A carbon-coated CeO2-modified Cu-based catalyst, its preparation method and application

Abstract

The application discloses a carbon-coated CeO2 modified Cu-based catalyst and a preparation method and application thereof, and relates to the technical field of catalyst preparation. The preparation method of the carbon-coated CeO2 modified Cu-based catalyst provided by the application utilizes a carbon coating layer to enable CeO2 and Cu to be closely dependent on each other, enables CeO2 to modify Cu, introduces oxygen vacancies, can not only increase defect sites, but also effectively reduces migration and agglomeration of Cu species, reduces the particle size of active component particles, enables the catalytic activity of the catalyst to be greatly improved when the catalyst is used to catalyze APRM, and thus, even when catalysis is performed at a temperature of 180 DEG C or below, the APRM reaction can be efficiently performed.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a carbon-coated CeO2-modified Cu-based catalyst, its preparation method, and its application. Background Technology

[0002] Energy is fundamental to human production and daily life. Hydrogen energy, characterized by its cleanliness, efficiency, safety, and sustainability, is considered one of the most promising clean energy sources for the 21st century. Among numerous hydrogen production technologies, APRM (aqueous-phase reforming of methanol) is a highly attractive and promising pathway with many advantages, such as low energy consumption, low reaction temperature, and the elimination of the need for gasification of the reactants, thus saving significant energy. Methanol is a widely available and readily accessible feedstock. The hydrogen production rate is high, and the resulting gas has a low CO concentration. The relatively low reaction temperature prevents the gasification and decomposition of the products, reducing the formation of byproducts. Furthermore, hydrogen can be separated and purified using pressure swing adsorption or membrane technology, effectively recovering and utilizing CO2.

[0003] High-temperature proton exchange membrane fuel cells (PEM fuel cells) primarily use methanol as fuel and operate and generate electricity at temperatures between 150 and 180°C. However, most existing APRM reactions require temperatures between 210°C and 350°C. Therefore, developing a low-temperature, high-efficiency hydrogen production catalyst is crucial for achieving heat exchange between the APRM reaction and high-temperature PEM fuel cells.

[0004] Existing technology discloses an ultrafine Cu-based catalyst for methanol steam reforming to hydrogen, its preparation method, and its application. Ultrafine rare earth oxide CeO2 particles are introduced as a support, increasing the catalyst's specific surface area and exposing more copper active sites. Simultaneously, the interfacial effect between Cu and rare earth elements enables the catalyst to catalyze the methanol reforming to hydrogen reaction at low temperatures of 150–200 °C. However, the primary reaction catalyzed by this catalyst is SRM (methanol steam reforming to hydrogen), which differs from APRM. Secondly, this catalyst cannot fully utilize the interaction between Cu and CeO2; therefore, when using this catalyst to catalyze the SRM reaction at 200 °C, the highest hydrogen production rate can only reach 17.6 mL·g. cat -1 ·min -1 That is, 13.2 μmol·g cat -1 ·s -1 This indicates that the efficiency of the catalyst in catalytic reactions at low temperatures still needs to be improved. Summary of the Invention

[0005] To address the problem that existing CeO2-modified Cu-based catalysts cannot fully utilize the interaction between Cu and CeO2, resulting in insufficient catalyst activity and difficulty in efficiently catalyzing APRM reactions at low temperatures, this invention provides a method for preparing a carbon-coated CeO2-modified Cu-based catalyst. The carbon coating layer allows CeO2 and Cu to adhere closely, enabling CeO2 to modify Cu and adjust the ratio of 0-valent to 1-valent copper in the catalytically active component. This significantly enhances the catalyst's activity in APRM catalysis, achieving excellent catalytic performance at temperatures not exceeding 180°C.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] A method for preparing a carbon-coated CeO2-modified Cu-based catalyst includes the following steps:

[0008] S1. Mix the Ce source, Cu source, carbon source and solvent thoroughly and allow them to react completely. After the reaction is complete, a complex is obtained.

[0009] S2. The complex obtained in step S1 is calcined in an inert atmosphere to obtain a carbon-coated complex;

[0010] S3. Place the carbon-coated composite obtained in step S2 in a reducing atmosphere and carry out a reduction reaction at 200-450℃. After the reaction is completed, a carbon-coated CeO2-modified Cu-based catalyst can be obtained.

[0011] The carbon source in step S1 contains carbonyl groups and / or hydroxyl groups, and the molar ratio of Cu source to Ce source is 7:(0.05~1).

[0012] Conventional Ce sources, Cu sources, carbon sources containing carbonyl groups and / or hydroxyl groups, and solvents in the art can all be used in step S1 of the present invention.

[0013] Specifically, the Ce source used in step S1 of this invention is cerium nitrate.

[0014] Specifically, the Cu source used in step S1 of this invention is copper nitrate.

[0015] Specifically, the carbon source containing a carbonyl group used in step S1 of the present invention can be PVP (polyvinylpyrrolidone).

[0016] Specifically, the hydroxyl-containing carbon source used in step S1 of the present invention is guar gum powder.

[0017] Specifically, the solvent used in step S1 of the present invention is water.

[0018] Step S1 is a reaction carried out using the sol-gel method. In this step, a carbon source containing carbonyl and / or hydroxyl groups is added to the solvent, and the carbonyl or hydroxyl groups in the carbon source can react with Cu. 2+ Complexation bonds form a gel framework in the reaction system, and the gel supports Cu. 2+ Ce ions and Ce ions (trivalent Ce) 3+ and tetravalent Ce 4+ (Coexistence) has an adsorption effect, which can make the two ions uniformly dispersed in the system and form a complex.

[0019] Any conventional inert atmosphere in the art can be applied to step S2 of the present invention.

[0020] Specifically, the inert atmosphere used in step S2 of the present invention is nitrogen.

[0021] The purpose of step S2 is to pyrolyze the carbon source and convert Cu and Ce ions into CuO and CeO2. In step S2, after pyrolysis, the carbon source forms carbon-coated composite particles that encapsulate CuO and CeO2. These particles have a core-shell structure, with CuO and CeO2 as the core and a carbon layer as the shell, which also serves as the carbon support for the catalyst. Simultaneously, elements such as H and O present in the carbon source are released as gases during pyrolysis, resulting in a porous carbon coating layer in the carbon-coated composite particles obtained in step S2. While calcination in the art can typically be carried out in air, the calcination in step S2 of this invention must be performed in an inert atmosphere. This is because air contains oxygen, and carbon is easily removed as CO2 and CO, making it difficult to form a carbon layer. Furthermore, this invention uses an inert atmosphere for calcination, during which the carbon source generates reducing gases such as H2 and CO, partially reducing the CuO and CeO2 content in the carbon source. 2+ Therefore, the Cu element in the carbon-coated composite particles obtained in step S2 of this invention may exist not only in the form of CuO, but also in elemental Cu and / or Cu2O. This is advantageous for selectively reducing Cu without reducing CeO2 in the subsequent step S3. Calcination in air, Cu... 2+ It is difficult to partially reduce. In this case, the reduction in step S3 needs to be carried out at a higher temperature, which will easily reduce CeO2 as well.

[0022] Any reducing atmosphere commonly used in the art can be applied to step S3 of the present invention.

[0023] Specifically, the reducing atmosphere used in step S3 of the present invention is hydrogen.

[0024] More specifically, when using a hydrogen atmosphere for the reduction reaction, the flow rate of hydrogen into the reaction system is 20 mL / min.

[0025] The purpose of step S3 is to reduce the CuO in the carbon-coated composite obtained in step S2 to elemental Cu with a zero valence, while ensuring that CeO2 is not reduced to elemental Ce. This is because elemental Ce does not have oxygen vacancies on its surface, and the interaction between elemental Ce and Cu is weak, making it difficult to suppress Cu dispersion and improve the catalytic activity of the catalyst. Therefore, step S3 requires controlling the reduction temperature to 200–450 °C to ensure that CeO2 is not reduced.

[0026] It should be noted that during the reduction of CuO in step S3 of this invention, the core-shell structure of the carbon-coated particles remains unchanged. Only the form of Cu in the core component changes (CuO is reduced). The carbon coating layer will hinder the reduction of CuO to a certain extent. Therefore, the Cu in the carbon-coated particles after reduction is not entirely in the form of zero-valent element, but also contains some 1-valent Cu, which exists in the form of Cu2O.

[0027] By adding CeO2, this invention can adjust the ratio between monovalent and devalent copper, presumably because the CeO2 surface contains abundant oxygen vacancies, which can capture oxygen from Cu2O. During the APRM reaction catalyzed by the copper-based catalyst, a suitable ratio of monovalent and devalent copper on the catalyst can interconvert. Cu, as the catalytically active component, can flexibly switch between "donating electrons to reactants" and "attracting electrons from reactants," thus significantly enhancing the catalytic activity of the catalyst obtained in this invention (increasing the number of pathways to achieve the catalytic reaction). When the content of monovalent copper is too high, the interconversion between devalent and monovalent copper becomes difficult, which is why this invention requires the introduction of CeO2 into the catalyst. Conversely, when the amount of CeO2 added is too high, the amount of monovalent copper is too low, making the interconversion between devalent and monovalent copper equally difficult. Furthermore, because CeO2 contains abundant oxygen vacancies, its introduction not only adjusts the ratio of monovalent and devalent copper, but also increases the proportion of monovalent and devalent copper in the catalyst's copper species (copper species are difficult to form CuO because oxygen is easily captured by oxygen vacancies on the CeO2 surface). Simultaneously, it promotes the formation of more reactive sites on the catalyst surface (oxygen vacancies are also catalytically active sites), improving the catalyst's electron transfer capacity and surface active site density, thereby enhancing its catalytic activity. Oxygen vacancies also promote strong interactions between the active component Cu and the carbon support, thus improving the catalyst's stability and resistance to poisoning.

[0028] Meanwhile, the addition of CeO2 in this invention can also improve the dispersibility of Cu, making it less likely for Cu to migrate and aggregate during the catalytic process.

[0029] For the reasons mentioned above, in step S1 of this invention, the molar ratio of Cu source to Ce source needs to be controlled to be 7:(0.05~1) in order to simultaneously adjust the ratio between monovalent copper and 0valent copper as well as the density of oxygen vacancies, and improve the dispersion of Cu element so that it is within a suitable range.

[0030] It should be noted that the primary purpose of introducing a carbon coating layer into the catalyst in this invention is to prevent the migration and aggregation of Cu elements. Based on the two-step process of carbon coating and the introduction of CeO2, the active component Cu element in the catalyst provided by this invention exhibits excellent dispersibility and maintains stable dispersion during catalysis, making it less prone to migration and aggregation. Furthermore, when the catalyst in this invention is applied to the APRM reaction, it operates under hydrothermal conditions. While metal elements have low hydrothermal stability, carbon has high hydrothermal stability; therefore, carbon coating can improve the catalytic stability of the catalyst, enabling it to catalyze for extended periods. Secondly, the carbon coating layer can coat both Cu and CeO2, ensuring close adhesion between them and fully utilizing their interaction.

[0031] It should be noted that, in the preparation method of this invention, the carbon source not only forms the carbon coating layer but also acts as a carbon support; the hollow shell-like layered carbon coating layer can be considered as the support. The core-shell structured carbon-coated composite particles obtained in step S2 of this invention stack together to form a larger sheet-like structure. After reduction in step S3, the morphology of the resulting catalyst remains unchanged, still consisting of a sheet-like structure formed by the stacking of carbon-coated particles.

[0032] Preferably, the molar ratio of Cu source to carbon source in step S1 is 7:(5-15).

[0033] By controlling the molar ratio of Cu source to carbon source to be 7:(5-15), when step S1 is fully completed, Cu ions can be fully loaded onto the gel framework, and steps S2-S3 do not affect the Cu loading. Therefore, the Cu and carbon content on the final catalyst can be controlled. At the same time, it is important to understand that carbon itself is not a catalytically active substance for the APRM reaction. If the amount of carbon source added is too high, the carbon coating layer in the catalyst will be too thick, which will lead to a decrease in catalyst activity. However, if the amount of carbon source added is too low, the catalyst will find it difficult to utilize the carbon coating effect to prevent the aggregation of active components.

[0034] Preferably, the molar ratio of Cu source to Ce source in step S1 is 7:(0.08~0.22).

[0035] When the molar ratio of Cu source to Ce source in step S1 is controlled to be 7:(0.08~0.22), the ratio of monovalent Cu to 0valent Cu in the obtained catalyst is more suitable for catalyzing the APRM reaction.

[0036] Preferably, the carbon source in step S1 is PVP.

[0037] When PVP (polyvinylpyrrolidone) is used as a carbon source, it may generate reducing gases during the subsequent calcination process in step S2, which facilitates the reduction of CuO in step S3. Simultaneously, as a nitrogen-containing polymer, PVP, after calcination, forms a nitrogen-doped carbon coating layer around Cu and CeO2, further enhancing catalytic activity. Furthermore, the pyrrolidone groups in PVP can form coordination bonds with metal ions, and this bonding persists after calcination, contributing to the stability of elemental Cu. The coating layer also forms a tighter bond with the core components (Cu and CeO2), ensuring high dispersion of the active components, i.e., the core components, during catalysis. In addition, the abundant mass transfer channels formed by PVP as a carbon source facilitate the transport of hydrogen from methanol and water during the APRM reaction, improving the catalyst's selectivity for hydrogen and enhancing catalytic efficiency.

[0038] Preferably, the calcination temperature in step S2 is 400–700°C.

[0039] When the calcination temperature is too low, the copper salt and carbon source cannot be fully pyrolyzed, failing to form a high-load catalyst or tightly coated carbon particles. This reduces both the catalytic activity and stability of the catalyst. Conversely, when the calcination temperature is too high, the copper metal sinters to form large particles, reducing the hydrogen production rate and CO selectivity of the final catalyst.

[0040] Preferably, the calcination time in step S2 is 2 to 5 hours.

[0041] Preferably, the reduction temperature in step S3 is 250–400°C.

[0042] Conducting the reduction reaction within this temperature range can better ensure the uniform dispersion of Cu species.

[0043] The present invention also protects a carbon-coated CeO2-modified Cu-based catalyst prepared by the above preparation method.

[0044] Preferably, the Cu content in the catalyst is 30–80 wt%.

[0045] More preferably, the Cu content in the catalyst is 60-70 wt%.

[0046] The catalyst prepared using the method provided in this invention exists not only in its elemental form but also as monovalent copper (Cu₂O). Furthermore, this invention employs both carbon coating and the introduction of CeO₂ to promote Cu dispersion. Therefore, when the Cu content is 30–80 wt%, more preferably 60–70 wt%, it demonstrates that this invention not only successfully prepared the desired catalyst but also achieved a suitable ratio of monovalent to oxidative copper on the catalyst. Excessive Cu content leads to the accumulation of active components; insufficient Cu content results in decreased catalytic activity.

[0047] Preferably, the carbon content of the catalyst is 5-15 wt%.

[0048] When the carbon content is too low, it will not only hinder the dispersion of copper, but also reduce the stability of the catalyst. However, when the carbon content is too high, it will reduce the exposure of the active components, thereby reducing the selectivity and catalytic efficiency of the catalyst.

[0049] The present invention also protects the use of the above-mentioned catalyst in the catalytic APRM reaction.

[0050] Preferably, the above-mentioned catalyst is used for catalysis, and the temperature of the APRM reaction during the catalytic process does not exceed 180°C.

[0051] Most existing APRM reactions are carried out at temperatures between 210 and 350°C. However, the copper-based catalyst provided by this invention exhibits excellent dispersibility of copper particles that do not agglomerate during use, thus demonstrating excellent catalytic activity even at low temperatures not exceeding 180°C. Catalysis at such temperatures further highlights the superior activity of the catalyst provided by this invention.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] The method for preparing carbon-coated CeO2-modified Cu-based catalyst provided by this invention utilizes carbon coating and CeO2 to modify Cu, adjusting the ratio of 0-valent copper to 1-valent copper in the catalytic active component and improving the catalyst activity. This allows the catalyst to maintain excellent catalytic performance during the APRM reaction under catalytic conditions, achieving a hydrogen production rate of 32.6 μmol·g at a catalytic temperature of 180°C. cat -1 ·s -1 Even at a catalytic temperature of 130℃, the hydrogen production rate can still reach 1.5 μmol·g. cat -1 ·s -1 This enables efficient hydrogen production at low temperatures. Attached Figure Description

[0054] Figure 1 This is a comparison chart showing the performance of the catalysts obtained in Comparative Examples 7 and 6 of Example 1 of the present invention in catalyzing the APRM reaction.

[0055] Figure 2 The above are comparative XRD spectra of the catalysts obtained in Comparative Example 1, Example 1, Example 6, Comparative Example 2 and Comparative Example 3 of the present invention.

[0056] Figure 3 The XRD comparison spectra of the catalysts obtained in Example 1, Comparative Example 1, Comparative Example 4 and Comparative Example 5 of the present invention are shown.

[0057] Figure 4 These are TEM images of the catalysts obtained in Example 1 and Comparative Example 1 of the present invention.

[0058] Figure 5 The image shows the FTIR spectrum of the catalyst obtained in Example 1 of this invention.

[0059] Figure 6 This is an EDS mapping elemental analysis diagram of the catalyst obtained in Example 1 of the present invention.

[0060] Figure 7 This is a graph showing the in-situ cycle stability test of the catalyst obtained in Example 1 of the present invention.

[0061] Figure 8 The graph shows the catalytic performance of the catalyst obtained in Example 1 of the present invention under different alcohol-to-water ratios.

[0062] Figure 9 The image shows the lattice fringes of the catalyst obtained in Example 1 of this invention via HRTEM.

[0063] Figure 10 This is the H2-TPR diagram of the catalyst obtained in Example 1 of the present invention. Detailed Implementation

[0064] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0065] Example 1

[0066] A method for preparing a carbon-coated CeO2-modified Cu-based catalyst includes the following steps:

[0067] S1. Cerium nitrate, copper nitrate, PVP and water are mixed and allowed to react completely. After the reaction is complete, a complex is obtained.

[0068] S2. The complex obtained in step S1 is placed in a nitrogen atmosphere and calcined at a temperature of 600℃ for 3 hours. After calcination, a carbon-coated complex is obtained.

[0069] S3. The carbon-coated composite obtained in step S2 is placed in a hydrogen atmosphere and a reduction reaction is carried out at 350°C for 2 hours. After the reaction is completed, the carbon-coated CeO2 modified Cu-based catalyst is obtained.

[0070] In step S1, the concentration of the carbon source is 0.4 mol / L, the molar ratio of Cu source to Ce source is 7:0.1, and the molar ratio of Cu source to carbon source is 7:10.3.

[0071] In the carbon-coated CeO2-modified Cu-based catalyst prepared in this embodiment, the Cu element content is 70.6 wt% and the carbon element content is 10.7 wt%.

[0072] Examples 2-7

[0073] A series of methods for preparing carbon-coated CeO2-modified Cu-based catalysts are provided. The specific preparation methods are carried out according to Example 1, and the differences are shown in Table 1 below.

[0074] Table 1. Control of parameters in the preparation methods provided in Examples 1-7

[0075]

[0076]

[0077] Comparative Examples 1-5

[0078] A series of catalyst preparation methods are provided, and the specific preparation methods are carried out according to Example 1. The differences are shown in Table 2 below.

[0079] Table 2. Parameter control in the preparation methods provided in Comparative Examples 1–5

[0080]

[0081] Comparative Example 6

[0082] This comparative example provides a commercial Raney copper catalyst.

[0083] Comparative Example 7

[0084] This comparative example provides a commercial platinum-carbon catalyst, specifically a 20% Pt / C catalyst.

[0085] Performance testing

[0086] APRM reaction catalytic performance test:

[0087] 50 mg of the catalyst obtained in the examples and comparative examples was added to 20 mL of a reaction solution of water and methanol with a molar ratio of 1:1. Hydrogen production performance was tested in a batch reactor using 2 MPa nitrogen as a protective gas. After reacting at 130 °C and 180 °C for 45 min, the reaction was cooled to room temperature, and the gaseous products were quantitatively analyzed by gas chromatography. The hydrogen production rate of the catalyst was calculated using the water displacement method, where the hydrogen production rate is the amount of hydrogen produced per gram of catalyst per second (μmol). Selectivity was calculated based on the amount of H2, CO, and CH4 in the products, where the hydrogen selectivity H2 (%) = n. H2 *100% / (n H2 +n CO +n CH4 ), Carbon monoxide selectivity CO (%) = n CO *100% / (n H2 +n CO +n CH4 ).

[0088] Specific performance test data are shown in Tables 3 and 4 below. Figures 1-10 As shown:

[0089] Table 3. Comparison of hydrogen production rates and selectivity of the catalysts used in the examples and comparative examples at 180°C.

[0090]

[0091] Table 4. Catalytic activity of the catalyst obtained in Example 1 of the present invention at 130°C and 180°C.

[0092]

[0093] The data in Tables 1-3 show that controlling the molar ratio of Cu source to Ce source in step S1 to be 7:(0.05-1) successfully prepares carbon-coated CeO2-modified Cu-based catalysts with excellent catalytic activity (Examples 1-6). However, the absence of a Ce source (Comparative Example 1) or the addition of excessive Ce source (Comparative Examples 2-3) both lead to a decrease in the performance of the obtained catalyst. Without a Ce source, the resulting catalyst lacks CeO2, making it difficult to modify Cu. However, adding too much Ce source (Comparative Examples 2-3) results in an insufficient amount of monovalent copper, making the interconversion reaction between divalent and monovalent copper difficult to occur, thus hindering the improvement of the catalyst's catalytic activity.

[0094] Combining the data from Tables 1 and 3, it can be seen that when the molar ratio of Cu source to Ce source is within the preferred range of 7:(0.08–0.22) (Examples 1–2), the resulting catalyst exhibits superior catalytic activity. This is because when this molar ratio is controlled within this range, the ratio between monovalent and devalent copper, the density of oxygen vacancies, and the dispersion of Cu are all within a range more suitable for catalyzing the APRM reaction. As the amount of Ce source added continuously increases (Examples 3–6), although the selectedivity for hydrogen in the APRM reaction remains excellent, the hydrogen production rate continuously decreases. This is because increasing the Ce source leads to an increase in the ratio between monovalent and devalent copper, while monovalent copper itself is not a catalytically active substance; its role in catalyzing the APRM reaction is due to its ability to be converted into elemental Cu. Based on the data from Examples 1 and 7, it can be seen that the catalyst obtained when the carbon source in step S1 is PVP has superior performance compared to guar gum powder.

[0095] The data from Tables 2 and 3 confirm that the catalyst without CeO2 (Comparative Example 1) and the catalyst without Cu (Comparative Example 4) are both difficult to catalyze. Furthermore, the data from Comparative Example 5 shows that carbon coating of the active component is also essential in this invention. Without a carbon coating layer, CeO2 and Cu elements cannot fully contact each other, and CeO2 cannot effectively improve the dispersion of Cu elements or adjust the ratio between monovalent and devalent copper. Therefore, the catalyst provided in Comparative Example 5 is also difficult to catalyze.

[0096] As can also be seen from Table 3, the catalyst provided by this invention has superior catalytic activity compared with the two commercially available catalysts (Comparative Example 6 and Comparative Example 7).

[0097] As can be seen from the data in Table 4, the catalyst provided by this invention can still achieve a hydrogen production rate of 1.5 μmol·g when catalyzed at a catalytic temperature of 130℃. cat -1 ·s -1 It can achieve efficient hydrogen production at low temperatures.

[0098] Figure 1 This is a comparison chart showing the performance of the catalysts obtained in Example 1, Comparative Example 7, and Comparative Example 6 of this invention in catalyzing the APRM reaction. From... Figure 1As can be seen, the catalyst of Example 1 exhibits a 99.96% selectivity for hydrogen and a CO selectivity of only 0.04% at 180°C, which is superior to the commercial Raney copper catalyst (Comparative Example 6). In contrast, the commercial platinum-carbon catalyst (20% Pt / C, Comparative Example 7) doped with noble metals shows a hydrogen selectivity of 98.09%, lower than that of Example 1, but a CO selectivity of 0.06%, higher than that of Example 1, and a catalytic hydrogen production rate of only 5.4 μmol·gcat. -1 ·s -1 The cost is higher than that of Example 1; while the hydrogen production rate of the catalyst in Example 1 is 32.6 μmol·gcat. -1 ·s -1 This represents a breakthrough in hydrogen production technology for methanol-water reforming using non-precious metal catalysts at a low temperature of 180℃, achieving a hydrogen production rate 54.33 times that of commercial Raney copper catalysts and 6.04 times that of commercial platinum-carbon catalysts under the same conditions. It improves catalytic efficiency while maintaining high hydrogen selectivity.

[0099] Figure 2 The XRD patterns of the catalysts obtained in Comparative Example 1 (Cu:Ce = 7:0), Example 1 (Cu:Ce = 7:0.1), Example 6 (Cu:Ce = 7:1), Comparative Example 2 (Cu:Ce = 7:2), and Comparative Example 3 (Cu:Ce = 7:3) are shown below. Figure 2 XRD analysis showed that when the Cu:Ce ratio of the catalyst was 7:0 and 7:0.1, the main active component was elemental copper, with a small amount of monovalent copper ions. These two valence states of copper could be converted during hydrogen production, ensuring the activity of the catalyst. When the Ce content increased to Cu:Ce of 7:1, Ce could be detected by XRD.

[0100] Figure 3The XRD patterns of the catalysts obtained in Example 1 (Cu-CeO2@PVP), Comparative Example 1 (Cu@PVP), Comparative Example 4 (CeO2@PVP), and Comparative Example 5 (Cu-CeO2) are shown. It can be seen that the main peaks of 0-valent and 1-valent copper in the catalyst without Ce (Comparative Example 1) are sharper than those in the carbon-coated CeO2-modified Cu catalyst, indicating a larger particle size and lower catalyst activity. Cu tends to agglomerate during high-temperature calcination, leading to reduced catalytic performance. Therefore, it can be inferred that Ce incorporation creates surface space barriers. In the sample without PVP (Comparative Example 5), the vast majority of copper species are divalent copper. This is presumably because without a carbon source, Cu species and CeO2 cannot easily contact each other, making it difficult for CeO2 to function. In the catalyst without copper (Comparative Example 4), CeN is present. Considering the overall reaction performance of the catalysts, catalysts that do not include any of the three sources (Ce, Cu, and carbon) in step S1 exhibit poor hydrogen production performance, while catalysts combining all three sources have better catalytic performance and significantly improve the hydrogen production rate.

[0101] Figure 4 These are TEM images of the catalysts obtained in Example 1 and Comparative Example 1 of the present invention. Figure 4 In the figure, Figures (a) and (b) are HRTEM images of the catalyst obtained in Comparative Example 1, and Figures (c) and (d) are HRTEM images of the catalyst obtained in Example 1. It can be seen from the comparison that the average particle size of the catalyst in Comparative Example 1 is about 16.10 nm, while the average particle size of the catalyst in Example 1 after doping with trace amounts of Ce is about 9.83 nm. It can be inferred that the addition of Ce is beneficial to the dispersion of Cu particles in the catalyst, reducing the particle size of nanoparticles, and increasing the contact area between the active sites on the catalyst and methanol and water, thereby improving the catalytic efficiency.

[0102] Figure 5 The image shows the FTIR spectrum of the catalyst obtained in Example 1 of this invention. Figure 5 This indicates that, compared to polyvinylpyrrolidone (PVP), the wavenumber of the carbonyl peak in the precursor is lower than that of polyvinylpyrrolidone (PVP), which is 1650 cm⁻¹. -1 It moved to 1606cm -1 It also produced two split peaks; the wavenumber of the CN peak increased from 1279 cm⁻¹. -1 It moved to 1288cm -1 This indicates that the carbonyl and CN bonds in PVP are coordinated with Cu and Ce ions.

[0103] Figure 6 This is an EDS mapping elemental analysis diagram of the catalyst obtained in Example 1 of the present invention. Figure 6It can be seen that the carbon-coated CeO2 modified Cu catalyst of this invention has a carbon-coated sheet-like structure. EDS mapping shows that Cu, Ce, N, C, and O are spatially uniformly distributed, further confirming that some Cu and Ce are supported on the polyvinylpyrrolidone support, while some Cu is embedded in the carbon layer. This is the main reason why the carbon-coated CeO2 modified Cu catalyst has high loading and high dispersion characteristics. By controlling the morphology of the catalyst support, the prepared catalyst can have high loading and high dispersion characteristics, resulting in high APRM catalytic activity and promoting mass transfer, causing reactant molecules to move towards the active center and product molecules to diffuse outward. The mapping diagram shows that the trace amount of Ce is relatively uniformly distributed in the catalyst, and the Cu element not only has a high loading but also a relatively uniform distribution. Therefore, it is inferred that the incorporation of Ce is beneficial to the dispersion of Cu particles.

[0104] Figure 7 This is a graph showing the in-situ cycle stability test of the catalyst obtained in Example 1 of this invention. From... Figure 7 As can be seen, the low temperature of 130℃ is beneficial for mitigating the hydrothermal stability problem of trace CeO2, resulting in a significant improvement in catalyst stability. Considering that "low-temperature hydrogen production" is currently the highlight, according to in-situ cycle stability testing, the catalyst still exhibits a high hydrogen production rate after 12 reactions at 130℃. In summary, the catalyst obtained in Example 1 of this invention demonstrates good stability at 130℃.

[0105] Figure 8 This is a graph showing the catalytic performance of the catalyst obtained in Example 1 of the present invention at different alcohol-to-water ratios. From... Figure 8 As can be seen from the comparison of the performance of the same catalyst under different alcohol-to-water ratios, the highest hydrogen production rate (1.47 μmol·gcat) is observed when the alcohol-to-water ratio is 3:1 at a low temperature of 130℃. -1 ·s -1 It is speculated that at this alcohol-to-water ratio, a large number of hydrogen atoms are released from methanol and water, resulting in a greater amount of gaseous hydrogen, while the CO selectivity remains at a low level. It is inferred that this alcohol-to-water ratio is conducive to promoting the WGS reaction (a partial reaction in the APRM reaction). Therefore, it is tentatively determined to be the better alcohol-to-water ratio for the APRM reaction catalyzed by this catalyst.

[0106] Figure 9 The image shows the lattice fringes of the catalyst obtained in Example 1 of this invention via HRTEM. Figure 9In the catalyst, the lattice fringe spacings of 0.181 nm, 0.208 nm, 0.243 nm, and 0.270 nm belong to the (100) plane of metallic Cu, the (111) plane of metallic Cu, the (111) plane of metallic Cu2O, and the (200) plane of CeO2, respectively. It can be inferred that both monovalent and devalent copper exist in a certain amount on this catalyst, and their synergistic effect is beneficial to promoting hydrogen production compared to catalysts with only devalent copper. The amount of Ce species observed under HRTEM is very small, and large CeO2 particles are basically not found. No diffraction peaks of CeO2 were observed in the catalyst in XRD, suggesting that Ce may exist in the catalyst at a sub-nanometer size.

[0107] Figure 10 This is the H2-TPR diagram of the catalyst obtained in Example 1 of the present invention. From... Figure 10 The reduction temperatures of the carbon-coated CeO2-modified Cu catalyst of this invention can be seen. The first reduction temperature is 97℃ (α peak), which is inferred to be the peak of the reduction of divalent copper to monovalent copper. The second reduction temperature is 104℃ (β peak), which is inferred to be the peak of the reduction of monovalent copper to oxidative copper. The synergistic effect of oxidative and monovalent copper in the catalyst is conducive to the large-scale hydrogen production from methanol and water. Therefore, it can be inferred that under the low-temperature condition of 130℃, the catalyst can achieve in-situ reduction in the hydrogen atmosphere it generates, ensuring that the catalyst contains a large amount of monovalent and oxidative copper, thereby stably promoting the hydrogen production from methanol and water. Furthermore, combined with... Figure 7 In-situ cycle stability testing showed that the catalyst has high stability, which is beneficial for promoting the continuous and efficient production of hydrogen from methanol and water.

[0108] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a carbon-coated CeO2-modified Cu-based catalyst, characterized in that, Includes the following steps: S1. Mix the Ce source, Cu source, carbon source and solvent thoroughly and allow them to react completely. After the reaction is complete, a complex is obtained. S2. The complex obtained in step S1 is calcined in an inert atmosphere to obtain a carbon-coated complex; S3. Place the carbon-coated composite obtained in step S2 in a reducing atmosphere and carry out a reduction reaction at 200~450℃. After the reaction is completed, a carbon-coated CeO2 modified Cu-based catalyst can be obtained. In step S1, the carbon source is PVP, and the molar ratio of Cu source to Ce source is 7:(0.05~1); the molar ratio of Cu source to carbon source is 7:(5~15). The calcination temperature in step S2 is 400~700℃; The reduction temperature in step S3 is 250~400℃.

2. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of Cu source to Ce source is 7: (0.08~0.22).

3. A carbon-coated CeO2-modified Cu-based catalyst prepared by the preparation method described in claim 1 or 2.

4. The catalyst as described in claim 3, characterized in that, The catalyst contains 30-80 wt% Cu.

5. The use of the catalyst of claim 3 or 4 in the catalytic APRM reaction.

6. The application as described in claim 5, characterized in that, The catalyst described in claim 3 or 4 is used for catalysis, and the temperature of the APRM reaction during the catalytic process does not exceed 180°C.

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