A copper / diamond composite electrocatalyst rich in high-density defects and a preparation method and application thereof

Abstract

The application discloses a copper / diamond composite electrocatalyst rich in high-density defects and a preparation method and application thereof, and belongs to the technical field of electrocatalysis and powder metallurgy. The preparation method of the copper / diamond composite electrocatalyst comprises the following steps: taking copper-plated diamond powder, performing discharge plasma sintering under the conditions of mechanical pressure and pulse direct current to obtain a copper / diamond sintering product; and performing high-pressure torsion treatment on the copper / diamond sintering product to complete the preparation. The prepared composite electrocatalyst takes diamond particles as a physical skeleton, and copper matrix and copper / diamond phase interfaces are distributed with high-density dislocations and grain boundary defects induced by severe plastic deformation. The composite electrocatalyst prepared by the method has excellent electrochemical activity and extreme structural stability, and no material peeling occurs in the alkaline water splitting and oxygen evolution reaction under a large current density, so that the composite electrocatalyst exhibits great industrial application potential.

Description

Technical Field

[0001] This invention relates to the fields of electrocatalysis and powder metallurgy, and in particular to a copper / diamond composite electrocatalyst rich in high-density defects, its preparation method, and its application. Background Technology

[0002] Electrochemical water splitting is a core technology for achieving large-scale clean hydrogen production. Currently, although precious metals (such as platinum, iridium, and ruthenium) exhibit excellent electrocatalytic activity, their high cost and resource scarcity limit their industrial application. Therefore, developing efficient and highly stable electrocatalysts based on non-precious metals (such as copper, nickel, cobalt, and molybdenum) has become a research hotspot.

[0003] Copper and its composites possess excellent electrical conductivity, but when used directly as water splitting catalysts, they often face problems such as insufficient catalytic active sites and a high susceptibility to material exfoliation and structural instability under high current densities. Diamond, with its extremely high chemical stability and mechanical strength, is an ideal catalyst framework or support material. However, traditional composite processes struggle to form a tight interfacial bond between copper and diamond, and also find it difficult to introduce a sufficient density of catalytic active centers into the copper matrix, requiring further improvements.

[0004] High-pressure torsion (HPT), a severe plastic deformation (SPD) technique, can significantly refine grains and introduce extremely high densities of defects such as grain boundaries and dislocations. These defects are often excellent electrocatalytic active sites. However, powders containing ultra-hard diamond particles are difficult to directly undergo HPT treatment. Therefore, there is an urgent need to develop a new process that can both achieve a dense bond between copper and diamond and fully unleash their electrocatalytic potential to meet the performance requirements of no shedding and no deactivation under industrial-grade high current densities. Summary of the Invention

[0005] The purpose of this invention is to provide a copper / diamond composite electrocatalyst rich in high-density defects, its preparation method, and its application, thereby solving the aforementioned problems in the background art. This invention utilizes SPS technology to rapidly densify copper-plated diamond powder, and then employs HPT technology to induce intense plastic deformation, introducing ultra-high-density active defects into a robust framework, thus obtaining a composite electrocatalyst that combines high catalytic activity with extreme structural stability.

[0006] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is to provide a method for preparing a copper / diamond composite electrocatalyst rich in high-density defects, comprising the following steps: Copper-plated diamond powder was subjected to discharge plasma sintering under mechanical pressure and pulsed DC current conditions to obtain copper / diamond sintered products. The copper / diamond sintered product was subjected to high-pressure torsion treatment to obtain the copper / diamond composite electrocatalyst.

[0007] Preferably, the copper-plated diamond powder contains 5-15% copper by volume and has an average particle size of 80-120 μm.

[0008] Preferably, the current output of the discharge plasma sintering is 400~8000 A, the voltage output is 2~12 V, the temperature is 500~800℃, the applied mechanical pressure is 30~45 MPa, and the heat and pressure holding time is 5~15 min.

[0009] Preferably, the discharge plasma sintering is performed under vacuum or a protective atmosphere.

[0010] More preferably, the protective atmosphere is Ar.

[0011] Preferably, the high-pressure torsion treatment includes the following steps: placing the copper / diamond sintered product between the anvils of a high-pressure torsion device, applying axial pressure, and simultaneously causing the anvils to rotate relative to each other to generate torsional shear strain.

[0012] More preferably, the axial pressure applied in the high-pressure torsion treatment is 2.0~6.0 GPa, the number of torsion rotations is 1~20, and the torsion speed is 0.5~2.0 rpm.

[0013] Preferably, the preparation method includes the following steps: (1) Raw material preparation: Select copper-plated diamond powder with a copper layer on the surface as a precursor; (2) Discharge plasma sintering: The copper-plated diamond powder is placed in a graphite mold, and mechanical pressure and pulsed DC current are applied under vacuum or protective atmosphere to perform discharge plasma sintering. After cooling, a dense copper / diamond sintered product is obtained. (3) High pressure torsion treatment: The copper / diamond sintered product obtained in step (2) is placed between the anvils of a high pressure torsion device, and axial high pressure is applied. At the same time, the anvils are rotated relative to each other to generate torsional shear strain. After the treatment is completed, the copper / diamond composite electrocatalyst is obtained.

[0014] More preferably, the inner diameter of the graphite mold is 20 mm.

[0015] More preferably, by controlling the molding quality of the copper-plated diamond powder, the average thickness of the copper / diamond sintered product after spark plasma sintering is 1~2 mm.

[0016] The second technical solution of the present invention provides a copper / diamond composite electrocatalyst rich in high-density defects obtained according to the above preparation method.

[0017] The third technical solution of the present invention provides an application of the above-mentioned copper / diamond composite electrocatalyst rich in high-density defects in the field of electrocatalytic water splitting.

[0018] The beneficial technical effects of the present invention are as follows: This invention provides a method for preparing a copper / diamond composite electrocatalyst rich in high-density defects. First, copper-plated diamond powder is used as a precursor, and rapid densification is achieved through spark plasma sintering (SPS) under the synergistic effect of pulsed current and mechanical pressure to obtain a copper / diamond sintered product with a metallurgical bonding interface. Then, axial high pressure and shear strain are applied to the sintered product using high-pressure torsion (HPT) technology to induce severe plastic deformation. The resulting composite electrocatalyst has diamond particles as its physical framework, with a copper layer encapsulating the surface of the diamond particles and forming a continuous matrix through metallurgical bonding. High-density dislocations and grain boundary defects induced by severe plastic deformation are distributed in the copper matrix and at the copper / diamond interface.

[0019] This invention utilizes the hard, non-deformable properties of diamond. Through single-factor comparative experiments and performance comparisons, it highlights the specificity of the preparation process defined in this invention. The results demonstrate that during the HPT process, stress is highly concentrated at the copper / diamond phase interface, inducing nanoscale grain refinement and ultra-high density of crystal defects such as dislocations, stacking faults, and grain boundaries in the phase interface and copper matrix. These high-energy defects, acting as electrocatalytic active centers, significantly reduce the overpotential of the water splitting reaction, endowing the material with excellent electrocatalytic activity. Simultaneously, diamond constructs a robust physical framework, and combined with the densification brought about by SPS sintering, this catalytic material effectively resists phase transitions and material shedding when faced with intense bubble precipitation at high current densities, exhibiting an industrial-grade lifespan.

[0020] The composite electrocatalyst prepared by this method has both excellent electrochemical activity and extreme structural stability. It exhibits no material shedding during high current density alkaline water splitting for hydrogen production and oxygen evolution reaction, demonstrating great potential for industrial applications.

[0021] In addition, this combined process of "sintering first and then deformation" avoids the problem of easy breakage when hard powder is directly deformed. SPS is short and HPT can complete the drastic strain at room temperature. It has the advantages of compact process and good repeatability, and is easy to prepare on a large scale. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The images shown are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) images of copper-plated diamond powder from Example 2.

[0024] Figure 2 The polarization curves of the copper / diamond composite electrocatalysts prepared in Examples 1-4 are obtained by hydrogen evolution test (HER) under alkaline conditions.

[0025] Figure 3 The polarization curves of the copper / diamond composite electrocatalysts prepared in Examples 5-6 under alkaline conditions are shown in the oxygen evolution response (OER) test. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0027] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. It should be noted that any aspects of this invention not described in detail are conventional practices in the art and are not the focus of this invention.

[0029] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0030] The diamond powder with uniformly chemically plated copper in this invention was purchased from Henan Feimeng Diamond Co., Ltd.

[0031] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0032] Unless otherwise specified, "room temperature" in this invention refers to 20±10℃.

[0033] The technical solution of the present invention will be further illustrated by the following embodiments.

[0034] Example 1 A method for preparing a copper / diamond composite electrocatalyst rich in high-density defects, comprising the following steps: Uniformly coated copper-plated diamond powder was selected as the raw material, with an average diamond particle size of 100 μm, a copper coating thickness of approximately 1.5 μm, and a copper volume percentage of approximately 10%. 3 g of the copper-plated diamond powder was accurately weighed and placed into a high-strength graphite mold with an inner diameter of 20 mm, lined with flexible graphite paper on the upper and lower surfaces and inner walls, and pre-compacted. The mold was then placed in a spark plasma sintering furnace and sintered under an Ar protective atmosphere with the following parameters: a heating rate of 50 °C / min, heating to 650 °C, and applying an axial pressure of 35 MPa at this temperature for 10 minutes. After sintering, the furnace was cooled, the mold was removed, and the surface graphite paper was removed. After polishing, a dense copper / diamond composite disc with a diameter of 20 mm and a thickness of 1.5 mm was obtained. This disc was then laser-cut into rectangular samples with dimensions of 15 mm × 10 mm, thus obtaining the copper / diamond composite electrocatalyst. The catalyst performance was tested using a three-electrode system, with the working electrode being the product of this embodiment, the counter electrode being a graphite rod, and the reference electrode being an Hg / HgO electrode. The electrolyte was a 1M KOH solution, and high-purity nitrogen gas was bubbled through the electrolyte for 30 min before the test to remove dissolved oxygen. The linear sweep voltammetry curve was scanned at a rate of 5 mV / s at room temperature.

[0035] Example 2 A method for preparing a copper / diamond composite electrocatalyst rich in high-density defects, comprising the following steps: Uniformly electroless copper-plated diamond powder was selected as the raw material, with an average diamond particle size of 100 μm, a copper coating thickness of approximately 1.5 μm, and a copper volume percentage of approximately 10%. 3 g of the copper-plated diamond powder was accurately weighed and placed into a high-strength graphite mold with an inner diameter of 20 mm, lined with flexible graphite paper on the upper and lower ends and inner walls, and pre-compacted. The mold was then placed in a spark plasma sintering furnace and sintered under an Ar protective atmosphere with the following parameters: a heating rate of 50 °C / min, heating to 550 °C, and applying an axial pressure of 30 MPa at this temperature for 5 minutes. After sintering, the mold was cooled with the furnace, demolded, and the surface graphite paper was removed. After polishing, a dense copper / diamond composite disc with a diameter of 20 mm and a thickness of 1.5 mm was obtained. Next, the obtained composite disc was placed in the upper and lower anvil grooves of a high-pressure torsion device. At room temperature, an axial static pressure of 2.0 GPa was applied to completely fill the cavity. Maintaining this pressure, the rotating anvil was started at 0.5 rpm and torsion was performed for 5 consecutive rotations before stopping. Finally, the pressure was released and the disc was removed. It was then laser-cut into rectangular samples of 15 mm × 10 mm, thus obtaining a copper / diamond composite electrocatalyst with ultra-high dislocation density. Catalyst performance testing was conducted using a three-electrode system. The working electrode was the product of this embodiment, the counter electrode was a graphite rod, and the reference electrode was a Hg / HgO electrode. A 1M KOH solution was used as the electrolyte, and high-purity nitrogen gas was bubbled through the sample for 30 min before testing to remove dissolved oxygen. The linear sweep voltammetry curve was scanned at a rate of 5 mV / s at room temperature.

[0036] Example 3 A method for preparing a copper / diamond composite electrocatalyst rich in high-density defects, comprising the following steps: Uniformly electroless copper-plated diamond powder was selected as the raw material, with an average diamond particle size of 100 μm, a copper coating thickness of approximately 1.5 μm, and a copper volume percentage of approximately 10%. 3 g of the copper-plated diamond powder was accurately weighed and placed into a high-strength graphite mold with an inner diameter of 20 mm, lined with flexible graphite paper on the upper and lower ends and inner walls, and pre-compacted. The mold was then placed in a spark plasma sintering furnace and sintered under an Ar protective atmosphere with the following parameters: a heating rate of 50 °C / min, heating to 650 °C, and applying an axial pressure of 35 MPa at this temperature, holding for 10 minutes. After sintering, the mold was cooled with the furnace, demolded, and the surface graphite paper was removed. After polishing, a dense copper / diamond composite disc with a diameter of 20 mm and a thickness of 1.5 mm was obtained. Next, the obtained composite disc was placed in the upper and lower anvil grooves of a high-pressure torsion device. At room temperature, an axial static pressure of 4.0 GPa was applied to completely fill the cavity. Maintaining this pressure, the rotating anvil was started at a speed of 1.0 rpm and continuously torsion for 10 revolutions before stopping. Finally, the pressure was released and the disc was removed. It was then laser-cut into rectangular samples of 15 mm × 10 mm, thus obtaining a copper / diamond composite electrocatalyst with ultra-high dislocation density. Catalyst performance testing was uniformly performed using a three-electrode system. The working electrode was the product of this embodiment, the counter electrode was a graphite rod, and the reference electrode was a Hg / HgO electrode. The electrolyte was a 1M KOH solution, and high-purity nitrogen gas was bubbled through the sample for 30 min before testing to remove dissolved oxygen. The linear sweep voltammetry curve was scanned at a rate of 5 mV / s at room temperature.

[0037] Example 4 A method for preparing a copper / diamond composite electrocatalyst rich in high-density defects, comprising the following steps: Uniformly electroless copper-plated diamond powder was selected as the raw material, with an average diamond particle size of 100 μm, a copper coating thickness of approximately 1.5 μm, and a copper volume percentage of approximately 10%. 3 g of the copper-plated diamond powder was accurately weighed and placed into a high-strength graphite mold with an inner diameter of 20 mm, lined with flexible graphite paper on the upper and lower ends and inner walls, and pre-compacted. The mold was then placed in a spark plasma sintering furnace and sintered under an Ar protective atmosphere with the following parameters: a heating rate of 50 °C / min, heating to 750 °C, and applying an axial pressure of 35 MPa at this temperature, holding for 15 minutes. After sintering, the mold was cooled with the furnace, demolded, and the surface graphite paper was removed. After polishing, a dense copper / diamond composite disc with a diameter of 20 mm and a thickness of 1.5 mm was obtained. Next, the obtained composite disc was placed in the upper and lower anvil grooves of a high-pressure torsion apparatus. At room temperature, an axial static pressure of 6.0 GPa was applied to completely fill the cavity. Maintaining this pressure, the rotating anvil was started at 1.0 rpm and continuously torsion for 15 revolutions before stopping. Finally, the pressure was released and the disc was removed. It was then laser-cut into rectangular samples of 15 mm × 10 mm, yielding a copper / diamond composite electrocatalyst with ultra-high dislocation density. The catalyst was tested for hydrogen evolution reaction in 1 M KOH solution. Catalyst performance testing employed a three-electrode system, with the working electrode being the product of this embodiment, the counter electrode being a graphite rod, and the reference electrode being a Hg / HgO electrode. The electrolyte was 1 M KOH solution, and high-purity nitrogen gas was bubbled through the electrolyte for 30 min before testing to remove dissolved oxygen. The linear sweep voltammetry curve was scanned at a rate of 5 mV / s at room temperature.

[0038] Example 5 A method for preparing a copper / diamond composite electrocatalyst rich in high-density defects, comprising the following steps: Uniformly electroless copper-plated diamond powder was selected as the raw material, with an average diamond particle size of 100 μm, a copper coating thickness of approximately 1.5 μm, and a copper volume percentage of approximately 10%. 3 g of the copper-plated diamond powder was accurately weighed and placed into a high-strength graphite mold with an inner diameter of 20 mm, lined with flexible graphite paper on the upper and lower ends and inner walls, and pre-compacted. The mold was then placed in a spark plasma sintering furnace and sintered under an Ar protective atmosphere with the following parameters: a heating rate of 50 °C / min, heating to 750 °C, and applying an axial pressure of 40 MPa at this temperature, holding for 10 minutes. After sintering, the mold was cooled with the furnace, demolded, and the surface graphite paper was removed. After polishing, a dense copper / diamond composite disc with a diameter of 20 mm and a thickness of 1.5 mm was obtained. Next, the obtained composite disc was placed in the upper and lower anvil grooves of a high-pressure torsion device. At room temperature, an axial static pressure of 6.0 GPa was applied to completely fill the cavity. Maintaining this pressure, the rotating anvil was started at a speed of 2.0 rpm and continuously torsion for 20 revolutions before stopping. Finally, the pressure was released and the disc was removed. It was then laser-cut into rectangular samples of 15 mm × 10 mm, thus obtaining a copper / diamond composite electrocatalyst with ultra-high dislocation density. Catalyst performance testing was uniformly performed using a three-electrode system. The working electrode was the product of this embodiment, the counter electrode was a graphite rod, and the reference electrode was a Hg / HgO electrode. The electrolyte was a 1M KOH solution, and high-purity nitrogen gas was bubbled through the sample for 30 min before testing to remove dissolved oxygen. The linear sweep voltammetry curve was scanned at a rate of 5 mV / s at room temperature.

[0039] Example 6 A method for preparing a copper / diamond composite electrocatalyst rich in high-density defects, comprising the following steps: Uniformly electroless copper-plated diamond powder was selected as the raw material, with an average diamond particle size of 100 μm, a copper coating thickness of approximately 1.5 μm, and a copper volume percentage of approximately 10%. 3 g of the copper-plated diamond powder was accurately weighed and placed into a high-strength graphite mold with an inner diameter of 20 mm, lined with flexible graphite paper on the upper and lower ends and inner walls, and pre-compacted. The mold was then placed in a spark plasma sintering furnace and sintered under an Ar protective atmosphere with the following parameters: a heating rate of 50 °C / min, heating to 750 °C, and applying an axial pressure of 45 MPa at this temperature, holding for 10 minutes. After sintering, the mold was cooled with the furnace, demolded, and the surface graphite paper was removed. After polishing, a dense copper / diamond composite disc with a diameter of 20 mm and a thickness of 1.5 mm was obtained. Next, the obtained composite disc was placed in the upper and lower anvil grooves of a high-pressure torsion device. At room temperature, an axial static pressure of 6.0 GPa was applied to completely fill the cavity. Maintaining this pressure, the rotating anvil was started at a speed of 2.0 rpm and continuously torsion for 20 revolutions before stopping. Finally, the pressure was released and the disc was removed. It was then laser-cut into rectangular samples of 15 mm × 10 mm, thus obtaining a copper / diamond composite electrocatalyst with ultra-high dislocation density. Catalyst performance testing was uniformly performed using a three-electrode system. The working electrode was the product of this embodiment, the counter electrode was a graphite rod, and the reference electrode was a Hg / HgO electrode. The electrolyte was a 1M KOH solution, and high-purity nitrogen gas was bubbled through the sample for 30 min before testing to remove dissolved oxygen. The linear sweep voltammetry curve was scanned at a rate of 5 mV / s at room temperature.

[0040] Figure 1 The images shown are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) images of copper-plated diamond powder from Example 2.

[0041] Figure 2 The polarization curves of the copper / diamond composite electrocatalysts prepared in Examples 1-4 are obtained by hydrogen evolution test (HER) under alkaline conditions.

[0042] Figure 3 The polarization curves of the copper / diamond composite electrocatalysts prepared in Examples 5-6 under alkaline conditions are shown in the oxygen evolution response (OER) test.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a copper / diamond composite electrocatalyst rich in high-density defects, characterized in that, Includes the following steps: Copper-plated diamond powder was subjected to discharge plasma sintering under mechanical pressure and pulsed DC current conditions to obtain copper / diamond sintered products. The copper / diamond sintered product was subjected to high-pressure torsion treatment to obtain the copper / diamond composite electrocatalyst.

2. The preparation method according to claim 1, characterized in that, The copper-plated diamond powder contains 5-15% copper by volume and has an average particle size of 80-120 μm.

3. The preparation method according to claim 1, characterized in that, The discharge plasma sintering process involves a current output of 400~8000 A, a voltage output of 2~12 V, a temperature of 500~800℃, an applied mechanical pressure of 30~45 MPa, and a holding time of 5~15 min.

4. The preparation method according to claim 1, characterized in that, The discharge plasma sintering is performed under vacuum or a protective atmosphere.

5. The preparation method according to claim 1, characterized in that, The high-pressure torsion treatment includes the following steps: placing the copper / diamond sintered product between the anvils of a high-pressure torsion device, applying axial pressure, and simultaneously causing the anvils to rotate relative to each other to generate torsional shear strain.

6. The preparation method according to claim 5, characterized in that, The axial pressure applied during the high-pressure torsion treatment is 2.0~6.0 GPa, the number of torsion rotations is 1~20, and the torsion speed is 0.5~2.0 rpm.

7. A copper / diamond composite electrocatalyst rich in high-density defects obtained by the preparation method according to any one of claims 1-6.

8. The application of the copper / diamond composite electrocatalyst rich in high-density defects as described in claim 7 in the field of electrocatalytic water splitting.

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