CN115491699A - A nano-copper-based catalyst, its preparation method and its application in the electrocatalytic reduction of carbon dioxide and carbon monoxide - Google Patents

Abstract

The invention discloses a nanometer copper-based catalyst, its preparation method and its application in electrocatalytic reduction of carbon dioxide and carbon monoxide. Dissolve copper chloride (or copper nitrate, copper acetate) in ultrapure water, and add sodium borohydride solution dropwise. Stir at room temperature for 5-60min, filter, and dry to obtain a nano-copper catalyst. Further, through a replacement reaction, nano-copper-palladium and copper-silver catalysts are obtained. The present invention is applied to the electrocatalytic reduction of carbon monoxide. In the membrane electrode (MEA) electrolyzer, the faradaic efficiency of the multi-carbon product (C ₂₊ ) can reach up to 95%, the partial current density can reach up to 3A cm- ² , and the energy efficiency of the full electrolytic cell Up to 39%, stable electrolysis at 1A cm ^‑2 for 30 hours. The nano-copper catalyst is applied to the electrocatalytic reduction of carbon dioxide. In the MEA electrolyzer, the C ₂₊ faradaic efficiency can reach up to 66%, and the partial current density can reach up to 331 mA cm ^‑2 .

Description

A kind of nanometer copper-based catalyst and its preparation method and in carbon dioxide and monoxide Applications in Carbon Electrocatalytic Reduction

technical field

The invention belongs to the field of catalysis, and in particular relates to a nanometer copper-based catalyst for the electrocatalytic reduction of carbon dioxide and carbon monoxide.

Background technique

Currently, with the depletion of fossil resources, sustainable production away from petrochemical and coal chemical-based chemicals has gradually become the focus of attention. Carbon dioxide electrocatalytic reduction reaction (CO ₂ RR ), which converts CO ₂ and water into fuels and chemicals using clean electrical energy, is an effective strategy for simultaneous carbon recycling and renewable energy storage. However, during the direct electroreduction of CO ₂ to multi-carbon (C ₂₊ ) products in alkaline electrolytes, a large amount of carbonate is generated. Whereas the formation of carbonates leads to _CO loss as well as high energy loss (up to 72% of energy consumed). A two-step electroreduction of CO ₂ to multi-carbon (C ₂₊ ) products can effectively avoid such problems, that is, CO ₂ is first converted to CO in a solid oxide electrolysis cell (SOEC) (first step), and then in a membrane electrode CO obtained in SOEC is converted to C ₂₊ in the (MEA) electrolyzer (second step), so that the loss of CO ₂ converted to carbonate can be eliminated, and the reduction of carbon monoxide has a lower overpotential and more efficient than carbon dioxide reduction. High selectivity of C ₂₊ products, thereby realizing high activity, high selectivity CO ₂ -C ₂₊ conversion and high CO ₂ utilization efficiency.

The key to achieving high-efficiency CO ₂ -C ₂₊ conversion is to improve the carbon-carbon (CC) coupling efficiency of CO to C ₂₊ conversion in MEA and the long-term stability of the MEA electrolytic cell. Therefore, it is of great significance to develop copper catalysts with high carbon monoxide electrocatalytic reduction (CORR) activity, low cost, easy availability and stability for the electrocatalytic reduction of carbon dioxide and carbon monoxide.

At present, the strategies to improve the activity of CORR catalysts mainly include the following: organic modification, doping, grain boundary and crystal plane engineering, etc. Literature (Joule 2021, 5, 706-719) designed a layered catalyst structure composed of metallic copper, N-toluene-tetrahydrobipyridyl and short side chain copolymer (SSC) ions, realized in the MEA electrolyzer The efficient conversion of CO into C ₂ H ₄ is achieved. The literature (Adv. Mater. 2020, 32, e2002382) reported a copper nitride (Cu ₃ N) nanocrystal catalyst with rich twin structure synthesized in ammonia solution, which has more than 90% C ₂₊ Faraday efficiency. Literature (EnergyEnviron.Sci.2020, 13, 2993-3006) reported a mixed metal oxide Ag ₂ Cu ₂ O ₃ catalyst as a starting template material for efficient electroreduction of CO to generate C ₂₊ products. CORR electrochemical test results show that the Faradaic efficiency of C ₂₊ products is close to 92% at 600mA cm ^-2 . Literature (Nat.Commun.2020, 11, 3685) reported a Pd-doped Cu catalyst, which weakened the adsorption of hydrogen and facilitated the hydrogenation of _C2 intermediates, promoting the formation of alcohols, which formed on the catalyst The Faradaic efficiency of the alcohol is 40%, and the partial current density is 277mA cm ^-2 . However, copper catalysts prepared using organic ligands, surfactants, etc. often require complex preparation processes, high cost, and poor stability. Therefore, there is an urgent need to develop a simple, rapid, and high-yield preparation method for high-efficiency copper catalysts.

Contents of the invention

Problems solved by the technology of the present invention: Overcoming the deficiencies of the prior art, a preparation method of nano-copper-based catalysts for the electrocatalytic reduction of carbon dioxide and carbon monoxide has been developed. The method is simple, fast, and high in yield. The prepared copper-based The catalyst has high CO electrocatalytic reduction activity, selectivity and stability.

To achieve the above object, the technical solution adopted in the present invention is:

A preparation method of nanometer copper-based catalyst, the steps are as follows:

Step 1: Dissolving the copper salt in ultrapure water to obtain a copper salt solution, the concentration of the copper salt solution is 0.01-0.2molL ⁻¹ ;

Step 2: Add sodium borohydride solution dropwise to the copper salt solution, stir at room temperature for 5-60 minutes, filter, and dry to obtain a nano-copper catalyst; the molar ratio of sodium borohydride to copper salt is 1-20, and boron The concentration of the sodium hydride solution is 0.1-1mol L ^-1 .

A preparation method of a nano-copper-based two-component catalyst, comprising the following steps:

Step 1: Dissolving the copper salt in ultrapure water to obtain a copper salt solution, the concentration of the copper salt solution is 0.01-0.2molL ⁻¹ ;

Step 2: Add sodium borohydride solution dropwise to the copper salt solution, stir at room temperature for 5-60 minutes, filter, and dry to obtain a nano-copper catalyst; the molar ratio of sodium borohydride to copper salt is 1-20, and boron The concentration of the sodium hydride solution is 0.1-1mol L ^-1 ;

Step 3: ultrasonically disperse the nano-copper catalyst in ultrapure water, add the second metal precursor under the protection of nitrogen, sonicate for 10-30 minutes, filter, and dry to obtain a nano-copper-based two-component catalyst. The second metal precursor is a soluble silver salt or a soluble palladium salt. The concentration of the second metal precursor is 0.01-0.2 mol L ^-1 . The molar ratio of the second metal precursor to the copper salt is 0.01-0.2.

Appropriate copper salt concentration can obtain copper nanoparticles with relatively uniform size. An appropriate ratio of sodium borohydride to copper salt is beneficial to ensure that the metal is completely reduced. Appropriate sodium borohydride concentration is beneficial to control the reduction rate of the reaction and obtain copper nanoparticles of appropriate size.

The use of ultrasound during the reaction is beneficial to speed up the reaction rate. The use of nitrogen protection during the reaction can avoid the oxidation of nano-copper-based catalysts. An appropriate concentration of the second metal precursor is conducive to the uniform dispersion of the second metal.

Based on the above scheme, preferably, the copper salt may be copper nitrate or copper chloride or copper acetate.

Based on the above scheme, preferably, the concentration of the copper salt solution is 0.01-0.1 mol L ⁻¹ .

Based on the above scheme, preferably, the molar ratio of sodium borohydride to copper salt is 5-10.

Based on the above scheme, preferably, the soluble silver salt is silver nitrate, and the soluble palladium salt is palladium chloride.

Based on the above scheme, preferably, the concentration of the second metal precursor is 0.01-0.1 mol L ⁻¹ ; the molar ratio of the second metal precursor to copper salt is 0.1-0.2.

The catalyst prepared by the above method of the present invention has a nanoporous structure. The catalyst is connected by particles with a particle size of 10-20nm; it has a porous structure with a pore size of 50-100nm; and it has a core-shell structure, with metallic copper inside and a layer of cuprous oxide of about 3-5nm on the outside. .

The catalyst prepared above in the present invention can be used for the electrocatalytic reduction reaction of carbon dioxide and/or carbon monoxide. The realization is: the nano-copper catalyst has a nano-porous structure with abundant defects and grain boundary structure. It is applied to the electrocatalytic reduction of carbon monoxide and exhibits high electrolytic performance. In the MEA electrolyzer, the C ₂₊ faradaic efficiency can reach up to 95%. , the current density can reach up to 3A cm ^-2 , the energy efficiency of the full electrolytic cell can reach up to 39%, and it can stably electrolyze at 1A cm ^-2 for 30 hours.

The advantage of the present invention relative to prior art is:

In the present invention, a gram-level nano-copper-based catalyst can be prepared in one step through a liquid-phase reduction method. The nano-copper catalyst has a nano-porous structure, has abundant defects and grain boundary structures, and the catalyst can produce C2 ₊ products by CORR in the MEA electrolyzer Excellent performance, C ₂₊ faradaic efficiency up to 95%, current density up to 3A cm ^-2 , full electrolytic cell energy efficiency up to 39%, stable electrolysis at 1A cm ^-2 for 30 hours. This invention provides an important research basis for promoting the industrial application of CO ₂ RR.

Description of drawings

Fig. 1 (left), (right) is the scanning electron microscope and the transmission electron microscope picture of embodiment 1 nano-copper catalyst respectively.

Fig. 2 is the X-ray diffraction spectrogram of embodiment 1 nano-copper catalyst.

3 is a CORR reaction performance diagram of the nano-copper catalyst of Example 1 in the MEA electrolyzer.

Fig. 4 is a graph showing the CO ₂ RR reaction performance of the nano-copper catalyst in Example 1 in the MEA electrolyzer.

Fig. 5 is a graph showing the test results of the CORR reaction stability of the nanometer copper catalyst in the MEA electrolyzer of Example 1.

Fig. 6 is a CORR reaction performance diagram of the nano-copper-palladium catalyst in the MEA electrolyzer of Example 2.

Figure 7 is the X-ray diffraction spectrum of the OD-Cu-350 catalyst of Comparative Example 1.

Fig. 8 is a transmission electron microscope image of the OD-Cu-350 catalyst of Comparative Example 1.

Fig. 9 is a graph of the CORR reaction performance of the OD-Cu-350 catalyst of Comparative Example 1 in the MEA electrolyzer.

Fig. 10 is the X-ray diffraction spectrum of comparative example 2 Cu-He-200, Cu-He-300, Cu-He-400, Cu-He-500 catalysts.

Fig. 11 is the X-ray diffraction spectrum of comparative example 3 Cu-H ₂ -150, Cu-H ₂ -250, Cu-H ₂ -350 catalysts.

Fig. 12 is a transmission electron microscope picture of the nano-copper catalyst.

detailed description

The whole process will be described in detail below through the accompanying drawings and embodiments, but the claims of the present invention are not limited by these embodiments. At the same time, the embodiment only provides some conditions for realizing this purpose, but it does not mean that these conditions must be met to achieve this purpose. The protection scope of the present invention should include all content of the claims.

Example 1

Weigh 1.7048g cupric chloride and dissolve in 300mL ultrapure water. Add 50mL of 1mol L ^-1 sodium borohydride solution dropwise into the cupric chloride solution. Stir for 20 min at room temperature, filter, and dry to obtain a nano-copper catalyst. Figure 1 (left) and (right) are the scanning and transmission electron microscope images of the nano-copper catalyst respectively. It can be seen from the figure that the catalyst is connected by particles with a particle size of 10-20 nm; it has a porous structure with a pore size of 50-20 nm. 100nm; and has a core-shell structure, with metallic copper in the middle and a layer of cuprous oxide of about 3-5nm on the outside. Figure 2 is the X-ray diffraction spectrum of the nano-copper catalyst, from which it can be seen that the catalyst consists of two phases of metallic copper and cuprous oxide.

The catalyst was painted on carbon paper to prepare a gas diffusion electrode with a catalyst loading of 1.5 mg cm ^-2 . In the MEA electrolyzer, the gas diffusion electrode is used as the working electrode, the Ti foam coated with iridium oxide is used as the counter electrode, and a layer of N-methylpiperidine-terphenyl copolymer (QAPPT) is sandwiched between the working electrode and the counter electrode. Anion membrane, the three form a membrane electrode sandwich structure. The cathode plate is a graphite plate with a gas flow field. The anode plate is a platinized titanium plate with a liquid flow field. In the actual reaction test, carbon monoxide or carbon dioxide gas is passed through the cathode, and KOH solution is passed through the anode. The test uses constant current mode. The cathode gas enters the chromatographic on-line analysis after being condensed, and the anode liquid is collected at the same time for liquid NMR analysis.

The reaction results in Figures 3, 4 and 5 show that the nano-copper catalyst is applied to the electrocatalytic reduction of carbon monoxide and exhibits high electrolytic performance. In the MEA electrolyzer, the C2 ₊ faradaic efficiency can reach up to 95%, and the current density can reach up to 3A cm ^-2 , the highest energy efficiency of the full cell is 39%, and it can be stably electrolyzed at 1A cm ^-2 for 30 hours. The catalyst is applied to the electrocatalytic reduction of carbon dioxide. In the MEA electrolyzer, the C ₂₊ faraday efficiency can reach 66%, and the partial current density can reach 331mA cm ^-2 .

Example 2

Get 50 mg of the nano-copper catalyst obtained in Example 1 in deoxygenated ultrapure water, sonicate for 30 minutes, add 1.39 mL of palladium chloride solution (1 g of palladium chloride is dissolved in 100 mL of 0.1 M hydrochloric acid), sonicate for 30 minutes, filter, and wash , dried to obtain nanometer copper palladium catalyst.

Under the same reaction conditions as in Example 1, it is used for the electrocatalytic reduction of carbon monoxide, and the reaction results in Fig. 6 show that the nano-copper palladium catalyst is applied to the electrocatalytic reduction of carbon monoxide, showing higher electrolytic performance, and in In the MEA electrolyzer, the C ₂₊ Faradaic efficiency reaches up to 93%, and the partial current density reaches up to 1.3A cm ^-2 . The comparison of Figure 6 with the data in Figure 3 in Example 1 shows that the introduction of palladium improves the selectivity of acetic acid, The Faradaic efficiency of acetic acid is up to 33%, and the partial current density is up to 572mA cm ^-2 .

Example 3

Take 50 mg of the nano-copper catalyst obtained in Example 1 in deoxygenated ultrapure water, sonicate for 30 minutes, add 2 mL of 25 mM silver nitrate solution, sonicate for 30 minutes, filter, wash, and dry to obtain the nano-copper-silver catalyst. The catalyst introduces the second component silver, which is beneficial to improve the selectivity of acetic acid, the faradaic efficiency of acetic acid is up to 42%, and the partial current density is up to 1012mAcm ^-2 .

Comparative example 1

50 mg of the nano-copper catalyst obtained in Example 1 was placed in a quartz boat, put into a muffle furnace, and heat-treated at 350° C. for 2 hours to obtain an OD-Cu-350 catalyst. Figure 7 is the X-ray diffraction spectrum of the OD-Cu-350 catalyst. It can be seen from the figure that the catalyst has only copper oxide phase. Figure 8 is the transmission electron microscope spectrum of OD-Cu-350 catalyst. It can be seen from the figure that after heat treatment, the particle size of the catalyst becomes larger, there is no core-shell structure, the crystallinity becomes better, and the grain boundary decreases.

The reaction results in Figure 9 show that the OD-Cu-350 catalyst is applied to the electrocatalytic reduction of carbon monoxide. In the MEA electrolyzer, the C ₂₊ faradaic efficiency is 92%, and the current density is 1.8A cm ^-2 , which is the same as the reaction in Example 1. Comparing the results, it can be seen that the nano-copper catalyst is not conducive to the improvement of catalytic performance after being roasted in the air. It is speculated that the reason is that the nano-copper catalyst completely becomes oxidized after being roasted in the air, loses the core-shell structure, and reduces the grain boundary. It is not conducive to the improvement of catalytic performance.

Comparative example 2

Take 50 mg of the nano-copper catalyst obtained in Example 1, place it in a quartz boat, put it into a quartz tube, and heat-treat it at 200, 300, 400, and 500° C. for 2 hours under the protection of high-purity helium gas to obtain Cu-He-200, Cu-He-300, Cu-He-400 Cu-He-500 catalyst. Fig. 10 is the X-ray diffraction spectrogram of Cu-He-200, Cu-He-300, Cu-He-400, Cu-He-500 catalyst, as can be seen from the figure, under inert atmosphere, heat treatment at different temperatures can The crystal phase of the catalyst changes, the higher the temperature, the more phases of cuprous oxide, and the higher the temperature, the larger the grain size and the reduction of the grain boundary, all of which will lead to the deterioration of the catalyst performance. When the Cu-He-300 catalyst is electrolyzed by CORR constant current, under the same current density condition, the voltage is 0.1V higher than that of the catalyst in Example 1, resulting in a decrease in energy efficiency.

Comparative example 3

Take 50 mg of the nano-copper catalyst obtained in Example 1, place it in a quartz boat, put it into a quartz tube, and heat-treat it at 150, 250, and 350°C for 3 hours under the protection of high-purity hydrogen to obtain Cu-H ₂ -150, Cu- H ₂ -250, Cu-H ₂ -350 catalysts. Fig. 11 is the X-ray diffraction spectrum of Cu-H ₂ -150, Cu-H ₂ -250, Cu-H ₂ -350 catalysts. It can be seen from the figure that after hydrogen reduction, there is only a metallic copper phase and no cuprous oxide phase, indicating that the oxide layer has been removed, and the higher the temperature, the sharper the peak shape, indicating that the grain size is larger. Compared with the nano-copper catalyst in Example 1, the CORR performance is much worse. Cu-H ₂ -150 catalyst under the same conditions, CORR electrolysis, C ₂₊ product faradaic efficiency is only 78%, the highest partial current density is only 946mA cm- ² . Cu-H ₂ -250 catalyst under the same conditions, CORR electrolysis, C ₂₊ product faradaic efficiency is only 88%, the highest partial current density is only 159mA cm- ² .

Example 4

Weigh 2.4160g copper nitrate and dissolve in 300mL ultrapure water. Add 50mL of 1mol L ^-1 sodium borohydride solution dropwise into the cupric chloride solution. Stir for 20 min at room temperature, filter, and dry to obtain a nano-copper catalyst. Figure 12 is a transmission electron microscope image of the nano-copper catalyst. It can be seen from the figure that the catalyst is connected by particles with a particle size of 10-20nm; it has a porous structure with a pore size of 50-100nm; and it has a core-shell structure with metallic copper in the middle and a layer of 3-5nm wrapped around it Cuprous oxide or so.

It can be seen from the above examples that the present invention can produce gram-level nano-copper catalysts in one step through the liquid phase reduction method. The nano-copper catalyst has a nano-porous structure with abundant defects and grain boundary structure. It is applied to the electrocatalytic reduction of carbon monoxide and exhibits high electrolytic performance. In the MEA electrolyzer, the C ₂₊ Faraday efficiency can reach up to 95%, and the current density The maximum energy efficiency can reach 3A cm ^-2 , and the energy efficiency of the whole battery can reach 39%, and it can be stably electrolyzed at 1A cm ^-2 for 30 hours. The catalyst is applied to the electrocatalytic reduction of carbon dioxide. In the MEA electrolyzer, the C ₂₊ Faradaic efficiency can reach 66%, and the partial current density can reach 331mA cm ^-2 .

It should be noted that, according to the above-mentioned embodiments of the present invention, those skilled in the art can fully realize the full scope of the independent claims and dependent rights of the present invention, and the implementation process and method are the same as the above-mentioned embodiments; and the present invention is not elaborated Some of them belong to well-known technologies in the art.

The above are only some specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

Claims (10)

1. a preparation method of nanometer copper-based catalyst, is characterized in that, comprises the following steps: Step 1: Dissolving the copper salt in ultrapure water to obtain a copper salt solution, the concentration of the copper salt solution is 0.01-0.2mol L ^-1 ; Step 2: adding sodium borohydride solution dropwise to the copper salt solution, stirring at room temperature for 5-60 minutes, filtering, and drying to obtain a nano-copper catalyst; the molar ratio of sodium borohydride to copper salt is 1-20, The concentration of the sodium borohydride solution is 0.1-1molL ^-1 . 2. a preparation method of nanometer copper-based two-component catalyst, is characterized in that, comprises the following steps: Step 1: Dissolving the copper salt in ultrapure water to obtain a copper salt solution, the concentration of the copper salt solution is 0.01-0.2mol L ^-1 ; Step 2: adding sodium borohydride solution dropwise to the copper salt solution, stirring at room temperature for 5-60 minutes, filtering, and drying to obtain a nano-copper catalyst; the molar ratio of sodium borohydride to copper salt is 1-20, The concentration of the sodium borohydride solution is 0.1-1molL ^-1 ; Step 3: Ultrasonically disperse the nano-copper catalyst in ultrapure water, add a second metal precursor under nitrogen protection, sonicate for 10-30 minutes, filter, and dry to obtain a nano-copper-based two-component catalyst; the The second metal precursor is soluble silver salt or soluble palladium salt; the concentration of the second metal precursor is 0.01-0.2mol L ^-1 ; the molar ratio of the second metal precursor to copper salt is 0.01 -0.2. 3. The preparation method according to claim 1 or 2, characterized in that: the copper salt is copper nitrate or copper chloride or copper acetate. 4. The preparation method according to claim 1 or 2, characterized in that: the concentration of the copper salt solution is 0.01-0.1 molL ^-1 . 5. the preparation method as claimed in claim 1 or 2 is characterized in that: the mol ratio of described sodium borohydride and copper salt is 5-10. 6. the preparation method as claimed in claim 2 is characterized in that: described soluble silver salt is silver nitrate, and soluble palladium salt is palladium chloride. 7. The preparation method according to claim 2, characterized in that: the concentration of the second metal precursor is 0.01-0.1mol L ^-1 ; the molar ratio of the second metal precursor to the copper salt is 0.1-0.2. 8. A catalyst prepared by the method according to claim 1 or 2, characterized in that, the catalyst is a nanoporous structure. 9. The catalyst according to claim 8, characterized in that: the catalyst is connected by particles with a particle size of 10-20 nm; it has a porous structure with a pore size of 50-100 nm; and it has a core-shell structure, and the interior is a metal Copper, surrounded by a layer of cuprous oxide of about 3-5nm. 10. The application of the catalyst according to claim 8 in the electrocatalytic reduction of carbon dioxide and/or carbon monoxide.

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