Fuel cell system, vehicle and associated decontamination process

Abstract

The invention relates to a fuel cell system (1) comprising: - a fuel cell (10) having an anodic compartment and a cathodic compartment, and - a power supply system (2) supplying the anodic compartment of the fuel cell with dihydrogen (H2) and comprising a first reservoir (21) adapted to store ammonia (NH3), a reforming stage (24) adapted to reform the ammonia from the first reservoir into dihydrogen and produce dinitrogen (N2), and a purification stage (25) adapted to filter the dinitrogen produced in the reforming stage. According to the invention, the purification stage communicates with a second reservoir (41) adapted to store the dinitrogen filtered by said purification stage, the second reservoir communicates with the cathodic compartment of the fuel cell, and means are provided for regulating the flow rate (42, 43) of dinitrogen circulating from the second reservoir to the cathodic compartment of the fuel cell.Figure for the abridged version: Fig.1.

Description

Title of the invention: Fuel cell system, vehicle and associated decontamination process. Technical field of the invention

[0001] The present invention relates generally to fuel cells.

[0002] It relates more particularly to a fuel cell system.

[0003] The invention finds a particularly advantageous application for decontaminating a fuel cell operating in polluted environments.

[0004] It also relates to a vehicle comprising such a fuel cell system, as well as an associated decontamination process. State of the art

[0005] It is known to generate an electric current using a fuel cell in which, on a first electrode, an oxidation reaction of a fuel (for example dihydrogen) takes place, and, on a second electrode, a reduction reaction of an oxidant.

[0006] As a general rule, such a fuel cell uses the dioxygen contained in the air as an oxidant.

[0007] These fuel cells, particularly those known as "proton exchange membrane fuel cells (PEMFCs)," are therefore very sensitive to air pollutants. They are especially sensitive, among other things, to sulfur dioxide (SO2). This pollutant accumulates on the surface of one of these electrodes, hindering the proper progress of the chemical reactions and thus reducing the overall efficiency of the fuel cell.

[0008] This progressive deterioration in fuel cell performance leads to increased maintenance costs and a reduction in the cell's lifespan. This deterioration is all the more rapid when the fuel cell is used in areas where the air is polluted (particularly in urban areas).

[0009] This deterioration is however reversible, provided that the concentration of pollutants on the electrodes is not too high.

[0010] Document US2003180586 thus proposes to inject nitrogen instead of air into the fuel cell in order to regenerate it.

[0011] This regeneration must be carried out regularly to avoid irreversible damage to the fuel cell, which proves costly in practice. Furthermore, this regeneration requires a supply of nitrogen, which constitutes an additional constraint for vehicle maintenance workshops and users. Presentation of the invention

[0012] In order to remedy the aforementioned drawbacks of the prior art, the present invention proposes to decontaminate fuel cells by injecting nitrogen produced during the reforming of the hydrogen required for the usual operation of the cell, and which will have been stored for this purpose.

[0013] More particularly, the invention proposes a fuel cell system comprising a fuel cell having an anodic compartment and a cathodic compartment, and a power supply system supplying the anodic compartment of the fuel cell with hydrogen (from an ammonia reforming reaction) and comprising a first reservoir adapted to store ammonia, a reforming stage adapted to reform the ammonia from the first reservoir into dihydrogen and to produce dinitrogen, and a purification stage adapted to filter the dinitrogen produced in the reforming stage, wherein the purification stage is provided to communicate with a second reservoir adapted to store the dinitrogen filtered by the purification stage, and the second reservoir communicates with the cathodic compartment of the fuel cell,and which also includes provisions for regulating the flow of nitrogen circulating from the second tank to the cathode compartment of the fuel cell.

[0014] Thus, thanks to the invention, the nitrogen produced in the reforming stage is advantageously reused to decontaminate the fuel cell of pollutants that may have accumulated there. In particular, sulfur dioxide (SO2) is removed from the electrode surface, extending the fuel cell's lifespan. This decontamination is facilitated by an in-situ supply of nitrogen (N2), instead of releasing it into the atmosphere at the end of the ammonia (NH3) reforming cycle, as is customary.

[0015] The storage of nitrogen (N2) produced during the reforming of ammonia (NH3) into hydrogen (H2) allows its recovery in order to increase the lifespan of fuel cells, without requiring any special maintenance for the supply of nitrogen (N2).

[0016] It even becomes possible to regenerate the fuel cell automatically, outside of any maintenance workshop.

[0017] Other advantageous and non-limiting features of the fuel cell system according to the invention, taken individually or in all technically possible combinations, are as follows: - A voltage controller is planned, adapted to apply a voltage between the cathode compartment and the anodic compartment of the fuel cell. - the system further includes a pollution sensor and a central control unit adapted to operate the regulation means and the voltage controller according to the pollution measured by the pollution sensor, - The pollution sensor includes a gas sensor adapted to measure atmospheric concentration of sulfur dioxide (SO2), - The pollution sensor includes a sensor adapted to measure a quantity internal to the fuel cell, - The nitrogen purification stage includes a palladium membrane-type system adapted to filter nitrogen, - The purification stage includes a unit adapted to convert ammonia into nitrogen, - The unit adapted to convert ammonia into nitrogen includes a pressure reversal adsorption device, - The unit adapted to convert ammonia into nitrogen includes a temperature-modulated adsorption device.

[0018] The invention also proposes a motor vehicle comprising a fuel cell system as described above.

[0019] Furthermore, a decontamination process for the fuel cell system described is also described within the framework of the invention, the process comprising the following steps: - reforming of the ammonia stored in the first tank into nitrogen and hydrogen by the reforming stage, - purification of the nitrogen from the reforming stage by the purification stage, - Nitrogen storage in the second tank, - decontamination of the fuel cell by injecting nitrogen from the second reservoir into the cathodic behavior of the fuel cell.

[0020] Of course, the different features, variants and embodiments of the invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive. Detailed description of the invention

[0021] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0022] On the attached drawings:

[0023] [Fig.1] is a schematic representation of a fuel cell system according to the invention, comprising a dihydrogen supply system;

[0024] [Fig.2] is a flowchart illustrating steps in a process implementing the fuel cell system of the [Fig.1].

[0025] Figure 1 shows a fuel cell system 1, designed to generate an electric current. This fuel cell system 1 can be used in various devices for diverse applications (stationary or not).

[0026] Here, it is carried in a motor vehicle, and more specifically in a land vehicle such as, for example, a car, a van or a truck.

[0027] It is specifically designed to provide the electrical current supply to an electric motor, directly or indirectly (via a battery of accumulators).

[0028] The fuel cell system 1 comprises a fuel cell 10, adapted to generate an electric current from a redox reaction. This reaction involves a fuel and an oxidant. The fuel cell system 1 therefore includes a power supply system 2 to provide the fuel to the cell and an air intake line 3 to supply the fuel cell 10 with oxidant. A decontamination system 4 is also provided, intended to extend the service life of the fuel cell 10.

[0029] Here, this fuel cell 10 is of the proton exchange membrane fuel cell (PEMFC) type. In particular, the cell considered transforms dihydrogen H2 (the fuel) and dioxygen O2 (the oxidant) into electrical power.

[0030] For this purpose, the fuel cell 10 comprises: - two electrodes, namely an anode, placed in an anodic compartment, and a cathode, placed in a cathodic compartment, - two bipolar plates, each with an inlet and an outlet between which a fluid can be circulated. The plates include a first plate in the anodic compartment to distribute the fuel (typically dihydrogen H2) towards the anode, and a second plate, located in the cathodic compartment, to distribute the oxidant (for example dioxygen O2) towards the cathode, - a proton exchange membrane acting as an insulating electrolyte (it blocks the passage of electrons while allowing the passage of H+ ions, also called protons).

[0031] When the cathode compartment is supplied with a flow of fuel (here, dihydrogen H2), an oxidation reaction occurs. A reduction reaction occurs within the anodic compartment, through the reaction between a flow of oxidant (here, dioxygen O2) and the H+ ions produced by the oxidation reaction.

[0032] Finally, the fuel cell 10 has two electrical terminals connected to the two electrodes.

[0033] The oxygen (or dioxygen O2) supplying the cathode compartment comes from ambient air, which makes the fuel cell 10 particularly susceptible to Risk of contamination by airborne pollutants, such as sulfur dioxide (SO2). This is particularly present in urban areas and accumulates within the fuel cell 10. This accumulation then progressively degrades the performance of the fuel cell 10.

[0034] As shown in [Fig. 1], the air inlet line 3 is intended to supply the cathode compartment with ambient air.

[0035] This air inlet line 3 comprises successively an air filter 31, drawing in and filtering air from the atmosphere, an air compressor 32 compressing the filtered air, an air cooler 33 which cools the compressed air and an air humidifier 34.

[0036] The anodic compartment is supplied by the hydrogen supply system 2 with dihydrogen H2, which is also shown in [Fig.1].

[0037] For optimization purposes, a recirculation loop for unconsumed hydrogen H2 is provided at the outlet of the anodic compartment. This unconsumed hydrogen H2 is reintroduced at the inlet of the anodic compartment, via a dedicated conduit 51, or vented to the outside / atmosphere by means of a drain 52.

[0038] For practical and safety reasons, the hydrogen H2 supplied to the anodic compartment is stored here by conversion into ammonia NH3, that is, in the form of ammonia NH3 and not pure hydrogen H2. Thus, the supply system 2 includes a first reservoir 21 adapted for storing ammonia NH3. This ammonia NH3 is then converted into hydrogen H2 to supply the anodic compartment.

[0039] In practice, ammonia NH3 is stored in liquid form at a pressure of approximately 10 bar and a temperature of 298.15 K. The first tank 21, for example, is made of stainless steel. It advantageously exhibits a boil-off rate of less than 0.04% per day.

[0040] The first reservoir 21 is connected to a pump 22, adapted to pump the ammonia NH3 in its liquid form, in order to circulate it through a series of heat exchangers 23. These heat exchangers 23 allow the ammonia NH3 to pass from a liquid state to a gaseous state.

[0041] The ammonia NH3, in gaseous form, then passes into a reforming stage 24, also called a cracking stage. This reforming stage 24 converts the incoming ammonia NH3 into dihydrogen H2 and dinitrogen N2 at its outlet. Thus, the reforming stage is adapted to reform ammonia into dihydrogen H2 and dinitrogen N2. Here, the following reaction is carried out in the reforming stage 24:

[0042] NH3 -> 0.5 N2 + 1.5 H2, AH° = +46.19 kJ.mol *.

[0043] This reforming stage 24 has a hydrogen (H2) yield with a volume fraction of 75% vol, and also produces nitrogen (N2) with a yield of 25% vol. Traces of ammonia (NH3) are present. remains after reforming stage 24, ammonia NH3 representing 250 to 500 parts per million by volume (ppmv) of the products after reforming stage 24.

[0044] This reforming stage 24 comprises a reformer, supplied with heat by a heating unit, also called a burner, not shown here. This heating unit is supplied with ammonia NH3 from the first reservoir 21 and with hydrogen H2 from the reformer. These two species are burned to produce sufficient heat for the reforming reaction of ammonia NH3 into hydrogen H2. This combustion leads to the production of nitrogen oxides NOx at the outlet of the heating unit.

[0045] The feed system 2 includes, downstream of the reforming stage 24, a purification stage 25 adapted in particular to purify the hydrogen H2 produced in the reforming stage 24 and to purify the nitrogen N2 produced in the same reforming stage 24. To this end, the purification stage 25 is adapted to separate the nitrogen N2 produced in the reforming stage 24 from the hydrogen H2, but also to separate the nitrogen N2 from any other residual products and / or reactants. In practice, this purification stage 25 is designed to supply the anodic compartment with the purest possible hydrogen H2. Indeed, injecting contaminated hydrogen H2 into the anodic compartment is detrimental to the lifespan of the fuel cell 10.

[0046] The purification stage 25 includes means for purifying dihydrogen H2, in particular by separating it from dinitrogen N2 produced at the outlet of the reforming stage 24.

[0047] Furthermore, the purification stage 25 also includes means for purifying, i.e. filtering, the nitrogen N2. In particular, here, the purification stage 25 includes means for filtering and / or removing traces of ammonia NH3 remaining at the outlet of the reforming stage 24.

[0048] Thus, the purification stage 25 makes it possible to obtain on the one hand hydrogen H2 to supply the anodic compartment, on the other hand dinitrogen N2, while eliminating other undesirable products and / or residual reagents, such as ammonia NH3.

[0049] Advantageously in the first embodiment described, the means for filtering and / or traces of ammonia NH3 are chosen so as to be able to produce dinitrogen N2.

[0050] Thus, the purification stage 25 comprises, in the normal direction of gas flow, a unit 251 adapted to filter ammonia NH3 and nitrogen N2, thereby purifying the hydrogen H2 from the reforming stage 24. A first outlet of the unit 251 adapted to filter ammonia NH3 and nitrogen N2 is connected to the anodic compartment in order to supply the fuel cell 10 with purified hydrogen H2. This first outlet of the unit 251 coincides with a first outlet of the purification stage 25. A second outlet of the unit 251 adapted to filter ammonia NH3 and nitrogen N2 is connected to a unit 252 adapted to convert Ammonia (NH3) is converted into nitrogen (N2). Unit 252 purifies the nitrogen (N2) by removing residual ammonia (NH3). The ammonia (NH3) and nitrogen (N2) filtered by unit 251 are directed to this second outlet of unit 251.

[0051] Advantageously, at the first outlet of the purification stage 25, the volume fraction of nitrogen N2 is less than 1 ppmv. Similarly, at the first outlet of the purification stage 25, the volume fraction of ammonia NH3 is less than 100 ppbv.

[0052] The unit 251, adapted to filter ammonia NH3 and nitrogen N2, purifies the hydrogen H2 from the reforming stage 24 to a quality suitable for injection into the fuel cell 10. To this end, the unit 251 separates, i.e., filters, the nitrogen N2 and ammonia NH3 from the hydrogen H2. In particular, the unit 251 includes, for example, a filtration system that separates the hydrogen H2 from the ammonia NH3 and nitrogen N2. Such a system includes a separation membrane, for example, a palladium Pd separation membrane.

[0053] This unit 251 allows the removal of ammonia NH3 and nitrogen N2 from the gas mixture supplied to the inlet of the purification stage 25. This gas mixture corresponds to the gas mixture supplied to the outlet of the reforming stage 24, and thus comprises a mixture of hydrogen H2, nitrogen N2 and traces of ammonia NH3.

[0054] Following the direction of gas flow, the gas mixture from the second outlet of unit 251 adapted to filter ammonia NH3 and dinitrogen N2 is injected into unit 252 adapted to convert ammonia NH3 into dinitrogen N2.

[0055] This unit 252, adapted to convert ammonia NH3 into nitrogen N2, uses the ammonia NH3 from the second outlet of unit 251 to convert nitrogen oxides NOx from the heating unit. A connection, not shown here, allows the nitrogen oxides NOx produced by the heating unit to be conveyed to the inlet of unit 252. This conversion of nitrogen oxides NOx by ammonia NH3 advantageously produces nitrogen N2.

[0056] At the outlet of unit 252, a volume fraction of dinitrogen N2 comes from the reforming stage, while another volume fraction of dinitrogen comes from the conversion of nitrogen oxides NOx.

[0057] An unused fraction of the ammonia NH3 is captured by a sorption column, included in unit 252. This sorption column thus purifies the nitrogen N2 by adsorbing the ammonia NH3, preventing its release into the atmosphere. For example, it could be a sorption column using a sorbent based on activated carbon impregnated with phosphoric acid.

[0058] An outlet of unit 252 supplies purified nitrogen N2 to a second reservoir 41 to which it is fluidly connected. This outlet of unit 252 is combined with a second outlet of the purification stage 25. Thus, the nitrogen N2 produced in the reforming stage 24 and separated from dihydrogen H2 by unit 251 and dinitrogen N2 obtained by the reaction of nitrogen oxides NOx and ammonia NH3 in unit 252 is stored in the second tank 41.

[0059] Also, the second tank 41 is suitable for storing nitrogen N2, for example in gaseous form. Alternatively, nitrogen N2 can be stored in liquid form.

[0060] This second reservoir 41, as shown in [Fig. 1], is included in the aforementioned decontamination system 4. This decontamination system 4 includes, in particular, flow control means 42, 43, adapted to control the flow rate of the gas between an outlet of the second reservoir 41 and the cathode compartment.

[0061] This decontamination system 4 makes it possible, in particular, to regenerate the performance of the fuel cell 10 when it is contaminated by atmospheric pollutants, especially sulfur dioxide (SO2). Here, it is proposed to regenerate the fuel cell 10 by injecting a controlled flow of nitrogen (N2) into the cathode compartment. Such decontamination of the fuel cell by nitrogen injection is described, for example, in US patent 2003180586.

[0062] However, in the fuel cell system 1 according to the invention, nitrogen N2 is supplied by the second tank 41

[0063] The flow rate of injected nitrogen N2 is controlled by the flow control means 42, 43 in a continuously variable manner, or in a bistable (open / closed) manner. Here, these means include, for example, two three-way valves 42, 43.

[0064] A first three-way valve 42 has an inlet connected to an outlet 44 of the second reservoir 41, and two outlets, a first outlet corresponding to a drain 46 and a second outlet corresponding to the inlet of a conduit 45 connected to the cathode compartment. Through the first three-way valve 42, the nitrogen N2 from the second reservoir 41 is either discharged to the outside via the drain 46, or into the conduit 45 connected to the inlet of the cathode compartment.

[0065] The purge 46 allows, for example, the second reservoir 41 to be emptied when it is too full in order to store an additional quantity of nitrogen from the supply system 2.

[0066] A second three-way valve 43 is connected to the air inlet line 3 described above. In particular, the second three-way valve 43 has one outlet and two inlets. The outlet is connected to the inlet of the cathode compartment. Regarding the two inlets, the first inlet supplies the inlet of the cathode compartment with humidified air, as part of the normal operation of the fuel cell 10, while the second inlet supplies nitrogen (N2) to the inlet of the cathode compartment, in order to decontaminate the fuel cell 10.

[0067] In particular, the second three-way valve also allows for mixing between the humidified airflow from the air inlet line 3 and the nitrogen N2 from the second reservoir 41.

[0068] The first three-way valve 42 and the second three-way valve 43 are both controlled by a central control unit 48. This central control unit 48 determines and applies a flow rate of nitrogen N2 to be supplied to the cathode compartment.

[0069] The decontamination system 4 also includes a voltage controller 47, in this case a DC-DC converter. This DC-DC converter is connected between the terminals of the fuel cell 10 and is adapted to apply a voltage between the anode and cathode compartments. More specifically, the DC-DC converter is controlled, for example by the central control unit 48, to apply voltage cycling between the terminals of the fuel cell 10 as part of a decontamination process (also called a regeneration process). This process involves injecting nitrogen (N2) from the second tank 41 into the cathode compartment and applying voltage cycling according to predefined patterns. This oxidizes the sulfur species (e.g., sulfur dioxide) accumulated on the fuel cell 10.

[0070] At the end of the decontamination process, the sulfur is evacuated by a fluid evacuation line 60. This fluid evacuation line communicates with the outlet of the anodic compartment and includes an exhaust silencer 61. The fluid evacuation line 60 serves in particular as an evacuation route to evacuate the water produced during the normal operation of the fuel cell 10.

[0071] In the first embodiment described here, the decontamination system 4 includes a pollution sensor 49. This pollution sensor 49 is functionally connected to the central control unit, in order to determine whether the decontamination process should be implemented.

[0072] In another embodiment, the decontamination process is applied to the fuel cell 10 at regular time intervals by the decontamination system 4, when the motor vehicle is stationary. In this context, no pollution sensor 49 is required.

[0073] Here, the pollution sensor 49 allows the decontamination system 4 to be activated only when necessary. In other words, the central control unit controls the flow regulation means 42, 43 and the voltage controller 47 according to the pollution measured by the pollution sensor 49. In order not to interfere with the normal operation of the combustion cell, the decontamination system 4 is activated when the vehicle is stationary.

[0074] For example, the pollution sensor includes a gas sensor adapted to measure atmospheric pollutant concentrations, in this case sulfur dioxide (SO2). Advantageously, the gas sensor is placed outside the vehicle's enclosure to measure pollutant concentrations in the ambient air. Here, it is assumed that the decontamination system 4 is activated when the sulfur dioxide (SO2) concentration exceeds a threshold concentration. For example, the threshold concentration is 50 ppb.

[0075] In one possible embodiment, the pollution sensor comprises a sensor adapted to measure an internal quantity of the fuel cell 10. For example, by internal quantity of the fuel cell 10, it may be understood as a resistance measurement, and / or a measurement of an ECSA parameter (for "electrochemically active surface"), and / or a measurement of a polarization curve. A suitable criterion is then defined based on the measured internal quantity, in order to implement the fuel cell decontamination strategy when deemed necessary.

[0076] The fuel cell system 1 described above makes it possible to implement a decontamination process (or strategy), some of the steps of which have already been detailed previously. Rather than releasing nitrogen into the atmosphere, the proposed process makes it possible to advantageously use the nitrogen N2 produced during the reforming reaction of ammonia NH3. The process, illustrated in [Fig. 2], comprises the following steps: - a reforming stage 71 of the ammonia NH3 stored in the first tank 21 into nitrogen N2 and hydrogen H2, by the reforming stage 24, - a purification step 72 of the nitrogen N2 from the reforming stage 24 by the purification stage 25, in order to isolate the nitrogen N2, - a storage step 73 of nitrogen N2 in the second tank, in which the nitrogen N2 is stored for use, - a decontamination step 74 of the fuel cell 10 by injection of nitrogen N2 from the second tank into the cathode compartment of the fuel cell 10.

[0077] In particular, as detailed previously, this decontamination step 64 can optionally be controlled by the central control unit. This unit is responsible for controlling and regulating the flow rate of nitrogen N2 to be supplied to the cathode compartment, based on information provided by the pollution sensor 49.

[0078] The present invention is in no way limited to the embodiment described and represented, but a person skilled in the art will be able to make any variation in accordance with the invention.

[0079] For example, in one possible embodiment, the purification stage may comprise different components, adapted to provide, on the one hand, dihydrogen Sufficiently pure hydrogen (H2) is supplied to the anodic compartment, and nitrogen is supplied to a second reservoir within the decontamination system. For example, the purification stage could include, in the order of gas flow, a unit specifically designed for filtering nitrogen (N2), followed by a unit designed for filtering ammonia (NH3), for example, using an adsorption system. The units would be arranged in series to produce purified hydrogen. The second reservoir would be connected to an outlet of the nitrogen filtration unit.

Claims

Demands

1. Fuel cell system (1) comprising: - a fuel cell (10) having an anodic compartment and a cathodic compartment, and - a power supply system (2) supplying the anodic compartment of said fuel cell (10) with dihydrogen (H2) and comprising a first reservoir (21) adapted to store ammonia (NH3), a reforming stage (24) adapted to reform the ammonia (NH3) from the first reservoir (21) into dihydrogen (H2) and to produce dinitrogen (N2), and a purification stage (25) adapted to filter the dinitrogen (N2) produced in the reforming stage (24), characterized in that the purification stage (25) communicates with a second reservoir (41) adapted to store the dinitrogen (N2) filtered by said purification stage (25), in that said second reservoir (41) communicates with the cathodic compartment of the fuel cell (10), and in that it is provided flow regulation methods (42,43) of nitrogen (N2) circulating from said second reservoir (41) to the cathode compartment of the fuel cell (10).

2. Fuel cell system (1) according to claim 1, wherein a voltage controller (47) is provided, adapted to apply a voltage between the cathode compartment and the anode compartment of the fuel cell (10).

3. Fuel cell system (1) according to claim 2, wherein a pollution sensor (49) and a central control unit (48) adapted to control the flow regulation means (42, 43) and the voltage controller (47) are provided as a function of the pollution measured by said pollution sensor (49).

4. Fuel cell system (1) according to claim 3, wherein said pollution sensor (49) comprises a gas sensor adapted to measure an atmospheric concentration of sulfur dioxide (SO2).

5. Fuel cell system (1) according to claim 3 or 4, wherein said pollution sensor (49) comprises a sensor adapted to measure a quantity internal to the fuel cell (10).

6. Fuel cell system (1) according to any one of claims 1 to 5, wherein the purification stage (25) includes a palladium membrane type system adapted to filter dinitrogen (N2).

7. Fuel cell system (1) according to any one of claims 1 to 6, wherein said purification stage (25) comprises a unit (252) adapted to convert ammonia (NH3) into dinitrogen (N2).

8. Fuel cell system (1) according to claim 7, wherein the unit (252) adapted to convert ammonia (NH3) into dinitrogen (N2) comprises a pressure reversal adsorption device.

9. Fuel cell system (1) according to any one of claims 7 or 8, wherein the unit (252) adapted to convert ammonia (NH3) into dinitrogen (N2) comprises a temperature-modulated adsorption device.

10. Motor vehicle comprising a fuel cell system (1) according to any one of claims 1 to 9.

11. A method for decontaminating a fuel cell system (1) according to any one of claims 1 to 9, said method comprising the following steps: - reforming (71) the ammonia (NH3) stored in the first tank (21) into nitrogen (N2) and hydrogen (H2) by the reforming stage (24), - purifying the nitrogen (N2) from the reforming stage (24) by the purification stage (25), - storing (73) the nitrogen (N2) in the second tank (41), - decontaminating (74) the fuel cell (10) by injecting nitrogen (N2) from the second tank (41) into the cathode compartment of the fuel cell (10).

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