Preparation method of ni (oh) 2 modified cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia

Abstract

The application discloses a preparation method of a Ni(OH)2 modified Cu catalyst for efficiently electrocatalytically reducing nitrate to ammonia, and comprises the following steps: taking a Ni(OH)2 / CuO nanowire electrode as a working electrode, taking a Pt sheet electrode and a Hg / HgO electrode as a counter electrode and a reference electrode respectively, and obtaining the Ni(OH)2 / Cu nanowire electrode through an in-situ electro-reduction process under electrolysis conditions; and the Ni(OH)2 modified Cu catalyst prepared by the method has good ammonia production activity and Faraday efficiency under a low bias voltage.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a Ni(OH)2 modified Cu catalyst, in particular to a preparation method of a high-efficiency Ni(OH)2 modified Cu catalyst for electrocatalytic reduction of nitrate to ammonia. BACKGROUND

[0002] Ammonia plays an important role in the rapid development of modern industry and agriculture, and the annual ammonia production worldwide exceeds 17.5 billion tons, 70% of which is used for chemical fertilizer production, and the rest is used for manufacturing plastics, explosives and synthetic fibers and other chemicals, while ammonia is also recently used as a clean energy carrier without carbon. At present, the production of ammonia mainly relies on the Haber-Bosch (HB) process, which converts N2 and H2 into NH3 on an iron-based catalyst under high temperature and high pressure (400-650 DEG C, 100-400 bar). The HB process has high energy consumption and greenhouse gas emissions, wherein the annual energy consumption of the ammonia synthesis industry accounts for 2% of the total global energy consumption, and the greenhouse gas emissions account for 1.3% of the total global greenhouse gas emissions. Based on this, the electrochemical method for ammonia production is concerned due to its sustainable development and mild reaction conditions. However, the ammonia yield (~10 -1 nmol s -1 cm -2 ) and faradic efficiency (<10%) of the electrocatalytic nitrogen reduction to ammonia reaction are far from the requirements of industrialization, which is mainly due to the chemical inertness of the nitrogen molecule and the existence of a serious competitive hydrogen evolution reaction. Compared with the stable N≡N (945 kJ mol -1 , the bond energy of N=O in nitrate is only 204 kJ mol -1 , so the overpotential required for the reduction of nitrate is lower. At the same time, the standard reduction potential of the reaction of nitrate reduction to ammonia is 0.69 V (vs. RHE), so the competition of the hydrogen evolution reaction is not serious. In summary, the electrocatalytic nitrate reduction to ammonia technology is a more feasible clean ammonia production route.

[0003] Cu-based catalysts are widely studied in the electroreduction of nitrate to ammonia due to their good ammonia production selectivity, but the ammonia production faradic efficiency of Cu catalysts at a lower bias is very low. This is because the reduction of nitrate to ammonia is a proton-coupled electron transfer reaction, which requires a large number of protons to participate, and the ability of Cu catalysis to produce protons under alkaline conditions is poor, so that the Cu catalyst only shows good ammonia production faradic efficiency in the hydrogen production potential range (<-0.4 V (vs. RHE)). In order to improve the energy efficiency of nitrate reduction, it is necessary to reduce the overpotential of the Cu catalyst for the reduction of nitrate to ammonia. SUMMARY

[0004] The present application aims to overcome the above-mentioned shortcomings of the prior art, and provides a preparation method of a Ni(OH)2 modified Cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia, which has good ammonia production activity and Faraday efficiency at low bias.

[0005] To achieve the above-mentioned purpose, the preparation method of the Ni(OH)2 modified Cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia provided by the present application comprises the following steps:

[0006] The Ni(OH)2 / Cu nanowire electrode (Ni(OH)2 modified Cu catalyst) is obtained by in-situ electro-reduction under electrolysis conditions, using the Ni(OH)2 / CuO nanowire electrode as the working electrode, and using the Pt sheet electrode and the Hg / HgO electrode as the counter electrode and the reference electrode, respectively.

[0007] In the in-situ electro-reduction under electrolysis conditions, the CuO is reduced to Cu by cyclic voltammetry in the voltage range of-0.4-0.2V (vs. RHE) at a scanning rate of 5-10mV / s for 5-10 cycles.

[0008] Further comprising:

[0009] 1) Preparation of Cu(OH)2 nanowire electrode;

[0010] 2) Preparation of CuO nanowire electrode based on Cu(OH)2 nanowire electrode;

[0011] 3) Preparation of Ni(OH)2 / CuO nanowire electrode based on CuO nanowire electrode.

[0012] The operation process of step 1) is as follows:

[0013] The foam copper electrode is ultrasonically cleaned in HCl solution, anhydrous ethanol and ultrapure water, respectively, to remove the oxides and impurities on the surface of the foam copper electrode, and then the cleaned foam copper electrode is immersed in a solution containing NaOH and ammonium persulfate, after soaking, the foam copper electrode is taken out and washed with ultrapure water, and after drying, a blue foam copper electrode with Cu(OH)2 nanowires grown on the surface is obtained.

[0014] The specific operation of step 1) is as follows:

[0015] The foam copper electrode is cleaned in 1-3 M HCl solution, anhydrous ethanol and ultrapure water respectively for 10 min by ultrasonic cleaning to remove the oxide and impurities on the surface of the foam copper electrode, the cleaned foam copper electrode is immersed in 10-50 mL of a solution containing 3-10 g of NaOH and 0.4-1 g of ammonium persulfate, and after soaking for 20-60 min, the foam copper electrode is taken out and washed with ultrapure water, and after drying, a blue foam copper electrode with Cu(OH)2 nanowires grown on the surface is obtained.

[0016] The operation process of step 2) is as follows:

[0017] The Cu(OH)2 nanowires are calcined to obtain a deep brown CuO nanowire electrode.

[0018] The specific operation of step 2) is as follows:

[0019] The Cu(OH)2 nanowires are placed in a muffle furnace and calcined at 180-250 DEG C for 2-5 h, wherein the heating rate is 2-5 DEG C / min, and then naturally cooled to room temperature to obtain a deep brown CuO nanowire electrode.

[0020] The operation process of step 3) is as follows:

[0021] The CuO nanowire electrode is immersed in NiCl2.6H2O, and after taking out, it is washed with ultrapure water to remove the NiCl2 on the surface of the electrode, and then dried to obtain a Ni(OH)2 / CuO nanowire electrode.

[0022] The specific operation of step 3) is as follows:

[0023] The CuO nanowire electrode is immersed in 0.1-0.3 M NiCl2.6H2O for 15-45 min, and after taking out, it is washed with ultrapure water to remove the NiCl2 on the surface of the electrode, and then dried in a 60 DEG C oven to obtain a Ni(OH)2 / CuO nanowire electrode.

[0024] The Cu nanowires are uniformly grown on the foam copper skeleton to provide abundant reaction sites for the catalytic reaction, and in use, the Ni(OH)2 interacts with alkali metal ions in the electrolyte and oxygen atoms in water molecules around the alkali metal, promoting the dissociation of water molecules to form adsorbed hydrogen species, and providing protons for the nitrate reduction to ammonia process.

[0025] The present application has the following beneficial effects:

[0026] The preparation method of the Ni(OH)2 modified Cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia provided by the present application uniformly grows Cu nanowires on the foam copper framework to provide abundant reaction sites for the catalytic reaction, and in use, the Ni(OH)2 interacts with alkali metal ions in the electrolyte and oxygen atoms in water molecules around the alkali metal, promotes the dissociation of water molecules to form adsorbed hydrogen species, provides protons for the nitrate reduction to ammonia process, so that the Ni(OH)2 modified Cu catalyst exhibits higher Faraday efficiency and ammonia production rate at a lower bias voltage.

[0027] Further, in the preparation process, the electrode raw material is commercialized foam copper, the treatment process is simple, the catalyst exhibits excellent stability, and has extremely high market development potential. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1a A scanning electron microscope picture of the Ni(OH)2 / Cu electrocatalyst prepared in Example 1;

[0029] Figure 1b A scanning electron microscope picture of the Ni(OH)2 / Cu electrocatalyst prepared in Example 1;

[0030] Figure 2a An element distribution map of the Ni(OH)2 / Cu electrocatalyst involved in the present application;

[0031] Figure 2b An element distribution map of the Ni(OH)2 / Cu electrocatalyst involved in the present application;

[0032] Figure 2c An element distribution map of the Ni(OH)2 / Cu electrocatalyst involved in the present application;

[0033] Figure 2d An energy spectrum map of the Ni(OH)2 / Cu electrocatalyst involved in the present application;

[0034] Figure 3 An X-ray diffraction spectrum (XRD) of the Ni(OH)2 / Cu electrocatalyst involved in the present application;

[0035] Figure 4 A Ni 2p XPS spectrum of the Ni(OH)2 / Cu electrocatalyst involved in the present application;

[0036] Figure 5a A hydrogen evolution reaction graph of the Ni(OH)2 / Cu electrocatalyst involved in the present application;

[0037] Figure 5b A linear sweep voltammetry (LSV) curve graph of the nitrate reduction reaction;

[0038] Figure 6a Electrocatalytic activity of nitrate to ammonia of Ni(OH)2 / Cu electrocatalyst involved in the present application;

[0039] Figure 6b Faraday efficiency of Ni(OH)2 / Cu electrocatalyst involved in the present application as a function of bias voltage;

[0040] Figure 7 Repeatability test of Ni(OH)2 / Cu electrocatalyst involved in the present application;

[0041] Figure 8 Electron paramagnetic resonance (EPR) test of Ni(OH)2 / Cu electrocatalyst involved in the present application. DETAILED DESCRIPTION

[0042] In order to better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments, and are not intended to limit the scope of the present application. In addition, in the following description, the description of the known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of the present application.

[0043] The structural schematic diagrams according to the disclosed embodiments of the present application are shown in the drawings. These diagrams are not drawn to scale, in which some details are exaggerated for the purpose of clear expression, and some details can be omitted. The shapes of various regions, layers shown in the diagrams and their relative sizes, positional relationships are only exemplary, and in actuality, there can be deviations due to manufacturing tolerances or technical limitations, and the regions / layers with different shapes, sizes, relative positions can be additionally designed by those skilled in the art according to actual needs.

[0044] Embodiment one

[0045] The preparation method of the Ni(OH)2modified Cu catalyst for electrocatalytic reduction of nitrate to ammonia according to the present application comprises the following steps:

[0046] 1) Preparation of Cu(OH)2nanowire electrode

[0047] The foam copper electrode was cleaned by ultrasonic in 1M HCl solution, absolute ethanol and ultrapure water respectively for 10 min to remove the oxide and impurities on the surface of the foam copper electrode. The cleaned foam copper electrode was immersed in 30 mL solution containing 3 g NaOH and 0.5 g ammonium persulfate, and soaked for 20 min. Then the foam copper electrode was taken out and washed with ultrapure water, and dried to obtain a blue foam copper electrode with Cu(OH)2nanowires grown on the surface;

[0048] 2) Preparation of CuO nanowire electrode

[0049] The Cu(OH)2nanowires were calcined in a muffle furnace at 200℃ for 3h, wherein the heating rate was 2℃ / min, and then naturally cooled to room temperature to obtain a dark brown CuO nanowire electrode;

[0050] 3) Preparation of Ni(OH)2 / CuO nanowire electrode

[0051] The CuO nanowire electrode was immersed in 0.1M NiCl2·6H2O for 30 min, and then taken out and washed with ultrapure water to remove NiCl2on the surface of the electrode. Then the electrode was dried in a 60℃ oven to obtain a Ni(OH)2 / CuO nanowire electrode;

[0052] 4) Preparation of Ni(OH)2 / Cu nanowire electrode

[0053] The Ni(OH)2 / CuO nanowire electrode was used as the working electrode, and the Pt sheet electrode and the Hg / HgO electrode were used as the counter electrode and the reference electrode, respectively. The Ni(OH)2 / Cu nanowire electrode was obtained by in-situ electro-reduction under electrolysis conditions. The CuO was reduced to Cu by cyclic voltammetry in the voltage range of-0.4-0.2V (vs. RHE) at a scan rate of 5mV / s for 10 cycles.

[0054] As shown in FIG. 1, the Ni(OH)2 / Cu electrocatalyst involved in the embodiment has a nanowire structure, which is uniformly distributed on the foam copper framework. The structure can expose a large number of reaction active sites. As can be seen from the element distribution map in FIG. 2, the Ni element is uniformly distributed on the Cu nanowire. Figure 3 XRD showed that the CuO was successfully reduced to Cu after in-situ reduction. As can be seen from the XPS spectrum in FIG. 3, Figure 4 In the XPS spectrum in FIG. 3, peaks at binding energies of 853.5eV and 871eV correspond to Ni 2+ 2p3 / 2 and Ni 2p1 / 2 in the spin-orbit doublet, with a spin energy separation of 17eV, which is close to the theoretical value of Ni(OH)2, so it can be determined that the modification on the Cu catalyst is Ni(OH)2.

[0055] Example 2

[0056] The preparation method of the Ni(OH)2 modified Cu catalyst for electrocatalytic reduction of nitrate to ammonia comprises the following steps:

[0057] 1) Preparation of Cu(OH)2 nanowire electrode

[0058] The foam copper electrode was ultrasonically cleaned in 1M HCl solution, anhydrous ethanol and ultrapure water for 10 min respectively to remove the oxides and impurities on the surface of the foam copper electrode. The cleaned foam copper electrode was immersed in 30 mL of a solution containing 3 g of NaOH and 0.5 g of ammonium persulfate, soaked for 20 min, then taken out and washed with ultrapure water. After drying, a blue foam copper electrode with Cu(OH)2 nanowires grown on the surface was obtained.

[0059] 2) Preparation of CuO nanowire electrode

[0060] The Cu(OH)2 nanowires were placed in a muffle furnace and calcined at 200℃ for 3h, with a heating rate of 2℃ / min, and then naturally cooled to room temperature to obtain a dark brown CuO nanowire electrode.

[0061] 3) Preparation of Ni(OH)2 / CuO nanowire electrode

[0062] The CuO nanowire electrode was immersed in 0.1M NiCl2·6H2O for 15 min, then taken out and washed with ultrapure water to remove the NiCl2 on the surface of the electrode. After drying in a 60℃ oven, a Ni(OH)2 / CuO nanowire electrode was obtained.

[0063] 4) Preparation of Ni(OH)2 / Cu nanowire electrode

[0064] Using the Ni(OH)2 / CuO nanowire electrode as the working electrode, the Pt sheet electrode and the Hg / HgO electrode as the counter electrode and the reference electrode respectively, the Ni(OH)2 / Cu nanowire electrode was obtained by in-situ electro-reduction under electrolysis conditions. The CuO was reduced to Cu by cyclic voltammetry in the voltage range of -0.4-0.2V (vs. RHE) with a scan rate of 5mV / s for 10 cycles.

[0065] Example 3

[0066] The preparation method of the Ni(OH)2 modified Cu catalyst for electrocatalytic reduction of nitrate to ammonia comprises the following steps:

[0067] 1) Preparation of Cu(OH)2 nanowire electrode

[0068] The foam copper electrode was cleaned by ultrasonic in 1M HC1 solution, absolute ethanol and ultrapure water for 10 min respectively to remove the oxide and impurities on the surface of the foam copper electrode. The cleaned foam copper electrode was immersed in 30 mL solution containing 3 g NaOH and 0.5 g ammonium persulfate, and soaked for 20 min. After that, the foam copper electrode was taken out and washed with ultrapure water, and dried to obtain a blue foam copper electrode with Cu(OH)2nanowires grown on the surface;

[0069] 2) Preparation of CuO nanowire electrode

[0070] The Cu(OH)2nanowires were calcined in a muffle furnace at 200℃ for 3h, with a heating rate of 2℃ / min, and then naturally cooled to room temperature to obtain a dark brown CuO nanowire electrode;

[0071] 3) Preparation of Ni(OH)2 / CuO nanowire electrode

[0072] The CuO nanowire electrode was immersed in 0.1M NiCl2·6H2O for 45 min, and then taken out and washed with ultrapure water to remove NiCl2on the surface of the electrode. After drying in a 60℃ oven, a Ni(OH)2 / CuO nanowire electrode was obtained;

[0073] 4) Preparation of Ni(OH)2 / Cu nanowire electrode

[0074] The Ni(OH)2 / CuO nanowire electrode was used as the working electrode, and the Pt sheet electrode and Hg / HgO electrode were used as the counter electrode and reference electrode, respectively. The Ni(OH)2 / Cu nanowire electrode was obtained by in-situ electro-reduction under electrolysis conditions. The CuO was reduced to Cu by cyclic voltammetry in the voltage range of-0.4-0.2V (vs. RHE) with a scan rate of 5mV / s for 10 cycles.

[0075] Comparative example

[0076] This comparative example is a Cu electrocatalyst sample without Ni(OH)2modification. Based on Example 1, step 3) was omitted.

[0077] By comparing the LSV curves of the hydrogen evolution reaction and nitrate reduction reaction of Example 1 and the comparative example, it can be seen that Ni(OH)2 / Cu exhibits better hydrogen evolution reaction activity in alkaline environment, proving that Ni(OH)2modification can improve the water splitting ability of Cu catalyst in alkaline environment. By comparing the nitrate reduction LSV curves of different samples, it can be seen that the Ni(OH)2 / Cu catalyst has better nitrate reduction activity.

[0078] The performance evaluation conditions for nitrate reduction to ammonia of different samples are as follows: 0.1M NO3- The average ammonia production rate and the faradaic efficiency of the Ni(OH)2 / Cu nanowire electrode in 30 min were tested under different bias voltages, using 1M KOH solution as the electrolyte, the prepared Ni(OH)2 / Cu nanowire electrode as the working electrode, a graphite rod and a Hg / HgO electrode as the counter electrode and the reference electrode respectively, and setting the rotor speed of the cathode chamber to 400 rpm to minimize the influence of mass transfer on the reaction.

[0079] In FIG. 5, the nitrate reduction ammonia production activity and the faradaic efficiency of the Ni(OH)2 / Cu catalyst are higher than those of the Cu catalyst under different bias voltages, indicating that the Ni(OH)2 / Cu catalyst has excellent nitrate reduction performance under bias voltage. In the long-term test as described in FIG. 6, the Ni(OH)2 / Cu catalyst exhibits excellent stability and exhibits stable ammonia production faradaic efficiency in a continuous 20-hour experiment.

[0080] Figure 7 The EPR signal intensity of the Ni(OH)2 / Cu catalyst in the test is higher than that of the Cu catalyst, indicating that the Ni(OH)2 / Cu catalyst can promote the dissociation of water to produce more hydrogen radicals, which is beneficial to the hydrogenation process of nitrate under low bias voltage.

[0081] Example Four

[0082] The preparation method of the Ni(OH)2 modified Cu catalyst for electrocatalytic reduction of nitrate to produce ammonia according to the present application comprises the following steps:

[0083] 1) Preparation of Cu(OH)2 nanowire electrode

[0084] The foam copper electrode was ultrasonically cleaned in 1M HCl solution, anhydrous ethanol and ultrapure water respectively for 10 min to remove the oxides and impurities on the surface of the foam copper electrode. The cleaned foam copper electrode was immersed in 10 mL of a solution containing 3 g of NaOH and 0.4 g of ammonium persulfate, and after soaking for 20 min, the foam copper electrode was taken out and washed with ultrapure water. After drying, a blue foam copper electrode with Cu(OH)2 nanowires grown on the surface was obtained.

[0085] 2) Preparation of CuO nanowire electrode

[0086] The Cu(OH)2 nanowires were placed in a muffle furnace and calcined at 180℃ for 2h, wherein the heating rate was 2℃ / min, and then naturally cooled to room temperature to obtain a dark brown CuO nanowire electrode.

[0087] 3) Preparation of Ni(OH)2 / CuO nanowire electrode

[0088] The CuO nanowire electrode is immersed in 0.1M NiCl2·6H2O for 15 minutes, and after being taken out, is cleaned with ultrapure water to remove NiCl2 on the surface of the electrode, and is dried in a 60℃ oven to obtain a Ni(OH)2 / CuO nanowire electrode;

[0089] 4) Preparation of the Ni(OH)2 / Cu nanowire electrode

[0090] The Ni(OH)2 / Cu nanowire electrode is obtained through an in-situ electro-reduction process under electrolysis conditions, with the Ni(OH)2 / CuO nanowire electrode as a working electrode, a Pt sheet electrode and a Hg / HgO electrode as a counter electrode and a reference electrode, respectively, and the CuO is reduced to Cu by cyclic voltammetry in a voltage range of -0.4-0.2V (vs. RHE) at a scanning rate of 5mV / s for 5 cycles.

[0091] Example Five

[0092] The preparation method of the Ni(OH)2 modified Cu catalyst for electrocatalytic reduction of nitrate to ammonia according to the application comprises the following steps:

[0093] 1) Preparation of the Cu(OH)2 nanowire electrode

[0094] The foam copper electrode is ultrasonically cleaned in 3M HCl solution, anhydrous ethanol and ultrapure water for 10 minutes to remove oxides and impurities on the surface of the foam copper electrode, the cleaned foam copper electrode is immersed in a solution containing 10g of NaOH and 1g of ammonium persulfate, and after being soaked for 60 minutes, the foam copper electrode is taken out and washed with ultrapure water, and after drying, a blue foam copper electrode with Cu(OH)2 nanowires grown on the surface is obtained;

[0095] 2) Preparation of the CuO nanowire electrode

[0096] The Cu(OH)2 nanowires are calcined in a muffle furnace at 250℃ for 5 hours, wherein the heating rate is 5℃ / min, and then naturally cooled to room temperature to obtain a dark brown CuO nanowire electrode;

[0097] 3) Preparation of the Ni(OH)2 / CuO nanowire electrode

[0098] The CuO nanowire electrode is immersed in 0.3M NiCl2·6H2O for 45 minutes, and after being taken out, is cleaned with ultrapure water to remove NiCl2 on the surface of the electrode, and is dried in a 60℃ oven to obtain a Ni(OH)2 / CuO nanowire electrode;

[0099] 4) Preparation of the Ni(OH)2 / Cu nanowire electrode

[0100] The Ni(OH)2 / CuO nanowire electrode is used as a working electrode, a Pt sheet electrode and a Hg / HgO electrode are used as a counter electrode and a reference electrode respectively, and the Ni(OH)2 / Cu nanowire electrode is obtained through an in-situ electro-reduction process under electrolysis conditions, wherein the CuO is reduced to Cu by adopting a cyclic voltammetry method, and the voltage interval range is-0.4-0.2V (vs.RHE), and the scanning rate is 10mV / s, and the CuO is reduced to Cu by 10 cycles.

[0101] Example six

[0102] The preparation method of the Ni(OH)2 modified Cu catalyst for electrocatalytic reduction of nitrate to ammonia provided by the application comprises the following steps:

[0103] 1) Preparation of a Cu(OH)2 nanowire electrode

[0104] The foam copper electrode is ultrasonically cleaned in 2M HCl solution, anhydrous ethanol and ultrapure water respectively for 10min to remove the oxides and impurities on the surface of the foam copper electrode, the cleaned foam copper electrode is immersed in 30mL of a solution containing 6g of NaOH and 0.4-1g of ammonium persulfate, the foam copper electrode is taken out after being soaked for 45min and is washed with ultrapure water, and after drying, a blue foam copper electrode with Cu(OH)2 nanowires grown on the surface is obtained;

[0105] 2) Preparation of a CuO nanowire electrode

[0106] The Cu(OH)2 nanowires are calcined in a muffle furnace at 220℃ for 3.5h, wherein the heating rate is 3.5℃ / min, and the deep brown CuO nanowire electrode is obtained after natural cooling to room temperature;

[0107] 3) Preparation of a Ni(OH)2 / CuO nanowire electrode

[0108] The CuO nanowire electrode is immersed in 0.2M NiCl2·6H2O for 30min, and after being taken out, the electrode is washed with ultrapure water to remove the NiCl2 on the surface of the electrode, and then the electrode is dried in a 60℃ oven to obtain the Ni(OH)2 / CuO nanowire electrode;

[0109] 4) Preparation of a Ni(OH)2 / Cu nanowire electrode

[0110] The Ni(OH)2 / CuO nanowire electrode is used as a working electrode, a Pt sheet electrode and a Hg / HgO electrode are used as a counter electrode and a reference electrode respectively, and the Ni(OH)2 / Cu nanowire electrode is obtained through an in-situ electro-reduction process under electrolysis conditions, wherein the CuO is reduced to Cu by adopting a cyclic voltammetry method, and the voltage interval range is-0.4-0.2V (vs.RHE), and the scanning rate is 10mV / s, and the CuO is reduced to Cu by 10 cycles.

[0111] Example Seven

[0112] The preparation method of the Ni(OH)2 modified Cu catalyst for electrocatalytic reduction of nitrate to ammonia comprises the following steps:

[0113] 1) Preparation of Cu(OH)2 nanowire electrode

[0114] The foam copper electrode is ultrasonically cleaned in 1.2M HCl solution, anhydrous ethanol and ultrapure water respectively for 10min to remove the oxides and impurities on the surface of the foam copper electrode. The cleaned foam copper electrode is immersed in 15mL of a solution containing 4g of NaOH and 0.5g of ammonium persulfate, and after soaking for 30min, the foam copper electrode is taken out and washed with ultrapure water. After drying, a blue foam copper electrode with Cu(OH)2 nanowires grown on the surface is obtained.

[0115] 2) Preparation of CuO nanowire electrode

[0116] The Cu(OH)2 nanowires are placed in a muffle furnace and calcined at 190℃ for 2.5h, wherein the heating rate is 2.5℃ / min, and then naturally cooled to room temperature to obtain a dark brown CuO nanowire electrode.

[0117] 3) Preparation of Ni(OH)2 / CuO nanowire electrode

[0118] The CuO nanowire electrode is immersed in 0.15M NiCl2·6H2O for 20min, and after taking out, it is washed with ultrapure water to remove the NiCl2 on the surface of the electrode, and then dried in a 60℃ oven to obtain a Ni(OH)2 / CuO nanowire electrode.

[0119] 4) Preparation of Ni(OH)2 / Cu nanowire electrode

[0120] The Ni(OH)2 / CuO nanowire electrode is used as the working electrode, and the Pt sheet electrode and the Hg / HgO electrode are used as the counter electrode and the reference electrode respectively. The Ni(OH)2 / Cu nanowire electrode is obtained by in-situ electro-reduction under electrolysis conditions, wherein the CuO is reduced to Cu by cyclic voltammetry in the voltage range of-0.4~0.2V (vs. RHE) with a scan rate of 6mV / s for 6 cycles.

[0121] Example Eight

[0122] The preparation method of the Ni(OH)2 modified Cu catalyst for electrocatalytic reduction of nitrate to ammonia comprises the following steps:

[0123] 1) Preparation of Cu(OH)2 nanowire electrode

[0124] The foam copper electrode is ultrasonically cleaned in 2.5M HCl solution, anhydrous ethanol and ultrapure water respectively for 10 min to remove the oxides and impurities on the surface of the foam copper electrode, the cleaned foam copper electrode is immersed in 40 mL of a solution containing 8 g of NaOH and 0.8 g of ammonium persulfate, and after soaking for 50 min, the foam copper electrode is taken out and washed with ultrapure water, and after drying, a blue foam copper electrode with Cu(OH)2nanowires grown on the surface is obtained;

[0125] 2) Preparation of CuO nanowire electrode

[0126] The Cu(OH)2nanowires are calcined in a muffle furnace at 240℃ for 4h, wherein the heating rate is 4℃ / min, and then naturally cooled to room temperature to obtain a dark brown CuO nanowire electrode;

[0127] 3) Preparation of Ni(OH)2 / CuO nanowire electrode

[0128] The CuO nanowire electrode is immersed in 0.25M NiCl2·6H2O for 40 min, and after taking out, it is washed with ultrapure water to remove NiCl2on the surface of the electrode, and then dried in a 60℃ oven to obtain a Ni(OH)2 / CuO nanowire electrode;

[0129] 4) Preparation of Ni(OH)2 / Cu nanowire electrode

[0130] The Ni(OH)2 / CuO nanowire electrode is used as the working electrode, and the Pt sheet electrode and the Hg / HgO electrode are used as the counter electrode and the reference electrode respectively, and the Ni(OH)2 / Cu nanowire electrode is obtained by in-situ electro-reduction under electrolysis conditions, wherein the CuO is reduced to Cu by cyclic voltammetry in the voltage range of-0.4-0.2V (vs. RHE) with a scan rate of 9mV / s for 9 cycles.

[0131] Example Nine

[0132] The preparation method of the Ni(OH)2modified Cu catalyst for electrocatalytic reduction of nitrate to ammonia according to the present application comprises the following steps:

[0133] 1) Preparation of Cu(OH)2nanowire electrode

[0134] The foam copper electrode is ultrasonically cleaned in 2.5M HCl solution, anhydrous ethanol and ultrapure water respectively for 10 min to remove the oxides and impurities on the surface of the foam copper electrode, the cleaned foam copper electrode is immersed in 40 mL of a solution containing 8 g of NaOH and 0.8 g of ammonium persulfate, and after soaking for 50 min, the foam copper electrode is taken out and washed with ultrapure water, and after drying, a blue foam copper electrode with Cu(OH)2nanowires grown on the surface is obtained;

[0135] 2) Preparation of CuO nanowire electrode

[0136] The Cu(OH)2 nanowire was placed in a muffle furnace and calcined at 230℃ for 2.5h, wherein the heating rate was 4.5℃ / min, and then naturally cooled to room temperature to obtain a dark brown CuO nanowire electrode;

[0137] 3) Preparation of Ni(OH)2 / CuO nanowire electrode

[0138] The CuO nanowire electrode was immersed in 0.25M NiCl2·6H2O for 35min, and after being taken out, was cleaned with ultrapure water to remove NiCl2 on the surface of the electrode, and then dried in a 60℃ oven to obtain a Ni(OH)2 / CuO nanowire electrode;

[0139] 4) Preparation of Ni(OH)2 / Cu nanowire electrode

[0140] The Ni(OH)2 / CuO nanowire electrode was used as a working electrode, and a Pt sheet electrode and a Hg / HgO electrode were used as a counter electrode and a reference electrode, respectively, and the Ni(OH)2 / Cu nanowire electrode was obtained through an in-situ electro-reduction process under electrolysis conditions, wherein the CuO was reduced to Cu by cyclic voltammetry in a voltage range of -0.4~0.2V (vs. RHE) with a scanning rate of 8mV / s for 7 cycles.

[0141] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application, but not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: the specific embodiments of the present application can be modified or replaced by the same, without departing from the spirit and scope of the present application, any modification or equivalent replacement, which should be covered in the protection scope of the claims of the present application.

Claims

1. A method for preparing a Ni(OH)2 modified Cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia, characterized in that, The method comprises the following steps: The method comprises the following steps: The CuO nanowire electrode is prepared based on the Cu(OH)2 nanowire electrode.

2. The method for preparing the Ni(OH)2 modified Cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia according to claim 1, characterized in that, In the in-situ electro-reduction process under the electrolysis condition, the CuO is reduced to Cu by cyclic voltammetry in the voltage range of -0.4-0.2V (vs. RHE) with a scanning rate of 5-10mV / s for 5-10 cycles. The method further comprises: 1) Preparation of the Cu(OH)2 nanowire electrode; 2) Preparation of the CuO nanowire electrode based on the Cu(OH)2 nanowire electrode; 3) Preparation of the Ni(OH)2 / CuO nanowire electrode based on the CuO nanowire electrode; The operation process of step 1) is as follows: The foam copper electrode is ultrasonically cleaned in an HCl solution, anhydrous ethanol and ultrapure water respectively to remove the oxides and impurities on the surface of the foam copper electrode, the cleaned foam copper electrode is immersed in a solution containing NaOH and ammonium persulfate, after soaking, the foam copper electrode is taken out and washed with ultrapure water, and after drying, a blue foam copper electrode with Cu(OH)2 nanowires grown on the surface is obtained. The operation process of step 2) is as follows: The Cu(OH)2 nanowires are calcined to obtain a dark brown CuO nanowire electrode. The operation process of step 3) is as follows:

3. The method for preparing the Ni(OH)2 modified Cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia according to claim 2, characterized in that, The CuO nanowire electrode is immersed in NiCl2·6H2O, taken out and washed with ultrapure water to remove the NiCl2 on the surface of the electrode, and then dried to obtain the Ni(OH)2 / CuO nanowire electrode. The specific operation of step 1) is as follows:

4. The method for preparing the Ni(OH)2 modified Cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia according to claim 2, characterized in that, The foam copper electrode is ultrasonically cleaned in an HCl solution with a concentration of 1-3M, anhydrous ethanol and ultrapure water for 10 minutes to remove the oxides and impurities on the surface of the foam copper electrode, the cleaned foam copper electrode is immersed in a solution containing 10-50mL of 3-10g NaOH and 0.4-1g ammonium persulfate, after soaking for 20-60 minutes, the foam copper electrode is taken out and washed with ultrapure water, and after drying, a blue foam copper electrode with Cu(OH)2 nanowires grown on the surface is obtained. The specific operation of step 2) is as follows:

5. The method for preparing Ni(OH)2 modified Cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia according to claim 2, characterized in that, The Cu(OH)2 nanowires are placed in a muffle furnace and calcined at 180-250℃ for 2-5h, wherein the heating rate is 2-5℃ / min, and then naturally cooled to room temperature to obtain a dark brown CuO nanowire electrode. The specific operation of step 3) is as follows:

6. The method for preparing the Ni(OH)2 modified Cu catalyst for efficient electrocatalytic reduction of nitrate to ammonia according to claim 1, characterized in that, The CuO nanowire electrode is immersed in 0.1-0.3M NiCl2·6H2O for 15-45 minutes, taken out and washed with ultrapure water to remove the NiCl2 on the surface of the electrode, and then dried in a 60℃ oven to obtain the Ni(OH)2 / CuO nanowire electrode. The Cu nanowires are uniformly grown on the foam copper framework to provide abundant reaction sites for the catalytic reaction, in use, the Ni(OH)2 interacts with the alkali metal ions in the electrolyte and the oxygen atoms in the water molecules around the alkali metal to promote the dissociation of water molecules to form adsorbed hydrogen species, thereby providing protons for the nitrate reduction to ammonia process.

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