Preparation method of catalyst for low-concentration CO2 reduction based on macroporous resin and electroplating wastewater and application thereof

Abstract

The present application relates to a kind of preparation method of catalyst for low concentration CO2 reduction based on macroporous resin and electroplating wastewater, the catalyst obtained by the preparation method, using macroporous adsorption resin as raw material, by atomic level uniform dispersion heavy metal Ni, and adding sodium stearate, using temperature programming means and changing carbonization atmosphere, the structure of heavy metal coordination in catalyst can be controlled, form the catalytic site mainly with pyridine N3-heavy metal, preparation can be used to reduce non-pure CO2 Single-atom level catalyst.The catalyst has good conductivity, and CO2 in 10%-100% concentration can be efficiently reduced to CO, with the measure of reverse potential, the efficient and stable operation of catalyst system can be realized, and the system stability can be extended by one time.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a method for preparing a catalyst based on macroporous resin and electroplating wastewater for the reduction of low-concentration CO2 and its application. Background Technology

[0002] Currently, the electrochemical CO2 reduction reaction (ECO2RR) to prepare C1-C3 products is one of the important research directions in the field of CO2 reduction, which can realize the resource utilization of CO2 while controlling carbon emissions. In particular, CO is an important chemical intermediate, and significant progress has been made in its electrocatalytic synthesis research. Related pilot-scale explorations are also being carried out intensively, and it has initially shown the potential for industrial application.

[0003] However, the CO2 feedstocks used in the aforementioned studies are almost all high-purity CO2, and the high selectivity and stability achieved depend to some extent on the purity of the CO2. This means that in practical applications, the CO2 purification process is an indispensable step, and the production of high-purity CO2 is itself a high-energy-consuming process, mainly relying on CO2 capture technology. In contrast, research on electrocatalysis for low-concentration CO2 feedstocks is still very limited, despite its significant importance in practical applications.

[0004] Low-concentration CO2 has a wide range of sources, the most representative being flue gas from thermal power plants, where the CO2 concentration is typically 5%–40%, with N2 as the main byproduct and small amounts of other impurities. Directly utilizing this type of low-concentration CO2 source for electrocatalytic reduction holds great promise, but also faces numerous technical challenges.

[0005] However, the following problems still exist in the current preparation of SACs: (1) The main problems include competition for oxygen reduction reaction, poisoning of catalyst active sites by harmful gases, low conversion efficiency and limited mass transfer. These problems will lead to deactivation of catalyst surface and decrease in catalyst stability.

[0006] (2) Poor selectivity for single products In non-pure CO2 reduction systems, the presence of other gases, especially N2, inhibits sufficient contact between CO2 gas molecules and catalytic sites, reduces the contact frequency, results in poor product selectivity, and exacerbates and dominates side reactions.

[0007] In conclusion, synthesizing catalysts with high product selectivity in non-pure CO2 reduction systems while maintaining system stability is of practical significance for promoting electrocatalytic CO2 reduction. Summary of the Invention

[0008] This invention provides a method for preparing a catalyst based on macroporous resin and electroplating wastewater for the reduction of low-concentration CO2, and its application. The invention utilizes macroporous adsorption resin as a raw material, uniformly disperses heavy metals Ni or Fe at the atomic level, and adds sodium stearate to prepare a single-atom-level catalyst for the reduction of impure CO2. This catalyst exhibits good electrical conductivity and can efficiently reduce CO2 concentrations from 10% to 100% to CO. Combined with a reverse potential mechanism, the catalyst system can operate efficiently and stably, potentially doubling its stability.

[0009] Therefore, it is necessary to provide a method for preparing a catalyst based on macroporous resin and electroplating wastewater for the reduction of low-concentration CO2, comprising the following steps: S1. Mix macroporous adsorption resin with a solution containing transition metal ions, heat to adsorb, and obtain intermediate product; S2. The intermediate product is mixed with sodium stearate and heated under an inert gas atmosphere. Then, the mixture is heated under a mixed gas atmosphere to obtain the catalyst for low-concentration CO2 reduction based on macroporous resin and electroplating wastewater. The mixed gas is a mixture of an inert gas and a reducing gas.

[0010] Furthermore, the transition metal is selected from one or more of Fe and Ni.

[0011] Furthermore, in step S1, the temperature of the heating adsorption is 35-45℃.

[0012] Furthermore, the concentration of the solution containing transition metal ions is 100-130 mg / L.

[0013] Furthermore, the macroporous adsorption resin is selected from one or more of the following: strong acid sulfuric acid resin, strong acid hydrochloric acid resin, strong acid phosphoric acid resin, and strong acid sulfonic acid resin.

[0014] Furthermore, in the mixed gas, the volume ratio of reducing gas to inert gas is 1-3:97-99.

[0015] Specifically, the inert gas is argon, and the reducing gas is hydrogen.

[0016] Further, in step S2, the mass ratio of the intermediate product to sodium stearate is 1-2:1-3.

[0017] Furthermore, in step S2, the temperature of the heating reaction is 500-600℃.

[0018] Furthermore, in step S2, the temperature of the heating reaction is 800-900℃.

[0019] It is worth mentioning that in this invention, the structure of heavy metal coordination in the catalyst can be controlled by programmed temperature rise and changes in the carbonization atmosphere, forming catalytic sites dominated by pyridine N3-heavy metal, which can efficiently reduce impure CO2 gas sources. Specifically, Ar is used as a protective gas, and the temperature is raised from room temperature to 500-600℃ to allow C3N4 to form stably; the reaction is then carried out at this temperature for a certain period of time to further stabilize C3N4; then H2 and Ar are used as reducing gases, and the temperature is raised to 800-900℃ to disintegrate C3N4 and stimulate the formation of surface catalytic sites.

[0020] The present invention also provides an application of the product prepared by the above preparation method in the reduction of CO2.

[0021] Specifically, by reversing the potential, an opposite potential is applied to the catalyst poisoned on the catalytic site surface, thereby clearing the surface-adsorbed state of the catalyst. CO is used to extend the overall lifespan of the system. The specific operating steps are as follows: In the electrocatalytic process, when the selectivity for CO drops below 70%, a reversal potential is applied to change the reduction potential to an oxidation potential.

[0022] Specifically, the applied oxidation potential is typically 1.0-1.8 V vs. RHE, and after about 5-10 min, the surface-adsorbed CO is oxidized. Then, it is used for CO2 reduction and electrocatalysis continues. When the selectivity for CO decreases to 70%, the above steps are repeated.

[0023] The present invention has the following beneficial effects: This invention utilizes macroporous adsorption resin as raw material, uniformly disperses heavy metal Ni at the atomic level, adds sodium stearate, and employs programmed temperature rise and alteration of the carbonization atmosphere to control the coordination structure of heavy metals in the catalyst, forming catalytic sites dominated by pyridine N3- heavy metal, enabling efficient reduction of impure CO2 gas sources. Specifically, Ar is used as a protective gas, raising the temperature from room temperature to 500-600℃ to stabilize the formation of C3N4; the reaction is then maintained at this temperature for a specified time to further stabilize C3N4; finally, H2 and Ar are used as reducing gases, and the temperature is raised to 800-900℃ to disintegrate C3N4 and stimulate the formation of surface catalytic sites.

[0024] The catalyst synthesized in this invention has a wide range of adaptability and can effectively reduce CO2 concentrations of 10%-100%. Its surface exhibits good resistance to poisoning, high selectivity, and stability. In addition, the catalyst has good electrical conductivity. Combined with reverse potential measures, the catalyst system can operate efficiently and stably, and the stability of the system can be doubled. Attached Figure Description

[0025] Figure 1 (a)-(j) show electron microscope images of the catalysts of Example 1 and Comparative Examples 1-3; Figure 2 (a) shows the catalyst BET and its pore distribution; Figure 2 (b) demonstrates the catalyst's CO2 adsorption capacity; Figure 3 (a) shows the molecular structure of the catalyst; Figure 3 (b) shows the EXANES results for the catalyst; Figure 3 (c) shows the wavelet radiation results of the catalyst; Figure 3 (d) shows the XPS peak fractionation results of the catalyst's N1s; Figure 4 The product selectivity of single-atom catalysts reducing CO2 of different concentrations was demonstrated; Figure 5 (a)-(j) show the long-term stability test of CO2 reduction at high current density with different concentrations; Figure 6 (a)-(j) show the long-term stability test of CO2 reduction at different concentrations after the application of reverse potential (100% CO2 not applied); Figure 7 The system stability under 100% CO2 reduction was demonstrated when the reverse potential was repeatedly applied. Detailed Implementation

[0026] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0027] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0028] It should be understood that, except in any operational instance or otherwise indicated, all figures representing the amounts of ingredients used, for example, in the specification and claims, should be understood to be modified in all cases by the term "about". Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximations varying with the desired performance to be obtained according to the invention.

[0029] Macroporous adsorption resin: HPR1200 Na ion strong acid resin, purchased from DuPont.

[0030] The Ni-containing electroplating wastewater was taken from the wastewater of an electroplating workshop in Meizhou City, with a Ni concentration of ~130 mg / L.

[0031] Example 1 A method for preparing a catalyst based on macroporous resin and electroplating wastewater for the reduction of low-concentration CO2 includes the following steps: S1. Place the macroporous adsorption resin in the adsorption filter and heat it to 40℃ to adsorb Ni-containing electroplating wastewater for 24 hours. Then, place the macroporous resin that adsorbs heavy metals in 0.1 mol / L hydrochloric acid for performance regeneration. Repeat the regeneration multiple times until the adsorbent can no longer adsorb heavy metals. After drying, the intermediate product is obtained. S2. The intermediate product is mixed with sodium stearate (the mass ratio of intermediate product to sodium stearate is 1:1). Under an Ar atmosphere, the temperature is increased from room temperature to 550°C at a rate of 2.5°C / min and maintained for 6 hours. Then, under a mixed gas atmosphere of H2 and Ar with a volume ratio of 1:99, the temperature is increased from 550°C to 900°C at a rate of 5°C / min and maintained at 900°C for 2 hours. After cooling, the mixture is acid-washed with 2 mol / L sulfuric acid to obtain the catalyst for low-concentration CO2 reduction based on macroporous resin and electroplating wastewater.

[0032] Example 2 A method for preparing a catalyst based on macroporous resin and electroplating wastewater for the reduction of low-concentration CO2 includes the following steps: S1. Place the macroporous adsorption resin in the adsorption filter and heat it to 42℃ to adsorb Ni-containing electroplating wastewater for 24 hours. Then, place the macroporous resin that adsorbs heavy metals in 0.1 mol / L hydrochloric acid for performance regeneration. Repeat the regeneration multiple times until the adsorbent can no longer adsorb heavy metals. After drying, the intermediate product is obtained. S2. The intermediate product is mixed with sodium stearate (the mass ratio of intermediate product to sodium stearate is 1:1). Under an Ar atmosphere, the temperature is increased from room temperature to 550°C at a rate of 2.5°C / min and maintained for 6 hours. Then, under a mixed gas atmosphere of H2 and Ar with a volume ratio of 1:99, the temperature is increased from 550°C to 900°C at a rate of 5°C / min and maintained at 900°C for 3 hours. After cooling, the mixture is acid-washed with 2 mol / L sulfuric acid to obtain the catalyst for low-concentration CO2 reduction based on macroporous resin and electroplating wastewater.

[0033] Example 3 A method for preparing a catalyst based on macroporous resin and electroplating wastewater for the reduction of low-concentration CO2 includes the following steps: S1. Place the macroporous adsorption resin in the adsorption filter and heat it to 37°C to adsorb Ni-containing electroplating wastewater for 24 hours. Then, place the macroporous resin that adsorbs heavy metals in 0.1 mol / L hydrochloric acid for performance regeneration. Repeat the regeneration multiple times until the adsorbent can no longer adsorb heavy metals. After drying, the intermediate product is obtained. S2. The intermediate product is mixed with sodium stearate (the mass ratio of intermediate product to sodium stearate is 1:1). Under an Ar atmosphere, the temperature is increased from room temperature to 550°C at a rate of 2.5°C / min and maintained for 6 hours. Then, under a mixed gas atmosphere of H2 and Ar with a volume ratio of 1:99, the temperature is increased from 550°C to 900°C at a rate of 5°C / min and maintained at 900°C for 2.5 hours. After cooling, the mixture is acid-washed with 2 mol / L sulfuric acid to obtain the catalyst for low-concentration CO2 reduction based on macroporous resin and electroplating wastewater.

[0034] Comparative Example 1 A method for preparing a catalyst based on macroporous resin and electroplating wastewater for the reduction of low-concentration CO2. The difference between this comparative example and Example 1 is that sodium stearate is replaced with sodium palmitate in step S2, while the other components and preparation methods are the same.

[0035] Comparative Example 2 A method for preparing a catalyst based on macroporous resin and electroplating wastewater for the reduction of low-concentration CO2. The difference between this comparative example and Example 1 is that step S2 is as follows: S2. The intermediate product is mixed with sodium stearate (the mass ratio of intermediate product to sodium stearate is 1:1). Under Ar atmosphere, the temperature is increased from room temperature to 550℃ at a rate of 2.5℃ / min and maintained for 6 hours. Then, under Ar atmosphere, the temperature is increased from 550℃ to 900℃ at a rate of 5℃ / min and maintained at 900℃ for 2 hours. After cooling, the mixture is acid-washed with 2 mol / L sulfuric acid to obtain the catalyst for low-concentration CO2 reduction based on macroporous resin and electroplating wastewater. The other components and preparation methods are the same.

[0036] Comparative Example 3 A nano-silver catalyst, the nano-silver catalyst being purchased from Maclean, brand name S699200.

[0037] Test Example 1 The catalysts obtained in Example 1 and Comparative Examples 1-3 were compared in terms of cost, performance, and morphology. The instruments used for testing included BET, scanning electron microscopy, transmission electron microscopy, solid conductivity meter, and aberration-corrected transmission electron microscopy. The results are shown in Table 1.

[0038] Table 1. Comparison of various parameters of the catalysts prepared in Example 1 and Comparative Examples 1-3 Test Example 2 The catalysts obtained in Example 1 and Comparative Examples 1-3 were compared by CO selectivity testing and other electrochemical tests.

[0039] The testing method involved applying different potentials or using the cyclic voltammetry method. The results are shown in Table 2.

[0040] Table 2 Electrochemical tests of Example 1 and Comparative Examples 1-3 As can be seen from Tables 1 and 2, compared to Comparative Examples 1-3, the single-atom catalyst of this invention exhibits excellent selectivity, similar to Comparative Examples 1 and 3, especially in the reduction of low-concentration CO2, where its selectivity for CO is significantly better than that of Comparative Example 3. The double-layer capacitance and electrochemically active specific surface area are both superior to those of Comparative Examples 1-3. In summary, the catalyst of this invention can achieve or even surpass the performance of commercially available products.

[0041] Test Example 3 The selectivity of the catalysts for CO, the distribution of single atoms on the catalyst surface, and the coordination of single atoms were tested for the catalysts of Example 1 and Comparative Examples 1-3. Test results are as follows Figure 1-7 As shown, Figure 1 As shown in (a)-(b), the carbonized catalyst in Example 1 has a large number of uniformly distributed single-atom Ni atoms on its surface; Figure 1 As shown in (c), the white bright spots, i.e. Ni single atoms, are uniformly distributed on the catalyst surface without any agglomeration. Figure 1 In (d)-(e), the catalyst after carbonization in Comparative Example 1 also exhibits a large number of uniformly distributed single-atom Ni atoms on its surface; such as Figure 1 As shown in (f), the white bright spots, i.e. Ni single atoms, are uniformly distributed on the catalyst surface without any agglomeration. Figure 1 In (g)-(h), the carbonized catalyst in Comparative Example 2 also exhibits Ni nanoparticles (white, reaching the size of grain cells) on its surface; it also contains composites of some Ni single atoms and clusters, such as... Figure 1 As shown in (i). Figure 1 (j) is an electron microscope image of Comparative Example 3, in which the particles are silver nanoparticles with a size of approximately 60-120 nm.

[0042] like Figure 1 As shown in (b), the scanning electron microscope image shows that after high-temperature carbonization, a large number of carbon nanotubes are generated on the surface. These carbon nanotubes have a diameter of about 200 nm and a loose and porous structure, which can provide a large specific surface area for the catalyst. Figure 2 (a) shows the catalyst BET and its pore distribution; Figure 2 (b) demonstrates the catalyst's CO2 adsorption capacity; it can be seen that the adsorption capacity for CO2 is also excellent.

[0043] like Figure 3 As shown in (a)-(d), the composition and coordination morphology of the single-atom Ni in this catalyst are shown. As can be seen from (a), the single-atom coordination morphology is Ni-N3 coordination. Figure 3 (b) and (c) show that the catalyst is a mixture of non-single atoms and nanoparticles with high purity. Figure 3 (d) indicates that the N in the catalyst is all pyridine N.

[0044] During electrochemical catalysis, this catalyst maintains a Faradaic efficiency (FE) of 70% or higher for CO within the 10%-100% CO2 range, while the selectivity for H2 is less than 10%, indicating that the catalyst has extremely high selectivity for CO. Figure 4 Comparative Example 1 showed similar performance to the Example, while Comparative Examples 2 and 3 were significantly weaker than the Example and Comparative Example 1 in low-concentration CO2 reduction systems. Direct ECO2RR in a commercial module could achieve a reduction rate of 100 mA / cm². 2 It can still maintain 90% FE under high current. CO Moreover, the corresponding full-cell potential difference is also relatively small, ensuring a certain energy efficiency. Furthermore, by applying the reversal potential, the stability of the system can be effectively extended. For the reduction of non-pure CO2, the service life can be doubled, while for the reduction of 100% CO2, the system stability and high CO selectivity can be maintained for 200 hours, thus showing certain prospects for large-scale application.

[0045] Figure 5 (a)-(j) show the long-term stability test of CO2 reduction at high current density with different concentrations; from Figure 5 (a)-(j) show that the higher the CO2 concentration, the longer the system remains stable. At 100% CO2 concentration, the stability exceeds 10 hours, but at 10% CO2 concentration, the stability is only maintained for 3 hours (FE). CO >70%).

[0046] Figure 6 (a)-(j) show the long-term stability test of CO2 reduction at different concentrations after the application of reverse potential (100% CO2 not applied); from Figure 6 (a)-(j) show that applying an oxidation potential (1.0 V vs. RHE) to the catalyst surface for 5 min removes the surface adsorbed state. CO is used to regenerate the electrode. After this technology is applied, the stability is significantly increased. Even at high current densities, it can improve the stability of low-concentration CO2 reduction, and the stability is generally extended by 80% or more.

[0047] Figure 7 The system stability during 100% CO2 reduction under repeated application of reverse potential is demonstrated; from Figure 7 It can be seen that by continuously implementing surface cleaning technology with 100% CO2 concentration, the stability can eventually be improved from... Figure 6 The 20h period has been extended to 200h.

[0048] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0049] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a catalyst based on macroporous resin and electroplating wastewater for the reduction of low-concentration CO2, characterized in that, Includes the following steps: S1. Mix macroporous adsorption resin with a solution containing transition metal ions, heat to adsorb, and obtain intermediate product; S2. The intermediate product is mixed with sodium stearate and heated under an inert gas atmosphere. Then, the mixture is heated under a mixed gas atmosphere to obtain the catalyst for low-concentration CO2 reduction based on macroporous resin and electroplating wastewater. The mixed gas is a mixture of an inert gas and a reducing gas.

2. The method for preparing the catalyst based on macroporous resin and electroplating wastewater for low-concentration CO2 reduction according to claim 1, characterized in that, The transition metal is selected from one or more of Fe and Ni.

3. The method for preparing the catalyst based on macroporous resin and electroplating wastewater for low-concentration CO2 reduction according to claim 1, characterized in that, In step S1, the temperature for heating and adsorption is 35-45℃.

4. The method for preparing the catalyst based on macroporous resin and electroplating wastewater for low-concentration CO2 reduction according to claim 1, characterized in that, The concentration of the solution containing transition metal ions is 100-130 mg / L.

5. The method for preparing the catalyst based on macroporous resin and electroplating wastewater for low-concentration CO2 reduction according to claim 1, characterized in that, The macroporous adsorption resin is selected from one or more of the following: strong acid sulfuric acid resin, strong acid hydrochloric acid resin, strong acid phosphoric acid resin, and strong acid sulfonic acid resin.

6. The method for preparing the catalyst based on macroporous resin and electroplating wastewater for low-concentration CO2 reduction according to claim 1, characterized in that, In the mixed gas, the volume ratio of reducing gas to inert gas is 1-3:97-99.

7. The method for preparing the catalyst based on macroporous resin and electroplating wastewater for low-concentration CO2 reduction according to claim 1, characterized in that, In step S2, the mass ratio of the intermediate product to sodium stearate is 1-2:1-3.

8. The method for preparing the catalyst based on macroporous resin and electroplating wastewater for low-concentration CO2 reduction according to claim 1, characterized in that, In step S2, the temperature of the heating reaction is 500-600℃.

9. The method for preparing the catalyst based on macroporous resin and electroplating wastewater for low-concentration CO2 reduction according to claim 1, characterized in that, In step S2, the temperature of the heating reaction is 800-900℃.

10. The application of a product prepared by any one of claims 1-9 in the reduction of CO2, characterized in that, Includes the following steps: In the electrocatalytic process, when the selectivity for CO drops below 70%, a reversal potential is applied to change the reduction potential to an oxidation potential.

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