Preparation method and application of foamy copper loaded CuGa2 alloy electrode

Abstract

The invention is suitable for the technical field of electro-catalytic material preparation, and provides a preparation method and application of a foamy copper loaded CuGa2 alloy electrode, according to the method, three-dimensional foamy copper is used as a conductive framework, liquid gallium is introduced in an alkaline environment, and a CuGa2 / foamy copper composite structure with a strong interface coupling effect is formed through an in-situ alloying reaction. In the obtained electrode, a continuous metal-metal interface is formed between the CuGa2 alloy and the copper substrate, so that electron transmission and adsorption activation of NO molecules can be effectively promoted, and the reaction rate and selectivity of ammonia generation are remarkably improved. According to the method, the reaction condition is mild, high-temperature heat treatment is not needed, uniform growth of CuGa2 can be achieved under the low-energy-consumption condition, and excellent structural stability is kept. The prepared CuGa2 / foamy copper composite electrode shows high ammonia yield and excellent Faraday efficiency under the condition of 0.1 V (vs. RHE), and shows good catalytic stability and industrial application potential.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic material preparation technology, and particularly relates to a method for preparing a copper foam-supported CuGa2 alloy electrode and its application. Background Technology

[0002] Nitrogen oxides (NO) x Nitric oxide (NO) is one of the major air pollutants, primarily originating from coal-fired power plants, chemical plants, steel smelting, transportation, and agricultural activities. Low concentrations of NO, in particular, are emitted in large quantities, are widely distributed, and have strong diffusion, making them difficult to control. NO can undergo complex reactions with oxygen, ozone, and particulate matter in the air to generate secondary pollutants such as ozone, nitrates, and fine particulate matter (PM2.5), directly harming human health and the ecological environment.

[0003] Electrocatalytic NO reduction reaction (NORR) is a green conversion technology that has been developed in recent years. It can be carried out at ambient temperature and pressure and has advantages such as simple operation, low energy consumption, and the ability to be coupled with renewable electricity. This method can not only efficiently utilize NO pollutants but also convert them into high-value ammonia (NH3), which has dual value in environmental governance and energy recycling. However, achieving efficient, stable, and low-cost catalysts remains a key scientific and technological challenge in this field.

[0004] Currently, commonly used catalysts for the electrocatalytic reduction of NO include noble metal materials (such as Pt, Pd, and Au), transition metal materials (such as Cu, Fe, and Co), and their compounds. However, noble metal catalysts are expensive and unsuitable for large-scale applications; while transition metal materials are lower in cost, they have shortcomings in terms of activity, selectivity, and long-term stability. Designing catalysts that combine highly efficient active sites, a suitable electronic structure, and stability is a bottleneck that urgently needs to be addressed.

[0005] CuGa2, as an intermetallic compound, possesses unique crystal structure and electronic properties. The synergistic effect between copper and gallium can effectively regulate surface electron density, enhance the adsorption and activation of NO molecules, thereby lowering the reaction energy barrier and improving the selectivity of ammonia production. However, existing CuGa2 preparation methods mostly employ high-temperature solid-state reactions, vapor deposition, or chemical vapor deposition processes, which require sophisticated equipment, consume large amounts of energy, and are costly. Furthermore, the resulting alloy particles often need to be supported on inert supports such as carbon nanotubes and graphene. Although these carbon-based supports have high specific surface areas, their conductivity and electronic coupling with CuGa2 are weak, resulting in poor interfacial contact. This can easily lead to the shedding of active components during long-term electrocatalysis, and the lack of metal-metal synergistic effects limits further improvements in reaction activity and stability.

[0006] Therefore, developing a CuGa2 electrode fabrication method that uses a metal conductive framework as support and can achieve strong interface coupling is of great scientific significance and practical application value. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a copper foam-supported CuGa2 alloy electrode and its application, aiming to solve the problems mentioned in the background art.

[0008] The present invention is implemented as follows: a method for preparing a copper foam-supported CuGa2 alloy electrode includes the following steps: Step 1: Copper foam pretreatment; The copper foam was ultrasonically cleaned sequentially with acetone and 1-3 mol / L hydrochloric acid solution to remove surface organic matter and oxide layer, and then rinsed with deionized water and dried. Step 2: Construction of an alkaline activation environment; Pretreated copper foam is immersed in a sodium hydroxide solution with a concentration of 0.1 M to 2 M to form an alkaline reaction system. Step 3: In-situ growth of CuGa2 alloy on the surface of copper foam; Metallic gallium is added to the alkaline reaction system and reacted at 60℃~90℃ for 3~5 hours to allow liquid gallium to react in situ with the surface of foamed copper to form a tightly bonded CuGa2 alloy layer. Step 4: Selectively remove unreacted gallium; After the reaction was completed, the sample was taken out and rinsed with 1 M to 3 M hydrochloric acid solution to remove unreacted free gallium. After washing with pure water and drying, CuGa2 / copper foam composite electrode (i.e. CuGa2 catalyst) was obtained.

[0009] In a further technical solution, in step 1, the acetone treatment time is 5-15 minutes, and the hydrochloric acid treatment time is 3-8 minutes.

[0010] In a further technical solution, in step 2, the reaction temperature is 60℃~90℃ and the reaction time is 3~5 hours.

[0011] In a further technical solution, in step 3, metallic gallium is directly added to and impregnates the foamed copper substrate in solid form.

[0012] Another objective of this invention is to provide an application of a copper foam-supported CuGa2 alloy electrode, which, based on the CuGa2 / copper foam composite electrode prepared by the above method, is applied to the electrocatalytic NO reduction reaction for ammonia synthesis.

[0013] In a further technical solution, the electrocatalytic reaction is carried out in a three-electrode electrolytic cell, the electrolyte is a pH-neutral sodium sulfate solution, the atmosphere introduced into the electrolyte is 2% NO and high-purity Ar, and the applied working potential range is -0.1 V to -0.7 V (vs. RHE).

[0014] The present invention provides a method for preparing a copper foam-supported CuGa2 alloy electrode and its application, the beneficial effects of which are as follows: (1) Simple process and low energy consumption: The reaction only needs to be carried out at about 80°C, without the need for vacuum or high temperature annealing, which significantly reduces energy consumption and avoids particle agglomeration.

[0015] (2) Low cost and scalable preparation: No precious metals or complex equipment are required, raw materials are widely available, and it is easy to expand industrially.

[0016] (3) Strong in-situ bonding and high structural stability: CuGa2 is generated directly on the surface of copper foam through in-situ alloying, forming a continuous transition interface. Compared with loading CuGa2 on inert supports such as carbon nanotubes, cerium oxide or MXene, it significantly improves mechanical and electrochemical stability and avoids problems such as powder shedding and conductivity loss.

[0017] (4) Three-dimensional porous structure enhances electrocatalytic performance: The unique three-dimensional conductive network of copper foam provides a high-speed channel for electron and ion transport, which fully exposes the active sites of CuGa2 and enhances the reaction kinetics in the electrocatalytic NO reduction process.

[0018] (5) Excellent catalytic performance: This electrode exhibits a low overpotential (-0.1 V vs. RHE) and a high ammonia generation rate (63 μg·h⁻¹) for 2% NO in a neutral electrolyte (0.5 M Na₂SO₄, pH=7). -1 ·cm -2 It is superior to powdered CuGa2 and other supported CuGa2 catalysts.

[0019] (6) Environmentally friendly: The entire preparation and application process is a low-energy-consumption and low-pollution system, which is in line with the concept of green chemistry. Attached Figure Description

[0020] Figure 1 Digital photographs of copper foam, copper foam after gallium impregnation (without hydrochloric acid treatment), and CuGa2 alloy after hydrochloric acid treatment; Figure 2 The image shows a scanning electron microscope (SEM) image of the prepared CuGa2 catalyst. Figure 3 The XRD pattern of the prepared CuGa2 catalyst is shown. Figure 4The LSV curve of the prepared CuGa2 catalyst in the electrocatalytic reduction of NO to ammonia synthesis; Figure 5 The ammonia yield of the prepared CuGa2 catalyst in the electrocatalytic reduction of NO to ammonia synthesis; Figure 6 The stability curve of the prepared CuGa2 catalyst in the electrocatalytic reduction of NO to ammonia synthesis is shown. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0023] An embodiment of the present invention provides a method for preparing a copper foam-supported CuGa2 alloy electrode, comprising the following steps: Step 1: Copper foam pretreatment; The copper foam was ultrasonically cleaned sequentially with acetone and 1-3 mol / L hydrochloric acid solution to remove surface organic matter and oxide layer, and then rinsed with deionized water and dried. Step 2: Construction of an alkaline activation environment; Pretreated copper foam is immersed in a sodium hydroxide solution with a concentration of 0.1 M to 2 M to form an alkaline reaction system. Step 3: In-situ growth of CuGa2 alloy on the surface of copper foam; Metallic gallium is added to the alkaline reaction system and reacted at 60℃~90℃ for 3~5 hours to allow liquid gallium to react in situ with the surface of foamed copper to form a tightly bonded CuGa2 alloy layer. Step 4: Selectively remove unreacted gallium; After the reaction was completed, the sample was taken out and rinsed with 1 M to 3 M hydrochloric acid solution to remove unreacted free gallium. After washing with pure water and drying, CuGa2 / copper foam composite electrode (i.e. CuGa2 catalyst) was obtained.

[0024] In a preferred embodiment of the present invention, in step 1, the acetone treatment time is 5-15 minutes and the hydrochloric acid treatment time is 3-8 minutes.

[0025] In a preferred embodiment of the present invention, in step 2, the reaction temperature is 60°C to 90°C and the reaction time is 3 to 5 hours.

[0026] In a preferred embodiment of the present invention, in step 3, metallic gallium is directly added to and impregnates the foamed copper substrate in solid form.

[0027] Another embodiment of the present invention provides an application of a copper foam-supported CuGa2 alloy electrode. Based on the CuGa2 / copper foam composite electrode prepared by the above method, the CuGa2 / copper foam composite electrode is applied to the electrocatalytic NO reduction reaction to synthesize ammonia.

[0028] In a preferred embodiment of the present invention, the electrocatalytic reaction is carried out in a three-electrode electrolytic cell, the electrolyte is a pH-neutral sodium sulfate solution, the atmosphere introduced into the electrolyte is 2% NO and high-purity Ar, and the applied working potential range is -0.1 V to -0.7 V (vs. RHE).

[0029] Several specific embodiments are provided below to verify the effectiveness of this method.

[0030] Example 1: First, copper foam with dimensions of 1 cm × 1.5 cm was pretreated sequentially with acetone and 1 M hydrochloric acid solution to thoroughly remove organic matter and oxide layers from its surface. Then, the substrate was rinsed with ultrapure water and dried with high-purity nitrogen. Next, the treated copper foam was immersed in a reaction vessel containing 50 mL of 0.1 M NaOH solution, and 1 g of metallic gallium was added. After reacting at a constant temperature of 80°C for 4 hours, the sample was removed. Finally, the sample was rinsed sequentially with 3 M HCl solution and deionized water to remove residual metallic gallium, and then vacuum dried at 60°C to obtain the target product.

[0031] Example 2: First, copper foam with dimensions of 1 cm × 1.5 cm was pretreated sequentially with acetone and 1 M hydrochloric acid solution to thoroughly remove organic matter and oxide layers from its surface. Then, the substrate was rinsed with ultrapure water and dried with high-purity nitrogen. Next, the treated copper foam was immersed in a reaction vessel containing 50 mL of 0.2 M NaOH solution, and 1 g of metallic gallium was added. After reacting at a constant temperature of 80°C for 4 hours, the sample was removed. Finally, the sample was rinsed sequentially with 3 M HCl solution and deionized water to remove residual metallic gallium, and then vacuum dried at 60°C to obtain the target product.

[0032] Example 3: First, copper foam with dimensions of 1 cm × 1.5 cm was pretreated sequentially with acetone and 1 M hydrochloric acid solution to thoroughly remove organic matter and oxide layers from its surface. Then, the substrate was rinsed with ultrapure water and dried with high-purity nitrogen. Next, the treated copper foam was immersed in a reaction vessel containing 50 mL of 0.5 M NaOH solution, and 1 g of metallic gallium was added. After reacting at a constant temperature of 80°C for 4 hours, the sample was removed. Finally, the sample was rinsed sequentially with 3 M HCl solution and deionized water to remove residual metallic gallium, and then vacuum dried at 60°C to obtain the target product.

[0033] Example 4: First, copper foam with dimensions of 1 cm × 1.5 cm was pretreated sequentially with acetone and 1 M hydrochloric acid solution to thoroughly remove organic matter and oxide layers from its surface. Then, the substrate was rinsed with ultrapure water and dried with high-purity nitrogen. Next, the treated copper foam was immersed in a reaction vessel containing 50 mL of 1 M NaOH solution, and 1 g of metallic gallium was added. After reacting at a constant temperature of 80°C for 4 hours, the sample was removed. Finally, the sample was rinsed sequentially with 3 M HCl solution and deionized water to remove residual metallic gallium, and then vacuum dried at 60°C to obtain the target product.

[0034] Example 5: First, copper foam with dimensions of 1 cm × 1.5 cm was pretreated sequentially with acetone and 1 M hydrochloric acid solution to thoroughly remove organic matter and oxide layers from its surface. Then, the substrate was rinsed with ultrapure water and dried with high-purity nitrogen. Next, the treated copper foam was immersed in a reaction vessel containing 50 mL of 2 M NaOH solution, and 1 g of metallic gallium was added. After reacting at a constant temperature of 80°C for 4 hours, the sample was removed. Finally, the sample was rinsed sequentially with 3 M HCl solution and deionized water to remove residual metallic gallium, and then vacuum dried at 60°C to obtain the target product.

[0035] Comparative Example 1: Copper foam with dimensions of 1 cm × 1.5 cm was pretreated sequentially with acetone and 1 M hydrochloric acid solution to thoroughly remove organic matter and oxide layer from its surface. Subsequently, the substrate was rinsed with ultrapure water and dried with high-purity nitrogen gas for later use. The pretreated Cu catalyst was obtained.

[0036] Digital images of Cu, CuGa2 without gallium removal, and CuGa2 are shown below. Figure 1 As shown, the scanning electron microscope image of the CuGa2 alloy prepared in Example 1 is as follows. Figure 2 As shown in the figure, the sample at this concentration is cubic in shape, with a large specific surface area, which is beneficial for providing more active sites and promoting the transport of reactants and products.

[0037] The XRD pattern of the product prepared in Example 1 is as follows: Figure 3 As shown, the analysis results confirm that it consists of two phases: Cu and CuGa2. The diffraction peaks at 43.3°, 50.5°, and 74.2° are consistent with the standard diffraction peaks of cubic Cu (PDF#99-0034), and can be indexed as its (111), (200), and (220) crystal planes, respectively. In addition, other diffraction peaks appearing in the spectrum, especially the three strongest peaks at 35.2°, 44.7°, and 45.5°, perfectly match the standard card of cubic CuGa2 (PDF#25-0275), and can be indexed as (101), (102), and (110) crystal planes, respectively. This result clearly confirms the successful synthesis of the CuGa2 catalyst.

[0038] Electrochemical tests of the CuGa2 / copper foam composite electrode were performed on a Chenhua CHI 660E electrochemical workstation using a standard three-electrode system. The working electrode was carbon paper loaded with the catalyst, the reference electrode was an Ag / AgCl electrode, and the counter electrode was a platinum sheet. The electrolyte was 80 mL of 0.5 M Na2SO4 solution. During the nitric oxide reduction reaction test, high-purity Ar was first introduced into the electrolyte to remove air, followed by a continuous introduction of 2% NO. The working electrode was prepared as follows: 10 mg of catalyst was dispersed in a mixed solvent consisting of 950 μL of anhydrous ethanol and 50 μL of Nafion (5%) solution, and ultrasonically treated to form a uniform dispersion. Subsequently, a total of 20 μL of the dispersion was uniformly drop-coated onto the pretreated carbon paper surface in four separate applications using a pipette, with a catalyst loading of 0.2 mg / cm³. -2 Finally, allow the electrodes to air dry at room temperature for 2 hours before use for testing.

[0039] Figure 4 The LSV curves of Cu and CuGa2 in the potential range of 0 to -1.0 V (vs. RHE) are shown. Under a NO / Ar atmosphere, the CuGa2 catalyst exhibits a higher current density gap than pure Cu, indicating its superior electrocatalytic activity for the NO reduction reaction (NORR).

[0040] Figure 5 The ammonia yields of Cu and CuGa2 catalysts were compared at potentials ranging from -0.1 V to -0.7 V. The results showed that CuGa2 exhibited a higher ammonia yield than Cu at all tested potentials, demonstrating a significant improvement in its catalytic performance. Particularly noteworthy was the achievement of an ammonia yield of 62.56 μg h⁻¹ at an extremely low potential of -0.1 V. -1 cm -2 This performance is superior to the vast majority of catalysts reported to date.

[0041] To evaluate the stability of the catalyst, a chronoamperometry test was performed on the CuGa2 catalyst for 1 hour at a constant potential of -0.1 V. Figure 6 As shown, the current density curve remained stable during the test without significant decay, which fully demonstrates the excellent electrochemical stability of the CuGa2 catalyst in the NORR process.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a foamed copper supported CuGa2 alloy electrode, characterized in that, The method comprises the following steps: Step 1: foam copper pretreatment; The foam copper is sequentially cleaned with acetone and 1-3 mol / L hydrochloric acid solution by ultrasonic cleaning to remove surface organic matter and oxide layer, and then washed with deionized water and dried; Step 2: construction of an alkaline activation environment; The pretreated foam copper is immersed in a sodium hydroxide solution with a concentration of 0.1 M-2 M to form an alkaline reaction system; Step 3: in-situ growth of CuGa2 alloy on the surface of foam copper; Metallic gallium is added to the alkaline reaction system, and the liquid gallium reacts with the foam copper surface in-situ to form a tightly bonded CuGa2 alloy layer under the condition of 60-90°C for 3-5 hours; Step 4: selective removal of unreacted gallium; After the reaction is completed, the sample is taken out, washed with 1 M-3 M hydrochloric acid solution to remove free gallium that does not participate in the reaction, washed with pure water and dried to obtain a CuGa2 / foam copper composite electrode.

2. The method for preparing a foamed copper supported CuGa2 alloy electrode according to claim 1, characterized by, In the step 1, the acetone treatment time is 5-15 minutes, and the hydrochloric acid treatment time is 3-8 minutes.

3. The method for preparing a foamed copper supported CuGa2 alloy electrode according to claim 1, characterized by, In the step 2, the reaction temperature is 60-90°C, and the reaction time is 3-5 hours.

4. The method for preparing a foamed copper supported CuGa2 alloy electrode according to claim 1, characterized by, In the step 3, the metallic gallium is directly added in solid form and infiltrates the foam copper substrate.

5. Use of a CuGa2 alloy electrode supported on a copper foam, based on the CuGa2 / copper foam composite electrode prepared according to the method for preparing a CuGa2 alloy electrode supported on a copper foam according to any one of claims 1 to 4, characterized in that, The CuGa2 / foam copper composite electrode is applied to the electrocatalytic NO reduction reaction for synthesizing ammonia.

6. Use of a foamed copper supported CuGa2 alloy electrode according to claim 5, characterized in that, The electrocatalytic reaction is carried out in a three-electrode electrolytic cell, the electrolyte is a neutral sodium sulfate solution, the atmosphere of the electrolyte is 2% NO and high-purity Ar, and the applied working potential ranges from-0.1 V to-0.7 V.

Images