Device for the separation of functional material

Abstract

Device for the deposition of functional material, comprising a galvanic tank (3) fillable with a liquid electrolyte (2) and at least one counter electrode (4) arranged in the galvanic tank (3), a substrate carrier (5) designed at least partially as a hollow body with an outer shell enclosing a cavity, wherein the outer shell has an inner side (5A) facing the cavity and an outer side (5B) facing away from the cavity, and a suction and / or extraction device (6) arranged in the cavity for extracting or sucking in the electrolyte (2), wherein, the outer shell is designed to be permeable to diffusion and the outer side (5B) can be coated with a substrate (7), the substrate carrier (5) in an operational state projects at least partially into the electroplating tank (3), the substrate carrier (5) is designed as a working electrode or the substrate carrier has an external working electrode arranged on the outside (5B), and a voltage can be applied between the counter electrode (4) and the working electrode, the removal and / or suction device (6) and the electroplating tank (3) are coupled to a pipe system (7), wherein the pipe system (7) is designed to ensure electrolyte transport between the removal and / or suction device (6) in the cavity of the substrate carrier (5) and the electroplating tank (3).

Description

The invention relates to a device for depositing functional material. More particularly, the invention relates to an apparatus for applying a functional material to a substrate. This method is intended to be used for the production of components of an electrochemical energy converter, such as a fuel cell, an electrolyser or a battery. It is intended that components such as electrolyte electrode assemblies or other media-permeable substrates, for example made of expanded metal, sintered material, perforated material, can be coated.Conventionally, for the production of such components in large quantities, a batch process or a process running partially continuously or continuously must be used. The coating process can be a substep of a plurality of process steps which are arranged in series and form a production chain. Due to the concatenation of these process steps, the slowest step specifies the maximum achievable process speed and can thereby limit the production speed. In the case of correspondingly flexible substrates which are to be coated, so-called roll-to-roll methods can generally be used. For the coating of less flexible substrates, a movable substrate carrier with a 2D or 3D geometry can be used, depending on the nature of the substrate.The description will be made clear below by way of example on the basis of the coating of a flexible substrate in a roll-to-roll installation. A substrate is unrolled from a roll and processed step by step in a production process to form an (intermediate) product, which is then guided on further rolls for processing and is then rolled up again for sale or further processing. In this case, the substrate to be coated is guided on a substrate carrier. The production process can include, among other things, functionalization, cleaning, drying and coating steps between the reeling-up side and the reeling-up side. In the coating step, the substrate is immersed in a liquid containing the functional material. During the contact between substrate and liquid, the coating takes place with the functional material which can be treated further downstream (e.g.Purification, chemical or physical changes). The coating of the substrate with functional material can take place in various ways and is influenced to varying extents by migration, diffusion or convection effects of the functional material in the liquid. The deposition can be of physical or chemical origin.In the present case, the term electrolyte refers to any liquid that is a functional material in the form of particles, precursors, electrostatically charged or in ionic form. By the deposition of functional material is meant the electrodeposition of ions, the electrophoresis of electrostatically charged particles and / or the deposition of materials from a liquid onto a substrate.In the example of functional material that is catalytically active, catalyst deposition conventionally occurs directly on substrate during the process flow, using a roll-to-roll process. The substrate is immersed in an electrolyte which contains catalyst ions, for example in the form of catalyst salts, which are converted to metallic catalysts by supplying current. The process step speed is critically dependent on the transport of the catalyst ions which have to be transported from the volume of the electrolyte to the deposition centers on the substrate surface. During catalyst deposition, the catalyst ions from the near surface electrolyte are reduced to the substrate by the supply of electrons to the substrate, thus forming metallic material which is the catalyst material. This deposition step reduces the concentration of catalyst ions in the electrolyte close to the surface. The refilling of the now ion-depleted areas with catalyst ions (regeneration of the electrolyte) takes a certain time, which is considered to be the regeneration time. Due to this sequence, only a slow deposition or a pulse-like deposition via current pulses (e.g. on / off) can be established. Depending on the location of the catalyst ions in the electrolyte, convection due to electrolyte movement, diffusion due to concentration differences or migration due to the applied electric field, are dominant as the driving force of the ion movement. In particular, convection can have a process-speed-inhibiting effect, since long transport paths have to be covered in the electrolyte. This stepwise ion transport continues until the concentration in the entire electrolyte is balanced and determines the regeneration time and thus the coating time of the electrochemical deposition (catalyst coating).Usually, the concentration gradient of the ions is tried to be kept low by means of mechanical stirring, for example by magnetic stirring with stirring fish, and thus to accelerate the ion transport process, whereby the regeneration time in the electrolyte can be shortened. However, this method is made more difficult by the roll-to-roll plant geometry and size, since, for example, drumbs can form when stirring vigorously. Due to the remaining regeneration time, an electrochemical catalyst deposition production process may only achieve slow process speeds that impede the process of scaling up and make it less competitive with other approaches, e.g., chemical catalyst deposition via catalyst powder.In order to avoid slow clock rates in roll-to-roll installations, the substrate is repeatedly immersed in an electrolyte and then ejected again, for example, via a plurality of rolls. Thus, the substrate surface area in contact with fresh electrolyte is increased and, consequently, the process speed is increased. The decisive disadvantage in this case is the high investment costs for such electrochemical superstructures, the increased space requirement and high operating costs. Furthermore, the use of large electroplating plants (multiple or long electroplating tanks) requires a high electrolyte volume, which additionally increases the running costs as a result of the metal-containing electrolytes. Large amounts of electrolytes must be conditioned and monitored. Mechanical stirring is generally not effective and complicated because of dead volumes that form and limited diffusion. This results in greater susceptibility to errors due to deviations from the ideal operating conditions, higher wear of a large number of components and a poorer quality of deposited catalyst layers.In addition, the complicated process management in catalyst deposition over large areas and the possible uneven deposition of catalyst material may necessitate the use of auxiliary electrodes. In general, despite the great effort, only a limited process speed and layer quality can be achieved in this way, which represents the complete process as being less attractive for the large-scale industrial production of components for electrochemical energy converters.EP 0 140 474 A1 describes a counter current device for a plating apparatus comprising a rotating drum substantially half immersed in a plating solution in a plating bath around which a metal strip to be plated runs in synchronism with the rotation of the rotating drum, and anodes spaced by radial distances from the strip to cause an electric current to flow between the strip and the anodes.EP 0 240 671 A1 describes an anodic roll electroplating method using an anodic roll device and providing flexible operating parameters. The anodic roll device consists of a perforated valve metal cylinder, for example in the form of a mesh. The cylinder has an electrocatalytic coating and an electrolyte-containing porous coating.DE 199 32 524 C1 describes a method for electrochemical treatment, in particular for electrochemically coating conductive or rendered conductive parts, in a container filled with electrolyte solution, in which two electrodes are arranged, which are applied to a direct voltage source, wherein the parts are permanently coated in the electrolyte solution in a rotating basket during the treatment, wherein the parts are connected cathodically via a hub of the basket and that the electrolyte solution is pumped around in the circuit through the container, wherein the container remains sealed in a gas-tight manner.The prior art devices for metal deposition do not yet allow a possibility for a more rapid regeneration of the electrolyte to be provided, which can be integrated particularly easily into conventional roll-to-roll installations. The same applies to plants in batch or partially continuous operation.On the basis thereof, it is the object of the invention to provide a device for coating with functional material which enables efficient regeneration of the electrolyte and thus the process speed can be increased and the investment and operating costs can be reduced.This object is achieved by the subject matter of claim 1. Preferred refinements are found in the dependent claims.According to the invention, a device for depositing functional material is thus provided, comprising a electroplating trough fillable with a liquid electrolyte and at least one electrode arranged in the electroplating trough, a substrate carrier configured at least partially as a hollow body with an outer shell enclosing a cavity, wherein the outer shell has an inner side facing the cavity and an outer side facing away from the cavity, and a suction and / or suction device arranged in the cavity for suction or suction of the electrolyte, wherein the substrate carrier is mounted rotatably about its longitudinal axis, the outer shell is configured so as to be open to diffusion and the outer side can be loaded with a substrate, the substrate carrier in an operational state protrudes at least partially into the electroplating trough, the substrate carrier is configured as a counter electrode or the substrate carrier has an external counter electrode arranged on the outer side, and a voltage can be applied between the electrode and the counter electrode, the draw-off and / or suction device and the electroplating trough are coupled to a pipe system, wherein the pipe system is configured to ensure an electrolyte transport between the draw-off and / or suction device in the cavity of the substrate carrier and the electroplating trough.In the present case, the term "electroplating trough" is intended to mean any structure suitable for electroplating, which has a volume into which an electrolyte can be introduced. This can also be, for example, a electroplating basin.A "substrate carrier" is understood in particular as a 3-dimensional hollow body which enables either a 2-dimensional substrate contacting or a 3-dimensional substrate contacting. The substrate carrier can preferably be configured to be movable, for example by means of a robot arm, and can be used for batch and / or (partially) continuous methods with a 2D or 3D geometry.By "open to diffusion" is meant a medium-permeable material.If the present reference is made to a pipe system, this means any embodiment of media-conducting structures and structures, for example pipe, hose, nozzle, valve, permeable material, flow guide or channel.The arrangement of the counter electrode and working electrode is selected in particular such that the counter electrode functions as a positive pole or anode, from which metal ions dissolved in the electrolyte transfer to the working electrode. The working electrode accordingly functions as a negative pole or cathode, so that a current flow arises overall between the anode and cathode. The metal ions dissolved in the electrolyte are deposited by electrochemical reduction on the substrate, which is electrically connected to the working electrode or cathode. If the metal ions are catalyst ions, catalytically active material is applied to the substrate by reducing the ions, so that the substrate is electroplated with a catalyst layer. During the deposition, positive and negative poles can also be reversed, possibly briefly, or pulses can be used during the deposition, whereby further degrees of freedom are established in the deposition.If electrodes are required for the deposition, the reference is made to working and counter electrodes. In particular, auxiliary electrodes or reference electrodes can be used for better process control. The working electrode and counter electrode can be attached in particular inside or outside the liquid. The substrate can, for example, itself conduct the electrical current into the liquid, wherein the contacting to the working electrode can take place outside the liquid. Deposition, e.g. by electrophoresis, may be achieved by generating an electromagnetic field, wherein one or both of the electrodes may be located outside or within the liquid.It is necessary that the substrate be in contact with the electrolyte so that the metal ions can transfer to the substrate. For this purpose, it is provided in the present case that the substrate carrier is arranged in such a way that it protrudes at least partially into the electroplating trough, that is to say in other words is partially immersed in the electrolyte in the case of a electroplating trough filled with the electrolyte.If the term external working electrode is used here, this preferably means electrical contacting which abuts the outer surface. The working electrode is electrically connected to the outer surface on which the substrate is placed, so that the working electrode is also electrically connected to the substrate and transfers the metal ions toward the substrate.A "suction and / or extraction device" is understood in the present case to mean a device which can extract and / or extract the electrolyte in particular on the basis of a pressure difference. This refers to the direction of flow of the electrolyte. If the electrolyte is suctioned off, it is suctioned out of the electroplating trough through the substrate and through the diffusion-open outer casing of the substrate carrier into the cavity of the substrate carrier and from there is returned from the electroplating trough. However, if the electrolyte is sucked in, it is sucked out of the electroplating trough, fed to the cavity, discharged through the diffusion-open outer casing and through the substrate back to the electroplating trough. The suction and / or extraction device is accordingly configured to transport the electrolyte in only one of the two or in both flow directions. During operation of the coating device, it is preferably possible to choose between one or both flow directions and / or to switch them back and forth between them and / or to temporarily expose the electrolyte flow.It is thus a decisive point of the invention that by the continuous or intermittent removal of the electrolyte through the substrate and the substrate carrier immediately after and / or during the deposition of functional material or catalyst material on the substrate surface, the depleted electrolyte is replaced by electrolyte from the volume with the initial concentration. This has the consequence that the deposition can be continued directly after the preceding deposition pulse and a new deposition pulse can be applied to the substrate directly after completion of the preceding deposition pulse. The regeneration time can thus be reduced to eliminated and help provide continuous deposition which is the fastest possible deposition method. Furthermore, this procedure allows the depth of penetration of the catalyst material into the substrate to be controlled and a concentration profile of the functional material to be adjusted over the depth of the substrate layer.Likewise, by-products which can impede homogeneous deposition can thus easily be removed (for example gas bubbles which remain on the substrate surface). Furthermore, by means of the pulsed removal or the selection of the electrolyte flow rate, an accurate control of the regeneration process in the depleted layer is possible, whereby the deposition result itself can be positively influenced.According to a preferred development of the invention, the substrate carrier comprises a hollow cylindrical roller. Further preferably, the substrate carrier is mounted rotatably about its longitudinal axis. The longitudinal direction of the substrate carrier then also refers to the length of the cylindrical shape. The substrate can be arranged on the outer side of the lateral surface. The rotation of the substrate carrier then takes place about the longitudinal axis of the cylinder. This has the advantage that the substrate can be rolled onto the substrate carrier along a wide surface and the surface of the substrate carrier can thus be used efficiently with one revolution.According to a preferred development of the invention, the outer casing has a multiplicity of openings which can be configured in particular in the form of slots or as holes. In the present case, a slot-shaped opening is understood to mean an elongate narrow opening through which the electrolyte can diffuse. The slots can preferably have a length of a few centimeters. Holes may have different sizes and distances from each other. In addition, the substrate carrier can consist of a material which is diffusion-open per se (for example sintered material, expanded metal, perforated material, nonwoven).According to a preferred development of the invention, the substrate carrier is arranged on a movement device. The substrate carrier can be moved via the movement device. In particular, the movement device comprises a robot arm, a rod or a cable.According to a preferred development of the invention, the electroplating trough has a base plate on which at least one inlet is arranged, for example via a pipe system. In this way, it is made possible for the electrolyte to be supplied from below, i.e. from the bottom or at another point, to the electroplating trough or to be sucked in from below, so that the electrolyte flow takes place through the entire volume of the electroplating trough and no dead volumes are produced.In principle, it is possible to ensure the electrolyte movement through the volume of the electroplating trough by a freely arising differential pressure. The electrolyte movement then arises, for example, on the basis of a geodetic height difference, on the basis of thermal forces or on the basis of the rotation of the substrate carrier. It is preferably provided that the suction and / or suction device comprises a plurality of suction nozzles arranged on the inner side of the outer casing, which are coupled to a suction device, such as a pump. The suction device thus actively draws or presses the electrolyte.According to a preferred development of the invention, it is provided that the suction direction can be varied. During operation of the coating device, it is preferably possible to choose between one or both flow directions and / or to switch them back and forth between them and / or to temporarily expose the electrolyte flow. Preferably, it is provided that the suction power is also variable and adjustable. The change in the suction direction and / or suction power makes it possible to adapt the flow profile, which can preferably be set as turbulent, laminar or as a mixture of the two variants, in order to be able to achieve the respectively desired mixing during the electrolyte regeneration and the deposition. The temporary change in direction of the electrolyte transport can also have the effect that products of possible secondary reactions, such as, for example, hydrogen evolution, which prevent or reduce homogeneous and efficient catalyst deposition, can be discharged.Preferably, the length of the suction and / or suction device corresponds to the length of the outer surface to which the substrate can be applied. In this way, the suction and / or extraction device extends over the entire length of the substrate, so that the electrolyte can be sucked uniformly through the substrate and a homogeneous flow profile is thus produced in the electroplating trough.According to a preferred development of the invention, the external working electrode comprises a chain having a plurality of links in the manner of an armour chain. The tank chain is understood to mean a chain whose links are each twisted by 90 degrees, so that the chain can lie flat. The chain can therefore be arranged flat on the outer surface of the substrate carrier, so that an electrical contact can be established between electrolyte, chain and substrate and the transport of the electrolyte can take place through a larger surface of the substrate. The contact area between electrolyte and substrate is thus increased, which has the result that the deposition process can be accelerated and homogenized by the 2D or 3D geometry.According to a preferred development of the invention, the substrate carrier is designed to be inert. The inert property of a material is characterized by a very limited readiness to undergo chemical reactions. In this way, it is ensured that no deposition of functional material takes place on the substrate carrier itself. Thus, the loss of functional material is prevented, so that only a deposition onto the substrate at the desired location is made possible. This ensures the most efficient possible deposition.According to the invention, the use of the above-described device for depositing functional material for the production of electrolyte electrode arrangements for electrochemical energy converters in a continuous or partially continuous process or batch process, such as the roll-to-roll process, is furthermore provided.The invention is explained in more detail below on the basis of a preferred exemplary embodiment with reference to the drawings.In the drawings, FIG. 1 schematically shows a electroplating apparatus with an apparatus according to a preferred exemplary embodiment of the invention in a perspective view, FIG. 2 schematically shows a section of the electroplating apparatus from FIG. 1 in a cross-sectional view, FIG. 3 shows the cavity of the substrate carrier according to a preferred embodiment of the invention in a perspective view.FIG. 1 schematically shows a coating apparatus 1 which comprises a device for metal deposition. The apparatus includes a electroplating trough 3 and a roller-shaped substrate carrier 5 which is rotated about its longitudinal axis L. The electroplating trough can be filled with a liquid electrolyte 2, so that the substrate carrier 5 is immersed in the electrolyte 2 and the substrate 7 is guided through the electrolyte bath. The substrate 7 to be coated is located on the substrate carrier 5. electrodes 4 (counter electrodes) are also arranged on the periphery of the electroplating trough 3. The substrate carrier 5 as working electrode itself or an electrical contact coupled to the substrate carrier 5 is likewise connected to the substrate 7. In this way, a current flow can be produced between the counter electrode 4 in the electroplating trough 3 via the electrolyte 2 as far as the working electrode or the substrate 7 to be coated. The use of a reference electrode is also possible by positioning it close to the substrate in the electrolyte 2. Metal ions must be dissolved in the electrolyte 2 so that they can transfer to the substrate 7. If the metal ions are catalyst ions, a catalytically active material is applied to the substrate 7 by reduction. The reduction takes place in the electrolyte layer close to the surface on the substrate 7, so that there is low metal ion. Therefore, imbalance of the metal ion concentration occurs in the electrolyte 2. In order to compensate for this imbalance again and to make it possible for further metal ions to flow in or to regenerate the electrolyte 2, the electrolyte 2 is transported away at the surface by the removal and / or suction device 6 and is fed back in a deeper region of the electroplating trough 3, so that a circuit is formed. The suction and / or suction device 6 is shown in FIG. 2.FIG. 2 shows a cross section through the electroplating trough 3 along the longitudinal axis and the substrate carrier 5. The electrolyte 2 can be pumped on the one hand from the electroplating trough 2, through the substrate 7 and through the substrate carrier 5 to the extraction and / or suction device 6, and can then be fed again to the electroplating trough via a pipe system 7 via two inlets 10 at the bottom of the electroplating trough 3. On the other hand, the electrolyte 2 can likewise be sucked from the electroplating trough 3 via the inlets 10 to the suction and / or extraction device 6, in order then to be pumped through the substrate carrier 5 and through the substrate 7 back into the electroplating trough 3 into the region close to the surface. In order that the electrolyte 2 can diffuse through the substrate support 5, it has a plurality of slot-shaped openings 8. Both directional options allow continuous electrolyte transport in a circuit, so that the metal ion concentration can be homogenized and the metal deposition on the substrate 7 can take place as effectively as possible and no delay due to high regeneration times arises.FIG. 3 shows the intermediate space between substrate carrier 5 and electroplating trough 3 in a more detailed illustration. The electroplating trough 3 comprises an inlet or outlet 10. The required differential pressure is realized, for example, by a pump, not shown here. The suction direction and the suction power can be varied and also controlled during operation, so that the flow profile of the electrolyte 2 can be changed at any time and adapted to specific conditions.List of reference characters1 Coating apparatus 2 electrolyte 3 electroplating trough 4 counterelectrode 5 substrate carrier / working electrode 5A inner side 5B outer side 6 suction and / or extraction device 7 substrate 8 openings 9 base plate 10 inlet / outlet L longitudinal axis

Claims

Device for depositing functional material, comprising a electroplating trough (3) fillable with a liquid electrolyte (2) and at least one counter electrode (4) arranged in the electroplating trough (3), a substrate carrier (5) at least partially designed as a hollow body with an outer casing enclosing a cavity, wherein the outer casing comprises an inner side (5A) facing the cavity and an outer side (5B) facing away from the cavity, and a suction and / or extraction device (6) arranged in the cavity for suction or extraction of the electrolyte (2), wherein, if the outer casing is designed open to diffusion and the outer side (5B) can be acted on by a substrate (7), the substrate carrier (5) projects at least partially into the electroplating trough (3) in an operational state, the substrate carrier (5) is designed as a working electrode or the substrate carrier has an external working electrode arranged on the outer side (5B), and a voltage can be applied between the counter electrode (4) and the working electrode, the draw-off and / or suction device (6) and the electroplating trough (3) are coupled to a pipe system (7), wherein the pipe system (7) is designed to ensure an electrolyte transport between the draw-off and / or suction device (6) in the cavity of the substrate carrier (5) and the electroplating trough (3).The device according to claim 1, wherein the substrate carrier (5) comprises a hollow cylindrical roller.Device according to claim 1 or 2, wherein the substrate carrier (5) is rotatable about its longitudinal axis (L).The device according to any one of the preceding claims, wherein the outer shell comprises a plurality of openings (8).Device according to one of the preceding claims, wherein the substrate carrier (5) is arranged on a movement device.Device according to one of the preceding claims, wherein the electroplating trough (2) has a base plate (9) and the pipe system (7) is connected to at least one inlet (10) arranged on the base plate (9).Device according to one of the preceding claims, wherein the suction and / or extraction device (6) is designed to change the direction of the electrolyte transport.Device according to one of the preceding claims, wherein the external working electrode comprises a string having a plurality of links in the manner of an armour string.Device according to one of the preceding claims, wherein the substrate carrier (5) is designed to be inert.Use of the device according to one of claims 1 to 9 for depositing functional material for the production of electrolyte electrode arrangements for electrochemical energy converters in a continuous or partially continuous process or batch process.

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