Preparation of p-doped Cu@C composite electrocatalyst by ball milling and calcination method and its application in electrocatalytic CO2 reduction

Abstract

The present invention discloses a p-doped Cu@C composite electrocatalyst prepared by a ball milling and calcining method and its electrocatalytic CO2 reduction application, and relates to the technical field of electrocatalysts. The present invention prepares a uniform mixed precursor of copper nitrate, ammonium dihydrogen phosphate and citric acid by a ball milling method, and then calcines the mixture at a high temperature to finally obtain a p-doped Cu@C electrocatalyst. The catalyst prepared by the present invention exhibits relatively outstanding electrocatalytic activity in the electroreduction of CO2 to CH4. The present invention is green and environmentally friendly, and the raw materials used in the invention are all cheap and readily available, with a short processing time, mild reaction, low energy consumption, and high application value and good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysts and preparation methods, and specifically to a p-doped Cu@C composite electrocatalyst prepared by a ball milling and calcining method and its application in electrocatalytic CO2 reduction. Background Art

[0002] CO₂ is widely recognized as the primary cause of climate change. With the continued consumption of fossil fuels, environmental problems are becoming increasingly severe. Reducing CO₂ and converting it into valuable chemicals is imperative from the perspectives of climate change mitigation and the development of new carbon resources. Renewable energy-driven electrocatalytic CO₂ reduction reactions can produce value-added downstream products with consumer potential, representing a key approach to closing the "carbon cycle." Currently, natural gas, primarily composed of CH₄, is the world's third-largest energy source. Liquefied natural gas, with a calorific value 15% higher than that of jet fuel, is widely used in transportation, energy, and other sectors. CH₄ is ​​also an important chemical feedstock, primarily used in the synthesis of products such as acetylene, synthetic ammonia, carbon black, carbon disulfide, and methyl chloride. Therefore, with the advent of the "dual carbon" strategy, CO₂ methanation technology has garnered increasing attention. However, from a kinetic and thermodynamic perspective, the complex proton coupling and electron transfer involved in electrocatalytic CO₂ reduction to CH₄, as well as uncontrollable intermediate adsorption at catalytic sites, result in poor activity and selectivity for specific products throughout the reaction. Therefore, the rational design and construction of efficient catalysts to control the reaction pathway to specific products is crucial.

[0003] Numerous research reports have shown that the diversity of products in electrocatalytic CO2 reduction mainly depends on the unique adsorption and bonding relationship between the catalyst surface and various characteristic intermediates during the reaction. With the development of in situ technology and theoretical calculations, the theory that the surface valence state of Cu-based catalysts can selectively regulate products has been widely accepted. It is worth noting that during the electrocatalytic CO2 reduction process, hydrogen evolution reaction will also occur as a side reaction. The proportion of proton-hydrogen substitution characteristic intermediates occupying the active sites of the reaction will greatly affect the catalytic performance of specific products. Therefore, designing and regulating the adsorption of characteristic intermediates on the catalyst surface is the key to efficient electrocatalytic CO2 reduction to CH4. Summary of the Invention

[0004] This invention addresses the issue of unclear coverage of key intermediates in the catalytic process of Cu-based catalytic materials. By simply ball-milling copper nitrate, ammonium dihydrogen phosphate, and citric acid into a uniform mixed precursor, the resulting mixture is calcined in a tubular furnace to produce a p-doped Cu@C electrocatalyst. This catalyst selectively modulates the Cu valence state, optimizes coverage of key intermediates, and precisely controls the ECO₂RR reaction pathway, resulting in excellent electrocatalytic CO₂ reduction to CH₄ performance.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solution: a method for preparing p-doped Cu@C composite electrocatalyst by ball milling and calcination, comprising the following preparation steps:

[0006] (1) Weigh a certain amount of metal salt containing divalent copper ions, ammonium dihydrogen phosphate, and citric acid and place them in a ball mill, and ball mill to form a homogeneous precursor;

[0007] (2) The homogeneous precursor obtained in step (1) is placed in a crucible, which is then placed in a tubular furnace, gas is introduced, and the mixture is heated to a certain temperature at a certain heating rate and maintained for a certain time to obtain a p-doped Cu@C composite electrocatalyst.

[0008] Furthermore, the mass of the metal salt containing divalent copper ions in step (1) is 1 to 2 g.

[0009] Furthermore, the mass of the ammonium dihydrogen phosphate in step (1) is 1 to 1.5 g.

[0010] Furthermore, the mass of the citric acid in step (1) is 0.5 to 1 g.

[0011] Furthermore, the ball milling time in step (1) is 20 to 35 minutes.

[0012] Furthermore, the metal salt in step (1) is any one of copper sulfate, copper nitrate or copper acetate.

[0013] Furthermore, the gas in step (2) is argon.

[0014] Furthermore, the heating rate of step (2) is 4-6°C / min.

[0015] Furthermore, the calcination temperature in step (2) is 300-700° C., and the holding time is 0.5-1.5 h.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention adopts the electrocatalytic material prepared by calcining by ball milling. The preparation method involved is simple and has high repeatability, is suitable for large-scale production, can be used in the fields of new energy and catalysis, and has high practicality and economy.

[0018] Compared with existing technologies, the present invention has significant advantages: the p-doped Cu@C composite electrocatalyst can precisely regulate the coverage of key intermediates at the catalytic interface and around the catalytic active sites, resulting in higher catalytic activity for specific products compared to other similar Cu-based electrocatalysts. Furthermore, the p-doped Cu@C composite electrocatalyst prepared by the ball milling method of the present invention has high yield, good reproducibility, strong controllability, and is environmentally friendly, making it suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 This is the XRD pattern of the p-doped Cu@C composite electrocatalyst prepared by the ball milling and calcination method in Example 3.

[0021] Figure 2 This is an SEM image of the p-doped Cu@C composite electrocatalyst prepared by the ball milling and calcination method in Example 3.

[0022] Figure 3 TEM and mapping images of the p-doped Cu@C composite electrocatalyst prepared by the ball milling and calcination method in Example 3.

[0023] Figure 4 Energy dispersive X-ray spectroscopy of a p-doped Cu@C composite electrocatalyst prepared by ball milling and calcination method in Example 3.

[0024] Figure 5 This is a comparison of the activity and current density of the p-doped Cu@C composite electrocatalyst prepared by ball milling and calcination in Example 3 and the catalyst products in Examples 1 and 2.

[0025] Figure 6 The product activity comparison of the p-doped Cu@C composite electrocatalyst prepared by the ball milling and calcination method in Example 3 and the catalysts in Examples 4 and 5 is shown. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0029] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0030] Example 1

[0031] (1) Place 1.45 g of copper nitrate trihydrate, 1.04 g of ammonium dihydrogen phosphate, and 0.63 g of citric acid in a ball mill and mill for 30 min to fully mix to form a uniform powder mixture precursor;

[0032] (2) The powder mixture precursor was transferred into a crucible, placed in a tube furnace, and heated to 300°C at a rate of 5°C / min under an argon atmosphere. The temperature was kept at that temperature for 1 hour, and then naturally cooled to obtain a p-doped Cu@C composite electrocatalyst (p-Cu@C-300).

[0033] Example 2

[0034] (1) Place 1.45 g of copper nitrate trihydrate, 1.04 g of ammonium dihydrogen phosphate, and 0.63 g of citric acid in a ball mill and mill for 30 min to fully mix to form a uniform powder mixture precursor;

[0035] (2) The powder mixture precursor was transferred into a crucible, placed in a tube furnace, and heated to 500°C at a rate of 5°C / min under an argon atmosphere. The temperature was kept at that temperature for 1 hour, and then naturally cooled to obtain a p-doped Cu@C composite electrocatalyst (p-Cu@C-500).

[0036] Example 3

[0037] (1) Place 1.45 g of copper nitrate trihydrate, 1.04 g of ammonium dihydrogen phosphate, and 0.63 g of citric acid in a ball mill and mill for 30 min to fully mix to form a uniform powder mixture precursor;

[0038] (2) The powder mixture precursor was transferred into a crucible, placed in a tube furnace, and heated to 700°C at a rate of 5°C / min under an argon atmosphere. The temperature was kept at that temperature for 1 hour, and then naturally cooled to obtain a p-doped Cu@C composite electrocatalyst (p-Cu@C).

[0039] Example 4

[0040] (1) Place 1.45 g of copper nitrate trihydrate and 0.63 g of citric acid in a ball mill and mill for 30 min to fully mix to form a uniform powder mixture precursor;

[0041] (2) The powder mixture precursor was transferred into a crucible, placed in a tube furnace, and heated to 700°C at a rate of 5°C / min under an argon atmosphere. The temperature was kept at that temperature for 1 hour, and then cooled naturally to obtain a Cu@C composite electrocatalyst (Cu@C-700).

[0042] Example 5

[0043] (1) Place 1.45 g of copper nitrate trihydrate and 1.04 g of ammonium dihydrogen phosphate in a ball mill and mill for 30 min to fully mix to form a uniform powder mixture precursor;

[0044] (2) The powder mixture precursor was transferred into a crucible, placed in a tube furnace, and heated to 700°C at a rate of 5°C / min under an argon atmosphere. The temperature was kept at that temperature for 1 hour, and then naturally cooled to obtain a p-doped Cu electrocatalyst (p-Cu-700).

[0045] The structure test of the prepared samples was carried out on a German Bruker D8 X-ray diffractometer (Cu-Kα radiation, The scanning range is 10°-80°) and the scanning rate is 7° / min. Figure 1 As shown, in Example 3, the XRD spectrum clearly shows the presence of metallic Cu in the structure of the prepared sample, indicating the successful preparation of the electrocatalyst.

[0046] Figure 2 This is a SEM image of the p-doped Cu@C composite electrocatalyst prepared by the ball milling and calcination method in Example 3. It can be clearly seen from the figure that the prepared sample is a plate-like structure of several tens of microns.

[0047] Figure 3 TEM and mapping images of a p-doped Cu@C composite electrocatalyst prepared by ball-milling and calcination in Example 3 show a lattice spacing of 0.21 nm, attributed to the (111) Cu plane, consistent with the XRD analysis results above. The mapping pattern further demonstrates the uniform distribution of Cu, P, C, and O in the prepared catalyst.

[0048] Figure 4 This is an energy-dispersive X-ray spectroscopy (EDS) spectrum of a p-doped Cu@C composite electrocatalyst prepared by the ball-milling and calcination method in Example 3. The results in the figure show that only small amounts of P and O elements can be detected in the prepared sample, and the main phase is also the metallic Cu. This result once again confirms the successful synthesis of the sample.

[0049] Electrocatalytic activity test: The electrocatalytic CO2 reduction performance test of the synthesized samples was carried out in a CHI660 electrochemical workstation produced by Shanghai Chenhua Company. Figure 5 The activity comparison and current density of the p-doped Cu@C composite electrocatalyst prepared by ball milling in Example 3 and the catalyst products prepared in Examples 1 and 2 are shown in the figure. It is clearly shown that as the calcination temperature increases, the FEC2 The FE of CH4 product of p-Cu@C catalyst is as high as 52.2% at -1.477V vs.RHE, and the total current density is -321.5mA·cm -2 .

[0050] Figure 6 This is a comparison chart of the product activities of the p-doped Cu@C composite electrocatalyst prepared by the ball milling and calcination method in Example 3 and the catalyst electrocatalysts prepared in Examples 4 and 5. The figure shows that the p-Cu@C catalyst has the highest performance for the electrocatalytic reduction of CO2 to CH4.

[0051] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing p-doped Cu@C composite electrocatalyst by ball milling and calcination, characterized in that: The method comprises the following preparation steps: (1) Weigh a certain amount of metal salt containing divalent copper ions, ammonium dihydrogen phosphate, and citric acid and place them in a ball mill, and ball mill to form a homogeneous precursor; (2) The homogeneous precursor obtained in step (1) is placed in a crucible, which is then placed in a tubular furnace, and gas is introduced. The crucible is heated to 700°C at a certain heating rate and maintained for 0.5 to 1.5 hours to obtain a p-doped Cu@C composite electrocatalyst.

2. The method for preparing p-doped Cu@C composite electrocatalyst by ball milling and calcination according to claim 1, characterized in that: The mass of the metal salt containing divalent copper ions in step (1) is 1-2 g.

3. The method for preparing p-doped Cu@C composite electrocatalyst by ball milling and calcination according to claim 1, characterized in that: The mass of the ammonium dihydrogen phosphate in step (1) is 1-1.5 g.

4. The method for preparing p-doped Cu@C composite electrocatalyst by ball milling and calcination according to claim 1, characterized in that: The mass of the citric acid in step (1) is 0.5-1 g.

5. The method for preparing p-doped Cu@C composite electrocatalyst by ball milling and calcination according to claim 1, characterized in that: The ball milling time in step (1) is 20 to 35 minutes.

6. The method for preparing p-doped Cu@C composite electrocatalyst by ball milling and calcination according to claim 1, characterized in that: The metal salt in step (1) is any one of copper sulfate, copper nitrate or copper acetate.

7. The method for preparing p-doped Cu@C composite electrocatalyst by ball milling and calcination according to claim 1, characterized in that: The gas in step (2) is argon.

8. The method for preparing p-doped Cu@C composite electrocatalyst by ball milling and calcination according to claim 1, characterized in that: The heating rate of step (2) is 4-6°C / min.

9. Use of the electrocatalyst prepared by the preparation method according to any one of claims 1 to 8 in the electrocatalytic reduction of CO2 to produce CH4.

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