阅读说明：本技术 一种复合催化剂及其制备方法和应用 (Composite catalyst and preparation method and application thereof ) 是由 王一菲 李严 付超 廖文俊 苏青 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种复合催化剂及其制备方法和应用。复合催化剂的制备方法包括如下步骤：(1)含氧化石墨烯和Y型分子筛的悬浮液经干燥,在惰性气氛条件下,进行还原反应,得还原氧化石墨烯-Y型分子筛复合材料,即rGO-Y复合材料；(2)在水中,rGO-Y复合材料经分散,得rGO-Y复合材料悬浮液,rGO-Y复合材料悬浮液与H-2PtCl-6进行混合,得混合物料A；混合物料A与还原剂进行反应,即可。本发明制得复合催化剂结构稳定,分散性好,不易发生团聚现象,导电性能良好；负载少量催化剂铂即可获得较高的催化活性,催化剂铂的利用率高,且催化性能稳定；本发明制得的复合催化剂可有效用于催化电解水制氢反应。(The invention discloses a composite catalyst and a preparation method and application thereof. The preparation method of the composite catalyst comprises the following steps: (1) drying the suspension containing the graphene oxide and the Y-type molecular sieve, and carrying out reduction reaction under the inert atmosphere condition to obtain a reduced graphene oxide-Y-type molecular sieve composite material, namely an rGO-Y composite material; (2) dispersing the rGO-Y composite material in water to obtain a rGO-Y composite material suspension, the rGO-Y composite material suspension and H 2 PtCl 6 Mixing to obtain a mixed material A; and (3) reacting the mixed material A with a reducing agent to obtain the catalyst. The composite prepared by the inventionThe catalyst has stable structure, good dispersibility, difficult agglomeration and good conductivity; a small amount of catalyst platinum is loaded to obtain higher catalytic activity, the utilization rate of the catalyst platinum is high, and the catalytic performance is stable; the composite catalyst prepared by the invention can be effectively used for catalyzing the hydrogen production reaction by water electrolysis.)

1. The preparation method of the composite catalyst is characterized by comprising the following steps:

(1) drying the suspension containing the graphene oxide and the Y-type molecular sieve, and carrying out reduction reaction under the inert atmosphere condition to obtain a reduced graphene oxide-Y-type molecular sieve composite material, namely an rGO-Y composite material;

(2) dispersing the rGO-Y composite material in water to obtain a rGO-Y composite material suspension, and mixing the rGO-Y composite material suspension with H₂PtCl₆Mixing to obtain a mixed material A; and reacting the mixed material A with a reducing agent to obtain the catalyst.

2. The method for preparing the composite catalyst according to claim 1, wherein the method for preparing graphene oxide comprises the following steps: h₂SO₄、H₃PO₄、KMnO₄Mixing the graphite and the graphite for the first time according to the mass ratio of 120:13:6:1, cooling to 35-40 ℃, and stirring at 50-55 ℃ to obtain a mixed material B; the mixed material B is sequentially mixed with ice water and H₂O₂Mixing the water solution for the second time, standing, centrifuging to collect the residue, and cleaningFiltering the filter residue to be neutral;

preferably, the graphite is flake graphite;

preferably, the stirring time is 10-15 h, more preferably 12-15 h;

preferably, the stirring operation further comprises a cooling operation, more preferably a cooling operation to room temperature;

preferably, the mass ratio of the ice water to the graphite is (350-450): 1, more preferably 400: 1;

preferably, said H₂O₂H in aqueous solution₂O₂The mass percent of (A) is 20-35%, more preferably 30-35%;

preferably, the graphite and the H₂O₂H in aqueous solution₂O₂The mass ratio of (0.26-0.45): 1, more preferably (0.30 to 0.45): 1;

preferably, the standing time is 10-15 h, more preferably 12-15 h;

preferably, the cleaning comprises the following steps: washing the filter residue to be neutral by using absolute ethyl alcohol, 30 mass percent of HCl and deionized water respectively;

preferably, the operation of cleaning further comprises an operation of drying.

3. The method for preparing the composite catalyst according to claim 1, wherein the Y-type molecular sieve is prepared by NaOH fusion-hydrothermal method in step (1), and preferably comprises the following steps: melting a mixture of natural zeolite and NaOH, mixing with water, aging and crystallizing to obtain the product;

preferably, the natural zeolite is clinoptilolite in Jinyun and/or mordenite in Jinyun;

preferably, the mole ratio of the silicon element to the aluminum element in the natural zeolite is (4.5-6): 1;

preferably, the mass ratio of the natural zeolite to the NaOH is 1: (1.2-1.3);

preferably, the melting temperature is 500-650 ℃, more preferably 550-600 ℃;

preferably, the melting time is 1.5 to 2.5 hours, more preferably 2 to 2.5 hours;

preferably, the mass ratio of the material prepared after melting to the water is 1: (4-5), more preferably 1: (4.5-5);

preferably, the aging time is 10-14 h, more preferably 12-14 h;

preferably, the crystallization temperature is 90-110 ℃, more preferably 100-110 ℃;

preferably, the crystallization time is 6 to 10 hours, and more preferably 8 to 10 hours;

preferably, the crystallization operation further comprises a water washing and/or drying operation; preferably, the drying temperature is 140-160 ℃; preferably, the drying time is 1.5 to 2.5 hours, and more preferably 2 to 2.5 hours.

4. The preparation method of the composite catalyst according to claim 1, wherein in the step (1), the mass ratio of the graphene oxide to the Y-type molecular sieve is 1: (4-6);

and/or in the step (1), in the suspension containing the graphene oxide and the Y-type molecular sieve, the concentration of the graphene oxide is 4-6 mg/mL;

and/or in the step (1), the drying operation comprises the following steps: stirring the mixture at 75-85 ℃ until the mixture is pasty, and drying the pasty mixture in an oven at the temperature of 45-50 ℃ to obtain the product;

and/or, in the step (1), the inert atmosphere is nitrogen;

and/or in the step (1), the temperature of the reduction reaction is 350-450 ℃;

and/or in the step (1), the time of the reduction reaction is 1.5-2.5 h;

and/or, in the step (1), the operation of the reduction reaction is further followed by a cooling operation.

5. The preparation method of the composite catalyst according to claim 4, wherein in the step (1), the mass ratio of the graphene oxide to the Y-type molecular sieve is 1: (4.5-5);

and/or in the step (1), in the suspension containing the graphene oxide and the Y-type molecular sieve, the concentration of the graphene oxide is 5 mg/mL;

and/or in the step (1), the temperature of the reduction reaction is 380-400 ℃;

and/or in the step (1), the time of the reduction reaction is 2-2.5 h;

and/or in the step (1), the cooling operation is cooling to room temperature.

6. The method for preparing the composite catalyst according to claim 1, wherein in the step (1), the method for preparing the suspension containing the graphene oxide and the Y-type molecular sieve comprises the following steps: (a) dispersing the graphene oxide in water to obtain graphene oxide gel; (b) dispersing the Y-type molecular sieve in the graphene oxide gel;

preferably, in step (a), the dispersing method is ultrasonic dispersing;

preferably, in step (b), the dispersing method is ultrasonic dispersing;

preferably, in the step (b), the dispersing time is 15-20 min, and more preferably 20 min;

preferably, in step (b), the dispersing operation is further followed by stirring operation; preferably, the rotation speed of the stirring is 800-1200 turns/min, more preferably 1000-1100 turns/min; preferably, the stirring time is 25-35 min, more preferably 30-35 min.

7. The method for preparing the composite catalyst according to any one of claims 1 to 6, wherein in the step (2), the mass-to-volume ratio of the rGO-Y composite material to the water is 0.4 to 0.6mg/mL, preferably 0.5 to 0.6 mg/mL;

and/or, in step (2), the rGO-Y composite material and H₂PtCl₆The mass ratio of the Pt elements is 1: (0.6-1), preferably 1: (0.7-0.8);

and/or, in the step (2), the reducing agent is NaHB₄And/or hydrazine hydrate, preferably NaHB₄(ii) a When the reducing agent is NaBH₄When, the NaBH₄With NaBH₄Added as an aqueous solution, the NaBH₄NaBH in aqueous solution₄The concentration of (b) is preferably 0.04 to 0.06mol/L, more preferably 0.05 to 0.06 mol/L;

and/or in the step (2), the molar ratio of the mass of the rGO-Y composite material to the reducing agent is 3-5 g/mol, preferably 3-4 g/mol;

and/or in the step (2), the dispersing method is ultrasonic dispersing;

and/or in the step (2), the dispersing time is 0.5-1.5 h, preferably 1 h;

and/or in the step (2), the mixing method is an ultrasonic dispersion method;

and/or, in the step (2), the mixing time is 35-45 min, preferably 40-45 min;

and/or, in the step (2), the addition method of the reducing agent is dropwise adding;

and/or in the step (2), the reaction time is 6-8 h;

and/or, in the step (2), the reaction operation further comprises any one or more of operations of centrifugally collecting filter residues, washing and drying; preferably, the washing method is to use distilled water to carry out the washing; preferably, the drying temperature is 35-45 ℃, more preferably 40-45 ℃; preferably, the drying time is 20 to 30 hours, and more preferably 24 to 30 hours.

8. A composite catalyst prepared by the method for preparing the composite catalyst according to any one of claims 1 to 7.

9. Use of the composite catalyst of claim 8 as a cathode catalyst in the field of proton exchange membrane fuel cells.

10. The application of the composite catalyst as a cathode catalyst in the field of hydrogen preparation by water electrolysis through a proton exchange membrane is characterized in that the composite catalyst is applied to the field of hydrogen preparation through water electrolysis through the proton exchange membrane.

Technical Field

The invention relates to a composite catalyst and a preparation method and application thereof.

Background

The development of chemicals based on clean energy and sustainable green raw materials is of great significance to the relief of problems such as environmental pollution and climate change caused by the use of fossil fuels. One prospective strategy is to convert atmospheric feedstocks of water, carbon dioxide, and nitrogen into important fuels or chemicals (including hydrogen, hydrocarbons, oxygenates, and ammonia, etc.) by coupling a renewable energy source (solar, wind, etc.) with an electrochemical process. In recent years, the cathodic process of water splitting (HER process) has attracted a high degree of attention as a sustainable source of clean energy, hydrogen. The product of the hydrogen production process by water electrolysis only contains hydrogen and oxygen, and no pollutant and carbon-containing compound are released; the method has simple process flow and simple and convenient operation, and is an ideal way for preparing high-purity hydrogen. The electrocatalyst plays a key role in the water electrolysis hydrogen production technology, and directly determines the reaction efficiency and the system energy consumption.

At present, platinum group noble metals (Pt, Ru, Pd, lr, etc.) are considered as the best electrocatalysts for cathode hydrogen production at low overpotential and high current density. However, the low natural reserves of precious metals present a high cost problem, limiting their widespread use in the electrolysis of water. The addition of the electrocatalyst carrier can not only improve the utilization rate of platinum and reduce cost, but also improve the activity of the catalyst. The size, dispersion and utilization efficiency of Pt nanoparticles in the electrocatalyst strongly depend on the catalyst support used and its surface properties. An ideal electrocatalyst support needs to satisfy the following conditions: (1) higher conductivity; (2) can be stably connected with the active component of the catalyst, and can not fall off; (3) higher specific surface area; (4) has a certain porous structure; (5) has excellent corrosion resistance.

Carbon is widely used as a catalyst carrier, wherein the carbon comprises Vulcan XC-72R carbon black (VC), Carbon Nanotubes (CNTs), Graphene (GE), Carbon Nanofibers (CNFs), and the like, wherein VC is most commonly used in commerce, and carbon black, which is a commonly used carrier at present, generally has a high specific surface area and good conductivity, is low in cost, and is easily available. However, carbon black particles also have some unavoidable problems when used as a carrier, and conductive carbon black generally has a pore size too small to accommodate platinum particles, so that the platinum particles are substantially adhered to the surface of the conductive carbon black; traditional carbon supported metal catalysts have poor stability and typically require high metal loadings to compensate for activity loss during long runs.

Graphene is a carbon material having a specific structure of a honeycomb shape, and its theoretical specific surface area (2630 m)²/g) and electrical conductivity (7200S/m) are much higher than other carbon materials. The two-dimensional structure of the graphene is beneficial to the uniform distribution of the platinum active component, and the capability of rapidly transferring electrons can be used for improving the electrode reaction speed. However, the two-dimensional structure of graphene still has limitations in the catalytic process, the graphene with a complete structure has high chemical stability, the surface of the graphene is in an inert state, and strong van der waals force exists between graphene sheets, so that aggregation is easy to generate and irreversible agglomeration occurs, and the specific surface area and specific capacity of the graphene are reduced.

The molecular sieve is a catalyst and a catalyst carrier material which are widely applied, and nano particles with different catalytic capacities can be compounded on the surface or in an open framework of the molecular sieve by an ion exchange method, a coprecipitation method, an impregnation method and the like. The molecular sieve microporous framework has larger specific surface area, which is beneficial to the uniform loading of active catalyst nano particles. However, molecular sieves have poor conductivity and are not suitable for direct use as a support for electrocatalysts.

Therefore, the development of a conductive material with stable structure, good dispersibility, difficult agglomeration and good conductivity is urgently needed in the field; the composite catalyst shows good catalytic performance with a small amount of supported platinum.

Disclosure of Invention

The invention aims to solve the technical problems of poor stability and dispersibility, easy agglomeration and poor conductivity of the composite catalyst in the prior art; the catalyst has the defects of low utilization rate, non-ideal catalytic performance and the like, and provides the composite catalyst and the preparation method and the application thereof. The composite catalyst prepared by the invention has the advantages of stable structure, good dispersibility, difficult agglomeration and good conductivity; a small amount of catalyst platinum is loaded to obtain higher catalytic activity, the utilization rate of the catalyst platinum is high, and the catalytic performance is stable; the composite catalyst prepared by the invention can be effectively used for catalyzing the hydrogen production reaction by water electrolysis.

The invention solves the technical problems through the following technical scheme.

The invention provides a preparation method of a composite catalyst, which specifically comprises the following steps:

(1) drying the suspension containing the graphene oxide and the Y-type molecular sieve, and carrying out reduction reaction under the inert atmosphere condition to obtain a reduced graphene oxide-Y-type molecular sieve composite material, namely an rGO-Y composite material;

(2) dispersing the rGO-Y composite material in water to obtain a rGO-Y composite material suspension, and mixing the rGO-Y composite material suspension with H₂PtCl₆Mixing to obtain a mixed material A; and reacting the mixed material A with a reducing agent to obtain the catalyst.

In the step (1), the graphene oxide may be an oxide of graphene conventionally used in the art.

In the step (1), the preparation method of the graphene oxide may be conventional in the art, and preferably is an improved Hummers method, and specifically includes the following steps: h₂SO₄、H₃PO₄、KMnO₄Mixing the graphite and the graphite for the first time according to the mass ratio of 120:13:6:1, cooling to 35-40 ℃, and stirring at 50-55 ℃ to obtain a mixed material B; the mixed material B is sequentially mixed with ice water and H₂O₂Mixing the water solution for the second time, standing, centrifuging, collecting filter residue, and cleaning the filter residue to neutrality. The improved Hummers method adopted by the preferable graphene oxide preparation method of the invention can reduce the surface area of grapheneThe defect, promote the productivity, avoid the release of toxic gas.

Wherein, the graphite can be graphite conventionally used in the field, and is preferably flake graphite.

The stirring time can be the time conventionally used in the field, and generally can be 10-15 h, preferably 12-15 h.

Wherein, the stirring operation can further comprise a cooling operation, and the temperature can be generally reduced to room temperature.

The ice water may be a two-phase mixture of liquid water and solid water, which is conventionally considered by those skilled in the art.

Wherein, the mass ratio of the ice water to the graphite is conventional in the field, and is preferably (350-450): 1, more preferably 400: 1.

wherein, the H₂O₂H in aqueous solution₂O₂The mass percentage of (b) may be conventional in the art, and may be generally 20 to 35%, preferably 30 to 35%.

Wherein the graphite is in contact with the H₂O₂H in aqueous solution₂O₂The mass ratio of (A) can be conventional in the field, and generally can be (0.26-0.45): 1, preferably (0.30 to 0.45): 1.

the standing time can be the time of the operation routine in the field, and generally the solid phase and the liquid phase in the system can be completely separated, preferably 10-15 h, and more preferably 12-15 h.

Wherein the washing conditions and methods may be those conventional in such operations in the art, and generally comprise the steps of: and respectively washing the filter residue to be neutral by using absolute ethyl alcohol, HCl with the mass percent of 30% and deionized water.

Wherein, the operation of cleaning can further comprise the operation of drying. The drying conditions and methods may be those conventional in such operations in the art and may generally be carried out in a vacuum oven. The drying temperature can be the temperature which is conventional in the operation of the type in the field, and is preferably 50-60 ℃.

In the step (1), the Y-type molecular sieve can be a molecular sieve with a molar ratio of silicon element to aluminum element (1.5-3) which is conventionally considered by a person skilled in the art: 1, FAU structure molecular sieve.

In step (1), the preparation method of the Y-type molecular sieve can be conventional in the art, preferably a NaOH melt-hydrothermal method, and more preferably comprises the following steps: the mixture of the natural zeolite and NaOH is melted, mixed with water, aged and crystallized to obtain the product.

Wherein the natural zeolite can be clinoptilolite in Jinyun and/or mordenite in Jinyun, which are conventionally used in the art. Compared with the Y-type molecular sieve prepared by taking silica sol and activated alumina as raw materials conventionally adopted in the field, the Y-type molecular sieve prepared by taking the natural zeolite as the raw material has low cost and simple preparation process.

Wherein, the mole ratio of silicon element and aluminum element in the natural zeolite can be conventional in the field, and is preferably (4.5-6): 1.

wherein the mass ratio of the natural zeolite to the NaOH may be conventional in the art, preferably 1: (1.2-1.3).

Wherein, the melting conditions and method can be the conditions and method which are conventional in the operation in the field, and the framework structure of the natural zeolite can be generally melted.

The melting temperature may be a temperature conventionally used in the art, and is preferably 500 to 650 ℃, and more preferably 550 to 600 ℃.

The melting time can be the time of the operation routine in the field, and is preferably 1.5 to 2.5 hours, and more preferably 2 to 2.5 hours.

Wherein, the mass ratio of the material prepared after melting to the water can be conventional in the field, and is preferably 1: (4-5), more preferably 1: (4.5-5).

Wherein the aging time can be the time of the operation routine in the field, preferably 10-14 h, more preferably 12-14 h.

The crystallization temperature may be a temperature conventionally used in the art, and is preferably 90 to 110 ℃, and more preferably 100 to 110 ℃.

The crystallization time can be the time of the conventional operation in the field, preferably 6 to 10 hours, and more preferably 8 to 10 hours.

Wherein, the crystallization operation can further comprise the operations of water washing and/or drying. The drying temperature can be the temperature conventional in the operation in the field, and is preferably 140-160 ℃. The drying time can be the time conventionally used in the art, and is preferably 1.5 to 2.5 hours, and more preferably 2 to 2.5 hours.

In the step (1), the mass ratio of the graphene oxide to the Y-type molecular sieve may be conventional in the art, and is preferably 1: (4-6), more preferably 1: (4.5-5).

In the step (1), in the suspension containing graphene oxide and the Y-type molecular sieve, the concentration of the graphene oxide may be conventional in the art, and is preferably 4-6 mg/mL, and more preferably 5 mg/mL. As is conventional in the art, a mixture in which the substance distributed in the liquid material is not dissolved but merely dispersed is referred to as a suspension.

In step (1), the preparation method of the suspension containing graphene oxide and Y-type molecular sieve may be conventional in the art, and may generally include the following steps: (a) dispersing the graphene oxide in water to obtain graphene oxide gel; (b) and dispersing the Y-type molecular sieve in the graphene oxide gel.

In step (a), the dispersing method may be a method conventional in such operations in the art, and may be ultrasonic dispersing in general.

In step (a), the dispersion time may be a time conventional in the operation in the field, and generally, the graphene oxide may be uniformly dispersed in the water.

Wherein, in the step (b), the dispersing method can be a method which is conventional in the operation in the field, and can be ultrasonic dispersing generally.

In the step (b), the dispersing time may be a time conventionally used in the art, and generally the Y-type molecular sieve may be uniformly dispersed in the graphene oxide gel, preferably 15 to 20min, and more preferably 20 min.

Wherein, in the step (b), the operation of dispersing can be further followed by the operation of stirring. The rotation speed of the stirring can be the rotation speed of the operation in the field, preferably 800-1200 turns/min, and more preferably 1000-1100 turns/min. The stirring time can be the time conventionally used in the field, preferably 25-35 min, more preferably 30-35 min.

In step (1), the conditions and methods of drying may be those conventional in such operations in the art, and generally include the following steps: stirring the mixture at 75-85 ℃ until the mixture is pasty, and drying the pasty mixture in an oven at the temperature of 45-50 ℃ to obtain the product.

In step (1), the inert atmosphere may be an inert atmosphere conventionally used in the art, for example, nitrogen.

In step (1), the conditions and method of the reduction reaction may be conventional in the art, and generally the graphene oxide may be reduced to reduced graphene oxide.

In the step (1), the temperature of the reduction reaction may be a temperature conventional in the art, preferably 350 to 450 ℃, and more preferably 380 to 400 ℃.

In the step (1), the time of the reduction reaction may be a time conventionally used in the art, and is preferably 1.5 to 2.5 hours, and more preferably 2 to 2.5 hours.

In step (1), the reduction reaction may be further followed by cooling, which may be generally to room temperature.

In the step (2), the mass-to-volume ratio of the rGO-Y composite material to the water may be conventional in the art, and is preferably 0.4 to 0.6mg/mL, more preferably 0.5 to 0.6 mg/mL.

In the step (2), the rGO-Y composite material and H₂PtCl₆The mass ratio of the Pt element(s) in (b) may be conventional in the art, and is preferably 1: (0.6-1), more preferably 1: (0.7-0.8).

In step (2), the reducing agent may be H which is conventionally used in the art₂PtCl₆Reducing agent for reduction to Pt metal, preferably NaHB₄And/or hydrazine hydrate, more preferably NaHB₄。

Wherein, when the reducing agent is NaBH₄When, the NaBH₄Can be prepared as NaBH according to the routine method in the field₄Added as an aqueous solution. Wherein, the NaBH₄NaBH in aqueous solution₄The concentration of (b) is a conventional concentration in the art, preferably 0.04-0.06 mol/L, more preferably 0.05-0.06 mol/L.

In the step (2), the molar ratio of the mass of the rGO-Y composite material to the reducing agent can be conventional in the art, preferably 3-5 g/mol, and more preferably 3-4 g/mol.

In step (2), the method of dispersion may be conventional in the art, and may be generally ultrasonic dispersion.

In the step (2), the dispersing time can be conventional in the art, and generally the rGO-Y composite material can be uniformly dispersed in the water, preferably 0.5 to 1.5 hours, and more preferably 1 hour.

In step (2), the mixing method may be a method conventional in such operations in the art, and may be generally an ultrasonic dispersion method.

In the step (2), the mixing time may be a time conventionally used in the art, and is preferably 35 to 45min, and more preferably 40 to 45 min.

In step (2), the method for adding the reducing agent may be conventional in the art, and may be generally dropwise.

In step (2), the reaction may be H on the surface and/or inside the rGO-Y composite material as conventionally considered by those skilled in the art₂PtCl₆A reaction of reducing the reducing agent to Pt metal.

In the step (2), the reaction time can be the time conventionally used in the reaction in the field, and is preferably 6-8 h.

In the step (2), the reaction operation may further include one or more of centrifuging, collecting the residue, washing, and drying.

The washing conditions and method may be those commonly used in the art, and the washing may be generally performed using distilled water.

The drying temperature may be a temperature conventionally used in the art, and is preferably 35 to 45 ℃, and more preferably 40 to 45 ℃.

The drying time can be the time of the operation routine in the field, preferably 20-30 h, and more preferably 24-30 h.

The invention also provides a composite catalyst, which is prepared by the preparation method of the composite catalyst.

The invention also provides an application of the composite catalyst as a cathode catalyst in the field of proton exchange membrane fuel cells.

Preferably, the composite catalyst is used as a cathode catalyst in the field of hydrogen preparation by water electrolysis through a proton exchange membrane.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The reagents and starting materials used in the present invention are commercially available.

The positive progress effects of the invention are as follows: and compounding the graphene oxide and the Y-type molecular sieve, and loading metal Pt to prepare the composite catalyst containing the reduced graphene oxide, the Y-type molecular sieve and the Pt metal catalyst. In the research and development process, the Y-type molecular sieve is compounded between layers of the reduced graphite oxide as a filling material to prevent the stacking of the reduced graphene oxide interlayer and prevent the agglomeration of the reduced graphene oxide carrier; the reduced graphene oxide is wrapped on the surface of the Y-shaped molecular sieve, so that the conductivity of the Y-shaped molecular sieve can be obviously improved, and the complementary advantages of the Y-shaped molecular sieve and the Y-shaped molecular sieve can be realized. The Y-type molecular sieve has a porous structure, so that the stability and the dispersion uniformity of the supported catalyst platinum are ensured, and a synergistic effect is achieved between the Y-type molecular sieve and the catalyst platinum; in the composite catalyst prepared by the invention, the number of active sites of platinum is increased, compared with the prior art, the utilization rate of the platinum catalyst is greatly improved, ideal catalytic performance can be realized by adopting a small amount of platinum catalyst, the cost of the composite catalyst is reduced, the catalytic performance is stable, and the initial voltage is still maintained at 98% after 1000 times of circulation.

Drawings

FIG. 1 is a LSV polarization curve of the composite catalysts prepared in examples 1-2 and comparative examples 1-2;

FIG. 2 is a graph showing the Tafel slopes of the composite catalysts prepared in examples 1 to 2 and comparative examples 1 to 2;

FIG. 3 is a CV curve of the composite catalyst prepared in example 1 at various sweep rates;

FIG. 4 is a CV curve of the composite catalyst prepared in example 2 at various sweep rates;

FIG. 5 is a CV curve of the composite catalyst prepared in comparative example 1 at various sweep rates;

FIG. 6 is a CV curve of the composite catalyst prepared in comparative example 2 at various sweep rates;

FIG. 7 is a graph showing the relationship between the current density of the composite catalysts obtained in examples 1 to 2 and comparative examples 1 to 2 and the change in the scanning rate;

FIG. 8 is an SEM photograph of the composite catalyst prepared in example 1;

fig. 9 is an XRD pattern of the composite catalyst prepared in example 1.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

Example 1

(1) Preparation of graphene oxide by improved Hummers method

First, H₂SO₄、H₃PO₄、KMnO₄Mixing the graphite powder and the crystalline flake graphite according to the mass ratio of 120:13:6:1, slightly releasing heat to 35-40 ℃, heating to 50 ℃, stirring for 12 hours, and cooling the product to room temperature; pouring ice water into the reaction kettle, and then adding 30 mass percent of H₂O₂Aqueous solution, flake graphite and H₂O₂H in aqueous solution₂O₂Is 0.3: 1, the product was observed to turn to dark yellow; standing for 12h, centrifuging, collecting the residue, and separatingWashing the filter residue to be neutral by using absolute ethyl alcohol, 30% HCl and deionized water, and drying in vacuum at 60 ℃ to obtain graphene oxide;

(2) preparation of Y-type molecular sieve by using natural zeolite as raw material

Jinyun mordenite (silicon to aluminium ratio 5.1: 1) and NaOH were mixed at a ratio of 7.5: 9, uniformly mixing in a nickel crucible, and melting for 2 hours at 550 ℃; adding a certain amount of water (the solid-liquid mass ratio is 1:4.5) into the molten product, uniformly mixing, stirring and aging in a plastic beaker for 12 hours, then transferring into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallizing at 100 ℃ for 8 hours; repeatedly washing the product with deionized water during suction filtration, and drying at 150 ℃ for 2 h;

(3) preparation of reduced graphene oxide-Y type molecular sieve composite material (rGO-Y composite material)

Adding a dispersed graphene oxide suspension with the concentration of 5mg/mL into the Y-type molecular sieve (the mass ratio of the graphene oxide to the Y-type molecular sieve is 1:5), carrying out ultrasonic dispersion for 20min, and then strongly stirring for 30min to obtain a suspension containing the graphene oxide and the Y-type molecular sieve; then, continuously stirring the suspension containing the graphene oxide and the Y-type molecular sieve at 80 ℃ to evaporate water, and drying the obtained paste in an oven at 45 ℃; finally, firing for 2h at 380 ℃ under the protection of nitrogen, and naturally cooling the obtained product to room temperature to obtain the reduced graphene oxide-Y type molecular sieve composite material (rGO-Y composite material);

(4) preparation of rGO-Y composite material loaded Pt composite catalyst

Dispersing 5mg of the newly prepared rGO-Y composite material obtained in the step (3) in 10mL of water, performing ultrasonic dispersion for 1H, and then adding 8.4mg of H₂PtCl₆(the mass of Pt contained in the solution is 4mg), and continuing to perform ultrasonic treatment for 40 min; then, 30mL of NaBH with a concentration of 0.05mol/L was added dropwise with stirring₄Stirring the solution for 8 hours to ensure that the solution fully reacts; and finally, centrifugally separating the product, collecting filter residues, repeatedly washing the filter residues by using distilled water, and drying the product at 40 ℃ for 24 hours in vacuum to obtain the composite catalyst. The amount of platinum carried in the composite catalyst obtained in this example was analyzed by ICP, and the result of the test was 44%, and the scanning electron micrograph thereof is shown in fig. 8. The XRD pattern is shown in FIG. 9, and it can be seen from FIG. 9And after the rGO is coated, the structure of the Y-type molecular sieve is not influenced, because the content of the rGO is less, the diffraction peak of the Y-type molecular sieve covers the diffraction peak of the rGO, and therefore the characteristic absorption peak of the rGO cannot be observed.

Example 2

(1) Preparation of Graphene Oxide (GO) by improved Hummers method

First, H₂SO₄、H₃PO₄、KMnO₄Mixing the graphite powder and the crystalline flake graphite according to the mass ratio of 120:13:6:1, slightly releasing heat to 35-40 ℃, heating to 50 ℃, stirring for 12 hours, and cooling the product to room temperature; pouring ice water into the reaction kettle, and then adding 30 mass percent of H₂O₂Aqueous solution, flake graphite and H₂O₂H in aqueous solution₂O₂Is 0.3: 1, the product was observed to turn to dark yellow; standing for 12h, centrifugally separating and collecting filter residues, respectively washing the filter residues to be neutral by using absolute ethyl alcohol, 30% HCl and deionized water, and drying in vacuum at 60 ℃ to obtain graphene oxide;

(2) preparation of Y-type molecular sieve by using natural zeolite as raw material

Clinoptilolite in Jinyun (silicon to aluminum ratio of 5.4: 1) and NaOH in a ratio of 7.5: 9, uniformly mixing in a nickel crucible, and melting for 2 hours at 550 ℃; adding a certain amount of water (the solid-liquid mass ratio is 1:4.5) into the molten product, uniformly mixing, stirring and aging in a plastic beaker for 12 hours, then transferring into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallizing at 100 ℃ for 8 hours; repeatedly washing the product with deionized water during suction filtration, and drying at 150 ℃ for 2 h;

(3) preparation of reduced graphene oxide-Y type molecular sieve composite material (rGO-Y composite material)

Adding a dispersed graphene oxide suspension with the concentration of 5mg/mL into the Y-type molecular sieve (the mass ratio of the graphene oxide to the Y-type molecular sieve is 1:4.5), carrying out ultrasonic dispersion for 20min, and then strongly stirring for 30min to obtain a suspension containing the graphene oxide and the Y-type molecular sieve; then, continuously stirring the suspension containing the graphene oxide and the Y-type molecular sieve at 80 ℃ to evaporate water, and drying the obtained paste in an oven at 45 ℃; finally, firing for 2h at 380 ℃ under the protection of nitrogen, and naturally cooling the obtained product to room temperature to obtain the reduced graphene oxide-Y type molecular sieve composite material (rGO-Y composite material);

(4) preparation of rGO-Y composite material loaded Pt composite catalyst

Dispersing 5mg of the newly prepared rGO-Y composite material obtained in the step (3) in 10mL of water, performing ultrasonic dispersion for 1H, and then adding 7.35mg of H₂PtCl₆(the mass of Pt contained in the solution is 3.5mg), and continuing to perform ultrasonic treatment for 40 min; then, 25mL of NaBH of 0.05mol/L concentration was added dropwise with stirring₄Stirring the solution for 8 hours to ensure that the solution fully reacts; and finally, centrifugally separating the product, collecting filter residues, repeatedly washing the filter residues by using distilled water, and drying the product at 40 ℃ for 24 hours in vacuum to obtain the composite catalyst. The amount of platinum carried in the composite catalyst obtained in this example was analyzed by ICP, and the result of the test was 41%.

Comparative example 1

An imported brand of commercial platinum carbon catalyst having a carrier of XC-72R carbon black and a platinum loading of 60% as measured by ICP was purchased as a comparative example. The amount of platinum carried was higher, unlike examples 1 and 2.

Comparative example 2

(1) Preparation of Y-type molecular sieve by using natural zeolite as raw material

Jinyun mordenite (silicon to aluminium ratio 5.1: 1) and NaOH were mixed at a ratio of 7.5: 9, uniformly mixing in a nickel crucible, and melting for 2 hours at 550 ℃; adding a certain amount of water (the solid-liquid mass ratio is 1:4.5) into the molten product, uniformly mixing, stirring and aging in a plastic beaker for 12 hours, then transferring into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallizing at 100 ℃ for 8 hours; repeatedly washing the product with deionized water during suction filtration, and drying at 150 ℃ for 2 h;

(2) preparation of graphene-Y type molecular sieve composite material (GE-Y composite material) A well-dispersed Graphene (GE) dispersion liquid with the concentration of 5mg/mL (GE and Y type molecular sieve are mixed according to the mass ratio of 1:5) is added into a Y type molecular sieve, the thickness of graphene is 1-5 nm, and after ultrasonic dispersion is carried out for 20min, strong stirring is carried out for 30min, so that uniform suspension is obtained. The suspension was then continuously stirred at 80 ℃ to evaporate water, and the resulting paste was dried in an oven at 45 ℃. And finally, firing for 2h at 380 ℃ under the protection of nitrogen, and naturally cooling the obtained product to room temperature to obtain the graphene-Y type molecular sieve composite material (GE-Y composite material).

(3) Preparation of composite catalyst of GE-Y composite material loaded with Pt

5mg of the GE-Y composite material newly prepared in the step (2) is dispersed in 10mL of water, ultrasonic dispersion is carried out for 1h, and 8.4mgH is added₂PtCl₆(the mass of Pt contained in the solution is 4mg), and continuing to perform ultrasonic treatment for 40 min; then, 30mL of NaBH with a concentration of 0.05mol/L was added dropwise with stirring₄Stirring the solution for 8 hours to ensure that the solution fully reacts; and finally, centrifugally separating the product, collecting filter residues, repeatedly washing the filter residues by using distilled water, and drying the product at 40 ℃ for 24 hours in vacuum to obtain the composite catalyst.

Comparative example 3

Compared with the example 1, the difference is only that the material adding sequence in the step (3) and the step (4) is different, specifically:

the steps (1) and (2) are the same as in example 1;

(3) preparation of Y-type molecular sieve-Pt composite material (Y-Pt composite material)

Dispersing 4mg of the newly prepared Y-type molecular sieve in the step (2) in 10mL of water, performing ultrasonic dispersion for 1H, and then adding 8.4mg of H₂PtCl₆(the mass of Pt contained in the solution is 4mg), and continuing to perform ultrasonic treatment for 40 min; then, 30mL of NaBH with a concentration of 0.05mol/L was added dropwise with stirring₄Stirring the solution for 8 hours to ensure that the solution fully reacts; finally, centrifuging the product, collecting filter residue, repeatedly cleaning the filter residue with distilled water, and vacuum-drying the product at 40 ℃ for 24 hours to obtain the Y-Pt composite material;

(4) preparation of composite catalyst

Adding a dispersed graphene oxide suspension with the concentration of 5mg/mL (the mass ratio of graphene oxide to the Y-type molecular sieve is 1:5) into the Y-Pt composite material prepared in the step (3), carrying out ultrasonic dispersion for 20min, and then strongly stirring for 30min to obtain a suspension; then, continuously stirring the suspension at 80 ℃ to evaporate water, and placing the obtained paste in a drying oven to be dried at 45 ℃; and finally, burning for 2h at 380 ℃ under the protection of nitrogen, and naturally cooling the obtained product to room temperature to obtain the composite material.

The composite material prepared by the comparative example has no Pt active site on graphene, and the overpotential (eta @10mA · cm) of the composite material is tested^-2geo) was 183.5mV, much higher than example 1, and the composite catalyst prepared by this comparative example had poor catalytic performance.

Comparative example 4

Compared with the example 1, the difference is only that the material adding sequence in the step (3) and the step (4) is different, specifically:

the steps (1) and (2) are the same as in example 1;

(3) preparation of graphene oxide-Pt composite material (GO-Pt composite material)

Dispersing 1mg of graphene oxide newly prepared in the step (1) in 10mL of water, performing ultrasonic dispersion for 1H, and then adding 8.4mg of H₂PtCl₆(the mass of Pt contained in the solution is 4mg), and continuing to perform ultrasonic treatment for 40 min; then, 30mL of NaBH with a concentration of 0.05mol/L was added dropwise with stirring₄Stirring the solution for 8 hours to ensure that the solution fully reacts; finally, centrifugally separating the product, collecting filter residue, repeatedly washing the filter residue with distilled water, and vacuum-drying the product at 40 ℃ for 24 hours;

(4) preparation of composite catalyst

Adding a dispersed GO-Pt composite material suspension into a Y-type molecular sieve, wherein the concentration of graphene oxide in the GO-Pt composite material suspension is 5mg/mL, the mass ratio of the graphene oxide to the Y-type molecular sieve is 1:5, and after ultrasonic dispersion is carried out for 20min, strongly stirring for 30min to obtain a GO-Pt composite material and Y-type molecular sieve suspension; then, continuously stirring the GO-Pt composite material and the suspension of the Y-type molecular sieve at 80 ℃ to evaporate water, and drying the obtained paste in a drying oven at 45 ℃; and finally, burning for 2h at 380 ℃ under the protection of nitrogen, and naturally cooling the obtained product to room temperature to obtain the composite material.

In the preparation process of the composite material prepared by the comparative example, the phenomenon that graphene oxide is easy to agglomerate is found, the load of Pt is small, a large amount of Pt is difficult to uniformly load on the surface of a small amount of GO, and the overpotential (eta @10 mA-cm) of the composite material is tested^-2geo) was 210.3mV, and the catalytic performance of the composite catalyst prepared in this comparative example was poor.

Effect example 1

(1) Electrode preparation

Electrochemical tests were performed at room temperature using an electrochemical workstation (autolab, wangton, switzerland). A standard three-electrode system was used in the test with a glassy carbon disk electrode (5 mm diameter, 0.204mg cm loading)^-2) As a working electrode, a platinum electrode was used as a counter electrode and an Ag/AgCl (3M KCl) electrode was used as a reference electrode. With Al₂O₃The powder mechanically polished the working electrode and then washed with ethanol and deionized water, respectively. The working electrode slurry was prepared as follows: 2mg of the catalyst was dispersed in 500. mu.L of a mixed solvent of water and isopropyl alcohol at a volume ratio of 4:1, and after adding 20. mu.L of Nafion solution (5%), the solution was ultrasonically dispersed for 3 hours to form a uniform slurry, wherein the catalyst was any one of the composite catalysts prepared in examples 1-2 and comparative examples 1-2. And uniformly dripping 10 mu L of slurry on the surface of the glassy carbon electrode, and naturally airing to obtain the working electrode.

(2) And respectively scanning the prepared working electrode for 30-50 times by a cyclic voltammetry until the signal is stable, collecting data, and calculating to obtain overpotential, Tafel slope, electric double layer capacitance and cyclic performance data.

1. Measuring overpotential (eta @10mA · cm)^-2geo)

The overpotential eta is an important parameter for measuring the catalytic activity of the composite catalyst, and the smaller the eta value is, the lower the actual voltage required by the current density is, and the relatively smaller the energy consumption is, which shows that the better the electrocatalysis performance is, and the higher the catalytic activity of the composite catalyst is. In order to quantitatively compare the performances of the composite catalysts, the current density of 10mA cm is selected^-2The results of comparing the catalytic performances of different composite catalysts with corresponding overpotential values are shown in Table 1.

2. Linear Sweep Voltammetry (LSV)

The Linear Sweep Voltammetry (LSV) test is to adopt each working electrode prepared in the step (1) respectively in 0.5M H electrolyte₂SO₄In solution at 2mV · s^-1The scan rate was tested to obtain an LSV polarization curve, the results of which are shown in fig. 1.

The Tafel slope (Tafel slope) is obtained from the LSV polarization curve, which reflects the kinetics of the electrochemical reaction. A tafel curve is obtained by redrawing the LS polarization curve (logarithmic plot of overpotential versus current density), which is shown in fig. 2, and then the tafel equation can be fitted according to the linear part of the tafel curve:

η＝a+b·log j

where η represents the overpotential, b represents the tafel slope, and j represents the current density. Tafel slope data is shown in Table 1, where a smaller Tafel slope indicates a faster increase in current density, indicating that the rate-determining step is at the end of the multiple electron transfer reaction, which is generally a good indicator of electrocatalyst.

3. Electrochemical active area (ECSA)

The electrochemical active specific surface area is one of important indexes for measuring the catalytic performance of the composite catalyst, and the electrochemical active surface area is measured by the capacitance value (C) of an electric double layer_dl) Measured by the value of the capacitance of the electric double layer (C) at the solid-liquid interface_dl) Is in direct proportion.

C_dlThe test method comprises the following steps: under the potential window without Faraday process, at different sweeping speeds (10-100 mV. multidot.s)^-1) For testing, 5-8 continuous scanning speeds are usually selected. The obtained Cyclic Voltammetry (CV) curve gradually takes a rectangular shape with the increase of the sweep rate, and in order to make the obtained data linear, the appropriate sweep rate needs to be selected. In the present effective example, 5 different sweep rates (10, 30, 50, 70, and 90mV · s) were used in a certain potential interval to obtain electric double layer capacitance data^-1) The CV curves of the composite catalysts prepared in example 1, example 2, comparative example 1 and comparative example 2 at different sweep rates were shown in fig. 3 to 6, respectively, by performing cyclic voltammetry. Then, respectively counting the difference (Δ j ═ ja-jc) between the current densities of the anode and the cathode corresponding to the same overpotential value (usually, the middle value of the selected voltage range) at different sweep rates, plotting with the sweep rate as the abscissa and the difference between the current densities as the ordinate, and performing linear regression fitting on the plotted plot to obtain the slope of the fitting equation, wherein one half of the slope is the capacitance value of the electric double layer, and the curve showing the relationship between the current density of the composite catalysts prepared in examples 1 to 2 and comparative examples 1 to 2 and the change of the scanning rate is shown in fig. 7, and the electric double layer is shown in fig. 7The capacitance results are shown in table 1. The larger the electric double layer capacitance is, the larger the active specific surface area and the more active sites of the catalyst are, and therefore, the catalyst has stronger catalytic activity.

4. Cycle performance test

Working electrodes made using the composite catalysts prepared in examples 1 and 2 above, at 2 mV. multidot.s^-1The scanning speed of the composite catalyst is 1000 times of cyclic scanning, and the result shows that the polarization curve of the composite catalyst has only slight change, and the initial voltage still maintains 98 percent.

TABLE 1

Composite catalyst	Overpotential (eta @10mA · cm)-2geo)	Tafel slope	Double electric layer capacitor
				Example 1	37.1mV	27.4mV/dec	59.98mF/cm2
Example 2	44.7mV	36.7mV/dec	55.49mF/cm2
				Comparative example 1	48.7mV	39.4mV/dec	30.65mF/cm2
Comparative example 2	53.7mV	40.7mV/dec	20.6mF/cm2

As is clear from the data in table 1 and fig. 1 to 7, the overpotential and tafel slope of the catalyst are reduced and the electric double layer capacitance of the catalyst is increased as compared with the commercial catalyst. The result shows that the compounding of the graphene and the Y-type molecular sieve is beneficial to stable and uniform dispersion of platinum nanoparticles, the utilization efficiency of platinum can be improved, and the ideal catalytic performance can be obtained under the condition of low platinum loading.