Fuel cell negative electrode catalyst and preparation method and application thereof

Abstract

The invention discloses a fuel cell negative electrode catalyst and a preparation method and application thereof, and belongs to the technical field of fuel cells. The preparation method comprises the following steps: S1, mixing glacial acetic acid and absolute ethyl alcohol, and dropwise adding butyl titanate to form a solution A; absolute ethyl alcohol and deionized water are mixed, CS / Cys-MWCNT is added, ultrasonic treatment is carried out, and a solution B is formed; dropwise adding the solution A into the solution B, then standing, aging, drying, carrying out heat treatment in a nitrogen atmosphere, and cooling to obtain TiO2 / CS / Cys-MWCNT; and S2, adding 0.05 mol / L of H2PtCl6 into ethylene glycol, then adding the TiO2 / CS / Cys-MWCNT obtained in the step S1, carrying out ultrasonic treatment for 1-2 hours, and carrying out heating reaction, centrifugation, washing and drying to obtain the negative electrode catalyst. The obtained catalyst shows the synergistic advantages of low initial potential, high peak current and high stability in the methanol oxidation reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fuel cells, in particular to a fuel cell negative electrode catalyst and a preparation method and application thereof. BACKGROUND

[0002] A fuel cell is a power generation device that converts chemical energy into electrical energy through electrochemical reactions. Fuel cells can be classified into alkaline fuel cells, solid oxide fuel cells, molten carbonate fuel cells, phosphoric acid fuel cells, and proton exchange membrane fuel cells according to the electrolyte used. Proton exchange membrane fuel cells, also known as polymer membrane fuel cells, are the fifth generation of fuel cells developed after alkaline fuel cells, solid oxide fuel cells, molten carbonate fuel cells, and phosphoric acid fuel cells.

[0003] Proton exchange membrane fuel cells (PEMFC) can be divided into two categories according to the fuel used: one is a fuel cell that uses hydrogen or reforming gas as fuel; the other is a fuel cell that directly uses methanol as fuel, also known as a direct methanol fuel cell (DMFC). Originally, a fuel cell that uses hydrogen / oxygen as fuel is the most ideal chemical power source, but a fuel cell that uses hydrogen / oxygen as fuel has safety issues during fuel preparation, transportation, storage, and use. Therefore, in recent years, the concept of a direct methanol fuel cell (DMFC) that directly uses methanol as fuel has been proposed. A direct methanol fuel cell (DMFC) does not need to convert methanol into hydrogen, but directly uses methanol as fuel for the positive electrode, and pure oxygen or air is used as the electrode active material for the negative electrode, and electrochemical reactions occur directly on the electrodes to convert chemical energy into electrical energy for use by the load. Compared with a fuel cell that uses hydrogen as fuel for the positive electrode and pure oxygen or air as the electrode active material for the negative electrode, a direct methanol fuel cell has the advantages of small size, light weight, simple structure, high reliability, easy fuel carrying and replenishment, and the like. In addition, a direct methanol fuel cell also has the functions of rapid start-up and fast response to load speed. Therefore, a direct methanol fuel cell is an ideal power source that can be used as a small household power station, a portable electronic appliance mobile power source, and a power source for electric vehicles, and has a broad application prospect.

[0004] Currently, Pt-based catalysts are the most widely used catalysts for methanol oxidation reactions due to their excellent catalytic activity, but they are easily deactivated due to the poisoning of intermediate species (CO-like), which reduces the durability of the catalysts. Patent CN118099455B describes a nitrogen-doped three-dimensional graphene-supported Pt-based catalyst and a preparation method and application thereof. In this patent, some GO nanosheets are converted into nitrogen-doped graphene, which improves the anchoring effect of the carrier on platinum particles and thus improves the stability of the catalyst. However, the electrocatalytic performance of this catalyst still needs to be improved. SUMMARY

[0005] The application provides a fuel cell negative electrode catalyst, a preparation method and application thereof, and can solve the problem that the electrocatalytic performance of a catalyst in the prior art needs to be improved.

[0006] The object of the application can be achieved by the following technical solutions. In a first aspect, the application provides a preparation method of a fuel cell negative electrode catalyst, comprising the following steps: S1, mixing glacial acetic acid and anhydrous ethanol, adding butyl titanate dropwise to form solution A; mixing anhydrous ethanol and deionized water, adding CS / Cys-MWCNT, and ultrasonicating to form solution B; adding solution A dropwise into solution B, and then standing, aging, drying, and heat treating under a nitrogen atmosphere to obtain TiO2 / CS / Cys-MWCNT; S2, adding 0.05 mol / L H2PtCl6 into ethylene glycol, and then adding TiO2 / CS / Cys-MWCNT obtained in step S1, ultrasonicating for 1-2 h, heat treating, centrifuging, washing, and drying to obtain a negative electrode catalyst.

[0007] Further, in step S1, the volume ratio of the glacial acetic acid, the anhydrous ethanol and the butyl titanate is 6:15:(5-6); the amount ratio of the anhydrous ethanol, the deionized water and the CS / Cys-MWCNT is 7 mL:10 mL:0.3 g; and the volume ratio of solution A to solution B is 1:1.

[0008] Further, in step S1, the heat treating under the nitrogen atmosphere is performed at a temperature of 600-700 DEG C for 2-3 h.

[0009] Further, in step S2, the amount ratio of H2PtCl6, ethylene glycol and TiO2 / CS / Cys-MWCNT is 1.5 mL:100-120 mL:1-1.4 g.

[0010] Further, in step S2, the heat treating is performed at a temperature of 150-170 DEG C for 3-4 h.

[0011] Further, the preparation method of the CS / Cys-MWCNT is as follows: S11, adding MWCNT into a mixed acid solution, ultrasonicating for 1-2 h, and then stirring at 55 DEG C for 6-7 h to obtain MWCNT-COOH; S12, dispersing MWCNT-COOH and L-cysteine in deionized water, and then adding EDC·HCl and NHS, stirring at room temperature for 22-24 h, centrifuging, washing, and drying to obtain Cys-MWCNT; S13, dissolve chitosan in 2% dilute acetic acid solution, stir for 12h, obtain CS solution; take Cys-MWCNT dispersed in deionized water, slowly add to the CS solution after ultrasonic for 30min, under the condition of condensation reflux, magnetically stir the mixed solution at 98℃ for 6h, after the mixed solution is cooled to room temperature, adjust the solution pH to 10 with dilute ammonia water, add glutaraldehyde, magnetically stir at 60℃ for 3h, wash, freeze-dry, obtain CS / Cys-MWCNT.

[0012] Further, in step S11, the use amount ratio of MWCNT to mixed acid solution is 2g:30-40mL; the mixed acid solution is composed of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1.

[0013] Further, in step S12, the use amount ratio of MWCNT-COOH, L-cysteine, deionized water, EDC·HCl and NHS is 0.2g:0.2-0.25g:50-60mL:1.2g:0.6g.

[0014] Further, in step S13, the use amount ratio of chitosan, dilute acetic acid solution, Cys-MWCNT, deionized water and glutaraldehyde is 0.8-1g:200mL:0.2g:20mL:1-1.2mL.

[0015] The second aspect of the present application provides a fuel cell negative catalyst, which is prepared by the preparation method in any one of the above contents.

[0016] The third aspect of the present application provides an application of the fuel cell negative catalyst in a direct methanol fuel cell.

[0017] The beneficial effects of the present application are: 1、The step S1 of the present application controls the hydrolysis rate of butyl titanate through the mixed system of glacial acetic acid and anhydrous ethanol, and realizes the in-situ controllable growth of TiO2 on the surface of double-modified carbon nanotubes by precise mixing with solution B containing CS / Cys-MWCNT, which not only utilizes the amino and mercapto functional groups of CS and Cys to form a stable complex with Ti 4+The coordination of the Cys ensures the uniform dispersion of the TiO2 nanoparticles and the formation of a firm interface between the MWCNT, and the TiO2 crystal form is optimized simultaneously through heat treatment in a nitrogen atmosphere, so that the composite carrier TiO2 / CS / Cys-MWCNT with high conductivity, rich anchoring sites and excellent stability is finally obtained; in step S2, H2PtCl6 is reduced in an ethylene glycol system, and the Pt precursor is uniformly adsorbed on the anchoring sites of the carrier through the reducing property and dispersing property of the ethylene glycol and 1-2h ultrasonic treatment, so that the controllable reduction and loading of Pt nanoparticles are realized under heating conditions, and finally the negative electrode catalyst with high Pt dispersity and strong metal-carrier interaction is obtained, which exhibits the synergistic advantages of low initial potential, high peak current and high stability in the methanol oxidation reaction.

[0018] 2. The CS / Cys-MWCNT prepared in the application is obtained by modifying the MWCNT with Cys, which improves the polarity of the MWCNT and the compatibility with chitosan (hydrophilicity), ensures the uniform coating of chitosan, provides a uniform substrate for subsequent glutaraldehyde crosslinking, and can form a uniform network structure, which is helpful to improve the electrocatalytic activity after subsequent sintering.

[0019] 3. The CS / Cys-MWCNT contains thiol and amino groups, which can serve as anchoring sites for Ti 4+ When the butyl titanate is condensed in situ to form TiO2, it grows around these anchoring sites, so that the uniform dispersion of TiO2 is realized and its own agglomeration is prevented, a stable conductive network is formed, the charge transfer resistance is greatly reduced, and the kinetic speed of the catalytic reaction is improved.

[0020] 4. After the in-situ polymerization of TiO2 on the CS / Cys-MWCNT, sintering can form a carrier doped with nitrogen and sulfur, the doping of nitrogen and sulfur elements can provide anchoring for the loading of Pt particles, strengthen the stability of the overall catalyst, and solve the problem of self-agglomeration of metal particles during the reduction process, reduce the CO stripping potential, and improve the poison resistance of the catalyst. The doping of nitrogen and sulfur elements can also improve the electrocatalytic performance of TiO2, the high conductivity of TiO2 plus the conductive network of CS / Cys-MWCNT can improve the electron transfer rate of the Pt active site, and accelerate the kinetics of the catalytic reaction. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application are described in detail below.

[0022] In a first aspect, the application provides a preparation method of a fuel cell negative electrode catalyst, comprising the following steps: S1, mixing glacial acetic acid and anhydrous ethanol, adding tetrabutyl titanate dropwise to form solution A; mixing anhydrous ethanol and deionized water, adding CS / Cys-MWCNT, ultrasonicating to form solution B; adding solution A dropwise into solution B, then standing, aging, drying, and heat treating under a nitrogen atmosphere to obtain TiO2 / CS / Cys-MWCNT; In the above steps, the hydrolysis rate of tetrabutyl titanate is delayed to form a stable solution A by solvation and chelation control of tetrabutyl titanate in a mixed system of glacial acetic acid and anhydrous ethanol; meanwhile, CS / Cys-MWCNT is uniformly dispersed and active functional groups such as surface thiol and amino groups are fully exposed by using the adaptability of the mixed solvent of anhydrous ethanol and deionized water in combination with ultrasonic dispersion to form solution B; after adding solution A dropwise into solution B, tetrabutyl titanate undergoes controllable hydrolysis to generate Ti 4+ under the synergistic action of the weak acid environment and the active functional groups of the carrier, and is anchored on the surface of CS / Cys-MWCNT through coordination, in-situ condensation is realized by standing and aging to form a uniformly dispersed TiO2 precursor, and subsequent drying and heat treatment under a nitrogen atmosphere not only completes the optimization of the crystal form of TiO2, but also enables the nitrogen source provided by CS and the sulfur source provided by Cys to be doped in-situ into the TiO2 crystal lattice and the carbon-based carrier, while part of the active functional groups on the surface of the carrier are retained, and finally a TiO2 / CS / Cys-MWCNT composite carrier with high conductivity, rich anchoring sites and excellent structural stability is obtained.

[0023] S2, adding 0.05 mol / L H2PtCl6 into ethylene glycol, then adding TiO2 / CS / Cys-MWCNT obtained in step S1, ultrasonicating for 1-2 h, heating and reacting, centrifuging, washing, and drying to obtain a negative electrode catalyst.

[0024] In the above steps, 0.05 mol / L H2PtCl6 is dissolved after ethylene glycol is used as a solvent and a reducing agent, and then TiO2 / CS / Cys-MWCNT composite carriers are added and ultrasonicated for 1-2 h, the active groups such as N / S doping sites on the surface of the carrier are fully exposed by using the cavitation and dispersion effect of ultrasonication, and then platinum ions in H2PtCl6 are precisely captured through coordination, realizing uniform adsorption of Pt precursors on the surface of the carrier; then under heating conditions, the adsorbed platinum ions are controllably reduced to Pt nanoparticles by ethylene glycol, and the dispersion of ethylene glycol can inhibit the agglomeration of Pt particles, and the interaction between the carrier and Pt enables the Pt nanoparticles to be firmly anchored on the surface of the carrier, and finally the unreacted precursors and byproducts are removed by centrifugation and washing, and a fuel cell negative electrode catalyst with high Pt dispersion, excellent electron transport efficiency, and strong structural stability is obtained after drying.

[0025] In some embodiments, in step S1, the volume ratio of the glacial acetic acid, anhydrous ethanol and butyl titanate is 6:15:(5-6); the dosage ratio of the anhydrous ethanol, deionized water and CS / Cys-MWCNT is 7 mL:10 mL:0.3 g; and the volume ratio of solution A to solution B is 1:1. The application precisely controls the dosage of the titanium source, and obtains the catalyst with the best catalytic effect. If the titanium source is excessive, TiO2 will be excessively coated on the surface of the CS / Cys-MWCNT, blocking the conductive network. If the titanium source is insufficient, the TiO2 loading is insufficient, and the corrosion resistance and anchoring auxiliary effect cannot be played. The volume ratio of 1:1 of solution A to solution B not only ensures that the CS / Cys-MWCNT is uniformly dispersed in the mixed system and the surface active functional groups are fully exposed, but also enables the TiO2 generated by the hydrolysis of butyl titanate to be efficiently coordinated with the functional groups of the CS / Cys-MWCNT, realizing the in-situ uniform growth of TiO2 on the surface of the CS / Cys-MWCNT. 4+ The volume ratio of 1:1 of solution A to solution B not only ensures that the CS / Cys-MWCNT is uniformly dispersed in the mixed system and the surface active functional groups are fully exposed, but also enables the TiO2 generated by the hydrolysis of butyl titanate to be efficiently coordinated with the functional groups of the CS / Cys-MWCNT, realizing the in-situ uniform growth of TiO2 on the surface of the CS / Cys-MWCNT.

[0026] In some embodiments, in step S1, the temperature of the heat treatment under a nitrogen atmosphere is 600-700 DEG C, and the time is 2-3 h. This can not only promote the full crystallization of the TiO2 precursor, but also realize the in-situ doping of CS (a nitrogen source) and Cys (a sulfur source), further strengthening the conductivity, structural stability and anchoring capacity of the composite carrier.

[0027] In some embodiments, in step S2, the dosage ratio of H2PtCl6, ethylene glycol and TiO2 / CS / Cys-MWCNT is 1.5 mL:100-120 mL:1-1.4 g. This can form an optimal ratio of the Pt precursor and the active sites of the carrier, ensuring the full adsorption and reduction of the Pt precursor, and avoiding the particle agglomeration caused by excessive Pt, while the sufficient dosage of ethylene glycol can take into account the reduction efficiency and dispersion effect, providing a guarantee for the high dispersion and high loading of Pt nanoparticles.

[0028] In some embodiments, in step S2, the temperature of the heating reaction is 150-170 DEG C, and the time is 3-4 h. This can accurately control the reduction rate of ethylene glycol, ensure that the platinum ions are smoothly reduced into Pt nanoparticles with uniform particle size, avoid particle agglomeration caused by high-temperature rapid reduction, and meanwhile, sufficient reaction time can strengthen the metal-carrier interaction between Pt and the carrier, make the Pt particles firmly anchored on the surface of the carrier, and improve the structural stability and catalytic activity of the catalyst.

[0029] In some embodiments, the preparation method of the CS / Cys-MWCNT is as follows: S11, MWCNT is added to a mixed acid solution, ultrasonic for 1-2 h, and then stirred at 55 DEG C for 6-7 h to obtain MWCNT-COOH; After adding MWCNT into mixed acid solution, ultrasonic treatment for 1-2 h can break the agglomerates of MWCNT, increase the contact area with mixed acid, and then stirring at 55℃ for 6-7 h, the strong oxidizing components in mixed acid can oxidize and etch the surface of MWCNT, introduce a large number of carboxyl groups (-COOH) on the graphitized skeleton, and remove the surface impurities and defective carbon, finally obtain MWCNT-COOH with rich active carboxyl groups on the surface and improved dispersion, which provides reaction sites for subsequent covalent grafting with L-cysteine.

[0030] S12, dispersing MWCNT-COOH and L-cysteine in deionized water, then adding EDC·HCl and NHS, stirring at room temperature for 22-24 h, centrifuging, washing, and drying to obtain Cys-MWCNT; After dispersing MWCNT-COOH and L-cysteine in deionized water, adding EDC HCl and NHS can activate the carboxyl groups on the surface of MWCNT-COOH, make them react with the amino groups in L-cysteine molecules to form stable amide bonds (-CONH-), and through stirring at room temperature for 22-24 h to ensure the reaction fully, after centrifuging, washing, and drying, realize the covalent grafting of L-cysteine on the surface of MWCNT, and obtain Cys-MWCNT rich in thiol groups (-SH).

[0031] S13, dissolving chitosan in 2% dilute acetic acid solution and stirring for 12 h to obtain CS solution; dispersing Cys-MWCNT in deionized water, slowly adding into the CS solution after ultrasonic treatment for 30 min, magnetically stirring the mixed solution at 98℃ for 6 h under the condition of condensation reflux, adjusting the pH of the solution to 10 with dilute ammonia water after the mixed solution is cooled to room temperature, adding glutaraldehyde, magnetically stirring at 60℃ for 3 h, washing, and freeze-drying to obtain CS / Cys-MWCNT.

[0032] First, dissolve chitosan in 2% dilute acetic acid solution and stir for 12 h to make the chitosan molecular chains fully stretch and disperse by the protonation of acetic acid, and form stable CS solution; disperse Cys-MWCNT in deionized water and slowly add into the CS solution after ultrasonic treatment for 30 min, under the condition of condensation reflux and magnetic stirring at 98℃ for 6 h, promote the formation of hydrogen bonds and electrostatic interactions between Cys-MWCNT and chitosan molecular chains by increasing the temperature, realize the uniform coating of chitosan; adjust the pH to 10 with dilute ammonia water after the mixed solution is cooled, to provide an alkaline environment for glutaraldehyde crosslinking, and the aldehyde groups (-CHO) of the added glutaraldehyde can react with the amino groups (-NH2) on the chitosan molecular chains to form Schiff base bonds, complete crosslinking and solidification by stirring at 60℃ for 3 h, and finally obtain CS / Cys-MWCNT composite carrier with stable structure and both thiol and amino active sites through washing and freeze-drying.

[0033] In some embodiments, in step S11, the amount ratio of the MWCNT to the mixed acid solution is 2g:30-40mL; the mixed acid solution is composed of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1. The mixed acid ratio of 3:1 of the concentrated sulfuric acid to the concentrated nitric acid and the amount can efficiently introduce abundant and uniform carboxyl groups on the surface of the carbon nanotube, provide high-density reaction sites for the subsequent covalent grafting of cysteine, and be the basis for constructing a stable functional interface.

[0034] In some embodiments, in step S12, the amount ratio of the MWCNT-COOH, L-cysteine, deionized water, EDC·HCl, and NHS is 0.2g:0.2-0.25g:50-60mL:1.2g:0.6g. This ratio ensures efficient amidation reaction of cysteine and carboxylated carbon nanotubes through the EDC / NHS catalytic system, successfully introduces the key functional groups, and creates conditions for subsequent chitosan crosslinking and metal anchoring.

[0035] In some embodiments, in step S13, the amount ratio of the chitosan, dilute acetic acid solution, Cys-MWCNT, deionized water, and glutaraldehyde is 0.8-1g:200mL:0.2g:20mL:1-1.2mL. This amount ratio enables chitosan to fully wrap the mercapto carbon nanotube and realize uniform and firm crosslinking between the two by using glutaraldehyde, forming a stable three-dimensional network structure.

[0036] In a second aspect, the present application provides a fuel cell negative electrode catalyst prepared by the preparation method described in any one of the above.

[0037] In a third aspect, the present application provides an application of a fuel cell negative electrode catalyst in a direct methanol fuel cell.

[0038] The specific embodiments of the present application are described in detail below, but it should be understood that the protection scope of the present application is not limited by the specific embodiments.

[0039] Preparation Example 1

[0040] In this preparation example, the preparation method of CS / Cys-MWCNT is as follows: S11, 2g of MWCNT is added to 30mL of a mixed acid solution composed of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1, ultrasonic treatment is performed for 1h, and then stirring reaction is performed at 55℃ for 6h to obtain MWCNT-COOH; S12, 0.2 g MWCNT-COOH and 0.2 g L-cysteine were dispersed in 50 mL deionized water, then 1.2 g EDC-HCl and 0.6 g NHS were added, stirred at room temperature for 22 h, centrifuged, washed, dried, and Cys-MWCNT was obtained; S13, 0.8 g chitosan was dissolved in 200 mL 2% dilute acetic acid solution, stirred for 12 h to obtain a CS solution; 0.2 g Cys-MWCNT was dispersed in 20 mL deionized water, and then slowly added to the CS solution after ultrasonic treatment for 30 min. The mixed solution was stirred at 98°C under magnetic stirring for 6 h under the condition of condensation reflux. After the mixed solution was cooled to room temperature, the pH of the solution was adjusted to 10 with dilute ammonia water, 1 mL glutaraldehyde was added, and the mixture was stirred at 60°C for 3 h. After washing and freeze-drying, CS / Cys-MWCNT was obtained.

[0041] Preparation Example 2

[0042] The preparation method of CS / Cys-MWCNT in this preparation example is as follows: S11, 2 g MWCNT was added to 35 mL mixed acid solution, the mixed acid solution was composed of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 3:1, and ultrasonic treatment was performed for 1.5 h, followed by stirring at 55°C for 6.5 h to obtain MWCNT-COOH; S12, 0.2 g MWCNT-COOH and 0.22 g L-cysteine were dispersed in 55 mL deionized water, then 1.2 g EDC-HCl and 0.6 g NHS were added, stirred at room temperature for 23 h, centrifuged, washed, dried, and Cys-MWCNT was obtained; S13, 0.9 g chitosan was dissolved in 200 mL 2% dilute acetic acid solution, stirred for 12 h to obtain a CS solution; 0.2 g Cys-MWCNT was dispersed in 20 mL deionized water, and then slowly added to the CS solution after ultrasonic treatment for 30 min. The mixed solution was stirred at 98°C under magnetic stirring for 6 h under the condition of condensation reflux. After the mixed solution was cooled to room temperature, the pH of the solution was adjusted to 10 with dilute ammonia water, 1.1 mL glutaraldehyde was added, and the mixture was stirred at 60°C for 3 h. After washing and freeze-drying, CS / Cys-MWCNT was obtained.

[0043] Preparation Example 3

[0044] The preparation method of CS / Cys-MWCNT in this preparation example is as follows: S11, 2 g MWCNT was added to 40 mL mixed acid solution, the mixed acid solution was composed of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 3:1, and ultrasonic treatment was performed for 2 h, followed by stirring at 55°C for 7 h to obtain MWCNT-COOH; S12, 0.2 g MWCNT-COOH and 0.25 g L-cysteine were dispersed in 60 mL deionized water, then 1.2 g EDC-HCl and 0.6 g NHS were added, stirred at room temperature for 24 h, centrifuged, washed, dried, and Cys-MWCNT was obtained; S13, 1 g chitosan was dissolved in 200 mL 2% dilute acetic acid solution, stirred for 12 h to obtain a CS solution; 0.2 g Cys-MWCNT was dispersed in 20 mL deionized water, and after ultrasonic treatment for 30 min, it was slowly added to the CS solution. Under the condition of condensation reflux, the mixed solution was magnetically stirred at 98°C for 6 h. After the mixed solution was cooled to room temperature, the pH of the solution was adjusted to 10 with dilute ammonia water, 1.2 mL glutaraldehyde was added, and the mixture was magnetically stirred at 60°C for 3 h. After washing and freeze-drying, CS / Cys-MWCNT was obtained.

[0045] Comparative Example 1

[0046] The difference between this comparative example and Preparation Example 1 is only that L-cysteine is omitted, and the specific steps are as follows: S11, 2 g MWCNT was added to 30 mL mixed acid solution, the mixed acid solution was composed of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 3:1, and ultrasonic treatment was performed for 1 h, followed by stirring at 55°C for 6 h to obtain MWCNT-COOH; S12, 0.8 g chitosan was dissolved in 200 mL 2% dilute acetic acid solution, stirred for 12 h to obtain a CS solution; 0.2 g MWCNT-COOH was dispersed in 20 mL deionized water, and after ultrasonic treatment for 30 min, it was slowly added to the CS solution. Under the condition of condensation reflux, the mixed solution was magnetically stirred at 98°C for 6 h. After the mixed solution was cooled to room temperature, the pH of the solution was adjusted to 10 with dilute ammonia water, 1 mL glutaraldehyde was added, and the mixture was magnetically stirred at 60°C for 3 h. After washing and freeze-drying, CS-MWCNT was obtained.

[0047] Comparative Example 2

[0048] The difference between this comparative example and Preparation Example 1 is only that L-cysteine and chitosan are omitted, and the specific steps are as follows: 2 g MWCNT was added to 30 mL mixed acid solution, the mixed acid solution was composed of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 3:1, and ultrasonic treatment was performed for 1 h, followed by stirring at 55°C for 6 h to obtain MWCNT-COOH.

[0049] Example 1

[0050] The present embodiment provides a preparation method of a fuel cell negative electrode catalyst, comprising the following steps: S1, 12 mL of glacial acetic acid and 30 mL of anhydrous ethanol were mixed, 10.5 mL of butyl titanate was added dropwise to form solution A; 7 mL of anhydrous ethanol and 10 mL of deionized water were mixed, 0.3 g of CS / Cys-MWCNT obtained in Preparation Example 1 was added, and ultrasonic was performed to form solution B; 10 mL of solution B was added dropwise into 10 mL of solution A, followed by standing, aging, drying, and heat treatment at 650°C under a nitrogen atmosphere for 2.5 h to obtain TiO2 / CS / Cys-MWCNT; S2, 1.5 mL of 0.05 mol / L H2PtCl6 was added to 110 mL of ethylene glycol, then 1.1 g of TiO2 / CS / Cys-MWCNT obtained in step S1 was added, ultrasonic was performed for 1.5 h, 160°C heat reaction was performed for 3.5 h, centrifugation, washing, and drying were performed to obtain the negative electrode catalyst.

[0051] Example 2

[0052] The embodiment provides a preparation method of a fuel cell negative electrode catalyst, comprising the following steps: S1, 12 mL of glacial acetic acid and 30 mL of anhydrous ethanol were mixed, 10.5 mL of butyl titanate was added dropwise to form solution A; 7 mL of anhydrous ethanol and 10 mL of deionized water were mixed, 0.3 g of CS / Cys-MWCNT obtained in Preparation Example 1 was added, and ultrasonic was performed to form solution B; 10 mL of solution B was added dropwise into 10 mL of solution A, followed by standing, aging, drying, and heat treatment at 650°C under a nitrogen atmosphere for 2.5 h to obtain TiO2 / CS / Cys-MWCNT; S2, 1.5 mL of 0.05 mol / L H2PtCl6 was added to 110 mL of ethylene glycol, then 1.1 g of TiO2 / CS / Cys-MWCNT obtained in step S1 was added, ultrasonic was performed for 1.5 h, 160°C heat reaction was performed for 3.5 h, centrifugation, washing, and drying were performed to obtain the negative electrode catalyst.

[0053] Example 3

[0054] The embodiment provides a preparation method of a fuel cell negative electrode catalyst, comprising the following steps: S1, 12 mL of glacial acetic acid and 30 mL of anhydrous ethanol were mixed, 10.5 mL of butyl titanate was added dropwise to form solution A; 7 mL of anhydrous ethanol and 10 mL of deionized water were mixed, 0.3 g of CS / Cys-MWCNT obtained in Preparation Example 1 was added, and ultrasonic was performed to form solution B; 10 mL of solution B was added dropwise into 10 mL of solution A, followed by standing, aging, drying, and heat treatment at 650°C under a nitrogen atmosphere for 2.5 h to obtain TiO2 / CS / Cys-MWCNT; S2, 1.5 mL of 0.05 mol / L H2PtCl6 was added to 110 mL of ethylene glycol, then 1.3 g of TiO2 / CS / Cys-MWCNT obtained in step S1 was added, ultrasonic treatment was performed for 1.5 h, reaction was performed at 160°C for 3.5 h, centrifugation, washing, drying were performed, and a cathode catalyst was obtained.

[0055] Example 4

[0056] The present example provides a method for preparing a fuel cell cathode catalyst, comprising the following steps: S1, 12 mL of glacial acetic acid and 30 mL of anhydrous ethanol were mixed, 12 mL of tetrabutyl titanate was added dropwise to form solution A; 7 mL of anhydrous ethanol and 10 mL of deionized water were mixed, 0.3 g of CS / Cys-MWCNT obtained in Preparation Example 3 was added, ultrasonic treatment was performed, and solution B was formed; 10 mL of solution A was added dropwise to 10 mL of solution B, followed by standing, aging, drying, and heat treatment at 700°C under a nitrogen atmosphere for 3 h to obtain TiO2 / CS / Cys-MWCNT; S2, 1.5 mL of 0.05 mol / L H2PtCl6 was added to 110 mL of ethylene glycol, then 1.3 g of TiO2 / CS / Cys-MWCNT obtained in step S1 was added, ultrasonic treatment was performed for 1.5 h, reaction was performed at 160°C for 3.5 h, centrifugation, washing, drying were performed, and a cathode catalyst was obtained.

[0057] Example 5

[0058] The present example provides a method for preparing a fuel cell cathode catalyst, comprising the following steps: S1, 12 mL of glacial acetic acid and 30 mL of anhydrous ethanol were mixed, 12 mL of tetrabutyl titanate was added dropwise to form solution A; 7 mL of anhydrous ethanol and 10 mL of deionized water were mixed, 0.3 g of CS / Cys-MWCNT obtained in Preparation Example 3 was added, ultrasonic treatment was performed, and solution B was formed; 10 mL of solution A was added dropwise to 10 mL of solution B, followed by standing, aging, drying, and heat treatment at 700°C under a nitrogen atmosphere for 3 h to obtain TiO2 / CS / Cys-MWCNT; S2, 1.5 mL of 0.05 mol / L H2PtCl6 was added to 120 mL of ethylene glycol, then 1.4 g of TiO2 / CS / Cys-MWCNT obtained in step S1 was added, ultrasonic treatment was performed for 2 h, reaction was performed at 170°C for 4 h, centrifugation, washing, drying were performed, and a cathode catalyst was obtained.

[0059] Comparative Example 1

[0060] The present comparative example is different from Example 1 only in that an equal amount of CS-MWCNT obtained in Comparative Example 1 is used to replace CS / Cys-MWCNT obtained in Preparation Example 1.

[0061] Comparative Example 2

[0062] The present comparative example is compared with Example 1, the only difference being that the CS / Cys-MWCNT obtained from Preparation Example 1 is replaced with an equal amount of MWCNT-COOH obtained from Comparative Example 2.

[0063] Comparative Example 3

[0064] The present comparative example is compared with Example 1, the only difference being that "10 mL of butyl titanate" in Step S1 is modified to "9 mL of butyl titanate".

[0065] Comparative Example 4

[0066] The present comparative example is compared with Example 5, the only difference being that "12 mL of butyl titanate" in Step S1 is modified to "13 mL of butyl titanate".

[0067] The electrocatalytic performance of the catalysts obtained from Examples 1-5 and Comparative Examples 1-4 for the electrochemical oxidation of methanol is characterized by cyclic voltammetry and chronoamperometry at room temperature. 5 mg of catalyst, 100 mg of Nafion solution and 250 mg of deionized water are mixed uniformly by ultrasonic treatment, 2.0 μL is taken by a pipette and coated on a glassy carbon electrode, and the working electrode is obtained after drying in an 80°C oven for 5 minutes. A saturated calomel electrode (SCE) is used as the reference electrode and a platinum electrode is used as the counter electrode. The electrolyte solution is a 2 mol / L CH3OH + 1 mol / L H2SO4 aqueous solution. Cyclic voltammetry is used to activate 5 cycles at a scan rate of 50 mV / s in the range of 0-1.0 V, and the onset potential and peak current for methanol oxidation are tested; chronoamperometry is used to monitor the current change at a fixed potential of 0.4 V for 1 hour, and the above test results are shown in Table 1.

[0068] Table 1

[0069] As can be seen from Table 1, the catalytic performance and stability of the catalysts prepared in Examples 1-5 are higher than those of the comparative examples. In Comparative Example 1, cysteine is omitted, and the catalytic performance and stability are lower than those of Example 1, indicating that the sulfhydryl group of cysteine can act as an anchoring site for Ti 4+ , and when butyl titanate condenses in situ to form TiO2, it grows around these anchoring sites, ultimately achieving uniform dispersion of TiO2, preventing its own agglomeration, forming a stable conductive network, greatly reducing the charge transfer resistance, and thus improving the kinetic speed of the catalytic reaction. Moreover, cysteine can achieve sulfur doping, providing anchoring for the Pt particle loading while also improving the electrocatalytic performance of TiO2.

[0070] Comparative Example 2 omits cysteine and chitosan, and its stability is lower than that of Example 1, indicating that the carriers obtained by the application have a synergistic effect of promoting the electrocatalytic performance.

[0071] Comparative Example 3 has too little titanium source, and Comparative Example 4 has too much titanium source, and their performances are lower than those of Example 1 and Example 5, respectively, indicating that the application precisely controls the amount of titanium source, and the catalyst with the best catalytic effect is obtained. If the titanium source is excessive, TiO2 will be excessively coated on the surface of CS / Cys-MWCNT, blocking the conductive network. If the titanium source is insufficient, the TiO2 loading is insufficient, and it cannot play its corrosion resistance and anchoring auxiliary role.

[0072] The above disclosure is only a few specific embodiments of the application, but the embodiments of the application are not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the protection scope of the application.

Claims

1. A method for producing a fuel cell negative electrode catalyst, characterized by, The preparation method comprises the following steps: S1, mixing glacial acetic acid and anhydrous ethanol, adding butyl titanate dropwise to form solution A; mixing anhydrous ethanol and deionized water, adding CS / Cys-MWCNT, and ultrasonicating to form solution B; adding solution A dropwise into solution B, and then standing, aging, drying, and heat treating under a nitrogen atmosphere to obtain TiO2 / CS / Cys-MWCNT; S2, adding 0.05 mol / L H2PtCl6 into ethylene glycol, adding TiO2 / CS / Cys-MWCNT obtained in step S1, ultrasonicating for 1-2 h, heat treating, centrifuging, washing, and drying to obtain a negative electrode catalyst.

2. The method for producing a fuel cell negative electrode catalyst according to claim 1, characterized by, In step S1, the volume ratio of glacial acetic acid, anhydrous ethanol, and butyl titanate is 6:15:(5-6). The amount ratio of anhydrous ethanol, deionized water, and CS / Cys-MWCNT is 7 mL:10 mL:0.3 g. The volume ratio of solution A and solution B is 1:

1.

3. The method for producing a fuel cell negative electrode catalyst according to claim 1, characterized by, In step S1, the heat treating temperature under a nitrogen atmosphere is 600-700 ℃, and the time is 2-3 h.

4. The method for producing a fuel cell negative electrode catalyst according to Claim 1, characterized by, In step S2, the amount ratio of H2PtCl6, ethylene glycol, and TiO2 / CS / Cys-MWCNT is 1.5 mL:100-120 mL:1-1.4 g. The heat treating temperature is 150-170 ℃, and the time is 3-4 h.

5. The method for producing a fuel cell negative electrode catalyst according to Claim 1, characterized by, The preparation method of the CS / Cys-MWCNT is as follows: S11, adding MWCNT into a mixed acid solution, ultrasonicating for 1-2 h, and then stirring at 55 ℃ for 6-7 h to obtain MWCNT-COOH; S12, dispersing MWCNT-COOH and L-cysteine in deionized water, then adding EDC·HCl and NHS, stirring at room temperature for 22-24 h, centrifuging, washing, and drying to obtain Cys-MWCNT; S13, dissolving chitosan in a 2% acetic acid solution, stirring for 12 h to obtain a CS solution; dispersing Cys-MWCNT in deionized water, ultrasonicating for 30 min, and then slowly adding into the CS solution; under the condition of condensation reflux, magnetically stirring the mixed solution at 98 ℃ for 6 h; after the mixed solution is cooled to room temperature, adjusting the pH of the solution to 10 with dilute ammonia water, and adding glutaraldehyde, magnetically stirring at 60 ℃ for 3 h, washing, and freeze-drying to obtain CS / Cys-MWCNT.

6. The method for producing a fuel cell negative electrode catalyst according to claim 5, characterized by, In step S11, the amount ratio of MWCNT and the mixed acid solution is 2 g:30-40 mL; the mixed acid solution is composed of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:

1.

7. The method for producing a fuel cell negative electrode catalyst according to claim 5, characterized by, In step S12, the amount ratio of MWCNT-COOH, L-cysteine, deionized water, EDC·HCl, and NHS is 0.2 g:0.2-0.25 g:50-60 mL:1.2 g:0.6 g.

8. The method for producing a fuel cell negative electrode catalyst according to Claim 5, characterized by, In step S13, the amount ratio of chitosan, the dilute acetic acid solution, Cys-MWCNT, deionized water, and glutaraldehyde is 0.8-1 g:200 mL:0.2 g:20 mL:1-1.2 mL.

9. A fuel cell negative electrode catalyst, characterized by, The preparation method is made by any one of claims 1-8.

10. Use of a fuel cell negative catalyst according to claim 9 in a direct methanol fuel cell.

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