阅读说明：本技术 一种用于二氧化碳的电化学还原的电化学反应器 (Electrochemical reactor for electrochemical reduction of carbon dioxide ) 是由 林柏霖 肖彦军 钱瑶 唐和华 于 2020-05-27 设计创作，主要内容包括：本发明提供了一种用于二氧化碳的电化学还原的电化学反应器,该装置属于三腔室反应器,由两种隔膜(即阴离子导电聚合物薄膜和聚丙烯薄膜气体扩散电极)分隔三块有精密尺寸凹槽和开孔的透明有机玻璃板材构成；所述三腔室反应器包含有：气体腔室、阴极电解液腔室和阳极电解液腔室。所述气体腔室包括聚丙烯薄膜气体扩散电极聚丙烯薄膜一侧,阴极电解液腔室包括由银基催化剂作阴极的聚丙烯薄膜气体扩散电极催化层一侧,所述阳极电解液腔室包括具有混合金属氧化物催化剂的阳极。本发明的电化学反应装置整体采用材质透明、硬度较高、既耐碱性又耐酸性的有机玻璃,易于精密加工和组装,便于直接监控、观测电化学反应,且反应测试期间无二次污染。(The invention provides an electrochemical reactor for electrochemical reduction of carbon dioxide, which belongs to a three-chamber reactor and is formed by separating three transparent organic glass plates with precise-sized grooves and openings by two diaphragms (namely an anion conducting polymer film and a polypropylene film gas diffusion electrode); the three-chamber reactor comprises: a gas chamber, a catholyte chamber, and an anolyte chamber. The gas chamber comprises a polypropylene film gas diffusion electrode and a polypropylene film side, the catholyte chamber comprises a polypropylene film gas diffusion electrode catalyst layer side with a silver-based catalyst as a cathode, and the anolyte chamber comprises an anode with a mixed metal oxide catalyst. The electrochemical reaction device provided by the invention integrally adopts organic glass which is transparent in material, higher in hardness, alkali-resistant and acid-resistant, is easy to precisely process and assemble, is convenient for directly monitoring and observing the electrochemical reaction, and has no secondary pollution during a reaction test period.)

1. An electrochemical reactor for the electrochemical reduction of carbon dioxide, characterized in that it belongs to a three-chamber reactor comprising: a gas chamber (2), a cathode chamber (5) and an anode chamber (7);

the three-chamber reactor is composed of three transparent organic glass plates with precise-sized grooves and openings, wherein the three transparent organic glass plates are formed by an anion conducting polymer film (9) and a polypropylene film gas diffusion electrode (11) to separate a gas chamber plate (1), a cathode chamber plate (4) and an anode chamber plate (6);

the cathode chamber is located between the gas diffusion electrode (11) and the anion conducting polymer membrane (9); the gas chamber (2) is positioned on the other side of the gas diffusion electrode (11), the anode chamber (7) is positioned on the other side of the anion conducting polymer film (9), and an anode of a mixed metal catalyst is arranged in the anode chamber;

the gas chamber (2) is provided with a gas inlet hole (13) and a gas outlet hole (12); the cathode chamber (5) is provided with an electrolyte inlet (16), an electrolyte outlet (15) and a reference electrode jack (10), a reference electrode is arranged in the reference electrode jack (10), and the gas diffusion electrode (11) is a cathode; an electrolyte inlet (18), an electrolyte outlet (17) and an anode mounting hole (8) are formed in the anode chamber (7), and an anode of a mixed metal catalyst is arranged in the anode mounting hole (8).

2. The electrochemical reactor for electrochemical reduction of carbon dioxide as claimed in claim 1, wherein the electrochemical reaction device is made of organic glass having a transparent material, a high hardness, and alkali and acid resistance.

3. The electrochemical reactor for the electrochemical reduction of carbon dioxide according to claim 1, wherein when the reactor is used for the electrochemical synthesis of CO, a 1M KOH solution is introduced into all the chambers.

4. The electrochemical reactor for electrochemical reduction of carbon dioxide as claimed in claim 1, wherein the anode is a Ni-Fe mixed metal catalyst prepared by: (1) cutting the foamed nickel substrate and the carbon paper, sequentially cleaning with acetone, ethanol and deionized water, and drying for later use; (2) respectively preparing ferric nitrate solution and nickel nitrate solution for later use; (3) respectively adding the ferric nitrate solution and the nickel nitrate solution with the concentrations into ethylene glycol, then adding deionized water and ammonium fluoride, and performing ultrasonic dispersion to form a uniform precursor solution; (4) putting clean foam nickel as a cathode and carbon paper as an anode into a precursor solution preheated to 40 ℃, and standing; (5) fixing the cathode and the anode, applying voltage at two ends by using a voltage-stabilized power supply, and maintaining for 5 min; (6) and taking down the foamed nickel deposited with the black catalyst, soaking the foamed nickel in absolute ethyl alcohol for a period of time, taking out the foamed nickel, and drying the foamed nickel to obtain the NiFe catalyst.

5. The electrochemical reactor for electrochemical reduction of carbon dioxide as claimed in claim 1, wherein the cathode is a multi-layered nanoporous metal-based flexible thin film gas diffusion electrode prepared by the steps of:

step 1: cutting the flexible film, sequentially cleaning with acetone, ethanol and deionized water, and drying for later use;

step 2: depositing a metal film on one side of the flexible film by a physical vacuum method;

and step 3: a lattice expansion and contraction strategy was used to build the layered nanopore structure: the metal film is subjected to anodic oxidation in the solution, and the metal nano particles are converted into metal salt or metal oxide micro domains, so that the metal lattice volume is expanded; the subsequent cathode reduction removes negative ions or oxygen atoms from metal salts or metal oxides to reduce the negative ions or oxygen atoms into metal simple substances, so that the crystal lattices contract in situ, domain boundary channels/gaps are formed at the domain boundaries, and pores in the domains are caused by the crystal lattice contraction and the loss of the negative ions or the oxygen atoms, and the multilayer nano-pore metal-based flexible film gas diffusion electrode is obtained.

6. The electrochemical reactor for electrochemical reduction of carbon dioxide as claimed in claim 5, wherein the metal comprises any one of silver, gold, copper, tin, bismuth, nickel.

7. The electrochemical reactor for electrochemical reduction of carbon dioxide as claimed in claim 5, wherein the flexible membrane in step 1 is a rice porous polypropylene membrane.

8. The electrochemical reactor for electrochemical reduction of carbon dioxide as claimed in claim 5, wherein the physical vacuum method in step 2 comprises electron beam evaporation, thermal evaporation and magnetron sputtering.

Technical Field

The present invention relates to the field of electrochemistry, in particular to the electrochemical reduction of carbon dioxide, and more particularly to the electrochemical reduction of carbon dioxide to carbon monoxide.

Background

Global climate change due to mass burning of fossil fuels is aggravated and greenhouse efficiency is more severe, and in view of the current trend, the residual carbon budget to achieve the temperature control target will be rapidly exhausted within the next 10-20 years, requiring immediate action to reduce the large carbon dioxide emissions caused by human factors. The artificial photosynthesis system can simultaneously perform CO₂Electrochemical reduction reaction (CO)₂RR) and water oxidation oxygen production reaction (OER), CO can be realized₂Substantial reduction in emissions and large-scale storage of intermittent solar energy in carbonaceous fuels. However, as an attractive new technology, the electrochemical conversion method of CO2 has to be developed and perfected in many ways, and the development of electrochemical reaction devices is one of the key points.

CO₂Electrochemical conversion is generally accomplished by means of a two-chamber type electrolytic cell having a cathode chamber and an anode chamber; the liquid inlet mode is double electrolyte solution feeding, i.e. strong alkali or bicarbonate solution is fed into the anode chamber to make oxygen evolution reaction, and dissolve or carry CO₂Into the cathode chamber as CO₂And (4) performing electrochemical reduction reaction. However, due to the CO in the cathode chamber electrolyte solution₂The lower solubility and the difficult mass transfer of liquid in the electrode cause the electrochemical reduction of CO in the electrode₂The selectivity and the activity of the compound are poor; secondly, the problems of electrolyte consumption and unstable electrolyte concentration in the cathode and anode chambers caused by the mass transfer of the electrolyte between the cathode and anode chambers, and the problems of insufficient long-term stability of the electrodes and high corrosion prevention requirements of pipeline equipment caused by the corrosion and the scouring of the electrolyte solutionAll cause CO₂Electrochemical reduction is difficult to apply commercially.

In addition, in the aspect of operation, the electrochemical reactor made of metal materials such as stainless steel and the like can be corroded and washed by electrolyte solution when being operated for a long time, so that the catalyst is polluted and poisoned; moreover, because it is not visualized, the operation of the electrochemical reaction cannot be directly observed and monitored in real time, which is not conducive to large-scale production and application.

Disclosure of Invention

The invention aims to develop a novel electrochemical reduction method for CO₂The reactor of (2) can overcome CO₂The problem of low solubility in electrolyte solution, and the problems of long-term stability of the electrode, corrosion by the electrolyte, pollution by other metals and the like can be solved.

In order to achieve the above object, the present invention provides an electrochemical reactor for electrochemical reduction of carbon dioxide, characterized in that the device belongs to a three-chamber reactor comprising: a gas chamber, a cathode chamber and an anode chamber;

the three-chamber reactor consists of three transparent organic glass plates with grooves and openings of precise sizes, wherein the three transparent organic glass plates are formed by separating a gas chamber plate, a cathode chamber plate and an anode chamber plate by an anion conducting polymer film and a polypropylene film gas diffusion electrode;

the cathode chamber is located between the gas diffusion electrode and the anion conducting polymer membrane; the gas chamber is positioned on the other side of the gas diffusion electrode, and the anode chamber is positioned on the other side of the anion conducting polymer film;

the gas chamber is provided with a gas inlet hole and a gas outlet hole; the cathode chamber is provided with an electrolyte inlet, an electrolyte outlet and a reference electrode jack, a reference electrode is arranged in the reference electrode jack, and the gas diffusion electrode is a cathode; an electrolyte inlet, an electrolyte outlet and an anode mounting hole are arranged in the anode chamber, and an anode mixed with a metal catalyst is arranged in the anode mounting hole.

Preferably, the whole electrochemical reaction device adopts organic glass which is transparent in material, high in hardness, alkali-resistant and acid-resistant, is easy to precisely process and assemble, facilitates direct monitoring and observation of the electrochemical reaction, and has no secondary pollution during a reaction test.

Preferably, when the reactor is used for CO electrochemical synthesis, 1M KOH solution is introduced into all chambers.

Preferably, the anode is a Ni-Fe mixed metal catalyst, which is prepared by: (1) cutting the foamed nickel substrate and the carbon paper, sequentially cleaning with acetone, ethanol and deionized water, and drying for later use; (2) respectively preparing ferric nitrate solution and nickel nitrate solution for later use; (3) respectively adding the ferric nitrate solution and the nickel nitrate solution with the concentrations into ethylene glycol, then adding deionized water and ammonium fluoride, and performing ultrasonic dispersion to form a uniform precursor solution; (4) putting clean foam nickel as a cathode and carbon paper as an anode into a precursor solution preheated to 40 ℃, and standing; (5) fixing the cathode and the anode, applying voltage at two ends by using a voltage-stabilized power supply, and maintaining for 5 min; (6) and taking down the foamed nickel deposited with the black catalyst, soaking the foamed nickel in absolute ethyl alcohol for a period of time, taking out the foamed nickel, and drying the foamed nickel to obtain the NiFe catalyst.

More preferably, the concentration of the ferric nitrate solution and the concentration of the nickel nitrate solution are both 309 mmol/L.

More preferably, the volume ratio of the ferric nitrate solution, the nickel nitrate solution, the deionized water and the ethylene glycol is 0.7:0.7:0.7:100, and the concentration of the ammonium fluoride in the precursor solution is 1.077-1.1 mg/mL.

Preferably, the cathode is a multi-level nano-pore metal-based flexible thin film gas diffusion electrode, and the preparation method comprises the following steps:

step 1: cutting the flexible film, sequentially cleaning with acetone, ethanol and deionized water, and drying for later use;

step 2: depositing a metal film on one side of the flexible film by a physical vacuum method;

and step 3: a lattice expansion and contraction strategy was used to build the layered nanopore structure: the metal film is subjected to anodic oxidation in the solution, and the metal nano particles are converted into metal salt or metal oxide micro domains, so that the metal lattice volume is expanded; the subsequent cathode reduction removes negative ions or oxygen atoms from metal salts or metal oxides to reduce the negative ions or oxygen atoms into metal simple substances, so that the crystal lattices contract in situ, domain boundary channels/gaps are formed at the domain boundaries, and pores in the domains are caused by the crystal lattice contraction and the loss of the negative ions or the oxygen atoms, and the multilayer nano-pore metal-based flexible film gas diffusion electrode is obtained.

More preferably, the metal includes silver, gold, copper, tin, bismuth, nickel, and the like.

More preferably, the flexible film in step 1 is a rice porous polypropylene film (nanoPP).

More preferably, the physical vacuum method in step 2 includes an electron beam evaporation method, a thermal evaporation method and a magnetron sputtering method.

More preferably, the cathode is a multi-layer nanoporous silver-based thin film gas diffusion electrode (npm-Ag) prepared by the steps of:

step 1: cutting a nano porous polypropylene film (nano PP), sequentially washing with acetone, ethanol and deionized water, and drying for later use;

step 2: depositing a silver film on one side of the polypropylene film by a physical vacuum method;

and step 3: a lattice expansion and contraction strategy was used to build the layered nanopore structure: anodic oxidation of the silver film occurs in the hydrochloric acid aqueous solution, and Ag nano particles are converted into AgCl micro domains; subsequent cathodic reduction removes chlorine atoms from the AgCl lattice, resulting in domain boundary channels/gaps at the domain boundaries, and in-domain pinholes due to lattice shrinkage and chloride ion loss, i.e., multi-layer nanoporous silver-based thin film gas diffusion electrodes.

Further, the pore diameter of the nano-porous polypropylene film (nano PP) in the step 1 is 15-800 nm.

Further, the physical vacuum method in the step 2 includes an electron beam evaporation method, a thermal evaporation method and a magnetron sputtering method.

Further, the physical vacuum method in step 2 is an electron beam evaporation method.

Further, the thickness of the silver film in the step 2 is 600-1800 nm.

Further, the thickness of the silver film in the step 2 is 600nm, 1200nm or 1800 nm.

Further, the silver film in the step 2 is formed by closely stacking irregular silver nano particles, and the particle size of the silver nano particles is 10-1000 nm.

Further, the size of the AgCl micron domain in the step 3 is 0.1-2.5 μm.

Further, the domain boundary channels/gaps in step 3 have a size of 10-1200 nm.

Furthermore, the size of the small holes in the domains in the step 3 is 10-200 nm.

The invention has the beneficial effects that:

1. the polypropylene film adopted by the invention has the advantages of low cost, uniform structure and stable property, and is used for electrocatalytic reduction of CO₂The gas diffusion electrode for reaction can provide a durable and stable gas-liquid-solid three-phase interface;

2. the multi-layer nano-pore metal-based flexible thin film gas diffusion electrode is applied to alkaline CO₂RR reaction, excellent performance and high efficiency reduction of CO₂Is CO;

3. CO in 1M KOH of the invention₂When the overpotential of RR is as low as 40mV, the CO Faraday conversion efficiency can reach 80%; at slightly higher overpotentials (90-290mV), the Faraday efficiency reached 100%, while the cell current density reached about 18.4mA cm^-2(ii) a The performance is far better than other reported catalysts.

4. The raw materials for preparing the reactor are all cheap raw materials, the processing technology is simple and efficient, the material is transparent, the property is stable, and the industrial application is very facilitated.

Drawings

FIG. 1 is a schematic view of the three-chamber electrochemical reactor;

FIG. 2 is a schematic diagram of the structure of the gas chamber of the three-chamber electrochemical reactor;

FIG. 3 is a schematic diagram of the structure of the cathode chamber of the three-chamber electrochemical reactor;

FIG. 4 is a schematic diagram of the structure of the anode chamber of the three-chamber electrochemical reactor;

wherein the reference numerals are as follows:

1 a gas chamber plate; 2 a gas chamber; 3 sealing the coil; 4 a cathode chamber plate; 5 a cathode chamber; 6 anode chamber plate; 7 an anode chamber; 8, an anode mounting hole; 9 an anion-conducting polymer film; 10 reference electrode receptacle; 11 a gas diffusion electrode; 12 gas chamber gas outlet holes; 13 gas chamber inlet holes; 14 bolt holes; 15 a cathode chamber electrolyte outlet; 16 a cathode chamber electrolyte inlet; 17 an anode chamber electrolyte outlet; 18 anode chamber electrolyte inlet.

FIG. 5 (A) useful in the electrochemical reduction of CO in the present invention₂The multilayer nano-porous silver-based polypropylene film gas diffusion electrode (npm-Ag); (B) scanning electron microscope images of a multi-level nanopore structured silver thin film gas diffusion electrode (npm-Ag); (C) cross-sectional Scanning Electron Microscope (SEM) images.

FIG. 6 CO of gas diffusion electrode of multi-layer nano-porous silver-based polypropylene film₂Electrochemical performance of RR. (A) Ar or CO of multi-level nano-pore silver-based polypropylene film gas diffusion electrode under standard atmospheric pressure₂Linear sweep voltammogram under atmosphere (sweep rate: 10mv s-1); (B) selectively generating the current distribution density of CO by the three silver film electrodes with different thicknesses; (C) the multi-level nano-pore silver-based polypropylene film gas diffusion electrode selectively produces the change relation of the real current density of CO along with the potential; (D) the faradaic efficiency and total current density of the sample nmp-Ag-1.44 μm for selective CO generation varied with potential and overpotential; (E) the Faraday efficiency and the total current density of a sample nmp-Ag-2.80 mu m for selectively generating CO are in the change relation with the potential and the overpotential; (F) the faradaic efficiency and total current density of sample nmp-Ag-4.50 μm selective CO generation varied with potential and overpotential.

FIG. 7 (A) sample nmp-Ag-2.80 μm in CO₂Representative of electrolyte solutions after RR test¹H-NMR spectra, in which DMSO was added as an internal standard of the solution. Determination of H by gas chromatography₂(B) And selectivity for CO (C), H₂And the retention times of CO were 0.88min and 5.08min, respectively.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

The preparation method of the multi-level nano-porous silver-based thin film gas diffusion electrode (npm-Ag) used in the following examples comprises the following specific steps:

1. cutting a nano porous polypropylene film (nano PP, the average pore diameter is about 166nm) into 2.5cm multiplied by 2.5cm, sequentially washing with acetone, ethanol and deionized water for 10min, and drying at 60 ℃ for later use;

2. depositing a silver film with a thickness of about 600nm, 1200nm or 1800nm on one side of the polypropylene film by an electron beam evaporation method (vacuum method); wherein the silver film is formed by closely packing irregular silver nanoparticles (about 252 +/-133 nm);

3. a lattice expansion and contraction strategy was used to build the layered nanopore structure: the silver film is anodized in hydrochloric acid aqueous solution, and Ag nano particles are converted into AgCl micro domains (0.848 +/-0.357 mu m). As the lattice expands, the corresponding AgCl film thickness increases by a factor of 2.4 (1.44 μm, 2.80 μm, or 4.50 μm); the subsequent cathodic reduction removes the chlorine atoms from the AgCl crystal lattice, resulting in the formation of a large number of domain boundary channels/gaps (average size: 534 + -153 nm) at the domain boundaries, and small pores in the domains due to lattice shrinkage and loss of chloride ions, the average size of the small pores being 68.5 + -26.0 nm, i.e., the multi-layer nano-pore silver-based thin film gas diffusion electrode is obtained.

FIG. 5 (A) useful in the electrochemical reduction of CO in the present invention₂The multilayer nano-porous silver-based polypropylene film gas diffusion electrode (npm-Ag); (B) scanning electron microscope images of the multi-level nano-pore structure silver thin film gas diffusion electrode (npm-Ag) show that the prepared AgCl thin film can simultaneously form abundant large channels (about 534 +/-153 nm) and small pores (about 68.5 +/-26.0 nm) after constant current reduction. Inset shows high resolutionScanning electron microscope images. (C) Cross-sectional Scanning Electron Microscope (SEM) images showed that npm-Ag had more large channels/gaps at the bottom than at the top. Inset shows a high resolution SEM image.

The Linear Sweep Voltammetry (LSV) tests performed under one atmosphere of argon and carbon dioxide showed that all the multi-layer nanoporous silver-based polypropylene thin film gas diffusion electrodes (designated nmp-Ag-1.44/2.80/4.50 μm) exhibited good CO at lower overpotentials₂RR electrocatalytic activity (fig. 6). CO2₂RR initiation potential is almost CO₂The RR standard electrode potentials (-0.11V) were the same (inset, FIG. 6A). The CO selectively produced at the lower overpotential is confirmed by gas chromatographic analysis, and¹no liquid phase product was detected by HNMR spectroscopy (fig. 10). In particular, for sample nmp-Ag-2.80 μm, at a very low potential, (-0.15Vvs. RHE, corresponding to an overpotential of 40 mV), the faradaic efficiency of CO selective generation is about 80%; when the potential is increased to 0.20V, the faradaic efficiency of CO selectively generated by all three silver film electrodes is 95-97%; faradaic efficiencies of about 100% for selective CO production from all electrodes were achieved with potentials between-0.3 and-0.4V, except for sample nmp-Ag-4.50 μm (FIGS. 6D, E, F); in CO₂RR post-test electrolyte solution¹No other carbon-containing small molecules were detected by H-NMR spectroscopy (FIG. 7). In contrast, using gold or non-noble metals as catalysts, CO₂When RR-CO is-0.2V, the faradaic efficiency of CO selective generation is about 40% -60%; faradaic efficiency for CO selective generation at-0.3 to-0.4V versus RHE is about 90% -95%. nmp-Ag-2.80 μm with current density up to 18.4mA cm at-0.4V^-2Is known to be all reported COs₂The RR catalyst has the highest fractional current density at lower overpotentials.

The preparation method of the Ni-Fe catalyst used in the following examples comprises the following specific steps:

step 1: cutting the foamed nickel substrate and the carbon paper into 0.5cm × 3.0cm, sequentially cleaning with acetone, ethanol and deionized water for 30min, and drying at 60 deg.C for use.

Step 2: 309mmol/L ferric nitrate and nickel nitrate solutions are prepared respectively for standby.

And step 3: respectively adding 0.7ml of ferric nitrate and nickel nitrate solution with the concentrations into 100ml of ethylene glycol, and then adding 0.7ml of deionized water and 0.11g of ammonium fluoride; sonicate for a period of time to form a homogeneous solution.

And 4, step 4: clean foamed nickel is used as a cathode, carbon paper is used as an anode, the clean foamed nickel and the carbon paper are parallel to each other and are spaced by about 2cm, and the working area is 2.0cm multiplied by 0.5 cm. Placed into the precursor solution which had been preheated to 40 ℃ and the depth into the solution was 2cm each. Standing for a period of time.

And 5: the cathode and the anode are kept fixed, and a voltage of 220V is applied to the two ends of the anode by a voltage-stabilized power supply and is maintained for 5 min.

Step 6: and taking down the foamed nickel deposited with the black catalyst, soaking the foamed nickel in absolute ethyl alcohol for a period of time, taking out the foamed nickel, and drying the foamed nickel at the temperature of 60 ℃ to obtain the Ni-Fe catalyst.