Non-noble metal-based bifunctional catalyst with high catalytic efficiency as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalyst preparation, and particularly discloses a high-catalytic-efficiency non-noble-metal-based bifunctional catalyst and a preparation method and application thereof.The preparation method comprises the following steps that transition metal salt and halogen element salt are dissolved in a mixed reagent of ethyl alcohol and water, the mixed reagent is dropped on a conductive substrate, and the conductive substrate is dried to obtain the high-catalytic-efficiency non-noble-metal-based bifunctional catalyst. The preparation method comprises the following steps: adding a halogen-doped non-noble metal-based bifunctional catalyst into a reaction kettle, carrying out a solvothermal reaction on a heating plate at a heating temperature of 80-120 DEG C for 5-10 h, drying the obtained material, and carrying out plasma treatment to obtain the halogen-doped non-noble metal-based bifunctional catalyst. By adopting the high-catalytic-efficiency non-noble metal-based bifunctional catalyst as well as the preparation method and the application thereof, the problems that most high-efficiency catalysts in the ENRR field in the prior art are composed of noble metals, are high in cost and are not beneficial to industrial treatment of nitrogen-containing wastewater; the problem that a noble metal-based catalyst is easily subjected to S poisoning in an anode SOR and is rapidly inactivated is solved, and the non-noble metal-based bifunctional catalyst with high catalytic efficiency is constructed.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, and in particular to high-efficiency non-precious metal-based bifunctional catalysts, their preparation methods, and applications. Background Technology

[0002] With the intensification of industrialization and agricultural activities, water pollution has become an increasingly serious problem, posing a major global challenge to ecosystems and human health. Nitrate (NO3) - ) and sulfide ions (S 2– Nitrogen and sulfur pollutants, such as nitrogen oxides and sulfur dioxide, are widely present in water bodies, primarily originating from agricultural fertilizer runoff, industrial wastewater discharge, and domestic sewage. These pollutants pose significant environmental and health risks through eutrophication, toxicity to aquatic life, and potential carcinogenic effects on humans. The United Nations Sustainable Development Goals emphasize the importance of ensuring access to clean water and sanitation for all, highlighting the urgent need for efficient water remediation technologies. Although traditional methods such as reverse osmosis, ion exchange, and biological denitrification are widely used, they often suffer from high operating costs, limited efficiency, and secondary pollution. Furthermore, these technologies primarily focus on pollutant removal rather than resource recovery; therefore, there is an urgent need to develop innovative methods that can simultaneously achieve pollutant transformation and resource recovery.

[0003] Renewable energy-driven electrochemical catalytic conversion methods offer a promising solution to this challenge. Under mild conditions, the electrocatalytic reduction of nitric acid (ENRR) can be used to convert pollutant nitrate into recyclable ammonia (NH3). Simultaneously, the sulfide oxidation reaction (SOR) provides a more energy-efficient alternative to the traditional anodic oxygen evolution reaction (OER), with a lower reaction potential (S0). 2– →S,E 0 =-0.48V vs. RHE) is significantly lower than OER (E 0 =1.23V vs. RHE), thus allowing the formation of elemental sulfur or polysulfides at lower voltages. Coupled ENRR with SOR, it is possible to simultaneously remove nitrates (NO3). - ) and sulfide ions (S 2– These two toxic groundwater pollutants can also generate NH3 and S at the cathode and anode respectively, forming a closed-loop resource recycling system upgrade.

[0004] However, despite progress in both ENRR and SOR fields in recent years, current high-efficiency catalysts in ENRR are mainly composed of noble metals (Pt, Pd, Ru, etc.), whose efficient water dissociation capabilities supply the active hydrogen required for the reaction. Therefore, their high cost is detrimental to the industrial treatment of nitrogen-containing wastewater. Furthermore, noble metal-based catalysts are easily poisoned by sulfur (S) in the anode SOR, leading to rapid deactivation. Compared to using two separate high-efficiency catalysts at the anode and cathode, non-noble metal-based bifunctional catalysts can effectively reduce the amount and types of catalysts used, thus lowering production costs. Therefore, researching and developing simple methods for the large-scale preparation of non-noble metal-based bifunctional catalysts and constructing non-noble metal-based bifunctional catalysts with high catalytic efficiency is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a high-efficiency non-precious metal-based bifunctional catalyst, its preparation method, and its application. This addresses the problems of existing ENRR (Enhanced Energizer Reduction) catalysts, which are mostly composed of precious metals, resulting in high costs and unfavorable conditions for industrial treatment of nitrogen-containing wastewater; the rapid deactivation of precious metal-based catalysts due to sulfur poisoning in the anode SOR (Sodium Oxide Reduction); and the high production costs resulting from using separate high-efficiency catalysts at both the anode and cathode, leading to large quantities and types of catalysts required. This invention provides a simple, large-scale preparation method to construct a high-efficiency non-precious metal-based bifunctional catalyst.

[0006] To achieve the above objectives, this invention provides a method for preparing a high-efficiency non-noble metal-based bifunctional catalyst, comprising the following steps: Transition metal salts and halogen element salts were dissolved in a mixture of ethanol and water, dropped onto a conductive substrate, and simultaneously placed on a heating plate for a solvothermal reaction at a temperature of 80-120℃ for 5-10 hours. After drying the resulting material, it was treated with plasma to obtain a halogen-doped non-noble metal-based bifunctional catalyst.

[0007] Preferably, the transition metal salt is selected from one or more of cobalt nitrate, nickel nitrate, and ferric nitrate.

[0008] Preferably, the halogen salt is selected from one or more of ammonium fluoride, ammonium iodide, and ammonium chloride.

[0009] Preferably, the atomic molar ratio of the corresponding metal to the halogen element in the transition metal salt and the halogen element salt is 10:1 to 1:10.

[0010] Preferably, the atomic molar ratio of the corresponding metal to the halogen element in the transition metal salt and the halogen element salt is 1:1.

[0011] Preferably, the plasma treatment conditions are: power 300W, pressure 70Pa, gas flow rate 200mL / min, treatment time 25-40 minutes, and the gas used is argon.

[0012] This invention also provides a high-efficiency non-precious metal-based bifunctional catalyst, which is prepared by the above-described preparation method.

[0013] This invention also provides the application of a high-efficiency non-precious metal-based bifunctional catalyst, which is used to simultaneously catalyze the cathode nitrate reduction reaction to produce ammonia and the anodic sulfide oxidation reaction to produce elemental sulfur.

[0014] The advantages and beneficial effects of this invention using the above-mentioned high-catalytic-efficiency non-noble metal-based bifunctional catalyst, its preparation method, and its application are as follows: 1. This invention provides low-cost and high-efficiency catalysis: by using non-precious metals (such as nickel, cobalt, and iron) to replace expensive precious metals such as platinum and palladium, the cost of catalyst materials is significantly reduced, which is conducive to large-scale industrial application.

[0015] 2. This invention features a dual-function integrated design, allowing the same catalyst to simultaneously and efficiently catalyze both ENRR and SOR reactions, simplifying system configuration, reducing the types and amounts of catalysts used, and improving system integration. It exhibits strong resistance to sulfur poisoning: halogen doping can regulate the d-band center of metals, promoting rapid desorption of elemental sulfur, effectively preventing catalyst deactivation due to sulfur accumulation, and significantly improving long-term operational stability. It also significantly enhances nitrate reduction activity: halogens (such as F) can promote the dissociation of interfacial water molecules, providing sufficient active hydrogen to participate in nitrate reduction, significantly improving ammonia yield and Faraday efficiency.

[0016] 3. The preparation process of this invention is advanced, combining solvothermal and plasma treatment technologies to achieve uniform embedding and high dispersion of halogen atoms on the metal surface, overcoming the problem of uneven element distribution in the traditional hydrothermal method, and resulting in better catalytic performance.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 A comparison of the nitrate reduction performance of metal catalysts supported on halogen atoms and pure metal catalysts without halogen atoms. Figure 2 A comparison of the SOR stability of metal catalysts supported on halogen atoms and pure metal catalysts without halogen atoms. Figure 3 Comparison of nitrate reduction performance of halogen atom-supported metal catalysts prepared by plasma treatment and conventional hydrothermal method; Figure 4 Scanning electron microscope image of a metal catalyst supported on halogen atoms; Figure 5 This is a performance comparison between noble metal-based catalysts and non-noble metal-based catalysts. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0021] The following examples are not intended to limit the invention, but are only for illustration. Unless otherwise specified, the experimental methods used in the following examples are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0022] Example 1 A method for preparing a high-efficiency non-noble metal-based bifunctional catalyst includes the following steps: (1) Dissolve transition metal salt (0.1-2g) and halogen element salt (0.1-2g) in a mixture of ethanol and water, drop them onto a conductive substrate, and place them on a heating plate for a solvothermal reaction. The heating temperature is 80-120℃ and the holding time is 5-10h.

[0023] (2) After drying the above catalyst, it is treated with plasma to obtain a non-precious metal-based bifunctional catalyst doped with halogen elements.

[0024] The transition metal salts include, but are not limited to, solutions of cobalt nitrate, nickel nitrate, and ferric nitrate. The halogen salt solutions include, but are not limited to, solutions of ammonium fluoride, ammonium iodide, and ammonium chloride. The atomic molar ratio of the corresponding metal to the halogen in the transition metal salt and the halogen salt is 10:1 to 1:10. To further conserve raw materials while ensuring the redox reaction proceeds fully, a 1:1 atomic molar ratio of the corresponding metal to the halogen in the transition metal salt and the halogen salt is preferred.

[0025] Furthermore, in step (2), the plasma treatment time is 25-40 min, the power is 300 W, the pressure is 70 Pa, and the gas flow rate is 200 mL / min. -1 When the catalyst undergoes plasma surface treatment, electrons from the plasma first reach the catalyst surface and form a stable plasma sheath. Electrons on the catalyst surface recombine with halide ions, thereby increasing the valence state of the element to the atomic level. This further leads to the formation of halogen atom intercalation on the transition metal surface, greatly improving the dispersion of halogen atoms and significantly enhancing the catalyst activity.

[0026] Considering that halogen elements such as F and I can form hydrogen bond networks with interfacial water on the catalyst surface, thereby promoting water dissociation, and given that traditional halogen-doped catalysts are typically prepared using hydrothermal methods or vapor deposition, the resulting catalysts often exhibit uneven halogen distribution and poor performance, this invention innovatively utilizes Joule heating technology to efficiently prepare halogen-doped electrocatalysts. Furthermore, due to the difference in electronegativity between halogen elements and metal active sites, they can effectively regulate the d-band center of the active sites, achieving S desorption and avoiding S poisoning.

[0027] Comparative Example 1 The conventional hydrothermal method for preparing halogen atom-supported metal catalysts includes the following steps: Add 50-200 mg of transition metal salt A (such as nickel nitrate, ferric nitrate, cobalt nitrate, etc.), 50-200 mg of halogen salt B (such as NH4F, NH4Cl, NH4Br, etc.), and 50-500 mg of urea to 20-100 mL of deionized water, and stir until homogeneous. Then, add the homogeneous solution to a hydrothermal reactor and react at 80-120℃ for 8-12 h. After washing and drying, place the reactor in a tube furnace containing a 3%-10% H2 / Ar reducing atmosphere and reduce at 400-800℃ for 6-10 h to obtain a halogen-supported metal catalyst prepared by the traditional hydrothermal method.

[0028] Figure 3 A comparison of the nitrate reduction performance of halogen-supported metal catalysts prepared by plasma treatment (Example 1) and conventional hydrothermal methods (Comparative Example 1) reveals that plasma preparation, through high-energy-driven rapid decomposition, high-speed diffusion, and uniform mixing, more easily achieves atomic-level uniform dispersion of halogen elements in transition metals. In contrast, the hydrothermal method suffers from poor dispersion uniformity due to dissolution-diffusion limitations and crystallization segregation, leading to performance differences. Uniformly dispersed halogen atoms can more efficiently regulate the electronic structure of the metal surface and promote the dissociation of water molecules to generate active hydrogen, thereby improving the ammonia yield and electron utilization efficiency of the ENRR reaction. Aggregated halogen atoms, on the other hand, cannot fully function and may even obscure active sites.

[0029] Example 2 A method for preparing a high-efficiency non-noble metal-based bifunctional catalyst includes the following steps: Step 1: Dissolve nickel nitrate (1g) and ammonium fluoride (1g) in a mixed reagent of ethanol and water in a volume ratio of 1:1, drop the solution onto a conductive substrate, and place it on a heating plate to carry out a solvothermal reaction at a heating temperature of 90℃ for 8 hours.

[0030] Step 2: After drying the catalyst, treat it with plasma. The treatment was performed using Ar plasma (commercial 13.56MHz RF source) for 25 min at a power of 300W, a pressure of 70Pa, and a gas flow rate of 200mL / min. -1 Once completed, the F-doped nickel-based bifunctional catalyst can be obtained.

[0031] Figure 1 A comparison of the nitrate reduction performance of halogen-supported metal catalysts and halogen-free pure metal catalysts reveals that the nitrate reduction performance is significantly improved when pure Ni is supported with halogen atoms (F). This improvement is likely due to F promoting the active hydrogen generated from water splitting. Halogen doping optimizes the electronic structure of the catalyst surface, reduces side reactions (such as hydrogen evolution), and improves electron utilization efficiency, allowing more electrons to be used for nitrate reduction. Halogen atoms are not simply physically supported but rather their chemical action modulates catalyst performance, providing core technological support for the design of non-noble metal-based ENRR catalysts.

[0032] Figure 2 A comparison of the SOR performance of metal catalysts supported on halogen atoms and pure metal catalysts without halogen atoms shows that the stability of SOR is significantly improved when pure metal Ni is supported on halogen atoms (F). This may be due to F altering the d-band center of Ni, thereby promoting the desorption of the product S and preventing catalyst poisoning and deactivation. Pure metal catalysts are prone to "sulfur poisoning" due to the accumulation of SOR reaction products (elemental sulfur) adsorbed on active sites, leading to a rapid decline in activity. Halogen atoms (such as F) regulate the d-band center of the metal, altering the interaction strength between the metal and sulfur, promoting rapid desorption of elemental sulfur, and preventing the active sites from being occupied. Halogen-supported catalysts can maintain stable SOR catalytic activity for a longer period, solving the key problem of easy deactivation of traditional non-precious metal catalysts in SOR.

[0033] Figure 4 The prepared halogen-loaded metal catalyst is a nanorod material with a diameter of about 200 nm and a length of about 1000 nm.

[0034] Comparative Example 2 The preparation method of the high-catalytic-efficiency noble metal-based bifunctional catalyst differs from that of Example 2 in that the ammonium fluoride in the preparation method of Example 2 is replaced with the noble metal salt ruthenium chloride, while the rest is the same as that of Example 2.

[0035] like Figure 5 As shown, when Ru-doped noble metal was selected as a control sample, it was found that the performance of the non-noble metal catalyst F-Ni was comparable to that of the noble metal catalyst Ru-Ni, and both exhibited excellent performance.

[0036] Example 3 A method for preparing a high-efficiency non-noble metal-based bifunctional catalyst includes the following steps: Step 1: Dissolve 1.5g of ferric nitrate and 1.5g of ammonium chloride in a 1:1 mixture of ethanol and water, drop the solution onto a conductive substrate, and place it on a heating plate for a solvothermal reaction at 100°C for 10 hours.

[0037] Step 2: After drying the catalyst, treat it with plasma. The treatment was performed using Ar plasma (commercial 13.56MHz RF source) for 35 minutes at a power of 300W, a pressure of 70Pa, and a gas flow rate of 200mL / min. -1 Once completed, a nitrogen-doped iron-based bifunctional catalyst can be obtained.

[0038] Example 4 A method for preparing a high-efficiency non-noble metal-based bifunctional catalyst includes the following steps: Step 1: Dissolve cobalt nitrate (0.5g) and ammonium iodide (0.5g) in a mixture of ethanol and water in a volume ratio of 1:1, drop the solution onto a conductive substrate, and place it on a heating plate to carry out a solvothermal reaction at a heating temperature of 80℃ for 5 hours.

[0039] Step 2: After drying the catalyst, treat it with plasma. The treatment was performed using Ar plasma (commercial 13.56MHz RF source) for 30 min at a power of 300W, a pressure of 70Pa, and a gas flow rate of 200mL / min. -1 Once completed, a nitrogen-doped cobalt-based bifunctional catalyst can be obtained.

[0040] Therefore, this invention employs the aforementioned high-efficiency non-precious metal-based bifunctional catalyst, its preparation method, and its application. By using non-precious metals (such as nickel, cobalt, and iron) to replace expensive precious metals such as platinum and palladium, the cost of catalyst materials is significantly reduced. The same catalyst can simultaneously and efficiently catalyze ENRR and SOR reactions, simplifying system configuration, reducing the types and amounts of catalysts used, and improving system integration. This addresses the problems in the existing ENRR field where most high-efficiency catalysts are composed of precious metals, resulting in high costs and hindering the industrial treatment of nitrogen-containing wastewater; precious metal-based catalysts are prone to sulfur poisoning and rapid deactivation in the anode SOR; and the use of separate high-efficiency catalysts at the anode and cathode leads to high catalyst usage and types, resulting in high production costs.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a high-efficiency non-noble metal-based bifunctional catalyst, characterized in that, Includes the following steps: Transition metal salts and halogen element salts were dissolved in a mixture of ethanol and water, dropped onto a conductive substrate, and simultaneously placed on a heating plate for a solvothermal reaction at a temperature of 80-120℃ for 5-10 hours. After drying the resulting material, it was treated with plasma to obtain a halogen-doped non-noble metal-based bifunctional catalyst.

2. The method for preparing a high-efficiency non-noble metal-based bifunctional catalyst according to claim 1, characterized in that: The transition metal salt is selected from one or more of cobalt nitrate, nickel nitrate, and ferric nitrate.

3. The method for preparing a high-efficiency non-noble metal-based bifunctional catalyst according to claim 1, characterized in that: The halogen salt is selected from one or more of ammonium fluoride, ammonium iodide, and ammonium chloride.

4. The method for preparing a high-efficiency non-noble metal-based bifunctional catalyst according to claim 1, characterized in that: The atomic molar ratio of the corresponding metal to the halogen element in the transition metal salt and halogen element salt is 10:1 to 1:

10.

5. The method for preparing a high-efficiency non-noble metal-based bifunctional catalyst according to claim 4, characterized in that: The atomic molar ratio of the corresponding metal to the halogen element in the transition metal salt and halogen element salt is 1:

1.

6. The method for preparing a high-efficiency non-noble metal-based bifunctional catalyst according to claim 1, characterized in that, The plasma treatment conditions are: power 300W, pressure 70Pa, gas flow rate 200mL / min, treatment time 25-40 minutes, and argon gas is used.

7. A high-efficiency non-precious metal-based bifunctional catalyst, characterized in that: It is prepared by the preparation method described in any one of claims 1-6.

8. The application of the high-efficiency non-noble metal-based bifunctional catalyst according to claim 7, characterized in that: It is applied to the simultaneous catalytic cathode nitrate reduction reaction to produce ammonia, and the anodic sulfide oxidation reaction to produce elemental sulfur.

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