US20080190781A1

US20080190781A1 - Electrochemical Method for Producing and Storing Hydrogen by the Redox of Zinc and Water

Info

Publication number: US20080190781A1
Application number: US11/912,213
Authority: US
Inventors: Chao Huang
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-04-28
Filing date: 2006-01-20
Publication date: 2008-08-14
Also published as: WO2006114034A1; JP2008539328A; CN1854063A

Abstract

Disclosed herein is an electrochemical method for producing and storing hydrogen, which is a closed system consisting of a gas-generating electrode, an electrolyte and a zinc electrode, the gas-generating electrode and zinc electrode are connected respectively to the external circuits; characterized in that switching on the external circuit of the gas-generating electrode and zinc electrode the hydrogen is to be released, the reduction reaction of water occurs on the gas-generating electrode producing hydrogen; zinc is oxidized on the zinc electrode generating the oxidation products of zinc; when the hydrogen is to be stored, supplementary water is supplied to the closed system, the negative pole of power source is connected to the external circuit of the zinc electrode, and the positive pole of power source is connected to the external circuit of the gas-generating electrode, switching on the direct current, the reduction reaction of zinc occurs on the zinc electrode, the oxidation products of zinc are reduced into zinc, renew the zinc electrode, the oxidation reaction of water occurs on the gas-generating electrode, the oxygen is generated and discharged. A simple and convenient process and widely applied are property of the present invention. It suits to provide hydrogen for hydrogen fuel cells. While providing the hydrogen, it can also generate electricity as secondary product, which generates the electricity together with a fuel cell.

Description

FIELD OF THE INVENTION

This invention relates to the technology of producing and storing hydrogen, particularly to the electrochemical method for producing and storing hydrogen by the redox of zinc and water.

BACKGROUND OF THE INVENTION

As consumption of petrochemical fuel and exhaustion of reserves of petrochemical fuel are daily on the increase, environmental protection has been gradually emphasized. Primary energy source including petroleum, coal and natural gas shall be finally replaced by clean and renewable energy source such as solar energy, wind energy, energy from the sea, biological energy, etc. As secondary energy source, without pollution, hydrogen energy is greatly valued by every country in the world due to considerable advantages of being rich in its resource, having high combustion heat quantity, producing water as its combustion product, and having no environmental pollution, etc. Especially, a hydrogen-oxygen (air) fuel cell that uses hydrogen as its fuel, rose in recent years, is one kind of highly efficient, clean and long-life electricity generation device, which will become the ideal power source of portable electronic products and electrically driven vehicles. Main cause of hindering its popularization is lack of appropriate source of hydrogen. At present, there are four main ways to supply the hydrogen for the fuel cell and that of: I. High-pressure hydrogen bottle method. 2. Low temperature fluidized method. 3. Hydrocarbon fuel reforming method; 4. Metal hydrides storing-hydrogen method. Wherein, the high-pressure hydrogen bottle method and the low temperature fluidized method have some serious shortcomings such as high cost, being poor in the aspect of safety etc. The hydrocarbon fuel reforming method, being poor in the aspect of purity of hydrogen gas, needs the relatively high temperature, the large equipment. Due to safety property, the metal hydrides storing-hydrogen method plays an importance role in the research and development of storing-hydrogen technology. However, the storing-hydrogen alloy is very expensive and easy to become chalking in the course of filling, which is relatively complicated, and releasing the hydrogen gas. Nowadays, a patent, in name of “Electrochemical Method and Equipment for Producing and Storing Hydrogen by Redox of Aluminum-Water” (its application number is 02148850.9) provided two phases circulating filtering closed system consisted of an aluminum alloy electrode-electrolyte-highly active hydrogen-generating catalytic plate electrode with advantages being of highly efficient, safe, without environment pollution, etc. However, its shortcomings are as follows: the aluminum alloy electrode is a disposable consumable material; it is needed to replace the aluminum alloy electrode after hydrogen generation every time; it has a high consumption; in addition, produced aluminum oxide must be eliminated by pump circulation filtering, and the hydrogen generation course is relatively complicated, which increases the cost.

SUMMARY OF THE INVENTION

The objective of the invention is to provide the electrochemical method for producing and storing hydrogen by the redox of zinc and water with high reliability, low cost, simple and convenient process wherein the zinc electrode can be used repeatedly.
In order to fulfill the objective above, the technology program of the invention is as follows.
The method comprises the closed system consisted of the gas-generating electrode-electrolyte-zinc electrode. Both the gas-generating electrode and the zinc electrode are connected respectively to the external circuit. When the hydrogen is to be produced, the external circuits of the gas-generating electrode and zinc electrode are connected, water is reduced into hydrogen on the gas-generating electrode, the reduction reaction of water occurs on the gas-generating electrode, zinc is oxidized on the zinc electrode generating the oxidation products of zinc. Switching off the external circuit, the releasing process of hydrogen gas stops immediately; when the hydrogen is to be stored, supplementary water is supplied to the closed system, and then the negative pole of power source is connected to the external circuit of zinc electrode, and the positive pole of power source is connected to the external circuit of gas-generating electrode, then the direct current is applied, the oxidation products of zinc are reduced into zinc on the zinc electrode, and water is oxidized into oxygen on the gas-generating electrode, and then the oxygen is released.
The gas-generating electrode used in this invention consists of the hydrogen-generating electrode and oxygen-generating electrode, or the hydrogen-generating electrode that is concurrently as the oxygen-generating electrode. The former uses a system that consists of the oxygen-generating electrode, electrolyte, zinc electrode, electrolyte and hydrogen-generating electrode or the oxygen-generating electrode-electrolyte-zinc electrode-electrolyte-hydrogen-generating electrode. When the hydrogen is to be released, the external circuits of the hydrogen-generating electrode and zinc electrode is connected; when the hydrogen is to be stored, the negative pole of power source is connected to the external circuit of zinc electrode, the positive pole of power source is connected to the external circuit of oxygen-generating electrode. The latter uses a system that consists of the zinc electrode, electrolyte, hydrogen-generating electrode that is concurrently as the oxygen-generating electrode or the zinc electrode-electrolyte-hydrogen-generating electrode, wherein hydrogen-generating electrode is concurrently used as the oxygen-generating electrode. When the hydrogen is to be released, the zinc electrode and hydrogen-generating electrode that is concurrently used as the oxygen-generating electrode are connected to the external circuit, and when the hydrogen is to be stored, the negative pole of power source is connected to the external circuit of zinc electrode, the positive pole of power source is connected to the external circuit of hydrogen-generating electrode that is concurrently used as the oxygen-generating electrode.
Generally, the electrolyte used in this invention is strong alkaline electrolyte aqueous solution so that the zinc electrode has good reversibility and great capability to discharge under the heavy electric current. The strong alkaline electrolyte is taken as an example thereafter to explain reaction principle of the electrochemistry occurred in the system for producing and storing hydrogen by the redox of zinc and water.
1. When the hydrogen is to be released, the reaction occurred is as follows.
Zinc Electrode:
Zn+2OH⁻−2e→Zn(OH)₂(E ⁰=−1.249 V)
Or, Zn+2O H⁻−2e→ZnO+H₂O(E ⁰=−1.260 V)
Gas-Generating Electrode:
2H₂O+2e2O H⁻+H₂↑ (E ⁰=−0.828 V)
The overall reaction is: Zn+2H₂O→Zn(OH)₂+H₂↑ (ΔE ⁰=0.421 V)
Or, Zn+2H₂O→ZnO+H₂↑ (ΔE ⁰=0.432 V)
Essentially, it is a course that water is reduced and zinc is oxidized to generate Zn (OH)₂or ZnO, producing the hydrogen and electric energy. The electric current with certain voltage can be obtained in the external circuit, and the theoretical electric potential is 0.42-0.43 V. The produced quantity of hydrogen can be controlled conveniently by controlling the electric current of the external circuit.
2. When the hydrogen is to be stored, the reaction occurred is as follows.
Zinc Electrode:
Zn(OH)₂+2e→Zn+2OH⁻(E ⁰=−1.249 V)
Or, ZnO+H₂O+2e→Zn+2O H⁻(E ⁰=−1.260 V)
Gas-Generating Electrode:
2O H⁻−2e→2H₂O+1/2O2 ↑ (E ⁰=0.401 V)
The overall reaction is: Zn(OH)₂→Zn+H₂O ↑ +1/2O2 ↑ (ΔE⁰=−1.650 V)
Or, ZnO→Zn+1/2O2 ↑ (ΔE ⁰=−1.661 V)
Essentially, it is a course that Zn (OH)₂or ZnO is electrolyzed and reduced into Zn to produce the oxygen. Due to a great overpotential, the practical decomposition voltage will be higher than the theoretical electric potential of 1.65-1.66 V, which can be up to about 2 V.
In the conditions of using other kinds of electrolytes, or in the initial stage of using the strong alkaline electrolyte, when zinc discharges, the zinc oxidation products that differ from Zn (OH)₂or ZnO can be generated. But the course and principle of charging and discharging of producing and storing the hydrogen are the same as the example mentioned above.
The zinc electrodes used in the method for producing and storing hydrogen in this invention are made of the zinc active substance, adhesive, additives and current-collecting device by using many physical and chemical methods such as the compacting, applying paste, agglomerating, boxing (piping), foaming, electrodeposition technology etc. The zinc active substance can be composed of the zinc compounds such as the zinc alloy powder, zinc oxide, zinc hydroxide, zincate, etc. or their combinations; the adhesive selected from the group consisting of carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE) emulsion, polyvinyl alcohol (PVA), hydroxypropyl emthylcellulose (HPMC), polyethylene oxide (PEO), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), hexafluoropropylene, or mixtures thereof; the additives selected from the group consisting of zinc oxide, calcium oxide, magnesium oxide, cadmium oxide, alumina, bismuth compounds, lead compounds, calcium hydroxide, graphite powder, acetylene black, carbon powder, electric carbon black, active carbon powder, short-cut fiber, carbon fibers, or mixtures thereof; the current-collecting device can be made of the foamed metal, metal mesh, metal tape (metal can be pure metal or alloy) by using the physical and chemical methods such as electroplating, composite plating to treat the surface oft metal; For example, they may be the foamed brass, lead plating or tin plating punched brass strip, brass screen. The zinc electrode described above can be the flaky and porous powder structure and preferably porous powder structure.
The electrolyte used in the method for producing and storing hydrogen in this invention is treated by using an aqueous solution electrolyte with the battery diaphragm to absorb. The pH of the aqueous solution is more than 4; The concentration of the aqueous solution is in range of 0.05 Mol/L˜15 Mol/L. The aqueous solution can be selected from the hydroxide aqueous solution of alkali metal or alkaline earth metal or their mixtures, and preferably KOH, NaOH aqueous solution or their mixtures, or the carbonate, sulfate, fluoride salt aqueous solution of alkali metal or alkaline earth metal or their mixtures, or the mixture of their hydroxide aqueous solution; the diaphragm can be made of any one selected from the group consisting of cellulose hydrate film, polyethylene graft film, cellophane paper, nylon cloth, hydrated cellulose paper, cotton paper, potassium titanate paper, polyethylene felt, zirconia fiber paper, vinyl on non-woven fabric, or mixtures thereof to form composite membrane.
The lower overpotential active hydrogen-generating electrode for hydrogen-generating can be used as the hydrogen-generating electrode in this invention. The active hydrogen-generating electrode is made of pure metal, metal oxide, alloy or metal and the composite material formed by alloy and oxide, by using physical and chemical methods such as the electroplating, composite plating, thermal decomposition, ion plating, ion implantation, ion sputtering, chemical plating, foamed metal technology, and also by comprehensively using the two or three kinds of technologies described above. Its composition can be the pure metals selected from the group consisting of lower overpotential metal for hydrogen-generating such as Ni, Co, Fe, Mo, W, Pt, Pd, Ru oxides such as RuO₂, TiO₂, ZrO2, alloys such as Ni—Mo, Ni—B, Ni—P, Ni—NiS, Ni—Pt, Ni—Ru, Co—Mo, Ni-Wo, Xi-Sn, Mo—W, Co—W, Ni-storing-hydrogen alloy, as well as Ni—P—Co—Mo—W, Ni—Co—Mo, Ni—Co—Mo—W, Ni—P—Mo—Co, Ni—P—W, Ni—P—Co—Mo—W, Ni.B—Co, Ni—B—Mo, Hi-B—Co—Mo, Ni—B—Co—Mo—W, Ni—B—W, Ni—Co— storing-hydrogen alloy, the composite materials formed by the metal or alloy with the oxide, in terms of the composite materials that adheres to the RuO₂, ZrO₂, carbon fine particles with the pure metal or alloy mentioned above or pure metal and alloy mixtures, such as Ni—RuO₂, Ni—Mo—RuO₂, Ni—NiS, Ni—Mo—W—RuO₂. The oxygen-generating electrode is made of metal steel, iron, nickel with the structures of mesh, strip, plate, sheet, foamed metal, by using the nickel plating or sulfur coated nickel plating method, or is the titanium-base platinum group oxide electrode, iridium system coating titanium electrode, manganese dioxide coating titanium electrode, perovskite structure of oxide electrode, which have a special catalytic force to the oxygen-generating course.
The hydrogen-generating electrode that is concurrently as the oxygen-generating electrode used in this invention can be made of the metallic materials such as the steel, iron, nickel with the structures such as mesh, strip, plate, sheet, foamed metal, and treated by using the physical and chemical methods such as the nickel plating or sulfur coated nickel plating.
The hydrogen-generating electrode, oxygen-generating electrode and hydrogen-generating that is concurrently as the oxygen-generating electrode described above, can be made into the a variety of structures such as flaky, meshy, porous structures, and the gas diffusion electrode structure that is similar to the fuel cell electrode can be selected.
The following two kinds of devices can be made according to this invention:
1. A device consists of a storage tank, liquid control valve, filling opening, hydrogen collecting chamber, hydrogen outlet, oxygen outlet, zinc electrode, compartment separator plate, hydrogen-generating electrode, oxygen-generating electrode and dash pot. The storage tank is located above the hydrogen collecting chamber. The electrolytic cell system, provided with a plurality of electrode chambers, is installed at the lower part of the hydrogen collecting chamber. The number of the chambers is determined according to the amount required to produce the hydrogen gas and the release rate of the hydrogen gas. The hydrogen-generating electrode, zinc electrode and oxygen-generating electrode are uniformly arranged in each electrode chamber. Each electrode chamber, which separates the electrodes from each other, is filled with diaphragms. Each electrode is connected to the external circuit. There is the filling opening on the storage tank for the electrolyte aqueous solution or water supplementing. The hydrogen outlet is set on the hydrogen collecting chamber, and the dash pot is equipped on the lower part of the electrolytic cell system, which is used for keeping the same liquor level of the electrolyte in the electrolytic cell system. When the hydrogen gas is to be released, the liquid control valve is firstly opened so as to make the electrolyte of the storage tank flowing into every electrode chamber and the dash pot in the electrolytic cell system through a duct on the bottom of storage tank, then to switch on the external circuit of the zinc electrode and hydrogen-generating electrode and form a loop. A large quantity of hydrogen gas begins to be produced on the hydrogen-generating electrode. The hydrogen gas is collected in the hydrogen collecting chamber and flows out through the hydrogen outlet. While the hydrogen gas flows out, the electric energy is sent out from the positive pole and negative pole of the electrochemical system for producing and storing hydrogen. By switching off the external circuit of the zinc electrode and hydrogen-generating electrode, the system immediately stops producing hydrogen. When the hydrogen gas is to be stored, at first supplementary sufficient water is applied into the electrolytic cell system through the filling opening, and then connect the positive pole of power source to the external circuit of the oxygen-generating electrode, connect the negative pole to the external circuit of the zinc electrode, switch on the direct current, the zinc electrode begins to be reduced into zinc and the oxygen-generating electrode begins to largely produce oxygen. The oxygen discharges directly from the oxygen outlet.
2. The device can be a structure that consists of the storage tank, the liquid control valve, the filling opening, the hydrogen collecting chamber, hydrogen outlet, the oxygen outlet, zinc electrode, the compartment separator plate, the hydrogen-generating electrode that is concurrently as the oxygen-generating electrode and the dash pot. The storage tank is located above the hydrogen collecting chamber. The electrolytic cell system, provided with a plurality of electrode chambers, is installed at the lower part of the hydrogen collecting chamber. The number of the chambers is determined according to the amount required to produce the hydrogen gas and the release rate of the hydrogen gas. The zinc electrode and hydrogen-generating electrode that is concurrently as the oxygen-generating electrode are uniformly arranged in each electrode chamber. Those electrodes are separated from each other. Each electrode is connected to the external circuit. Each electrode chamber is filled with diaphragms, which separates the electrodes from each other. There is the filling opening on the storage tank for the electrolyte aqueous solution or water supplementing. The hydrogen outlet is set on the hydrogen collecting chamber, and the dash pot is equipped on the lower part of the electrolytic cell system, which is used for keeping the same liquor level of the electrolyte in the electrolytic cell system. When the hydrogen gas is to be produced, the liquid control valve is firstly opened to make the electrolyte in the storage tank flowing into every electrode chamber and the dash pot in the electrolytic cell system through the duct on the bottom of storage tank, then to switch on the external circuit of the zinc electrode and hydrogen-generating that is concurrently as the oxygen-generating electrode and form a loop. A large quantity of hydrogen gas begins to be produced on the hydrogen generating electrode that is concurrently as the oxygen-generating electrode. The hydrogen gas is collected in the hydrogen collecting chamber and flows out through the hydrogen outlet. While the hydrogen gas flows out, the electric energy is sent out from the positive pole and negative pole of the electrochemical system for producing and storing hydrogen. By switching off the external circuit of the zinc electrode and hydrogen-generating electrode, the system immediately stops producing hydrogen. When the hydrogen gas is to be stored, at first supplementary sufficient water is applied into the electrolytic cell system through the filling opening, and then to connect the positive pole of power source to the external circuit of the oxygen-generating electrode, connect the negative pole to the external circuit of the zinc electrode, and switch on the direct current, the zinc electrode begins to be reduced into zinc and the hydrogen-generating that is concurrently as the oxygen-generating electrode begins to produce massive product of oxygen. The oxygen discharges directly from the oxygen outlet.
New concept of the invention, utilizing the electrochemistry technology and the system for producing and storing the hydrogen formed by the combination of the zinc electrode and the gas-generating electrode in the electrolyte, shown that of the electrochemical system for producing and storing hydrogen with high efficiency, high reliability, low cost being used repeatedly, which obviously is different from all kinds of traditional sources of hydrogen.
The differences are shown as follows:
I. Having safe, convenient character, and good controllability, as well as size free adjusting property.
The process of producing and storing hydrogen, belongs to the battery reaction, can be done under the condition of the normal temperature and normal pressure. The output of hydrogen can be controlled only by controlling the amount of the electric current with the rapid and convenient process of the operations of starting and stopping. The system of this invention can be designed in the way of modularization. Therefore, it is easy for the disassembly, assembly and combination. The source of hydrogen can be made into the miniature and small size on a large scale with movable or fixable model.
2. With high density of the stored energy, good purity of the hydrogen gas and a wide working range of the invention.
It shows that the density of the stored energy of zinc itself is high. The purity of hydrogen produced in the condition of the strong base electrolyte is high, and working condition can be low temperature, the range of its application is wide.
3. Having characters of low cost, rich in the source of the raw material, without pollution and in favor of environmental protection.
Because of an electrochemical reaction of zinc and water and what is stored in the system is water and zinc, the cost of the system of present invention is greatly lower than the cost of the alloy for storing hydrogen. In addition, it is rich in the zinc resource. Due to using the raw materials that do not contain hydrargyrum, the invention can be used with safe and reliability and not resulting in environmental pollution.
4. Having convenient and chargeable and reusable feature.
Because this system uses the way of charging to store the hydrogen energy, therefore, it is not necessary to have inconvenient sources of hydrogen such as a hydrogen station or hydrogen bottle. In other words, the hydrogen can be stored only by having electricity and water. It can also be used repeatedly for many times.
5. The hydrogen gas and the electric energy producing at the same time.
When the hydrogen is to be released, the electric energy can be produced without an external electricity supply.
Lying with the advantages mentioned above, this invention has a great application value in the aspect of portable and movable source of hydrogen. Especially, it is suitable to provide hydrogen for hydrogen fuel cells. While providing the hydrogen, it can also generate electricity as secondary product, which generates the electricity together with a fuel cell.
This invention is also suitable for the following technical fields: providing a convenient movable source of hydrogen environment with equipments such as the laboratory equipment and welding equipment; the circumstances of jointly using electricity and hydrogen or exclusively using electricity or hydrogen using a heat source, field lighting, etc. This invention can be also used in the aspect of energy storage. For example, the superfluous electric power is stored in the lowest electricity-used period and the electric power generated by solar energy is stored. The energy storage ways are the joint storage of hydrogen and electric energy.

DESCRIPTION OF THE INVENTION IN DETAIL

EXAMPLE 1

Taking 1.5 g electric carbon black together with 6.0 g zinc oxides, 1.5 g zinc powder without hydrargyrum, 3.3 ml polyvinyl alcohol aqueous solution (concentration 3%), 25 ml sodium carboxymethyl cellulose aqueous solution (concentration 2%), 4 ml polytetrafluoroethylene (PTFE) emulsion (10% mass concentration), uniformly stirring and heating it into a lump, rolling the lump into a sheet, pressing the sheet onto the 60-mesh brass screen, which is taken as the zinc electrode. PPAT-AS-SL8 film from Shanghai Shilong Company is as the diaphragm, foamed nickel sheet is as the oxygen-generating electrode, and the foamed nickel sheet that is coated with Pt/C (Platinum is attached on the electric carbon black) catalyst is as the hydrogen-generating electrode, 5 Mol/L KOH aqueous solution is as the electrolyte. The electrolyte submerges the most parts of the electrode.
The effective area of this single battery electrode is five square centimeters.
Constant Current Charge: The zinc electrode is connected to the negative pole, and the foamed nickel sheet is connected to the positive pole. The electric current is 50 mA charging for 3 hours. After charging, it stands for 15 minutes. When charging, the gas is produced on the positive pole. No gas is produced on two poles when standing.
Discharge and Hydrogen Production: the zinc electrode is as the negative pole and the foamed nickel sheet that is coated with Pt/C catalyst is as the positive pole. When the battery discharges, discharging current and voltage are measured by using a universal meter. After the circuit is supplied, the electric current begins with 0.5 A furiously bubbling up. The gas production rate is up to 3.3 ml per minute. When reducing the electric current, the gas production rate is reduced. If the circuit is not supplied during the processing, hydrogen production stops. When switching on the circuit again, the hydrogen production starts again. In this way, the charge and discharge are repeated for three times, and the electric current and voltage slightly changed only and the same in phenomenon.

EXAMPLE 2

Taking 2.5 g zinc powder without hydrargyrum together with 7.5 g zinc oxides, 3 ml polyvinyl alcohol aqueous solution (concentration 3%), mixing them into a slurry, applying it on the foamed nickel, after it is baked to drying, it is pressed into a sheet, which is taken as the zinc electrode. The PPAT-AS-SL8 film is as the diaphragm, foamed nickel sheet is as the hydrogen-generating that is concurrently as the oxygen-generating electrode, 5 Mol/L NaOH aqueous solution is as the electrolyte. The electrolyte submerges the most parts of the electrode. The effective area of the single battery electrode is ten square centimeters.
Constant Current Charge: The zinc electrode is connected to the negative pole, and the foamed nickel sheet is connected to the positive pole. The electric current is 60 mA charging for 5 hours. After charging, it stands for 15 minutes. When charging, the gas is produced on the positive pole. No gas is produced on two poles when standing.
Discharge and Hydrogen Production: the zinc electrode is as the negative pole and the foamed nickel sheet is as the positive pole. When the battery discharges, discharging current and voltage are measured by using a universal meter. Switch on the circuit, the discharging current is 70 mA and the voltage is 46 mV, bubbling up soon. After two hours, the voltage still is 65 mV while the discharging current is 36 mA.
Collecting the produced gas, the discharging begins with being up to 0.5 ml per minute. When adjusting the electric current, in this way, charge and discharge are repeated for three times, and the electric current and voltage slightly changed only and the same in phenomenon.

EXAMPLE 3

Taking 0.5 g electric carbon black together with 7 g zinc oxides, 1.5 g zinc powder without hydrargyrum, polyvinyl alcohol 3.3 ml aqueous solution (concentration 3%), 25 ml sodium carboxymethyl cellulose aqueous solution concentration 3%), 4 ml polytetrafluoroethylene (PTFE) emulsion (10% mass concentration), uniformly stirring and heating it into a lump, rolling the lump into a sheet, pressing the sheet onto the 60-mesh brass screen, which is taken as the zinc electrode. The PPAT-AS-SL8 film is as the diaphragm, foamed nickel sheet is the hydrogen-generating that is concurrently as the oxygen-generating electrode, 5 Mol/L KOH aqueous solution is the electrolyte. The electrolyte submerges the most parts of the electrode.
The effective area of this single battery electrode is 12 square centimeters.
Constant Current Charge: The zinc electrode is connected to the negative pole, and the foamed nickel sheet is connected to the positive pole. The electric current is 100 mA charging for 5 hours. After charging, it stands for 15 minutes. When charging, the gas is produced on the positive pole. No gas is produced on two poles when standing.
Discharge and Hydrogen Production: the zinc electrode is as the negative pole and the foamed nickel sheet is as the positive pole. When the battery discharges, discharging current and voltage are measured by using a universal meter. The electric current begins with 0.5 A, after an hour, the electric current is 0.1 A, and after 3.5 hours, 62 mA, furiously bubbling up occurs as the charge begins. The gas production rate is up to 3.3 ml per minute. When reducing the electric current, the gas production rate is reduced. When switching off the circuit, hydrogen production stops. When switching on the circuit again, the hydrogen production starts again.
In this example, the charge and discharge are repeated for three times in the way of referenced above, there is slightly change in the electric current and voltage and no change in phenomenon.
With regard to all the combinations and methods disclosed and revealed in this invention, the disclosed content in this document can be used for reference. Although they have been described partly by giving the executive examples, the people in this filed can change, splice, add or reduce this invention in the condition of not obviously divorcing from the contents, spirits and range, which are obvious to those professionals in this field. But their changes are included in the contents, spirits and range in this invention.

Claims

1. An electrochemical method for producing and storing hydrogen in a closed system consisting of a gas-generating electrode, an electrolyte and a zinc electrode, the gas-generating electrode and zinc electrode are connected respectively to the external circuit; wherein switching on the external circuit of the gas-generating electrode and zinc electrode the hydrogen is to be released, the reduction reaction of water occurs on the gas-generating electrode producing hydrogen, zinc is oxidized on the zinc electrode generating the oxidation products of zinc; when the hydrogen is to be stored, supplementary water is supplied to the closed system, the negative pole of power source is connected to the external circuit of the zinc electrode, and the positive pole of power source is connected to the external circuit of the gas-generating electrode, switching on the direct current, the oxidation products of zinc are reduced into zinc on the zinc electrode, renew the zinc electrode, the oxidation reaction of water occurs on the gas-generating electrode, the oxygen is generated and discharged.

2. The electrochemical method for producing and storing hydrogen described according to claim 1, wherein the gas-generating electrode consists of the hydrogen-generating electrode and oxygen-generating electrode; or consists of the hydrogen-generating electrode that is concurrently as the oxygen-generating electrode.

3. The electrochemical method for producing and storing hydrogen described according to claim 1, wherein the zinc electrode is made of zinc active substance, adhesive, additives, current-collecting device by using physical methods such as compacting, applying paste, agglomerating, boxing or piping, foaming, electrodeposition technology, and is composed of zinc active substance selected from the group consisting of zinc alloy powder, zinc oxide, zinc hydroxide, zinc compound such as zincate or mixtures their of; the adhesive selected from the group consisting of carboxymethyl cellulose, polytetrafluoroethylene emulsion, polyvinyl alcohol, hydroxypropyl emthylcellulose, polyethylene oxide, polyacrylic acid or polyvinylidene fluoride, hexafluoropropylene, or mixture thereof; the additives selected from the group consisting of zinc oxides, calcium oxide, magnesium oxide, cadmium oxide, alumina, indium compounds, bismuth compounds, lead compounds, calcium hydroxide, graphite powder, acetylene black, carbon powder, electric carbon black, active carbon powder, short-cut fiber, or carbon fibers, or mixtures thereof; current-collecting device being made of any one selected from the group consisting of foamed metal, metal mesh, metal tape (metal can be pure metal or alloy) by using the physical and chemical methods such as electroplating, composite plating to treat the surface of the metal; and preferably the punched brass strip, brass screen of the foamed brass, lead plating or tin plating.

4. The electrochemical method for producing and storing hydrogen described according to claim 1, wherein the zinc electrode is a flaky or porous powder structure, and preferably the porous powder structure.

5. The electrochemical method for producing and storing hydrogen described according to claim 1, wherein the electrolyte is an aqueous solution electrolyte, and is absorbed by the battery diaphragm, the pH of the aqueous solution is more than 4, and concentration of the aqueous solution is in range of 0.05 Mol/L-15 Mol/L; the hydroxide aqueous solution selected from the alkali metal or alkaline earth metal or their mixtures, the optimized selection is KOH, NaOH aqueous solution or their mixture, or selected from the group consisting of carbonate, sulfate, fluoride salt aqueous solution of the alkali metal or alkaline earth metal or mixtures thereof, or the mixture mixed with their hydroxide aqueous solution; the diaphragm is selected from the group of materials consisting of hydrated cellulose film, polyethylene graft film, cellophane paper, nylon cloth, hydrated cellulose paper, cotton paper, potassium titanate paper, polyethylene felt, zirconia fiber paper, vinylon non-woven fabric or mixtures of a composite membrane thereof.

6. The electrochemical method for producing and storing hydrogen described according to claim 1, wherein the hydrogen-generating electrode is made of pure metal, metal oxide, and the composite materials made by the alloy or metal and alloy and oxide, by using several physical and chemical methods such as electroplating, composite plating, thermal decomposition, ion plating, ion implantation, ion sputtering, chemical plating, foamed metal technology, or made by combining two or three kinds of technologies; the hydrogen-generating electrode selected from the group preferably consisting of pure metal such as Co, Fe, Mo, W, Pt, Pd, Ru; oxide such as RuO₂, TiO₂, ZrO₂; alloy such as Ni—Mo, Ni—B, Ni—P, Ni—NiS, Ni—Pt, Ni—Ru, Co—Mo, Ni-Wo, Ni—Sn, Mo—W, Co—W, Ni-storing-hydrogen alloy, and Ni—P—Co—No—W, Ni—Co—Mo, Ni—Co—Mo—W, Ni—P—Mo—Co, Ni—P—W, Ni—P—Co—Mo—W, Ni—B—Co, Ni—B—Mo, Ni—B—Co—Mo, Ni—B—Co—Mo—W, Ni—B—W, Ni—Co-storing-hydrogen alloy; composite material of the metal or alloy with oxide such as Ni—RuO, Ni—Mo—RuO, Ni—NiS, Ni—Mo—W—RuO₂.

7. The electrochemical method for producing and storing hydrogen described according to claim 1, wherein the oxygen-generating electrode is made of steel, iron, or nickel by using methods of nickel plating, or sulfur coated nickel plating on structures such as mesh, strip, plate, sheet, foamed metal to treat the surface, or the electrode is any one selected from the group consisting of titanium-base platinum group oxide electrode, iridium system coating titanium electrode, manganese dioxide coating titanium electrode, perovskite type oxide electrode.

8. The electrochemical method for producing and storing hydrogen described according to claim 1, wherein the hydrogen-generating electrode that is concurrently as the oxygen-generating electrode described is made of steel, iron, nickel by using methods of the nickel plating or sulfur coated nickel plating on structures such as mesh, strip, plate, sheet and foamed metal to treat the surface.

9. The electrochemical method for producing and storing hydrogen described according to claim 1, wherein the hydrogen-generating electrode, oxygen-generating electrode, and hydrogen-producing electrode that is concurrently as the oxygen-generating electrode described are structured flaky, meshy, porous, gas diffusion electrode.

10. The electrochemical method for producing and storing hydrogen described according to claim 3, wherein the zinc electrode is a flaky or porous powder structure, and preferably the porous powder structure.

11. The electrochemical method for producing and storing hydrogen described according to claim 2, wherein the hydrogen-generating electrode is made of pure metal, metal oxide, and the composite materials made by the alloy or metal and alloy and oxide, by using several physical and chemical methods such as electroplating, composite plating, thermal decomposition, ion plating, ion implantation, ion sputtering, chemical plating, foamed metal technology, or made by combining two or three kinds of technologies; the hydrogen-generating electrode selected from the group preferably consisting of pure metal such as Co, Fe, Mo, W, Pt, Pd, Ru; oxide such as RuO₂, TiO₂, ZrO₂; alloy such as Ni—Mo, Ni—B, Ni—P, Ni—NiS, Ni—Pt, Ni—Ru, Co—Mo, Ni-Wo, Ni—Sn, Mo—W, Co—W, Ni-storing-hydrogen alloy, and Ni—P—Co—No—W, Ni—Co—Mo, Ni—Co—Mo—W, Ni—P—Mo—Co, Ni—P—W, Ni—P—Co—Mo—W, Ni—B—Co, Ni—B—Mo, Ni—B—Co—Mo, Ni—B—Co—Mo—W, Ni—B—W, Ni—Co-storing-hydrogen alloy; composite material of the metal or alloy with oxide such as Ni—RuO, Ni—Mo—RuO, Ni—NiS, Ni—Mo—W—RuO₂.

12. The electrochemical method for producing and storing hydrogen described according to claim 2, wherein the oxygen-generating electrode is made of steel, iron, or nickel by using methods of nickel plating, or sulfur coated nickel plating on structures such as mesh, strip, plate, sheet, foamed metal to treat the surface, or the electrode is any one selected from the group consisting of titanium-base platinum group oxide electrode, iridium system coating titanium electrode, manganese dioxide coating titanium electrode, perovskite type oxide electrode.

13. The electrochemical method for producing and storing hydrogen described according to claim 2, wherein the hydrogen-generating electrode that is concurrently as the oxygen-generating electrode described is made of steel, iron, nickel by using methods of the nickel plating or sulfur coated nickel plating on structures such as mesh, strip, plate, sheet and foamed metal to treat the surface.

14. The electrochemical method for producing and storing hydrogen described according to claim 2, wherein the hydrogen-generating electrode, oxygen-generating electrode, and hydrogen-producing electrode that is concurrently as the oxygen-generating electrode described are structured flaky, meshy, porous, gas diffusion electrode.