In-situ growth copper nanosheet electrocatalyst as well as preparation method and application thereof

Abstract

The invention relates to an in-situ growth copper nanosheet electrocatalyst and a preparation method and application thereof.The preparation method comprises the steps that foam metal is soaked in a copper salt solution, the copper nanosheet array electrocatalyst growing on the foam metal in situ is obtained through reaction, and the foam metal is selected from metal more active than copper. Compared with the prior art, the in-situ growth strategy avoids the use of an adhesive, and the prepared copper nanosheet array structure which grows on the foam iron in situ and is regularly arranged is beneficial to accelerating diffusion mass transfer of a catalytic reaction and accelerating rapid desorption of accumulated bubbles and has a large specific surface area, so that active sites are fully exposed; the reaction kinetics is improved, and the catalytic activity and stability can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to an in-situ grown copper nanosheet electrocatalyst and a preparation method and application thereof. Background Art

[0002] Due to the burning of fossil fuels, excessive use of fertilizers and discharge of industrial wastewater, nitrate (NO3 - ) concentration continues to grow, threatening human health. Excessive nitrate content in drinking water increases the risk of diseases such as methemoglobinemia, diabetes and gastric cancer.

[0003] Electrocatalytic nitrate reduction reaction (NO3 - RR) is an effective way to treat nitrate wastewater, converting harmful NO3 - Converting into harmless NH3 not only reduces environmental pollution but also increases economic value. In addition, ammonia is a very promising fuel. It occupies an indispensable position in modern industry and agriculture, and its importance is self-evident. However, the traditional Haber-Bosch process for preparing ammonia consumes a lot of energy and also emits large amounts of carbon dioxide, aggravating the greenhouse effect. Therefore, it is very meaningful to develop highly active non-precious metal electrocatalysts for nitrate reduction to produce ammonia. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the current traditional ammonia production process, such as high energy consumption and emission of large amounts of greenhouse gases, and to provide an in-situ grown copper nanosheet electrocatalyst and its preparation method and application.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The technical solution of the present invention is to provide a method for preparing an in-situ grown copper nanosheet electrocatalyst: immersing a foam metal in a copper salt solution, and reacting to obtain a copper nanosheet array electrocatalyst grown in-situ on the foam metal, wherein the foam metal is a metal that is more active than copper.

[0007] In some specific embodiments, the copper salt in the copper salt solution is selected from any one of copper nitrate trihydrate, copper chloride, and copper sulfate.

[0008] In some specific embodiments, the solvent of the copper salt solution is deionized water.

[0009] In some specific embodiments, the concentration of the copper salt in the copper salt solution is 10-200 mM.

[0010] In some specific embodiments, the metal foam is iron foam (IF).

[0011] In some specific embodiments, the reaction temperature is room temperature, and the reaction time is (1 to 60) min.

[0012] As the reaction time increases, the Cu catalyst loading on the surface of the metal foam increases, and the Cu catalyst has a better effect on nitrate reduction. If the reaction time is too long, the skeleton of the metal foam will be corroded, making the catalyst unusable.

[0013] In some specific embodiments, the reaction temperature is room temperature and the reaction time is 30 min.

[0014] The second technical solution of the present invention is to provide an in-situ grown copper nanosheet array electrocatalyst, which is obtained based on the method described in one of the above technical solutions.

[0015] A third technical solution of the present invention is to provide an application of an in-situ grown copper nanosheet array electrocatalyst as described in one of the above technical solutions, wherein the in-situ grown copper nanosheet array electrocatalyst is used to treat nitrate wastewater into value-added chemicals.

[0016] In some specific embodiments, the in situ grown copper nanosheet array electrocatalyst catalyzes the reduction of nitrate wastewater into ammonia under alkaline conditions.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The in-situ growth strategy of the present invention avoids the use of adhesives, ensures close contact between the copper nanosheet array electrocatalyst and the foam metal conductive substrate interface, and promotes rapid charge transfer.

[0019] (2) The preparation method of the present invention is simple, and the prepared electrocatalyst is beneficial to accelerate the diffusion mass transfer of the catalytic reaction, accelerate the rapid desorption of accumulated bubbles, and has a large specific surface area, so that the active sites are fully exposed, the reaction kinetics are improved, the catalytic activity and stability can be effectively improved, and it has good nitrate reduction performance.

[0020] (3) The preparation method of the present invention is low-cost, easy to operate, has zero energy consumption, and is scalable. The prepared product has good NO3RR electrocatalytic activity in alkaline electrolyte and can achieve the production of value-added chemical ammonia at a relatively low voltage input. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Scanning electron microscopy (SEM) (A, B) and transmission electron microscopy (TEM) (C) images of Cu / IF catalyst.

[0022] Figure 2 Element distribution diagram of Cu / IF catalyst.

[0023] Figure 3 This is the X-ray diffraction pattern (XRD) of the Cu / IF catalyst.

[0024] Figure 4 NO3RR linear sweep voltammogram of Cu / IF catalyst in 1.0M KOH and electrolyte containing 0.1M KNO3 (A), NO3RR linear sweep voltammogram of Cu / IF with different immersion time (B) and the corresponding Tafel slope value graph (C).

[0025] Figure 5 Cyclic voltammetry curves of Cu / IF catalyst at different scan rates (A); double layer capacitance of Cu / IF catalyst (B).

[0026] Figure 6 Electrochemical impedance spectroscopy of Cu / IF catalyst at different voltages.

[0027] Figure 7 NO3RR stability diagram of Cu / IF catalyst. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0029] In the following examples and comparative examples, copper nitrate trihydrate was purchased from Shanghai McLean Biochemical Technology Co., Ltd., and electrochemical data were collected by CHI760E (Shanghai Chenhua). Other raw materials, products or processing technologies not specifically described are indicated to be conventional commercial products or conventional processing technologies in the art.

[0030] Embodiment 1:

[0031] Weigh 0.966 g of copper nitrate trihydrate and dissolve it in 20 mL of deionized water to form a uniform solution. Add the solution to a beaker containing clean foam iron. After 30 minutes of reaction at room temperature, a copper nanosheet array loaded on the foam iron can be obtained. Place it in a vacuum drying oven at 80°C and dry it for use, which is recorded as Cu / IF.

[0032] Embodiment 2:

[0033] Compared with Example 1, most of the aspects are the same, except that the reaction is carried out at room temperature for 1 min to prepare a copper nanosheet array supported on the foamed iron.

[0034] Embodiment 3:

[0035] Compared with Example 1, most of the aspects are the same, except that the reaction is carried out at room temperature for 5 minutes to prepare a copper nanosheet array supported on the foamed iron.

[0036] Embodiment 4:

[0037] Compared with Example 1, most of the aspects are the same, except that the reaction is carried out at room temperature for 60 minutes to prepare a copper nanosheet array supported on the foamed iron.

[0038] Comparative Example 1:

[0039] Compared with Example 1, most of them are the same, and the only difference is that the immersion of copper nitrate trihydrate is omitted, that is, the raw material of foamed iron is recorded as IF.

[0040] Comparative Example 2:

[0041] Compared with the embodiment, most of them are the same, and the only difference is that the copper nanosheet array supported on the foamed iron is prepared by reacting at room temperature for 2 hours.

[0042] like Figure 1 As shown, it is the morphology characterization of Cu / IF, and it can be seen that it is a nanosheet structure.

[0043] like Figure 2 As shown, it is the element distribution diagram of Cu / IF, indicating that the product is mainly composed of two elements, Fe and Cu.

[0044] like Figure 3 Shown is the X-ray diffraction pattern of Cu / IF, indicating that the sample contains elemental copper and cuprous oxide components.

[0045] The Cu / IF catalysts prepared in Examples 1 to 4 and the IF prepared in the comparative example were used as NO3RR catalysts:

[0046] At room temperature, the reaction system was a three-electrode system, with the Cu / IF catalyst used as the working electrode, the graphite rod used as the counter electrode, and mercury / mercuric oxide used as the reference electrode.

[0047] (1) HER tests were performed in 1.0 M KOH solution.

[0048] (2) NO3RR test was carried out in 1.0 M KOH solution containing 0.1 M KNO3.

[0049] (3) The scanning rate of cyclic voltammetry and linear sweep voltammetry was 5 mV s -1 .

[0050] (4) Electrochemical impedance spectroscopy (EIS) measurements were performed in the frequency range of 1 MHz to 0.01 Hz with an amplitude of 5 mV.

[0051] (5) The Tafel slope is obtained from the LSV plot using a linear fit applied to the points in the Tafel region.

[0052] (6) The double-layer capacitance (Cdl) was calculated by CV in the potential range of 0.324 V to 0.426 V (vs. RHE) at different scan rates.

[0053] (7) The catalyst stability was evaluated by constant current chronopotentiometry.

[0054] The results of evaluating the NO3RR performance of Cu / IF catalyst are as follows:

[0055] like Figure 4 As shown in A, compared with HER, NO3RR in 0.1M KNO3 solution has a larger current. Figure 4 As shown in Figure B, compared with the Cu / IF catalysts with other immersion times, the Cu / IF electrode synthesized for 30 min exhibits a larger current density and a lower overpotential. Figure 4 C is the Tafel slope of the corresponding catalysts. It can be seen from the figure that the Cu / IF catalyst synthesized in 30 min has a smaller Tafel slope value of only -138.9 mV dec. -1 , which indicates that the prepared catalyst has faster ammonia production kinetics.

[0056] like Figure 5 As shown in A, it is the cyclic voltammetry curve of Cu / IF catalyst at different scan rates (scan rate from 10mv / s to 60mv / s, each time increasing by 10mv / s for detection). Half of the difference between the oxidation current and the reduction current at 0.374V is selected as the capacitive current. The scan rate is the horizontal axis and the capacitive current at different scan rates is the vertical axis. The capacitive current is proportional to the scan rate. The slope of this straight line is the double-layer capacitance of the material (5B), and the electrochemical active area is proportional to the double-layer capacitance. The double-layer capacitance value of the Cu / IF catalyst synthesized in 30min is 31.27mF cm -2 , indicating that it has more active sites for ammonia production.

[0057] like Figure 6 As shown, the electrochemical impedance spectroscopy shows that the Cu / IF catalyst synthesized in 30 min has a faster charge transfer rate and a lower electrode / electrolyte interface resistance as the voltage decreases.

[0058] like Figure 7 As shown, it indicates that the Cu / IF catalyst also has good ammonia production stability.

[0059] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing an in-situ grown copper nanosheet electrocatalyst, characterized in that: The foam metal is immersed in a copper salt solution to react and obtain a copper nanosheet array electrocatalyst in situ grown on the foam metal, wherein the foam metal is a metal that is more active than copper.

2. The preparation method according to claim 1, characterized in that: The copper salt in the copper salt solution is selected from any one of copper nitrate trihydrate, copper chloride and copper sulfate.

3. The preparation method according to claim 1, characterized in that: The solvent of the copper salt solution is deionized water.

4. The preparation method according to claim 1, characterized in that: The concentration of the copper salt in the copper salt solution is 10-200 mM.

5. The preparation method according to claim 1, characterized in that: The foam metal is foam iron.

6. The preparation method according to claim 1, characterized in that: The reaction temperature is room temperature, and the reaction time is (1 to 60) min.

7. The preparation method according to claim 6, characterized in that: The reaction temperature was room temperature and the reaction time was 30 min.

8. An in-situ grown copper nanosheet array electrocatalyst, characterized in that: Obtained based on the preparation method according to any one of claims 1 to 7.

9. An application of the in-situ grown copper nanosheet array electrocatalyst as claimed in claim 8, characterized in that: The in situ grown copper nanosheet array electrocatalyst is used to treat nitrate wastewater into value-added chemicals.

10. The use according to claim 9, characterized in that: The in-situ grown copper nanosheet array electrocatalyst catalytically reduces nitrate wastewater to generate ammonia.

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