Preparation method and application of carbon-nitrogen-oxygen-controllable copper monatomic catalyst
By controlling the calcination atmosphere to prepare copper single-atom catalysts, the problems of large overpotential and poor stability of copper-based electrocatalysts in the nitrate reduction process were solved, achieving efficient conversion of nitrate to ammonia and simplifying the production process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI UNIV
- Filing Date
- 2026-02-11
- Publication Date
- 2026-06-30
Smart Images
Figure CN122303937A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of single-atom materials technology, and in particular to the preparation method and application of copper single-atom catalysts with tunable carbon, nitrogen, and oxygen. Background Technology
[0002] Ammonia (NH3) is an important raw material in the fertilizer, pharmaceutical, and chemical industries. It is also considered a renewable energy source, boasting zero carbon emissions and high energy density (22.5 MJ / kg⁻¹). -1 Ammonia, with its advantages such as high energy consumption and easy liquefaction, is receiving widespread global attention. Unfortunately, current ammonia synthesis technologies (such as the Haber-Bosch process) are energy-intensive and have huge carbon emissions. Therefore, there is an urgent need for more sustainable ammonia production methods. The overuse of oxygen-containing substances, such as fertilizers, and industrial and wastewater discharges have led to the accelerated accumulation of nitrogenous pollutants in ecosystems. Nitrates and nitrites are the most common inorganic nitrogen pollutants and are major culprits of global eutrophication and algal blooms in natural waters. Producing ammonia while reducing nitrate pollution has long been a real challenge in "turning waste into wealth."
[0003] Electrocatalytic nitrate reduction (NO3RR) is considered a promising strategy to remove nitrates and convert them into ammonia using renewable electricity. Copper-based electrocatalysts are widely used in NO3RR research due to their abundant reserves, flexible electrochemical activity, and tunable electronic structure. However, copper-based electrocatalysts suffer from problems such as large overpotentials, accumulation of nitrite intermediates, and poor stability. Therefore, researchers have proposed various strategies to promote nitrate reduction, including specific crystal facet design, defect engineering, copper oxide species regulation, alloying and doping strategies, and electrolytic cell engineering optimization. In recent years, copper-based single-atom catalysts have shown great potential in the field of electrocatalysis, thanks to the following characteristics of the material: (1) Isolated active sites solve the problems of NN coupling side reactions and low atom utilization, enabling high selectivity. (2) Strong metal-support interactions solve the shortcomings of poor stability and poor anti-interference ability, allowing them to adapt well to complex practical scenarios. (3) Good catalytic activity can be achieved with relatively low loading. However, precise control of the single-atom coordination environment has always been a core challenge. Summary of the Invention
[0004] Based on the technical problems existing in the background technology, this invention proposes a copper single-atom catalyst, a strategy of substitutable coordinating atoms and its application. This catalyst can not only effectively reduce the onset potential of the catalytic process and promote the conversion of nitrates, but also improve the Faradaic efficiency of the product ammonia and enhance the catalytic activity of the catalyst NO3RR.
[0005] The present invention proposes a method for preparing a copper single-atom catalyst with tunable carbon, nitrogen, and oxygen content, the method steps of which are as follows:
[0006] S1: A copper source is dispersed in a solvent, then a nitrogen source is added, and after mixing, the mixture is electrospun to obtain a precursor material. The precursor material is pre-oxidized in air and then annealed under an inert atmosphere to obtain a nitrogen-substituted copper single-atom catalyst.
[0007] S2: The nitrogen-substituted copper single-atom catalyst is calcined in a mixed atmosphere of hydrogen and inert gas to obtain a carbon-substituted copper single-atom catalyst.
[0008] S3: The nitrogen-substituted copper single-atom catalyst is calcined in an air atmosphere to obtain an oxygen-substituted copper single-atom catalyst.
[0009] Preferably, the copper source in S1 is one or more of copper chloride and its hydrate, copper nitrate and its hydrate, and copper sulfate and its hydrate, and the nitrogen source is one or more of polyacrylonitrile, polymethyl methacrylate, and polyvinylpyrrolidone.
[0010] Preferably, the solvent in S1 is one or more of N,N-dimethylformamide, ethanol, and water.
[0011] Preferably, the mass ratio of copper source to nitrogen source in S1 is 0.5-1:2.
[0012] Preferably, the pre-oxidation conditions in S1 are: temperature 180-300℃, time 1-3h.
[0013] Preferably, the annealing conditions in S1 are: temperature 500℃-750℃, time 1-2h.
[0014] Preferably, the calcination conditions in S2 under a mixed atmosphere of hydrogen and inert gas are: temperature 300℃-600℃, time 1-3h, and volume ratio of hydrogen to inert gas 5:95.
[0015] Preferably, the calcination conditions in S3 under air atmosphere are: temperature 300℃-500℃, time 5-30min.
[0016] The present invention proposes a copper single-atom catalyst with tunable carbon, nitrogen, and oxygen, which is prepared by the above-described method.
[0017] This invention proposes the application of a carbon, nitrogen, and oxygen tunable copper single-atom catalyst in the electrocatalytic reduction of nitrates, the catalyst being described above.
[0018] Beneficial technical effects of the present invention:
[0019] This invention provides a method for preparing copper single-atom catalysts with tunable carbon, nitrogen, and oxygen coordination atoms. A precursor is obtained through electrospinning, followed by a one-step calcination to obtain single-atom catalysts with different coordination environments, thus exhibiting good catalytic performance. This method is simple to operate and easy to synthesize in large quantities.
[0020] This invention utilizes different calcination atmospheres to introduce C, N, and O atoms with different electronegativity, enabling them to bond with copper atoms and form different single-atom coordination structures.
[0021] The single-atom catalyst with differentiated coordination environment regulated by this invention has excellent catalytic performance, enhances the adsorption and conversion of nitrate ions, improves electron transfer efficiency, and greatly improves the efficiency of nitrate reduction to ammonia. Attached Figure Description
[0022] Figure 1 These are X-ray diffraction (XRD) patterns of the copper single-atom catalyst prepared in this invention; where (a) is Example 1, (b) is Example 2, and (c) is Example 3.
[0023] Figure 2 These are aberration-corrected transmission electron microscopy (HAADF-STEM) images of copper-based single-atom catalysts with different coordination environments prepared in this invention; where (a) is Example 1, (b) is Example 2, and (c) is Example 3.
[0024] Figure 3 These are XAFS images of the copper single-atom catalyst prepared in this invention; where (a) is the K-edge XANES spectrum of Cu in Examples 1-3 and the standard sample, and (b) is the FT-EXAFS spectrum of Cu in R space for Examples 1-3 and the standard sample.
[0025] Figure 4 Here are model structural diagrams of the copper single-atom catalyst prepared in this invention; where (a) is Example 1, (b) is Example 2, and (c) is Example 3;
[0026] Figure 5 These are performance graphs of the copper single-atom catalyst prepared by the present invention; where (a) is the linear sweep voltammetry graph of Example 1, and (b) is the Faraday efficiency graph of the product ammonia of Example 1.
[0027] Figure 6 These are performance graphs of the copper single-atom catalyst prepared in this invention; where (a) is the linear sweep voltammetry graph of Example 2, and (b) is the Faraday efficiency graph of the product ammonia of Example 2.
[0028] Figure 7These are performance graphs of the copper single-atom catalyst prepared in this invention. (a) is the linear sweep voltammetry graph of Example 3, and (b) is the Faraday efficiency graph of the product ammonia in Example 3. Detailed Implementation
[0029] The present invention will be further explained below with reference to specific embodiments.
[0030] Example 1
[0031] 682 mg CuCl2·2H2O was dissolved in 20 mL N,N-dimethylformamide and stirred for 10 min. Then, 2.0 g polyacrylonitrile was added and stirred for 12 h to obtain a uniformly dispersed precursor solution. Then, a fiber membrane was prepared by electrospinning and dried for 12 h.
[0032] The material was subjected to air pre-oxidation treatment at 250 °C for 2 h, and then placed in a ceramic boat and oxidized at 3 °C for 3 min under a nitrogen atmosphere. -1 The temperature was increased to 600 °C in a tube furnace and annealed for 2 h. Subsequently, 30 mg of material was taken out and calcined at 500 °C for 60 min in a hydrogen-argon reducing atmosphere. After cooling, it was ground for later use.
[0033] Example 2
[0034] 782 mg Cu(NO3)2·3H2O was dissolved in 20 mL of a mixed solution of ethanol and N,N-dimethylformamide in equal proportions. The mixture was stirred for 10 min, and 2.0 g of polymethyl methacrylate was added. The mixture was stirred for 12 h to obtain a uniformly dispersed precursor solution. Then, a fiber membrane was prepared by electrospinning and dried for 12 h.
[0035] The material was subjected to air pre-oxidation treatment at 180 °C for 3 h, and then placed in a porcelain boat under a nitrogen atmosphere at 3 °C for 3 min. -1 The heating rate was increased to 500 °C in a tube furnace, annealed for 3 h, cooled, and then ground for later use.
[0036] Example 3
[0037] Dissolve 800 mg CuSO4·5H2O in 20 mL of a mixture of N,N-dimethylformamide and water in equal proportions, stir for 10 min, add 2.0 g polyvinylpyrrolidone, stir for 12 h to obtain a uniformly dispersed precursor solution, and then prepare a fiber membrane by electrospinning and dry for 12 h.
[0038] The material was subjected to air pre-oxidation treatment at 300 °C for 1 h, and then placed in a ceramic boat and oxidized at 3 °C for 1 min under a nitrogen atmosphere. -1The temperature was increased to 750 °C in a tube furnace and annealed for 1 h. Subsequently, 30 mg of material was taken out and calcined in air at 450 °C for 10 min. After cooling, it was ground for later use.
[0039] Five mg of the catalysts prepared in Examples 1-3 were placed in centrifuge tubes, and then 1 mL of ethanol was added for ultrasonic dispersion. Following this, 30 μL of ionic liquid reagent was added, and the mixture was thoroughly ultrasonicated to form an ink. Then, 100 μL of the ink was evenly coated multiple times onto a 1×0.5 cm² plate. -2 The electrolyte was prepared on carbon paper for later use. Additionally, a mixed solution of 0.5M K₂SO₄ and 0.5M KNO₃ was used for performance testing. Before testing, high-purity argon gas was continuously introduced into the pre-prepared electrolyte for 30 minutes to remove dissolved oxygen. Test conditions: Linear sweep voltammetry (LSV) was used with a test range of 0 to -1.2 V vs RHE and a scan rate of 50 mV / s.
[0040] As attached Figure 1 As shown, X-ray diffraction patterns of copper single-atom catalysts were obtained by calcining under different atmospheres. Two large broad diffraction peaks appeared at approximately 26° and 44°, corresponding to the (002) and (100) planes of carbon, respectively. No diffraction peaks of copper species and related oxide species were observed, indicating that the phase of the catalyst was not changed after calcination under different atmospheres.
[0041] As attached Figure 2 As shown in the HAADF-STEM images, single-atom catalysts obtained by calcining under different atmospheres all exhibit multiple isolated tiny bright spots, indicating that copper is dispersed in the carbon support in the form of single atoms.
[0042] As attached Figure 3 As shown, the K-edge absorption edge of Cu in the copper single-atom catalyst obtained by calcination under different atmospheres is located between the Cu foil and copper oxide, indicating that the valence state of Cu in the treated catalyst is between 0 and +2. The highest valence state of Cu is obtained after air oxidation, while the lowest valence state is obtained in the single-atom catalyst obtained after treatment with a hydrogen-argon reducing atmosphere. Furthermore, the FT-EXAFS curves in R-space show that all three catalysts exhibit a Cu-N / O / C main peak at approximately 1.47 Å, with varying radial distances, indicating that the coordination structure of the Cu-based single-atom catalyst was altered by controlling the calcination atmosphere.
[0043] As attached Figure 4As shown, the material obtained by calcination in a nitrogen atmosphere has a single-atom structure of Cu-N3O1. After treatment in a hydrogen-argon reducing atmosphere, C atoms with lower electronegativity are introduced to coordinate with the metal, forming a single-atom coordination form of Cu-N3C1. After air oxidation treatment, O atoms with higher electronegativity are introduced to coordinate with metallic copper, forming a coordination structure of Cu-N2O2.
[0044] As attached Figure 5 As shown, the single-atom material obtained by treatment in a hydrogen-argon reducing atmosphere exhibits a Faraday efficiency of up to 91% for ammonia production in a neutral nitrate reducing system over a wide potential range of -0.2 to -1.2 V vs RHE, with a current density reaching 465 mA cm⁻¹ at -1.2 V vs RHE. -2 This demonstrates that this coordination form of the single-atom catalyst has high activity for ammonia production from nitrates.
[0045] As attached Figure 6 As shown, the single-atom material obtained by nitrogen atmosphere treatment, under the same electrolysis system, exhibits a Faraday efficiency of up to 96% for ammonia production over a wide potential range of -0.1 to -1.2 V vs RHE, and a current density of 540 mA cm⁻¹ at -1.2 V vs RHE. -2 This indicates that this coordination form of the single-atom catalyst has high activity for ammonia production from nitrates.
[0046] As attached Figure 7 As shown, the single-element catalyst obtained by air atmosphere treatment, under the same test conditions, exhibits a lower onset potential and a current density reaching 800 mA cm⁻¹ at -1.2 V vs RHE. -2 Within the applied voltage range of 0 to -1.2 V vsRHE, the Faraday efficiency for ammonia production can reach up to 98%, indicating that this coordination form of single-atom catalyst has high activity for ammonia production from nitrates.
[0047] Therefore, the experimental results show that by controlling the calcination atmosphere, coordinating atoms with different electronegativity can be introduced to coordinate with the metal, forming single-atom catalysts with different coordination environments. Furthermore, catalysts that coordinate with O atoms, which have greater electronegativity, exhibit better catalytic performance.
[0048] This invention provides a technique for controlling the coordination structure of single atoms. By simply changing the calcination environment, Cu-based single-atom catalysts with different coordination forms can be obtained, effectively reducing the onset potential of the catalytic process, promoting nitrate conversion, and improving the Faradaic efficiency of the product ammonia. Furthermore, this method is simple to operate, low in cost, and conducive to the large-scale synthesis and preparation of materials. This invention provides a new solution to the problems of precise control of single-atom coordination structure and low efficiency of catalytic reduction of nitrate to ammonia.
[0049] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.
Claims
1. A method for preparing a carbon-nitrogen-oxygen-tunable copper monatomic catalyst, characterized in that, The steps are as follows: S1: A copper source is dispersed in a solvent, then a nitrogen source is added, and after mixing, the mixture is electrospun to obtain a precursor material. The precursor material is pre-oxidized in air and then annealed under an inert atmosphere to obtain a nitrogen-substituted copper single-atom catalyst. S2: The nitrogen-substituted copper single-atom catalyst is calcined in a mixed atmosphere of hydrogen and inert gas to obtain a carbon-substituted copper single-atom catalyst. S3: The nitrogen-substituted copper single-atom catalyst is calcined in an air atmosphere to obtain an oxygen-substituted copper single-atom catalyst.
2. The method for preparing the carbon-nitrogen-oxygen-tunable copper monatomic catalyst according to claim 1, characterized in that, In S1, the copper source is one or more of copper chloride and its hydrate, copper nitrate and its hydrate, and copper sulfate and its hydrate, and the nitrogen source is one or more of polyacrylonitrile, polymethyl methacrylate, and polyvinylpyrrolidone.
3. The method for preparing the carbon-nitrogen-oxygen-tunable copper single-atom catalyst according to claim 1, characterized in that, The solvent in S1 is one or more of N,N-dimethylformamide, ethanol, and water.
4. The method for preparing the carbon-nitrogen-oxygen-tunable copper single-atom catalyst according to claim 1, characterized in that, The mass ratio of copper source to nitrogen source in S1 is 0.5-1:
2.
5. The method for preparing the carbon-nitrogen-oxygen-tunable copper single-atom catalyst according to claim 1, characterized in that, The pre-oxidation conditions in S1 are: temperature 180-300℃, time 1-3h.
6. The method for preparing the carbon-nitrogen-oxygen-tunable copper single-atom catalyst according to claim 1, characterized in that, The annealing conditions in S1 are: temperature 500℃-750℃, time 1-2h.
7. The method for preparing a carbon-nitrogen-oxygen-tunable copper single-atom catalyst according to claim 1, characterized in that, The calcination conditions for S2 in a mixed atmosphere of hydrogen and inert gas are: temperature 300℃-600℃, time 1-3h, and volume ratio of hydrogen to inert gas 5:
95.
8. The method for preparing the carbon-nitrogen-oxygen-tunable copper single-atom catalyst according to claim 1, characterized in that, The calcination conditions for S3 in air atmosphere are: temperature 300℃-500℃, time 5-30min.
9. A copper single-atom catalytic catalyst with tunable carbon, nitrogen, and oxygen content, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.
10. The application of a carbon-nitrogen-oxygen-tunable copper single-atom catalyst in the electrocatalytic reduction of nitrates, characterized in that, The catalyst is as described in claim 9.