Method for manufacturing an alkaline ammonia electrolysis cell with ammonia corrosion resistance and operating the same stably

Description

FIELD OF THE INVENTION

The present invention relates to a method for manufacturing an alkaline ammonia electrolysis cell, and more particularly to a method for manufacturing and reliably driving an alkaline ammonia electrolysis cell that is ammonia corrosion resistant.

BACKGROUND

Hydrogen is a clean fuel that can be produced and supplied in large quantities and is attracting attention as an energy carrier, capable of storing and transporting other energy sources alongside electrical energy through hydrogen production by water electrolysis. When utilized as an energy medium, hydrogen, due to its higher energy density and eco-friendliness compared to liquid fuels or batteries, offers an optimal solution to offset the instability of grids powered by intermittent renewable sources such as wind energy.

Utilizing hydrogen as an energy carrier necessitates the development of storage forms suitable for mass storage and transportation. Research is ongoing for hydrogen storage in forms such as high-pressure hydrogen, liquefied hydrogen, LOHC, and ammonia. Ammonia, in particular, is noteworthy as a hydrogen storage medium because of its existing infrastructure, high energy density, and reduced explosion risk.

The most extensively researched and applied method for hydrogen extraction from ammonia is ammonia pyrolysis. At the laboratory scale, ammonia decomposes over 95% at temperatures above 400° C., but the low activity of commercial catalysts necessitates temperatures above 600° C. to improve the degradation rate. Moreover, the pyrolysis method faces challenges in achieving high purity due to the limitations of adsorbents and requires large-scale plants, making it costly as tens of thousands of Nm³/h capacity is needed.

The Ammonia Electrolysis Cell (AEC), utilizing an electrochemical technique for hydrogen extraction, involves the Ammonia Oxidation Reaction (AOR, NH₃ into N₂) at the oxidation electrode and the Hydrogen Evolution Reaction (HER, Water into H₂) at the reduction electrode. The overall reaction, 2NH₃→3H₂+N₂, at an energy level of E=0.06, boasts about a 95% lower voltage requirement compared to the E=1.23 needed for water electrolysis. Additionally, compared to ammonia pyrolysis, it benefits from a significantly low theoretical voltage of 0.06V and employs a simplified electrochemical system composed of a cathode, anode, and diaphragm.

However, the AOR occurring at the AEC's oxidation electrode, a six-electron reaction, exhibits a high overvoltage above 0.4V, generally restricting catalysts to precious metals. The reaction intermediates strongly adhere to the surface, causing significant activity loss due to surface poisoning. Moreover, as ammonia pyrolysis has been more extensively researched, numerous components such as the catalysts, electrodes, and separators in the AEC require further optimization. Additionally, the high corrosiveness of ammonia can lead to the corrosion of materials commonly used in conventional electrolysis and fuel cells, such as aluminum, carbon, and rubber.

Currently, platinum (Pt), used as a primary catalyst for AOR, exhibits the highest activity among precious metals but also presents an overpotential of 0.6-0.7V in the AEC, with a very high N Species Adsorption Energy, leading to significant surface poisoning. Notably, studies using Differential Electrochemical Mass Spectroscopy (DEMS) and Surface-enhanced Raman Spectroscopy (SERS) have shown that during the AOR process, *N, completely deprotonated of H, not only facilitates N₂ production but also progresses to oxidize *NH_x and OH⁻ (x=0, 1, 2, 3) at higher voltages, acting as poisoning species.

SUMMARY OF THE INVENTION

Therefore, the present invention aims to provide an alkaline ammonia electrolysis cell and a cell driving method that allows the use of a Pt catalyst as an AEC electrode by addressing the issue of electrode surface poisoning, which significantly reduces reaction current density.

In particular, the present invention seeks to improve durability and performance by establishing operating conditions and cell configurations that prevent poisoning in the reaction mechanism through the Anode & Cathode Pulse Sequence Method.

The problems addressed by the present invention are not limited to those mentioned above, and other issues not specified will become apparent to those skilled in the art from the following description.

Accordingly, an alkaline ammonia electrolysis cell system according to the present invention includes an end plate, first and second collector plates, a separator plate, a porous transport layer, a membrane, and a voltage driving part. The separator plate includes a fluid flow path through which ammonia and electrolyte are supplied, and hydrogen and nitrogen are released. The voltage driving part can apply a driving voltage for a first period and a rest voltage for a second time period between the first and second collector plates to remove *NH_x and OH⁻.

In this case, the drive voltage may be at least 0.6V and no more than 0.9V, and more preferably the drive voltage may be at least 0.7V and no more than 0.8V.

Furthermore, the rest voltage may be 0.2 V or less.

Furthermore, the voltage driving part may drive voltages such that the first collector plate and the second collector plate be applied to in reverse.

Further, the ammonia electrolysis cell system may be operated at temperatures above 70° C.

Further, the separator plate may comprise Ni, and the end plate may comprise epoxy.

It further comprises a separator gasket receiving the porous transport layer, a porous transport layer support gasket, and a membrane support gasket, wherein the separator gasket comprises polytetrafluoroethylene (PTFE), the porous transport layer support gasket comprises polyphenylsulfone (PPSU), and the membrane support gasket may comprise an ethylene-propylene diene monomer (EPDM).

Further, the first period may be at least one minute, and the second time period may be authorized at 20% to 100% of the first period.

A method of driving an ammonia electrolysis cell according to one embodiment of the present invention, wherein an ammonia electrolysis cell system comprising an end plate, first and second collector plates, a separator plate, a porous transport layer, a membrane, and a voltage drive part, the separator plate comprising a fluid flow path, the fluid flow path being supplied with ammonia and electrolyte through the fluid flow path; applying a driving voltage between the first and second collector plates for a first period by the voltage drive part; hydrogen and nitrogen being released through the fluid flow path; and applying a rest voltage for a second hour by the voltage drive part to remove *NH_x and OH⁻.

Specific details of other embodiments are included in the detailed description and drawings.

Accordingly, the present invention provides an alkaline ammonia electrolysis cell and a cell operation method that enable the use of a Pt catalyst as an AEC electrode by addressing the issue of electrode surface poisoning and significantly reducing the reaction current density.

In particular, the present invention can improve durability and performance by establishing operating conditions and cell configurations that prevent poisoning in the reaction mechanism through the Anode & Cathode Pulse Sequence Method.

Meanwhile, the present invention pertains to a device that converts ammonia, a favorable energy carrier in terms of transport, storage, and infrastructure, into hydrogen, an indispensable technology for Korea, which relies heavily on energy imports. Currently, several major Korean corporations, including KEPCO, Hyundai Oil Bank, Lotte Chemical, and POSCO, are researching the importation and utilization of ammonia as an energy source. Most hydrogen production presently relies on pyrolysis, which suffers from the drawback of incomplete reaction between ammonia and hydrogen. Therefore, this invention can initially be utilized for converting unreacted ammonia into hydrogen, ranging from small-scale ammonia conversion devices to ones capable of direct ammonia-to-hydrogen conversion at gas stations inland, should the transportation of ammonia be feasible. Ammonia has similar phase change properties to LPG, enabling the use of existing LPG infrastructure; thus, converting locally transported ammonia into hydrogen at refueling stations could address the issues of hydrogen transport and storage.

Should the invention be scalable and applicable on a larger scale, it could serve as a device to produce hydrogen from ammonia with greater efficiency, potentially replacing pyrolysis entirely.

The effects of the present invention are not limited to the examples cited above, and other benefits will be apparent to those skilled in the art from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are schematic diagrams of an alkaline water electrolysis cell according to one embodiment of the present invention.

FIG. 3A is a graph showing a polarization curve according to one embodiment of the present invention and FIG. 3B is a graph showing the variation of current density with applied voltage over time.

FIGS. 4A and 4B illustrate an experiment in accordance with one embodiment of the present invention, wherein FIG. 4A is a graph of an electrolysis experiment in which 0.8 V was applied continuously to an ammonia electrolysis cell for 20 minutes, and FIG. 4B is a graph of the polarization curve after the 20-minute electrolysis experiment.

FIGS. 5A and 5B are a graph representing an experiment according to one embodiment of the present invention, wherein FIG. 5A is a graph of an electrolysis experiment for 10 minutes when an oxidation electrode and a reduction electrode are applied with a switching potential of 0.8 V and 0 V between them, and FIG. 5B is a graph representing the polarization curve of the switching voltage application.

FIGS. 6A to 6C and FIGS. 7A and 7B are a graph representing experiments in accordance with one embodiment of the present invention, wherein in FIG. 6A the current density is plotted when the anode and cathode are subjected to an intervening voltage of 0.8 V for 1 minute and 0 V for 10 seconds; in FIG. 6B, 0.8 V for 3 minutes and 0 V for 30 seconds, and in FIG. 60 0.8 V for 5 minutes and 0 V for 60 seconds. Moreover, FIG. 7A presents a graph depicting an embodiment of the present invention, where 0.8 V is applied for 5 minutes followed by 0 V for 3 minutes, repeated over a 5-hour period while FIG. 7B shows a graph where a steady voltage of 0.8 V is applied continuously for 5 hours.

FIGS. 8A and 8B show the calibration graph for UV-vis.

FIGS. 9A and 9B are UV-vis experimental graphs based on CV and pulse experiments according to one embodiment of the present invention.

FIGS. 10A to 13C are graphs showing the variation of current when 0.8 V and 0 V are applied across 0.8 V and 0 V for various times, according to one embodiment of the present invention.

FIG. 14 is a graph depicting current density over time to illustrate durability when operating voltage and rest voltage are applied for extended periods of time in accordance with one embodiment of the present invention.

FIG. 15A is a graph showing the case where no rest voltage is applied, FIG. 15B is a graph showing the case where a voltage with reversed polarity is applied, and FIG. 15C is a graph showing the current density over time in the case where a voltage with reversed polarity is applied from the state in FIG. 15B.

FIGS. 16A to 17 are graphs of current density as a function of temperature, in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. However, the technology disclosed herein is not limited to the embodiments described herein and may be embodied in other forms. However, the technology disclosed herein is not limited to the embodiments described herein and may be embodied in other forms. In the drawings, the dimensions, such as width and thickness, of the components of each apparatus are somewhat enlarged in order to clearly depict the components of the apparatus.

Also, while only a portion of the components are shown for ease of illustration, those skilled in the art will readily recognize the remaining components. Throughout, the drawings are described from an observer's perspective and whenever an element is referred to as being located above or below another element, this is intended to include both the sense that the element may be located directly above or below the other element or that additional elements may be interposed between them.

Further, one of ordinary skill in the art will be able to implement the ideas of the present application in various other forms without departing from the technical ideas of the present application. And, in the plurality of drawings, like numerals refer to substantially the same elements.

In addition, expressions in the singular shall be understood to include the plural unless the context clearly indicates otherwise, and terms such as include or have are intended to specify the presence of the described feature, number, step, action, component, part, or combination thereof, and not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

Further, in carrying out the method or method of manufacture, the steps comprising the method may occur in a different order from that specified unless the context clearly indicates a particular order, i.e., the steps may occur in the same order as specified, may occur substantially simultaneously, or may occur in reverse order.

The present invention will now be described in more detail.

FIGS. 1 and 2 are drawings illustrating an ammonia electrolysis cell system 100 according to one embodiment of the present invention. Referring to FIGS. 1 and 2, the ammonia electrolysis cell system 100 according to the present invention includes: end plates 110, 210; current collector plates including a first collector plate 120 and a second collector plate 220; bipolar plates 130, 230; bipolar plate gaskets 140, 240; porous transport layer support gaskets 150, 250; porous transport layer 160, 260; membrane support gaskets 170 and membrane 180. The electrolyte cell of the ammonia electrolyzer system 100 is composed of active and durable materials that can withstand high concentrations of ammonia alkali conditions, including corrosion-resistant materials.

The end plates 110, 210 allow the bolts/nuts to uniformly crimp and engage the respective configurations when assembling the ammonia electrolyzer system 100, and protect the separator plates 130, 230 when engaged and crimped. The end plates 110, 210 may include, for example, epoxy as a material.

The collector plates 120, 220, including the first collector plate 120 and the second collector plate 220, can be connected to a power source to supply the entire system with the current (electrons) required for water electrolysis. The manner in which the power source is driven according to the present invention will be described in detail later. The collector plates 120, 220 may comprise, for example, copper with gold plating (Au/Cu) as a material. According to one embodiment of the present invention, a drive voltage, e.g., a drive voltage of 0.6 V to 0.9 V, preferably 0.7 to 0.8 V, may be applied between the first collector plate 120 and the second collector plate 220 for a first period, followed by a rest voltage for a second period.

The separator plates 130, 230 have fluid flow paths formed therein, through which an electrolyte (e.g., KOH) is supplied and through which nitrogen generated by the oxidation reaction in the cathode and hydrogen generated by the reduction reaction in the anode are discharged. The separator plates 130, 230 may be made of, for example, Ni.

The separator gaskets 140, 240 can be made of, for example, polytetrafluoroethylene (PTFE), which can maintain airtightness while also resisting corrosion.

The porous transport layer support gaskets 150, 250 may be made of polyphenylsulfone (PPSU), for example, to facilitate support of the porous transport layers 160, 260, such as nickel foam, while maintaining airtightness and preventing corrosion.

The porous transport layer electrodes 160, 260 may comprise, for example, Pt, Pt/C as a catalyst, and may be made of, for example, nickel foam as a catalyst coating support.

The membrane support gasket 170 may support the membrane 180 and may be made of, for example, an ethylene-propylene diene monomer (EPDM) to maintain airtightness.

The membrane 180 is electrically insulating and acts as a medium for transferring hydroxide (OH⁻) ions during hydrogen production, while also physically separating hydrogen from oxygen.

The membrane material must be durable in a strongly basic (30% KOH) environment above 80° C. and have low gas permeability to prevent the hydrogen and oxygen gases from both electrodes from mixing. At the same time, high ionic conductivity is required. The membrane 180 may be made of, for example, Zirfon or the like.

The power drive 300 supplies a drive voltage to the collector plates 120, 220 or a rest voltage to drive the collector plates 120, 220 to minimize poisoning. The power drive 300 according to one embodiment of the present invention will be described in more detail when describing the operation of the ammonia electrolyzer system 100.

One of the important factors in ammonia alkaline cells is the corrosivity of ammonia. Ammonia is corrosive, which makes it difficult to drive the cell. Conventional aluminum end plates are corroded by ammonia, and carbon separator plates are also corroded by ammonia, which greatly reduces their durability.

To solve this problem, the present invention uses epoxy end plates and Ni separator plates to produce a cell that is durable even when reactions occur in high concentration ammonia and alkali environments.

A method of driving an ammonia electrolysis cell according to one embodiment of the present invention, wherein an ammonia electrolysis cell system comprising: end plates; first and second collector plates; a separator plate; a porous transport layer; a membrane; and a voltage drive part, the separator plate comprising: a fluid flow path, the fluid flow path being supplied with ammonia and electrolyte through the fluid flow path; applying a drive voltage between the first and second collector plates for a first period by the voltage drive part; wherein hydrogen and nitrogen are released through the fluid flow path; and wherein the voltage drive part applies a rest voltage for a second time period to remove *NH_x and OH⁻.

In this case, the drive voltage may be at least 0.6V and no more than 0.9V, and more preferably the drive voltage may be at least 0.7V and no more than 0.8V.

Furthermore, the rest voltage may be 0.2V or less.

Furthermore, the voltage driving part may apply a voltage to the first collector plate as the rest voltage and a voltage to the second collector plate in reverse.

Further, the ammonia electrolysis cell system can be operated at temperatures above 70° C.

Further, the first period may be at least one minute, and the second time period may be authorized at 20% to 100% of the first period.

Hereinafter, with reference to FIGS. 3-6, a method of operating the ammonia electrolyzer system 100 according to one embodiment of the present invention will be described in more detail.

The ammonia electrolysis cell system 100 used in one embodiment of the present invention has the configuration shown in FIGS. 1 and 2, wherein ammonia and KOH solutions are injected on both sides of the membrane 180. The solution injected into the membrane 180 is then contacted with catalysts on the surface of the porous transport layer electrodes 160 and 260 on both sides, resulting in an ammonia oxidation reaction (AOR) at the oxidation electrode 160 of the porous transport layer electrodes 160 and 260 and a hydrogen evolution reaction (HER) at the reduction electrode 260 of the porous transport layer electrodes 160 and 260.

The porous transport layer electrodes 160, 260 all used the same porous transport layer electrodes 160, 260 as oxidation/reduction electrodes, for example, the porous transport layer electrodes 160, 260 incorporated Pt/C into nickel foam as a catalyst. In this case, each electrode produces nitrogen and hydrogen, and the hydroxide ions (OH⁻) produced at the reduction electrode 260 migrate across the membrane to the oxidation electrode 160, where they are used in the ammonia oxidation reaction. The theoretical reaction voltage between ammonia oxidation and hydrogen evolution is 0.06V. However, as with all electrochemical reactions, an overpotential causes the reaction to occur above 0.06 V.

Referring to the polarization curve in FIG. 3A, it can be seen that the applied driving voltage is approximately 0.6 V and no more than 0.9 V when the highest current produces the most hydrogen.

More specifically, referring to FIG. 3B, the current density during ammonia electrolysis was measured for each applied voltage, and the graph shows that the current density starts to increase above 0.5 V, steadily increases until 0.8 V, and then starts to decrease rapidly after a certain period of time from 0.9 V. Therefore, it can be seen that the voltage at which the most hydrogen is produced is approximately between 0.6 V and 0.9 V, and preferably between 0.7 V and 0.8 V. Therefore, it can be seen that the voltage at which the most hydrogen is produced is roughly between 0.6V and 0.9V, preferably between 0.7V and 0.8V, and that hydrogen is produced most efficiently between 0.6V and 0.9V.

Referring to FIGS. 4 and 5, the data in FIG. 4A and FIG. 4B are measurements of the polarization curve from 0 to 1 V after undergoing Ammonia Electrolysis with a driving voltage of 0.8 V applied for 20 minutes under 8 M KOH+1 M NH₃ conditions. The data in FIG. 5A and FIG. 5B were then subjected to an Anode & Cathode pulse sequence technique for 5 minutes to remove the *NH_x and OH⁻ materials attached to the electrode surface, after which the polarization curves were measured again to confirm the activity of the electrode.

The present study confirms that *NH_x and OH⁻ covering the electrode surface are reduced back to produce NH₃ at a rest voltage of +0.2 V or less, and that the problem of electrode surface toxicity of the ammonia electrolysis cell system 100 can be solved. In particular, it was confirmed that when a voltage of 0.2V is applied to the electrode of the ammonia electrolysis cell system 100, *NH_x and OH⁻ can be removed temporarily to increase the reduced activity again.

Referring to FIG. 5, it can be seen that the porous transport layer electrodes 160, 260 were subjected to a technique in which a potential of 0.8 V and 0 V was repeatedly switched between the oxidation and reduction electrodes from a power source (hereinafter referred to as the Anode & Cathode Pulse Sequence Method), and the problem of poisoning of the oxidation electrode 160 was solved. During the Anode & Cathode Pulse Sequence Method, an oxidation potential (cathodic potential) is applied to the electrode that has been poisoned by ammonia, and a voltage of 0.2V or less is applied to remove the *NH_x and OH-substances attached to the electrode surface to increase the decreased activity again.

As shown in FIGS. 4 and 5, when the polarization curve was measured after conducting ammonia electrolysis at 0.8 V for 20 minutes, the peak current demonstrated an activity of merely about 200 mA/cm². However, after applying the Anode and Cathode Pulse Sequence Method, the measured polarization curve showed an increased activity up to 1000 mA/cm².

Meanwhile, FIG. 6 illustrates the current density when voltages were applied under the conditions of 3M KOH+3M NH₃, sequentially from left to right: 0.8V driving voltage for 1 minute, 0V rest voltage for 10 seconds, 0.8V driving voltage for 3 minutes, 0V rest voltage for 30 seconds, 0.8V driving voltage for 5 minutes, and OV rest voltage for 60 seconds. When OV and 0.8V are alternated as the driving voltage for electrolysis, it is observed that the current density significantly increases as the *NH_x and OH⁻ substances are eliminated during the OV rest voltage period. With the alternating application of OV and 0.8V, the hourly current density is noted to reach a substantial 800 mA/cm².

Referring to FIG. 7, the pulsed experiment first applied 0.8V for 5 min and OV for 3 min, and repeated for 5 hours. The constant voltage experiment applied 0.8V for 5 hours, and these experiments are named pulse and CV experiments, respectively. The pulse experiment showed a relatively high current, and the maximum current was about 300 mA cm⁻².

Referring to FIG. 8, a UV-vis experiment was conducted to measure the ammonia consumed during the experiment. The UV-vis is an instrument that measures concentration based on color change related to ammonia concentration, by adding a colored solution. Calibration was performed from 0.001M to 0.004M, and a linear graph was obtained.

Referring to FIG. 9 and Tables 1 and 2, it can be observed that in the cyclic voltammetry (CV) experiment, about 77% of the ammonia reacted within 5 hours, while in the pulse experiment, the reaction exceeded 99%. Thus, it is evident that the results proposed by the present invention are significantly more effective.

On the other hand, FIGS. 10A to 13C and Table 3 are graphs of the relationship between voltage run time and downtime. The experiments in FIGS. 10A to 13C are experiments to investigate the relationship between voltage run time and rest time when a pulse pressurization experiment is performed. In the experiments, the operating voltage was set to 0.8 V and the off voltage was set to 0 V, and the operating time was set as shown in the following table.

Referring to FIGS. 10A to 13C, each experiment was conducted for the duration listed in the table, and the average charge was calculated by integrating the charge over the duration of the experiment and then dividing by the total hours. In electrochemical reactions, the quantity of charge is equivalent to the amount of reaction; therefore, a larger Q value indicates more ammonia to hydrogen conversion occurs within the same time period. Although a longer rest time results in higher current values, no electrochemical reaction occurs during this time, thus an appropriate rest duration is necessary. When calculated using the average current, experiments with 5 minutes of voltage application followed by 5 and 3 minutes of rest, and 1 minute of voltage application followed by 30 and 20 seconds of rest, showed higher current values.

In summary, experiments were conducted with the drive voltage applied for 5 minutes (first period), setting the rest voltage from 0.5 to 5 minutes (second period); with the drive voltage applied for 1 minute, setting the rest voltage from 0.3 to 1 minute; and with the drive voltage applied for 10 seconds, setting the rest voltage from 3 to 10 seconds. The results showed high current density when the drive voltage was applied for 5 minutes and the rest voltage was applied for 2 minutes or more, and when the drive voltage was applied for 1 minute and the rest voltage was applied for 20 seconds or more. Thus, it was found that high current density occurs when the drive voltage is applied for 1 minute or more and the rest voltage is applied for 20% to 100% of the drive voltage application time. This indicates that when the drive voltage application time is short, the current density is low because the current supplied is small, so the current must be supplied for a certain period, and the rest voltage must be applied for a sufficient duration to ensure adequate time for the removal of toxic substances.

As mentioned above, when a rest voltage is applied between voltage applications (including the case of applying 0 V), it was confirmed that the toxicity problem of the oxidation electrode 160 in the ammonia electrolysis cell system 100 is resolved over the long term, and the durability is increased. Referring to FIG. 14, it can be seen that applying a rest voltage between the voltage applications in the ammonia electrolysis cell system 100 maintains a stable current density even with long-term use, indicating increased durability.

The embodiment above illustrates an experiment where drive voltage and rest voltage are alternately applied between the collector plates. However, the inventors of the present application continued the experiment by applying a voltage with reversed polarity as the rest voltage. In this case, reversing the polarity of the initially applied power source means, for example, if 0.8 V was applied to the first collector plate 120 and 0 V to the second collector plate 220, applying a voltage with reversed polarity might mean applying 0 V to the first collector plate 120 and 0.8 V to the second collector plate 220. The reverse case can also be considered as applying the drive voltage by reversing the polarity.

FIG. 15A shows the case where no rest voltage is applied, FIG. 15B shows the case where a voltage with reversed polarity is applied, and FIG. 15C is a graph showing the current density over time in the case where a voltage with reversed polarity is applied from the state in FIG. 15B.

In FIG. 15A, it can be observed that the current density rapidly decreases over time, while in FIGS. 15B and 15C, the current density decreases slowly when the polarity is reversed, and the voltage is applied.

FIGS. 16 and 17 are graphs showing the variation of current density when a drive voltage and a rest voltage are applied as a function of the temperature of the ammonia electrolyzer system 100. FIG. 16A is a graph showing the change in current density when no ammonia is supplied to the electrolytic cell system 100, and FIG. 16B is a graph showing the change in current density when no ammonia is supplied to the electrolytic cell system 100.

Referring to FIGS. 16A and 16B, it can be seen that the current is only generated when ammonia is supplied, thus confirming that the change is temperature dependent during ammonia electrolysis. FIG. 17 is a graph of the voltage change from applying the drive voltage to applying the rest voltage in the case of FIG. 16B, and it can be seen that the current density changes rapidly until the temperature is 60° C. However, when the temperature is above 70° C., the change in current density rapidly becomes smaller.

Accordingly, according to the present invention, it can be seen that the rapid drop in the current density caused by the poisoning disappears depending on whether a rest voltage is applied (0.2 V or less), the magnitude of the driving voltage (a voltage of 0.6 V or more but not more than 0.9 V), whether a voltage of opposite polarity is applied, and the temperature (70° C. or more), and it can be seen that the current density changes gradually. Accordingly, according to the present invention, an alkaline ammonia electrolysis cell and a cell driving method in which a Pt catalyst can be used as an AEC electrode can be provided by solving the problem that the reaction current density is greatly reduced due to the poisoning of the electrode surface. In particular, the present invention establishes operating conditions and cell configurations that prevent poisoning in the reaction mechanism through the Anode & Cathode Pulse Sequence Method, which may result in improved durability and performance.

On the other hand, according to the present invention, an apparatus for converting ammonia, an energy carrier that is advantageous in terms of transportation storage and infrastructure, into hydrogen may be provided, thereby solving the problem of transportation and storage of hydrogen by converting ammonia into hydrogen at a charging station.

Embodiments of the present invention have been described in more detail with reference to the accompanying drawings, but the invention is not necessarily limited to these embodiments and may be practiced in various modifications without departing from the technical ideas of the invention. Accordingly, the embodiments disclosed herein are intended to illustrate and not to limit the technical ideas of the present invention, and the scope of the technical ideas of the present invention is not limited by these embodiments. Therefore, the embodiments described above are exemplary in all respects and should be understood as non-limiting. The scope of protection of the present invention shall be construed in accordance with the following claims, and all technical ideas within the scope thereof shall be construed as falling within the scope of the present invention.