CN110571443B

CN110571443B - Porous alloy nanotube catalyst with adjustable structure and preparation method thereof

Info

Publication number: CN110571443B
Application number: CN201910938640.XA
Authority: CN
Inventors: 徐峰; 林本锋
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2019-09-30
Filing date: 2019-09-30
Publication date: 2022-07-08
Anticipated expiration: 2039-09-30
Also published as: CN110571443A

Abstract

The invention discloses a porous alloy nanotube catalyst with an adjustable structure, which comprises noble metal-based alloy particles and carbon particles, wherein the diameters of the alloy particles and the carbon particles are 3-300 nm, and the diameter of a pore is 5-60 nm. The diameter of the porous alloy nanotube is 15-1000 nm, and the length of the porous alloy nanotube is 50-100000 nm. The adjustment of the catalyst alloy and the core-shell structure is realized by changing the addition amounts of the noble metal and the polyvinylpyrrolidone.

Description

Porous alloy nanotube catalyst with adjustable structure and preparation method thereof

Technical Field

The invention belongs to the field of proton exchange membrane fuel cells, and particularly relates to a porous alloy nanotube catalyst with an adjustable structure.

Description of the background

The proton exchange membrane fuel cell has the advantages of low price of fuel methanol, convenient storage and transportation and the like, but the oxidation efficiency of the anode to the methanol and the oxygen reduction reaction efficiency in the cathode are lower, so that the integral activity of the proton exchange membrane fuel cell is insufficient. To solve these problems, researchers have developed many catalysts with novel structures, such as alloys, core-shell structures, porous structures, etc. According to the preparation method, the addition amounts of the polyvinylpyrrolidone and the noble metal are changed, so that the alloy with different metal ratios and the porous nanotube catalyst with the core-shell structure can be respectively prepared.

Disclosure of Invention

The invention aims to provide a structure-adjustable porous alloy nanotube catalyst for a proton exchange membrane fuel cell and a preparation method thereof.

In order to realize the purpose, the invention adopts the following technical scheme:

a porous alloy nanotube catalyst with an adjustable structure is composed of alloy particles @ noble metal layer core-shell structure particles and carbon particles, or hollow alloy particles and carbon particles, or alloy particles and carbon particles.

Furthermore, the diameter of the catalyst is 15-1000 nm, and the length of the catalyst is 50-100000 nm.

Further, when the catalyst consists of alloy particles and carbon particles, the diameters of the alloy particles and the carbon particles are both 3-300 nm, and the diameters of pores are both 5-60 nm.

Further, the alloy particles are alloy particles of precious metals and non-precious metals, wherein the mass of the precious metals is 5-95% of the total mass of the alloy particles.

Further, the noble metal is one or more of gold, silver, platinum, ruthenium, rhodium, palladium, osmium and iridium; the non-noble metal is one or more of copper, cobalt, nickel and iron.

The preparation method of the porous alloy nanotube catalyst with the adjustable structure comprises the following steps:

1) preparing non-noble metal nanowires;

2) further, dispersing the non-noble metal nanowires prepared in the step 1) in a solution of alkali and polyvinylpyrrolidone, stirring for 3-24 hours, filtering and washing;

3) dispersing the product obtained in the step 2) in a noble metal precursor solution, reducing the noble metal, and then filtering, washing and drying;

4) carrying out heat treatment on the product obtained in the step 3) for 1-24 hours in a protective atmosphere;

5) dispersing the product obtained in the step 4) in an acid solution, stirring for 1-24 hours, and filtering, washing and drying to obtain the porous alloy nanotube catalyst.

Further, the non-noble metal nanowires in step 1) are prepared by the following methods:

(1) Z. Q. Xu, X. H. He, M. W. Liang, L. J. Sun, D. Li, K. N. Xie, L. Liao. Catalytic reduction of 4-nitrophenol over graphene supported Cu@Ni bimetallic nanowires. Materials Chemistry and Physics, 227 (2019) 64-71.

(2) Y. B. Ren, S.C. Zhang, R. X. Lin, X. Wei. Electro-catalytic performance of Pd decorated Cu nanowires catalyst for the methanol oxidation. International Journal of Hydrogen Energy, 40 (20150 2621-2630.

(3) J. M. Li, X. Jin, R. G. Li, Y. Zhao, X. Q. Wang, X. D. Liu, H. Jiao. Copper oxide nanowires for efficient photoelectrochemical water splitting. Applied Catalysis B: Environmental 240 (2019) 1–8.

further, in the solution of alkali and polyvinylpyrrolidone in the step 2), the alkali is sodium hydroxide or potassium hydroxide, and the concentration is 0.1-20 mol/L; the molecular weight of the polyvinylpyrrolidone is 8000-; the solvent is one or more of water, methanol, ethanol, ethylene glycol, pentanediol, isopropanol, glycerol, acetone, and butanol.

Further, the noble metal precursor in step 3) is one or more of platinum acetylacetonate, palladium acetylacetonate, gold acetylacetonate, ruthenium acetylacetonate, osmium acetylacetonate, silver acetylacetonate, platinum nitrate, palladium nitrate, gold nitrate, ruthenium nitrate, osmium nitrate, silver nitrate, platinum chloride, palladium chloride, gold chloride, ruthenium chloride, osmium chloride, silver chloride, chloroplatinic acid, chloroauric acid, chloropalladic acid, chlororuthenic acid, chloroaosmic acid, ammonium chloroplatinate, ammonium chloropalladate, ammonium chlororuthenate and ammonium chloroosmium; the molar ratio of the noble metal precursor to the non-noble metal nanowire is 0.01-10: 1.

Further, the method for reducing the noble metal precursor in the step 3) specifically comprises the following steps: adding a reducing agent or introducing hydrogen into the solution, then heating to 100-200 ℃, and preserving heat for 1-10 h; the reducing agent is sodium borohydride or potassium borohydride.

Further, the protective atmosphere in the step 4) is one or more of hydrogen, nitrogen, argon and helium; the heat treatment temperature is 300-800 ℃.

Further, the acid in the step 5) comprises one or more of hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, hypochlorous acid and hydrofluoric acid, the solvent comprises one or more mixed solutions of water, methanol, ethanol, ethylene glycol, pentanediol, isopropanol, glycerol, acetone and butanol, and the concentration of the acid is 0.1-10 mol/L.

The invention has the following remarkable advantages: the invention uses a preparation method, and changes of different structures of alloy, core shell and porous are realized by changing the addition amount of the noble metal and the polyvinylpyrrolidone. When the molar ratio of the noble metal precursor to the non-noble metal nanowire is less than or equal to 0.1:1, the noble metal precursor and the non-noble metal nanowire cannot form an alloy with all non-noble metals, so that the non-alloyed non-noble metal is dissolved by an acid solution to form hollow alloy particles, and the hollow alloy particles are not influenced by the addition amount of polyvinylpyrrolidone; when the molar ratio of the noble metal precursor to the non-noble metal nanowire is higher than 0.1:1, alloy particles can be formed, but in the heat treatment process of the step 4), part of noble metal can move to the surface of the particles to form a noble metal layer, and a core-shell structure of the alloy particles @ the noble metal layer is formed; the added polyvinylpyrrolidone can be carbonized in the heat treatment process in the step 4), when the mass ratio of the polyvinylpyrrolidone to the non-noble metal nanowires is higher than 1:4, rich carbon atoms and metals can form stronger bond force, and the bond force between the polyvinylpyrrolidone and the non-noble metals can block the movement of noble metals, so that the core-shell structure of the alloy particles @ the noble metal layer cannot be formed, and the structure of the alloy particles is still maintained; and the activity of the catalyst is greatly improved compared with that of a commercial Pt/C catalyst.

Description of the drawings:

FIG. 1 is a transmission electron microscope image of the catalysts prepared in examples 1, 5 and 6; wherein FIGS. A and B are transmission electron micrographs of the catalyst prepared in example 1 (5 nm on the scale in FIG. B); FIGS. C and D are TEM pictures of the catalyst prepared in example 5; FIGS. E and F are TEM pictures of the catalyst prepared in example 6;

FIG. 2 is a graph comparing the methanol oxidation activity of the catalysts prepared in examples 1, 5, 6 with commercial Pt/C;

FIG. 3 shows the oxygen reduction reaction activity of the catalysts prepared in examples 1, 5 and 6 with commercial Pt/C.

Detailed Description

The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples.

Example 1

1) Preparation of copper nanowires, preparation method reference (2);

2) dispersing 150 mg of copper nanowires in 200 mL of mixed solution of sodium hydroxide and polyvinylpyrrolidone, stirring for 3 hours, filtering and washing; wherein the concentration of the sodium hydroxide is 10mol/L, the mass of the polyvinylpyrrolidone is 30 mg, and the molecular weight is 8000; the solvent is ethanol;

3) dispersing the product obtained in the step 2) and 20 mg of chloroplatinic acid into 200 mL of ethylene glycol together, adding sodium borohydride, heating to 130 ℃, preserving heat for 5 hours, and then filtering, washing and drying;

4) carrying out heat treatment on the product obtained in the step 3) for 5 hours at 400 ℃ in a nitrogen atmosphere;

5) dispersing the product obtained in the step 4) in a nitric acid solution with the concentration of 3mol/L, stirring for 4 hours, and then filtering, washing and drying; and obtaining the platinum-copper alloy nanotube catalyst, wherein the particle size of the platinum-copper alloy is 3-200 nm, the platinum-copper alloy accounts for 80% of the total mass of the catalyst, and the pore diameter is 5-20 nm. The diameter of the alloy nanotube is 50-200 nm, and the length of the alloy nanotube is 50-1000 nm; as can be seen from the graphs A and B, the prepared catalyst has high content of noble metal and less addition of polyvinylpyrrolidone, and a porous nanotube structure consisting of alloy particles @ noble metal layer core-shell structure particles and carbon particles is formed.

Example 2

1) Preparation of iron nanowires, preparation method reference (1);

2) dispersing 300 mg of iron nanowires in 200 mL of mixed solution of sodium hydroxide and polyvinylpyrrolidone, stirring for 24 hours, filtering and washing; wherein the concentration of the sodium hydroxide is 0.1mol/L, the mass of the polyvinylpyrrolidone is 10000 mg, and the molecular weight is 700000; the solvent is ethanol;

3) dispersing the product obtained in the step 4) and 200 mg of chloropalladic acid into 200 mL of ethanol, adding sodium borohydride, heating to 200 ℃, preserving heat for 1 h, and then filtering, washing and drying;

4) carrying out heat treatment on the product obtained in the step 3) at 300 ℃ for 24 hours in a hydrogen atmosphere;

5) dispersing the product obtained in the step 4) in a nitric acid solution with the concentration of 10mol/L, stirring for 3 hours, and then filtering, washing and drying.

The obtained palladium-iron alloy nanotube catalyst is a porous nanotube structure composed of alloy particles and carbon particles, wherein the particle size of the palladium-iron alloy is 5-200 nm, the palladium-iron alloy accounts for 30% of the total mass of the catalyst, and the pore diameter is 100-300 nm. The diameter of the alloy nanotube is 15-200 nm, and the length of the alloy nanotube is 50-3000 nm;

example 3

1) Preparation of nickel nanowires, preparation method reference (1);

2) dispersing 200 mg of nickel nanowires in 200 mL of mixed solution of sodium hydroxide and polyvinylpyrrolidone, stirring for 12 hours, filtering and washing; wherein the concentration of the sodium hydroxide is 1mol/L, the mass of the polyvinylpyrrolidone is 1000 mg, and the molecular weight is 16000; the solvent is methanol;

3) dispersing the product obtained in the step 2) and 100 mg of acetylacetone gold together in 100 mL of methanol, adding potassium borohydride, heating to 150 ℃, preserving heat for 10 hours, and then filtering, washing and drying;

4) carrying out heat treatment on the product obtained in the step 3) at 800 ℃ for 12 hours in an argon atmosphere;

5) dispersing the product obtained in the step 4) in a hydrochloric acid solution with the concentration of 5mol/L, stirring for 3 hours, and then filtering, washing and drying.

The obtained gold-nickel alloy nanotube catalyst is a porous nanotube structure consisting of alloy particles and carbon particles, wherein the particle size of the gold-nickel alloy is 5-200 nm, the palladium-iron alloy accounts for 30% of the total mass of the catalyst, and the pore diameter is 100-300 nm. The diameter of the alloy nanotube is 100-300 nm, and the length of the alloy nanotube is 5000-10000 nm.

Example 4

1) Preparation of cobalt nanowires, preparation method reference (1);

2) dispersing 100 mg of cobalt nanowires in 200 mL of mixed solution of sodium hydroxide and polyvinylpyrrolidone, stirring for 12 hours, filtering and washing; wherein the concentration of sodium hydroxide is 1mol/L, the mass of polyvinylpyrrolidone is 5000 mg, and the molecular weight is 300000; the solvent is ethylene glycol;

3) dispersing the product obtained in the step 4) and 100 mg of ruthenium acetylacetonate into 100 mL of isopropanol, introducing hydrogen, heating to 100 ℃, preserving heat for 5 hours, and then filtering, washing and drying;

4) carrying out heat treatment on the product obtained in the step 3) for 10 hours at 600 ℃ under the argon atmosphere;

5) dispersing the product obtained in the step 4) in a sulfuric acid solution with the concentration of 1mol/L, stirring for 3 hours, and then filtering, washing and drying.

The obtained ruthenium-cobalt alloy nanotube catalyst is a porous nanotube structure composed of alloy particles and carbon particles, wherein the particle size of the ruthenium-cobalt alloy is 8-20 nm, the ruthenium-cobalt alloy accounts for 60% of the total mass of the catalyst, and the pore diameter is 100-150 nm. The diameter of the alloy nanotube is 100-200 nm, and the length is 1000-5000 nm.

Example 5

1) Same as in example 1.

2) Same as in example 1.

3) Same as in example 1.

4) The difference was that polyvinylpyrrolidone was added in an amount of 300 mg, as in example 1.

5) The same as in example 1, except that chloroplatinic acid was added in an amount of 60 mg.

6) Same as in example 1.

7) Same as in example 1.

The particle size of the platinum-copper alloy is 3-200 nm, the platinum-copper alloy accounts for 60% of the total mass of the catalyst, and the diameter of the hole is 5-30 nm. The diameter of the alloy nanotube is 50-200 nm, and the length of the alloy nanotube is 50-1000 nm; it can be seen from fig. C and D that the catalyst has a low noble metal content and a large polyvinylpyrrolidone addition amount, and a porous nanotube structure composed of hollow alloy particles and carbon particles is formed.

Example 6

1) Same as in example 1.

2) Same as in example 1.

3) Same as in example 1.

5) Same as in example 1.

6) Same as in example 1.

7) Same as in example 1.

The particle size of the platinum-copper alloy is 3-100 nm, the platinum-copper alloy accounts for 60% of the total mass of the catalyst, and the diameter of the hole is 5-30 nm. The diameter of the alloy nanotube is 50-200 nm, and the length is 50-1000 nm. It can be seen from fig. E and F that the catalyst has a high noble metal content and a large amount of polyvinylpyrrolidone added, and a porous nanotube structure composed of alloy particles and carbon particles is formed.

And (3) performance testing:

firstly, weighing 4 mg of catalyst, adding 2 mL of isopropanol and 20 mu L of perfluorosulfonic acid resin, and dripping 10 mu L of catalyst on the surface of a glassy carbon electrode after ultrasonic dispersionϕ=5 mm) and dried to obtain the working electrode. The counter electrode and the reference electrode are respectively a Pt wire and an Ag/AgCl electrode. The electrolyte was an aqueous solution of 1M methanol and 0.5M sulfuric acid. During the test, the potential is cyclically scanned between 0 and 1.2V (Vs. RHE) and cyclic voltammograms are recorded.

And (4) analyzing results: the peak current density of the methanol oxidation peak 1 of the catalysts prepared in examples 1, 5 and 6 was increased by 2.73, 5.19 and 1.27 times compared with that of commercial Pt/C, respectively, and showed good methanol oxidation activity.

FIG. 3 shows the oxygen reduction reaction activity of the catalysts prepared in examples 1, 5 and 6 with commercial Pt/C. The test method is as follows: the electrode preparation was the same as the fig. 2 test, except that the catalyst was dropped onto the surface of the rotating disk electrode. The electrolyte was a 0.1M aqueous solution of perchloric acid. During testing, linear scanning is carried out, the scanning potential is 1.2-0V (Vs. RHE), and a linear scanning curve is recorded.

And (4) analyzing results: the catalysts prepared in examples 1, 5 and 6 have initial potentials of oxygen reduction of 1.02, 1.08 and 1.02V, respectively, which are higher than 0.98V of commercial Pt/C, indicating that the oxygen reduction activities of the prepared catalysts are improved.

Claims

1. A preparation method of a porous alloy nanotube catalyst with an adjustable structure is characterized by comprising the following steps: the method comprises the following steps: 1) Preparing non-noble metal nanowires; 2) Dispersing the non-noble metal nanowires prepared in the step 1) in a solution of alkali and polyvinylpyrrolidone, stirring for 3-24 hours, filtering and washing; 3) Dispersing the product obtained in the step 2) in a noble metal precursor solution, reducing the noble metal, and then filtering, washing and drying; 4) Carrying out heat treatment on the product obtained in the step 3) for 1-24 hours in a protective atmosphere; 5) Dispersing the product obtained in the step 4) in an acid solution, stirring for 1-24 hours, and filtering, washing and drying to obtain a porous alloy nanotube catalyst; the non-noble metal in the step 2) is one or more of copper, cobalt, nickel and iron; the noble metal precursor in the step 3) is one or more of platinum acetylacetonate, palladium acetylacetonate, gold acetylacetonate, ruthenium acetylacetonate, osmium acetylacetonate, silver acetylacetonate, platinum nitrate, palladium nitrate, gold nitrate, ruthenium nitrate, osmium nitrate, silver nitrate, platinum chloride, palladium chloride, gold chloride, ruthenium chloride, osmium chloride, silver chloride, chloroplatinic acid, chloroauric acid, chloropalladic acid, chlororuthenac acid, chloroaosmic acid, ammonium chloroplatinate, ammonium chloropalladate, ammonium chlororuthenate and ammonium chloroosmium; the molar ratio of the noble metal precursor to the non-noble metal nanowire is 0.01-10: 1; the mass ratio of the polyvinylpyrrolidone to the non-noble metal nanowires is 0.01-100: 1; the protective atmosphere in the step 4) is one or more of hydrogen, nitrogen, argon and helium; the heat treatment temperature is 300-800 ℃; the catalyst consists of alloy particles @ noble metal layer core-shell structure particles and carbon particles, or consists of hollow alloy particles and carbon particles, or consists of alloy particles and carbon particles.

2. The preparation method according to claim 1, wherein in the solution of the alkali and the polyvinylpyrrolidone in the step 2), the alkali is sodium hydroxide or potassium hydroxide, and the concentration is 0.1-20 mol/L; the molecular weight of the polyvinylpyrrolidone is 8000-; the solvent is one or more of water, methanol, ethanol, ethylene glycol, pentanediol, isopropanol, glycerol, acetone, and butanol.

3. The method according to claim 1, wherein the step 3) of reducing the noble metal precursor is specifically: adding a reducing agent or introducing hydrogen into the solution, then heating to 100-200 ℃, and preserving heat for 1-10 hours; the reducing agent is sodium borohydride or potassium borohydride.

4. A structurally tunable porous alloy nanotube catalyst prepared by the preparation method according to any one of claims 1 to 3, characterized in that: the catalyst consists of alloy particles @ noble metal layer core-shell structure particles and carbon particles, or consists of hollow alloy particles and carbon particles, or consists of alloy particles and carbon particles.

5. The porous alloy nanotube catalyst with adjustable structure of claim 4, wherein the diameter of the catalyst is 15-1000 nm, and the length of the catalyst is 50-100000 nm.

6. The structurally-tunable porous alloy nanotube catalyst of claim 4, wherein the alloy particles are alloy particles of noble metals and non-noble metals, wherein the mass of the noble metals is 5-95% of the total mass of the alloy particles.

7. The porous alloy nanotube catalyst with adjustable structure of claim 4, wherein the catalyst comprises alloy particles and carbon particles, the diameters of the alloy particles and the carbon particles are both 3-300 nm, and the diameters of pores are both 5-60 nm.