Indium-doped cobaltosic oxide catalyst as well as preparation method and application thereof
By doping indium tricobalt tetroxide catalyst, the problems of low activity and poor selectivity of existing catalysts in the nitrite electrochemical reduction and synthesis of ammonia are solved, and efficient and low-cost ammonia production is achieved, which improves ammonia yield and Faraday efficiency.
Patent Information
- Application Number
- CN202510477215.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-16
- Publication Date
- 2025-06-06
AI Technical Summary
The existing catalysts have low activity and poor selectivity in the synthesis of ammonia by electrochemical reduction of nitrite, and the cost of precious metal catalysts is high. The reaction kinetic hysteresis of non-precious metal catalysts leads to low ammonia Faraday efficiency.
By doping the indium tricobalt tetroxide catalyst, its morphology and composition are regulated, and the catalyst's electrochemical reduction nitrite ammonia production activity and selectivity are improved.
It is achieved without using precious metals, improving ammonia yield and Faraday efficiency, reducing production costs, and optimizing the electronic structure of the catalyst, enhancing the adsorption configuration of nitrite and the efficiency of ammonia generation.
Smart Images
Figure CN120099561A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of new materials, and in particular to an indium-doped cobalt tetroxide catalyst and a preparation method and application thereof. Background Art
[0002] Nitrite (NO 2 - ) electrochemical reduction to synthesize ammonia (NH 3 ) is a technology that has the potential for both wastewater remediation and green ammonia synthesis, but its industrial application is limited by the low activity and low selectivity of the catalyst. Currently, although precious metal catalysts (such as Pt and Ru) can achieve higher ammonia yields, their high cost and scarcity make it difficult to meet large-scale demand. Non-precious metal-based materials (such as pure Co 3 O 4 ) is low-cost, but its intrinsic electronic structure leads to sluggish reaction kinetics and side reaction dominance, accompanied by severe competitive hydrogen evolution reaction or nitrogen generation, resulting in the Faradaic efficiency of ammonia generally being less than 60%. In addition, NO 2 - The reduction involves a multi-step proton-coupled electron transfer process, including *NO 2 - →*NO→*NH 2 →NH 3 etc., the traditional Co 3 O 4 Due to the uneven distribution of electron density at surface active sites, it is difficult to synergistically optimize the adsorption energy barriers of each step, resulting in intermediate desorption or excessive hydrogenation, further reducing ammonia selectivity.
[0003] In recent years, transition metal doping has been used to tune Co 3 O 4 electronic structure to improve catalytic performance, but existing research focuses on oxygen evolution or oxygen reduction reactions. 2 - There are still significant defects in the directional design of reduction to ammonia. For example, although Fe doping can enhance the 3 O 4 conductivity, but its regulation of the d-band center of the Co site is limited and cannot effectively reduce the NH 2 →NH 3 desorption energy barrier; Ni doping induces lattice strain, but it easily leads to Co 3+ Excessive oxidation weakens the stable adsorption of NO intermediates. More importantly, the existing doping strategies fail to effectively inhibit the N─N coupling side reaction, the root cause of which is the lack of precise control of the local electronic state of the active site. Summary of the invention
[0004] In order to solve the above technical problems, the present invention discloses a method for preparing an indium-doped cobalt tetroxide catalyst, and the present invention also provides an indium-doped cobalt tetroxide catalyst prepared thereby and its application. The morphology and composition of the catalyst are regulated by indium doping, thereby improving the activity and selectivity of the catalyst in electrochemical reduction of nitrite to produce ammonia.
[0005] To achieve the above object, the present invention is implemented by the following technical scheme: a method for preparing an indium-doped cobalt tetroxide catalyst, characterized in that it is prepared according to the following method:
[0006] 1) Dissolve cobalt nitrate, urea and ammonium chloride in deionized water and stir to obtain a clear reaction solution without precipitation;
[0007] 2) transferring the reaction solution to a reaction vessel containing nickel foam, and performing a hydrothermal reaction to obtain nickel foam loaded with the sample;
[0008] 3) Washing the nickel foam loaded with the sample after the reaction with ethanol and water, and drying;
[0009] 4) Soaking the dried nickel foam loaded with the sample in an indium chloride solution, stirring for reaction, and vacuum drying to obtain indium-doped cobalt tetroxide.
[0010] In the above scheme: in step 1), the concentration of cobalt nitrate is 0.15-0.20 mol / L. Preferably, the concentration of cobalt nitrate is 0.196 mol / L.
[0011] In the above scheme: in step 1), the concentration of urea is 0.08-0.1 mol / L. Preferably, the concentration of urea is 0.98 mol / L. Preferably, the concentration of ammonium chloride is 0.27 mol / L.
[0012] In the above scheme: Step 2) the temperature of the hydrothermal reaction is 120°C and the reaction time is 6h.
[0013] In the above scheme: in step 4), the concentration of the indium chloride solution is 20 mM, and the reaction time is 1-16 h.
[0014] In the above scheme: in step 4), the stirring speed is 100-200 rpm.
[0015] The indium-doped cobalt tetroxide catalyst prepared by the preparation method of the indium-doped cobalt tetroxide catalyst.
[0016] The indium-doped cobalt tetroxide catalyst is used in the electrocatalytic reduction of nitrite in water to prepare ammonia. The prepared indium-doped cobalt tetroxide catalyst supported by nickel foam is used as a working electrode.
[0017] Indium (In) is a late transition metal with high electronegativity and large atomic radius. Its doping induces Co3 O 4 Lattice distortion and electron redistribution reconstruct the charge density of Co active sites, thereby optimizing *NO 2 - adsorption configuration and weaken the tendency of N─N bond formation.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] (1) In-Co provided by the present invention 3 O 4 Can be used for electrochemical reduction of NO 2 - NH 3 , no precious metal loading, low cost.
[0020] (2) The preparation method provided by the present invention has low equipment requirements, is simple to operate, and is easy to repeat.
[0021] (3) Revealing In-doped Co 3 O 4 In electrocatalytic NO 2 - Advantages in reduction, improving ammonia yield and Faraday efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 In-Co prepared with different doping time 3 O 4 SEM comparison images.
[0023] Figure 2 In-Co with different doping time 3 O 4 Comparison of electrochemical performance of electrode systems
[0024] Figure 3 In-Co prepared in the present invention 3 O 4 Diagram of nitrite nitrogen removal and ammonia production by electrocatalytic reduction of nitrite.
[0025] Figure 4 For the present invention, In-Co 3 O 4 The Faraday efficiency and ammonia yield of electrocatalytic reduction of nitrite to produce ammonia. The Faraday efficiency can reach 98%. DETAILED DESCRIPTION
[0026] The present invention is further described below in conjunction with the accompanying drawings and embodiments.
[0027] Example 1
[0028] Dissolve 2.0 g of cobalt nitrate hexahydrate, 2.06 g of urea, and 0.506 g of ammonium chloride in 35 mL of deionized water, stir for 30 min, and obtain a red clear solution. Transfer the solution to a 2*4 cm 2 The nickel foam was placed in a 50 mL reactor and heated in an oven at 120 °C for 6 h. The nickel foam was washed with deionized water and ethanol and dried in a vacuum oven at 50 °C for 1 h.
[0029] Cut 4 pieces of 2*1.5 cm 2 The nickel foam loaded with cobalt tetroxide was immersed in 10 mL 20 mM InCl 3 The solution was reacted at 100-200 rpm for 1 h, 4 h, 8 h, and 16 h, respectively, and then taken out and dried in a vacuum drying oven at 40° C. for 1.5 h to obtain an indium-doped cobalt tetroxide catalyst supported on nickel foam.
[0030] The catalyst prepared in the above example was used as the working electrode, Ir-Ru / Ti as the counter electrode, and Ag / AgCl as the reference electrode. 100 mL of 50 mg-N / L nitrite solution was prepared using sodium nitrite, 0.5M PBS was added to increase the conductivity of the solution and maintain the pH of the electrolyte, the linear polarization curve was tested in the potential range of 0 to -1.4 V, and the constant potential reduction experiment of nitrite was carried out at a potential of -0.8 V for 2 h. 2.0 mL of sample was taken out for testing every 20 min, and the performance of indium-doped cobalt tetroxide electrocatalytic reduction of nitrite to produce ammonia was calculated at different reaction times, and compared with the performance of undoped catalyst (0 h). The results are shown in Figure 1-4 As shown, from Figure 1 It can be seen that the undoped Co 3 O 4 A regular nanorod array structure is formed on the nickel foam substrate. As the In doping time increases, the In content in the material gradually increases, and the surface morphology of the nanorods changes significantly. The initial smooth surface gradually transforms into a rough structure, accompanied by the formation of secondary nanostructures, indicating that the doping process has an important regulatory effect on the physicochemical properties of the material.
[0031] Figure 2 a is a linear sweep voltammetry test graph. It can be seen from the figure that a moderate doping time can significantly improve the cathode current response of the material, and the current density is significantly improved after doping with indium. Among them, the 1-hour doping sample showed the best catalytic activity. The comparative experiment further revealed ( Figure 2 b-Indium doping reaction time 1h), In doping significantly enhanced the Co 3 O 4 The electrochemical activity of NO 2 -After that, the material current response showed an order of magnitude increase, which clearly confirmed that In doping can effectively improve Co 3 O 4 Electrocatalytic performance for nitrite reduction reaction.
[0032] Figure 3 and Figure 4 The test graph of the sample doped for 1 hour shows that the indium-doped cobalt tetroxide catalyst supported by the nickel foam provided by the present invention can achieve efficient nitrite removal and ammonia production. In the same test time, indium doping showed a higher nitrite removal rate and ammonia production rate.
[0033] Figure 4 This is the Faradaic efficiency and ammonia yield of the electrocatalytic reduction of nitrite to ammonia over indium-doped cobalt tetroxide catalyst supported on nickel foam. 3 O 4 Compared with the conventional method, the Faraday efficiency of ammonia production is increased by 24%, and the Faraday efficiency can reach 98%. The ammonia production rate is increased by 1 times, indicating that the In-Co 3 O 4 The catalyst showed good performance in producing ammonia from nitrite.
[0034] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing an indium-doped cobalt oxide catalyst, characterized in that: Prepared as follows: 1) Dissolve cobalt nitrate, urea and ammonium chloride in deionized water and stir to obtain a clear reaction solution without precipitation; 2) transferring the reaction solution to a reaction vessel containing nickel foam, and performing a hydrothermal reaction to obtain nickel foam loaded with the sample; 3) Washing the nickel foam loaded with the sample after the reaction with ethanol and water, and drying; 4) Soaking the dried nickel foam loaded with the sample in an indium chloride solution, stirring for reaction, and vacuum drying to obtain indium-doped cobalt tetroxide.
2. The method for preparing the indium-doped cobalt tetroxide catalyst according to claim 1, characterized in that: In step 1), the concentration of cobalt nitrate is 0.15-0.20 mol / L.
3. The method for preparing the indium-doped cobalt tetroxide catalyst according to claim 2, characterized in that: In step 1), the concentration of urea is 0.08-0.1 mol / L.
4. The method for preparing the indium-doped cobalt tetroxide catalyst according to claim 3, characterized in that: In step 1), the concentration of ammonium chloride is 0.2-0.3 mol / L.
5. The method for preparing the indium-doped cobalt tetroxide catalyst according to any one of claims 1 to 4, characterized in that: Step 2) The temperature of the hydrothermal reaction is 120°C and the reaction time is 6h.
6. The method for preparing the indium-doped cobalt tetroxide catalyst according to claim 5, characterized in that: In step 4), the concentration of the indium chloride solution is 20 mM, and the reaction time is 1-16 h.
7. The method for preparing the indium-doped cobalt tetroxide catalyst according to claim 6, characterized in that: In step 4), the stirring speed is 100-200 rpm.
8. An indium-doped cobalt tetroxide catalyst prepared by the method for preparing an indium-doped cobalt tetroxide catalyst according to any one of claims 1 to 7.
9. Use of the indium-doped cobalt oxide catalyst according to claim 8 in the electrocatalytic reduction of nitrite in water to produce ammonia.