阅读说明：本技术 一种催化氧还原反应的花状氢化钯催化剂及其制备方法 (Flower-shaped palladium hydrogenation catalyst for catalyzing oxygen reduction reaction and preparation method thereof ) 是由 王鸿静 周同庆 王自强 许友 王亮 于 2021-06-11 设计创作，主要内容包括：一种催化氧还原反应的花状氢化钯催化剂,由如下方法制备：分别取质量为1～50mg之间的氯钯酸钠、六羰基钨,加入1～20mL的N,N-二甲基甲酰胺溶液,溶液充分混合后,再加入1～10mL之间的乙酸溶液；溶液充分混合后,置于油浴锅中加热到50～200℃之间,反应1～10h后,洗涤、离心、干燥,得到花状钯；取质量为1～10mg之间的制好的花状钯,再加入1～50mL的N,N-二甲基甲酰胺溶液,混合均匀后,置于油浴锅中加热到50～200℃之间,反应1～30h后,洗涤、离心、干燥,得到花状氢化钯催化剂。以及提供该催化剂的制备方法。本发明制备工艺简单,制得的材料具有优异的电化学氧化还原性能。(A flower-shaped palladium hydride catalyst for catalyzing oxygen reduction reaction is prepared by the following steps: respectively taking 1-50 mg of sodium chloropalladate and tungsten hexacarbonyl, adding 1-20 mL of N, N-dimethylformamide solution, fully mixing the solutions, and then adding 1-10 mL of acetic acid solution; after the solutions are fully mixed, placing the mixture in an oil bath pot, heating the mixture to 50-200 ℃, reacting for 1-10 hours, washing, centrifuging and drying to obtain flower-shaped palladium; taking the prepared flower-shaped palladium with the mass of 1-10 mg, adding 1-50 mL of N, N-dimethylformamide solution, uniformly mixing, placing in an oil bath pan, heating to 50-200 ℃, reacting for 1-30 h, washing, centrifuging and drying to obtain the flower-shaped palladium hydride catalyst. And a method for preparing the catalyst. The preparation method is simple in preparation process, and the prepared material has excellent electrochemical oxidation-reduction performance.)

1. A flower-shaped palladium hydride catalyst for catalyzing oxygen reduction reaction is prepared by the following steps:

(1) respectively taking 1-50 mg of sodium chloropalladate and tungsten hexacarbonyl, then adding 1-20 mL of N, N-dimethylformamide solution, fully mixing the solutions, and then adding 1-10 mL of acetic acid solution; after the solutions are fully mixed, placing the mixture in an oil bath pot, heating the mixture to 50-200 ℃, reacting for 1-10 hours, washing, centrifuging and drying to obtain flower-shaped palladium;

(2) taking 1-10 mg of prepared flower-shaped palladium, adding 1-50 mL of N, N-dimethylformamide solution, uniformly mixing, placing in an oil bath pan, heating to 50-200 ℃, reacting for 1-30 h, washing, centrifuging, and drying to obtain the flower-shaped palladium hydrogenation catalyst for catalyzing the oxygen reduction reaction.

2. A method for preparing a flower-like palladium hydride catalyst for catalyzing an oxygen reduction reaction according to claim 1, comprising the steps of:

(1) respectively taking 1-50 mg of sodium chloropalladate and tungsten hexacarbonyl, then adding 1-20 mL of N, N-dimethylformamide solution, fully mixing the solutions, and then adding 1-10 mL of acetic acid solution; after the solutions are fully mixed, placing the mixture in an oil bath pot, heating the mixture to 50-200 ℃, reacting for 1-10 hours, washing, centrifuging and drying to obtain flower-shaped palladium;

(2) taking 1-10 mg of prepared flower-shaped palladium, adding 1-50 mL of N, N-dimethylformamide solution, uniformly mixing, placing in an oil bath pan, heating to 50-200 ℃, reacting for 1-30 h, washing, centrifuging, and drying to obtain the flower-shaped palladium hydrogenation catalyst for catalyzing the oxygen reduction reaction.

3. The method of preparing a flower-shaped palladium hydride catalyst for catalytic oxygen reduction according to claim 2, wherein the shape and structure of the flower-shaped palladium hydride is controlled by controlling the amount of sodium chloropalladate, tungsten hexacarbonyl and the volume of the N, N-dimethylformamide solution, acetic acid, and the temperature and time of the reaction.

Technical Field

The invention relates to a flower-shaped palladium hydrogenation catalyst for catalyzing oxygen reduction reaction and a preparation method thereof.

Background

The excessive consumption of fossil fuels and the growing energy demand of modern society, there is an urgent need to develop renewable energy sources that can replace fossil fuels. The conversion of chemical energy into electrical energy is a promising energy conversion technology. Among them, fuel cells are drawing attention because of their high energy density, environmental friendliness, and high energy conversion efficiency. Fuel cells rely primarily on two important chemical processes, the oxygen reduction reaction and the fuel oxidation reaction. However, the lag in the kinetics of the fuel cell cathode oxygen reduction reaction has been a bottleneck in the development of fuel cells. There is an urgent need to solve this problem. Expensive platinum-based materials are often used to catalyze oxygen reduction reactions due to their excellent intrinsic properties. However, because platinum reserves are relatively small and susceptible to poisoning deactivation, many relatively inexpensive metals have to be sought in place of platinum. Palladium, as a platinum group element, is chemically very similar to platinum and has better methanol resistance, and is considered as a promising metal that can replace platinum. However, it is difficult for a pure palladium catalyst to achieve oxygen reduction activity close to that of platinum due to its inherent electronic structure.

Therefore, many strategies have been proposed to solve this problem, such as alloying (palladium silver, palladium copper, palladium cobalt, palladium nickel, palladium iron, palladium bismuth, palladium lead, etc.), introducing surface strain, adjusting microstructure and heteroatom doping. We provide herein a method of introducing hydrogen atoms. A hydrogen atom is the most suitable atom for implantation into the palladium lattice because it has the smallest atomic radius and has good affinity for various atoms. Hydrogen readily penetrates metals to enlarge the lattice spacing, which has been a significant concern. In essence, small atomic radii readily penetrate into the metal lattice, resulting in an increase in lattice spacing, while changes in lattice parameters result in differences in charge transfer behavior between host and guest, thereby forming a catalytic electronic structure.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a flower-shaped palladium hydrogenation catalyst for catalyzing oxygen reduction reaction, a preparation method thereof and research on catalyzing electrochemical oxidation reduction reaction.

The technical scheme adopted by the invention is as follows:

a flower-shaped palladium hydride catalyst for catalyzing oxygen reduction reaction is prepared by the following steps:

(1) respectively taking 1-50 mg of sodium chloropalladate and tungsten hexacarbonyl, then adding 1-20 mL of N, N-dimethylformamide solution, fully mixing the solutions, and then adding 1-10 mL of acetic acid solution; after the solutions are fully mixed, placing the mixture in an oil bath pot, heating the mixture to 50-200 ℃, reacting for 1-10 hours, washing, centrifuging and drying to obtain flower-shaped palladium;

(2) taking 1-10 mg of prepared flower-shaped palladium, adding 1-50 mL of N, N-dimethylformamide solution, uniformly mixing, placing in an oil bath pan, heating to 50-200 ℃, reacting for 1-30 h, washing, centrifuging, and drying to obtain the flower-shaped palladium hydrogenation catalyst for catalyzing the oxygen reduction reaction.

The selection of reaction conditions has important influence on the structure of the flower-shaped palladium hydride, and the invention selects tungsten hexacarbonyl as a structure directing agent, which can effectively control the growth of the flower shape and prevent agglomeration. In addition, tungsten hexacarbonyl decomposes at high temperature, and the generated CO excites flaky seeds, eventually leading to the formation of flower-like palladium hydride. And CO can be adsorbed on the flower-shaped sheet to form a porous structure, and finally, the flower-shaped palladium hydride with the pores is formed. In the preparation process, the appearance and the structure of the flower-shaped palladium hydride can be controlled by changing the adding proportion of the precursor.

A method of preparing a flower-like palladium hydride catalyst for catalyzing an oxygen reduction reaction, the method comprising the steps of:

(1) respectively taking 1-50 mg of sodium chloropalladate and tungsten hexacarbonyl, then adding 1-20 mL of N, N-dimethylformamide solution, fully mixing the solutions, and then adding 1-10 mL of acetic acid solution; after the solutions are fully mixed, placing the mixture in an oil bath pot, heating the mixture to 50-200 ℃, reacting for 1-10 hours, washing, centrifuging and drying to obtain flower-shaped palladium;

(2) taking 1-10 mg of prepared flower-shaped palladium, adding 1-50 mL of N, N-dimethylformamide solution, uniformly mixing, placing in an oil bath pan, heating to 50-200 ℃, reacting for 1-30 h, washing, centrifuging, and drying to obtain the flower-shaped palladium hydrogenation catalyst for catalyzing the oxygen reduction reaction.

Further, the shape and structure of the flower-shaped palladium hydride are controlled by controlling the amount of the sodium chloropalladate and the tungsten hexacarbonyl, the volume of the N, N-dimethylformamide solution and the acetic acid, and the temperature and the time of the reaction.

Carrying out electrochemical catalytic oxidation-reduction reaction at normal temperature and normal pressure, wherein the specific performance test operation process is as follows:

(1) weighing 1-5 mg of sample, dispersing in ultrapure water, performing ultrasonic treatment for 30 minutes to obtain a uniform dispersion liquid, dripping 1-10 mu L of the dispersion liquid on the surface of a glassy carbon electrode, drying at 50 ℃, and then dripping 1-10 mu L of Nafion solution (0.5 wt%) to cover the surface of a catalyst to prepare a working electrode. Meanwhile, a platinum wire electrode is used as a counter electrode, and an Ag/AgCl electrode is used as a reference electrode to form a three-electrode system for carrying out oxidation reduction test;

(2) before the test, 0.1M sodium hydroxide solution is added into the electrolytic cell, the solution is saturated with oxygen by introducing oxygen for 30 minutes, the test programs of cyclic voltammetry and linear sweep voltammetry are selected, and the current conditions of the working electrode at different sweep rates are monitored by a computer. And finally, calculating the Tafel slope, the number of transferred electrons and the yield of hydrogen peroxide according to the measured data and a corresponding formula to evaluate the oxygen reduction performance of the catalyst.

The invention provides an efficient flower-like palladium hydride porous nanosheet, which is simply treated with N, N-dimethylformamide in an oil bath at 160 ℃ for 16 hours, and meanwhile, the electrocatalytic performance of the nanosheet on alkaline oxygen reduction is researched. The prepared flower-shaped palladium hydride not only shows obviously enhanced electrocatalytic oxygen reduction activity, but also has extremely front oxidation potential. This method provides a direction for improving the oxygen reduction performance of palladium-based catalysts.

The flower-shaped palladium hydride catalyst for catalyzing oxygen reduction reaction and the preparation method thereof provided by the invention have the main beneficial effects that:

(1) the preparation method is novel, the product can be obtained by adding N, N-dimethylformamide solution, and the flower-like palladium hydride yield is high.

(2) The morphology and the structure of the flower-shaped palladium hydride can be controlled by changing the reaction time.

(3) The synthesized flower-like palladium hydrogenation catalyst shows outstanding activity and stability in the oxidation-reduction reaction, and the palladium-based material has good application prospect as an electrocatalyst.

Drawings

FIG. 1 is an SEM image of flower-like palladium hydride according to embodiment 1 of the present invention.

FIG. 2 is a TEM image of flower-like palladium hydride according to embodiment 1 of the present invention.

FIG. 3 is an XRD pattern of flower-like palladium hydride according to embodiment 1 of the present invention.

FIG. 4 is an XPS map of flower-like palladium hydride according to embodiment 1 of the present invention.

FIG. 5 shows the linear sweep voltammetry, mass activity and area activity, Tafel slope, onset potential and half-wave potential at 1600 rpm for flower-like palladium hydride according to example 1 of the present invention.

FIG. 6 is a linear sweep voltammogram, a half-wave potential, and a polarographic current-time curve of flower-like palladium hydride before and after 10000 cycles of cyclic voltammetry according to example 1 of the present invention.

FIG. 7 is a linear sweep voltammogram and the number of transferred electrons at various rotation speeds of flower-like palladium hydride, and a RRDE curve according to example 1 of the present invention.

FIG. 8 is an SEM image of flower-like palladium of example 2 of the present invention.

FIG. 9 shows the linear sweep voltammetry, mass activity and area activity, Tafel slope, onset potential and half-wave potential at 1600 rpm for palladium flower of example 2 of the present invention.

FIG. 10 is a plot of linear sweep voltammograms and number of transferred electrons, as well as RRDE curves at various rotation speeds for flower-like palladium in accordance with example 2 of the present invention.

Detailed Description

The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto:

referring to fig. 1 to 10, in this example, the performance test of oxygen reduction of the flower-like palladium hydride was performed on a CHI 760E electrochemical workstation, and the operation process was as follows:

firstly, weighing 1-5 mg of sample, dispersing the sample in ultrapure water, carrying out ultrasonic treatment for 0-60 minutes to obtain uniform dispersion liquid, dripping 0-10 mu L of the dispersion liquid on the surface of a glassy carbon electrode, drying the glassy carbon electrode at 0-100 ℃, and dripping 0-10 mu L of Nafion solution (0.5 wt%) to cover the surface of a catalyst to prepare a working electrode. Meanwhile, a platinum wire electrode is used as a counter electrode, and an Ag/AgCl electrode is used as a reference electrode to form a three-electrode system for carrying out an oxygen reduction test;

and secondly, before testing, adding 0.1M potassium hydroxide solution into the electrolytic cell, introducing oxygen for 0-60 minutes to saturate the solution with oxygen, selecting test programs of cyclic voltammetry and linear sweep voltammetry, and monitoring the current condition of the working electrode at different sweep rates by using a computer. And finally, calculating the Tafel slope, the number of transferred electrons and the yield of hydrogen peroxide according to the measured data and a corresponding formula to evaluate the oxygen reduction performance of the catalyst.

Example 1:

a method of preparing a flower-like palladium hydride catalyst for catalyzing an oxygen reduction reaction, the method comprising the steps of:

1) respectively taking 10mg of sodium chloropalladate and 30mg of tungsten hexacarbonyl, adding 8mL of N, N-dimethylformamide solution, fully mixing the solutions, and then adding 2mL of acetic acid solution; and after the solutions are fully mixed, placing the mixture in an oil bath pot, heating the mixture to 140 ℃, reacting for 2 hours, washing, centrifuging and drying to obtain the flower-shaped palladium.

2) And (2) adding 20mL of N, N-dimethylformamide solution into prepared flower-shaped palladium with the mass of 4mg, uniformly mixing, placing in an oil bath pot, heating to 160 ℃, reacting for 16h, washing, centrifuging and drying to obtain the flower-shaped palladium hydride oxygen reduction catalyst.

The SEM image of the flower-like palladium hydride obtained is shown in fig. 1. The TEM image of the flower-like palladium hydride obtained is shown in fig. 2. The XRD pattern of the obtained flower-like palladium hydride is shown in FIG. 3. The XPS pattern of the flower-like palladium hydride obtained is shown in fig. 4. The linear sweep voltammetry, mass activity and area activity, tafel slope, initial potential and half-wave potential of the obtained flower-like palladium hydride at 1600 rpm are shown in fig. 5. The linear sweep voltammetry curve, half-wave potential and polarographic current time curve of the obtained flower-shaped palladium hydride after 10000 cycles of cyclic voltammetry are shown in figure 6. The obtained flower-like palladium hydride is subjected to linear sweep voltammogram and transferred electron number, rotary plate current, transferred electron number and hydrogen peroxide yield under different rotating speeds, and is shown in FIG. 7.

As seen from the SEM image, the yield of flower-like palladium hydride is high, and each flower-like structure is composed of several overlapped sheets and is a typical flower-like structure. As seen from the TEM image, each flower is not smooth and has many small holes thereon, and this structure is effective in increasing the specific surface area and thus the electrochemically active sites. By XRD and XPS analysis, flower-like palladium hydride is formed and H atoms are incorporated into the crystal lattice of palladium, causing lattice expansion of palladium. The linear sweep voltammetry curve, the half-wave potential and the polarographic current time curve of the flower-shaped palladium hydride before and after 10000 cycles of cyclic voltammetry can be seen through the linear sweep voltammetry curve. Has positive initial potential (1.05V vs. Ag/AgCl) and half-wave potential (1.02V vs. Ag/AgCl) for catalyzing oxygen reduction, and has good mass activity and area activity of 2.83mA cm/cm^-2And 1.52mA μ g^-1. Calculating the tafel slope to be 53.2mV dec according to the linear sweep voltammogram^-1The transfer of the first electron during oxygen reduction was demonstrated to be the rate controlling step. From the linear sweep voltammetry curve before and after 10000 circles and the polarographic current-time curve, the mass activity before and after the reaction is respectively 1.52mA mu g^-1And 1.49mA μ g^-1It can be seen that flower-like palladium hydride has good stability. The four-electron reaction can be seen through the linear sweep voltammetry curve, the number of transfer electrons, the rotary return plate current, the number of transfer electrons and the yield of hydrogen peroxide under different rotating speeds, and the intermediate products are few.

Example 2:

a method of preparing a sponge palladium hydride alloy catalyst for catalyzing an oxygen reduction reaction, the method comprising the steps of:

1) respectively taking 1mg of sodium chloropalladate and 1mg of tungsten hexacarbonyl, adding 1mL of N, N-dimethylformamide solution, fully mixing the solutions, and then adding 1mL of acetic acid solution; and after the solutions are fully mixed, placing the mixture in an oil bath pot, heating the mixture to 50 ℃, reacting for 1h, washing, centrifuging and drying to obtain the spongy palladium hydride.

2) And taking the prepared spongy palladium hydride with the mass of between 4mg, adding 1mL of N, N-dimethylformamide solution, uniformly mixing, placing in an oil bath pan, heating to 50 ℃, reacting for 1h, washing, centrifuging and drying to obtain the spongy palladium hydride oxygen reduction catalyst.

The SEM image of the sponge-like palladium hydride obtained is shown in fig. 8, and the linear sweep voltammetry, mass activity and area activity, tafel slope, onset potential and half-wave potential at 1600 rpm are shown in fig. 9. The obtained sponge-like palladium hydride was subjected to linear sweep voltammograms and the number of transfer electrons at different rotation speeds, and the current, the number of transfer electrons and the yield of hydrogen peroxide were shown in FIG. 10.

From the SEM images, it can be seen that the sponge palladium hydride formation is mainly due to the change in morphology resulting from the change in the amount of precursor. From the linear sweep voltammogram, it can be seen that the sponge palladium hydride has a positive initial potential (0.99V vs. Ag/AgCl) for catalyzing oxygen reduction and a half-wave potential (0.91V vs. Ag/AgCl). The Tafel slope is calculated to be 68.7mV dec according to a linear sweep voltammogram^-1The transfer of the first electron during oxygen reduction was demonstrated to be the rate controlling step.

Example 3:

a method of preparing a flower-like palladium hydride catalyst for catalyzing an oxygen reduction reaction, the method comprising the steps of:

1) respectively taking 50mg of sodium chloropalladate and 50mg of tungsten hexacarbonyl, then adding 20mL of N, N-dimethylformamide solution, fully mixing the solutions, and then adding 10mL of acetic acid solution; and after the solutions are fully mixed, placing the mixture in an oil bath pot, heating the mixture to 200 ℃, reacting the mixture for 10 hours, washing, centrifuging and drying the mixture to obtain a product.

2) And taking the prepared product with the mass of 10mg, adding 50mL of N, N-dimethylformamide solution, uniformly mixing, placing in an oil bath pot, heating to 200 ℃, reacting for 30h, washing, centrifuging and drying to obtain the catalyst.

In the process, the mass of the sodium chloropalladate and the tungsten hexacarbonyl is larger, so the size of the synthesized catalyst is larger; in addition, the original pH of the system can be changed after the amount of the acetic acid is increased, so that the flower-shaped palladium hydrogenation catalyst synthesized by the method has poor appearance.