CN112133926A - Preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst - Google Patents

Abstract

The invention provides a method for preparing a platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst, and relates to the field of electrode catalysts. Titanium nanosheets, then ultrasonically disperse the titanium carbide nanosheets in ethylene glycol solution, add graphene oxide to it, perform ultrasonic mixing again, then add platinum salt solution, stir to fully mix, and then perform hydrothermal reaction, A hydrogel-like product is obtained, washed with water by dialysis, and freeze-dried to obtain a platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst. The invention uses titanium carbide nanosheets and graphene as templates, and deposits crystalline platinum nanoparticles on the surfaces thereof, and the prepared composite electrode catalyst has the advantages of three-dimensional porous structure, high catalytic activity and high toxicity resistance.

Description

Preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst

technical field

The present invention relates to a preparation method of an electrode catalyst, in particular, to a preparation method of a platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst.

Background technique

With the increasingly prominent problems of energy crisis and environmental pollution in today's world, the development of efficient and clean energy production systems is of great practical significance for the sustainable development of modern society. Direct methanol fuel cells have attracted extensive attention due to their high energy density, low pollution emissions, simple structure, and easy fuel storage. Metal platinum is recognized as the best catalyst material for methanol oxidation, but the high price and easy poisoning properties of platinum hinder its large-scale commercial application to a great extent. Therefore, the synthesis of new composite platinum-based catalysts with high catalytic activity, high anti-toxicity and other excellent properties and relatively low cost can effectively promote the commercialization of direct methanol fuel cells.

Transition metal carbides or carbon/nitride _MXenes are a new member of the family of two-dimensional materials, _two -dimensional _Ti3C2Tx nanosheets, which are structurally similar to graphene, with good hydrophilicity and unique electrochemical properties. Studies have shown that Ti ₃ C ₂ T _x nanosheets can be used as a carrier material to improve the utilization efficiency of metallic platinum, which is mainly based on: (1) Ti ₃ C ₂ T _x nanosheets have a large specific surface area, and the surface of the material has a large number of -OH and -F functional groups, which provide abundant growth sites for the deposition of noble metal particles; ( _{2 ) the good electrical conductivity of Ti3C2Tx nanosheets} can reduce the charge transfer resistance of the catalyst, thereby further improving the composite The electrocatalytic activity of the system; (3) Ti ₃ C ₂ T _x nanosheets can tune the electronic structure of metal platinum, improve its intrinsic electrocatalytic activity, and enhance the anti-poisoning of metal platinum to reaction by-products (mainly CO) ability. So far, some studies have directly supported Pt nanoparticles on the surface of graphene or titanium carbide nanosheets to synthesize platinum/graphene or platinum/titanium carbide nanosheet catalysts (Li Y, Gao W, et al. Catalytic performance of Ptnanoparticles on reduced graphene oxide for methanol electro-oxidation, Carbon, 2010, 48, 1124-1130; Wang Y, Wang J, et al. Pt decorated Ti ₃ C ₂ MXene forenhanced methanol oxidation reaction, Ceramics International, 2019, 45, 2411-2417) , and the use of graphene and titanium carbide nanosheets to build a three-dimensional composite carrier and to support platinum nanoparticles has not been reported yet.

Chinese Patent No. CN201710324833.7 discloses a preparation method of a two-dimensional titanium carbide/carbon nanotube-supported platinum particle composite material. The _two -dimensional titanium carbide is prepared by chemically exfoliating the aluminum atomic layer in _Ti3AlC2 by using HF. The solvothermal method makes Two-dimensional titanium carbide is combined with MWNTs and loaded with platinum nanoparticles to obtain Ti ₃ C ₂ /MWNTs-Pt nanocomposites; however, similar to other two-dimensional sheet materials in structure, Ti ₃ C ₂ nanosheets have different lamellae. Due to the strong attraction between them, they are prone to agglomeration and stacking, and the interlayer spacing is small. These problems greatly limit the transport speed of electrolyte ions in the material, and will cause part of the reactive sites to be covered. While reducing the catalytic efficiency, the electrochemical activity of Ti ₃ C ₂ /MWNTs-Pt nanocomposites is seriously reduced.

Therefore, developing a new preparation method to reduce the stacking of _{Ti3C2 nanosheets} in the composite system, so that its unique advantages can be effectively exerted in the field of electrocatalysis, has become the focus and difficulty of the work.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned defects and deficiencies in the prior art, the present invention provides a method for preparing a platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst. The method uses titanium carbide nanosheets and graphene as templates, and Crystal platinum nanoparticles are deposited on its surface, and the prepared composite electrode catalyst has the advantages of three-dimensional porous structure, high catalytic activity and high anti-toxicity.

The preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst comprises the following steps:

S1, prepare titanium carbide nanosheet dispersion;

S2, adding graphene oxide to the titanium carbide nanosheet dispersion liquid of step S1, and ultrasonically dispersing to obtain a titanium carbide nanosheet/graphene oxide binary composite solution, wherein the amount of graphene oxide and titanium carbide added is by mass ratio Calculated as 1~9: 1~9;

S3, adding potassium chloroplatinite solution to the binary composite solution of step S2, stirring evenly, to obtain potassium chloroplatinite/titanium carbide nanosheet/graphene oxide ternary composite solution, the chloroplatinite The addition amount of platinum element and titanium carbide nanosheet/graphene oxide binary composite in the potassium solution is 1-20:1-20 in mass ratio;

S4, the ternary compound solution of step S3 is carried out hydrothermal reaction to obtain hydrogel-like product, then dialysate washing, freeze-drying, promptly obtain platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst.

In the present invention, titanium carbide and graphene oxide are used as carriers, platinum is used as catalyst, two-dimensional titanium carbide is generated by chemical etching method, and the two-dimensional titanium carbide sheet is peeled off by ultrasonic to obtain single-layer or few-layer titanium carbide nano-sheets, and then carbonization is prepared. The mixed solution of titanium nanosheets and graphene oxide is then added with potassium chloroplatinite solution, and platinum ions are adsorbed on the surface of titanium carbide through ion exchange with oxygen-containing functional groups on the surface of titanium carbide. Graphene oxide is combined, and at the same time, with the increase of temperature, platinum ions are reduced to platinum nanoparticles supported in the three-dimensional pores formed by titanium carbide nanosheets and graphene oxide.

A "bottom-up" synthesis method was used to self-assemble graphene and titanium carbide nanosheets together into a three-dimensional porous hybrid aerogel structure. The microporous channels in the three-dimensional porous network framework of graphene-titanium carbide nanosheets formed mutual The connected microporous network can not only facilitate the dispersion of platinum metal nanoparticles, but also its unique pore structure is conducive to the formation of more electrochemically active sites, and also enables the external electrolyte to easily enter the material. The fast ion transfer capability and efficient electrochemically active surface are beneficial to obtain better electrochemical properties. In contrast, the tight and dense 2D structure of the directly stacked 2D layered titanium carbide greatly limits the rapid transport of electrolyte ions in the material and severely reduces the catalytic performance of the material; The electrochemical performance of the three-dimensional porous network framework constructed by the like material is better.

Further, in step S2, the amount of graphene oxide and titanium carbide added is 1-4:5-9 in terms of mass ratio.

Further, in step S3, the addition amount of platinum element and titanium carbide nanosheet/graphene oxide binary composite in the potassium chloroplatinite solution is 1:4～9 by mass ratio.

Further, in step S3, the stirring conditions are: stirring at a temperature of 0-50° C. for 0.2-5 h.

Further, in step S4, the hydrothermal reaction conditions are: placing the hydrothermal reaction at a temperature of 80-120° C. for 8-14 hours.

Further, in step S4, the dialysis water washing time is 3-10 d, and the drying pressure during the freeze-drying is 0-200 Pa.

Further, the step S1 to prepare the titanium carbide nanosheet dispersion specifically includes the following steps:

P1, use lithium fluoride and hydrochloric acid to etch carbon-aluminum-titanium, and then centrifugally wash with water to obtain a multi-layer titanium carbide precipitate;

P2, add a small amount of distilled water to the multi-layer titanium carbide precipitate, ultrasonically peel off and freeze-dry to obtain monolayer or few-layer titanium carbide nanosheets;

P3, dissolving the titanium carbide nanosheets in an ethylene glycol solution, and ultrasonically dispersing to obtain a titanium carbide nanosheet dispersion.

Further, in step P1, the etching reaction conditions are as follows: the etching reaction time is 24-60 h, the reaction temperature is 10-50° C., and the concentration of hydrochloric acid is 6-12 mol/L.

Further, in step P1, the centrifugal washing conditions are as follows: the centrifugal speed is 3500-8000 rpm, and the water washing is performed until the pH of the supernatant is close to neutral.

Further, in step P2, the ultrasonic peeling conditions are as follows: the ultrasonic peeling time is 0.5-6 h, the protective gas argon is continuously introduced during ultrasonication, and after the ultrasonication is completed, it is subjected to centrifugal screening at 5000-8000 rpm rotating speed, and the centrifugal supernatant is taken. The liquid is freeze-dried to obtain monolayer or few-layer titanium carbide nanosheets.

Further, in step P3, the concentration of the titanium carbide nanosheet dispersion liquid is 0.1-10 g/L.

Further, in step P3 and step S1, the ultrasonic conditions are as follows: ultrasonic time is 0.5-6 h, and ultrasonic temperature is 0-50°C.

Beneficial technical effect achieved by the present invention:

1. The preparation method of the platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst provided by the present invention, the prepared electrode catalyst has the advantages of high catalytic activity, three-dimensional porous structure, good stability, high anti-toxicity and high utilization rate of precious metals ; The platinum/titanium carbide nanosheet/graphene ternary composite electrode catalyst prepared by the invention has good application prospects and economic benefits in the fields of direct methanol fuel cells and the like.

2. The preparation method provided by the present invention is simple and controllable, has good repeatability and low cost, and is favorable for large-scale industrial production.

Description of drawings

Fig. 1 is a schematic flow diagram of the present invention;

Figure 2 is an external view of the gel-like product of Example 3 of the present invention;

The X-ray diffraction (XRD) pattern (Fig. A) and the Raman spectrogram (Fig. B) of the platinum/titanium carbide nanosheet/graphene composite electrode catalyst prepared by the method of the embodiment of the present invention 3;

The Field Emission Scanning Electron Microscope (FE-SEM) photo of the platinum/titanium carbide nanosheet/graphene composite electrode catalyst prepared by the method of Embodiment 3 of the present invention;

The transmission electron microscope (TEM) photo of the platinum/titanium carbide nanosheet/graphene composite electrode catalyst prepared by the method of the embodiment of the present invention 3;

The nitrogen adsorption-desorption curve diagram of the platinum/titanium carbide nanosheet/graphene composite electrode catalyst prepared by the method of the embodiment of the present invention 3;

7 platinum/titanium carbide nanosheets/graphene composite electrode catalyst (Pt/G-Ti ₃ C ₂ T _x ) and platinum/titanium carbide nano sheets (Pt/Ti ₃ C ₂ ) prepared by the method of Example 3 of the present invention Cyclic voltammetry curves of T _x ), platinum/graphene (Pt/G), platinum/carbon nanotubes (Pt/CNT) and platinum/carbon black (Pt/C) materials in 0.5mol/LH ₂ SO ₄ solution ( Figure 7A) and the cyclic voltammetry curves in 0.5mol/LH ₂ SO ₄ and 0.5mol/L CH ₃ OH mixed solution (Figure 7B);

Fig. 8 The platinum/titanium carbide nanosheet/graphene composite electrode catalyst (Pt/G-Ti ₃ C ₂ T _x ) and the platinum/titanium carbide nano sheet (Pt/Ti ₃ C ₂ ) prepared by the method of Example 3 of the present invention Potentiostatic oxidation tests of T _x ), platinum/graphene (Pt/G), platinum/carbon nanotubes (Pt/CNT) and platinum/carbon black (Pt/C) materials (Fig. 8A); chronopotentiodynamic test curves ( Figure 8B).

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in Figure 1, a preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst, comprising the following steps:

S1, prepare titanium carbide nanosheet dispersion;

S2, adding graphene oxide to the titanium carbide nanosheet dispersion in step S1, the amount of graphene oxide and titanium carbide added is 1-9:9-1 in terms of mass ratio, and ultrasonicating at a temperature of 0-50 °C Disperse for 0.5 to 6 hours to obtain a titanium carbide nanosheet/graphene oxide binary composite solution;

S3, adding potassium chloroplatinite solution to the binary composite solution of step S4, the addition amount of platinum element and titanium carbide nanosheet/graphene oxide binary composite in the potassium chloroplatinite solution is by mass ratio Calculated as 1～20:1～20, stir at 0～50℃ for 0.2～5h to obtain potassium chloroplatinite/titanium carbide nanosheet/graphene oxide ternary composite solution;

S4. The ternary complex solution of step S3 is placed in a hydrothermal reaction at a temperature of 80 to 120° C. for 8 to 14 hours to obtain a hydrogel-like product, which is then dialyzed and washed for 3 to 10 days, freeze-dried, and the drying pressure is 0 to 200 Pa, that is, A platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst is obtained.

The step S1 to prepare the titanium carbide nanosheet dispersion specifically includes the following steps:

P1. Use lithium fluoride and hydrochloric acid to etch carbon-aluminum-titanium, the etching reaction time is 24～60h, the reaction temperature is 10～50℃, and the concentration of hydrochloric acid is 6～12mol/L; then centrifuge at 3500～8000rpm , washed with water until the pH of the supernatant is close to neutral, to obtain a multi-layered titanium carbide precipitate;

P2. Add a small amount of distilled water to the multi-layer titanium carbide precipitate, and ultrasonically peel it off for 0.5-6h. While ultrasonicating, the protective gas argon is continuously introduced, and after the ultrasonication is completed, it is screened by centrifugation at 5000-8000 rpm, and the centrifugal supernatant is taken. Liquid freeze-drying to obtain monolayer or few-layer titanium carbide nanosheets;

P3. Dissolving the titanium carbide nanosheets in an ethylene glycol solution, and ultrasonically dispersing them at a temperature of 0 to 50°C for 0.5 to 6 hours to obtain a dispersion of 0.1 to 10 g/L of titanium carbide nanosheets;

Example 1

A preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst, comprising the following steps:

S1, prepare titanium carbide nanosheet dispersion;

S2, adding graphene oxide to the titanium carbide nanosheet dispersion in step S1, the amount of graphene oxide and titanium carbide added is 9:1 by mass ratio, and ultrasonically dispersing at a temperature of 10 ° C for 1 hour to obtain titanium carbide Nanosheet/graphene oxide binary composite solution;

S3, adding potassium chloroplatinite solution to the binary composite solution of step S2, the addition amount of platinum element and titanium carbide nanosheet/graphene oxide binary composite in the potassium chloroplatinite solution is by mass ratio Calculated as 1:9, and stirred at 20 °C for 40 min to obtain a potassium chloroplatinite/titanium carbide nanosheet/graphene oxide ternary composite solution;

S4. The ternary composite solution of step S3 is placed in a hydrothermal reaction at a temperature of 120° C. for 11 hours to obtain a hydrogel-like product, which is then dialyzed and washed with water for 4 days, freeze-dried, and the drying pressure is 200 Pa, to obtain platinum/titanium carbide nanosheets/ Graphene three-dimensional composite electrode catalyst.

The step S1 to prepare the titanium carbide nanosheet dispersion specifically includes the following steps:

P1. Use lithium fluoride and hydrochloric acid to etch carbon-aluminum-titanium, the etching reaction time is 24h, the reaction temperature is 25°C, and the concentration of hydrochloric acid is 6mol/L; then centrifuge at 5000rpm and wash with water until the pH of the supernatant is close to medium to obtain multi-layer titanium carbide precipitates;

P2. Add a small amount of distilled water to the multi-layer titanium carbide precipitate, and ultrasonically peel it off for 1 h. While ultrasonicating, the protective gas argon is continuously introduced, and after the ultrasonication is completed, it is centrifuged and screened at 7000 rpm, and the centrifugal supernatant is taken and freeze-dried. Obtain single-layer or few-layer titanium carbide nanosheets;

P3, dissolving the titanium carbide nanosheets in an ethylene glycol solution, and ultrasonically dispersing at a temperature of 10° C. for 1 hour to obtain a 5g/L titanium carbide nanosheet dispersion.

Example 2

A preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst, comprising the following steps:

S1, prepare titanium carbide nanosheet dispersion;

S2, adding graphene oxide to the titanium carbide nanosheet dispersion in step S1, and the amount of graphene oxide and titanium carbide added is 4:5 in mass ratio; ultrasonically dispersing at 30°C for 3 hours to obtain titanium carbide Nanosheet/graphene oxide binary composite solution;

S3, adding potassium chloroplatinite solution to the binary composite solution of step S2, the addition amount of platinum element and titanium carbide nanosheet/graphene oxide binary composite in the potassium chloroplatinite solution is by mass ratio Calculated as 1:7, and stirred at 10 °C for 30 min to obtain a potassium chloroplatinite/titanium carbide nanosheet/graphene oxide ternary composite solution;

S4. The ternary complex solution of step S3 is placed in a hydrothermal reaction at a temperature of 100 ° C for 10 hours to obtain a hydrogel product, as shown in Figure 2, and then dialyzed and washed with water for 5 days, freeze-dried, and the drying pressure is 100Pa, that is, platinum/carbonized products are obtained Titanium nanosheet/graphene three-dimensional composite electrode catalyst.

The step S1 to prepare the titanium carbide nanosheet dispersion specifically includes the following steps:

P1. Use lithium fluoride and hydrochloric acid to etch carbon-aluminum-titanium, the etching reaction time is 36h, the reaction temperature is 35°C, and the concentration of hydrochloric acid is 9mol/L; then centrifuge at 6000rpm, and wash with water until the pH of the supernatant is close to medium to obtain multi-layer titanium carbide precipitates;

P2. Add a small amount of distilled water to the multi-layer titanium carbide precipitate, and ultrasonically peel it off for 1 h. While ultrasonicating, the protective gas argon is continuously introduced, and after the ultrasonication is completed, it is centrifuged at 8000 rpm for screening, and the centrifugal supernatant is taken and freeze-dried. Obtain single-layer or few-layer titanium carbide nanosheets;

P3, dissolving the titanium carbide nanosheets in an ethylene glycol solution, and ultrasonically dispersing at a temperature of 30° C. for 3 hours to obtain a 5g/L titanium carbide nanosheet dispersion.

Example 3

A preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst, comprising the following steps:

S1, prepare titanium carbide nanosheet dispersion;

S2, adding graphene oxide to the titanium carbide nanosheet dispersion in step S1, the amount of graphene oxide and titanium carbide added is 3:7 in mass ratio, and ultrasonically dispersing at 0°C for 0.5h to obtain carbonization Titanium nanosheet/graphene oxide binary composite solution;

S3, adding potassium chloroplatinite solution to the binary composite solution of step S2, the addition amount of platinum element and titanium carbide nanosheet/graphene oxide binary composite in the potassium chloroplatinite solution is by mass ratio Calculated as 1:4, and stirred at 10 °C for 30 min to obtain a potassium chloroplatinite/titanium carbide nanosheet/graphene oxide ternary composite solution;

S4. The ternary complex solution of step S3 is placed in a hydrothermal reaction at a temperature of 100° C. for 10 hours to obtain a hydrogel-like product, as shown in Figure 2, and then dialyzed and washed with water for 5d, freeze-dried, and the drying pressure is 25Pa, that is, platinum/carbonized products are obtained. Titanium nanosheet/graphene three-dimensional composite electrode catalyst.

The step S1 to prepare the titanium carbide nanosheet dispersion specifically includes the following steps:

P1. Use lithium fluoride and hydrochloric acid to etch carbon-aluminum-titanium, the etching reaction time is 36h, the reaction temperature is 35°C, and the concentration of hydrochloric acid is 9mol/L; then centrifuge at 6000rpm, and wash with water until the pH of the supernatant is close to medium to obtain multi-layer titanium carbide precipitates;

P2. Add a small amount of distilled water to the multi-layer titanium carbide precipitate, and ultrasonically peel it off for 1 h. While ultrasonicating, the protective gas argon is continuously introduced, and after the ultrasonication is completed, it is centrifuged at 8000 rpm for screening, and the centrifugal supernatant is taken and freeze-dried. Obtain single-layer or few-layer titanium carbide nanosheets;

P3. Dissolving titanium carbide nanosheets in ethylene glycol solution, ultrasonically dispersing at 0°C for 0.5h, to obtain 5g/L titanium carbide nanosheet dispersion.

Example 4

The difference between Example 4 and Example 3 is that, in step S2, the added amount of graphene oxide and titanium carbide is 1:5 by mass ratio; ultrasonically dispersed for 2h at a temperature of 0°C.

Example 5

A preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst, comprising the following steps:

S1, prepare titanium carbide nanosheet dispersion;

S2, adding graphene oxide to the titanium carbide nanosheet dispersion in step S1, the amount of graphene oxide and titanium carbide added is 1:9 by mass ratio, and ultrasonically dispersing at a temperature of 20 ° C for 4 hours to obtain titanium carbide Nanosheet/graphene oxide binary composite solution;

S3, adding potassium chloroplatinite solution to the binary composite solution of step S2, the addition amount of platinum element and titanium carbide nanosheet/graphene oxide binary composite in the potassium chloroplatinite solution is by mass ratio Calculated as 9:1, and stirred at 0 °C for 60 min to obtain a potassium chloroplatinite/titanium carbide nanosheet/graphene oxide ternary composite solution;

S4. The ternary complex solution of step S3 is placed in a hydrothermal reaction at a temperature of 80° C. for 12 hours to obtain a hydrogel-like product, which is then dialyzed and washed with water for 5 d, freeze-dried, and the drying pressure is 25 Pa to obtain platinum/titanium carbide nanosheets/ Graphene three-dimensional composite electrode catalyst.

The step S1 to prepare the titanium carbide nanosheet dispersion specifically includes the following steps:

P1. Use lithium fluoride and hydrochloric acid to etch carbon-aluminum-titanium, the etching reaction time is 60h, the reaction temperature is 45°C, and the concentration of hydrochloric acid is 10mol/L; then centrifuge at 6000rpm, and wash with water until the pH of the supernatant is close to medium properties, to obtain multi-layer titanium carbide precipitates;

P2. Add a small amount of distilled water to the multi-layered titanium carbide precipitate, and ultrasonically peel it for 2 hours. While ultrasonicating, the protective gas argon is continuously introduced, and after the ultrasonication is completed, it is centrifuged at 5000 rpm for screening, and the centrifugal supernatant is taken and freeze-dried. Obtain single-layer or few-layer titanium carbide nanosheets;

P3, dissolving the titanium carbide nanosheets in an ethylene glycol solution, and ultrasonically dispersing at a temperature of 20° C. for 4 hours to obtain a titanium carbide nanosheet dispersion of 8 g/L.

Comparative Example 1

The difference between Comparative Example 1 and Example 3 is that, in step S2, the addition of the graphene oxide and titanium carbide is 1:12 by mass ratio; stirring at 0°C for 60min.

Comparative Example 2

The difference between Comparative Example 2 and Example 3 is that, in step S2, the addition of the graphene oxide and titanium carbide is 12:1 by mass ratio; stirring at 0°C for 60min.

Comparative Example 3

The difference between Comparative Example 3 and Example 3 is that carbon nanotubes are used to replace graphene oxide, and the addition of said carbon nanotubes is the same as graphene oxide, and the preparation method is the same as in Example 3.

Application example performance characterization

The performance was characterized by taking the platinum/titanium carbide nanosheet/graphene composite electrode catalyst prepared by the method of Example 3 as an example.

1) Appearance of the hydrogel-like product

Fig. 2 is an electron photograph of the hydrogel product of platinum/titanium carbide nanosheets/graphene prepared by the method of Example 3. It can be seen from Fig. 2 that titanium carbide and graphene form a three-dimensional structure through hydrothermal action. Hydrogel structure.

2) X-ray powder diffraction pattern and Raman spectrum analysis

Fig. 3 is the X-ray powder diffraction pattern and Raman spectrum of the platinum/titanium carbide nanosheet/graphene composite electrode catalyst prepared by the method of Example 3, and the metal platinum can be clearly seen from the XRD pattern of Fig. 3A and graphite oxide characteristic peaks, indicating that the composite product contains these two components, and there is no obvious characteristic peak of titanium carbide in the XRD spectrum, mainly because the three-dimensional porous network structure can effectively prevent the agglomeration of titanium carbide nanosheets. Figure 3B is the Raman spectrum of the platinum/titanium carbide nanosheet/graphene composite electrode catalyst, from which the characteristic peaks of titanium carbide and graphite oxide can be clearly seen. exist.

3) Field emission scanning electron microscopy analysis

As can be seen from Figure 4A and Figure 4B, the catalyst has an obvious three-dimensional porous network structure, and both graphene and titanium carbide components exist in the form of two-dimensional flakes, in which Figure 4C and Figure 4D are titanium carbide and graphene, respectively. It can be seen from the figure that the platinum particles are evenly distributed on the two lamellae, forming a good dispersion.

4) TEM image analysis

Figure 5 is a transmission electron microscope image of the platinum/titanium carbide nanosheet/graphene composite electrode catalyst. Figure 5A further proves that the distribution of platinum particles on the titanium carbide nanosheets and graphene hybrid framework is relatively uniform, and there is no obvious agglomeration phenomenon; The lattice fringes of the platinum particles can be clearly seen in Figure 5B.

The above results show that the platinum/titanium carbide nanosheet/graphene composite electrode catalyst of the present invention has an anti-stacking three-dimensional porous network framework, a large specific surface area, and enables metal platinum nanoparticles to be uniformly distributed on the three-dimensional framework, and has higher catalytic performance. and electrochemical activity.

5) Nitrogen adsorption and desorption test

It can be seen from the adsorption-desorption test curve graph in Fig. 6 that the catalyst has a specific surface area of 214.6 m ² g ^-1 and a significant pore structure.

6) Catalytic activity test

The electrochemical tests of the samples were all carried out on the CHI760E electrochemical workstation. The test system was a conventional three-electrode system, in which a platinum wire was the counter electrode, and the saturated calomel electrode was the reference electrode. A carbon electrode was used as the working electrode. The preparation process of the working electrode was as follows: 2 mg of catalyst powder was weighed and dispersed in a mixed solution of 0.5 mL of deionized water, 0.5 mL of ethanol and 0.05 mL of Nafion, and sonicated for 30 min. Take 0.005 mL of the dispersion of the above catalyst sample and drop it on the surface of the glassy carbon electrode, and test it after drying at room temperature for 0.5 hours. The electrochemically active surface area (ECSA) of the catalyst and the catalytic activity for methanol oxidation were both measured by cyclic voltammetry with electrolytes of 0.5 mol/LH ₂ SO ₄ and 0.5 mol/LH ₂ SO ₄ and 0.5 mol/LH 2 SO 4 , respectively. L CH ₃ OH mixed solution, the scanning rate is 20mV.s ^-1 . The stability and methanol tolerance of the catalyst were evaluated by potentiostatic oxidation and chronopotentiometry. The conductivity of the catalyst was studied by electrochemical AC impedance test, the frequency range was from 10 ⁵ to 0.02 Hz, and the amplitude was 10 mV.

By calculating the area of the curve in Figure 7A in the hydrogen adsorption region, it can be found that the platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode has the highest electrochemically active surface area (90.1 m ² g ^-1 ). The catalytic performance of the titanium nanosheet/graphene catalyst was tested for methanol oxidation, as shown in Figure 7B, and the forward current density of the catalyst was 1102.0 mA mg ^-1 . In order to further illustrate the catalytic activity of the catalyst, the applicant also compared the cyclic voltammetry tests of different materials for methanol oxidation. It can be seen from Figure 7 that the platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst has no activity The surface area and the forward peak current density were significantly higher than the other four comparative samples, indicating the highest catalytic activity.

The electrochemical stability of platinum/titanium carbide nanosheets/graphene three-dimensional coincident catalysts was tested by potentiostatic oxidation method. It can be seen from Figure 8A that the platinum/titanium carbide nanosheet/graphene three-dimensional composite catalyst has always maintained the lowest current decay rate and the highest oxidation current density during the test time of 2000s, indicating good catalytic durability. It can be clearly observed from Fig. 8B that under the galvanostatic test conditions, the catalyst can stay at low potential for a longer time. It can be seen from the figure that the catalytic durability and anti-toxicity of the catalyst are better than the other four comparative samples.

The catalysts prepared by the methods of Examples 1 to 5 were tested for methanol oxidation reaction, and the results are shown in Table 1.

Table 1 Performance index of catalysts prepared in Examples 1-5 for methanol oxidation reaction

As can be seen from Table 1, the catalysts prepared by the methods of Examples 1-5 all have higher catalytic activity and stable catalytic activity. With the increase of the addition amount of titanium carbide in the titanium carbide nanosheet/graphene oxide binary composite solution, the active surface area, mass activity and apparent activity of the catalyst all increase, but the addition amount of titanium carbide is further improved, see Implementation In Example 5, the performance of the catalyst was lower than that of Example 3 and Example 4. When its content increased to that of Comparative Example 1, the performance of the catalyst decreased sharply; this was because titanium carbide itself could not form a three-dimensional network structure. Adding a large amount of titanium carbide will cause the agglomeration of titanium carbide itself and the reduction of active sites, thereby reducing the catalytic activity. Therefore, the ratio of titanium carbide and graphene added is very important. An appropriate proportion of graphene and titanium carbide is conducive to the formation of good three-dimensional porous structure. A good three-dimensional porous structure of graphene/titanium carbide is conducive to the uniform dispersion of platinum nanoparticles and the rapid transport of electrolyte during the reaction process, thereby effectively improving the catalytic performance. Comparative Example 2 Compared with Examples 1 to 5, the content of titanium carbide nanosheets in the titanium carbide nanosheet/graphene oxide binary composite solution is too low, which on the one hand cannot provide sufficient growth sites for metal platinum particles, on the other hand. On the one hand, the electronic structure of platinum cannot be effectively regulated, resulting in its poor resistance to CO poisoning, which will lead to the decline of catalytic performance. Compared with Example 3, carbon nanotubes are used to replace graphene oxide, and the catalyst performance is significantly reduced. This is because the surface of carbon nanotubes is hydrophobic and the bonding force with titanium carbide nanosheets is not strong, which will aggravate titanium carbide. The agglomeration of nanosheets is not conducive to the dispersion of Pt nanoparticles, thus leading to a decrease in catalyst performance.

The catalytic reaction is only a surface reaction. Only the atoms on the surface can play a catalytic role, while the atoms inside do not participate in the reaction. Therefore, the amount of platinum added can only play a good catalytic activity under appropriate conditions, and the platinum loading is too high. , reducing the uniform dispersion of platinum nanoparticles, and some platinum atoms are stacked together, becoming ineffective catalysts, reducing the utilization rate, and the content is too low, which will also lead to the reduction of catalytic activity. The present application has determined the ratio of each component of the present invention through a large number of experiments, and each component can obtain a catalyst for methanol direct fuel cell with good catalytic performance only under the above-mentioned ratio and content.

Claims (10)

1. the preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst, is characterized in that, comprises the following steps: S1, prepare titanium carbide nanosheet dispersion; S2, adding graphene oxide to the titanium carbide nanosheet dispersion liquid of step S1, and ultrasonically dispersing to obtain a titanium carbide nanosheet/graphene oxide binary composite solution, wherein the amount of graphene oxide and titanium carbide added is by mass ratio Calculated as 1~9: 1~9; S3, adding potassium chloroplatinite solution to the binary composite solution of step S2, stirring evenly, to obtain potassium chloroplatinite/titanium carbide nanosheet/graphene oxide ternary composite solution, the chloroplatinite The addition amount of platinum element and titanium carbide nanosheet/graphene oxide binary composite in the potassium solution is 1-20:1-20 in terms of mass ratio; S4. The ternary composite solution in step S3 is subjected to a hydrothermal reaction to obtain a hydrogel-like product, which is then dialyzed and washed with water, and freeze-dried to obtain a platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst. 2. the preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst as claimed in claim 1, is characterized in that, in step S2, the addition of described graphene oxide and titanium carbide is counted by mass ratio as 1 to 4: 5 to 9. 3. the preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst as claimed in claim 1, is characterized in that, in step S3, in described potassium chloroplatinite solution, platinum element and titanium carbide nanosheet The addition amount of the /graphene oxide binary composite is 1:4-9 in terms of mass ratio. 4. The preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst according to claim 1, wherein in step S3, the stirring condition is: stirring at a temperature of 0～50°C for 0.2～5h . 5. The preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst as claimed in claim 1, characterized in that, in step S4, the hydrothermal reaction conditions are: placed in water at a temperature of 80～120°C Thermal reaction 8 ~ 14h. 6. The preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst as claimed in claim 1, characterized in that, in step S4, the dialysis water washing time is 3～10d, and the time during the freeze-drying The drying pressure is 0-200Pa. 7. The preparation method of the platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst according to any one of claims 1 to 6, wherein the step S1 for preparing the titanium carbide nanosheet dispersion specifically comprises the following steps : P1, use lithium fluoride and hydrochloric acid to etch carbon-aluminum-titanium, and then centrifugally wash with water to obtain a multi-layer titanium carbide precipitate; P2, adding a small amount of distilled water to the multi-layered titanium carbide precipitate, ultrasonically peeled off and freeze-dried to obtain single-layer or few-layer titanium carbide nanosheets; P3, dissolving the titanium carbide nanosheets in an ethylene glycol solution, and ultrasonically dispersing to obtain a titanium carbide nanosheet dispersion. 8. The preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst according to claim 7, wherein in step P1, the etching reaction conditions are: the etching reaction time is 24～60h , the reaction temperature is 10～50℃, and the concentration of hydrochloric acid is 6～12mol/L. 9. the preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst as claimed in claim 7, is characterized in that, in step P1, described centrifugal washing condition is: centrifugal rotating speed is 3500～8000rpm, washing until The pH of the supernatant was close to neutral. 10. The preparation method of platinum/titanium carbide nanosheet/graphene three-dimensional composite electrode catalyst according to claim 7, wherein in step P2, the ultrasonic peeling conditions are: ultrasonic peeling time is 0.5～6h, ultrasonic peeling At the same time, the protective gas argon was continuously introduced, and after the ultrasonication was finished, it was screened by centrifugation at 5000-8000 rpm, and the centrifugal supernatant was taken and freeze-dried to obtain monolayer or few-layer titanium carbide nanosheets.

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