A biomass carbon-modified carbon nitride supported cobalt metal catalyst, its preparation method and application

Abstract

This invention relates to the fields of materials and energy catalysis technology, and particularly to a biomass carbon-modified carbon nitride supported cobalt catalyst, its preparation method, and its application. The invention first involves mixing a nitrogen-containing precursor dispersion with biomass and subjecting it to a hydrothermal reaction to obtain a biomass-modified nitrogen-containing precursor. Then, the biomass-modified nitrogen-containing precursor is calcined to obtain a biomass carbon-modified carbon nitride material. Finally, a biomass carbon-modified carbon nitride material dispersion, a cobalt salt solution, and a boron reducing agent aqueous solution are mixed and reacted to obtain the biomass carbon-modified carbon nitride supported cobalt catalyst. The catalyst prepared by this invention has a suitable specific surface area, an adjustable pore structure, uniform metal dispersion, good reusability, and both thermocatalytic and photocatalytic activity. It can catalyze the hydrolysis of sodium borohydride to produce hydrogen under ambient temperature conditions, and can also produce hydrogen through photocatalytic sodium borohydride hydrolysis.

Description

Technical Field

[0001] This invention relates to the fields of materials and energy catalysis technology, and in particular to a biomass carbon-modified carbon nitride supported cobalt metal catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen storage and production are among the key issues to be addressed in the utilization of hydrogen energy. Chemical hydride hydrogen storage offers unparalleled advantages over traditional methods, such as high energy density and mild reaction conditions, making it particularly attractive in applications requiring high-energy-density hydrogen supply. Sodium borohydride is a representative chemical hydride with a hydrogen storage capacity of 10.6% (mass fraction). Catalytic hydrolysis of sodium borohydride is a convenient, practical, and effective novel hydrogen supply technology for producing high-purity hydrogen. When releasing hydrogen, water becomes the hydrogen source, with a theoretical hydrogen storage mass fraction of 21.2%.

[0003] Previous studies have shown that supported metal nanoparticles exhibit excellent catalytic performance in hydrogen production from liquid chemical hydrogen storage materials due to their small size effect, large synergistic effect, and strong metal-support interaction. Supported catalysts include noble metal catalysts such as Pt, Ru, and Au, and non-noble metal catalysts such as Co and Ni. Among many non-noble metal catalysts, Co-based catalysts are considered the most suitable catalysts for the sodium borohydride hydrogen production reaction due to their good overall performance.

[0004] Graphitic carbon nitride possesses a two-dimensional conjugated large π-bond structure, which is stable and resistant to acids and alkalis, making it suitable as a catalyst or catalyst support in various catalytic reactions. Patent CN116212930A discloses a cobalt-boron co-doped carbon nitride catalyst and its preparation method, while patent CN114534759A discloses a method for preparing a single-atom cobalt-supported tubular carbon nitride catalyst. These catalysts are prepared using a high-temperature calcination method, with cobalt oxide as the active component, and are used in the degradation of antibiotics in water. Although carbon nitride has advantages such as simple preparation, good chemical stability, and good visible light photocatalytic activity, its layered morphology results in a small specific surface area, limiting its use as a support. Patent CN107376972A discloses a method for preparing a biomass-modified carbon nitride composite photocatalyst and its applications, while CN113083347A discloses a biochar-based supramolecular self-assembled carbon nitride composite photocatalyst. Combining biomass carbon with carbon nitride is expected to overcome the low specific surface area limitation of carbon nitride as a support. However, there are currently no publicly reported applications of biomass carbon-modified carbon nitride-supported cobalt metal for photocatalytic sodium borohydride hydrolysis to produce hydrogen. Summary of the Invention

[0005] The purpose of this invention is to provide a biomass carbon-modified carbon nitride supported cobalt metal catalyst, its preparation method, and its application, so as to solve the problems existing in the prior art.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a biomass carbon-modified carbon nitride supported cobalt metal catalyst, comprising the following steps:

[0008] (1) A nitrogen-containing precursor dispersion was mixed with biomass and subjected to a hydrothermal reaction to obtain a biomass-modified nitrogen-containing precursor;

[0009] (2) The biomass-modified nitrogen-containing precursor was calcined to obtain biomass carbon-modified carbon nitride material, denoted as C@C3N4;

[0010] (3) The C@C3N4 dispersion, cobalt salt solution and boron reducing agent aqueous solution are mixed and reacted to generate a biomass carbon modified carbon nitride supported cobalt metal catalyst, denoted as Co / C@C3N4.

[0011] Preferably, in step (1), the nitrogen-containing precursor includes at least one of melamine, dicyandiamide and urea; the biomass includes at least one of coffee grounds, orange peel and straw; and the particle size of the biomass is 100-200 mesh.

[0012] Preferably, in step (1), the ratio of nitrogen-containing precursor to water in the nitrogen-containing precursor dispersion is 1-10 g: 100 mL; and the mass ratio of nitrogen-containing precursor to biomass is 1-10: 1.

[0013] Preferably, the temperature of the hydrothermal reaction in step (1) is 140-180°C and the time is 4-6 hours;

[0014] In step (2), the calcination is carried out by heating the temperature to 500-550℃ at a rate of 2-8℃ / min and holding it at that temperature for 3-5 hours.

[0015] Preferably, the biomass carbon-modified carbon nitride material in step (2) is a mesoporous material with a specific surface area ≥ 40 m². 2 ·g -1 .

[0016] Preferably, the cobalt salt solution in step (3) contains Co(NO3)2; the concentration of the cobalt salt solution is 0.05–0.2 mol / L.

[0017] In step (3), the boron reducing agent includes sodium borohydride or dimethylamine borane; the concentration of the aqueous solution of the boron reducing agent is 0.1 to 0.3 mol / L.

[0018] Preferably, in step (3), the ratio of C@C3N4 to water in the C@C3N4 dispersion is 0.05–0.2 g: 10 mL;

[0019] In step (3), the ratio of C@C3N4, boron reducing agent aqueous solution and cobalt salt solution is 0.05-0.2g: 5-10mL: 1.27mL;

[0020] Step (3) is carried out under ice-water bath conditions, and the reaction time is 2 to 4 hours.

[0021] The present invention also provides a biomass carbon modified carbon nitride supported cobalt metal catalyst prepared by the above preparation method.

[0022] This invention also provides the application of the above-mentioned biomass carbon-modified carbon nitride supported cobalt metal catalyst in the catalytic hydrolysis of sodium borohydride to produce hydrogen.

[0023] Preferably, the conditions for the catalyst to catalyze the hydrolysis of sodium borohydride to produce hydrogen are room temperature catalysis or photocatalysis.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention first improves the interaction between biomass and nitrogen-containing precursors through a hydrothermal reaction; then, a biochar-modified carbon nitride composite material is prepared by high-temperature calcination. During the thermal polymerization process, both carbon nitride and biomass carbon are generated simultaneously, achieving heterogeneous modification of biochar with carbon nitride. The resulting composite material combines the advantages of both carbon nitride and biochar. Furthermore, cobalt metal is loaded using an impregnation-reduction method to prepare a highly dispersed biochar-modified carbon nitride supported nano-cobalt metal catalyst. This catalyst possesses a suitable specific surface area, tunable pore structure, uniform metal dispersion, good reusability, and both thermocatalytic and photocatalytic activity. It can catalyze the hydrolysis of sodium borohydride to produce hydrogen at room temperature, and also through photocatalytic hydrolysis of sodium borohydride to produce hydrogen. Attached Figure Description

[0026] Figure 1 SEM images of the Co / C@C3N4 catalyst (a) prepared in Example 1 and the Co / C3N4 catalyst (b) prepared in Comparative Example 1;

[0027] Figure 2 The N2 adsorption-desorption curves of the Co / C@C3N4 catalyst prepared in Example 1 and the Co / C3N4 catalyst prepared in Comparative Example 1 are shown.

[0028] Figure 3 500nm TEM image (a) and 5nm TEM image (b) of the Co / C@C3N4 catalyst prepared in Example 1;

[0029] Figure 4 The XRD pattern of the Co / C@C3N4 catalyst prepared in Example 1;

[0030] Figure 5 The graphs show the catalytic performance of the Co / C@C3N4 catalyst prepared in Example 1 and the Co / C3N4 catalyst prepared in Comparative Example 1 in producing hydrogen by catalytic hydrolysis of sodium borohydride.

[0031] Figure 6 The graphs show the photocatalytic performance of the Co / C@C3N4 catalyst prepared in Example 1 and the Co / C3N4 catalyst prepared in Comparative Example 1 in the hydrolysis of sodium borohydride to produce hydrogen.

[0032] Figure 7 The graph shows the reusability of the Co / C@C3N4 catalyst prepared in Example 1.

[0033] Figure 8 The graphs show the performance of the Co / C@C3N4 catalysts prepared in Examples 1, 2, and 3 in catalytic hydrogen production via sodium borohydride hydrolysis. Detailed Implementation

[0034] This invention provides a method for preparing a biomass carbon-modified carbon nitride supported cobalt metal catalyst, comprising the following steps:

[0035] (1) A nitrogen-containing precursor dispersion was mixed with biomass and subjected to a hydrothermal reaction to obtain a biomass-modified nitrogen-containing precursor;

[0036] (2) The biomass-modified nitrogen-containing precursor was calcined to obtain biomass carbon-modified carbon nitride material, denoted as C@C3N4;

[0037] (3) The C@C3N4 dispersion, cobalt salt solution and boron reducing agent aqueous solution are mixed and reacted to generate a biomass carbon modified carbon nitride supported cobalt metal catalyst, denoted as Co / C@C3N4.

[0038] In this invention, the nitrogen-containing precursor in step (1) includes at least one of melamine, dicyandiamide and urea; the biomass includes at least one of coffee grounds, orange peel and straw; the particle size of the biomass is 100-200 mesh, preferably 120-180 mesh, and more preferably 150-160 mesh.

[0039] In this invention, the ratio of nitrogen-containing precursor to water in the nitrogen-containing precursor dispersion in step (1) is 1-10 g: 100 mL, preferably 3-8 g: 100 mL, more preferably 4-7 g: 100 mL, and even more preferably 5-6 g: 100 mL.

[0040] The mass ratio of nitrogen-containing precursor to biomass is 1 to 10:1, preferably 3 to 8:1, more preferably 4 to 7:1, and even more preferably 5 to 6:1.

[0041] In this invention, the temperature of the hydrothermal reaction in step (1) is 140-180°C, preferably 145-175°C, more preferably 150-170°C, and even more preferably 160-165°C, and the time is 4-6 hours, preferably 4.5-5.5 hours, and even more preferably 5 hours.

[0042] In step (2), the calcination is carried out at a rate of 2-8℃ / min, preferably 3-6℃ / min, more preferably 4-5℃ / min, to 500-550℃, preferably 510-540℃, more preferably 520-530℃, and held for 3-5 hours, preferably 3.5-4.5 hours, more preferably 4 hours.

[0043] In this invention, the biomass carbon-modified carbon nitride material in step (2) is a mesoporous material with a specific surface area ≥40m². 2 ·g -1 Preferably ≥50m 2 ·g -1 Further preferred is ≥60m 2 ·g -1 .

[0044] In this invention, step (2) involves placing the biomass-modified nitrogen-containing precursor in a muffle furnace for calcination, cooling the sample, grinding it evenly, and sieving it to obtain biomass carbon-modified carbon nitride material, denoted as C@C3N4.

[0045] The sieve mesh size is 100-300 mesh, preferably 150-250 mesh, and more preferably 200 mesh.

[0046] In this invention, the cobalt salt solution in step (3) contains Co(NO3)2; the concentration of the cobalt salt solution is 0.05-0.2 mol / L, preferably 0.07-0.18 mol / L, more preferably 0.1-0.15 mol / L, and even more preferably 0.12-0.14 mol / L;

[0047] In step (3), the boron reducing agent includes sodium borohydride or dimethylamine borane, preferably sodium borohydride; the concentration of the aqueous solution of the boron reducing agent is 0.1-0.3 mol / L, preferably 0.13-0.26 mol / L, more preferably 0.15-0.24 mol / L, and even more preferably 0.17-0.2 mol / L.

[0048] In this invention, the ratio of C@C3N4 to water in the C@C3N4 dispersion in step (3) is 0.05-0.2g:10mL, preferably 0.07-0.18g:10mL, more preferably 0.1-0.15g:10mL, and even more preferably 0.12-0.14g:10mL;

[0049] In step (3), the ratio of C@C3N4, the boron reducing agent aqueous solution, and the cobalt salt solution is 0.05-0.2g: 5-10mL: 1.27mL, preferably 0.07-0.18g: 6-9mL: 1.27mL, more preferably 0.1-0.15g: 6.5-8mL: 1.27mL, and even more preferably 0.12-0.14g: 7-7.5mL: 1.27mL;

[0050] Step (3) is carried out under ice-water bath conditions, and the reaction time is 2 to 4 hours, preferably 2.5 to 3.5 hours, and more preferably 3 hours.

[0051] In this invention, the mixing method of step (3) is as follows:

[0052] C@C3N4 was ultrasonically dispersed in water, then a cobalt salt solution was added and magnetically stirred. The boron-containing reducing agent aqueous solution was then added dropwise under ice-water bath conditions. After washing, centrifugation and drying, a biomass carbon-modified carbon nitride supported cobalt metal catalyst was obtained, denoted as Co / C@C3N4.

[0053] In this invention, the ultrasonic dispersion time is 20-40 min, preferably 25-35 min, and more preferably 30 min; the magnetic stirring time is 1-4 h, preferably 1.5-3.5 h, and more preferably 2-3 h.

[0054] The present invention also provides a biomass carbon modified carbon nitride supported cobalt metal catalyst prepared by the above preparation method.

[0055] This invention also provides the application of the above-mentioned biomass carbon-modified carbon nitride supported cobalt metal catalyst in the catalytic hydrolysis of sodium borohydride to produce hydrogen.

[0056] In this invention, the catalyst catalyzes the hydrolysis of sodium borohydride to produce hydrogen under the conditions of room temperature catalysis or photocatalysis.

[0057] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] 10g of melamine was weighed into 100mL of water and stirred for 20min to obtain a melamine dispersion. 5g of waste coffee grounds with a particle size of 100-200 mesh was added, and the mixture was stirred to obtain a suspension. This suspension was then transferred to a hydrothermal reactor and kept at 140℃ for 4h. The mixture was then removed, filtered, dried, and ground to obtain a coffee grounds-modified melamine precursor. The precursor was placed in a crucible and covered, then placed in a muffle furnace and heated to 550℃ at a rate of 5℃ / min, and held for 3h. After cooling, the sample was removed, ground evenly, and passed through a 200-mesh sieve to obtain a biomass carbon-modified carbon nitride material with a specific surface area of ​​40.2m². 2 / g; Weigh 0.1g of biomass-modified carbon nitride and add it to 10mL of water. After ultrasonic dispersion for 30min, add 1.27mL of 0.1M Co(NO3)2 solution and stir magnetically for 2h. Then, add 7.5mL of 0.17M sodium borohydride solution dropwise under ice-water bath conditions and continue stirring for 2h. After centrifugation and drying, the biomass-modified carbon nitride supported cobalt catalyst is obtained, denoted as Co / C@C3N4.

[0060] Example 2

[0061] The only difference from Example 1 is that the mass ratio of melamine to coffee grounds is 10:1.

[0062] Example 3

[0063] The only difference from Example 1 is that the mass ratio of melamine to coffee grounds is 1:1.

[0064] Example 4

[0065] The only difference from Example 1 is that the nitrogen-containing precursor is urea.

[0066] Example 5

[0067] The only difference from Example 1 is that the biomass is orange peel.

[0068] Example 6

[0069] The only difference from Example 1 is that the temperature in the hydrothermal reactor is 180°C.

[0070] Example 7

[0071] The only difference from Example 1 is that the reducing agent is dimethylamineborane.

[0072] Comparative Example 1

[0073] 10g of melamine was weighed and placed in a muffle furnace. The temperature was raised to 550℃ at a rate of 5℃ / min and held for 3 hours. After cooling, the sample was taken out, ground evenly, and passed through a 200-mesh sieve to obtain carbon nitride material. 0.1g of carbon nitride was weighed and added to 10mL of water. After ultrasonic dispersion for 30 minutes, 1.27mL of 0.1M Co(NO3)2 solution was added and magnetically stirred for 2 hours. Then, 7.5mL of 0.17M sodium borohydride solution was added dropwise under ice-water bath conditions and stirred continuously for 2 hours. After centrifugation and drying, carbon nitride-supported cobalt catalyst was obtained, denoted as Co / C3N4.

[0074] Figure 1 SEM images of the Co / C@C3N4 catalyst (a) prepared in Example 1 and the Co / C3N4 catalyst (b) prepared in Comparative Example 1 are shown. It can be seen that the Co / C3N4 catalyst exhibits a tightly packed structure, and after modification with biomass carbon, the Co / C@C3N4 catalyst displays a rich porous structure.

[0075] Figure 2 The N2 adsorption-desorption curves of the Co / C@C3N4 catalyst prepared in Example 1 and the Co / C3N4 catalyst prepared in Comparative Example 1 are shown. The Co / C3N4 catalyst exhibits the typical mesoporous characteristics of layered C3N4 materials, while the Co / C@C3N4 catalyst demonstrates the microporous-mesoporous characteristics of biomass carbon modified with carbon nitride. The specific surface area of ​​Co / C3N4 is 12.5 m². 2 ·g -1 The specific surface area of ​​Co / C@C3N4 is 40.2 m². 2 ·g -1 This indicates that biomass carbon modification can improve the specific surface area of ​​the catalyst.

[0076] Figure 3 The image shows a TEM image of the Co / C@C3N4 catalyst prepared in Example 1. It can be seen that the catalyst exhibits the typical layered structure of C3N4 materials, with the (111) crystal plane of metallic Co present at the interface between biomass carbon and carbon nitride.

[0077] Figure 4 The XRD pattern of the Co / C@C3N4 catalyst prepared in Example 1 is shown. It can be seen that the diffraction peak at 27.1° is a characteristic peak of C3N4, and the diffraction peak at around 45° corresponds to highly dispersed metallic cobalt.

[0078] Test case

[0079] Add 5 mL of a 0.02 g / mL sodium borohydride alkaline solution (NaOH concentration 6 wt.%) to a 50 mL three-necked flask and place it in a 30°C constant temperature water bath. Weigh 14.3 mg of catalyst and quickly add it to the three-necked flask, then tighten the rubber stopper. Collect the generated hydrogen gas using the water displacement method, and record the water level in the graduated cylinder to measure the amount of gas produced during the reaction. The photocatalytic reaction is carried out under the same reaction conditions in a photochemical reactor, using a 300 W xenon lamp with a 420 nm filter as the light source.

[0080] Figure 5 The performance of the Co / C@C3N4 catalyst prepared in Example 1 and the Co / C3N4 catalyst prepared in Comparative Example 1 in catalyzing the hydrolysis of sodium borohydride to produce hydrogen is compared. It can be seen that the performance of the Co / C@C3N4 catalyst is significantly improved compared to that of Co / C3N4.

[0081] Figure 6 The photocatalytic hydrogen production performance of the Co / C@C3N4 catalyst prepared in Example 1 and the Co / C3N4 catalyst prepared in Comparative Example 1 was compared. Compared with the light-shielded condition, the hydrogen production rate of Co / C@C3N4 and Co / C3N4 under light conditions was increased by approximately 14% and 21%, respectively.

[0082] Figure 7 The reusability of the Co / C@C3N4 catalyst prepared in Example 1 is shown. It can be seen that the Co / C@C3N4 catalyst exhibits unchanged performance after four cycles, demonstrating good reusability.

[0083] Figure 8 The graphs show the performance of the Co / C@C3N4 catalysts prepared in Examples 1, 2, and 3 in the catalytic hydrolysis of sodium borohydride to produce hydrogen. It can be seen that the hydrogen production rate in Example 1 is 17857 mL·min. -1 ·gCo -1 The hydrogen production rate in Example 2 was 13889 mL·min. -1 ·gCo -1 The hydrogen production rate in Example 3 was 10331 mL·min. -1 ·gCo -1 The hydrogen production rate in Example 4 was tested to be 16599 mL·min. -1 ·gCo -1 The hydrogen production rate in Example 5 was 15631 mL·min. -1 ·gCo -1 The hydrogen production rate in Example 6 was 17932 mL·min. -1 ·gCo -1 The hydrogen production rate in Example 7 was 17502 mL·min. -1 ·gCo -1 .

[0084] As can be seen from the above embodiments, the present invention provides a biomass carbon-modified carbon nitride supported cobalt metal catalyst, its preparation method, and its application. The biomass carbon-modified carbon nitride supported nano-cobalt metal catalyst prepared by the present invention has a suitable specific surface area, tunable pore structure, uniform metal dispersion, good reusability, and both thermal and photocatalytic activity. It can catalyze the hydrolysis of sodium borohydride to produce hydrogen under ambient temperature conditions, and can also produce hydrogen through photocatalytic sodium borohydride hydrolysis.

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a biomass carbon-modified carbon nitride supported cobalt metal catalyst for catalytic hydrogen production by hydrolysis of sodium borohydride, characterized in that, Includes the following steps: (1) A nitrogen-containing precursor dispersion was mixed with biomass and subjected to a hydrothermal reaction to obtain a biomass-modified nitrogen-containing precursor; (2) The biomass-modified nitrogen-containing precursor is calcined to obtain biomass carbon-modified carbon nitride material, denoted as C@C3N4; (3) After mixing C@C3N4 dispersion, cobalt salt solution and boron reducing agent aqueous solution, the reaction is carried out to generate biomass carbon modified carbon nitride supported cobalt metal catalyst, denoted as Co / C@C3N4; The hydrothermal reaction in step (1) is carried out at a temperature of 140~180℃ for 4~6h; the mass ratio of nitrogen-containing precursor to biomass in step (1) is 1~10:

1. In step (2), the calcination is carried out by heating to 500-550℃ at a rate of 2-8℃ / min and holding for 3-5 hours; the biomass carbon-modified carbon nitride material is a mesoporous material with a specific surface area ≥40 m². 2 •g -1 ; In step (3), the concentration of the boron reducing agent aqueous solution is 0.1~0.3mol / L; the ratio of C@C3N4, boron reducing agent aqueous solution and cobalt salt solution is 0.05~0.2g: 5~10mL: 1.27mL; step (3) is carried out under ice-water bath conditions, and the reaction time is 2~4h.

2. The preparation method according to claim 1, characterized in that, In step (1), the nitrogen-containing precursor includes at least one of melamine, dicyandiamide and urea; the biomass includes at least one of coffee grounds, orange peel and straw; and the particle size of the biomass is 100-200 mesh.

3. The preparation method according to claim 2, characterized in that, Step (1) The ratio of nitrogen-containing precursor to water in the nitrogen-containing precursor dispersion is 1~10g:100mL.

4. The preparation method according to claim 1, characterized in that, In step (3), the cobalt salt solution contains Co(NO3)2; the concentration of the cobalt salt solution is 0.05~0.2 mol / L. In step (3), the boron reducing agent includes sodium borohydride or dimethylamine borane.

5. The preparation method according to any one of claims 1, 2, and 3, characterized in that, In step (3), the ratio of C@C3N4 to water in the C@C3N4 dispersion is 0.05~0.2g:10mL.

6. The biomass carbon modified carbon nitride supported cobalt metal catalyst prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the biomass carbon-modified carbon nitride supported cobalt metal catalyst according to claim 6 in the catalytic hydrolysis of sodium borohydride to produce hydrogen.

8. The application according to claim 7, characterized in that, The catalyst is used to catalyze the hydrolysis of sodium borohydride to produce hydrogen under ambient temperature catalysis or photocatalysis.

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