Manufacturing process for a porous nano-architectural ceramic for electrolysis cell electrode

Abstract

A method for manufacturing a porous nano-architectural ceramic (200) for an electrolyzer cell electrode (100), in particular for a high-temperature electrolyzer cell electrode (also known as EHT), the method comprising the following steps: supplying a resin comprising a polymeric photoreagent, a solvent, for example an organic solvent, and a filler comprising at least one mineral precursor of the ceramic; 3D printing the resin according to a predetermined pattern so as to form a porous nano-architectural skeleton (300), for example in the form of a honeycomb or in the form of a tetrakaidecahedral skeleton; and sintering the porous nano-architectural skeleton (300) so as to obtain a porous nano-architectural ceramic (200). Figure 4

Description

Title of the invention: Method for manufacturing a porous nano-architectural ceramic for an electrolyzer cell electrode. Technical field of the invention

[0001] The invention relates to the field of hydrogen production by electrolysis of water vapor.

[0002] The invention relates in particular to a method for manufacturing a porous nanoarchitectural ceramic to constitute an electrode for an electrolyzer cell.

[0003] According to a second aspect, the invention also proposes a method for producing an electrolyzer cell.

[0004] According to a third aspect, the invention relates to a porous nanoarchitectural ceramic obtained by implementing the manufacturing process. State of the art

[0005] In the current energy context, where fossil fuel reserves are dwindling, energy consumption is constantly rising, and the need for clean, sustainable, and greenhouse gas-free technologies is becoming increasingly urgent, hydrogen appears as an energy carrier capable of directly competing with electricity and heat. However, since hydrogen is rare in nature, it is necessary to implement technological solutions to produce it on a large scale at a competitive cost.

[0006] One possibility among others relies on high-temperature steam electrolysis (also known by the acronym HTE). The process consists of dissociating the water molecule into hydrogen and oxygen at high temperatures. This requires supplying heat, which can be sourced from nuclear or renewable energy sources (geothermal or solar). Another technological challenge lies in developing an electrolyzer, and in particular an electrochemical cell, capable of withstanding operating temperatures of up to 900°C and exhibiting very good stability in oxidizing and reducing environments. The electrochemical cell comprises three ceramic layers: an oxygen electrode, an electrolyte, and a hydrogen electrode where the hydrolysis of water into hydrogen takes place, which includes a composite ceramic or metal-ceramic (also called cermet).

[0007] The electrolyte consists of a material exhibiting gas tightness (density greater than 95%, zero open porosity), good ionic conductivity (greater than 10⁻² S.cm⁻¹ at operating temperature), a coefficient of expansion close to that of the electrodes (the objective being to limit mechanical stresses), a chemical inertness with respect to electrode materials, stability in oxidizing and reducing environments, and finally mechanical stability under operating conditions.

[0008] Regarding the electrodes, the material used must have high electronic conductivity (greater than 100 S / cm) with, if possible, a degree of ionic conductivity to limit ohmic losses and delocalize the electrochemical reaction within the electrode volume. These electrodes are characterized by their high porosity, which is an essential property for the diffusion of water vapor, as well as for the removal of hydrogen at the cathode and oxygen at the anode. This porosity must be optimized to avoid local overpressures that tend to delaminate the layers constituting the electrodes. More specifically, the hydrogen electrode requires both catalytic properties essential for the reduction of water and the ability to remain stable in a reducing environment. As for the oxygen electrode, it exhibits catalytic properties for the oxidation of O2 ions while remaining stable in an oxidizing environment.

[0009] With the objective of developing an economically viable process, it is important that all the materials constituting the electrochemical cells be available in large quantities and at low cost. Object of the invention

[0010] Also, one of the aims of the present invention is to propose a method for manufacturing material for the electrode of the electrochemical cell which addresses at least one of the aforementioned problems.

[0011] To this end, the present invention proposes a method for manufacturing a porous nanoarchitectural ceramic for an electrolyzer cell electrode, in particular for a high-temperature electrolyzer cell electrode, the method comprising the following steps: a. supply of a resin comprising a polymeric photoreagent, a solvent, and a filler comprising at least one mineral precursor of the ceramic, b. 3D printing of the resin according to a predetermined pattern to form a porous nano-architectural skeleton, and c. sintering of the porous nano-architectural skeleton to obtain a porous nano-architectural ceramic.

[0012] The resin is in particular a resin with shear-thinning rheology. The solvent is, for example, an organic solvent. The mineral precursor is, in particular, YSZ, nickel / cerine, nickel / zirconia, other nickel derivatives, or titanates for a dihydrogen electrode, or a lanthanum derivative with a perovskite structure, such as LSM, LSC, LSCF, or Nd2NiO4-type nickelate for a dioxygen electrode. The porous nanoarchitectural skeleton is, for example, in the form of honeycomb or tetrakaidecahedral form. Porous nanoarchitectural ceramics include ceramic oxides, cermets, and perovskite-structured ceramics.

[0013] This porous nano-architectural ceramic, thus fabricated, can be used as an electrode in the electrolyzer cell, which advantageously allows for reduced material consumption compared to conventional electrodes, while simultaneously boosting their properties. Indeed, using 3D printing makes it possible to structure the layers in such a way as to create an optimal material architecture at the nanoscale, allowing for a reduction in layer thickness and / or the amount of raw material by developing more or less porous skeletons with mechanical resistance equivalent to that of conventional ceramics. The porous nano-architectural skeleton can be developed and optimized by printing, for example, in a honeycomb or tetrakaidecahedral form (see [Fig. 1]).It features increased porosity, facilitating the passage of water vapor while optimizing the number of triple points, leading to electrodes and cells with optimal properties.

[0014] In this document, the acronym YSZ refers to yttrium oxide stabilized zirconium oxide or yttrium zirconia.

[0015] In this document, the acronym LSCF refers to strontium-doped lanthanum ferrocobaltite La(i_x)SrxCo(i_y)FeyO3, LSM is strontium-doped lanthanum manganite of the type Lal-xSrxMnO3, and LSCo is lanthanum cobaltite.

[0016] Sintering advantageously allows the material to be densified and stabilized. According to one possibility, step c) of sintering is carried out at a temperature between 900 and 1600°C.

[0017] According to one provision, the duration of the sintering step is between 1 and a few hours, in particular between 1 and 6 hours and for example 2 hours.

[0018] According to one possibility, the photoreactive polymer is chosen from acrylate-based resins, such as Polymethylmethacrylate (PMMA), and an organic solvent is of the acetone type.

[0019] According to one possibility, the porous nanoarchitecturally designed skeletons obtained in step b) can then be impregnated or doped with other materials so as to improve their physicochemical properties.

[0020] According to one provision, step b) of 3D printing is followed by a step b') of pre-sintering, for example at a temperature between 500°C and 800°C, in particular for a duration of between 1 and several hours, in particular about one hour, so as to allow the removal of the polymeric photoreagent and, for example, of the residual organic solvent. The pre-sintering step b') allows, in particular, the pyrolysis of said organic materials resulting in their elimination leaving little residue.

[0021] According to one possibility, the resin supplied in step a) further comprises a metallic precursor, mixed with the mineral precursor, such as NiO, nitrate salt in the case of a YSZ mineral precursor, or the resin supplied in step a) comprises a mineral precursor doped with the metallic precursor, such as coated nanoparticles (or "core shell nanoparticles" in Anglo-Saxon terminology), the nanoparticles being made of the mineral precursor material of the ceramic and the coating of the metallic precursor. This possibility leads to the formation of a cermet or a metal-ceramic that can be used in the manufacture of a dihydrogen electrode.

[0022] According to one possibility, the resin supplied in step a) further comprises a metallic precursor, mixed with the mineral precursor, such as a La,Sr,Fe,Co nitrate or another nickelate-type oxide material when the mineral precursor is cerium oxide, or the resin supplied in step a) comprises a mineral precursor doped with the metallic precursor. This possibility leads to the formation of a material that can be used in the manufacture of a dioxygen electrode.

[0023] According to one provision, step a) includes supplying a resin whose composition changes during the 3D printing process to obtain a composition gradient for the porous nano-architectural ceramic. It is thus possible to vary the concentration of the metallic precursor (or said other material) in the resin, and / or the mineral precursor of the ceramic in the resin, to allow for one or more composition gradients and optimize the porous nano-architectural ceramic for its application. It is then possible to manufacture buffer layers to manage the different coefficients of expansion between the various constituent materials used, for example, between the material of the supporting electrolyte and that of an electrode.

[0024] According to one provision, the process includes, prior to step c), an impregnation step i) of the porous nanoarchitectural skeleton with an impregnation solution comprising at least the metallic precursor, in particular by immersing the porous nanoarchitectural skeleton in an impregnation solution, such as an impregnation solution comprising nitrate salt in water and at least one wetting agent, in particular intended to reduce the surface tension of the porous nanoarchitectural skeleton and ensure good infiltration (for example, a silicone base). This impregnation step i) constitutes another means of modulating the composition of the final porous nanoarchitectural ceramic in order to improve its properties.

[0025] According to one possibility, the impregnation step i) is carried out under vacuum, for several hours, for example between 1 and 12 hours.

[0026] According to one provision, the impregnation step i) is carried out at room temperature.

[0027] According to one embodiment, the impregnation step i) is carried out hot. Typically, the temperature may be between 20 and 50°C.

[0028] According to one possibility, at least one 3D printing parameter of step b) is modified during printing so as to vary the predetermined pattern, so as to modify the porosity of the porous nanoarchitectural skeleton.

[0029] The variation of said at least one 3D printing parameter may have an impact on the shape and / or size of the cells of the porous nanoarchitectural skeleton.

[0030] According to one provision, at least one 3D printing parameter of step b) is gradually modified during printing so as to gradually vary the predetermined pattern.

[0031] According to one variant, at least one 3D printing parameter of step b) is modified in steps during printing so as to vary the predetermined pattern in steps.

[0032] This constitutes a new lever in the constitution of the electrode, or of the cell, according to the varied porosity requirements in the different constituent layers.

[0033] According to a second aspect, the invention proposes a method for producing an electrolyzer cell structure, in particular a high-temperature electrolyzer cell, the method comprising the following steps:

[0034] 1) supply of a supporting electrolyte,

[0035] m) fabrication of a dihydrogen electrode as previously described on a first face of the supporting electrolyte, and

[0036] n) fabrication of a dioxygen electrode such as previously described on a second face opposite to the first face of the supporting electrolyte.

[0037] According to a particular embodiment, the support electrolyte provided in step 1) comprises mainly of, or is made up of, YSZ and the process includes, before the manufacture of a dihydrogen electrode according to step m), a step of forming f) a first intermediate layer comprising a 3D printing step, the intermediate layer comprising a decreasing concentration gradient in YSZ or CGO and an increasing concentration gradient in NiO away from the support electrolyte, until the composition of the porous nanoarchitectural skeleton for the dihydrogen electrode is obtained.

[0038] According to another particular embodiment, the process includes, prior to the fabrication of a dioxygen electrode according to step n), a step of forming f') a second intermediate layer comprising a 3D printing step, the second intermediate layer comprising a decreasing concentration gradient of gadolinium oxide CGO (i.e. a doped cerine) and a concentration gradient of a perovskite-structured lanthanum derivative, in particular in LSCF, in LSM, in LSC, or in nickelate of the Nd2NiO4 type, which increases away from the supporting electrolyte, until the composition of the porous nanoarchitectural skeleton for the dioxygen electrode is obtained.

[0039] According to a third aspect, the invention provides a porous nano-architectural ceramic for an electrolyzer cell electrode, obtained by the process described above, which comprises a pore volume to material volume ratio of between 30 and 70%. It is understood that said ceramic is a perovskite-structured lanthanum derivative for a dioxygen electrode and said ceramic is a metal-ceramic (or cermet) for a dihydrogen electrode. Summary description of the drawings

[0040] Other features and advantages will become apparent from the detailed description below, of a non-limiting implementation example, made with reference to the attached figures in which:

[0041] [Fig.1] represents a schematic view illustrating a conventional electrolyzer cell of the prior art.

[0042] [Fig.2] represents a schematic view illustrating the different possibilities of porous nano-architectural ceramics obtained by 3D printing according to an embodiment of the invention.

[0043] [Fig.3] represents a schematic view of the manufacturing process of a ceramic porous nanoarchitectural according to a first embodiment of the invention.

[0044] [Fig.4] represents a schematic view of the manufacturing process of a ceramic porous nanoarchitectural according to a second embodiment of the invention.

[0045] [Fig. 5] represents a schematic view of the manufacturing process of a ceramic porous nanoarchitectural according to a third embodiment of the invention.

[0046] [Fig.6] represents a schematic view of an electrochemical cell of a electrolyzer obtained by the manufacturing process of a porous nanoarchitectural ceramic according to an embodiment of the invention. Detailed description

[0047] In the figures and throughout the description, the same reference numerals represent identical or similar elements. Furthermore, the various elements are not drawn to scale in order to enhance the clarity of the figures. Moreover, the different embodiments and variants are not mutually exclusive and may be combined.

[0048] Unless otherwise stipulated, the term "substantially" means, in this document, "exactly or to within 10% or to within 10°".

[0049] Figure 1 illustrates an example of a conventional electrochemical cell 1 for a high-temperature electrolyzer. Two metallic interconnectors (a) are present on either side of cell 1 to make electrical contacts. The electrochemical cell 1 is made of ceramic, and includes an electrolyte labeled (b), an oxygen electrode (d) labeled (d) and a hydrogen electrode labeled (c) on either side of the electrolyte (b).

[0050] As illustrated in [Fig. 2], the present invention proposes an improved method for manufacturing said ceramics, particularly those constituting the electrodes 3, 4, by 3D printing. This technique makes it possible to use predetermined printing patterns leading to a nanostructured design, thereby increasing the porosity of the ceramic, reducing the amount of material required, while providing the same mechanical resistance and thermal cycling properties as conventional ceramics. It is thus possible to choose from a large number of architectures, such as stochastic cellular structures A of the closed-cell type B or open-cell type C, or non-stochastic cellular structures D comprising a two-dimensional network E or a three-dimensional network F, in order to obtain the porous nanostructured ceramic 200 with the desired properties.

[0051] By "3D printing" we mean a three-dimensional printing method by additive manufacturing in successive passes, each pass comprising the deposition of a layer of resin, the deposited resin adhering to the resin of at least one previously deposited layer, the resin deposition at each layer being controlled at each pass in such a way that the stacking of resin deposited during said successive passes constitutes the porous nanoarchitectural skeleton 300.

[0052] Figure 3 illustrates an embodiment of the process for manufacturing a NiO-YSZ dihydrogen electrode. It comprises a step a) of supplying a resin comprising a mixture of at least one photoreactive polymer (for example, an acrylate-based resin such as Polymethyl Methacrylate, also known by the acronym PMMA), dissolved in an organic solvent (for example, acetone), a mineral precursor of YSZ comprising a powder of a mixture of ZrO2 and Y2O3 and a metallic precursor NiO. The resin is then printed by a 3D printing device, for example, in a honeycomb pattern to form a porous nanoarchitectural skeleton (step b).A pre-sintering heat treatment, also known as 'debinding', is applied at a temperature of approximately 700-800°C to degrade the porous solvent and the photoreactive polymer, leaving only the inorganic materials in the nano-architectural skeleton 300 (step b'). A sintering step at a temperature of approximately 1400°C (step c) is then applied to obtain a porous nano-architectural metal-ceramic (or cermet) 200.

[0053] The second embodiment illustrated in [Fig. 4] differs from the previous one in that the mineral precursor of the ceramic used in the resin is directly doped by the metallic precursor, for example in the form of NiO-coated ZrO2 and Y2O3 nanoparticles. 3D printing of the resin and application of the sintering heat treatment at approximately 1400°C leads to a porous nano-architectural metal-ceramic 200, exhibiting the same properties as those obtained previously.

[0054] A third embodiment is illustrated in [Fig. 5]. In this embodiment, the resin printed in step b) is free of metallic precursor filler. The resulting nanostructured skeleton 300 is impregnated with an aqueous nitrate salt solution under vacuum for 1 to 12 hours at room temperature. The sintering step then leads to a porous nanostructured ceramic 200 with properties similar to those obtained previously.

[0055] These three modes of implementation allow three different access routes to the same porous nanoarchitectural ceramic 200. They thus allow different access routes to the targeted ceramic, which broadens the possibilities regarding the precursor materials that can be used.

[0056] According to a particular embodiment illustrated in [Fig. 6], the invention is adapted to the manufacture of the electrolyzer cell 100 of an electrolyzer. To this end, the process includes supplying a support electrolyte 2 made of dense YSZ ceramic (step 1). This support electrolyte 2 is used as a support for the fabrication of the electrodes 3, 4. A resin comprising a powder of ZrO2 and Y2O3 and NiO metal oxide is deposited by 3D printing onto a first face of the support electrolyte 2 (step m). The 3D printing parameters are adjusted during the printing process so as to increase the porosity of the ceramic as it moves away from the support electrolyte 2 in order to achieve the desired porosity for the dihydrogen electrode 5.Similarly, the concentrations of the reagents in the resin supplied to the 3D printing device evolve during printing to create a compositional gradient from an 8 mol% yttrite content to 3 mol% as you move away from the supporting electrolyte 2, ultimately reaching the target composition for a dihydrogen electrode 3. This allows the formation of a first intermediate layer 5 with an increasing porosity gradient and an increasing NiO content gradient until the desired parameters for the nano-architectural metal-ceramic of the dihydrogen electrode 5 are smoothly achieved (step f). This first intermediate layer 5 acts as a buffer layer, absorbing the difference in the coefficient of thermal expansion within the structure during temperature changes, particularly during the sintering and cooling stages, and during the operation of the electrolyzer cell 100, thus limiting the risk of delamination.The first intermediate layer 5 also allows for the absorption of dimensional differences or changes in printing pattern in the nanoarchitecture 200, which are put in place to ensure the . changes in porosity and which are likely to weaken the cohesion of the three layers of the electrolyzer cell 100. A sintering treatment at 1400°C is then carried out in order to obtain the targeted cermet 200.

[0057] Conversely, a second intermediate layer 6 is formed on the second face opposite the first face of the support electrolyte 2 (step f') in order to adapt the difference in thermal expansion between the material of the support electrolyte 2 and that of a thin barrier layer 6 in CGO (cerine oxide CeO2 substituted by gadolinium oxide Gd2O3) intended to prevent the reaction between the material for the dioxygen electrode 4 in LSCF and that of the support electrolyte 2. Thus, the second intermediate layer 6 is formed to include a concentration gradient between the YSZ and the CGO and to prevent delamination between the layers of the electrolyzer cell 100.

[0058] Thus, the present invention makes it possible to obtain porous nanoarchitecturated ceramics 200 reducing the cost of raw materials while leaving a great deal of latitude to refine the parameters of composition, porosity and mechanical properties according to the needs targeted for the electrodes 3,4 of electrolyzer cells 100.

Claims

Demands

1. A method for manufacturing a porous nano-architectural ceramic (200) to constitute an electrode for an electrolyzer cell (100), the manufacturing method comprising the following steps: a. supplying a resin comprising a polymeric photoreagent, a solvent, and a filler comprising at least one mineral precursor of the ceramic, b. 3D printing the resin according to a predetermined pattern so as to form a porous nano-architectural skeleton (300), and c. sintering the porous nano-architectural skeleton (300) so as to obtain a porous nano-architectural ceramic (200).

2. A manufacturing method according to claim 1, wherein step b) of 3D printing is followed by a step b') of pre-sintering carried out so as to allow the removal of the polymeric photoreagent.

3. A manufacturing process according to claim 1 or 2, wherein the resin supplied in step a) further comprises a metallic precursor, the metallic precursor being mixed with the mineral precursor, or the mineral precursor being doped with the metallic precursor.

4. A manufacturing method according to claim 3, wherein step a) comprises supplying a resin whose composition evolves during 3D printing so as to obtain a composition gradient of the porous nanoarchitectural ceramic (200).

5. A manufacturing method according to claim 3, which includes, prior to step c), an impregnation step i) of the porous nanoarchitectural skeleton with an impregnation solution comprising the metallic precursor.

6. A manufacturing method according to any one of claims 1 to 5, wherein during step b), at least one 3D printing parameter is modified in such a way as to vary the predetermined pattern in order to modify the porosity of the porous nanoarchitectural skeleton (300).

7. A method for producing an electrolyzer cell structure (100), comprising the following steps: 1) supplying a supporting electrolyte (2), m) manufacturing a dihydrogen electrode (3) by implementing the manufacturing process according to any one of claims 1 to 6 on a first face of the support electrolyte (2), and n) manufacturing a dioxygen electrode (4) by implementing the manufacturing process according to any one of claims 1 to 6 on a second face of the support electrolyte (2), opposite to the first face.

8. A production method according to claim 7, wherein the support electrolyte (2) supplied in step 1) comprises predominantly, or is made up of, YSZ, and wherein the production method comprises, prior to step m), a step f) of forming a first intermediate layer (5) comprising a 3D printing step such that the first intermediate layer (5) comprises a decreasing concentration gradient of YSZ or CGO and an increasing concentration gradient of NiO away from the support electrolyte (2), until a desired composition of the porous nanoarchitectural skeleton (300) for the dihydrogen electrode (3) is obtained.

9. A production method according to claim 7 or 8, comprising, prior to step n), a step f') of forming a second intermediate layer (6) comprising a 3D printing step such that the second intermediate layer (6) comprises a decreasing concentration gradient in CGO and a concentration gradient in perovskite structure lanthanum derivative increasing away from the supporting electrolyte (2), until the composition of the porous nanoarchitectural skeleton (300) for the dioxygen electrode (4) is obtained.

10. Porous nanoarchitectural ceramic (200) for electrolyzer cell electrode (100) manufactured by implementing the manufacturing process according to any one of claims 1 to 6, wherein the ratio between the pore volume and the material volume is between 30% and 70%.

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