Co-Co3B interface double-active-site modified wood charcoal catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of ammonia borane hydrolysis hydrogen desorption, and discloses a Co-Co3B interface double-active-site modified wood charcoal catalyst as well as a preparation method and application thereof. The catalyst is of a core-shell structure and takes BNC as a shell and a Co-Co3B heterostructure as a core; the catalyst has double active sites: Co nanoparticles and Co3B nanoparticles, and an interface structure exists between Co and Co3B; wherein the BNC is boron nitride modified wood charcoal and has a porous structure. The Co-Co3B interface double-active-site modified wood charcoal catalyst is creatively designed, the existence of a BNC shell not only avoids catalyst deactivation but also limits agglomeration of metal particles, the introduction of Co3B increases active sites, meanwhile, an interface structure also exists between Co and Co3B, the electronic structure and coordination environment of the catalyst are optimized, and the catalytic activity of the catalyst is improved. Compared with the prior art, the catalyst provided by the invention has the advantages that the dissociation energy barrier of reactant molecules is reduced, the catalytic activity is improved, the catalyst has excellent catalytic performance in an NH3BH3 hydrolysis reaction performance test, and the hydrogen production rate of the catalyst reaches 10492 mL. Min <-1 >. GCo <-1 >.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen desorption technology of ammonia boronane water, specifically relating to a lignocarbon catalyst modified with dual active sites at the Co-Co3B interface, its preparation method, and its application. Background Technology

[0002] With the development of human society, fossil fuels are gradually being depleted, and the ecological environment is deteriorating. Developing and utilizing clean, renewable, and potentially viable energy sources is of paramount importance. Hydrogen energy, as the only energy carrier capable of achieving "zero carbon emissions" throughout its entire life cycle, possesses advantages such as high calorific value, high energy density, and no pollution after combustion, making it considered an ideal substitute for fossil fuels. However, finding new catalytic processes and materials for the safe storage and transportation of hydrogen energy remains a significant challenge. Among hydrogen storage materials, ammonia borane (NH3BH3) stands out due to its high hydrogen content (19.6 wt%) and low molecular weight (30.9 g·mol⁻¹). -1 With its significant advantages such as non-toxicity, ease of production, and long-term stability, it exhibits enormous potential for hydrogen production. Therefore, developing a novel catalyst for the hydrolysis of ammonia borane is highly promising.

[0003] The hydrolysis of NH3BH3 at room temperature is kineticly slow. Although noble metal-based catalysts exhibit good catalytic activity for the hydrolysis of NH3BH3, their high cost and scarcity limit their widespread industrial application. Therefore, there is an urgent need to prepare non-noble metal catalysts with high catalytic performance to catalyze the hydrolysis of borohydrides. Currently, efficient and low-cost transition metal (TMs) catalysts (Fe, Co, Ni, Cu) have been used to improve the hydrolysis activity of NH3BH3. Among them, cobalt is considered a promising transition metal catalyst due to its low price, abundant reserves, and tunable composition and structure. Recently, CoP... x Nanoparticles (NPs), CoN x NPs and Co-CoO x NPs have been proven to be highly efficient catalysts for hydrogen production by hydrolysis of NH3BH3. However, severe metal agglomeration and poor mass transfer efficiency of these catalysts hinder the improvement and stability of NH3BH3 hydrolysis performance.

[0004] Biomass-derived char has attracted widespread attention and research due to its advantages such as low cost, renewability, and cleanliness. However, standalone biomass char lacks catalytically active sites and exhibits weak interactions with catalytically active materials. Introducing heteroatom doping (N, P, B, etc.) can achieve uniform metal-support interactions on the carbon framework, thereby enhancing catalyst activity. Hexagonal boron nitride (h-BN), with its two-dimensional structure, consists of boron and nitrogen atoms arranged in sp... 2The structure is a hybrid composition with unique electronic and band structures. Introducing h-BN onto the carbon framework can effectively modulate the different electronegativity of C, B, and N to induce surface charge redistribution. The π-π interactions between h-BN and the carbon framework facilitate the formation of a uniform electronic structure. The support formed by the composite of h-BN and the carbon framework exhibits good mass transfer performance and can promote the uniform distribution of metal nanoparticles.

[0005] Furthermore, the hydrolysis of NH3BH3 requires the separate activation of H2O and NH3BH3 molecules. The rational construction of interfacial active sites can optimize the reaction energy barrier, thereby improving catalytic activity. When two nanostructures come into contact, electron redistribution occurs at the heterojunction, thereby regulating the Fermi level of adjacent components and promoting electron transfer. Interfacial active sites can alter the electron cloud density of the active material, enhancing the adsorption and dissociation of reaction components and significantly improving the hydrogen production performance of NH3BH3 hydrolysis. However, the rational design of non-noble metal catalysts with interfacial active sites to promote the hydrolysis of NH3BH3 remains a significant challenge. Zhang et al. found that metal borides modify the electronic structure of the metal center, effectively reducing the kinetic energy barrier. In addition, metal borides possess advantages such as high active site concentration and good cycle stability. Therefore, designing novel composite catalysts with metal boride-based interfacial active sites will play a crucial role in further improving the catalytic activity of the NH3BH3 hydrolysis reaction. Summary of the Invention

[0006] To address the following problems in existing technologies: ① Noble metal-based catalysts are expensive and scarce; ② Metal particle catalysts are prone to agglomeration, reducing catalyst efficiency; ③ Metal catalysts have poor stability in the hydrolysis of ammonia borane to produce hydrogen. The purpose of this invention is to provide a lignocarbon catalyst modified with dual active sites at the Co-Co3B interface, its preparation method, and its application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A lignocarbon catalyst modified with dual active sites at the Co-Co3B interface is disclosed. The catalyst has a core-shell structure with BNC as the shell and a Co-Co3B heterostructure as the core. The catalyst has dual active sites: Co nanoparticles and Co3B nanoparticles, and there is an interfacial structure between Co and Co3B. The BNC is boron nitride-modified lignocarbon with a porous structure.

[0008] A method for preparing a lignocarbon catalyst modified with dual active sites at the Co-Co3B interface, wherein the mass parts are in mg, the volume parts are in mL, and the molar parts are in mmol, the preparation steps are as follows: (1) After high-temperature purification treatment (removing surface dust and impurities), h-BN is peeled off to obtain h-BN nanosheets; (2) Disperse 20-100 parts by weight of the h-BN nanosheets obtained in step (1) evenly into 20-100 parts by volume of ethanol, add 980 parts by weight of wood charcoal powder, stir evenly, and then perform hydrothermal reaction at 160-180℃ for 6-7 h, and dry to obtain BNC; (3) Dissolve 3-9 moles of water-soluble cobalt salt in 8-24 volume parts of ethanol, then add all the BNC obtained in step (2) into the solution, stir evenly, dry, and obtain BNC with cobalt salt deposited. (4) Dissolve 4 times the molar amount of water-soluble cobalt salt dimethylimidazole in 8-24 volume parts of ethanol, then add all the BNC with cobalt salt deposited in step (3) into the solution and let it stand for impregnation. Then remove the supernatant, dry it, pyrolyze it at 700-750℃ for 2-2.5h in an inert atmosphere, passivate it with ethanol, and obtain the target catalyst. In steps (3) and (4), the molar amount of water-soluble cobalt salt is calculated based on the cobalt element therein.

[0009] Preferably, in step (1), the high-temperature impurity removal treatment is performed at a temperature of 800~900℃ for 1~2h.

[0010] Preferably, in step (2), the wood charcoal powder is cedar charcoal powder.

[0011] Preferably, in step (2), the fir charcoal powder is obtained by pyrolyzing fir blocks at 850~900℃ for 2~2.5 h.

[0012] Preferably, in step (3), the water-soluble cobalt salt is cobalt nitrate or cobalt chloride.

[0013] Preferably, in steps (2) to (4), the ethanol involved is anhydrous ethanol.

[0014] Application of a lignocarbon catalyst modified with dual active sites at the Co-Co3B interface in the hydrolysis of ammonia borane to produce hydrogen.

[0015] In this invention, the method for stripping h-BN is a known technique. This invention is preferred but not limited to the reference: H. Zhang et al. Atomic-bridge structure in B-Co-P dual-active sites on boronnitridenanosheets for catalytic hydrogen generation. Applied Catalysis B:Environmental 314 (2022)121495.

[0016] This invention is not only applicable to wood charcoal, but can also be extended to biochar.

[0017] Beneficial effects: (1) This invention creatively designs a lignocarbon catalyst modified with dual active sites at the Co-Co3B interface. The presence of the BNC shell not only avoids catalyst deactivation but also restricts the aggregation of metal particles. The introduction of Co3B increases the number of active sites. At the same time, there is also an interface structure between Co and Co3B, which optimizes the electronic structure and coordination environment of the catalyst, lowers the dissociation energy barrier of reactant molecules (NH3BH3 and H2O), and improves the catalytic activity. In the NH3BH3 hydrolysis reaction performance test, this catalyst has excellent catalytic performance, and its hydrogen production rate reaches 10492 mL·min. -1 ·g Co -1 ; (2) The catalyst of this invention achieves the synergistic effect of carbon-based support and catalytic active components, and has both high catalytic activity and excellent stability, providing a theoretical basis for the high-value conversion of wood charcoal waste resources and the design of new non-precious metal catalysts; (3) The present invention reduces the cost of catalyst and improves catalytic performance by modifying wood-based charcoal materials with h-BN and Co. Attached Figure Description

[0018] Figure 1 X-ray diffraction patterns of catalysts Co-Co3B@BNC-4, Co-Co3B@BNC-5, Co-Co3B@BNC-6, Co@C-1, Co@C-2, and Co@C-3 prepared in Examples 1-3 and Comparative Examples 1-3.

[0019] Figure 2 Co 2p XPS spectrum of the catalyst Co-Co3B@BNC-5 prepared in Example 2.

[0020] Figure 3 B 1s XPS spectrum of the catalyst Co-Co3B@BNC-5 prepared in Example 2.

[0021] Figure 4 TEM (left) and HRTEM characterization (right) of the catalyst Co-Co3B@BNC-5 prepared in Example 2.

[0022] Figure 5 BET diagrams (a) and pore size distribution diagrams (b) of the catalysts Co-Co3B@BNC-4, Co-Co3B@BNC-5, Co-Co3B@BNC-6, Co@C-1, Co@C-2, and Co@C-3 prepared in Examples 1-3 and Comparative Examples 1-3.

[0023] Figure 6 Hydrogen production curves of ammonia borane hydrolysis for catalysts Co-Co3B@BNC-4, Co-Co3B@BNC-5, Co-Co3B@BNC-6, Co@C-1, Co@C-2, and Co@C-3 prepared in Examples 1-3 and Comparative Examples 1-3.

[0024] Figure 7 Example 2: Hydrogen production curves of 6 cycles of ammonia borane hydrolysis of the catalyst Co-Co3B@BNC-5 prepared. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0026] Example 1

[0027] A method for preparing a lignochar catalyst modified with dual active sites at the Co-Co3B interface, comprising the following steps: (1) Weigh 1.500g of purchased h-BN (hexagonal boron nitride) and place it in a quartz boat. In a muffle furnace, rapidly heat the material to 850℃ in 60min and maintain the temperature for 2h. After the sample cools to room temperature, disperse the obtained h-BN material in deionized water and alternately stir and sonicate for 30min each for a total of 5h. Centrifuge the solution slowly at 1500rpm for 15min, centrifuge the supernatant at 10000rpm for 10min, and finally dry it under vacuum overnight at 60℃ to obtain the exfoliated h-BN nanosheets. (2) Take a 1.5*1.5*0.5cm (length*width*height) cedar block and heat it in a tube furnace at 5℃·min -1 The heating rate was increased to 900℃, pyrolyzed for 2 hours, and then ground to obtain cedar charcoal powder; (3) Add 20 mg of exfoliated h-BN nanosheet powder to 20 mL of anhydrous ethanol, stir and sonicate alternately for 30 min each, for a total of 2 h, to form a uniformly dispersed solution. Add 980 mg of cedar charcoal powder, stir for 12 h, pour into a 50 mL reaction vessel, hydrothermally react at 180 °C for 6 h, and vacuum dry at 35 °C to obtain BNC. (4) Dissolve 6 mmol of Co(NO3)2·6H2O in 15 mL of anhydrous ethanol, then add all the BNC obtained in step (3) into the solution, stir for 6 h, and dry under vacuum at 35 °C to obtain BNC with cobalt salt deposited. (5) Dissolve 24 mmol of dimethylimidazole in 15 mL of anhydrous ethanol to form a solution, and then add all the BNC with cobalt salt deposited in step (4) into the solution. After standing and soaking for 24 h, remove the supernatant and dry under vacuum at 35 °C. (6) Grind the dried material obtained in step (5) into powder and place it in a porcelain boat. Then, in a tube furnace, heat the powder at 5°C·min under a N2 atmosphere. -1 The temperature was increased to 700℃ and pyrolyzed for 2 hours. After pyrolysis, the sample was naturally cooled to room temperature. When disassembling the tube furnace, the ceramic boat was quickly pulled out and anhydrous ethanol was quickly added to cover the entire sample for passivation. After the anhydrous ethanol evaporated until the sample in the ceramic boat no longer flowed, the sample was dried under vacuum at 35℃ to obtain the target catalyst, which was labeled as Co-Co3B@BNC-4.

[0028] Example 2

[0029] The difference from Example 1 is that in step (3), the amount of the exfoliated h-BN nanosheet powder is changed to 60 mg; all other conditions are the same as in Example 1.

[0030] The catalyst prepared in this embodiment is labeled as Co-Co3B@BNC-5.

[0031] Example 3

[0032] The difference from Example 1 is that in step (3), the amount of the exfoliated h-BN nanosheet powder is changed to 100 mg; all other conditions are the same as in Example 1.

[0033] The catalyst prepared in this embodiment is labeled as Co-Co3B@BNC-6.

[0034] Comparative Example 1 The difference from Example 1 is that h-BN was not used to modify the cedar charcoal powder. The specific preparation steps are as follows: (1) Take a 1.5*1.5*0.5cm (length*width*height) cedar block and heat it in a tube furnace at 5℃·min -1 The heating rate was increased to 900℃, pyrolyzed for 2 hours, and then ground to obtain cedar charcoal powder; (2) Dissolve 3 mmol of Co(NO3)2·6H2O in 15 mL of anhydrous ethanol, add 980 mg of cedar charcoal powder to the solution, stir for 6 h, let stand overnight to settle, remove the supernatant, and dry under vacuum at 35 °C to obtain the Co / C precursor. (3) Dissolve 4n (n is the molar amount of Co(NO3)2·6H2O) dimethylimidazole in 15mL of anhydrous ethanol to form a solution, then add all of the Co / C precursor obtained in step (2) into the solution, let it stand for 24h to soak, remove the supernatant, and dry it under vacuum at 35℃. (4) Grind the dried material obtained in step (4) into powder and place it in a porcelain boat. Then, in a tube furnace, heat the powder at 5°C·min under a N2 atmosphere. -1 The temperature was increased to 700℃ and pyrolyzed for 2 hours. After pyrolysis, the sample was naturally cooled to room temperature. When disassembling the tube furnace, the ceramic boat was quickly pulled out and anhydrous ethanol was quickly added to cover the entire sample for passivation. After the anhydrous ethanol evaporated and the sample in the ceramic boat stopped flowing, it was vacuum dried at 35℃ to obtain the control catalyst sample, labeled as Co@C-1.

[0035] Comparative Example 2 The difference from Comparative Example 1 is that in step (2), the amount of Co(NO3)2·6H2O was changed to 6 mmol, and the amount of dimethylimidazole in step (3) was adjusted accordingly; all other conditions were the same as those in Comparative Example 1.

[0036] The control catalyst sample obtained in this comparative example was labeled as Co@C-2.

[0037] Comparative Example 3 The difference from Comparative Example 1 is that in step (2), the amount of Co(NO3)2·6H2O was changed to 9 mmol, and the amount of dimethylimidazole in step (3) was adjusted accordingly; all other conditions were the same as those in Comparative Example 1.

[0038] The control catalyst sample obtained in this comparative example was labeled as Co@C-3.

[0039] Product structure characterization Figure 1 X-ray diffraction patterns of catalysts Co-Co3B@BNC-4, Co-Co3B@BNC-5, Co-Co3B@BNC-6, Co@C-1, Co@C-2, and Co@C-3 prepared in Examples 1-3 and Comparative Examples 1-3. Figure 1 As can be seen, catalysts Co-Co3B@BNC-4, Co-Co3B@BNC-5, and Co-Co3B@BNC-6 all correspond to the PDF standard card (PDF Card No. 15-0806) for Co and the PDF standard card (PDF Card No. 12-0443) for Co3B.

[0040] Figure 2 and Figure 3XPS spectra of Co 2p and B 1s for the catalyst Co-Co3B@BNC-5 prepared in Example 2 are shown.

[0041] Figure 4 TEM (left) and HRTEM (right) characterization of the catalyst Co-Co3B@BNC-5 prepared in Example 2, from... Figure 4 It can be seen that the catalyst Co-Co3B@BNC-5 is a catalyst with BNC as the shell and Co-Co3B heterostructure as the core. The measured lattice spacing is about 0.205 nm and 0.184 nm, which are in good agreement with the inter-crystal spacing of Co (111)(15-0806) and Co3B (202)(12-0443), respectively. Furthermore, there is an interface structure between Co and Co3B.

[0042] Figure 5 BET plots (a) and pore size distribution diagrams (b) of the catalysts Co-Co3B@BNC-4, Co-Co3B@BNC-5, Co-Co3B@BNC-6, Co@C-1, Co@C-2, and Co@C-3 prepared for Examples 1-3 and Comparative Examples 1-3 are shown. Figure 5 It can be seen that the BNC shell or C shell of Co-Co3B@BNC-4, Co-Co3B@BNC-5, Co-Co3B@BNC-6, Co@C-1, Co@C-2, and Co@C-3 mainly exist in the form of micropores and mesopores. The porous structure can restrict the aggregation of metal nanoparticles and facilitate the adsorption of reactants at active sites, thereby improving the catalytic activity of NH3BH3 hydrolysis to produce hydrogen.

[0043] Performance testing The catalysts Co-Co3B@BNC-4, Co-Co3B@BNC-5, Co-Co3B@BNC-6, Co@C-1, Co@C-2, and Co@C-3 prepared in Examples 1-3 and Comparative Examples 1-3 were used for hydrogen production from ammonia borane. The experimental procedure was as follows: (1) Weigh 0.2000g of sodium hydroxide and dissolve it completely in 5mL of ultrapure water to prepare NaOH aqueous solution. Place it in a 30℃ water bath and keep it warm for later use. (2) Add 10 mg of catalyst and 2.5 mL of the NaOH aqueous solution prepared in step (1) to a 25 mL round-bottom flask, place it in an ultrasonic cleaner and shake the solution for 2 min. After ultrasonication, place the round-bottom flask in a constant temperature water bath at 30 °C and stir magnetically at a speed of 500 r·min. -1 ; (3) Weigh 44 mg of ammonia borane and pour it into the remaining 2.5 mL of NaOH aqueous solution from step (1). After the ammonia borane is fully dissolved, quickly use a dropper to draw it out and squeeze it into the round-bottom flask from step (2). Quickly connect the rubber tubing and start timing. After the reaction starts, record the time every 5 mL of hydrogen produced until the reading no longer changes. Calculate the hydrogen production rate. The rate of the catalyst-catalyzed reaction is expressed as r. B (This represents the average hydrogen production rate of ammonia borane catalyzed by the catalyst, in mL·min) -1 ·g Co -1 It is measured by the total mass of Co in the catalyst.

[0044] Figure 6 Hydrogen production curves of ammonia borane hydrolysis for catalysts Co-Co3B@BNC-4, Co-Co3B@BNC-5, Co-Co3B@BNC-6, Co@C-1, Co@C-2, and Co@C-3 prepared for Examples 1-3 and Comparative Examples 1-3. Figure 6 It can be seen that: the r of Co@C-1, Co@C-2, Co@C-3, Co-Co3B@BNC-4, Co-Co3B@BNC-5, and Co-Co3B@BNC-6 B The values ​​were 1959, 2051, 981, 4193, 10492, and 5389 mL·min, respectively. -1 ·g Co -1 For Co@C catalysts, the catalytic activity is improved with the continuous introduction of Co. However, excessive Co content can cause the aggregation of metal nanoparticles, leading to the coverage of active sites and thus affecting the catalytic activity. After the introduction of h-BN, not only is the formation of dual active sites of Co and Co3B promoted, but there is also an interfacial structure between the Co-Co3B dual active sites. These features significantly improve the catalytic performance of the catalyst, with Co-Co3B@BNC-5 showing the best catalytic effect.

[0045] Figure 7 The hydrogen production curves from the six-cycle ammonia borane hydrolysis of the catalyst Co-Co3B@BNC-5 prepared in Example 2 are shown. Figure 7 It can be seen that after 6 cycles of testing, the r of Co-Co3B@BNC-5 B The value is 9023 mL·min -1 ·g Co -1 The performance remains at 86%, exhibiting good catalytic stability. This is because the presence of the BNC shell prevents catalyst deactivation.

Claims

1. A Co-Co3B interfacial bi-active site modified lignocellulosic char catalyst, characterized in that: The catalyst is a core-shell structure and has BNC as the shell and Co-Co3B heterostructure as the core; the catalyst has double active sites: Co nanoparticles and Co3B nanoparticles, and there is an interface structure between Co and Co3B; wherein the BNC is boron nitride modified wood charcoal and has a porous structure.

2. A method for preparing a lignochar catalyst modified with dual active sites at the Co-Co3B interface as described in claim 1, characterized in that, The mass parts are in mg, the volume parts are in mL, and the mole parts are in mmol, and the preparation steps are as follows: (1) After high-temperature impurity removal treatment, the h-BN is exfoliated to obtain h-BN nanosheets; (2) 20-100 parts by mass of the h-BN nanosheets obtained by exfoliation in step (1) are uniformly dispersed in 20-100 parts by volume of ethanol, 980 parts by mass of wood charcoal powder is added, and after stirring uniformly, hydrothermal reaction is carried out at 160-180°C for 6-7h, and then drying is carried out to obtain BNC; (3) 3-9 mole parts of a water-soluble cobalt salt is dissolved in 8-24 parts by volume of ethanol, and then the BNC obtained in step (2) is added to the solution, stirred uniformly, and dried to obtain BNC deposited with the cobalt salt; (4) 4 times the mole parts of the water-soluble cobalt salt of dimethylimidazole is dissolved in 8-24 parts by volume of ethanol, and then the BNC deposited with the cobalt salt obtained in step (3) is added to the solution and soaked, and then the supernatant is removed, dried, and pyrolyzed at 700-750°C under an inert atmosphere for 2-2.5h, and then ethanol is passivated to obtain the target catalyst; In steps (3) and (4), the mole parts of the water-soluble cobalt salt are calculated based on the cobalt element therein.

3. The method for preparing the lignocarbon catalyst modified with dual active sites at the Co-Co3B interface as described in claim 2, characterized in that: In step (1), the high-temperature impurity removal treatment is carried out at a temperature of 800-900°C for 1-2h.

4. The method for preparing the lignocarbon catalyst modified with dual active sites at the Co-Co3B interface as described in claim 2, characterized in that: In step (2), the wood charcoal powder is cedar charcoal powder.

5. The method of preparing Co-Co3B interfacial bi-active site modified wood charcoal catalyst as claimed in claim 4, wherein: In step (2), the cedar charcoal powder is obtained by pyrolyzing cedar blocks at 850-900°C for 2-2.5h.

6. The method of preparing Co-Co3B interfacial bi-active site modified wood charcoal catalyst as claimed in claim 2, wherein: In step (3), the water-soluble cobalt salt is cobalt nitrate or cobalt chloride.

7. The method for preparing the lignochar catalyst modified with dual active sites at the Co-Co3B interface as described in claim 2, characterized in that: In steps (2)-(4), the ethanol involved is anhydrous ethanol.

8. Use of the Co-Co3B interface double active site modified wood charcoal catalyst according to claim 1 in the hydrogen production by hydrolysis of ammonia borane.

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