Preparation method of co-nc nanocube supported monometallic rh catalyst and application thereof in methanol hydrogen evolution

Abstract

The application provides a preparation method of a Co-NC nanocube loaded monometallic Rh nano-catalyst and application thereof in methanol hydrogen evolution, wherein a Co-NC nanocube precursor is prepared by combining metal ions with organic ligands, a Co-NC nanocube is obtained by high-temperature calcination, and then a reducing agent, sodium borohydride, is used to reduce Rh in situ 3+ Metal ions, a Co-NC nanocube loaded monometallic Rh catalyst is prepared, and the catalyst is applied in catalyzing the reaction of tetrahydroxydiboron and methanol to produce hydrogen, and the hydrogen conversion frequency value in the catalytic hydrogen production reaches 161 (L(H2)·g Cat. ‑1 ·h ‑1 ) above. The nanocatalyst obtained by the technical scheme of the application has the advantages of simple preparation process, high selectivity and catalytic activity for the reaction of tetrahydroxydiboron and methanol to produce hydrogen, and high catalytic activity at very low temperature.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a Co-NC nanocube-supported monometallic Rh catalyst, belonging to the field of energy materials. Background Technology

[0002] Since the beginning of the 21st century, the sustained development of the global economy and the steady expansion of the population have powerfully driven the continuous rise in global energy demand. The latest statistics show that more than 80% of global energy consumption still relies on fossil fuels, encompassing natural gas, oil, and coal. However, the excessive exploitation and rapid consumption of fossil fuels, along with the resulting greenhouse gas emissions, have inevitably led to negative impacts such as global warming and environmental pollution. Therefore, developing renewable and green fuel alternatives such as hydropower, solar photovoltaic, wind power, hydrogen energy, and tidal energy has become a critical issue for solving the current environmental dilemma and achieving long-term sustainable development.

[0003] Chemical hydrogen storage materials, with their excellent hydrogen density, mild and safe reaction conditions, superior storage and transportation performance, and core advantages of being non-flammable and non-toxic, are considered one of the most promising pathways for producing pure hydrogen under normal pressure through hydrogen desorption processes. Hydrogen itself, due to its ultra-high energy density and zero-emission characteristics, is widely recognized as a clean and renewable energy carrier and is one of the best candidates to replace traditional fossil fuels in future energy systems.

[0004] Tetrahydroxydiboron, as a high-quality chemical hydrogen storage material, boasts a theoretical hydrogen storage capacity of up to 10 wt%. It exhibits excellent stability in air and aqueous solutions, poses no risk of spontaneous combustion, and can release hydrogen under controlled conditions, producing only H2 and environmentally friendly boric acid as products. Its simple synthesis, good water solubility, and balance of high capacity and practicality make it suitable for vehicle-mounted and portable energy applications, attracting widespread attention in the hydrogen energy field.

[0005] This invention discloses a method for preparing a Co-NC nanocube-supported monometallic Rh catalyst, using Rh / Co-NC as the catalyst to achieve efficient catalytic decomposition of tetrahydroxydiboron methanol to produce hydrogen. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing Rh / Co-NC nanocube catalysts and their application in catalyzing the hydrogen release from methanol using tetrahydroxydiboron. The method uses benzimidazole, methanol, triethylamine, cobalt nitrate, and rhodium nitrate as raw materials. These materials are then mixed in a solution, allowed to stand for aging, centrifuged, washed, dried, and calcined to obtain Co-NC nanocubes. Rhodium is then loaded onto these nanocubes using a wet chemical reduction method to obtain the Rh / Co-NC nanocube catalyst. This catalyst is then applied to the catalytic reaction of tetrahydroxydiboron with methanol to produce hydrogen. This catalyst achieves a significantly higher hydrogen conversion frequency in the catalytic reaction with extremely low noble metal loading.

[0007] The technical solution of this invention is a method for preparing Rh / Co-NC nanocube catalyst, comprising the following steps:

[0008] (1) Dissolve benzimidazole in methanol, add triethylamine, and obtain solution A;

[0009] (2) Dissolve cobalt nitrate in methanol to obtain solution B;

[0010] (3) Add liquid B to liquid A, stir the reaction under constant temperature water bath, let it stand for aging, centrifuge and wash, and dry to obtain the precursor;

[0011] (4) The precursor was calcined at high temperature under a nitrogen atmosphere to obtain Co-NC nanocube carrier;

[0012] (5) Disperse the Co-NC nanocube carrier in water and add rhodium salt solution and stir to mix;

[0013] (6) Add a reducing agent solution to the mixture, stir the reaction, wash and dry to obtain Rh / Co-NC nanocube catalyst.

[0014] Furthermore, the molar ratio of benzimidazole to triethylamine is 3-10:1, and the molar ratio of cobalt nitrate to benzimidazole is 1:1-3.

[0015] Furthermore, in step 3, the water bath temperature is 30-40 ℃, the stirring time is 5-8 hours, the standing temperature is 30-40 ℃, and the aging time is 1-2 hours.

[0016] Furthermore, in step 3, the vacuum drying temperature is 50-60℃ and the drying time is 10-12 h.

[0017] Furthermore, in step 4, the material is placed in a tube furnace during calcination, and heated at 1-5 °C / min under a N2 atmosphere until it reaches 600 °C to 1000 °C. The calcination time is 1 to 4 hours.

[0018] The rhodium salt is at least one of rhodium nitrate, rhodium chloride, or their hydrates; the reducing agent is at least one of sodium borohydride, hydrazine hydrate, ascorbic acid, or hydrogen.

[0019] Furthermore, in step 5, the mass ratio of Co-NC nanocubes to deionized water is 1:150-200, the concentration of rhodium nitrate solution is 0.01-0.03 mol / L, and the stirring time is 1-2 h.

[0020] Furthermore, in step 6, the concentration of the sodium borohydride solution is 0.1-1.0 mol / L, the stirring time is 0.5-1 h, the vacuum drying temperature is 50-60 ℃, and the drying time is 10-12 h.

[0021] The present invention also relates to Rh / Co-NC nanocube catalysts prepared according to the above method.

[0022] The present invention also relates to a Rh / Co-NC nanocubic catalyst prepared according to the above method. The catalyst has a uniform cubic structure with an average particle size of 1.6 ± 0.2 μm, in which Co atoms are encapsulated inside the cube and Rh is uniformly distributed on it.

[0023] This invention also relates to the application of the catalyst in the catalytic desorption of hydrogen from tetrahydroxydiboronic methanol.

[0024] This catalyst has the advantages of high catalytic activity, simple synthesis method and wide environmental adaptability.

[0025] The equation for the reaction of tetrahydroxydiboron with methanol to produce hydrogen is:

[0026] 2MeOH + B2(OH)4→ 2MeOB(OH)2+ H2↑;

[0027] In the application of catalytic reaction of tetrahydroxydiboron with methanol to produce hydrogen, it exhibits high catalytic selectivity, and the initial TOF value of the reaction can be calculated using the following formula:

[0028] TOF 0.75min = .

[0029] Where t = 0.75 min, and V(gas) is the volume of gas produced when tetrahydroxydiboron reacts with methanol for 0.75 minutes.

[0030] The present invention has the following beneficial effects:

[0031] 1. In the synthesis of the Co-NC support, this invention achieves spatial confinement through precursor synthesis and further high-temperature calcination. This confined dispersion and stabilization of Co atoms prevents Co atom aggregation and leaching during the reaction process, thereby enhancing the stability of the catalyst.

[0032] 2. Rh loaded onto the Co-NC support via reduction forms an alloy with Co. The bimetallic synergistic effect enhances electron transfer, precisely controls reaction selectivity, and significantly improves catalytic performance.

[0033] 3. The catalyst provided by this invention has a simple preparation step, a short synthesis cycle, mild conditions for catalytic reactions, and a certain degree of environmental adaptability. Attached Figure Description

[0034] Figure 1 The images shown are SEM and TEM images of the Rh / Co-NC nanocube catalyst prepared in Example 1 of this invention. In the images, a is a scanning electron microscope (SEM) image of the catalyst, b is a particle size distribution map of the catalyst, and c is a transmission electron microscope (TEM) image of the catalyst.

[0035] Figure 2 The graph (a) shows the relationship between the reaction time and the amount of hydrogen produced in the reaction of B2(OH)4 with methanol catalyzed by the Rh / Co-NC, Pd / Co-NC, Pt / Co-NC, Au / Co-NC, and Ru / Co-NC catalysts prepared in Examples 1, 1-1, 1-2, 1-3, and 1-4 of this invention, and the corresponding TOF values ​​(b).

[0036] Figure 3 The graph (a) shows the relationship between the reaction time and the amount of hydrogen produced in the reaction of B2(OH)4 with methanol catalyzed by the Rh / Co-NC, Rh / Co3O4, Rh / MoS2, Rh / ZnO, and Rh / CeO2 catalysts prepared in Examples 1 and 3 of this invention, and the corresponding TOF values ​​(b).

[0037] Figure 4 The graph (a) shows the relationship between the reaction time and the amount of hydrogen produced in the reaction of B2(OH)4 with methanol, ethanol and propanol catalyzed by the Rh / Co-NC catalyst prepared in Example 1 of this invention and the corresponding TOF value (b).

[0038] Figure 5 This is a graph showing the relationship between the reaction time and the amount of hydrogen produced when the Rh / Co-NC catalyst prepared in Example 1 of this invention reacts with B2(OH)4 and methanol at -10 degrees Celsius to produce hydrogen. Detailed Implementation

[0039] To better explain the present invention, it is further described in detail below with reference to specific embodiments and accompanying drawings. However, it should not be construed that the scope of the present invention described above is limited to the following embodiments.

[0040] Example 1

[0041] The specific preparation method of Rh / Co-NC nanocube catalyst includes the following steps:

[0042] Step 1: Dissolve 2.36 g of benzimidazole in 150 mL of methanol and then add 600 μL of triethylamine to obtain solution A.

[0043] Step 2: Dissolve 2.8 g of cobalt nitrate in 250 mL of methanol to obtain solution B.

[0044] Step 3: Under stirring in a 30 ℃ water bath, add solution B dropwise to solution A. After the addition is complete, stir for 8 h and let stand for 1 h to age. Centrifuge and wash with methanol several times, then vacuum dry to obtain the precursor.

[0045] Step 4: The precursor obtained in Step 3 is calcined in an N2 atmosphere at a heating rate of 5℃ / min to 800℃ and held for 2h to obtain Co-NC nanocubes.

[0046] Step 5: Disperse 100 mg of the Co-NC nanocubes obtained in Step 4 in 15 mL of deionized water, and add 0.03 mol·L⁻¹ dropwise. -1 Mix 1 mL of rhodium nitrate solution with stirring for 1 h to form a mixture.

[0047] Step 6: Add 0.9 mol·L⁻¹ dropwise to the mixture from step 5. -1 1 mL of sodium borohydride solution was stirred for 30 min, and then washed with water several times and dried under vacuum to obtain the Rh / Co-NC nanocube catalyst.

[0048] Figure 1 These are SEM and TEM images of the Rh / Co-NC nanocube catalyst prepared in Example 1 of this invention. The images show that a Co-NC support with a nanocube structure was prepared, and Rh... 3+ Metal ions are uniformly reduced onto the support. From Figure 1 As shown in (a), a catalyst with a nanocubic structure was prepared, and the cubic particle size distribution is as follows: Figure 1 As shown in (b), its average particle size is 1.59 μm. Rh 3+ Metal ions are reduced in situ onto the Co-NC support, and their distribution is uniform.

[0049] Example 1-1

[0050] The method and steps are the same as in Example 1, except that Na2PdCl4 solution is added in step 5. This yields a Pd / Co-NC nanocube catalyst.

[0051] Examples 1-2

[0052] The method and steps are the same as in Example 1, except that PtCl4 solution is added in step 5. This yields a Pt / Co-NC nanocube catalyst.

[0053] Examples 1-3

[0054] The method and steps are the same as in Example 1, except that HAuCl4 solution is added in step 5. Au / Co-NC nanocube catalyst is obtained.

[0055] Examples 1-4

[0056] The method and steps are the same as in Example 1, except that RuCl3 solution is added in step 5. This yields a Ru / Co-NC nanocube catalyst.

[0057] Example 2

[0058] Application of Rh / Co-NC, Pd / Co-NC, Pt / Co-NC, Au / Co-NC, and Ru / Co-NC catalysts prepared according to Examples 1, 1-1, 1-2, 1-3, and 1-4 in the catalytic reaction of B2(OH)4 with methanol to produce hydrogen.

[0059] The specific steps of the Rh / Co-NC catalyst in catalyzing the reaction of B2(OH)4 with methanol to produce hydrogen are as follows:

[0060] Step 1: Place the Rh / Co-NC catalyst prepared in Example 1 and 2 mmol B2(OH)4 into a 10 mL reactor, and then place the reactor in a 30 ℃ water bath and stir magnetically to mix them thoroughly.

[0061] Step 2: Quickly inject 4 mL of anhydrous methanol into the reactor from Step 1. Start timing as soon as gas begins to be generated, and record the volume of gas generated at each 15-second interval.

[0062] The graph shows the relationship between the reaction time and the amount of hydrogen produced in the reaction of B2(OH)4 with methanol catalyzed by the Rh / Co-NC catalyst prepared in Example 1 of this invention. Figure 2 As shown in (a), it can be seen that the catalyst produces hydrogen at an extremely fast rate, with a hydrogen conversion rate of 100%.

[0063] The specific steps for the Pd / Co-NC, Pt / Co-NC, Au / Co-NC, and Ru / Co-NC catalysts in catalyzing the reaction of B2(OH)4 with methanol to produce hydrogen are the same as those for the Rh / Co-NC catalyst.

[0064] Performance tests of the catalysts described in Examples 1, 1-1, 1-2, 1-3, and 1-4, conducted in Example 2, clearly demonstrate that the Rh / Co-NC catalyst prepared in this invention exhibits excellent catalytic activity and H2 selectivity. It demonstrates extremely high catalytic activity even with very low noble metal loading (0.3 mol%), with a TOF value as high as 161.24 (L(H2)·g). Cat. -1 ·h -1 It is far higher than that of Pd / Co-NC (TOF=75.66 (L(H2)·g)). Cat. -1 ·h-1 )), Pt / Co-NC(TOF=21.71(L(H2)·g Cat. -1 ·h -1 )), Au / Co-NC(TOF=13.02(L(H2)·g Cat. -1 ·h -1 )), Ru / Co-NC(TOF=0(L(H2)·g Cat. -1 ·h -1 The TOF value of the catalyst.

[0065] Example 3

[0066] According to the steps of Rh / Co-NC catalyst preparation in Example 1, the Co-NC support used in step 5 was replaced with commercially available Co3O4, MoS2, ZnO, and CeO2 purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., respectively, to prepare Rh / Co3O4, Rh / MoS2, Rh / ZnO, and Rh / CeO2 catalysts, and their applications in catalyzing the reaction of different methanols with B2(OH)4 to produce hydrogen.

[0067] The specific steps of using the catalyst to catalyze the reaction of methanol with B2(OH)4 to produce hydrogen are as follows:

[0068] Step 1: Place the catalysts prepared in Example 3 (Rh / Co3O4, Rh / MoS2, Rh / ZnO, Rh / CeO2 catalysts) and 2 mmol B2(OH)4 into a 10 mL reactor, and then place the reactor in a 30 ℃ water bath and stir magnetically to mix them thoroughly.

[0069] Step 2: Quickly inject 4 mL of anhydrous methanol into the reactor from Step 1. Start timing as soon as gas begins to be generated, and record the volume of gas generated at each 15-second interval.

[0070] The graph shows the relationship between the reaction time and the amount of hydrogen produced in the reaction of methanol and B2(OH)4 catalyzed by the catalyst prepared in Example 3 of this invention. Figure 3 As shown, the Rh / Co3O4, Rh / MoS2, Rh / ZnO, and Rh / CeO2 catalysts all exhibit low catalytic activity at the same Rh loading (0.3 mol%). Compared with the Rh / Co-NC catalyst prepared in Example 1, which catalyzes the reaction of methanol with B2(OH)4 to produce hydrogen, the catalyst prepared in Example 1 has superior catalytic activity.

[0071] Example 4

[0072] The application of the Rh / Co-NC catalyst prepared according to Example 1 in the catalytic reaction of different alcohols with B2(OH)4 to produce oxygen.

[0073] The specific steps of the Rh / Co-NC catalyst in catalyzing the reaction of different alcohols with B2(OH)4 to produce hydrogen are as follows:

[0074] Step 1: Place the Rh / Co-NC catalyst prepared in Example 1 and 2 mmol B2(OH)4 into a 10 mL reactor, and then place the reactor in a 30 ℃ water bath and stir magnetically to mix them thoroughly.

[0075] Step 2: Quickly inject 4 mL of anhydrous alcohols (including anhydrous methanol, anhydrous ethanol, and anhydrous propanol) into the reactor from Step 1. Start timing as soon as gas begins to be generated, and record the volume of gas generated at each 15-second interval.

[0076] The graph shows the relationship between the reaction time and the amount of hydrogen produced in the reaction of different alcohols with B2(OH)4 catalyzed by the Rh / Co-NC catalyst prepared in Example 1 of this invention. Figure 4 As shown, in different alcohol systems, this catalyst exhibits excellent catalytic activity and high selectivity for the reaction of methanol with B2(OH)4 to produce hydrogen.

[0077] Example 5

[0078] Application of the Rh / Co-NC catalyst prepared according to Example 1 in the catalytic reaction of methanol with B2(OH)4 to produce hydrogen at -10 degrees Celsius.

[0079] The specific steps for the Rh / Co-NC catalyst to catalyze the reaction of methanol with B2(OH)4 to produce hydrogen at -10°C are as follows:

[0080] Step 1: Place the Rh / Co-NC catalyst prepared in Example 1 and 2 mmol B2(OH)4 into a 10 mL reactor, and then place the reactor in a water bath at -10 degrees Celsius and stir magnetically to mix them thoroughly.

[0081] Step 2: Quickly inject 4 mL of anhydrous methanol into the reactor from Step 1. Start timing as soon as gas begins to be generated, and record the volume of gas generated at each 15-second interval.

[0082] The graph shows the relationship between the reaction time and the amount of hydrogen produced in the reaction of methanol and B2(OH)4 with the Rh / Co-NC catalyst prepared in Example 1 at -10°C. Figure 5 As shown, the catalyst retains good catalytic activity even at extremely low temperatures (-10℃).

[0083] The above description represents the preferred embodiments of the present invention. It should be noted that any improvements and modifications made without departing from the principles of the present invention are also considered to be within the scope of protection of the present invention.

Claims

1. The application of a Rh / Co-NC nanocube catalyst in the catalytic reaction of tetrahydroxydiboron with alcohols to produce hydrogen, wherein the preparation method of the Co-NC nanocube supported single-metal Rh catalyst includes the following steps: (1) Dissolve benzimidazole in methanol, add triethylamine, and obtain solution A; (2) Dissolve cobalt nitrate in methanol to obtain solution B; (3) Add liquid B to liquid A, stir the reaction under constant temperature water bath, let it stand for aging, centrifuge and wash, and dry to obtain the precursor; (4) The precursor was calcined at high temperature under a nitrogen atmosphere to obtain Co-NC nanocube carrier; (5) Disperse the Co-NC nanocube carrier in water and add rhodium salt solution and stir to mix; (6) Add a reducing agent solution to the mixture, stir and react, then wash and dry to obtain a Co-NC nanocube supported monometallic Rh catalyst.

2. The application according to claim 1, characterized in that, The molar ratio of benzimidazole to triethylamine is 3-10:1, and the molar ratio of cobalt nitrate to benzimidazole is 1:1-3.

3. The application according to claim 1, characterized in that, The calcination temperature in step (4) is 600℃ to 1000℃, and the calcination time is 1h to 4h.

4. The application according to claim 1, characterized in that, The rhodium salt is at least one of rhodium nitrate, rhodium chloride, or their hydrates; the reducing agent is at least one of sodium borohydride, hydrazine hydrate, ascorbic acid, or hydrogen.

5. The application according to claim 1, characterized in that, The alcohol is at least one of methanol, ethanol, and propanol, and the reaction temperature is from -20°C to 50°C.

6. The application according to claim 5, characterized in that, The loading of Rh in the catalyst is from 0.1 mol% to 1.0 mol%.

7. The application according to claim 5, characterized in that, The catalyst used for the reaction of methanol with tetrahydroxydiboron to produce hydrogen has a hydrogen conversion frequency (TOF) of not less than 160 L·g. -1 ·h -1 .

8. A catalytic hydrogen production system, characterized in that, This includes a reactor, which contains Rh / Co-NC nanocube catalyst, tetrahydroxydiboron, and methanol. The preparation method of Co-NC nanocube supported single metal Rh catalyst includes the following steps: (1) Dissolve benzimidazole in methanol, add triethylamine, and obtain solution A; (2) Dissolve cobalt nitrate in methanol to obtain solution B; (3) Add liquid B to liquid A, stir the reaction under constant temperature water bath, let it stand for aging, centrifuge and wash, and dry to obtain the precursor; (4) The precursor was calcined at high temperature under a nitrogen atmosphere to obtain Co-NC nanocube carrier; (5) Disperse the Co-NC nanocube carrier in water and add rhodium salt solution and stir to mix; (6) Add a reducing agent solution to the mixture, stir and react, then wash and dry to obtain a Co-NC nanocube supported monometallic Rh catalyst.

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