A method for producing controllable proportions of syngas based on a solid oxide electrolyzer.

Abstract

This invention provides a method for the controllable electrolysis of reduced water and carbon dioxide using a solid oxide electrolyzer. The method includes the following steps: a mixed gas of carbon dioxide, hydrogen, and water vapor is introduced into the solid oxide electrolyzer; after electrolysis, syngas is obtained. The syngas comprises carbon monoxide, carbon dioxide, hydrogen, and water vapor; the molar ratio of hydrogen to carbon monoxide in the syngas is related to the molar ratio of water vapor to carbon dioxide in the mixed gas. This invention is based on a hollow tube high-temperature solid oxide electrolyzer and employs high-temperature co-electrolysis technology. By controlling the composition of the raw gas, the proportion of syngas generated can be adjusted. The yield of syngas can be controlled by changing the current without altering the gas composition. The operating conditions are simple and controllable, the cost is low, it is safe and environmentally friendly, and the efficiency is high. This method achieves long-term stable production of SOEC and provides a new approach for syngas preparation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid oxide electrolysis cell electrolysis of carbon dioxide, and relates to a method and system for controllable electrolytic reduction of water and carbon dioxide based on a solid oxide electrolysis cell, in particular to a method for producing a controllable proportion of synthesis gas based on a solid oxide electrolysis cell, and a method and system for controllable electrolytic reduction of water and carbon dioxide based on a solid oxide electrolysis cell. BACKGROUND

[0002] Since the industrial revolution, human society has made rapid progress, but in the process of social progress, the demand for energy of industrial production, transportation and living power has been increasing, resulting in a large amount of consumption of fossil energy such as oil and coal, which has produced a large amount of carbon dioxide and other greenhouse gases, and thus caused a series of climate changes such as sea level rise and glacier melting. Therefore, how to effectively control the emission of greenhouse gases and alleviate the problem of climate change has become a very important task in today's society.

[0003] It is of great significance to reduce carbon dioxide emissions and improve the utilization rate of renewable resources to convert carbon dioxide and water into synthesis gas or other hydrocarbon energy by electrochemical catalysis. This method can use clean and renewable energy to generate electricity. Since industrial waste gas often contains a large amount of water vapor and carbon dioxide, the mixture of hydrogen and carbon monoxide obtained by this method can be used to generate higher energy fuels or chemical products such as methane and methanol through the Fischer-Tropsch reaction. This method is of great significance to reduce industrial carbon dioxide emissions and improve the utilization rate of renewable energy.

[0004] There are generally two methods of electrochemical catalysis, one is low-temperature solution electrolysis cell electrolysis catalysis method, and the other is high-temperature solid oxide electrolysis cell electrolysis catalysis method. The low-temperature solution electrolysis cell electrolysis catalysis method is often used for electrolysis of water, and is rarely used for electrolysis of carbon dioxide. Because the carbon-oxygen double bond of carbon dioxide is relatively stable, and the solubility of carbon dioxide in water is low. And in the selection of electrode, platinum catalyst is often selected, resulting in high cost. For the high-temperature solid oxide electrolysis cell electrolysis catalysis method, it is concerned because of its high efficiency, safety and environmental protection. Because the working temperature of the cell is generally 600-1000℃, the high working temperature reduces the demand for electricity of electrolysis, so it can be used for electrolysis of water and carbon dioxide. The mainstream structure of the high-temperature solid oxide electrolysis cell is flat plate and tube.

[0005] Currently, the most widely used structure of high-temperature solid oxide electrolysis cell is flat plate type and tube type. However, the traditional flat plate type and tube type electrolysis cells have some problems. The flat plate type is easy to cause the electrolysis cell to warp due to thermal stress and the like, and the thin support layer is easy to break due to oxidation. The flat plate type has high sealing requirement and is difficult to collect fuel product gas. For the tube type electrolysis cell, the current collecting capacity is weak due to the special structure, the volume power density and the specific surface area power density are not high, the assembly is difficult, and the cost is high. Moreover, more importantly, the existing high-temperature solid oxide electrolysis cell has poor controllability when electrolyzing water and carbon dioxide.

[0006] Therefore, how to find a simple operation, low cost, safe and efficient method to realize the controllable electrolysis of water and carbon dioxide by using a high-temperature solid oxide electrolysis cell has become one of the focuses of many front-line researchers in the field. SUMMARY

[0007] Therefore, the technical problem to be solved by the present application is to provide a method for producing synthesis gas with controllable proportion, in particular to a method for controllable electrolysis and reduction of water and carbon dioxide based on a solid oxide electrolysis cell. The method provided by the present application can control the yield of synthesis gas by only changing the current size, without changing the gas composition of synthesis gas, and the operation condition is simple and easy to control, the cost is low, safe and environmentally friendly, and the efficiency is high.

[0008] The present application provides a method for controllable electrolysis and reduction of water and carbon dioxide based on a solid oxide electrolysis cell, comprising the following steps:

[0009] The mixed gas of carbon dioxide, hydrogen and water vapor is introduced into the solid oxide electrolysis cell, and after electrolysis, synthesis gas is obtained;

[0010] The synthesis gas comprises carbon monoxide, carbon dioxide, hydrogen and water vapor;

[0011] The molar ratio of hydrogen to carbon monoxide in the synthesis gas is associated with the molar ratio of water vapor to carbon dioxide in the mixed gas.

[0012] Preferably, the controllable includes that the molar ratio of hydrogen to carbon monoxide in the synthesis gas is only associated with the molar ratio of water vapor to carbon dioxide in the mixed gas;

[0013] The yield of synthesis gas can be controlled by controlling the current value of the electrolysis;

[0014] The controllable also includes that changing the current value of the electrolysis does not change the molar ratio of hydrogen to carbon monoxide in the synthesis gas;

[0015] The volume content of hydrogen in the mixed gas is 1% to 20%.

[0016] The solid oxide electrolytic cell includes a hollow flat tube type high-temperature solid oxide electrolytic cell.

[0017] Preferably, the electrolysis includes electrolytic catalysis;

[0018] The electrolytic reduction temperature is 600–850°C;

[0019] The current density for the electrolytic reduction is 0.01–2 A / cm². -2 ;

[0020] The voltage for the electrolytic reduction is 1–3V;

[0021] The power source for the electrolytic reduction is a DC power source.

[0022] Preferably, the solid oxide electrolytic cell comprises, from bottom to top:

[0023] Support layer, fuel electrode, electrolyte, barrier layer, and air electrode;

[0024] The support layer is provided with gas flow channels;

[0025] The gas flow channel includes a fuel electrode gas flow channel and a synthesis gas flow channel;

[0026] An air electrode flow channel is provided in the air electrode.

[0027] Preferably, the specific process of the electrolytic reduction is as follows:

[0028] A mixture of hydrogen, carbon dioxide, and water vapor is introduced into the fuel electrode gas channel of the electrolytic cell, while air is introduced into the air electrode channel. An electric current is applied to the electrolytic cell, and an electrochemical reaction occurs to produce syngas.

[0029] Preferably, the material of the support layer includes NiO-YSZ;

[0030] The thickness of the support layer is 4.5–5.5 mm;

[0031] The material of the fuel electrode includes NiO-YSZ;

[0032] The thickness of the fuel electrode is 10–20 μm;

[0033] The electrolyte material includes YSZ;

[0034] The thickness of the electrolyte is 8–12 μm.

[0035] Preferably, the material of the barrier layer includes GDC;

[0036] The thickness of the barrier layer is 1–5 μm;

[0037] The material of the air electrode includes LSCF-GDC;

[0038] The thickness of the air electrode is 10–20 μm.

[0039] This invention provides a system for the controllable electrolysis of reduced water and carbon dioxide based on a solid oxide electrolytic cell, comprising a gas supply unit, a heating unit, and an electrolysis unit;

[0040] The gas supply unit includes a steam generator;

[0041] The heating unit includes a heating device;

[0042] The electrolysis unit includes a flat-tube high-temperature solid oxide electrolytic cell and a power supply;

[0043] The gas outlet of the steam generator is connected to the mixed gas inlet of the flat-tube high-temperature solid oxide electrolytic cell;

[0044] The heating device is used to heat a flat-tube high-temperature solid oxide electrolytic cell.

[0045] The power source is connected to a flat-tube high-temperature solid oxide electrolytic cell.

[0046] Preferably, the air supply unit further includes an air source;

[0047] The air outlet of the air source is connected to the air electrode channel of the flat-tube high-temperature solid oxide electrolytic cell.

[0048] The gas supply unit also includes a hydrogen source and a carbon dioxide source;

[0049] The hydrogen source and carbon dioxide source are connected to the air inlet of the steam generator, either individually or together.

[0050] Preferably, the power source includes a DC power source;

[0051] The electrolysis unit also includes a current collector;

[0052] One end of the current collector is connected to a power source, and the other end is connected to an electrolytic cell;

[0053] The system also includes a gas chromatograph;

[0054] The gas chromatograph is connected to the syngas outlet of the flat-tube high-temperature solid oxide electrolyzer.

[0055] This invention provides a method for the controlled electrolytic reduction of water and carbon dioxide using a solid oxide electrolyzer, comprising the following steps: a mixed gas of carbon dioxide, hydrogen, and water vapor is introduced into the solid oxide electrolyzer; after electrolysis, syngas is obtained; the syngas comprises carbon monoxide, carbon dioxide, hydrogen, and water vapor; and the molar ratio of hydrogen to carbon monoxide in the syngas is related to the molar ratio of water vapor to carbon dioxide in the mixed gas. Compared with existing technologies, the method for the controlled electrolytic reduction of carbon dioxide using a solid oxide electrolyzer provided by this invention is a method for preparing a hydrogen and carbon monoxide mixed gas with controllable proportions, based on a hollow tube high-temperature solid oxide electrolyzer. This method employs high-temperature co-electrolysis technology, with an operating temperature of 700–800°C; the fuel electrode gas consists of water vapor, carbon dioxide, and hydrogen; air is introduced into the air electrode; and the electrolysis current is controlled. This invention achieves adjustable syngas production by controlling the gas composition (the ratio of H2O to CO2). The syngas yield can be controlled by varying the current without altering the gas composition. The operating conditions are simple and controllable, cost-effective, safe, environmentally friendly, and highly efficient, providing a new approach to syngas production. Furthermore, the hollow tube-type electrolytic cell design provided by this invention, with a support layer as the main body and from bottom to top consisting of a support layer, fuel electrode layer, electrolyte layer, barrier layer, and cathode layer, enhances the electrolytic cell's mechanical strength and possesses extremely high specific surface area power density. This enables long-term syngas production using a tube-type high-temperature solid oxide electrolytic cell.

[0056] This invention uses water vapor and carbon dioxide as raw materials. These two gases are produced in large quantities during industrial production, are readily available, and their proportions can be adjusted to produce different proportions of syngas. Furthermore, different electrolysis currents do not alter the composition of the syngas. In the high-temperature solid oxide electrolytic cell, the high-temperature environment of the cell reduces the electrical energy required for the electrolysis of carbon dioxide and water, resulting in high conversion efficiency. Syngas can be obtained at a lower electrolysis voltage, achieving the conversion and storage of electrical energy into chemical energy.

[0057] This invention employs a high-temperature solid oxide electrolyzer with a hollow flat-tube structure. The main structural element is a support layer, and the fuel electrode gas flow channel is located within this support layer. Gas enters the fuel electrode from within the flow channel, generating hydrogen and carbon monoxide synthesis gas, which then exits from the flow channel. This ensures gas collection and sealing. Furthermore, this electrolyzer structure exhibits excellent current collection efficiency, achieving high power density, and possesses high mechanical strength. It is also easy to process and seal, significantly contributing to improved long-term battery stability and electrolytic performance.

[0058] This invention extends the battery's lifespan by controlling the ratio of carbon dioxide to water and using a unique flat-tube structure for SOEC. It achieves long-term stable production of syngas by SOEC, effectively solving the problem that existing solid oxide electrolyzers for co-electrolysis to generate syngas lack industrial-scale finished products. The main technical challenge is that water vapor and carbon dioxide under SOEC operating conditions easily lead to fuel degradation and carbon buildup, resulting in a decline in power generation performance.

[0059] Experimental results show that, using the method for controlled electrolytic reduction of carbon dioxide based on a solid oxide electrolyzer provided in this invention, when the hydrogen content in the fuel electrode gas remains constant at 0.2, the water vapor ratio increases from 0.2 to 0.5 (while the carbon dioxide ratio decreases from 0.6 to 0.3), and the H2 / CO ratio increases from 0.52 to 2.04. The H2 / CO ratio increases with the increase of the water vapor ratio. When the fuel electrode gas composition remains constant, changing the current density does not affect the H2 / CO ratio, indicating that changes in current do not affect the H2 / CO ratio. Durability tests also demonstrate its feasibility for long-term syngas production. Attached Figure Description

[0060] Figure 1 This is a simplified schematic diagram of the hollow flat tube high-temperature solid oxide electrolytic cell structure used in this invention;

[0061] Figure 2 This is a simplified cross-sectional diagram of the hollow flat tube high-temperature solid oxide electrolytic cell used in this invention along the flow channel direction.

[0062] Figure 3 This is a schematic diagram of the connection structure of the syngas preparation system provided by the present invention;

[0063] Figure 4 The graph shows the change in the proportion of syngas produced by the electrolytic cell provided by this invention over time. Detailed Implementation

[0064] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0065] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0066] There are no particular restrictions on the purity of any raw materials used in this invention. However, it is preferable to use materials of analytical grade or those with conventional purity in the field of solid oxide electrolysis cells.

[0067] This invention provides a method for the controlled electrolysis of reduced water and carbon dioxide using a solid oxide electrolyzer, comprising the following steps:

[0068] A mixture of carbon dioxide, hydrogen, and water vapor is passed into a solid oxide electrolytic cell, and after electrolysis, syngas is obtained.

[0069] The synthesis gas includes carbon monoxide, carbon dioxide, hydrogen, and water vapor;

[0070] In the synthesis gas, the molar ratio of hydrogen to carbon monoxide is related to the molar ratio of water vapor to carbon dioxide in the mixed gas.

[0071] For gases, the molar ratio is equivalent to the volume ratio. In this invention, the molar ratio of the gases is the same as the volume ratio.

[0072] In this invention, the controllability preferably includes the fact that the molar ratio of hydrogen to carbon monoxide in the synthesis gas is only related to the molar ratio of water vapor to carbon dioxide in the mixed gas, and is not related to the electrolysis current value.

[0073] In this invention, the controllable preferred method further includes changing the current value of electrolysis without changing the molar ratio of hydrogen to carbon monoxide in the synthesis gas.

[0074] In this invention, the production of syngas can preferably be controlled by controlling the current value of the electrolysis.

[0075] In this invention, the volume content of hydrogen in the mixed gas is preferably 1% to 20%, more preferably 5% to 16%, and even more preferably 9% to 12%.

[0076] In this invention, the solid oxide electrolytic cell preferably includes a hollow flat tube type high-temperature solid oxide electrolytic cell.

[0077] In this invention, the electrolytic reduction temperature is preferably 600-850°C, more preferably 650-800°C, and even more preferably 700-750°C.

[0078] In this invention, the preferred current density for the electrolytic reduction is 0.01–2 A / cm². -2 More preferably, it is 0.4–1.6 Acm. -2 More preferably, it is 0.8–1.2 Å cm. -2 .

[0079] In this invention, the voltage for electrolytic reduction is preferably 1 to 3V, more preferably 1.4 to 2.6V, and even more preferably 1.8 to 2.2V.

[0080] In this invention, the power source for the electrolytic reduction is preferably a DC power source.

[0081] In this invention, the solid oxide electrolytic cell preferably comprises, from bottom to top:

[0082] Support layer, fuel electrode, electrolyte, barrier layer and air electrode.

[0083] In this invention, the support layer preferably has a gas flow channel;

[0084] In this invention, the gas flow channel preferably includes a fuel electrode gas flow channel and a synthesis gas flow channel;

[0085] In this invention, the air electrode preferably has an air electrode flow channel.

[0086] In this invention, the preferred specific process of the electrolytic reduction is as follows:

[0087] A mixture of hydrogen, carbon dioxide, and water vapor is introduced into the fuel electrode gas channel of the electrolytic cell, while air is introduced into the air electrode channel. An electric current is applied to the electrolytic cell, and an electrochemical reaction occurs to produce syngas.

[0088] In this invention, the material of the support layer preferably includes NiO-YSZ.

[0089] In this invention, the thickness of the support layer is preferably 4.5-5.5 mm, more preferably 4.7-5.3 mm, and even more preferably 4.9-5.1 mm.

[0090] In this invention, the material of the fuel electrode preferably includes NiO-YSZ.

[0091] In this invention, the thickness of the fuel electrode is preferably 10-20 μm, more preferably 12-18 μm, and even more preferably 14-16 μm.

[0092] In this invention, the electrolyte material preferably includes YSZ.

[0093] In this invention, the thickness of the electrolyte is preferably 8-12 μm, more preferably 8.5-11.5 μm, more preferably 9-11 μm, and even more preferably 9.5-10.5 μm.

[0094] In this invention, the material of the barrier layer preferably includes GDC.

[0095] In this invention, the thickness of the barrier layer is preferably 1 to 5 μm, more preferably 1.5 to 4.5 μm, more preferably 2 to 4 μm, and even more preferably 2.5 to 3.5 μm.

[0096] In this invention, the material of the air electrode preferably includes LSCF-GDC.

[0097] In this invention, the thickness of the air electrode is preferably 10-20 μm, more preferably 12-18 μm, and even more preferably 14-16 μm.

[0098] The above steps of the present invention provide a method for controllable electrolysis of reduced water and carbon dioxide based on a solid oxide electrolytic cell, namely a method for preparing a mixed gas of hydrogen and carbon monoxide with controllable proportions.

[0099] This invention, based on a hollow tube-type high-temperature solid oxide electrolyzer with a specific structure, achieves a controllable syngas production method by maintaining a constant variety of feed gas types through a co-electrolysis method, thereby changing the feed gas ratio. The syngas preparation method based on the tube-type high-temperature solid oxide electrolyzer provided by this invention has advantages such as simple operation, low cost, safety, and high efficiency. This method can achieve the electrolysis of water and carbon dioxide at low voltage to generate hydrogen and carbon monoxide syngas.

[0100] This invention provides a system for the controllable electrolysis of reduced water and carbon dioxide based on a solid oxide electrolytic cell, comprising a gas supply unit, a heating unit, and an electrolysis unit.

[0101] In this invention, the gas supply unit preferably includes a steam generator.

[0102] In this invention, the heating unit preferably includes a heating device.

[0103] In this invention, the electrolysis unit preferably includes a flat-tube high-temperature solid oxide electrolytic cell and a power source.

[0104] In this invention, the gas outlet of the steam generator is preferably connected to the mixed gas inlet of the flat-tube high-temperature solid oxide electrolytic cell.

[0105] In this invention, the heating device is preferably used to heat a flat-tube high-temperature solid oxide electrolytic cell.

[0106] In this invention, the power source is preferably connected to a flat-tube high-temperature solid oxide electrolytic cell.

[0107] In this invention, the air supply unit preferably includes an air source.

[0108] In this invention, the air outlet of the air source is preferably connected to the air electrode channel of the flat-tube high-temperature solid oxide electrolytic cell.

[0109] In this invention, the hydrogen source and the carbon dioxide source are preferably connected to the air inlet of the steam generator, either separately or together.

[0110] In this invention, the power supply preferably includes a DC power supply.

[0111] In this invention, the electrolysis unit preferably includes a current collector.

[0112] In this invention, the current collector is preferably connected at one end to a power source and at the other end to an electrolytic cell. Specifically, the current collector contacts the electrolytic cell by applying pressure with screws, a silver mesh is placed on the contact surface to improve contact performance, and a stainless steel rod is connected to the current collector, which is then connected to the power supply wires.

[0113] In this invention, the system preferably includes a gas chromatograph.

[0114] In this invention, the gas chromatography is preferably connected to the syngas outlet of the flat-tube high-temperature solid oxide electrolyzer.

[0115] See Figure 1 , Figure 1 This is a simplified schematic diagram of the hollow flat-tube high-temperature solid oxide electrolytic cell structure used in this invention. In the diagram, 1-support layer, 2-flow channel, 3-active fuel electrode, 4-electrolyte layer, 5-barrier layer, and 6-air electrode.

[0116] See Figure 2 , Figure 2 This is a simplified cross-sectional diagram of the hollow flat-tube high-temperature solid oxide electrolytic cell used in this invention, along the flow channel direction. In the diagram, 1-support layer, 2-flow channel, 3-active fuel electrode, 4-electrolyte layer, 5-barrier layer, and 6-air electrode.

[0117] The structure of the flat-tube high-temperature solid oxide electrolytic cell used in this invention is as follows: Figure 1 , Figure 2 As shown, the support layer is the main body of the battery, and a gas flow channel is provided in the support layer. The battery structure from bottom to top consists of the support layer, fuel electrode, electrolyte, barrier layer and air electrode.

[0118] Specifically, 1-Support layer, composition: NiO-3mol% YSZ (nickel oxide-3mol% yttrium-stabilized zirconium oxide). 3-Active fuel electrode, composition: NiO-8mol% YSZ (nickel oxide-8mol% yttrium-stabilized zirconium oxide). 4-Electrolyte layer, composition: 8mol% YSZ (8mol% yttrium-stabilized zirconium oxide). 5-Barrier layer, composition: GDC (gadolinium oxide-doped cerium oxide). 6-Air electrode, composition: LSCF (lanthanum strontium cobalt iron)-GDC (gadolinium oxide-doped cerium oxide).

[0119] More specifically, the support layer material is NiO-3mol%YSZ with a thickness of 4.5–5.5 mm. The fuel electrode material is NiO-8mol%YSZ with a thickness of 10–20 μm. The electrolyte material is 8mol%YSZ with a thickness of 8–12 μm. The barrier layer material is GDC with a thickness of 1–5 μm. The air electrode material is LSCF-GDC with a thickness of 20 μm.

[0120] This invention utilizes a flat-tube solid oxide electrolyzer for syngas production. A mixture of water vapor and carbon dioxide is introduced into the SOEC, and hydrogen and carbon monoxide syngas are generated through electrolysis. This electrolyzer structure facilitates syngas collection and improves battery stability and durability. The higher operating temperature reduces the electrical energy required to generate syngas. Furthermore, this invention controls the syngas ratio by controlling the electrolysis conditions. The syngas ratio is precisely controlled by adjusting the ratio of water vapor to carbon dioxide, and changing the electrolysis current does not alter the syngas ratio.

[0121] See Figure 3 , Figure 3 This is a schematic diagram of the connection structure of the syngas preparation system provided by the present invention. In the diagram, 7-air compressor, 8-high-pressure gas cylinder, 9-steam generator, 10-flow controller, 11-electric furnace, 12-current collector, 13-flat-tube high-temperature solid oxide electrolytic cell, 14-DC power supply, and 15-gas chromatograph.

[0122] The syngas preparation system used in this invention is as follows: Figure 3 As shown, the system includes a gas supply unit, a heating unit, and an electrolysis unit. The gas supply system provides a stable and continuous supply of hydrogen, carbon dioxide, and water vapor. A temperature-controlled electric furnace in the heating unit heats and maintains the temperature of the electrolysis unit. The electrolysis unit includes an electrolytic cell, a DC power supply, and a current collector. The generated syngas is analyzed by gas chromatography.

[0123] To complete and refine the overall process route, better ensure the controllability of the syngas ratio, and further improve the stability and efficiency of the process, the above-mentioned method for the controllable electrolytic reduction of carbon dioxide based on a solid oxide electrolyzer can also be combined with corresponding detection steps, specifically including the following steps:

[0124] The preferred steps for preparing syngas based on the above-mentioned flat-tube solid oxide electrolytic cell and its system are as follows:

[0125] 1. After assembling the electrolytic cell and current collector, place them in an electric furnace and connect them to a DC power supply to form an electrolysis unit. The current collector is made of stainless steel.

[0126] 2. Heat to 600-850℃ using an electric furnace and maintain a constant temperature.

[0127] 3. A mixture of hydrogen, carbon dioxide and water vapor is introduced into the fuel electrode channel of the electrolytic cell, and air is introduced into the air electrode channel of the individual electrolytic cells.

[0128] 4. Current is applied to the electrolytic cell through a DC power supply, causing an electrochemical reaction to produce syngas. The operating voltage is 1–3V.

[0129] 5. The synthesis gas production is controlled by controlling the ratio of water vapor and carbon dioxide in the mixed gas, as well as the ratio of hydrogen and carbon monoxide to syngas, and by controlling the magnitude of the electrolysis current. Changing the electrolysis current will not cause a change in the syngas ratio.

[0130] 6. The reaction process is as follows: A mixture of carbon dioxide and water undergoes an electrolytic reaction at the fuel electrode three-phase interface to produce carbon monoxide and hydrogen, and oxygen ions are generated. Driven by the oxygen concentration gradient, the oxygen ions are conducted through the electrolyte to the air electrode, where they lose electrons and desorb to generate oxygen. The electrolytic reaction equation is as follows:

[0131] Fuel electrode: CO2 + H2O + 4e - =CO + H2 + 2O 2-

[0132] Air pole: 2O 2- =O2+4e -

[0133] Overall reaction: CO2 + H2O - =CO + H2 + O2

[0134] 7. A mixture of CO, H2, H2O, and CO2 is collected at the outlet of the fuel polar flow channel. Water is separated from the mixture by lowering the gas temperature.

[0135] More preferably, the present invention provides a process and testing method for producing syngas from an example battery:

[0136] After assembling the example electrolytic cell and current collector, the cell was placed in an electric furnace and heated to 750°C, and the temperature was maintained at a constant temperature.

[0137] (1) After assembling the electrolytic cell and current collector, the example cell was placed in an electric furnace and heated to 750°C and the temperature was kept constant.

[0138] (2) 0.3 SLM of hydrogen gas is introduced into the fuel electrode channel of the electrolytic cell and 1.0 SLM of air is introduced into the air electrode. This step is used to reduce the nickel oxide of the support layer and the fuel electrode to metallic nickel. During the reduction process, the open circuit voltage of the electrolytic cell is monitored until the open circuit voltage is stable for more than 3 hours.

[0139] (3) Stop supplying hydrogen to the fuel electrode and switch to water vapor, carbon dioxide, and a small amount of hydrogen. The role of hydrogen is to protect the electrolytic cell from oxidation. Specifically, hydrogen and carbon dioxide are introduced into a water vapor generator. The ratio of water vapor is adjusted by controlling the temperature of the water vapor generator. The three gases are mixed in the water vapor generator and then introduced into the fuel electrode of the electrolytic cell through the inlet pipe. The ratio and flow rate of water vapor and carbon dioxide are determined according to the actual situation.

[0140] (4) Based on the actual situation, the electrolytic cell is subjected to constant current electrolysis at a specific current, and the product gas is analyzed by gas chromatography.

[0141] The present invention provides a method for producing syngas with a controllable ratio based on a solid oxide electrolyzer, and a method and system for the controllable electrolysis of reduced water and carbon dioxide based on a solid oxide electrolyzer. Based on a hollow tube high-temperature solid oxide electrolyzer, this invention proposes a method for preparing a mixed gas of hydrogen and carbon monoxide with a controllable ratio. This method employs high-temperature co-electrolysis technology, operating at 700–800°C. The fuel electrode gas consists of water vapor, carbon dioxide, and hydrogen, while air is introduced into the air electrode, and the electrolysis current is controlled. This invention achieves the generation of syngas with an adjustable ratio by controlling the gas composition (H₂O to CO₂ ratio); the syngas yield is controlled by changing the current without altering the gas composition; and the operating conditions are simple and easy to control, with low cost, safety, environmental friendliness, and high efficiency, providing a new approach for syngas production. Furthermore, the hollow tube-type electrolytic cell structure design provided by this invention has a support layer as the main body, and from bottom to top, the structure consists of a support layer, a fuel electrode layer, an electrolyte layer, a barrier layer, and a cathode layer. This structure improves the mechanical strength of the electrolytic cell and has an extremely high specific surface area power density, thus enabling long-term syngas production using the tube-type high-temperature solid oxide electrolytic cell.

[0142] This invention uses water vapor and carbon dioxide as raw materials. These two gases are produced in large quantities during industrial production, are readily available, and their proportions can be adjusted to produce different proportions of syngas. Furthermore, different electrolysis currents do not alter the composition of the syngas. In the high-temperature solid oxide electrolytic cell, the high-temperature environment of the cell reduces the electrical energy required for the electrolysis of carbon dioxide and water, resulting in high conversion efficiency. Syngas can be obtained at a lower electrolysis voltage, achieving the conversion and storage of electrical energy into chemical energy.

[0143] This invention employs a high-temperature solid oxide electrolyzer with a hollow flat-tube structure. The main structural element is a support layer, and the fuel electrode gas flow channel is located within this support layer. Gas enters the fuel electrode from within the flow channel, generating hydrogen and carbon monoxide synthesis gas, which then exits from the flow channel. This ensures gas collection and sealing. Furthermore, this electrolyzer structure exhibits excellent current collection efficiency, achieving high power density, and possesses high mechanical strength. It is also easy to process and seal, significantly contributing to improved long-term battery stability and electrolytic performance.

[0144] This invention extends the battery's lifespan by controlling the ratio of carbon dioxide to water and using a unique flat-tube structure for SOEC. It achieves long-term stable production of syngas by SOEC, effectively solving the problem that existing solid oxide electrolyzers for co-electrolysis to generate syngas lack industrial-scale finished products. The main technical challenge is that water vapor and carbon dioxide under SOEC operating conditions easily lead to fuel degradation and carbon buildup, resulting in a decline in power generation performance.

[0145] Experimental results show that, using the method for controlled electrolytic reduction of carbon dioxide based on a solid oxide electrolyzer provided in this invention, when the hydrogen content in the fuel electrode gas remains constant at 0.2, the water vapor ratio increases from 0.2 to 0.5 (while the carbon dioxide ratio decreases from 0.6 to 0.3), and the H2 / CO ratio increases from 0.52 to 2.04. The H2 / CO ratio increases with the increase of the water vapor ratio. When the fuel electrode gas composition remains constant, changing the current density does not affect the H2 / CO ratio, indicating that changes in current do not affect the H2 / CO ratio. Durability tests also demonstrate its feasibility for long-term syngas production.

[0146] To further illustrate the present invention, the following describes in detail a method and system for controlled electrolysis of reduced water and carbon dioxide based on a solid oxide electrolytic cell, in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0147] Example 1

[0148] (1) After assembling the example electrolytic cell and current collector, the cell was placed in an electric furnace and heated to 750°C and the temperature was kept constant.

[0149] (2) 0.3 SLM of hydrogen gas is introduced into the fuel electrode channel of the electrolytic cell and 1.0 SLM of air is introduced into the air electrode. This step is used to reduce the nickel oxide of the support layer and the fuel electrode to metallic nickel. During the reduction process, the open circuit voltage of the electrolytic cell is monitored until the open circuit voltage is stable for more than 3 hours.

[0150] (3) Stop supplying hydrogen to the fuel electrode and switch to water vapor, carbon dioxide, and a small amount of hydrogen. The role of hydrogen is to protect the electrolytic cell from oxidation. Specifically, hydrogen and carbon dioxide are introduced into a water vapor generator. The ratio of water vapor is adjusted by controlling the temperature of the water vapor generator. The three gases are mixed in the water vapor generator and then introduced into the fuel electrode of the electrolytic cell through the inlet pipe. The ratio and flow rate of water vapor and carbon dioxide are determined according to the actual situation.

[0151] (4) Based on the actual situation, the electrolytic cell is subjected to constant current electrolysis at a specific current, and the product gas is analyzed by gas chromatography.

[0152] Based on the above steps, syngas was prepared by electrolysis at 750℃ using a hollow flat-tube high-temperature solid oxide electrolytic cell. The composition of the reaction gas was changed and the composition of the product gas under different currents was analyzed. The composition of the obtained syngas is shown in Table 1. It can be seen that by changing the H2O / CO2 ratio, the product H2 / CO ratio also changes. The specific ratios are shown in Table 1.

[0153] See Table 1, which shows the composition of the synthesis gas under different reaction gas components.

[0154] Table 1

[0155]

[0156] Example 2

[0157] Syngas was prepared by electrolysis at 750℃ using a hollow tube high-temperature solid oxide electrolytic cell. The composition of the product gas was analyzed by changing the electrolysis current. A 1:1 molar ratio of H2O / CO2 mixture was introduced at the fuel electrode, and air was introduced at the air electrode. The composition of the syngas obtained when the electrolysis current was controlled at 0, 5, 10, 20, and 30 A is shown in Table 2. It can be seen that when the gas composition at the fuel electrode is kept constant, the H2 / CO ratio of the product gas also remains constant. When the gas composition is 20% H2 + 40% H2O + 40% CO2, the H2 / CO ratio is approximately 1.2:1, indicating that the product yield can be controlled by changing the electrolysis current.

[0158] See Table 2, which shows the composition of the synthesis gas under different currents.

[0159] Table 2

[0160]

[0161] Example 3

[0162] A hollow tube-type high-temperature solid oxide electrolyzer was used for constant-current electrolysis at 750℃ with a current of 18A. A 1:1 molar ratio of H₂O / CO₂ mixture was introduced at the fuel electrode, and air was introduced at the air electrode. The electrolyzer operated for 1000 hours, and the product gas ratio was measured at regular intervals. During the 1000-hour test, the product gas production of the electrolyzer was stable, with an H₂:CO ratio of 1.2:1. This demonstrated excellent stability and durability, proving the feasibility of using a hollow tube-type high-temperature solid oxide electrolyzer for long-term syngas production.

[0163] See Figure 4 , Figure 4 The graph shows the change in the proportion of syngas produced by the electrolytic cell provided by this invention over time.

[0164] The foregoing has provided a detailed description of a method for producing a controllable proportion of syngas based on a solid oxide electrolyzer, and a method and system for the controllable electrolysis of reduced water and carbon dioxide based on a solid oxide electrolyzer. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of the embodiments above are merely to help understand the method and core ideas of the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for the controllable electrolytic reduction of water and carbon dioxide based on a solid oxide electrolysis cell, characterized in that, The method comprises the following steps: a mixed gas of carbon dioxide, hydrogen and water vapor is introduced into a solid oxide electrolysis cell, and after electrolysis, a synthesis gas is obtained; the synthesis gas comprises carbon monoxide, carbon dioxide, hydrogen and water vapor; in the synthesis gas, the molar ratio of hydrogen to carbon monoxide is only related to the molar ratio of water vapor to carbon dioxide in the mixed gas; the controllability further comprises changing the current value of electrolysis, without changing the molar ratio of hydrogen to carbon monoxide in the synthesis gas; the solid oxide electrolysis cell is a hollow flat tube type high temperature solid oxide electrolysis cell, which comprises from bottom to top: a support layer, a fuel electrode, an electrolyte, a barrier layer and an air electrode; the support layer is provided with a gas flow channel; the gas flow channel comprises a fuel electrode gas flow channel and a synthesis gas flow channel; the air electrode is provided with an air electrode flow channel; the material of the support layer comprises NiO-YSZ; the thickness of the support layer is 4.5-5.5mm; the material of the fuel electrode comprises NiO-YSZ; the thickness of the fuel electrode is 10-20μm; the material of the electrolyte comprises YSZ; the thickness of the electrolyte is 8-12μm; the material of the barrier layer comprises GDC; the thickness of the barrier layer is 1-5μm; the material of the air electrode comprises LSCF-GDC; the thickness of the air electrode is 10-20μm; the specific process of the electrolytic reduction is: a mixed gas of hydrogen, carbon dioxide and water vapor is introduced into the fuel electrode gas flow channel of the electrolysis cell, air is introduced into the air electrode flow channel of the electrolysis cell, and a current is applied to the electrolysis cell to produce synthesis gas through electrochemical reaction; the temperature of the electrolytic reduction is 600-850℃; The current density of the electrolytic reduction is 0.01-2 A cm -2 .

2. The method of claim 1, wherein, in the mixed gas, the volume content of hydrogen is 1%-20%.

3. The method of claim 1, wherein, the voltage of the electrolytic reduction is 1-3V.

4. The method of claim 1, wherein, the power source of the electrolytic reduction is a direct current power source.

5. A system for controllable electrolytic reduction of water and carbon dioxide based on a solid oxide electrolysis cell, characterized in that, the system comprises a gas supply unit, a heating unit and an electrolysis unit; the gas supply unit comprises a water vapor generator; the heating unit comprises a heating device; the electrolysis unit comprises the hollow flat tube type high temperature solid oxide electrolysis cell and the power source in the method according to any one of claims 1-4; the gas outlet of the water vapor generator is in communication with the mixed gas inlet of the flat tube type high temperature solid oxide electrolysis cell; the heating device is used for heating the flat tube type high temperature solid oxide electrolysis cell; the power source is connected with the flat tube type high temperature solid oxide electrolysis cell.

6. The system of claim 5, wherein, the gas supply unit further comprises an air source; the air outlet of the air source is in communication with the air electrode flow channel of the flat tube type high temperature solid oxide electrolysis cell; the gas supply unit further comprises a hydrogen source and a carbon dioxide gas source; the hydrogen source and the carbon dioxide gas source are respectively or together in communication with the gas inlet of the water vapor generator.

7. The system of claim 5, wherein, the power source comprises a direct current power source; the electrolysis unit further comprises a current collecting device; one end of the current collecting device is connected with the power source, and the other end is connected with the electrolysis cell; the system further comprises a gas chromatograph; the gas chromatograph is in communication with the synthesis gas outlet of the flat tube type high temperature solid oxide electrolysis cell.

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