A crystalline red phosphorus-loaded RuCu alloy photocatalyst for CO2 reduction to CH4

Abstract

A crystalline red phosphorus-loaded RuCu alloy photocatalyst for CO2 reduction to CH4 relates to the field of photocatalytic materials. First, a CRP carrier is prepared by chemical vapor deposition (CVD), then RuCu alloy nanoparticles are obtained by oil phase one-step reduction, and finally, RuCu alloy nanoparticles are loaded onto the surface of the CRP carrier by impregnation-calcination to obtain the final RuCu / CRP photocatalyst. The RuCu alloy nanoparticles in the catalyst act as co-catalysts, which, on the one hand, effectively promote the separation and transfer of photogenerated charges of the CRP carrier, and on the other hand, regulate the reaction path of CO2 reduction, so that the CH4 yield of the optimized RuCu / CRP photocatalyst reaches 19.7 μmol h ‑1 g ‑1 , with a selectivity of up to 96%.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and more specifically, relates to a photocatalyst using crystalline red phosphorus as a carrier and loaded with RuCu alloy, and a preparation method and application thereof for efficient photocatalytic reduction of CO2 to generate CH4. Background Art

[0002] As the global warming problem intensifies, the reduction and resource utilization of CO2 has become an urgent problem to be solved. Using photocatalytic technology to convert CO2 and water into high value-added hydrocarbons, especially methane (CH4), can not only alleviate the greenhouse gas emission problem, but also provide a sustainable energy solution. However, since the conversion of CO2 to CH4 requires overcoming a high kinetic barrier, the development of efficient photocatalysts has become the key.

[0003] Crystalline red phosphorus (CRP) is widely used in the field of photocatalysis due to its excellent light absorption ability and tunable band gap structure. Although CRP shows the potential to convert CO2 into CH4, its limitations in terms of rapid recombination of photogenerated carriers and lack of highly selective catalytic sites restrict its application. Therefore, it is particularly important to develop a CRP-based photocatalytic system with better structure and performance.

[0004] The study pointed out that the method of loading precious metal catalysts can effectively adjust the electronic structure of the supported catalyst and provide the necessary adsorption and activation sites for the CO2 reduction reaction, thereby improving the activity of photocatalytic CO2 reduction and the selectivity of the product. Among the many precious metals, ruthenium (Ru) has shown great potential in the study of photocatalytic CO2 reduction to various valuable products (including CH4) due to its excellent CO2 adsorption and activation ability. Although single Ru metal performs well in promoting CO2 reduction efficiency, it has limitations in CH4 selectivity and high cost, and further structural regulation is needed to solve these problems.

[0005] Therefore, in order to improve the performance and reduce the cost, the present invention proposes a CRP-loaded RuCu alloy (RuCu / CRP) photocatalyst, which regulates the electronic structure of Ru through an alloying strategy and utilizes CRP as a carrier, aiming to provide a cost-effective and excellent photocatalytic CO2 reduction scheme. Summary of the invention

[0006] The present invention proposes a RuCu / CRP photocatalyst for efficient photocatalytic reduction of CO2 to CH4. The preparation method of the catalyst is characterized by comprising the following steps:

[0007] (1) Commercial red phosphorus was purified by hydrothermal method to remove surface oxides.

[0008] (2) The CRP photocatalyst was prepared by chemical vapor deposition (CVD) method: purified commercial red phosphorus and iodine were mixed and vacuum sealed in a quartz tube, and then placed in a muffle furnace for high-temperature calcination. The final product was washed several times with ethanol and water, and CRP was obtained after centrifugal drying.

[0009] (3) RuCu alloy nanoparticles were prepared by an oil phase one-step reduction method: under N2 protection, ruthenium acetylacetonate (Ru(acac)3), copper acetylacetonate (Cu(acac)2) and oleylamine were uniformly mixed, and then a borane-tert-butylamine complex was added. The solution was stirred at high temperature to obtain RuCu alloy nanoparticles. After cooling to room temperature, the solution was washed several times by centrifugation with anhydrous ethanol and cyclohexane, and the RuCu alloy nanoparticles obtained after centrifugation were dispersed in cyclohexane for storage.

[0010] (4) CRP and RuCu alloy nanoparticles were added to ethanol and stirred, and the catalyst was collected by rotary evaporation and then calcined in a H2 / Ar atmosphere to obtain the final RuCu / CRP sample.

[0011] The hydrothermal purification conditions in (1) are: 200°C, 12h.

[0012] The high temperature calcination process in (2) is as follows: heating to 550°C at a heating rate of 2°C / min, keeping at this temperature for 4 hours, then cooling to 280°C at a rate of 1°C / min, keeping for 4 hours, and finally cooling to room temperature at a rate of 0.2°C / min.

[0013] The high temperature stirring conditions in (3) are: 200°C, 1.5h. The molar ratio of Ru:Cu is 1:0.3-1:1.7, preferably 1:0.5.

[0014] The calcination condition in (4) is calcination at 200° C. for 2 h, and the loading amount of RuCu in RuCu / CRP is 0.96-1.04 wt %, preferably 0.98 wt %.

[0015] The specific operating steps for evaluating the photocatalytic CO2 reduction performance of the RuCu / CRP photocatalyst prepared by the present invention are as follows: 30 mg of RuCu / CRP photocatalyst is evenly applied on a quartz glass substrate and placed in a reactor; 5 mL of deionized water is placed in a culture dish in the reactor; high-purity CO2 is introduced into the reactor to remove the air in the reactor; a 300 W xenon lamp is used as a light source to irradiate the sample, and 1 mL of the gas sample in the reactor is extracted every 2 hours and injected into a GC 7920-TF2Z gas chromatograph for component analysis.

[0016] The raw materials of the present invention are cheap and readily available, the preparation process is simple, and it exhibits good photocatalytic CO2 reduction activity under light. Among them, RuCu / CRP with a RuCu molar ratio of 1:0.5 has the highest CO2 reduction to CH4 performance, and the CH4 yield reaches 19.7 μmol h -1 g -1 , CH4 selectivity is as high as 96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 , (a) SEM, (b) TEM, (c) HRTEM, (d) STEM, (eg) corresponding EDS element distribution diagrams of RuCu / CRP (Ru:Cu=1:0.5), indicating the uniform loading of RuCu alloy nanoparticles on the CRP surface.

[0018] Figure 2 , are XRD spectra of the prepared CRP and RuCu / CRP (Ru:Cu=1:0.5) samples. It proves that the CRP carrier in the RuCu / CRP sample is crystalline red phosphorus, and the loading of RuCu alloy does not change the bulk crystal structure of the CRP carrier.

[0019] Figure 3 , are UV-Vis spectra of the prepared CRP and RuCu / CRP (Ru:Cu=1:0.5) samples. It proves that the loading of RuCu alloy effectively improves the visible light absorption capacity of CRP carrier.

[0020] Figure 4 , which is the photocatalytic CO2 reduction activity and CH4 selectivity comparison of the prepared samples. The RuCu / CRP sample with a RuCu molar ratio of 1:0.5 exhibited excellent photocatalytic performance: the CH4 yield reached 19.7 μmol h -1 g -1 , which is 28 times that of CRP; CH4 selectivity reaches 96%, which is 22% higher than CRP. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0022] Example 1: Purification of commercial red phosphorus. Weigh 2 g of commercial red phosphorus into a beaker, add 50 mL of deionized water, and stir magnetically for 1 h; put the above solution into a polytetrafluoroethylene-lined autoclave (100 mL), heat it in an oven at 200°C for 12 h; centrifuge, wash, and dry to obtain a purified red phosphorus precursor.

[0023] Example 2: Preparation of CRP (CVD method). 200 mg of purified red phosphorus precursor and 10 mg of iodine were mixed, vacuum sealed in a quartz tube, heated at 550°C for 4 h, then cooled to 280°C at a rate of 1°C / min, kept warm for another 4 h, and finally cooled to room temperature at a rate of 0.2°C / min. The sample was washed several times with ethanol and water, and collected after centrifugal drying.

[0024] Example 3: Preparation of RuCu alloy nanoparticles (oil phase one-step reduction method). 80 mg of Ru(acac)3 and different masses of Cu(acac)2 (11, 13, 18, 27 mg) and 4 mL of oleylamine were mixed and placed in a three-necked flask, and stirred for 1.5 h at 80°C under N2 protection to make them uniformly mixed (solution A). At the same time, in another three-necked flask, 200 mg of borane tert-butylamine complex (TBAB), 7 mL of 1-octadecene and 4 mL of oleylamine (solution B) were added and stirred for 1.5 h at 100°C under N2 protection. Subsequently, solution A was quickly added to solution B and stirred at 200°C for 1.5 h. After cooling, the solution was centrifuged and washed with ethanol and cyclohexane, and finally the obtained RuCu alloy nanoparticles were dispersed in cyclohexane for storage.

[0025] Example 4: Preparation of RuCu / CRP (impregnation-calcination method). 200 mg of CRP and different volumes of RuCu alloy nanoparticle cyclohexane solution were mixed in ethanol and stirred for 12 h. Then, the sample was collected by rotary evaporation and then calcined at 200 ° C for 2 h under H2 / Ar atmosphere, with a RuCu loading of 0.98 wt%.

[0026] The raw materials used in the invention are cheap and readily available, and the preparation process is simple. The prepared RuCu / CRP catalyst with a RuCu molar ratio of 1:0.5 has the best photocatalytic CO2 reduction activity and CH4 selectivity.

Claims

1. A method for preparing a crystalline red phosphorus CRP-loaded RuCu alloy RuCu / CRP photocatalyst for CO2 reduction to CH4, characterized in that: The preparation method comprises the following steps: (1) Purify commercial red phosphorus using a hydrothermal method to remove surface oxides; (2) Preparation of CRP photocatalyst by chemical vapor deposition (CVD): Purified commercial red phosphorus and iodine were mixed and vacuum sealed in a quartz tube, and then placed in a muffle furnace for high-temperature calcination. The final product was washed several times with ethanol and water, and then centrifuged and dried to obtain CRP. (3) Preparation of RuCu alloy nanoparticles by one-step reduction method in oil phase: under N2 protection, ruthenium acetylacetonate Ru(acac)3, copper acetylacetonate Cu(acac)2 and oleylamine were uniformly mixed, and then borane-tert-butylamine complex was added. The solution was stirred at high temperature to obtain RuCu alloy nanoparticles. After cooling to room temperature, the solution was washed by centrifugation with anhydrous ethanol and cyclohexane for several times, and the RuCu alloy nanoparticles obtained after centrifugation were dispersed in cyclohexane for storage. (4) CRP and RuCu alloy nanoparticles were added to ethanol and stirred, the catalyst was collected by rotary evaporation, and then calcined in H2 / Ar atmosphere to obtain the final RuCu / CRP sample; In the above step (3), the molar ratio of Ru:Cu is 1:0.3 – 1:1.

7.

2. The method according to claim 1, characterized in that The hydrothermal purification conditions in step (1) are: 200 °C, 12 h.

3. The method according to claim 1, characterized in that The high temperature calcination process in step (2) is as follows: heating to 550°C at a heating rate of 2°C / min, maintaining at this temperature for 4 h, then cooling to 280°C at a rate of 1°C / min, maintaining for 4 h, and finally cooling to room temperature at a rate of 0.2°C / min.

4. The method according to claim 1, characterized in that The high temperature stirring conditions in step (3) are: 200°C, 1.5 h; the molar ratio of Ru:Cu is 1:0.

5.

5. The method according to claim 1, characterized in that The calcination condition in step (4) is calcination at 200 °C for 2 h, and the loading amount of RuCu in RuCu / CRP is 0.96-1.04 wt%.

6. The method according to claim 5, characterized in that The loading amount of RuCu in RuCu / CRP is 0.98 wt%.

7. The crystalline red phosphorus CRP loaded RuCu alloy RuCu / CRP photocatalyst prepared by the method according to any one of claims 1 to 6.

8. Application of the crystalline red phosphorus CRP loaded RuCu alloy RuCu / CRP photocatalyst prepared by the method according to any one of claims 1 to 6, characterized in that: Applied to photocatalytic CO2 reduction to produce CH4.

9. The use according to claim 8, characterized in that The RuCu / CRP photocatalyst was evenly coated on a quartz glass substrate and placed in a reactor. An appropriate amount of deionized water was placed in a culture dish in the reactor. High-purity CO2 was introduced into the reactor to remove the air in the reactor. A 300 W xenon lamp was used as a light source to irradiate the sample, and the product components in the reactor were analyzed by GC 7920-TF2Z gas chromatography.

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