IL257361A - Solid oxide fuel cell and method of operating same - Google Patents

Description

257361/2 SOLID OXIDE FUEL CELL AND METHOD OF OPERATING SAME BACKGROUND OF THE INVENTION

[001] Solid oxide fuel cells (SOFC) operated with ammonia are a known way for producing electricity. Solid oxide fuel cells are operated at elevated temperatures, usually temperatures higher than 800 °C to achieve high efficiency. Solid oxide fuel cells utilize inexpensive electrocatalysts and are highly reliable. However, their largest drawback is the slow starting of the electrochemical reaction until the cell reaches the required temperature, which limits their use in electric vehicles.

[002] There are two types of SOFCs, a tubular SOFC and a planar SOFC. These two types are fundamentally different. In tubular SOFC the anode, the solid oxide electrolyte and the cathode have tubular shape and are located one inside the other, as disclosed and illustrated in G.B. Patent Application Publication No. 2393320. The publication discloses a fuel cell having ammonia as the input fuel and an iron-based catalyst. An yttria stabilized zirconia electrolyte is used as a solid oxide electrolyte together with a packed-bed catalyst that is being used for cracking the ammonia. Tubular SOFC such as the one disclosed in G.B. 2393320 are not suitable for modern days requirements of the automotive industry due to the relatively large volume the tubular SOFC occupies. Furthermore, packed-bed catalysts having typical porosity of 40-50% are known to cause an additional pressure drop of the fuel across the catalyst. It is almost impossible to connect and stack a plurality of tubular SOFC having a single inlet and single outlet.

[003] Planar SOFC are, as named, relatively thin planar elements that are configured to be easily packed/stacked into a stack made from a plurality of planar SOFC. An example for such planar SOFCs is given in J.P. Patent Application Publication No. 2011-204416 which discloses a fuel electrode material for a solid oxide fuel cell (hereinafter called SOFC), in the SOFC using gas containing ammonia as fuel, without the need of an ammonia 1 November 6, 2018 November 6, 2018 257361/2 decomposition reactor. For achieving the above the fuel electrode material contains: an ammonia decomposition catalyst of at least one kind selected from a group consisting of metals of 6th to 10th group elements of the periodic table; an electrode catalyst; and solid electrolyte particles. Another example for such a planar SOFC is given in U.S. Patent Publication No. 7,157,166 B2 which discloses an ammonia fuel cell for generating electrical energy including a catalyst being in contact with a high temperature proton conducting membrane and the catalyst comprising at least one decomposition catalyst which causes NH to decompose to N and H and at least one catalytic anode which dissociates and 3 2 2 + ionizes H into H and electrons, the fuel cell further including at least one catalytic cathode 2 + for reaction of H , electrons and oxygen to form H2O.

[004] Additional explanation as to how the tubular and planar SOFC are built and work can be found in Irvine et al. “Solid Oxide Fuels Cells: Facts and Figures”, Chapter 1, Springer-Verlag London 2013.

[005] Solid oxide fuel cells may utilize direct oxidizing of ammonia on the anode using the following reaction I: 2- - I. 4 NH + 6 O 2 N + 12 e + 6 H O 3 2 2

[006] Alternatively or additionally, ammonia may be cracked to nitrogen and hydrogen according to reaction II. The hydrogen is then supplied to the anode for oxidation and electricity production.

II. 2NH ? 3H + N 3 2 2

[007] The known anode catalysts such as Ni-YSZ (nickel-yttria-stabilized zirconia) require operating the fuel cell at temperatures between 800-1000 °C. SOFC current architectures usually comprise metallic contact layers in contact with the anodes, these 2 November 6, 2018 November 6, 2018 257361/2 contact layers have very low surface areas. The surface area may be measured using the Brunauer, Emmett, Teller (BET) adsorption isotherms method. For example, the measured 2 surface areas of currently used anode contact layers are <0.1 m /g, such that their BET surface areas are equal to their geometrical surfaces. Therefore, these layers have low catalytic performance in NH cracking at temperatures below 800°C. 3

[008] Accordingly, there is a need for a solid oxide fuel cell that may operate with ammonia fuel at temperatures lower than 800°C at high efficiency. Such a fuel cell may include a catalyst for promoting reaction II to efficiently crack ammonia below 800°C.

SUMMARY OF THE INVENTION

[009] Some embodiments of the present invention may be directed to a planar solid oxide fuel cell. The planar solid oxide fuel cell may include: a planar cathode; a planar solid oxide electrolyte and a planar anode. The planar solid oxide fuel cell may further include at least one porous metallic element comprising a metallic catalyst for conversion of fuel to 2 2 hydrogen, said element having a surface area between 0.1 [m /g]-30 [m /g], located at the fuel path between the fuel entrance and the planar anode. In some embodiments, the surface 2 area of the porous metallic element may be equal to or larger than 0.5 [m /g], equal or larger 2 than 1 [m /g] or larger.

[0010] In some embodiments, the thickness of the porous metallic element may be equal to or smaller than 3 mm, for example, equal to or smaller than 2 mm.

[0011] In some embodiments, the at least one porous metallic element may be a porous metallic layer located in proximity to the planar anode. In some embodiments, the at least one porous metallic element is a porous metallic layer located between the planar anode and the fuel channels of an interconnect. In some embodiments, the at least one porous metallic element may be a porous metallic element located in the fuel channels of an interconnect. 3 November 6, 2018 November 6, 2018 257361/2 In some embodiments, the at least one porous metallic element may be an element located in the fuel supply system. In some embodiments, the porous metallic element may include a metal selected from a group consisting of: nickel, nickel alloys, ruthenium and ruthenium alloys. In some embodiments, the porous metallic element is selected from the group consisting of: a metallic foam, a metallic mesh, a metallic grid, a metallic net and a metallic felt

[0012] Some embodiments of the present invention may be directed to a planar solid oxide fuel cell. The planar solid oxide fuel cell may include: a planar cathode; a planar solid oxide electrolyte and a planar anode. The solid oxide fuel cell may further include at least one porous metallic element having a surface area in an amount sufficient to convert into hydrogen most of the fuel supplied to the solid oxide fuel cell. In some embodiments, at least one porous metallic element may have a porosity level of at least 70%, for example, at least 80%. In some embodiments, the porous metallic element may have a surface area in an amount sufficient to crack at least 95% of the fuel supplied to the solid oxide fuel cell. In some embodiments, the porous metallic element may have a surface area in an amount sufficient to crack at least 99% of the fuel supplied to the solid oxide fuel cell. In some embodiments, the porous metallic element may have a surface area in an amount sufficient to crack 100% of the fuel supplied to the solid oxide fuel cell. In some embodiments, the fuel supplied to the fuel cell may be ammonia (e.g., pure ammonia or ammonia in a gas mixture).

[0013] In some embodiments, the thickness of the porous metallic element may be equal to or smaller than 3 mm, for example, equal to or smaller than 2 mm.

[0014] Some embodiments of the present invention may be directed to solid oxide fuel cell.

The solid oxide fuel cell may include: a cathode; a solid oxide electrolyte and an anode. The 4 November 6, 2018 November 6, 2018 257361/2 solid oxide fuel cell may further include at least one porous metallic element having a surface area in an amount sufficient to crack the fuel supplied to the solid oxide fuel cell and allow operation of the solid oxide fuel cell at temperatures below 800°C.

[0015] In some embodiments, the at least one porous metallic element has a surface area in an amount sufficient to crack the fuel supplied to the solid oxide fuel cell and allow operation of the solid oxide fuel cell at temperatures below 750°C. In some embodiments, the fuel supplied to the fuel cell may include ammonia.

[0016] Some aspects of the invention may be directed to a method of operating a planar solid oxide fuel cell. The method may include operating the planar solid oxide fuel cell at temperatures lower than 800 °C; supplying a fuel to be cracked to the solid oxide fuel cell; flowing the fuel via at least one porous metallic element, comprising a catalytically active metal, located along a path between the fuel entrance and the planar anode; and cracking the fuel on the surface of the porous metallic element.

[0017] In some embodiments, operating the solid oxide fuel cell is at temperatures lower than 750 °C. In some embodiments, a surface area of the porous metallic element may be 2 equal to or larger than 0.1 [m /g]. In some embodiments, the fuel may include ammonia such that cracking the fuel may include cracking the ammonia to hydrogen and nitrogen. In some embodiments, the method may include collecting and conducting electrons from the anode via the porous metallic element.

[0018] In some embodiments, the method may include evacuating heat from at least the anode of the fuel cell using the porous metallic element.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to November 6, 2018 257361/2 organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0020] Fig. 1 is an illustration of a solid oxide fuel cell according to some embodiments of the invention;

[0021] Fig. 2 is an illustration of a solid oxide fuel cell according to some embodiments of the invention;

[0022] Fig. 3 is an illustration of a solid oxide fuel cell stack according to some embodiments of the invention; and

[0023] Fig. 4 is a flowchart of a method of operating a solid oxide fuel cell according to some embodiments of the invention.

[0024] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. 6 257361/2 DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0025] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0026] Some aspects of the invention may be related to a planar solid oxide fuel cell utilizing ammonia as the fuel. Such planar solid oxide fuel cell may crack the ammonia at temperatures lower than 800°C, for example, 750°C, 700°C or lower. In order to do so, a planar solid oxide fuel cell according to some embodiments of the invention may include at least one porous metallic element that includes a metallic catalyst for conversion of fuel to hydrogen. In some embodiments, the element may have a surface area equal to or larger 2 than 0.1 [m /g] and may be located at the fuel path between the fuel entrance and the anode.

In some embodiments, the high surface area of the at least one porous metallic element may provide much higher number of sites for reaction II to occur.

[0027] Reference is now made to Fig. 1 which is an illustration of a solid oxide fuel cell according to some embodiments of the invention. A planar solid oxide fuel cell 100 may include a planar cathode 10, a planar solid oxide electrolyte 20, a planar anode 30 and at least one porous metallic element 40. In some embodiments, planar SOFC100 may further include interconnect 50 for connecting cell 100 to an adjacent cell 100 (as illustrated in Fig. 3). In some embodiments, planar SOFC 100 may further include one or more seals 38 for sealing fuel cell 100.

[0028] Planar cathode 10 may include any cathode suitable for oxygen reduction in solid oxide fuel cell 100, for example, a thin porous layer attached to planar solid oxide electrolyte 7 November 6, 2018 November 6, 2018 November 6, 2018 257361/2 . The planar cathode material may be electronically conductive, an example for cathode materials may include: strontium-doped lanthanum manganite (LSM), strontium-doped lanthanum ferrite (LSF), strontium-doped lanthanum cobaltite (LSC), strontium-doped lanthanum cobalt ferrite (LSCF). Solid oxide electrolyte 20 may include any solid oxide electrolyte known in the art. Solid oxide electrolyte 20 may include a dense ceramic layer capable of conducting oxygen ions, for example, planar solid oxide electrolyte 20 may include yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (ScSZ), gadolinium doped ceria (GDC) and the like.

[0029] Planar anode 30 may include any material suitable for catalyzing oxidation of hydrogen, for example, material such as Ni-YSZ (nickel-yttria-stabilized zirconia). Planar anode 30 may include a porous ceramic or metallic layer that may allow the fuel to flow towards the solid electrolyte 20.

[0030] At least one porous metallic element 40 may include a metallic catalyst for conversion of fuel (e.g., ammonia) to hydrogen. In some embodiments, at least one porous metallic element 40 may have a surface area in an amount sufficient to crack the fuel (e.g., ammonia) supplied to solid oxide fuel cell 100. In some embodiments, the use of porous metallic element 40 may allow operation of solid oxide fuel cell 100 at temperatures below 800°C, for example, below 780°C, below 750°C, below 730°C, below 700°C and lower. In some embodiments, solid oxide fuel cell 100 may be operated at 600-800°C. In some embodiments, in order to allow the operation of solid oxide fuel cell 100 at such low temperatures at least one porous metallic element 40 may have a surface area equal to or 2 2 larger than 0.1 [m /g], for example, equal to or larger than 0.5 [m /g], equal to or larger than 2 1 [m /g] or more. In some embodiments, the at least one porous metallic element 40 may 2 2 have a surface area of between 0.1 [m /g] to 30 [m /g]. In some embodiments, in order to 8 November 6, 2018 257361/2 reduce the size of the SOFC and allow staking of a plurality of SOFCs, the thickness of at least one porous metallic element 40 may be kept as low as possible, for example, less than 3 mm, less than 2 mm or even lower.

[0031] In some embodiments, at least one porous metallic element 40 may have a surface area in an amount sufficient to crack most of the fuel supplied to the solid oxide fuel cell.

For example, at least one porous metallic element 40 may have a surface area in an amount sufficient to crack at least 95% of the fuel, at least 99% of the fuel or even 100% of the fuel.

In some embodiments, porous metallic element 40 may include a metal selected from a group consisting of: nickel, nickel alloys, ruthenium and ruthenium alloys. In some embodiments, at least one porous metallic element 40 may be selected from a group consisting of: a metallic foam, a metallic mesh, a metallic net, a metallic felt, and a metallic grid.

[0032] In some embodiments, at least one porous metallic element 40 may be located at the fuel path between the fuel entrance and the anode, for example, in proximity to planar anode as illustrated in Fig. 1. In some embodiments, at least one porous metallic element 40 may be in direct contact with planar anode 30.

[0033] In some embodiments, in order to obtain high surface area and high porosities of porous elements, such as, foam, mesh, net, felt, grid, etc. macrostructure different treatments and modifications can be applied. For example, thin Raney-type porous outer-layers can be created on the wires/mesh that constitute these macrostructures. For example, an alloy of nickel-aluminum (Ni-Al) may be formed via solid-solid reaction with aluminum powder, followed by etching out the aluminum in an acidic or alkaline aqueous solution, yielding a skeletal metal layer with high (Brunauer–Emmett–Teller) BET surface areas (e.g., 20 2 [m /g]). In order to reduce the pyrophoricity of the Ni foam, an oxidation step in an open 9 November 6, 2018 257361/2 atmosphere may be conducted. Similar Raney-type porous outer-layers may be obtained 2 with Ru having high BET surface areas (e.g., 30 [m /g]).

[0034] In yet another example, molten metal may be sprayed on the porous macrostructure with spraying conditions controlling the final porosity. In some embodiments, two types of metals may be co-sprayed on the porous macrostructure, following by chemically etching one of the metals, to form the required high surface area.

[0035] In some embodiments, interconnect 50 may include a metallic or ceramic layer that sits between two cells 100 and configured to connect the two cells in series (as illustrated in Fig. 3), as to allow the voltage produced each cell 100 to be combined. Since interconnect 50 may be exposed to the high temperatures in cell 100, interconnect 50 must include materials stable at these SOFC operating temperatures. Since the use of at least one porous metallic element 40 may allow to operate fuel cell 100 at 600-800°C, interconnect 50 may be made from cheaper materials such as steel-based alloys (e.g., Crofer 22 APU and the like) rather than the more expensive ceramics used for fuel cells operated at 800-1000°C.

Interconnect 50 may include fuel channels 55 for providing fuel to anode 30.

[0036] In some embodiments, solid oxide fuel cell 100 may include a cathode porous contact layer element 13. Element 13 may include a cathode-like ceramic contact layer, or a composite contact layer containing silicon-based glasses, or a porous metallic contact layer (for example, a copper-manganese foam). In some embodiments, element 13 may ensure a proper and durable electrical contact between cathode 10 and the air side of the interconnect.

[0037] Reference is now made to Fig. 2 which is an illustration of a planar solid oxide fuel cell according to some embodiments, of the invention. A solid oxide fuel 200 may include planar cathode 10, cathode porous contact layer element 13, planar solid oxide electrolyte and planar anode 30. In some embodiments, solid oxide fuel cell 200 may further include November 6, 2018 257361/2 interconnect 50 for connecting cell 200 to an adjacent cell 200 (as illustrated in Fig. 3) and one or more seals 38. Cathode 10, cathode porous contact layer element 13, solid oxide electrolyte 20, anode 30, interconnect 50 and seals 38 may be substantially the same as the ones disclosed with respect to solid oxide fuel cell 100 illustrated in Fig. 1.

[0038] Planar solid oxide fuel cell 200 may further include at least one porous metallic element 40 and/or 45 comprising a metallic catalyst for conversion of fuel to hydrogen. In some embodiments, at least one porous metallic element 40 and/or 45 may have a surface area in an amount sufficient to crack the fuel (e.g., ammonia) supplied to planar solid oxide fuel cell 200 and allow operation of solid oxide fuel cell 200 at temperatures below 800°C.

At least one porous metallic element 40 may be substantially the same and may be located at same place as element 40 of fuel cell 100. In some embodiments, at least one porous metallic element 45 may be located at the fuel path between the fuel entrance and the anode.

For example, at least one porous metallic element 45 may be located in fuel channels 55 of interconnect 50, as illustrated in Fig. 2. In some embodiments, at least one porous metallic element 40 may be located between anode 30 and the fuel channels 55 of interconnect 50, as illustrated in both Fig. 1 and Fig. 2.

[0039] In some embodiments, porous metal of element 45 may include a metal selected from a group consisting of: nickel, nickel alloys, ruthenium and ruthenium alloys and may be made (e.g., manufactured) using similar methods and may have the same properties as the porous metal of element 40. In some embodiments, at least one porous metallic element 45 may be selected from a group consisting of: a metallic foam, a metallic mesh, a metallic net, a metallic felt, and a metallic grid. In some embodiments, at least one porous metallic element 45 may have a surface area in an amount sufficient to crack most (e.g., 95%, 99% or 100%) of the fuel supplied to the solid oxide fuel cell. In some embodiments, at least one 11 November 6, 2018 257361/2 2 porous metallic element 45 may have a surface area equal to or larger than 0.1 [m /g] (e.g., 2 2 equal to or larger than 0.5 [m /g], equal to or larger than 1 [m /g]). In some embodiments, 2 the at least one porous metallic element 45 may have a surface area of between 0.1 [m /g] 2 to 30 [m /g]. In some embodiments, in order to reduce the size of the SOFC and allow staking of a plurality of SOFCs, the thickness of at least one porous metallic element 45 may be kept as low as possible, for example, less than 3 mm, less than 2 mm or even lower.

[0040] Reference is now made to Fig. 3 which is an illustration of a solid oxide fuel cell stack according to some embodiments of the invention. A stack 300 may include two or more planar solid oxide fuel cells 100 and/or two or more planar solid oxide fuel cells 200 or any two or more solid oxide fuel cells known in the art. The fuel cells of stack 300 may include a cathode porous contact layer element 13 to ensure a proper and durable electrical contact between cathode 10 and interconnects 50. In some embodiments, stack 300 may further include a fuel (e.g., ammonia) supply system 60 having a fuel entrance 65 to introducing fuel to the two or more solid oxide fuel cells. In some embodiments, at least one porous metallic element 48 may be located at the fuel path between fuel entrance 65 and anodes 30 of each fuel cell. For example, at least one porous metallic element 48 may be located along fuel supply system 60 before the entrance to the fuel channels. In some embodiments, porous metallic element 48 may include a metal selected from a group consisting of: nickel, nickel alloys, ruthenium and ruthenium alloys. In some embodiments, the fuel cells and stack 300 may further include a plurality of seals 68 for sealing each fuel cell.

[0041] In some embodiments, porous metal of element 48 may include a metal selected from a group consisting of: nickel, nickel alloys, ruthenium and ruthenium alloys and may be made (e.g., manufactured) using similar methods and may have the same properties as 12 November 6, 2018 257361/2 the porous metal of element 40. For example, at least one porous metallic element 48 may have a surface area in an amount sufficient to crack most (e.g., 95%, 99% or 100%) of the fuel supplied to the solid oxide fuel cell. In yet another example, at least one porous metallic 2 element 48 may have a surface area equal to or larger than 0.1 [m /g] (e.g., equal to or larger 2 2 than 0.5 [m /g], equal to or larger than 1 [m /g]). In some embodiments, the at least one 2 2 porous metallic element 48 may have a surface area of between 0.1 [m /g] to 30 [m /g].In some embodiments, at least one porous metallic element 48 may be selected from a group consisting of: a metallic foam, a metallic mesh, a metallic net, a metallic felt, and a metallic grid.

[0042] Reference is now made to Fig. 4 which is a flowchart of a method of operating a planar solid oxide fuel cell according to some embodiments of the invention. The method of Fig. 4 may be used for operating fuel cells 100, 200 and stack 300. In box 410, solid oxide fuel cell (e.g., planar cells 100, 200 or stack 300) may be operated at temperatures lower than 800 °C, for example, 750°C, 730 °C, 700 °C, 650 °C and lower. In box 420, a fuel (e.g., ammonia) to be cracked and supplied to the solid oxide fuel cell. For example, ammonia may be supplied via fuel entrance 65 of fuel supply system 60 to at least one solid oxide fuel cell 100 or 200.

[0043] In box 430, the fuel (e.g., ammonia) may flow via at least one porous metallic element (e.g., elements 40, 45 and/or 48) that may include a catalytically active metal. The at least one porous metallic element (e.g., elements 40, 45 and/or 48) may be located along a path between the fuel entrance (e.g., entrance 65) and the anode (e.g., anode 30).

[0044] In box 440, the fuel may be cracked on the surface of the porous metallic element.

For example, ammonia may be cracked to hydrogen and nitrogen using reaction II on the surface of porous metallic element 40, 45 and/or 48. In some embodiments, the produced 13 November 6, 2018 257361/2 hydrogen may be supplied to the catalyst of anode 30 to be oxidized and produce electricity using oxygen ions migrated from cathode 10 via solid oxide electrolyte 20. In some embodiments, the produced electrons may further be collected and conducted from anode via at least one porous metallic element (e.g., elements 40 and/or 45).

[0045] In some embodiments, heat may be evacuated via at least one porous metallic element (e.g., elements 40 and/or 45 and/or 48). Reaction II is an endothermal reaction (=+46 ) therefore, the at least one porous metallic element may act as a cooler for removing excess heat from fuel cell 100 or 200. This effect may be beneficial to the overall energy efficiency of the system. Solid oxide fuel cells are commonly cooled by the incoming air flow using an air compressor. If some of the heat may be removed (e.g., consumed) by reaction II, the required air flow may be reduced. Accordingly, the power supplied to the cell's air compressor may be lowered, and the overall efficiency of the system may be increased.

[0046] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. 14

Claims (17)

:

1. A planar solid oxide fuel cell, comprising: a planar cathode; a planar solid oxide electrolyte; a planar anode; and at least one porous metallic element comprising a metallic catalyst for conversion of ammonia fuel to hydrogen, said element having a surface area between 0.1 2 2 [m /g] and 30 [m /g], located at the fuel path between the fuel entrance and the anode, wherein the porous metallic element includes a metal selected from a group consisting of: nickel, nickel alloys, ruthenium and ruthenium alloys.

2. The planar solid oxide fuel cell according to claim 1, wherein the thickness of the porous metallic element is equal to or smaller than 3 mm.

3. The planar solid oxide fuel cell according to claim 1, wherein the thickness of the porous metallic element is equal to or smaller than 2 mm.

4. The planar solid oxide fuel cell according to any one of the preceding claims, wherein the at least one porous metallic element is a porous metallic layer located between the anode and the fuel channels of an interconnect. 15 November 6, 2018 257361/4

5. The planar solid oxide fuel cell according to any one of claims 1-3, wherein the at least one porous metallic element is a porous metallic element located in the fuel channels of an interconnect.

6. The planar solid oxide fuel cell according to any one of claims 1-3, wherein the at least one porous metallic element is an element located in the ammonia supply system.

7. The planar solid oxide fuel cell according to any one of the preceding claims, wherein the porous metallic element is selected from the group consisting of: a metallic foam, a metallic mesh, a metallic grid, a metallic net and a metallic felt.

8. A planar solid oxide fuel cell, comprising: a planar cathode; a planar solid oxide electrolyte; a planar anode; and at least one porous metallic element comprising a metallic catalyst for conversion of ammonia fuel to hydrogen, said element having a porosity level of at least 70%, wherein the porous metallic element includes a metal selected from a group consisting of: nickel, nickel alloys, ruthenium and ruthenium alloys.

9. The planar solid oxide fuel cell of claim 8, wherein the porous metallic element having a porosity level of at least 80%.

10. The planar solid oxide fuel cell according to any one of claims 8-9, wherein the ammonia fuel supplied to the fuel cell is one of: pure ammonia and ammonia in a gas mixture. 16 November 6, 2018 257361/4

11. A planar solid oxide fuel cell according to any one of claims 8-10, wherein the thickness of the porous metallic element is equal to or smaller than 3 mm

12. .The planar solid oxide fuel cell according to any one of claims 8-11, wherein the thickness of the porous metallic element is equal to or smaller than 2 mm .

13. A method of operating a planar solid oxide fuel cell, comprising: operating a planar solid oxide fuel cell according to any one of claims 1-12 at temperatures lower than 800 °C; supplying ammonia to be converted into hydrogen to the planar solid oxide fuel cell; flowing the ammonia via at least one porous metallic element, comprising a catalytically active metal, located along a path between the ammonia entrance and the anode; and converting into hydrogen the ammonia on the surface of the porous metallic element.

14. The method of claim 13, wherein operating the planar solid oxide fuel cell is at temperatures lower than 750 °C

15. The method according to any one of claims 13-14, wherein converting into hydrogen the ammonia comprises cracking the ammonia to hydrogen and nitrogen.

16. The method according to any one of claims 13-15, further comprising; collecting and conducting electrons from the planar anode via the porous metallic element. 17 November 6, 2018 257361/4

17. The method according to any one of claims 13-16, further comprising; evacuating heat from at least the planar anode of the fuel cell using the porous metallic element. 18