Medium-temperature carbon dioxide electrochemical reduction system and method

Abstract

The invention discloses a medium-temperature carbon dioxide electrochemical reduction system and method, and belongs to the technical field of medium-temperature carbon dioxide reduction. The reduction system disclosed by the invention comprises a programmable direct-current power supply, a membrane electrode assembly electrolytic bath, a stepping temperature control module, a gas-liquid linkage feeding unit and an online analysis module, the programmable direct-current power supply is respectively connected with a cathode and an anode in the membrane electrode assembly electrolytic bath; the gas-liquid linkage feeding unit is connected with the front end of the membrane electrode assembly electrolytic bath; the stepping temperature control module is connected with the membrane electrode assembly electrolytic cell; and the rear end of the membrane electrode assembly electrolytic bath is connected with the online analysis module. All parts of the system act synergistically, and the technical problem that an existing device is difficult to have the advantages of temperature adaptability, gas flow control and system stability at the same time is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of medium-temperature carbon dioxide reduction, and particularly relates to a medium-temperature carbon dioxide electrochemical reduction system and method. Background Art

[0002] Currently, in the field of electrolytic carbon dioxide reduction technology, commercial applications mainly rely on two major types of electrolyzer systems: ambient-temperature electrolyzers (also known as low-temperature electrolyzers) and solid oxide electrolysis cells (SOECs). These two types of electrolyzers have their own characteristics, with different technical routes and application potentials. Ambient-temperature electrolyzers usually operate at ambient temperature (about 20 - 80°C). With their high technology maturity and relatively low manufacturing cost, they have become one of the mainstream choices in the current market. However, the reaction kinetics process at low temperature is relatively slow, resulting in a bottleneck in improving the electrolysis efficiency and making it difficult to further break through the performance limit. In contrast, SOECs take a different approach. By operating at high temperature (above 600°C), they exhibit significant thermodynamic advantages and an increased reaction rate. The high-temperature environment not only promotes the ionic conduction performance of the electrolyte material but also enhances the electrode reaction activity, thus greatly improving the electrolysis efficiency and hydrogen production rate. However, this technical route also faces severe challenges: the high-temperature environment poses extremely stringent requirements on the thermal stability of the electrolyzer materials, and problems such as material aging and phase change frequently occur; at the same time, the system startup process is slow, the thermal management mechanism is complex, and precise control of the temperature gradient is required to avoid thermal stress damage. These factors all limit the large-scale application and commercialization process of SOEC technology. Ambient-temperature electrolyzers and SOECs have their own advantages and disadvantages in the electrolytic carbon dioxide reduction technology. The future technical development direction needs to comprehensively consider various factors such as efficiency improvement, cost reduction, material innovation, and system integration to achieve a comprehensive breakthrough and sustainable development of the electrolytic carbon dioxide technology.

[0003] There is a gap in the existing technology between these two temperature ranges, lacking an electrolyzer that can operate efficiently in the medium-temperature range (100 - 200°C). If a new type of electrolyzer can be developed to work at 100 - 200°C, it is expected to combine the advantages of rapid response, material stability of low-temperature electrolyzers and high-efficiency reaction kinetics of high-temperature electrolyzers. In addition, this temperature range can utilize industrial waste heat or solar heat sources to further reduce energy consumption and improve the overall system economy. Therefore, developing a new type of electrolyzer technology suitable for the medium-temperature range has important industrial application value. Summary of the Invention

[0004] The purpose of the present invention is to provide a medium-temperature carbon dioxide electrochemical reduction system and method to solve the technical problem that existing devices are difficult to simultaneously possess the advantages of temperature adaptability, gas flow control, and system stability.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions:

[0006] The present invention discloses a medium-temperature carbon dioxide electrochemical reduction system, including a programmable DC power supply, a membrane electrode assembly electrolytic cell, a stepwise temperature control module, a gas-liquid linkage feeding unit, and an on-line analysis module; the programmable DC power supply is respectively connected to the cathode and anode in the membrane electrode assembly electrolytic cell; the gas-liquid linkage feeding unit is connected to the front end of the membrane electrode assembly electrolytic cell; the stepwise temperature control module is connected to the membrane electrode assembly electrolytic cell; the rear end of the membrane electrode assembly electrolytic cell is connected to the on-line analysis module.

[0007] Further, the stepwise temperature control module includes a heating jacket, a thermocouple, and a PID control module; the heating jacket is wrapped outside the membrane electrode assembly electrolytic cell; the thermocouple is inserted into the reaction chamber of the membrane electrode assembly electrolytic cell; the heating jacket and the thermocouple are respectively connected to the PID control module.

[0008] Further, the gas-liquid linkage feeding unit includes a humidification module, a liquid constant temperature module, a back pressure valve, and a gas flow control module; the cathode gas source and the anode gas source are respectively connected to the front end of the membrane electrode assembly electrolytic cell through pipelines in sequence with the gas flow control module, the humidification module; the liquid constant temperature module is connected to the humidifier; the inert gas source is divided into two paths, one path is communicated with the pipeline connecting the cathode gas source and the gas flow control module, and the other path is communicated with the pipeline connecting the anode gas source and the gas flow control module; the back pressure valve is connected to the rear end of the membrane electrode assembly electrolytic cell.

[0009] Further, the gas flow control module includes a first gas flow controller and a second gas flow controller; the humidification module includes a first gas humidifier and a second gas humidifier; the liquid constant temperature module includes a first constant temperature box and a second constant temperature box; the cathode gas source is connected to the front end of the membrane electrode assembly electrolytic cell through pipelines in sequence with the first gas flow controller, the first constant temperature box; the anode gas source is connected to the front end of the membrane electrode assembly electrolytic cell through pipelines in sequence with the second gas flow controller, the second constant temperature box; the inert gas source is divided into two paths, one path is communicated with the pipeline connecting the cathode gas source and the first gas flow controller, and the other path is communicated with the pipeline connecting the anode gas source and the second gas flow controller; the back pressure valve is connected to the rear end of the membrane electrode assembly electrolytic cell.

[0010] Further, the on-line analysis module includes a condenser and an on-line analysis instrument; the condenser and the on-line analysis instrument are sequentially connected to the rear end of the membrane electrode assembly electrolytic cell; the pipeline connecting the condenser to the rear end of the membrane electrode assembly electrolytic cell is also connected to the back pressure valve.

[0011] Further, the on-line analysis instrument is a gas chromatograph.

[0012] Further, one pipeline of the inert gas source connected to the anode gas source and the first gas flow controller is connected through a three-way solenoid valve; the other pipeline of the inert gas source connected to the anode gas source and the second gas flow controller is connected through a three-way solenoid valve.

[0013] Further, the main material of the membrane electrode assembly electrolytic cell is titanium metal; an anion exchange membrane and a cation exchange membrane are arranged between the cathode and the anode of the membrane electrode assembly electrolytic cell.

[0014] The present invention also discloses a method for using the above medium-temperature carbon dioxide electrochemical reduction system, including the following steps:

[0015] Connect the stepwise temperature control module to the membrane electrode assembly electrolytic cell, and then use the gas-liquid linkage feeding unit to purge the inside of the membrane electrode assembly electrolytic cell until the oxygen content reaches the set value; heat the inside of the membrane electrode assembly electrolytic cell to the set temperature through the stepwise temperature control module;

[0016] Subsequently, use the gas-liquid linkage feeding unit to evaporate the liquid into a gaseous reactant, and introduce the gas into the membrane electrode assembly electrolytic cell through a carrier gas to achieve precise supply of the gas flow rate, so that the water vapor pressure in the reaction chamber of the membrane electrode assembly electrolytic cell reaches the preset value;

[0017] Subsequently, apply a voltage to the membrane electrode assembly electrolytic cell through a programmable DC power supply to carry out the carbon dioxide electrochemical reduction reaction.

[0018] Further, the temperature of the liquid constant temperature module in the gas-liquid linkage feeding unit is normal temperature to 90 °C;

[0019] The pressure of the back pressure valve in the gas-liquid linkage feeding unit is 1 to 5 bar.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention discloses a medium-temperature carbon dioxide electrochemical reduction system. By setting a programmable DC power supply, a membrane electrode assembly electrolytic cell, a stepwise temperature control module, a gas-liquid linkage feeding unit, and an on-line analysis module, it innovatively realizes gas feeding by the scrubbing method through the gas-liquid linkage feeding unit, improves the precise supply of gas flow rate, significantly reduces the fluctuation of gas flow rate, reduces the reaction cost. At the same time, the gas-liquid linkage feeding unit is provided with a front-section inert gas purging function to ensure that the oxygen content and humidity in the reaction environment meet the standards, and can keep the gas path clean and stable. The adopted humidity can combine the PID algorithm to correct the heating power in real time, realize the segmented heating strategy, ensure that the temperature of the electrolytic cell is always stable in the target range, avoid catalyst sintering or membrane material degradation caused by overheating, and improve the repeatability of test results. The on-line analysis module detects the reaction state in real time, improving the reaction accuracy. The above components and modules cooperate with each other to achieve precise regulation of all parameters in the electrolysis reaction process, and solve the technical bottlenecks of traditional electrolytic cells in terms of temperature adaptability, gas flow control, and system stability.

[0022] Further, a programmable DC power supply is adopted, which supports constant voltage, constant current, and pulse modes, providing stable and flexible electrical energy input for the electrolysis reaction. The membrane electrode assembly electrolytic cell uses metallic titanium as the main material, and a dense oxide layer (TiO 2 ) can be naturally formed on its surface, which remains stable in the range of pH = 0 - 14 and is applicable to various electrolysis reactions such as H 2 O, CO 2 , N 2 .

[0023] Further, the gas-liquid linkage feeding unit includes a humidification module, a liquid constant temperature module, a back pressure valve, and a gas flow control module, which evaporates the liquid into a gaseous reactant by the scrubbing method, and realizes the precise supply of gas flow rate by combining the linkage control of the back pressure valve and the vapor pressure of the liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of the medium-temperature carbon dioxide electrochemical reduction system of the present invention;

[0025] Wherein: 1 - programmable DC power supply; 2 - membrane electrode assembly electrolytic cell; 3 - heating jacket; 4 - cathode gas source; 5 - anode gas source; 6 - inert gas source; 7 - first gas flow controller; 8 - first gas humidifier; 9 - first constant temperature box; 10 - second gas flow controller; 11 - second gas humidifier; 13 - back pressure valve; 14 - condenser; 15 - on-line analysis instrument; 16 - PID control module. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0028] The present invention discloses a medium-temperature (100 - 200 °C) carbon dioxide electrochemical reduction system, which is particularly suitable for the precise testing and process optimization of carbon dioxide reduction electrochemical reactions. It includes a programmable DC power supply 1, a membrane electrode assembly electrolytic cell 2, a step-by-step temperature control module, a gas-liquid linkage feeding unit, and an on-line analysis module; realizing the precise regulation of all parameters in the electrolysis reaction process and solving the technical bottlenecks of traditional electrolytic cells in terms of temperature adaptability, gas flow control, and system stability.

[0029] Among them, the programmable DC power supply 1 adopts a high-precision digital power supply, supports constant voltage, constant current, and pulse modes, and provides stable and flexible electrical energy input for the electrolysis reaction.

[0030] The membrane electrode assembly electrolytic cell 2 uses metallic titanium (Ti) as the main material of the electrolytic cell body, and is suitable for various electrolysis reactions such as H 2 O, CO 2 , N 2 and so on.

[0031] The step-by-step temperature control module includes a heating jacket 3, a thermocouple 17, and a PID control module 16, and is used to stably control the temperature of the entire system.

[0032] The gas-liquid linkage feeding unit includes a humidification module, a liquid constant temperature module, a back pressure valve 13, and a gas flow control module; evaporating the liquid into a gaseous reactant by the scrubbing method, and realizing the precise supply of gas flow by combining the linkage control of the back pressure valve 13 and the vapor pressure of the liquid.

[0033] The on-line analysis module includes a condenser 14 and an on-line analyzer 15. The condenser 14 is used to separate the liquid product, and then connected to the on-line analyzer 15 for real-time monitoring of the gas composition (such as H 2 , O 2 , CO, CH 4 , etc.).

[0034] The present invention will be further described in detail below with reference to the accompanying drawings:

[0035] See Figure 1 As shown, a medium-temperature carbon dioxide electrochemical reduction system disclosed by the present invention includes a programmable DC power supply 1, a membrane electrode assembly electrolytic cell 2, a stepwise temperature control module, a gas-liquid linkage feeding unit, and an on-line analysis module; the programmable DC power supply 1 is respectively connected to the cathode and anode in the membrane electrode assembly electrolytic cell 2; the gas-liquid linkage feeding unit is connected to the front end of the membrane electrode assembly electrolytic cell 2; the stepwise temperature control module is connected to the membrane electrode assembly electrolytic cell 2; the rear end of the membrane electrode assembly electrolytic cell 2 is connected to the on-line analysis module.

[0036] Among them, the stepwise temperature control module includes a heating jacket 3, a thermocouple 17, and a PID control module 16; the heating jacket 3 is coated outside the membrane electrode assembly electrolytic cell 2; the thermocouple 17 is inserted into the reaction chamber of the membrane electrode assembly electrolytic cell 2; the heating jacket 3 and the thermocouple 17 are respectively connected to the PID control module 16; when the traditional electrolytic cell is heated to the target temperature, the actual temperature often exceeds the set value due to thermal inertia (such as reaching 240°C when setting 200°C), affecting the structure of the electrode active layer or causing side reactions; the present invention adopts a segmented heating strategy, combines the PID algorithm to correct the heating power in real time, ensures that the temperature of the electrolytic cell is always stable in the target range (such as 100-200°C ± 0.5°C), avoids catalyst sintering or membrane material degradation caused by overheating, and improves the repeatability of test results.

[0037] The gas-liquid linked feeding unit includes a humidification module, a liquid constant temperature module, a back pressure valve 13 and a gas flow control module; the cathode gas source 4 and the anode gas source 5 are respectively connected to the front end of the gas flow control module, the humidification module and the membrane electrode assembly electrolytic cell 2 through pipelines in sequence; the liquid constant temperature module is connected to the humidifier; the inert gas source 6 is divided into two paths, one of which is communicated with the pipeline connecting the cathode gas source 4 and the gas flow control module, and the other is communicated with the pipeline connecting the anode gas source 5 and the gas flow control module; the back pressure valve 13 is connected to the rear end of the membrane electrode assembly electrolytic cell 2; the setting of this unit innovatively adopts the gas washing method for feeding. The liquid (such as water, organic electrolyte) is placed in the liquid constant temperature module, and its vapor pressure is adjusted by precise temperature control (such as 25 °C or 60 °C), and then the vapor is carried into the membrane electrode assembly electrolytic cell 2 by the inert carrier gas (such as Ar) in the inert gas source 6. At the same time, the back pressure valve 13 automatically adjusts the system back pressure according to the target gas partial pressure (such as CO 2 partial pressure = 0.5 bar) to make the gas flow strictly match the reaction demand; for example, in CO 2 electrolysis, by adjusting the opening of the back pressure valve 13 and the liquid temperature, the CO 2 concentration can be controlled within the range of 1% - 50%, and the error ≤ 2%.

[0038] In addition, the inert gas source 6 in the gas-liquid linked feeding unit can realize the gas purging function: to avoid the interference of air (such as O 2 , H 2 O) on the electrolysis reaction, before the system starts, the pipeline and the electrolytic cavity are purged by the inert gas (such as N 2 , Ar) in the inert gas source 6, the purging flow rate ≥ 200 sccm, and the duration ≥ 10 minutes, ensuring that the oxygen content in the reaction environment < 10 ppm and the humidity < 1% RH. This function is especially suitable for reactions sensitive to trace impurities (such as nitrogen reduction to ammonia).

[0039] The main part material of the membrane electrode assembly electrolytic cell 2 is selected as titanium metal, and a dense oxide layer (TiO 2 ) can be naturally formed on its surface, which remains stable in the range of pH = 0 - 14, and the contact resistance can be further reduced (< 0.1 Ω·cm 2 ) by surface plating with platinum or carbon coating.

[0040] The present invention also discloses a usage method of the above medium-temperature carbon dioxide electrochemical reduction system, including the following steps:

[0041] Step 1: Spray the silver catalyst on the hydrophobic carbon paper and place it on the cathode side of the titanium bipolar plate, spray IrO 2 on the hydrophilic carbon paper and place it on the anode side of the titanium bipolar plate, and load the intermediate with infiltrated H 3 PO 4The polybenzimidazole (PBI) film is hot-pressed (pressure 5 MPa, temperature 150 °C, time 5 minutes) to form a membrane electrode assembly, and then assembled into a membrane electrode assembly electrolyzer 2; bolt fastening (torque 12 N·m), the membrane electrode assembly electrolyzer 2 is connected to a heating tape and a thermocouple probe, and connected to an external PID control module 16;

[0042] Step 2: Argon in the inert gas source 6 (flow rate 10 - 250 sccm) is passed through the membrane electrode assembly electrolyzer 2 and the connecting pipeline for 10 minutes, and the oxygen content of the tail gas at the rear end of the membrane electrode assembly electrolyzer 2 is measured by a gas chromatograph until the content < 5 ppm;

[0043] Step 3: Set the target temperature of the thermocouple 17 to 150 °C, and use the PID control module 16 to implement real-time correction of the power by the PID algorithm to prevent the membrane electrode assembly electrolyzer 2 from overheating due to thermal inertia, and finally make the temperature in the reaction chamber inside the membrane electrode assembly electrolyzer 2 stable at 150 ± 0.5 °C;

[0044] Step 4: Set the temperatures of the first thermostat 9 and the second thermostat 12 in the liquid constant temperature module to 80 °C, introduce water vapor into the electrode chamber of the membrane electrode assembly electrolyzer 2 through the carrier gas, and adjust the pressure value of the back pressure valve 13 to 2 bar so that the water vapor pressure inside the electrode chamber reaches the preset value;

[0045] Step 5: Apply a voltage of 2 V to the membrane electrode assembly electrolyzer 2 through the programmable DC power supply 1, monitor the current density and hydrogen production rate in real time, and the system automatically records the temperature fluctuation (±0.5 °C), gas flow error (≤1%), and voltage-current curve;

[0046] Step 6: After Step 5 is completed, switch the valve back to purge gas purge (100 sccm, 30 minutes), and cool down to room temperature.

[0047] Preferably, the function of the gas flow controller is to control the flow rate of the raw material gas CO 2 flow rate.

[0048] Preferably, different concentrations of carbon dioxide are introduced into the cathode of the membrane electrode assembly electrolyzer 2 as a carbon source, and the CO 2 gas ratio is 1% - 100%.

[0049] Preferably, a proton source that can undergo an oxidation reaction and provide protons is introduced into the anode of the membrane electrode assembly electrolyzer 2.

[0050] Preferably, when water vapor needs to be introduced into the cathode and anode, it is brought in through a bubbling or steam generating device.

[0051] Preferably, the ionic current between the cathode and anode of the membrane electrode assembly electrolyzer 2 is realized through an ion exchange membrane, including an anion exchange membrane and a cation exchange membrane.

[0052] Preferably, the range of the current density applied per unit electrode area on the cathode side of the membrane electrode assembly electrolyzer 2 is 1000 A - 20000 A.

[0053] Preferably, the PID control module 16 achieves a temperature control accuracy of ±0.5°C.

[0054] Preferably, the back pressure valve 13 on the outlet side of the membrane electrode assembly electrolyzer 2 adjusts the pressure of the electrode reaction, and the pressure range is 1 - 30 bar.

[0055] Example 1

[0056] A method for using a medium-temperature carbon dioxide electrochemical reduction system, comprising the following steps:

[0057] Step 1: Spray a silver catalyst (1 mg / cm -2 , poly(piperidine) ionomer) on a hydrophobic carbon paper and place it on the cathode side of a titanium bipolar plate. Spray IrO 2 on a hydrophilic carbon paper and place it on the anode side of the titanium bipolar plate. Load a polybenzimidazole (PBI) membrane infiltrated with H 3 PO 4 in the middle and hot press it (pressure 5 MPa, temperature 150°C, time 5 minutes) to form a membrane electrode assembly, and then assemble it into the membrane electrode assembly electrolyzer 2; fasten it with bolts (torque 12 N·m). Connect the membrane electrode assembly electrolyzer 2 to a heating tape and a thermocouple probe, and connect it to an external PID control module 16;

[0058] Step 2: Flush the membrane electrode assembly electrolyzer 2 and the connecting pipeline with argon (flow rate 100 sccm) from the inert gas source 6 for 10 minutes, and measure the oxygen content in the tail gas at the rear end of the membrane electrode assembly electrolyzer 2 through a gas chromatograph until the content < 5 ppm;

[0059] Step 3: Set the target temperature of the thermocouple 17 to 150°C, and use the PID control module 16 to implement real-time correction of the power through the PID algorithm to prevent the membrane electrode assembly electrolyzer 2 from overheating due to thermal inertia, and finally make the temperature in the reaction chamber inside the membrane electrode assembly electrolyzer 2 stable at 150 ± 0.5°C;

[0060] Step 4: Set the temperatures of the first constant temperature box 9 and the second constant temperature box 12 in the liquid constant temperature module to 80°C. Introduce water vapor into the electrode chamber of the membrane electrode assembly electrolyzer 2 through a carrier gas, and adjust the pressure value of the back pressure valve 13 to 2 bar to make the water vapor pressure inside the electrode chamber reach the preset value;

[0061] Step 5: Apply a voltage of 2 V to the membrane electrode assembly electrolyzer 2 through the programmable DC power supply 1, monitor the current density and hydrogen production rate in real time, and the system automatically records the temperature fluctuation (±0.5 °C), gas flow error (≤1%), and voltage-current curve;

[0062] Step 6: After Step 5 is completed, switch the valve back to purge gas purging (100 sccm, 30 minutes), and cool down to room temperature.

[0063] Example 2

[0064] A method for using a medium-temperature carbon dioxide electrochemical reduction system, comprising the following steps:

[0065] Step 1: Spray the silver catalyst (2 g / cm -2 , poly(piperidine) ionomer) on the hydrophobic carbon paper and place it on the cathode side of the titanium bipolar plate, and spray IrO 2 on the hydrophilic carbon paper and place it on the anode side of the titanium bipolar plate. Load the intermediate with a polystyrene benzimidazole (PBI) membrane infiltrated with H 3 PO 4 and hot press it (pressure 5 MPa, temperature 150 °C, time 5 minutes) to make a membrane electrode assembly, and then assemble it into a membrane electrode assembly electrolyzer 2; fasten it with bolts (torque 12 N·m), connect the membrane electrode assembly electrolyzer 2 to a heating tape and a thermocouple probe, and connect it to an external PID control module 16;

[0066] Step 2: Flush the membrane electrode assembly electrolyzer 2 and the connecting pipeline with argon (flow rate 1100 sccm) from the inert gas source 6 for 10 minutes, and measure the oxygen content of the tail gas at the rear end of the membrane electrode assembly electrolyzer 2 through a gas chromatograph until the content <5 ppm;

[0067] Step 3: Set the target temperature of the thermocouple 17 to 150 °C, and use the PID control module 16 to achieve real-time correction of the power through the PID algorithm to prevent the membrane electrode assembly electrolyzer 2 from overheating due to thermal inertia, and finally make the temperature in the reaction chamber inside the membrane electrode assembly electrolyzer 2 stable at 150 ± 0.5 °C;

[0068] Step 4: Set the temperatures of the first constant temperature box 9 and the second constant temperature box 12 in the liquid constant temperature module to 80 °C, introduce water vapor into the electrode chamber of the membrane electrode assembly electrolyzer 2 through the carrier gas, and adjust the pressure value of the back pressure valve 13 to 2 bar to make the water vapor pressure inside the electrode chamber reach the preset value;

[0069] Step 5: Apply a voltage of 2 V to the membrane electrode assembly electrolyzer 2 through the programmable DC power supply 1, monitor the current density and hydrogen production rate in real time, and the system automatically records the temperature fluctuation (±0.5 °C), gas flow error (≤1%), and voltage-current curve;

[0070] Step 6: After step 5 is completed, switch the valve back to purge gas purging (100 sccm, 30 minutes), and cool down to room temperature.

[0071] Example 3

[0072] A method for using a medium-temperature carbon dioxide electrochemical reduction system, comprising the following steps:

[0073] Step 1: Spray a silver catalyst (2 g / cm -2 , poly(piperidine) ionomer) on a hydrophobic carbon paper and place it on the cathode side of a titanium bipolar plate. Spray IrO 2 on a hydrophilic carbon paper and place it on the anode side of the titanium bipolar plate. Load a polybenzimidazole (PBI) membrane infiltrated with H 3 PO 4 in the middle and hot press it (pressure 5 MPa, temperature 150 °C, time 5 minutes) to form a membrane electrode assembly, and then assemble it into a membrane electrode assembly electrolyzer 2; fasten it with bolts (torque 12 N·m). Connect the membrane electrode assembly electrolyzer 2 to a heating tape and a thermocouple probe, and connect it to an external PID control module 16;

[0074] Step 2: Pass argon (flow rate 100 cm) from an inert gas source 6 through the membrane electrode assembly electrolyzer 2 and the connecting pipeline for 10 minutes, and measure the oxygen content of the tail gas at the rear end of the membrane electrode assembly electrolyzer 2 by a gas chromatograph until the content < 5 ppm;

[0075] Step 3: Set the target temperature of the thermocouple 17 to 120 °C, and use the PID control module 16 to implement real-time correction of power by the PID algorithm to prevent the membrane electrode assembly electrolyzer 2 from overheating due to thermal inertia, and finally make the temperature in the reaction chamber inside the membrane electrode assembly electrolyzer 2 stable at 120 ± 0.5 °C;

[0076] Step 4: Set the temperatures of the first constant temperature box 9 and the second constant temperature box 12 in the liquid constant temperature module to 80 °C, introduce water vapor into the electrode chamber of the membrane electrode assembly electrolyzer 2 through a carrier gas, and adjust the pressure value of the back pressure valve 13 to 2 bar so that the water vapor pressure inside the electrode chamber reaches the preset value;

[0077] Step 5: Apply a voltage of 2 V to the membrane electrode assembly electrolyzer 2 through a programmable DC power supply 1, monitor the current density and hydrogen production rate in real time, and the system automatically records the temperature fluctuation (±0.5 °C), gas flow error (≤1%), and voltage-current curve;

[0078] Step 6: After step 5 is completed, switch the valve back to purge gas purging (100 sccm, 30 minutes), and cool down to room temperature.

[0079] Example 4

[0080] A method for using a medium-temperature carbon dioxide electrochemical reduction system, comprising the following steps:

[0081] Step 1: Spray a silver catalyst (2 g / cm -2 , poly(piperidine) - based ionomer) on a hydrophobic carbon paper and place it on the cathode side of a titanium bipolar plate. Spray IrO 2 on a hydrophilic carbon paper and place it on the anode side of the titanium bipolar plate. Load a polybenzimidazole (PBI) membrane infiltrated with H 3 PO 4 in the middle and hot - press it (pressure 5 MPa, temperature 150 °C, time 5 minutes) to form a membrane - electrode assembly, and then assemble it into a membrane - electrode assembly electrolyzer 2; Fasten it with bolts (torque 12 N·m). Connect the membrane - electrode assembly electrolyzer 2 to a heating tape and a thermocouple probe, and connect it to an external PID16 control module;

[0082] Step 2: Flush the membrane - electrode assembly electrolyzer 2 and the connecting pipeline with argon (flow rate 100 cm) from an inert gas source 6 for 10 minutes, and measure the oxygen content of the tail gas at the rear end of the membrane - electrode assembly electrolyzer 2 through a gas chromatograph until the content < 5 ppm;

[0083] Step 3: Set the target temperature of the thermocouple 17 to 180 °C, and use the PID control module 16 to implement real - time correction of power by the PID algorithm to prevent the membrane - electrode assembly electrolyzer 2 from overheating due to thermal inertia, and finally make the temperature in the reaction chamber inside the membrane - electrode assembly electrolyzer 2 stable at 180 ± 0.5 °C;

[0084] Step 4: Set the temperatures of the first thermostat 9 and the second thermostat 12 in the liquid constant - temperature module to 80 °C. Introduce water vapor into the electrode chamber of the membrane - electrode assembly electrolyzer 2 through a carrier gas, and adjust the pressure value of the back - pressure valve 13 to 2 bar so that the water vapor pressure inside the electrode chamber reaches the preset value;

[0085] Step 5: Apply a voltage of 2 V to the membrane - electrode assembly electrolyzer 2 through a programmable DC power supply 1, and monitor the current density and hydrogen production rate in real - time. The system automatically records the temperature fluctuation (±0.5 °C), gas flow error (≤1%), and voltage - current curve;

[0086] Step 6: After step 5 is completed, switch the valve back to purge gas for purging (100 sccm, 30 minutes), and cool down to room temperature.

[0087] Example 5

[0088] A method for using a medium - temperature carbon dioxide electrochemical reduction system, comprising the following steps:

[0089] Step 1: Spray a silver catalyst (2 g / cm -2 , poly(piperidine) - based ionomer) on a hydrophobic carbon paper and place it on the cathode side of a titanium bipolar plate. Spray IrO 2Sprayed on hydrophilic carbon paper and placed on the anode side of the titanium bipolar plate, with a PBI (polyphenylene benzimidazole) membrane infiltrated with H 3 PO 4 in the middle and hot-pressed (pressure 5 MPa, temperature 150 °C, time 5 minutes) to make a membrane electrode assembly, and then assembled into a membrane electrode assembly electrolyzer 2; bolted and fastened (torque 12 N·m), the membrane electrode assembly electrolyzer 2 is connected to a heating tape and a thermocouple probe, and connected to an external PID control module 16;

[0090] Step 2: Fill the membrane electrode assembly electrolyzer 2 and the connecting pipeline with argon (flow rate 100 cm) from the inert gas source 6 for 10 minutes, and measure the oxygen content of the tail gas at the rear end of the membrane electrode assembly electrolyzer 2 through a gas chromatograph until the content < 5 ppm;

[0091] Step 3: Set the target temperature of the thermocouple 17 to 150 °C, and use the PID control module 16 to implement real-time correction of power by the PID algorithm to prevent the membrane electrode assembly electrolyzer 2 from overheating due to thermal inertia, and finally make the temperature in the reaction chamber inside the membrane electrode assembly electrolyzer 2 stable at 150 ± 0.5 °C;

[0092] Step 4: Set the temperatures of the first constant temperature box 9 and the second constant temperature box 12 in the liquid constant temperature module to 80 °C, introduce water vapor into the electrode chamber of the membrane electrode assembly electrolyzer 2 through a carrier gas, and adjust the pressure value of the back pressure valve 13 to 1 bar so that the water vapor pressure inside the electrode chamber reaches the preset value;

[0093] Step 5: Apply a voltage of 2 V to the membrane electrode assembly electrolyzer 2 through a programmable DC power supply 1, and monitor the current density and hydrogen production rate in real time. The system automatically records the temperature fluctuation (±0.5 °C), gas flow error (≤1%), and voltage-current curve;

[0094] Step 6: After step 5 is completed, switch the valve back to purge gas for purging (100 sccm, 30 minutes), and cool down to room temperature.

[0095] Example 6

[0096] A method for using a medium-temperature carbon dioxide electrochemical reduction system, comprising the following steps:

[0097] Step 1: Spray a silver catalyst (2 g / cm -2 , poly(piperidine) ionomer) on hydrophobic carbon paper and place it on the cathode side of the titanium bipolar plate, and spray IrO 2 on hydrophilic carbon paper and place it on the anode side of the titanium bipolar plate, with a PBI (polyphenylene benzimidazole) membrane infiltrated with H 3 PO 4The polybenzimidazole (PBI) film is hot-pressed (pressure 5 MPa, temperature 150 °C, time 5 minutes) to form a membrane electrode assembly, and then assembled into a membrane electrode assembly electrolyzer 2; bolt fastening (torque 12 N·m), the membrane electrode assembly electrolyzer 2 is connected to a heating tape and a thermocouple probe, and connected to an external PID control module 16;

[0098] Step 2: Argon in the inert gas source 6 (flow rate 1100 cm) is passed through the membrane electrode assembly electrolyzer 2 and the connecting pipeline for 10 minutes, and the oxygen content of the tail gas at the rear end of the membrane electrode assembly electrolyzer 2 is measured by a gas chromatograph until the content < 5 ppm;

[0099] Step 3: Set the target temperature of the thermocouple 17 to 150 °C, and use the PID control module 16 to implement real-time correction of power by the PID algorithm to prevent the membrane electrode assembly electrolyzer 2 from overheating due to thermal inertia, and finally make the temperature in the reaction chamber inside the membrane electrode assembly electrolyzer 2 stable at 150 ± 0.5 °C;

[0100] Step 4: Set the temperatures of the first thermostat 9 and the second thermostat 12 in the liquid constant temperature module to 80 °C, introduce water vapor into the electrode chamber of the membrane electrode assembly electrolyzer 2 through the carrier gas, and adjust the pressure value of the back pressure valve 13 to 5 bar so that the water vapor pressure inside the electrode chamber reaches the preset value;

[0101] Step 5: Apply a voltage of 2 V to the membrane electrode assembly electrolyzer 2 through the programmable DC power supply 1, and monitor the current density and hydrogen production rate in real time. The system automatically records the temperature fluctuation (±0.5 °C), gas flow error (≤1%), and voltage-current curve;

[0102] Step 6: After Step 5 is completed, switch the valve back to purge gas purging (100 sccm, 30 minutes), and cool down to room temperature.

[0103] Table 1 shows the statistical data of the catalytic performance of medium-temperature carbon dioxide reduction under different example conditions. It can be seen from the table that as the electrolysis temperature increases, the Faraday efficiency of CO shows a downward trend. This phenomenon is mainly attributed to the intensification of competitive reactions and the decrease in catalyst stability in a high-temperature environment. Under higher temperature conditions, the kinetic process of the hydrogen evolution reaction (HER) is significantly enhanced, forming a competitive relationship with the CO 2 reduction reaction, resulting in the tilt of the electron transfer efficiency towards HER; at the same time, high temperature will accelerate the agglomeration and inactivation of the catalyst. Especially for metal-based catalysts, high temperature may cause sintering and surface reconstruction of nanoparticles, thereby reducing their catalytic activity and selectivity. Increasing the system pressure has an obvious promoting effect on the CO 2 electroreduction. The pressurization operation can significantly increase the CO 2coverage on the electrode surface, improving the mass transfer efficiency of reactants on the catalyst surface, while suppressing the rapid escape of gaseous products and prolonging the residence time of reaction intermediates on the catalyst surface, which is beneficial to the cleavage of C-O bonds and the formation of CO. Increasing the catalyst loading is another effective strategy to enhance the 2 electroreduction performance of CO. A higher catalyst loading means more active sites are exposed, which not only increases the effective contact area of the reaction but also promotes key steps such as C-C coupling through the synergistic effect of adjacent active sites. Generally speaking, the coordinated regulation of these three key parameters, temperature, pressure, and catalyst loading, is crucial for achieving efficient 2 electroreduction of CO to CO and requires systematic experimental optimization to find the optimal operating window.

[0104] Table 1: Catalytic performance of medium-temperature carbon dioxide reduction under different conditions

[0105] Embodiment 1 2 3 4 5 6 <![CDATA[FE CO / %]]> 3.18 5.21 6.32 1.63 3.47 4.84

[0106] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A medium-temperature carbon dioxide electrochemical reduction system, characterized in that: The invention comprises a programmable direct current power supply (1), a membrane electrode assembly electrolyzer (2), a step-by-step temperature control module, a gas-liquid linkage feeding unit and an online analysis module; the programmable direct current power supply (1) is respectively connected to the cathode and the anode in the membrane electrode assembly electrolyzer (2); the gas-liquid linkage feeding unit is connected to the front end of the membrane electrode assembly electrolyzer (2); the step-by-step temperature control module is connected to the membrane electrode assembly electrolyzer (2); and the rear end of the membrane electrode assembly electrolyzer (2) is connected to the online analysis module.

2. A medium-temperature carbon dioxide electrochemical reduction system according to claim 1, characterized in that: The step-by-step temperature control module comprises a heating jacket (3), a thermocouple (17) and a PID control module (16); the heating jacket (3) is coated on the outside of a membrane electrode assembly electrolyzer (2); the thermocouple (17) is inserted into a reaction chamber of the membrane electrode assembly electrolyzer (2); the heating jacket (3) and the thermocouple (17) are respectively connected to the PID control module (16).

3. The medium-temperature carbon dioxide electrochemical reduction system according to claim 1, characterized in that: The gas-liquid linkage feeding unit comprises a humidification module, a liquid constant temperature module, a back pressure valve (13) and a gas flow control module; the cathode gas source (4) and the anode gas source (5) are respectively connected to the gas flow control module, the humidification module and the front end of the membrane electrode assembly electrolyzer (2) through pipelines; the liquid constant temperature module is connected to the humidifier; the inert gas source (6) is divided into two paths, one of which is connected to the pipeline connecting the cathode gas source (4) and the gas flow control module, and the other is connected to the pipeline connecting the anode gas source (5) and the gas flow control module; the back pressure valve (13) is connected to the rear end of the membrane electrode assembly electrolyzer (2).

4. A medium-temperature carbon dioxide electrochemical reduction system according to claim 3, characterized in that: The gas flow control module comprises a first gas flow controller (7) and a second gas flow controller (10); the humidification module comprises a first gas humidifier (8) and a second gas humidifier (11); the liquid thermostatic module comprises a first thermostatic box (9) and a second thermostatic box (12); the cathode gas source (4) is connected to the first gas flow controller (7), the first thermostatic box (9) and the front end of the membrane electrode assembly electrolyzer (2) in sequence through a pipeline; the anode gas source (5) is connected to the second gas flow controller (10), the second thermostatic box (12) and the front end of the membrane electrode assembly electrolyzer (2) in sequence through a pipeline; the inert gas source (6) is divided into two paths, one of which is connected to the pipeline of the cathode gas source (4) and the first gas flow controller (7), and the other is connected to the pipeline connecting the anode gas source (5) and the second gas flow controller (10); the back pressure valve (13) is connected to the rear end of the membrane electrode assembly electrolyzer (2).

5. The medium-temperature carbon dioxide electrochemical reduction system according to claim 4, characterized in that: The online analysis module comprises a condenser (14) and an online analysis instrument (15); the condenser (14) and the online analysis instrument (15) are connected to the rear end of the membrane electrode assembly electrolyzer (2) in sequence; the pipeline connecting the condenser (14) and the rear end of the membrane electrode assembly electrolyzer (2) is also connected to a back pressure valve (13).

6. A medium-temperature carbon dioxide electrochemical reduction system according to claim 5, characterized in that: The online analysis instrument (15) is a gas chromatograph.

7. The medium-temperature carbon dioxide electrochemical reduction system according to claim 4, characterized in that: One of the pipelines of the inert gas source (6) connected to the anode gas source (4) and the first gas flow controller (7) is connected via a three-way solenoid valve; the other pipeline of the inert gas source (6) connected to the anode gas source (5) and the second gas flow controller (10) is connected via a three-way solenoid valve.

8. The medium-temperature carbon dioxide electrochemical reduction system according to claim 1, characterized in that: The main body material of the membrane electrode assembly electrolytic cell (2) is titanium metal; an anion exchange membrane and a cation exchange membrane are arranged between the cathode and the anode of the membrane electrode assembly electrolytic cell (2).

9. A method for using a medium-temperature carbon dioxide electrochemical reduction system according to any one of claims 1 to 8, characterized in that: The following steps are involved: Connecting the step-type temperature control module to the membrane electrode assembly electrolyzer (2), and then using a gas-liquid linkage feeding unit to purge the inside of the membrane electrode assembly electrolyzer (2) until the oxygen content reaches a set value; heating the inside of the membrane electrode assembly electrolyzer (2) to a set temperature through the step-type temperature control module; Subsequently, a gas-liquid linkage feeding unit is used to evaporate the liquid into a gaseous reactant, and the gas is introduced into the membrane electrode assembly electrolyzer (2) through a carrier gas to achieve accurate supply of gas flow, so that the water vapor pressure in the reaction chamber of the membrane electrode assembly electrolyzer (2) reaches a preset value; Then, a voltage is applied to the membrane electrode assembly electrolyzer (2) through a programmable direct current power supply (1) to carry out an electrochemical reduction reaction of carbon dioxide.

10. The method for using the medium-temperature carbon dioxide electrochemical reduction system according to claim 9, characterized in that: The temperature of the liquid constant temperature module in the gas-liquid linkage feeding unit is room temperature to 90°C; The pressure of the back pressure valve (13) in the gas-liquid linkage feeding unit is 1 to 5 bar.

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