A method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing formic acid decomposition to produce hydrogen

Abstract

The present invention discloses a method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing the decomposition of formic acid to produce hydrogen, and belongs to the technical field of catalytic hydrogen production. The steps of the preparation method include: immersing highly oriented pyrolytic graphite in a dioctadecylamine solution, standing, washing, and drying to obtain highly oriented pyrolytic graphite modified by dioctadecylamine self-assembly; dissolving a soluble zinc salt and a soluble platinum salt in water, and adding the highly oriented pyrolytic graphite modified by dioctadecylamine self-assembly; obtaining highly oriented pyrolytic graphite modified by ZnO-coated Pt nanoparticles after hydrothermal reaction; and removing ZnO in the highly oriented pyrolytic graphite modified by ZnO-coated Pt nanoparticles by acid immersion to obtain a highly dispersed Pt nanoparticle array catalyst. The highly dispersed Pt in the highly dispersed Pt nanoparticle array catalyst prepared by the present invention has good dispersibility, high stability of the catalyst, easy separation and recycling, and can reduce costs and reduce environmental burden.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic hydrogen production, and specifically relates to a method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing formic acid decomposition to produce hydrogen. Background Art

[0002] At present, the development and utilization of clean energy has always been a research hotspot in the global energy field. Among them, hydrogen production by decomposition of formic acid is a potential way of hydrogen storage and energy conversion, which has the advantages of high energy density, easy storage and transportation. The key link in the decomposition of formic acid to produce hydrogen is the design and preparation of catalysts to promote the decomposition reaction of formic acid. Traditional catalysts usually use precious metals, such as platinum (Pt) and gold (Au), to improve the efficiency of catalytic reactions. However, the high cost and limited resources of precious metals make it an important research topic to find ways to effectively utilize precious metals. In this context, some researchers have begun to study and develop new catalysts to improve the efficiency of catalytic reactions and reduce the use of precious metals. Highly oriented pyrolytic graphite (HOPG) materials have attracted widespread attention from researchers due to their good mechanical properties, excellent conductivity and chemical stability. However, due to its special structure and characteristics, it is still a challenge to directly modify precious metals onto HOPG and maintain good dispersion. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing the decomposition of formic acid to produce hydrogen. The method uses HOPG as a supporting framework, uses a self-assembled molecular film of dioctadecylamine (DOA) as a nucleation site of the nanoparticle array, and then coats ZnO on the surface of the Pt nanoparticles to form a co-modification by a pyrolysis method. The ZnO coating layer plays a double-layer role: first, ZnO can limit the size of the Pt nanoparticles; second, ZnO can be removed by acid washing to increase the porosity and dispersibility of the Pt nanocatalyst. Since the nano Pt nanoparticle array has the characteristics of small particles, high order, high dispersibility and strong catalytic activity, the catalyst exhibits excellent performance in the process of formic acid decomposition to produce hydrogen. In addition, the introduction of DOA self-assembled molecular film modified HOPG not only improves the support performance and adsorption sites of the catalyst, but also enhances the proton capture ability of the catalyst surface, thereby improving the catalytic activity of formic acid catalytic hydrogen production. The highly dispersed Pt nanoparticle array catalyst of the present invention has important application potential, can effectively improve the efficiency of hydrogen production by decomposing formic acid, save precious metal materials and improve the stability of the catalyst. This will promote the development of the hydrogen energy field and promote the application of sustainable energy.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] One of the technical solutions of the present invention is to provide a method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing the decomposition of formic acid to produce hydrogen, comprising the following steps:

[0006] The highly oriented pyrolytic graphite is immersed in a dioctadecylamine solution, left to stand, washed, and dried to obtain the highly oriented pyrolytic graphite modified by dioctadecylamine self-assembly;

[0007] A soluble zinc salt and a soluble platinum salt are co-dissolved in water, and the dioctadecylamine self-assembled modified highly oriented pyrolytic graphite is added; after a hydrothermal reaction, a ZnO-coated Pt nanoparticle-modified highly oriented pyrolytic graphite is obtained; and acid soaking is performed to remove ZnO in the ZnO-coated Pt nanoparticle-modified highly oriented pyrolytic graphite, thereby obtaining a highly dispersed Pt nanoparticle array catalyst.

[0008] The present invention immerses HOPG in a DOA solution, so that DOA molecules form an ordered self-assembled structure adsorbed on the surface of HOPG; further, the self-assembled DOA molecules are used as nucleation sites to grow ZnO-coated Pt nanoparticles through a high-temperature hydrothermal reaction, and then the ZnO in the ZnO-coated Pt nanoparticles is removed through acid leaching to obtain a catalyst with uniformly dispersed Pt nanoparticles.

[0009] Preferably, the concentration of the dioctadecylamine solution is 10 -6 ~10 -5 mol / L.

[0010] Preferably, the standing time is 1 to 6 hours.

[0011] Preferably, the soluble zinc salt is zinc sulfate, nitrate or chloride; and the soluble platinum salt is zinc sulfate, nitrate or chloride.

[0012] Preferably, the molar ratio of zinc in the soluble zinc salt to platinum in the soluble platinum salt is (1-10):1.

[0013] Preferably, the temperature of the hydrothermal reaction is 300° C. and the time is 1 to 4 hours.

[0014] Preferably, the acid soaking is soaking in a sulfuric acid solution with a concentration of 1 to 4 mol / L, and the soaking time is 12 to 24 hours.

[0015] The second technical solution of the present invention is to provide a highly dispersed Pt nanoparticle array catalyst for catalyzing the decomposition of formic acid to produce hydrogen, which is prepared according to the above preparation method.

[0016] The beneficial technical effects of the present invention are as follows:

[0017] The present invention uses DOA molecules to self-assemble to form a monolayer modified HOPG as a template, and uses highly ordered secondary amino groups as nucleation sites to anchor the ZnO-coated nano Pt particle array. The ZnO coating layer can control the size of the Pt nanoparticles and, as a sacrificial agent, improve the porosity and dispersibility of the nano Pt particle array.

[0018] High dispersion: When Pt nanoparticles are highly dispersed on the carrier surface, they can provide more surface active sites for reactant molecules, which will greatly improve the effectiveness and efficiency of the catalyst.

[0019] High stability: DOA self-assembled film modified HOPG as a carrier of Pt nanoparticles can form an orderly array of nanoparticles, effectively preventing the agglomeration of catalyst particles during the reaction process, thereby ensuring the long-term stability of the material.

[0020] Easy to separate and recycle: The self-supporting structure of HOPG allows the catalyst to be easily separated from the reaction system, which is conducive to the recovery and reuse of the catalyst, reducing costs and reducing environmental burden. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is a flow chart for preparing a highly dispersed Pt nanoparticle array catalyst in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0023] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0024] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0025] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0026] The preparation flow chart of the highly dispersed Pt nanoparticle array catalyst in the embodiment of the present invention is shown in Figure 1 .

[0027] Example 1

[0028] Preparation of highly dispersed Pt nanoparticle array catalyst:

[0029] (1) Preparation of DOA molecular self-assembly modified HOPG: HOPG was washed with a mixed solution of water and ethanol and then dried at low temperature. The uneven graphite layer on the surface was removed by tape stripping. HOPG was suspended and submerged in 50 mL 5.0 × 10 -6 M of DOA toluene solution, let it stand for 2h, then wash HOPG three times with anhydrous ethanol and dry it at 50℃ to finally form DOA molecular self-assembly modified HOPG.

[0030] (2) Preparation of ZnO-coated Pt nanoparticle array: 0.15 mM zinc nitrate and 0.05 mM platinum nitrate were dissolved in 20 mL of deionized water to form a mixed solution, and the DOA molecules self-assembled and modified HOPG formed in step (1) were placed in a high-temperature reactor containing the mixed solution, reacted at 300°C for 3 h, and then cooled. After washing with water, the mixture was vacuum dried at 60°C to form a ZnO-coated Pt nanoparticle array modified HOPG.

[0031] (3) Preparation of highly dispersed Pt nanoparticle arrays: The ZnO-coated Pt nanoparticle array-modified HOPG formed in step (2) was immersed in a 3 mol / L sulfuric acid solution for 18 h to remove the ZnO coating layer, and then washed with water and dried in a vacuum at 60°C to obtain a highly dispersed Pt nanoparticle array catalyst.

[0032] Example 2

[0033] Preparation of highly dispersed Pt nanoparticle array catalyst:

[0034] (1) Preparation of DOA molecular self-assembly modified HOPG: HOPG was washed with a mixed solution of water and ethanol and then dried at low temperature. The uneven graphite layer on the surface was removed by tape stripping. HOPG was suspended and submerged in 50 mL 2.0 x 10 -6 M of DOA toluene solution, let it stand for 4 hours, then wash HOPG three times with anhydrous ethanol and dry it at 50°C to finally form DOA molecular self-assembled modified HOPG.

[0035] (2) Preparation of ZnO-coated Pt nanoparticle arrays: 0.25 mM zinc nitrate and 0.05 mM platinum nitrate were dissolved in 20 mL of deionized water to form a mixed solution. The DOA molecules self-assembled and modified HOPG formed in step (1) was placed in a high-temperature reactor containing the mixed solution. The mixture was reacted at 300°C for 4 hours and then cooled. After washing with water, the mixture was vacuum dried at 60°C to form a ZnO-coated Pt nanoparticle array modified HOPG.

[0036] (3) Preparation of highly dispersed Pt nanoparticle arrays: The ZnO-coated Pt nanoparticle array-modified HOPG formed in step (2) was immersed in a 4 mol / L sulfuric acid solution for 21 h to remove the ZnO coating layer. The catalyst was then washed with water and dried under vacuum at 60°C to obtain a highly dispersed Pt nanoparticle array catalyst.

[0037] Comparative Example 1

[0038] Highly dispersed ZnO coated Pt nanoparticle array catalyst:

[0039] Prepare according to steps (1) and (2) in Example 1.

[0040] The pore sizes and the performance of decomposing formic acid to produce hydrogen of the catalysts prepared in Examples 1-2 and Comparative Example 1 were tested. The test results are shown in Table 1.

[0041] Table 1 Comparison of physical properties of various catalysts and catalytic formic acid hydrogen evolution performance

[0042]

[0043] It can be seen from Table 1 that acid washing can significantly increase the pores of the catalyst, that is, it can increase the catalytic specific surface area. In addition, after removing the ZnO coating layer, the conversion frequency and mass specific activity of the catalyst for catalytic hydrogen evolution from formic acid are significantly improved.

[0044] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing the decomposition of formic acid to produce hydrogen, characterized in that: The following steps are involved: The highly oriented pyrolytic graphite is immersed in a dioctadecylamine solution, left to stand, washed, and dried to obtain the highly oriented pyrolytic graphite modified by dioctadecylamine self-assembly; A soluble zinc salt and a soluble platinum salt are co-dissolved in water, and the dioctadecylamine self-assembled modified highly oriented pyrolytic graphite is added; after a hydrothermal reaction, a ZnO-coated Pt nanoparticle-modified highly oriented pyrolytic graphite is obtained; and acid soaking is performed to remove ZnO in the ZnO-coated Pt nanoparticle-modified highly oriented pyrolytic graphite, so as to obtain a highly dispersed Pt nanoparticle array catalyst.

2. The method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing formic acid decomposition to produce hydrogen according to claim 1, characterized in that: The concentration of the dioctadecylamine solution is 10 -6 ~10 -5 mol / L.

3. The method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing formic acid decomposition to produce hydrogen according to claim 1, characterized in that: The standing time is 1 to 6 hours.

4. The method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing the decomposition of formic acid to produce hydrogen according to claim 1, characterized in that: The soluble zinc salt is zinc sulfate, nitrate or chloride; the soluble platinum salt is zinc sulfate, nitrate or chloride.

5. The method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing formic acid decomposition to produce hydrogen according to claim 1, characterized in that: The molar ratio of zinc in the soluble zinc salt to platinum in the soluble platinum salt is (1-10):

1.

6. The method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing the decomposition of formic acid to produce hydrogen according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 300° C. and the time is 1 to 4 hours.

7. The method for preparing a highly dispersed Pt nanoparticle array catalyst for catalyzing the decomposition of formic acid to produce hydrogen according to claim 1, characterized in that: The acid soaking is soaking in a sulfuric acid solution with a concentration of 1 to 4 mol / L, and the soaking time is 12 to 24 hours.

8. A highly dispersed Pt nanoparticle array catalyst for catalyzing the decomposition of formic acid to produce hydrogen, prepared according to the preparation method according to any one of claims 1 to 7.

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