Ni-doped Co3O4 bimetallic spinel material as well as preparation method and application thereof
By using Ni-doped Co3O4 bimetallic spinel material, the problem of slow proton supply in catalysts under alkaline conditions was solved, achieving efficient nitrate reduction to ammonia production with excellent cycle stability and Faraday efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANCHANG HANGKONG UNIVERSITY
- Filing Date
- 2026-02-11
- Publication Date
- 2026-04-21
AI Technical Summary
Existing catalysts exhibit slow proton supply under alkaline conditions, resulting in limited efficiency and selectivity in the conversion of nitrates to ammonia, and failing to effectively address the problem of high energy barriers for water molecule dissociation.
By using Ni-doped Co3O4 bimetallic spinel material, nickel ions replace cobalt ions, inducing the electronic structure to transition from a low-spin state to a medium-spin state. Combined with a three-dimensional conductive substrate of nickel foam, an integrated electrode is constructed to optimize electron transport and proton generation.
It achieves a Faraday efficiency of up to 98.26% at low overpotentials, excellent cycle stability, and effectively suppresses side reactions, providing an efficient and sustainable electrocatalytic nitrate reduction to ammonia production scheme.
Smart Images
Figure CN121896673A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of electrocatalysts and electrochemical environmental remediation technology, and in particular to a Ni-doped Co3O4 bimetallic spinel material, its preparation method, and its application. Background Technology
[0002] With the acceleration of industrialization, nitrate pollution in water bodies has become increasingly serious, posing a significant threat to ecosystems and human health. Alkaline electrocatalytic reduction (NO3RR) can directly reduce NO3-... - Converting ammonia (NH3) into high-value ammonia presents a promising path for both pollution control and resource utilization, making it a highly attractive option. This reaction involves a multi-step proton-coupled electron transfer process, and its reaction kinetics in an alkaline environment are highly dependent on the catalyst dissociating water molecules to donate protons (H+). + However, most current catalysts suffer from slow proton supply under alkaline conditions, severely limiting the production of NO3. - Conversion efficiency and selectivity to NH3.
[0003] Currently, strategies to improve the performance of alkaline NO3RR mainly focus on constructing dual active sites to separately activate reactants and water dissociation, or on optimizing the proton transport environment by controlling the hydrophilicity of the catalyst surface and the interfacial ionic layer. While these methods alleviate proton shortages to some extent, they mostly focus on proton transport rather than generation, and fail to fundamentally solve the high energy barrier problem of the initial step of water molecule dissociation. Summary of the Invention
[0004] The purpose of this invention is to provide a Ni-doped Co3O4 bimetallic spinel material, its preparation method, and its applications, by introducing nickel ions (Ni... 2+ Selective doping to replace cobalt ions at the octahedral sites in spinel Co3O4 (Co 3+ This process induces an electronic structure transition from a low-spin to a medium-spin state, and an integrated electrode is constructed using a three-dimensional conductive substrate of nickel foam. This synergistically optimizes electron transport and proton generation efficiency, thereby fundamentally solving the core problems of high water molecule dissociation energy barrier and slow proton supply in alkaline nitrate reduction reaction. This provides an innovative and practical solution for efficient and sustainable electrocatalytic nitrate reduction to ammonia production.
[0005] To achieve the above objectives, the present invention provides a method for preparing Ni-doped Co3O4 bimetallic spinel material, comprising the following steps: S1. Mix NiCl2·4H2O, Co(NO3)2·6H2O, CO(NH2)2, NH4F, ethanol, and water, and stir to obtain a mixed solution; S2. The nickel foam is placed in the mixed solution for hydrothermal reaction, washed, dried, and annealed in air to obtain Ni-doped Co3O4 bimetallic spinel material on the nickel foam, denoted as Ni. 0.4 Co 2.6 O4.
[0006] Preferably, in S1, the mass-to-volume ratio of NiCl2·4H2O, Co(NO3)2·6H2O, CO(NH2)2, NH4F, water, and ethanol is 80-100mg:700-800mg:150-200mg:20-40mg:40-60mL:10-20mL, and the stirring time is 8-15min.
[0007] Preferably, in S2, the size of the nickel foam is 1cm × 1-3cm.
[0008] Preferably, in S2, the hydrothermal reaction temperature is 100-150℃ and the hydrothermal reaction time is 8-12h.
[0009] Preferably, in step S2, the drying temperature is 40-80℃ and the drying time is 4-8h.
[0010] Preferably, in S2, the annealing temperature is 200-500℃ and the annealing time is 1-3h.
[0011] The present invention also provides a Ni-doped Co3O4 bimetallic spinel material, which is prepared by the above preparation method.
[0012] This invention also provides an application of Ni-doped Co3O4 bimetallic spinel material, in which the Ni-doped Co3O4 bimetallic spinel material prepared by the above preparation method is used for electrocatalytic nitrate reduction reaction to synthesize ammonia.
[0013] This invention aims to address the issue of proton (H+) concentration in the alkaline nitrate reduction reaction (NO3RR) by introducing nickel (Ni) into spinel Co3O4, thereby resolving the problem at the atomic and electronic levels. + The fundamental problem of insufficient supply lies in Ni. 2+ Selective substitution of Co in octahedral sites of the Co3O4 lattice 3+ The resulting lattice distortion and electron redistribution significantly reduced the Co content at this site. 3+ The crystal field splitting energy induces a transition in its electronic configuration from a low-spin to a medium-spin state. This spin-state transition is key to improving catalytic performance: Co in the medium-spin state... 3+ Its eg orbital (d_z 2 d_x 2 -y 2The catalyst possesses unpaired electrons, which exhibit stronger spatial orientation and reactivity. During electrocatalysis, these unpaired eg electrons undergo strong orbital hybridization with water molecules (H₂O) adsorbed at the active site, and through a significant "metal-ligand anti-donation" effect, feed electrons back into the OH σ antibonding orbitals of the H₂O molecule. This process directly and effectively weakens the OH bonds of the water molecule, thereby significantly lowering the reaction energy barrier of the surface water dissociation step. Thus, the catalyst can efficiently and continuously dissociate water molecules under alkaline conditions, generating abundant surface-adsorbed hydrogen species, which are crucial for NO₃⁻ production. - The stepwise hydrogenation reduction provides NH3 with a sufficient and rapid proton source, fundamentally overcoming the limitation of reaction kinetics caused by the lack of protons in alkaline media.
[0014] Therefore, the present invention, employing the aforementioned Ni-doped Co3O4 bimetallic spinel material, its preparation method, and its application, has the following beneficial effects: (1) This invention introduces nickel ions (Ni 2+ Selective doping to replace cobalt ions at the octahedral sites in spinel Co3O4 (Co 3+ This process induces an electronic structure transition from a low-spin to a medium-spin state, and an integrated electrode is constructed using a three-dimensional conductive substrate of nickel foam. This synergistically optimizes electron transport and proton generation efficiency, fundamentally solving the core problems of high water molecule dissociation energy barrier and slow proton supply in alkaline nitrate reduction reaction. Ultimately, it achieves a Faraday efficiency of up to 98.26% at low overpotential (-0.4V vs. RHE), excellent cycling stability, and effective suppression of side reactions, providing an innovative and practical solution for efficient and sustainable electrocatalytic nitrate reduction to ammonia production.
[0015] (2) This invention, through a "spin-state engineering" strategy, fundamentally enhances the catalyst's ability to generate native protons in alkaline media, and nickel ions (Ni 2+ Doping-induced generation of medium-spin cobalt ions (Co) 3+ The active sites, through enhanced orbital hybridization, efficiently dissociate water molecules, providing a sufficient and rapid proton source for nitrate reduction. This mechanism fundamentally solves the problem of slow proton supply in the nitrate reduction reaction. Simultaneously, metallic nickel (nickel foam substrate), as a three-dimensional conductive framework, ensures high-speed electron transport to these highly active sites. The synergistic effect of both allows this catalyst to exhibit ammonia yields far exceeding those of existing catalysts and near-limiting Faraday efficiency without relying on external proton sources or complex interface modifications.
[0016] (3) In this invention, the spin state sites ensure a continuous and rapid supply of protons, and nitrate ions (NO3) -The hydrogenation-reduction reaction to produce ammonia (NH3) is kinetically dominant. This intrinsic high selectivity brought about by nickel ion doping, combined with the excellent conductivity provided by the nickel foam substrate, effectively suppresses the occurrence of side reactions such as the competitive hydrogen evolution reaction (HER).
[0017] (4) This invention directly grows active materials on nickel foam using a hydrothermal method, forming an integrated electrode structure. The metallic nickel substrate not only provides mechanical support, but its stable three-dimensional structure also prevents the active nanowires from detaching and aggregating during the reaction process. The doping of nickel ions into the spinel lattice also enhances the stability of the material itself. This dual stabilizing effect from the macroscopic structure to the microscopic lattice enables the catalyst to maintain its activity for a long time, demonstrating good potential for practical applications.
[0018] (5) This invention combines spin state engineering with substrate engineering, and directly optimizes key elementary reaction steps by regulating the intrinsic spin state of active sites. This strategy provides an important and universal approach to solving other electrocatalytic reactions involving small molecule activation.
[0019] 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
[0020] Figure 1 This is a scanning electron microscope image of the Ni-doped Co3O4 bimetallic spinel material prepared in Example 1 of this invention; Figure 2 These are magnetic characterization diagrams of the Ni-doped Co3O4 bimetallic spinel material prepared in Example 1 of this invention and the Co3O4 in Comparative Example 1. Figure 3 These are Raman characterization images of the Ni-doped Co3O4 bimetallic spinel material prepared in Example 1 of this invention and the Co3O4 in Comparative Example 1. Figure 4 These are XPS characterization images of the Ni-doped Co3O4 bimetallic spinel material prepared in Example 1 of this invention and the Co3O4 in Comparative Example 1. Figure 5 This is an application example 1 of the present invention, Ni. 0.4 Co 2.6 Comparison of the Faradaic efficiency (FE) of O4 in the electrocatalytic nitrate reduction reaction in 1M KOH and 0.1M KNO3 electrolytes; Figure 6 Example 1 of the application of the present invention Ni 0.4 Co 2.6 Cyclic performance graph of O4 after 10 cycles at a voltage of -0.4V. Detailed Implementation
[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.
[0022] 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.
[0023] In this invention, unless otherwise specified, the test materials and instruments are all conventional test materials in the field and can be purchased through commercial channels.
[0024] Example 1 A method for preparing Ni-doped Co3O4 bimetallic spinel material includes the following steps: S1. Dissolve 94.8 mg NiCl2·4H2O, 758.6 mg Co(NO3)2·6H2O, 180 mg CO(NH2)2 and 37 mg NH4F in a beaker containing 15 mL anhydrous ethanol and 50 mL deionized water, and stir for 10 min to form a homogeneous mixed solution. S2. Place a 1cm × 2cm piece of nickel foam into the mixed solution, transfer it to an autoclave, and perform a hydrothermal reaction at 120℃ for 10 hours. After the reaction, allow the autoclave to cool naturally to room temperature, remove the nickel foam, and sonicate it in deionized water for 1 minute to remove loose, adhered powder. Then, dry the nickel foam in an oven at 60℃ for 6 hours, and anneal it in air at 350℃ for 2 hours to obtain Ni-doped Co3O4 bimetallic spinel material on the nickel foam, denoted as Ni. 0.4 Co 2.6 O4.
[0025] Example 2 A method for preparing Ni-doped Co3O4 bimetallic spinel material includes the following steps: S1. Dissolve 100 mg NiCl2·4H2O, 795 mg Co(NO3)2·6H2O, 180 mg CO(NH2)2 and 37 mg NH4F in a beaker containing 20 mL anhydrous ethanol and 40 mL deionized water, and stir for 10 min to form a homogeneous mixed solution. S2. Place a 1cm × 2cm piece of nickel foam into the mixed solution, transfer it to an autoclave, and perform a hydrothermal reaction at 150℃ for 8 hours. After the reaction, allow the autoclave to cool naturally to room temperature, remove the nickel foam, and sonicate it in deionized water for 1 minute to remove loose, adhered powder. Then, dry the nickel foam in an oven at 60℃ for 6 hours, and anneal it in air at 350℃ for 2 hours to obtain Ni-doped Co3O4 bimetallic spinel material on the nickel foam, denoted as Ni. 0.4 Co 2.6 O4.
[0026] Example 3 A method for preparing Ni-doped Co3O4 bimetallic spinel material includes the following steps: S1. Dissolve 87.4 mg NiCl2·4H2O, 700 mg Co(NO3)2·6H2O, 180 mg CO(NH2)2 and 37 mg NH4F in a beaker containing 10 mL anhydrous ethanol and 60 mL deionized water, and stir for 10 min to form a homogeneous mixed solution. S2. Place a 1cm × 2cm piece of nickel foam into the mixed solution, transfer it to an autoclave, and perform a hydrothermal reaction at 100℃ for 12 hours. After the reaction, allow the autoclave to cool naturally to room temperature, remove the nickel foam, and sonicate it in deionized water for 1 minute to remove loose, adhered powder. Then, dry the nickel foam in an oven at 60℃ for 6 hours, and anneal it in air at 350℃ for 2 hours to obtain Ni-doped Co3O4 bimetallic spinel material on the nickel foam, denoted as Ni. 0.4 Co 2.6 O4.
[0027] Comparative Example 1 Commercially available Co3O4.
[0028] Application Example 1 Take the Ni prepared in Example 1 0.4 Co 2.6 Using O4 as the cathode of the working electrode, a 1cm×1cm Pt sheet as the counter electrode, and Hg / HgO as the reference electrode, an electrochemical reaction was carried out in an electrolyte of 1M KOH and 0.1M KNO3.
[0029] The Ni prepared in Example 1 was examined using a scanning electron microscope (SEM). 0.4 Co 2.6 O4 was used for characterization, and the results are as follows: Figure 1 As shown. From Figure 1 It can be seen from this that Ni 0.4 Co 2.6 O4 exhibits a densely packed nanowire structure.
[0030] Ni prepared in Example 1 0.4 Co 2.6 Magnetic properties (MH) of O4 and Co3O4 (Comparative Example 1) were measured, and the results are as follows: Figure 2 As shown. From Figure 2 It can be seen from this that Ni 0.4 Co 2.6 The saturation magnetization of O4 is higher than that of Co3O4, which indicates that Ni doping leads to the generation of more spin electrons, thereby transitioning the magnetic structure from a low-spin state to a medium-spin state.
[0031] Ni prepared in Example 1 0.4 Co 2.6 O4 and Co3O4 (Comparative Example 1) were characterized by Raman and XPS, and the results are as follows: Figure 3-4 As shown, where Figure 3 Raman characterization diagram, Figure 4 XPS characterization plot. From Figure 3 and Figure 4 It can be seen from this that Ni 0.4 Co 2.6 Nickel O4 is doped at cobalt tetroxide octahedral sites.
[0032] Applying the electrochemical reaction of Example 1, potentiostatic electrolysis was performed for 1 hour at different potentials in 50 mL of 1 M KOH and 0.1 M KNO3 electrolyte. All potentials were determined according to the following formula: E(vs.RHE)=E(vs.Ag / AgCl)+0.197V+0.059×pH; This is converted to the potential relative to the reversible hydrogen electrode (RHE). The cathode electrolyte was filtered through a 0.45 μm polytetrafluoroethylene (PTEF) membrane filter to obtain the reaction filtrate. The concentration of ammonia in the product was determined using a UV spectrophotometer. 2 mL of the diluted electrolyte from the electrochemical reaction was mixed with 2 mL of 1.0 M NaOH solution containing 5 wt% salicylic acid and 5 wt% sodium citrate. Then, 1 mL of 0.05 M NaClO solution and 0.2 mL (1 wt%) sodium nitroferricyanide solution were added, and the mixture was thoroughly mixed to ensure homogeneity. The reaction was carried out in the dark for 2 hours. Subsequently, the absorbance of the solution at 662 nm was measured using a UV spectrophotometer, and the concentration of NH4+ in the electrolyte was calculated. + The Faraday efficiency (FE) is as follows: Figure 5 As shown. From Figure 5 As can be seen from this, at a voltage of -0.4V vs. RHE, Ni 0.4 Co 2.6 Both O4 and Co3O4 exhibited the best performance, while Ni... 0.4 Co 2.6 The FE of O4 is 98.26%, while that of Co3O4 is 89.15%.
[0033] Stability is another important indicator for evaluating the practical application of electrocatalysts. Application Example 1 underwent 10 cycle tests at a voltage of -0.4V, and the results are as follows: Figure 6 As shown, from Figure 6 It can be seen from this that Ni 0.4 Co 2.6When O4 is used as the cathode material, the ammonia yield and Faraday efficiency remain almost unchanged in the electrocatalytic reduction of nitrate to ammonia, proving that the Ni-doped CO3O4 bimetallic spinel material prepared in Example 1 has excellent stability.
[0034] Therefore, this invention employs the aforementioned Ni-doped Co3O4 bimetallic spinel material, its preparation method, and its application, by introducing nickel ions (Ni... 2+ Selective doping to replace cobalt ions at the octahedral sites in spinel Co3O4 (Co 3+ This process induces an electronic structure transition from a low-spin to a medium-spin state, and an integrated electrode is constructed using a three-dimensional conductive substrate of nickel foam. This synergistically optimizes electron transport and proton generation efficiency, thereby fundamentally solving the core problems of high water molecule dissociation energy barrier and slow proton supply in alkaline nitrate reduction reaction. This provides an innovative and practical solution for efficient and sustainable electrocatalytic nitrate reduction to ammonia production.
[0035] 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 Ni-doped Co3O4 bimetallic spinel material, characterized in that: Includes the following steps: S1. Mix NiCl2·4H2O, Co(NO3)2·6H2O, CO(NH2)2, NH4F, ethanol, and water, and stir to obtain a mixed solution; S2. The nickel foam is placed in the mixed solution for hydrothermal reaction, washed, dried, and annealed in air to obtain Ni-doped Co3O4 bimetallic spinel material on the nickel foam, denoted as Ni. 0.4 Co 2.6 O4.
2. The method for preparing a Ni-doped Co3O4 bimetallic spinel material according to claim 1, characterized in that: In S1, the mass-to-volume ratio of NiCl2·4H2O, Co(NO3)2·6H2O, CO(NH2)2, NH4F, water, and ethanol is 80-100mg:700-800mg:150-200mg:20-40mg:40-60mL:10-20mL, and the stirring time is 8-15min.
3. The method for preparing a Ni-doped Co3O4 bimetallic spinel material according to claim 1, characterized in that: In S2, the size of the nickel foam is 1cm × 1-3cm.
4. The method for preparing a Ni-doped Co3O4 bimetallic spinel material according to claim 1, characterized in that: In S2, the hydrothermal reaction temperature is 100-150℃, and the hydrothermal reaction time is 8-12h.
5. The method for preparing a Ni-doped Co3O4 bimetallic spinel material according to claim 1, characterized in that: In S2, the drying temperature is 40-80℃ and the drying time is 4-8h.
6. The method for preparing a Ni-doped Co3O4 bimetallic spinel material according to claim 1, characterized in that: In S2, the annealing temperature is 200-500℃ and the annealing time is 1-3h.
7. A Ni-doped Co3O4 bimetallic spinel material, characterized in that: It is prepared by the method for preparing Ni-doped Co3O4 bimetallic spinel material according to any one of claims 1-6.
8. An application of a Ni-doped Co3O4 bimetallic spinel material, characterized in that: The Ni-doped Co3O4 bimetallic spinel material prepared by the method described in any one of claims 1-6 is used for electrocatalytic nitrate reduction reaction to synthesize ammonia.