Selective etching and sequential adsorption synthesis of pd-cu diatomic electrocatalyst and preparation method and application thereof

Abstract

The application provides a selective etching and sequential adsorption synthesis Pd-Cu diatomic electrocatalyst and a preparation method and application thereof, and relates to the technical field of diatomic electrocatalytic materials. Through the selective etching and sequential adsorption strategy, the defect structure of the carrier and the distribution of the anchoring sites are precisely controlled, the metal atomic dispersion and the controllable loading are realized, the atomic-level dispersed Pd-Cu heteronuclear diatomic site electrocatalytic material is successfully constructed and anchored on the nitrogen-doped carbon carrier, and the problems that the prior art cannot accurately synthesize the heteronuclear diatomic pair catalyst and the performance of the single metal catalyst is limited in the complex electrocatalytic reaction are solved. The preparation process of the application is simple, the cost is low, can be extended to other diatomic catalysts, and provides a new path for the preparation of high-performance diatomic electrocatalytic materials.

Description

Technical Field

[0001] This invention relates to the field of diatomic electrocatalytic materials technology, and in particular to a selective etching and sequential adsorption synthesis of Pd-Cu diatomic electrocatalysts, their preparation methods, and applications. Background Technology

[0002] Ammonia (NH3), as an important chemical raw material and clean energy carrier, has attracted much attention for its green and efficient synthesis technology. The traditional Haber process for ammonia synthesis requires high temperature and pressure conditions, resulting in high energy consumption and large carbon emissions. However, nitrate (NO3)... - Electrocatalytic reduction ammonia production technology uses NO3 in water... - Using nitrogen as a raw material, NH3 can be synthesized at room temperature and pressure, which has the dual value of nitrogen resource utilization and environmental governance, and has become the research frontier of the field of electrocatalysis in recent years.

[0003] Diatom catalysts (DACs) offer an ideal solution to overcome the technical bottleneck of low activity and poor selectivity in the electroreduction of nitrate to ammonia due to their synergistic electronic effects between adjacent metal atoms, high atom utilization, and strong substrate compatibility. Among them, Pd-Cu-based diatomic catalysts exhibit particularly high catalytic activity of Pd for the reduction reaction and high catalytic activity of Cu for NO3-. - The unique advantages of adsorption and intermediate regulation in NO3 - Pd-Cu diatomic catalysts have shown great potential in the electroreduction reaction for ammonia production. However, current methods for preparing and applying Pd-Cu diatomic catalysts still face multiple challenges, specifically: 1. Poor metal site dispersion, traditional methods easily lead to atomic aggregation and the formation of nanoparticles, resulting in the loss of the synergistic advantages of diatomic pairs; 2. The lack of precise anchoring sites on the support makes it difficult to achieve controllable loading and stable existence of Pd-Cu diatomic pairs, leading to insufficient catalyst cycle stability; 3. Existing catalysts have low selectivity for NH3 and are prone to NO3- generation. - Excessive reduction to N2 or generation of NO2 - Side reactions reduce ammonia yield; 4. The preparation process is complex and the cost is high, which is not conducive to large-scale application.

[0004] To address the aforementioned issues, developing a simple, low-cost method for preparing Pd-Cu diatomic pairs that enables highly dispersed and stable loading of diatomic sites and precise synthesis has become an urgent need to promote the practical application of Pd-Cu diatomic catalysts. Summary of the Invention

[0005] Therefore, this invention proposes a selective etching and sequential adsorption synthesis method for Pd-Cu diatomic electrocatalysts, along with its preparation and application. By selectively etching and sequentially adsorbing, the defect structure and anchoring site distribution of the support can be precisely controlled, enabling the directional construction of Pd and Cu diatomic sites and providing a new pathway for the preparation of high-performance diatomic electrocatalytic materials.

[0006] The technical solution of this invention is implemented as follows: A selective etching and sequential adsorption synthesis method for Pd-Cu diatomic electrocatalyst, wherein the Pd-Cu diatomic electrocatalyst uses nitrogen-doped carbon as a support, and Pd atoms and Cu atoms are dispersed on the support surface in the form of diatomic pair sites; The molar ratio of Pd to Cu in the Pd-Cu diatomic electrocatalyst is 1:4-7; The specific surface area of ​​the Pd-Cu diatomic electrocatalyst is 100-150 m². 2 / g, exhibiting a loose, rough, porous, and stacked state.

[0007] A method for preparing Pd-Cu diatomic electrocatalysts through selective etching and sequential adsorption, comprising the following specific steps: S1. Add copper and zinc sources to an organic amide solvent, sonicate, place in a high-pressure reactor for solvothermal reaction, filter, wash, and dry to obtain the precursor; S2. Under an inert atmosphere, the precursor is heated and calcined, and then cooled in the furnace to obtain nitrogen-doped carbon-anchored Cu single-atom material. S3. Nitrogen-doped carbon-anchored Cu single-atom material is added to an ethanol solution, ultrasonically dispersed, oxidant is added and stirred, and then placed in a high-pressure reactor for hydrothermal reaction. After filtration, washing and drying, etched nitrogen-doped carbon-anchored Cu single-atom material is obtained. S4. The etched nitrogen-doped carbon-anchored Cu single-atom material was added to an ethanol solution and ultrasonically dispersed. The palladium source solution was added while stirring at 450-500 rpm. The stirring was continued, and the product was filtered, dried, and collected. S5. After mixing and grinding the solid product and nitrogen source, the mixture is calcined under an inert atmosphere and cooled in the furnace to obtain the target Pd-Cu diatomic electrocatalyst.

[0008] Furthermore, in step S1, the molar ratio of the copper source to the zinc source is 1:15-20; The copper source is any one of copper chloride, copper nitrate, and copper sulfate; The zinc source is any one of zinc chloride, zinc nitrate, and zinc sulfate; The organic amide solvent is at least one selected from formamide, N,N-dimethylformamide, N,N-diethylformamide, and N-methylpyrrolidone; The liquid-to-solid ratio of the organic amide solvent to the copper source is 1.2-1.5:1 L / g; The solvothermal reaction is carried out at a temperature of 150-200℃ for 8-15 hours. The ultrasonic treatment was performed at 35-40 kHz and 450-500 W for 25-35 minutes.

[0009] Furthermore, in step S2, the inert atmosphere is argon or nitrogen, and the flow rate is 30-50 mL / min; The heating and calcination process involves heating to 800-1000℃ at a rate of 2-5℃ / min and calcining for 1-3 hours.

[0010] Furthermore, in step S3, the solid-liquid ratio of the nitrogen-doped carbon-anchored Cu single-atom material to the ethanol solution is 1-2:1 mg / mL. The concentration of the ethanol solution is 40-60% v / v; The ultrasonic dispersion is performed at 35-40 kHz and 450-500 W for 1-2 hours. The oxidant is ammonium persulfate, 10wt% sodium hypochlorite solution, or 30% hydrogen peroxide; The mass ratio of ammonium persulfate to nitrogen-doped carbon-anchored Cu single-atom material is 12-15:1; The liquid-solid ratio of the 10wt% sodium hypochlorite solution to the nitrogen-doped carbon-anchored Cu single-atom material is 3.5-4.5:100mL / mg; The liquid-solid ratio of the 30% hydrogen peroxide to the nitrogen-doped carbon-anchored Cu single-atom material is 0.5-0.7:100 mL / mg; The hydrothermal reaction is carried out at a temperature of 80-130℃ for 3-6 hours.

[0011] Furthermore, in step S4, the solid-liquid ratio of the etched nitrogen-doped carbon-anchored Cu single-atom material to the ethanol solution is 2-4:1-2 mg / mL; The ultrasonic dispersion is performed at 35-40 kHz and 450-500 W for 1-2 hours. The palladium source solution is prepared by adding the palladium source to an ethanol solution, and the mass concentration of the palladium source solution is 5-15 mg / mL.

[0012] Furthermore, the concentration of the ethanol solution is 40-60% v / v; The palladium source is any one of palladium nitrate dihydrate, palladium chloride, and palladium acetate.

[0013] Furthermore, in step S5, the nitrogen source is any one of melamine, urea, and dicyandiamide; The mass ratio of the solid product to the nitrogen source is 1:3-10; The inert atmosphere is argon or nitrogen, and the flow rate is 30-50 mL / min; The calcination process involves heating to 700-1000℃ at a rate of 2-5℃ / min and calcining for 0.2-2 hours.

[0014] Application of Pd-Cu diatomic electrocatalysts prepared by any of the above methods in electrocatalytic reactions.

[0015] Furthermore, the electrocatalytic reaction is a potassium nitrate electrocatalytic reduction reaction, with 0.1M KOH + 0.1M KNO3 aqueous solution as the electrolyte, the Pd-Cu diatomic electrocatalyst as the catalyst, the operating temperature being 20-60℃, the operating pressure being atmospheric pressure, and Ar gas continuously being introduced at the cathode.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention employs a selective etching and sequential adsorption strategy to precisely control the defect structure and anchoring site distribution of the support, achieving atomic-level metal dispersion and controllable loading. This successfully constructs an atomically dispersed Pd-Cu heteronuclear diatomic site anchored on a nitrogen-doped carbon support for electrocatalytic materials. This solves the problems of existing technologies' difficulty in accurately synthesizing heteronuclear diatomic pair catalysts and the limited performance of single metal catalysts in complex electrocatalytic reactions. The preparation process of this invention is simple and low-cost, and can be extended to other diatomic catalysts, providing a new pathway for the preparation of high-performance diatomic electrocatalytic materials.

[0017] 2. The preparation method of the present invention not only achieves nearly 100% utilization of metal atoms and effectively prevents the aggregation of metal atoms, but also effectively controls the adsorption behavior of reactants and the conversion path of intermediate products through the close synergy of Pd and Cu at the atomic scale, thereby significantly improving the activity and selectivity of the electrocatalyst. When the Pd-Cu diatomic catalyst of the present invention is applied to electrocatalysis, it exhibits excellent ammonia yield and selectivity in the electroreduction of nitrate to ammonia, with a Faradaic efficiency greater than 80%. Attached Figure Description

[0018] Figure 1 The image shows a scanning electron microscope image of the Pd-Cu diatomic electrocatalyst prepared in Example 1.

[0019] Figure 2 X-ray diffraction patterns of the atomic electrocatalyst materials prepared in Example 1 and Comparative Examples 1-4.

[0020] Figure 3 The X-ray diffraction pattern of the sample prepared in Example 2.

[0021] Figure 4 The X-ray diffraction pattern of the sample prepared in Example 3.

[0022] Figure 5 The image shows the X-ray diffraction pattern of the sample prepared in Example 4.

[0023] Figure 6The graph shows the electrocatalytic ammonia production performance of the atomic electrocatalyst materials prepared in Example 1 and Comparative Examples 1-4. Detailed Implementation

[0024] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0025] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0026] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0027] Example 1 A method for preparing Pd-Cu diatomic electrocatalysts by selective etching and sequential adsorption, the specific preparation steps of which include: S1. Add 0.0205 g of copper chloride and 0.408 g of zinc chloride to 30 mL of formamide, treat at 40 kHz and 500 W for 30 min, place in a high-pressure reactor, heat at 180 °C for 12 h, filter, wash three times alternately with deionized water and anhydrous ethanol, and vacuum dry for 12 h to obtain the precursor. S2. The precursor was placed in a tube furnace and calcined at 900℃ for 2 h at a heating rate of 2℃ / min under an argon atmosphere with a flow rate of 40 mL / min. The furnace was then cooled to obtain nitrogen-doped carbon-anchored Cu single-atom material. S3. Add 400 mg of nitrogen-doped carbon-anchored Cu single-atom material to 200 mL of 50% v / v ethanol solution, and ultrasonically disperse at 40 kHz and 500 W for 1 h. Add 2.4 mL of 30% H2O2 and stir for 30 min. Place in a polytetrafluoroethylene-lined high-pressure reactor and hydrothermally react at 110 °C for 3 h. After the reaction is completed, filter, wash 3 times with deionized water, and freeze-dry for 12 h to obtain etched nitrogen-doped carbon-anchored Cu single-atom material. S4. Add 50 mg of etched nitrogen-doped carbon-anchored Cu single-atom material to 50 mL of 50% v / v ethanol solution and sonicate at 40 kHz and 500 W for 1 h. Under stirring at 450 rpm, add 68 μL of a 10 mg / mL solution containing palladium nitrate dihydrate (prepared by adding palladium nitrate dihydrate to 50% v / v ethanol solution), continue stirring for 2 h, filter, dry at 80 °C for 12 h, and collect the solid product. S5. Mix the solid product and melamine in a mass ratio of 1:5, grind them in a ceramic boat, and then calcine them at a heating rate of 2℃ / min to 800℃ under an argon atmosphere with a flow rate of 40mL / min for 1h. Cool them in the furnace to obtain the Pd-Cu diatomic electrocatalyst.

[0028] Example 2 Based on Example 1, the formamide in step S1 was replaced with N,N-dimethylformamide, N,N-diethylformamide and N-methylpyrrolidone, respectively, to screen for amide compounds.

[0029] Example 3 Based on Example 1, the 0.0205 g copper chloride in step S1 was replaced with 0.0410 g, 0.0101 g and 0.0051 g respectively to screen the reaction conditions for nitrogen-doped carbon-anchored Cu single-atom materials.

[0030] Example 4 Based on Example 1, the hydrothermal reaction temperature of 110°C in step S3 was replaced with 130°C and 150°C respectively, and the hydrothermal reaction time of 3h was replaced with 6h to screen the etching conditions.

[0031] In step S4, the 68 μL of the 10 mg / mL palladium nitrate dihydrate solution was replaced with 34 μL, 136 μL, and 205 μL, respectively, to screen the Pd adsorption capacity.

[0032] Comparative Example 1 The difference from Example 1 is that steps S3-S5 are missing, meaning that the prepared product is a nitrogen-doped carbon-anchored Cu single-atom electrocatalyst; otherwise, it is the same as Example 1.

[0033] Comparative Example 2 The difference from Example 1 is that a nitrogen-doped carbon-supported Pd single-atom catalyst was prepared.

[0034] The specific preparation steps include: S1. Add 0.408 g of zinc chloride to 30 mL of formamide, treat at 40 kHz and 500 W for 30 min, place in a high-pressure reactor, heat at 180 °C for 12 h, filter, wash three times alternately with deionized water and anhydrous ethanol, and vacuum dry for 12 h to obtain the precursor. S2. The precursor was placed in a tube furnace and calcined at 900°C for 2 h at a heating rate of 2°C / min under an argon atmosphere with a flow rate of 40 mL / min. The furnace was then cooled to obtain nitrogen-doped carbon. S3. Add 400 mg of nitrogen-doped carbon to 200 mL of 50% v / v ethanol solution, and ultrasonically disperse at 40 kHz and 500 W for 1 h. Add 2.4 mL of 30% H2O2 and stir for 30 min. Place in a polytetrafluoroethylene-lined high-pressure reactor and hydrothermally react at 110 °C for 3 h. After the reaction is completed, filter, wash 3 times with deionized water, and freeze-dry for 12 h to obtain etched nitrogen-doped carbon. S4. Add 50 mg of etched nitrogen-doped carbon to 50 mL of 50% v / v ethanol solution and sonicate at 40 kHz and 500 W for 1 h. Add 68 μL of 10 mg / mL palladium nitrate dihydrate solution (prepared by adding palladium nitrate dihydrate to 50% v / v ethanol solution) while stirring at 450 rpm. Continue stirring for 2 h, filter, dry at 80 °C for 12 h, and collect the solid product. S5. Mix the solid product and melamine in a mass ratio of 1:5, grind them in a ceramic boat, and then calcine them at a temperature of 2℃ / min to 800℃ under an argon atmosphere with a flow rate of 40mL / min. After calcination for 1h, the mixture is cooled in the furnace to obtain a nitrogen-doped carbon-supported Pd single-atom catalyst.

[0035] Comparative Example 3 The difference from Example 1 is that the Pd-Cu diatomic catalyst was synthesized according to the coordination-mediated pyrolysis-in-situ polymerization synthesis method.

[0036] The specific preparation steps include: S1. Mix 0.45mM copper nitrate and 0.45mM potassium chloride palladiumate, add 5 g dicyandiamide, 4 mL formaldehyde solution and 30 mL deionized water, disperse by ultrasonication, evaporate by rotary evaporation, and collect the solid product. S2. The solid product was placed in a tube furnace and pyrolyzed at 600℃ for 2 h under an argon atmosphere at a flow rate of 40 mL / min and a heating rate of 2℃ / min. The product was cooled with the furnace and washed sequentially with 1M hydrochloric acid solution and deionized water to obtain the Pd-Cu diatomic catalyst.

[0037] Comparative Example 4 The difference from Example 1 is that the Pd-Cu diatomic catalyst was synthesized using a secondary pyrolysis method.

[0038] The specific preparation steps include: 1 g of melamine was placed in a tube furnace and pyrolyzed at 500 °C for 3 h under a nitrogen atmosphere at a flow rate of 40 mL / min and a heating rate of 2 °C / min. Then, it was pyrolyzed at 620 °C for 2 h at a heating rate of 2 °C / min to obtain a secondary pyrolysis product. The secondary pyrolysis product was added to deionized water to prepare a 5 mg / mL solution. 0.93 mL of 1.25 mg / mL palladium chloride solution and 1.06 mL of 1 mg / mL copper chloride solution were added and stirred for 12 h. The solution was then frozen, thawed by xenon lamp irradiation, washed, and filtered to obtain a Pd-Cu diatomic catalyst.

[0039] Test Example 1 1. The Pd-Cu diatomic electrocatalyst prepared in Example 1 was subjected to scanning electron microscopy testing, see [reference needed]. Figure 1As can be seen, the Pd-Cu diatomic electrocatalyst prepared in Example 1 exhibits a loose and rough porous packing state, which is consistent with the microscopic characteristics of a nitrogen-doped carbon-based support with high specific surface area.

[0040] 2. X-ray diffraction tests were performed on the atomic electrocatalyst materials prepared in Example 1 and Comparative Examples 1-4, see [reference needed]. Figure 2 As can be seen, no obvious metal diffraction peaks were observed, only nitrogen-doped carbon-based diffraction peaks appeared, indicating that the metal exists in atomic form and the atomic catalysts were successfully prepared.

[0041] 3. X-ray diffraction tests were performed on each sample selected from the screening of amide compounds in Example 2, see [reference needed]. Figure 3 It can be seen that the Pd-Cu diatomic catalyst materials prepared from N,N-dimethylformamide, N,N-diethylformamide, and N-methylpyrrolidone all exhibit sharp diffraction peaks formed by single metal agglomeration, indicating that amide compounds N,N-dimethylformamide, N,N-diethylformamide, and N-methylpyrrolidone cannot be used to synthesize Pd-Cu diatomic catalysts.

[0042] 4. X-ray diffraction tests were performed on each sample selected from the screening of reaction conditions for nitrogen-doped carbon-anchored Cu single-atom materials in Example 3. See [link to relevant documentation]. Figure 4 It can be seen that the optimal reaction mass of CuCl2 with nitrogen-doped carbon-anchored Cu single-atom catalyst is 0.0205 g.

[0043] 5. X-ray diffraction tests were performed on each sample selected for etching conditions and Pd adsorption amount selection in Example 4. See [reference needed]. Figure 5 It can be seen that the optimal reaction conditions are a hydrothermal temperature of 110℃, a hydrothermal time of 3 h, and 68 μL of a 10 mg / mL solution containing palladium nitrate dihydrate.

[0044] Test Example 2 The atomic electrocatalyst materials prepared in Example 1 and Comparative Examples 1-4 were tested for nitrate catalytic activity. Test method: A three-electrode system was used, with carbon paper clamped by electrode clips as the working electrode, a silver / silver chloride electrode as the reference electrode, and a platinum sheet as the counter electrode. The reduction activity was measured under Ar gas purging using a mixed electrolyte solution of 0.1M KNO3 + 0.1M KOH. The applied voltage range was -0.09 volts (reversible hydrogen electrode) to -0.69 volts (reversible hydrogen electrode), and the test duration was 1 h. The ammonia production performance of the atomic electrocatalyst materials prepared in Example 1 and Comparative Examples 1-4 under constant voltage was tested.

[0045] The results are as follows Figure 6It can be seen that the optimal reaction voltage is -0.59 volts (reversible hydrogen electrode), and when the voltage is -0.59 volts (reversible hydrogen electrode), the Faraday efficiency of the atomic electrocatalyst material in Example 1 is greater than 80%, which is much greater than the Faraday efficiency of Comparative Examples 1-4.

[0046] The ammonia production performance in the constant potential experiment at the optimal potential of -0.59 volts (reversible hydrogen electrode) is shown in Table 1.

[0047] Table 1

[0048] As can be seen from Table 1, compared with the single-atom catalysts of Examples 1 and 2, which have limited functionality, and the uneven distribution of diatomic sites caused by the simple mixed loading in Comparative Examples 3 and 4, which cannot accurately construct diatomic pair sites, the nitrogen-doped carbon-based Pd-Cu diatomic electrocatalytic material synthesized by selective etching and sequential adsorption in Example 1 of this invention accurately constructs diatomic pair sites, exhibits excellent electrocatalytic performance, and has high efficiency.

[0049] 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, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A selective etching and sequential adsorption synthesis method for Pd-Cu diatomic electrocatalysts, characterized in that, The Pd-Cu diatomic electrocatalyst uses nitrogen-doped carbon as a support, with Pd atoms and Cu atoms dispersed on the support surface in the form of diatomic pair sites. The molar ratio of Pd to Cu in the Pd-Cu diatomic electrocatalyst is 1:4-7; The specific surface area of ​​the Pd-Cu diatomic electrocatalyst is 100-150 m². 2 / g, exhibiting a loose, rough, porous, and stacked state.

2. The method for preparing a Pd-Cu diatomic electrocatalyst through selective etching and sequential adsorption as described in claim 1, characterized in that, The specific preparation steps include: S1. Add copper and zinc sources to an organic amide solvent, sonicate, place in a high-pressure reactor for solvothermal reaction, filter, wash, and dry to obtain the precursor; S2. Under an inert atmosphere, the precursor is heated and calcined, and then cooled in the furnace to obtain nitrogen-doped carbon-anchored Cu single-atom material. S3. Nitrogen-doped carbon-anchored Cu single-atom material is added to an ethanol solution, ultrasonically dispersed, oxidant is added and stirred, and then placed in a high-pressure reactor for hydrothermal reaction. After filtration, washing and drying, etched nitrogen-doped carbon-anchored Cu single-atom material is obtained. S4. The etched nitrogen-doped carbon-anchored Cu single-atom material was added to an ethanol solution, ultrasonically dispersed, a palladium source solution was added and stirred, filtered and dried, and the solid product was collected. S5. After mixing and grinding the solid product and nitrogen source, the mixture is calcined under an inert atmosphere and cooled in the furnace to obtain the target Pd-Cu diatomic electrocatalyst.

3. The method for preparing a Pd-Cu diatomic electrocatalyst through selective etching and sequential adsorption as described in claim 2, characterized in that, In step S1, the molar ratio of the copper source to the zinc source is 1:15-20; The copper source is any one of copper chloride, copper nitrate, and copper sulfate; The zinc source is any one of zinc chloride, zinc nitrate, and zinc sulfate; The organic amide solvent is at least one selected from formamide, N,N-dimethylformamide, N,N-diethylformamide, and N-methylpyrrolidone; The liquid-to-solid ratio of the organic amide solvent to the copper source is 1.2-1.5:1 L / g; The solvothermal reaction is carried out at a temperature of 150-200℃ for 8-15 hours.

4. The method for preparing a Pd-Cu diatomic electrocatalyst through selective etching and sequential adsorption as described in claim 2, characterized in that, In step S2, the inert atmosphere is argon or nitrogen, and the flow rate is 30-50 mL / min; The heating and calcination process involves heating to 800-1000℃ at a rate of 2-5℃ / min and calcining for 1-3 hours.

5. The method for preparing a Pd-Cu diatomic electrocatalyst by selective etching and sequential adsorption as described in claim 2, characterized in that, In step S3, the solid-liquid ratio of the nitrogen-doped carbon-anchored Cu single-atom material to the ethanol solution is 1-2:1 mg / mL; The concentration of the ethanol solution is 40-60% v / v; The oxidant is ammonium persulfate, 10 wt% sodium hypochlorite solution, or 30% hydrogen peroxide; The mass ratio of ammonium persulfate to nitrogen-doped carbon-anchored Cu single-atom material is 12-15:1; The liquid-solid ratio of the 10wt% sodium hypochlorite solution to the nitrogen-doped carbon-anchored Cu single-atom material is 3.5-4.5:100mL / mg; The liquid-solid ratio of the 30% hydrogen peroxide to the nitrogen-doped carbon-anchored Cu single-atom material is 0.5-0.7:100mL / mg; The hydrothermal reaction is carried out at a temperature of 80-130℃ for 3-6 hours.

6. The method for preparing a Pd-Cu diatomic electrocatalyst by selective etching and sequential adsorption as described in claim 2, characterized in that, In step S4, the solid-liquid ratio of the etched nitrogen-doped carbon-anchored Cu single-atom material to the ethanol solution is 2-4:1-2 mg / mL; The palladium source solution is prepared by adding the palladium source to an ethanol solution, and the mass concentration of the palladium source solution is 5-15 mg / mL.

7. The method for preparing a Pd-Cu diatomic electrocatalyst by selective etching and sequential adsorption as described in claim 6, characterized in that, The concentration of the ethanol solution is 40-60% v / v; The palladium source is any one of palladium nitrate dihydrate, palladium chloride, and palladium acetate.

8. The method for preparing a Pd-Cu diatomic electrocatalyst by selective etching and sequential adsorption as described in claim 2, characterized in that, In step S5, the nitrogen source is any one of melamine, urea, and dicyandiamide; The mass ratio of the solid product to the nitrogen source is 1:3-10; The inert atmosphere is argon or nitrogen, and the flow rate is 30-50 mL / min; The calcination process involves heating to 700-1000℃ at a rate of 2-5℃ / min and calcining for 0.2-2 hours.

9. The application of the Pd-Cu diatomic electrocatalyst obtained by the preparation method according to any one of claims 2-8 in electrocatalytic reactions.

10. The application as described in claim 9, characterized in that, The electrocatalytic reaction is a potassium nitrate electrocatalytic reduction reaction, with 0.1M KOH + 0.1M KNO3 aqueous solution as the electrolyte, and the Pd-Cu diatomic electrocatalyst as the catalyst. The operating temperature is 20-60℃, and the operating pressure is atmospheric pressure.

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