Composite semiconductor catalyst and its use in the reduction of carbon dioxide

Abstract

The application discloses a kind of composite semiconductor catalyst and its application in carbon dioxide reduction;High-temperature semiconductor in the composite semiconductor catalyst is selected from SiC, with Cu-Ru alloy as active component, the main feature of the catalyst is to break through the influence of current high temperature on catalyst temperature, the upper limit of temperature used by catalyst is increased to more than 300 degrees Celsius, the activation of semiconductor is realized at high temperature, and the light absorption range is expanded;Compared with single-component metal loading, it has higher carbon dioxide conversion efficiency, solar energy utilization rate and carbon dioxide conversion rate, can convert carbon dioxide into more high-value alkane products, solar energy conversion rate is more than 5%, carbon dioxide conversion rate is more than 11%, and has strong practical application prospect.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis, and more specifically to a high-temperature semiconductor catalyst supported on a copper-ruthenium alloy that can efficiently utilize photocatalysis to reduce CO2 into high-value hydrocarbons. Background Technology

[0002] With economic and social development, people's demand for energy is increasing daily. Fossil fuels and mineral energy, as the main energy sources, have brought unavoidable environmental problems and caused an energy crisis. The CO2 emitted from the combustion of fossil fuels disrupts the natural carbon cycle balance, leading to a continuous increase in atmospheric CO2 concentration, and the greenhouse effect is having an increasingly prominent impact on human life. To address such severe global environmental and energy problems, in December 2015, nearly 200 parties to the United Nations Framework Convention on Climate Change reached the Paris Agreement.

[0003] Photocatalysis technology has been explored since the last century. In 1972, Japanese scholar Honda Fujishima discovered that photocatalysis could be used to split water to produce hydrogen, which has since attracted much attention from researchers. Currently, utilizing abundant and clean renewable energy sources like sunlight, and using CO2, a major component of greenhouse gases, as a carbon source to reduce CO2 into high-value-added products, we can not only turn waste into treasure and obtain clean energy, but also eliminate environmental hazards and reduce the negative impacts of the greenhouse effect.

[0004] Although many researchers have devoted considerable effort to exploring the use of photocatalysis to reduce CO2, to date, the vast majority of reported photocatalytic reaction rates do not exceed tens to hundreds of μmol·g. -1 ·h -1 The photocatalytic efficiency is extremely low, leaving considerable room for improvement. The main reason is that most currently used photocatalysts are wide-bandgap semiconductor catalysts, which only respond to high-energy-density ultraviolet light. Furthermore, ultraviolet light constitutes only about 5% of the solar spectrum reaching the Earth's surface, while the quantum efficiency of photocatalysis is no higher than 20%. Therefore, the utilization efficiency of photocatalysis is only around 1%.

[0005] To improve the efficiency of photocatalytic CO2 reduction, many researchers aim to develop broad-spectrum absorption catalysts that extend the absorption range of the catalyst into the visible light region to gain more electrons. Simultaneously, they utilize the increased electron-hole recombination and the heat generated by visible and infrared light to raise the temperature of the catalytic reaction, thereby improving the photocatalytic reduction efficiency of CO2. This method, combining the advantages of photocatalysis and thermal catalysis, is called photothermal catalysis. Under photothermal catalytic conditions, catalysts often exhibit superior catalytic performance. Therefore, many researchers have made significant strides in this area; for example, Ozin et al. used vertically aligned SiNWs as In2O3(OH)₂. yThese hybrid nanostructured materials serve as active supports for indium-based gas-phase photocatalysts, reducing CO2 to CO via a RWGS reaction. Compared to using In2O3(OH) alone... y The particles can utilize more sunlight. Zhang and his colleagues used sunlight-driven and heated conditions to conduct a series of Fischer-Tropsch synthesis reactions to investigate the performance of Co-based catalysts, etc.

[0006] As research into photothermal catalysis systems deepens, the development of new materials, namely high-temperature semiconductors, is needed to ensure that catalysts maintain stable catalytic performance and high CO2 conversion rates even under conditions of increased energy density. Traditional semiconductor materials, such as TiO2 (anatase), transform into TiO2 (rutile) under high temperatures, significantly reducing their catalytic activity for CO2 reduction. Such materials are clearly unsuitable for photothermal catalysis. High-temperature semiconductors, however, can overcome the problem of other semiconductor materials' inability to withstand high temperatures, maintaining stable physical structures and chemical properties even under these conditions. This allows for raising reaction temperatures above 150°C, overcoming the negative impact of high temperatures on catalytic reaction performance.

[0007] This invention proposes a novel high-temperature semiconductor catalyst supported on a copper-ruthenium alloy and applies it to the CO2 reduction process. This photocatalyst uses high-temperature semiconductor SiC as a support and Cu-Ru alloy as the active component, maintaining excellent catalytic performance even at high temperatures. It achieves high solar energy utilization efficiency and CO2 conversion rate, transforming CO2 into high-value-added hydrocarbons. Summary of the Invention

[0008] To address the aforementioned issue of catalysts needing high-temperature resistance under photothermal catalysis conditions, this invention provides a novel high-temperature semiconductor catalyst. This catalyst overcomes the influence of temperature on photocatalyst performance, extending the operating temperature range to over 300 degrees Celsius. It achieves semiconductor activation at high temperatures, expands the light absorption range, and enables the conversion of carbon dioxide into more high-value alkane products.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] This invention provides a composite semiconductor catalyst, which is prepared by the following method:

[0011] Pretreated SiC is placed at the focal point of a xenon lamp light source, and an aqueous solution of metal salt is sprayed onto the surface of the pretreated SiC under irradiation to obtain sprayed SiC; the sprayed SiC is ultrasonicated for 10-30 minutes, dried, and calcined in air at 300-500℃ for 1-3 hours (preferably calcined at 400℃ for 2 hours) to obtain the composite semiconductor catalyst.

[0012] The aqueous solution of the metal salt contains copper nitrate and ruthenium chloride. The theoretical mass ratio of copper in the copper nitrate to the theoretical mass ratio of the metal element in the aqueous solution of the metal salt is 20-80:100 (preferably 50:100). The theoretical mass ratio of the metal element in the aqueous solution of the metal salt is 0.1%-2% (more preferably 0.3%-0.4%) of the theoretical mass ratio of the metal element in the aqueous solution of the metal salt and the total mass of the pretreated SiC.

[0013] The principle for selecting anions of metal salts is to choose nitrate salts as much as possible, with chloride salts as the second choice. Anions such as sulfate are toxic after calcination and their catalytic activity will decrease, so they are not suitable for the catalyst of this invention.

[0014] The high-temperature semiconductor catalyst supported on copper-ruthenium alloy of the present invention is composed of a metal alloy component and a semiconductor material;

[0015] The semiconductor material used as a carrier is a high-temperature resistant semiconductor with a high operating temperature window, selected from SiC, etc.

[0016] The metal alloy in question is composed of Cu and Ru.

[0017] Based on the total mass of the catalyst, the mass percentage of CuRu alloy is 0.1% to 2.0%, with the remainder being semiconductor materials, meaning the loading of the metal alloy is between 0.1% and 2.0%.

[0018] Furthermore, the pretreated SiC is obtained by the following pretreatment: SiC is immersed in a 1 mol / L NaOH aqueous solution and stirred for 2 hours, washed by centrifugation with water, dried (in one embodiment of the present invention, vacuum drying at 40°C for 12 hours), and calcined at 800°C in air for 2 hours to obtain the pretreated SiC. The purpose of the NaOH aqueous solution treatment is to remove the irregular oxide layer on the semiconductor surface.

[0019] In one embodiment of the present invention, the power of the xenon lamp light source is 1000W. The power only affects the water evaporation time and does not affect the performance.

[0020] Furthermore, the total concentration of the metal salt in the aqueous solution of the metal salt is 0.01 mol·L⁻¹. -1 That is, the total concentration of the two metal salts is 0.01 mol·L⁻¹. -1 .

[0021] In one embodiment of the present invention, the ultrasound duration is 20 minutes, and the drying temperature is 100-110°C for 10-12 hours.

[0022] In addition, the present invention also provides an application of the above-mentioned composite semiconductor catalyst in the photocatalytic CO2 reduction reaction.

[0023] Furthermore, the application is as follows: using a xenon lamp or natural light as the light source, the composite semiconductor catalyst as the catalyst, and CO2 and H2O as reactants, a CO2 reduction reaction is carried out.

[0024] Specifically, the pressure of the CO2 is 0.1–1.0 MPa, and the light intensity of the light source is 10–1000 kW / m². 2 The temperature of the CO2 reduction reaction is 150–550°C.

[0025] The working principle of this reaction is as follows: the selected high-temperature semiconductor has high-temperature resistance, and SiC has a narrow bandgap, enabling it to utilize more sunlight under high-temperature conditions, thereby improving CO2 conversion rate and solar energy utilization efficiency. The high-temperature semiconductor catalyst supported on copper-ruthenium alloy described in this invention can efficiently convert CO2 and H2O into high-value-added organic products, with a maximum solar energy utilization efficiency approaching 5% and a carbon dioxide conversion rate exceeding 11%.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This paper presents a novel, practical, and efficient high-temperature semiconductor catalyst supported on a copper-ruthenium alloy and its application in the CO2 reduction reaction. It overcomes the limitations of current high-temperature conditions on catalyst performance, raising the upper limit of catalyst operating temperature to over 300 degrees Celsius. Semiconductor activation is achieved at high temperatures, and the light absorption range is expanded. Compared with single-component metal-supported catalysts, it exhibits higher CO2 conversion efficiency, solar energy utilization rate, and CO2 conversion rate, converting CO2 into more high-value alkane products. The solar energy conversion rate exceeds 5%, and the CO2 conversion rate exceeds 11%, demonstrating strong practical application prospects. Detailed Implementation

[0028] The present invention will be further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0029] Unless otherwise specified, all solutions in the following examples are aqueous solutions.

[0030] In Examples 7-12, the light intensity was controlled at 800 kW / m² by focusing. 2 The reaction temperature is controlled at 350℃ by controlling the temperature of the introduced carbon dioxide.

[0031] Example 1:

[0032] 5g of SiC (40nm, Aladdin) was placed in a 1mol / L NaOH solution and stirred for 2 hours. The SiC was then washed with deionized water by centrifugation and dried under vacuum at 40℃ for 12 hours to obtain pure SiC. This pure SiC was then calcined at 800℃ in air for 2 hours. The pure SiC obtained was used as a reference catalyst, and its pore volume was measured to be 0.04 cm³. 3 / g.

[0033] Example 2

[0034] Prepare a solution with a concentration of 0.01 mol·L⁻¹ -1 A Cu(NO3)2 solution is prepared for use.

[0035] 0.6 g of SiC prepared according to the method in Example 1 was placed in the focal region formed by focusing light from a 1000W xenon lamp. This focal region, at room temperature (25°C), can generate local temperatures exceeding 300°C, allowing for rapid evaporation of excess moisture. 2.5 mL of Cu(NO3)2 solution was uniformly loaded onto the surface of the semiconductor material carrier using a spraying method. During the spraying process, the photothermal environment created by the focused light rapidly evaporated excess moisture that could not be absorbed by the catalyst channels, while retaining the metal components. Subsequently, this sample (containing a small amount of moisture within the channels) was ultrasonically dispersed for 20 min to further enhance the dispersion of the metal within the channels. Finally, the sample was placed in a 100°C oven for 12 h to remove moisture from the channels, and then calcined in a muffle furnace at 400°C for 2 h to obtain a Cu / SiC catalyst with a loading of 0.3%.

[0036] Example 3:

[0037] Prepare 0.01 mol·L -1 RuCl3 solution is available for later use.

[0038] 0.6 g of SiC prepared according to the method in Example 1 was placed in the focal region formed by focusing light from a 1000W xenon lamp. This focal region, at room temperature (25°C), can generate local temperatures exceeding 300°C, allowing for rapid evaporation of excess moisture. 2.5 mL of Ru(NO3)2 solution was uniformly loaded onto the surface of the semiconductor material carrier using a spraying method. During the spraying process, the photothermal environment created by the focused light rapidly evaporated excess moisture that could not be absorbed by the catalyst channels, while retaining the metal components. Subsequently, this sample (containing a small amount of moisture within the channels) was ultrasonically dispersed for 20 min to further enhance the dispersion of the metal within the channels. Finally, the sample was placed in a 100°C oven for 12 h to remove moisture from the channels, and then calcined in a muffle furnace at 400°C for 2 h to obtain a 0.4% Ru / SiC catalyst.

[0039] Example 4:

[0040] Prepare a solution with a total ion concentration of 0.01 mol·L⁻¹ -1 A CuRu solution (copper nitrate and ruthenium chloride) with a mass ratio of Cu:Ru = 1:1.

[0041] 0.6 g of SiC prepared according to the method in Example 1 was placed in the focal region formed by focusing light from a 1000W xenon lamp. This focal region, at room temperature (25°C), can generate local temperatures exceeding 300°C, allowing for rapid evaporation of excess moisture. 2.5 mL of copper-ruthenium solution was uniformly loaded onto the surface of the semiconductor material carrier using a spraying method. During the spraying process, the photothermal environment created by the focused light rapidly evaporated excess moisture that could not be absorbed by the catalyst channels, while retaining the metal components. Subsequently, this sample (containing a small amount of moisture within the channels) was ultrasonically dispersed for 20 min to further enhance the dispersion of the metal within the channels. Finally, the sample was placed in a 100°C oven for 12 h to remove moisture from the channels, and then calcined in a muffle furnace at 400°C for 2 h to obtain a Cu1Ru1 / SiC catalyst with a loading of 0.3%.

[0042] Example 5:

[0043] Prepare a solution with a total ion concentration of 0.01 mol·L⁻¹ -1 A CuRu solution with a mass ratio of Cu:Ru = 8:2 was prepared. 0.6 g of SiC prepared according to the method in Example 1 was placed in the focal region formed by focusing light from a 1000W xenon lamp. This focal region, at room temperature (25°C), could generate local temperatures exceeding 300°C, allowing for rapid evaporation of excess moisture. 2.5 mL of a copper-ruthenium solution was uniformly loaded onto the surface of the semiconductor material carrier using a spraying method. During the spraying process, the photothermal environment created by the focused light rapidly evaporated excess moisture that could not be absorbed by the catalyst channels, while retaining the metal components. Subsequently, this sample (containing a small amount of moisture in the channels) was ultrasonically dispersed for 20 min to further enhance the dispersion of the metal within the channels. Finally, the sample was placed in a 100°C oven for 12 h to remove moisture from the channels, and then calcined in a muffle furnace at 400°C for 2 h to obtain a Cu8Ru2 / SiC catalyst with a loading of 0.3%.

[0044] Example 6:

[0045] Prepare a solution with a total ion concentration of 0.01 mol·L⁻¹ -1A CuRu solution with a mass ratio of Cu:Ru = 2:8 was prepared. 0.6 g of SiC prepared according to the method in Example 1 was placed in the focal region formed by focusing light from a 1000W xenon lamp. This focal region, at room temperature (25°C), could generate local temperatures exceeding 300°C, allowing for rapid evaporation of excess moisture. 2.5 mL of a copper-ruthenium solution was uniformly loaded onto the surface of the semiconductor material carrier using a spraying method. During the spraying process, the photothermal environment created by the focused light rapidly evaporated excess moisture that could not be absorbed by the catalyst channels, while retaining the metal components. Subsequently, this sample (containing a small amount of moisture in the channels) was ultrasonically dispersed for 20 min to further enhance the dispersion of the metal within the channels. Finally, the sample was placed in a 100°C oven for 12 h to remove moisture from the channels, and then calcined in a muffle furnace at 400°C for 2 h to obtain a Cu2Ru8 / SiC catalyst with a loading of 0.3%.

[0046] Example 7:

[0047] The catalyst performance was tested using an intermittent photocatalytic reaction system. CO2 and H2O were used as reactants. Initially, 2 mL of H2O and 0.1 MPa of CO2 were added to the reactor. 0.5 g of pure SiC was weighed out. The reactor volume was 100 mL. A 1000 W xenon lamp was used as the light source. After 5 hours of reaction, the methane yield was measured to be 100.44 μmol·g⁻¹. -1 The ethylene yield was 17.17 μmol·g. -1 The yield of ethane was 7.34 μmol·g. -1 .

[0048] Example 8:

[0049] The catalyst performance was tested using an intermittent photocatalytic reaction system. CO2 and H2O were used as reactants. Initially, 2 mL of H2O and 0.1 MPa of CO2 were added to the reactor. 0.5 g of Cu / SiC with a loading of 0.3% was weighed out. The reactor volume was 100 mL, and a 1000 W xenon lamp was used as the light source. After 5 h of reaction, the methane yield was monitored to be 840.17 μmol·g. -1 The ethylene yield was 3.19 μmol·g. -1 The yield of ethane was 8.65 μmol·g. -1 .

[0050] Example 9:

[0051] The catalyst performance was tested using an intermittent photocatalytic reaction system. CO2 and H2O were used as reactants. Initially, 2 mL of H2O and 0.1 MPa of CO2 were added to the reactor. 0.5 g of Ru / SiC was weighed, and the reactor volume was 100 mL. Natural light was used as the light source. After 5 hours of reaction, significant hydrocarbons were produced. The main product was methane, with a yield of 1578.32 μmol·g. -1 .

[0052] Example 10:

[0053] The catalyst performance was tested using an intermittent photocatalytic reaction system. CO2 and H2O were used as reactants. Initially, 2 mL of H2O and 0.1 MPa of CO2 were added to the reactor. 0.5 g of Cu1Ru1 / SiC was weighed, and the reactor volume was 100 mL. A 1000 W xenon lamp was used as the light source. After 5 hours of reaction, significant hydrocarbons were produced, with methane as the main product, yielding 2900.96 μmol·g. -1 Based on this, the solar energy conversion efficiency exceeds 5%, and the CO2 conversion rate exceeds 11%.

[0054] Example 11:

[0055] The catalyst performance was tested using a continuous photocatalytic reaction system. CO2 and H2O were used as reactants. Initially, 2 mL of H2O and 0.1 MPa of CO2 were added to the reactor. 0.5 g of Cu2Ru8 / SiC was weighed, and the reactor volume was 100 mL. A 1000 W xenon lamp was used as the light source. After 5 hours of reaction, significant hydrocarbons were produced, with methane as the main product, yielding 1145.15 μmol·g⁻¹. -1 .

[0056] Example 12:

[0057] The catalyst performance was tested using an intermittent photocatalytic reaction system. CO2 and H2O were used as reactants. Initially, 2 mL of H2O and 0.1 MPa of CO2 were added to the reactor. 0.5 g of a commercially available P25 TiO2 catalyst (a standard photocatalyst) was weighed out. The reactor volume was 100 mL, and a 1000 W xenon lamp was used as the light source. After 5 hours of reaction, significant hydrocarbons were produced, with methane as the main product, yielding 50.19 μmol·g⁻¹. -1 The catalytic effect is far lower than that of this patent.

[0058] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Many aspects of the present invention can be improved without departing from the overall concept, and those skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A composite semiconductor catalyst, characterized in that... The composite semiconductor catalyst is prepared according to the following method: Pretreated SiC is placed at the focal point of a xenon lamp light source, and an aqueous solution of metal salt is sprayed onto the surface of the pretreated SiC under irradiation to obtain sprayed SiC; the sprayed SiC is ultrasonicated for 10-30 minutes, dried, and calcined in air at 300-500℃ for 1-3 hours to obtain the composite semiconductor catalyst. The aqueous solution of the metal salt contains copper nitrate and ruthenium chloride. The theoretical mass ratio of copper in the copper nitrate to the theoretical mass of the metal element in the aqueous solution of the metal salt is 20-80:

100. The theoretical mass of the metal element in the aqueous solution of the metal salt is 0.1%-2% of the theoretical mass of the metal element in the aqueous solution of the metal salt and the total mass of the pretreated SiC.

2. The composite semiconductor catalyst as described in claim 1, characterized in that... The pretreated SiC was obtained by the following pretreatment: SiC was immersed in a 1 mol / L NaOH aqueous solution and stirred for 2 hours, washed by centrifugation with water, dried, and calcined at 800°C for 2 hours in air atmosphere to obtain the pretreated SiC.

3. The composite semiconductor catalyst as described in claim 1, characterized in that: The power of the xenon lamp light source is 1000W.

4. The composite semiconductor catalyst as described in claim 1, characterized in that: The total concentration of the metal salt in the aqueous solution is 0.01 mol·L⁻¹. -1 .

5. The composite semiconductor catalyst as described in claim 1, characterized in that: The theoretical mass ratio of copper in the copper nitrate to the theoretical mass ratio of the metal element in the aqueous solution of the metal salt is 50:

100.

6. The composite semiconductor catalyst as described in claim 1, characterized in that: The theoretical mass of the metal element contained in the aqueous solution of the metal salt is 0.3%-0.4% of the theoretical mass of the metal element contained in the aqueous solution of the metal salt and the total mass of the pretreated SiC.

7. The composite semiconductor catalyst as described in claim 1, characterized in that: The drying temperature is 100-110℃, and the time is 10-12h.

8. The application of the composite semiconductor catalyst as described in claim 1 in the photocatalytic CO2 reduction reaction.

9. The application as described in claim 8, characterized in that... The application is as follows: using a xenon lamp or natural light as the light source, the composite semiconductor catalyst as the catalyst, and CO2 and H2O as reactants, a CO2 reduction reaction is carried out.

10. The application as described in claim 9, characterized in that... The CO2 pressure is 0.1-1.0 MPa, and the light intensity of the light source is 10-1000 kW / m². 2 The temperature of the CO2 reduction reaction is 150-550℃.