WO2024001709A1 - 交替进行尿素电解制氢和碳还原的系统及方法和应用系统 - Google Patents

交替进行尿素电解制氢和碳还原的系统及方法和应用系统 Download PDF

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WO2024001709A1
WO2024001709A1 PCT/CN2023/098978 CN2023098978W WO2024001709A1 WO 2024001709 A1 WO2024001709 A1 WO 2024001709A1 CN 2023098978 W CN2023098978 W CN 2023098978W WO 2024001709 A1 WO2024001709 A1 WO 2024001709A1
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Prior art keywords
carbon dioxide
outlet
urea
electrode
storage tank
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PCT/CN2023/098978
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English (en)
French (fr)
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张畅
郭海礁
徐显明
王金意
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中国华能集团清洁能源技术研究院有限公司
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Publication of WO2024001709A1 publication Critical patent/WO2024001709A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • C25B9/21—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms two or more diaphragms
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/01—Products
    • C25B3/07—Oxygen containing compounds
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/25—Reduction
    • C25B3/26—Reduction of carbon dioxide

Definitions

  • the present disclosure relates to the fields of hydrogen production technology and carbon dioxide utilization technology, and specifically relates to a system, method and application system for alternately performing hydrogen production by urea electrolysis and carbon reduction.
  • urea can theoretically reduce the theoretical energy consumption of electrolytic hydrogen production (only 1/5 of direct electrolysis of water), and urea can be obtained from industrial waste or human and animal urine, while obtaining hydrogen It has the additional effect of wastewater purification and is a good way to reduce costs of hydrogen production.
  • the electrolytic hydrogen production system that adds urea as the electrolyte has the following problems: the carbon dioxide produced by the anode is easily converted into carbonate in an alkaline environment, and carbonic acid crystals are easily formed, causing membrane clogging and affecting the performance of electrolytic hydrogen production. It will cause voltage increase, lifespan reduction, etc.; the consumption of alkaline ions by carbon dioxide will also cause additional costs. In addition, even if carbon dioxide is not converted into carbonate, its emission will cause pollution; the mixing of carbon dioxide and hydrogen through the membrane will cause the quality of hydrogen to decrease, leading to an increase in subsequent purification costs. Therefore, it is necessary to solve the problem of carbon dioxide produced during the electrolysis of urea to produce hydrogen, to avoid the direct emission of carbon dioxide and pollution of hydrogen, as well as the consumption of alkaline ions by carbon dioxide and the fouling of carbonate.
  • Converting carbon dioxide into liquid organic matter such as formic acid and methanol through reduction reactions can be further used as industrial raw materials or fuels in chemical production, fuel cell power generation and other fields. It is a good way to convert carbon dioxide, but the carbon dioxide conversion reaction will cause additional costs.
  • Electrochemical reduction is a mild and efficient production method, but a suitable system needs to be designed to couple urea electrolysis and carbon dioxide reduction.
  • an object of the present disclosure is to propose a system that alternately performs urea electrolysis for hydrogen production and carbon reduction, so that the hydrogen evolution reaction of water can occur in the first polar chamber, and the hydrogen evolution reaction of urea can alternately occur in the second polar chamber and the third polar chamber.
  • the oxidation reaction and carbon dioxide reduction reaction can make the carbon dioxide produced by urea electrolysis be converted in time during the reaction process, reduce the mixing pollution of carbon dioxide to the product hydrogen, improve the efficiency of electrolytic hydrogen production, and reduce the overall cost of the process; at the same time, through electrochemical reaction , Carbon dioxide is reduced to form valuable products, and the release of carbon dioxide is also avoided, achieving the goal of zero carbon emissions.
  • Another object of the present disclosure is to provide a method for alternately performing hydrogen production and carbon reduction through urea electrolysis.
  • Another object of the present disclosure is to provide a system for hydrogen production and carbon reduction through urea electrolysis.
  • the embodiment of the first aspect of the present disclosure proposes a system for alternately performing hydrogen production by urea electrolysis and carbon reduction, including a housing, a first pole chamber, a second pole chamber and a third pole chamber;
  • a first electrode, a first diaphragm, a second electrode, a second diaphragm and a third electrode are arranged in sequence in the housing, and the first electrode, the first diaphragm, the second electrode, the second diaphragm and the third electrode are adjacent to each other. Leave a space between them;
  • the first polar chamber is a closed cavity formed by the first electrode, the first diaphragm and the inner wall of the housing, and is used for hydrogen evolution reaction to occur; the first polar chamber is provided with a first gas outlet, a first inlet and a first outlet;
  • the second polar chamber is a closed cavity formed by the first diaphragm, the second diaphragm and the inner wall of the housing; the second electrode is disposed in the second polar chamber, and a second gas outlet is disposed on the second polar chamber. second entrance and second exit;
  • the third pole chamber is a closed cavity formed by the second diaphragm, the third electrode and the inner wall of the housing; the second pole chamber is provided with a third gas outlet, a third inlet and a third outlet; the third pole chamber is provided with a third gas outlet, a third inlet and a third outlet.
  • the oxidation reaction of urea and the reduction reaction of carbon dioxide can occur alternately in the polar chamber and the second polar chamber.
  • the system of the disclosed embodiments that alternately performs urea electrolysis for hydrogen production and carbon reduction can produce hydrogen evolution reaction of water in the first polar chamber, and alternately produce urea oxidation reaction and carbon dioxide reduction reaction in the second polar chamber and the third polar chamber. It can make the carbon dioxide produced by urea electrolysis be converted in time during the reaction process, reduce the mixing pollution of carbon dioxide to the product hydrogen, improve the efficiency of electrolytic hydrogen production, and reduce the overall cost of the process; at the same time, through electrochemical reaction, carbon dioxide is reduced to form valuable products also avoid the release of carbon dioxide and achieve zero carbon emissions.
  • an alkaline aqueous solution is disposed in the first polar chamber; in the second polar chamber and the third polar chamber, an alkaline urea solution is disposed in the polar chamber where the oxidation reaction of urea occurs.
  • the polar chamber for the carbon dioxide reduction reaction is equipped with a CO 2 saturated bicarbonate solution.
  • the second polar chamber is also provided with a second gas inlet
  • the third polar chamber is also provided with a third gas inlet; the alkaline aqueous solution, alkaline urea solution and CO 2 saturated
  • the bicarbonate solution circulates.
  • the alkaline aqueous solution is a 20-30 wt% potassium hydroxide solution
  • the alkaline urea solution is a mixed solution of potassium hydroxide, urea and water, and the hydroxide in the mixed solution
  • the contents of potassium and urea are 20-30wt% and 1-10wt% respectively
  • the pH of the CO2 - saturated bicarbonate solution is 7-11
  • the concentration of bicarbonate in the CO2 - saturated bicarbonate solution It is 0.1-1M
  • the bicarbonate is sodium bicarbonate or potassium bicarbonate.
  • the first electrode is a conductive substrate with a load layer on the surface; the conductive substrate is a metal plate or a porous plate; the load layer is made of Pt, Ru, Rh, Ir, One or more alloys of Ni, Co, Fe, Zn and Ti.
  • both the first separator and the second separator are porous separators or have OH - conducting functions.
  • An anion exchange membrane is used; the porous membrane is a Zirfon membrane; the anion exchange membrane is a polyarylene ether membrane, polyethylene membrane, polystyrene membrane, polytetrafluoroethylene membrane or polyphenylene membrane modified with cationic groups;
  • the cationic group is a polyalkylammonium salt, an imidazole salt, a pyridine salt or a piperidine salt.
  • the second electrode and the third electrode are both surface-loaded with a mesh conductive matrix of an active catalytic layer; the mesh conductive matrix is made of metal or carbon; the active catalytic layer is The material includes a first active component and a second active component; the first active component is a component with electrocatalytic activity for carbon dioxide reduction, and the second active component is a component with electrocatalytic activity for urea oxidation. point.
  • the first active component is one or an alloy of two or more of Cu, Pb, Hg, Tl, In, Sn, Cd, and Bi; the second active component It is one or more alloys among Pt, Ru, Rh, Ir, Ni, Co, Fe, Zn and Ti.
  • the embodiment of the second aspect of the present disclosure proposes a method of alternating urea electrolysis for hydrogen production and carbon reduction, including:
  • both the first electrode and the third electrode are connected to the negative electrode of the external power supply, and the second electrode is connected to the positive electrode of the external power supply.
  • a hydrogen evolution reaction occurs in the first electrode chamber, and urea oxidation occurs in the second electrode chamber.
  • reaction the reduction reaction of carbon dioxide occurs in the third pole chamber;
  • both the first electrode and the second electrode are connected to the negative electrode of the external power supply, and the third electrode is connected to the positive electrode of the external power supply.
  • a hydrogen evolution reaction occurs in the first electrode chamber, and carbon dioxide reduction occurs in the second electrode chamber.
  • reaction the oxidation reaction of urea occurs in the third pole chamber;
  • the first working cycle and the second working cycle are carried out alternately; there are the following four sources of carbon dioxide for the carbon dioxide reduction reaction in the first working cycle and the second working cycle:
  • the carbon dioxide that undergoes the carbon dioxide reduction reaction in the first working cycle and the second working cycle is the carbon dioxide produced by the oxidation of urea;
  • the carbon dioxide in which the carbon dioxide reduction reaction occurs in the first working cycle and the second working cycle is the carbon dioxide produced by the oxidation of urea and the carbon dioxide obtained after separation and purification of the gas after the carbon dioxide reduction reaction;
  • the carbon dioxide that undergoes the carbon dioxide reduction reaction in the first working cycle and the second working cycle is the carbon dioxide produced by urea oxidation and exogenous carbon dioxide;
  • the carbon dioxide that undergoes the carbon dioxide reduction reaction in the first working cycle and the second working cycle is the carbon dioxide produced by the oxidation of urea, the carbon dioxide obtained after separation and purification of the gas after the carbon dioxide reduction reaction, and exogenous carbon dioxide.
  • the beneficial effects of the method of alternately performing hydrogen production by urea electrolysis and carbon reduction in the embodiment of the present disclosure are basically the same as the beneficial effects of the system of alternately performing hydrogen production by urea electrolysis and carbon reduction in the embodiment of the present disclosure, and will not be described again here.
  • the embodiment of the third aspect of the present disclosure proposes a system for hydrogen production by urea electrolysis and carbon reduction, including the system for alternately performing hydrogen production by urea electrolysis and carbon reduction as described above, an external power supply, and an alkaline aqueous solution.
  • Storage tank, alkaline urea solution storage tank and product storage tank the first gas outlet is connected to the hydrogen storage tank or hydrogen pipeline, the first inlet is connected to the outlet of the alkaline aqueous solution storage tank, and the first outlet is connected to the alkaline aqueous solution storage tank.
  • the external power supply includes at least one positive pole and at least two negative poles.
  • the first electrode and the third electrode are respectively connected to a negative electrode, and the second electrode is connected to Positive electrode; the second inlet is connected to the outlet of the alkaline urea solution storage tank, and the second outlet is connected to the inlet of the alkaline urea solution storage tank; the third inlet is connected to the outlet of the alkaline aqueous solution storage tank or the outlet of the alkali liquid storage tank, and the third inlet is connected to the outlet of the alkaline aqueous solution storage tank or the outlet of the alkaline solution storage tank.
  • the outlet is connected to the inlet of the product storage tank, the third gas outlet is connected to the nitrogen carbon dioxide gas separator, and the carbon dioxide outlet of the nitrogen carbon dioxide gas separator is connected to the third gas inlet; the third gas inlet is connected to the external carbon dioxide pipeline.
  • the first electrode and the second electrode are respectively connected to a negative electrode, and the third electrode is connected to The positive electrode;
  • the third inlet is connected to the outlet of the alkaline urea solution storage tank, and the third outlet is connected to the inlet of the alkaline urea solution storage tank;
  • the second inlet is connected to the outlet of the alkaline aqueous solution storage tank or the outlet of the alkaline solution storage tank, and the second The outlet is connected to the inlet of the product storage tank, the second gas outlet is connected to the nitrogen carbon dioxide gas separator, and the carbon dioxide outlet of the nitrogen carbon dioxide gas separator is connected to the second gas inlet;
  • the second gas inlet is connected to the external carbon dioxide pipeline.
  • the beneficial effects of the system of urea electrolysis for hydrogen production and carbon reduction in the embodiment of the present disclosure are basically the same as the beneficial effects of the system of alternating urea electrolysis of hydrogen production and carbon reduction according to the embodiment of the present disclosure, and will not be described again here.
  • the first inlet is connected to the outlet of the alkaline aqueous solution storage tank on the connecting pipeline.
  • a circulation pump is installed on the connecting pipeline between the inlet and the outlet of the alkaline aqueous solution storage tank or the outlet of the alkali liquid storage tank, and on the connecting pipeline between the third outlet and the inlet of the product storage tank.
  • the first On the communication pipeline between the outlet and the outlet of the alkaline aqueous solution storage tank, on the communication pipeline between the third inlet and the outlet of the alkaline urea solution storage tank, on the communication pipeline between the third outlet and the inlet of the alkaline urea solution storage tank, the second A circulation pump is installed on the connecting pipeline between the inlet and the outlet of the alkaline aqueous solution storage tank or the outlet of the alkali solution storage tank, and on the connecting pipeline between the second outlet and the inlet of the product storage tank.
  • Figure 1 is a simple structural schematic diagram of a system that alternately performs urea electrolysis for hydrogen production and carbon reduction according to an embodiment of the present disclosure.
  • Figure 2 is a simple structural schematic diagram of a working state of a system for hydrogen production and carbon reduction through urea electrolysis according to an embodiment of the present disclosure (the oxidation reaction of urea occurs in the second pole chamber, and the reduction reaction of carbon dioxide occurs in the third pole chamber).
  • Figure 3 is a simple structural diagram of another working state of the system for hydrogen production and carbon reduction through urea electrolysis according to an embodiment of the present disclosure (reduction reaction of carbon dioxide occurs in the second pole chamber, and oxidation reaction of urea occurs in the third pole chamber).
  • the raw materials and equipment involved in the embodiments of the present disclosure are all commercially available raw materials and equipment; the methods involved in the embodiments of the present disclosure, unless otherwise specified, are conventional experimental methods.
  • Figure 1 is a simple structural schematic diagram of a system that alternately performs urea electrolysis for hydrogen production and carbon reduction according to an embodiment of the present disclosure.
  • a system for alternately performing urea electrolysis for hydrogen production and carbon reduction includes a housing 1, a first pole chamber 2, a second pole chamber 3 and a third pole chamber 4; A first electrode 5, a first separator 6, a second electrode 7, a second separator 8 and a third electrode 9 are arranged in sequence, and the first electrode 5, the first separator 6, the second electrode 7, the second separator 8 and the third There is a gap between the three adjacent electrodes 9; the first polar chamber 2 is a closed cavity composed of the first electrode 5, the first diaphragm 6 and the inner wall of the housing 1, which is used for the hydrogen evolution reaction to occur; the first polar chamber 2 There is a first gas outlet, a first inlet and a first outlet; the second polar chamber 3 is a closed cavity formed by the first diaphragm 6, the second diaphragm 8 and the inner wall of the housing 1; the second polar chamber 3 There is a second electrode 7 inside, and the second pole chamber 3 is provided with
  • the system of the disclosed embodiments that alternately performs urea electrolysis for hydrogen production and carbon reduction can produce hydrogen evolution reaction of water in the first polar chamber, and alternately produce urea oxidation reaction and carbon dioxide reduction reaction in the second polar chamber and the third polar chamber. It can make the carbon dioxide produced by urea electrolysis be converted in time during the reaction process, reduce the mixing pollution of carbon dioxide to the product hydrogen, improve the efficiency of electrolytic hydrogen production, and reduce the overall cost of the process; at the same time, through electrochemical reaction, carbon dioxide is reduced to form valuable products also avoid the release of carbon dioxide and achieve zero carbon emissions.
  • the first electrode and the third electrode can be in close contact with the inner wall of the housing immediately adjacent to them; in other embodiments of the present disclosure, the first electrode and the third electrode can also be in close contact with the inner wall of the housing immediately adjacent to them. Leave some space between them (as shown in Figure 1).
  • the first electrode 5 , the first diaphragm 6 , the second electrode 7 , the second diaphragm 8 and the third electrode 9 can all be welded to the inner wall of the housing 3 or connected to the inner wall of the housing 1 through sealing rings and bolts. For sealed connection, just ensure that the first pole chamber, the second pole chamber and the third pole chamber are all sealed chambers.
  • the shape of the housing 1 is not limited, and can be rectangular, cube, cylindrical, etc.; the material of the housing is also not limited, and can be metal materials such as stainless steel, or corrosion-resistant materials such as polytetrafluoroethylene. Plastic material.
  • the first electrode 5, the first separator 6, the second electrode 7, the second separator 8 and the third electrode 9 can be arranged parallel to each other, or can be arranged inclined at different angles to each other, as long as the first electrode, the first separator and the housing can
  • the first polar chamber, the first diaphragm, the second diaphragm and the casing can form the second polar chamber, and the second diaphragm, the third electrode and the casing can form the third polar chamber.
  • the housing is in the shape of a rectangular parallelepiped or a cube, and the first electrode 5, the first diaphragm 6, the second electrode 7, the second diaphragm 8 and the third electrode 9 are arranged in parallel, and are all arranged parallel to The top and bottom of the housing are set vertically.
  • the first polar chamber 2 is provided with an alkaline aqueous solution
  • the alkaline aqueous solution is preferably a 20-30 wt% potassium hydroxide solution.
  • the pole chamber where the oxidation reaction of urea occurs is provided with an alkaline urea solution
  • the pole chamber where the reduction reaction of carbon dioxide occurs is provided with a CO2 - saturated bicarbonate solution.
  • the alkaline urea solution is a mixed solution of potassium hydroxide, urea and water.
  • the contents of potassium hydroxide and urea in the mixed solution are 20-30wt% and 1-10wt% respectively; CO2 saturated bicarbonate solution
  • the pH is 7-11, preferably 9-10, to improve the selectivity of carbon dioxide reduction relative to HER;
  • the concentration of bicarbonate in the CO2 - saturated bicarbonate solution is 0.1-1M, and the bicarbonate is sodium bicarbonate or Potassium bicarbonate.
  • the second polar chamber 3 is also provided with a second gas inlet
  • the third polar chamber 4 is also provided with a third gas inlet.
  • Alkaline aqueous solution, alkaline urea solution and CO2 saturated bicarbonate solution all circulate, which can promote the gas and liquid in each pole chamber Mixing and mass transfer improve reaction kinetics.
  • a feasible way is: when in use, the first inlet and the outlet of the alkaline aqueous solution storage tank 200 pass through The first pipeline is connected, the first outlet is connected to the inlet of the alkaline aqueous solution storage tank 200 through the second pipeline, and the second inlet is connected to the outlet of the alkaline urea solution storage tank 300 and the alkaline water through the third pipeline and the fourth pipeline respectively.
  • the outlet of the aqueous solution storage tank 200 or the outlet of the alkali solution storage tank 800 is connected, the second outlet is connected to the inlet of the alkaline urea solution storage tank 300 and the inlet of the product storage tank 400 through the fifth pipeline and the sixth pipeline respectively, and the third outlet is connected to the inlet of the alkaline urea solution storage tank 300 and the inlet of the product storage tank 400.
  • the three inlets are respectively connected to the outlet of the alkaline urea solution storage tank 300 and the outlet of the alkaline aqueous solution storage tank 200 or the outlet of the alkali solution storage tank 800 through the seventh pipeline and the eighth pipeline, and the third outlet is respectively connected through the ninth pipeline and
  • the tenth pipeline is connected to the inlet of the alkaline urea solution storage tank 300 and the inlet of the product storage tank 400, and a circulating pump and valve are installed on each pipeline (as shown in Figures 2 and 3, in the figure the circulating pump and valve not shown).
  • the circulation flow of the alkaline aqueous solution in the first pole chamber can be controlled by controlling the opening of valves on different connecting pipelines.
  • the alkaline aqueous solution storage tank connected to the first inlet of the first polar chamber is shared, and when the third inlet of the third polar chamber or the second inlet of the second polar chamber where the reduction reaction of carbon dioxide occurs is connected to the alkaline solution storage tank,
  • the alkali solution storage tank is a separately installed potassium hydroxide solution storage tank.
  • the alkaline aqueous solution storage tank needs to be replenished regularly to maintain a certain alkali concentration. It should also be noted that in order to ensure that there is enough CO 2 saturated bicarbonate solution in the third pole chamber or the second pole chamber where the carbon dioxide reduction reaction occurs, it is necessary to enter the third pole chamber or the second pole chamber where the carbon dioxide reduction reaction occurs.
  • the alkali solution and carbon dioxide in the chamber are mixed with each other to reach a saturated state.
  • the third electrode chamber or the second electrode chamber where the carbon dioxide reduction reaction takes place performs a period of pre-reaction without electricity, so that the third electrode or the third electrode
  • the carbon dioxide produced by the second electrode (or the carbon dioxide produced by the third electrode or the second electrode and the carbon dioxide input from the external source) reaches saturation with the circulating alkali solution entering the third polar chamber or the second polar chamber where the carbon dioxide reduction reaction occurs, and then begins.
  • Electrification reaction is the reaction.
  • the preparation of the alkaline urea solution in the alkaline urea solution storage tank can be by introducing the potassium hydroxide solution in the potassium hydroxide solution storage tank and the urea solution in the urea solution storage tank respectively according to the proportion.
  • the alkaline urea solution storage tank is formed by uniform mixing; the potassium hydroxide solution storage tank can be shared with the alkaline aqueous solution storage tank of the first polar chamber where the hydrogen evolution reaction occurs.
  • the first gas outlet, the first inlet and the first outlet are all provided on the housing 1 corresponding to the first pole chamber 2 , for example, the first gas outlet and the first inlet are provided on the shell 1 At the top, the first outlet is located at the bottom of the housing 1.
  • the second gas inlet, the second gas outlet, the second inlet and the second outlet are all located opposite the second pole chamber 3
  • the third gas inlet, the third gas outlet, the third inlet and the third outlet are all located on the corresponding housing 1 of the third pole chamber 4, for example: the second gas inlet, the second gas
  • the outlet, the second inlet, the third gas inlet, the third gas outlet, and the third inlet are all located at the top of the housing 1
  • the second outlet and the third outlet are located at the bottom of the housing 1 .
  • the first electrode 5 is a conductive substrate with a load layer on its surface.
  • the conductive substrate can be a metal plate, such as a copper plate, a stainless steel plate, etc.
  • the conductive substrate can be a porous plate such as foam metal or carbon material, where the foam metal can be nickel foam, copper foam, etc. , foamed iron-nickel alloy, foamed nickel-molybdenum alloy, etc.
  • the carbon materials can be graphite, activated carbon, etc.
  • the load layer is made of one or more alloys selected from Pt, Ru, Rh, Ir, Ni, Co, Fe, Zn, and Ti.
  • the thickness of the conductive substrate is 100-500 microns, and the thickness of the load layer is 5-100 nanometers.
  • the preparation method of the conductive substrate with the load layer on the surface is: forming the material of the load layer on the conductive substrate through electrodeposition, dipping, etc.
  • the specific formation method and process The conditions and the like are common techniques in the art and are not the focus of the embodiments of the present disclosure.
  • the electrochemical reaction on the surface of the first electrode is as follows: 6H 2 O+6e - ⁇ 3H 2 +6OH - .
  • the first electrode When in use, the first electrode is connected to an external power supply.
  • both the first separator 6 and the second separator 8 can choose porous separators, such as commercial Zirfon membrane (polysulfone loaded with 85 wt% ZrO nanoparticles).
  • both the first membrane 6 and the second membrane 8 may be anion exchange membranes with OH - conduction.
  • the anion exchange membrane can be a polyarylene ether membrane, a polyethylene membrane, a polystyrene membrane, a polytetrafluoroethylene membrane or a polyphenylene membrane modified with cationic groups, in which the cationic groups can be polyalkylammonium salts. , imidazole salt, pyridine salt or piperidine salt.
  • trialkyl quaternary ammonium salts, trimethyl quaternary ammonium salts, etc. can be selected.
  • the preparation method of an anion exchange membrane with OH - conduction is: monomer polymerization (direct polymerization of monomers modified with cationic groups and structural groups.
  • monomer polymerization direct polymerization of monomers modified with cationic groups and structural groups.
  • QAPPT quaternary ammonium poly(N-methyl) -Piperidine-co-terphenyl)
  • both the second electrode 7 and the third electrode 9 are surface-loaded with a mesh conductive matrix of an active catalytic layer.
  • the mesh conductive substrate can be made of metal materials such as stainless steel and copper, or carbon materials such as graphite and activated carbon.
  • the surface mesh diameter of the mesh conductive substrate is 0.5-1mm, and the surface area ratio is more than 80%, which is conducive to the passage of gas. .
  • the material of the active catalytic layer includes a first active component and a second active component, where the first active component is a component with electrocatalytic activity for carbon dioxide reduction, such as Cu, Pb, Hg, Tl, In , one or more alloys of Sn, Cd, Bi, etc.; the second active component is a component with electrocatalytic activity for urea oxidation, such as Pt, Ru, Rh, Ir, Ni, Co, Fe, One or more alloys of Zn and Ti, etc.
  • the second electrode and the third third electrode are simultaneously active in catalyzing urea oxidation and carbon dioxide reduction by utilizing an active catalytic layer with multiple active components.
  • the thickness of the mesh conductive matrix is 100-500 microns; the thickness of the active catalytic layer is 5-100 nanometers.
  • the preparation method of the mesh conductive substrate with the active catalytic layer loaded on the surface is: forming the material of the catalytic active layer on the mesh conductive substrate through electrodeposition, impregnation and other methods.
  • the specific formation method is as follows: Process conditions and the like are common techniques in the art and are not the focus of the embodiments of the present disclosure.
  • the second electrode/third electrode is connected to the positive electrode of the external power supply.
  • the electrochemical reaction on the surface of the second electrode/third electrode is as follows: CO(NH 2 ) 2 +6OH - ⁇ N 2 +5H 2 O+CO 2 +6e - .
  • the second electrode/third electrode is connected to the negative electrode of the external power supply, and the electrochemical reaction on the surface is as follows: CO 2 +H 2 O+2e - ——>HCOOH+OH - ; CO 2 +3H 2 O+4e - ——>HCHO+4OH - ; CO 2 +3H 2 O+6e - ——>CH 3 OH+2OH - .
  • the continuous process of urea electrolysis to produce carbon dioxide and carbon dioxide reduction to produce valuable products can be realized, and exogenous urea and exogenous carbon dioxide can be continuously consumed, with good resource conversion benefits. .
  • valves can be installed at each gas outlet, gas inlet, liquid inlet and liquid outlet as needed.
  • the working principle of the system of alternating urea electrolysis for hydrogen production and carbon reduction in the embodiment of the present disclosure is (that is, the method of alternating urea electrolysis for hydrogen production and carbon reduction) is as follows:
  • the first gas outlet When in use, the first gas outlet is connected to the hydrogen storage tank 500 or the hydrogen pipeline, the first inlet is connected to the outlet of the alkaline aqueous solution storage tank 200, the first outlet is connected to the inlet of the alkaline aqueous solution storage tank 200, and between the first inlet and the third A circulation pump is installed on the connecting pipeline between the first outlet and the alkaline aqueous solution storage tank 200.
  • the alkaline aqueous solution enters the first polar chamber 2 and circulates in the first polar chamber 2.
  • both the first electrode 5 and the third electrode 9 are connected to the negative pole of the external power supply, the second electrode 7 is connected to the positive pole of the external power supply, the second gas inlet and the second The gas outlet is closed, the second inlet is connected to the outlet of the alkaline urea solution storage tank 300, the second outlet is connected to the inlet of the alkaline urea solution 300, the third gas outlet is connected to the nitrogen carbon dioxide gas separator 600, the third gas inlet can be closed without ventilation, Or connect the external carbon dioxide pipeline 700 for waste gas capture from thermal power plants, chemical plants, steelmaking, etc., or/and connect to the nitrogen carbon dioxide gas separator 600
  • the carbon dioxide outlet, the third inlet is connected to the outlet of the alkaline aqueous solution storage tank 200, the third outlet is connected to the inlet of the product storage tank 400, and a circulation pipeline is installed on the connecting pipeline between the second inlet, the second outlet and the alkaline urea solution storage tank 300.
  • a circulation pump is installed on the connecting pipeline between the third inlet and the alkaline aqueous solution storage tank 300, and the connecting pipeline between the third outlet and the inlet of the product storage tank 400.
  • the alkaline urea aqueous solution enters the second polar chamber and flows in the second polar chamber. Circulation flows in the pole chamber 3.
  • the alkaline aqueous solution enters the third pole chamber 4 and circulates in the third pole chamber 4.
  • the electrolysis of the alkaline aqueous solution in the first pole chamber 2 undergoes a hydrogen evolution reaction, and the generated hydrogen passes through the hydrogen storage tank 500.
  • OH - enters the second polar chamber 3 through the first diaphragm 6, the oxidation reaction of urea occurs in the second polar chamber 3, and the generated carbon dioxide enters the third polar chamber 4 through the second diaphragm 8.
  • the electrode 9 is initially de-energized, causing the carbon dioxide produced by the urea oxidation reaction in the second pole chamber (or the carbon dioxide produced by the urea oxidation reaction in the second pole chamber and the carbon dioxide input from an external source; or the urea oxidation reaction in the second pole chamber).
  • the carbon dioxide produced by the carbon dioxide produced in the second polar chamber and the gas after the carbon dioxide reduction reaction in the third polar chamber are separated and purified; or the carbon dioxide produced by the urea oxidation reaction in the second polar chamber, after the carbon dioxide reduction reaction in the third polar chamber.
  • the carbon dioxide obtained after separation and purification of the gas and the carbon dioxide input from external sources) react with the circulating alkali liquid entering the third pole chamber 4 to reach saturation, ensuring that the third pole chamber 4 is saturated with CO 2 that can be used for the carbon dioxide reduction reaction. of bicarbonate solution, and then the third electrode 9 starts to energize and react, and the reduction reaction of carbon dioxide occurs in the third electrode chamber 4.
  • the carbon dioxide from the second pole chamber 3 or the carbon dioxide from the second pole chamber 3 reacts with the external carbon dioxide entering from the third gas inlet and the CO2 saturated bicarbonate solution to convert the carbon dioxide into formic acid. , methanol, and formaldehyde flow out of the third pole chamber 4 through the third outlet and are collected by the product storage tank 400.
  • a small amount of unreacted carbon dioxide and nitrogen generated from urea oxidation in the second pole chamber 3 enter nitrogen and carbon dioxide gas through the third gas outlet.
  • the separator 600 performs separation, and the separated carbon dioxide can be returned to the third pole chamber 4 for reuse, and nitrogen is transported out as a product.
  • the nitrogen and carbon dioxide gas separator adopts a membrane separator.
  • the first electrode surface reacts: 2H 2 O+2e - ⁇ H 2 +2OH - ;
  • the first electrode surface reacts: 2H 2 O+2e - ⁇ H 2 +2OH - ;
  • the criterion for the end of the first working cycle is: the carbon dioxide produced in the second pole chamber 3 is absorbed by the alkali solution in the third pole chamber 4, and at the same time, a certain concentration of carbon dioxide is controlled in the second pole chamber 3 to prevent the first diaphragm 6 and The second membrane 8 is clogged with carbonate.
  • the criterion for switching from the first working cycle to the second working cycle is: the pressure in the second pole chamber 3 increases by 5-10% (connect a pressure gauge for monitoring).
  • the criterion for the end of the second working cycle is: the carbon dioxide produced in the third pole chamber 4 is absorbed by the alkali solution in the second pole chamber 3, and at the same time, a certain concentration of carbon dioxide is controlled in the third pole chamber 4 to prevent the second diaphragm 8 from being Carbonate blockage.
  • the criterion for switching from the second working cycle to the first working cycle is: the pressure in the third pole chamber 4 increases by 5-10% (connect a pressure gauge for monitoring).
  • the system for hydrogen production and carbon reduction through urea electrolysis includes a system 100 for alternately performing hydrogen production through urea electrolysis and carbon reduction according to the embodiment of the present disclosure, and an external power supply (not shown in the figure).
  • the first gas outlet is connected to the hydrogen storage tank 500 or the hydrogen pipeline, and the first inlet is connected to the outlet of the alkaline aqueous solution storage tank 200, The first outlet is connected to the inlet of the alkaline aqueous solution storage tank 200;
  • the external power supply includes at least one positive electrode and at least two negative electrodes.
  • the first electrode 5 and the third electrode 9 are respectively connected to a negative electrode, and the second electrode 7 is connected to the positive electrode;
  • the second inlet is connected to the outlet of the alkaline urea solution storage tank 300, and the second outlet is connected to the inlet of the alkaline urea solution storage tank 300;
  • the third inlet is connected to the outlet of the alkaline aqueous solution storage tank 200 or the outlet of the alkali liquid storage tank 800.
  • the outlet is connected to the inlet of the product storage tank 400, the third gas outlet is connected to the nitrogen carbon dioxide gas separator 600, the carbon dioxide outlet of the nitrogen carbon dioxide gas separator 600 is connected to the third gas inlet; the third gas inlet is connected to the external carbon dioxide pipeline 700.
  • the first electrode 5 and the second electrode 7 are connected to a negative electrode respectively, and the third electrode 9 is connected to the positive electrode; the third inlet is connected to the alkaline
  • the three outlets are connected to the inlet of the alkaline urea solution storage tank 300; the second inlet is connected to the outlet of the alkaline aqueous solution storage tank 200 or the outlet of the alkali liquid storage tank 800, the second outlet is connected to the inlet of the product storage tank 400, and the second gas outlet is connected to nitrogen.
  • the carbon dioxide gas separator 600 and the carbon dioxide outlet of the nitrogen carbon dioxide gas separator 600 are connected to the second gas inlet; the second gas inlet is connected to the external carbon dioxide pipeline 700 .
  • the nitrogen and carbon dioxide gas separator adopts a membrane separator.
  • the beneficial effects of the urea electrolysis hydrogen production and carbon reduction system in the embodiment of the present disclosure are basically the same as the above-mentioned system of alternating urea electrolysis hydrogen production and carbon reduction, and will not be described again.
  • the third Circulation pumps are installed on the connecting pipelines between the three inlets and the outlet of the alkaline aqueous solution storage tank 200 or the outlet of the alkali solution storage tank 800, and on the connecting pipelines between the third outlet and the inlet of the product storage tank 400.
  • the third Circulation pumps are installed on the connecting pipelines between the second inlet and the outlet of the alkaline aqueous solution storage tank 200 or the outlet 800 of the alkaline solution storage tank, and on the connecting pipelines between the second outlet and the inlet of the product storage tank 400 .
  • valves can be installed on each pipeline as needed. This is a conventional technology in this field and does not belong to the focus of protection of the present disclosure.
  • the working principle of the system of urea electrolysis for hydrogen production and carbon reduction in the embodiment of the present disclosure is basically the same as the working principle of the system of alternate urea electrolysis of hydrogen production and carbon reduction of the embodiment of the present disclosure, and will not be described again here.
  • the terms “one embodiment,” “some embodiments,” “example,” “specific examples,” or “some examples” or the like mean that a particular feature, structure, material, or other feature is described in connection with the embodiment or example.
  • Features are included in at least one embodiment or example of the disclosure.
  • the schematic expressions of the above terms are not necessarily directed to the same embodiment or example.
  • the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
  • those skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples described in this specification unless they are inconsistent with each other.

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Abstract

本申请公开了一种交替进行尿素电解制氢和碳还原的系统及方法和应用系统，其中交替进行尿素电解制氢和碳还原的系统，包括壳体、第一极室、第二极室和第三极室；壳体内依次设置有第一电极、第一隔膜、第二电极、第二隔膜和第三电极；第一极室为第一电极、第一隔膜和壳体内壁构成的封闭空腔，用于发生析氢反应；第三极室和第二极室可交替发生尿素的氧化反应和二氧化碳的还原反应。

Description

交替进行尿素电解制氢和碳还原的系统及方法和应用系统
相关申请的交叉引用
本申请基于申请号为2022107700381、申请日为2022年7月1日的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本公开涉及制氢技术及二氧化碳利用技术领域，具体涉及一种交替进行尿素电解制氢和碳还原的系统及方法和应用系统。
背景技术
目前，电解水制氢是唯一能够实现工业绿氢生产的技术途径，对双碳目标的实现具有重要意义。为了提高电解水制氢所生产绿氢的成本竞争力，需要进一步降低电解水制氢电耗。尿素作为一种电解液添加剂，能够从原理上降低电解制氢的理论能耗(仅为直接电解水的1/5)，并且尿素可从工业废料或人畜尿液中获取，在获得氢气的同时具有废水净化的附加效果，是一种良好的制氢降本途径。
然而，添加尿素作为电解液的电解制氢体系存在如下问题：阳极产生的二氧化碳容易在碱性环境下转化为碳酸盐，容易形成碳酸类晶体，造成膜堵塞，影响电解制氢的性能表现，造成电压升高、寿命降低等；二氧化碳对碱性离子的消耗也会造成额外成本。另外，即使二氧化碳不被转化为碳酸盐，其排放也会造成污染；二氧化碳与氢气的过膜混合会造成氢气品质下降，导致后续纯化成本增加。因此，需要解决尿素电解制氢过程中产生的二氧化碳的问题，避免二氧化碳的直接排放和对氢气的污染，以及二氧化碳对碱性离子的消耗和碳酸盐的污堵。
通过还原反应将二氧化碳转化为甲酸、甲醇等液态有机物，进一步作为工业原料或燃料，应用于化工生产、燃料电池发电等领域，是一种二氧化碳转化的良好途径，但二氧化碳转化反应会造成额外成本。电化学还原是一种温和、高效的生产方式，但需要设计合适的体系实现尿素电解与二氧化碳还原的耦合。
发明内容
由此，本公开的一个目的在于提出一种交替进行尿素电解制氢和碳还原的系统，可在第一极室发生水的析氢反应，在第二极室和第三极室交替发生尿素的氧化反应和二氧化碳还原反应，能够使尿素电解产生的二氧化碳在反应的过程中及时被转化，降低二氧化碳对产品氢气的掺混污染，提高电解制氢效率，降低过程的整体成本；同时通过电化学反应， 二氧化碳被还原形成有价值的产品，也避免了二氧化碳的释放，达到零碳排放的目的。
本公开的另一个目的在于提出一种交替进行尿素电解制氢和碳还原的方法。
本公开的又一个目的在于提出一种尿素电解制氢和碳还原的系统。
为达到上述目的，本公开第一方面的实施例提出了一种交替进行尿素电解制氢和碳还原的系统，包括壳体、第一极室、第二极室和第三极室；
所述壳体内依次设置有第一电极、第一隔膜、第二电极、第二隔膜和第三电极，且第一电极、第一隔膜、第二电极、第二隔膜和第三电极相邻两者之间留有间距；
所述第一极室为第一电极、第一隔膜和壳体内壁构成的封闭空腔，用于发生析氢反应；第一极室上设有第一气体出口、第一入口和第一出口；
所述第二极室为第一隔膜、第二隔膜和壳体内壁构成的封闭空腔；所述第二极室内设有所述第二电极，第二极室上设有第二气体出口、第二入口和第二出口；
所述第三极室为第二隔膜、第三电极和壳体内壁构成的封闭空腔；所述第二极室上设有第三气体出口、第三入口和第三出口；所述第三极室和第二极室可交替发生尿素的氧化反应和二氧化碳的还原反应。
本公开实施例的交替进行尿素电解制氢和碳还原的系统，可在第一极室发生水的析氢反应，在第二极室和第三极室交替发生尿素的氧化反应和二氧化碳还原反应，能够使尿素电解产生的二氧化碳在反应的过程中及时被转化，降低二氧化碳对产品氢气的掺混污染，提高电解制氢效率，降低过程的整体成本；同时通过电化学反应，二氧化碳被还原形成有价值的产品，也避免了二氧化碳的释放，达到零碳排放的目的。
在本公开的一些实施例中，所述第一极室内设有碱性水溶液；所述第二极室和第三极室中，发生尿素的氧化反应的极室内设有碱性尿素溶液，发生二氧化碳的还原反应的极室内设有CO2饱和的碳酸氢盐溶液。
在本公开的一些实施例中，所述第二极室还设有第二气体入口，第三极室还设有第三气体入口；所述碱性水溶液、碱性尿素溶液和CO2饱和的碳酸氢盐溶液均循环流动。
在本公开的一些实施例中，所述碱性水溶液为20-30wt％的氢氧化钾溶液；所述碱性尿素溶液为氢氧化钾、尿素和水的混合溶液，所述混合溶液中氢氧化钾和尿素的含量分别为20-30wt％和1-10wt％；所述CO2饱和的碳酸氢盐溶液的pH为7-11；所述CO2饱和的碳酸氢盐溶液中碳酸氢盐的浓度为0.1-1M，碳酸氢盐为碳酸氢钠或碳酸氢钾。
在本公开的一些实施例中，所述第一电极为表面设有负载层的导电基板；所述导电基板为金属板或多孔板；所述负载层的材质为Pt、Ru、Rh、Ir、Ni、Co、Fe、Zn、Ti中的一种或两种以上的合金。
在本公开的一些实施例中，所述第一隔膜和第二隔膜均为多孔隔膜或具有OH-传导作 用的阴离子交换膜；所述多孔隔膜为Zirfon膜；所述阴离子交换膜为修饰有阳离子基团的聚芳醚膜、聚乙烯膜、聚苯乙烯膜、聚四氟乙烯膜或聚苯膜；所述阳离子基团为多烷基铵盐、咪唑盐、吡啶盐或哌啶盐。
在本公开的一些实施例中，所述第二电极和第三电极均表面负载有活性催化层的网状导电基体；所述网状导电基体为金属材质或碳材质；所述活性催化层的材质包括第一活性组分和第二活性组分；所述第一活性组分为对二氧化碳还原具有电催化活性的组分，所述第二活性组分为对尿素氧化具有电催化活性的组分。
在本公开的一些实施例中，所述第一活性组分为Cu、Pb、Hg、Tl、In、Sn、Cd、Bi中的一种或两种以上的合金；所述第二活性组分为Pt、Ru、Rh、Ir、Ni、Co、Fe、Zn、Ti中的一种或两种以上的合金。
为达到上述目的，本公开第二方面的实施例提出了一种交替进行尿素电解制氢和碳还原的方法，包括：
在第一个工作周期内，将第一电极和第三电极均与外接电源的负极连接，第二电极与外接电源的正极连接，第一极室内发生析氢反应，第二极室内发生尿素的氧化反应，第三极室内发生二氧化碳的还原反应；
在第二个工作周期内，将第一电极和第二电极均与外接电源的负极连接，第三电极与外接电源的正极连接，第一极室内发生析氢反应，第二极室内发生二氧化碳的还原反应，第三极室内发生尿素的氧化反应；
所述第一个工作周期和第二个工作周期交替进行；所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳来源有以下四种：
第一种，所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳为尿素氧化产生的二氧化碳；
第二种，所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳为尿素氧化产生的二氧化碳和二氧化碳还原反应后的气体经分离提纯后获得的二氧化碳；
第三种，所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳为尿素氧化产生的二氧化碳和外源二氧化碳；
第四种，所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳为尿素氧化产生的二氧化碳、二氧化碳还原反应后的气体经分离提纯后获得的二氧化碳和外源二氧化碳。
本公开实施例的交替进行尿素电解制氢和碳还原的方法的有益效果与本公开实施例的交替进行尿素电解制氢和碳还原的系统的有益效果基本相同，在此不再赘述。
在本公开的一些实施例中，当第一个工作周期内第二极室内的压力升高5-10％时，切换至第二个工作周期；当第二个工作周期内第三极室内的压力升高5-10％时，切换至第一个工作周期。
为达到上述目的，本公开第三方面的实施例提出了一种尿素电解制氢和碳还原的系统，包括如上所述的交替进行尿素电解制氢和碳还原的系统、外接电源、碱性水溶液储槽、碱性尿素溶液储槽和产品储槽；所述第一气体出口连通氢气储罐或氢气管线，第一入口连通碱性水溶液储槽的出口，第一出口连通碱性水溶液储槽的入口；所述外接电源包括至少一个正极和至少两个负极。
在本公开的一些实施例中，基于第二极室发生尿素的氧化反应、第三极室发生二氧化碳的还原反应，所述第一电极和第三电极分别连接一个负极，所述第二电极连接正极；第二入口连通碱性尿素溶液储槽的出口，第二出口连通碱性尿素溶液储槽的入口；所述第三入口连通碱性水溶液储槽的出口或碱液储槽出口，第三出口连通产品储槽的入口，第三气体出口连通氮气二氧化碳气体分离器，氮气二氧化碳气体分离器的二氧化碳出口连通第三气体入口；所述第三气体入口连通外源二氧化碳管线。
在本公开的一些实施例中，基于第二极室发生二氧化碳的还原反应、第三极室发生尿素的氧化反应，所述第一电极和第二电极分别连接一个负极，所述第三电极连接正极；第三入口连通碱性尿素溶液储槽的出口，第三出口连通碱性尿素溶液储槽的入口；所述第二入口连通碱性水溶液储槽的出口或碱液储槽出口，第二出口连通产品储槽的入口，第二气体出口连通氮气二氧化碳气体分离器，氮气二氧化碳气体分离器的二氧化碳出口连通第二气体入口；所述第二气体入口连通外源二氧化碳管线。
本公开实施例的尿素电解制氢和碳还原的系统的有益效果与本公开实施例的交替进行尿素电解制氢和碳还原的系统的有益效果基本相同，在此不再赘述。
在本公开的一些实施例中，基于第二极室发生尿素的氧化反应、第三极室发生二氧化碳的还原反应，所述第一入口与碱性水溶液储槽的出口的连通管线上、第一出口与碱性水溶液储槽的出口的连通管线上、第二入口与碱性尿素溶液储槽的出口的连通管线上、第二出口与碱性尿素溶液储槽的入口的连通管线上、第三入口与碱性水溶液储槽的出口或碱液储槽出口的连通管线上、第三出口与产品储槽的入口的连通管线上均安装有循环泵。
在本公开的一些实施例中，基于第二极室发生二氧化碳的还原反应、第三极室发生尿素的氧化反应，所述第一入口与碱性水溶液储槽的出口的连通管线上、第一出口与碱性水溶液储槽的出口的连通管线上、第三入口与碱性尿素溶液储槽的出口的连通管线上、第三出口与碱性尿素溶液储槽的入口的连通管线上、第二入口与碱性水溶液储槽的出口或碱液储槽出口的连通管线上、第二出口与产品储槽的入口的连通管线上均安装有循环泵。
本公开附加的方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本公开的实践了解到。
附图说明
本公开上述的和/或附加的方面和优点从下面结合附图对实施例的描述中将变得明显和容易理解，其中：
图1为根据本公开一个实施例的交替进行尿素电解制氢和碳还原的系统的简单结构示意图。
图2为根据本公开一个实施例的尿素电解制氢和碳还原的系统一个工作状态(第二极室发生尿素的氧化反应、第三极室发生二氧化碳的还原反应)的简单结构示意图。
图3为根据本公开一个实施例的尿素电解制氢和碳还原的系统另一个工作状态(第二极室发生二氧化碳的还原反应、第三极室发生尿素的氧化反应)的简单结构示意图。
附图标记：
1-壳体；2-第一极室；3-第二极室；4-第三极室；5-第一电极；6-第一隔膜；7-第二电
极；8-第二隔膜；9-第三电极；100-交替进行尿素电解制氢和碳还原的系统；200-碱性水溶液储槽；300-碱性尿素溶液储槽；400-产品储槽；500-氢气储罐；600-氮气二氧化碳气体分离器；700-外源二氧化碳管线；800-碱液储槽。
具体实施方式
下面详细描述本公开的实施例，所述实施例的示例在附图中示出。下面通过参考附图描述的实施例是示例性的，旨在用于解释本公开，而不能理解为对本公开的限制。
本公开实施例中所涉及的原料和设备，如无特殊说明，均为可通过商业途径获得的原料和设备；本公开实施例中所涉及的方法，如无特殊说明，均为常规实验方法。
下面参考附图描述本公开实施例的一种交替进行尿素电解制氢和碳还原的系统、交替进行尿素电解制氢和碳还原的方法和尿素电解制氢和碳还原的系统。
图1为根据本公开一个实施例的交替进行尿素电解制氢和碳还原的系统的简单结构示意图。
如图1所示，本公开实施例的交替进行尿素电解制氢和碳还原的系统，包括壳体1、第一极室2、第二极室3和第三极室4；壳体1内依次设置有第一电极5、第一隔膜6、第二电极7、第二隔膜8和第三电极9，且第一电极5、第一隔膜6、第二电极7、第二隔膜8和第三电极9相邻两者之间留有间距；第一极室2为第一电极5、第一隔膜6和壳体1内壁构成的封闭空腔，用于发生析氢反应；第一极室2上设有第一气体出口、第一入口和第一出口；第二极室3为第一隔膜6、第二隔膜8和壳体1内壁构成的封闭空腔；第二极室3 内设有第二电极7，第二极室3上设有第二气体出口、第二入口和第二出口；第三极室4为第二隔膜8、第三电极9和壳体1内壁构成的封闭空腔；第二极室3上设有第三气体出口、第三入口和第三出口；第三极室4和第二极室3可交替发生尿素的氧化反应和二氧化碳的还原反应。
本公开实施例的交替进行尿素电解制氢和碳还原的系统，可在第一极室发生水的析氢反应，在第二极室和第三极室交替发生尿素的氧化反应和二氧化碳还原反应，能够使尿素电解产生的二氧化碳在反应的过程中及时被转化，降低二氧化碳对产品氢气的掺混污染，提高电解制氢效率，降低过程的整体成本；同时通过电化学反应，二氧化碳被还原形成有价值的产品，也避免了二氧化碳的释放，达到零碳排放的目的。
在本公开的一些实施例中，第一电极和第三电极可以与其紧邻的壳体内壁紧贴；在本公开的另一些实施例中，第一电极和第三电极也可以与其紧邻的壳体之间留有间距(如图1所示)。
在一些实施例中，第一电极5、第一隔膜6、第二电极7、第二隔膜8和第三电极9均可以与壳体3内壁焊接或者通过密封圈和螺栓等与壳体1内壁密封连接，只要保证第一极室、第二极室和第三极室均为密闭腔室即可。
需要说明的是，壳体1形状不限，可以是长方体状、正方体状、圆柱状等；壳体的材质也不限，可以是不锈钢等金属材质，也可以是聚四氟乙烯等耐腐蚀的塑料材质。第一电极5、第一隔膜6、第二电极7、第二隔膜8和第三电极9可以相互平行设置，也可以各自相互成不同角度倾斜设置，只要第一电极和第一隔膜与壳体能构成第一极室、第一隔膜和第二隔膜与壳体能构成第二极室、第二隔膜和第三电极与壳体能构成第三极室即可。较佳的，为了方便加工和安装，壳体为长方体或正方体状，第一电极5、第一隔膜6、第二电极7、第二隔膜8和第三电极9五者平行设置，且均与壳体顶部和底部垂直设置。
在一些实施例中，第一极室2内设有碱性水溶液，碱性水溶液优选为20-30wt％的氢氧化钾溶液。第二极室3和第三极室4中，发生尿素的氧化反应的极室内设有碱性尿素溶液，发生二氧化碳的还原反应的极室内设有CO2饱和的碳酸氢盐溶液。较佳的，碱性尿素溶液为氢氧化钾、尿素和水的混合溶液，混合溶液中氢氧化钾和尿素的含量分别为20-30wt％和1-10wt％；CO2饱和的碳酸氢盐溶液的pH为7-11，优选9-10，以提高二氧化碳还原相对于HER的选择性；CO2饱和的碳酸氢盐溶液中碳酸氢盐的浓度为0.1-1M，碳酸氢盐为碳酸氢钠或碳酸氢钾。
在一些实施例中，为了可以引入外源二氧化碳或/和发生二氧化碳还原反应后混合气体中的二氧化碳，在第二极室3还设有第二气体入口，第三极室4还设有第三气体入口。碱性水溶液、碱性尿素溶液和CO2饱和的碳酸氢盐溶液均循环流动，可以促进各极室内气液 混合和传质，提高反应动力学速率。为了实现碱性水溶液、碱性尿素溶液和CO2饱和的碳酸氢盐溶液均循环流动的目的，一种可行的方式为：在使用时，将第一入口与碱性水溶液储槽200的出口通过第一管线连通，将第一出口与碱性水溶液储槽200的入口通过第二管线连通，将第二入口分别通过第三管线和第四管线与碱性尿素溶液储槽300的出口和碱性水溶液储槽200的出口或碱液储槽800的出口连通，将第二出口分别通过第五管线和第六管线与碱性尿素溶液储槽300的入口和产品储槽400的入口连通，将第三入口分别通过第七管线和第八管线与碱性尿素溶液储槽300的出口和碱性水溶液储槽200的出口或碱液储槽800的出口连通，将第三出口分别通过第九管线和第十管线与碱性尿素溶液储槽300的入口和产品储槽400的入口连通，且在各管线上均安装有循环泵和阀门(如图2和图3所示，图中循环泵和阀门未画出)。这样，无论是第一极室发生析氢反应、第二极室发生尿素的氧化反应、第三极室发生二氧化碳的还原反应的情形，还是第一极室发生析氢反应、第二极室发生二氧化碳的还原反应、第三极室发生尿素的氧化反应的情形，都可以通过控制不同连通管线上阀门的开启，控制碱性水溶液在第一极室内的循环流动，碱性尿素溶液在发生尿素氧化反应的第二极室或第三极室内的循环流动，CO2饱和的碳酸氢盐溶液在发生二氧化碳的还原反应的第三极室或第二极室内的循环流动。需要说明的是，当发生二氧化碳的还原反应的第三极室的第三入口或第二极室的第二入口与碱性水溶液储槽连通时，该碱性水溶液储槽可以与发生析氢反应的第一极室的第一入口连通的碱性水溶液储槽共用，而当发生二氧化碳的还原反应的第三极室的第三入口或第二极室的第二入口与碱液储槽连通时，该碱液储槽为另行单独设置的氢氧化钾溶液储槽。碱性水溶液储槽需定期补水，维持一定的碱浓度。还需要说明的是，为了保证发生二氧化碳还原反应的第三极室或第二极室内有足够的CO2饱和的碳酸氢盐溶液，需要将进入发生二氧化碳还原反应的第三极室或第二极室的碱液和二氧化碳相互混合达到饱和状态，这就需要在二氧化碳还原反应初期，发生二氧化碳还原反应的第三极室或第二极室进行一段时间的不通电预反应，使第三电极或第二电极产生的二氧化碳(或第三电极或第二电极产生的二氧化碳及外源输入的二氧化碳)与进入发生二氧化碳还原反应的第三极室或第二极室内的循环碱液反应达到饱和，然后开始通电反应。此外，还需要说明的是，碱性尿素溶液储槽中碱性尿素溶液的配制，可以是将氢氧化钾溶液储槽中的氢氧化钾溶液和尿素溶液储槽中的尿素溶液分别按配比引入碱性尿素溶液储槽，混合均匀形成；其中氢氧化钾溶液储槽可以与发生析氢反应的第一极室的碱性水溶液储槽共用。
在一些实施例中，第一气体出口、第一入口和第一出口均设在第一极室2所对应的壳体1上，比如将第一气体出口和第一入口设在壳体1的顶部，将第一出口设在壳体1的底部。类似的，第二气体入口、第二气体出口、第二入口和第二出口均设在第二极室3所对 应的壳体1上，第三气体入口、第三气体出口、第三入口和第三出口均设在第三极室4所对应的壳体1上，比如：第二气体入口、第二气体出口、第二入口、第三气体入口、第三气体出口、第三入口均设在壳体1顶部，第二出口和第三出口设在壳体1底部。
在一些实施例中，第一电极5为表面设有负载层的导电基板。在一些实施例中，导电基板可以选择金属板，比如铜板、不锈钢板等，在另一些实施例中，导电基板可以选择泡沫金属或碳材料等多孔板，其中泡沫金属可以选择泡沫镍、泡沫铜、泡沫铁镍合金、泡沫镍钼合金等，碳材料可以选择石墨、活性炭等。在一些实施例中，负载层的材质为Pt、Ru、Rh、Ir、Ni、Co、Fe、Zn、Ti中的一种或两种以上的合金。在本公开的一些实施例中，导电基板厚度为100-500微米，负载层的厚度为5-100纳米。
需要说明的是，在本公开的一些实施例中，表面设有负载层的导电基板的制备方法为：通过电沉积、浸渍等方法将负载层的材质形成于导电基板上，具体形成方法和工艺条件等为本领域常规技术，不是本公开实施例的重点。
第一电极表面的电化学反应如下：
6H2O+6e-→3H2+6OH- 。
使用时，第一电极与外接电源的连接。
在本公开的一些实施例中，第一隔膜6和第二隔膜8均可以选择多孔隔膜，比如商业Zirfon膜(负载有85wt％ZrO2纳米颗粒的聚砜)等。在本公开的另一些实施例中，第一隔膜6和第二隔膜8均可以选择具有OH-传导作用的阴离子交换膜。较佳的，阴离子交换膜可以选择修饰有阳离子基团的聚芳醚膜、聚乙烯膜、聚苯乙烯膜、聚四氟乙烯膜或聚苯膜，其中阳离子基团可以选择多烷基铵盐、咪唑盐、吡啶盐或哌啶盐，比如多烷基铵盐可以选择三烷基季铵盐、三甲基季铵盐等。
在本公开的一些实施例中，具有OH-传导作用的阴离子交换膜的制备方法为：单体聚合(将修饰有阳离子基团的单体与结构基团直接聚合。例如：季铵聚(N甲基-哌啶-共-对三联苯)(QAPPT)：
1)在三氟甲磺酸和三氟乙酸的催化下，对三联苯与N-甲基-4-哌啶酮反应形成线性聚合物。2)将聚合物的哌啶基团转化为季铵盐：在NMP/DMSO混合溶剂中，在70℃下与CH3I反应。3)带有OH-的QAPPT的最终形成：用KOH溶液处理一段时间，或后修饰改性(将高分子膜直接进行阳离子基团修饰改性。例如，以聚四氟乙烯膜为基体材料，通过接枝反应向其上修饰氯甲基苯乙烯，再使用三甲胺溶液和KOH溶液进行季铵化和碱化反应)。
在一些实施例中，第二电极7和第三电极9均表面负载有活性催化层的网状导电基体。其中，网状导电基体可以选择不锈钢、铜等金属材质，也可以选择石墨、活性炭等碳材质；网状导电基体的表面网孔直径为0.5-1mm，面孔率为80％以上，有利于气体通过。在一些 实施例中，活性催化层的材质包括第一活性组分和第二活性组分，其中第一活性组分为对二氧化碳还原具有电催化活性的组分，比如Cu、Pb、Hg、Tl、In、Sn、Cd、Bi中的一种或两种以上的合金等；第二活性组分为对尿素氧化具有电催化活性的组分，比如Pt、Ru、Rh、Ir、Ni、Co、Fe、Zn、Ti中的一种或两种以上的合金等。利用多活性组分的活性催化层使第二电极、第三三电极同时具有催化尿素氧化和催化二氧化碳还原的活性。在一些实施例中，网状导电基体的厚度为100-500微米；活性催化层的厚度为5-100纳米。
在本公开的一些实施例中，表面负载有活性催化层的网状导电基体的制备方法为：通过电沉积、浸渍等方法将催化活性层的材质形成于网状导电基体上，具体形成方法和工艺条件等为本领域常规技术，不是本公开实施例的重点。
在尿素氧化反应阶段，第二电极/第三电极与外接电源的正极相连。
第二电极/第三电极表面的电化学反应如下：
CO(NH2)2+6OH-→N2+5H2O+CO2+6e-。
在二氧化碳还原阶段，第二电极/第三电极与外接电源的负极相连，表面的电化学反应如下：
CO2+H2O+2e-——>HCOOH+OH-；
CO2+3H2O+4e-——>HCHO+4OH-；
CO2+3H2O+6e-——>CH3OH+2OH-。
通过切换第二电极、第三电极的阴极和阳极属性，可实现尿素电解产二氧化碳-二氧化碳还原产生有价值产品的连续过程，能够连续地消耗外源尿素和外源二氧化碳，具有良好的资源转化效益。
需要说明的是，可根据需要在各气体出口、气体入口、液体入口和液体出口安装阀门。
本公开实施例的交替进行尿素电解制氢和碳还原的系统的工作原理为(也即本公开实施例的交替进行尿素电解制氢和碳还原的方法)为：
使用时，将第一气体出口连通氢气储罐500或氢气管道，第一入口连通碱性水溶液储槽200的出口，第一出口连通碱性水溶液储槽200的入口，且在第一入口、第一出口与碱性水溶液储槽200的连通管线上均安装循环泵，碱性水溶液进入第一极室2，并在第一极室2内循环流动。
如图2所示，在第一个工作周期内，将第一电极5和第三电极9均与外接电源的负极连接，第二电极7与外接电源的正极连接，第二气体入口和第二气体出口关闭，第二入口连通碱性尿素溶液储槽300的出口，第二出口连通碱性尿素溶液300的入口，第三气体出口连通氮气二氧化碳气体分离器600，第三气体入口可不通气关闭，或者连接来自火电厂、化工厂、炼钢等废气捕集的外源二氧化碳管线700，或/和连通氮气二氧化碳气体分离器600 的二氧化碳出口，第三入口连通碱性水溶液储槽200的出口，第三出口连通产品储槽400的入口，第二入口、第二出口与碱性尿素溶液储槽300的连通管线上安装有循环泵，第三入口与碱性水溶液储槽300的连通管线上、第三出口与产品储槽400的入口的连通管线上安装有循环泵，碱性尿素水溶液进入第二极室，并在第二极室3内循环流动，碱性水溶液进入第三极室4，并在第三极室4内循环流动，第一极室2内电解碱性水溶液发生析氢反应，产生的氢气经氢气储罐500收集或经氢气管道利用，OH-经第一隔膜6进入第二极室3，第二极室3内发生尿素的氧化反应，产生的二氧化碳经第二隔膜8进入第三极室4，第三电极9刚开始不通电，使第二极室内尿素氧化反应中产生的二氧化碳(或第二极室内尿素氧化反应中产生的二氧化碳产生的二氧化碳及外源输入的二氧化碳；或第二极室内尿素氧化反应中产生的二氧化碳产生的二氧化碳和第三极室二氧化碳还原反应后的气体经分离提纯后获得的二氧化碳；或第二极室内尿素氧化反应中产生的二氧化碳产生的二氧化碳、第三极室二氧化碳还原反应后的气体经分离提纯后获得的二氧化碳和外源输入的二氧化碳)与进入第三极室4内的循环碱液反应达到饱和，保证第三极室4内有可用于发生二氧化碳还原反应的CO2饱和的碳酸氢盐溶液，然后第三电极9开始通电反应，第三极室4内发生二氧化碳的还原反应。第三极室4内来自第二极室3的二氧化碳或者来自第二极室3的二氧化碳和自第三气体入口进入的外源二氧化碳和CO2饱和的碳酸氢盐溶液反应，将二氧化碳转化为甲酸、甲醇、甲醛，经第三出口流出第三极室4再经产品储槽400收集，未反应完全的少量二氧化碳和来自第二极室3尿素氧化产生的氮气经第三气体出口进入氮气二氧化碳气体分离器600进行分离，分离后的二氧化碳可重回第三极室4重新利用，氮气作为产品外运。较佳的，氮气二氧化碳气体分离器采用膜分离器。
在第一个工作周期内，在第一极室，第一电极表面发生反应：2H2O+2e-→H2+2OH- ；
在第二极室，第二电极表面发生反应：
CO(NH2)2+6OH-→N2+5H2O+CO2+6e- ；
在第三极室，第三电极表面发生反应：
CO2+H2O+2e-——>HCOOH+OH- ；
CO2+3H2O+4e-——>HCHO+4OH- ；
CO2+3H2O+6e-——>CH3OH+2OH- 。
如图3所示，在第二个工作周期内，与第一个周期类似，只是将第一电极5和第二电极7均与外接电源的负极连接，第三电极9与外接电源的正极连接，第一极室2内发生析氢反应，第二极室3内发生二氧化碳的还原反应，第三极室4内发生尿素的氧化反应。
在第二个工作周期内，在第一极室，第一电极表面发生反应：2H2O+2e-→H2+2OH- ；
在第二极室，第二电极表面发生反应：
CO2+H2O+2e-——>HCOOH+OH- ；
CO2+3H2O+4e-——>HCHO+4OH- ；
CO2+3H2O+6e-——>CH3OH+2OH- ；
在第三极室，第三电极表面发生反应：
CO(NH2)2+6OH-→N2+5H2O+CO2+6e- 。
整个工作过程中，第一个工作周期和第二个工作周期交替进行。第一个工作周期结束的准则为：第二极室3内产生的二氧化碳被第三极室4内碱液吸收，同时控制第二极室3内有一定的二氧化碳浓度以防止第一隔膜6和第二隔膜8被碳酸盐堵塞。第一个工作周期需切换至第二个工作周期的判断标准为：第二极室3压力升高5-10％(连接压力表进行监测)。第二个工作周期结束的准则为：第三极室4内产生的二氧化碳被第二极室3内碱液吸收，同时控制第三极室4内有一定的二氧化碳浓度以防止第二隔膜8被碳酸盐堵塞。第二个工作周期需切换至第一个工作周期的判断标准为：第三极室4压力升高5-10％(连接压力表进行监测)。
本公开实施例的交替进行尿素电解制氢和碳还原的系统的整个工作过程中，通过二氧化碳的转化反应与尿素氧化反应的切换，在时间上实现连续的尿素消耗和电解体系内二氧化碳的及时转化消耗，避免二氧化碳对第一极室碱性体系内氢氧根离子的消耗，降低电解隔膜(第一隔膜)的污堵，提高电解制氢反应效率；二氧化碳被还原形成有价值的液体产品，有利于下一周期促使电解反应平衡向正向移动，提高整体反应效率的同时也降低二氧化碳对产品氢气的掺混污染，也避免了二氧化碳的释放，达到零碳排放的目的。
如图2和图3所示，本公开实施例的尿素电解制氢和碳还原的系统，包括如本公开实施例的交替进行尿素电解制氢和碳还原的系统100、外接电源(图中未画出)、碱性水溶液储槽200、碱性尿素溶液储槽300和产品储槽400；第一气体出口连通氢气储罐500或氢气管线，第一入口连通碱性水溶液储槽200的出口，第一出口连通碱性水溶液储槽200的入口；外接电源包括至少一个正极和至少两个负极。
在一些实施例中，基于第二极室3发生尿素的氧化反应、第三极室4发生二氧化碳的还原反应，第一电极5和第三电极9分别连接一个负极，第二电极7连接正极；第二入口连通碱性尿素溶液储槽300的出口，第二出口连通碱性尿素溶液储槽300的入口；第三入口连通碱性水溶液储槽200的出口或碱液储槽800出口，第三出口连通产品储槽400的入口，第三气体出口连通氮气二氧化碳气体分离器600，氮气二氧化碳气体分离器600的二氧化碳出口连通第三气体入口；第三气体入口连通外源二氧化碳管线700。基于第二极室3发生二氧化碳的还原反应、第三极室4发生尿素的氧化反应，第一电极5和第二电极7分别连接一个负极，第三电极9连接正极；第三入口连通碱性尿素溶液储槽300的出口，第 三出口连通碱性尿素溶液储槽300的入口；第二入口连通碱性水溶液储槽200的出口或碱液储槽800出口，第二出口连通产品储槽400的入口，第二气体出口连通氮气二氧化碳气体分离器600，氮气二氧化碳气体分离器600的二氧化碳出口连通第二气体入口；第二气体入口连通外源二氧化碳管线700。较佳的，氮气二氧化碳气体分离器采用膜分离器。
本公开实施例的尿素电解制氢和碳还原的系统与上述交替进行尿素电解制氢和碳还原的系统的有益效果基本相同，再此不再赘述。
在一些实施例中，基于第二极室3发生尿素的氧化反应、第三极室4发生二氧化碳的还原反应，第一入口与碱性水溶液储槽200的出口的连通管线上、第一出口与碱性水溶液储槽200的出口的连通管线上、第二入口与碱性尿素溶液储槽300的出口的连通管线上、第二出口与碱性尿素溶液储槽300的入口的连通管线上、第三入口与碱性水溶液储槽200的出口或碱液储槽800出口的连通管线上、第三出口与产品储槽400的入口的连通管线上均安装有循环泵。
在一些实施例中，基于第二极室3发生二氧化碳的还原反应、第三极室4发生尿素的氧化反应，第一入口与碱性水溶液储槽200的出口的连通管线上、第一出口与碱性水溶液储槽200的出口的连通管线上、第三入口与碱性尿素溶液储槽300的出口的连通管线上、第三出口与碱性尿素溶液储槽300的入口的连通管线上、第二入口与碱性水溶液储槽200的出口或碱液储槽出口800的连通管线上、第二出口与产品储槽400的入口的连通管线上均安装有循环泵。
需要说明的是，本公开实施例的尿素电解制氢和碳还原的系统，各管线上可以根据需要安装阀门，这属于本领域的常规技术，不属于本公开的保护重点。
本公开实施例的尿素电解制氢和碳还原的系统的工作原理与本公开实施例的交替进行尿素电解制氢和碳还原的系统的工作原理基本相同，在此不再赘述。
在本公开中，术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本公开的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不必须针对的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任一个或多个实施例或示例中以合适的方式结合。此外，在不相互矛盾的情况下，本领域的技术人员可以将本说明书中描述的不同实施例或示例以及不同实施例或示例的特征进行结合和组合。
尽管上面已经示出和描述了本公开的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本公开的限制，本领域的普通技术人员在本公开的范围内可以对上述实施例进行变化、修改、替换和变型。

Claims (13)

  1. 一种交替进行尿素电解制氢和碳还原的系统，包括壳体、第一极室、第二极室和第三极室；
    所述壳体内依次设置有第一电极、第一隔膜、第二电极、第二隔膜和第三电极，且第一电极、第一隔膜、第二电极、第二隔膜和第三电极相邻两者之间留有间距；
    所述第一极室为第一电极、第一隔膜和壳体内壁构成的封闭空腔，用于发生析氢反应；第一极室上设有第一气体出口、第一入口和第一出口；
    所述第二极室为第一隔膜、第二隔膜和壳体内壁构成的封闭空腔；所述第二极室内设有所述第二电极，第二极室上设有第二气体出口、第二入口和第二出口；
    所述第三极室为第二隔膜、第三电极和壳体内壁构成的封闭空腔；所述第二极室上设有第三气体出口、第三入口和第三出口；所述第三极室和第二极室可交替发生尿素的氧化反应和二氧化碳的还原反应。
  2. 根据权利要求1所述的交替进行尿素电解制氢和碳还原的系统，其特征在于，所述第一极室内设有碱性水溶液；所述第二极室和第三极室中，发生尿素的氧化反应的极室内设有碱性尿素溶液，发生二氧化碳的还原反应的极室内设有CO2饱和的碳酸氢盐溶液。
  3. 根据权利要求1或2所述的交替进行尿素电解制氢和碳还原的系统，其特征在于，所述第二极室还设有第二气体入口，第三极室还设有第三气体入口；所述碱性水溶液、碱性尿素溶液和CO2饱和的碳酸氢盐溶液均循环流动。
  4. 根据权利要求2或3所述的交替进行尿素电解制氢和碳还原的系统，其特征在于，所述碱性水溶液为20-30wt％的氢氧化钾溶液；所述碱性尿素溶液为氢氧化钾、尿素和水的混合溶液，所述混合溶液中氢氧化钾和尿素的含量分别为20-30wt％和1-10wt％；所述CO2饱和的碳酸氢盐溶液的pH为7-11；所述CO2饱和的碳酸氢盐溶液中碳酸氢盐的浓度为0.1-1M，碳酸氢盐为碳酸氢钠或碳酸氢钾。
  5. 根据权利要求1至4中任一项所述的交替进行尿素电解制氢和碳还原的系统，其特征在于，所述第一电极为表面设有负载层的导电基板；所述导电基板为金属板或多孔板；所述负载层的材质为Pt、Ru、Rh、Ir、Ni、Co、Fe、Zn、Ti中的一种或两种以上的合金。
  6. 根据权利要求1至5中任一项所述的交替进行尿素电解制氢和碳还原的系统，其特征在于，所述第一隔膜和第二隔膜均为多孔隔膜或具有OH-传导作用的阴离子交换膜；所述多孔隔膜为Zirfon膜；所述阴离子交换膜为修饰有阳离子基团的聚芳醚膜、聚乙烯膜、聚苯乙烯膜、聚四氟乙烯膜或聚苯膜；所述阳离子基团为多烷基铵盐、咪唑盐、吡啶盐或哌啶盐。
  7. 根据权利要求1至6中任一项所述的交替进行尿素电解制氢和碳还原的系统，其特征在于，所述第二电极和第三电极均表面负载有活性催化层的网状导电基体；所述网状导电基体为金属材质或碳材质；所述活性催化层的材质包括第一活性组分和第二活性组分；所述第一活性组分为对二氧化碳还原具有电催化活性的组分，所述第二活性组分为对尿素氧化具有电催化活性的组分。
  8. 根据权利要求7所述的交替进行尿素电解制氢和碳还原的系统，其特征在于，所述第一活性组分为Cu、Pb、Hg、Tl、In、Sn、Cd、Bi中的一种或两种以上的合金；所述第二活性组分为Pt、Ru、Rh、Ir、Ni、Co、Fe、Zn、Ti中的一种或两种以上的合金。
  9. 一种利用如权利要求1至8中任一项所述的系统交替进行尿素电解制氢和碳还原的方法，包括：
    在第一个工作周期内，将第一电极和第三电极均与外接电源的负极连接，第二电极与外接电源的正极连接，第一极室内发生析氢反应，第二极室内发生尿素的氧化反应，第三极室内发生二氧化碳的还原反应；
    在第二个工作周期内，将第一电极和第二电极均与外接电源的负极连接，第三电极与外接电源的正极连接，第一极室内发生析氢反应，第二极室内发生二氧化碳的还原反应，第三极室内发生尿素的氧化反应；
    所述第一个工作周期和第二个工作周期交替进行；所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳来源有以下四种：
    第一种，所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳为尿素氧化产生的二氧化碳；
    第二种，所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳为尿素氧化产生的二氧化碳和二氧化碳还原反应后的气体经分离提纯后获得的二氧化碳；
    第三种，所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳为尿素氧化产生的二氧化碳和外源二氧化碳；
    第四种，所述第一个工作周期和第二个工作周期内的发生二氧化碳还原反应的二氧化碳为尿素氧化产生的二氧化碳、二氧化碳还原反应后的气体经分离提纯后获得的二氧化碳和外源二氧化碳。
  10. 根据权利要求9所述的方法，其特征在于，当第一个工作周期内第二极室内的压力升高5-10％时，切换至第二个工作周期；当第二个工作周期内第三极室内的压力升高5-10％时，切换至第一个工作周期。
  11. 一种尿素电解制氢和碳还原的系统，包括如权利要求1至8中任一项所述的交替 进行尿素电解制氢和碳还原的系统、外接电源、碱性水溶液储槽、碱性尿素溶液储槽和产品储槽；所述第一气体出口连通氢气储罐或氢气管线，第一入口连通碱性水溶液储槽的出口，第一出口连通碱性水溶液储槽的入口；所述外接电源包括至少一个正极和至少两个负极。
  12. 根据权利要求11所述的系统，其特征在于，基于第二极室发生尿素的氧化反应、第三极室发生二氧化碳的还原反应，所述第一电极和第三电极分别连接一个负极，所述第二电极连接正极；第二入口连通碱性尿素溶液储槽的出口，第二出口连通碱性尿素溶液储槽的入口；所述第三入口连通碱性水溶液储槽的出口或碱液储槽出口，第三出口连通产品储槽的入口，第三气体出口连通氮气二氧化碳气体分离器，氮气二氧化碳气体分离器的二氧化碳出口连通第三气体入口；所述第三气体入口连通外源二氧化碳管线；
    基于第二极室发生二氧化碳的还原反应、第三极室发生尿素的氧化反应，所述第一电极和第二电极分别连接一个负极，所述第三电极连接正极；第三入口连通碱性尿素溶液储槽的出口，第三出口连通碱性尿素溶液储槽的入口；所述第二入口连通碱性水溶液储槽的出口或碱液储槽出口，第二出口连通产品储槽的入口，第二气体出口连通氮气二氧化碳气体分离器，氮气二氧化碳气体分离器的二氧化碳出口连通第二气体入口；所述第二气体入口连通外源二氧化碳管线。
  13. 根据权利要求11所述的系统，其特征在于，基于第二极室发生尿素的氧化反应、第三极室发生二氧化碳的还原反应，所述第一入口与碱性水溶液储槽的出口的连通管线上、第一出口与碱性水溶液储槽的出口的连通管线上、第二入口与碱性尿素溶液储槽的出口的连通管线上、第二出口与碱性尿素溶液储槽的入口的连通管线上、第三入口与碱性水溶液储槽的出口或碱液储槽出口的连通管线上、第三出口与产品储槽的入口的连通管线上均安装有循环泵；
    基于第二极室发生二氧化碳的还原反应、第三极室发生尿素的氧化反应，所述第一入口与碱性水溶液储槽的出口的连通管线上、第一出口与碱性水溶液储槽的出口的连通管线上、第三入口与碱性尿素溶液储槽的出口的连通管线上、第三出口与碱性尿素溶液储槽的入口的连通管线上、第二入口与碱性水溶液储槽的出口或碱液储槽出口的连通管线上、第二出口与产品储槽的入口的连通管线上均安装有循环泵。
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