Method for producing compressed hydrogen using an electrochemical system

Abstract

According to embodiments of the present disclosure, a method of producing hydrogen in a fuel cell includes passing ammonia under pressure to a cathode of the fuel cell, wherein the ammonia is decomposed into nitrogen and protons. The fuel cell includes an anode, a cathode, and a proton-conducting electrolyte between the cathode and the anode. The cathode includes an ammonia decomposition catalyst. The method further includes purging the nitrogen from the cathode, passing the protons through the proton-conducting electrolyte to the anode, and passing electrons from the cathode to the anode, wherein the protons and the electrons react under pressure to produce substantially pure hydrogen.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application Serial No. 63 / 048,264, filed July 6, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments described herein generally relate to methods for producing hydrogen, and more specifically to methods for producing compressed hydrogen from ammonia using fuel cells. Background Technology

[0004] Hydrogen has been studied as an energy source because it does not contain carbon dioxide (CO2), a major component of greenhouse gas (GHG) emissions. However, hydrogen has a low gravitational energy density and is difficult to handle due to its low liquefaction temperature. Various hydrogen carriers have been investigated, with ammonia being the most promising. In particular, ammonia has a low liquefaction pressure at room temperature and can be stored and transported efficiently. Furthermore, ammonia does not contain CO2 and has a 17 wt% higher hydrogen capacity compared to other liquid organic hydrogen carriers.

[0005] However, thermal decomposition is required to produce hydrogen from ammonia. Furthermore, the process typically includes a pressurization step to compress the hydrogen for final use in a hydrogen refueling station. Thermal decomposition and pressurization make the process inefficient and result in high operating and capital costs. Summary of the Invention

[0006] Based on the above, methods for hydrogen production and compression with improved efficiency may be required. The various embodiments described herein address these needs and relate to methods for producing and compressing hydrogen, as well as fuel cells for implementing these methods. In some embodiments, the fuel cell includes a positive electrode, a negative electrode, and a proton-conducting electrolyte disposed between the negative electrode and the positive electrode. The negative electrode includes an ammonia decomposition catalyst.

[0007] According to embodiments of this disclosure, a method for producing hydrogen in a fuel cell includes delivering ammonia to the negative electrode of the fuel cell under pressure, wherein the ammonia is decomposed into nitrogen and protons. The fuel cell includes a positive electrode, a negative electrode, and a proton-conducting electrolyte between the negative and positive electrodes. The negative electrode includes an ammonia decomposition catalyst. The method further includes venting the nitrogen from the negative electrode, allowing the protons to reach the positive electrode via the proton-conducting electrolyte, and transferring the electrons from the negative electrode to the positive electrode, wherein the protons and electrons react under pressure to produce substantially pure hydrogen.

[0008] These and other embodiments are described in more detail in the following detailed description and accompanying drawings. The accompanying drawings are included to provide a further understanding of the various embodiments and are incorporated in and form a part of this specification. The drawings illustrate the various embodiments described herein and, together with the description, serve to explain the principles and operation of the claimed subject matter. Attached Figure Description

[0009] Now refer to the exemplary embodiments in the accompanying drawings:

[0010] Figure 1 Illustrations of exemplary fuel cells according to one or more embodiments shown and described herein; and

[0011] Figure 2 This is another illustration of an exemplary fuel cell according to one or more embodiments shown and described herein. Detailed Implementation

[0012] Specific embodiments of this application will now be described. However, this disclosure may be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

[0013] Figure 1 An exemplary fuel cell 100 is shown. The fuel cell 100 includes a negative electrode 102, an electrolyte 104, and a positive electrode 106.

[0014] In various embodiments, the negative electrode 102 is formed of a perovskite material, such as strontium-doped lanthanum iron cobalt oxide (LSCF)-based perovskite, for example, La. 0.6 Sr 0.4 CoO 3-δ Other exemplary negative electrode compositions include strontium-doped lanthanum ferrite (LSF) materials and lanthanum strontium manganate (LSM) materials. In one embodiment, negative electrode 102 is formed from a metal substrate, such as nickel. In another embodiment, negative electrode 102 is a composite material formed from nickel and an electrolyte. For example, the electrolyte may be the same material used to form electrolyte 104.

[0015] The negative electrode 102 also includes an ammonia decomposition catalyst. This ammonia decomposition catalyst is configured to convert ammonia (NH3) into protons (H) according to the following reaction. + ), electron (e - ) and nitrogen (N2):

[0016] 2NH3→6H + +N2+6e -

[0017] Protons (H) produced by ammonia decomposition catalyst + The proton feed is provided to the positive electrode 106 via the electrolyte 104. Nitrogen gas (N2) produced by the ammonia decomposition catalyst is purged from the negative electrode 102 through the outlet 108 of the fuel cell 100. Electrons (e) are then transferred to the positive electrode. - It is transmitted to the positive electrode 106 through electronic circuit 110.

[0018] In various embodiments, the ammonia decomposition catalyst is a metal-based decomposition catalyst. This metal-based decomposition catalyst can be, for example, an ammonia decomposition catalyst based on nickel, cobalt, iron, ruthenium, or combinations thereof.

[0019] Electrolyte 104 is a proton-conducting electrolyte that transports protons from the negative electrode 102 to the positive electrode 106. The proton-conducting electrolyte can be a solid oxide electrolyte. It may include, for example, doped barium cerate or barium zirconate, SrCeO3, BaZrO3, or combinations thereof. Other proton-conducting solid materials known to those skilled in the art are also considered.

[0020] In various embodiments, the cathode 106 comprises, for example, a perovskite material, such as a strontium-doped lanthanum iron cobalt oxide (LSCF)-based perovskite, such as La 0.6 Sr 0.4 CoO 3-δ Other exemplary cathode compositions include strontium-doped lanthanum ferrite (LSF) materials and lanthanum strontium manganate (LSM) materials. In an embodiment, cathode 106 may be formed from a metal substrate, such as nickel.

[0021] In operation, such as Figure 1 and Figure 2 As shown, ammonia feed forces ammonia (NH3) into the system under pressure. For example, as... Figure 2 As shown, ammonia can be supplied from ammonia tank 202 to negative electrode 102 via booster pump 204. When NH3 comes into contact with negative electrode 102, the ammonia decomposition catalyst decomposes ammonia into nitrogen (N2) and protons (H2O). + ) and electrons (e - Nitrogen (N2) gas is purged from the negative electrode through outlet 108 along with excess ammonia. Figure 2 As shown, N2 and NH3 can be sent to separator 208 through cooler 206, where N2 is purged from the system and NH3 is returned to ammonia tank 202.

[0022] Proton (H) + Protons travel from the negative electrode 102 through the proton-conducted electrolyte 104 to the pressurized positive electrode 106, while electrons are transferred to the positive electrode 106 via the electronic circuit 110. At the positive electrode 106, protons (H+)... + ) Accept electrons (e -The following reaction produces essentially pure compressed hydrogen gas (H2):

[0023] 2H + +2e - →H2

[0024] Electronic circuit 110 uses an electron flow to power the device.

[0025] Negative electrode 102, positive electrode 106, or both negative electrode 102 and positive electrode 106 can be independently pressurized using, for example, a pump, valve, regulator, or a combination thereof. In some embodiments, positive electrode 106 can be pressurized via a pressure reducing valve or back pressure regulator, while negative electrode 102 can be pressurized via a back pressure regulator at the nitrogen exhaust line. Figure 2 As shown, H2 enters the hydrogen tank 212 through the pressure reducing valve 210. In this embodiment, the positive electrode 106 can be pressurized to the set value of the pressure reducing valve 210. It should be understood that there are no particular limitations on the means of pressurizing the positive electrode 106, the negative electrode 102, or both the negative electrode 102 and the positive electrode 106, as long as the pressure can be controlled. Without being constrained by theory, it is believed that pressure control at the negative electrode 102 can improve the thermodynamic characteristics of the electrochemical reaction. Furthermore, it is believed that pressurizing the negative electrode can reduce the pressure difference applied to the battery and the sealant.

[0026] The various embodiments described herein enable the single-step separation and compression of hydrogen from ammonia. This single-step separation and compression can drive the pressurization of pure H2 without requiring energy-intensive mechanical compressors or additional H2 purification processes. Furthermore, the various embodiments described herein can generate pure H2 from NH3 without using precious metal catalysts, such as platinum, which can be expensive and deactivated at high current densities.

[0027] According to one aspect, alone or in combination with any other aspect, a method for converting ammonia into substantially pure hydrogen (H2) in a fuel cell includes delivering ammonia under pressure to the negative electrode of the fuel cell, wherein the fuel cell includes a negative electrode having an ammonia decomposition catalyst, a positive electrode, and a proton-conducting electrolyte disposed between the negative electrode and the positive electrode, and wherein ammonia is decomposed into nitrogen (N2) and protons (H2). + ); purge the nitrogen gas (N2) from the negative electrode; so that the protons (H) + The protons conduct the electrolyte and enter the positive electrode; and the electrons (e) are transferred to the positive electrode. - ) is transferred from the negative electrode to the positive electrode, wherein the protons (H) are transferred from the negative electrode to the positive electrode. + ) accept the electron (e - ( ), to produce essentially pure hydrogen gas (H2) under pressure.

[0028] According to the second aspect, alone or in combination with any other aspect, the proton-conducting electrolyte includes a solid oxide electrolyte.

[0029] According to the third aspect, alone or in combination with any other aspect, the proton-conducting electrolyte comprises doped barium cerate or barium zirconate.

[0030] According to the fourth aspect, alone or in combination with any other aspect, the ammonia decomposition catalyst comprises a metal-based decomposition catalyst.

[0031] According to the fifth aspect, alone or in combination with any other aspect, the metal-based decomposition catalyst comprises one or more metals selected from the group consisting of nickel, cobalt, iron, ruthenium, and combinations thereof.

[0032] According to the sixth aspect, alone or in combination with any other aspect, the negative electrode comprises a complex of nickel and an electrolyte.

[0033] According to the seventh aspect, alone or in combination with any other aspect, the positive electrode comprises perovskite.

[0034] According to aspect eight, alone or in combination with any other aspect, the perovskite includes La 0.6 Sr 0.4 CoO 3-δ .

[0035] According to the ninth aspect, the negative electrode may be pressurized by a pump, valve, or combination thereof, alone or in combination with any other aspect.

[0036] According to aspect ten, the positive electrode may be pressurized by a pump, valve, or combination thereof, alone or in combination with any other aspect.

[0037] Having described the subject matter of this disclosure in detail and with reference to specific embodiments, it should be noted that the various details described herein should not be construed as implying that such details relate to elements that are fundamental components of the various embodiments described herein, even where specific elements are illustrated in each of the accompanying figures. Rather, the appended claims should be considered the sole expression of the breadth of this disclosure and the corresponding scope of the various embodiments described herein. Furthermore, it will be apparent that modifications and variations are possible without departing from the scope of the appended claims.

[0038] Unless the context clearly specifies otherwise, the singular forms “a,” “an,” and “the” include plural indicators.

[0039] For the purposes of describing and defining this disclosure, it should be noted that the term "about" is used in this disclosure to indicate the degree of uncertainty attributable to any quantitative comparison, numerical value, measurement, or other representation. The term "about" is also used in this disclosure to indicate the extent to which a quantitative representation may differ from the stated reference value without causing a fundamental change in the function of the subject matter.

[0040] As used in this disclosure and the appended claims, the words “comprise,” “have,” and “include,” and all their grammatical variations, are intended to have an open, non-limiting meaning and do not exclude other elements or steps.

[0041] Furthermore, the term "substantially composed of" is used in this disclosure to refer to a quantitative value that does not materially affect the essential and novel features of this disclosure. For example, a chemical stream "substantially composed of" a particular chemical component or group of chemical components should be understood to include at least about 99.5% of that particular chemical component or group of chemical components.

[0042] It should be understood that any two quantitative values ​​assigned to an attribute can constitute a range of that attribute, and all combinations of ranges formed by all stated quantitative values ​​of a given attribute are considered in this disclosure.

[0043] As used in this disclosure, terms such as “first” and “second” are arbitrarily designated and are used merely to distinguish two or more instances or components. It should be understood that the words “first” and “second” have no other use and are not part of the component name or description, nor do they necessarily define the relative position, location, or order of the components. Furthermore, it should be understood that the mere use of “first” and “second” does not require the existence of any “third” component, although such a possibility is considered within the scope of this disclosure.

Claims

1. A method for converting ammonia into substantially pure hydrogen (H2) in a fuel cell, comprising: Ammonia is delivered to the pressurized negative electrode of the fuel cell under pressure using a booster pump. The fuel cell includes a pressurized negative electrode with an ammonia decomposition catalyst, a positive electrode, and a proton-conducting electrolyte disposed between the pressurized negative electrode and the pressurized positive electrode, and decomposes ammonia into nitrogen (N2), protons, and electrons. The nitrogen (N2) is purged from the pressurized negative electrode through an exhaust line including a back pressure regulator. The protons conduct electrolyte through the protons and enter the pressurized positive electrode; and The electrons are transferred from the pressurized negative electrode to the pressurized positive electrode, wherein the protons accept the electrons to produce the substantially pure hydrogen gas (H2) under pressure; and The substantially pure hydrogen (H2) at the pressurized positive electrode is pressurized by passing it through a pressure reducing valve, wherein the combination of a booster pump, a back pressure regulator for the exhaust line, and the pressure reducing valve pressurizes the pressurized negative electrode and the pressurized positive electrode.

2. The method according to claim 1, wherein the proton-conducting electrolyte comprises a solid oxide electrolyte.

3. The method according to claim 1, wherein the proton-conducting electrolyte comprises doped barium cerate or barium zirconate.

4. The method according to claim 1, wherein the ammonia decomposition catalyst comprises a metal-based decomposition catalyst.

5. The method of claim 4, wherein the metal-based decomposition catalyst comprises one or more metals selected from the group consisting of nickel, cobalt, iron, ruthenium, and combinations thereof.

6. The method of claim 1, wherein the pressurized negative electrode comprises a complex of nickel and an electrolyte.

7. The method of claim 1, wherein the pressurized positive electrode comprises perovskite.

8. The method of claim 7, wherein the perovskite comprises La 0.6 Sr 0.4 CoO 3-δ .

9. The method of claim 6, wherein the electrolyte of the composite comprises doped barium cerate, doped barium zirconate, SrCeO3, BaZrO3, or a combination thereof.

10. The method according to claim 1, further comprising: Excess ammonia and nitrogen are purged together through the exhaust line; Nitrogen gas and excess ammonia are exposed to a cooler to form cooled nitrogen gas and cooled ammonia gas. and The cooled ammonia is separated from the cooled nitrogen gas by a separator.

11. The method of claim 10 further comprises returning the cooled ammonia to the ammonia tank and then recirculating it together with the ammonia in the ammonia tank to the pressurized negative electrode to form additional nitrogen (N2) and protons.

12. The method of claim 1, wherein the pressure reducing valve is connected to the hydrogen tank such that pressurized hydrogen is transferred from the positive pressure electrode to the hydrogen tank via the pressure reducing valve.

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