific electrodeposition technique that involves applying periodic on-off cycles of electrical current during the deposition or plating process. This technique utilizes short bursts of current followed by brief periods of no current, creating a pulsating pattern. The pulse plating method allows for better control and manipulation of the electrochemical deposition process. During pulse, the electrodeposited material is selectively deposited onto the electrode surface by applying controlled pulses of current. These pulses enable the deposition of the desired elements onto the electrode surface while minimizing undesirable side reactions. The periodic on-off cycles facilitate the diffusion of metal ions into the electrode surface, ensuring better adhesion and interfacial bonding between the electrocatalyst and the electrode. This technique promotes improved adhesion of the electrodeposited material to the electrode surface, ensuring the stability and durability of the electrocatalyst. It helps minimize surface defects such as cracks or voids, which can compromise the catalytic performance of the material. Additionally, pulse plating allows for precise control over the deposition process, resulting in a uniform coating and efficient utilization of materials. Furthermore, Pulse plating can significantly enhance the electrocatalytic activity of the deposited material. The periodic variation in current density during pulse plating promotes the formation of highly active sites on the surface of the electrocatalyst. These active sites facilitate the adsorption and subsequent reaction of urea molecules, leading to improved urea oxidation kinetics. The tailored electrocatalytic activity achieved through pulse plating enables higher conversion rates and overall efficiency in the UOR. Lastly, plating allows for efficient utilization of the electrodeposited materials. By controlling the deposition parameters, such as the duty cycle (ratio of on-time to total cycle time), it becomes possible to optimize the deposition efficiency. This means that a higher percentage of the electrodeposited material contributes to the desired electrocatalytic properties, minimizing wastage and improving the overall cost-effectiveness of the process.

[0053] In a preferred embodiment of the invention, the electrodeposited coating comprises at least one element selected from the group of Fe, Cu, Co, Mo, W, P. In the preferred embodiment of the invention, the electrodeposited coating for the production of the nickel-based electrocatalyst comprises at least one element chosen from the group of Fe, Cu, Co, Mo, W, and P. This selection of elements serves specific purposes and offers several advantages in the context of the invention, which involves the urea oxidation reaction (UOR) and the production of an efficient electrocatalyst.

[0054] The inclusion of iron in the electrodeposited coating brings about enhanced catalytic activity. Iron is known for its favorable catalytic properties and can significantly improve the kinetics and stability of the electrocatalyst. By incorporating iron-based alloys or composites, the overall performance of the urea oxidation reaction can be boosted, resulting in improved efficiency.

[0055] Copper can be chosen due to its excellent conductivity and remarkable electrocatalytic properties. Including copper in the electrodeposited coating enhances the conductivity of the electrocatalyst, facilitating efficient electron transfer during the urea oxidation reaction. Moreover, copper-based materials offer high surface area and active sites, which are advantageous for promoting effective urea electrooxidation. The addition of cobalt to the electrodeposited coating is another valuable choice. Cobalt possesses exceptional catalytic properties that positively influence the electrocatalyst's activity and stability. Utilizing cobalt-based materials in the coating composition enhances the electrocatalytic activity, leading to improved efficiency in the desired urea oxidation reaction.

[0056] The presence of molybdenum further contributes to the electrodeposited coating's catalytic performance. Molybdenum is renowned for its catalytic activity and incorporating it into the coating enhances the overall electrocatalytic behavior. The inclusion of molybdenum-based compounds aids in the oxidation of urea, resulting in improved reaction kinetics and overall efficiency.

[0057] Tungsten, known for its robustness and stability, can also be selected for its beneficial characteristics. Including tungsten in the electrocatalyst enhances its mechanical strength and resistance to degradation. This ensures that the electrocatalyst maintains its structural integrity and catalytic activity over prolonged usage, increasing its longevity and reliability.

[0058] Lastly, phosphorus may be chosen as an element that can modify the composition and morphology of the electrodeposited coating. The inclusion of phosphorus influences the structural and chemical properties of the electrocatalyst, thereby affecting its catalytic behavior. Phosphorus-based compounds contribute to the electrocatalyst's overall performance and stability.

[0059] In a preferred embodiment of the invention, the method comprises performing an ion beam implantation treatment of the electrodeposited material, thereby obtaining a modified catalytic surface. Ion beam implantation or ionic implantation is a process in which high-energy ions are accelerated and directed towards a target material, causing the ions to penetrate the material's surface. Ionic implantation is preferably a post-treatment method to further enhance the catalytic properties of the electrodeposited structured material.

[0060] The effect of ion beam implantation is twofold. Firstly, it allows for the introduction of foreign ions into the electrodeposited material, leading to doping or alloying effects. By implanting ions of different elements into the material, the composition and properties of the catalytic surface can be modified. This can result in improved catalytic activity, enhanced stability, and altered surface reactivity, all of which are desirable for the effective urea oxidation reaction UOR. Secondly, ion beam implantation can induce structural changes in the material, such as the creation of defects, lattice distortions, or phase transformations. These structural modifications can influence the material's surface morphology, crystalline structure, and surface area, which in turn can impact the electrocatalytic performance. By controlling the implantation parameters, such as ion species, energy, and dose, it is possible to tailor the surface characteristics to optimize the catalytic behavior for the UOR.

[0061] In a preferred embodiment of the invention, said ion beam implantation treatment comprises doping with electronegative elements selected from the group of nitrogen, sulfur, oxygen, phosphorus, fluorine and combinations thereof. By doping with electronegative elements such as nitrogen, sulfur, oxygen, phosphorus, fluorine, and their combinations, the ion beam implantation treatment aims to enhance the catalytic properties of the electrodeposited material. These dopants can modify the electronic structure, introduce functional groups, promote catalytic synergy, and provide surface passivation, all of which contribute to an improved electrocatalyst for the urea oxidation reaction.

[0062] Electronegative elements have a higher affinity for electrons, which can alter the electronic structure of the material. Incorporating electronegative dopants can introduce additional electron-rich sites or modify the charge distribution, leading to improved charge transfer kinetics and enhanced catalytic activity. Electronegative dopants can introduce functional groups or reactive sites on the material's surface. For example, oxygen and sulfur can create oxygen-containing or sulfur-containing functional groups, respectively. These functional groups can facilitate the adsorption and activation of reactant molecules, such as urea, and promote specific reaction pathways, thereby increasing the efficiency of the urea oxidation reaction.

[0063] Doping with electronegative elements can promote synergistic effects between different elements in the material. For instance, the presence of nitrogen and sulfur dopants can form active sites for electrocatalytic reactions and enhance the catalytic performance of the nickel-based electrocatalyst. The combination of different electronegative elements can create a unique catalytic environment, leading to improved catalytic activity and selectivity.

[0064] Electronegative elements can also act as passivating agents, reducing the formation of undesired side reactions or corrosion processes on the catalytic surface. This passivation effect can enhance the stability and durability of the electrodeposited material, prolonging its catalytic performance over time.

[0065] In a preferred embodiment of the invention, the method further comprises codeposition of microparticles of metallic or non-metallic compounds, preferably ceramic particles selected from the group consisting of WC, WS2, M0S2, MOO2, CeC>2, and combinations thereof, onto the electrodeposited coating. By incorporating microparticles of metallic and non-metallic compounds into the previously microstructured coating achieved through preferably the DHBT method, the specific surface area is maintained while introducing beneficial modifications. Ceramic particles such as WC, WS2, M0S2, MOO2, and CeC>2 are seamlessly integrated into the predominantly nickel-based metallic matrix through either electrolytic or electroless processes. The incorporation of these microparticles serves to significantly improve both the catalytic activity and erosion resistance properties of the electrocatalyst, thereby enhancing its overall durability. Achieving optimal results necessitates meticulous control of the hydrodynamic conditions, as it represents a critical parameter in regulating the rate of particle incorporation. It is imperative to maintain a constant suspension of particles without agglomeration, demanding careful attention to the electrolysis cell geometry and electrolyte agitation.

[0066] In a further or alternative embodiment of the invention, the method comprises an electrolytic co-deposition process. Electrolytic co-deposition involves the use of an electric current to facilitate the deposition of microparticles onto the electrodeposited coating. In this process, the microparticles are dispersed in an electrolyte solution containing suitable metal salts. When an electric current is applied, metal ions are reduced and deposited onto the electrodeposited coating, while simultaneously incorporating the microparticles into the growing coating. This results in the simultaneous deposition of metal and ceramic particles, effectively co-depositing them onto the surface. By adjusting the parameters such as current density, deposition time, and bath composition, it is possible to control the deposition rate and particle distribution within the coating. This control allows for precise engineering of the coating's microstructure and properties. Electrolytic co-deposition promotes strong adhesion between the microparticles and the electrodeposited coating. The electrochemical nature of the process ensures good interfacial bonding, resulting in improved mechanical stability and resistance to particle detachment during usage. Since the base electrodeposited coating is already obtained through an electrochemical process, electrolytic co-deposition is a natural extension. The compatibility between the processes simplifies the manufacturing steps and provides a seamless integration of the co-deposited particles into the existing coating.

[0067] In a further or alternative embodiment of the invention, the method comprises an electroless co-deposition process. Electroless co-deposition, also known as autocatalytic deposition, is a chemical deposition process that does not require the application of an electric current. In this process, the microparticles act as nucleation sites for the reduction of metal ions from a solution containing suitable metal precursors. The reduction occurs spontaneously on the surface of the microparticles, leading to the deposition of both metal and ceramic particles onto the electrodeposited coating. Electroless co-deposition enables the deposition of microparticles even on complex-shaped electrode surfaces or within narrow cavities. The process ensures uniform coating thickness and deposition across the entire surface, resulting in conformal coverage of the electrodeposited coating. Electroless co-deposition is particularly advantageous when the electrodeposited coating is non- electrically conductive. Since the process relies on chemical reactions rather than electrical conductivity, it allows for deposition on a wider range of materials. Electroless co-deposition operates at lower temperatures compared to some electrolytic processes. This lower temperature reduces the potential for stress- induced damage to the electrode surface or the electrodeposited coating, especially when dealing with temperature-sensitive materials.

[0068] In a preferred embodiment of the invention, the co-deposition includes ultrasonic agitation to maintain particle suspension without agglomeration. Ultrasonic agitation refers to the use of high-frequency sound waves to create mechanical vibrations and induce cavitation in a liquid medium during the co-deposition process. It involves the application of ultrasonic energy to maintain the suspension of microparticles without agglomeration. Ultrasonic agitation enhances the co-deposition process by dispersing and suspending microparticles. High-frequency sound waves create cavitation bubbles that collapse, generating turbulence and dispersing particles uniformly. This stability prevents clumping and ensures even distribution within the metallic matrix. Ultrasonic agitation maintains particle suspension, preventing settling and agglomeration. Microstreaming and shear forces disrupt settling and keep particles suspended, leading to a homogeneous distribution. This promotes a high-quality, well-adhered coating with improved catalytic performance. Additionally, ultrasonic agitation can influence particle size and morphology. Controlling intensity and duration can result in finer, more uniformly shaped particles, allowing customization of coating properties such as surface area and reactivity.

[0069] In a preferred embodiment of the invention, the method further comprises magnetron sputtering using high-power impulse magnetron sputtering (HIPIMS) or bipolar high voltage (BHV) to produce nanoparticles and sub-stoichiometric oxides or hydroxides. Magnetron sputtering is a physical vapor deposition technique used for thin coating deposition. It involves the bombardment of a target material with ions in a low-pressure gas environment, resulting in the ejection of atoms or molecules from the target surface. These ejected species then deposit onto an electrode surface to form a thin coating. High-power impulse magnetron sputtering (HIPIMS) and bipolar high voltage (BHV) are advanced variations of magnetron sputtering that provide unique advantages. HIPIMS involves applying short, high- power pulses to the target material, resulting in intense plasma generation and a high degree of ionization. BHV, on the other hand, utilizes a pulsed bipolar power supply to induce ionization and improve the coating properties.

[0070] The high-power pulsing and ionization conditions in HIPIMS and BHV promote the generation of nanoparticles during the sputtering process. These nanoparticles can have unique properties and characteristics, such as high surface area, enhanced reactivity, and improved catalytic performance. The deposition of sub-stoichiometric oxides or hydroxides refers to the formation of thin coatings with a composition slightly deviating from the stoichiometric ratio of the target material. This can be achieved by controlling the sputtering conditions, such as the gas pressure and target power. Sub-stoichiometric coatings can exhibit specific properties, such as increased defect density or modified electronic structure, which can be advantageous for certain applications, including catalysis.

[0071] In a preferred embodiment of the invention, the method comprises aerosol-assisted chemical vapor deposition (CVD) or spray pyrolysis, thereby obtaining metallic oxides, nitrides, and phosphides. Aerosol-assisted chemical vapor deposition and spray pyrolysis are both widely used techniques for the synthesis of thin coatings and coatings. They involve the generation of a fine aerosol or spray containing precursor materials, which are then delivered to a heated electrode surface where they undergo chemical reactions to form the desired compounds. Aerosol-assisted CVD and spray pyrolysis allow for the deposition of a wide range of materials, including metallic oxides, nitrides, and phosphides. This versatility enables the fabrication of diverse compositions and structures tailored to specific catalytic or functional requirements.

[0072] These deposition techniques offer excellent conformal coating capabilities, meaning that the resulting coating can uniformly cover complex or irregularly shaped electrode surfaces. This is particularly advantageous when coatings intricate electrodeposited morphologies or three-dimensional structures, ensuring uniformity and coverage over the entire surface. By carefully selecting the precursor materials and optimizing the process parameters, aerosol-assisted CVD and spray pyrolysis allow for precise control over the composition and morphology of the deposited coatings. This control enables the fine-tuning of catalytic properties, surface area, crystallinity, and other key characteristics that influence the performance of the electrodeposited coating.

[0073] In a second aspect, the invention provides a nickel-based electrocatalyst, wherein the nickel-based electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus.

[0074] In a preferred embodiment, the invention provides a nickel-based electrocatalyst for a urea oxidation reaction, wherein the nickel-based electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus. The nickel-based electrocatalyst described in the second aspect of the invention offers remarkable advantages that make it highly effective for the urea oxidation reaction. The electrocatalyst is composed of nickel and at least two elements chosen from cobalt, iron, copper, molybdenum, tungsten, titanium, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus and their combinations. This specific composition contributes to the exceptional qualities of the nickel-based electrocatalyst, providing numerous benefits for its application. One advantage of the nickel-based electrocatalyst is its enhanced catalytic activity. The inclusion of aforementioned elements modifies the electronic structure and surface properties of the electrocatalyst, resulting in significantly improved reactivity towards the OER. This heightened catalytic activity leads to faster reaction kinetics, allowing for more efficient conversion of urea to desired oxidation products. The combination of nickel with other elements enhances the electrocatalyst's resistance to degradation and corrosion, ensuring long-term stability and sustained catalytic performance even under demanding reaction conditions. This durability is crucial for achieving stable and reliable performance in urea oxidation processes.

[0075] In a more preferred embodiment, the nickel-based electrocatalyst is a nickel-based tri-metallic alloy incorporated with at least one non-metallic dopant and oxygen. In a preferred embodiment, the nickel-based electrocatalyst comprises, more preferably consists essentially of, most preferably consists of: Nix-Mi,y-M2,z-Ep-Oq, wherein Ni is nickel; wherein Ml and M2 are two different metallic elements independently selected from the list of: cobalt, iron, copper, molybdenum, titanium, tungsten or zirconium; wherein E is selected from: silicon, germanium, boron, nitrogen, sulfur, carbon or phosphorus; and wherein O is oxygen. Subscripts x, y, z, p and q represent the relative atomic fractions of each element. In a further preferred embodiment, the nickel-based electrocatalyst is a surface layer of at least 2pm, more preferably at least 3pm, more preferably at least 4pm, most preferably at least 5 pm; and having an atomic composition of Nix-Mi,y-M2,z-Ep-Oq, wherein x, y, z, p and q represent the relative atomic fractions as measured by EDX analysis over said depth. More preferably, EDX measured at an electronic accelerating voltage of 15 keV. In another preferred embodiment, EDX measured at a depth of between 1 pm and 2pm, more preferably between 1 pm and 3 pm; more preferably between 1 pm and 4 pm; more preferably between 1 pm and 5 pm. As represented herein, x, y, z, p and q are relative atomic fractions, wherein the total alloy composition is 1. In a more preferred embodiment:

[0076] - x is at least 0.20, more preferably at least 0.30, more preferably at least 0.40, more preferably at least 0.45, more preferably at least 0.50, more preferably at least 0.55, more preferably at least 0.60, more preferably at least 0.70, more preferably at least 0.75. In a preferred embodiment, x is at most 0.90, more preferably at most 0.85, more preferably at most 0.80, more preferably at most 0.75, more preferably at most 0.70, more preferably at most 0.65, more preferably at most 0.60, most preferably at most 0.50.

[0077] - y is at least 0.01, more preferably at least 0.05, more preferably at least 0.10, more preferably at least 0.15, more preferably at least 0.20. In a preferred embodiment, y is at most 0.50, more preferably at most 0.40, more preferably at most 0.30, more preferably at most 0.25, more preferably at most 0.20. In a particular preferred embodiment, Ml is tungsten (W) and y is the abovementioned values.

[0078] - z is at least 0.01, more preferably at least 0.05, more preferably at least 0.10, more preferably at least 0.15, more preferably at least 0.20. In a preferred embodiment, z is at most 0.50, more preferably at most 0.40, more preferably at most 0.30, more preferably at most 0.25, more preferably at most 0.20. In a further preferred embodiment, M2 is iron (Fe) and z is the abovementioned values. p is at least 0.001, more preferably at least 0.005, more preferably at least 0.01, more preferably at least 0.02, more preferably at least 0.03, more preferably at least 0.04, more preferably at least 0.05, more preferably at least 0.07, more preferably at least 0.10. In a preferred embodiment, p is at most 0.30, more preferably at most 0.20, more preferably at most 0.15, more preferably at most 0.12, more preferably at most 0.10, more preferably at most 0.07. In a further preferred embodiment, E is preferably chosen from phosphor (P) or nitrogen (N) and p is the abovementioned values. - q is at least 0.001, more preferably at least 0.005, more preferably at least 0.01, more preferably at least 0.02, more preferably at least 0.03, more preferably at least 0.04, more preferably at least 0.05, more preferably at least 0.07, more preferably at least 0.10. In a preferred embodiment, q is at most 0.30, more preferably at most 0.20, more preferably at most 0.15, more preferably at most 0.12, more preferably at most 0.10, more preferably at most 0.07. In a preferred embodiment, z is at least 0.01, more preferably at least 0.05, more preferably at least 0.10, more preferably at least 0.15, more preferably at least 0.20.

[0079] In a particular preferred embodiment, the nickel-based catalyst comprising a surface layer over a depth of at least 1 pm, more preferably at least 2 pm, more preferably at least 3pm, more preferably at least 4pm, said surface layer comprising, more preferably consisting essentially of, most preferably consisting of :

[0080] Nickel (Ni) in an average amount of 10 to 80 at% over said depth; preferably in an average amount of 30 to 70 at% over said depth; most preferably the remainder relative to the other elements W, Fe, P and O is Ni;

[0081] - Tungsten (W) in an average amount of 4 to 30 at% over said depth, more preferably in an amount of 4 to 20 at% over said depth;

[0082] Iron (Fe) in an average amount of 10 to 30 at% over said depth, more preferably in an amount of 10 to 25 at% over said depth, most preferably in an amount of 15 to 25 at% over said depth;

[0083] Phosphor (P) in an average amount of 1 to 15 at% over said depth, more preferably in an amount of 1 to 15 at% over said depth, most preferably 1 to 10 at% over said depth; and

[0084] - Oxygen (O) in an average amount of 5 to 25 at% over said depth, more preferably in an amount of 10 to 25 at% over said depth, more preferably in an amount of 10 to 20 at% over said depth, most preferably in an amount of 15 to 20 at% over said depth; and

[0085] Optionally additional elements chosen from : cobalt, copper, molybdenum, titanium, zirconium; silicon, germanium, boron, nitrogen, sulfur, carbon or combinations thereof; more preferably said additional element is nitrogen; each additional element in an average amount of at most 15 at% over said depth, preferably at most 10 at% over said depth, more preferably at most 5 at% over said depth, more preferably at most 3 at% over said depth, most preferably at most 1 at% over said depth. This results in a highly active and stable electrocatalyst surface layer with improved performance, stability, and selectivity, non-corrosion for urea oxidation, hydrogen production, carbonates and bicarbonates in particular when the medium is basic.

[0086] In a preferred embodiment, the tri-metallic alloy incorporated with at least one non- metallic dopant and oxygen is created utilizing electrodeposition and optionally subsequent cold plasma treatments (including ion implementation). Electrodeposition is particularly advantageous for producing complex metallic alloys through the simple mixing of respective electrolytes, with rapid decomposition rates proportional to the current applied. Co-dispersing non-metallic compounds (e.g. phosphorus, sulfur and also semiconductors such as silicon and germanium) can advantageously be achieved via a co-electrolyte, incorporating these non-metallic elements into the metallic alloy through electrolyte reduction. Alternatively, these non-metallic elements may be added as nano-particles.

[0087] In addition, electrodeposition allows for the creation of in situ multi-scale structured materials, such as coatings, electrodes, fine-tuned nano- to micro-porosity and nano to macro deterministic structuring. As electrodeposition provides a wide range of control over the structure of the material, improvements to catalytic activity, electrical conductivity (thereby influencing conversion efficiency) and gas exchange at the electrodes can all be achieved.

[0088] Subsequent cold plasma treatments can be used to enhance the surface properties by:

[0089] Minimizing the presence and formation of non-conductive native oxides, thereby reducing the series resistance and improving conversion efficiency; Depositing complementary materials, to improve catalytic performance, improve corrosion resistance and other functions, on the surface of electrocatalytic materials produced by electrodeposition; and

[0090] Enhancing or maintaining electrocatalytic performance through ion implantation, which increases material density over several microns, thereby improving electrical conductivity, hardness and wear resistance, and electrochemical corrosion resistance in operational conditions.

[0091] The combination of these techniques allows for the production of tri-metallic alloy incorporated with at least one non-metallic dopant and oxygen, having a formula of: Nix-Mi,y-M2,z-Ep-Oq, for the previously mentioned options for Ml, M2 and E. In addition, this results in materials which have high catalytic activity, are resistant to basic media and have relatively high conductivity as desired for electrocatalysts used in high pH environments.

[0092] In a preferred embodiment, an nickel-based electrocatalyst with a surface structure of Nix-Mi,y-M2,z-Ep-Oq ; having a surface thickness of at least 2 pm is created by first coating, preferably through electroplating, a substrate said substrate preferably being an iron or steel substrate; with a bulk nickel (Ni) layer with a thickness larger than 2 pm, preferably at least 3pm, more preferably about 5pm. This can be achieved through nickel sulfamate electroplating. Preferred conditions are 1-10 A / dm2, at an elevated temperature between 40°C and 70°C, more preferably 50°C to 60°C and an acidic pH, such as between 2 and 5, preferably between 3 and 4. This bulk nickel layer ensures appropriate adhesion between the substrate and the nickel-based electrocatalyst alloy. It also improves the stability of the downstream process steps, thereby providing consistent results when coating complex surface structures.

[0093] Preferably, in a next step a surface structure of Nix-Mi,y-M2,z-Epis coated onto said bulk nickel layer, preferably through electroplating, More preferably, the surface structure to be coated is an Ni-W-Fe-P alloy coating. Preferably, the temperature during this electroplating process is higher, such as 50°C to 80°C, more preferably 60°C to 75°C, most preferably 60°C to 70°C. Preferably, the pH is rather neutral to basic, such as a pH between 6 and 10, more preferably between 7 and 9, more preferably between 8 and 9. Further more preferably, a Ni-W-Fe-P alloy coating can be achieved by electroplating of nickel sulfate hexahydrate, sodium tungstate dihydrate, iron (II) sulfate heptahydrate and sodium hypophosphite monohydrate. Additives to improve process control can be included as necessary.

[0094] Preferably, the surface structure of Nix-Mi,y-M2,z-Ep is subsequently activated, preferably through oxidation, more preferably in a hydroxide solution thereby resulting in a nickel-based electrocatalyst with a surface structure of Nix-Mi,y-M2,z- Ep-Oq. More preferably, the hydroxide solution is an alkali or earth alkaline hydroxide solution, more preferably KOH.

[0095] In a further preferred embodiment, the activation may be achieved through cyclic voltammetry in a hydroxide solution, preferably KOH, more preferably at 3M to 10M, more preferably at 3M to 7M, most preferably at 4M to 6M, versus Ag / AgCl. This method of activation produces highly reproducible surface conditions. Preferably, the voltammetry is repeated over at least 5 cycles, more preferably at least 10 cycles, more preferably at least 20 cycles, more preferably at least 30 cycles, more preferably at least 40 cycles, most preferably at least 50 cycles.

[0096] In terms of selectivity and specificity, the nickel-based electrocatalyst offers improved control over the urea oxidation reaction. By directing the reaction towards desired product formation and minimizing unwanted side reactions, the electrocatalyst enhances the selectivity and purity of the oxidation products. This selectivity is vital for applications that require high-quality output and precise control over the reaction outcomes.

[0097] The utilization of abundant and cost-effective elements such as nickel, cobalt, iron, copper, molybdenum, and tungsten contribute to the overall cost-effectiveness of the nickel-based electrocatalyst. Compared to precious metals commonly used in catalysis, these elements offer a more economical solution without compromising performance. This cost-effectiveness makes the electrocatalyst a practical choice for various industrial and commercial applications.

[0098] Furthermore, the versatility of the electrocatalyst composition allows for tailored catalytic properties of the nickel-based electrocatalyst. By adjusting the proportions and combinations of the selected elements, the performance of the electrocatalyst can be fine-tuned to suit specific application requirements. This versatility enables broader applicability of the nickel-based electrocatalyst in different urea oxidation reaction systems, expanding its potential in fields such as energy conversion, electrocatalysis, and sensor technologies.

[0099] In a preferred embodiment of the invention, the nickel-based electrocatalyst according to the second aspect is obtainable by the method of the first aspect. More preferably the electrocatalyst according to the second aspect is obtained by the method of the first aspect.

[0100] In a third aspect, the invention relates to the use of the method according the first aspect of the invention, or the nickel-based electrocatalyst according the second aspect of the invention, for the production of a nickel-based electrocatalyst. A nickel- based electrocatalyst is advantageous for several reasons. Firstly, nickel exhibits high catalytic activity, effectively facilitating electrochemical reactions. Secondly, nickel is durable and corrosion-resistant, ensuring long-lasting performance even under harsh conditions. Its versatility allows for customization to suit specific applications and reactions. Nickel-based electrocatalysts are widely used in energy conversion and storage technologies, playing crucial roles in processes like hydrogen evolution, oxygen evolution, and carbon dioxide reduction. In a preferred embodiment, the invention relates to the use of the method according the first aspect of the invention, or the nickel-based electrocatalyst according the second aspect of the invention, for the production of a nickel-based electrocatalyst for a urea oxidation reaction. Nickel-based electrocatalysts have demonstrated excellent catalytic activity for urea oxidation, efficiently converting urea into desired reaction products. They exhibit stability and durability in the corrosive environment of urea oxidation reactions. Moreover, nickel is a cost-effective and abundant material compared to precious metals. Designing a nickel-based electrocatalyst specifically for urea oxidation allows for optimization of its composition and structure, leading to improved performance tailored to the requirements of the reaction.

[0101] In a preferred embodiment, the invention relates to the use of the method according the first aspect of the invention, or the nickel-based electrocatalyst according the second aspect of the invention, for the production of hydrogen. Hydrogen is a clean and sustainable energy carrier that holds immense potential for addressing environmental concerns and transitioning to a low-carbon economy. By using the method or electrocatalyst proposed in the invention, hydrogen production can be achieved through a more efficient and environmentally friendly process. This contrasts with conventional methods that often rely on fossil fuels, resulting in greenhouse gas emissions and contributing to climate change.

[0102] The method or nickel-based electrocatalyst enables the electrochemical splitting of urea, a readily available and economically viable resource, to preferably generate hydrogen. Urea is a nitrogen-rich compound commonly used as a fertilizer and industrial chemical, making it a renewable feedstock for hydrogen production. By harnessing urea as a precursor for hydrogen, the invention offers a sustainable and abundant source of this clean energy carrier.

[0103] Furthermore, the method or electrocatalyst demonstrates high catalytic activity, selectivity, and stability in the urea oxidation reaction. This translates to efficient conversion of urea into hydrogen, ensuring maximum yield and minimizing energy losses. The electrocatalytic process facilitated by the invention allows for precise control over the hydrogen production rate, making it adaptable to various energy demands and storage requirements.

[0104] The use of the method or electrocatalyst also aligns with the growing emphasis on energy storage and utilization of intermittent renewable energy sources such as solar and wind power. Hydrogen serves as an excellent medium for energy storage and can be effectively utilized for power generation, transportation, and industrial processes. The invention's ability to produce hydrogen through a clean and efficient electrochemical route contributes to the overall development of sustainable energy systems and promotes the integration of renewable energy sources into the grid.

[0105] Moreover, the method or electrocatalyst offers scalability and versatility in hydrogen production. The electrochemical process can be easily implemented on different scales, from small-scale applications such as portable hydrogen generators to large- scale industrial setups. This scalability allows for the adoption of the method or electrocatalyst across various sectors, ranging from residential and commercial use to industrial and infrastructure applications.

[0106] In a preferred embodiment, urea is electrolyzed with an electrocatalyst as per the first or second aspect, particularly preferred are the nickel-based tri-metallic alloy incorporated with at least one non-metallic dopant having a formula of: Nix-Mi,y-M2,z- Ep-Oq. When urea is electrolyzed, hydrogen gas, nitrogen gas and CO2 are produced. In an aqueous, basic medium the production of CO2 results in a mixture of bicarbonate (HCO3 ) and carbonate (CO32) species. As the pH increases, the equilibrium shifts towards the carbonate species. This allows the production of biocarbonates and bio-bicarbonates simultaneously with green hydrogen. Consequently, the process can be utilized for CO2 capture, green hydrogen production and the production of high value bio-bicarbonates and bio-carbonates simultaneously.

[0107] In a preferred embodiment, the invention relates to the use of the electrocatalysts as per the first or second aspect, for the electrolysis of urea in an aqueous basic medium, thereby producing hydrogen and a mixture comprising carbonates or bicarbonates. Preferably, said aqueous basic medium has a pH of at least 8, more preferably at least 9, more preferably at least 10, more preferably at least 11, more preferably at least 12, more preferably at least 13. In a preferred embodiment, the aqueous basic medium comprises a mixture of water and an alkali hydroxide, more preferably NaOH and I or KOH. The use of alkali hydroxides results in alkali carbonate or alkali bicarbonate species. However, it is clear that the invention is not limited to this application. One alternative use is in the field of electrocatalysis for other reactions beyond urea oxidation. The nickel-based electrocatalyst, wherein the nickel-based electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus, exhibits excellent catalytic properties. These properties make it suitable for a wide range of electrochemical reactions. For example, the electrocatalyst can be applied in oxygen evolution reactions (OER) or hydrogen evolution reactions (HER), which are essential processes in electrochemical water splitting. Efficient and durable electrocatalysts are crucial for achieving high conversion rates and minimizing energy losses in these reactions. The nickel-based electrocatalyst's unique composition and structural properties make it a promising candidate for enhancing the performance and stability of electrochemical water splitting systems.

[0108] Additionally, the electrocatalyst can find applications in other energy conversion technologies such as fuel cells, where electrocatalysts play a vital role in facilitating efficient and selective electrochemical reactions. By leveraging the advantages of the nickel-based electrocatalyst, improved fuel cell performance, enhanced durability, and extended operational lifetimes can be achieved.

[0109] Furthermore, the electrocatalyst's unique properties can also be utilized in sensor technologies. Electrochemical sensors rely on the catalytic activity of the sensing material to detect and quantify specific analytes in various environments. The high catalytic activity, selectivity, and stability of the nickel-based electrocatalyst make it a promising candidate for sensor applications, enabling sensitive and accurate detection of target analytes.

[0110] The invention is further described by the following non-limiting examples which further illustrate the invention, and are not intended to, nor should they be interpreted to, limit the scope of the invention.

[0111] EXAMPLES

[0112] The present invention will now be further exemplified with reference to the following examples. The present invention is in no way limited to the given examples or to the embodiments presented in the figures.

[0113] Example 1: Hydrogen Generation from Urea using Nickel-Based Electrocatalyst

[0114] In this example, a nickel-based electrocatalyst is developed specifically for the urea oxidation reaction using a combination of deposition techniques. The method involves NiMo deposition, NiMo deposition followed by anodic polarization, and Ni deposition with M0S2 fillers. Each step contributes to the synthesis of distinct catalysts with enhanced properties for urea oxidation. Additionally, future prospects for further improvement and exploration of the electrocatalyst are considered. Firstly, NiMo deposition is employed, where nickel and molybdenum are co-deposited onto the electrode surface. This deposition process enhances the catalytic activity and stability of the electrocatalyst. The resulting NiMo deposition catalyst exhibits improved performance in urea oxidation.

[0115] Building upon the NiMo deposition, anodic polarization is performed, inducing oxidation and transformation of the deposited materials. This additional step leads to the formation of NiMoO, a catalyst with further improved electrocatalytic properties. The anodic polarization process enhances the overall activity and stability of the catalyst, making it highly efficient in facilitating urea oxidation reactions.

[0116] In another approach, Ni deposition is carried out with the addition of M0S2 fillers at a concentration of 10 g / L. This method results in the formation of NiMoS?. The incorporation of M0S2 particles into the nickel matrix enhances the catalytic performance of the electrocatalyst. The resulting NiMoS2 catalyst exhibits superior activity, stability, and selectivity in urea oxidation.

[0117] To further improve the electrocatalyst and explore future prospects, several areas of research can be considered. One such aspect involves texturing the electrodes to increase their specific surface area. By creating structured morphologies on the electrode surfaces, such as foam-shaped or pyramid-shaped structures, the electrocatalyst's surface area can be significantly increased. This texturing technique promotes efficient catalytic activity by providing more active sites for the urea oxidation reaction.

[0118] Additionally, exploring the production of Ni-based alloys with different chemical compositions offers another avenue for enhancement. By incorporating elements beyond nickel and molybdenum, such as cobalt, iron, or other transition metals, the catalytic properties of the electrocatalyst can be further tuned to optimize urea oxidation performance.

[0119] Furthermore, the influence of ion implantation, such as nitrogen (N), oxygen (O), nitric oxide (NO), or other reactive species, on the catalytic properties of the electrodes can be investigated. This process aims to modify the electrocatalyst's performance by introducing specific active sites and modifying its electronic structure. For instance, ion implantation with nitrogen could lead to the formation of NixN compounds, which have shown promising catalytic activity in oxygen reduction reactions (ORR). These future prospects and ongoing research efforts contribute to the continuous improvement and exploration of the nickel-based electrocatalyst for urea oxidation. By incorporating NiMo deposition, NiMoO formation through anodic polarization, and Ni deposition with M0S2 fillers, the electrocatalyst already demonstrates enhanced catalytic performance. Through further advancements, such as texturing techniques, alloy composition optimization, and ion implantation studies, the electrocatalyst's efficiency, selectivity, and stability for urea oxidation can be further improved. This research paves the way for the application of the electrocatalyst in hydrogen generation, fuel cells, wastewater treatment, and other urea-based processes, addressing various technological and environmental challenges.

[0120] Results:

[0121] The results, shown in table 1, show the performance of various electrode configurations during urea oxidation under different experimental conditions. The surface area of the electrodes, tension applied, duration of the experiments and hydrogen production (VH2) are recorded.

[0122] Furthermore, it was observed that the addition of molybdenum (NiMo) in the deposition process leads to improved hydrogen production per unit of energy. Additionally, anodic polarization after NiMo deposition results in the formation of NiMoO, further enhancing the hydrogen production.

[0123] Lastly, the introduction of M0S2 fillers during Ni deposition significantly increases the energy efficiency of the hydrogen production of the resulting NiMoS2 catalyst, thus demonstrating enhanced performance in urea oxidation.

[0124] In terms of future prospects, the obtained results provide insights for further research and development. The specific surface area of the electrodes can be textured to increase their efficiency in urea oxidation. Moreover, exploring the production of Ni-based alloys with different chemical compositions can lead to catalysts with improved catalytic properties. Additionally, the influence of ion implantation, such as nitrogen (N), oxygen (O), nitric oxide (NO), and other species, on the catalytic properties of the electrodes can be investigated to optimize the electrocatalyst's performance.

[0125] Table 1 : Performance evaluation of electrodes in UOR.

[0126] *E= electrodes, Part. = particles, S=surface, T= tension, D=Duration

[0127] Example 2

[0128] Mild steel coupons of surface area 0.2 dm2were used as substrate. Surface cleaning in alkaline degreasing in order to remove oil and dirt from the surface. The surface was then rinsed with deionized water.

[0129] Subsequent acid etching in aqueous HCI 10 vol% in order to remove oxides; again followed by rinsing with deionized water.

[0130] A nickel layer was electroplated onto said cleaned surface by nickel sulfamate electroplating. The thickness of the nickel layer was targeted at 5 pm. This was achieved by electroplating, at 5A / dm2, a temperature of 55°C and a pH of 3.5 with Ni anodes.

[0131] The electroplating composition is shown in table 2.

[0132] Subsequently, the nickel layer was electroplated with a coating having an alloy structure of Ni-W-Fe-P. The formulation of the electrolyte and the operating conditions for Nickel alloy electroplating depend on the desired composition and characteristics of the nickel alloy. The target thickness was 5 pm. The current density was 10 A / dm2, at a temperature of 65°C and a pH of 8.5-9. The anodes were titanium plated.

[0133] The electrolyte composition to obtain a Ni47W24Fe25P4 alloy coating is shown in table 2.

[0134] Table 2: Electrolyte compositions used during electroplating

[0135] The alloy structure was measured by EDX analysis and showed a composition of Ni47W24Fe25P4 (in at.%).

[0136] This alloy was then electrochemically activated in hydroxide solution. Electrochemical activation and analysis were carried out in a three electrode glass cell provided with a platinum foil counter electrode and an Ag / AgCI reference (KCI 3M). The electrocatalytic coatings acted as working electrode (1 cm2geometric area)

[0137] Before activation and any electrochemical study, the surface deposits are cleaned by immersion in acetone and separately demineralized water for 10 minutes. Activation was performed by cyclic voltammetry (back and forth) in KOH 5M : an electrical potential from 0 to 800 mV (vs Ag / AgCI) was applied to obtain reproducible surface conditions. The activation was repeated over 50 cycles. The scan rate was 100 mV / s.

[0138] After this step, the EDX analysis, with analysis depth between 1 and 2 pm at an electronic accelerating voltage of 15 KeV showed a surface layer having an (average) composition of Ni40W20Fe21P3016 (in at.%).

[0139] Example 3

[0140] The process of example 2 was repeated; varying the concentrations of the Ni-W-Fe- P coating by variation of the electrolyte concentrations; whereby a coating having an average composition of Ni65W7Fel7Pll (in at.%) was obtained prior to activation.

[0141] Example 4

[0142] The process of examples 2 and 3 was repeated; but the coating of an Ni-W-Fe-P alloy was adjusted to a coating of a NiP alloy by adjusting the electrolyte composition.

[0143] The NiP alloy was subsequently subjected to N2 ion implantation; thereby obtaining a coating having an average composition of Ni90P9Nl (in at.%) prior to activation.

[0144] Electrochemical measurements

[0145] The electrocatalytic properties of the coatings were characterized with cyclic voltammetry.

[0146] The catalysts of example 2, 3 and 4 were tested. In addition, the nickel layer without additional coated alloy, achieved as described in the first step of example 2 was included as reference.

[0147] All substrates underwent the activation step in hydroxide solution as described in example 2; in an identical manner.

[0148] Before activation and subsequent electrochemical study, the surface deposits are cleaned by immersion in acetone and separately demineralized water for 10 minutes.

[0149] Electrochemical measurements were taken at room temperature and 5M KOH + 0.33M Urea. Electrocatalytic properties were measured by cyclic voltammetry (back and forth) in KOH 5M + 0.33M Urea; with a electrical potential range from 0 to 800 mV (vs Ag / AgCI) applied. The voltage was varied back and forth. The scan rate was 10 mV / s.

[0150] Electrochemical activation and analysis were carried out in a three electrode glass cell provided with a platinum foil counter electrode and an Ag / AgCI reference (KCI 3M). The electrocatalytic coatings acted as working electrode (1 cm2geometric area).

[0151] The results are shown in table 3 x- Initial Peak Peak current

[0152] Catalyst surface y . . , potential for potential for density composition (at.%) ' . . UOR (mVvs UOR (mVvs for UOR before activation . ' 2.

[0153] Ag / AgCI) Ag / AgCI) (mA / cm )

[0154] Ex. 4 Ni90P9Nl 265 484 77

Claims

CLAIMS1. A method for producing a nickel-based electrocatalyst for a urea oxidation reaction (UOR), wherein the method comprises electrodepositing nickel or an alloy thereof, thereby obtaining an electrodeposited coating, optionally further modifying said electrodeposited coating thereby obtaining a nickel- based electrocatalyst, wherein the nickel-based electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus.

2. Method according to claim 1, wherein the nickel-based electrocatalyst comprises nickel, at least one element selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium and at least one element selected from the group of: boron, nitrogen, oxygen, sulfur, phosphorus.

3. Method according to claim 1 or 2, wherein said nickel-based electrocatalyst having a formula of: Nix-Mi,y-M2,z-Ep-Oq, wherein Ni is nickel; wherein Ml and M2 are two different metallic elements independently selected from the list of: cobalt, iron, copper, molybdenum, titanium, tungsten or zirconium; wherein E is selected from: silicon, carbon, germanium, boron, nitrogen, sulfur or phosphorus; and wherein O is oxygen.

4. Method according to any of the claims 1-3, wherein the nickel-based electrocatalyst has a surface layer with a thickness of at least 1 pm, said surface layer comprising: o Nickel (Ni- in an average amount of at least 30 at%; o Tungsten (W) in an average amount of at least 4 at%; o Iron (Fe) in an average amount of at least 10 at%; o Phosphor (P) in an average amount of at least 1 at%; and o Oxygen (O) in an average amount of at least 5 at%.

5. Method according to any of the claims 1-4, wherein the nickel-based electrocatalyst has a surface layer with a thickness of at least 1 pm, said surface layer comprising: o Nickel (Ni- in an average amount of 30 to 70 at%; o Tungsten (W) in an average amount 4 to 20 at%;o Iron (Fe) in an average amount of 10 to 30 at%; o Phosphor (P) in an average amount of 1 to 15 at%; o Oxygen (O) in an average amount of 5 to 25 at%; and o Optionally additional elements chosen of: cobalt, copper, molybdenum, titanium, zirconium; silicon, germanium, boron, nitrogen, sulfur, carbon or combinations thereof; more preferably said additional element is nitrogen; each additional element in an average amount of at most 15 at% over said depth, preferably at most 10 at% over said depth, more preferably at most 5 at% over said depth, more preferably at most 3 at% over said depth, most preferably at most 1 at% over said depth.

6. Method according to any of the claims 1-5, wherein the electrodepositing comprises dynamic hydrogen bubble template electrodepositing to obtain a structured material, preferably to create structured morphologies such as foam-shaped or pyramid-shaped structures.

7. Method according to any of the previous claims 1 to 6, wherein the electrodepositing comprises pulse plating.

8. Method according to any of the claims 1 to 7, wherein the electrodeposited coating comprises at least one element selected from the group of Fe, Cu, Co, Mo, W, P.

9. Method according to any of the previous claims 1 to 8, wherein the method comprises performing an ion beam implantation treatment of the electrodeposited material, thereby obtaining a modified catalytic surface.

10. Method according to claim 9, wherein said ion beam implantation treatment comprises doping with electronegative elements selected from the group of: nitrogen, sulfur, oxygen, phosphorus, fluorine and combinations thereof.

11. Method according to any of the previous claims 1 to 10, wherein the method further comprises co-deposition of microparticles of metallic or non-metallic compounds, preferably ceramic particles selected from the group consisting of WC, WS2, MoS2, MoO2, CeO2, and combinations thereof, onto the electrodeposited coating.

12. Method according to claim 11, wherein the co-deposition of microparticles is carried out through an electrolytic or electroless process.

13. Method according to any of the previous claims 11 or 12, wherein the codeposition includes ultrasonic agitation to maintain particle suspension without agglomeration.

14. Method according to any of the previous claims 1 to 13, wherein the method further comprises magnetron sputtering using high-power impulse magnetron sputtering or bipolar high voltage.

15. Method according to any of the previous claims 1 to 14, wherein the method comprises aerosol-assisted chemical vapor deposition or spray pyrolysis.

16. A nickel-based electrocatalyst for a urea oxidation reaction, wherein the nickel-based electrocatalyst comprises nickel, and at least two elements selected from the group of: cobalt, iron, copper, molybdenum, titanium, tungsten, zirconium, boron, nitrogen, oxygen, sulfur, phosphorus.

17. Nickel-based electrocatalyst according to claim 16, obtainable by the method according to any of claims 1 to 15.

18. Use of the method according to at least one of claims 1 to 15, or the nickel- based electrocatalyst according to at least one of claims 16 to 17, for the production of hydrogen.

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