COPPER NANOCATALYST, METHOD FOR PREPARING THE SAME, AND APPLICATION OF THE SAME IN THE SYNTHESIS OF ACETATE OR AMMONIA

Abstract

A copper nanocatalyst, a method for preparing the copper nanocatalyst, and an application of the copper nanocatalyst in the synthesis of acetate or ammonia are provided. The copper nanocatalyst includes a substrate and an active agent loaded on the substrate. The method includes: preparing a cleaning agent by using an ethanol and a deionized; immersing the active agent in the cleaning agent, ultrasonically cleaning for 5-10 min at a frequency of 410.sup.4 Hz-810.sup.4 Hz, and drying for later use; mixing the cleaned active agent and a conductive binder according to a mass ratio of 1:19-9:1 of the active agent to the conductive binder, adding the ethanol, and fully stirring and dispersing to obtain a slurry; coating the slurry on a surface of the carbon paper, and drying the carbon paper by blowing through nitrogen flow to obtain the catalyst.

Claims

1. A copper nanocatalyst, comprising a substrate and an active agent loaded on the substrate, wherein a loading amount of the active agent on the substrate is 0.1-3.0 mg/cm.sup.2, and the active agent is a copper nanomaterial with an exposed 50%-99% (111) crystal face.

2. The copper nanocatalyst according to claim 1, wherein, the substrate comprises a carbon paper, a carbon cloth, a silicon oxide film, or an aluminum oxide film.

3. The copper nanocatalyst according to claim 1, wherein, the active agent is a copper nanosheet, a copper nanopolyhedron or a copper nanowire, and the copper nanosheet, the copper nanopolyhedron or the copper nanowire has the exposed 50%-99% (111) crystal face.

4. The copper nanocatalyst according to claim 3, wherein, the copper nanopolyhedron is at least one selected the group consisting of a copper regular nanotetrahedron, a copper nanocube, a copper regular nanooctahedron and a copper regular nanoicosahedron.

5. The copper nanocatalyst according to claim 1, wherein, the loading amount of the active agent on the substrate is 1.0 mg/cm.sup.2.

6. A method for preparing the copper nanocatalyst according to claim 1, comprising the following steps: (1) preparing a cleaning agent by using an ethanol and a deionized water, wherein a volume ratio of the ethanol to the deionized water in the cleaning agent is 5-90:10-95; immersing the active agent in the cleaning agent, ultrasonically cleaning the active agent for 5-10 min at a frequency of 410.sup.4 Hz-810.sup.4 Hz to obtain a cleaned active agent, and drying the cleaned active agent for later use; (2) mixing the cleaned active agent and a conductive binder according to a mass ratio of 1:19-9:1 of the cleaned active agent to the conductive binder to obtain a mixture, adding the ethanol to the mixture to obtain a first solution, and fully stirring and dispersing the first solution to obtain a slurry; and (3) coating the slurry on a surface of the substrate and drying the substrate by blowing through nitrogen flow to obtain the copper nanocatalyst.

7. The method according to claim 6, wherein, a method for preparing the active agent comprises the following steps: dissolving and stirring copper nitrate, ascorbic acid, hexamethylenetetramine and hexadecyltrimethylammonium bromide in the deionized water to form a homogeneous solution, placing the homogeneous solution in an oil bath at 70-100 C. to react for 1-5 h to obtain a second solution, cooling the second solution, washing the second solution with a mixed solution of the ethanol and water to obtain a third solution, centrifuging the third solution to obtain a precipitate, and drying the precipitate to obtain the active agent.

8. The method according to claim 7, wherein, a molar ratio of the copper nitrate, the ascorbic acid, the hexamethylenetetramine and the hexadecyltrimethylammonium bromide is 1:0.1-0.5:0.1-0.5:0.5-1.

9. The method according to claim 7, wherein, the conductive binder is Nafion, and a mass ratio of the Nafion to the active agent is 4:1.

10. A method of synthesizing acetate or ammonia, comprising: using the copper nanocatalyst according to claim 1.

11. The method according to claim 6, wherein, the substrate comprises a carbon paper, a carbon cloth, a silicon oxide film, or an aluminum oxide film.

12. The method according to claim 6, wherein, the active agent is a copper nanosheet, a copper nanopolyhedron or a copper nanowire, and the copper nanosheet, the copper nanopolyhedron or the copper nanowire has the exposed 50%-99% (111) crystal face.

13. The method according to claim 12, wherein, the copper nanopolyhedron is at least one selected the group consisting of a copper regular nanotetrahedron, a copper nanocube, a copper regular nanooctahedron and a copper regular nanoicosahedron.

14. The method according to claim 6, wherein, the loading amount of the active agent on the substrate is 1.0 mg/cm.sup.2.

15. The method according to claim 10, wherein, the substrate comprises a carbon paper, a carbon cloth, a silicon oxide film, or an aluminum oxide film.

16. The method according to claim 10, wherein, the active agent is a copper nanosheet, a copper nanopolyhedron or a copper nanowire, and the copper nanosheet, the copper nanopolyhedron or the copper nanowire has the exposed 50%-99% (111) crystal face.

17. The method according to claim 16, wherein, the copper nanopolyhedron is at least one selected the group consisting of a copper regular nanotetrahedron, a copper nanocube, a copper regular nanooctahedron and a copper regular nanoicosahedron.

18. The method according to claim 10, wherein, the loading amount of the active agent on the substrate is 1.0 mg/cm.sup.2.

Description

DETAILED DESCRIPTION OF THE DRAWINGS

[0021] FIGS. 1A-1C show a structural characterization of a copper nanosheet;

[0022] FIGS. 2A-2C show a structural representation of a copper nanocube;

[0023] FIG. 3 is a schematic diagram showing a route for ammonia synthesis via electroreduction of nitrate; and

[0024] FIGS. 4A-4D show the results of the electroreduction of nitrate to ammonia.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The present invention is described in detail below in conjunction with the embodiments.

Embodiment 1

[0026] A copper nanocatalyst includes a carbon paper substrate and a copper nanosheet loaded on the carbon paper, wherein the loading capacity of the copper nanosheet on the carbon paper is about 1.0 mg/cm.sup.2. The method for preparing the catalyst is as follows.

[0027] (1) Synthesis of copper nanosheet: the copper nitrate, ascorbic acid, hexamethylenetetramine and hexadecyltrimethylammonium bromide are dissolved in deionized water according to the molar ratio of 1:0.1:0.5:0.5, and are stirred to form a homogeneous solution. The solution is placed in an oil bath at 100 C. to react for 2 hours, and is then cooled. The mixed solution of ethanol and water is added to the solution for washing and centrifuging, and a precipitate is taken to dry to obtain an active agent, wherein the active agent is the copper nanosheet.

[0028] (2) Cleaning of copper nanosheet: the ethanol and the deionized water are adopted to prepare a cleaning agent, wherein the volume ratio of the ethanol to the deionized water in the prepared cleaning agent is 1:9. The active agent is immersed in the cleaning agent and is ultrasonically cleaned for 8 min at a frequency of 610.sup.4 Hz, and is then dried for later use.

[0029] (3) Preparation of slurry: the Nafion conductive binder with a concentration of 10% is added into the cleaned active agent, wherein the mass ratio of the added Nafion to the active agent is 4:1, and then a proper amount of ethanol is added, and after fully stirring and dispersing, the slurry is obtained.

[0030] (4) Preparation of catalyst: the slurry is uniformly coated on the surface of the carbon paper, and is then dried by blowing through nitrogen flow to obtain the catalyst.

Embodiment 2

[0031] A copper nanocatalyst includes a carbon cloth substrate and a copper nanocube loaded on the carbon cloth, wherein the loading capacity of the copper nanocube on the carbon cloth is about 3.0 mg/cm.sup.2. The method for preparing the catalyst is as follows.

[0032] (1) Cleaning of copper nanocube: the ethanol and the deionized water are adopted to prepare a cleaning agent, wherein the volume ratio of the ethanol to the deionized water in the prepared cleaning agent is 1:1. The prepared copper nanocube is then immersed in the cleaning agent and is ultrasonically cleaned for 5 min at a frequency of 810.sup.4 Hz, and is then dried for later use.

[0033] (2) Preparation of slurry: the Nafion conductive binder with a concentration of 10% is added into the cleaned active agent, wherein the mass ratio of the added Nafion to the active agent is 1:1, and then a proper amount of ethanol is added, and after fully stirring and dispersing, the slurry is obtained.

[0034] (3) Preparation of catalyst: the slurry is uniformly coated on the surface of the carbon cloth, and is then dried by blowing through nitrogen flow to obtain the catalyst.

Embodiment 3

[0035] A copper nanocatalyst includes a carbon paper substrate and a copper nanowire loaded on the carbon paper, wherein the loading amount of the copper nanowire on the carbon paper is about 0.5 mg/cm.sup.2. The method for preparing the catalyst is as follows.

[0036] (1) Cleaning of copper nanowire: the ethanol and the deionized water are adopted to prepare a cleaning agent, wherein the volume ratio of the ethanol to the deionized water in the prepared cleaning agent is 4:1. The prepared copper nanowire is immersed into the cleaning agent and is ultrasonically cleaned for 10 min at a frequency of 410.sup.4 Hz, and is then dried for later use.

[0037] (2) Preparation of slurry: the Nafion conductive binder with a concentration of 10% is added into the cleaned active agent, wherein the mass ratio of the added Nafion to the active agent is 1:4, and then a proper amount of ethanol is added, and after fully stirring and dispersing, the slurry is obtained.

[0038] (3) Preparation of catalyst: the slurry is uniformly coated on the surface of the carbon paper and is then dried by blowing through nitrogen flow to obtain the catalyst.

[0039] Analysis of Results

[0040] The copper nanosheet synthesized in Embodiment 1 was taken to analyze the structure thereof, and the result is shown in FIGS. 1A-1C, wherein, FIG. 1A represents transverse electric and magnetic field (TEM), FIG. 1B represents high resolution transmission electron microscopy (HRTEM) and FIG. 1C represents X-Ray Diffraction (XRD). The copper nanocube synthesized in Embodiment 2 was taken to analyzethe structure thereof, and the result is shown in FIGS. 2A-2C, wherein, FIG. 2A represents TEM, FIG. 2B represents HRTEM, and FIG. 2C represents XRD. From FIGS. 1A-1C and FIGS. 2A-2C, it can be seen that the copper nanomaterials have regular morphology and a well-defined structure.

[0041] The catalyst prepared in the Embodiment 1 was adopted to test the electrochemical reduction of nitrate to ammonia, and the test path is shown in FIG. 3, wherein the test condition is ambient temperature and pressure, and the applied potential is from 0.1 to 1.0V (vs RHE). The test results are shown in FIGS. 4A-4D, wherein, FIG. 4A is electrochemical data, and the test conditions are as follows: 0.1M potassium hydroxide solution (dotted line), 0.1 M potassium hydroxide solution presence of 10 mM potassium nitrate solution (solid line), scanning speed 20 mA/s, and the inset is the .sup.1H nuclear magnetic resonance spectrogram calibrated by K.sup.15NO.sub.3 (98 atom % .sup.15N); FIG. 4B is the current density. From FIG. 4A and FIG. 4B, it can be seen that nitrate can be converted to ammonia at lower potentials by the catalyst of the present invention, and the conversion rate increases as the current increases. And FIG. 4C is the synthesis rate of the ammonia; FIG. 4D is faradaic efficiency (i.e., yield). From FIG. 4C and FIG. 4D, it can be seen that at 0.15V versus RHE, the ammonia yield of the catalyst with the copper nanosheet as the active agent is 390.1 mug mg.sup.1.sub.Cu h.sup.1, and is close to 100%, which shows that the catalyst of the present invention can efficiently convert nitrate into ammonia, and has the advantages of low energy consumption, no pollution, and meeting the requirements of the green chemical industry.

[0042] Although the embodiments of the present invention has been described in detail above, they should not be construed as a limitation to the scope of the present invention. Various modifications and variations made by those skilled in the art within the scope described in the claims without creative work shall fall within the scope of protection of the present invention.