In-situ grown copper nanosheet electrocatalyst and preparation method and application thereof

Abstract

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

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to an in-situ grown copper nanosheet electrocatalyst, its preparation method, and its application. Background Technology

[0002] The burning of fossil fuels, excessive use of chemical fertilizers, and discharge of industrial wastewater have led to an increase in nitrates (NO3) in the environment. - The concentration of nitrates continues to rise, threatening human health. Excessive nitrate levels in drinking water can increase the risk of diseases such as methemoglobinemia, diabetes, and stomach cancer.

[0003] Electrocatalytic nitrate reduction reaction (NO3) - RR is an effective method for treating nitrate wastewater, removing harmful NO3. - The conversion of nitrates into harmless NH3 reduces environmental pollution while increasing economic value. Furthermore, ammonia is a highly promising fuel, playing an indispensable role in modern industry and agriculture; its importance is self-evident. However, the traditional Haber-Bosch ammonia production process is energy-intensive and emits large amounts of carbon dioxide, exacerbating the greenhouse effect. Therefore, developing highly active non-precious metal electrocatalysts for nitrate reduction to ammonia production is of great significance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of traditional ammonia production processes, such as high energy consumption and large emissions of greenhouse gases, and to provide an in-situ grown copper nanosheet electrocatalyst, its preparation method, and its application.

[0005] The objective of this invention can be achieved through 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, reacting to obtain an in-situ grown copper nanosheet array electrocatalyst on the foam metal, wherein the foam metal is selected from metals more reactive 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 for the copper salt solution is deionized water.

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

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

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

[0012] As the reaction time increases, the Cu catalyst loading on the foam metal surface increases, and the Cu catalyst has a good effect on nitrate reduction. However, if the reaction time is too long, it will corrode the foam metal framework, rendering the catalyst unusable.

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

[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] The third technical solution of the present invention is to provide an application of the 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, under alkaline conditions, the in-situ grown copper nanosheet array electrocatalyst catalytically reduces nitrate wastewater to ammonia.

[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. The prepared electrocatalyst is conducive to accelerating the diffusion and mass transfer of the catalytic reaction, accelerating the rapid desorption of accumulated bubbles, and having a large specific surface area, thereby fully exposing the active sites, improving the reaction kinetics, effectively improving the catalytic activity and stability, and having good nitrate reduction performance.

[0020] (3) The preparation method of the present invention is low in cost, easy to operate, has zero energy consumption, is scalable, and the product obtained has good NO3RR electrocatalytic activity in alkaline electrolyte, which can realize the production of the value-added chemical ammonia under a low voltage input. Attached Figure Description

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

[0022] Figure 2 This is an elemental distribution diagram of the Cu / IF catalyst.

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

[0024] Figure 4 The figure shows the linear sweep voltammetry curves of NO3RR for Cu / IF catalyst in 1.0 M KOH and electrolyte containing 0.1 M KNO3 (A), the linear sweep voltammetry curves of NO3RR for Cu / IF with different soaking times (B), and the corresponding Tafel slope values ​​(C).

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

[0026] Figure 6 The electrochemical impedance spectroscopy (EIS) spectra of Cu / IF catalysts at different voltages are shown.

[0027] Figure 7 This is a graph showing the NO3RR stability of the Cu / IF catalyst. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection 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 Maclean Biochemical Technology Co., Ltd., and electrochemical data was collected by CHI760E (Shanghai Chenhua). Other raw materials or processing technologies not specifically described are all conventional commercially available products or conventional processing technologies in the field.

[0030] Example 1:

[0031] Weigh 0.966 g of copper nitrate trihydrate and dissolve it in 20 mL of deionized water to form a homogeneous solution. Add the solution to a beaker containing clean foamed iron. After reacting at room temperature for 30 min, a copper nanosheet array loaded on the foamed iron can be obtained. Dry it in a vacuum drying oven at 80 °C for later use. This array is denoted as Cu / IF.

[0032] Example 2:

[0033] Compared with Example 1, most of the results are the same, except that the copper nanosheet array loaded on iron foam was prepared by reacting at room temperature for 1 min.

[0034] Example 3:

[0035] Compared with Example 1, most of the results are the same, except that the copper nanosheet array loaded on iron foam was prepared by reacting at room temperature for 5 minutes.

[0036] Example 4:

[0037] Compared with Example 1, most of the results are the same, except that the copper nanosheet array loaded on iron foam was prepared by reacting at room temperature for 60 minutes.

[0038] Comparative Example 1:

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

[0040] Comparative Example 2:

[0041] The process is largely the same as the previous examples, except that the copper nanosheet array loaded on iron foam was prepared by reacting at room temperature for 2 hours.

[0042] like Figure 1 As shown, the morphology of Cu / IF is characterized, revealing its nanosheet structure.

[0043] like Figure 2 The figure shows the elemental distribution of Cu / IF, indicating that the product is mainly composed of Fe and Cu.

[0044] like Figure 3 The image shows 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 1-4 and the IF catalyst prepared in the comparative example were used as NO3RR catalysts:

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

[0047] (1) The HER test was performed in 1.0M KOH solution.

[0048] (2) The NO3RR test was performed in a 1.0M KOH solution containing 0.1M KNO3.

[0049] (3) The scan rate for the cyclic voltammetry curve and the linear scan voltammetry curve is 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) is calculated by CV at different scan rates in the potential range of 0.324V to 0.426V (vs. RHE).

[0053] (7) The catalyst stability was evaluated by chronopotential testing.

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

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

[0056] like Figure 5 Figure A shows the cyclic voltammetry curves of the Cu / IF catalyst at different scan rates (scan rate from 10 mV / s to 60 mV / s, increasing by 10 mV / s each time). Half the difference between the oxidation and reduction currents at 0.374 V was selected as the capacitance current. The scan rate was plotted on the x-axis, and the capacitance current at different scan rates on the y-axis. The capacitance current is directly proportional to the scan rate, and the slope of this straight line represents the double-layer capacitance (5B) of the material. The electrochemically active area is also directly proportional to the double-layer capacitance. The double-layer capacitance of the Cu / IF catalyst synthesized in 30 min was 31.27 mF cm⁻¹. -2 This indicates that it has more ammonia-producing active sites.

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

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

[0059] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any 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 invention should be within the protection scope of the present invention.

Claims

1. A method for preparing an in-situ grown copper nanosheet electrocatalyst, characterized in that, A copper nanosheet array electrocatalyst was obtained by immersing a metal foam in a copper salt solution and reacting the resulting material. The copper salt in the copper salt solution is selected from any one of copper nitrate trihydrate, copper chloride, and copper sulfate. The concentration of copper salt in the copper salt solution is 10-200 mM; The foamed metal is foamed iron; The reaction temperature was room temperature, and the reaction time was (1~60) min.

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

3. The preparation method according to claim 1, characterized in that, The reaction was carried out at room temperature for 30 minutes.

4. An in-situ grown copper nanosheet array electrocatalyst, characterized in that, It is obtained based on the preparation method described in any one of claims 1 to 3.

5. An application of the in-situ grown copper nanosheet array electrocatalyst as described in claim 4, characterized in that, The in-situ grown copper nanosheet array electrocatalyst is used to treat nitrate wastewater into value-added chemicals.

6. The application according to claim 5, characterized in that, The in-situ grown copper nanosheet array electrocatalyst catalytically reduces nitrate wastewater to ammonia.

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