CN107623131B

CN107623131B - Preparation and application of membrane electrode based on platinum or platinum alloy nanotube

Info

Publication number: CN107623131B
Application number: CN201610553993.4A
Authority: CN
Inventors: 邵志刚; 曾亚超; 俞红梅; 郭晓倩; 宋微; 张洪杰; 衣宝廉
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2016-07-14
Filing date: 2016-07-14
Publication date: 2020-11-13
Anticipated expiration: 2036-07-14
Also published as: CN107623131A

Abstract

The invention discloses preparation and application of a membrane electrode based on platinum or platinum alloy nanotubes, which comprises formation of an ordered electrode microstructure, preparation of platinum or platinum alloy nanotubes and assembly of the membrane electrode. Firstly, growing a Co-OH-CO3 nanorod array with regular orientation on a substrate, then carrying a catalyst on the array, annealing the Co-OH-CO3 nanorod array carrying the catalyst, finally hot-pressing the array on an ion exchange membrane to obtain a membrane electrode, and purifying the membrane electrode, wherein the constructed membrane electrode can be applied to a fuel cell. The membrane electrode constructed by the invention has the advantages of low catalyst loading capacity, high catalyst utilization rate, easy amplification and the like.

Description

Preparation and application of membrane electrode based on platinum or platinum alloy nanotube

Technical Field

The invention relates to a preparation method of a membrane electrode, belonging to the field of fuel cells.

Background

A fuel cell is an efficient energy conversion device that can efficiently convert chemical energy stored in chemical substances into electrical energy. At present, fuel cells have been used in various fields such as electric vehicles, distributed power stations, and aviation. Proton exchange membrane fuel cells are receiving wide attention due to their advantages of high power density, fast start-up speed, high conversion efficiency, environmental friendliness, etc.

The Membrane Electrode Assembly (MEA) is the core component of the electrochemical reaction of a fuel cell and consists of a catalytic layer and gas diffusion layers located on both sides of a proton exchange membrane. The membrane Electrode is mainly classified into a Gas Diffusion Electrode (GDE), a thin-film coated Electrode (CCM), and an ordered Electrode (ordered MEAs) represented by a nano-thin-film Electrode (NSTF) of 3M company, usa. The GDE is prepared by adopting the processes of screen printing, electrostatic spraying and the like, catalyst slurry consisting of a catalyst, a water repellent and an organic solvent is brushed on a gas diffusion layer, and Naifon solution is sprayed on the surface of a catalyst layer after high-temperature treatment to realize the three-dimensional electrode; CCM is currently generally prepared by spraying, transferring and other processes, in which a slurry composed of a catalyst, an ion conductor resin and an organic solvent is sprayed onto a membrane, or the slurry is sprayed onto other carriers and then transferred onto the membrane to form a membrane-catalyst integrated electrode. The traditional CCM electrode and GDE electrode are mature in preparation process, but the catalyst layer of the electrode is large in thickness, and the catalyst is disorderly stacked, so that the catalyst is high in usage amount and low in catalyst utilization rate. In order to solve the problems of high precious metal consumption and low catalyst utilization rate of fuel cells, 3M company developed an ordered Thin Film electrode (NSTF electrode), which has the characteristics of microscopic order, low catalyst loading capacity and the like, and can effectively reduce mass transfer resistance and improve the catalyst utilization rate.

Patent US5039561 describes a method for preparing an ordered nanowhisker array, which comprises depositing an organic thin film on a substrate, and annealing the organic thin film at high temperature and high vacuum to obtain a highly ordered nanowhisker array. The nano whisker array prepared by the method has excellent chemical stability and mechanical strength.

Patent US20110151353a1 describes a method for preparing an NSTF electrode, specifically, metals such as Pt, Mn, Co, Ir and the like are deposited on an ordered nanowhisker array by a magnetron sputtering technique, and then a nanorod array carrying a catalyst is transferred to one side or both sides of an ion exchange membrane, so that the prepared electrode is suitable for fuel cells and water electrolysis cells. The electrode prepared by the invention has the advantages of low noble metal consumption, high electrochemical activity, good stability, small mass transfer resistance and the like.

Patent No. cn201310690828.x introduces a preparation method of a self-supporting catalyst layer, specifically, an ordered nanorod array is prepared by a hydrothermal method, then a catalyst is loaded on the array by a magnetron sputtering technology, and finally the catalyst is transferred to an ion exchange membrane. The electrode prepared by the patent has the characteristics of low carrying capacity and thin thickness, but the catalyst layer prepared by the patent is formed by mechanical mixture of platinum and other metals, and is a disordered macroporous film electrode.

The invention prepares a membrane electrode based on platinum and an alloy nanotube thereof on the basis of a patent of CN201310690828. X. The prepared electrode is composed of platinum or platinum alloy nanotubes. The prepared electrode has the appearance and the composition different from those of a patent CN201310690828. X. The method adopted by the invention has mild conditions and simple operation, and can effectively reduce the consumption of noble metal of the electrode.

Disclosure of Invention

A preparation method of a membrane electrode based on platinum or platinum alloy nanotubes comprises the following steps:

1) preparing a reaction solution; the reaction solution is an aqueous solution of ammonium fluoride with the concentration of 1-30mM, urea with the concentration of 1-30mM and cobalt nitrate with the concentration of 1-50 mM;

2) soaking the substrate in the reaction solution, reacting in a high-pressure reaction kettle at 90-150 deg.C for 30min-24h to obtain Co-OH-CO on the substrate₃An array; the adopted substrate can be glass, nickel sheet, nickel net, stainless steel or titanium sheet;

3) in the presence of Co-OH-CO₃The array supports a catalyst, the method for supporting the catalyst comprises physical vapor deposition and chemical vapor deposition, the supported catalyst is one or more of Pt, Pd, Ru, Co, Ni, Fe, Cu, Au, Ag, Mn, Ir and Cr, and the atomic ratio of Pt to other metals is 1: 5-9: 1;

4) to Co-OH-CO carrying catalyst₃Annealing the array at 200-1000 deg.c in H atmosphere₂，N₂Ar, He, or H₂-Ar、H₂-N₂、H₂Mixed gas of-He and H in the mixed gas₂The content of (A) is 1 vol.% to 99 vol.%, and annealing is performedThe fire time is 10min-7 days;

5) transferring the annealed array to one side or two sides of an ion exchange membrane by a transfer method, and removing the substrate; the pressure applied during transfer printing is 0.1-50 MPa, the time is 1 s-30 min, the temperature is 20-200 ℃, and the adopted ion exchange membrane is a cation exchange membrane or an anion exchange membrane;

6) the ion exchange membrane transferred with the catalyst layer is subjected to acid washing treatment, wherein HCl and H can be selected for acid washing₂SO₄、HNO₃Or HF solution with acid concentration of 1mM-10M, acid washing temperature of 20-100 deg.C, acid washing time of 1min-24 h;

7) washing the acid-washed membrane electrode with water at 25-100 ℃ for 1min-24h to remove acid remaining in the membrane electrode;

8) dipping the electrode in a hydrogen peroxide aqueous solution to remove organic matters introduced in the electrode preparation process, wherein the mass concentration of the hydrogen peroxide is 1-10%, the dipping temperature is 25-100 ℃, and the dipping time is 1min-24 h;

9) placing the electrode in a sulfuric acid solution at the temperature of 20-100 ℃ and boiling for 30 min-1 h, wherein the mass concentration of sulfuric acid is 1-30 wt%;

10) and (3) washing the electrode subjected to the steps for 20s-24h at the washing temperature of 20-100 ℃.

The invention has the following characteristics:

1. the catalyst layer of the membrane electrode prepared by the invention is composed of platinum or platinum alloy nanotubes;

2. the electrode preparation method described by the invention has the characteristics of mild preparation conditions and simple operation;

3. the membrane electrode prepared by the invention has the characteristics of low consumption of noble metal, adjustable catalyst components and thin catalyst layer thickness;

4. the full-cell test shows that the electrode based on the platinum or platinum alloy nanotube membrane has high mass specific power and catalyst utilization rate

Drawings

Fig. 1 is a flow chart of the preparation of a membrane electrode of example 1.

FIG. 2 shows Co-OH-CO prepared in example 1₃Scanning electron microscope image of nanorod array.

FIG. 3 is a scanning electron microscope image of the platinum nanorod array prepared in example 1.

Fig. 4 is a scanning electron micrograph of the membrane electrode prepared in example 1.

Fig. 5 is an XRD pattern of the membrane electrode prepared in example 1.

Fig. 6 is an I-V performance curve of the membrane electrode prepared in example 1 in a fuel cell.

FIG. 7 is a scanning electron microscope image of the Pt-Co nanorod array prepared in example 2.

Fig. 8 is a scanning electron micrograph of the membrane electrode prepared in example 2.

Fig. 9 is an XRD pattern of the membrane electrode prepared in example 2.

Fig. 10 is an I-V performance curve of the membrane electrode prepared in example 2 in a fuel cell.

FIG. 11 is a scanning electron microscope image of the Pt-Fe nanorod array prepared in example 3.

Fig. 12 is a scanning electron micrograph of the membrane electrode prepared in example 3.

Fig. 13 is an XRD pattern of the membrane electrode prepared in example 3.

FIG. 14 is an I-V performance curve of the membrane electrode prepared in example 3 in a fuel cell.

Detailed Description

The following examples are further illustrative of the present invention while protecting obvious modifications and equivalents.

Example 1

Preparing Co-OH-CO by using stainless steel as a substrate and adopting a hydrothermal method₃And (4) array. The reaction solution was 10mM ammonium fluoride, 25mM urea, and 5mM cobalt nitrate. Reacting for 5 hours at 120 ℃ in a high-pressure reaction kettle to prepare Co-OH-CO on a substrate₃And (4) array. FIG. 2 shows the preparation of Co-OH-CO₃Scanning electron microscope image of nanorod array. Co-OH-CO can be seen from the figure₃The nanorod array is uniformly grown on the substrate with the growth direction substantially perpendicular to the substrate. Co-OH-CO₃The length of the nano-rod is about 3 mu m, the diameter is about 100nm, and the nano-rod is Co-OH-CO₃The surface density of the nano-rod is 3-4 e⁹/cm²。

By adopting a magnetron sputtering method on Co-OH-CO₃Pt was supported on the array. The magnetron sputtering power is 150W, the sputtering time is 10min, and the operating pressure is 1.0 Pa. Loading Pt on Co-OH-CO₃Array at 300 ℃ H₂-Ar(H₂Volume fraction of 5%) for 60 min. FIG. 3 is a scanning electron microscope image of the prepared nanorod array. It can be seen from the figure that magnetron sputtering is performed on Co-OH-CO₃The array supported a uniform layer of Pt, which was about 20nm thick. The annealing treatment does not destroy the order of the array, and the Pt-loaded Co-OH-CO₃The nanorods were approximately 2 μm in length and approximately 140nm in diameter.

Transferring the annealed platinum nanorod array to one side of an ion exchange membrane by adopting the ion exchange membrane

212 film. The transfer printing pressure is 4MPa, the transfer printing temperature is 140 ℃, and the transfer printing time is 1 min. ICP test shows that the platinum loading of the prepared membrane electrode is 68.1 mu g cm^-2。

Removing the stainless steel substrate, and purifying the membrane electrode, wherein the treatment process comprises the following steps: placing the ion exchange membrane loaded with the catalyst layer in 0.5M sulfuric acid solution to remove Co-OH-CO serving as a template₃And (3) array, washing the membrane electrode in deionized water, and removing residual acid liquor. Boiling the membrane electrode in 0.5M sulfuric acid solution at 80 ℃ for 30min, washing away residual acid solution in deionized water, boiling in 5% hydrogen peroxide water solution at 80 ℃ for 30min, boiling the electrode in deionized water at 80 ℃ for 30min, drying the membrane electrode, and packaging into a membrane electrode assembly. Fig. 4 is a scanning electron microscope image of the prepared membrane electrode, and it can be seen from the image that the prepared catalytic layer is composed of nanotubes, the diameter of the nanotubes is 140nm, the length is about 2 μm, and the thickness of the tube wall is about 20 nm. Fig. 5 is an XRD pattern of the prepared electrode, from which it can be seen that the catalytic layer prepared by magnetron sputtering is composed of a single element of platinum.

The prepared membrane electrode is packaged into a membrane electrode assembly, the packaging pressure is 0.5MPa, and the packaging temperature is 140 ℃. The anode of the membrane electrode assembly adopts a gas diffusion electrode, and the Pt/C (70 wt.% of Johnson Matthey) supporting amount of the anode is 0.2mg cm^-2The electrolyte separator is

212 film.

The battery test conditions are as follows: h₂/O₂Flow rate: 50/100 sccm; the temperature of the battery is 75 ℃, the saturation and humidification are carried out, and the back pressure of the battery is 0.2 MPa. FIG. 6 shows the I-V performance curve in a platinum nanotube based membrane electrode fuel cell with a maximum output power of 736mW cm^-2. It can be seen from the figure that the mass specific power of a single cell is up to 2.745kW g^-1Pt。

Example 2

Preparing Co-OH-CO by using stainless steel as a substrate and adopting a hydrothermal method₃And (4) array. The reaction solution was 10mM ammonium fluoride, 25mM urea, and 5mM cobalt nitrate. Reacting for 4 hours at 120 ℃ in a high-pressure reaction kettle to prepare Co-OH-CO on a substrate₃And (4) array.

By adopting a magnetron sputtering method on Co-OH-CO₃PtCo was supported on the array (atomic ratio 3: 1). The magnetron sputtering power is 100W, the sputtering time is 20min, and the operating pressure is 1.0 Pa. To carry PtCo-loaded Co-OH-CO₃Array at 400 ℃ H₂-Ar(H₂Volume fraction of 5%) for 1 h. FIG. 7 is a scanning electron microscope image of the prepared platinum-cobalt nanotube array. It can be seen from the figure that magnetron sputtering is performed on Co-OH-CO₃The surface of the nanorod array is loaded with a uniform PtCo catalyst, the thickness of the PtCo coating is about 18nm, and the order of the array is not damaged by annealing treatment. Co-OH-CO carrying PtCo coating₃The nanorods were approximately 3 μm in length and approximately 136nm in diameter.

212 film. The transfer pressure is 0.5MPa and the transfer temperature isThe temperature was 150 ℃ and the transfer time was 2 min. ICP test shows that the Pt supporting amount of the prepared membrane electrode is 40.15 mu g cm^-2The Co content is 3.825 μ g cm^-2。

The stainless steel substrate was removed and the membrane electrode was cleaned, as in example 1. FIG. 8 is a scanning electron microscope image of the prepared membrane electrode, from which it can be seen that the diameter of the PtCo nanotube is about 136nm, the thickness of the tube wall is about 18nm, and the length of the PtCo nanotube is about 2-3 μm. Fig. 9 is an XRD pattern of the fabricated electrode. XRD tests show that the prepared nanotubes are PtCo alloy nanotubes, and part of Pt atoms and Co form an alloy.

212 film. The battery test conditions are as follows: h₂/O₂Flow rate: 50/100 sccm; the temperature of the battery is 75 ℃, the saturation and humidification are carried out, and the back pressure of the battery is 0.2 MPa. FIG. 10 shows the I-V performance curve of a membrane electrode fuel cell based on a platinum-cobalt nanotube array, the maximum output power of the cell being 685mWcm^-2The figure shows that the mass specific power of a single cell is as high as 2.85kW g^-1Pt。

Example 3

Co-OH-CO₃The preparation of the arrays is shown in example 2.

By adopting a magnetron sputtering method on Co-OH-CO₃The array supported PtFe (atomic ratio 1: 1). The magnetron sputtering power is 100W, the sputtering time is 20min, and the operating pressure is 1.0 Pa. To carry PtFe-loaded Co-OH-CO₃Array at 600 ℃ H₂-Ar(H₂Volume fraction of 5%) for 1 h. FIG. 11 is a scanning electron microscope image of the prepared nanorod array, which shows that the prepared PtFe nanorods vertically grow on the substrate in a certain orientation, and carry Co-OH-CO of the PtFe plating layer₃The nanorods were approximately 2.5 μm in length and approximately 130nm in diameter.

See example 2 for a membrane electrode preparation scheme. FIG. 12 is a scanning electron microscope image of the prepared membrane electrode, from which it can be seen that the prepared catalytic layer is composed of PtFe nanotubes, the diameter of the nanotubes is about 130nm, the thickness of the tube wall is about 15nm, and the length is about 1-2.5 μm. The ICP test shows that the Pt loading of the prepared membrane electrode is 49.735 mu g cm^-2The amount of Fe supported was 1.875. mu.g cm^-2. Fig. 13 is an XRD pattern of the prepared electrode, in which the diffraction peak position of PtFe is located between the peak positions of the PtCo alloy and the PtFe alloy, indicating that the prepared electrode is an alloy of PtFe.

212 film. The battery test conditions are as follows: h₂/O₂Flow rate: 50/100 sccm; the battery temperature is 75 ℃, the saturation humidification is carried out, and the battery back pressure is 0.2MP_a. FIG. 14 is a block diagram based on PtF_eThe maximum output power of the nano-tube membrane electrode fuel cell is 830mW cm^-2The mass specific power of the battery is 3.32kW g^-1Pt。

Claims

1. A membrane electrode based on platinum alloy nanotubes is characterized in that: the catalyst layer of the membrane electrode is composed of platinum alloy nanotubes which are annealed, and the prepared catalyst layer is positioned on one side or two sides of the ion exchange membrane; the tube wall of the nanotube is of an open structure;

the catalyst layer is composed of platinum alloy nanotubes with the diameter of 10 nm-200 nm and the length of 50 nm-5 mu m, the thickness of the catalyst layer is 50 nm-10 mu m, and the adopted ion exchange membrane is a cation exchange membrane or an anion exchange membrane;

the transition metal other than platinum, which constitutes the platinum alloy, is one or more of Fe, Co, Ni, Cu, Au, Ru, Pd, Ir, Mn, Cr and Ag, and the atomic ratio of platinum to transition metal is 1:5 to 9: 1.

2. A method for producing the membrane electrode of claim 1, characterized in that:

(1) growing Co-OH-CO vertical to substrate on substrate by hydrothermal method₃A nanorod array;

(2) in the presence of Co-OH-CO₃The nano-rods uniformly support a metal catalyst;

(3) Co-OH-CO loaded with catalyst₃Carrying out annealing treatment on the array;

(4) transferring the nanorod array loaded with the catalyst to one side or two sides of the ion exchange membrane;

(5) and (5) purifying the membrane electrode.

3. The method for producing a membrane electrode according to claim 2, wherein: the substrate in the step (1) is glass, a nickel sheet, a nickel net, a stainless steel sheet or a titanium sheet;

Co-OH-CO in step (1)₃The growth of the array is prepared by a high pressure hydrothermal method, comprising the following steps:

A. preparing a reaction solution, wherein the reaction solution is an aqueous solution containing 1-30mM of ammonium fluoride, 1-30mM of urea and 1-50mM of cobalt nitrate;

B. soaking the substrate in the reaction solution in a high-pressure reaction kettle for 90-150 times^oReacting for 30min-24h under C to prepare Co-OH-CO on the substrate₃And (4) array.

4. The method for producing a membrane electrode according to claim 2, wherein: the method for supporting the catalyst in the step (2) comprises physical vapor deposition or chemical vapor deposition;

the catalyst carried in the step (2) is a platinum alloy, the catalyst is composed of Pt or platinum and one or more than two elements of Fe, Co, Ni, Cu, Au, Pd, Ru, Ir, Mn, Cr and Ag, the atomic ratio of platinum to other metals is 1: 5-9: 1, and the catalyst loading is 1 mu g cm^-2~5 mg cm^-2。

5. The method for producing a membrane electrode according to claim 2, wherein: the annealing temperature in the step (3) is 200-1000 ℃, and the annealing atmosphere is H₂、N₂Ar, He, or H₂-Ar、 H₂-N₂、H₂Mixed gas of-He and H in the mixed gas₂The content of (1) vol% to 99 vol%, and the annealing time is 10min to 7 days;

in the step (4), the pressure applied during transfer printing is 0.1-50 MPa, the time is 1 s-30 min, and the temperature is 20-200 ℃.

6. The method for producing a membrane electrode according to claim 2, wherein: the membrane electrode purification step in the step (5) is as follows:

(1) pickling the washed membrane electrode; the adopted acid is nitric acid, sulfuric acid or hydrochloric acid, the concentration is 5 mM-10M, the acid treatment temperature is 20-100 ℃, and the acid treatment time is 1min-24 h;

(2) washing the membrane electrode after acid washing with water at the temperature of 20-100 ℃;

(3) cleaning the membrane electrode in a hydrogen peroxide aqueous solution; the mass concentration of the hydrogen peroxide is 1-10%, and the cleaning temperature is 20-100 ℃;

(4) placing the membrane electrode in sulfuric acid solution for cleaning; the mass concentration of the sulfuric acid is 1-30 wt%, and the cleaning temperature is 20-100 ℃;

(5) and (3) cleaning the membrane electrode in deionized water at the temperature of 20-100 ℃.

7. Use of a membrane electrode according to claim 1, characterized in that: the prepared electrode is used for a fuel cell.