WO2020115712A1

WO2020115712A1 - Electrochemical reactor

Info

Publication number: WO2020115712A1
Application number: PCT/IB2019/060517
Authority: WO
Inventors: Seyyed Mohammad HOSSEINI HASHEMI; Demetri Psaltis
Original assignee: Ecole Polytechnique Federale De Lausanne (Epfl)
Priority date: 2018-12-06
Filing date: 2019-12-06
Publication date: 2020-06-11

Abstract

In an electrochemical reactor (R) for producing oxygen and hydrogen by means of electrolysis of an electrolyte (16), wherein the electrochemical reactor (R) comprises a first electrode set (S) and wherein the first electrode set (S) comprises a first electrode (7) and a second electrode (8), the first electrode (7) comprises a multitude of pores, the second electrode (8) comprises a multitude of pores, and the first electrode (7) is arranged inside the second electrode (8), such that an electrolyte channel (15) is formed between the first electrode (7) and the second electrode (8).

Description

Title:

“Electrochemical reactor”

Technical Field

The invention relates to an electrochemical reactor according to the preamble of claim 1 . The invention furthermore relates to a method for producing oxygen and hydrogen according to claim 10.

Background Art

One possibility to produce hydrogen, which is for example used in fuel cells, is by carrying out electrolysis in an electrochemical reactor. In order to make fuel cells a true alternative to, for example, combustion engines, possibilities to produce hydrogen in an efficient and economical way are needed. The electrochemical reactors known in the art have several disadvantages. For example, they make the creation of stacks difficult and thus also make it difficult to upscale the reactors. Furthermore, they often have a complicated structure, often comprising a large multitude of components. Furthermore, such known electrochemical reactors are bulky and it is costly and complicated to make them robust for high pressure, for example due to a multitude of components.

Problem to be Solved

It is the object of the invention to solve or to at least diminish the above-mentioned disadvantages.

Solution to the Problem

This problem is solved by an electrochemical reactor for producing oxygen and hydrogen by means of electrolysis of an electrolyte, wherein the electrochemical reactor comprises a first electrode set, wherein the first electrode set comprises a first electrode and a second electrode, wherein the first electrode comprises a multitude of pores, the second electrode comprises a multitude of pores, and the first electrode is arranged inside the second electrode such that an electrolyte channel is formed between the first electrode and the second electrode.

Such an electrochemical reactor makes it possible to produce oxygen and hydrogen by means of electrolysis in a simple and straightforward manner: in particular, it makes it possible to feed an electrolyte into the electrolyte channel and to then carry out electrolysis by making one of the electrodes a cathode and one of the electrodes an anode (in particular by applying different voltage potentials to the two electrodes). Since both electrodes have pores, gaseous hydrogen and/or gaseous oxygen mixed with electrolyte is carried through the pores of the electrodes in the form of gas bubbles, for example gas bubbles of hydrogen and gas bubbles of oxygen. At the exit of the electrochemical reactor, electrolyte carrying hydrogen on one hand and electrolyte carrying oxygen on the other hand can then easily be separated for further processing.

In the context of this application, the expression“electrochemical reactor” is to be understood as referring to a device that is able to perform an electrochemical reaction. In principle, such a device can therefore be used for producing oxygen and hydrogen by means of electrolysis of an electrolyte, but it can for example also be a fuel cell for transforming chemical energy into electrical energy. The expression “electrode set” is to be understood as referring to a set of two electrodes, wherein the electrodes are typically configured to be set to different electrical potentials, thereby configuring one of the electrodes as cathode and one of the electrodes as anode. The expression“pores” is to be understood as referring to pores or perforations in the nm or mm range. Each electrode typically comprises hundreds or thousands of such pores, for example 10 to 1000 pores per cm², in particular 20 to 750 pores per cm², particularly 10 to 500 pores per cm².The electrodes can therefore also be referred to as mesh-electrodes, because the multitude of pores leads to the creation of a mesh. In the context of this application, the expression“electrolyte channel” is to be understood as a space of any form and/or size between the electrodes, where the electrolyte can at least partially flow. The expression“the first electrode is arranged inside the second electrode” is to be understood such that the second electrode is arranged at least partially around the first electrode. In typical embodiments, the electrodes are non-planar.

In typical embodiments, the first electrode and/or the second electrode has/have an essentially cylindrical form and/or a dimension, preferably a diameter, of the first electrode is smaller than a dimension, preferably a diameter, of the second electrode. Such forms and dimensions of the electrodes make it particularly easy to arrange the first electrode inside the second electrode. Furthermore, the inventors have found that a cylindrical form is particularly advantageous for creating an electrochemical reactor with a well-functioning and simple design. In this context,“cylindrical” refers to any type of hollow cylinder, in particular to a hollow cylinder with a circular cross-section. However, other cross-sections are also possible for these hollow shapes, for example elliptical cross-sections or cross-sections in the form of polygons, for example rectangular or square cross- sections. In typical embodiments, the first electrode is arranged inside the second electrode in a coaxial manner. This has the advantage of leading to a very symmetrical design, which is for example advantageous for high-pressure applications. A cylindrical form is however not absolutely necessary. It is for example also possible for the electrodes to have the form of cuboids or spheres or the like. Furthermore, it is possible that the first electrode only partially has a smaller dimension than the second electrode.

In typical embodiments, the electrochemical reactor comprises at least one additional electrode set. In typical embodiments, at least one and/or several and/or all of the additional electrode sets comprises a first electrode and a second electrode having, at least partly, the same characteristics as the previously described electrodes. In principle, any number of electrode sets can be comprised in an electrochemical reactor according to the invention, for example a total of 3, 5, 9, 12 or more electrode sets. Foreseeing a multitude of electrode sets in an electrochemical reactor has the advantage of increasing the production capacity for hydrogen and oxygen of the electrochemical reactor. However, it is not necessary for an electrochemical reactor to have a multitude of electrode sets. In principle, one single electrode set is sufficient for the electrochemical reactor to function. In typical embodiments, all electrode sets are arranged in a coaxial manner and/or all electrodes are arranged in a coaxial manner. The advantage of such a coaxial arrangement of the electrode sets and/or the electrodes offers a very interesting possibility for stacking and therefore for increasing the production capacity of the electrochemical reactor. In other words: in typical embodiments, all electrode sets and/or all electrodes are coaxial and/or share a common longitudinal axis (at least in cases where the electrodes have a cylindrical or partly cylindrical form). If the electrodes do not have a cylindrical form (for example because they have the form of spheres), all electrode sets and/or all electrodes are typically arranged in a concentric manner. In typical embodiments, at least some of the electrodes are cylinders and are arranged in a coaxial and/or concentric manner. Such an arrangement of the different electrode sets and/or the electrodes leads to a symmetric and compact design, and therefore to a compact form factor of the electrochemical reactor and to a robust mechanical structure for high-pressure operations.

In typical embodiments, the electrochemical reactor is membrane-less. In other words: in typical embodiments, the electrochemical reactor does not comprise a membrane. The inventors have found that a membrane is not absolutely necessary in an electrochemical reactor according to the invention and the omission of such a membrane therefore leads to a simpler and more efficient design. However, it is also possible to foresee a membrane inside one or more of the electrode sets, in particular in between the two electrodes of one or more or all of the electrode sets. In typical embodiments, such a membrane also has the form of a hollow cylinder and is inserted inside the electrolyte channel between the two electrodes.

In typical embodiments, the electrochemical reactor comprises a separation wall or a multitude of separation walls arranged around each electrode set. Such a separation wall typically has the same form as the electrodes and separates one electrode set from the other. In typical embodiments, the electrochemical reactor comprises such separation walls between the different electrode sets plus one additional separation wall serving as outer wall - that is, a separation wall that forms an external wall of a main body of the electrochemical reactor, wherein the main body of the electrochemical reactor comprises all electrode sets. The one or more separation walls are preferably of cylindrical form and are preferably arranged in a coaxial manner.

In typical embodiments, the electrochemical reactor comprises an inlet manifold, wherein the inlet manifold preferably comprises one entry port, wherein the inlet manifold is configured to supply the electrolyte to the electrolyte channel(s) exclusively. In typical embodiments, such an inlet manifold comprises an inlet channel system configured to connect the entry port to the one or more electrolyte channels, wherein the inlet channel system is typically at least partially cylindrical. Such an inlet manifold has the advantage of making the supply of electrolyte to the electrolyte channels simple and straightforward. However, it is also possible to supply the electrolyte to the one or more electrolyte channels differently, for example by means of separate pipes or hoses or the like.

In typical embodiments, the electrochemical reactor comprises an outlet manifold, wherein the outlet manifold preferably comprises two exit ports, wherein the outlet manifold is configured to collect and guide the hydrogen to one exit port and to collect and guide the oxygen to the other exit port. In typical embodiments, the outlet manifold comprises an outlet channel system, which is configured to lead the hydrogen, possibly mixed with electrolyte, to one exit port, and the oxygen, possibly mixed with electrolyte, to the other exit port. In typical embodiments, the outlet channel system is at least partially funnel-shaped. Such a design of the electrochemical reactor with an outlet manifold is particularly straightforward and makes it easy to obtain the produced hydrogen and oxygen in a simple and straightforward manner. However, such an outlet manifold is not necessarily mandatory, it would also be possible to foresee for example two or more hoses or pipes for evacuating the hydrogen or oxygen from the electrochemical reactor.

In typical embodiments, a distance between the first electrode and the second electrode of at least one, preferably all, electrode set(s) is between 1 pm and 30 mm, preferably between 300 pm and 10 mm, more preferably between 500 pm and 5 mm. The inventors have found, that such dimensions are preferably advantageous for an efficient production of hydrogen and oxygen. The distances between the first electrode and the second electrode are not necessarily equal for all electrode sets, but they can be equal. In typical embodiments, the electrodes have a diameter between 1 cm and 80 cm, typically between 2 cm and 60 cm, advantageously between 3 cm and 40 cm. In typical embodiments, the electrodes have a height between 1 cm and 100 cm, typically between 2 cm and 80 cm, more advantageously between 3 cm and 60 cm. In typical embodiments, all electrodes have essentially the same height. In the context of this application, the expression “essentially” can preferably be understood as referring to“+I- 10 %”. In typical embodiments, all electrodes have different diameters. In other words: in typical embodiments, all electrodes are of different sizes.

In typical embodiments, the pores at least partially have different sizes and/or are distributed along at least one of the electrodes, preferably along all of the electrodes, in an inhomogeneous manner. By choosing different pore sizes and an inhomogeneous distribution of the pores, it is possible to better control the pressure drops inside the electrochemical reactor, and for example to reach a homogeneous creation of hydrogen and oxygen along a height of the electrochemical reactor. However, it is also possible, for all pores to have equal sizes and/or for all pores to be distributed across the electrodes in a homogeneous - or in other words: even - manner. A method for producing oxygen and hydrogen by means of an electrochemical reactor according to any of the above-mentioned embodiments comprises the steps:

- feeding an electrolyte into the electrolyte channel(s),

- in at least one electrode set, setting up one electrode as anode and the other electrode as cathode, thereby creating an electric field between the electrodes,

- extracting hydrogen, which has travelled through the pores of the cathode, from the electrochemical reactor, and

- extracting oxygen, which has travelled through the pores of the anode, from the electrochemical reactor.

FIGURES

In the following, the invention is described in detail by means of drawings, wherein show:

Figure 1 : a schematic perspective view of an electrochemical reactor according to one embodiment,

Figure 2: a schematic vertical cut view of an electrochemical reactor according to one embodiment,

Figure 3: a schematic horizontal cut view through a main body of an electrochemical reactor according to one embodiment (one electrode set),

Figure 4: a schematic vertical cut view through a main body of an electrochemical reactor (corresponding to the embodiment shown in Figure 3),

Figure 5: a schematic horizontal cut view through a main body of an electrochemical reactor according to one embodiment (three electrode sets), and

Figure 6: a schematic vertical cut view through a main body of an electrochemical reactor (corresponding to the embodiment shown in Figure 5).

Description of Preferred Embodiments

Figure 1 shows a schematic perspective view of an electrochemical reactor R according to one embodiment of the invention. The electrochemical reactor R comprises an inlet manifold 1 , an outlet manifold 2 and a main body 3. In the embodiment shown in Figure 1 , the inlet manifold 1 is arranged at a bottom side of the electrochemical reactor R, the outlet manifold 2 is arranged on a top side of the electrochemical reactor R and the main body 3 is arranged in between the inlet manifold 1 and the outlet manifold 2. The inlet manifold 1 comprises an entry port 4 for feeding an electrolyte into the electrochemical reactor R. The main body 3 of the electrochemical reactor R comprises one or more electrode sets S. Each electrode set S comprises a first electrode and a second electrode by means of which an electrolysis of the electrolyte for producing hydrogen and oxygen can be carried out. The outlet manifold 2 comprises a first exit port 5 and a second exit port 6. One of the two exit ports 5, 6 can be used for extracting oxygen from the electrochemical reactor R, and the other one can be used for extracting hydrogen from the electrochemical reactor R. Which one of the exit ports 5, 6 is used for hydrogen and which one is used for oxygen depends on the configuration of the electrodes inside the electrode set S. Figure 1 furthermore shows two electrical connections, namely a cathode connection 10 and an anode connection 11 . Even though only two electrical connections 10, 11 are shown in Figure 1 , it is possible for the electrochemical reactor to comprise a multitude of cathode connections and/or a multitude of anode connections in order to make the charge distribution inside the electrode set S more uniform. As can be taken from Figure 1 , the electrode set S is cylindrical, with a circular cross-section. The electrode set S comprises two hollow-cylindrical, coaxial electrodes with circular cross-sections, even if this is not visible in Figure 1. Two cut directions A-A and B-B are indicated in Figure 1 . Views according to these cut directions will be presented in some of the following Figures.

Figure 2 shows a schematic vertical cut view of an electrochemical reactor R according to one embodiment of the invention. The embodiment shown in Figure 2 in principle corresponds to the embodiment shown in Figure 1 , with the exception that the electrical connections 10, 11 shown in Figure 1 are not shown in Figure 2 but are replaced by another type of connections (explained below). The electrochemical reactor R shown in Figure 2 therefore also comprises an inlet manifold 1 , an outlet manifold 2 and a main body 3. Since the embodiment in Figure 2 is shown in a vertical cut view, it can be seen in Figure 2 that the electrode set S arranged inside the main body 3 comprises a first electrode 7 and a second electrode 8, which are of cylindrical shape and which are arranged in a coaxial manner inside the electrochemical reactor R. It can also be observed that the two electrodes 7, 8 each comprise a large multitude of pores. This is a bit difficult to observe in Figure 2 due to the large number of pores, but it will become much easier to observe in the following Figures. The inlet manifold 1 comprises two power source access holes 9.1 , 9.2. The power access hole 9.1 is configured to allow an electrical connection of the second electrode 8 to be connected to a power source (not shown) and the power source access hole 9.2 is configured to allow an electrical connection of the first electrode 7 to the power source. It can furthermore be observed in Figure 2, that the inlet manifold 1 comprises an inlet channel system 12 (which is connected to the entry port 4 shown in Figure 1 ), which at least partially has the form of an annulus, and which makes it possible to supply an electrolyte to the main body 3, in particular into a space between the first electrode 7 and the second electrode 8. This space between the electrodes 7, 8 is referred to as electrolyte channel and is not equipped with a reference sign in Figure 2 for reasons of clarity (but will be explained in more detail later). Outlet manifold 2 comprises an outlet channel system 13,14 comprising a first part 13 and a second part 14. It can be observed that the second part 14 is connected to the second exit port 6 and the first part 13 is connected to the first exit port 5. It can furthermore be observed that the first part 13 of the outlet channel system

13, 14 is connected to an interior of the first electrode 7. It thereby allows an evacuation of gas and/or electrolyte from the inside of the inner electrode 7. It can further be observed that the second part 14 of the outlet channel system 13, 14 is connected to the second exit port 6 and has a partially funnel-shaped form, which is connected to the main body 3 in such a way as to allow electrolyte and/or gas from a region located outside the second electrode 8 to be evacuated from the electrode set S and into the second part 14 of the outlet channel system 13,

14.

Figure 3 is a schematic horizontal cut view through a main body 3 of an electrochemical reactor according to one embodiment, namely an embodiment with one electrode set. This cut view basically corresponds to the cut direction A- A indicated in Figure 1 . The main body 3 shown in Figure 3 comprises a first electrode 7, a second electrode 8 and a separation wall 17. The first electrode 7 has a diameter that is smaller than a diameter of the second electrode 8, and both electrodes 7, 8 are arranged in a coaxial manner. Both electrodes 7, 8 are drawn in dashed lines in Figure 3. This is supposed to indicate that both electrodes 7, 8 comprise a large multitude of pores, therefore making the electrodes 7, 8 electrodes with a mesh-like structure. The separation wall 17 is arranged around the two electrodes 7, 8 in a coaxial manner and separates the exterior of the main body 3 from its interior. In other words: the separation wall 17 shown in Figure 3 is the outer wall of the main body 3. Since the first electrode 7 has a diameter that is smaller than the diameter of the second electrode 8, a space is created between the two electrodes 7, 8. This space is referred to as electrolyte channel 15 and it can be seen that it has the form of a wall of a hollow cylinder. The inside of the first electrode 7 is referred to as interior outlet channel 18 and the area between the separation wall 17 and the second electrode 8 is referred to as exterior outlet channel 19. When an electrolyte (not shown in Figure 3) is fed into the electrolyte channel 15, and different electrical potentials are applied to electrodes 7, 8 (thereby making the electrodes 7, 8 an anode and a cathode, respectively), then the resulting electric field between the two electrodes 7, 8 leads to gas evolution of Fte and O2 and their separation into the interior outlet channel 18 for one gas into the exterior outlet channel 19 for the other gas. The concept of this electrolysis will be understood even better from the following Figures.

Figure 4 shows a schematic vertical cut view through a main body of an electrochemical reactor corresponding to the embodiment already shown in Figure 3. This cut view basically corresponds to the cut direction B-B indicated in Figure 1. It can be seen in Figure 4 that the main body 3 comprises a first electrode 7, serving as interior electrode, and a second electrode 8, serving as exterior electrode. The two electrodes 7, 8 form an electrode set. Because the diameter of the first electrode 7 is smaller than the diameter of the second electrode 8, the electrolyte channel 15, which has the form of a wall of a hollow cylinder, is created between the two electrodes 7, 8. In the embodiment shown in Figure 4, the first electrode 7 is set to a positive potential and the second electrode 8 is set to a negative potential. Therefore, the electrolyte 16 entering into the electrolyte channel 15 from below (indicated by arrows) is submitted to an electrolysis. This electrolysis leads to the formation of hydrogen bubbles H2 at the second electrode 8 and oxygen bubbles O2 at the first electrode 7. From these areas, they are evacuated towards the output manifold (not shown in Figure 4) by the electrolyte which flows through the pores. The separation wall 17 is also shown in Figure 4. Figure 5 now shows a schematic horizontal cut view through a main body 3.1 of an electrochemical reactor according to one embodiment of the invention. The main body 3.1 shown in Figure 5 comprises three electrode sets. The first electrode set is formed by a first electrode 7 and a second electrode 8. The second electrode set is formed by the first electrode 7.1 and the second electrode 8.1 . The third electrode set is formed by the first electrode 7.2 and the second electrode 8.2. The first electrode set is separated from the second electrode set by the separation wall 17. The second electrode set is separated from the third electrode set by the separation wall 17.1 . The separation wall 17.2 separates the interior of the main body 3.1 from its exterior. It is clearly shown in Figure 5 that all electrodes and separation walls have a circular cross-section and different diameters and are arranged in a coaxial manner in this embodiment. It can furthermore be observed that all electrodes have a mesh-like structure because they comprise all a large multitude of pores. Between each first electrode 7, 7.1 , 7.2 and its corresponding second electrode 8, 8.1 , 8.2, a corresponding electrolyte channel 15, 15.1 , 15.2 is created. It is easily understandable that the embodiment shown in Figure 5 corresponds to an electrochemical reactor which is stacked, in other words: which comprises a stack of three electrode sets. Compared to the embodiments shown in Figures 1 to 4, the production capacity of the embodiment shown in this Figure 5 is therefore increased. The cut view of Figure 5 basically corresponds to the cut direction A- A indicated in Figure 1 (if one imagines that the main body 3 of Figure 1 comprises three electrode sets).

Figure 6 now shows a schematic vertical cut view through a main body 3.1 of an electrochemical reactor, which corresponds to the embodiment already shown in Figure 5. The cut view of Figure 6 basically corresponds to the cut direction B-B indicated in Figure 1 (if one imagines that the main body 3 of Figure 1 comprises three electrode sets). Yet again, it is shown in Figure 6 that the main body 3.1 comprises a multitude of cylindrical electrodes which are all arranged in a coaxial manner around the longitudinal axis L. In the centre of the main body 3.1 lies a first electrode set formed by the first electrode 7 and the second electrode 8. The first electrode 7 and the second electrode 8 have different diameters and therefore an electrolyte channel 15 is created between these two electrodes. A second electrode set comprising the first electrode 7.1 . and the second electrode 8.1 is arranged around the first electrode set and is separated from the first electrode set by means of the cylindrical separation wall 17. Circled around the second electrode set and the first electrode set is a third electrode set comprising the first electrode 7.2 and the second electrode 8.2. The third electrode set is separated from the second electrode set by means of the separation wall 17.1 . The third electrode set is separated from an exterior of the main body 3.1 by means of the separation wall 17.2. In other words: it can be seen in Figure 6, that this embodiment of the electrochemical reactor comprises six electrodes of different diameter arranged in three electrode sets, namely three first electrodes 7, 7.1 , 7.2 and three second electrodes 8, 8.1 , 8.2. The main body 3.1 furthermore comprises three separation walls 17, 17.1 , 17.2. Furthermore, each electrode set comprises an electrolyte channel 15, 15.1 , 15.2. When an electrolyte (represented by arrows in Figure 6, but not equipped with reference signs for clarity reasons) is fed into the electrolyte channels 15, 15.1 , 15.2, an electrolysis like the one already explained with regard to Figure 4 is initiated by means of each electrode set. When the first electrodes 7, 7.1 , 7.2 are configured as anodes and the second electrodes 8, 8.1 , 8.2 are configured as cathodes, oxygen evolves at the first electrodes 7, 7.1 , 7.2 and hydrogen evolves at the second electrodes 8, 8.1 , 8.2. Oxygen gas then moves out of the main body 3.1 through the respective interior outlet channels (not equipped with reference signs for reasons of clarity). Likewise, hydrogen gas travels out of the main body 3.1 through the respective exterior outlet channels (also not equipped with reference signs in Figure 6 for reasons of clarity). The functioning of an electrochemical reactor R with a single electrode set S (an “electrode set” can also be referred to as“cell”) can be summarized as follows (referring to Figures 1 to 4). Electrolysis of water is considered as the model reaction here to describe the working mechanism of the invention. Acidic (such as sulfuric acid) or basic (such as potassium hydroxide) electrolyte enters into the electrochemical reactor R through the port 4 of the inlet manifold 1 . This inlet manifold 1 is typically chemically compatible with the electrolyte and provides electrical insulation between the electrodes. In typical embodiments, it is made from plastic material (such as Teflon) or a composite of metal (such as Hastelloy) and plastic (such as Teflon). The electrolyte flows inside the electrochemical reactor R through the inlet channel system 12 (which, in typical embodiments, has the shape of an annulus duct) and reaches the space between the mesh electrodes 7 and 8 (see for example Figure 2 and Figure 4). Depending on the type of reaction and electrolyte, these mesh electrodes 7, 8 are typically made from or coated with an appropriate material such as platinum, nickel, and/or mixed metal oxides. These electrodes 7, 8 are connected to an external power source, for example through the power source access holes 9.1 and 9.2. Hydrogen evolves on one of the electrodes (for instance electrode 8) and oxygen on the other electrode (for instance electrode 7). The electrolyte will flow to the exterior space of electrode 8 and interior space of electrode 7 through the pores and carries with itself the products evolved on each electrode to these spaces.

At the end (that is, the top of the main body 3, see for example Figure 2 and Figure 4) of the mesh electrodes 7, 8, separate mixtures of electrolyte with hydrogen on one hand and electrolyte with oxygen on the other hand exit the main body 3. The mixture of electrolyte with hydrogen then exits through one of the two exit ports (for instance exit port 6) and a mixture of electrolyte and oxygen exits through the other exit port (for instance exit port 5). These exit ports 5, 6 are integrated in the outlet manifold 2 with similar or same characteristics (for example in terms of material choices) as the inlet manifold 1 described above. The electrodes 7, 8 are contained in the main body 3 of the electrochemical reactor R. In typical embodiments, the main body 3 and/or the separation wall 17 are chemically compatible with the electrolyte. In typical embodiments, the main body 3 and/or the separation wall 17 comprise a plastic material (such as Teflon), a metal (such as Hastelloy), and/or a combination of both. The electrodes 7, 8 are typically mounted on the inlet manifold 1 through the power source access holes 9.1 , 9.2 but they can also be mounted - using either screws or other fastening methods - on the outlet manifold 2 or both of these manifolds as well. The two manifolds 1 , 2 and the main body 3 are typically assembled by means of screws or the like.

The functioning of an electrochemical reactor R with multiple electrode sets S is in principle very much comparable to the functioning of an electrochemical reactor R with a single electrode set S as explained for example in previous paragraph. One difference, however, is that once the electrolyte has entered the inlet manifold 1 , it is not only distributed to a single electrolyte channel 15 in the main body 3, but to a multitude of electrolyte channels 15, 15.1 , 15.2 (one electrolyte channel per electrode set). In the embodiment shown in Figures 5 and 6, there are three electrode sets and thus three electrolyte channels 15, 15.1 , 15.2. In typical embodiments, the electrochemical reactor R comprises even more electrode sets, for example at least 5, at least 7 or at least 9 electrode sets and therefore also at least 5, at least 7 or at least 9 electrolyte channels. In the embodiment with three electrode sets shown in Figures 5 and 6, the electrolyte, after flowing through the inlet manifold (not shown in Figures 5 and 6 - it is preferably an inlet manifold comprising an inlet channel system adapted to guide the electrolyte to each of the different electrolyte channels) reaches the spaces between each pair (or set) of the mesh electrodes 7 and 8, 7.1 and 8.1 , 7.2 and

8.2. These spaces are precisely the circular electrolyte channels 15, 15.1 and

15.2, respectively, which run between the two electrodes of each electrode set. The characteristics (e.g. material, connection to power source etc.) are in principle the same as explained for the embodiment with a single electrode set. Oxygen evolves on one of the electrodes of each pair (for instance the first electrodes 7, 7.1 , 7.2) and hydrogen on the other electrodes (for instance the second electrodes 8, 8.1 , 8.2). The electrolyte and hydrogen mixture will flow to the spaces between the second electrodes 8, 8.1 , 8.2 and the separating walls 17, 17.1 , 17.2 through the pores of the second electrodes 8, 8.1 , 8.2.

The electrolyte and oxygen mixture will flow in the opposite directions in each of the electrode sets and through the pores of the first electrodes 7, 7.1 , 7.2, namely to the space between the first electrode 7.2 and the separation wall 17.1 in the case of the third electrode set, to the space between the first electrode 7.1 and the separation wall 17 in the case of the second electrode set and into the interior of the first electrode 7 in the case of the first electrode set.

At the end of the mesh electrodes 7, 7.1 , 7.2, 8, 8.1 , 8.2 (see for example the upper part of Figure 6) separate mixtures of electrolyte with hydrogen F on one hand and electrolyte with oxygen O2 on the other hand exit the electrode sets. The mixture of electrolyte with hydrogen then exits through one of the two exit ports and a mixture of electrolyte and oxygen exits through the other exit port, much as described above for the embodiment with one single electrode set. In the case of a multitude of electrode sets (or cells), the outlet manifold, in particular the outlet channel system of this outlet manifold, is preferably configured to guide all electrolyte/hydrogen flows to one of the two exit ports and all electrolyte/oxygen flows to the other exit port. Otherwise, the outlet manifold and/or other elements of the electrochemical reactor typically have the same characteristics as explained for the embodiment with one single electrode set (where appropriate).

Once the gas-carrying electrolytes have exited the outlet manifold through the exit ports 5, 6, respectively, they are then degassed outside the electrochemical reactor R and then fed back into the reactor to continue the reaction. The electrolyte is typically circulated inside the electrochemical reactor R using one or more appropriate pumps. In typical embodiments and/or depending on the application, a pressure inside the electrochemical reactor R can be increased in order to store the generated gases at a higher pressure.

In a particular embodiment, the electrochemical reactor comprises a multitude of concentric mesh electrodes. When an electrolyte flow is guided into interelectrode spaces, oxidation and reduction products are evolved at anode and cathode electrodes respectively, and are carried out of the interelectrode spaces with the electrolyte flow through the pores of the mesh electrodes. If any of the products are in gaseous form, they are maintained close to the electrodes structure in the interelectrode space through inertial fluidic forces before leaving these regions. This fluidic based separation mechanism removes the need for integration of an ion conductive membrane or separator. In typical embodiments, the pores size and density are tuned to provide an equal pressure drop along the cell in order to maintain an almost equal flowrate in all regions of the cell. In typical embodiments, the cylindrical mesh electrodes with engineered pores are additively manufactured. This part can be used as a template for electroplating the desired catalyst for each reaction if necessary. The cylindrical shape of the electrodes provides a compact form factor for the stack and a robust mechanical structure for high pressure operations. In particular embodiments, the electrochemical reactor is configured to be used for any electrochemical reaction such as electrolysis of water or brine.

In principle, the described electrochemical reactor can also be used as a fuel cell instead of a hydrogen/oxygen generator if configured in the opposite direction. However, in this case, a membrane will be necessary.

In a typical embodiment, the electrochemical reactor is not used for splitting water but for another chemical reaction, for example for a Chlor-Alkali process.

The invention is not limited to the preferred embodiments described here. The scope of protection is defined by the claims.

Furthermore, the following claims are hereby incorporated into the Description of Preferred Embodiments, where each claim may stand on its own as a separate embodiment. While each claim may stand on its own as a separate embodiment, it is to be noted that - although a dependent claim may refer in the claims to a specific combination with one or more other claims - other embodiments may also include a combination of the dependent claim with the subject matter of each other dependent or independent claim. Such combinations are proposed herein unless it is stated that a specific combination is not intended. Furthermore, it is intended to include also features of a claim to any other independent claim even if this claim is not directly made dependent to the independent claim.

It is further to be noted that methods disclosed in the specification or in the claims may be implemented by a device having means for performing each of the respective acts of these methods.

Reference list

1 Inlet manifold

2 Outlet manifold

3, 3.1 Main body (of electrochemical reactor)

4 Entry port

5 First exit port

6 Second exit port

7, 7.1 , 7.2 First electrodes

8, 8.1 , 8.2 Second electrodes

9.1 , 9.2 Power source access hole

10 Cathode connection

11 Anode connection

12 Inlet channel system

13 Outlet channel system (first part)

14 Outlet channel system (second part)

15, 15.1 , 15.2 Electrolyte channels

16 Electrolyte

17, 17.1 , 17.2 Separation wall

18 Interior outlet channel

19 Exterior outlet channel

L Longitudinal axis

R Electrochemical reactor

S Electrode Set

Claims

Patent Claims

1. Electrochemical reactor (R) for producing oxygen and hydrogen by means of electrolysis of an electrolyte (16),

- wherein the electrochemical reactor (R) comprises a first electrode set (S),

- wherein the first electrode set (S) comprises a first electrode (7) and a second electrode (8), characterized in that

- the first electrode (7) comprises a multitude of pores,

- the second electrode (8) comprises a multitude of pores, and

- the first electrode (7) is arranged inside the second electrode (8), such that an electrolyte channel (15) is formed between the first electrode (7) and the second electrode (8).

2. Electrochemical reactor (R) according to claim 1 , characterized in that the first electrode (7) and/or the second electrode (8) has/have an essentially cylindrical form and/or in that a dimension, preferably a diameter, of the first electrode (7) is smaller than a dimension, preferably a diameter, of the second electrode (8).

3. Electrochemical reactor (R) according to any of the previous claims, characterized in that the electrochemical reactor (R) comprises at least one additional electrode set.

4. Electrochemical reactor (R) according to any of the previous claims, characterized in that all electrode sets are arranged in a coaxial manner and/or all electrodes are arranged in a coaxial manner.

5. Electrochemical reactor (R) according to any of the previous claims, characterized in that the electrochemical reactor (R) is membrane-less.

6. Electrochemical reactor (R) according to any of the previous claims, characterized in that the electrochemical reactor (R) comprises a separation wall (17) or a multitude of separation walls (17, 17.1 , 17.2) arranged around each electrode set.

7. Electrochemical reactor (R) according to any of the previous claims, characterized in that the electrochemical reactor (R) comprises an inlet manifold (1 ), wherein the inlet manifold (1 ) preferably comprises one entry port, (4) wherein the inlet manifold (1 ) is configured to supply the electrolyte (16) to the electrolyte channel(s) (15, 15.1 , 15.2) exclusively.

8. Electrochemical reactor (R) according to any of the previous claims, characterized in that the electrochemical reactor (R) comprises an outlet manifold (2), wherein the outlet manifold (2) preferably comprises two exit ports (5, 6), wherein the outlet manifold (2) is configured to collect and guide the hydrogen to one exit port and to collect and guide the oxygen to the other exit port.

9. Electrochemical reactor (R) according to any of the previous claims, characterized in that a distance between the first electrode (7, 7.1 , 7.2) and the second electrode (8, 8.1 , 8.2) of at least one, preferably all, electrode set(s) is between 100 pm and 30 mm, preferably between 300 pm and 10 mm, more preferably between 500 pm and 5 mm.

10. Method for producing oxygen and hydrogen by means of an electrochemical reactor (R) according to any of the previous claims, comprising the steps:

- feeding an electrolyte (16) into the electrolyte channel (15, 15.1 , 15.2),

- extracting hydrogen, which has travelled through the pores of the cathode, from the electrochemical reactor (R), and

- extracting oxygen, which has travelled through the pores of the anode, from the electrochemical reactor (R).