A high-activity, high-selectivity, low-price, non-toxic photo-thermal catalytic carbon dioxide reduction catalyst
By loading cobalt tetroxide onto the surface of hydroxyapatite to form a Co-HAP catalyst, the problem of low selectivity of Co-based photothermal catalytic materials was solved, achieving high-activity and low-toxicity photothermal catalytic reduction of carbon dioxide, thus promoting the commercial application of carbon dioxide reduction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANYANG NORMAL UNIV
- Filing Date
- 2022-03-23
- Publication Date
- 2026-06-26
AI Technical Summary
Existing Co-based photothermal catalytic materials fail to effectively combine photochemistry and photothermal catalysis in the catalytic reduction of carbon dioxide, resulting in CH4 as the main product with low selectivity, which is difficult to meet the needs of practical industrial applications.
A solid hindered Lewis acid-base pair catalyst, Co-HAP, formed by supporting cobalt tetroxide on the surface of hydroxyapatite, was prepared by a deposition-precipitation method. The valence state of cobalt was controlled by adjusting the reaction conditions and calcination temperature, thereby improving the catalytic activity and selectivity.
It achieves highly active, highly selective, and low-toxicity photothermal catalytic reduction of carbon dioxide. The catalyst has good stability and is suitable for large-scale carbon dioxide reduction, which promotes the commercial application of photothermal catalytic reduction of carbon dioxide.
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Figure CN114984982B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, specifically to a highly active, highly selective, low-cost, and non-toxic photothermal catalytic reduction catalyst for carbon dioxide. Background Technology
[0002] Hindered Lewis acid-base pair (FLP) catalysts possess a strong ability to catalyze and activate molecules, enabling highly efficient catalysis without precious metals. This makes the catalytic process more environmentally friendly. FLP catalysts are low-cost, low-toxicity, and highly stable, better meeting the needs of future industrial applications of photothermal catalytic reduction of carbon dioxide. Currently, the catalytic mechanism of Co-based photothermal catalytic materials often involves converting light energy into heat energy on the surface of the catalytic material, and then using the heat energy to drive the catalytic reaction in situ. This fails to effectively combine photochemical catalysis and photothermal catalysis, thus their performance is still insufficient to meet the requirements of practical applications. Furthermore, the cobalt oxides synthesized by existing deposition-precipitation methods often exhibit mixed valence states of +2 and +3 Co. Consequently, CH4 is the main product in the photothermal catalytic reduction of carbon dioxide using Co materials, and the selectivity is not high, reducing the efficiency of photothermal gas-phase catalytic carbon dioxide reduction and thus limiting its practical application. Therefore, how to effectively combine photochemical catalysis and photothermal catalysis to improve product selectivity is a key scientific problem that needs to be solved in the field of photothermal catalytic reduction of carbon dioxide using cobalt-based FLP catalysts. It is also a bottleneck that needs to be overcome for the commercial application of photothermal gas-phase catalytic carbon dioxide hydrogenation. To this end, a highly active, highly selective, low-cost, and non-toxic photothermal catalytic reduction of carbon dioxide catalyst is proposed. Summary of the Invention
[0003] The purpose of this invention is to provide a highly active, highly selective, low-cost, and non-toxic photothermal catalytic reduction catalyst for carbon dioxide, in order to solve the problems mentioned in the background art.
[0004] To achieve the above objectives, the present invention provides a highly active, highly selective, low-cost, and non-toxic photothermal catalytic reduction catalyst for carbon dioxide, which is composed of cobalt tetroxide (chemical formula Co3O4) and hydroxyapatite (English abbreviation HAP). The cobalt tetroxide is supported on the surface of the hydroxyapatite to form a solid hindered Lewis acid-base pair catalyst cobalt-hydroxyapatite (English abbreviation Co-HAP).
[0005] Based on the above-mentioned highly active, highly selective, low-cost, and non-toxic photothermal catalytic reduction catalyst for carbon dioxide, the present invention proposes a preparation method, the specific steps of which are as follows:
[0006] Step 1: Calcium nitrate tetrahydrate and diammonium hydrogen phosphate are used as precursors for the preparation of hydroxyapatite, and cobalt nitrate hexahydrate is used as a precursor for cobalt.
[0007] Step 2: Dissolve calcium nitrate tetrahydrate and cobalt nitrate hexahydrate in distilled water, and adjust the mixed solution to alkalinity with ammonia water to form solution A;
[0008] Step 3: Dissolve diammonium hydrogen phosphate in distilled water, and adjust the mixed solution to alkaline with ammonia water to form solution B;
[0009] Step 4: Under stirring conditions, solution B is added dropwise to solution A, and the reaction is carried out under alkaline conditions to obtain reaction solution C. After aging reaction solution C, it is filtered, washed and dried in sequence to obtain semi-finished product D. Finally, semi-finished product D is calcined in air to obtain the finished solid hindered Lewis acid-base pair catalyst cobalt-hydroxyapatite.
[0010] In this preferred embodiment, the mass ratio of calcium nitrate tetrahydrate, cobalt nitrate hexahydrate, and distilled water in step two is 10-30:1-5:2000.
[0011] In this preferred embodiment, the mass ratio of diammonium hydrogen phosphate to distilled water in step three is 5-20:2000.
[0012] In this preferred embodiment, the pH values of solution A, solution B, and reaction solution C in steps two, three, and four are all controlled to be 10-12.
[0013] In this preferred embodiment, the reaction temperature of the reaction solution C in step four is controlled at 70-100℃, and the reaction time is 1-6 hours.
[0014] In this preferred embodiment, the aging time in step four is 6-18 hours, the temperature is controlled at 400-600℃ during air calcination, and the calcination time is 4-10 hours.
[0015] Compared with the prior art, the beneficial effects of the present invention are:
[0016] This highly active, highly selective, low-cost, and non-toxic photothermal catalytic reduction catalyst for carbon dioxide reduces carbon dioxide by using Ca... 2+ / Co 2+ Co-HAP samples with different cobalt contents were prepared by mixing with a phosphate precursor solution, stirring, aging, and separating the synthesized product by filtration. With increasing cobalt content, the color of the samples changed from pink to increasingly deeper purple after calcination at high temperatures. Using surface engineering strategies, calcination was performed at different temperatures under a hydrogen atmosphere. As the calcination temperature increased, the valence state of cobalt transitioned from a mixture of +2 and +3 valences to a single +2, +3, and metallic valence, thus allowing for the investigation of the role of different valence states of Co in improving the selectivity of the photothermal catalytic reduction of carbon dioxide.
[0017] The low cost, low toxicity, stability, and scalability of the photothermal catalytic reduction catalyst Co-HAP make it a very promising candidate for large-scale carbon dioxide reduction. The synthesized material can be commercially sold as an industrial RWGS photocatalytic product. The discovery of this viable catalyst material is a key step forward in carbon dioxide catalysis, and its further development will have a significant impact, particularly on climate change and renewable energy technologies. By continuing to advance this practical catalytic approach, it is possible to complete the important energy transition from fossil fuels to renewable energy without sacrificing economic growth. Attached Figure Description
[0018] Figure 1 This is a flowchart of the preparation method of the present invention;
[0019] Figure 2 The in-situ XPS spectra of Co 2p of 10% Co-HAP (a) and Co3O4 (b) proposed in this invention are obtained at 2 sccm CO2-2 sccm H2, 25℃ and 300℃ for 30 minutes.
[0020] Figure 3 The image shows the photothermal catalytic performance of the 10% Co-HAP and Co3O4 samples proposed in this invention.
[0021] Figure 4 The DRIFTS diagrams of 10% Co-HAP proposed in this invention are shown in atmospheres of 20 sccm H2 (a), 20 sccm CO2 (b), and 2 sccm H2-2 sccm CO2-16 sccm He (c). Detailed Implementation
[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0023] It should be noted that in the description of this invention, the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0024] Furthermore, it should be understood that, for ease of description, the dimensions of the various components shown in the accompanying drawings are not drawn to actual scale; for example, the thickness or width of some layers may be exaggerated relative to other layers.
[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined or described in one figure, it will not need to be discussed or described in detail in the description of the subsequent figures.
[0026] In recent years, the combustion of fossil fuels and vehicle emissions have led to a continuous rise in global carbon emissions, severely impacting the natural carbon cycle and exacerbating global warming. Against this backdrop and given the challenging international situation regarding materials and energy technologies, research on solar-thermal gas-phase catalytic carbon dioxide hydrogenation has attracted significant attention. Compared to traditional liquid-phase photochemical catalysis for carbon dioxide conversion, photothermal catalysis offers advantages such as a wider range of catalytic material selection, higher light energy utilization, and superior catalytic performance. It effectively combines photochemical and photothermal catalysis to efficiently convert carbon dioxide into fuel, reducing carbon dioxide emissions while also providing clean and renewable energy—a promising method for achieving carbon neutrality.
[0027] This invention synthesized FLP catalysts Co-HAP with different Co contents using a deposition-precipitation method and tested their photothermal catalytic reduction performance of carbon dioxide. The chemical formula of calcium hydroxyphosphate is Ca2+. 10 (PO4)6(OH)2, commonly known as hydroxyapatite (HAP), is found both in the mineral apatite and in animal bones and teeth. HAP can be easily prepared through the precipitation of calcium and phosphate precursors, making it readily synthesized in large quantities. Furthermore, it contains abundant, non-toxic elements, which has driven its development in biomedicine, healthcare, cosmetics, agriculture, and even catalysis. Therefore, modified HAP would be an ideal component for large-scale RWGS reactors. Previous studies have shown that loading metal oxides onto the surface of HAP can significantly improve the activity of heterogeneous catalysts; therefore, this method has also been chosen for HAP modification.
[0028] like Figure 1 As shown, based on HAP, the present invention provides a technical solution: a highly active, highly selective, low-cost, and non-toxic photothermal catalytic reduction catalyst for carbon dioxide, which is composed of cobalt tetroxide and hydroxyapatite, wherein the cobalt tetroxide is supported on the surface of the hydroxyapatite to form a solid hindered Lewis acid-base pair catalyst cobalt-hydroxyapatite (Co-HAP).
[0029] This technical solution proposes a method for preparing a highly active, highly selective, low-cost, and non-toxic photothermal catalytic reduction catalyst for carbon dioxide. The preparation steps are as follows:
[0030] Step 1: Calcium nitrate tetrahydrate and diammonium hydrogen phosphate are used as precursors for the preparation of hydroxyapatite, and cobalt nitrate hexahydrate is used as a precursor for cobalt.
[0031] Step 2: Dissolve 0.2125g of calcium nitrate tetrahydrate and 0.029g of cobalt nitrate hexahydrate in 20g of distilled water, and adjust the pH of the mixed solution to 11 with ammonia water to form solution A;
[0032] Step 3: Dissolve 0.08g of diammonium hydrogen phosphate in 20g of distilled water, and adjust the pH of the mixed solution to 11 with ammonia water to form solution B;
[0033] Step 4: Under stirring conditions, solution B is added dropwise to solution A, and the reaction is carried out at a pH of 11, a reaction temperature of 85℃, and a reaction time of 2 hours to obtain reaction solution C. After aging reaction solution C for 12 hours, it is then filtered, washed, and dried to obtain semi-finished product D. Finally, semi-finished product D is calcined in air at a temperature of 500℃ for 5 hours to obtain the finished solid hindered Lewis acid-base pair catalyst cobalt-hydroxyapatite.
[0034] The cobalt-hydroxyapatite obtained in this example is compared with cobalt tetroxide:
[0035] like Figure 2 As shown, in-situ X-ray photoelectron spectroscopy (XPS) measurements were performed under simulated reaction conditions of 2 sccm CO2-2 sccm H2 atmosphere, 25 °C, and 300 °C for 30 minutes. High-resolution Co2p XPS spectra revealed the Co content of Co-HAP. 2+ and Co 3+ The characteristic peaks were 779.6 and 780.9 eV, respectively, and showed almost no change under the conditions of 2 sccm CO2-2 sccm H2 atmosphere, 25 °C, and 300 °C. In-situ XPS measurements of Co3O4 indicated that, under the reaction conditions, Co... 3+ Restored to Co 2+ (779.6eV) and Co 0 (778.9 eV). H2-programmed temperature reduction (H2-TPR) further confirmed the presence of Co. 3+ Reduction on Co3O4 was observed, while Co-HAP showed no activity at these temperatures. Based on these results, HAP showed reactivity against Co. 3+ To Co 2+ and Co 0 The effective inhibition of sustained reduction occurred in Co-HAP, resulting in a significantly increased CO selectivity, and the synthesis of Co from CH4 on Co3O4 was determined. 0 Active site.
[0036] like Figure 3 The figures show the photothermal catalytic activity of (a) Co-HAP and (b) Co3O4 in a flow reactor, and the selectivity of CO and CH4 products generated by (c) Co-HAP and (d) Co3O4 under dark and light conditions. Activity test reaction conditions: atmospheric pressure, light intensity approximately 2.0 W / cm². -2 With an H2 / CO2 flow rate ratio of 1:1 and a total flow rate of 4 sccm, catalytic results showed that Co-HAP exhibited higher CO yields than CH4 yields under conditions of 240-300℃, regardless of sunlight exposure. Specifically, under sunlight at 300℃, Co-HAP achieved CO and CH4 yields of 33,942 and 1,452 μmolg, respectively. Co -1 h -1 As can be seen, the CO production rate increases significantly with increasing temperature. However, the production rates of CH4 and CO from the photothermal gas-phase catalytic reduction of carbon dioxide by Co3O4 only increase slightly. Under 300℃ illumination, the CH4 production rate drops sharply to 1,014 μmol / g. Co -1 h -1 Furthermore, based on the CH4 and CO selectivity results ( Figure 2 (c and 2d) Compared with Co3O4, Co-HAP has a significantly improved CO selectivity, approaching 100% at 240-300℃, while Co3O4 has CH4 as the main product, with CO and CH4 selectivities of approximately 70% and 30% respectively under 300℃ light irradiation conditions.
[0037] Furthermore, according to the corresponding Arrhenius plots, the photothermal activation energies for CH4 and CO production are lower than the thermochemical activation energies for both Co-HAP and Co3O4. The Arrhenius plot for CO products from Co-HAP shows a two-stage linearity. These results suggest that the enhanced CO selectivity, due to the presence of HAP in Co-HAP, may be related to different active sites.
[0038] To investigate the catalytic reaction mechanism of Co-HAP, DRIFTS tests were performed on Co-HAP under atmospheres of 20 sccm H2, 20 sccm CO2, and 2 sccm H2-2 sccm CO2-16 sccm He. Figure 4 As shown, the results indicate that the photochemical pathway proceeds via a formic acid reaction intermediate, which is formed by the reaction of carbon dioxide and Co. 3+ ...(PO4) 3- (CoH) generated by the uncontrolled Lewis acid-base pair dissociation of H2 2+ ...(PO3OH) 2-The reaction yielded [the product]. In contrast, the thermochemical route proceeds via a bicarbonate reaction intermediate, which is formed by the reaction of carbon dioxide with H2 in Co [a solution]. 2+ ...(PO4) 3- Cu formed by the unhindered dissociation of Lewis acid-base pairs 0 ...(PO3OH) 2- The reaction produces... Subsequently, formate and bicarbonate react with (PO3OH)... 2- The proton reaction forms CO and H2O, thus completing the reverse water gas shift catalytic cycle.
[0039] Experimental results show that after 20 hours of testing under the reaction conditions, the photothermal catalytic activity and CO product selectivity of Co-HAP did not decrease significantly, indicating that Co-HAP has high reaction stability.
[0040] The experimental results above demonstrate that the embodiments of the present invention have prepared a Co-HAP FLP photothermal catalytic material with high activity, high stability, and high CO product selectivity, and have achieved the combination of photochemical catalysis and photothermal catalysis. At the same time, the reaction mechanism of its photothermal catalytic reduction of carbon dioxide is elucidated, the key factors affecting product selectivity and the enhancement mechanism are clarified, and an efficient photothermal synergistic catalytic gas phase carbon dioxide hydrogenation system is constructed, which can promote the commercial application of FLP catalyst photothermal catalytic gas phase carbon dioxide hydrogenation.
[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. The application of a highly active, highly selective, low-cost, and non-toxic photothermal catalytic reduction catalyst for carbon dioxide in the photothermal catalytic reduction of carbon dioxide, characterized in that: The catalyst is composed of cobalt tetroxide and hydroxyapatite, with the cobalt tetroxide supported on the surface of the hydroxyapatite to form a solid hindered Lewis acid-base pair catalyst, cobalt-hydroxyapatite. The catalyst is prepared via the following steps: Step 1: Calcium nitrate tetrahydrate and diammonium hydrogen phosphate are used as precursors for the preparation of hydroxyapatite, and cobalt nitrate hexahydrate is used as a precursor for cobalt. Step 2: Dissolve calcium nitrate tetrahydrate and cobalt nitrate hexahydrate in distilled water, and adjust the mixed solution to alkalinity with ammonia water to form solution A; Step 3: Dissolve diammonium hydrogen phosphate in distilled water, and adjust the mixed solution to alkaline with ammonia water to form solution B; Step 4: Under stirring conditions, solution B is added dropwise to solution A, and the reaction is carried out under alkaline conditions to obtain reaction solution C. After aging reaction solution C, it is filtered, washed and dried in sequence to obtain semi-finished product D. Finally, semi-finished product D is calcined in air to obtain the finished solid hindered Lewis acid-base pair catalyst cobalt-hydroxyapatite. In step two, the mass ratio of calcium nitrate tetrahydrate, cobalt nitrate hexahydrate, and distilled water is 10-30:1-5:2000, respectively. In step three, the mass ratio of diammonium hydrogen phosphate to distilled water is 5-20: 2000.
2. The application according to claim 1, characterized in that: The pH values of solutions A, B, and reaction solution C in steps two, three, and four are all controlled to be 10-12.
3. The application according to claim 1, characterized in that: In step four, the reaction temperature of reaction solution C is controlled at 70-100 °C, and the reaction time is 1-6 hours.
4. The application according to claim 1, characterized in that: In step four, the aging time is 6-18 hours, and the temperature is controlled at 400-600 °C during air calcination, with a calcination time of 4-10 hours.