Cu / cu2o / moo2 catalyst and preparation method and application thereof

Abstract

This invention belongs to the field of photocatalytic materials technology, and discloses a Cu / Cu2O / MoO2 catalyst, its preparation method, and its applications. The preparation method includes: co-precipitating copper salt and molybdate, followed by thermal calcination to obtain a Cu3Mo2O9 precursor, and then activating it in a CO2 / H2 atmosphere at 150-300℃ to obtain the three-phase composite catalyst. This method is mild, uses inexpensive raw materials, and has a simple process. The obtained catalyst contains three phases: Cu, Cu2O, and MoO2, forming a dual heterojunction structure, and achieves a CO generation rate of 335.73 μmol·g in the photocatalytic CO2 hydrogenation reaction. ‑1 ·h ‑1 It has a selectivity of 98% and excellent cycle stability, and can be used for solar-driven CO2 resource conversion.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a Cu / Cu2O / MoO2 catalyst, its preparation method, and its application. Background Technology

[0002] With the continued exacerbation of the global greenhouse effect and the dwindling of fossil fuels, the resource utilization of carbon dioxide (CO2) has become a research hotspot in the fields of energy, chemical engineering, and environmental governance. Photocatalytic CO2 hydrogenation technology, which leverages solar energy to achieve high-value conversion of CO2 and carbon resource recycling, has attracted considerable attention. Currently, noble metal single-atom (Pt, Au, Pd, Ag) catalysts exhibit excellent catalytic performance in this field, but their inherent drawbacks of high cost and low reserves severely restrict their large-scale and industrial application. Therefore, developing high-performance, low-cost, and environmentally friendly non-noble metal-based photocatalysts has become an inevitable trend in this field.

[0003] Currently, research on non-precious metal-based photocatalysts mainly focuses on metals and their oxides such as Cu, Co, Ti, and Mo. Among them, copper-based materials (such as Cu2O) have suitable band structures, excellent visible light response, and good CO2 hydrogenation catalytic activity and product selectivity, making them one of the most promising photocatalysts. Patent document CN116586066A describes a Cu2O@MgO catalyst prepared through physical impregnation and high-temperature calcination at 500℃. This catalyst not only has high energy consumption but also exhibits excellent performance under high-temperature conditions. + Valence states are difficult to maintain stably, and oxidation or disproportionation reactions, grain growth or agglomeration are prone to occur, leading to a reduction in active sites. Another promising class of molybdenum-based materials (such as MoO2) have abundant oxygen vacancies on their surface, which can efficiently adsorb and activate CO2, making them ideal photocatalytic modification materials. The MoO2 / Mo2N composite material disclosed in patent document CN119524897A requires high-temperature calcination of the MoO3 precursor in an ammonia atmosphere at 400~700 ℃, which is a harsh reaction condition, and the ammonia used is highly toxic and corrosive. Patent document CN109659512A discloses a method for preparing flower-shaped TiO2 / MoO2 composite nanomaterials, which requires multiple steps such as hydrothermal synthesis, hydrogen ion exchange, ammonium molybdate hydrolysis and high-temperature calcination, which is a complex process with high energy consumption.

[0004] In recent years, researchers have begun to explore the construction of heterojunction photocatalysts by combining Cu2O and MoO2. For example, Wang et al. (Chemistry of Materials, 2026) reported a MoO2 / Cu2O binary heterojunction catalyst, which utilizes Mo... 4+Valence state modulation strategies promote the separation of photogenerated carriers and have shown certain potential in the field of visible light catalysis. However, the system still has the following shortcomings: (1) The catalyst consists of only two phases, MoO2 and Cu2O, and lacks a metallic Cu phase, which cannot provide efficient H2 dissociation and overflow sites, thus limiting the overall efficiency of CO2 hydrogenation reaction; (2) Only a single pn heterojunction is constructed, and a double heterojunction structure is not formed, so there is still room for improvement in the separation efficiency of photogenerated carriers; (3) The catalytic performance evaluation of CO2 hydrogenation reaction is not clearly defined, especially the key indicators such as the selectivity and stability of photocatalytic CO2 reduction to CO have not been reported.

[0005] In summary, existing catalyst preparation methods generally suffer from drawbacks such as high temperature, high energy consumption, or the use of toxic atmospheres, while the latest MoO2 / Cu2O binary heterojunction system remains imperfect in terms of component design and catalytic function. Therefore, there is an urgent need to develop a non-noble metal-based catalyst with a simple preparation process, mild reaction conditions, low energy consumption, and both high stability and high activity. Summary of the Invention

[0006] The purpose of this invention is to provide a Cu / Cu2O / MoO2 catalyst, its preparation method, and its application, which solves the problems of complex preparation processes, harsh conditions, and unsatisfactory catalytic performance (especially CO yield and selectivity) of existing CO2 hydrogenation photocatalysts.

[0007] This invention is achieved through the following technical solution: A method for preparing a Cu / Cu2O / MoO2 catalyst includes the following steps: Dissolve the copper salt in deionized water to form solution A; Dissolve molybdate in deionized water to form solution B; Solution B is added dropwise to solution A under stirring, and stirring continues, resulting in the formation of a precipitate; The precipitate was washed, filtered, dried, and calcined to obtain a Cu3Mo2O9 sample. The Cu3Mo2O9 sample was activated by a CO2 hydrogenation atmosphere at a reaction temperature of 150-300 °C to obtain a Cu / Cu2O / MoO2 catalyst.

[0008] Furthermore, the conditions for the thermal calcination are: reaction temperature 350-450 ℃, reaction time 1-3 hours.

[0009] Furthermore, the activation reaction conditions are: continuous flow of CO2 / H2 mixed gas, atmospheric pressure, and reaction time of 10 hours.

[0010] Furthermore, the flow rate ratio of the CO2 / H2 mixed gas flow is CO2 / H2=1:3.

[0011] Furthermore, the copper salt is Cu(NO3)2·3H2O; the molybdate is Na2MoO4·2H2O.

[0012] The present invention also discloses a Cu / Cu2O / MoO2 catalyst, wherein the Cu / Cu2O / MoO2 catalyst comprises a Cu phase, a Cu2O phase and a MoO2 phase, wherein Cu and Cu2O form a Schottky junction and Cu2O and MoO2 form a pn junction, constituting a double heterojunction structure.

[0013] Furthermore, the catalyst has a microstructure consisting of nanosheets and nanoparticles attached to the nanosheets.

[0014] Furthermore, the catalyst exhibits a carbon monoxide generation rate of no less than 90 μmol·g in the photocatalytic CO2 hydrogenation reaction. -1 ·h -1 The carbon monoxide selectivity is not less than 98%, and the performance degradation does not exceed 5% after multiple cycle tests.

[0015] Furthermore, the MoO2 phase is amorphous and contains oxygen vacancies on its surface.

[0016] The present invention also discloses the application of the Cu / Cu2O / MoO2 catalyst, which serves as a photocatalyst for the photocatalytic hydrogenation reaction of CO2, and is used to convert CO2 and H2 into CO.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for preparing a Cu / Cu2O / MoO2 catalyst, comprising preparing a copper nitrate solution and a sodium molybdate solution, co-precipitating to form a precipitate, washing, filtering, drying, and hot calcining to obtain a Cu3Mo2O9 sample, and then performing an activation reaction in a CO2 hydrogenation atmosphere at 150-300 °C. By combining co-precipitation and hot calcination with mild CO2 hydrogenation atmosphere heat treatment, the harsh conditions of high-temperature calcination above 500 °C or the use of toxic ammonia gas in traditional methods are avoided, thus simplifying the preparation process and mildening the reaction conditions. Simultaneously, the raw materials are inexpensive and readily available, significantly reducing the catalyst preparation cost. The 150-300 °C range effectively forms the target three-phase structure and dual heterojunction, thereby achieving excellent catalytic activity. The technical advantage of this preferred temperature range is that it achieves significantly improved catalytic performance at a lower energy cost, achieving a balance between process economy and catalytic efficiency.

[0018] Furthermore, the conditions for thermal calcination were specified as a reaction temperature of 300-450 ℃ and a reaction time of 1-3 hours. Thermal calcination within this temperature and time range ensures that the precursor is fully converted into a pure-phase Cu3Mo2O9 sample, providing a structurally complete and crystalline-phase precursor material for subsequent activation reactions, thereby guaranteeing the quality and performance consistency of the final catalyst.

[0019] Furthermore, the activation reaction conditions were specified as a continuous flow of CO2 / H2 mixed gas, atmospheric pressure, and a reaction time of 10 hours. Using a continuous flow of mixed gas and atmospheric pressure avoids the use of high-pressure equipment, lowering the process threshold and equipment costs. On the other hand, the flowing atmosphere can promptly remove reaction byproducts and provide fresh reducing gas, which is beneficial for the uniform and complete reduction reaction.

[0020] Furthermore, the flow rate ratio of the CO2 / H2 mixed gas stream was limited to CO2 / H2 = 1:3. This specific ratio provides a suitable reducing atmosphere, preventing over-reduction that could lead to phase loss or under-reduction that would prevent the formation of the target three-phase structure. This ensures that the Cu3Mo2O9 precursor is partially reduced to a composite material in which Cu, Cu2O, and MoO2 coexist, which is one of the key process conditions for realizing the dual heterojunction structure.

[0021] This invention also discloses a Cu / Cu2O / MoO2 catalyst comprising a Cu phase, a Cu2O phase, and a MoO2 phase, wherein Cu and Cu2O form a Schottky junction, and Cu2O and MoO2 form a pn junction, constituting a double heterojunction structure. Raman and XRD spectra and HRTEM images show that the three phases coexist and form a double heterojunction structure. The Schottky junction promotes electron transfer at the metal-semiconductor interface, while the pn junction separates photogenerated carriers under the influence of the built-in electric field of the semiconductor. The synergistic effect of the two heterostructures significantly suppresses electron-hole recombination, thereby greatly improving the photocatalytic quantum efficiency. This is the structural basis for the high CO yield and high selectivity of this catalyst.

[0022] Furthermore, the microstructure of the catalyst was defined as nanosheets and nanoparticles attached to the nanosheets. SEM and TEM images show that the nanosheet structure provides a large specific surface area and abundant reaction sites, while the nanoparticles attached to the nanosheets form a tight interfacial contact with the nanosheets. This unique morphological feature is conducive to electron transfer and mass transport between the three phases, while the nanosize effect also enhances light absorption, jointly promoting the improvement of catalytic performance.

[0023] Furthermore, the catalyst was limited to a carbon monoxide generation rate of no less than 90 μmol·g in the photocatalytic CO2 hydrogenation reaction. -1 ·h -1The carbon monoxide selectivity is not less than 98%, and the performance degradation does not exceed 5% after multiple cycle tests. (See Table 1 and...) Figure 5 Cyclic stability tests confirmed that the CO production rate in Example 1 reached 335.73 μmol·g⁻¹. -1 ·h -1 This is significantly higher than the comparative values ​​of 20.53, 16.44, and 56.74 μmol·g⁻¹. -1 ·h -1 The selectivity reached 98%, and the performance remained stable after multiple cycles. These performance parameters quantitatively demonstrate that the catalyst has achieved an excellent activity level among non-precious metal-based photocatalysts. At the same time, the good cycling stability indicates that the catalyst has a robust structure, strong resistance to deactivation, and practical application value.

[0024] Furthermore, the MoO2 phase was defined as amorphous with oxygen vacancies on its surface. Compared to the crystalline phase, the amorphous MoO2 phase has more unsaturated coordination sites and structural defects. The abundant oxygen vacancies on its surface can serve as trapping and activation sites for CO2 molecules, promoting the conversion of CO2 into intermediate products. At the same time, the presence of oxygen vacancies can also regulate the electronic structure of the material, enhance the absorption of visible light, and form a complementary synergy with the H2 dissociation function of the Cu / Cu2O component. This is one of the important microscopic mechanisms by which this catalyst achieves high selectivity and high stability.

[0025] This invention also discloses the application of the catalyst, namely, as a photocatalyst for the photocatalytic hydrogenation reaction of CO2, used to convert CO2 and H2 into CO. Under simulated sunlight irradiation, this catalyst directly converts CO2 and H2 into CO, realizing solar-driven CO2 resource utilization. The CO selectivity reaches 98%, effectively suppressing the formation of other byproducts such as methane. Furthermore, the preparation process itself is green and low-consumption, showing clear industrial application prospects in the field of carbon capture, utilization, and storage. Attached Figure Description

[0026] Figure 1 This is the Raman spectrum of the Cu / Cu2O / MoO2 catalyst provided in Example 1 of this invention; Figure 2 The XRD patterns of Cu3Mo2O9 and Cu / Cu2O / MoO2 catalysts provided in Example 1 of this invention; Figure 3 The morphology diagram of the Cu / Cu2O / MoO2 catalyst provided in Example 1 of this invention; Figure a is a TEM image, Figure b is an HRTEM image, and Figure c is an elemental mapping map. Figure 4 This is a SEM image of the Cu / Cu2O / MoO2 catalyst provided in Example 1 of the present invention; Figure 5 Cyclic stability test of the Cu / Cu2O / MoO2 catalyst provided in Example 1 of this invention; Figure 6 These are the XRD patterns of the catalysts provided in Comparative Examples 1-3 of this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0028] The detailed description of the embodiments of the present invention provided in the following figures is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the figures and embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0029] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0030] Example 1 This embodiment discloses a method for preparing a Cu / Cu2O / MoO2 catalyst, including the following steps: S1. Dissolve 0.82 g Cu(NO3)2·3H2O in 40 mL of deionized water to form solution A; S2. Dissolve 0.4 g Na2MoO4·2H2O in 40 mL of deionized water to form solution B; S3. Under room temperature and stirring conditions, solution B is slowly added dropwise to solution A, and stirring is continued for a certain period of time. The precipitate is then washed, filtered, and dried, and then calcined at a reaction temperature of 400 °C for 2 hours to obtain Cu3Mo2O9 sample. S4. Place the obtained Cu3Mo2O9 sample in a micro-reaction device and react for 10 hours at a reaction temperature of 300 ℃, a CO2 / H2 mixed gas flow ratio of 1:3 (CO2 and H2 flow rates of 2 mL / min and 6 mL / min, respectively), and atmospheric pressure to obtain the Cu / Cu2O / MoO2 catalyst.

[0031] Product characterization tests: Raman and XRD tests were performed on the prepared Cu / Cu2O / MoO2 samples. Raman tests were also performed on pure phase Cu2O and MoO2 samples as controls, and XRD tests were performed on the Cu3Mo2O9 sample obtained in step S3 as a control. The results are as follows: Figure 1 and Figure 2 As shown in the figure, the final synthesized material is a Cu / Cu2O / MoO2 composite material.

[0032] The prepared Cu / Cu2O / MoO2 samples were subjected to TEM and HRTEM tests. The TEM results are as follows: Figure 3 As shown in Figure a, the HRTEM results are as follows: Figure 3 As shown in Figure b, the final synthesized Cu / Cu2O / MoO2 sample exhibits a microstructure consisting of numerous nanosheets and tightly attached nanoparticles; according to Figure 3 The elemental mapping diagram shown in Figure c shows that the final synthesized sample is composed of three elements: Cu, Mo, and O, further confirming the conclusion that the final product is a Cu / Cu2O / MoO2 composite material.

[0033] like Figure 4 The SEM image shown indicates that the catalyst has a microstructure consisting of nanosheets and nanoparticles attached to the nanosheets. The thickness of the nanosheets is 10 nm, and the diameter of the nanoparticles is 40-70 nm.

[0034] like Figure 5 As shown, the CO generation rate and CO selectivity in the cyclic photocatalytic CO2 hydrogenation of the catalyst remained at a relatively stable level with minimal fluctuations after multiple cycles of reaction. This fully demonstrates that the Cu / Cu2O / MoO2 sample has excellent photocatalytic stability in the CO2 hydrogenation reaction.

[0035] Example 2 The difference from Example 1 is that in S4, the reaction temperature is 250 °C, which yields a Cu / Cu2O / MoO2 catalyst.

[0036] Example 3 The difference from Example 1 is that in S4, the reaction temperature is 200 °C, and a Cu / Cu2O / MoO2 catalyst is obtained.

[0037] Example 4 The difference from Example 1 is that in S4, the reaction temperature is 150 °C, and a Cu / Cu2O / MoO2 catalyst is obtained.

[0038] Example 5 The difference from Example 1 is that in S3, the conditions for hot calcination are: reaction temperature 350 °C and reaction time 3 hours.

[0039] Example 6 The difference from Example 1 is that in S3, the conditions for hot calcination are: reaction temperature 450 °C and reaction time 1 hour.

[0040] Comparative Example 1 The difference from Example 1 is that in S4, the reaction temperature is 100 °C, and a catalyst is obtained.

[0041] Comparative Example 2 The difference from Example 1 is that in S4, the reaction temperature is 75 °C, and a catalyst is obtained.

[0042] Comparative Example 3 The difference from Example 1 is that in S4, the reaction temperature is 400 °C, and a catalyst is obtained.

[0043] XRD tests were performed on the products obtained from comparative examples 1-3, and the results are as follows: Figure 6 As shown, the products of Comparative Examples 1-2 are mainly Cu3Mo2O9, with no obvious Cu, Cu2O and MoO2 phases. Although Comparative Example 3 contains the MoO2 phase, the Cu2O phase has been partially over-reduced, and the ratio of the three phases deviates from the optimal state.

[0044] The Cu / Cu₂O / MoO₂ catalyst prepared in the above examples and the product prepared in the comparative example were placed into batch reactors. Before the reaction, the reactors were repeatedly purged with argon gas to remove residual air, and then a mixed gas of CO₂ / H₂ = 1 / 4 (0.16 MPa) was introduced. The light source for the photocatalytic reaction was a CEL-PF300-T3 Xe lamp (Beijing Zhongjiao Jinyuan), with an output light power of approximately 600 mW·cm⁻¹. -2 After irradiating with a xenon lamp for 3 hours, the products of photocatalytic CO2 hydrogenation were tested using a gas chromatograph (GC-7920). The performance evaluation results of the products prepared in the above examples and comparative examples for CO preparation are shown in Table 1.

[0045] Table 1 Evaluation Results

[0046] Combination Figures 1-4 The structural characterization results and the performance data in Table 1 show that the Cu / Cu2O / MoO2 catalyst prepared in Example 1 of this invention forms a double heterojunction structure with the Cu / Cu2O Schottky junction and the Cu2O / MoO2 p-n junction. It is this unique structure that enables the efficient separation of photogenerated carriers. Simultaneously, the oxygen-vacancy-rich amorphous MoO2 and Cu / Cu2O provide functionally complementary active sites for CO2 activation and H2 dissociation, respectively. The efficient synergistic effect among the three components Cu, Cu2O, and MoO2 results in excellent catalytic performance of the Cu / Cu2O / MoO2 catalyst, with a CO generation rate of 335.73 mmol / g / h, far exceeding that of the comparative example and other examples, and a selectivity of 98%. Furthermore, it maintains excellent stability in multiple cycle tests.

[0047] The purpose of setting up the above comparative examples is to investigate the effect of activation reaction temperature on the phase composition and catalytic performance of the final product. When the activation temperature is too low (75 ℃, 100 ℃), the reduction ability of the CO2 / H2 mixture on the Cu3Mo2O9 precursor is insufficient, making it difficult to effectively convert the precursor into the target three phases (Cu, Cu2O, MoO2), thus failing to effectively construct the Cu / Cu2O Schottky junction and form a complete three-phase synergistic system. As shown in Table 1, the CO generation rates of Comparative Examples 1 and 2 are only 20.53 and 16.44 μmol·g, respectively. -1 ·h -1 This is significantly lower than the 93.52 μmol·g in Example 4 (150 °C). -1 ·h -1 And 335.73 μmol·g in Example 1 (300°C) -1 ·h -1 This demonstrates the decisive influence of activation temperature on catalyst activity. When the activation temperature is increased to 150 °C or above, the reducing atmosphere can effectively regulate the degree of precursor reduction, ensuring that the ratio of Cu, Cu₂O, and MoO₂ in the product is within a suitable range, thereby forming a dual heterojunction structure and exerting a synergistic catalytic effect of the three components. However, a higher activation temperature is not always better; when the temperature is further increased to 400 °C (Comparative Example 3), the CO formation rate is only 56.74 μmol·g⁻¹. -1 ·h -1 Although the temperature range improved compared to the lower-temperature comparative sample, it was still significantly lower than that of the 300 °C activated sample. This indicates that excessively high temperatures may lead to over-reduction of Cu₂O to metallic Cu, damaging the Cu / Cu₂O Schottky junction interface, or causing over-reduction of MoO₂ and even particle sintering, thus weakening the three-phase synergistic effect. Therefore, the above comparative samples, from the perspectives of insufficient low temperature and excessive high temperature, jointly verify the critical significance of the activation reaction temperature range (especially 150-300 °C) defined in this invention for the preparation of high-performance Cu / Cu₂O / MoO₂ catalysts.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a Cu / Cu2O / MoO2 catalyst, characterized in that, Includes the following processes: Dissolve the copper salt in deionized water to form solution A; Dissolve molybdate in deionized water to form solution B; Solution B is added dropwise to solution A under stirring, and stirring continues, resulting in the formation of a precipitate; The precipitate was washed, filtered, dried, and calcined to obtain a Cu3Mo2O9 sample. The Cu3Mo2O9 sample was activated by a CO2 hydrogenation atmosphere at a reaction temperature of 150-300 °C to obtain a Cu / Cu2O / MoO2 catalyst.

2. The method for preparing the Cu / Cu2O / MoO2 catalyst according to claim 1, characterized in that, The conditions for the thermal calcination are: reaction temperature 350-450 ℃, reaction time 1-3 hours.

3. The method for preparing the Cu / Cu₂O / MoO₂ catalyst according to claim 1, characterized in that, The activation reaction conditions are: continuous flow of CO2 / H2 mixed gas, atmospheric pressure, and reaction time of 10 hours.

4. The method for preparing the Cu / Cu2O / MoO2 catalyst according to claim 3, characterized in that, The flow rate ratio of the CO2 / H2 mixed gas flow is CO2 / H2=1:

3.

5. The method for preparing the Cu / Cu₂O / MoO₂ catalyst according to claim 1, characterized in that, The copper salt is Cu(NO3)2·3H2O; the molybdate is Na2MoO4·2H2O.

6. A Cu / Cu₂O / MoO₂ catalyst prepared by the method according to any one of claims 1-5, characterized in that, The Cu / Cu2O / MoO2 catalyst comprises a Cu phase, a Cu2O phase, and a MoO2 phase, wherein Cu and Cu2O form a Schottky junction, and Cu2O and MoO2 form a pn junction, constituting a double heterojunction structure.

7. The Cu / Cu₂O / MoO₂ catalyst according to claim 6, characterized in that, The catalyst has a microstructure consisting of nanosheets and nanoparticles attached to the nanosheets.

8. The Cu / Cu₂O / MoO₂ catalyst according to claim 6, characterized in that, The catalyst exhibits a carbon monoxide generation rate of no less than 90 μmol·g in the photocatalytic CO2 hydrogenation reaction. -1 ·h -1 The carbon monoxide selectivity is not less than 98%, and the performance degradation does not exceed 5% after multiple cycle tests.

9. The Cu / Cu₂O / MoO₂ catalyst according to claim 6, characterized in that, The MoO2 phase is amorphous and contains oxygen vacancies on its surface.

10. The application of the Cu / Cu₂O / MoO₂ catalyst according to any one of claims 6-9, characterized in that, The Cu / Cu2O / MoO2 catalyst serves as a photocatalyst for the photocatalytic hydrogenation reaction of CO2, converting CO2 and H2 into CO.

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