Method for photosynthesis of aldehyde intermediate from CO2 source and multi-carbon carbohydrate compound
By combining an organic fused-ring semiconductor photocatalyst with a copper diatomic site co-catalyst, the problems of low energy conversion efficiency and poor product selectivity of the photocatalyst were solved, efficient synthesis of polysaccharide compounds was achieved, and the process flow was simplified.
Patent Information
- Application Number
- CN202510778759.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-11
- Publication Date
- 2025-09-23
AI Technical Summary
Existing photocatalysts have low energy conversion efficiency, poor product selectivity, and complex polysaccharide synthesis pathways, making them difficult to apply on a large scale.
By using a combination of an organic fused-ring semiconductor photocatalyst and a copper diatomic site co-catalyst, the selective reduction of CO2 to formaldehyde and ethanolaldehyde is promoted by adjusting the conduction band reduction potential and local electron delocalization, and carbon-carbon coupling is carried out, simplifying the reaction into a two-step synthesis of polysaccharide compounds.
It significantly improves the selectivity of CO2 reduction to aldehyde intermediates, reduces the recombination rate of photogenerated charges, improves the conversion efficiency of solar energy to chemical energy, and simplifies the process flow.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of photocatalysis and resource utilization, and specifically to an organic fused-ring semiconductor photocatalyst, a catalyst composition, a method for preparing aldehyde intermediates and polysaccharide compounds, and a photogenerated charge directional transport device. Background Art
[0002] With the advancement of the "dual carbon" strategy, the use of solar energy to convert CO2 into high-value-added chemicals has become a research hotspot in the field of energy and environmental protection. Sugars, as the core energy material for life activities, are currently mainly produced by agricultural photosynthesis, but the energy conversion efficiency of natural photosynthesis is extremely low (<0.5%), which is difficult to meet the needs of sustainable development. Photocatalytic CO2 reduction technology is regarded as a potential way to break through the bottleneck of natural efficiency due to its advantages such as direct use of sunlight and mild reaction conditions. However, existing technologies still face the following key problems: (1) Low energy conversion efficiency: Traditional photocatalysts (such as TiO2, CdS) have insufficient utilization of visible light, and the photogenerated electron-hole recombination is serious, resulting in a solar energy to chemical energy conversion efficiency generally below 0.1%. (2) Poor product selectivity: Existing systems mostly generate low-value-added C1 products (such as CO, formic acid), while the key aldehyde intermediates required for chemical polysaccharides (formaldehyde, ethanolaldehyde) are easily over-reduced or oxidized, and their selectivity is difficult to control. (3) Complex polysaccharide synthesis pathway: Artificial photosynthesis of C5+ sugars requires multi-step enzyme catalysis or high-temperature and high-pressure reactions. The cascade is highly complex and expensive, making it difficult to apply on a large scale.
[0003] In recent years, researchers have improved the CO2 reduction activity through photocatalyst band modulation (such as doping, surface modification) and co-catalyst design (such as single-atom sites), but there is still a lack of in-depth understanding of the directed synthesis of aldehyde intermediates and the carbon-carbon coupling mechanism. For example, although pyrene-based organic framework materials can regulate the reduction potential, their selectivity and stability for aldehyde products are insufficient; and although copper-based co-catalysts can promote CC coupling, there is the problem of difficulty in desorption of aldehyde products. In addition, the high charge recombination rate in existing photocatalytic devices makes it difficult to break through the overall efficiency. Based on this, the photocatalysts used to reduce CO2 still need further improvement.
[0004] It should be noted that the above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art. Summary of the Invention
[0005] In its first aspect, the present application proposes an organic fused-ring semiconductor photocatalyst comprising a conjugated central unit and carboxyl-bearing side chains. This photocatalyst improves visible light utilization, enhances carbon dioxide reduction activity, and achieves selective reduction of carbon dioxide to formaldehyde and glycolaldehyde, thereby facilitating the efficient synthesis of polysaccharide compounds.
[0006] In addition, the organic fused-ring semiconductor photocatalyst according to the above embodiment of the present application may also have the following additional technical features:
[0007] In some embodiments of the present application, the conjugated central unit includes at least one of coronene, perylene, pyrene, and heptazoline. This can adjust the conduction band reduction potential of the organic fused-ring semiconductor photocatalyst, thereby improving the selective reduction of carbon dioxide by the organic fused-ring semiconductor photocatalyst.
[0008] In some embodiments of the present application, the carboxyl side chain group includes at least one of p-carboxyphenyl, p-carboxynaphthyl, and p-carboxyphenylalkynyl, thereby facilitating the selective reduction of carbon dioxide by the organic fused-ring semiconductor photocatalyst.
[0009] In some embodiments of the present application, the organic fused-ring semiconductor photocatalyst includes at least one of 4-(p-carboxyphenyl)coronene, 4-(p-carboxyphenyl)perylene, 4-(p-carboxyphenyl)pyrene, 4-(p-carboxynaphthyl)pyrene, 4-(p-carboxyphenylalkynyl)pyrene, and 3-(p-carboxyphenyl)heptazine. This can suppress the overreduction of aldehyde intermediates (formaldehyde, glycolaldehyde) and achieve selective CO2 reduction.
[0010] In some embodiments of the present application, the conduction band reduction potential of the organic fused-ring semiconductor photocatalyst is less than or equal to -0.69 V vs. NHE. This can inhibit the excessive reduction of aldehyde intermediates (formaldehyde, glycolaldehyde) and achieve selective reduction of CO2.
[0011] In its second aspect, this application proposes a catalyst composition comprising the organic fused-ring semiconductor photocatalyst described in the first aspect of this application and a copper diatomic site co-catalyst. This catalyst composition selectively reduces CO2 to formaldehyde and glycolaldehyde intermediates, promoting carbon-carbon coupling and lowering the desorption barrier of aldehyde products, thereby improving the efficiency of solar-to-chemical energy conversion.
[0012] In some embodiments of the present application, the copper diatomic site loading in the copper diatomic site co-catalyst is 0.2 wt% to 10.8 wt%; in other embodiments of the present application, the copper diatomic site loading in the copper diatomic site co-catalyst is 1 wt% to 8 wt%; in still other embodiments of the present application, the copper diatomic site loading in the copper diatomic site co-catalyst is 1.5 wt% to 5 wt%; and in some specific examples of the present application, the copper diatomic site loading in the copper diatomic site co-catalyst is 1.8 wt% to 3 wt%. This is conducive to further promoting the formation and desorption of aldehyde intermediates.
[0013] In some embodiments of the present application, the mass fraction of cyano groups in the copper diatomic site promoter is 3 wt% to 20 wt%; in other embodiments of the present application, the mass fraction of cyano groups is 5 wt% to 20 wt%; in other embodiments of the present application, the mass fraction of cyano groups is 10 wt% to 20 wt%; in other embodiments of the present application, the mass fraction of cyano groups is 13 wt% to 20 wt%; and in some specific examples of the present application, the mass fraction of cyano groups is 15 wt% to 20 wt%. This allows for the regulation of local electron delocalization and the reduction of the desorption energy barrier of aldehyde products.
[0014] In some embodiments of the present application, the copper diatomic site promoter is prepared by the following method: mixing melamine and cyanoacetic acid and then performing a first calcination treatment to obtain a cyano-modified polymeric carbon nitride; dispersing CuCl2 and the cyano-modified polymeric carbon nitride in formamide and stirring to obtain a precursor; and performing a second calcination treatment on the precursor to obtain the copper diatomic site promoter. This method can promote the formation and desorption of aldehyde intermediates and improve the selectivity of aldehyde intermediates.
[0015] In its third aspect, the present application provides a method for preparing an aldehyde intermediate, comprising: using the catalyst composition described in the second aspect of the present application to reduce carbon dioxide in a photogenerated charge directed transport device to produce the aldehyde intermediate. This method enables the selective reduction of CO2 to formaldehyde and glycolaldehyde intermediates, thereby improving the efficiency of solar-to-chemical energy conversion.
[0016] In a fourth aspect of the present application, the present application proposes a method for preparing a polysaccharide compound, comprising:
[0017] Obtaining an aldehyde intermediate using the method described in the third aspect of the present application;
[0018] The aldehyde intermediate is subjected to a formaldehyde polysaccharide reaction to obtain the polysaccharide compound.
[0019] The present application prepares polysaccharide compounds through the above-mentioned method, which significantly improves the selectivity of carbon dioxide reduction to aldehyde intermediates, breaking through the selectivity bias of traditional photocatalytic systems for C1 products; at the same time, it reduces the photogenerated charge recombination rate, improves the conversion efficiency of solar energy to chemical energy, and simplifies the process flow. Only two-step cascade reaction (photocatalytic carbon dioxide reduction + formaldehyde polysaccharide reaction) is required to synthesize polysaccharide compounds, reducing complex enzyme catalysis or high-pressure conditions.
[0020] In some embodiments of the present application, the photogenerated charge directional transport device includes a photoanode and a photocathode connected in series, thereby reducing the charge recombination rate and improving the conversion efficiency of solar energy to chemical energy.
[0021] In some embodiments of the present application, the method for preparing the photocathode includes: sequentially cleaning and ultraviolet ozone treating fluorine-doped tin oxide to obtain the fluorine-doped tin oxide layer; and sequentially spin-coating a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate hole transport layer, a composite layer of an organic fused-ring semiconductor photocatalyst and a copper diatomic site co-catalyst, or an organic fused-ring semiconductor photocatalyst layer and a copper diatomic site co-catalyst layer on the surface of the fluorine-doped tin oxide layer to obtain the photocathode. This helps to improve the selectivity of formaldehyde intermediates and glycolaldehyde intermediates and the conversion efficiency of solar energy to chemical energy.
[0022] In some embodiments of the present application, the method for preparing the photoanode includes: sequentially polishing, cleaning, and acid-etching a titanium sheet to obtain a titanium sheet layer; placing the titanium sheet layer in a container containing a cobalt-doped bismuth vanadate precursor solution, sequentially performing a hydrothermal reaction and a third calcination process to obtain the photoanode. This helps further improve the conversion efficiency of solar energy to chemical energy.
[0023] In some embodiments of the present application, the cobalt doping amount in the cobalt-doped bismuth vanadate precursor solution is 2 at %, thereby facilitating improved selectivity of formaldehyde intermediates and glycolaldehyde intermediates.
[0024] In some embodiments of the present application, the temperature of the hydrothermal reaction is 180° C., and the time of the hydrothermal reaction is 6 to 12 hours, which is conducive to increasing the reaction rate and making the reaction more complete.
[0025] In some embodiments of the present application, the temperature of the third calcination treatment is 450° C., and the time of the third calcination treatment is 2 hours, thereby facilitating the improvement of crystallinity.
[0026] In a fifth aspect of the present application, a photogenerated charge directional transport device is provided, comprising the catalyst composition described in the third aspect of the present application. Thus, the photogenerated charge directional transport device has lower recombination losses and higher solar-to-chemical energy conversion efficiency.
[0027] In some embodiments of the present application, the photogenerated charge directional transport device includes a photoanode and a photocathode connected in series, wherein the photoanode includes a titanium layer and a cobalt-doped bismuth vanadate layer stacked in sequence; and the photocathode includes a fluorine-doped tin oxide layer, a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate hole transport layer, and a catalytic layer stacked in sequence. As a result, the photogenerated charge directional transport device has low recombination losses and high solar-to-chemical energy conversion efficiency.
[0028] In some embodiments of the present application, the catalyst layer comprises a composite layer of an organic fused-ring semiconductor photocatalyst and a copper diatomic site co-catalyst, or alternatively, the catalyst layer comprises an organic fused-ring semiconductor photocatalyst layer and a copper diatomic site co-catalyst layer. Thus, the catalyst layer can selectively reduce CO2 to formaldehyde and glycolaldehyde, thereby facilitating the synthesis of polysaccharide compounds. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:
[0030] Figure 1 This is a schematic structural diagram of a photogenerated charge directional transport device according to an embodiment of the present application ( Figure 1 Figure a), schematic diagram of the artificial photosynthesis pathway from CO2 to multi-carbon sugar compounds ( Figure 1 Figure b), the structure of organic fused-ring semiconductor photocatalyst and the corresponding conduction band reduction potential ( Figure 1 Figure c);
[0031] Figure 2 Schematic diagram of the local electron delocalization mechanism of the copper diatomic site in this application ( Figure 2 Figure a), the relationship between the selectivity of formaldehyde and glycolaldehyde and the cyanide content ( Figure 2 Figure b) and the relationship between solar-electrical energy conversion efficiency and time ( Figure 2 c);
[0032] Figure 3 Current density curve of photogenerated charge directional transport device ( Figure 3 Figure a) and final sugar product distribution ( Figure 3 (middle panel b). DETAILED DESCRIPTION
[0033] The following describes the embodiments of the present application in detail. Examples of the embodiments are shown in the accompanying drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary lengthiness in the following description and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.
[0034] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).
[0035] The terms "include" and "have" in the description and claims of this application and any variations thereof are open expressions, that is, including the contents specified in this application but not excluding other contents.
[0036] In the description of this application, regardless of whether the word "about" or "approximately" is used, all numbers disclosed herein are approximate values. The value of each number may vary by less than 10% or by a reasonable difference considered by a person skilled in the art, such as 1%, 2%, 3%, 4% or 5%.
[0037] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
[0038] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the technical features indicated. "First feature" and "second feature" may include one or more of the features.
[0039] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.
[0040] In this application, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), indicating that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.
[0041] In its first aspect, the present application proposes an organic fused-ring semiconductor photocatalyst comprising a conjugated central unit and carboxyl-bearing side chains. This photocatalyst improves visible light utilization, enhances carbon dioxide reduction activity, and achieves selective reduction of carbon dioxide to formaldehyde and glycolaldehyde, thereby facilitating the efficient synthesis of polysaccharide compounds.
[0042] In addition, the organic fused-ring semiconductor photocatalyst according to the above embodiment of the present application may also have the following additional technical features:
[0043] In some embodiments of the present application, the conjugated central unit includes at least one of coronene, perylene, pyrene, and heptazoline. This can adjust the conduction band reduction potential of the organic fused-ring semiconductor photocatalyst, thereby improving the selective reduction of carbon dioxide by the organic fused-ring semiconductor photocatalyst.
[0044] In some embodiments of the present application, the carboxyl side chain group includes at least one of p-carboxyphenyl, p-carboxynaphthyl, and p-carboxyphenylalkynyl, thereby facilitating the selective reduction of carbon dioxide by the organic fused-ring semiconductor photocatalyst.
[0045] In some embodiments of the present application, the organic fused-ring semiconductor photocatalyst includes at least one of 4-(p-carboxyphenyl)coronene, 4-(p-carboxyphenyl)perylene, 4-(p-carboxyphenyl)pyrene, 4-(p-carboxynaphthyl)pyrene (TNAP), 4-(p-carboxyphenylalkynyl)pyrene, and 3-(p-carboxyphenyl)heptazine, and its specific structure can be referred to. Figure 1Figure c. As can be understood, TNAP is a monomer molecule dissolved in solution, which self-assembles into HOF-TNAP. This suppresses the overreduction of aldehyde intermediates (formaldehyde and glycolaldehyde), achieving selective CO2 reduction.
[0046] In some embodiments of the present application, the conduction band reduction potential of the organic fused-ring semiconductor photocatalyst is less than or equal to -0.69V vs. NHE, for example, -0.69V vs. NHE, -0.79V vs. NHE, -0.84V vs. NHE, -0.88V vs. NHE, -0.92V vs. NHE, or -1.13V vs. NHE, etc. It can be understood that by regulating the side chain groups and conjugated structure of the organic fused-ring semiconductor molecular crystal, the conduction band reduction potential of the photocatalyst is adjusted so that it can selectively reduce CO2 to form formaldehyde intermediates and glycolaldehyde intermediates under visible light. In this way, the excessive reduction of aldehyde intermediates (formaldehyde, glycolaldehyde) can be suppressed, and the selective reduction of CO2 can be achieved.
[0047] In its second aspect, the present application proposes a catalyst composition comprising the organic fused-ring semiconductor photocatalyst of the first aspect and a copper diatomic site co-catalyst. This catalyst composition selectively reduces CO2 to formaldehyde and glycolaldehyde intermediates, promoting carbon-carbon coupling and lowering the desorption barrier of aldehyde products, thereby improving the efficiency of solar-to-chemical energy conversion.
[0048] In some embodiments of the present application, the loading amount of copper diatomic sites in the copper diatomic site co-catalyst is 0.2 wt% to 10.8 wt%, for example, 0.2 wt%, 1 wt%, 2 wt%, 5 wt%, 8 wt%, 10.8 wt%, etc. In other embodiments of the present application, the loading amount of copper diatomic sites in the copper diatomic site co-catalyst is 1 wt% to 8 wt% In other embodiments of the present application, the loading amount of copper diatomic sites in the copper diatomic site co-catalyst is 1.5 wt% to 5 wt% In some specific examples of the present application, the loading amount of copper diatomic sites in the copper diatomic site co-catalyst is 1.8 wt% to 3 wt%. Inductively coupled plasma spectroscopy (ICP-OES) is generally used to test the elemental content of the catalyst after digestion in concentrated nitric acid. This is conducive to further promoting the formation and desorption of aldehyde intermediates.
[0049] In some embodiments of the present application, the mass fraction of cyano groups in the copper diatomic site co-catalyst is 3 wt% to 20 wt%, for example, it can be 3 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt% or 20 wt%, etc.; in other embodiments of the present application, the mass fraction of cyano groups is 5 wt% to 20 wt%; in other embodiments of the present application, the mass fraction of cyano groups is 10 wt% to 20 wt%; in other embodiments of the present application, the mass fraction of cyano groups is 13 wt% to 20 wt%; in some specific examples of the present application, the mass fraction of cyano groups is 15 wt% to 20 wt%. The mass fraction of cyano groups refers to the ratio of nitrogen atoms of cyano groups to all nitrogen atoms in the polymer. X-ray photoelectron spectroscopy (XPS) is generally used for quantification. The chemical state of nitrogen (N 1s) is analyzed to distinguish cyano groups from other nitrogen species. The N1s spectrum is subjected to peak fitting, and the ratio of the peak area corresponding to cyano groups to the total nitrogen peak area is calculated. The relationship between the mass fraction of cyano groups and the selectivity of formaldehyde and ethanolaldehyde is shown in the figure below. Figure 2 As shown in Figure b, when the mass fraction of the cyano group is within the above range, the local electron delocalization can be regulated and the desorption energy barrier of the aldehyde product can be reduced.
[0050] In some embodiments of the present application, the copper diatomic site co-catalyst is prepared by the following method: mixing melamine and cyanoacetic acid and performing a first calcination treatment to obtain a cyano-modified polymer carbon nitride; dispersing CuCl2 and the cyano-modified polymer carbon nitride in formamide and stirring to obtain a precursor; and performing a second calcination treatment on the precursor to obtain a copper diatomic site co-catalyst. The present application introduces cyano-modified N6 coordination vacancies in a two-dimensional carbon nitrogen polymer (PCN) substrate to load copper diatomic sites (Cu2-PCN), regulates local electron delocalization by the mass fraction of cyano groups, and reduces the desorption energy barrier of aldehyde products. The schematic diagram of the local electron delocalization mechanism of the copper diatomic site is shown in the figure. Figure 2 As shown in Figure a, the generation and desorption of aldehyde intermediates can be promoted, thereby improving the selectivity of aldehyde intermediates.
[0051] In its third aspect, the present application provides a method for preparing an aldehyde intermediate, comprising: using the catalyst composition of the second aspect of the present application to reduce carbon dioxide in a photogenerated charge directed transport device to produce the aldehyde intermediate. This method enables the selective reduction of CO2 to formaldehyde and glycolaldehyde intermediates, thereby improving the efficiency of solar-to-chemical energy conversion.
[0052] In the fourth aspect of the present application, the present application proposes a method for preparing a polysaccharide compound, referring to Figure 1 Figure b, including:
[0053] S1: Obtain an aldehyde intermediate using the method of the third aspect of the present application.
[0054] S2: allowing the aldehyde intermediate to undergo a formaldehyde polysaccharide reaction to obtain a polysaccharide compound.
[0055] In this step, the liquid from the photocatalytic system in step S1 can be directly used in the formaldehyde polysaccharide reaction. Specifically, 60 mM Ca(OH)2 can be added to 3 mL of the reaction liquid, and the reaction can be maintained at 60°C for 30 minutes. The reaction system quickly develops the characteristic burnt yellow color of sugar products, and the product can be analyzed by electrospray ionization mass spectrometry (ESI-MS).
[0056] In some embodiments of the present application, the polysaccharide compound includes at least one of D-(+)-glucose, D-(-)-ribose, and L-threonic acid. Thus, the polysaccharide compound can be efficiently synthesized, realizing resource utilization of carbon dioxide.
[0057] The present application prepares polysaccharide compounds through the above-mentioned method, which significantly improves the selectivity of carbon dioxide reduction to aldehyde intermediates, breaking through the selectivity bias of traditional photocatalytic systems for C1 products; at the same time, it reduces the photogenerated charge recombination rate, improves the conversion efficiency of solar energy to chemical energy, and simplifies the process flow. Only two-step cascade reaction (photocatalytic carbon dioxide reduction + formaldehyde polysaccharide reaction) is required to synthesize polysaccharide compounds, reducing complex enzyme catalysis or high-pressure conditions.
[0058] The above-mentioned preparation method of the present application has at least the following beneficial effects:
[0059] (1) The selectivity of carbon dioxide reduction to aldehyde intermediates is significantly improved, breaking through the selectivity bias of traditional photocatalytic systems towards C1 products;
[0060] (2) The recombination rate of photogenerated charges is reduced, and the conversion efficiency of solar energy to chemical energy is significantly improved;
[0061] (3) The process is simplified, and only two-step cascade reaction (photocatalytic carbon dioxide reduction + formaldehyde polysaccharide reaction) is required to synthesize C5+ sugars, reducing complex enzyme catalysis or high-pressure conditions.
[0062] In some embodiments of the present application, a photogenerated charge directional transport device includes a photoanode and a photocathode connected in series, thereby reducing the charge recombination rate and improving the conversion efficiency of solar energy to chemical energy.
[0063] In some embodiments of the present application, a method for preparing a photocathode includes: sequentially cleaning and ultraviolet ozone treating a fluorine-doped tin oxide to obtain a fluorine-doped tin oxide layer; and sequentially spin-coating a poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate hole transport layer, a composite layer of an organic fused-ring semiconductor photocatalyst and a copper diatomic site co-catalyst, or an organic fused-ring semiconductor photocatalyst layer and a copper diatomic site co-catalyst layer on the surface of the fluorine-doped tin oxide layer to obtain a photocathode. This helps improve the selectivity of formaldehyde intermediates and glycolaldehyde intermediates, as well as the conversion efficiency of solar energy to chemical energy.
[0064] As an example, a specific method for preparing the photocathode may include:
[0065] i) FTO substrate pretreatment: sequentially cleaned with detergent, deionized water, acetone, and isopropyl alcohol ultrasonically, and then treated with UV ozone;
[0066] ii) Spin coating of a PEDOT:PSS hole transport layer: dilute the PEDOT:PSS stock solution at a mass ratio of 1:3, add 5% dimethyl sulfoxide (DMSO), spin-coat at 3000-4000 rpm, and anneal at 150°C for 15 minutes.
[0067] iii) Preparation of TNAP:Cu2 composite layer: TNAP solution and Cu2-PCN dispersion were mixed in a mass ratio of 9:1, the spin coating parameters were 2000 rpm to 2500 rpm, and the annealing condition was 120°C in a nitrogen atmosphere for 30 minutes.
[0068] In some embodiments of the present application, a method for preparing a photoanode includes: sequentially polishing, cleaning, and acid-etching a titanium sheet to obtain a titanium sheet layer; placing the titanium sheet layer in a container containing a cobalt-doped bismuth vanadate precursor solution, sequentially performing a hydrothermal reaction and a third calcination process to obtain the photoanode. This helps further improve the conversion efficiency of solar energy to chemical energy.
[0069] In some embodiments of the present application, the cobalt doping amount in the cobalt-doped bismuth vanadate precursor solution is 2 at %, thereby facilitating improved selectivity of formaldehyde intermediates and glycolaldehyde intermediates.
[0070] In some embodiments of the present application, the temperature of the hydrothermal reaction is 180° C., and the hydrothermal reaction time is 6 to 12 hours (eg, 6 hours, 8 hours, 10 hours, or 12 hours, etc.), thereby increasing the reaction rate and making the reaction more complete.
[0071] In some embodiments of the present application, the temperature of the third calcination treatment is 450° C. and the time of the third calcination treatment is 2 hours, which is beneficial to improving the crystallinity.
[0072] As an example, a specific method for preparing the photoanode may include:
[0073] i) Titanium sheet pretreatment: mechanical polishing, acetone / ethanol / deionized water ultrasonic cleaning, and 1M HCl acid etching;
[0074] ii) Preparation of BiVO4:Co precursor solution: Bi(NO3)3·5H2O, NH4VO3 and Co(NO3)2·6H2O as raw materials, with Co doping amount of 2at%;
[0075] iii) Hydrothermal synthesis: reaction at 180°C for 6 to 12 hours, and calcination at 450°C for 2 hours.
[0076] In a fifth aspect of the present application, a photogenerated charge directional transport device is provided, comprising the catalyst composition of the third aspect of the present application. Thus, the photogenerated charge directional transport device has lower recombination loss and higher solar-to-chemical energy conversion efficiency.
[0077] In some embodiments of the present application, the photogenerated charge directional transport device includes a photoanode and a photocathode connected in series, Figure 1 In Figure a, the photoanode (Ti / BiVO4:Co) includes a titanium layer and a cobalt-doped bismuth vanadate layer stacked in sequence; the photocathode (FTO|PEDOT:PSS|TNAP:Cu2) includes a fluorine-doped tin oxide layer (FTO), a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate hole transport layer (PEDOT:PSS), and a catalyst layer stacked in sequence. Based on the obtained catalyst layer, the gradient Fermi level difference between the photoanode and the photocathode is constructed and matched to form an electron-hole directional separation channel. Constructing the aforementioned photogenerated charge directional transport device can reduce the charge recombination rate and improve the conversion efficiency of solar energy to chemical energy.
[0078] In some embodiments of the present application, the catalytic layer comprises a composite layer of an organic fused-ring semiconductor photocatalyst and a copper diatomic site co-catalyst (PCN-Cu2), or alternatively, the catalytic layer comprises an organic fused-ring semiconductor photocatalyst layer and a copper diatomic site co-catalyst layer. Thus, the catalyst layer can selectively reduce CO2 to formaldehyde and glycolaldehyde, thereby facilitating the synthesis of polysaccharide compounds.
[0079] The present invention will be described below by way of specific examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, they are determined according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments not specified by manufacturer are all commercially available conventional products.
[0080] Example 1
[0081] 1. Preparation of Ti / BiVO4:Co photoanode:
[0082] (1) Titanium sheet pretreatment
[0083] Mechanical polishing: Use 800-grit sandpaper to polish the surface of the titanium sheet (size 2 cm × 3 cm) until it is smooth and remove the oxide layer;
[0084] Ultrasonic cleaning: ultrasonic cleaning in acetone, anhydrous ethanol, and deionized water for 10 minutes each to remove organic pollutants adsorbed on the surface of the titanium sheet;
[0085] Acid treatment: Immerse the titanium sheet in 1 M HCl solution for 10 minutes, rinse with deionized water, and blow dry with nitrogen gas for later use.
[0086] (2) Preparation of BiVO:Co precursor solution
[0087] Dissolve 2.425g of Bi(NO3)3·5H2O in 10mL of concentrated nitric acid (65%) and stir magnetically until transparent. Separately, dissolve 0.585g of NH4VO3 in 30mL of deionized water, heat to 60°C, and stir until the solution is transparent. Add 0.029g of Co(NO3)2·6H2O (Co doping level: 2at%) to the vanadium solution and stir for 10 minutes. Slowly add the bismuth solution dropwise to the vanadium solution and continue stirring for 30 minutes to obtain an orange-yellow transparent sol.
[0088] (3) Hydrothermal synthesis
[0089] Tilt the pretreated titanium sheet in a 50mL polytetrafluoroethylene-lined container and pour the precursor solution until the titanium sheet is submerged. Seal the reactor and place it in an oven at 180°C for 8 hours. After cooling naturally, remove the titanium sheet, rinse with deionized water, and dry it at 60°C.
[0090] (4) Calcination treatment
[0091] The sample obtained in step (3) was placed in a muffle furnace, heated to 450°C at 2°C / min in an air atmosphere, kept warm for 2 hours, and naturally cooled to obtain a Ti / BiVO4:Co photoanode.
[0092] 2. Preparation of copper diatomic site co-catalyst:
[0093] (1) Synthesis of cyano-modified polymeric carbon nitride (PCN)
[0094] Weigh 10g of melamine and 1.5g of cyanoacetic acid into a ball mill and mill at 300 rpm for 30 minutes to obtain a uniform mixture. Place the mixture in a tube furnace, purge the air with nitrogen, and heat it to 400°C at a rate of 3°C / min and hold for 1.5 hours. Then, heat it to 580°C at a rate of 2°C / min and hold for 3 hours.
[0095] (2) Synthesis of Cu2-PCN precursor
[0096] 0.64 g of CuCl2 and 0.70 g of exfoliated PCN were dispersed in 200 mL of formamide and sonicated for 10 minutes. The mixture was then transferred to a precisely temperature-controlled metal bath and stirred at 120°C for 12 hours. The precipitate was collected by centrifugation, washed three times with ethanol, and dried at 80°C.
[0097] (3) High temperature coordination curing treatment
[0098] The Cu2-PCN precursor powder was placed in a tube furnace, heated to 500°C at 2°C / min under a N2 atmosphere, and kept warm for 5 hours to obtain a copper diatomic site co-catalyst (Cu loading of 1.8 wt% and cyanide mass fraction of 15 wt%).
[0099] 3. Preparation of FTO|PEDOT:PSS|TNAP:Cu2 photocathode:
[0100] (1) FTO substrate pretreatment
[0101] FTO glass (2 cm × 2 cm) was ultrasonically cleaned with deionized water, acetone, and isopropanol for 15 minutes each, dried with nitrogen, and then treated with UV ozone for 10 minutes.
[0102] (2) Spin coating of PEDOT:PSS hole transport layer
[0103] Dilute the PEDOT:PSS stock solution with deionized water at a mass ratio of 1:3, add 5% DMSO, filter through a 0.22 μm filter, and spin-coat the pretreated FTO substrate. Spin coating parameters: 3500 rpm for 30 seconds; annealing conditions: bake at 150°C in air for 15 minutes, to form a film approximately 40 nm thick.
[0104] (3) Preparation of TNAP:Cu2 composite layer
[0105] Preparation of TNAP solution: Dissolve 100 mg of TNAP powder in 10 mL of N,N-dimethylformamide (DMF) and stir magnetically for 2 h until completely dissolved;
[0106] Preparation of Cu2-PCN dispersion: 5 mg of Cu2-PCN powder was added to 50 mL of DMF and ultrasonicated for 1 h in an ice bath (power of 300 W);
[0107] The TNAP solution and the Cu2-PCN dispersion were mixed in a mass ratio of 9:1 and stirred for 12 h.
[0108] Spin coating parameters: 2200 rpm, 40 seconds; annealing conditions: baking at 120°C in nitrogen atmosphere for 30 minutes.
[0109] 4.CO2 photoreduction and formaldehyde polysaccharide reaction:
[0110] (1) Photocatalytic CO2 reduction test
[0111] The photoanode (Ti / BiVO4:Co) and the photocathode (FTO|PEDOT:PSS|TNAP:Cu2) were connected in series, placed in deionized water, and then CO2 was introduced to saturation.
[0112] Simulate sunlight in AM 1.5G (100mW / cm 2 ) irradiated by the photoanode, oxygen was rapidly generated, and the corresponding photocurrent density reached 2.08 mA cm -2 ; The photocathode reduces CO2, and the corresponding photocurrent density is -2.73mA cm -2 , the photocurrent density test results of the photoanode and photocathode are as follows Figure 3 As shown in a. After 6 hours of reaction, the liquid product was analyzed by HPLC, and the formaldehyde selectivity was 34.8%, the ethanolaldehyde selectivity was 5.0%, and the solar energy to chemical energy conversion efficiency was 0.62%. The relationship between the solar energy to chemical energy conversion efficiency and time is shown in the figure below. Figure 2 As shown in Figure c.
[0113] (2) Formaldehyde polysaccharide reaction
[0114] The liquid in the photocatalytic system was directly used for the formaldehyde polysaccharide reaction. To 3 mL of the reaction liquid, 60 mM Ca(OH)2 was added and the reaction was maintained at 60°C for 30 minutes. The reaction system quickly turned into a burnt yellow color unique to sugar products. The products were analyzed by electrospray mass spectrometry (ESI-MS). The final sugar product distribution was as follows Figure 3 As shown in Figure b, the total concentration of sugar products reached 60 mM, generating D-(+)-glucose, D-(-)-ribose, and L-threonic acid, with a glucose selectivity of 62.7%.
[0115] Example 2
[0116] The difference from Example 1 is that the mass fraction of cyanide groups in the copper diatomic site co-catalyst is 5 wt%.
[0117] Test results showed that the formaldehyde selectivity was 14.9%, the ethanolaldehyde selectivity was 2.3%, and the solar-to-chemical energy conversion efficiency was 0.41%.
[0118] Example 3
[0119] The difference from Example 1 is that the mass fraction of cyanide groups in the copper diatomic site co-catalyst is 10 wt %.
[0120] Test results showed that the formaldehyde selectivity was 33.1%, the ethanolaldehyde selectivity was 3.2%, and the solar-to-chemical energy conversion efficiency was 0.55%.
[0121] Example 4
[0122] The difference from Example 1 is that the mass fraction of cyanide groups in the copper diatomic site co-catalyst is 20 wt%.
[0123] Test results showed that the formaldehyde selectivity was 34.8%, the ethanolaldehyde selectivity was 5.0%, and the solar-to-chemical energy conversion efficiency was 0.62%.
[0124] Example 5
[0125] The difference from Example 1 is that the loading amount of copper diatomic sites in the copper diatomic site co-catalyst is 0.9 wt %.
[0126] Test results showed that the formaldehyde selectivity was 16.8%, the ethanolaldehyde selectivity was 2.5%, and the solar-to-chemical energy conversion efficiency was 0.26%.
[0127] Example 6
[0128] The difference from Example 1 is that the loading amount of copper diatomic sites in the copper diatomic site co-catalyst is 2.7 wt %.
[0129] Test results showed that the formaldehyde selectivity was 22.6%, the ethanolaldehyde selectivity was 2.1%, and the solar-to-chemical energy conversion efficiency was 0.40%.
[0130] Example 7
[0131] The difference from Example 1 is that the loading amount of copper diatomic sites in the copper diatomic site co-catalyst is 3.6 wt %.
[0132] Test results showed that the formaldehyde selectivity was 15.0%, the ethanolaldehyde selectivity was 1.7%, and the solar-to-chemical energy conversion efficiency was 0.21%.
[0133] Example 8
[0134] The difference from Example 1 is that the prepared TNAP solution and Cu2-PCN dispersion were spin-coated layer by layer in a mass ratio of 9:1, and other conditions were the same.
[0135] The test results show that the photocurrent density corresponding to the photoanode is reduced to 0.52 mA cm -2 .
[0136] Example 9
[0137] The difference from Example 1 is that TNAP in the photocathode is replaced with 4-(p-carboxyphenyl)pyrene.
[0138] The test results showed that the production of ethanolaldehyde per unit time was 11.8% lower than that of TNAP.
[0139] Example 10
[0140] The difference from Example 1 is that Co(NO3)2·6H2O was not added during the preparation of the photoanode Ti / BiVO4, and other conditions were the same.
[0141] The test results show that the photocurrent density corresponding to the photoanode is reduced to 1.18 mA cm -2 .
[0142] Example 11
[0143] The difference from Example 1 is that the TNAP in the photocathode is replaced with perylenetetracarboxylic acid (the conduction band reduction potential is -0.60 V vs. NHE).
[0144] The test results showed that only a small amount of glycolaldehyde product was detected.
[0145] Comparative Example 1
[0146] The difference from Example 1 is that the TNAP in the photocathode is replaced with 4-naphthylpyrene (without carboxyl modification).
[0147] The test results showed that no glycolaldehyde product was detected in the product.
[0148] Comparative Example 2
[0149] The difference from Example 1 is that there is no organic condensed-ring semiconductor photocatalyst in the catalyst layer of the photocathode.
[0150] The test results showed that the production of ethanolaldehyde per unit time was reduced by 88.1% compared with TNAP.
[0151] In summary, this application achieves the selective reduction of CO2 to formaldehyde and ethanolaldehyde through precise control of the conduction band potential of an organic fused-ring photocatalyst; combines the copper diatomic sites supported on nitrogen-doped carbon carriers to promote the generation and desorption of aldehyde intermediates; and constructs a photogenerated charge directional transport device to reduce recombination losses. Ultimately, C5+ carbohydrate compounds (such as glucose, with a selectivity of 62.7%) are efficiently synthesized through the formaldehyde polysaccharide reaction. This technical solution provides a new approach for artificial photosynthesis of carbohydrates from CO2, combining the advantages of high energy efficiency and the simplified two-step process of "photocatalysis-formaldehyde polysaccharide reaction", and can be applied to the fields of clean energy conversion and agricultural circular economy.
[0152] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.
Claims
1. An organic fused-ring semiconductor photocatalyst, characterized in that: include: Conjugated central unit and side chain groups with carboxyl groups.
2. The organic fused-ring semiconductor photocatalyst according to claim 1, characterized in that: The conjugated central unit comprises at least one of coronene, perylene, pyrene and heptazoline; and / or The side chain group with a carboxyl group includes at least one of p-carboxyphenyl, p-carboxynaphthyl, and p-carboxyphenylalkynyl.
3. The organic fused-ring semiconductor photocatalyst according to claim 1, characterized in that: The organic fused-ring semiconductor photocatalyst includes at least one of 4-(p-carboxyphenyl)coronene, 4-(p-carboxyphenyl)perylene, 4-(p-carboxyphenyl)pyrene, 4-(p-carboxynaphthyl)pyrene, 4-(p-carboxyphenylalkynyl)pyrene, and 3-(p-carboxyphenyl)heptazine.
4. The organic fused-ring semiconductor photocatalyst according to claim 1, characterized in that The conduction band reduction potential of the organic fused-ring semiconductor photocatalyst is less than or equal to -0.69 V vs. NHE.
5. A catalyst composition, characterized in that include: The organic fused-ring semiconductor photocatalyst and the copper diatomic site co-catalyst according to any one of claims 1 to 4.
6. The catalyst composition according to claim 5, characterized in that The loading amount of the copper diatomic site in the copper diatomic site co-catalyst is 0.2 wt% to 10.8 wt%, preferably 1 wt% to 8 wt%, more preferably 1.5 wt% to 5 wt%, and most preferably 1.8 wt% to 3 wt%.
7. The catalyst composition according to claim 5, characterized in that The mass fraction of cyano groups in the copper diatomic site promoter is 3 wt% to 20 wt%, preferably 5 wt% to 20 wt%, more preferably 10 wt% to 20 wt%, more preferably 13 wt% to 20 wt%, and most preferably 15 wt% to 20 wt%.
8. The catalyst composition according to claim 5, characterized in that The copper diatomic site co-catalyst is prepared by the following method: Mixing melamine and cyanoacetic acid and then performing a first calcination treatment to obtain a cyano-modified polymeric carbon nitride; Dispersing CuCl2 and the cyano-modified polymer carbon nitride in formamide and stirring to obtain a precursor; The precursor is subjected to a second calcination treatment to obtain the copper diatomic site promoter.
9. A method for preparing an aldehyde intermediate, characterized in that: include: The catalyst composition according to any one of claims 5 to 8 is used to reduce carbon dioxide to generate aldehyde intermediates in a photogenerated charge directional transport device.
10. A method for preparing a polysaccharide compound, characterized in that: include: Obtaining an aldehyde intermediate using the method according to claim 9; The aldehyde intermediate is subjected to a formaldehyde polysaccharide reaction to obtain the polysaccharide compound.
11. The method according to claim 9, characterized in that The photogenerated charge directional transport device includes a photoanode and a photocathode connected in series.
12. The method according to claim 11, characterized in that The method for preparing the photocathode comprises: sequentially cleaning and ultraviolet ozone treating the fluorine-doped tin oxide to obtain the fluorine-doped tin oxide layer; A poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate hole transport layer, a composite layer of an organic condensed-ring semiconductor photocatalyst and a copper diatomic site cocatalyst, or an organic condensed-ring semiconductor photocatalyst layer and a copper diatomic site cocatalyst layer are sequentially spin-coated on the surface of the fluorine-doped tin oxide layer to obtain the photocathode.
13. The method according to claim 11, characterized in that The method for preparing the photoanode comprises: The titanium sheet is polished, cleaned and acid-etched in sequence to obtain a titanium sheet layer; The titanium sheet is placed in a container filled with a cobalt-doped bismuth vanadate precursor solution and subjected to a hydrothermal reaction and a third calcination treatment in sequence to obtain the photoanode.
14. The method according to claim 13, characterized in that The cobalt doping amount in the cobalt-doped bismuth vanadate precursor solution is 2 at %; and / or The temperature of the hydrothermal reaction is 180° C., and the time of the hydrothermal reaction is 6 h to 12 h; and / or The temperature of the third calcination treatment is 450° C., and the time of the third calcination treatment is 2 hours.
15. A photogenerated charge directional transport device, characterized in that: The catalyst composition comprises the catalyst composition according to any one of claims 5 to 8.
16. The photogenerated charge directional transport device according to claim 15, characterized in that: It includes a photoanode and a photocathode connected in series, wherein The photoanode comprises a titanium sheet layer and a cobalt-doped bismuth vanadate layer stacked in sequence; The photocathode comprises a fluorine-doped tin oxide layer, a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate hole transport layer, and a catalytic layer which are stacked in sequence.
17. The photogenerated charge directional transport device according to claim 16, characterized in that: The catalytic layer comprises a composite layer of an organic condensed-ring semiconductor photocatalyst and a copper diatomic site cocatalyst, or the catalytic layer comprises an organic condensed-ring semiconductor photocatalyst layer and a copper diatomic site cocatalyst layer.