Preparation method and application of copper-based alloy photo-thermal catalyst loaded by alumina carrier

Abstract

The invention belongs to the technical field of photo-thermal methanol cracking hydrogen production catalysts, and discloses a preparation method and application of a photo-thermal catalyst with a copper-based alloy loaded on an alumina carrier. The preparation method comprises the following steps: firstly, synthesizing a layered double hydroxide CuMAl-LDH (metal M is Co or Ni) nanosheet as a precursor through a coprecipitation method, and preparing through a gas-phase thermal reduction method, namely reducing the layered double hydroxide (CuMAl-LDH) into a copper-based alloy through hydrogen reduction in a high-temperature tubular furnace, and loading the copper-based alloy on aluminum oxide to obtain the photo-thermal catalyst. And the catalyst is applied to photo-thermal methanol cracking hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of photothermal methanol cracking hydrogen production catalyst technology, specifically referring to a method for preparing and applying a copper-based alloy photothermal catalyst supported on an alumina carrier. Background Technology

[0002] With the continuous growth of global energy demand, the massive consumption of traditional fossil fuels has led to a surge in carbon dioxide emissions, causing environmental pollution and the greenhouse effect that urgently need to be addressed. Against this backdrop, building a new energy system that is "low-carbon, safe, clean, and efficient" has become a global consensus. Hydrogen energy, with its high calorific value (140 MJ / kg, approximately three times that of petroleum, 4.5 times that of coal, twice that of methane, and four times that of ethanol), zero carbon emissions, convenient storage and transportation, and abundant resources, is considered a key carrier for achieving an energy revolution. In the industrial sector, it can serve as a basic chemical raw material for the synthesis of ammonia and methanol, and in the transportation sector, fuel cell technology can significantly reduce carbon emissions and dependence on fossil fuels. However, the low density, high diffusivity, flammability, and explosiveness of hydrogen pose significant challenges to its storage and transportation, hindering its widespread application. Overcoming the bottlenecks in efficient and low-cost hydrogen production and safe storage and transportation technologies is crucial for realizing the large-scale application of hydrogen energy. With the rapid development of renewable energy sources such as wind and solar power and water electrolysis technology, renewable energy coupled with water electrolysis for hydrogen production has become the most promising green hydrogen production solution. However, its industrialization process is still constrained by bottlenecks such as high energy costs, large investment intensity, and significant water resource consumption. Against this backdrop, the concept of "liquid sunshine" provides an innovative solution for hydrogen energy carriers. Methanol, due to its multiple advantages, has become an ideal hydrogen energy carrier: firstly, it is abundant in resources, has a mature synthesis process, and is economically viable; secondly, its high hydrogen-to-carbon ratio (H / C) and lack of C–C bonds endow it with a wide temperature range for hydrogen production; and thirdly, its liquid nature allows for storage, transportation, and refueling using existing gas station infrastructure, or low-cost, safe, and convenient hydrogen transportation via pipelines, offering significant advantages over high-pressure hydrogen storage technology. Based on this, methanol-to-hydrogen technology, which enables in-situ hydrogen production, is increasingly attracting attention from the academic community.

[0003] Among various methods for producing hydrogen from methanol, partial oxidation and autothermal reforming of methanol are exothermic reactions, leading to catalyst deactivation and low hydrogen production rates. Methanol steam reforming (MSR, CH3OH + H2O → CO2 + 3H2) and methanol cracking (MD, CH3OH → CO + 2H2) are endothermic reactions, requiring additional heat input. Methanol cracking is considered one of the simplest hydrogen production methods because it does not require additional reactants such as steam and oxygen. Furthermore, methanol dehydrogenation can produce syngas (a mixture of hydrogen and carbon monoxide), which has a variety of applications. Syngas can be used not only for power generation, transportation fuel production, and as a gasoline substitute, but also as an important chemical intermediate for the production of hydrogen (via water-gas shift reaction), hydrocarbons (via Fischer-Tropsch synthesis), and high-chain alcohols / aldehydes (via oxidation processes).

[0004] In recent years, introducing light energy into traditional thermocatalysis has become a highly promising strategy. Photo-induced activation of reactants can achieve faster conversion rates. Sunlight, as an abundant and sustainable energy source, can help reduce dependence on polluting fossil fuels if effectively collected and utilized. Photocatalysis utilizes photo-excited redox reactions to convert solar energy into chemical energy, opening up new avenues for solar energy utilization. Compared to traditional thermocatalysis, photocatalysis can proceed under milder conditions, helping to reduce energy consumption and improve product selectivity. However, single photocatalytic technologies are limited by narrow solar absorption range, easy recombination of photogenerated electrons and holes, harsh reaction conditions, and low quantum efficiency, and have not yet been widely applied. Photothermal catalysis combines photo- and thermal effects in a catalytic process. The introduction of light helps trigger the reaction and reduce heat input, while the introduction of heat can promote the reaction process and improve the mobility of photogenerated carriers or the selectivity of products. Solar energy, as an important clean energy source, can drive energy industry innovation when coupled with efficient hydrogen production technologies. Photothermal coupling-driven methanol-to-hydrogen technology, by introducing light energy, significantly improves methanol conversion and hydrogen yield, and has become a research hotspot in the field of energy catalysis.

[0005] Introducing solar energy into methanol-to-hydrogen production is an attractive and sustainable approach, allowing for solar energy storage while conserving non-renewable energy sources. This has attracted domestic and international scholars to conduct research on the synergistic photovoltaic (PVP) methanol-to-hydrogen project, resulting in some groundbreaking advancements. Current technological innovations and breakthroughs in this field mainly focus on two directions: noble metal-based composite catalytic systems and non-noble metal-based composite catalytic systems. Among these, noble metal-based catalytic systems, due to their excellent catalytic activity, reaction selectivity, and stability, have become the most promising area of ​​early research, yielding representative research results from several university teams and providing crucial support for the development of PTP methanol-to-hydrogen technology. For example, Professor Wang Shufang's team at Hebei University, starting with innovative optimization of catalyst preparation processes, developed a bimetallic deposition method using graphene oxide as a template to address the industry pain points of poor dispersion and low utilization of noble metal active sites. This method allows for precise control of the Pt loading and dispersion state, successfully synthesizing Pt-doped CeO2 nanosheets (Pt-CeO2) catalytic materials with a Pt doping content of 7.4%. This catalytic material, thanks to the extremely high utilization rate of active sites of single-atom Pt and the excellent electronic regulation and oxygen vacancy adjustment capabilities of the CeO2 support, exhibits outstanding catalytic performance in the methanol dehydrogenation reaction at 300℃, with a hydrogen production rate of up to 111.02 mol·g per unit mass of Pt. -1 Pt ·h -1 This significantly improves the utilization efficiency of precious metals and further highlights the advantages of precious metal-based catalysts in efficient hydrogen production (BAI X, YUAN D, LI Y, et al. iScience, 2021, 24(2)). Professor Wei Jinjia's team at Xi'an Jiaotong University, addressing the problems of low photothermal driving efficiency and significant energy conversion loss, focused on the core requirements of photothermal synergistic hydrogen production and developed a Pt-Cu / Cu2O / CuO multi-element heterojunction catalytic system. This system, by constructing a multi-element heterojunction interface, effectively enhances photothermal absorption capacity and charge separation efficiency, reduces recombination losses of photogenerated carriers, and achieves an optimal hydrogen yield of 1600 mmol·g under conditions of irradiation with 15 equivalent solar intensities and a reaction temperature of 180℃. -1 ·h -1The corresponding solar-to-hydrogen efficiency reached 7%, significantly breaking through the technical bottleneck of low energy conversion efficiency in traditional solar thermal hydrogen production systems and demonstrating good potential for industrial application (LI D, SUNJ, MA R, et al. Journal of Energy Chemistry, 2022, 71: 460-9.). Although the aforementioned developed noble metal-based catalysts have all shown impressive catalytic performance in the solar thermal methanol-to-hydrogen reaction, with hydrogen evolution rate, solar-to-hydrogen efficiency, and hydrogen production capacity per unit of noble metal active site all reaching high levels in the industry, it is undeniable that the irreplaceable nature of noble metals as the core active sites of catalysis inevitably and significantly increases the capital cost of catalyst preparation, restricting large-scale application. This, to some extent, limits the sustainability and economic viability of the catalysts.

[0006] Based on the inherent limitations of noble metal-based catalysts, developing low-cost, high-performance non-noble metal-based catalytic systems has become a key path to overcome the industrialization bottleneck of photothermal methanol-to-hydrogen technology. Consequently, non-noble metal-based photothermal methanol-to-hydrogen systems have become a current research hotspot and core direction in this field. Among numerous non-noble metal materials, copper (Cu) stands out due to its unique advantages, possessing both significant localized surface plasmon resonance (LSPR) effects and efficient hot carrier generation capabilities. It can efficiently absorb light energy and convert it into heat energy, and rapidly transfer hot carriers to participate in catalytic reactions, effectively enhancing the photothermal synergy. Therefore, it has become a highly promising core material for replacing noble metal catalysts and achieving large-scale hydrogen production (XIN Y, YU K, ZHANG L, et al. Advanced Materials, 2021, 33(32)). Professor Zhang Tierui's team at the University of Chinese Academy of Sciences innovated the catalyst preparation method, successfully preparing a novel L-Cu photothermal catalyst by reducing CuAl layered double hydroxide (CuAl-LDH) nanosheets. This catalyst was then applied to the photo-driven methanol vapor reforming (MSR) hydrogen production reaction. Due to its unique layered structure and excellent photothermal conversion performance, this L-Cu catalyst exhibited outstanding photothermal catalytic activity for the conversion of methanol and water under full UV-Vis irradiation, achieving a hydrogen evolution rate as high as 577.8 mmol·g⁻¹. -1 ·h -1 This rate is much higher than the hydrogen production activity of L-Cu catalyst under dark conditions at the same temperature, which fully demonstrates the significant improvement effect of photothermal synergy on the performance of copper-based catalysts (LI Z, LIU J, ZHAO J, et al. Advanced Functional Materials, 2022, 33(11).). Although the aforementioned research has achieved some breakthroughs in optimizing the performance and mitigating deactivation of copper-based catalysts, significantly improving their photothermal catalytic activity and stability, two core shortcomings remain unresolved from the perspective of practical industrial applications: First, the photothermal synergistic catalytic efficiency is still relatively low, making it difficult to meet the demands of large-scale, efficient hydrogen production; its hydrogen evolution rate and solar energy conversion efficiency are still significantly lower than those of noble metal-based catalysts. Second, catalytic stability remains poor, and deactivation is prone to occur. During long-term continuous operation, the problems of Cu active particle agglomeration, oxidation, and sintering have not been fundamentally solved, making it unsuitable for the actual scenario of industrial continuous hydrogen production. Therefore, developing non-noble metal Cu-based catalysts with high activity and cycle stability, capable of suppressing carbon deposition, is a key challenge to meet practical application requirements. Summary of the Invention

[0007] The purpose of this invention is to provide a new direction and approach for synthesizing a catalyst for photothermal synergistic methanol cracking to produce hydrogen. Firstly, layered double hydroxide (CuMAl-LDH—metal M including Co or Ni) nanosheets are synthesized via a co-precipitation method as a precursor. Then, a gas-phase thermal reduction method is used to prepare the catalyst, specifically, the layered double metal hydroxide (CuMAl-LDH) is reduced to a copper-based alloy supported on alumina in a high-temperature tube furnace via hydrogen reduction to obtain a photothermal catalyst. This catalyst is then applied to photothermal methanol cracking to produce hydrogen.

[0008] The specific technical solution of this invention includes the following steps: (1) Dissolve Cu(NO3)3, M(NO3)2·6 H2O and Al(NO3)3·9 H2O in ultrapure water in proportion to obtain solution A; (2) Weigh out sodium carbonate (Na2CO3) according to the proportion and dissolve it completely in ultrapure water to obtain solution B; Weigh out sodium hydroxide (NaOH) according to the specified ratio and dissolve it completely in ultrapure water to obtain solution C; (3) Under the condition of continuous stirring and maintaining the pH value of 9.5, solution A and solution C are slowly added dropwise to solution B at the same time. The resulting mixed solution is then heated and stirred at 60~80℃ for 6~24 hours. The product is washed with deionized water and centrifuged until the pH value of the supernatant is close to 7. Then it is vacuum dried to obtain the precursor CuMAl-LDH. (4) The precursor CuMAl-LDH obtained in step (3) is calcined at high temperature in a tube furnace by passing a hydrogen-argon mixture to obtain a copper-based alloy photothermal catalyst CuM-Al2O3 supported on an alumina carrier.

[0009] In step (1), M(NO3)2·6 H2O is Co(NO3)2·6 H2O or Ni(NO3)2·6 H2O; (Cu)2+ +M 2+ ) and Al 3+ The molar ratio is 2:1 or 3:1; where Cu 2+ and M 2+ The molar ratios are 6:1, 4:1, 2:1, 1:1, 1:4, 1:2 or 1:6; In solution A, Al 3+ The concentration was 0.25 mol / L.

[0010] In step (2), the concentration of Na2CO3 in solution B is 0.0059 g / mL; the concentration of NaOH in solution C is 1.5 mol / L.

[0011] In step (3), the volume ratio of solution A, solution B, and solution C is 2:18:3, and the Na2CO3 and Al... 3+ The molar ratio is 2:1.

[0012] The centrifugation speed was 8000 r / min, the vacuum drying temperature was 60 ℃, and the time was 12 hours.

[0013] In step (4), the hydrogen-argon mixture has a hydrogen volume percentage concentration of 5%; the calcination temperature is 400~600 ℃, the heating rate is 5℃ / min, the gas flow rate is 40 mL / min, and the calcination reduction time is 1~5 hours.

[0014] The copper-based alloy photothermal catalyst CuM-Al2O3 supported on an alumina support prepared in this invention is used for photothermal methanol cracking to produce hydrogen.

[0015] The beneficial effects of this invention are: (1) In this invention, a bilayer metal hydroxide CuMAl-LDH is synthesized by a simple co-precipitation method, and CuM alloy supported on an alumina support can be obtained by hydrogen reduction. As a photothermal catalyst, it has excellent photothermal conversion performance, thereby significantly improving the photothermal catalytic performance in the photothermal methanol cracking reaction.

[0016] (2) Due to their compositional flexibility, bilayer metal hydroxide nanosheets contain divalent and trivalent metal cations (such as Cu). 2+ Co 2+ Ni 2+ Al 3+ (etc.), representing an ideal precursor platform for synthesizing various highly dispersed metal or alloy supported catalysts through heat treatment. CuMAl-LDH obtained CuM alloy catalysts supported on alumina by simply adjusting parameters such as the ratio of divalent and trivalent metal cations and the hydrogen reduction time. These parameters have a significant impact on catalyst performance.

[0017] (3) The CuM alloy supported on alumina is synthesized by co-precipitation and hydrogen reduction under high temperature calcination in this invention. The preparation process is simple, the preparation process requirements are low, the product structure is stable, the process is green and pollution-free, and it is suitable for mass production. Attached Figure Description

[0018] Figure 1 XRD patterns of bilayer metal hydroxides CuCoAl-LDH and CuNiAl-LDH and bilayer metal hydroxide Cu6Al2(OH) were obtained by synthesizing them via a simple coprecipitation method. 16 CO3 4H2O standard card (PDF#34-1181).

[0019] Figure 2 XRD patterns of CuCo alloys supported on alumina after hydrogen reduction of the precursor CuCoAl-LDH at 500℃ for different hours (1h, 2h, 3h, 5h).

[0020] Figure 3 XRD patterns of CuCo alloys (different molar ratios, Cu:Co = 4:1, 2:1, 1:1, 1:2, 1:4) supported on alumina, obtained by reducing CuCoAl-LDH with hydrogen at 500℃ for 2 hours.

[0021] Figure 4 Performance of CuCo alloy samples (molar ratio Cu:Co = 4:1, 2:1, 1:1, 1:2, 1:4) under full-spectrum irradiation for photothermal catalytic methanol cracking to hydrogen production.

[0022] Figure 5 The XRD pattern is shown for CuNi alloy (molar ratio Cu:Ni = 2:1) supported on an alumina support, obtained by reducing CuNiAl-LDH with hydrogen at 500℃ for 2 hours.

[0023] Figure 6 The performance of CuNi alloy samples (molar ratio Cu:Co = 2:1, 1:1, 1:2) supported on alumina under full-spectrum irradiation for photothermal catalytic methanol cracking to produce hydrogen. Detailed Implementation

[0024] The present invention will be described in detail below with reference to embodiments, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0025] Example 1

[0026] Step 1: Mix 6.67 mmol Cu(NO3)3, 3.33 mmol Co(NO3)2·6 H2O, and 5 mmol Al(NO3)3·9 H2O in a molar ratio M 2+ M 3+ Weigh the contents in a 2:1 ratio and pour them into a beaker containing 20 mL of ultrapure water to dissolve them completely, thus obtaining solution A.

[0027] Step 2: Weigh 1.06 g of Na2CO3 powder and pour it into a beaker containing 180 mL of ultrapure water to dissolve it completely, thus obtaining solution B; Weigh 1.8 g of NaOH and pour it into a beaker containing 30 mL of ultrapure water to dissolve it completely, thus obtaining solution C.

[0028] Step 3: Under continuous stirring and while maintaining a pH of 9.5, solutions A and C were simultaneously and slowly added dropwise to solution B. The resulting mixture was then heated at 70°C for 6 hours. The product was washed with deionized water and centrifuged 5 times at 8000 r / min until the pH of the supernatant was close to 7. Then, it was vacuum dried at 60°C for 12 hours to obtain sample D, denoted as precursor Cu2Co1Al-LDH.

[0029] Step 4: 0.2 g of sample Cu2Co1Al-LDH was calcined in a tube furnace at 500℃ for 2 h with a hydrogen-argon mixture (hydrogen concentration of 5%) and a gas flow rate of 40 mL / min. The resulting sample E was denoted as Cu2Co1-Al2O3.

[0030] in addition, With other conditions remaining unchanged, by only changing the calcination time in step 4, the present invention also prepared products with hydrogen reduction times of 1h, 3h, and 5h.

[0031] With other conditions remaining unchanged, products were also prepared with Cu and Co molar ratios of 4:1, 1:1, 1:2, and 1:4 by changing only the ratio of Cu to Co in step 1.

[0032] By reducing layered double hydroxide (CuCoAl-LDH) nanosheets, a Cu2Co1 alloy catalyst supported on Al2O3 was successfully prepared. The Co-Cu alloy interface effectively induced the activation of reactants under light irradiation, significantly reducing the apparent activation energy. This catalyst can be used for efficient hydrogen production from photothermal methanol cracking, demonstrating the great potential of photothermal catalysis in the energy field.

[0033] Example 2

[0034] Step 1: Mix 6.67 mmol Cu(NO3)3, 3.33 mmol Ni(NO3)2·6H2O, and 5 mmol Al(NO3)3·9H2O in a molar ratio M 2+ M 3+ Weigh the contents in a 2:1 ratio and pour them into a beaker containing 20 mL of ultrapure water to dissolve them completely, thus obtaining solution A.

[0035] Step 2: Weigh 1.06 g of Na2CO3 powder and pour it into a beaker containing 180 mL of ultrapure water to dissolve it completely, thus obtaining solution B; Weigh 1.8 g of NaOH and pour it into a beaker containing 30 mL of ultrapure water to dissolve it completely, thus obtaining solution C.

[0036] Step 3: Under continuous stirring and while maintaining a pH of 9.5, solutions A and C were simultaneously and slowly added dropwise to solution B. The resulting mixture was then heated at 70°C for 6 hours. The product was washed with deionized water and centrifuged 5 times at 8000 r / min until the pH of the supernatant was close to 7. Then, it was vacuum dried at 60°C for 12 hours to obtain sample D, denoted as precursor Cu2Ni1Al-LDH.

[0037] Step 4: 0.2 g of sample Cu2Ni1Al-LDH was calcined in a tube furnace at 500℃ for 2 h with a hydrogen-argon mixture (hydrogen concentration of 5%) and a gas flow rate of 40 mL / min. The resulting sample E is denoted as Cu2Ni1-Al2O3.

[0038] In addition, under the condition that other factors remain unchanged, products with a Cu to Ni molar ratio of 1:1 and 1:2 were also prepared by changing only the Cu to Ni ratio in step 1.

[0039] By reducing layered double hydroxide (CuNiAl-LDH) nanosheets, a Cu2Ni1 alloy catalyst supported on Al2O3 was successfully prepared. The Ni-Cu alloy interface effectively induced the activation of reactants under light irradiation, significantly reducing the apparent activation energy. This catalyst can be used for efficient hydrogen production from photothermal methanol cracking, demonstrating the great potential of photothermal catalysis in the energy field.

[0040] Figure 1 The images show the XRD patterns of CuCoAl-LDH from Example 1 and CuNiAl-LDH from Example 2, and the bilayer metal hydroxide Cu6Al2(OH). 16The CO3 4H2O standard card (PDF#34-1181) was used. Compared with the standard card, the prepared CuCoAl-LDH and CuNiAl-LDH samples showed clear and symmetrical diffraction peaks at 2θ values ​​of 11.6, 23.3, 34.7, 39.2, and 46.7, corresponding to the (003), (006), (012), (015), and (018) crystal planes of LDH in the standard card, respectively, indicating that the hydrotalcite structure is well crystallized. This demonstrates that the LDH structure in the samples of this invention has high purity.

[0041] Figure 2 The XRD patterns of CuCo alloys supported on alumina were obtained after hydrogen reduction of the precursor CuCoAl-LDH at 500℃ for different hours (1h, 2h, 3h, 5h). Compared with the standard cards for copper and cobalt, the diffraction peaks of the prepared samples were shifted; this indicates that the structure of CuCoAl-LDH changed after hydrogen reduction, and CuCo alloys were formed in samples with reduction times of 1h, 2h, 3h, and 5h.

[0042] Figure 3 The XRD patterns are shown for CuCo alloys (different molar ratios, Cu:Co = 4:1, 2:1, 1:1, 1:2, and 1:4) supported on alumina, obtained by hydrogen reduction of CuCoAl-LDH at 500℃ for 2 hours. Compared with the standard card for copper and cobalt, the diffraction peaks of the CuCoAl-LDH samples with different copper-cobalt molar ratios all shifted; this indicates that after hydrogen reduction for 2 hours, the structure of CuCoAl-LDH samples with different copper-cobalt molar ratios changed, and a CuCo alloy was formed.

[0043] Figure 4 The figures show the performance of CuCo alloy samples supported on alumina (molar ratios Cu:Co = 4:1, 2:1, 1:1, 1:2, 1:4) under full-spectrum irradiation for photothermal catalytic methanol cracking to hydrogen. After methanol cracking under full-spectrum illumination, the hydrogen production performance of the alumina-supported CuCo alloy samples with different Cu:Co molar ratios varied, with Cu2Co1-Al2O3 showing the best performance. This indicates that changing the Cu:Co molar ratio affects the alumina-supported CuCo alloy, leading to different hydrogen production performance of the catalyst.

[0044] Figure 5 The image shows the XRD pattern of CuNi alloy (molar ratio Cu:Ni = 2:1) supported on an alumina support, obtained by hydrogen reduction of CuNiAl-LDH at 500℃ for 2 hours. Compared with the standard card for copper and nickel, the diffraction peaks of the prepared sample are shifted; this indicates that the structure of CuNiAl-LDH changes after hydrogen reduction, resulting in the formation of a CuNi alloy.

[0045] Figure 6 The figures show the performance of CuNi alloy samples supported on alumina (molar ratios Cu:Ni = 2:1, 1:1, 1:2) under full-spectrum irradiation for photothermal catalytic methanol cracking to hydrogen production. After methanol cracking under full-spectrum illumination, the hydrogen production performance of the alumina-supported CuNi alloy samples with different Cu:Ni molar ratios varied, with Cu2Ni1-Al2O3 showing the best performance. This indicates that changing the Cu:Ni molar ratio affects the alumina-supported CuNi alloy, leading to different hydrogen production performance of the catalyst.

Claims

1. A method for preparing a copper-based alloy photothermal catalyst supported on an alumina carrier, characterized in that, Includes the following steps: (1) Dissolve Cu(NO3)3, M(NO3)2·6 H2O and Al(NO3)3·9 H2O in ultrapure water in proportion to obtain solution A; (2) Weigh out sodium carbonate (Na2CO3) according to the proportion and dissolve it completely in ultrapure water to obtain solution B; Weigh out sodium hydroxide (NaOH) according to the specified ratio and dissolve it completely in ultrapure water to obtain solution C; (3) Under the condition of continuous stirring and maintaining a certain pH value, solution A and solution C are slowly added dropwise to solution B at the same time. The resulting mixed solution is then heated and stirred at 60~80℃ for 6~24 hours. The product is washed with deionized water and centrifuged until the pH value of the supernatant is close to 7. Then it is vacuum dried to obtain the precursor CuMAl-LDH. (4) The precursor CuMAl-LDH obtained in step (3) is calcined at high temperature in a tube furnace by passing a hydrogen-argon mixture to obtain a copper-based alloy photothermal catalyst CuM-Al2O3 supported on an alumina carrier.

2. The preparation method according to claim 1, characterized in that, In step (1), M(NO3)2·6 H2O is Co(NO3)2·6 H2O or Ni(NO3)2·6 H2O.

3. The preparation method according to claim 1, characterized in that, In step (1), (Cu 2+ +M 2+ ) and Al 3+ The molar ratio is 2:1 or 3:1; where Cu 2+ and M 2+ The molar ratios are 6:1, 4:1, 2:1, 1:1, 1:4, 1:2, or 1:6; in solution A, Al 3+ The concentration was 0.25 mol / L.

4. The preparation method according to claim 1, characterized in that, In step (2), the concentration of Na2CO3 in solution B is 0.0059 g / mL; the concentration of NaOH in solution C is 1.5 mol / L.

5. The preparation method according to claim 1, characterized in that, In step (3), the volume ratio of solution A, solution B, and solution C is 2:18:3, and the Na2CO3 and Al... 3+ The molar ratio is 2:

1.

6. The preparation method according to claim 1, characterized in that, In step (3), the stirring is continued and the pH value is maintained at 9.

5.

7. The preparation method according to claim 1, characterized in that, In step (3), the centrifugation speed is 8000 r / min, the vacuum drying temperature is 60 ℃, and the time is 12 hours.

8. The preparation method according to claim 1, characterized in that, In step (4), the volume percentage concentration of hydrogen in the hydrogen-argon mixture is 5%.

9. The preparation method according to claim 1, characterized in that, In step (4), the calcination temperature is 400~600 ℃, the heating rate is 5℃ / min, the air flow rate is 40 mL / min, and the calcination reduction time is 1~5 hours.

10. The use of the copper-based alloy photothermal catalyst CuM-Al2O3 supported on an alumina support prepared by any one of claims 1 to 9 for photothermal methanol cracking to produce hydrogen.

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