Bimetallic oxide catalysts and their preparation methods and methods for CO reduction to CO

Abstract

This application discloses a bimetallic oxide catalyst, its preparation method, and a method for CO reduction to CO, belonging to the field of chemical engineering. The bimetallic oxide in this application has the chemical formula Cu-M1O / M2M3-LDO; Cu includes Cu... 0 and Cu + M1 is Ni, Co, or Fe; M2 includes Cu. 2+ And an auxiliary divalent metal ion, the auxiliary divalent metal ion being Mg 2+ Zn 2+ Co 2+ Fe 2+ and Ni 2+ At least one of them; M3 is Al 3+ Fe 3+ Mn 3+ or Ga 3+ The bimetallic oxide catalyst provided in this application effectively modulates the structure, electronic valence state distribution, and defects of M2M3-LDO by introducing M1O, thereby increasing the number of active sites Cu. + The quantity and oxygen vacancy defects of the catalyst enable improved CO2-to-CO selectivity under mild reaction conditions; the catalyst can achieve excellent performance without precious metals, thus improving the large-scale application of DACC.

Description

Technical Field

[0001] This application relates to the field of chemical technology, and in particular to a bimetallic oxide catalyst, its preparation method, and a method for reducing CO2 to produce CO. Background Technology

[0002] Against the backdrop of global warming and the continued intensification of the greenhouse effect, carbon dioxide (CO2) emission reduction has become a core issue of international concern. Compared with traditional point-source carbon capture technologies, Direct Air Carbon Capture and Conversion (DACC) technology has gradually become a research hotspot due to its potential for "negative carbon emissions" and its advantages of not being geographically restricted by emission sources. This technology can directly capture CO2 in the air environment and achieve in-situ catalytic conversion, avoiding the energy-intensive gas separation and long-distance transportation steps in traditional carbon capture processes, thus theoretically offering lower system energy consumption and greater process flexibility.

[0003] However, existing DACC technology still faces significant challenges in practical applications. On the one hand, in the capture stage, the volume fraction of CO2 in the air is only about 0.04%, and its ultra-low concentration significantly reduces the adsorption driving force. Moreover, fluctuations in ambient humidity can easily lead to competitive adsorption or instability of material structure. Existing studies have shown that porous solid adsorbents generally suffer from decreased adsorption capacity and insufficient cycle stability under humid air conditions. In the literature "On CO2Capture Capacity and Mechanisms for Zeolite Templated Carbon, MOF-199, and 13X Zeolite in Dry and Humid Conditions," Separation and Purification Technology, 363 (2025) 132080, the authors found that under humid conditions, the CO2 adsorption capacity of MOF-199 decreased by 16.7%, and that of 13X zeolite decreased by 15.4%. This indicates that because H2O molecules in the air are smaller and more polar, they preferentially occupy adsorption sites, leading to a direct reduction in CO2 adsorption capacity. On the other hand, in the conversion process, CO2 molecules possess high thermodynamic stability, and their conversion typically relies on high temperatures or additional energy input, making it difficult to meet the low-energy consumption requirements of air capture scenarios. To reduce system costs and improve conversion efficiency, non-precious metal catalysts have gradually gained attention, among which Cu-based catalysts, due to their unique d-electron structure, are advantageous... The formation of key intermediates such as COOH promotes the reverse water-gas shift reaction (RWGS). Simultaneously, Cu exhibits multivalent state characteristics, including metallic Cu... 0It possesses moderate hydrogen activation capability, while Cu + This is beneficial for the adsorption and activation of carbonyl-containing species, and the synergistic effect of the two can significantly improve CO2 conversion efficiency. However, in the actual reaction process, Cu... + The valence state is prone to change and the catalyst's microstructure stability is insufficient, leading to catalytic performance degradation and limiting its long-term application in DACC systems. In the paper "Integrated CO2Capture and Conversion by a Robust Cu(I)-Based Metal-Organic Framework," J. Am. Chem. Soc. 2024, 146, 39, 27006–27013, the authors found through capture-conversion experiments that traditional Cu(I)-MOF is easily oxidized to Cu(II) in the presence of air and moisture, resulting in a sharp decrease in CO2 capture selectivity and conversion activity. Framework collapse and Cu species aggregation during the reaction further exacerbate performance degradation, indicating that Cu... + Instability is a key factor limiting its long-term application in DACC systems; therefore, it is urgent to address the Cu content in the catalyst. + Instability issues. Summary of the Invention

[0004] This application provides a bimetallic oxide catalyst and its preparation method, as well as a method for CO2 reduction to CO. The main purpose is to solve the problems of poor catalyst stability and low catalytic activity, which in turn lead to low CO2 adsorption capacity and low selectivity.

[0005] To achieve the above objectives, according to one aspect of this application, a bimetallic oxide catalyst is provided, the chemical formula of which is Cu-M1O / M2M3-LDO; wherein,

[0006] Cu in Cu-M1O includes Cu 0 and Cu + ; M1 is a non-precious metal, and M1 can be Ni, Co, or Fe; M2 is a divalent metal ion, including Cu. 2+ And auxiliary divalent metal ions, the auxiliary divalent metal ions being selected from Mg 2+ Zn 2+ Co 2+ Fe 2+ and Ni 2+ At least one of them; M3 is a trivalent metal ion, M3 is Al 3+ Fe 3+ Mn 3+ or Ga 3+ ; M2M3-LDO is a mixed metal oxide composed of M2 and M3; Cu-M1O loaded on M2M3-LDO.

[0007] Furthermore, Cu-M1O consists of Cu nanoparticles, cuprous oxide particles, and M1O nanoparticles, while M2M3-LDO is a defect-type mixed metal oxide composed of M2 and M3; Cu nanoparticles, cuprous oxide particles, and M1O nanoparticles are all loaded on the surface and within the pores of M2M3-LDO.

[0008] Furthermore, the framework material of M2M3-LDO contains Cu. + .

[0009] Furthermore, the weight of M1O nanoparticles is 1 to 5% of the weight of M2M3-LDO.

[0010] Furthermore, the ratio of the total molar amount of M2 and M3 to the molar amount of M1 is (20~30):1, preferably (22~26):1.

[0011] Furthermore, Cu in bimetallic oxide catalysts + species relative to Cu species, Cu + The relative atomic percentage of species is 35-50%, among which Cu species include Cu². + Cu + and Cu 0 .

[0012] Furthermore, Cu in bimetallic oxide catalysts + species relative to Cu species, Cu + The relative atomic percentage of species is 38-45%.

[0013] Furthermore, M1 is Ni or Co.

[0014] Furthermore, M2 is Mg 2+ Zn 2+ or Ni 2+ .

[0015] Furthermore, M3 is Al 3+ Fe 3+ or Mn 3+ .

[0016] Further, Cu-M1O / M2M3-LDO is Cu-NiO / CuMgAl-LDO, Cu-CoO / CuZnAl-LDO, Cu-NiO / CuMgFe-LDO, Cu-FeO / CuNiGa-LDO, Cu-NiO / CuZnMn-LDO, Cu-NiO / CuMgZnAl-LDO or Cu-NiO / CuMgCoAl-LDO; Furthermore, the specific surface area of ​​the bimetallic oxide catalyst is 120~200 m². 2 / g.

[0017] Furthermore, the pore volume of the bimetallic oxide catalyst is 0.5~0.9 cm³. 3 / g.

[0018] According to a second aspect of this application, a method for preparing a bimetallic oxide catalyst is provided, the method comprising the following steps: Step S1: Mix M2 salt, M3 salt and alkaline solution I, and react I to obtain the hydrotalcite precursor M2M3-LDH; wherein, M2 salt includes a divalent copper salt and an auxiliary divalent metal salt, the auxiliary divalent metal salt being selected from at least one of divalent magnesium salt, divalent zinc salt, divalent cobalt salt, divalent iron salt and divalent nickel salt; M3 salt is a trivalent aluminum salt, trivalent iron salt, trivalent manganese salt or trivalent gallium salt; Step S2: Mix M2M3-LDH and M1 salt II to obtain M1 / M2M3-LDH precursor; wherein, M1 salt is a divalent nickel salt, a divalent cobalt salt, or a divalent iron salt; Step S3: The M1 / M2M3-LDH precursor is subjected to heating reduction treatment to obtain the supported bimetallic oxide catalyst Cu-M1O / M2M3-LDO.

[0019] Furthermore, in step S1, the M2 salt is M2 nitrate.

[0020] Furthermore, M3 salt is M3 nitrate.

[0021] Furthermore, the alkaline solution is an aqueous solution of potassium hydroxide and / or an aqueous solution of sodium hydroxide.

[0022] Furthermore, the concentration of the alkaline solution is 0.70 mol / L to 1.20 mol / L.

[0023] Further, Mixture I specifically includes: first mixing M2 salt, M3 salt and deionized water I to obtain a metal salt mixture; then mixing the metal salt mixture with an alkaline solution to obtain mixture I.

[0024] Furthermore, reaction I is a coprecipitation reaction.

[0025] Further, in step S1, the molar ratio of salt M2 to salt M3 is (0.015~0.025):(0.005~0.010).

[0026] Furthermore, the molar ratio of M2 salt to M3 salt is (2~4):1.

[0027] Furthermore, deionized water I does not contain CO2.

[0028] Furthermore, the pH value of mixture I is 9-10.

[0029] Furthermore, reaction I is carried out in a nitrogen atmosphere.

[0030] Furthermore, the temperature of reaction I is 75~85℃.

[0031] Furthermore, the product of reaction I was successively washed, separated, and vacuum dried to obtain the hydrotalcite precursor.

[0032] Furthermore, in step S2, salt M1 is nitrate M1.

[0033] Furthermore, based on the weight of element M1, the weight ratio of M1 salt to M2M3-LDH is (0.8~5):100.

[0034] Furthermore, the weight ratio of M1 salt to M2M3-LDH is (1~5):100.

[0035] Further, Mixture II specifically includes: mixing M2M3-LDH, M1 salt and deionized water II in an inert atmosphere to obtain Mixture II; then evaporating the solvent in Mixture II to obtain the M1 / M2M3-LDH precursor.

[0036] Furthermore, deionized water II does not contain CO2.

[0037] Furthermore, in step S3, the conditions for the heating reduction treatment include: being carried out in a hydrogen-nitrogen mixed atmosphere, with a heating rate of 2~10℃, a heating temperature of 250~350℃, and a heating time of 2~4h.

[0038] Furthermore, the heating temperature is 250~300℃, and the heating time is 2~3 hours.

[0039] According to a third aspect of this application, a method for preparing CO by CO2 reduction is provided, comprising a catalyst; the catalyst is the above-described bimetallic oxide catalyst or the bimetallic oxide catalyst obtained by the above preparation method.

[0040] Compared with the prior art, the technical solution of this application has at least the following technical effects: The bimetallic oxide catalyst Cu-M1O / M2M3-LDO provided in this application effectively modulates the structure, electronic valence state distribution, and defects of M2M3-LDO by introducing M1O, thereby increasing the number of active sites Cu. + By reducing the number of oxygen vacancies and defects, the selectivity of CO products can be improved under mild reaction conditions; moreover, the catalyst can achieve excellent performance without precious metals, reducing material and energy costs and improving the economic feasibility of large-scale application of DACC technology. Attached Figure Description

[0041] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application. The illustrative embodiments and descriptions of the application are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The X-ray diffraction (XRD) pattern of the bimetallic oxide catalyst prepared in Example 1 of this application. Figure 2 This is one of the high-resolution transmission electron microscopy (HERTEM) images of the bimetallic oxide catalyst prepared in Example 1 of this application. Figure 3 This is the second high-resolution transmission electron microscope image (HERTEM) of the bimetallic oxide catalyst prepared in Example 1 of this application. Figure 4 This is one of the X-ray photoelectron spectra (XPS) of the bimetallic oxide catalyst prepared in Example 1 of this application. Figure 5 The second X-ray photoelectron spectrum (XPS) of the bimetallic oxide catalyst prepared in Example 1 of this application. Figure 6 Raman Auger spectrum of the bimetallic oxide catalyst prepared in Example 1 of this application. Figure 7 The electron paramagnetic resonance (EPR) image of the bimetallic oxide catalyst prepared in Example 1 of this application. Figure 8 This is a bar chart showing the in-situ conversion results of the bimetallic oxide catalyst prepared in Example 1 of this application under a hydrogen atmosphere; Figure 9 and Figure 10 This is a bar chart showing the cyclic stability of the bimetallic oxide catalyst prepared in Example 1 of this application during the capture-conversion process. Detailed Implementation

[0042] As described in the background section, traditional catalysts are structurally unstable or have low activity. This research focuses on layered double hydroxides (LDHs), which possess a unique layered structure and tunable basic sites, showing promising application prospects in CO2 capture. Their interlayer anions and surface basic sites effectively promote the synergistic reaction of CO2 and H2O to form carbonates or bicarbonates, thereby achieving efficient CO2 fixation and providing a new approach to coupling capture and conversion processes. LDHs exhibit certain stability under humid air conditions, and their adsorption performance can be optimized by controlling the metal composition. Furthermore, layered double oxides (LDHs) obtained from the thermal conversion of LDHs further demonstrate excellent catalytic performance. LDOs materials are typically rich in lattice oxygen, metal-oxygen bridging structures, and oxygen vacancy defects. These structural features synergistically form high-density active basic centers, significantly enhancing the Lewis basicity of the material surface and facilitating the activation of CO2 molecules. In addition, LDOs retain the good structural tunability of LDHs, and the adsorption-catalysis performance can be optimized by adjusting the type and ratio of metals.

[0043] Therefore, this application develops a novel bifunctional material system. By rationally constructing an LDO structure and introducing stable Cu active sites, it achieves synergistic enhancement of efficient CO2 capture and low-temperature catalytic conversion, while improving the structural stability and recyclability of the bifunctional material. This system does not require the use of precious metals, significantly reducing material usage costs and greatly improving the economics of DACC technology in large-scale applications. It provides a new approach for carbon capture and low-temperature CO conversion in air pollution scenarios.

[0044] According to one aspect of this application, a bimetallic oxide catalyst is provided, the chemical formula of which is Cu-M1O / M2M3-LDO; Cu in Cu-M1O includes Cu 0 and Cu + ; M1 is a non-precious metal, and M1 can be Ni, Co, or Fe; Cu-M1O is a complex of Cu and M1O; M2 is a divalent metal ion, including Cu. 2+ And auxiliary divalent metal ions, the auxiliary divalent metal ions being selected from Mg 2+ Zn 2+ Co 2+ Fe 2+ and Ni 2+ At least one of them; M3 is a trivalent metal ion, M3 is Al 3+Fe 3+ Mn 3+ or Ga 3+ ; M2M3-LDO is a mixed metal oxide composed of M2 and M3; Cu-M1O loaded on M2M3-LDO.

[0045] The Cu-NiO / CuMgAl-LDO catalyst of this application is formed by reducing and calcining an LDH precursor to create a defect-type mixed metal oxide framework, the surface of which is rich in lattice oxygen (O²⁻). - The LDO framework contains metal-oxygen bridging structures (M–O–M) and abundant oxygen vacancy defects. These structural units synergistically construct high-density basic active centers, significantly enhancing the Lewis basicity of the material surface, thereby improving the adsorption and activation capacity for CO2 molecules. Specifically, the Mg–O basic sites facilitate the chemisorption of CO2 molecules and the formation of carbonate / bicarbonate intermediates; bridging structures such as Cu–O–Mg and Cu–O–Al can regulate local electron distribution, promoting electron transfer to CO2 molecules and achieving polarization and bending activation of CO2 molecules. Simultaneously, oxygen vacancy defects in the LDO framework can serve as electron enrichment centers, further enhancing the adsorption strength of CO2 and stabilizing key reaction intermediates. On the other hand, the highly dispersed Cu formed during the reduction process... + / Cu 0 A synergistic interface is formed between the active sites and NiO nanoparticles, in which Cu 0 The site is conducive to the dissociation of H2 to generate active hydrogen species, Cu + The site promotes the adsorption and activation of CO2 and oxygen-containing intermediates, while NiO can further regulate the electronic structure of Cu species and enhance the surface oxygen migration ability, thereby achieving efficient coupling of CO2 capture and hydrogenation conversion process.

[0046] Specifically, the bimetallic oxide catalyst provided in this application can selectively capture low-concentration CO2 from the air and convert it in situ into CO and CH4 under low-temperature conditions in a H2 / N2 reducing atmosphere; the introduction of M1O effectively regulates the electronic structure and reduction behavior of Cu species by constructing the M1–O–Cu interface and enhancing the metal-support interaction, thereby inhibiting Cu²⁺… + Excessive reduction to Cu 0 This improves the Cu content on the catalyst surface. + The proportion of active sites. Simultaneously, M1O induces more oxygen vacancy defects and local lattice distortion in the LDO framework, promoting surface electron redistribution and enhancing the adsorption, polarization, and activation capabilities of CO2 molecules. Among these, Cu... + Sites and oxygen vacancies favor CO2 and The stability of key intermediates such as COOH, and Cu 0These sites promote H2 dissociation and the generation of active hydrogen species. During the CO2 capture-in-situ hydrogenation conversion process, the Cu on the catalyst surface... + / Cu 0 The ratio and oxygen vacancy concentration will be dynamically reconstructed and cyclically adjusted as the reaction proceeds, thereby achieving synergistic coupling of CO2 activation and H2 hydrogen donation, inhibiting deep hydrogenation reactions, and improving CO product selectivity.

[0047] In some specific embodiments, Cu-M1O in Cu-M1O / M2M3-LDO consists of Cu nanoparticles, cuprous oxide particles, and M1O nanoparticles, while M2M3-LDO is a defect-type mixed metal oxide composed of M2 and M3. The Cu nanoparticles, cuprous oxide particles, and M1O nanoparticles are all loaded onto the surface and within the channels of M2M3-LDO. The particle size of the Cu nanoparticles is 4.0~6.3 nm. The weight of the M1O nanoparticles is 1~5% of the weight of M2M3-LDO, for example, any value from 1%, 2%, 3%, 4%, 5%, or any range between two values. The framework material of M2M3-LDO contains Cu. + .

[0048] In some specific embodiments, the ratio of the total molar amount of M2 and M3 to the molar amount of M1 is (20~30):1, for example (22~26):1, or even 1:(24~25), specifically 1:24.4. Controlling this ratio is beneficial for promoting catalyst structural stability and improving the catalyst's ability to capture CO2.

[0049] In some specific embodiments, Cu in the bimetallic oxide catalyst + species relative to Cu species, Cu + The relative atomic percentage of a species is 35-50%, for example, any value or range between 35%, 38%, 40%, 42%, 45%, 48%, and 50%, or 38-45%, specifically 40-42%; Cu species include Cu². + Cu + and Cu 0 .like Figure 4 and Figure 5 XPS results showed that Cu²⁺ was present on the catalyst surface. + With partially reduced Cu species (Cu) + / Cu 0 The reduced Cu may originate from the reduction of some Cu species in the LDO framework and the active sites of highly dispersed Cu nanoparticles formed by surface enrichment; the proportion of monovalent copper in the copper species can be determined by Raman spectroscopy; the role of monovalent copper is in the CO2 capture-hydrogenation conversion process, where Cu... +The site is mainly responsible for the adsorption and activation of CO2 molecules, and for stabilizing the COOH intermediate, ultimately generating the products CH4 and CO; Cu species Cu + The proportion is 35-50%; the Cu species on the catalyst surface + The proportion remained in the range of 35% to 50%, indicating that the catalyst surface also contained a relatively abundant amount of Cu. + With Cu 0 Cooperative active sites. Moderate Cu content. + The ratio ensures that the catalyst has strong CO2 adsorption and activation capabilities while avoiding Cu... 0 Excessive Cu content leads to a tendency for deep hydrogenation. + The site is conducive to the polarization adsorption of CO2 molecules and The stability of key intermediates such as COOH promotes the activation of C–O bonds and the reaction pathway of reverse water-gas shift (RWGS); while an appropriate amount of Cu 0 This facilitates the dissociation of H2 into active hydrogen species, achieving a synergistic coupling between CO2 activation and hydrogen supply processes. Therefore, 35-50% Cu + The ratio can achieve a better balance between CO2 adsorption activation capacity and H2 activation capacity, thereby improving the efficiency of CO and CH4 generation, and is conducive to regulating the selectivity of CO products and inhibiting the occurrence of side reactions, which helps to improve the CO2 capture and conversion effect in DACC technology.

[0050] In some specific embodiments, M1 is Ni or Co, preferably Ni; M2 is Mg. 2+ Zn 2+ and Ni 2+ At least one of them, preferably Mg 2+ Zn 2+ or Ni 2+ Mg is the preferred choice. 2+ or Zn 2+ M3 is Al 3+ Fe 3+ or Mn 3+More specifically, the bimetallic oxide catalyst Cu-M1O / M2M3-LDO is Cu-NiO / CuMgAl-LDO, Cu-CoO / CuZnAl-LDO, Cu-NiO / CuMgFe-LDO, Cu-FeO / CuNiGa-LDO, Cu-NiO / CuZnMn-LDO, Cu-NiO / CuMgZnAl-LDO, or Cu-NiO / CuMgCoAl-LDO. Using the bimetallic oxide catalysts with the above structures, the CO2 capture capacity is 1.69–1.84 mmol / g at room temperature and 18% relative humidity, representing a 159% improvement in capture capacity. After reacting at 220℃ for 2 hours, the conversion rate is >90%, the total yield of CH4 and CO products reaches 1.51–1.64 mmol / g, and the CO selectivity reaches 40–45%.

[0051] In some specific embodiments, the LDO forms a defect-type continuous mixed metal oxide framework after the LDH layer collapses due to dehydroxylation; some Cu species are reduced to form highly dispersed Cu. + / Cu 0 Nanoparticles, along with NiO nanoparticles, are co-supported on the surface and pore structure of M2M3-LDO; the specific surface area of ​​the bimetallic oxide catalyst is 120~200 m² / g. 2 / g; the pore volume of the bimetallic oxide catalyst is 0.5~0.9cm³. 3 / g.

[0052] According to a second aspect of this application, a method for preparing the above-mentioned bimetallic oxide catalyst is provided, comprising the following steps: Step S1: Mix M2 salt, M3 salt and alkaline solution I, and react I to obtain the hydrotalcite precursor M2M3-LDH; wherein, M2 salt includes a divalent copper salt and an auxiliary divalent metal salt, the auxiliary divalent metal salt being selected from at least one of divalent magnesium salt, divalent zinc salt, divalent cobalt salt, divalent iron salt and divalent nickel salt; M3 salt is a trivalent aluminum salt, trivalent iron salt, trivalent manganese salt or trivalent gallium salt; Step S2: Mix M2M3-LDH and M1 salt II to obtain M1 / M2M3-LDH precursor; wherein, M1 salt is a divalent nickel salt, a divalent cobalt salt, or a divalent iron salt; Step S3: The M1 / M2M3-LDH precursor is subjected to heating reduction treatment to obtain a supported bimetallic oxide catalyst, denoted as Cu-M1O / M2M3-LDO.

[0053] In some specific embodiments, in step S1, the divalent copper salt is soluble copper nitrate, such as copper nitrate hydrate, specifically Cu(NO3)2·3H2O; the divalent magnesium salt, divalent zinc salt, divalent cobalt salt, divalent iron salt, and divalent nickel salt are soluble nitrates, such as Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, and Ni(NO3)2·6H2O; the M3 salt is soluble M3 nitrate, such as M3 nitrate hydrate, specifically Al(NO3)3·9H2O, Fe(NO3)3·9H2O, Ga(NO3)3·9H2O, and Mn(NO3)3·6H2O. Before use, a metal salt solution is prepared using deionized water to remove CO2. The purpose of using deionized water to remove CO2 is to minimize the introduction of CO2 from the layered bimetallic oxide, thereby ensuring accurate measurement of the catalyst's CO2 capture efficiency.

[0054] In some specific embodiments, the alkaline solution is an aqueous solution of potassium hydroxide and / or an aqueous solution of sodium hydroxide; the alkaline solution is obtained by dissolving alkali in CO2-free deionized water III; the concentration of the alkaline solution is 0.70 mol / L to 1.20 mol / L. In the co-precipitation preparation of M2M3-LDH, the purpose of adding NaOH alkaline solution is to adjust the pH of the system, so that Cu, M2, and M3 ions co-precipitate, forming a layered bimetallic hydroxide precursor containing an M–OH–M (M=Cu, M2, M3) lamellar structure, which is beneficial to the subsequent formation and stability of the LDH layered structure.

[0055] In some specific embodiments, in step S1, M2M3-LDH is synthesized by co-precipitation; wherein, the pH of the raw material mixing system is adjusted to 9-10, and alkaline conditions help to form layered bimetallic hydroxides; the reaction is carried out in a nitrogen atmosphere; a water bath is used for heating, and the reaction temperature is 75-85°C, for example 80°C; the product after the reaction is washed sequentially with deionized water to remove CO2, centrifuged until the supernatant is neutral, and the separated solid is vacuum dried for 24 hours to obtain the hydrotalcite precursor.

[0056] In some specific embodiments, mixture I specifically includes: first mixing M2 salt, M3 salt, and deionized water I to obtain a metal salt mixture; then mixing the metal salt mixture with an alkaline solution to obtain mixture I; wherein the molar ratio of M2 salt to M3 salt is (0.015~0.025):(0.005~0.010), for example, the molar ratio of M2 salt to M3 salt is (2~4):1; for example, 2:1, 3:1, 4:1. The total concentration of M2 ions and M3 ions in the metal salt mixture is 0.25~0.65 mol / L. In the LDH structure, the molar ratio of divalent metal to trivalent metal is controlled within the range of (2~4):1. By adjusting the appropriate amount of trivalent metal to replace divalent metal, a suitable positive charge density can be imparted to the layers, thereby achieving structural stability through interlayer anions. If the trivalent metal content is too low, the layer charge will be insufficient, which is not conducive to the formation of the layered structure. If the trivalent metal content is too high, it will easily lead to lattice distortion and impurity phase generation. Therefore, (2~4):1 is the appropriate ratio range for forming a stable LDH structure.

[0057] In some specific embodiments, Mixture II specifically includes: mixing M2M3-LDH, M1 salt, and deionized water II in an inert atmosphere to obtain Mixture II, and then evaporating the solvent in Mixture II to obtain the M1 / M2M3-LDH precursor; wherein, the deionized water II does not contain CO2. The weight ratio of M1 salt to M2M3-LDH, based on the weight of M1 element, is (0.8~5):100, for example (1~5):100; another example is (2~5):100, and yet another example is (3~5):100. After impregnation within this range followed by calcination, the resulting M1O nanoparticles effectively regulate the electronic structure and reduction behavior of Cu species, inhibiting Cu²⁺… + Excessive reduction to Cu 0 This improves the Cu content on the catalyst surface. + The proportion of active sites. Simultaneously, NiO induces more oxygen vacancy defects and local lattice distortion in the LDO framework, promoting surface electron redistribution and enhancing the adsorption, polarization, and activation capabilities of CO2 molecules, thus contributing to improved CO2 capture and conversion efficiency in DACC technology.

[0058] In some specific embodiments, the conditions for the heating reduction treatment in step S3 include: being carried out in a hydrogen-nitrogen atmosphere, with a heating rate of 2~10°C, a heating temperature of 250~350°C, and a heating time of 2~4 hours; for example, the heating temperature is any value of 250°C, 280°C, 300°C, 320°C, or 350°C, or a range between any two, and the heating time is 2, 3, or 4 hours; the hydrogen volume content in the hydrogen-nitrogen atmosphere is 8~12%, for example, 10%.

[0059] According to a third aspect of this application, a method for preparing CO by CO2 reduction is provided, comprising a catalyst; the catalyst is the above-described bimetallic oxide catalyst or the bimetallic oxide catalyst obtained by the above preparation method.

[0060] This application provides a more specific method for preparing a bimetallic oxide catalyst, comprising: Step S1: Dissolve soluble nitrates containing M2 and M3 in deionized water after removing CO2 to prepare mixed solution A, wherein M2 is a divalent metal ion, including Cu. 2+ In addition, it also includes Mg 2+ Zn 2+ Co 2+ Fe 2+ Ni 2+ One or more of the following; M3 is a trivalent metal ion selected from Al. 3+ Fe 3+ Mn 3+ Ga 3+ One of them; the molar ratio of M2 to M3 is 2~4:1; the alkali is dissolved in deionized water to remove CO2, and a precipitant solution B is prepared. The total ion concentration of M2 and M3 is 0.25mol / L~0.65mol / L, the alkali is NaOH or KOH, and the alkali concentration of solution B is 0.70mol / L~1.20mol / L; Step S2: Add no more than 1 / 3 of the container volume of deionized water to the reactor to remove CO2. Under a nitrogen atmosphere, add equal volumes of solution A and solution B dropwise into the reactor. During the titration, maintain the pH of the solution at 9-10. After the titration is complete, wash and centrifuge until the supernatant is neutral. Vacuum dry solid A to obtain the hydrotalcite precursor, denoted as M2M3-LDH. Step S3: Place the hydrotalcite precursor obtained in step S2 under an inert atmosphere, add deionized water to remove CO2 and stir. Add a non-precious metal M1 salt solution dropwise, so that the mass ratio of non-precious metal M1 to LDH precursor in the bifunctional material is 1~5%. Set the water bath temperature to 60℃. Stir until the solvent in the beaker evaporates to dryness, and then dry it in a 60℃ oven for 5 hours to obtain M1 / M2M3-LDH precursor. The non-precious metal M1 is one of Ni, Co and Fe. Step S4: The M1 / M2M3-LDH precursor obtained in step S2 is heated to 250-350℃ in a 10% H2 / N2 atmosphere at a heating rate of 2-10℃, held for 2-4h, and then cooled to room temperature to obtain the supported Cu-M1O / M2M3-LDO bifunctional material.

[0061] According to a third aspect of this application, the application of the above-described bimetallic oxide catalyst or the bimetallic oxide catalyst obtained by the above preparation method in CO2 reduction conversion is provided; for example, CO2 reduction to prepare CO and CH4.

[0062] The LDO bifunctional material for direct air carbon capture and low-temperature CO conversion provided in this application can capture CO2 from the air at room temperature and perform low-temperature in-situ hydrogenation conversion in a fixed-bed reactor. The specific application process of this bifunctional material includes two stages: (1) Room temperature adsorption and capture stage: The bifunctional material selectively captures CO2 in humid air at room temperature, and CO2 is adsorbed on the material surface in the form of carbonate and bicarbonate species. (2) Low-temperature in-situ conversion stage: Carbonate and bicarbonate species on the material surface are hydrogenated in a hydrogen atmosphere to convert into CO and CH4, which improves the high selectivity of CO under mild reaction conditions and realizes the coupling of direct air carbon capture and low-temperature conversion to CO.

[0063] According to a third aspect of this application, a method for preparing CO by CO2 reduction is provided, comprising a catalyst; the catalyst is the above-described bimetallic oxide catalyst or the bimetallic oxide catalyst obtained by the above preparation method.

[0064] In some specific implementations, the method includes the following steps: Step S1: Contact CO2 with the catalyst to capture CO2, obtaining catalyst A; Step S2: Catalyst A is brought into contact with hydrogen-containing gas to carry out a hydrogenation reaction to obtain CO.

[0065] In some specific embodiments, the ratio of catalyst to CO2 is (1~3) g: (300~500) ppm.

[0066] In some specific embodiments, the temperature of the hydrogenation reaction is 100~250℃, and the reaction time is 1~2h.

[0067] More specifically, the bimetallic oxide catalyst provided in this application can perform direct air carbon capture and low-temperature conversion to CO according to the following steps: (1) Mix 0.2g Cu-M1O / M2M3-LDO bifunctional material and 1.8g quartz sand evenly, use it as a reaction medium, load it into the middle of a quartz glass tube, load it into a steel tube, load it into a reactor device, and then pass 400ppm CO2 raw material gas to carry out the collection process under normal temperature conditions. (2) After the collection is completed, the air in the reactor is purged with an inert gas stream and the flow rate of the inert gas is controlled by a flow meter. Then, 0.1 MPa H2 / N2 mixed gas is introduced into the reactor and sealed. The gas flow in the reactor is circulated by a peristaltic pump. The reaction temperature is 100~250℃ and the reaction is carried out at a constant temperature for 1~2 hours. Every 1 hour, 5 mL of gas is taken with a syringe and injected into the gas chromatograph for detection. The catalyst reaction activity is evaluated by detecting the concentration of the product in the gas. (3) After the reaction, the reactor is cooled down. After it is cooled to room temperature, CO2 in the 400ppmCO2 feed gas is selectively captured again in the presence of water vapor. The carbonate and bicarbonate species adsorbed on the surface of the bifunctional material are used in the next hydrogenation reaction.

[0068] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0069] All raw materials used in the embodiments of this application are existing technologies.

[0070] Example 1 A method for preparing a bimetallic oxide catalyst includes the following steps: Step S1: Weigh 0.007 mol of Cu(NO3)2·3H2O solid, 0.010 mol of Mg(NO3)2·6H2O solid, and 0.008 mol of Al(NO3)3·9H2O solid. Dissolve the three soluble metal salts in a beaker containing 100 mL of deionized water to remove CO2 to prepare metal salt mixed solution A. Weigh 0.075 mol of NaOH solid and dissolve it in a beaker containing 100 mL of deionized water to remove CO2 to prepare precipitant solution B.

[0071] Step S2: CuMgAl-LDH was synthesized using a co-precipitation method. The water bath temperature was set to 80℃. Under a N2 atmosphere, 100 mL of deionized water (with CO2 removed) was added to a three-necked flask. Solutions A and B from step S1 were added dropwise to a 500 mL three-necked flask. During titration, the pH of the solution was maintained at 9, and the temperature was kept at 80℃. After titration, the precipitate was washed with deionized water (with CO2 removed), centrifuged until the supernatant was neutral, and the solid was vacuum-dried in a freeze dryer for 24 h to obtain the hydrotalcite precursor, denoted as CuMgAl-LDH.

[0072] Step S3: Weigh 0.3g of the hydrotalcite precursor obtained in step S2 and dissolve it in deionized water to remove CO2. Under an inert atmosphere, add 1.990mL of 0.05140mol / L Ni(NO3)2·6H2O dropwise, which is denoted as solution C. Set the water bath temperature to 60℃ and stir until the solvent in the beaker evaporates to dryness. Then, place it in a 60℃ oven to dry for 5h to obtain the Ni(NO3)2 / CuMgAl-LDH precursor.

[0073] Step S4: The Ni(NO3)2 / CuMgAl-LDH precursor obtained in step S3 is heated to 250℃ in a 10% H2 / N2 atmosphere at a heating rate of 5℃, held for 2 hours, and then cooled to room temperature to obtain the Cu-NiO / CuMgAl-LDO bifunctional material; the material structure is as follows. Figures 1-7 As shown; the specific surface area is 147.7 m². 2 / g, pore volume 0.63cm 3 / g; relative to Cu species (Cu 2+ Cu + and Cu 0 Cu + The relative atomic percentage of the species is 40.1%.

[0074] Example 2 Step S1: Weigh 0.007 mol of Cu(NO3)2·3H2O solid, 0.012 mol of Zn(NO3)2·6H2O solid, and 0.008 mol of Al(NO3)3·9H2O solid. Dissolve the three soluble metal salts in a beaker containing 100 mL of deionized water to remove CO2 to prepare metal salt mixed solution A. Weigh 0.080 mol of NaOH solid and dissolve it in a beaker containing 100 mL of deionized water to remove CO2 to prepare precipitant solution B.

[0075] Step S2: CuZnAl-LDH was synthesized using a co-precipitation method. The water bath temperature was set to 80℃. Under a N2 atmosphere, 100 mL of deionized water (with CO2 removed) was added to a three-necked flask. The two solutions A and B from step S1 were added dropwise to a 500 mL three-necked flask. During the titration, the pH of the solution was maintained at 9, and the temperature was maintained at 80℃. After titration, the precipitate was washed with deionized water (with CO2 removed) and centrifuged until the supernatant was neutral. The solid was then placed in a freeze dryer and vacuum dried for 24 h to obtain the hydrotalcite precursor, denoted as CuZnAl-LDH.

[0076] Step S3: Weigh 0.3g of the hydrotalcite precursor obtained in step S2 and dissolve it in deionized water to remove CO2. Under an inert atmosphere, add 2.100mL of 0.04850mol / L Co(NO3)2·6H2O dropwise, which is denoted as solution C. Set the water bath temperature to 60℃ and stir until the solvent in the beaker evaporates to dryness. Then, place it in a 60℃ oven and dry for 5h to obtain the Co(NO3)2 / CuZnAl-LDH precursor.

[0077] Step S4: The Co(NO3)2 / CuZnAl-LDH precursor obtained in step S3 was heated to 250℃ in a 10% H2 / N2 atmosphere at a heating rate of 10℃, held for 2 hours, and then cooled to room temperature to obtain the Cu-CoO / CuZnAl-LDO bifunctional material; its structure is similar to that of Example 1; the specific surface area is 136.5 m². 2 / g, pore volume 0.56cm 3 / g; relative to Cu species (Cu 2+ Cu + and Cu 0 Cu + The relative atomic percentage of the species is 39.7%.

[0078] Example 3 Step S1: Weigh 0.006 mol of Cu(NO3)2·3H2O solid, 0.012 mol of Mg(NO3)2·6H2O solid, and 0.006 mol of Fe(NO3)3·9H2O solid. Dissolve the three soluble metal salts in a beaker containing 100 mL of deionized water to remove CO2 to prepare metal salt mixed solution A. Weigh 0.095 mol of NaOH solid and dissolve it in a beaker containing 100 mL of deionized water to remove CO2 to prepare precipitant solution B.

[0079] Step S2: CuMgFe-LDH was synthesized using a co-precipitation method. The water bath temperature was set to 80℃. Under a N2 atmosphere, 100 mL of deionized water (with CO2 removed) was added to a three-necked flask. The two solutions A and B from step S1 were added dropwise to a 500 mL three-necked flask. During the titration, the pH of the solution was maintained at 10, and the temperature was maintained at 80℃. After titration, the precipitate was washed with deionized water (with CO2 removed) and centrifuged until the supernatant was neutral. The solid was then placed in a freeze dryer and vacuum dried for 24 h to obtain the hydrotalcite precursor, denoted as CuMgFe-LDH.

[0080] Step S3: Weigh 0.3g of the hydrotalcite precursor obtained in step S2 and dissolve it in deionized water to remove CO2. Under an inert atmosphere, add 1.990mL of 0.05140mol / L Ni(NO3)2·6H2O dropwise, which is denoted as solution C. Set the water bath temperature to 60℃ and stir until the solvent in the beaker evaporates to dryness. Then, place it in a 60℃ oven to dry for 5h to obtain the Ni(NO3)2 / CuMgFe-LDH precursor.

[0081] Step S4: The Ni(NO3)2 / CuMgFe-LDH precursor obtained in step S3 was heated to 300℃ in a 10% H2 / N2 atmosphere at a heating rate of 2℃, held for 3 hours, and then cooled to room temperature to obtain the Cu-NiO / CuMgFe-LDO bifunctional material; its structure is similar to that of Example 1; the specific surface area is 149.1 m². 2 / g, pore volume 0.52cm 3 / g; relative to Cu species (Cu 2+ Cu + and Cu 0 Cu + The relative atomic percentage of the species is 38.6%.

[0082] Example 4 Step S1: Weigh 0.006 mol of Cu(NO3)2·3H2O solid, 0.015 mol of Ni(NO3)2·6H2O solid, and 0.006 mol of Ga(NO3)3·9H2O solid. Dissolve the three soluble metal salts in a beaker containing 100 mL of deionized water to remove CO2 to prepare metal salt mixed solution A. Weigh 0.100 mol of NaOH solid and dissolve it in a beaker containing 100 mL of deionized water to remove CO2 to prepare precipitant solution B.

[0083] Step S2: CuNiGa-LDH was synthesized using a co-precipitation method. The water bath temperature was set to 80℃. Under a N2 atmosphere, 100mL of deionized water (with CO2 removed) was added to a three-necked flask. The two solutions A and B from step S1 were added dropwise to a 500mL three-necked flask. During the titration, the pH of the solution was maintained at 10, and the temperature was maintained at 80℃. After titration, the precipitate was washed with deionized water (with CO2 removed) and centrifuged until the supernatant was neutral. The solid was then placed in a freeze dryer and vacuum dried for 24 hours to obtain the hydrotalcite precursor, denoted as CuNiGa-LDH.

[0084] Step S3: Weigh 0.3g of the hydrotalcite precursor obtained in step S2 and dissolve it in deionized water to remove CO2. Under an inert atmosphere, add 2.058mL of 0.05220mol / L Fe(NO3)2·9H2O dropwise, which is denoted as solution C. Set the water bath temperature to 60℃ and stir until the solvent in the beaker evaporates to dryness. Then, place it in a 60℃ oven to dry for 5h to obtain the Fe(NO3)2 / CuNiGa-LDH precursor.

[0085] Step S4: The Fe(NO3)2 / CuNiGa-LDH precursor obtained in step S3 was heated to 300℃ in a 10% H2 / N2 atmosphere at a heating rate of 2℃, held for 3 hours, and then cooled to room temperature to obtain the Cu-FeO / CuNiGa-LDO bifunctional material; its structure is similar to that of Example 1; the specific surface area is 152.8 m². 2 / g, pore volume 0.61cm 3 / g; relative to Cu species (Cu 2+ Cu + and Cu 0 Cu + The relative atomic percentage of species is 38.2%.

[0086] Example 5 Step S1: Weigh 0.006 mol of Cu(NO3)2·3H2O solid, 0.009 mol of Zn(NO3)2·6H2O solid, and 0.006 mol of Mn(NO3)3·6H2O solid. Dissolve the three soluble metal salts in a beaker containing 100 mL of deionized water to remove CO2 to prepare metal salt mixed solution A. Weigh 0.080 mol of NaOH solid and dissolve it in a beaker containing 100 mL of deionized water to remove CO2 to prepare precipitant solution B.

[0087] Step S2: CuZnMn-LDH was synthesized using a co-precipitation method. The water bath temperature was set to 80℃. Under a N2 atmosphere, 100 mL of deionized water (with CO2 removed) was added to a three-necked flask. The two solutions from step S1 were then added dropwise to a 500 mL three-necked flask. During titration, the pH of the solution was maintained at 9.5, and the temperature was maintained at 80℃. After titration, the precipitate was washed with deionized water (with CO2 removed) and centrifuged until the supernatant was neutral. The solid was then vacuum-dried in a freeze dryer for 24 h to obtain the hydrotalcite precursor, denoted as CuZnMn-LDH.

[0088] Step S3: Weigh 0.3g of the hydrotalcite precursor obtained in step S2 and dissolve it in deionized water to remove CO2. Under an inert atmosphere, add 1.990mL of 0.05140mol / L Ni(NO3)2·6H2O dropwise, which is denoted as solution C. Set the water bath temperature to 60℃ and stir until the solvent in the beaker evaporates to dryness. Then, place it in a 60℃ oven to dry for 5h to obtain the Ni(NO3)2 / CuZnMn-LDH precursor.

[0089] Step S4: The Ni(NO3)2 / CuZnMn-LDH precursor obtained in step S3 was heated to 250℃ in a 10% H2 / N2 atmosphere at a heating rate of 5℃, held for 2 hours, and then cooled to room temperature to obtain the Cu-NiO / CuZnMn-LDO bifunctional material; its structure is similar to that of Example 1; the specific surface area is 142.4 m². 2 / g, pore volume 0.65cm 3 / g; relative to Cu species (Cu 2+ Cu + and Cu 0 Cu + The relative atomic percentage of the species is 41.3%.

[0090] Example 6 The difference between Example 6 and Example 1 is that CuMgAl-LDH in step S2 is replaced with CuMgZnAl-LDH; Step S1: Weigh 0.007 mol of Cu(NO3)2·3H2O solid, 0.005 mol of Mg(NO3)2·6H2O solid, 0.005 mol of Zn(NO3)2·6H2O solid, and 0.008 mol of Al(NO3)3·9H2O solid. Dissolve the four soluble metal salts in a beaker containing 100 mL of deionized water (after removing CO2) to prepare metal salt mixed solution A. Weigh 0.075 mol of NaOH solid and dissolve it in a beaker containing 100 mL of deionized water (after removing CO2) to prepare precipitant solution B.

[0091] Step S2: CuMgZnAl-LDH was synthesized using a co-precipitation method. The water bath temperature was set to 80℃. Under a N2 atmosphere, 100 mL of deionized water (with CO2 removed) was added to a three-necked flask. Solutions A and B from step S1 were added dropwise to a 500 mL three-necked flask. During titration, the pH of the solution was maintained at 9, and the temperature was kept at 80℃. After titration, the precipitate was washed with deionized water (with CO2 removed), centrifuged until the supernatant was neutral, and the solid was vacuum-dried in a freeze dryer for 24 h to obtain the hydrotalcite precursor, denoted as CuMgZnAl-LDH.

[0092] Step S3: Weigh 0.3g of the hydrotalcite precursor obtained in step S2 and dissolve it in deionized water to remove CO2. Under an inert atmosphere, add 1.990mL of 0.05140mol / L Ni(NO3)2·6H2O dropwise, which is denoted as solution C. Set the water bath temperature to 60℃ and stir until the solvent in the beaker evaporates to dryness. Then, place it in a 60℃ oven to dry for 5h to obtain the Ni(NO3)2 / CuMgZnAl-LDH precursor.

[0093] Step S4: The Ni(NO3)2 / CuMgZnAl-LDH precursor obtained in step S3 was heated to 250℃ in a 10% H2 / N2 atmosphere at a heating rate of 5℃, held for 2 hours, and then cooled to room temperature to obtain the Cu-NiO / CuMgZnAl-LDO bifunctional material; its structure is similar to that of Example 1; the specific surface area is 161.3 m². 2 / g, pore volume 0.70cm 3 / g; relative to Cu species (Cu 2+ Cu + and Cu 0 Cu + The relative atomic percentage of the species is 38.5%.

[0094] Example 7 The difference between Example 7 and Example 1 is that CuMgAl-LDH in step S2 is replaced with CuMgCoAl-LDH; Step S1: Weigh 0.007 mol of Cu(NO3)2·3H2O solid, 0.005 mol of Mg(NO3)2·6H2O solid, 0.005 mol of Co(NO3)2·6H2O solid, and 0.008 mol of Al(NO3)3·9H2O solid. Dissolve the four soluble metal salts in a beaker containing 100 mL of deionized water (after removing CO2) to prepare metal salt mixed solution A. Weigh 0.075 mol of NaOH solid and dissolve it in a beaker containing 100 mL of deionized water (after removing CO2) to prepare precipitant solution B.

[0095] Step S2: CuMgCoAl-LDH was synthesized using a co-precipitation method. The water bath temperature was set to 80℃. Under a N2 atmosphere, 100 mL of deionized water (with CO2 removed) was added to a three-necked flask. Solutions A and B from step S1 were added dropwise to a 500 mL three-necked flask. During titration, the pH of the solution was maintained at 9, and the temperature was kept at 80℃. After titration, the precipitate was washed with deionized water (with CO2 removed), centrifuged until the supernatant was neutral, and the solid was vacuum-dried in a freeze dryer for 24 h to obtain the hydrotalcite precursor, denoted as CuMgCoAl-LDH.

[0096] Step S3: Weigh 0.3g of the hydrotalcite precursor obtained in step S2 and dissolve it in deionized water to remove CO2. Under an inert atmosphere, add 1.990mL of 0.05140mol / L Ni(NO3)2·6H2O dropwise, which is denoted as solution C. Set the water bath temperature to 60℃ and stir until the solvent in the beaker evaporates to dryness. Then, dry it in a 60℃ oven for 5h to obtain the Ni(NO3)2 / CuMgCoAl-LDH precursor.

[0097] Step S4: The Ni(NO3)2 / CuMgCoAl-LDH precursor obtained in step S3 was heated to 250℃ in a 10% H2 / N2 atmosphere at a heating rate of 5℃, held for 2 hours, and then cooled to room temperature to obtain the Cu-NiO / CuMgCoAl-LDO bifunctional material; its structure is similar to that of Example 1; the specific surface area is 168.5 m². 2 / g, pore volume 0.73cm 3 / g; relative to Cu species (Cu 2+ Cu + and Cu 0 Cu + The relative atomic percentage of the species is 39.2%.

[0098] Example 8 The difference between Example 8 and Example 1 is that the heating temperature of the Ni(NO3)2 / CuMgAl-LDH precursor in step S4 is replaced with 350°C and maintained for 2 hours to obtain the Cu-NiO / CuMgAl-LDO bifunctional material; the other steps are the same.

[0099] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the prepared bimetallic oxide does not contain the nickel oxide active component; the other steps are the same. Specifically, it includes: Step S1: Weigh 0.007 mol of Cu(NO3)2·3H2O solid, 0.010 mol of Mg(NO3)2·6H2O solid, and 0.008 mol of Al(NO3)3·9H2O solid. Dissolve the three soluble metal salts in a beaker containing 100 mL of deionized water to remove CO2 to prepare metal salt mixed solution A. Weigh 0.075 mol of NaOH solid and dissolve it in a beaker containing 100 mL of deionized water to remove CO2 to prepare precipitant solution B.

[0100] Step S2: CuMgAl-LDH was synthesized using a co-precipitation method. The water bath temperature was set to 80℃. Under a N2 atmosphere, 100 mL of deionized water (with CO2 removed) was added to a three-necked flask. Solutions A and B from step S1 were added dropwise to a 500 mL three-necked flask. During titration, the pH of the solution was maintained at 9, and the temperature was kept at 80℃. After titration, the precipitate was washed with deionized water (with CO2 removed), centrifuged until the supernatant was neutral, and the solid was vacuum-dried in a freeze dryer for 24 h to obtain the hydrotalcite precursor, denoted as CuMgAl-LDH. Step S3: The CuMgAl-LDH precursor obtained in step S2 is heated to 250℃ in a 10% H2 / N2 atmosphere at a heating rate of 5℃, held for 2h, and then cooled to room temperature to obtain Cu / CuMgAl-LDO bifunctional material.

[0101] Application examples The bifunctional materials prepared in Examples 1-8 and Comparative Example 1 were applied to direct air carbon capture and low-temperature CO conversion according to the following steps: 0.2g of Cu-M1O / CuM2M3-LDO bifunctional material and 1.8g of quartz sand were uniformly mixed and used as a reaction medium. The mixture was then loaded into the middle of a quartz glass tube, which was then loaded into a steel tube and finally into a reactor. 400ppm CO2 raw material gas was then introduced to carry out the collection process under normal temperature conditions. After the collection was completed, the air inside the reactor was purged with an inert gas stream, and the flow rate of the inert gas was controlled by a flow meter. Then, a 0.1 MPa H2 / N2 mixture was introduced into the reactor and sealed. The gas flow inside the reactor was circulated using a peristaltic pump until the reaction temperature was raised to 220℃. The reaction was carried out at a constant temperature for 2 hours. Every hour, 5 mL of gas was taken with a syringe and injected into a gas chromatograph for detection. The catalyst activity was evaluated by detecting the concentration of the product in the gas. After the reaction, the reactor is cooled down to room temperature. Then, CO2 in the 400 ppm CO2 feed gas is selectively captured again in the presence of water vapor. The carbonate and bicarbonate species adsorbed on the surface of the bifunctional material are used in the next hydrogenation reaction.

[0102] Performance testing: (1) The XRD equipment was a Rigaku Ultima Ⅲ, used to detect the catalysts Cu-NiO / CuMgAl-LDO and Cu / CuMgAl-LDO; (2) The HRTEM equipment model is ThermoFisher Talos F200X, used to detect the catalyst Cu-NiO / CuMgAl-LDO; (3) The XPS equipment model is ESCALAB250, used to detect the catalysts Cu-NiO / CuMgAl-LDO and Cu / CuMgAl-LDO; (4) The Raman equipment model is Renishaw inVia Reflex, used to test the catalysts Cu-NiO / CuMgAl-LDO and Cu / CuMgAl-LDO; (4) The EPR equipment model is JES-FA200, used to test the catalysts Cu-NiO / CuMgAl-LDO and Cu / CuMgAl-LDO; (5) Experimental results of the in-situ conversion process of the bimetallic oxide catalyst under hydrogen atmosphere were detected by Shimadzu gas chromatograph (GC-2014C), including the yield of CO and CH4. (6) The cyclic stability of the bimetallic oxide catalyst during the capture-conversion process was detected using a Shimadzu gas chromatograph (GC-2014C).

[0103] Table 1

[0104] The test results in Table 1 show that the bifunctional materials prepared in Examples 1-8 of this application have a CO2 capture capacity of 1.57-1.84 mmol / g in humid air; in a reducing conversion atmosphere, the total yield of CO and CH4 products is 1.42-1.64 mmol / g, and the CO selectivity is 40-45%. Figure 7 and Figure 8 As shown, this illustrates that in an integrated reaction device, bifunctional materials can effectively couple the capture and conversion steps together, improving the capture amount of CO2 in humid air and the selectivity of the product CO.

[0105] Figure 1 The X-ray diffraction pattern of the bimetallic oxide catalyst in Example 1 shows characteristic diffraction peaks of the (111), (200), and (220) crystal planes of Cu nanoparticles, as well as the (111) crystal plane of NiO nanoparticles; indicating that the LDH precursor loses its interlayer structure and transforms into LDO, and the crystal plane diffraction peaks of metallic Cu and NiO appear.

[0106] Figure 2 and Figure 3 The image shows an HRTEM image of the bimetallic oxide catalyst in Example 1. The presence of Cu and NiO particles confirms that NiO was successfully supported on the Cu-LDO support. The Cu particles have a diameter of 6.30 nm.

[0107] Figure 4 , Figure 5 and Figure 6The figures show the XPS and LMM spectra of the bimetallic oxide catalyst in Example 1. The figures indicate that the introduction of NiO suppressed Cu... + To Cu 0 Further reduction of Cu increased + The ratio of Cu-NiO / CuMgAl-LDO increases, while simultaneously generating more oxygen vacancies. Specifically: after NiO loading, the Cu-NiO / CuMgAl-LDO ratio increases. + / Cu 0 The shift of the 2p peak to higher binding energies may originate from Ni. 2+ Electron interactions with Cu species lead to Cu + / Cu 0 The electron cloud density of the species decreased. Furthermore, Cu was found in Cu-NiO / CuMgAl-LDO. + (Cu 0 ) / Cu 2+ The ratio is 1.01, while Cu / CuMgAl-LDO Cu + (Cu 0 ) / Cu 2+ The proportion was only 0.86. This result indicates that the loading of NiO altered the Cu content. 2+ The degree of reduction. Further analysis of Cu LMMs in Cu / CuMgAl-LDO and Cu-NiO / CuMgAl-LDO reveals that Cu in Cu-NiO / CuMgAl-LDO... + The proportion was 40.1%, significantly higher than that of Cu / CuMgAl-LDO. + The proportion of 31.2% further illustrates that loading NiO suppressed Cu. + To Cu 0 Further reduction of Cu increased + The ratio of Cu + and Cu 0 The synergistic effect between them can further improve the performance of subsequent hydrogenation reactions.

[0108] Figure 7 The EPR diagram of the bimetallic oxide catalyst in Example 1 shows that Cu-NiO / CuMgAl-LDO has significantly more oxygen vacancy defects than Cu / CuMgAl-LDO; oxygen vacancies may enhance surface electron transfer efficiency by modulating the electronic structure of the bifunctional material.

[0109] Figure 8 The figure shows the experimental performance of the bimetallic oxide catalyst in Example 1 during the in-situ conversion process under a hydrogen atmosphere, demonstrating that the synergistic effect between NiO and Cu after NiO loading enhances the ability of CO2 hydrogenation conversion.

[0110] Figure 9 and Figure 10 The bar chart shows the cyclic stability of the bimetallic oxide catalyst prepared in Example 1 during the capture-conversion process, indicating a conversion rate >90% and a CO selectivity that remains stable at around 45%.

[0111] Compared to Cu-NiO / CuMgAl-LDO, the Cu / CuMgAl-LDO prepared in Comparative Example 1, lacking the regulatory effect of NiO on the electronic structure and valence state of Cu species, is more prone to Cu oxidation during reduction and reaction. + To Cu 0 The deep reduction leads to Cu on the catalyst surface + Insufficient active sites. Although Cu 0 It is beneficial for H2 dissociation, but its adsorption and polarization ability for CO2 molecules is weak, which is not conducive to H2 dissociation. The stabilization of key intermediates such as COOH reduces CO2 activation capacity and CO2 conversion rate. Simultaneously, the lack of Ni–O–Cu interfacial synergy decreases the oxygen vacancy concentration and electron redistribution capacity on the catalyst surface, further weakening CO2 chemisorption and electron transfer processes. Furthermore, excess Cu... 0 It also easily promotes deep hydrogenation and Cu particle agglomeration, reduces the exposure of active sites, and weakens Cu. + / Cu 0 The ability to construct synergistic interfaces leads to a significant decrease in CO selectivity and overall catalytic performance.

[0112] By applying the bimetallic oxide catalyst provided in this application, the introduction of M1O effectively reduces Cu. 2+ The reducing power of Cu was improved. + The increased proportion of Cu and the increased oxygen vacancy defect concentration promote electron redistribution on the catalyst surface, providing abundant active sites for subsequent in-situ hydrogenation conversion. This catalyst can selectively capture low-concentration CO2 from the air and convert it in-situ to CO and CH4 under low-temperature conditions in a H2 / N2 reducing atmosphere. During the CO2 capture and in-situ conversion process, Cu... δ+ / Cu 0 The dynamic changes in oxygen vacancy concentration are used to regulate the selectivity of CO product. For example, at room temperature and 18% relative humidity, the CO2 capture capacity is as high as 1.84 mmol / g, which is 159% higher than that of CO. When reacted at 220℃ for 2 hours, the conversion rate is >90%, the total yield of CH4 and CO products is 1.64 mmol / g, and the CO selectivity is 45%.

[0113] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A bimetallic oxide catalyst, characterized in that, The chemical formula of the bimetallic oxide catalyst is Cu-M1O / M2M3-LDO; wherein, Cu in Cu-M1O includes Cu 0 and Cu + ; M1 is a non-precious metal, specifically Ni, Co, or Fe. M2 is a divalent metal ion, wherein M2 includes Cu. 2+ and auxiliary divalent metal ions, wherein the auxiliary divalent metal ions are selected from Mg 2+ Zn 2+ Co 2+ Fe 2+ and Ni 2+ At least one of them; M3 is a trivalent metal ion, wherein M3 is Al 3+ Fe 3+ Mn 3+ or Ga 3+ ; M2M3-LDO is a mixed metal oxide composed of M2 and M3; The Cu-M1O is loaded on the M2M3-LDO.

2. The bimetallic oxide catalyst according to claim 1, characterized in that, The Cu-M1O consists of Cu nanoparticles, cuprous oxide particles, and M1O nanoparticles; the M2M3-LDO is a defect-type mixed metal oxide composed of M2 and M3; the Cu nanoparticles, the cuprous oxide particles, and the M1O nanoparticles are all loaded on the surface and within the pores of the M2M3-LDO. And / or, the framework material of the M2M3-LDO contains Cu. + ; Preferably, the weight of the M1O nanoparticles is 1 to 5% of the weight of the M2M3-LDO.

3. The bimetallic oxide catalyst according to claim 1 or 2, characterized in that, The ratio of the total molar amount of M2 and M3 to the molar amount of M1 is (20~30):1, preferably (22~26):1; And / or, Cu in the bimetallic oxide catalyst + Species relative to Cu species, the Cu + The relative atomic percentage of the species is 35-50%, wherein the Cu species includes Cu². + Cu + and Cu 0 ; Preferably, Cu in the bimetallic oxide catalyst + Species relative to Cu species, the Cu + The relative atomic percentage of species is 38-45%.

4. The bimetallic oxide catalyst according to claim 1 or 2, characterized in that, M1 is either Ni or Co; And / or, the M2 is Mg 2+ Zn 2+ or Ni 2+ ; And / or, the M3 is Al 3+ Fe 3+ or Mn 3+ ; And / or, the Cu-M1O / M2M3-LDO is Cu-NiO / CuMgAl-LDO, Cu-CoO / CuZnAl-LDO, Cu-NiO / CuMgFe-LDO, Cu-FeO / CuNiGa-LDO, Cu-NiO / CuZnMn-LDO, Cu-NiO / CuMgZnAl-LDO or Cu-NiO / CuMgCoAl-LDO; And / or, the specific surface area of ​​the bimetallic oxide catalyst is 120~200 m². 2 / g; And / or, the pore volume of the bimetallic oxide catalyst is 0.5~0.9 cm³. 3 / g.

5. A method for preparing a bimetallic oxide catalyst according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: Step S1: Mix M2 salt, M3 salt, and alkaline solution I, and react I to obtain the hydrotalcite precursor M2M3-LDH; wherein, the M2 salt includes a divalent copper salt and an auxiliary divalent metal salt, the auxiliary divalent metal salt being selected from at least one of divalent magnesium salt, divalent zinc salt, divalent cobalt salt, divalent iron salt, and divalent nickel salt; the M3 salt is a trivalent aluminum salt, trivalent iron salt, trivalent manganese salt, or trivalent gallium salt; Step S2: Mix the M2M3-LDH and M1 salt II to obtain the M1 / M2M3-LDH precursor; wherein, the M1 salt is a divalent nickel salt, a divalent cobalt salt, or a divalent iron salt; Step S3: The M1 / M2M3-LDH precursor is subjected to heating reduction treatment to obtain the supported bimetallic oxide catalyst Cu-M1O / M2M3-LDO.

6. The method for preparing the bimetallic oxide catalyst according to claim 5, characterized in that, In step S1, the M2 salt is M2 nitrate; And / or, the M3 salt is M3 nitrate; And / or, the alkaline solution is an aqueous solution of potassium hydroxide and / or an aqueous solution of sodium hydroxide; preferably, the concentration of the alkaline solution is 0.70 mol / L to 1.20 mol / L; And / or, the mixture I specifically includes: first mixing the M2 salt, the M3 salt, and deionized water I to obtain a metal salt mixture; then mixing the metal salt mixture with the alkaline solution to obtain mixture I; And / or, reaction I is a coprecipitation reaction.

7. The method for preparing the bimetallic oxide catalyst according to claim 6, characterized in that, In step S1, the molar ratio of salt M2 to salt M3 is (0.015~0.025):(0.005~0.010). Preferably, the molar ratio of the M2 salt to the M3 salt is (2~4):1; And / or, the deionized water I does not contain CO2; And / or, the pH value of mixture I is 9-10; And / or, reaction I is carried out in a nitrogen atmosphere; And / or, the temperature of reaction I is 75~85°C; And / or, the product of reaction I is sequentially washed, separated, and vacuum dried to obtain the hydrotalcite precursor.

8. The method for preparing the bimetallic oxide catalyst according to claim 5 or 6, characterized in that, In step S2, the M1 salt is M1 nitrate; And / or, based on the weight of element M1, the weight ratio of the M1 salt to the M2M3-LDH is (0.8~5):100, preferably (1~5):100; And / or, the mixture II specifically includes: mixing the M2M3-LDH, the M1 salt, and deionized water II in an inert atmosphere to obtain mixture II; then evaporating the solvent in mixture II to obtain the M1 / M2M3-LDH precursor; Preferably, the deionized water II does not contain CO2.

9. The method for preparing the bimetallic oxide catalyst according to claim 5 or 6, characterized in that, In step S3, the conditions for the heating reduction treatment include: being carried out in a hydrogen-nitrogen mixed atmosphere, with a heating rate of 2~10℃, a heating temperature of 250~350℃, and a heating time of 2~4h; Preferably, the heating temperature is 250~300℃ and the heating time is 2~3h.

10. A method for preparing CO by reduction of CO2, comprising a catalyst; characterized in that, The catalyst is a bimetallic oxide catalyst according to any one of claims 1 to 4 or a bimetallic oxide catalyst obtained by any one of claims 5 to 9.

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