Electrolytic tank hydrogen production device and hydrogen production method

Abstract

The invention discloses an electrolytic tank hydrogen production device and a hydrogen production method. The device comprises an anion exchange membrane ammonia electrolytic tank, a direct ammonia fuel cell and a temperature and humidity increasing tank, an anode collector plate of the direct ammonia fuel cell is in contact connection with a cathode collector plate of the anion-exchange membrane ammonia electrolytic tank, and a cathode collector plate of the direct ammonia fuel cell is connected with an anode collector plate of the anion-exchange membrane ammonia electrolytic tank through a wire; the temperature and humidity increasing tank is respectively connected with an anode inlet of the direct ammonia fuel cell, an anode inlet of the anion exchange membrane ammonia electrolytic tank and a cathode inlet of the direct ammonia fuel cell; oxygen is introduced into a cathode inlet of the direct ammonia fuel cell, and an ammonia-alkali mixed solution is introduced into an anode inlet of the anion exchange membrane ammonia electrolytic tank and an anode inlet of the direct ammonia fuel cell. The electrolytic hydrogen production device is highly integrated, power supply and hydrogen production can be achieved at the same time, and compared with a conventional electrolytic tank and a fuel cell, the device is simpler.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by electrolysis of ammonia, and in particular to an electrolytic cell hydrogen production device and a hydrogen production method. Background Art

[0002] Hydrogen energy can be divided into three categories according to its production source: "grey hydrogen", "blue hydrogen" and "green hydrogen". At present, my country's hydrogen mainly comes from grey hydrogen. In the future, the electrolysis of water to produce green hydrogen in conjunction with large-scale photovoltaic power generation or wind power generation will become a development trend. Off-grid hydrogen production does not take electricity from the power grid, but uses green electricity such as wind power and photovoltaic power generation to produce hydrogen. This not only enables new energy to be consumed locally, but also drives a significant reduction in the electricity cost of hydrogen production. Off-grid hydrogen production will become an effective way to improve the cost competitiveness of green hydrogen. Off-grid hydrogen production can ensure that hydrogen is completely produced from renewable energy (such as photovoltaics, wind power, electrolysis of water, etc.), avoiding the impact of non-renewable energy electricity that may exist in the power grid on the purity of green hydrogen, thereby ensuring zero carbon emissions and high quality of green hydrogen. With the increase in green hydrogen demand, the traditional grid access model is difficult to support the demand for large-scale green hydrogen production. The off-grid hydrogen production technology route is the key to achieving large-scale production of green hydrogen, and can solve the safety and stability needs of power grid peak regulation and chemical production.

[0003] The existing ways to obtain green hydrogen in off-grid areas mainly include hydrogen production through alkaline electrolyzers, proton exchange membrane electrolyzers, and anion exchange membrane water electrolysis. When hydrogen is produced by alkaline electrolyzers, a liquid electrolyte of potassium hydroxide (KOH) is used to increase the conductivity, but alkaline electrolyzers have problems coping with power fluctuations. When hydrogen is produced by proton exchange membrane (PEM) electrolyzers, solid electrolytes are required. Although the response speed is fast and it can better adapt to power fluctuations, its cost is relatively high. Hydrogen production by anion exchange membrane water electrolysis is efficient, but the energy consumption is high. Summary of the invention

[0004] Based on the above background technology, the present invention connects an anion exchange membrane ammonia electrolyzer in series with a direct ammonia fuel cell, and directly supplies the power of the direct ammonia fuel cell to the anion exchange membrane ammonia electrolyzer, so that hydrogen can be produced without any power supply, thereby realizing the electrochemical conversion of ammonia to hydrogen with zero external power input. This may have advantages in off-grid areas or areas with high electricity prices and low ammonia costs.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] In one aspect, the present invention provides an electrolytic cell hydrogen production device, the device comprising an anion exchange membrane ammonia electrolytic cell (HEMAC), a direct ammonia fuel cell (DAFC) and a heating and humidification tank;

[0007] The anode current collecting plate of the direct ammonia fuel cell is in contact with and connected to the cathode current collecting plate of the anion exchange membrane ammonia electrolyzer, and the cathode current collecting plate of the direct ammonia fuel cell is connected to the anode current collecting plate of the anion exchange membrane ammonia electrolyzer via a wire;

[0008] The heating and humidifying tank is respectively connected to the anode inlet of the direct ammonia fuel cell, the anode inlet of the anion exchange membrane ammonia electrolysis cell and the cathode inlet of the direct ammonia fuel cell;

[0009] Oxygen is introduced into the cathode inlet of the direct ammonia fuel cell, and an ammonia-alkali mixed solution is introduced into the anode inlet of the anion exchange membrane ammonia electrolysis cell and the anode inlet of the direct ammonia fuel cell.

[0010] In the above technical solution, further, the anion exchange membrane ammonia electrolysis cell and the direct ammonia fuel cell are both assembled by sandwiching a membrane electrode between two graphite plates.

[0011] In the above technical solution, further, the membrane electrode of the anion exchange membrane ammonia electrolysis cell and the direct ammonia fuel cell comprises an anode catalyst layer, an anode diffusion layer, a membrane, a cathode diffusion layer and a cathode catalyst layer.

[0012] In the above technical solution, further, the membrane electrode of the anion exchange membrane ammonia electrolysis cell and the direct ammonia fuel cell is composed of an anode diffusion layer electrode, a membrane and a cathode diffusion layer electrode stacked in sequence; the anode diffusion electrode is formed by coating an anode catalyst on the anode diffusion layer, and the cathode diffusion electrode is formed by coating a cathode catalyst on the cathode diffusion layer; the anode diffusion layer is a carbon cloth substrate, and the cathode diffusion layer is a carbon paper substrate.

[0013] The anode catalyst of the anion exchange membrane ammonia electrolysis cell and the direct ammonia fuel cell is PtIr / C, one of Pt, Ru, Ir and their binary and ternary alloys, Ni, and Cu; the cathode catalyst of the anion exchange membrane ammonia electrolysis cell and the direct ammonia fuel cell is Pt / C.

[0014] The membrane of the anion exchange membrane ammonia electrolysis cell is a polyarylpiperidine (TP100) type anion exchange membrane;

[0015] The membrane of the direct ammonia fuel cell is a polyarylpiperidine type anion exchange membrane or a polybenzimidazole type ion solvation membrane.

[0016] Another aspect of the present invention provides a method for producing hydrogen from the electrolytic cell hydrogen production device, the method comprising the following steps:

[0017] (1) The ammonia-alkali mixed solution enters the heating and humidification tank and is heated to a preset temperature. The heated ammonia-alkali mixed solution enters the anode of the direct ammonia fuel cell and the anode of the anion exchange membrane ammonia electrolysis cell in turn;

[0018] (2) The oxygen is heated to a preset temperature by a heating and humidification tank, and the oxygen humidified to 100% enters the cathode of the direct ammonia fuel cell;

[0019] (3) The anode of the direct ammonia fuel cell and the cathode of the anion exchange membrane ammonia electrolysis cell are connected to a load respectively to start hydrogen production. The gas production is adjusted by adjusting the load, and the hydrogen purity of the produced gas is tested by a gas chromatograph.

[0020] In the above technical solution, further, the preset temperature of the heating and humidifying tank is 50-90°C.

[0021] In the above technical solution, further, in the anion exchange membrane ammonia electrolysis cell, the feed flow rate of the ammonia-alkali mixed solution is 2-5 mL min -1 .

[0022] In the above technical solution, further, the ammonia-alkali mixed solution is a mixed solution of ammonia water and KOH, wherein the concentration of KOH is 2-7M and the concentration of ammonia water is 2-7M.

[0023] The beneficial effects of the present invention are:

[0024] (1) The present invention combines fuel cells and electrolysis technologies to directly supply the power of ammonia fuel cells to anion exchange membrane ammonia electrolysis cells, and successfully develops a prototype of a series cell that directly converts ammonia into hydrogen, proving that ammonia can be directly converted into hydrogen by electrochemical methods without the need for additional voltage input. The present invention may have advantages in off-grid areas or especially in areas with high electricity prices and low ammonia costs, and can be used as a potential technology for on-site hydrogen production in off-grid areas without any electricity input.

[0025] (2) The present invention uses a direct ammonia fuel cell as a power generation device and an alkaline anion exchange membrane electrolyzer as a hydrogen production device in a series manner. At the cathode of the direct ammonia fuel cell, oxygen is reduced to OH - , OH - Migrate through the membrane to the anode where ammonia reacts with OH - Oxidation reaction occurs to generate electrons; the electrons are transferred to the cathode of the anion exchange membrane ammonia electrolyzer, where water is electrolyzed and reduced to H2 and OH - The gas at the cathode outlet is absorbed to remove ammonia and OH - Migrate through the anion exchange membrane to the anode of the ammonia electrolyzer, where ammonia reacts with OH - Oxidation occurs to generate electrons, which are then transferred to the cathode of the direct ammonia fuel cell, where oxygen is reduced to OH - , OH -They migrate through the membrane to the anode, generate electrons at the anode and then transfer them to the cathode of the anion exchange membrane ammonia electrolyzer, thus achieving continuous power supply to the anion exchange membrane ammonia electrolyzer.

[0026] (3) The device of the present invention adopts an alkaline anion exchange membrane ammonia electrolytic cell, the distance between the electrode and the membrane is zero, and the ohmic resistance is small. At the same time, the hydrogen production side and the oxygen supply side of the present invention are separated separately, and the safety is improved. The electrolytic cell hydrogen production device of the present invention is highly integrated and integrated. Compared with conventional electrolytic cells and fuel cells, the device is simpler.

[0027] (4) The membrane electrode used in the direct ammonia fuel cell and ammonia electrolyzer of the present invention can be a gas diffusion layer (GDE) type membrane electrode, that is, the positive / negative catalyst layer is first coated on the diffusion layer to form a positive / cathode diffusion layer electrode, and then the positive / cathode diffusion layer electrode and the membrane are assembled to form a gas diffusion electrode (GDE) type membrane electrode (MEA). The hydrogen evolution reaction at the cathode in the HEMAE is made in a hydrophobic environment, which can avoid the problem of high impedance (ASR) of the HEMAE caused by the use of hydrophilic ionomers in the CCM type MEA.

[0028] (5) The electrolytic hydrogen production device in the present invention is highly integrated and can simultaneously realize power supply and hydrogen production. Compared with conventional electrolytic cells and fuel cells, the device is simpler.

[0029] Based on the above reasons, the present invention can be widely promoted in the fields of hydrogen separation technology and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a physical photo of the electrolytic cell hydrogen production device;

[0031] Figure 2 It is a schematic diagram of the principle of the electrolytic cell hydrogen production device;

[0032] Figure 3 The effects of different flow rates and different concentrations of NH3 and KOH mixed solutions on the performance of anion exchange membrane ammonia electrolysis cell in Example 1, a is the flow rate, b is the KOH concentration, and c is the NH3 concentration;

[0033] Figure 4 is a Faraday efficiency diagram of the anion exchange membrane ammonia electrolysis cell in Example 2;

[0034] Figure 5 : are the polarization curve and Nyquist curve of the electrolytic cell hydrogen production device in Example 3, a is the polarization curve, b is the Nyquist curve;

[0035] Figure 6 The stability test diagram and hydrogen purity test diagram of the electrolytic cell hydrogen production device in Example 3;

[0036] Figure 7 This is the polarization curve of the anion exchange membrane ammonia electrolysis cell of the membrane electrode assembled with GDE and CCM in Example 4. DETAILED DESCRIPTION

[0037] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0038] The invention provides an electrolytic cell hydrogen production device, comprising an anion exchange membrane ammonia electrolytic cell, a direct ammonia fuel cell and a temperature increasing and humidifying tank; the anode current collecting plate of the direct ammonia fuel cell is in contact with and connected to the cathode current collecting plate of the anion exchange membrane ammonia electrolytic cell, and the cathode current collecting plate of the direct ammonia fuel cell is connected to the anode current collecting plate of the anion exchange membrane ammonia electrolytic cell through a wire; the temperature increasing and humidifying tank is respectively connected to the anode inlet of the direct ammonia fuel cell, the anode inlet of the anion exchange membrane ammonia electrolytic cell and the cathode inlet of the direct ammonia fuel cell; oxygen is introduced into the cathode inlet of the direct ammonia fuel cell, and an ammonia-alkali mixed solution is introduced into the anode inlet of the anion exchange membrane ammonia electrolytic cell and the anode inlet of the direct ammonia fuel cell.

[0039] The anion exchange membrane ammonia electrolyzer is assembled by sandwiching the membrane electrode between two graphite plates. The actual picture of the electrolyzer hydrogen production device is as follows Figure 1 As shown, two gold-plated copper terminals are added to each graphite plate for testing. The direct ammonia fuel cell uses the same membrane electrode (MEA) assembly method and battery assembly method as the anion exchange membrane ammonia electrolyzer, and then the two are assembled together with appropriate torque.

[0040] The polyaryl piperidine (TP-100) type anion exchange membrane used in the present invention can be purchased commercially or homemade. In the embodiment of the present invention, a homemade anion exchange membrane is used. The specific preparation method is referred to Journal of Power Sources, Volume 443, 15 December 2019, 227219. MEA has 5 cm 2The effective area of ​​the anion exchange membrane ammonia electrolyzer is composed of a PtIr / C coated on a carbon cloth substrate as an anode catalyst, a polyaryl piperidine (TP-100) type anion exchange membrane (HEM, about 30 μm thick), and a Pt / C coated on a carbon paper substrate as a cathode catalyst to form a gas diffusion electrode membrane electrode (MEA); the anion exchange membrane ammonia electrolyzer and the direct ammonia fuel cell have the same membrane electrode composition and assembly method. The anodes of the anion exchange membrane ammonia electrolyzer and the direct ammonia fuel cell both undergo ammonia oxidation reaction, but the cathode of the anion exchange membrane ammonia electrolyzer undergoes a hydrogen evolution reaction, and the cathode of the direct ammonia fuel cell undergoes an oxygen reduction reaction. The anode catalyst ink is mixed with isopropanol as a solvent and PTFE as a binder (PtIr / C:PTFE mass ratio is 5:1 to 9:1). For other anode cases, PtIr / C is replaced by Pt / C or Pt / C mixed with Ir black (Pt / Ir = 3:1, 2:1, 1:1, 1:2 or 1:3). The cathode catalyst ink is a mixture of ethanol as solvent and PTFE as binder (Pt / C:PTFE weight ratio is 5:5, 5.5:4.5, 6:4, 6.5:3.5, 7:3, 7.5:2.5 or 8:2). These catalyst inks are ultrasonically treated in an ice water bath to form a uniform dispersion, which is then coated on the substrate in sequence. The anode loading is 1mg~2mgPGM cm -2 , cathode loading is 0.2mg~0.6mgPGMcm -2 The cathode in the form of a catalyst-coated membrane was prepared by spraying the cathode catalyst ink onto the exchange membrane soaked in 1.0 M KOH solution. The binder used was the ionomer used to prepare the membrane. All membranes were soaked in 1 M KOH for 24 hours before use to exchange OH. - form.

[0041] The method for producing hydrogen using the electrolytic cell hydrogen production device comprises the following steps:

[0042] (1) The ammonia-alkali mixed solution enters the heating and humidification tank and is heated to a preset temperature. The heated ammonia-alkali mixed solution enters the anode of the direct ammonia fuel cell and the anode of the anion exchange membrane ammonia electrolysis cell in turn;

[0043] (2) The oxygen is heated to a preset temperature by a heating and humidification tank, and the heated oxygen enters the cathode of the direct ammonia fuel cell;

[0044] (3) The anode of the direct ammonia fuel cell and the cathode of the anion exchange membrane ammonia electrolysis cell are connected to a load respectively to start hydrogen production. The gas production is adjusted by adjusting the load, and the hydrogen purity of the produced gas is tested by a gas chromatograph.

[0045] The schematic diagram of the principle of hydrogen production by electrolysis cell is as follows Figure 2The working principle is as follows: In the cathode of a direct ammonia fuel cell (DAFC), oxygen is reduced to OH - These ions migrate to the anode of the DAFC through the anion exchange membrane, and ammonia reacts with the migrated OH - The reaction is oxidized at the anode to generate electrons. These electrons are then transferred to the cathode of the ion exchange membrane ammonia electrolyzer (HEMAE), where water is reduced to H2 and OH - Meanwhile, OH - Migrate through the anion exchange membrane to the anode of the anion exchange membrane ammonia electrolyzer, while carrying out another ammonia oxidation reaction. The core concept of the device is that the anion exchange membrane ammonia electrolyzer can be directly driven by the coupled direct ammonia fuel cell without the need for an external power source.

[0046] The direct ammonia fuel cell reaction is as follows:

[0047] Anode reaction:

[0048] 2NH3+6OH - →N2+6H2O+6e - E 0 =-0.77 V(SHE) (1)

[0049] Cathode reaction:

[0050] 3 / 2O2+3H2O+6e - →6OH - E 0 = +0.40 V (SHE) (2)

[0051] Battery reaction:

[0052] 2NH3+3 / 2O2→N2+3H2O E cell =1.17 V (3)

[0053] The reaction of anion exchange membrane ammonia electrolysis cell is as follows:

[0054] Anode reaction:

[0055] 2NH3+6OH - →N2+6H2O+6e - E 0 =-0.77 V(SHE) (4)

[0056] Cathode reaction:

[0057] 6H2O+6e - →3H2+6OH - E 0 =-0.83 V(SHE) (5)

[0058] Battery reaction:

[0059] 2NH3→N2+3H2 E cell =0.06 V (6)

[0060] The assembled electrolytic cell hydrogen production device is subjected to an electrolytic ammonia test. The raw ammonia-alkali mixture is pumped by a dedicated ammonia pump, and then sent to the anode of the DAFC after passing through the heating and humidification tank, and then flows into the anode of the ammonia electrolytic cell. The raw material can be heated to a specified temperature in the heating and humidification tank. The pipe between the heating and humidification tank and the fixture is wrapped with insulation cotton to maintain the temperature. The electronic load is connected to both sides of the electrolytic cell hydrogen production device, and the polarization curve experiment of the electrolytic cell hydrogen production device is tested by adjusting the resistance of the electronic load. When testing the stability of the electrolytic cell hydrogen production device, the two ends of the electrolytic cell hydrogen production device are connected with wires to form an external short circuit state, so that the electric energy required for HEMAE can be directly supplied by DAFC.

[0061] Oxygen is passed through the cathode of DAFC, and the gas can be humidified and heated to a specified state in the humidification tank. The oxygen on the cathode of DAFC is reduced to OH - These ions migrate to the anode of DAFC through the anion exchange membrane, and the ammonia in the anode of DAFC reacts with the migrated OH - Reaction, oxidation reaction occurs at the anode to generate electrons. These electrons are then transferred to the cathode of HEMAE, where the water on the cathode is electrolyzed and reduced to H2 and OH - The gas at the cathode outlet of HEMAE is subjected to absorption to remove ammonia and then passed into a gas chromatograph to analyze the gas composition. - It then migrates to the anode of HEMAE through the anion exchange membrane, where another ammonia oxidation reaction takes place. The electrons generated at the anode of HEMAE are then transferred to the cathode of DAFC, where the oxygen on the cathode is reduced to hydroxide ions.

[0062] Example 1

[0063] The anion exchange membrane ammonia electrolyzer was assembled by sandwiching the MEA between two graphite plates, using two gaskets to prevent short circuits and leakage of the solution. The MEA was composed of PtIr / C coated on a carbon cloth substrate as an anode catalyst, a polyarylpiperidine (TP-100) type anion exchange membrane (HEM, about 30 μm thick) and Pt / C coated on a carbon paper substrate as a cathode catalyst, and the anode loading was 2 mg. PGM cm -2 , cathode loading is 0.4 mg PGM cm -2 .

[0064] Mixed solutions of NH3 and KOH (hereinafter referred to as ammonia-alkali mixed solutions) of different concentrations were fed into the anode to evaluate the effect of feed concentration on the performance of anion exchange membrane ammonia electrolyzer. Voltage was applied by a DC power supply (eTOMMENS-6010C, with an accuracy of 10mA / mV), the upper voltage limit was set to 0.8V, and polarization curve data were collected. The test was carried out at 80°C.

[0065] The effect of flow rate on the performance of anion exchange membrane ammonia electrolysis cell was investigated. Figure 3 As shown in a, when the feed rate is 1 mL min -1 When the current density increases to 500 mA cm -2 When the voltage was increased from 0.6 V to 0.8 V, the feed rate was set to 2 mL min -1 ~5mL ​​min -1 When the current density is 1000mA cm -2 When the voltage is 0.82 V to 0.84 V, it is shown that the anode flow rate will affect the performance of the anion exchange membrane ammonia electrolysis cell, and the cell has excellent performance within the protection scope of the present invention.

[0066] Secondly, the effect of alkali (KOH) concentration was investigated, such as Figure 3 As shown in b. Due to OH - It is one of the reactants, so when its concentration is low (1M), the overpotential of the electrode reaction will be large. When the concentration is 3M, the overpotential of the electrode reaction and the voltage of the anion exchange membrane ammonia electrolysis cell can be significantly reduced, and when the voltage is 0.82V, the current density is about 958mA cm -2 . Further increase OH - When the concentration reaches 7M, the performance of the electrolytic cell tends to decline. When the voltage is 0.85V, the current density is only 638mA cm -2 This shows that when the KOH concentration is 2-7M, the performance is excellent. Too high an alkali concentration increases the viscosity of the raw material solution. - The diffusion rate of ammonia to the electrode surface slows down, which in turn slows down the electrode reaction. The effect of ammonia concentration was then investigated, such as Figure 3 c. When the ammonia concentration gradually increases from 1M to 3M, the electrolysis performance gradually improves. When the current density is 956mA cm -2 , the voltage is 0.84V.

[0067] Example 2

[0068] The same anion exchange membrane ammonia electrolysis cell as in Example 1 was used to test the Faraday efficiency. The voltage was applied by a DC power supply (eTOMMENS-6010C, with an accuracy of 10 mA / mV). The ammonia-alkali mixture was introduced at a feed rate of 3 mL / min with a KOH and ammonia concentration of 3 M. The test was carried out at 90°C.

[0069] After determining the purity of hydrogen, the volume of hydrogen produced is collected in the gas pipe by the drainage gas collection method to calculate the Faraday efficiency. Figure 4 As shown, it can be seen that there is a linear relationship between the hydrogen production rate and the current, and the fitting slope is 0.505, indicating that the hydrogen evolution reaction follows a two-electron transfer pathway, that is, each electron can produce 0.505 hydrogen (greater than 0.5 may be due to errors in gas collection), thereby achieving a Faraday efficiency close to 100%.

[0070] Example 3

[0071] Example 3 provides an electrolytic cell hydrogen production device, the purpose of which is to directly convert ammonia into hydrogen without requiring any other electricity input.

[0072] HEMAE is assembled by sandwiching MEA between two graphite plates, using two gaskets to prevent short circuit and solution leakage, and MEA in the form of gas diffusion electrode is composed of PtIr / C coated on a carbon cloth substrate as an anode catalyst, a homemade polyaryl piperidine (TP-100) type anion exchange membrane (about 30 μm thick) and Pt / C coated on a carbon paper substrate as a cathode catalyst. HEMAE adopts the same MEA and battery assembly method as DAFC, and the membrane electrode is the same, specifically the same as the membrane electrode in Example 1. Then the two are assembled together with a suitable torque, and the membrane liquid used in DAFC is a homemade polyaryl piperidine (TP-100) type anion exchange membrane.

[0073] The ammonia-alkali mixture was introduced with a KOH and ammonia concentration of 3 M and a feed rate of 3 mL / min. The DAFC cathode feed rate was 500 mL min -1 of O2, the test was carried out at 90°C.

[0074] First, the polarization curves of DAFC and HEMAE in the electrolytic cell hydrogen production device were tested respectively. The results are as follows: Figure 5 a. DAFC at a current density of 160 mA cm -2 The operating voltage was 0.42V, achieving 67mW cm -2 At the same time, HEMAE achieved a voltage of 0.34 V at the same current density.

[0075] like Figure 5As shown in b, the impedance values ​​(ASR) of DAFC and HEMAE under open circuit conditions are 49mΩcm 2 and 39mΩcm 2 The impedance value (ASR) of the entire electrolytic cell hydrogen production device is 88mΩcm 2 , which is equal to the sum of the ASR values ​​of DAFC and HEMAE, indicating a good contact between the two cells.

[0076] Next, the stability test of the electrolytic cell hydrogen production device that continuously produces hydrogen was carried out without any applied voltage. Figure 6 As shown in the figure, during the 9h stability test, the voltage of DAFC dropped slightly from 0.42V to 0.38V, which is within a reasonable range. At the same time, the current density changes of HEMAE (0.37V) and DAFC (0.39V) were tested at a constant voltage, which is basically consistent with the results in the electrolytic cell hydrogen production device, as shown below Figure 6 As shown in Figure 2, the current density gradually decreased over time and finally stabilized at 20 mA cm -2 The hydrogen purity of the product was also monitored, and the results showed that it gradually decreased from 89% to about 70% (the residual gas was nitrogen) during the stability test.

[0077] Example 4

[0078] In the study of direct ammonia fuel cells (DAFC), it was found that the performance of the cell assembled with membrane electrode (MEA) in the form of gas diffusion layer (GDE) is better than that of MEA in the form of catalyst coated membrane (CCM). The same rule is followed in anion exchange membrane ammonia electrolyzer (HEMAE), such as Figure 7 As shown, the specific operating conditions are the same as those in Example 1.

[0079] The composition of CCM membrane electrode is the same as that of GDE membrane electrode, but GDE membrane electrode adopts hot pressing method to coat the catalyst on gas diffusion layer (GDL), and then hot presses GDL on both sides of anion exchange membrane (HEM) to form membrane electrode; while CCM membrane electrode directly coats the slurry composed of catalyst and ionomer on both sides of anion exchange membrane to form catalyst coated membrane (CCM), and then hot presses gas diffusion layer on both sides of CCM to form membrane electrode.

[0080] like Figure 7 As shown in Figure 2, the HEMAE assembled with CCM MEA can only obtain 100 mA cm at a voltage limit of 0.8 V. -2The current density is about 100 mΩcm, which is much lower than the performance of the electrolytic cell assembled with GDE MEA. This is because the cathode of HEMAE requires a hydrophobic environment for hydrogen evolution reaction. CCM MEA uses hydrophilic ionomers, which is not conducive to the formation of bubbles, resulting in the ASR of CCM HEMAE as high as 150 mΩcm. 2 , much higher than the 50mΩcm of GDE 2 , which directly leads to the deterioration of battery performance.

[0081] The electrolytic cell hydrogen production device of the present invention proves that ammonia can be directly converted into hydrogen by electrochemical methods without the need for additional voltage input. This technology may have advantages in off-grid areas or especially in areas with high electricity prices and low ammonia costs.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolytic cell hydrogen production device, characterized in that: The device comprises an anion exchange membrane ammonia electrolysis cell, a direct ammonia fuel cell and a heating and humidification tank; The anode current collecting plate of the direct ammonia fuel cell is in contact with and connected to the cathode current collecting plate of the anion exchange membrane ammonia electrolyzer, and the cathode current collecting plate of the direct ammonia fuel cell is connected to the anode current collecting plate of the anion exchange membrane ammonia electrolyzer via a wire; The heating and humidifying tank is respectively connected to the anode inlet of the direct ammonia fuel cell, the anode inlet of the anion exchange membrane ammonia electrolysis cell and the cathode inlet of the direct ammonia fuel cell; Oxygen is introduced into the cathode inlet of the direct ammonia fuel cell, and an ammonia-alkali mixed solution is introduced into the anode inlet of the anion exchange membrane ammonia electrolysis cell and the direct ammonia fuel cell.

2. The electrolytic cell hydrogen production device according to claim 1, characterized in that: The anion exchange membrane ammonia electrolyzer and the direct ammonia fuel cell are both assembled by sandwiching a membrane electrode between two graphite plates.

3. The electrolytic cell hydrogen production device according to claim 2, characterized in that: The membrane electrode of the anion exchange membrane ammonia electrolyzer and the direct ammonia fuel cell comprises an anode catalyst layer, an anode diffusion layer, a membrane, a cathode diffusion layer and a cathode catalyst layer.

4. The electrolytic cell hydrogen production device according to claim 2 or 3, characterized in that: The membrane electrode of the anion exchange membrane ammonia electrolysis cell and the direct ammonia fuel cell consists of an anode diffusion layer electrode, a membrane and a cathode diffusion layer electrode stacked in sequence; the anode diffusion electrode is formed by coating an anode catalyst on an anode diffusion layer, and the cathode diffusion electrode is formed by coating a cathode catalyst on a cathode diffusion layer; the anode diffusion layer is a carbon cloth substrate, and the cathode diffusion layer is a carbon paper substrate.

5. The electrolytic cell hydrogen production device according to claim 2 or 3, characterized in that: The anode catalysts of the anion exchange membrane ammonia electrolysis cell and the direct ammonia fuel cell are both PtIr / C, one of Pt, Ru, Ir and their binary and ternary alloys, Ni, and Cu, and the cathode catalysts of the anion exchange membrane ammonia electrolysis cell and the direct ammonia fuel cell are both Pt / C.

6. The electrolytic cell hydrogen production device according to claim 1, characterized in that: The membrane of the anion exchange membrane ammonia electrolysis cell is a polyarylpiperidine type anion exchange membrane; The membrane of the direct ammonia fuel cell is also a polyarylpiperidine type anion exchange membrane or a polybenzimidazole type ion solvation membrane.

7. A method for producing hydrogen using the electrolytic cell hydrogen production device according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: (1) The ammonia-alkali mixed solution enters the heating and humidification tank and is heated to a preset temperature. The heated ammonia-alkali mixed solution enters the anode of the direct ammonia fuel cell and the anode of the anion exchange membrane ammonia electrolysis cell in turn; (2) The oxygen is heated to a preset temperature by a heating and humidification tank, and then humidified to 100% before entering the cathode of the direct ammonia fuel cell; (3) The anode of the direct ammonia fuel cell and the cathode of the anion exchange membrane ammonia electrolysis cell are connected to a load respectively to start hydrogen production. The gas production is adjusted by adjusting the load, and the hydrogen purity of the produced gas is tested by a gas chromatograph.

8. The hydrogen production method according to claim 7, characterized in that: The preset temperature of the heating and humidifying tank is 50-90°C.

9. The hydrogen production method according to claim 7, characterized in that: In the anion exchange membrane ammonia electrolysis cell, the feed flow rate of the ammonia-alkali mixed solution is 2-5 mL min -1 .

10. The hydrogen production method according to claim 7, characterized in that: The ammonia-alkali mixed solution is a mixed solution of ammonia water and KOH, wherein the concentration of KOH is 2-7M and the concentration of ammonia water is 2-7M.

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