Tubular composite electrode for lunar soil molten salt electrolysis oxygen production, preparation method and application

Abstract

The invention discloses a tubular composite electrode for lunar soil fused salt electrolysis oxygen production, a preparation method and application, and belongs to the technical field of in-situ utilization of lunar soil resources of the moon. The tubular composite electrode for lunar soil molten salt electrolysis oxygen production is of a multi-layer nested tubular structure and sequentially comprises a porous anode layer, a compact electrolyte layer and a porous cathode layer from inside to outside, the compact electrolyte layer is made of yttria-stabilized zirconia; the porous anode layer is made of metal iridium, platinum or a mixture of metal iridium and yttria-stabilized zirconia; the porous cathode layer is made of a mixture of metal molybdenum and gadolinium oxide doped cerium oxide; according to the composite electrode structure, through the compact solid oxide electrolyte, generated oxygen is concentrated in the middle hollow structure, metal oxidation caused by anode oxygen at the middle hollow structure is avoided, and the electrolytic efficiency can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of in-situ utilization of lunar soil resources, and specifically relates to a tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt, a preparation method and an application thereof. Background Art

[0002] Lunar soil is the most readily available important resource on the lunar surface, which is rich in oxides such as silicon dioxide and iron oxide. Extracting oxygen from the lunar soil as life support materials and rocket fuel is conducive to achieving self-sufficiency of the lunar base and also provides an important guarantee for the long-term residence of humans on the moon.

[0003] Molten salt electrolysis oxygen production technology is a typical electrochemical metallurgical technology. In short, it is to dissolve the lunar soil in molten cryolite molten salt. By applying direct current between the cathode and the cathode, the metal ions migrate to the cathode under the drive of the electric field, and obtain electrons at the cathode to be reduced to metal. The oxygen ions migrate to the anode side under the drive of the electric field, and lose electrons at the anode to generate oxygen. Molten salt electrolysis technology on the ground usually uses a consumable carbon anode, that is, the oxygen at the anode reacts with carbon to generate CO or CO2 and emit it into the atmosphere. However, in view of the oxygen preparation needs on the lunar surface, the ideal anode material should meet the following conditions: good conductivity, resistance to molten salt corrosion, high temperature resistance, and oxidation resistance. However, the molten salt electrolysis reaction temperature of the lunar soil is above 900 degrees Celsius, and the molten molten salt is usually highly corrosive. The anode faces the challenges of high-temperature oxidation of oxygen, electrochemical oxidation, and erosion of molten salt. Conventional materials are difficult to withstand, which seriously restricts the long-term use of the electrode. On the other hand, the oxygen produced by the anode is easy to react again with the metal generated by the cathode reduction reaction, thereby reducing the overall efficiency of oxygen production. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a tubular composite electrode for oxygen production by lunar soil molten salt electrolysis, a preparation method and an application, thereby solving the problems in the prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The tubular composite electrode used for the electrolysis of lunar soil molten salt to produce oxygen is a multi-layer nested tubular structure, which includes, from the inside to the outside, a porous anode layer, a dense electrolyte layer, and a porous cathode layer;

[0007] The material of the dense electrolyte layer is yttria-stabilized zirconia;

[0008] The porous anode layer is made of metal iridium, platinum or a mixture of metal iridium and yttria-stabilized zirconia;

[0009] The porous cathode layer is made of a mixture of metallic molybdenum and gadolinium oxide-doped cerium oxide.

[0010] Furthermore, the porosity of the dense electrolyte layer is less than 2%; the porosity of the porous cathode layer is 20-30%; and the porosity of the porous anode layer is 20-50%.

[0011] Furthermore, in the dense electrolyte layer, the mass fraction of yttrium oxide is 5-8%.

[0012] Furthermore, in the porous cathode layer, the mass percentage of metal molybdenum is 20-50%.

[0013] The method for preparing the above-mentioned tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt comprises the following steps:

[0014] S1, grinding and mixing the active material of the porous anode layer with the pore former, the binder and the solvent, forming a cylindrical green embryo by extrusion molding or isothermal cold pressing, drying and sintering to prepare the porous anode layer;

[0015] S2, applying an electrolyte layer by dip coating on the outside of the porous anode layer, and obtaining a tubular dense electrolyte layer after drying and sintering;

[0016] S3, dip coating on the outside of the dense electrolyte layer: the active material of the porous cathode layer, the pore former, the binder and the gadolinium oxide-doped cerium oxide material are first prepared into a mixed solution, and then coated on the outside of the dense electrolyte layer, and dried and pre-sintered to form a porous cathode layer, thereby obtaining a composite electrode embryo;

[0017] S4, placing the composite electrode embryo in the air for calcination treatment to prepare a tubular composite electrode for lunar soil molten salt electrolysis to produce oxygen.

[0018] Furthermore, the pore-forming agent is corn starch or graphite powder, with a mass fraction of 10-30%; the binder is polyvinyl alcohol, with a mass fraction of 10-15%; and the solvent is anhydrous ethanol.

[0019] Furthermore, the pre-sintering temperature is 800-1400°C; and the calcining temperature is 500-1000°C.

[0020] The above-mentioned tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt is used in producing oxygen by electrolysis of lunar soil molten salt.

[0021] A lunar soil molten salt electrolysis oxygen production device includes the above-mentioned tubular composite electrode for lunar soil molten salt electrolysis oxygen production.

[0022] Furthermore, the lunar soil molten salt electrolysis oxygen production device also includes a furnace body, in which cryolite molten salt is placed, and a lunar soil storage tank, a feed control valve and an oxygen outlet are arranged at the upper end of the furnace body; lunar soil is added to the lunar soil storage tank and is controlled to enter the furnace body through the feed control valve, and a tubular composite electrode for lunar soil molten salt electrolysis oxygen production is located in the furnace body and connected to a DC power supply, and oxygen generated by electrolysis is discharged from the oxygen outlet;

[0023] A sliding slag discharge nozzle is arranged at the lower end of the furnace body, and the switch of the sliding slag discharge nozzle is controlled by arranging a connecting rod control motor and a nozzle control connecting rod outside the furnace body.

[0024] Beneficial effects of the present invention:

[0025] 1. The lunar soil molten salt electrolysis technology is limited by the low efficiency of anode electrolysis. In the conventional electrode structure, the oxygen generated by the anode diffuses into the molten salt and is easily consumed by reacting with the metal generated by the cathode, thereby reducing the efficiency of electrolytic oxygen production. The composite electrode structure uses a dense solid oxide electrolyte to concentrate the generated oxygen in the hollow structure in the middle, avoiding the oxidation of the metal produced by the anode oxygen here, which helps to improve the electrolysis efficiency.

[0026] 3. The electrode structure separates the cathode and the anode through a dense solid oxide electrolyte layer, which is helpful for the separation and collection of products.

[0027] 4. The composite electrode structure is highly integrated, simple in structure and easy to scale up.

[0028] 5. The composite electrode structure greatly shortens the distance between the cathode and the anode, which helps to reduce the impedance between the electrodes and reduce electrical and thermal losses.

[0029] 6. The porous structure of the anode has a large specific surface area, which helps to improve the utilization rate of precious metals such as platinum and iridium, reduce the amount of precious metals used, and achieve efficient electrolytic oxygen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A top view of the composite electrode structure used to produce oxygen by electrolysis of lunar soil molten salt;

[0032] Figure 2 A side view of the composite electrode structure used for oxygen production by electrolysis of lunar soil molten salt;

[0033] Figure 3 Schematic diagram of the device for producing oxygen by electrolysis of lunar soil molten salt;

[0034] In the figure, 1-porous anode layer, 2-dense electrolyte layer, 3-porous cathode layer; 4-feed control valve, 5-lunar soil storage tank, 6-oxygen outlet, 7-furnace body, 8-composite electrode, 9-sliding slag discharge outlet, 10-outlet control connecting rod, 11-connecting rod control motor. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] like Figure 1 and Figure 2 As shown, the tubular composite electrode for oxygen production by lunar soil molten salt electrolysis is a multi-layer nested tubular structure, which includes, from the inside to the outside: a porous anode layer 3, a dense electrolyte layer 2, and a porous cathode layer 1;

[0037] Among them, the dense electrolyte layer 2 is used to isolate the anode from the contact with the lunar soil molten salt. The porous anode layer 3 is located in the innermost layer of the tubular structure, which can realize concentrated oxygen production and help oxygen collection. The porous cathode layer 1 is located on the outside of the tubular structure to realize the reduction of metal cations and generate metals on the outside.

[0038] The dense electrolyte layer 2 has a porosity of less than 2%, and is made of an oxide having oxygen ion conductivity at high temperatures. The electrolyte material is a zirconium-based oxide, such as yttria-stabilized zirconium oxide, and the yttria content (mass fraction) is 2% to 20%.

[0039] The porous anode layer 3 has a porosity of 20-50% and a length slightly shorter than that of the dense electrolyte layer 2; the material is metal iridium, platinum or a mixture of metal iridium and yttria-stabilized zirconia.

[0040] The porous cathode layer 1 has a porosity of 20-30% and is a mixture of metallic molybdenum and gadolinium oxide-doped cerium oxide, and has a length slightly shorter than that of the dense electrolyte layer 2. In the mixture, the mass percentage of metallic molybdenum is 20-50%.

[0041] The preparation process of the composite electrode includes the following steps:

[0042] S1, the active material of the porous anode layer 3 is fully ground and mixed with a pore former, a binder, and a solvent, and is formed into a cylindrical green embryo by extrusion molding or isothermal cold pressing, and then dried and sintered to prepare the porous anode layer 3;

[0043] S2, a layer of electrolyte layer is dip-coated on the outside of the porous anode layer 3, and a tubular dense electrolyte layer 2 is obtained after drying and sintering;

[0044] S3, dip coating on the outside of the dense electrolyte layer 2: the active material of the porous cathode layer 1, the pore former, the binder and the gadolinium oxide-doped cerium oxide material are first prepared into a mixed solution, and then coated on the outside of the dense electrolyte layer 2, and dried and pre-sintered to form a porous cathode layer 1, and obtain a composite electrode embryo.

[0045] S4, placing the composite electrode embryo in the air for calcination treatment to remove organic matter such as pore-forming agents, and preparing a tubular composite electrode for lunar soil molten salt electrolysis to produce oxygen.

[0046] The pore-forming agent may be corn starch, graphite powder, etc., with a mass fraction of 10-30%, and the binder may be polyvinyl alcohol, etc., with a mass fraction of 10-15%. The solvent used is anhydrous ethanol.

[0047] In S1, the drying method is forced air drying, the drying temperature can be 90-150°C, and the drying time is 10-24h; the sintering temperature is 500-1600°C;

[0048] In S2, the drying temperature is 80-150°C; the sintering temperature is 800-1400°C;

[0049] In S3, the drying temperature is 90-150°C; the pre-sintering temperature is 800-1400°C;

[0050] In S4, the calcination temperature is 500-1000°C.

[0051] The technical solution of the present invention is specifically described below by the following embodiments:

[0052] Example 1

[0053] The tubular composite electrode for the electrolysis of lunar soil molten salt to produce oxygen is a multi-layer nested tubular structure, which includes, from the inside to the outside: a porous anode layer 3, a dense electrolyte layer 2 and a porous cathode layer 1;

[0054] The porous anode layer 3 has a porosity of 50%, a length of 150 mm, an outer diameter of 10 mm, and an inner diameter of 7.5 mm. The material is a mixture of metal platinum and yttria-stabilized zirconia, wherein the mass fraction of platinum is 20% and the mass fraction of yttria in the yttria-stabilized zirconia is 8%.

[0055] The dense electrolyte layer 2 has a porosity of less than 2%, a wall thickness of 1 mm, and a length of 150 mm, which is equivalent to the porous anode layer 3; the material is yttria-stabilized zirconia, in which the mass fraction of yttria is 8%.

[0056] The porous cathode layer 1 is located at the outermost layer, with a porosity of 30%, a wall thickness of 50um, and a length of 140mm, which is slightly shorter than the thickness of the dense electrolyte layer 2. The porous cathode layer 1 is made of a mixture of molybdenum and gadolinium oxide-doped cerium oxide, wherein molybdenum is used as a cathode active species with a mass fraction of 30%, and gadolinium oxide-doped cerium oxide is used as an ion conductor to transfer oxygen ions and provide a certain electronic conductivity under high temperature conditions. The doping amount of gadolinium oxide in the gadolinium oxide-doped cerium oxide is 5%.

[0057] In this embodiment, a preparation process of the composite electrode is also disclosed, comprising the following steps:

[0058] S1, the active material of the porous anode layer 3 (a mixture of metal iridium and yttria-stabilized zirconia) is fully ground and mixed with a pore-forming agent, a binder, and a solvent, and is formed into a cylindrical green embryo by extrusion molding or isothermal cold pressing, and then sintered after drying to prepare a porous anode layer 3;

[0059] S2, a layer of electrolyte layer is dip-coated on the outside of the porous anode layer 3, and a tubular dense electrolyte layer 2 is obtained after drying and sintering;

[0060] S3, dip-coating on the outside of the dense electrolyte layer 2: the active material of the porous cathode layer 1 (a mixture of metallic molybdenum and gadolinium oxide-doped cerium oxide), pore-forming agent, and binder are prepared into a mixed solution, coated on the outside of the electrolyte layer, dried and pre-sintered to form a porous cathode layer 1, and a composite electrode embryo is obtained.

[0061] S4, placing the composite electrode embryo in the air for calcination treatment to remove organic matter such as pore-forming agents, and preparing a tubular composite electrode for lunar soil molten salt electrolysis to produce oxygen.

[0062] Among them, in S1, the pore-forming agent is corn starch with a mass fraction of 20%, the binder is polyvinyl alcohol with a mass fraction of 5%, and the solvent is anhydrous ethanol.

[0063] In S1, the drying method is forced air drying, the drying temperature is 120°C, and the drying time is 24h; the sintering temperature is 1400°C;

[0064] In S2, the drying method is forced air drying, the drying temperature can be 150°C, and the drying time is 24h; the sintering temperature is 1200°C;

[0065] In S3, the drying method is forced air drying, the drying temperature is 120°C, and the drying time is 24h; the sintering temperature is 1400°C;

[0066] In S4, the calcination temperature is 800°C.

[0067] Example 2

[0068] like Figure 1 As shown, the tubular composite electrode for oxygen production by lunar soil molten salt electrolysis is a multi-layer nested tubular structure, which includes, from the inside to the outside: a porous anode layer 3, a dense electrolyte layer 2, and a porous cathode layer 1;

[0069] The porous anode layer 3 has a porosity of 40%, a length of 120 mm, a thickness of 50 μm, and is made of metal iridium.

[0070] The dense electrolyte layer 2 has a porosity of less than 2%, a wall thickness of 3 mm, and a length of 130 mm; the material is yttria-stabilized zirconia, wherein the mass fraction of yttria is 5%.

[0071] The porous cathode layer 1 is located at the outermost layer, with a porosity of 20%, a wall thickness of 50um, and a length of 120mm, which is equivalent to the length of the porous anode layer 3; the material of the porous cathode layer 1 is a mixture of molybdenum and gadolinium oxide-doped cerium oxide, in which the mass fraction of molybdenum is 40%, and the doping amount of gadolinium oxide in the gadolinium oxide-doped cerium oxide is 5%.

[0072] In this embodiment, a preparation process of the composite electrode is also disclosed, comprising the following steps:

[0073] S1, the active material (metal iridium) of the porous anode layer 3 is fully ground and mixed with a pore former, a binder, and a solvent, and is formed into a cylindrical green body by extrusion molding or isothermal cold pressing, and then sintered after drying to prepare the porous anode layer 3;

[0074] S2, a layer of electrolyte layer is dip-coated on the outside of the porous anode layer 3, and a tubular dense electrolyte layer 2 is obtained after drying and sintering;

[0075] S3, dip-coating the following materials: the active material of the porous cathode layer 1 (cerium oxide doped with molybdenum and gadolinium oxide), pore-forming agent, and binder on the outside of the dense electrolyte layer 2, drying and pre-sintering to form the porous cathode layer 1, and obtaining a composite electrode embryo.

[0076] S4, placing the composite electrode embryo in the air for calcination treatment to remove organic matter such as pore-forming agents, and preparing a tubular composite electrode for lunar soil molten salt electrolysis to produce oxygen.

[0077] Among them, in S1, the pore-forming agent is graphite powder with a mass fraction of 10%, the binder is polyvinyl alcohol with a mass fraction of 10%, and the solvent is anhydrous ethanol.

[0078] In S1, the drying method is forced air drying, the drying temperature is 120°C, and the drying time is 12h; the sintering temperature is 1400°C;

[0079] In S2, the drying method is forced air drying, the drying temperature is 100°C, and the drying time is 12h; the sintering temperature is 1200°C;

[0080] In S3, the drying method is forced air drying, the drying temperature is 120°C, and the drying time is 12h; the sintering temperature is 1400°C;

[0081] In S4, the calcination temperature is 800°C.

[0082] Example 3

[0083] In this embodiment, a lunar soil molten salt electrolysis oxygen production device is disclosed, such as Figure 3 As shown, it includes the composite electrode 8 described in Example 1;

[0084] The lunar soil molten salt electrolysis oxygen production device also includes: a furnace body 7, in which cryolite molten salt is placed, and a lunar soil storage tank 5, a feed control valve 4 and an oxygen outlet 6 are arranged at the upper end of the furnace body 7; a lunar soil storage tank, in which lunar soil is added to the lunar soil storage tank 5, and is controlled by the feed control valve 4 to enter the furnace body 7, the composite electrode 8 is located in the furnace body 7 and is connected to a DC power supply, and the oxygen generated by electrolysis is discharged from the oxygen outlet 6.

[0085] In this embodiment, the porous cathode layer 1 and the porous anode layer 3 in the composite electrode 8 are connected to the negative electrode and the positive electrode of the DC power supply respectively through wires, and the wires are platinum wires or iridium wires.

[0086] A sliding slag discharge nozzle 6 is provided at the lower end of the furnace body 7, and a connecting rod control motor 11 and a nozzle control connecting rod 10 are provided on the outside of the furnace body 7 to control the switch of the sliding slag discharge nozzle 9;

[0087] The metal ions are reduced at the cathode and deposited to the bottom of the furnace body 7 under the action of gravity, and the electrolysis voltage fluctuation is detected in real time; when a significant change in the electrolysis voltage is detected, the connecting rod control motor 11 controls the water inlet control connecting rod 10 to drive the sliding slag discharge water inlet 9 to open, allowing the metal deposited at the bottom of the furnace body 7 to flow out.

[0088] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0089] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt, characterized in that: It is a multi-layer nested tubular structure, which includes, from the inside to the outside: a porous anode layer, a dense electrolyte layer and a porous cathode layer; The material of the dense electrolyte layer is yttria-stabilized zirconia; The porous anode layer is made of metal iridium, platinum or a mixture of metal iridium and yttria-stabilized zirconia; The porous cathode layer is made of a mixture of metallic molybdenum and gadolinium oxide-doped cerium oxide.

2. The tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt according to claim 1 is characterized in that: The porosity of the dense electrolyte layer is less than 2%; the porosity of the porous cathode layer is 20-30%; and the porosity of the porous anode layer is 20-50%.

3. The tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt according to claim 1 is characterized in that: In the dense electrolyte layer, the mass fraction of yttrium oxide is 5-8%.

4. The tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt according to claim 1 is characterized in that: In the porous cathode layer, the mass percentage of metal molybdenum is 20-50%.

5. The method for preparing a tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, grinding and mixing the active material of the porous anode layer with the pore former, the binder and the solvent, forming a cylindrical green embryo by extrusion molding or isothermal cold pressing, drying and sintering to prepare the porous anode layer; S2, applying an electrolyte layer by dip coating on the outside of the porous anode layer, and obtaining a tubular dense electrolyte layer after drying and sintering; S3, dip coating on the outside of the dense electrolyte layer: the active material of the porous cathode layer, the pore former, the binder and the gadolinium oxide-doped cerium oxide material are first prepared into a mixed solution, and then coated on the outside of the dense electrolyte layer, and dried and pre-sintered to form a porous cathode layer, thereby obtaining a composite electrode embryo; S4, placing the composite electrode embryo in the air for calcination treatment to prepare a tubular composite electrode for lunar soil molten salt electrolysis to produce oxygen.

6. The method for preparing a tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt according to claim 5, characterized in that: The pore-forming agent is corn starch or graphite powder, with a mass fraction of 10-30%; the binder is polyvinyl alcohol, with a mass fraction of 10-15%; and the solvent is anhydrous ethanol.

7. The method for preparing a tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt according to claim 5, characterized in that: The pre-sintering temperature is 800-1400°C; the calcining temperature is 500-1000°C.

8. Application of the tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt as described in any one of claims 1 to 4 in producing oxygen by electrolysis of lunar soil molten salt.

9. A lunar soil molten salt electrolysis oxygen production device, characterized in that: It comprises a tubular composite electrode for producing oxygen by electrolysis of lunar soil molten salt as described in any one of claims 1-4.

10. The lunar soil molten salt electrolysis oxygen production device according to claim 9, characterized in that: It also includes a furnace body, in which cryolite molten salt is placed, and a lunar soil storage tank, a feed control valve, and an oxygen outlet are arranged at the upper end of the furnace body; lunar soil is added to the lunar soil storage tank and is controlled to enter the furnace body through the feed control valve, a tubular composite electrode for electrolyzing lunar soil molten salt to produce oxygen is located in the furnace body and is connected to a DC power supply, and oxygen produced by electrolysis is discharged from the oxygen outlet; A sliding slag discharge nozzle is arranged at the lower end of the furnace body, and the switch of the sliding slag discharge nozzle is controlled by arranging a connecting rod control motor and a nozzle control connecting rod outside the furnace body.

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