Distributed membrane electrode, preparation method thereof and electrolysis system

Abstract

The invention belongs to the technical field of synthesis gas preparation through electrolysis of carbon dioxide, and particularly relates to a distributed membrane electrode, a preparation method thereof and an electrolysis system. The preparation method comprises the following steps: preparing a first catalyst (the first catalyst is a catalyst for preparing carbon monoxide through carbon dioxide electrolysis), preparing a second catalyst (the second catalyst is a catalyst for producing hydrogen in a carbon dioxide liquid phase electrolysis process) and preparing the distributed membrane electrode. According to the distributed membrane electrode disclosed by the invention, the proportion of carbon monoxide and hydrogen in synthesis gas and the current density can be regulated and controlled by regulating and controlling the distribution and the loading capacity of the catalyst on the surface of the membrane electrode, under the condition of using the same silver catalyst, the regular distributed membrane electrode can obtain the synthesis gas with a higher carbon monoxide proportion; and the method is more economical. Besides, according to the electrolysis system provided by the invention, a flue gas carbon dioxide capture-utilization integrated process is used, real-time regeneration of the electrolyte is realized, the operation is simple and convenient, and the electrolysis system has important industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolyzing carbon dioxide to produce synthesis gas, and in particular relates to a distributed membrane electrode, a preparation method thereof and an electrolysis system. Background Art

[0002] Energy is an important foundation for the world's economic and social development. The combustion of fossil fuels is the main way to obtain energy at present and for a long time to come. However, the negative impact of carbon dioxide emissions generated by the combustion of fossil fuels on the atmospheric environment has become an environmental issue that urgently needs to be addressed.

[0003] Electrochemical reduction of carbon dioxide to produce synthesis gas (carbon monoxide and hydrogen) has found a good outlet for the utilization of carbon dioxide. In the process of electrolysis of carbon dioxide, catalysts and membrane electrodes play a decisive role. By changing the composition of the catalyst, the composition ratio of carbon monoxide and hydrogen in the synthesis gas can be adjusted to meet the downstream demand for synthesis gas and further prepare green chemicals. Electrochemical reduction of CO2 uses a large amount of metal Ag catalyst to convert CO2 into CO in an aqueous electrolyte with high selectivity. For example, the document (ACS Energy Letters, 2018, 3, 1301-1306) forms Ag2CO3 by anodic etching of Ag, and then prepares a silver catalyst by electrochemical etching, which runs for more than 100h while maintaining a CO selectivity of about 90%. The document (Nature Energy, 2022, 7, 978-988) uses a membrane electrode prepared with a silver catalyst and Nafion211 membrane for electrochemical reduction of carbon dioxide, with a CO selectivity of 92% and a run of 210h. Patent CN112176360A discloses that a gold-based bimetallic catalyst is used for electrochemical reduction of carbon dioxide to produce synthesis gas, which can improve the Faraday efficiency of the product synthesis gas and can regulate the ratio of carbon monoxide to hydrogen in the synthesis gas.

[0004] Although scientists have conducted a lot of research in the field of electrochemical reduction of carbon dioxide to produce synthesis gas, they mainly focus on adjusting the composition of the catalyst to change the carbon dioxide electroreduction activity, product selectivity and service life.

[0005] The present invention adopts completely different technical means, and prepares a distributed membrane electrode by regulating the composition and structure of the membrane electrode, which is used for carbon dioxide electrolysis to produce synthesis gas, thereby achieving the purpose of regulating the ratio of carbon monoxide to hydrogen in the product. Combined with the carbon dioxide capture-utilization integrated liquid phase electrolysis system and the real-time regeneration technology of the electrolyte, it can meet the needs of industrial production. Summary of the invention

[0006] The present invention mainly achieves the purpose of regulating the ratio of carbon monoxide to hydrogen in synthesis gas by regulating the distribution of different catalysts on the surface of the membrane electrode and the loading per unit area. Compared with the method of regulating the composition of synthesis gas by regulating the composition and structure of the catalyst, the method of the present invention can efficiently, simply and low-cost prepare a distributed membrane electrode for electrolyzing carbon dioxide to produce synthesis gas.

[0007] In order to solve the problems existing in the prior art, the present invention provides a method for preparing a distributed membrane electrode, the preparation method comprising the following steps:

[0008] (I) preparing a first catalyst, wherein the first catalyst is a catalyst for electrolyzing carbon dioxide to produce carbon monoxide

[0009] (I-1) dispersing carbon black in water, adding a first metal salt and polyethylene glycol, and stirring and mixing to obtain a first premixed solution;

[0010] (I-2) adding a sodium citrate aqueous solution to the first premixed solution, stirring for reaction, and then adding a vitamin C aqueous solution and continuing to stir for reaction to obtain a first reaction solution;

[0011] (I-3) After filtering the first reaction liquid, taking the precipitate and drying it, and then reducing it to obtain the first catalyst;

[0012] (II) preparing a second catalyst, wherein the second catalyst is a catalyst for producing hydrogen during the liquid phase electrolysis of carbon dioxide

[0013] (II-1) dispersing carbon black in water, adding a second metal salt and polyethylene glycol, and stirring to obtain a second premixed solution;

[0014] (II-2) adding an aqueous sodium hypophosphite solution to the second premixed solution, stirring the solution, and then adding an aqueous sodium hydroxide solution and continuing to stir the solution to obtain a second reaction solution;

[0015] (II-3) After filtering the second reaction liquid, taking the precipitate and drying it, and then reducing it to obtain the second catalyst;

[0016] (III) Preparation of distributed membrane electrode

[0017] (III-1) dispersing the first catalyst in a mixed solution of naphthol and n-propanol to obtain a first catalyst dispersion; dispersing the second catalyst in a mixed solution of naphthol and n-propanol to obtain a second catalyst dispersion;

[0018] (III-2) covering the upper surface of the cationic membrane with a template, spraying the first catalyst dispersion onto the blank area of ​​the template, and loading it onto the cationic membrane;

[0019] (III-3) The template is replaced, and the second catalyst dispersion is sprayed on the blank area of ​​the template and loaded on the cationic membrane to obtain the distributed membrane electrode.

[0020] In order to facilitate the understanding of the present invention, the preparation method includes the following more detailed steps:

[0021] (I) Preparation of the first catalyst: 3 g of carbon black was dispersed in 2 L of deionized water, 56 g of silver nitrate and 6 g of polyethylene glycol were added, and the mixture was stirred for 2 to 3 h; 500 mL of an aqueous sodium citrate solution (1 to 1.5 mol / L) was added dropwise, and the mixture was stirred for 1 to 2 h; then 360 mL of an aqueous vitamin C solution (1.2 to 1.5 mol / L) was added dropwise, and the mixture was stirred for 1 to 2 h; the mixture was filtered, dried at 80° C. for 24 h, crushed in a pulverizer, and reduced at 350° C. for 2 h in a 10% H2 / Ar atmosphere to obtain a nano Ag / C catalyst (similarly, Au / C catalyst, Ag-Ni / C catalyst, Au-Ag / C catalyst, etc. can also be prepared as the first catalyst by a similar method).

[0022] (II) Preparation of the second catalyst: 2.6 g of carbon black was dispersed in 1.5 L of deionized water, and 60 g of nickel sulfate and 5 g of polyethylene glycol were added, and the mixture was stirred for 2 to 3 h; 400 mL of an aqueous sodium hypophosphite solution (1.2 to 1.5 mol / L) was added dropwise, and the mixture was stirred for 1 to 2 h, and then 100 mL of an aqueous sodium hydroxide solution (4 to 5 mol / L) was added dropwise, and the mixture was stirred for 1 to 2 h; the mixture was filtered, dried at 80° C. for 24 h, crushed in a pulverizer, and reduced at 600° C. for 2 h in a 20% H2 / Ar atmosphere to obtain a nano Ni / C catalyst (similarly, a Ni-Pt / C catalyst, a Pt / C catalyst, a Ru / C catalyst, a Pd-Pt-Ru / C catalyst, etc. can also be prepared as the second catalyst by a similar method).

[0023] (III) Preparation of distributed membrane electrode: weigh about 26 g of the first catalyst (such as Ag / C catalyst) and disperse it in a mixed solution of 60 mL of naphthol and 220 mL of n-propanol, and ultrasonically disperse it for 1 h. The cationic membrane is spread on a vacuum heating plate at 50-90°C. A template is covered on the cationic membrane, and the blank area of ​​the template is covered with the first catalyst (such as Ag / C catalyst) by spraying. The catalyst loading is 2-12 mg / cm 2 Between, preferably 4 to 8 mg / cm 2 Then, the covering template on the cationic membrane is replaced, and about 25 g of the second catalyst (such as Ni / C catalyst) is weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol, and ultrasonically dispersed for 1 h. The blank part of the template is covered with the second catalyst (such as Ni / C catalyst) by spraying, and the catalyst loading is 0.5-6 mg / cm 2Between, preferably 2 to 4 mg / cm 2 Finally, a distributed membrane electrode with a regular distribution of catalysts for electrolyzing carbon dioxide to produce carbon monoxide and hydrogen is formed, with a membrane electrode area of ​​5 to 2500 cm 2 .

[0024] Among them, the Ag / C catalyst for preparing the membrane electrode can be a catalyst for electrochemical reduction of carbon dioxide to produce carbon monoxide, including one or a combination of two or more of Au, Ag, Ni, etc., and the combination can be, for example, NiAg, NiAu, AgAu, ZnAg, AgSn, etc.; the Ni / C catalyst can be a catalyst for producing hydrogen in the process of liquid phase electrolysis of carbon dioxide, including one or a combination of two or more of Ni, Pt, Ru, Pd, Mo, etc., and the combination can be, for example, NiPt, NiRu, PtPd, NiPtRu, etc.

[0025] The template structure can be a combination of one or more shapes such as square, polygonal, circular, etc., to adjust the spraying area of ​​different catalysts. The catalyst loading is mainly controlled by the spraying amount. The Ag / C catalyst loading is 2-12 mg / cm 2 The Ni / C catalyst loading is between 0.5 and 6 mg / cm 2 Finally, regularly distributed Ag / C and Ni / C distributed membrane electrodes are formed.

[0026] Based on the same technical concept, the present invention further provides an electrolysis system, which includes a carbon dioxide enrichment system, an electrolyte circulation system, a carbon dioxide electroreduction system and a gas-liquid separation system; wherein:

[0027] The carbon dioxide enrichment system comprises a carbon dioxide alkali solution absorption tower; the carbon dioxide alkali solution absorption tower is used to collect carbon dioxide and complete the enrichment of low partial pressure carbon dioxide to form a mixed aqueous solution of KHCO3 and K2CO3;

[0028] The electrolyte circulation system comprises a cathode electrolyte circulation system and an anode electrolyte circulation system;

[0029] The carbon dioxide electric reduction system comprises a power supply and an electrolyzer, wherein the electrolyzer comprises the distributed membrane electrode; the power supply supplies power to the electrolyzer;

[0030] The gas-liquid separation system comprises a cathode gas-liquid separator, an anode gas-liquid separator and an electrolyte storage tank; after the formed synthesis gas and electrolyte are separated in the cathode gas-liquid separator, the electrolyte flows back to the electrolyte storage tank; after the formed oxygen and electrolyte are separated in the anode separator, the electrolyte flows back to the electrolyte storage tank;

[0031] The carbon dioxide alkali solution absorption tower, cathode electrolyte circulation system, electrolytic cell, cathode gas-liquid separator, and electrolyte storage tank constitute a first closed circulation loop; the anode electrolyte circulation system, electrolytic cell, anode gas-liquid separator, and electrolyte storage tank constitute a second closed circulation loop.

[0032] In order to facilitate the understanding of the present invention, the detailed parameters of the electrolysis system are as follows:

[0033] In the carbon dioxide enrichment system, (10%-100%) CO2 gas is introduced into the carbon dioxide alkali solution absorption tower at a flow rate of 1000mL / min to complete the enrichment of low partial pressure CO2 and form a mixed aqueous solution of KHCO3 and K2CO3 of about 2mol / L.

[0034] In the electrolyte circulation system, a circulation pump is used to introduce electrolyte into the electrolytic cell for electrolyzing carbon dioxide, and the electrolyte is introduced into the cathode and anode of the electrolytic cell at a flow rate of 1000 mL / min.

[0035] In the carbon dioxide electroreduction system, the electrolyzer uses a distributed membrane electrode and diffusion layer structure, and the cathode catalyst is silver carbon and nickel carbon with a loading of 2 to 12 mg / cm 2 The anode catalyst is iridium oxide, with a loading of about 1 mg / cm 2 The cathode diffusion layer is graphite felt. The electrolysis voltage is between 2.8V and 3.6V, and the total current density is 20mA / cm 2 Up to 200mA / cm 2 The CO:H2 molar ratio can be adjusted between 9:1 and 1:4.

[0036] The beneficial effects of the present invention are:

[0037] The distributed membrane electrode described in the present invention can regulate the ratio of carbon monoxide and hydrogen in the synthesis gas and the current density by regulating the distribution and loading amount of the catalyst on the membrane electrode surface. Under the condition of using the same silver catalyst, the regular distributed membrane electrode can obtain synthesis gas with a high CO ratio, which is more economical.

[0038] In addition, the electrolysis system provided by the present invention uses a flue gas carbon dioxide capture-utilization integrated process to achieve real-time regeneration of the electrolyte, is easy to operate, and has important industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 This is the SEM image of the nano-Ag / C catalyst of Example 1.

[0041] Figure 2 This is the SEM image of the nano Ni / C catalyst of Example 1.

[0042] Figure 3 This is the XRD diagram of the nano Ni / C catalyst of Example 1.

[0043] Figure 4 This is the SEM image of the Ag / C membrane electrode surface of Example 1.

[0044] Figure 5 This is the SEM image of the Ni / C membrane electrode surface in Example 1.

[0045] Figure 6 This is a schematic diagram of the Ag / C and Ni / C distributed membrane electrodes of Example 1.

[0046] Figure 7 These are photos of the Ag / C and Ni / C distributed membrane electrodes of Example 1.

[0047] Figure 8 is a schematic diagram of the electrolysis system.

[0048] Fig. 9 This is a graph showing the variation of the product gas CO / H2 volume ratio with the electrolysis voltage in Example 1 and Comparative Example 1.

[0049] Fig.10 This is the gas chromatogram of Example 1 with a carbon-hydrogen ratio (CO / H2) of 1.21.

[0050] Fig.11 This is the gas chromatogram of Comparative Example 1 with a carbon-hydrogen ratio (CO / H2) of 0.38.

[0051] Fig.12 Graph showing the total current density of Example 1 as a function of the electrolysis voltage.

[0052] Fig.13 This is a graph showing the variation of total current density with electrolysis temperature in Example 1.

[0053] Fig.14 This is a graph showing how the volume ratio of the product gas CO / H2 changes with the electrolysis temperature in Example 1.

[0054] Fig.15 It is a graph showing the change of the total electrolysis current density of Example 1 with the test time.

[0055] Fig.16 This is a graph showing the change in the carbon-hydrogen ratio of the product synthesis gas of Example 1 over the test time.

[0056] Fig.17 This is a graph showing the change in the product synthesis gas integral fraction of Example 1 versus the test time.

[0057] Fig.18 This is a schematic diagram of the Ag / C and Ni / C distributed membrane electrodes of Example 2.

[0058] Fig.19 These are photos of the Ag / C and Ni / C distributed membrane electrodes of Example 2.

[0059] Fig. 20 These are photos of the Ag / C and Ni / C distributed membrane electrodes of Example 3.

[0060] Fig.21 This is a schematic diagram of the Ag / C and Ni / C distributed membrane electrodes of Example 4.

[0061] Fig. 22 This is a schematic diagram of the Ag / C and Ni / C distributed membrane electrodes of Example 5.

[0062] Fig.23 This is a photograph of the membrane electrode of the Ag / C and Ni / C mixed catalyst of Comparative Example 1.

[0063] The accompanying drawings in the figure are marked as follows:

[0064] 1-carbon dioxide alkali liquid absorption tower; 2-cathode circulation pump; 3-anode circulation pump; 4-power supply; 5-electrolyzer; 51-distributed membrane electrode; 52-cathode; 53-anode; 6-cathode gas-liquid separator; 7-anode gas-liquid separator; 8-electrolyte storage tank. DETAILED DESCRIPTION

[0065] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0066] Example 1

[0067] This embodiment provides a method for preparing a silver-carbon catalyst, a nickel-carbon catalyst, and a distributed membrane electrode, the preparation method comprising the following steps:

[0068] (I) Preparation of silver-carbon catalyst: 3 g of carbon black was dispersed in 2 L of deionized water, 56 g of silver nitrate and 6 g of polyethylene glycol were added, and the mixture was stirred for 2 h; 500 mL of sodium citrate aqueous solution (1 mol / L) was added dropwise, and the mixture was stirred for 1 h; then 360 mL of vitamin C aqueous solution (1.2 mol / L) was added dropwise, and the mixture was stirred for 1 h; the mixture was filtered, dried at 80° C. for 24 h, crushed in a pulverizer, and reduced at 350° C. for 2 h in a 10% H2 / Ar atmosphere to obtain a nano Ag / C catalyst, as shown in the SEM image. Figure 1 shown.

[0069] (II) Preparation of nickel-carbon catalyst: 2.6 g of carbon black was dispersed in 1.5 L of deionized water, 60 g of nickel sulfate and 5 g of polyethylene glycol were added, and the mixture was stirred for 2 h; 400 mL of sodium hypophosphite aqueous solution (1.2 mol / L) was added dropwise, and the mixture was stirred for 1 h; then 100 mL of sodium hydroxide aqueous solution (5 mol / L) was added dropwise, and the mixture was stirred for 1 h; the mixture was filtered, dried at 80° C. for 24 h, crushed in a pulverizer, and reduced at 600° C. for 2 h in a 20% H2 / Ar atmosphere to obtain a nano Ni / C catalyst, as shown in the SEM image. Figure 2 As shown, the XRD pattern is Figure 3 shown.

[0070] (III) Distributed membrane electrode preparation: About 26 g of Ag / C cathode catalyst was weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h. The cationic membrane was spread flat on a vacuum heating plate at 70 °C. A square hollow template was covered on the cationic membrane. The blank space of the template was covered with Ag / C catalyst by spraying. The Ag / C catalyst loading was 6 mg / cm 2 , surface SEM images are shown as Figure 4 Then, the square hollow template on the membrane electrode was replaced, and about 25 g of Ni / C cathode catalyst was weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h, and the blank part of the template was covered with Ni / C catalyst by spraying. The Ni / C catalyst loading was 2 mg / cm 2 , surface SEM images are shown as Figure 5 As shown in the figure, a square-shaped distributed Ag / C and Ni / C distributed membrane electrode (Ag / C and Ni / C are distributed in alternating arrays, multiple rows and multiple columns) is finally formed, with a membrane electrode area of ​​200 cm 2 , the schematic diagram is as follows Figure 6 As shown in the membrane electrode photo Figure 7 shown.

[0071] As a similar technical concept, this embodiment also provides a system for electrolyzing carbon dioxide to produce synthesis gas (electrolysis system), which includes a carbon dioxide enrichment system, an electrolyte circulation system, a carbon dioxide electroreduction system and a gas-liquid separation system. The schematic diagram of the electrolysis system is shown in FIG. Figure 8 shown.

[0072] Carbon dioxide enrichment system: A mixed gas containing 30% CO2 is introduced into the carbon dioxide alkali solution absorption tower 1 at a flow rate of 1000 mL / min to complete the enrichment of low partial pressure carbon dioxide and form a mixed aqueous solution of KHCO3 and K2CO3 of about 2 mol / L.

[0073] Electrolyte circulation system: Use a circulation pump to pass the electrolyte into the electrolytic cell 5 for electrolyzing carbon dioxide; use a cathode electrolyte circulation system (cathode circulation pump 2) to pass the electrolyte from the carbon dioxide absorption tower 1 to the cathode 52 of the electrolytic cell 5 at a flow rate of 1000 mL / min; use an anode electrolyte circulation system (anode circulation pump 3) to pass the electrolyte from the electrolyte storage tank 8 to the anode 53 of the electrolytic cell 5 at a flow rate of 1000 mL / min.

[0074] Carbon dioxide electroreduction system: includes power source 4 and electrolyzer 5, electrolyzer 5 uses distributed membrane electrode 51 and diffusion layer structure, cathode catalyst is silver carbon (loading amount 6mg / cm 2 ) and nickel carbon (loading 2 mg / cm 2 ) catalyst, the anode catalyst is iridium oxide, with a loading of about 1 mg / cm 2 The cathode diffusion layer is graphite felt. The synthesis gas and electrolyte produced by the cathode 52 of the electrolytic cell 5 enter the cathode gas-liquid separator 6, and the oxygen and electrolyte produced by the anode 53 enter the anode gas-liquid separator 7.

[0075] Gas-liquid separation system: after the formed synthesis gas and electrolyte are separated in the cathode gas-liquid separator 6, the cathode electrolyte flows back to the electrolyte storage tank 8; after the formed oxygen and electrolyte are separated in the anode gas-liquid separator 7, the anode electrolyte flows back to the electrolyte storage tank 8.

[0076] Test results:

[0077] like Fig. 9 As shown, when the electrolysis temperature is 60°C and the electrolysis voltage is between 2.6 and 3.6V, when the cathode is a silver carbon and nickel carbon distributed membrane electrode (Example 1), the product synthesis gas carbon-hydrogen ratio (CO / H2) is 0.58 to 1.21, wherein the gas chromatogram of the carbon-hydrogen ratio (CO / H2) = 1.21 is as shown Fig.10 As shown, when the cathode is a membrane electrode prepared using a silver-carbon and nickel-carbon mixed catalyst (Comparative Example 1), the product synthesis gas carbon-hydrogen ratio (CO / H2) = 0.21-0.38, wherein the gas chromatogram of the carbon-hydrogen ratio (CO / H2) = 0.38 is as shown Fig.11 As shown, the results show that the carbon-hydrogen ratio of Example 1 is significantly higher than that of Comparative Example 1.

[0078] like Fig.12 As shown in the figure, the electrolysis temperature is 60℃, the electrolysis voltage increases from 2.6V to 3.6V, and the total current density increases from 41mA / cm 2 Increased to 158mA / cm 2 .like Fig.13 As shown, the electrolysis voltage is 3.0V, the electrolysis temperature increases from 30℃ to 80℃, and the total current density increases from 35mA / cm 2 Increased to 121mA / cm 2 .like Fig.14 As shown in the figure, when the electrolysis voltage is 3.0V and the electrolysis temperature increases from 30℃ to 50℃, the carbon-hydrogen ratio of the product synthesis gas increases from 1.03 to 1.16. When the electrolysis temperature is further increased to 80℃, the carbon-hydrogen ratio of the product synthesis gas decreases from 1.16 to 0.63. Then, at the electrolysis voltage of 3.0V, the stability of the membrane electrode is tested. During the one-month test, the total current density is maintained at 81mA / cm 2 To 89mA / cm 2 Between (such as Fig.15 The carbon-hydrogen ratio of the product synthesis gas is maintained between 0.87 and 1.02 (as shown in Fig.16 The product synthesis gas volume fraction is maintained between 51% and 58% (as shown in FIG. Fig.17 As shown). It can be seen from the test results that the distributed membrane electrode of the present invention exhibits high catalytic activity and long-term stability for electrochemical reduction of carbon dioxide, and improves the carbon-hydrogen ratio of the product synthesis gas.

[0079] Example 2

[0080] This embodiment provides a method for preparing a distributed membrane electrode, the method comprising the following steps:

[0081] (I) The preparation of silver-carbon catalyst was the same as in Example 1.

[0082] (II) The nickel-carbon catalyst was prepared in the same manner as in Example 1.

[0083] (III) Preparation of distributed membrane electrode: About 26 g of Ag / C cathode catalyst was weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h. The cationic membrane was spread on a vacuum heating plate at 70 °C. A rectangular hollow template was covered on the cationic membrane. The blank area of ​​the template was covered with Ag / C catalyst by spraying. The Ag / C catalyst loading was 4 mg / cm 2Then, the covering template on the membrane electrode was replaced, and about 25 g of Ni / C cathode catalyst was weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h, and the blank part of the template was covered with Ni / C catalyst by spraying. The Ni / C catalyst loading was 4 mg / cm 2 Finally, a regularly distributed Ag / C and Ni / C membrane electrode (Ag / C and Ni / C are distributed alternately, in a single row and multiple columns) is formed, with a membrane electrode area of ​​200cm 2 , the schematic diagram is as follows Fig.18 As shown in the membrane electrode photo Fig.19 shown.

[0084] As the same technical concept, this embodiment also provides an electrolysis system. The electrolysis system for electrolyzing carbon dioxide to produce synthesis gas is the same as that in embodiment 1, except that the cathode distributed membrane electrode has a silver carbon loading of 4 mg / cm 2 and nickel carbon loading 4 mg / cm 2 .

[0085] Test results:

[0086] The electrolysis temperature is 60°C, and the electrolysis voltage is between 2.6 and 3.6 V. When the cathode is a silver-carbon and nickel-carbon distributed membrane electrode (Example 2 silver-carbon loading 4 mg / cm 2 and nickel carbon loading 4 mg / cm 2 ), the product synthesis gas carbon-hydrogen ratio (CO / H2) = 0.41 ~ 0.98, the total current density from 53mA / cm 2 Increased to 171mA / cm 2 The electrolysis voltage was 3.0V, the electrolysis temperature increased from 30℃ to 80℃, and the total current density increased from 43mA / cm 2 Increase to 145mA / cm 2 Then, the stability of the distributed membrane electrode was tested at an electrolysis voltage of 3.0 V. During the one-month test, the carbon-hydrogen ratio of the product synthesis gas was maintained between 0.76 and 0.85. The test results show that the distributed membrane electrode of the present invention exhibits high electrochemical reduction of carbon dioxide catalytic activity and long-term stability, and improves the carbon-hydrogen ratio of the product synthesis gas.

[0087] Example 3

[0088] This embodiment provides a method for preparing a membrane electrode, the method comprising the following steps:

[0089] (I) The preparation of silver-carbon catalyst was the same as in Example 1.

[0090] (II) Membrane electrode preparation: About 26 g of Ag / C cathode catalyst was weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h. The cationic membrane was spread on a vacuum heating plate at 70 °C. A rectangular hollow template was covered on the cationic membrane. The blank area of ​​the template was covered with Ag / C catalyst by spraying. The Ag / C catalyst loading was 8 mg / cm 2 , forming a regularly distributed Ag / C membrane electrode with a membrane electrode area of ​​200cm 2 , membrane electrode photos such as Fig. 20 shown.

[0091] As the same technical concept, this embodiment also provides an electrolysis system. The electrolysis system for electrolyzing carbon dioxide to produce synthesis gas is the same as that in embodiment 1, except that the cathode distributed membrane electrode has a silver carbon loading of 8 mg / cm 2 , nickel-free carbon catalyst.

[0092] Test results:

[0093] The electrolysis temperature is 60°C, the electrolysis voltage is between 2.6-3.6V, and when the cathode is a silver-carbon distributed membrane electrode (Example 3 silver-carbon loading 8mg / cm 2 ), the product synthesis gas carbon hydrogen ratio (CO / H2) = 1.20 ~ 2.52, the total current density from 26mA / cm 2 Increase to 105mA / cm 2 Then, the stability of the distributed membrane electrode was tested at an electrolysis voltage of 3.0 V, and the carbon-hydrogen ratio of the product synthesis gas was maintained between 2.01 and 2.25 for stable operation. It can be seen from the test results that the distributed membrane electrode of the present invention exhibits a high carbon-hydrogen ratio and long-term stability.

[0094] Example 4

[0095] This embodiment provides a method for preparing a distributed membrane electrode, the method comprising the following steps:

[0096] (I) The preparation of silver-carbon catalyst was the same as in Example 1.

[0097] (II) The nickel-carbon catalyst was prepared in the same manner as in Example 1.

[0098] (III) Preparation of distributed membrane electrode: About 26 g of Ag / C cathode catalyst was weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h. The cationic membrane was spread on a vacuum heating plate at 70 °C. A rectangular hollow template was covered on the cationic membrane. The blank area of ​​the template was covered with Ag / C catalyst by spraying. The Ag / C catalyst loading was 4 mg / cm 2Then, the covering template on the membrane electrode was replaced, and about 25 g of Ni / C cathode catalyst was weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h, and the blank part of the template was covered with Ni / C catalyst by spraying. The Ni / C catalyst loading was 4 mg / cm 2 Finally, a regularly distributed Ag / C and Ni / C membrane electrode is formed with a membrane electrode area of ​​200cm 2 , where the Ag / C and Ni / C membrane electrode area ratio is 2:1, as shown in the schematic diagram Fig.21 shown.

[0099] As the same technical concept, this embodiment also provides an electrolysis system. The electrolysis system for electrolyzing carbon dioxide to produce synthesis gas is the same as that in embodiment 1, except that the cathode distributed membrane electrode has a silver carbon loading of 4 mg / cm 2 and nickel carbon loading 4 mg / cm 2 , and the Ag / C and Ni / C membrane electrode area ratio is 2:1.

[0100] Test results:

[0101] The electrolysis temperature is 60℃, the electrolysis voltage is between 2.6 and 3.6V, the product synthesis gas carbon-hydrogen ratio (CO / H2) is 0.71 to 1.35, and the total current density is from 43mA / cm 2 Increased to 152mA / cm 2 Then, the stability of the distributed membrane electrode was tested at an electrolysis voltage of 3.0 V, and the carbon-hydrogen ratio of the product synthesis gas was maintained between 1.02 and 1.15 for stable operation. The test results show that the distributed membrane electrode of the present invention exhibits high electrochemical reduction of carbon dioxide catalytic activity and long-term stability, and improves the carbon-hydrogen ratio of the product synthesis gas.

[0102] Example 5

[0103] This embodiment provides a method for preparing a distributed membrane electrode, the method comprising the following steps:

[0104] (I) The preparation of silver-carbon catalyst was the same as in Example 1.

[0105] (II) The nickel-carbon catalyst was prepared in the same manner as in Example 1.

[0106] (III) Preparation of distributed membrane electrode: About 26 g of Ag / C cathode catalyst was weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h. The cationic membrane was spread on a vacuum heating plate at 70 °C. A rectangular hollow template was covered on the cationic membrane. The blank area of ​​the template was covered with Ag / C catalyst by spraying. The Ag / C catalyst loading was 4 mg / cm 2Then, the covering template on the membrane electrode was replaced, and about 25 g of Ni / C cathode catalyst was weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h, and the blank part of the template was covered with Ni / C catalyst by spraying. The Ni / C catalyst loading was 4 mg / cm 2 Finally, a regularly distributed Ag / C and Ni / C membrane electrode is formed with a membrane electrode area of ​​200cm 2 , where the Ag / C and Ni / C membrane electrode area ratio is 1:2, as shown in the schematic diagram Fig. 22 shown.

[0107] As the same technical concept, this embodiment also provides an electrolysis system. The electrolysis system for electrolyzing carbon dioxide to produce synthesis gas is the same as that in embodiment 1, except that the cathode distributed membrane electrode has a silver carbon loading of 4 mg / cm 2 and nickel carbon loading 4 mg / cm 2 , and the Ag / C and Ni / C membrane electrode area ratio is 1:2.

[0108] Test results:

[0109] The electrolysis temperature is 60℃, the electrolysis voltage is between 2.6 and 3.6V, the product synthesis gas carbon-hydrogen ratio (CO / H2) is 0.39 to 0.56, and the total current density is from 65mA / cm 2 Increase to 205mA / cm 2 Then, the stability of the distributed membrane electrode was tested at an electrolysis voltage of 3.0V, and the carbon-hydrogen ratio of the product synthesis gas was maintained between 0.43 and 0.54 for more than 720 hours. The test results show that the distributed membrane electrode of the present invention exhibits high electrochemical reduction of carbon dioxide catalytic activity and long-term stability, and improves the carbon-hydrogen ratio of the product synthesis gas.

[0110] Example 6

[0111] This embodiment provides a method for preparing a distributed membrane electrode, the method comprising the following steps:

[0112] (I) Silver catalyst was purchased from commercial sources.

[0113] (II) Nickel catalyst was purchased from commercial sources.

[0114] (III) The membrane electrode was prepared in the same manner as in Example 1, with an Ag catalyst loading of 6 mg / cm 2 , Ni catalyst loading is 2 mg / cm 2 Finally, a square-shaped Ag / C and Ni / C distributed membrane electrode is formed with a membrane electrode area of ​​200 cm 2 , the schematic diagram is the same as that of Example 1.

[0115] As the same technical concept, this embodiment also provides an electrolysis system, and the electrolysis system for electrolyzing carbon dioxide to produce synthesis gas is the same as that in embodiment 1.

[0116] Test results:

[0117] When the electrolysis temperature is 60℃ and the electrolysis voltage is between 2.6V and 3.6V, the carbon-hydrogen ratio of the product synthesis gas (CO / H2) is 0.36-0.86. When the electrolysis temperature is 60℃ and the electrolysis voltage is increased from 2.6V to 3.6V, the total current density is increased from 28mA / cm 2 Increased to 103mA / cm 2 The electrolysis voltage was 3.0 V, the electrolysis temperature increased from 30°C to 80°C, and the total current density increased from 18 mA / cm 2 Increase to 115mA / cm 2 The test results show that the distributed membrane electrode prepared by the present invention using commercially purchased catalysts also exhibits high electrochemical reduction of carbon dioxide catalytic activity and high synthesis gas carbon-hydrogen ratio.

[0118] Comparative Example 1

[0119] This comparative example provides a method for preparing a distributed membrane electrode, the preparation method comprising the following steps:

[0120] (I) The preparation of silver-carbon catalyst was the same as in Example 1.

[0121] (II) The nickel-carbon catalyst was prepared in the same manner as in Example 1.

[0122] (III) Membrane electrode preparation: 18 g of Ag / C and 6 g of Ni / C cathode catalyst were weighed and dispersed into a mixed solution of 60 mL of naphthol and 220 mL of n-propanol. Ultrasonic dispersion was performed for 1 h. The cationic membrane was spread on a vacuum heating plate at 70 °C and the Ag / C and Ni / C mixed catalyst loading of 4 mg / cm was obtained by spraying. 2 , membrane electrode area 200cm 2 , membrane electrode photos such as Fig.23 shown.

[0123] As the same technical concept, this embodiment also provides an electrolysis system, and the electrolysis system for electrolyzing carbon dioxide to produce synthesis gas is the same as that in embodiment 1.

[0124] Test results:

[0125] The electrolysis temperature is 60°C, the electrolysis voltage is between 2.6 and 3.6V, and the CO:H2 molar ratio is between 0.21 and 0.38.

[0126] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a distributed membrane electrode, characterized in that: The preparation method comprises the following steps: (I) preparing a first catalyst, wherein the first catalyst is a catalyst for electrolyzing carbon dioxide to produce carbon monoxide (I-1) dispersing carbon black in water, adding a first metal salt and polyethylene glycol, and stirring and mixing to obtain a first premixed solution; (I-2) adding a sodium citrate aqueous solution to the first premixed solution, stirring for reaction, and then adding a vitamin C aqueous solution and continuing to stir for reaction to obtain a first reaction solution; (I-3) After filtering the first reaction liquid, taking the precipitate and drying it, and then reducing it to obtain the first catalyst; (II) preparing a second catalyst, wherein the second catalyst is a catalyst for producing hydrogen during the liquid phase electrolysis of carbon dioxide (II-1) dispersing carbon black in water, adding a second metal salt and polyethylene glycol, and stirring to obtain a second premixed solution; (II-2) adding an aqueous sodium hypophosphite solution to the second premixed solution, stirring the solution, and then adding an aqueous sodium hydroxide solution and continuing to stir the solution to obtain a second reaction solution; (II-3) After filtering the second reaction liquid, taking the precipitate and drying it, and then reducing it to obtain the second catalyst; (III) Preparation of distributed membrane electrode (III-1) dispersing the first catalyst into a mixed solution of naphthol and n-propanol to obtain a first catalyst dispersion; dispersing the second catalyst into a mixed solution of naphthol and n-propanol to obtain a second catalyst dispersion; (III-2) covering the upper surface of the cationic membrane with a template, spraying the first catalyst dispersion onto the blank area of ​​the template, and loading it onto the cationic membrane; (III-3) The template is replaced, and the second catalyst dispersion is sprayed on the blank area of ​​the template and loaded on the cationic membrane to obtain the distributed membrane electrode.

2. The method for preparing a distributed membrane electrode according to claim 1, characterized in that: In step (I-1), the first metal salt is silver nitrate, silver acetate, silver trifluoromethanesulfonate, or silver acetylacetonate; and the stirring and mixing time is 2 to 3 hours; And / or, in step (II-1), the second metal salt is nickel sulfate, nickel chloride, nickel nitrate, nickel acetate, nickel sulfamate, or nickel acetylacetonate; and the stirring and mixing time is 2 to 3 hours.

3. The method for preparing a distributed membrane electrode according to claim 1, characterized in that: In step (I-2), 1-1.5 mol / L sodium citrate aqueous solution is added to the first premixed solution, stirred for reaction for 1-2 hours, and then 1.2-1.5 mol / L vitamin C aqueous solution is added and stirred for reaction for 1-2 hours to obtain a first reaction solution; And / or, in step (II-2), add 1.2-1.5 mol / L sodium hypophosphite aqueous solution to the second premixed solution, stir and react for 1-2 hours, then add 4-5 mol / L sodium hydroxide aqueous solution and continue to stir and react for 1-2 hours to obtain a second reaction solution.

4. The method for preparing a distributed membrane electrode according to claim 1, characterized in that: In step (I-3), after the first reaction liquid is filtered, the precipitate is taken and dried at 80-85° C. for 20-24 h, and then reduced at 350° C. for 2 h in a 10% H2 / Ar atmosphere to obtain a first catalyst; And / or, in step (II-3), after filtering the second reaction liquid, the precipitate is taken and dried at 80-85°C for 20-24h, and then reduced at 600°C for 2h in a 20% H2 / Ar atmosphere to obtain the second catalyst.

5. The method for preparing a distributed membrane electrode according to claim 1, characterized in that: In step (III-2), the loading amount of the first catalyst on the cationic membrane is 2 to 12 mg / cm 2 .

6. The method for preparing a distributed membrane electrode according to claim 1, characterized in that: In step (III-3), the loading amount of the second catalyst on the cationic membrane is 0.5 to 6 mg / cm 2 .

7. A distributed membrane electrode obtained by the preparation method according to any one of claims 1 to 6.

8. An electrolysis system, characterized in that: The electrolysis system comprises a carbon dioxide enrichment system, an electrolyte circulation system, a carbon dioxide electroreduction system and a gas-liquid separation system; wherein: The carbon dioxide enrichment system comprises a carbon dioxide alkali solution absorption tower; the carbon dioxide alkali solution absorption tower is used to collect carbon dioxide and complete the enrichment of low partial pressure carbon dioxide to form a mixed aqueous solution of KHCO3 and K2CO3; The electrolyte circulation system comprises a cathode electrolyte circulation system and an anode electrolyte circulation system; The carbon dioxide electroreduction system comprises a power supply and an electrolyzer, wherein the electrolyzer comprises the distributed membrane electrode according to claim 7; the power supply supplies power to the electrolyzer; The gas-liquid separation system comprises a cathode gas-liquid separator, an anode gas-liquid separator and an electrolyte storage tank; after the formed synthesis gas and electrolyte are separated in the cathode gas-liquid separator, the electrolyte flows back to the electrolyte storage tank; after the formed oxygen and electrolyte are separated in the anode separator, the electrolyte flows back to the electrolyte storage tank; The carbon dioxide alkali solution absorption tower, cathode electrolyte circulation system, electrolytic cell, cathode gas-liquid separator, and electrolyte storage tank constitute a first closed circulation loop; the anode electrolyte circulation system, electrolytic cell, anode gas-liquid separator, and electrolyte storage tank constitute a second closed circulation loop.

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