Composite catalyst for hydrogen production from KBH4 and preparation method thereof

Abstract

A composite catalyst for the production of hydrogen from KBH4 comprising a Ti3C2Tx / rGO carrier, a carbon nanotube (CNT) and a nitrogen doped cobalt compound. A method for preparing the Co-N / CNT / Ti3C2T

Description

[0001] The present disclosure relates to the technical field of catalyst preparation, in particular to a Co-N / CNT / TisCzTx / rGO composite catalyst for hydrogen production from KBIL BACKGROUND

[0002] With a wide range of sources, high energy density, and green products, hydrogen energy is considered to be an effective alternative to solve energy shortages. However, there are still many unsolved problems in the development and utilization of hydrogen energy, such as a lack of low-cost hydrogen production methods, a low density of hydrogen products, and flammable and explosive properties of hydrogen itself. Among the various hydrogen storage materials, KBH4 has attracted wide attention due to safe storage, high hydrogen-storage capacity, and easy hydrogen production.

[0003] A KBH4 solution is extremely stable in an alkaline solution, but may undergo extremely slow hydrolysis to release hydrogen under a neutral or acidic environment. The solution is generally preserved under an alkaline condition, and Hi is released quickly when needed, which requires a suitable catalyst. As early as the 1950s, it was found that cobalt chloride can accelerate the hydrolysis of NaBH4. Recently, a new type of graphene-like material, MXene, has attracted great attention. MXene can anchor metal nanoparticles due to abundant -OH and -F functional groups on its surface, and the MXene has desirable surface hydrophilicity, making it a very promising carrier material. A problem to be solved by the present disclosure is to prepare a catalyst for hydrogen production from KBH4 using an MXene structure-based material as a carrier. SUMMARY

[0004] In view of this, the present disclosure provides a Co-N / CNT / TiiCiTx / rGO composite catalyst for hydrogen production from KBH4. The Co-N catalyst based on carbon nanotube (CNT) arrays on a surface of the MXene graphene makes up for the shortcomings such as easy agglomeration of catalytic particles, insufficient reactive sites, and poor material conductivity. In addition, the catalyst avoids a slow hydrogen evolution rate, and has a lower cost than the commonly-used noble metal catalysts. Therefore, the catalyst can be widely used to produce hydrogen by hydrolysis of the KBH4 under mild conditions in a controllable manner.

[0005] The present disclosure provides a Co-N / C\T / Ti<>Tx / rGO composite catalyst for hydrogen production from KBH4, including a ThC2Tx / rGO carrier, a carbon nanotube (CNT), and a Co-N compound.

[0006] The present disclosure further provides a preparation method of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4, including the following steps:

[0007] (1) dissolving TiaCaTx and graphene oxide (GO) powders in deionized water separately, conducting an ultrasonic treatment under an argon atmosphere for 2 h, collecting precipitates after centrifugation, and conducting freeze-drying; placing treated TisCzTx and GO powders in a tubular furnace porcelain boat, heating to 200°C at 2°C / min under a hydrogen-argon mixture atmosphere and holding for 1 h, and naturally cooling to a room temperature to obtain a ThCbTx / rGO carrier (rGO represents reduced graphene oxide);

[0008] (2) dissolving the Ti'C2Tx / rGO carrier prepared in step (1) in methanol, and conducting the ultrasonic treatment for 1 h to 2 h under the argon atmosphere to obtain a Ti-GTxTGO suspension;

[0009] (3) dissolving the Co-N compound in the methanol, dispersing by stirring for 1 h to obtain a Co-N compound solution; dissolving 2-methylimidazole in the methanol, adding the CNT, and completely dispersing by stirring to obtain a 2-methylimidazole solution;

[0010] (4) adding the Co-N compound solution to the Ti3C2Tx / rGO suspension prepared in step (2), stirring for 1 h, quickly pouring an obtained mixed solution into the 2-methylimidazole solution, and stirring for 7 h to 8 h under an argon atmosphere; subjecting an obtained mixture to centrifugation with the methanol, and drying a resulting suspension in a watch glass under vacuum at 70°C to 80°C to obtain a black-purple powder; and

[0011] (5) heating the black-purple powder obtained in step (4) to 700°C to 800°C at 2°C / min to 3°C / min under the hydrogen-argon mixture atmosphere, and holding for 2 h to 5 h to obtain the Co-N / CNT / Ti3C2Tx / rGO composite catalyst.

[0012] Preferably, in step (1), the Ti3C2Tx and the GO have a mass ratio of (l-4):(l-3); and the TisC2Tx and the deionized water have a mass-volume ratio of 2 mg: 1 mL.

[0013] Preferably, in step (1), the freeze-drying is conducted at -10°C for 48 h.

[0014] Preferably, in step (1), the hydrogen-argon mixture has H2 and Ar at a ratio of 1:9.

[0015] Preferably, in step (2), the TisCiTx / rGO and the methanol have a mass-volume ratio of 8 mg: (4-5) mL.

[0016] Preferably, in step (3), the Co-N compound is Co(NO3)2 6H2O; and the Co-N compound and the methanol have a mass-volume ratio of (2.5-3) g: (30-40) mL.

[0017] Preferably, in step (3), the 2-methylimidazole and the methanol have a mass-volume ratio of (3-3.2) g: (30-40) mL, and the 2-methylimidazole and the CNT have a mass ratio of (300-310):(2-3).

[0018] Preferably, in step (4), the Ti-^Tx / rGO suspension, the Co-N compound solution, and the 2-methylimidazole solution have a volume ratio of (4-5):(3-4):(3-4).

[0019] The present disclosure further provides use of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 in catalyzing the hydrogen production from an aqueous solution with a KOH concentration of 3% and a KBH4 concentration of 2% to 5%.

[0020] A reaction equation is as follows:

[0021] KBH4+2H2O^KBO2+4H2

[0022] In the present disclosure, hydrolysis is conducted in an aqueous solution containing KOH and KBH4 using the Co-N / CNT / TLCiTx / rGO as a catalyst to achieve stable hydrogen evolution, so as to obtain high-purity hydrogen.

[0023] The present disclosure has the following beneficial effects over the prior art:

[0024] The Co-N / CNT / Ti3C2Tx / rGO catalyst uses Ti'C2Tx / rGO as a carrier to grow a CNT array on a surface of the catalyst, and Co-N nanoparticles are uniformly distributed on a surface of CNT / Ti3C2Tx / rGO. The Ti3C2Tx is a material with an MXene structure, which is rich in a large number of -OH and -F functional groups on a surface. In addition, rGO and CNT are rich in a large number of -OH and =0 functional groups on their surfaces, such that the carrier can anchor Co-N nanoparticles, with a defect-rich structure capable of effectively inhibiting the agglomeration of metal nanoparticles and increasing active sites of the catalyst; N doping acts as an atomic barrier to significantly increase a surface area of a Co catalyst by avoiding agglomeration; N further acts as an electron donor to increase an electron density of Co, thereby further enhancing a catalytic activity of Co. An open porous structure formed by the Co-N / CNT / Ti3C2Tx / rGO has a desirable conductivity, which is beneficial to diffusion of an aqueous solution and timely desorption and release of hydrogen generated. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The present disclosure is further described below with reference to examples.

[0026] Example 1

[0027] A Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 was prepared by the following steps:

[0028] (1) 40 mg of TisCiTx and 40 mg of GO were dissolved in 20 mL of deionized water separately, an ultrasonic treatment was conducted under an argon atmosphere for 2 h, precipitates were collected after centrifugation, and freeze-drying was conducted at -10°C for 48 h; treated Ti3C2Tx and GO powders were placed in a tubular furnace porcelain boat, heated to 200°C at 2°C / min under a hydrogen-argon mixture atmosphere with H2 and Ar at a ratio of 1:9 and held for 1 h, and naturally cooled to a room temperature to obtain Ti-.C2Tx / rGO;

[0029] (2) 80 mg of the Ti3C2Tx / rGO prepared in step (1) was dissolved in 40 mL of methanol, and the ultrasonic treatment was conducted for 1 h under the argon atmosphere to obtain a Ti3C2Tx / rGO suspension;

[0030] (3) 2.91 g of Co(NO3)2 6H2O was dissolved in 30 mL of methanol, dispersed by stirring for 1 h; 3.08 g of 2-methylimidazole was dissolved in 30 mL of the methanol, 20 mg of CNT was added, and completely dispersed by stirring;

[0031] (4) an obtained Co(NO3)2 6H2O solution was added to the Ti3C2Tx / rGO suspension prepared in step (2), stirred for 1 h, an obtained mixed solution was quickly poured into an obtained 2-methylimidazole solution, and stirred for 8 h under an argon atmosphere; an obtained mixture was subjected to centrifugation with the methanol, and a resulting suspension was dried in a watch glass under vacuum at 70°C for 24 h to obtain a black-purple powder; and

[0032] (5) the black-purple powder was heated to 800°C at 2°C / min under the hydrogen-argon mixture atmosphere, and held for 2 h to obtain the Co-N / CNT / Ti3C2Tx / rGO composite catalyst.

[0033] Hydrogen production from KBH4 was conducted using the catalyst prepared in Example 1, including the following steps: catalysis was conducted by the Co-N / CNT / Ti3C2Tx / rGO at 30°C with a KOH concentration of 3% and a KBH4 concentration of 3%, to obtain a hydrogen evolution rate of 5,400 mL-min4-g4 and a reaction activation energy of 40.0 kJ mol4.

[0034] Example 2

[0035] A Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 was prepared by the following steps:

[0036] (1) 40 mg of Ti3C2Tx and 40 mg of GO were dissolved in 20 mL of deionized water separately, an ultrasonic treatment was conducted under an argon atmosphere for 2 h, precipitates were collected after centrifugation, and freeze-drying was conducted at -10°C for 48 h; treated Ti3C2Tx and GO powders were placed in a tubular furnace porcelain boat, heated to 200°C at 2°C / min under a hydrogen-argon mixture atmosphere with H2 and Ar at a ratio of 1:9 and held for 1 h, and naturally cooled to a room temperature to obtain Ti3C2Tx / rGO;

[0037] (2) 80 mg of the Ti3C2Tx / rGO prepared in step (1) was dissolved in 40 mL of methanol, and the ultrasonic treatment was conducted for 1 h under the argon atmosphere to obtain a Ti3C2Tx / rGO suspension;

[0038] (3) 2.91 g of Co(NO3)2 6H2O was dissolved in 40 mL of methanol, dispersed by stirring for 1 h; 3.08 g of 2-methylimidazole was dissolved in 40 mL of the methanol, 30 mg of CNT was added, and completely dispersed by stirring;

[0039] (4) an obtained Co(NO3)2 6H2O solution was added to the Ti3C2Tx / rGO suspension prepared in step (2), stirred for 1 h, an obtained mixed solution was quickly poured into an obtained 2-methylimidazole solution, and stirred for 8 h under an argon atmosphere; an obtained mixture was subjected to centrifugation with the methanol, and a resulting suspension was dried in a watch glass under vacuum at 80°C for 12 h to obtain a black-purple powder; and

[0040] (5) the black-purple powder was heated to 800°C at 2°C / min under the hydrogen-argon mixture atmosphere, and held for 2 h to obtain the Co-N / CNT / Ti3C2Tx / rGO composite catalyst.

[0041] Hydrogen production from KBH4 was conducted using the catalyst prepared in Example 2, including the following steps: catalysis was conducted by the Co-N / CNT / lnCiTx / rGO at 30°C with a KOH concentration of 3% and a KBH4 concentration of 3%, to obtain a hydrogen evolution rate of 5,261 mLmin4g4 and a reaction activation energy of 45.0 kJmol4.

[0042] Example 3

[0043] A Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 was prepared by the following steps:

[0044] (1) 40 mg of Ti3C2Tx and 30 mg of GO were dissolved in 20 mL of deionized water separately, an ultrasonic treatment was conducted under an argon atmosphere for 2 h, precipitates were collected after centrifugation, and freeze-drying was conducted at -10°C for 48 h; treated Ti3C2Tx and GO powders were placed in a tubular furnace porcelain boat, heated to 200°C at 2°C / min under a hydrogen-argon mixture atmosphere with H2 and Ar at a ratio of 1:9 and held for 1 h, and naturally cooled to a room temperature to obtain Ti3C2Tx / rGO;

[0045] (2) 80 mg of the Ti3C2Tx / rGO prepared in step (1) was dissolved in 50 mL of methanol, and the ultrasonic treatment was conducted for 2 h under the argon atmosphere to obtain a Ti3C2Tx / rGO suspension;

[0046] (3) 2.91 g of Co(NO3)2 6H2O was dissolved in 30 mL of methanol, dispersed by stirring for 1 h; 3.08 g of 2-methylimidazole was dissolved in 30 mL of the methanol, 20 mg of CNT was added, and completely dispersed by stirring;

[0047] (4) an obtained Co(NO3)2 6H2O solution was added to the Ti3C2Tx / rGO suspension prepared in step (2), stirred for 1 h, an obtained mixed solution was quickly poured into an obtained 2-methylimidazole solution, and stirred for 8 h under an argon atmosphere; an obtained mixture was subjected to centrifugation with the methanol, and a resulting suspension was dried in a watch glass under vacuum at 70°C for 24 h to obtain a black-purple powder; and

[0048] (5) the black-purple powder was heated to 700°C at 2°C / min under the hydrogen-argon mixture atmosphere, and held for 5 h to obtain the Co-N / CNT / Ti3C2Tx / rGO composite catalyst.

[0049] Hydrogen production from KBH4 was conducted using the catalyst prepared in Example 3, including the following steps: catalysis was conducted by the Co-N / CNT / Ti3C2Tx / rGO at 30°C with a KOH concentration of 3% and a KBH4 concentration of 3%, to obtain a hydrogen evolution rate of 5,095 mLmin4g4 and a reaction activation energy of 47.5 kJ mol4.

[0050] Comparative Example 1

[0051] The catalysis was conducted by CO3O4 at 30°C with a KOH concentration of 3% and a KBH4 concentration of 3%, to obtain a hydrogen evolution rate of 3,447 mL min^ g’1 and a reaction activation energy of 65.0 kJ moT1.

[0052] Comparative Example 2

[0053] The catalysis was conducted by an iron-boron alloy Fe-B (with a boron content of 1% to 5%) at 30°C with a KOH concentration of 3% and a KBH4 concentration of 3%, to obtain a hydrogen evolution rate of 1,590 mL min^ g’1 and a reaction activation energy of 87.0 kJmol'1.

[0054] Comparative Example 3

[0055] The catalysis was conducted by a ruthenium-nickel alloy RuNi (with a ruthenium content of 1% to 5%) at 30°C with a KOH concentration of 3% and a KBH4 concentration of 3%, to obtain a hydrogen evolution rate of 4,321 mLmin^g'1 and a reaction activation energy of 48.0 kJmol’1.

[0056] The above descriptions are merely preferred implementations of the present disclosure. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, but such improvements and modifications should be deemed as falling within the protection scope of the present disclosure.

Claims

03 07 231. A Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4, comprising a Ti3C2Tx / rGO carrier, a carbon nanotube (CNT), and a Co-N compound.

2. A preparation method of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 according to claim 1, comprising the following steps:(1) dissolving Ti3C2Tx and graphene oxide (GO) powders in deionized water, conducting an ultrasonic treatment under an argon atmosphere for 2 h, collecting precipitates after centrifugation, and conducting freeze-drying; placing treated TisC2Tx and GO powders in a tubular furnace porcelain boat, heating to 200°C at 2°C / min under a hydrogen-argon mixture atmosphere and holding for 1 h, and naturally cooling to a room temperature to obtain a Ti3C2Tx / rGO carrier;(2) dissolving the Ti3C2Tx / rGO carrier prepared in step (1) in methanol, and conducting the ultrasonic treatment for 1 h to 2 h under the argon atmosphere to obtain a Ti3C2Tx / rGO suspension;(3) dissolving the Co-N compound in the methanol, dispersing by stirring for 1 h to obtain a Co-N compound solution; dissolving 2-methylimidazole in the methanol, adding the CNT, and completely dispersing by stirring to obtain a 2-methylimidazole solution;(4) adding the Co-N compound solution to the Ti3C2Tx / rGO suspension prepared in step (2), stirring for 1 h, quickly pouring an obtained mixed solution into the 2-methylimidazole solution, and stirring for 7 h to 8 h under an argon atmosphere; subjecting an obtained mixture to centrifugation with the methanol, and drying a resulting suspension in a watch glass under vacuum at 70°C to 80°C for 12 h to 24 h to obtain a powder; and(5) heating the powder obtained in step (4) to 700°C to 800°C at 2°C / min to 3°C / min under the hydrogen-argon mixture atmosphere, and holding for 2 h to 5 h to obtain the Co-N / CNT / Ti3C2Tx / rGO composite catalyst.

3. The preparation method of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 according to claim 2, wherein in step (1), the Ti3C2Tx and the GO have a mass ratio of (1 -4):(1 -3); and the TisC2Tx and the deionized water have a mass-volume ratio of 2 mg: 1 mL.

4. The preparation method of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 according to claim 2, wherein in step (1), the freeze-drying is conducted at -10°Cfor48 h.03 07 235. The preparation method of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 according to claim 2, wherein in step (1), the hydrogen-argon mixture has H2 and Ar at a ratio of 1:9.

6. The preparation method of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 according to claim 2, wherein in step (2), the Ti3C2Tx / rGO and the methanol have a mass-volume ratio of 8 mg: (4-5) mL.

7. The preparation method of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 according to claim 2, wherein in step (3), the Co-N compound is Co(NOs)2 6H2O: and the Co-N compound and the methanol have a mass-volume ratio of (2.5-3) g: (30-40) mL.

8. The preparation method of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 according to claim 2, wherein in step (3), the 2-methylimidazole and the methanol have a mass-volume ratio of (3-3.2) g: (30-40) mL, and the 2-methylimidazole and the CNT have a mass ratio of (300-310):(2-3).

9. The preparation method of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 according to claim 2, wherein in step (4), the Ti3C2Tx / rGO suspension, the Co-N compound solution, and the 2-methylimidazole solution have a volume ratio of (4-5):(3-4):(3-4).

10. Use of the Co-N / CNT / Ti3C2Tx / rGO composite catalyst for hydrogen production from KBH4 according to claim 1 in catalyzing the hydrogen production from an aqueous solution with a KOH concentration of 3% and a KBH4 concentration of 2% to 5%.