Copper-phosphorus / cobalt foam composite catalyst, preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of catalysts. Disclosed are a copper-phosphorus / cobalt foam composite catalyst, a preparation method therefor, and a use thereof. The preparation method comprises the following steps: S1: acquiring cobalt foam and pretreating the cobalt foam; S2: performing alkali treatment on the pretreated cobalt foam to obtain a cobalt oxyhydroxide precursor having a double-layer hydroxide structure; S3: preparing a copper plating electrolyte and placing the cobalt oxyhydroxide precursor in the copper plating electrolyte for electrodeposition to obtain a copper / cobalt foam precursor; and S4: performing phosphorization annealing treatment on the copper / cobalt foam precursor to obtain the copper-phosphorus / cobalt foam composite catalyst. The preparation method of the present invention is simple and has low costs. The prepared copper-phosphorus / cobalt foam composite catalyst has excellent activity and stability, is suitable for a reaction of electrochemical nitrate reduction for ammonia synthesis, and reduces the kinetic barrier to the nitrate reduction to ammonia, thereby significantly improving the ammonia production efficiency.

Description

A copper-phosphorus / foamed cobalt composite catalyst, its preparation method and application Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a copper-phosphorus / foamed cobalt composite catalyst, its preparation method, and its application. Background Technology

[0002] With the global energy structure shifting towards cleaner and lower-carbon energy, green ammonia synthesis technology, as an important chemical production process, has attracted widespread attention. Ammonia is not only a key raw material for fertilizer production but is also considered a potential clean energy carrier. The traditional Haber-Bosch process is currently the main method for industrial ammonia synthesis, but it relies on fossil fuels as a hydrogen source, requires harsh reaction conditions (high temperature and high pressure), and is accompanied by large amounts of carbon dioxide emissions, which is detrimental to sustainable development. Therefore, developing green and low-carbon ammonia synthesis technology has become a current research hotspot.

[0003] Electrochemical synthesis of ammonia is a promising green ammonia production route, utilizing an electrochemical reaction to convert nitrogen or nitrate into ammonia. However, when using nitrogen as the nitrogen source, the ammonia yield is extremely low (approximately 0.1–100 μg / h⁻¹) due to its poor solubility in water, the strong N≡N bond energy which makes activation difficult, and the limitation imposed by competing hydrogen evolution reactions. -1 mg cat -1 Therefore, this technology cannot yet be used for large-scale ammonia production. Using nitrates as a nitrogen source not only enables the resource utilization of nitrates in wastewater but also reduces dependence on fossil fuels and lowers carbon emissions. However, the core challenge of the nitrate reduction electrochemical reaction lies in developing efficient and stable catalysts.

[0004] Currently, noble metal catalysts such as platinum, palladium, and ruthenium possess high catalytic activity, but their high cost and scarcity limit their large-scale application. Furthermore, high-performance catalysts, such as single-crystal copper, suffer from stability issues due to the strong adsorption of nitrogen-containing substances in the middle, making them prone to rapid deactivation during reduction. Moreover, at low overpotentials, the weak adsorption of Cu by hydrogen radicals limits the hydrogenation rate, while at high overpotentials, the dominant hydrogen evolution reaction leads to insufficient conversion of ammonia products.

[0005] Cobalt-based materials are considered promising candidates for non-precious metal catalysts due to their abundant natural resources, low cost, and good performance. However, pure cobalt materials exhibit insufficient activity and selectivity in the nitrate reduction reaction to ammonia, making it difficult to meet practical application requirements. Summary of the Invention

[0006] To address the aforementioned problems, this invention aims to provide a copper-phosphorus / foamed cobalt composite catalyst, its preparation method, and its application.

[0007] The technical solution of the present invention is as follows:

[0008] On the one hand, a method for preparing a copper-phosphorus / foamed cobalt composite catalyst is provided, comprising the following steps:

[0009] S1: Obtain cobalt foam and pretreat the cobalt foam;

[0010] S2: The pretreated cobalt foam is subjected to alkali treatment to obtain a cobalt hydroxyl oxide precursor with a double-layer hydroxyl structure.

[0011] S3: Prepare a copper plating electrolyte and place the cobalt hydroxyoxide precursor in the copper plating electrolyte for electrodeposition to obtain a copper / foamed cobalt precursor;

[0012] S4: The copper / cobalt foam precursor is subjected to phosphating annealing treatment to obtain the copper-phosphorus / cobalt foam composite catalyst.

[0013] Preferably, in step S1, the pretreatment includes ultrasonic cleaning with hydrochloric acid solution, anhydrous ethanol and deionized water in sequence.

[0014] Preferably, in step S2, when performing alkali treatment, the pretreated cobalt foam is placed in a sodium hydroxide solution and kept at 75–85°C for 12–14 hours.

[0015] Preferably, the concentration of the sodium hydroxide solution is 1–4 mol / L.

[0016] Preferably, in step S3, the electrolyte in the copper plating electrolyte is any one or more of copper chloride, copper sulfate, and copper nitrate.

[0017] Preferably, the concentration of the copper plating electrolyte is 1–4 mol / L.

[0018] Preferably, in step S3, electrodeposition is performed at a constant voltage of -2 to -2.5V vs. RHE for 100 to 600 seconds.

[0019] Preferably, step S4, which involves phosphating and annealing the copper / cobalt foam precursor, specifically includes the following sub-steps: placing the copper / cobalt foam precursor and sodium hypophosphite powder in a tube furnace, heating to 400°C at a rate of 1–3°C / min in an argon atmosphere, and holding at that temperature for 20–30 min.

[0020] On the other hand, a copper-phosphorus / cobalt foam composite catalyst prepared by any one of the above methods is also provided, and its application in the synthesis of ammonia by nitrate reduction.

[0021] The beneficial effects of this invention are:

[0022] The preparation method of this invention is simple and low in cost. The copper-phosphorus / foamed cobalt composite catalyst obtained has excellent electrochemical activity and stability, and can be used for the electrocatalytic reduction of nitrate to ammonia synthesis reaction, reducing the reaction kinetic energy of nitrate reduction to ammonia production and significantly improving the ammonia production efficiency. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0024] Figure 1 is a schematic flowchart of the preparation method of the copper-phosphorus / foamed cobalt composite catalyst of the present invention;

[0025] Figure 2 is a surface SEM image of the copper-phosphorus / cobalt foam composite catalyst in Example 1;

[0026] Figure 3 is a TEM image of the copper-phosphorus / foamed cobalt composite catalyst of Example 1;

[0027] Figure 4 shows the XRD patterns of the electrochemical ammonia synthesis reaction before and after using the copper-phosphorus / foamed cobalt composite catalyst in Example 1.

[0028] Figure 5 shows the ammonia production activity and Faraday efficiency of the copper-phosphorus / foamed cobalt composite catalyst in Example 1.

[0029] Figure 6 shows the long-term electrolytic stability test of the copper-phosphorus / foamed cobalt composite catalyst of Example 1 at -0.3V vs. RHE;

[0030] Figure 7 shows the change in product content over time during the nitric acid reduction process of the copper-phosphorus / foamed cobalt composite catalyst in Example 1.

[0031] Figure 8 shows the cyclic performance test of the copper-phosphorus / foamed cobalt composite catalyst of Example 1 at -0.3V vs. RHE. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0033] On one hand, as shown in Figure 1, the present invention provides a method for preparing a copper-phosphorus / foamed cobalt composite catalyst, comprising the following steps:

[0034] S1: Obtain cobalt foam and pretreat the cobalt foam.

[0035] In one specific embodiment, the pretreatment includes ultrasonic cleaning sequentially with hydrochloric acid solution, anhydrous ethanol, and deionized water. Optionally, the concentration of the hydrochloric acid solution is 0.5–1 mol / L, and the ultrasonic cleaning time is 15–20 min.

[0036] It should be noted that the purpose of pretreatment is to remove impurities such as oxides and organic matter from the surface of the cobalt foam. In addition to the preferred pretreatment method in the above embodiments, other pretreatment methods in the prior art that can achieve this purpose are also applicable to the present invention.

[0037] S2: The pretreated cobalt foam is subjected to alkali treatment to obtain a cobalt hydroxyl oxide precursor with a double-layer hydroxyl structure.

[0038] In one specific embodiment, during alkali treatment, the pretreated cobalt foam is placed in a sodium hydroxide solution and kept at 75–85°C for 12–14 hours. Optionally, the concentration of the sodium hydroxide solution is 1–4 mol / L.

[0039] It should be noted that the purpose of alkali treatment is to hydroxylate the foamed cobalt, thereby forming a cobalt hydroxyl oxide precursor with a double-layered hydroxyl structure. In addition to the alkali treatment method described in the above embodiments, any alkali treatment method that achieves the purpose by changing the type of alkali (such as potassium hydroxide), the concentration of the alkali, the temperature and time of the alkali treatment can also be applied to this invention.

[0040] S3: Prepare a copper plating electrolyte and place the cobalt hydroxyoxide precursor in the copper plating electrolyte for electrodeposition to obtain a copper / foamed cobalt precursor.

[0041] In one specific embodiment, the electrolyte in the copper plating electrolyte is any one or more of copper chloride, copper sulfate, and copper nitrate. Optionally, the concentration of the copper plating electrolyte is 1–4 mol / L.

[0042] In one specific embodiment, electrodeposition is performed at a constant voltage of -2 to -2.5V vs. RHE for 100 to 600 seconds.

[0043] It should be noted that copper electrodeposition is an existing technology, and the copper plating electrolyte and electrodeposition parameters in the above embodiments are only preferred embodiments of the present invention. Other copper plating electrolytes and electrodeposition parameters that can also achieve copper electrodeposition can also be applied to the present invention.

[0044] S4: The copper / cobalt foam precursor is subjected to phosphating annealing treatment to obtain the copper-phosphorus / cobalt foam composite catalyst.

[0045] In a specific embodiment, the phosphating annealing treatment of the copper / cobalt foam precursor specifically includes the following sub-steps: placing the copper / cobalt foam precursor and sodium hypophosphite powder in a tube furnace, heating to 400°C at 1-3°C / min in an argon atmosphere, and holding at that temperature for 20-30min.

[0046] It should be noted that phosphating annealing is a prior art, and the phosphating annealing parameters in the above embodiments are only preferred embodiment parameters of the present invention. Other parameters that can also achieve phosphating annealing can also be applied to the present invention.

[0047] In this invention, the preparation method of the copper-phosphorus / foamed cobalt composite catalyst uses foamed cobalt as a substrate, and then covers the foamed cobalt substrate with a coating layer composed of phosphorus nanoparticles and copper nanoparticles. This preserves the macroporous framework structure of the foamed cobalt substrate. The phosphorus nanoparticles and the copper nanoparticles are uniformly distributed on the surface of the foamed cobalt substrate, forming a sheet-like structure of nanoparticle stacking.

[0048] On the other hand, the present invention also provides a copper-phosphorus / cobalt foam composite catalyst prepared by the preparation method of any one of the above-described copper-phosphorus / cobalt foam composite catalysts and its application in the synthesis of ammonia by nitrate reduction.

[0049] In a specific embodiment, when using the copper-phosphorus / foamed cobalt composite catalyst of the present invention to synthesize ammonia by nitrate reduction, the copper-phosphorus / foamed cobalt composite catalyst is used as the cathode electrode and the nitrate solution is used as the electrolyte. The ammonia is produced by electrocatalytic reduction of nitrate in a three-electrode electrochemical system.

[0050] Optionally, the nitrate solution is any one or more of sodium nitrate solution, potassium nitrate solution, sodium nitrite solution, and potassium nitrite solution, the concentration of the nitrate solution is 0.1–2 mol / L, the solvent of the nitrate solution is sodium hydroxide solution or potassium hydroxide solution, the pH of the nitrate solution is 13–14, and the voltage of the electrocatalytic reduction of nitrate is 0 to -0.3 V relative to the hydrogen standard electrode potential. In this embodiment, by using an alkaline nitrate solution, the conductivity of the solution can be increased and the rate of electrolysis reaction can be accelerated.

[0051] It should be noted that the use of catalyst electrochemical synthesis of ammonia is an existing technology, and the electrochemical synthesis parameters of the above embodiments are only the preferred embodiment parameters of the present invention. Other methods of catalyst electrochemical synthesis of ammonia with different parameters can also be applied to the present invention.

[0052] Example 1

[0053] A copper-phosphorus / foamed cobalt composite catalyst is prepared by the following steps:

[0054] (1) Obtain cobalt foam (size 2.0cm×2.0cm×0.2cm) and pretreat the cobalt foam. Specifically, it is ultrasonically cleaned for 15min in dilute hydrochloric acid solution (concentration 1mol / L) and ethanol respectively to remove surface oil and oxides. Then it is ultrasonically cleaned for 15min in deionized water, rinsed and dried for later use.

[0055] (2) The pretreated foam cobalt was placed in 70 mL of sodium hydroxide solution (concentration of 4 mol / L) and kept in an oil bath at 80 °C for 12 h. After the heat preservation was completed, it was cooled, cleaned and dried to obtain a cobalt hydroxyl oxide precursor with a double-layer hydrogen-oxygen structure.

[0056] (3) Prepare a copper plating electrolyte (a copper chloride solution with a concentration of 4 mol / L) as the electrodeposition solution, use the cobalt hydroxyoxide precursor as the working electrode and a platinum sheet as the counter electrode, and use an electrochemical workstation to electrodeposit for 300 s at a constant voltage of -2.0107 V vs. RHE to obtain a copper / foam cobalt precursor.

[0057] (4) The copper / foamed cobalt precursor is placed in a tube furnace, and 0.5g and 0.1g of sodium hypophosphite powder are placed upstream and downstream respectively. The temperature is raised to 400℃ at 2℃ / min in an argon atmosphere and held for 30min to obtain the copper-phosphorus / foamed cobalt composite catalyst.

[0058] Example 2

[0059] Unlike Example 1, the electrodeposition times in step (3) of this example are 100s, 200s, 400s, 500s, and 600s.

[0060] Example 3

[0061] Unlike Example 1, the phosphating annealing time in step (4) of this example is 1h, 1.5h and 2h respectively.

[0062] Comparative Example 1

[0063] Unlike Example 1, this comparative example does not include steps (2) to (4), that is, using pretreated foamed cobalt as a pure cobalt catalyst.

[0064] Comparative Example 2

[0065] Unlike Example 1, this comparative example does not include step (3), that is, directly subjecting the cobalt hydroxyoxide precursor to phosphating annealing to obtain a phosphorus / foamed cobalt catalyst.

[0066] Comparative Example 3

[0067] Unlike Example 1, this comparative example does not include step (4), i.e., it does not perform phosphating annealing to obtain a copper / foamed cobalt catalyst.

[0068] Comparative Example 4

[0069] Unlike Example 1, the substrate in step (1) of this comparative example is copper foam, and step (3) involves preparing a cobalt plating electrolyte (a cobalt chloride solution with a concentration of 4 mol / L) for electrodeposition of cobalt to obtain a cobalt-phosphorus / copper foam catalyst.

[0070] Comparative Example 5

[0071] Unlike Example 1, this comparative example does not include step (2), i.e., no alkali treatment is performed to obtain an untreated copper-phosphorus / foam cobalt catalyst.

[0072] Test case

[0073] The morphology of the catalysts in each embodiment and comparative example was observed using a Geminisem 300 scanning electron microscope (SEM, Zeiss, Germany) and a transmission electron microscope. Figure 2 shows the SEM image of the copper-phosphorus / cobalt foam composite catalyst of Example 1, and Figure 3 shows the TEM image of the copper-phosphorus / cobalt foam composite catalyst of Example 1. As can be seen from Figures 2 and 3, the surface of the copper-phosphorus / cobalt foam composite catalyst of this invention exhibits an irregularly packed matrix morphology and polycrystalline properties. This is because the copper-phosphorus / cobalt foam composite catalyst of this invention is composed of many copper nanoparticles and phosphorus nanoparticles with different orientations.

[0074] The structures of the catalysts in each embodiment and comparative example were observed using X-ray diffraction. Figure 4 shows the XRD pattern of the copper-phosphorus / cobalt foam composite catalyst of Example 1, where (a) is the XRD pattern before the electrochemical ammonia synthesis reaction of the copper-phosphorus / cobalt foam composite catalyst of the present invention, and (b) is the XRD pattern after 200 h of electrochemical ammonia synthesis reaction of the copper-phosphorus / cobalt foam composite catalyst of the present invention. As can be seen from Figure 4, the main peak positions did not shift before and after the reaction, and the types of peaks did not decrease significantly. This indicates that the structure of the copper-phosphorus / cobalt foam composite catalyst of the present invention did not collapse after continuous reaction, demonstrating that the copper-phosphorus / cobalt foam composite catalyst of the present invention has good material structural stability. Combined with SEM and TEM images, this shows that the irregular stacking matrix can improve the stability of the catalyst material.

[0075] Nitrate reduction to ammonia synthesis was performed using the catalysts from each embodiment and comparative example. Electrochemical measurements were conducted on a three-electrode electrochemical workstation (CHI760E) in an electrolyte of 1 mol / L KOH + 0.1 mol / L KNO3 at a voltage of -0.3 V vs. RHE. The Faradaic efficiency and ammonia production rate were analyzed. Long-term and multiple-cycle nitrate reduction was performed at -0.3 V vs. RHE to verify the stability of the copper-phosphorus / foamed cobalt composite catalyst. The copper-phosphorus / foamed cobalt composite catalyst, platinum sheet, and Hg / HgO were used as the working electrode, counter electrode, and reference electrode, respectively. Linear sweep voltammetry (LSV) was performed at a scan rate of 10 mV / s. -1 The ammonia production test was conducted by taking reaction solutions after constant potential nitric acid reduction for 30 min at different potentials, diluting the concentration appropriately, and measuring the absorbance using the salicylic acid colorimetric method. The ammonia production rate was calculated based on the fitting formula of the standard curve, and the Faraday efficiency was calculated using the formula FE = (number of moles of product × molar mass of product) / (number of input charges × electron charges). Some test results are shown in Table 1 and Figures 5-8.

[0076] Table 1. Performance test results for each embodiment and comparative example.

[0077] As shown in Figure 5, the Faraday efficiency of the copper-phosphorus / foamed cobalt composite catalyst prepared in Example 1 ranged from 60% to approximately 80% from 0V to -0.4V vs. RHE, showing a trend of first increasing and then decreasing, reaching a maximum of 80.2% at -0.3V vs. RHE. The ammonia production rate showed a trend of gradually increasing and then stabilizing.

[0078] Figure 6 shows the yield of ammonium and nitrite, and the consumption of nitrate, of the copper-phosphorus / cobalt foam composite catalyst prepared in Example 1 at -0.3V vs. RHE. Specifically, as time increases, NO3... - The -N content ranged from 0.0135 min. -1 Gradually increased to 0.0398 min -1 This is due to increased electron availability or the presence of more negative potentials for atomic hydrogen radicals. As the potential continues to rise, the nitrate removal rate tends to stabilize, indicating that the increase in removal rate may not offset the decrease in energy utilization caused by high voltage, and excess hydrogen tends to recombine into hydrogen. Furthermore, the generation of hydrogen bubbles hinders the reactive active sites, impeding the adsorption of nitrates and other intermediates. The copper-phosphorus / foamed cobalt composite catalyst described in this invention exhibits highly efficient catalytic activity at low overpotentials.

[0079] As can be seen from Figure 7, the copper-phosphorus / foamed cobalt composite catalyst prepared in Example 1 did not show a sharp change in current density during long-term electrolysis in a strong alkaline solution, indicating that the copper-phosphorus / foamed cobalt composite catalyst of the present invention has good stability.

[0080] As can be seen from Figure 8, the copper-phosphorus / foamed cobalt composite catalyst prepared in Example 1 did not show significant changes in the yield of electrocatalytic nitric acid reduction to ammonia and the Faraday efficiency throughout the entire cycle during 22 nitric acid reduction processes at a potential of -0.3V vs. RHE, indicating that the copper-phosphorus / foamed cobalt composite catalyst of the present invention has good stability.

[0081] As can be seen from Table 1, neither the pure cobalt catalyst (Comparative Example 1) nor the phosphorus / foamed cobalt catalyst without copper electrodeposition (Comparative Example 2) can achieve the ammonia production rate and Faradaic efficiency achievable by this invention. Although the unphosphated copper / foamed cobalt catalyst (Comparative Example 3) can achieve a Faradaic efficiency of about 71%, its stability is poor. The cobalt-phosphorus / foamed copper catalyst (Comparative Example 4) obtained by using foamed copper as a substrate, then plating cobalt on it, and then phosphating and annealing, as well as the unalkali-treated copper-phosphorus / foamed cobalt catalyst (Comparative Example 5) obtained without alkali treatment, cannot achieve the ammonia production efficiency achievable by this invention, nor can they achieve the Faradaic efficiency achievable by this invention. Furthermore, particle aggregation occurs during the stability test.

[0082] In summary, this invention enables the preparation of copper-phosphorus / cobalt foam catalysts with good catalytic activity, high stability, and no aggregation. Compared with the prior art, this invention represents a significant advancement.

[0083] The above description is merely a representative embodiment of the present invention and is not intended to limit the present invention in any way. Any embodiment made by those skilled in the art without departing from the scope of the present invention and utilizing the disclosed technical content is an equivalent embodiment of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

A method for preparing a copper-phosphorus / foamed cobalt composite catalyst, characterized in that, Includes the following steps: S1: Obtain cobalt foam and pretreat the cobalt foam; S2: The pretreated cobalt foam is subjected to alkali treatment to obtain a cobalt hydroxyl oxide precursor with a double-layer hydroxyl structure. S3: Prepare a copper plating electrolyte and place the cobalt hydroxyoxide precursor in the copper plating electrolyte for electrodeposition to obtain a copper / foamed cobalt precursor; S4: The copper / cobalt foam precursor is subjected to phosphating annealing treatment to obtain the copper-phosphorus / cobalt foam composite catalyst. The method for preparing the copper-phosphorus / foamed cobalt composite catalyst according to claim 1 is characterized in that, In step S1, the pretreatment includes ultrasonic cleaning with hydrochloric acid solution, anhydrous ethanol and deionized water in sequence. The method for preparing the copper-phosphorus / foamed cobalt composite catalyst according to claim 1 is characterized in that, In step S2, during the alkali treatment, the pretreated cobalt foam is placed in a sodium hydroxide solution and kept at 75–85°C for 12–14 hours. The method for preparing the copper-phosphorus / foamed cobalt composite catalyst according to claim 3, characterized in that, The concentration of the sodium hydroxide solution is 1–4 mol / L. The method for preparing the copper-phosphorus / foamed cobalt composite catalyst according to claim 1 is characterized in that, In step S3, the electrolyte in the copper plating electrolyte is any one or more of copper chloride, copper sulfate, and copper nitrate. The method for preparing the copper-phosphorus / foamed cobalt composite catalyst according to claim 5, characterized in that, The concentration of the copper plating electrolyte is 1–4 mol / L. The method for preparing the copper-phosphorus / foamed cobalt composite catalyst according to claim 1 is characterized in that, In step S3, during electrodeposition, electrodeposition is performed at a constant voltage of -2 to -2.5V vs. RHE for 100 to 600 seconds. The method for preparing the copper-phosphorus / foamed cobalt composite catalyst according to claim 1 is characterized in that, In step S4, the phosphating annealing treatment of the copper / cobalt foam precursor specifically includes the following sub-steps: placing the copper / cobalt foam precursor and sodium hypophosphite powder in a tube furnace, heating to 400°C at 1-3°C / min in an argon atmosphere, and holding at that temperature for 20-30min. A copper-phosphorus / foamed cobalt composite catalyst characterized in that, It is prepared by the method described in any one of claims 1-8 for the preparation of copper-phosphorus / foamed cobalt composite catalyst. The application of the copper-phosphorus / foamed cobalt composite catalyst as described in claim 9 in the synthesis of ammonia by nitrate reduction.

Images