Patent Application
20220143555
The invention relates to a capacitive electrode, a membrane stack comprising such electrode and a method for manufacturing such a capacitive electrode.
Electro-membrane processes, such as (reverse) electrodialysis, are known from practice. Such processes mostly involve redox reactions at the electrodes, which convert ion flux into electrical current and vice versa. A disadvantage of such redox-based processes is that it often requires the use of expensive and/or rare materials for the electrodes, such as platinum. The use of such electrodes increases the cost of the electro-membrane device. Another disadvantage of such electrodes for redox-based electro-membrane processes is that the redox processes lead to the formation of hazardous and/or explosive gases, such as chlorine and hydrogen, at the electrodes.
In order to obviate these disadvantages, it is known that capacitive electrodes may be used. Such capacitive electrodes comprise a current feeder on which a capacitive layer is provided. The capacitive layer is provided to the current feeder using a binder, which in some cases is toxic, and/or applying high pressure to the capacitive layer to establish a bond between the current feeder and the capacitive layer. The capacitive electrode is configured to, during use, store ions and conduct electrons. The capacity of the electrode to do so is mostly determined by the thickness of the capacitive layer that is provided on the current feeder.
A disadvantage of the known capacitive electrodes is that the thickness of the capacitive layer, and thus the capacity of the electrode, is limited due to the fact that delamination of the capacitive layer from the current feeder occurs at increasing thicknesses of the capacitive layer. As a result, the thickness of the layer in practice is limited to 1-2.5 mm thickness.
The invention is aimed at obviating or at least reducing the abovementioned problems. More particularly, the invention aims to provide an electrode having an increased capacity.
To that end, the invention comprises a capacitive electrode, the capacitive electrode comprising:
An advantage of the capacitive electrode according to the invention is that the layer thickness can be increased compared to known capacitive electrodes, which leads to an increase in capacity. The increase of the capacitive layer is possible due to the fact that the capacitive layer, during use of the electrode, is a flexible, moist layer that is kept enclosed in the housing by the gel layer. In other words, by providing a flexible, moist capacitive layer that is enclosed in the housing with a gel layer, the problem of delamination is obviated. This allows the thickness of the capacitive layer to be increased above the thicknesses currently possible in the known electrodes.
Moreover, the capacitive electrode according to the invention has the surprising other advantage that it provides a substantially linear relation between electrode thickness and electrode capacity.
This for example means that an increase of thickness of the capacitive layer with a factor two results in an increase of the capacity with about a factor two. This is, amongst others, due to the fact that the presence of a binder is obviated in the capacitive layer according to the invention.
A capacitive electrode requires an electrical connection to allow it to function properly, yet does not necessarily require the capacitive material to be integrally formed with the current feeder, such as is the case with a binder and/or with highly compressed particles of capacitive material.
Another advantage of the capacitive electrode according to the invention is that it does not contain any binder and/or closely pressed particles of capacitive material, because the capacitive layer is contained by the gel of the gel layer. This reduces manufacturing cost, increases conductivity and, in case of a binder, obviates the use of toxic and/or expensive binders such as for example PVDF or PTFE.
Another advantage of the capacitive electrode according to the invention is that the capacitive layer and/or the gel layer can be easily exchanged for a new layer. This is due to the fact that both layers are not integrally formed with the current feeder.
Yet another advantage of the capacitive electrode according to the invention is that the gel layer obviates the use of an additional ion-selective membrane that is positioned between the electrode and the membrane stack. This obviates the use of a (specific) end membrane and/or allows the use of (other) intermediates, such as a flow compartment, and/or a gasket or a spacer of a flow compartment.
Yet another advantage of the capacitive electrode according to the invention is that the effective surface area of the electrode is increased due to the lack of binder and the decreased interparticle space in the capacitive material layer. This also decreases electrical resistance and facilitates increased salt/ion transport. Differently said, clogging of the openings of the capacitive particles (as present with binders) is obviated, and the particles can settle closer to each other due to the absence of binder in between them, thus facilitating better salt/ion transport and decreases electrical resistance.
In this respect it is noted that electrodes according to the prior art often use (inert polymeric) binder, such as PVDF or PTFE, to keep and/or bind the capacitive particles together and to bond the capacitive layer to the current feeder (surface). Such binders, usually having 5-10 wt % of the capacitive layer, are known to block a significant amount of pores within the capacitive layer. The use of a binder thus increases resistance and limits capacity of the electrodes. In addition, such binders are expensive and/or require toxic solvents (such as NMP). Therefore, the electrodes according to the invention have significant advantages with respect to capacity compared to prior art electrodes.
In an embodiment according to the invention, the current feeder is provided with at least one connector that extends at least partially outside the electrode housing.
An advantage of providing a connector that at least partially extends outside the housing is that the current feeder is easily connectable to an external source. The connector may be provided as a separate connector that is connected to the current feeder after it is manufactured, such as by means of welding, clicking or any suitable connection. The current feeder and the connector may also be integrally formed. This for example may take the form of a mesh current feeder or a (perforated) foil-shaped current feeder, for example a (perforated) graphite foil or an expanded flexible graphite foil, which is near one or more sides thereof cut to form a connector that at least partially extends beyond the housing.
In another example, the current feeder may comprise a mesh and the connector is formed by a wire or ring that is at least partially embedded in a portion of the housing, for example in a side wall, or preferably, near the opening of the housing. Such a wire or ring may be extending along the circumference of the opening and be connected to the current feeder. This may for example be performed by folding the current feeder, especially a mesh type current feeder, against or over the ring or wire.
In an embodiment according to the invention, the gel layer is provided adjacent with the end membrane of the membrane stack.
An advantage of providing the gel layer and the end membrane adjacent, preferably contiguous, with each other is that a good sealing of the housing space is achieved.
In an embodiment according to the invention, the capacitive electrode comprises a separator layer, preferably a filter paper layer, that is positioned between the gel layer and the capacitive layer.
An advantage of this embodiment is that the capacitive layer can have increased moisture level when the gel layer is applied without mixing between capacitive layer and gel layer. The filter paper layer may be manufactured of any suitable material including (thermoplastic) polymers such as polypropylene, cellulose or paper. It also provides the advantage that the capacitive layer, during manufacturing, does not need to be dried or needs less drying.
In an embodiment according to the invention, the gel layer is an ion-conducting layer and/or wherein the gel is chosen from a group of a hydrogel, gelatin, a PVA based gel, a PMMA based gel, agar-agar or a superabsorbent polymer (SAP) that is conditioned in a salt solution.
Gels, and hydrogels in particular, have the advantage that they allow ion and a limited amount of water transport through the gel layer to the capacitive layer, whereas they simultaneously prevent an excess of water to traverse the gel that would lead the capacitive layer to become too wet. This is amongst others due to osmosis which reduces the water transfer to the capacitive layer.
Another advantage of gels is that such layers also function as a cation and/or anion source or sink or buffer, which increases efficiency of the capacitive electrode.
Yet another advantage of gels is that, due to its flexibility and elasticity, they provide a constant containing force on the capacitive layer, which prevents the particles of the capacitive layer from moving with respect to each other. At the same time, these properties also reduce the risk of mechanical damage and/or penetration by impurities reaching the capacitive layer.
An advantage of a superabsorbent polymer (SAP) that is conditioned in a salt solution is, additionally to the abovementioned advantages, that it even more strongly enhances conductivity.
In an embodiment according to the invention, the housing is an end-plate of a membrane-based device, such as an electrodialysis device, a reverse electrodialysis device or a fuel cell.
By providing the housing as an end plate of the membrane-based device, a compact and cost-effective solution is achieved, because a separate end plate is obviated. In addition, the capacitive electrode according to the invention does not require a fluid electrolyte (i.e. an electrode rinse solution) and, therefore, does not require a fluid entry and/or exit opening in the housing for the electrolyte. As a result, the end plate that is formed by the housing has a compact and efficient lay-out, which increases efficiency and reduces material use and cost.
In an embodiment according to the invention, the capacitive layer is an activated carbon layer.
An advantage of an activated carbon layer is that it provides a good capacitance and electrical conductivity and, in contrast to other suitable materials, is highly cost-effective in terms of manufacturing and handling. Furthermore, activated carbon is readily available and not a scarce resource.
In an embodiment according to the invention, the capacitive layer comprises one or more of activated carbon, carbon black and/or graphite.
By providing one or more of the abovementioned substances, especially activated carbon with one or both of carbon black and graphite, the electrical conductivity of the capacitive layer is improved even further.
In an embodiment according to the invention, the capacitive layer comprises beads of capacitive material or capacitive material in the form of powder or a mixture of beads and powder.
An advantage of providing the activated carbon layer in the form of beads and/or powder is that, due to settling of the beads and/or the powder, a porous structure with an extensive network of fine channels and pores and small voids is formed. This enhances ion transport into and inside the capacitive layer. In other words, the accessibility for ions into and inside the capacitive layer is increased.
By providing the capacitive layer as beads, powder or a mixture thereof, an increased density of the material can be achieved, which increases the prospective (i.e. potential) capacity of the layer. This is at least partly due to the abovementioned increased accessibility. It is noted that the accessibility both relates to in-layer accessibility as well as the interlayer accessibility between the capacitive layer and the current feeder. By providing beads only, the capacitive layer has an additional advantage of being easily manufacturable, since it only requires providing the beads and, optionally, compressing the beads to a more dense capacitive layer. Providing the capacitive layer as powder has an advantage in that it provides a very dense layer with a low amount of pores and voids and an even more increased capacity. In a specific embodiment, beads and powder are both used in conjunction with each other, which results in a layer in which the voids between beads are filled with powder. This provides the advantage of an excellent electric conductivity and simultaneously an excellent ion accessibility.
Another advantage of this embodiment is that the handling and/or manufacturability of the capacitive layer is also increased when the layer is formed of beads, powder and/or a combination thereof.
In an embodiment according to the invention, the capacitive layer has a thickness in the range of 0.5-50 mm, and preferably has a thickness in the range of 1-10 mm.
It is found that a capacitive electrode according to the invention has a capacity that is linearly dependent on the thickness of the capacitive layer. Therefore, an increased thickness is preferable over a smaller thickness. However, the thickness may on the other hand be limited in order to reduce the space occupied by the electrode when placed in a membrane stack assembly. An advantage of providing a thickness in the range of 0.5-50 mm is that a good balance is provided between the capacity of the layer and the size of the electrode.
In an embodiment according to the invention, the gel layer has a thickness in the range of 0.5-50 mm, and preferably has a thickness in the range of 1-10 mm.
The gel layer primarily functions to separate fluid, especially water from the membrane stack, from the capacitive layer. In addition, the gel layer also functions as an at least partially conductive layer for the transport of ions between the capacitive layer and the gel layer. In order to fulfill these functions, the gel layer isolates and/or encapsulates the capacitive layer.
By providing a thickness in the abovementioned range, a good balance is struck between space occupied by the gel layer and the functions performed by the gel layer. In other words, a gel layer in the abovementioned range provides good insulating and conductive properties without taking up an unduly amount of space within the housing. It has been found that the layer with the abovementioned thickness also provides excellent positioning abilities in that it holds the capacitive layer in place against the current feeder.
In an embodiment according to the invention, the gel layer and the capacitive layer have a substantially equal thickness.
In an embodiment according to the invention the current feeder is chosen from a (perforated) carbon foil, a (perforated) carbon plate, a graphite foil, a graphite plate, a platinum coated titanium mesh, a platinum coated titanium (perforated) plate, a platinum coated titanium (perforated) foil or a mesh coated with (mixed) metal oxides, a (perforated) plate coated with (mixed) metal oxides, or a (perforated) foil coated with (mixed) metal oxides.
The abovementioned materials provide a high conductivity against relatively low cost. Another advantage is that, by providing a foil, a mesh or a plate of the abovementioned materials, a large contact surface is obtained between the current feeder and the capacitive layer.
In an embodiment according to the invention, the gel layer comprises a reinforcement layer, wherein the reinforcement layer preferably comprises a netting or a non-woven.
An advantage of a reinforcing layer is that the gel layer is provided with additional stability, which further enhances mechanical stability. It also further enhances dimensional stability in that the dimensions of the gel layer substantially do not vary under varying circumstances, thus maintaining the sealing properties.
In an embodiment according to the invention, the reinforcement layer has a thickness in the range of 0.5-50 mm, and preferably has a thickness in the range of 1-10 mm.
In an embodiment according to the invention, the housing comprises a lining or rim that extends around the opening and that is in electrical contact with the current feeder, wherein the lining or rim is preferably copper or graphite.
The current feeder may be connectable with an external source by means of a copper lining, copper ring or copper rim that is positioned near the opening of the housing.
An advantage thereof is that the electrical connection with the current feeder is positioned with the outer circumference of the housing and is therewith protected from outside damage.
Another advantage is that, due to the fact that the copper extends around the circumference of the opening, the current feeder is connectable at one or more different locations along the circumference. This increases reliability of the connection and allows the current feeder to operate even if a single connection would be malfunctioning.
In an embodiment, the copper ring, rim or lining could be provided in a groove in the housing that extends around the circumference of the opening.
In an embodiment according to the invention, the electrode additionally comprises a second capacitive layer and a second gel layer, such that, when viewed from the opening towards the housing space, the electrode comprises the gel layer, the capacitive layer, the current feeder, the second capacitive layer and the second gel layer.
An advantage of providing multiple capacitive and gel layers is that the capacity of the capacitive electrode is increased. In addition, by providing multiple capacitive layers (which are each connected to the current feeder) in between which gel layers are provided, a redundant and reliable capacitive electrode is provided. As such, a double layer capacitive electrode is achieved.
In an embodiment according to the invention, the current feeder is integrated in the capacitive layer, wherein the current feeder preferably extends in the capacitive layer in a direction substantially parallel to the opening.
An advantage of this embodiment is that an improved connection between the current feeder and the capacitive layer is achieved, which (further) increases performance of the capacitive electrode. In an embodiment according to the invention, the gel comprises a salt composition, such as NaCl or KCl, wherein the composition is preferably a solution in the range of 0.1 M<salt<6 M.
The advantage of applying a salt composition, such as NaCl or KCl, to the gel an increased conductivity of the gel with respect to ions can be achieved. Naturally, other salts may also be used.
In an embodiment according to the invention, the capacitive layer is manufactured from a compressed base material, such as activated carbon, and preferably activated carbon beads, powder or a mixture thereof.
An advantage of compressing the base material of the capacitive layer is that excess water is expelled during manufacturing, while simultaneously providing a high density capacitive layer. It is noted that the compressing is preferably performed during the application, or more specific the formation, of the capacitive layer on the current feeder. In other words, the base material is compressed on the current feeder to form the capacitive layer.
Another advantage is that the compression results in an enhanced capacity due to the settling of the particles (i.e. beads and/or powder) in the capacitive layer.
In an embodiment according to the invention, the housing is provided with at least one drainage channel that is configured for draining off water from the housing.
An advantage of providing at least one drainage channel is that water can be drained off, for example if the moisture level in the gel layer exceeds a predetermined level. As a result, the excess water is prevented from reaching the capacitive layer which obviates oversaturation of the capacitive layer and thus enhances prevention of destabilization and/or degeneration of the capacitive layer. It also obviates the formation of a water layer between the gel layer and the membrane stack, which may increase electrical resistance.
The invention also relates to a membrane-based device for performing a membrane-based process, such as electrodialysis and/or reverse electrodialysis, the device comprising:
It is noted that the contact between (the opening and/or gel layer of) the electrode and the end membrane may also be provided by means of indirect contact via a flow compartment of the membrane stack and/or a gasket of the flow compartment and/or spacer of the flow compartment that is positioned at the end of the membrane stack. It is also possible that the end membrane is a membrane of a flow compartment of the membrane stack.
The membrane-based device for performing a membrane-based process according to the invention provides similar effects and advantages as the capacitive electrode according to the invention.
The membranes of the membrane-based device may be anion exchange membranes (AEM), cation exchange membranes (CEM) and/or bipolar membranes. Preferably, the membrane stack comprises alternatingly AEM and CEM.
It is noted that, when using the capacitive electrode according to the invention, the end membrane of the stack may be directly contiguous with the capacitive electrode and more specifically with the housing and the gel layer within the housing space.
In an embodiment according to the invention, the membrane-based device is an electrodialysis—device or a reverse electrodialysis device.
The invention also relates to a method for manufacturing a capacitive electrode for a membrane-based process, the method comprising the steps of:
It is noted that the opening may in the method be positioned contiguous with the end membrane or may be contiguous with a spacer and/or gasket that is provided on the end membrane, thus forming an indirect connection between the end membrane and the opening. It may even be that the end membrane is a membrane of a flow compartment of the membrane stack.
The method according to the invention provides similar effects and advantages as the capacitive electrode and/or the membrane-based device for performing a membrane-based process according to the invention.
In an embodiment of the method according to the invention, the connector of the current feeder may be a separate connector, wherein the method additionally may comprise the step of connecting the connector to the current feeder, or the connector of the current feeder may be integrally formed with the current feeder and may thus be an integral part thereof.
In an embodiment of the method according to the invention, the step of providing a capacitive layer to the electrode housing comprises:
The step of drying the slurry can be provided using any suitable means and may for example comprise drying the slurry using heat to evaporate the water or may comprise (com)pressing the slurry (and the current feeder) to expel excess water.
In an embodiment of the method according to the invention, the step of applying the gel layer comprises pouring a liquid gel, which may be a warm liquid gel, on top of the capacitive layer, and wherein the step of applying the gel layer optionally also comprises applying a filter paper layer between the gel and the capacitive layer.
In an alternative method according to the invention, the alternative method for manufacturing a capacitive electrode for a membrane-based process may comprise the steps of:
The alternative method according to the invention provides similar effects and advantages as the capacitive electrode and/or the membrane-based device for performing a membrane-based process according to the invention and/or the method according to the invention. More specifically, the embodiments of the method according to the invention may also freely be combined with the alternative method according to the invention.
Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:
In a first example, capacitive electrode 2 comprises housing 4 with housing walls 6, 8 and opening 10 that together delineate housing space 12. In this example, housing 4 is a housing in which housing wall 6 is side wall 6 and housing wall 8 forms bottom wall 8. Housing walls 6, 8 together enclose housing space 12, while opening 10 provides access to housing space 12.
Furthermore, opening 10 is delineated by end section 14 of end wall 6, which end section is configured to be adjacent to end membrane 16 of a membrane stack. In this example, end membrane 16 is a CEM-membrane. Naturally, it may also be a different type of membrane, depending on the configuration of the membrane stack to which the capacitive electrode is connected. Moreover, it may even be a flow compartment of the membrane stack.
Housing space 12, when viewed in first direction x that is parallel to central axis A, subsequently comprises gel layer 18, capacitive layer 20, which in this example is manufactured from (powdered) activated carbon, and current feeder 22 with connector 24. Gel layer 18 extends in second direction y, which is perpendicular to first direction x, over the entire surface area of housing space 12. As such, gel layer 18 forms a seal between end membrane 16 and capacitive layer 20 in housing space 12 (see
In a second example, capacitive electrode 102 comprises housing 104 with housing walls 106, 108 and opening 110 that together delineate housing space 112. In this example, housing 104 is a housing in which housing wall 106 is side wall 106 and housing wall 108 forms bottom wall 108.
Housing walls 106, 108 together enclose housing space 112, while opening 110 provides access to housing space 112.
Furthermore, opening 110 is delineated by end section 114 of end wall 106, which end section is configured to be adjacent to end membrane 116 of a membrane stack. In this example, end membrane 116 is a CEM-membrane. Naturally, it may also be a different type of membrane, depending on the configuration of the membrane stack to which the capacitive electrode is connected. Moreover, it may even be a flow compartment of the membrane stack.
Housing space 112 when viewed in first direction x that is parallel to central axis A, subsequently comprises gel layer 118, capacitive layer 120, which in this example is manufactured from (powdered) activated carbon, current feeder 122 with connector 124 and gel layer 130. Gel layer 118 extends in second direction y, which is perpendicular to first direction x, over the entire surface area of housing space 112. As such, gel layer 118 forms a seal between end membrane 116 and capacitive layer 120 in housing space 112 (see
Bottom wall 108 in this example is provided with an opening through which connector 124 extends. Connector 124 extends through gel layer 130 and is connected to, or integrally formed with, current feeder 122 and forms a connection to connect an external power source or power sink to current feeder 122. As such, a direct electrical connection exists between connector 124 and current feeder 122, as well as between current feeder 122, capacitive layer 120 and gel layer 118.
In a third example, capacitive electrode 202 comprises housing 204 with housing walls 206, 208 and opening 210 that together delineate housing space 212. In this example (see
Furthermore, opening 210 is delineated by end section 214 of end wall 206, which end section is configured to be adjacent to end membrane 216 of a membrane stack. In this example, end membrane 216 is a CEM-membrane. Naturally, it may also be a different type of membrane, depending on the configuration of the membrane stack to which the capacitive electrode is connected. Moreover, it may even be a flow compartment of the membrane stack.
Housing space 212, when viewed in first direction x that is parallel to central axis A, subsequently comprises gel layer 218, capacitive layer 220, which in this example is manufactured from (powdered) activated carbon and gel layer 230. Gel layer 218 extends in second direction y, which is perpendicular to first direction x, over the entire surface area of housing space 212. As such, gel layer 218 forms a seal between end membrane 216 and capacitive layer 220 in housing space 212 (see
Second gel layer 230 is further in contact with bottom wall 208 of housing 204. Bottom wall 208 in this example is a completely closed bottom 208.
In a fourth example (see
Furthermore, opening 310 is delineated by end section 314 of end wall 306, which end section is configured to be adjacent to end membrane 316 of a membrane stack. In this example, end membrane 316 is a CEM-membrane. Naturally, it may also be a different type of membrane, depending on the configuration of the membrane stack to which the capacitive electrode is connected. Moreover, it may even be a flow compartment of the membrane stack.
Housing space 312, when viewed in first direction x that is parallel to central axis A, subsequently comprises gel layer 318, capacitive layer 320, which in this example is manufactured from (powdered) activated carbon and gel layer 330. Gel layer 318 extends in second direction y, which is perpendicular to first direction x, over the entire surface area of housing space 312. As such, gel layer 318 forms a seal between end membrane 316 and capacitive layer 320 in housing space 312 (see
Bottom wall 308 in this example is a completely closed bottom 308.
Furthermore, the example shown in
In a fifth example (see
Furthermore, opening 410 is delineated by end section 414 of end wall 406, which end section is configured to be adjacent to end membrane 416 of a membrane stack. In this example, end membrane 416 is a CEM-membrane. Naturally, it may also be a different type of membrane, depending on the configuration of the membrane stack to which the capacitive electrode is connected. Moreover, it may even be a flow compartment of the membrane stack.
Housing space 412, when viewed in first direction x that is parallel to central axis A, subsequently comprises current feeder 422, capacitive layer 420, which in this example is manufactured from (powdered) activated carbon, and gel layer 430. Current feeder 422 extends in second direction y, which is perpendicular to first direction x, over the entire surface area of housing space 412 or over a part thereof. Current feeder 422 in this example extends parallel to end membrane 416 and over end section 414 to outside housing 402. In this example, end section 414 is provided with conductor 440 which extends over at least a part of the circumference of housing 402. In this example, conductor 440 is copper ring 440 that extends in groove 442 in end section 414 along the entire circumference of housing 402. Part of copper ring 440 extends above the surface of end section 414 and is in direct electrical contact with current feeder 422. Capacitive layer 420 extends in second direction y directly adjacent to and in contact with current feeder 422 and, on an opposite side, with gel layer 430. In the example of
In an example the method 1000 for manufacturing a capacitive electrode according to the invention comprises the steps of providing 1002 providing an electrode housing having a number of housing walls that enclose a housing space and an opening that is operatively connected to the housing space. In a subsequent step, the method comprises the step of providing 1004 a current feeder to the electrode housing, wherein the current feeder comprises a connector that extends at least partially outside the electrode housing and providing 1006 a capacitive layer to the electrode housing and applying 1008 a gel layer near or in the opening, such that the gel layer is in contact with the capacitive layer and seals the opening.
An embodiment of the capacitive electrode according to the invention was tested in a lab-test using an in-house designed 10×10 cm2 lab cross-flow membrane assembly operated in capacitive reverse electrodialysis (CRED) mode with 30 cells (=cell pairs; N=30).
The membrane assembly comprised ion exchange membranes (cation exchange membranes and anion exchange membranes) stacked in a membrane stack, which was provided with side-plates and two end-plates, which were positioned at opposite ends of the membrane stack. The end plates were formed by the capacitive electrodes according to the invention. The electrode compartment comprised an activated carbon layer, a gel layer and a current feeder/collector. A platinum coated titanium mesh electrode was used as current feeder. It should be noted that for economic reasons the preferred current feeder may be constructed from mainly carbon/graphite based materials.
The low concentration feed solution had a salinity of 1.0 gram/liter NaCL (conductivity of ˜2.0 mS/cm at a temperature of approximately 23° C.) and the high concentration feed solution had a salinity of 32.6 gram/liter (conductivity of ˜49.6 mS/cm at a temperature of approximately 26° C.).
The measurements were conducted at an average temperature of approximately 25 degrees ° C. using a potentiostat. The feed solutions were made using NaCl and tap water.
The gel layer was made of using an agar-agar gel powder and an 3 M NaCl solution. The activated carbon layer was made by performing the steps of:
In order to prepare the slurry, activated carbon powder and water were mixed with a predetermined content ratio, which preferably is a content ratio between activated carbon powder and demi-water of 1:2 (w/w). For the first experiment, 50 grams of demi-water was added to 25 grams of activated carbon powder (see also
The gel layer was prepared using agar-agar powder (Boom B.V.), demi-water and NaCl (ESCO food grade, 99.8% purity). The ratio between agar-agar and demi-water is 1:50 (w/w). Thus, 2 grams of agar-agar power is boiled in 100 ml of a 3 M NaCl solution for 5-8 minutes during continuous stirring at 500 rpm. After removing air bubbles from the solution, the prepared gel was poured on top of the activated carbon layer and subsequently left to cool down.
The results from the experiments were captured in a CRED performance graph showing two power producing cycles with 25 g activated carbon (
The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023035 | Apr 2019 | NL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NL2020/050274 | 4/30/2020 | WO | 00 |
