CN112886031B

CN112886031B - Oxygen reduction catalyst

Info

Publication number: CN112886031B
Application number: CN202110241420.9A
Authority: CN
Inventors: 陈凤英; 邸友莹; 刘萍; 任有良; 张国春; 赵永利
Original assignee: Shangluo University
Current assignee: Shangluo University
Priority date: 2021-03-04
Filing date: 2021-03-04
Publication date: 2022-07-19
Anticipated expiration: 2041-03-04
Also published as: CN112886031A; AU2021101838A4

Abstract

The invention discloses an oxygen reduction catalyst, which is prepared by the following method: accurately weighing a proper amount of copper sulfate pentahydrate, dissolving the copper sulfate pentahydrate by using distilled water, placing the copper sulfate pentahydrate at the bottom of a test tube, taking a methanol-water mixed solution with a volume ratio of 1:1 as a buffer layer, dropwise adding the buffer layer into the test tube by using an injector, then mixing 2-oxo-propionic acid-4-nitrobenzoylhydrazone with 1-methylimidazole, dropwise adding the mixture into the test tube after dissolving the buffer layer by using methanol, placing the test tube on the upper layer of the solution, finally sealing the opening of the test tube by using a preservative film, and standing for two weeks to obtain dark green needle crystals, namely complex crystals, at the interface of the solution on the wall of the test tube; and respectively weighing a proper amount of complex crystals and carbon nano tubes according to different proportions, placing the complex crystals and the carbon nano tubes in ethanol, and ultrasonically dispersing for 1-2 hours to obtain the catalyst ink. The catalyst of the invention has simple preparation, easily obtained raw materials and low cost compared with Pt/C. In the optimal proportioning, the one-step 4-electron reduction of oxygen molecules on the electrode is realized.

Description

Oxygen reduction catalyst

Technical Field

The invention relates to the field of chemical industry, and particularly relates to an oxygen reduction catalyst.

Background

Energy and environmental problems become important subjects restricting economic development, and countries around the world invest huge resources in developing and researching clean energy. As a new energy source, fuel cells do not produce pollutants during use, and therefore development and research of fuel cells are receiving more and more attention. Direct Methanol Fuel Cells (DMFCs), which are one type of fuel cells, are highly spotlighted because of their advantages, such as convenience, rapidity, and high specific energy. At present, DMFC cathode catalysts are mainly Pt/C, platinum is expensive and limited in resource, and methanol permeating into a cathode discharges on the Pt/C catalyst to reduce catalytic activity, and carbon monoxide generated by discharge poisons the catalyst. Therefore, the research on the oxygen reduction catalyst with higher catalytic activity and better methanol resistance is one of the key technologies to be solved by the direct methanol fuel cell.

With the continued search for fuel cells make internal disorder or usurp, it has become increasingly recognized that catalyst support materials play an important role in the performance of catalysts. The particle size and the shape of the catalyst carrier have important influence on the performance of the catalyst, and the good catalyst carrier can also effectively promote the mass transfer process and reduce the resistance of charge transfer, so that the selection of the good catalyst carrier is beneficial to exerting the performance of the catalyst, and the catalytic activity of the catalyst is effectively improved under the synergistic effect of the catalyst and the good catalyst carrier.

Disclosure of Invention

In order to solve the problems, the invention provides an oxygen reduction catalyst, which takes carbon nano tubes as a catalyst carrier, so that the electronic performance of the catalyst is greatly improved.

In order to achieve the purpose, the invention adopts the technical scheme that:

an oxygen reduction catalyst prepared by the following method:

s1, accurately weighing 0.2 mmol of copper sulfate pentahydrate (CuSO)₄⋅5H₂O) is dissolved by 5mL of distilled water and placed at the bottom of a test tube, 5mL of a methanol-water mixed solution with the volume ratio of 1:1 is used as a buffer layer, the buffer layer is dripped into the test tube by using a syringe, about 0.2 mmol of 2-oxo-propionic acid-4-nitrobenzoylhydrazone is mixed with about 0.8 mmol of 1-methylimidazole, the buffer layer is dissolved by 5mL of methanol solution, the mixture is carefully dripped into the test tube, and the test tube is placed in the solutionSealing the test tube mouth with a preservative film, standing for two weeks, and obtaining dark green needle crystals, namely complex crystals, at the interface of solution layering on the test tube wall;

s2, weighing a proper amount of complex crystals and carbon nanotubes according to different proportions, respectively, placing the complex crystals and the carbon nanotubes in 2-5 mL of absolute ethyl alcohol, and performing ultrasonic dispersion for 1-2 h to obtain the catalyst ink.

Further, the mass ratio of the complex crystal to the carbon nanotube is 0:5, 1:4, 2:3, 3:2, 4:1 or 5: 0.

The invention has the following beneficial effects:

the catalyst of the invention has simple preparation, easily obtained raw materials and low cost compared with Pt/C. In the optimal proportioning, the one-step 4-electron reduction of oxygen molecules on the electrode is realized. In the presence of methanol, no oxidation/reduction peak of methanol occurs, and the methanol resistance is better.

Drawings

FIG. 1 is a crystal structure of a complex in an embodiment of the present invention;

FIG. 2 is a unit cell stacking diagram of a complex in an example of the present invention;

FIG. 3 is a CV curve of catalyst modified electrodes of different ratios in an oxygen saturated alkaline solution;

FIG. 4 is a linear sweep voltammogram of a rotating disk electrode modified with an optimally proportioned catalyst in an alkaline solution;

FIG. 5 shows that the optimal ratio of catalyst modified rotating disk electrode to oxygen reduction reaction is-0.8Vj ^–1And withω ^–1/2A relation curve;

FIG. 6 shows the optimum ratio of the catalyst in the modified glassy carbon electrode in oxygen saturated alkaline solution and alkaline solution + 0.5 mol. L^-1 CH₃Cyclic voltammogram in OH solution (solid line represents basic solution, dashed line represents basic solution + 0.5 mol. L)^-1 CH₃OH solution).

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

Examples

Dissolving 2-oxo-propionic acid-4-nitrobenzoyl hydrazone and 1-methylimidazole in absolute ethyl alcohol according to a certain substance quantity ratio (0:5, 1:4, 2:3, 3:2, 4:1 and 5:0), dissolving copper sulfate in distilled water, and then adopting a test tube diffusion method to prepare a complex monocrystal, specifically, accurately weighing 0.2 mmol of copper sulfate pentahydrate (CuSO)₄⋅5H₂O) dissolving with 5mL of distilled water, placing the solution at the bottom of a test tube, taking 5mL of a methanol-water mixed solution with the volume ratio of 1:1 as a buffer layer, dropwise adding the buffer layer into the test tube by using an injector, mixing about 0.2 mmol of 2-oxo-propionic acid-4-nitrobenzoylhydrazone with about 0.8 mmol of 1-methylimidazole, dissolving with 5mL of a methanol solution, carefully dropwise adding the solution into the test tube, placing the test tube on the upper layer of the solution, finally sealing the opening of the test tube by using a preservative film, standing for two weeks, and obtaining dark green needle crystals, namely complex crystals, at the interface of solution layering on the wall of the test tube; the single crystal structure, the crystallographic data and the partial bond length angle data of the complex are shown in tables 1 and 2, and the structure and unit cell stacking diagram of the complex are shown in fig. 1 and 2.

TABLE 1 crystallographic data for the complexes

TABLE 2 bond lengths and bond angles of the complexes

Preparation of the catalyst: respectively weighing complex crystals and carbon nanotubes with different masses according to the proportion of 0:5, 1:4, 2:3, 3:2, 4:1 and 5:0, placing the complex crystals and the carbon nanotubes into 2-5 mL of ethanol, and ultrasonically dispersing for 1-2 hours to prepare catalyst ink with different proportions. And transferring 5-15 mu L of catalyst ink by using a liquid transfer gun, dropwise adding the catalyst ink onto the surface of the glassy carbon electrode in several times, and airing for later use.

And (3) testing the catalytic performance: the catalytic oxygen reduction performance of the catalyst is tested by adopting a three-electrode system and an alkaline electrolyte solution, before the test, oxygen is introduced into the electrolyte solution until the electrolyte solution is saturated, and then the catalytic oxygen reduction performance of the catalyst is tested.

Determining the optimal proportion by cyclic voltammetry: according to the magnitude of the cyclic voltammetry current, the optimal ratio of the complex to the carbon nanotube is 2:3 as seen from fig. 3.

Electron transfer number for the best matched catalyst to catalyze the oxygen reduction reaction (fig. 5): through calculation, the electron transfer number of the optimal proportioning catalyst for catalyzing the oxygen reduction reaction is 3.7, and the one-step 4-electron reduction of oxygen molecules can be realized.

Methanol resistance: as can be seen from FIG. 6, in the presence of methanol, the oxidation peak of methanol does not appear in the cyclic voltammetry curve of the catalyst, but the peak current is slightly reduced, and the peak potential of the oxygen reduction reaction is not negatively shifted, which indicates that the catalyst sample has better methanol poisoning resistance.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims

1. An oxygen reduction catalyst characterized by: the preparation method comprises the following steps:

s1, accurately weighing 0.2 mmol of copper sulfate pentahydrate, dissolving the copper sulfate pentahydrate in 5mL of distilled water, placing the solution at the bottom of a test tube, taking 5mL of a methanol-water mixed solution with a volume ratio of 1:1 as a buffer layer, dropwise adding the buffer layer into the test tube by using an injector, mixing 0.2 mmol of 2-oxo-propionic acid-4-nitrobenzoylhydrazone with 0.8 mmol of 1-methylimidazole, dissolving the buffer layer in 5mL of a methanol solution, dropwise adding the solution into the test tube, placing the test tube on the upper layer of the solution, sealing the opening of the test tube by using a preservative film, and standing for two weeks to obtain dark green needle-like crystals, namely complex crystals, at the interface of solution layering on the wall of the test tube;

2. An oxygen reduction catalyst as claimed in claim 1, wherein: the mass ratio of the complex crystal to the carbon nanotube is 1:4, 2:3, 3:2 or 4: 1.