CN113921835B - A kind of preparation method of high temperature proton exchange membrane fuel cell cathode catalyst - Google Patents

Abstract

The invention provides a method for preparing a cathode catalyst of a high-temperature proton exchange membrane fuel cell. Firstly, a black phosphorus nanosheet material is prepared, and then the black phosphorus nanosheet and the graphene sheet activated by alkaline solution are used for mechanical ball milling. Heating in the reaction kettle effectively forms a heterogeneous structure between black phosphorus and activated graphene, and finally adds metal precursors and reducing agents in a certain proportion to obtain noble metal particles supported by black phosphorus-activated graphene composites, which effectively improves The electrochemical activity, utilization and stability of the noble metal catalysts were improved.

Description

A kind of preparation method of high temperature proton exchange membrane fuel cell cathode catalyst

technical field

The invention belongs to the field of materials science, and relates to a high-temperature proton exchange membrane fuel cell cathode catalyst material, in particular to a method for preparing black phosphorus-activated graphene composite material loaded noble metal nanoparticles.

Background technique

Compared with low-temperature proton exchange membrane fuel cells that work at 60°C-80°C, phosphoric acid-doped PBI-based high-temperature proton exchange membrane fuel cells (HT-PEMFC) generally work at 160°C-180°C, with electrode reaction kinetics Fast, strong carbon monoxide resistance, simple water and heat management and other advantages, it has broad application prospects in the fields of military special power supplies, portable power supplies, fixed power stations and auxiliary power supplies. However, the commonly used catalysts for HT-PEMFC cathodes are carbon-supported platinum or carbon-supported platinum alloys, which have the problems of low utilization rate, high loading capacity and poor stability of noble metal catalysts, which severely limit the application of HT-PEMFC.

Contents of the invention

The object of the present invention is to overcome above-mentioned defect, provide a kind of preparation method of high-temperature proton exchange membrane fuel cell (HT-PEMFC) cathode catalyst, at first prepared black phosphorus nanosheet material, and then utilize black phosphorus nanosheet layer and lye activation The graphene sheet is mechanically milled, and the heterostructure is effectively formed between the black phosphorus and the activated graphene by heating in the reactor, and finally the metal precursor and the reducing agent are added in a certain proportion to obtain the black phosphorus-activated fossil The noble metal particles supported by the graphene composite material can effectively improve the electrochemical activity, utilization and stability of the noble metal catalyst.

In order to realize the foregoing invention object, the present invention provides following technical scheme:

A method for preparing a high-temperature proton exchange membrane fuel cell cathode catalyst, comprising the following steps:

(1) After the surface oxide layer is removed from the massive red phosphorus, the red phosphorus powder is obtained by grinding;

(2) Red phosphorus powder, Sn, and _SnI are heated under vacuum conditions, and block black phosphorus is obtained after cooling and washing, and black phosphorus powder is obtained after grinding;

(3) adding the black phosphorus powder into the NMP solution, after ultrasonic stripping under inert gas conditions, take the supernatant to further continue the ice-bath ultrasonication, and obtain the black phosphorus nanosheet material after centrifugation;

(4) Carry out mechanical ball milling under inert gas conditions with the black phosphorus nano-sheet material and the graphene sheet material activated by lye to obtain a composite material precursor;

(5) The composite material precursor is dispersed in ethylenediamine, and after heating in the reactor, the black phosphorus-activated graphene composite material is obtained through cooling, washing, and vacuum drying;

(6) Disperse the black phosphorus-activated graphene composite material in isopropanol, and add the noble metal precursor to stir;

(7) After adjusting the pH of the dispersion obtained in step (6), the reducing agent was slowly added dropwise, stirred for 2 hours, and the obtained product was washed by centrifugation, and vacuum-dried to obtain black phosphorus-activated graphene composite loaded noble metal nanoparticles.

Further, in step (1), the method for removing the surface oxide layer of red phosphorus is to place red phosphorus and deionized water together in a reaction kettle, and heat them under water at 160-180° C. for more than 15 hours.

Further, in step (2), the mass ratio of red phosphorus powder, Sn, and _SnI4 is 1: (0.02～0.08): (0.01～0.06); in step (2), the method of vacuum heating is red Phosphorus powder, Sn, and SnI ₄ are added to the quartz tube to be vacuumed and sealed, followed by heating up, keeping warm, cooling down, and keeping warm; in step (2), wash with toluene and acetone.

Further, in step (2), the method of vacuum heating is to add red phosphorus powder, Sn, and SnI ₄ into a quartz tube to evacuate and seal it, and heat it to ^600-600 ~ Keep warm at 700°C for 2-3h, then cool down to 450-500°C, and keep warm for 5-7h.

Further, in step (3), the NMP solution is NMP solution saturated with NaOH, and the inert gas is argon; in step (3), the method of ultrasonic stripping is ultrasonic stripping in a cell pulverizer under the condition of 400-600W for 12~ 16h.

Further, in step (4), the graphene activated by lye is graphene activated by a potassium hydroxide solution of 6 to 7 mol/L, and the activation method is after the graphene is stirred in the potassium hydroxide solution for 8 to 10 hours, Centrifuge and wash with isopropanol, absolute ethanol and deionized water for 3 to 5 times respectively, then dry and grind the obtained samples, then raise the temperature to 600°C in nitrogen at 5°C/min and keep it for 30min, then increase the temperature at 2°C/min Min was heated to 800°C and kept for 2h.

Further, in step (4), the mass ratio of the black phosphorus nanosheet material to the graphene sheet material activated by alkali solution is 1:0.5～2; in the step (4), utilize a ball mill to Carry out mechanical ball milling, the rotating speed of the ball mill is 500-700 rpm, and the time of mechanical ball milling is 45-60h.

Further, in step (5), the composite material precursor is dispersed in ethylenediamine, heated to 140°C in the reactor, reacted for 12h, and cooled naturally, and centrifuged with isopropanol, absolute ethanol and deionized water respectively Washing for 3 to 5 times, and vacuum drying at a temperature of 50 to 60° C. to obtain a black phosphorus-activated graphene composite material.

Further, in step (6), the noble metal precursor is platinum, palladium or gold chloride.

Further, in step (7), after adjusting the pH of the dispersion liquid obtained in step (6) to 8-11, add the reducing agent sodium borohydride or hydrazine hydrate; the metal precursor added in step (6) and the step (7 ) The mass ratio of the reducing agent added in is 1:1-80.

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

(1) In the preparation method of a kind of high-temperature proton exchange membrane fuel cell cathode catalyst of the present invention, the heating condition of red phosphorus is designed, makes it stable, efficient conversion into black phosphorus, black phosphorus is obtained by ultrasonic stripping in NMP solution Black phosphorus nanosheet material with stable structure;

(2) in the preparation method of a kind of high-temperature proton exchange membrane fuel cell cathode catalyst of the present invention, utilize the graphene sheet layer activated by black phosphorus nanosheet layer and lye to carry out mechanical ball milling, and make black phosphorus and The heterogeneous structure is effectively formed between the activated graphene, which is beneficial to the electron transfer in the reaction process; the present invention further designs the ratio of the black phosphorus nanosheet and the graphene sheet activated by alkali solution, so that the heterostructure has optimal performance;

(3) in the preparation method of a kind of high-temperature proton exchange membrane fuel cell cathode catalyst of the present invention, utilize the graphene sheet layer activated by black phosphorus nanosheet layer and lye to carry out mechanical ball milling, and make black phosphorus and Activated graphene forms black phosphorus-activated graphene composites. As a matrix material loaded with noble metals, black phosphorus-activated graphene composites have more defects, which makes the metal active sites of the catalyst material obtained after loading better. Exposure improves the oxygen reduction activity and electrochemical stability of the catalyst;

(4) In the preparation method of a high-temperature proton exchange membrane fuel cell cathode catalyst of the present invention, the loading and uniform dispersion of noble metal nanoparticles is realized, and the electrochemical activity, utilization rate and stability of the noble metal catalyst are effectively improved.

(5) in the preparation method of a kind of high-temperature proton exchange membrane fuel cell cathode catalyst of the present invention, prepared catalyst, base material is black phosphorus-activated graphene heterojunction, after forming heterostructure, graphene is to black phosphorus Play a certain protective role, the stability of the material is greatly enhanced, and can be used in high temperature environments.

Description of drawings

Fig. 1 is the TEM figure of the black phosphorus-activated graphene composite material that the embodiment of the present invention 1 gains;

Fig. 2 is the cyclic voltammogram of black phosphorus-activated graphene composite loaded platinum nanoparticles in _0.1MHClO solution obtained in Example 1 of the present invention;

Fig. 3 is the linear sweep voltammogram of black phosphorus-activated graphene composite loaded platinum nanoparticles and commercial catalyst Pt/C obtained in Example 1 of the present invention in _0.1M HClO solution;

Fig. 4 is a diagram showing the stability test results of black phosphorus-activated graphene composite material loaded platinum nanoparticles in _0.1M HClO solution obtained in Example 1 of the present invention.

Detailed ways

The following describes the present invention in detail, and the features and advantages of the present invention will become more clear and definite along with these descriptions.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or better than other embodiments. While various aspects of the embodiments are shown in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The invention provides a method for preparing a high-temperature proton exchange membrane fuel cell (HT-PEMFC) cathode catalyst, specifically, a method for preparing a black phosphorus-activated graphene composite material loaded with noble metal nanoparticles, which includes first passing through a high-temperature Calcination to prepare black phosphorus, and then prepare black phosphorus-activated graphene composite material: the exfoliated black phosphorus nanosheet material and the graphene sheet material activated by alkali solution are ball milled under the protection of argon according to a certain ratio, and then treated with iso Propanol, absolute ethanol and deionized water are centrifugally washed several times and vacuum-dried and collected; finally, the composite material is dispersed in isopropanol, and a metal precursor is added (the metal in the metal precursor is platinum, palladium or gold), After adjusting the pH, adding a reducing agent, stirring and vacuum drying to obtain black phosphorus-activated graphene composite material loaded noble metal nanoparticles. In the present invention, the black phosphorus-activated graphene heterojunction provides a stable substrate for the composite material, and there are many defects on the substrate, which is conducive to the full exposure of the metal active site and provides a good channel for electron transfer to the metal active site , effectively improving the electrocatalytic oxygen reduction activity and stability of the catalyst.

The invention provides a method for preparing a high-temperature proton exchange membrane fuel cell cathode catalyst, comprising the following steps:

1) Preparation of black phosphorus nanosheets: Weigh 1-3g red phosphorus (RP), put it in a reaction kettle together with 15-25mL deionized water, and heat it at 160-180°C for more than 15h to remove the surface oxide layer. Dry and grind into powder, add 400-600mg RP, 18-24mg Sn and 10-15mg _SnI4 into the quartz tube to evacuate and seal, heat to 650°C at a heating rate of 5°C min ^-1 for 2-3h, then Cool down to 450-500°C, keep warm for 5-7h and then cool to room temperature. The obtained black phosphorus (BP) crystals were washed several times with hot toluene and acetone, and placed in a glove box with Ar for use. In a glove box filled with argon, weigh 200 mg blocky BP crystals, grind them into powder with an agate mortar, add to 50-70 mL NMP (N-methylpyrrolidone) solution, and grind in a cell pulverizer at 400- 600W ultrasonic stripping for 12h. Centrifuge at 4000rpm and collect the supernatant, after that, the supernatant is further ultrasonicated in batches in an ice bath, centrifuged at 10000rpm and vacuum-dried to obtain black phosphorus nanosheets.

2) Preparation of black phosphorus-activated graphene composite material: mechanical ball milling of black phosphorus nanosheets and alkali-activated graphene under argon protection for 45-60 h, the mass ratio of black phosphorus to graphene is 1 : 1～2, the set speed of the ball mill is 600 rev/min, the obtained precursor is placed in 30-40mL ethylenediamine, stirred for 0.5h, then transferred to the reactor, reacted at 140°C for 12h, and then waited It cools naturally. Afterwards, centrifuge washing with isopropanol, absolute ethanol and deionized water for 3 to 5 times respectively, and then vacuum dry the above product at a temperature of 50-60° C. to obtain a black phosphorus-activated graphene composite material.

3) Preparation of black phosphorus-activated graphene composite material loaded noble metal nanoparticles: disperse black phosphorus-activated graphene composite material in isopropanol, add metal precursor after ultrasonic treatment, the metal in the metal precursor For platinum, palladium or gold, continuous stirring for 10-14h. After the pH is adjusted, a reducing agent is added, the reducing agent is sodium borohydride or hydrazine hydrate, the mass ratio of the metal precursor to the reducing agent is 1:1-80, and the black phosphorus-activated graphene isocyanate is obtained after vacuum drying. Mass junction loaded noble metal nanoparticles.

Further, the NMP solution used to disperse and store black phosphorus in step 1) is a saturated NaOH NMP solution.

Further, the lye used for activating graphene in step 2) is 7mol/L potassium hydroxide solution.

Further, in step 2), the mass ratio of the black phosphorus nanosheets to the lye-activated graphene is 1:1-2.

Further, the reducing agent described in step 3) is sodium borohydride or hydrazine hydrate.

Further, the environment for the reaction in step 3) is pH 8-11.

In the present invention, the exfoliated black phosphorus nano-sheet material and the graphene sheet material activated by lye are ball-milled in a certain proportion under the protection of argon and hydrothermally treated in ethylenediamine, and then treated with isopropanol and absolute ethanol Centrifuge and wash with deionized water for several times, vacuum dry and collect; ultrasonically treat black phosphorus-activated graphene dispersed in isopropanol, add metal precursor and reducing agent in a certain proportion, stir and dry, and collect to obtain black phosphorus - Activation of noble metal particles supported by graphene composites.

Through TEM test and characterization, it can be seen that black phosphorus and activated graphene effectively form a heterostructure, and realize the loading and uniform dispersion of noble metal nanoparticles. The formation of the heterostructure is beneficial to the electron transfer during the reaction, and there are more defects on the substrate material, which makes the metal active sites better exposed and improves the oxygen reduction activity and electrochemical stability of the catalyst. Compared with the prior art, the invention effectively improves the electrochemical activity, utilization rate and stability of the noble metal catalyst.

Example 1

A preparation method of black phosphorus-activated graphene composite material loaded platinum nanoparticles, specifically comprising the following steps:

(1) Preparation of black phosphorus-activated graphene composites

①Preparation of black phosphorus nanosheets: Weigh 2g of red phosphorus (RP), put it in a reaction kettle together with 25mL of deionized water, and heat it at 160-180℃ for more than 15h to remove the surface oxide layer. Dry and grind into powder, add 400-600mg RP, 18-24mg Sn and 10-15mg _SnI4 into a quartz tube to vacuumize and seal it, heat it to 650°C at a heating rate of 5°C min ^-1 and keep it for 3h, then cool down to 500°C, keep warm for 6h and then cool to room temperature. The obtained black phosphorus (BP) crystals were washed several times with hot toluene and acetone at 70 °C, and placed in a glove box filled with Ar for use. In a glove box filled with argon gas, weigh 200 mg of bulk BP crystals, grind them into powder with an agate mortar, add to 50–70 mL of NMP solution, and ultrasonically peel at 400–600 W in a cell pulverizer for 12 h. Centrifuge at 4000 rpm and collect the supernatant to obtain the supernatant of BP nanoflakes dispersed in NMP solution.

②Activation of graphene: Stir graphene in 6M potassium hydroxide solution for 8-10 hours, centrifuge and wash the obtained samples with isopropanol, absolute ethanol and deionized water for 3-5 times respectively, and then put the samples in Dry it in an oven at 70°C for 24 hours, take it out and grind it with an agate mortar for 30 minutes, then raise the temperature to 600°C at 5°C/min and keep it for 30 minutes in nitrogen, then raise the temperature to 800°C at 2°C/min and keep it for 2 hours. After being naturally cooled to room temperature, the activated graphene was collected.

③Preparation of black phosphorus-activated graphene heterojunction material: the black phosphorus nanosheet material and the graphene sheet material activated by lye were mechanically ball milled for 40-50h under the protection of argon, and the black phosphorus nanosheet The mass ratio of the layer material to the graphene nanosheet material is 1:0.5～1.5, the set speed of the ball mill is 600 rpm, the obtained precursor is placed in 40mL ethylenediamine, stirred for 0.5h, and then transferred to the reaction In the kettle, react at 140°C for 12h, and then allow it to cool naturally. Afterwards, centrifuge and wash five times with isopropanol, absolute ethanol and deionized water respectively, and then vacuum-dry the above product at 60° C. to obtain the black phosphorus-activated graphene heterojunction material.

(2) Preparation of platinum nanoparticles supported by black phosphorus-activated graphene composites

Disperse the black phosphorus-activated graphene composite material in isopropanol, add sodium chloroplatinate after ultrasonic treatment, and keep stirring for 10-14h. Adjust the pH to 10-11, then slowly add the reducing agent sodium borohydride with a peristaltic pump, the mass ratio of the metal precursor to the reducing agent is 1:1-80, and after vacuum drying, the platinum-supported black phosphorus-activated graphene composite material can be obtained Nanoparticles.

The TEM image of the black phosphorus-activated graphene composite obtained above is shown in Figure 1. It can be seen from the figure that both black phosphorus and graphene have a sheet structure, and black phosphorus and graphene form a heterostructure.

Figure 2 corresponds to the cyclic voltammogram of black phosphorus-activated graphene composites loaded with platinum nanoparticles in 0.1M HClO ₄ solution, and the catalyst has a reduction peak at about 0.55V.

Figure 3 is a linear sweep voltammogram of black phosphorus-activated graphene composites loaded with platinum nanoparticles in 0.1M HClO ₄ solution. It can be seen from the figure that the onset potential of the catalyst is about -0.07V, which is slightly lower than 0V on Pt/C. The limiting current density of the catalyst is 6.24mAcm ^-2 , which is higher than 4.93mAcm ^-2 of Pt/C. The half-wave potential of the catalyst is 0.82V, which is close to 0.86V of Pt/C. It shows that the catalyst has better ORR activity in acidic conditions.

Figure 4 corresponds to the cycle stability test of black phosphorus-activated graphene composite loaded platinum nanoparticles in 0.1M HClO ₄ solution. After 2000 cycles, it can be seen that the performance of the catalyst is similar to that of Pt/C, and compared with Pt/C, the attenuation of the half-wave potential is smaller, indicating that the catalyst has better electrochemical stability.

The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent replacements, modifications or improvements can be made to the technical solutions and implementations of the present invention, all of which fall within the scope of the present invention. The protection scope of the present invention shall be determined by the appended claims.

The content that is not described in detail in the description of the present invention belongs to the well-known technology of those skilled in the art.

Claims (7)

1. A preparation method for a high-temperature proton exchange membrane fuel cell cathode catalyst, characterized in that, comprising the following steps: (1) After the surface oxide layer is removed from the massive red phosphorus, the red phosphorus powder is obtained by grinding; (2) Red phosphorus powder, Sn, and _SnI are heated under vacuum conditions, and block black phosphorus is obtained after cooling and washing, and black phosphorus powder is obtained after grinding; (3) adding the black phosphorus powder into the NMP solution, after ultrasonic stripping under inert gas conditions, take the supernatant to further continue the ice-bath ultrasonication, and obtain the black phosphorus nanosheet material after centrifugation; (4) Carry out mechanical ball milling under inert gas conditions with the black phosphorus nano-sheet material and the graphene sheet material activated by lye to obtain a composite material precursor; (5) The composite material precursor is dispersed in ethylenediamine, and after heating in the reactor, the black phosphorus-activated graphene composite material is obtained through cooling, washing, and vacuum drying; (6) Disperse the black phosphorus-activated graphene composite material in isopropanol, and add the noble metal precursor to stir; (7) After adjusting the pH of the dispersion obtained in step (6), add a reducing agent dropwise, after stirring and centrifugal washing, vacuum-dry to obtain black phosphorus-activated graphene composite material loaded noble metal nanoparticles; In the step (3), the NMP solution is a saturated NaOH NMP solution, and the inert gas is argon; in the step (3), the method of ultrasonic peeling is ultrasonic peeling under the condition of 400-600W in a cell pulverizer for 12 ~16h; In the step (4), the mass ratio of the black phosphorus nanosheet material to the graphene sheet material activated by alkali solution is 1:0.5～2; in the step (4), utilize a ball mill to carry out Mechanical ball milling, the speed of the ball mill is 500-700 rpm, and the time of mechanical ball milling is 45-60h; In the step (5), the composite material precursor is dispersed in ethylenediamine, heated to 140°C in the reaction kettle, reacted for 12h, cooled naturally, and washed by centrifugation with isopropanol, absolute ethanol and deionized water respectively 3 to 5 times, vacuum drying at a temperature of 50 to 60° C. to obtain a black phosphorus-activated graphene composite material. 2. the preparation method of a kind of high-temperature proton exchange membrane fuel cell cathode catalyst according to claim 1 is characterized in that, in step (1), the method for red phosphorus to remove surface oxide layer is, red phosphorus and deionized water Put them together in a reaction kettle, and heat them with water at 160-180°C for more than 15 hours. 3. the preparation method of a kind of high temperature proton exchange membrane fuel cell cathode catalyst according to claim 1, is characterized in that, in step (2), red phosphorus powder, Sn, and the mass ratio of SnI ₄ is 1:( 0.02～0.08): (0.01～0.06); in step (2), the method of vacuum heating is to add red phosphorus powder, Sn, and SnI ₄ into the quartz tube to vacuumize and seal it, then heat up, keep warm, and cool down in sequence , insulation; in step (2), wash with toluene and acetone. 4. the preparation method of a kind of high-temperature proton exchange membrane fuel cell cathode catalyst according to claim 3 is characterized in that, in step (2), the method for vacuum heating is that red phosphorus powder, Sn, and _SnI Add Vacuumize and seal the quartz tube, heat to 600-700°C at a heating rate of 3-10°C min ^-1 for 2-3 hours, then cool down to 450-500°C and hold for 5-7 hours. 5. the preparation method of a kind of high-temperature proton exchange membrane fuel cell cathode catalyst according to claim 1, is characterized in that, in described step (4), the graphene activated by lye is the hydrogen of 6～7mol/L Graphene activated by potassium oxide solution, the activation method is to stir the graphene in potassium hydroxide solution for 8-10 hours, then centrifuge and wash it with isopropanol, absolute ethanol and deionized water for 3-5 times, and then the obtained sample After drying and grinding, the temperature was raised to 600°C at 5°C/min and kept for 30 minutes in nitrogen, and then raised to 800°C at 2°C/min and kept for 2 hours. 6. The preparation method of a high-temperature proton exchange membrane fuel cell cathode catalyst according to claim 1, characterized in that, in the step (6), the noble metal precursor is platinum, palladium or gold chloride. 7. the preparation method of a kind of high-temperature proton exchange membrane fuel cell cathode catalyst according to claim 1, is characterized in that, in described step (7), after adjusting the pH of step (6) gained dispersion liquid to be 8～11 , adding a reducing agent sodium borohydride or hydrazine hydrate; the mass ratio of the metal precursor added in step (6) to the reducing agent added in step (7) is 1:1-80.

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