阅读说明：本技术 用于电化学模块的功能化的多孔的气体传导零件 (Functionalized porous gas conducting part for electrochemical modules ) 是由 克里斯汀·比纳特 沃尔夫冈·沙夫鲍尔 马蒂亚斯·鲁汀格 于 2018-02-22 设计创作，主要内容包括：本发明涉及一种用于电化学模块(20)的多孔或者至少分段多孔的气体传导零件(10,10‘)。所述电化学模块(20)具有：至少一个电化学电池单元(21),其具有带有至少一个电化学活性层的层结构(23)、和金属的气密性外壳(24；25),所述气密性外壳与所述电化学电池单元(21)形成气密性工艺气体空间(26)。所述外壳(24；25)在至少一侧上延伸超过所述电化学电池单元(21)的区域,并形成开放到所述电化学电池单元的工艺气体传导空间(27；27’),并在所述工艺气体传导空间(27；27’)的区域中具有至少一个气体通道开口(28；28’),以用于供给和/或除去所述工艺气体。此处所述的气体传导零件(10,10‘)适于排列在工艺气体传导空间(27；27‘)内,并且它的表面被功能化以与所述工艺气体相互作用。(The invention relates to a porous or at least sectionally porous gas-conducting part (10, 10') for an electrochemical module (20). The electrochemical module (20) has: at least one electrochemical cell (21) having a layer structure (23) with at least one electrochemically active layer and a gas-tight housing (24; 25) of metal, which forms a gas-tight process gas space (26) with the electrochemical cell (21). The housing (24; 25) extends on at least one side beyond the area of the electrochemical cell (21) and forms a process gas conducting space (27; 27 ') which opens out into the electrochemical cell and has at least one gas passage opening (28; 28 ') in the area of the process gas conducting space (27; 27 ') for supplying and/or removing the process gas. The gas-conducting part (10, 10 ') described herein is adapted to be arranged in a process gas conducting space (27; 27') and its surface is functionalized to interact with said process gas.)

1. A porous gas-conducting part (10, 10 ') or an at least sectionally porous gas-conducting part (10, 10') for an electrochemical module (20), wherein the electrochemical module (20) has:

at least one electrochemical cell (21), the electrochemical cell (21) having a layer structure (23) with at least one electrochemically active layer, and a gas-tight housing (24; 25) of metal, the gas-tight housing (24; 25) forming a gas-tight process gas space (26) with the electrochemical cell (21),

wherein the housing (24; 25) extends beyond the area of the electrochemical cell (21) on at least one side and forms a process gas conducting space (27; 27 ') which is open to the electrochemical cell and has at least one gas passage opening (28; 28 ') in the area of the process gas conducting space (27; 27 ') for supplying and/or removing process gas,

characterized in that the gas-conducting part (10, 10 ') is adapted to be arranged in the process gas conducting space (27; 27') and that the surface of the gas-conducting part is functionalized to interact with the process gas.

2. The gas-conducting part according to claim 1, characterized in that the gas-conducting part (10, 10') is designed as a separate component from the electrochemical cell (21).

3. The gas conducting part according to claim 1 or 2, characterized in that the gas conducting part (10, 10') is adapted to support the housing on both sides along the stacking direction of the electrochemical modules.

4. A porous gas-conducting part (10 ", 10" ') or an at least sectionally porous gas-conducting part (10 ", 10"') for an electrochemical module (20 '), wherein the electrochemical module (20') has:

at least one electrochemical cell (21), the electrochemical cell (21) having: a layer structure (23) with at least one electrochemically active layer, and a gas-tight housing of metal, which forms a gas-tight process gas space (26) with the electrochemical cell,

wherein the housing extends on at least one side beyond the area of the electrochemical cell (21) and forms a process gas conducting space (27; 27 ') which is open to the electrochemical cell and has at least one gas channel opening (28; 28') in the area of the process gas conducting space for supplying and/or removing process gas,

characterized in that the gas-conducting part (10 ') is designed as a housing part of the process gas conducting space (27; 27'), and that the surface of the gas-conducting part facing the process gas conducting interior is functionalized for interacting with the process gas.

5. Gas-conducting part according to claim 4, characterized in that the gas-conducting part (10 ", 10"') is formed integrally with a metallic support substrate (22) of the electrochemical cell (21).

6. The gas conducting part according to any one of the preceding claims, characterized in that the gas conducting part (10, 10 '; 10 ", 10"') is functionalized for catalytic reforming of a reactant gas.

7. Gas-conducting part according to claim 6, characterized in that the functionalization for catalytic reforming is done by introducing nickel, platinum and/or palladium and/or oxides of these metals.

8. Gas conducting part according to any one of claims 1-5, characterized in that the gas conducting part (10, 10 '; 10 ", 10"') is functionalized for purifying the reactant gas, more particularly for purifying its sulphur, chlorine, oxygen and/or carbon.

9. The gas-conducting part according to claim 8, characterized in that the functionalization of sulphur and/or chlorine for purifying the reactant gases is done by introducing nickel, cobalt, chromium and/or cerium.

10. The gas-conducting part according to claim 8, characterized in that the functionalization of oxygen for purifying the reactant gas is done by introducing chromium, copper and/or titanium.

11. The gas-conducting part according to claim 8, characterized in that the functionalization of carbon (soot) for purifying the reactant gas is done by introducing titanium.

12. Gas conducting part according to any one of claims 1-5, characterized in that the gas conducting part (10, 10 '; 10 ", 10"') is functionalized for purifying the product gas, more particularly for purifying its chromium and/or oxygen.

13. Gas conducting part according to claim 12, characterized in that the functionalization of chromium for purifying the product gas is done by introducing oxide ceramics, more particularly by Cu-Ni-Mn spinel.

14. The gas conducting part according to claim 12, characterized in that the functionalization for purifying oxygen is done by introducing Ti and/or Cu or a spinel compound in an under stoichiometric ratio.

15. Gas-conducting part according to any one of claims 7, 9, 10, 11, 13 or 14, characterized in that the introduction is done by alloying or by a coating procedure, more particularly by means of vapour deposition, dip coating or a method of applying a suspension or paste.

16. Gas-conducting part according to any one of the preceding claims, characterized in that the base material for the gas-conducting part (10, 10 '; 10 ", 10"') is a ferritic alloy produced by powder metallurgy and based on iron and/or chromium.

17. Gas conducting part according to any of the preceding claims, characterized in that the gas conducting part (10, 10 '; 10 ", 10"') has at least one gas guiding structure (12).

18. An electrochemical module (20; 20') having:

an essentially plate-shaped electrochemical cell (21), the cell (21) having a layer structure (23) with at least one electrochemically active layer, and a gas-tight housing (24; 25) of metal, which forms a gas-tight process gas space (26) with the electrochemical cell (21), wherein the housing (24; 25) extends over the area of the electrochemical cell (21) on at least one side, and the housing (24; 25) forms a process gas conducting space (27; 27 ') which opens into the electrochemical cell, and has at least one gas passage opening (28; 28 ') in the area of the process gas conducting space (27; 27 ') for supplying and/or removing the process gas,

characterized in that in the process gas conducting space (27; 27 ') in the region of the gas channel openings, at least one gas conducting part (10, 10') according to claim 1 or any one of claims 2, 3 and 6 to 17 as dependent on claim 1 is arranged, which gas conducting part (10, 10 ') serves to support the housing in the stacking direction (B) of the electrochemical modules (20; 20'),

and/or the housing of the process gas conducting space is formed at least in sections by at least one gas conducting part (10 ", 10"') according to claim 4 or any of claims 5-17 as dependent on claim 4.

19. Electrochemical module according to claim 18, characterized in that the housing (24; 25) extends over the area of the electrochemical cell (21) on at least two sides, forming a first process gas conducting space (27) and a second process gas conducting space (27 '), the first process gas conducting space (27) having at least one gas inlet opening (28) for a reactant gas, at least one first gas conducting part (10; 10 ") being assigned to the first process gas conducting space (27), the second process gas conducting space (27') having at least one gas outlet opening (28 ') for a product gas, at least one second gas conducting part (10'; 10" ') being assigned to the second process gas conducting space (27'), wherein the functionalization of the first gas conducting part (10; 10 ") assigned to the first process gas conducting space is different from the functionalization of the second gas conducting part assigned to the second process gas conducting space Functionalization of a second gas-conducting part (10 '; 10') of the process gas-conducting space.

20. The electrochemical module according to claim 19, characterized in that the first gas-conducting part (10; 10 ") is functionalized for treating the reactant gas and/or the second gas-conducting part (10 '; 10"') is functionalized for post-treating the product gas.

Technical Field

The present invention relates to a functionalized porous gas-conducting part for arrangement in an electrochemical module according to claim 1 and claim 4 and to an electrochemical module according to claim 18.

Background

The porous gas-conducting parts of the invention are used in electrochemical modules which can be used as high temperature fuel cells or Solid Oxide Fuel Cells (SOFC), solid oxide electrolysis cells (SOEC; solid oxide electrolyser cells) and as reversible solid oxide fuel cells (R-SOFC) and the like. In a basic configuration, the electrochemically active cells of the electrochemical module comprise a gas-tight solid-state electrolyte arranged between a gas-permeable anode and a gas-permeable cathode. The electrochemically active components (here, for example, the anode, the electrolyte and the cathode) are often designed as comparatively thin layers. The resulting required mechanical support function can be provided by one of the electrochemically active layers, for example by the electrolyte, the anode or the cathode, for example each of which is designed with a corresponding thickness in that case (in which case the system is referred to as an electrolyte-supported, anode-supported or cathode-supported cell, respectively), or by a component designed separately from these functional layers, such as a ceramic or metal support substrate, for example. In the case of the latter solution, a separately designed metal support substrate is used, the system being referred to as a metal substrate supported battery (MSC; metal supported battery). Depending on the MSC, the electrolyte (whose resistance decreases with decreasing thickness and increasing temperature) may be given a relatively thin design (e.g., 2 to 10 μm thickness), and the MSC may operate at relatively low operating temperatures of about 600 ℃ to 800 ℃ (while, for example, electrolyte-supported cells operate at operating temperatures of up to 1000 ℃ in some cases). Due to their particular advantages, MSCs are particularly suitable for mobile applications, such as for example power supplies for passenger cars or commercial vehicles (APU-auxiliary power unit).

The electrochemically active cells are typically designed as flat individual elements arranged on top of each other, connected with corresponding (metal) housing parts (e.g. interconnectors, frame panels, gas lines, etc.) to form a stack, and electrically contacted in series. The respective housing parts in the individual cells of the stack bring about the supply of the process gases separately from one another in each case (in the case of a fuel cell, the supply of a fuel, for example hydrogen, or a hydrocarbon-containing fuel, for example natural gas or biogas, to the anode and an oxidant (oxygen, air) to the cathode) and the removal of the gases formed in the electrochemical reaction on the anode side and on the cathode side. Based on a single electrochemical cell, process gas spaces are formed on either side of the electrolyte in the stack, and in order to functionalize the stack it is essential that these spaces have a reliable gas-tight isolation from each other. The stack may be embodied as a closed structure or as an open structure as exemplarily described in EP1278259B1, in which case only one process gas space is sealed in a gas-tight manner, for example an anode-side process gas space in the case of a fuel cell, in which fuel is supplied and/or reaction products are withdrawn, while an oxidant, for example, flows freely through the stack.

In particular in the case of operation of the electrochemical module as a fuel cell using a hydrocarbon-containing fuel, for example natural gas, there are several challenges in use: the fuel cells are very sensitive to sulfur or chlorine impurities of the fuel, for example, which are significantly detrimental to efficiency and life, and for which corresponding precautions have to be taken. Furthermore, hydrogen must be produced from the hydrocarbon-containing fuel for the electrochemical reaction. One method established industrially for this is steam reforming, in which hydrogen is released in an endothermic reaction, usually in a plant which is spatially isolated upstream of the stack. In addition to this external reforming, there is also known the so-called internal reforming, in which hydrogen generation and the electrochemical reaction take place together at the anode, and for that purpose a reforming catalyst is placed directly at the anode, or in the case of MSC, directly on the supporting substrate of the electrochemically active metal, in which the electrochemical reaction of the fuel cell takes place. An example of this is described in US2012/0121999a1, wherein the electrochemically active regions of the support substrate are functionalized with a reforming catalyst. One advantage of linking these two reactions is direct heat transfer, since the electrochemical reaction is an exothermic reaction and the reforming is endothermic. However, disadvantageously, the active area of the cell, particularly at the anode, may be subject to carbon deposition or coking, among other possibilities, which may adversely affect the electrochemical function of the cell.

It is important for the high efficiency of the electrochemical module to supply the process gases uniformly to the electrochemically active layer, i.e. on the one hand to supply the reactant gases uniformly and to remove the formed reactant gases uniformly, respectively. The pressure drop is as small as possible. Within the electrochemical module, the supply is performed in a horizontal direction by means of a distribution structure, which is usually integrated into the interconnector. The interconnector, which also has the function of electrically contacting adjacent electrochemical cells, has gas-conducting structures on both sides for this purpose, and these structures may have, for example, a handle-shaped, rib-shaped or wave-shaped design. For many applications, the interconnectors are formed by suitably shaped sheet metal parts, similar to the other components of the stack, in which they may be extremely thin for weight optimization purposes. In the case of stack manufacture or operation, in particular in the case of mechanical stresses of this type occurring at the edge regions, such a thin construction can easily lead to deformation situations and/or to cracks in the case of welds, thereby jeopardizing the necessary gas tightness.

Uniform supply of hydrogen is a challenge, especially in the case of internal reforming, as in US2012/0121999a1, since the formation of hydrogen depends on the incoming fuel gas flow and is in addition closely related to the temperature distribution of the fuel cell.

Disclosure of Invention

It is an object of the present invention to further develop an electrochemical module and to provide a gas-conducting part with which the performance of the electrochemical module and/or its lifetime is positively influenced.

This object is achieved by a gas-conducting part according to claim 1 and claim 4 and by an electrochemical module according to claim 18. Advantageous developments are described in the dependent claims.

The gas conducting parts of the invention are used in electrochemical modules which can be used as high temperature fuel cells or Solid Oxide Fuel Cells (SOFCs), as solid oxide electrolysis cells (SOECs; solid oxidant electrolyzer cells) and as reversible solid oxide fuel cells (R-SOFCs). The basic structure of an electrochemical module of this type is characterized by an electrochemical cell having a layer structure with at least one electrochemically active layer and may also comprise a support substrate. The electrochemically active layer is herein understood to mean an anode, an electrolyte or a cathode layer or the like, and the layer structure may optionally also have further layers (e.g. made of cerium gadolinium oxide between the electrolyte and the cathode). Not all of the electrochemically active layers need be present here; alternatively, the layer structure may also have only one electrochemically active layer (e.g. anode), preferably two electrochemically active layers (e.g. anode and electrolyte), and further layers, in particular those for completing an electrochemical cell, which may not be applied until subsequently. The electrochemical cell can be designed as an electrolyte-supported cell, an anode-supported cell or a cathode-supported cell (the layer giving the cell its name has a thicker construction and has the function of bearing mechanical loads). In the case of metal substrate supported cells (MSCs), in a preferred embodiment of the invention, the layer stack is arranged on a porous plate-type metal support substrate, the preferred thickness of which is typically 170 μm to 1.5mm, more particularly 250 μm to 800 μm, in the gas permeable central region. The support substrate in this case forms part of an electrochemical cell. The layers of the layer stack are applied in a known manner, preferably by PVD (PVD: physical vapor deposition), such as for example by sputtering, and/or by thermal coating methods such as for example flame spraying or plasma spraying, and/or by wet-chemical methods such as for example screen printing, wet powder coating, etc.; two or more of these methods may also be combined in order to achieve the overall layer structure of the electrochemical cell. Typically, the anode is an electrochemically active layer proximate to a supporting substrate, while the cathode is formed on the side of the electrolyte remote from the supporting substrate. Alternatively, however, an inverted arrangement of the two electrodes is also possible.

Not only the anode (formed, for example, from a composite material consisting of nickel and zirconium dioxide sufficiently stabilized with yttrium oxide in the case of MSC), but also the cathode (formed, for example, from a perovskite having mixed electrical conductivity, such as (La, Sr) (Co, Fe) O₃Formed) has a breathable design. Formed between the anode and the cathode is a gas-tight solid electrolyte comprising a solid ceramic material made of metal oxide (e.g., yttria-sufficiently stabilized zirconia) that is conductive to oxygen ions, but not to electrons. Optionally, the solid electrolyte is also proton conductive, and thisIt relates to a newer generation SOFC (e.g., a solid electrolyte of metal oxide, more specifically barium zirconium oxide, barium cerium oxide, lanthanum tungsten oxide, or lanthanum niobium oxide).

The electrochemical module additionally has at least one metal gas-tight housing that forms a gas-tight process gas space with the electrochemical cell. In the region of the electrochemical cell, the process gas space is delimited by a gas-tight electrolyte. On the opposite side, the process gas space is usually delimited by an interconnector, which for the purposes of the present invention is also considered to be a part of the housing. The interconnector is connected in a gas-tight manner to a gas-tight element of the electrochemical cell, optionally in combination with further housing parts, more particularly bounding frame panels or the like, which form the rest of the process gas space delimitation. In the case of MSCs, the gas-tight connection of the interconnectors is preferably done by means of soldering joints and/or soldering joints via further housing parts, examples being bounding frame panels, which in turn are connected to the support substrate in a gas-tight manner and thus form, together with the gas-tight electrolyte, a gas-tight process gas space. In the case of electrolyte-supported cells, the connection can be made by means of a sinter bond or by applying a sealant (e.g. glass solder).

"hermeticity" in connection with the present invention particularly means the rate of leakage for a sufficient amount of hermeticity based on a standard<10^-3hPa*dm³/cm²s (hPa: hectopa, dm)³: liter, cm²: square centimeter, s: seconds) (measured under air by a pressurized method using an Integra DDV instrument from dr. wiesner, rem saider, at a pressure difference dp of 100 hPa).

The housing extends beyond the area of the electrochemical cell on at least one side of the electrochemical cell and forms a process gas conducting space as a sub-space of a process gas space, which opens out into the electrochemical cell. The process gas space is therefore subdivided (theoretically) into two sub-regions, into an inner region directly beneath the layer structure of the electrochemical cell and into a process gas conducting space which surrounds the inner region.

In the process gas conducting space region, there is a gas passage opening made in the housing for the supply and/or removal of process gas. The gas passage opening can be integrated, for example, into an edge region of the interconnector and a housing part, for example, a bounding frame panel.

The supply of the electrochemical cells in the inner region of the process gas space is effected by means of a distribution structure, which is preferably integrated into the interconnector. The interconnector is preferably configured as a suitably shaped sheet metal part, for example having a handle-shaped, rib-shaped or wave-shaped design.

In operation of the electrochemical module as a SOFC, a fuel (e.g. hydrogen or a conventional hydrocarbon, such as methane, natural gas, biogas, etc., optionally having been previously completely or partially reformed) is supplied to the anode via the distribution structure of the gas passage openings and the interconnectors, and this fuel is catalytically oxidized there, giving off electrons. The electrons are conducted out of the fuel cell and towards the cathode via a current-consuming element. At the cathode, an oxidant (e.g., oxygen or air) is reduced by receiving electrons. The electrical circuit is closed by the flow of oxygen ions formed at the cathode to the anode via the electrolyte (in the case of an electrolyte that is conductive to oxygen ions), and reacts with the fuel at the respective interfaces.

In operation of the electrochemical module as a Solid Oxide Electrolysis Cell (SOEC), the redox reaction is driven using an electric current, for example converting water into hydrogen and oxygen. The structure of the SOEC basically corresponds to that of the SOFC described above, and has a role of switching the cathode and the anode. Reversible solid oxide fuel cells (R-SOFCs) can be operated as SOECs or as SOFCs.

According to the invention, a gas-conducting part is provided which is preferably produced by powder metallurgy and is therefore porous or at least sectionally porous if it is post-treated, for example by compression or local melting at the edges and/or on the surface. Such gas-conducting parts are arranged in the region of the process gas-conducting space. The porous structure of the gas-conducting part serves to increase the surface area which is able to interact with the process gas in the region of the process gas-conducting space. The surface of the gas-conducting part is at least sectionally functionalized, thereby providing a reactive or catalytically active surface for treating the process gas. By means of said functionalized surface, the gas can be treated on the reactant side and in particular can be purified and/or reformed, and the gas on the product side can be treated later, more particularly purified. The functionalization of the gas-conducting part is accomplished by incorporating into the material of the gas-conducting part, and/or applying as a surface coating such material for catalytic and/or reactive interaction with the process gas. The catalytic and/or reactive material can thus be mixed into the actual starting powder to produce a sintered gas-conducting part ("alloying addition") and/or can be applied by a coating procedure to the surface of the gas-conducting part which is in contact with the process gas after the sintering operation. Such coating procedures can be carried out by conventional methods known to the person skilled in the art, for example by means of different deposition methods from the vapour phase (physical vapour deposition, chemical vapour deposition), by dip coating, in which the component is impregnated or infiltrated with a melt or solution containing the respective functional material, or by means of methods of applying suspensions or pastes, in particular for the functionalization of ceramic materials. For surface enlargement it is advantageous if the porous surface structure remains during the coating procedure, i.e. the porous surface is not covered by the top layer, but mainly only the (inner) surface of the porous structure is coated. Functionalization by surface coating is particularly advantageous as a whole, since it entails the use of relatively less catalytic and/or reactive material than is necessary to mix it into the material for the gas-conducting part.

By arranging the functionalized gas-conducting parts in the region of the process gas-conducting space, the chemical reaction for treating the process gas takes place separately from the electrochemical reaction, which takes place directly on the electrochemical cell. This separation has important advantages: any deposits or degradation on the gas-conducting parts do not have any direct adverse effect on the reactions in the electrochemical cell. Furthermore, different functionalisations are possible for the gas supply zone and the gas removal zone and can be optimised independently for specific requirements.

In a preferred variant embodiment, the gas conducting part is configured as a separate component from the electrochemical cell and the housing. The gas conducting parts are in this case adapted to be arranged in the process gas conducting space; in other words, its shape is adapted to the interior of the process gas conducting space. Such a gas conducting part is preferably flat and has a flat body with one plane of main extent. In an advantageous variant, the gas-conducting part is configured as a support element in the vertical direction (in the stacking direction of the electrochemical modules). Its thickness is in this case selected according to the in-space height of the process gas conducting space, so that its upper housing part, which rests against the process gas conducting space, and its lower side bears against the lower housing part of the process gas conducting space, which means that a crushing of the housing edge region when an applied pressure is applied is prevented. Furthermore, in the case of a flat gas-conducting part, the flexural and torsional rigidity of the housing edge region is increased and the housing edge region is thus protected against deflection or other deformation. As a result, additional stresses on welds or other joining points, such as welded or sintered joining points between individual housing parts and/or electrochemical cells, which in practice often represent weak points in the gas-tight state, can be avoided in the edge regions of the module.

In operation of the electrochemical module, the respectively executed gas conducting parts are arranged in the process gas conducting space, advantageously completely in the process gas conducting space, i.e. directly underneath the layer structure of the electrochemical cell, completely outside the region.

Instead of separate components arranged inside the process gas conducting space, the functionalized gas conducting parts can in another embodiment be implemented as a boundary of the process gas conducting space and/or a section thereof (in other words as a part of the housing of the process gas conducting space). In which case the surface is functionalized by alloying or on the surface of the gas-conducting part facing the interior of the process gas-conducting space. In the case of an MSC, the gas-conducting part is preferably formed by an edge region of a metallic support substrate, which extends beyond the area of the electrochemical cell. The gas-conducting part is therefore formed by the edge-side part of the metallic support substrate, on which the electrochemically active layer is not present. The gas-conducting part is in this case produced in line with the support substrate, preferably monolithic, i.e. produced from a single sheet. The functionalization is preferably carried out here by means of elements or compounds which have not yet been included in the base material of the support substrate. In particular in case the support substrate contains Fe and/or Cr, further elements or further compounds are provided as functionalization. The gas-conducting part can thus fulfill its function as a housing in this region, the porous gas-conducting part of course having to be made gas-tight, which can sometimes be achieved, for example, by compression and/or local surface melting on the side facing away from the process gas conducting space. In a preferred variant, the gas-conducting part is implemented as an integral part of a supporting substrate, and the functionalization is not done by alloying, but instead by coating the surface, in particular by means of a vapour-deposition method, dip-coating or a method for applying a suspension or paste. Flexibility is achieved here, since the functionalization can be configured differently for different regions at a relatively favourable cost and can be optimized for specific requirements. For example, the functionalization of the edge region of the support substrate, through which the process gas is supplied via its gas passage openings, may be different from the functionalization of the edge region of the support substrate, through which the process gas is removed.

Apart from handling the process gas and the mechanical functions (mainly in the case of separately implemented gas-conducting parts), an important task of the gas-conducting parts is to improve the flow of the gas in the process gas-conducting space. To optimize the gas flow, there may be gas guide structures formed on the gas conducting part to convey the gas flowing through the gas passage openings into the interior region of the process gas space to the gas guide structures of the interconnector and to respectively guide the gas flowing out of the interior region of the process gas space to the gas passage openings, which are directed out. The gas guiding structure may here be designed differently depending on whether the gas conducting part fulfils the function of a gas distributor or a gas collector. The functionalization of the gas conducting part may be associated with a shape of the gas conducting structure; in other words, it can be intentionally made denser in those surface regions that have more intimate contact with the process gas.

The following text uses examples of separately implemented gas conducting parts for the optimization of the gas guiding structure that may be formed. Where appropriate, the individual aspects can of course be exchanged for gas-conducting parts which are implemented as parts of the housing and for which the functionalized surface facing the process gas-conducting space has corresponding gas-guiding structures. A continuous gas passage opening may be integrated into the gas conducting part and in the arrangement of the electrochemical modules the gas passage opening of the gas conducting part may be aligned with the gas passage opening of the process gas conducting space (housing), thereby creating a vertical continuous gas passage in the stack. The gas conducting part is gas permeable in at least one direction from the gas passage opening up to a plane facing the main extent of the side of the interior of the process gas space. For this purpose, the gas-conducting part may generally or at least in this direction have an open continuous porosity, and in this case in particular the inner surface through which the process gas flows is functionalized. In order to optimize the gas flow, the gas permeability (porosity) of the gas-conducting part can be varied spatially here (for example by porosity grading or by locally different densification of the gas-conducting part, in particular as a result of non-uniform compression), and/or for higher gas passage rates the gas-conducting part can alternatively or additionally have at least one channel or a plurality of channels along the main extent plane. The channel, the surface of which is advantageously functionalized, is preferably superficially formed and can be produced in the surface of the gas-conducting part (gas-conducting part embodied as housing part, or part embodied separately therefrom), for example by grinding, pressing or rolling with a corresponding structure. For the purposes of this specification, a gas-conducting part having closed-cell porosity and a shallow channel structure (which extends upwardly from the gas channel opening to the side) porous is also considered to be gas-permeable from the gas channel opening up to the side. It is also conceivable that the channels extend at least sectionally over the entire thickness of the gas-conducting part, and that the channels are therefore not formed only superficially. A high gas passage rate is advantageous in the case of this embodiment, but it must be ensured that the components remain one piece and do not separate. To prevent this, the channels extending through the thickness undergo a transition over their travel to a shallow channel structure or porous structure. The number and shape of the channels are optimized for flow performance and desired reaction.

The gas-conducting part according to the invention is produced by powder metallurgy, and the material for functionalization is added to the starting powder during the production of the sintered component itself, and/or the surface of the component which is at least sectionally covered with the material is produced only after the sintering operation. The starting material used for producing the gas-conducting part is preferably a metal-containing powder, more preferably a corrosion-stable alloy powder, for example a powder such as a material combination based on Cr (chromium) and/or Fe (iron), which means that Cr and Fe are at least 50% by weight in total, preferably at least 80% by weight in total, more preferably at least 90% by weight in total. The gas-conducting part consists in this case of a ferritic alloy. The gas-conducting part is preferably produced by powder metallurgy in a known manner by compressing a starting powder (optionally with addition of a functionalizing material), optionally with addition of an organic binder, and subsequent sintering.

In the case where the gas-conducting part is used as a separately formed component in an MSC, the gas-conducting part is preferably composed of the same material or substantially the same material as the support substrate of the MSC (i.e. only functionalised material has been added). This is advantageous because in this case the thermal expansion is the same and there is no temperature induced strain.

As mentioned above, the gas conducting parts of the invention can be used in electrochemical modules, in particular MSCs. In a preferred embodiment, the electrochemical module has gas-conducting parts, each of which is designed differently for the supply and removal of process gases. In this case, the gas-conducting parts may differ, for example, in the materials used, their shape, the porosity, the shape of the gas-guiding structure formed, for example the channel structure, etc. In particular, the functionalization may be different in the case of the gas-conducting parts for supplying and removing process gases and may be optimized for different tasks. While the gas-conducting part, which is used for supplying process gas (reactant gas), is suitable for the treatment of reactant gas, the gas-conducting part, which is used for removing process gas (product gas), is suitable for the post-treatment of product gas.

Particularly in the case of use in SOFCs, the gas conducting parts may be functionalized for catalytic reforming of the reactant gases. For catalytic reforming, the following materials are identified (in particular when using gas-conducting parts produced by powder metallurgy and made of alloys based on iron and/or chromium): nickel (Ni), platinum (Pt), palladium (Pd) and/or oxides of these metals such as NiO, for example. In the case of homogeneous alloying, the fractions of these metals and/or metal oxides should amount to at least 1 wt.%, preferably at least 2 wt.%. As a result of this functionalization, additional hydrogen gas is produced for the electrochemical reaction and the reactant gas flow rate is unchanged. For said preferred effect, these materials can be alloyed into the base material and/or applied by a coating method to the surface against and/or over which the process gas flows (for example by dip coating (suspension dip coating) or a deposition technique other than gas phase), in which case the alloying and gas phase deposition methods are preferred over the dip coating methods, due to the wetting effect, which is detrimental to the porous structure.

The gas conducting parts may be further functionalized for purifying impurities of the reactant gases, such as, for example, sulfur, chlorine, oxygen, and/or carbon. The impurities react with the introduced material, thus reducing the risk of potentially damaging the electrochemically active layers of the battery cell. The elements (gettering atoms) used to purify the reactant gases to remove sulfur and/or chlorine are as follows: ni, cobalt (Co), chromium (Cr), scandium (Sc) and/or cerium (Ce), and Ni is preferred due to its properties relating to catalytic reforming as described above, and Ce is also preferred. Preferred elements for purifying the product gas with respect to oxygen are Cr, copper (Cu) and/or titanium (Ti), and Ti is particularly advantageous due to its retention effect on carbon and thus its simultaneous effect of preventing soot formation. While these gettering atoms can generally be maintained only in residual amounts in the ppm range, they have a measurable positive effect on the performance and lifetime of the electrochemical module. Here too, the material is introduced into the base material by alloying, dip coating with a suspension or a vapour deposition method, and the vapour deposition method is preferred because of its flexibility.

Functional centers for the working up of the product gas can likewise be introduced. The product gas (effluent gas) can be purified by corresponding functionalized gas conducting parts, in particular impurities containing volatile Cr ions. The corresponding functionalization with respect to Cr impurities can be accomplished by oxide ceramics, such as, for example, structure AB₂O₄And B is the element manganese (Mn), and may be performed by a vapor deposition method, a dip coating method, or a method of applying a suspension and/or paste, or by conversion from a metal element.

To prevent back diffusion of oxygen from the outgoing gas line, the gas conducting part may be functionalized with an oxygen getter. These getters are intended to prevent anodic oxidation. Suitable oxygen absorbers are the following: ti, Cu or spinel compounds in an insufficient stoichiometric ratio, and preferably Ti and/or Cu are used. The two metals are preferably applied to the porous surface of the gas-conducting part by vapour deposition. The suppression of back diffusion may optionally be additionally supported by means of a suitable gas conducting structure.

In summary, especially for use in SOFCs, the gas conducting parts may be functionalized with Ni, Pt, Pd (and/or oxides of these metals), Co, Cr, Sc, cerium, Cu and/or Ti on the reactant gas side. Possible functionalisations of the gas-conducting part on the product side include Ti, Cu and/or oxide ceramics, in particular Cu-Ni-Mn spinel. Preferred combinations of functionalization of the gas conducting parts on the reactant gas side and product gas side include Ni or NiO on the reactant gas side and Ti on the product gas side, as well as Ni or NiO on the reactant gas side and Cu on the product gas side, and the like.

Drawings

Further advantages of the invention will become apparent from the following description of exemplary embodiments and with reference to the accompanying drawings, wherein the dimensional proportions are not always given in exact proportions for the purpose of illustrating the invention. In different figures, the same reference numerals are used for the same components.

In the drawings:

FIG. 1 a: a functionalized gas-conducting part of a first embodiment for an electrochemical module is shown in perspective view;

FIG. 1 b: the gas-conducting part of figure 1a is shown in plan view; and

FIG. 1 c: the gas-conducting part of figure 1a is shown in side view;

FIG. 2: the electrochemical module of the first embodiment is shown in exploded view with the gas-conducting parts according to fig. 1a-c, respectively, for the process gas conducting spaces for the supply or removal of process gas (it has to be noted here that the electrochemical module of fig. 2 is shown turned on its head for improved visibility of the channels, compared to the module of fig. 3);

FIG. 3: a stack is shown in cross-section with three electrochemical modules according to figure 2;

FIG. 4: an electrochemical module of a second embodiment is shown in exploded view, and

FIG. 5: a stack with three electrochemical modules according to figure 4 is shown in cross-section.

Detailed Description

Fig. 1a shows in perspective view a functionalized gas-conducting part (10) of a first embodiment, configured as a separate component and arranged within the process gas-conducting space in the electrochemical module, in particular a SOFC. One possible arrangement in the process gas conducting space is apparent from the following figures 2 and 3. Fig. 1b shows the gas-conducting part (10) in plan view and it is shown in fig. 1c in side view from the side (a), which in the arrangement of the electrochemical modules (20) faces the interior of the process gas space. The gas-conducting part (10) is produced by powder metallurgy from an Fe-based alloy having >50 wt% Fe and 15-35 wt% Cr. The powder with a particle size <150 μm, more particularly <100 μm, is selected such that the porosity of the porous gas-conducting part after the sintering operation is preferably 20-60%, more particularly 40-50%. The thinner the gas conducting part to be formed, the smaller the selected particle size. And preferably open porosity (i.e., the possibility of having gas exchange between individual adjacent pores). The thickness of the part is preferably 170 μm to 1.5mm, more particularly 250 μm to 800 μm. The flat gas-conducting part has a plurality of gas passage openings (11), which in the variant shown have three central gas passage openings (11), through which process gases are supplied and removed in the operation of the electrochemical module, respectively. The process gas flow is furthermore controlled by a gas guiding structure, in this exemplary embodiment by a star-shaped channel (12), which is superficially formed and extends from the gas channel opening up to the side (a). The channels, which initially branch off from the gas channel openings (11) in a direction away from the inner process gas space, are here redirected in an arc towards the side (a) in the direction of the inner process gas space. At the remaining side (13), remote from side (a), the gas-conducting part has been compressed in a gas-tight manner. In operation of the electrochemical module, the process gas flows from the gas channel openings (11) through the channels (12) and through the holes to the side (a) of the gas-conducting part, from where it flows into the inner process gas space, which is supplied extremely uniformly through the plurality of channels. When the gas conducting part is used to remove process gas, the gas flows in the opposite direction.

For the functionalization, the surface of the gas-conducting component on the side with the channels is coated with a functional layer (14) having a thickness of <1 μm in a PVD unit. In this operation, care is taken to ensure that the porous surface structure of the gas-conducting part is preserved during the coating process, i.e. the open porous surface is not covered by the top coat, so that there is a continuous functionalized surface area which is larger than a smooth surface. Care is also taken to ensure that in particular the process gas flows over the channel surfaces and that they are therefore in fairly close contact with the process gas, being sufficiently coated.

A plurality of gas-conducting parts with different functionalisations for treating or post-treating process gases, respectively, are produced, which are intended for SOFCs. The gas-conducting part of the first exemplary embodiment was coated with Ni and the second embodiment was coated with NiO. Both gas conducting parts can be used for treating combustion gases; the functionalized surfaces of both exemplary embodiments act as catalysts for reforming combustion gases and also have a gettering effect on chlorine and sulfur. For gas-conducting parts used to post-treat the effluent gas, a Ti coating is selected that filters Cr ions from the effluent gas stream.

Fig. 2 and 3 show the arrangement of the gas-conducting parts (10, 10') in an electrochemical module. Fig. 2 shows an electrochemical module (20) in an exploded view with corresponding functionalized gas-conducting parts (10, 10'); fig. 3 shows a stack (30) in cross-section, with three electrochemical modules (20) stacked on top of each other. It should be noted that in fig. 2, the electrochemical module is shown turned around at its head in comparison to the module of fig. 3, in order to better see the channels (12). The electrochemical modules (20) each have an electrochemical cell (21) which is composed of a porous metal support substrate (22), which has been produced by a powder metallurgy process, having a layer structure (23) with at least one electrochemically active layer applied to the substrate (22) in the gas permeable region. The support substrates (22) with the layer structure (23) are pressed together at the edges in a gas-tight manner and have a plate-type substrate structure, which in variant embodiments serves to enlarge the surface area and can also have a local curvature over a smaller length, for example a wave-shaped design. Located on the side of the support substrate (22) which is opposite the layer structure described here is in each case an interconnector (24) which has a rib structure (24a) in the region in which it bears on the support substrate (22). The longitudinal direction of the rib structure extends here in the cross-sectional plane of fig. 3. The interconnectors (24) extend on two opposite sides beyond the area of the electrochemical cells (21) and are carried at their outer edges on frame panels (25) bounding the electrochemical cells. A boundary frame panel (25) is joined to an inner edge of the electrochemical cells (21) in a gas-tight manner via a boundary weld joint and to an outer edge of the interconnector (24) in a gas-tight manner. The frame panel (25) and the interconnector (24) thus form part of a metal gas-tight housing, which delimits a gas-tight process gas space (26) with the electrochemical cells (21). The process gas space (26) is subdivided into (conceptually) two opposing sub-spaces: two process gas conducting spaces (27, 27'), and the subspaces each extend over an area outside the electrochemical cell (21) area and open in the direction of the electrochemical cell (21). In this arrangement, a first process gas conducting space (27) is used for supplying process gas via a respective gas inlet opening (28) in the housing (frame panel and interconnector), while an opposite process gas conducting space (27 ') is used for removing process gas via a respective gas outlet opening (28') (the gas passage openings are not shown in fig. 3, since the cross-section is located at the side of the gas passage openings). The conduction of the gas in the stack takes place in the vertical direction (stacking direction of stack (B)) by means of corresponding channel structures, which are formed in the region of the gas channel openings, typically by means of separate inlays (29), sealing strips and by controlled application of a sealant, for example glass solder.

Arranged in the process gas conducting space (27) for supply is a gas conducting part (10) whose surface is functionalized for the treatment of the reactant gases (reforming, cleaning). Gas-conducting parts (10 ') which are functionalized for the aftertreatment of the product gas are arranged in the opposite process gas-conducting space (27') for the removal of the product gas. The gas-conducting parts (10, 10') for supply and removal therefore preferably have different functionalisations. The gas-conducting parts can of course also have different other properties (base material, shape, porosity, channel geometry, etc.) and can be optimized independently of one another for their intended use.

The gas-conducting parts (10, 10') are preferably configured as support elements in the stacking direction (B) of the electrochemical modules. For this purpose, the shape of the gas-conducting parts is adapted in each case to the interior of the respective process gas-conducting space. Each of said gas conducting parts (10, 10 ') is carried by its top side against a frame panel (25), which is the upper boundary of the respective process gas conducting space (27, 27'), and by its bottom side against an interconnector (24), which is the lower boundary of the respective process gas conducting space. A flat contact is advantageous, in particular at the top side and/or at the bottom side of the respective gas-conducting part. The thickness of the gas-conducting parts thus corresponds to the internal spatial height of the respective process gas-conducting space (27, 27'). A shallowly formed channel (12) is located on the bottom side of the gas conducting part (10, 10'). Because of the flat configuration of the gas-conducting parts, the flexural and torsional rigidity of the housing edge region, which consists of the thin frame panel (25) and the thin interconnectors (24), is decisively increased and the risk of weld cracks under mechanical load is therefore reduced. In an advantageous variant embodiment, the functionalized gas-conducting part is spot-welded to the housing and is thus fixed.

Fig. 4 and 5 show an electrochemical module (20 ') of a second exemplary embodiment, wherein the gas conducting part (10 ", 10" ') forms part of the housing and is integrally embodied with a support substrate (22 '). The porous support substrate (22 ') is pressed onto the two opposite sides in a gastight manner, in each case at the edge region, there being an integrated gas channel opening (11, 11') in each of said sides. The edge region can also be produced gas-tight on the side facing the layer structure (23) by means of a melting operation, which is carried out, for example, by laser beam melting. These opposite edge zones of the support substrate are outside the gas-permeable zone with the layer structure (23). They each represent a gas conducting part (10 ", 10" ') and delimit two process gas conducting spaces (27, 27') towards the top. Optionally, during the compression process, a gas guiding structure (12) may be integrated on the underside of the edge region of the support substrate (the side facing the interior of the process gas conducting space). In a variant that is implemented, the edge region (10 ") of the support substrate that is distributed to supply the combustion gases is coated on its underside with Ni; the edge region (10') which is assigned to the removal of the outflowing gas is coated on its underside with Ti. Treating the combustion gas and purging the effluent gas is accomplished in an exemplary embodiment similar to fig. 1-3.

Functionalization other than Ni and/or NiO and Ti coating is of course conceivable not only for the exemplary embodiments shown in fig. 1-3 (with separate gas-conducting parts), but also for the exemplary embodiments shown in fig. 4 and 5 (with integrated gas-conducting parts). For use in SOFCs, the gas conducting part may be functionalized on the reactant gas side with not only Ni or NiO but also Pt, Pd (and/or oxides of both metals), Co, Cr, Sc, cerium, Cu and/or Ti. Possible functionalisations of the gas-conducting part on the product side include Ti, Cu and/or oxide ceramics, more particularly Cu-Ni-Mn spinel.