Hydrogen production by electrolysis of seawater

Abstract

A device for electrolyzing seawater to produce hydrogen is disclosed. The device includes a single-pole electrolytic cell configured to operate in a cathode-cathode mode and configured to reduce the production of chlorine and / or oxygen.

Description

[0001] Priority document

[0002] This application claims priority to Australian Provisional Patent Application No. 2020901163, filed on April 12, 2020, entitled “Advanced Commercial Seawater Electrolysis for Hydrogen Production,” the contents of which are incorporated herein by reference in their entirety.

[0003] By incorporating via reference

[0004] The following publications are cited in this application, the contents of which are incorporated herein by reference in their entirety:

[0005] • Australian Patent 2008209322;

[0006] • British Patent GB2460000;

[0007] Chinese Patent ZL200880012716;

[0008] • South African Patent 2011 / 04916;

[0009] • Hong Kong Patent HK1137408; and

[0010] • US Patent 10,316,416. Technical Field

[0011] This disclosure relates to hydrogen production from seawater. Background Technology

[0012] Hydrogen energy is produced from hydrogen and has a variety of uses, such as as a fuel for transportation or heating, or as a way to store electricity. For most countries, hydrogen is an important component of a clean and safe energy future.

[0013] Hydrogen can be produced using many different methods. Thermochemical methods utilize thermal and chemical reactions to release hydrogen from organic materials and biomass, such as fossil fuels. Microorganisms, such as bacteria and algae, can produce hydrogen through biological processes. Alternatively, water can be split into hydrogen and oxygen using electrolysis or solar energy.

[0014] The applicant of this application has previously developed a method for producing hydrogen involving the unipolar electrolysis of seawater (see, for example, Australian Patent 2008209322). While this technology has proven feasible and can produce hydrogen from seawater, it may also result in the simultaneous production of oxygen and / or chlorine, which could be problematic.

[0015] An electrolysis system for producing hydrogen from seawater is needed that minimizes the production of chlorine and / or oxygen. Summary of the Invention

[0016] According to a first aspect, an apparatus for electrolyzing seawater to produce hydrogen is provided, the apparatus comprising a monopolar electrolyzer configured to operate in a cathode-cathode mode and configured to reduce the production of chlorine and / or oxygen.

[0017] In some embodiments, the device is configured to reduce the generation of chlorine and / or oxygen by lowering the voltage at the cathode and / or anode.

[0018] In some embodiments, the device includes one or more resistors for reducing the voltage at the cathode and / or anode.

[0019] In some embodiments, the device includes:

[0020] A cathode cell, which includes a cathode electrode and a cathode cell solution electrode;

[0021] An anode cell, which includes an anode electrode and an anode cell solution electrode;

[0022] The cell gap between the cathode electrode and the cathode solution electrode, and the cell gap between the anode electrode and the anode solution electrode, are configured to reduce the voltage at the cathode and / or anode.

[0023] In some embodiments, the device includes:

[0024] Multiple anode cells connected in series, with gaps between the electrodes of each anode cell; and

[0025] Multiple cathode cells connected in series, with gaps between the electrodes of each cathode cell.

[0026] The gap between electrodes in the cathode pool is larger than the gap between electrodes in the anode pool.

[0027] In some embodiments, the cathode cell and the anode cell are connected in a cathode configuration in a diaphragmless electrolytic cell.

[0028] In some embodiments, the cathode cell and the anode cell are equipped with low-resistance electrodes coated with at least one catalyst.

[0029] In some embodiments, the apparatus includes a diaphragmless electrolytic cell with more anode cells having smaller gaps between electrodes and fewer cathode cells having larger gaps between electrodes.

[0030] In some embodiments, the device includes five anode cells with an electrode gap of 4 mm and four cathode cells with an electrode gap of 6 mm.

[0031] In some embodiments, the electrodes of the diaphragmless electrolysis system are made of a high-conductivity material and coated with a protective coating and / or a catalyst coating. The high-conductivity material can be selected from the group consisting of copper and graphene. The catalyst coating can include Hastelloy 276c. The protective coating can include ruthenium / iridium metal or its oxides.

[0032] In some embodiments, the device includes a cathode cell and an anode cell, and a membrane located between the anode cell and the cathode cell, the membrane being configured to allow only electrons to pass from the cathode cell to the anode cell, thereby making the cathode electrolyte negatively charged and the anode electrolyte positively charged, and also includes another set of electrolytic cells through which the negatively charged cathode electrolyte and the positively charged anode electrolyte can pass to generate an electric current and produce hydrogen and oxygen.

[0033] In some embodiments, the cathode-cathode mode includes an electrical connection in which the negative terminal of the DC power supply is connected to the cathode electrode, the cathode solution electrode is connected to the anode electrode, and the positive terminal of the DC power supply is connected to the anode solution electrode.

[0034] According to a second aspect, a method for producing hydrogen from seawater is provided, the method comprising introducing seawater into an apparatus according to a first aspect and producing hydrogen therefrom. Attached Figure Description

[0035] Embodiments of this disclosure will be discussed with reference to the accompanying drawings, in which:

[0036] Figure 1 This is a schematic diagram of a prior art unipolar electrolysis device described, for example, in Australian Patent 2008209322;

[0037] Figure 2 This is a schematic diagram of an electrolysis apparatus for producing hydrogen from seawater according to an embodiment of the present disclosure;

[0038] Figure 3 This is a schematic diagram of an electrolysis apparatus for producing hydrogen from seawater according to another embodiment of the present disclosure;

[0039] Figure 4 This is a schematic diagram of an electrolysis apparatus for producing hydrogen from seawater that can be commercially viable according to embodiments of this disclosure;

[0040] Figure 5 This is a schematic diagram of a commercially viable electrolysis apparatus for producing hydrogen from seawater according to another embodiment of this disclosure; and

[0041] Figure 6 This is a schematic diagram of an electrolysis apparatus for producing hydrogen from seawater using a membrane cell, which is applicable to commercial applications according to embodiments of this disclosure.

[0042] In the following description, in all the accompanying drawings, similar reference numerals denote similar or corresponding parts. Detailed Implementation

[0043] The applicant of this application has been granted Australian Patent 2008209322, British Patent GB2460000, Chinese Patent ZL200880012716, South African Patent 2011 / 04916, and Hong Kong Patent HK1137408 for methods involving the unipolar electrolysis of seawater to produce hydrogen. The apparatus disclosed in these patents is as follows: Figure 1 As shown. In short, the device includes a DC power supply 10, which is electrically connected to a modulator 14. The modulator is electrically connected to a cathode cell 22 and an anode cell 38. Cathode cell 22 includes a cathode electrode 24 and a solution electrode 32. Anode cell 38 includes an anode electrode 36 and a solution electrode 34. Anode cell 38 serves as the cathode. The components of the device are connected by wires 12, 16, 28, and 40. Seawater 30 is introduced into each cell 22, 38, and hydrogen 18 and alkaline seawater 20 are generated at cathode cell 22 and anode cell 38.

[0044] Figure 1 The problem with the unipolar electrolysis apparatus and method described is that oxygen and chlorine may be produced at the cathode cell 22 if the cell voltage exceeds 0.828 volts, and at the anode cell 38, oxygen and chlorine may be produced at the cathode cell 22 if the voltage exceeds 0.401 volts. This voltage limitation reduces the system's ability to produce pure hydrogen 18, as shown in Table 1.

[0045] Table 1 - Voltage estimation in unipolar electrolysis of seawater

[0046] Anode gap, mm 4.8675

[0047] Cathode gap, mm 10.0506

[0048]

[0049]

[0050] There is a need for an apparatus and method that allows for the production of pure hydrogen 18 in higher yields from the electrolysis of seawater 30 by allowing for higher pool voltages without producing any significant amounts of chlorine or oxygen.

[0051] This document discloses an apparatus for electrolyzing seawater 30 to produce hydrogen 18. The apparatus includes a unipolar electrolyzer configured to operate in a cathode-cathode mode and configured to reduce the production of chlorine and / or oxygen.

[0052] exist Figure 2In some embodiments of this disclosure, the device includes a resistor located at the cathode or anode circuit for reducing the voltage at the cathode or anode and preventing the generation of chlorine or oxygen. The device includes a DC power supply 10 electrically connected to a modulator 14. The modulator is electrically connected to a cathode cell 22 and an anode cell 38. The cathode cell 22 includes a cathode electrode 24 and a solution electrode 32. The anode cell 38 includes an anode electrode 36 and a solution electrode 34. Components of the device are connected via wires 12, 16, 28, and 40. Figure 1 Hydrogen 18 is produced in the same manner as in the illustrated unipolar electrolysis apparatus, at both the cathode cell 22 and the anode cell 38. Figure 2 In the embodiment shown, resistor 46 is located before cathode cell 22, and resistor 48 is located before anode cell 38. Resistors 46 and 48 are capable of reducing the voltage at cathode 22 and the voltage at anode 38, respectively, to minimize or prevent the generation of chlorine or oxygen in each cell.

[0053] exist Figure 2 In the illustrated embodiment, based on a current of 100 amperes, the cell voltage is 2.1 volts, but the voltage across cathode cell 22 is 0.828 volts, of which resistor 46 accounts for 0.222 volts. At anode cell 38, resistor 48 accounts for 0.65 volts, resulting in a cell voltage of 0.401 volts across anode cell 38. The cell gap 50 at cathode 22 and the cell gap 52 at anode 38 are each 6 mm.

[0054] Resistors are inefficient because they consume power without producing hydrogen. Therefore, in some other embodiments of this disclosure, the cell gap at the cathode and anode is utilized to reduce the voltage at the cathode or anode and prevent the production of chlorine or oxygen. The voltage across the cell is proportional to the gap between the cathode or anode electrode and the corresponding solution electrode. Figure 1 As shown and described in, for example, Australian Patent 2008209322, in a conventional unipolar electrolysis apparatus, the cell gap at the anode cell is 4.8675 mm and the cell gap at the cathode is 10.0506 mm. It should be understood that, as used herein, the term "cell gap" refers to the distance between two electrodes in an electrolytic cell, such as the distance between the anode electrode 36 and the anode solution electrode 34 in the anode cell 38, or the distance between the cathode electrode 24 and the cathode solution electrode 32 in the cathode cell 22. In embodiments of this disclosure, the cell gap 50 at the cathode 22 and the cell gap 52 at the anode 38 are each 6 mm. It is understood that other cell gaps can be used, such as about 4 mm, about 4.5 mm, about 5 mm, about 5.5 mm, about 6 mm, about 6.5 mm, about 7 mm, about 7.5 mm, or about 8 mm. It should be understood that the optimal gap between the anode electrode 36 and the cathode electrode 24 for a particular apparatus can be determined empirically.

[0055] In certain other embodiments of this disclosure, the overall cell voltage is reduced without increasing the cell voltages of the anode and cathode by installing the cathode and anode cells in series. This allows for a higher overall cell voltage without increasing the cathode or anode cell voltage, which could potentially lead to unwanted chlorine or oxygen production. This embodiment... Figure 3 As shown in the figure, Figure 3 Five anode cells 38 with a cell gap 52 of 4 mm and four cathode cells 22 with a cell gap 50 of 6 mm are shown. (As...) Figure 2 Each anode cell 38 includes an anode electrode 36 and a solution electrode 34, and each cathode cell 22 includes a cathode electrode 24 and a solution electrode 32. The cathode electrode 24 can be any suitable electrode material, such as Pt / Ir (90:10) coated on a titanium mesh. The solution electrode 32 can be any suitable material, such as Ir / Ru or Mo / Co / Mn on titanium. Figure 3 The device also includes a DC power supply 10, which is electrically connected to a modulator 14, which in turn is electrically connected to a cathode cell 22 and an anode cell 38. The components of the device are connected by wires 12, 16, 28, 40, and 54.

[0056] Seawater is pumped into each pool at 200 lpm via valve 56, and hydrogen 18 is generated at each cathode pool 22 and each anode pool 38.

[0057] With a total cell voltage of 4 volts, the predicted voltage at anode cell 38 is 0.36 volts, while the predicted cell voltage at cathode cell 22 is 0.545 volts. The predicted voltages are based on the total gap 52 at anode cell 38 and the total gap 50 at cathode cell 22. Table 2 shows the cell voltages with a total cell voltage of 4 volts.

[0058] Table 2 - Voltages of Multiple Anode and Cathode Pools

[0059] Cathode gap, mm 6

[0060] Anode gap, mm 4

[0061]

[0062] In some implementations, the electrode material is made of a high-conductivity material such as copper or graphene.

[0063] Figure 4 The diagram illustrates the arrangement of pools in a commercial facility that electrolyzes seawater to produce only pure hydrogen. This technology also produces alkaline seawater, which can sequester carbon dioxide. This will help carbon-polluting plants using coal or natural gas, such as coal-fired power plants and cement plants, to sequester their carbon emissions. Figure 4The illustrated device includes three sets of cathode cells 22 and four sets of anode cells 38. Each set of cathode cells 22 and anode cells 38 is electrically connected to a DC power supply 10, which is electrically connected to a modulator 14, which in turn is electrically connected to the cathode cells 22 and anode cells 38. Figure 4 In the illustrated embodiment, there are eight sets of cathode cells 22 and eight sets of anode cells 38. It should be understood that the number of sets of cathode cells 22 and anode cells 38 can vary.

[0064] Seawater 30 is supplied to the seawater pump 70. Figure 4 In the apparatus, seawater passes through filter 72 and enters pump housing 35. Seawater 30 flows from pump housing 35 through valve 56 and control panel 64 into the bottom of each cathode pool 22 and each anode pool 38. Hydrogen 18 generated in each pool 22, 38 is removed and supplied to separation tank 74, where it is separated from alkaline seawater 20. Hydrogen 18 is removed from each separation tank 74 by vacuum pump 60, and then purified by passing hydrogen 18 through moisture collector 62 and silica gel 79. The purified hydrogen 18 then passes through mass flow meter 66 and hydrogen percentage meter 68.

[0065] exist Figure 5 The middle shows Figure 4 Another alternative version of the device shown is available. This version can be adapted for installation, for example, on a truck or in a shipping container. It can be placed near carbon emissions to demonstrate the production of hydrogen while simultaneously sequestering its carbon emissions.

[0066] Secondly, seawater is supplied to the ocean via a seawater pump 70 placed in ocean 31. Figure 5 In the apparatus, seawater 30 passes through screen 83 and enters pump box 35, where the filtered initial seawater is stored. Excess seawater 33 is allowed to drain. Seawater from pump box 35 passes through valve 56 into the bottom of each cathode pool 22 and each anode pool 38. The flow rate of seawater is controlled by valves 89 and 92. Hydrogen 18 generated in each pool is removed, and its flow rate is controlled by ball valve 80. Ball valve 80 is also used to remove alkaline seawater 20. Pressure valve 82 (150 lpm) and Maric valve 84 are also used to control the hydrogen flow rate. pH and Cl content are measured using pH meter 88 and chlorinometer 86, respectively. Hydrogen 18 is then supplied to separation tank 74, where it is separated from alkaline seawater 20. Hydrogen 18 is removed from each separation tank 74 by passing an inert gas 76 (e.g., nitrogen) through the separation tank 74. Baffle 78 is used to prevent alkaline seawater 20 from flowing out of the tank and into the hydrogen output line. The generated hydrogen 18 is then removed by vacuum pump 60 and purified by passing it through moisture collector 62 and desiccant 96. The gas flow rate is controlled by valve 94. The purified hydrogen 18 then passes through hydrogen percentage meter 68 and mass flow meter 66. The system is powered by a 50 kVA diesel generator 58.

[0067] In this embodiment, the cathode and anode electrodes are copper meshes coated with Hastelloy 276c. The solution electrode is copper-plated or graphene-plated with a ruthenium-iridium alloy or oxide.

[0068] To achieve higher hydrogen production capacity, the current needs to be increased, which necessitates increasing the pool voltage. For the diaphragmless pool described in the above embodiments, increasing the pool voltage above a certain point may result in the production of oxygen and chlorine in the same pool where hydrogen is produced. To avoid this, a membrane-type pool as described in US Patent 10,316,416 can be used, but instead of using an alkaline electrolyte in the anode pool and an acidic electrolyte in the cathode pool, only alkaline seawater is passed through both the anode and cathode pools. The electrodes and membrane are made of conductive materials, such as copper or graphene coated with a catalyst, which also prevents corrosion. The conductive membrane only allows electrons to pass through, thus hydroxide ions accumulate at the cathode, while H+ ions accumulate at the cathode. + Ions accumulate at the anode. Therefore, the seawater leaving the cathode pool is negatively charged, while the seawater leaving the anode pool is positively charged. As this seawater passes through another set of neutralization pools, the electrolytes are neutralized, an electric current flows, and, according to Faraday's law, another batch of oxygen and hydrogen is produced.

[0069] like Figure 6 As shown in Figure A, in the membrane cell seawater electrolysis, the seawater is alkaline. In this embodiment, the apparatus includes a cathode cell 22 and an anode cell 38 separated by a membrane 130. The total cell potential E0 = 1.229 volts, the anode cell 38 potential E0 = 0.401 volts, and the cathode cell 22 potential E0 = 0.828 volts. Hydrogen 18 is generated and hydroxide ions accumulate at the cathode cell 22, while oxygen 104 is generated and H+ ions accumulate at the anode cell 38. The anode electrolyte becomes positively charged, while the cathode electrolyte becomes negatively charged.

[0070] After treatment in the rechargeable battery, the electrolyte is degassed and then supplied to the neutralization tank, such as... Figure 6 As shown in B. In the neutralization tank, electrolyte 118 is positive, while electrolyte 120 is negative. According to Faraday's law, current flows and produces more hydrogen 18 and oxygen 104.

[0071] Figure 6 C shows including Figure 6 A's rechargeable battery and Figure 6The system of neutralization tanks B. Seawater 30 is supplied to a rechargeable battery comprising an anode tank 110 and a cathode tank 112. Anode tanks 110 and 112 are electrically connected to a DC power supply 10. Oxygen 104 generated in anode tank 110 is separated at oxygen outlet 108, while hydrogen 18 generated in cathode tank 112 is separated at hydrogen outlet 114. Anode electrolyte 118 and cathode electrolyte 120 then pass through a neutralization tank that is short-circuited to include anode tank 106 and cathode tank 116. Hydrogen 18 is generated in anode tank 106 and oxygen 104 is generated in cathode tank 116. Waste seawater 30 is removed from each tank.

[0072] The apparatus and method described herein could be used for the commercial production of pure hydrogen from seawater, which would greatly facilitate the use of hydrogen to replace carbon fuels. Wherever seawater is available, it would allow for hydrogen production in many parts of the world.

[0073] It should be understood that, unless otherwise stated or implied, the terms “comprise” and “include” as used in this specification, and any of their derivatives (e.g., “comprises,” “comprising,” “includes,” “including”), will be considered to include the features referred to by the terms and will not exclude the existence of any additional features.

[0074] Any reference to prior art in this specification is not, and should not be construed as, any form of admission that such prior art constitutes common general knowledge.

[0075] Those skilled in the art will understand that this disclosure is not limited in its use to the specific one or more applications described. This disclosure also does not limit preferred embodiments of the particular elements and / or features described or depicted herein. It should be understood that this disclosure is not limited to the disclosed one or more embodiments, but allows for various rearrangements, modifications, and substitutions without departing from the scope set forth and defined by the appended claims.

Claims

1. An apparatus for electrolysis of seawater to produce hydrogen, the apparatus comprising a single-pole electrolytic cell configured to operate in a cathode-cathode mode, and the apparatus configured to reduce the production of chlorine and / or oxygen by reducing the voltage at the cathode and / or anode, the apparatus comprising: one or more resistors to reduce the voltage at the cathode and / or anode, and / or a cathode cell comprising a cathode electrode and a cathode cell solution electrode; an anode cell comprising an anode electrode and an anode cell solution electrode; wherein the intercell gap between the cathode electrode and the cathode cell solution electrode and the intercell gap between the anode electrode and the anode cell solution electrode are configured to reduce the voltage at the cathode and / or anode; wherein the device comprises: a plurality of anode cells in series, each anode cell having a gap between its electrodes; and a plurality of cathode cells in series, each cathode cell having a gap between its electrodes, wherein the gap between the electrodes in the cathode cells is greater than the gap between the electrodes in the anode cells.

2. The apparatus of claim 1, wherein, The cathode cells and the anode cells are membraneless electrolytic cells connected in a cathode mode.

3. The apparatus of claim 2, wherein, The cathode cells and the anode cells are equipped with low resistance electrodes coated with at least one catalyst.

4. The device of claim 1, comprising membraneless electrolytic cells, the anode cells having a smaller gap between the electrodes being more numerous and the cathode cells having a larger gap between the electrodes being less numerous.

5. The apparatus of claim 4, wherein, The device comprises five anode cells with a 4 mm electrode gap and four cathode cells with a 6 mm electrode gap.

6. The apparatus of claim 2, wherein, The electrodes of the membraneless electrolytic cells are made of a high conductivity material and are coated with a protective coating and / or a catalyst coating.

7. The apparatus of claim 6, wherein, The high conductivity material is selected from the group consisting of copper and graphene.

8. The apparatus of claim 6, wherein, The catalyst coating comprises Hastelloy 276c.

9. The apparatus of claim 6, wherein, The protective coating comprises ruthenium / iridium metal or oxides thereof.

10. The apparatus of any one of claims 1 to 9, wherein, The cathode-cathode mode comprises an electrical connection wherein the negative pole of a DC power source is connected to the cathode electrode, the cathode cell solution electrode is connected to the anode electrode, and the positive pole of the DC power source is connected to the anode cell solution electrode.

11. A method for producing hydrogen from seawater, the method comprising introducing seawater into a device according to any one of claims 1 to 10 and producing hydrogen therefrom.

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