Nickel ferrite catalytic material as well as preparation method and application of nickel ferrite catalytic material with adjustable crystal face
By controlling the crystal structure of nickel ferrite using magnetron sputtering technology, the problems of low conductivity and insufficient exposure of active sites in existing nickel ferrite catalysts have been solved, achieving a highly efficient and stable electrolysis reaction for hydrogen production and oxygen evolution.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-27
- Publication Date
- 2026-03-31
AI Technical Summary
Existing nickel ferrite catalysts suffer from low intrinsic conductivity, insufficient exposure of active sites, and difficulty in controlling crystal structure, which limits their catalytic performance in oxide reactions.
By employing magnetron sputtering technology, the electronic structure and surface adsorption/desorption energy barrier of nickel ferrite are influenced by the change in target-substrate distance, thereby forming a strong bond with the conductive substrate and optimizing the electronic structure and active site exposure of the catalyst.
It significantly improves catalytic activity and stability, reduces charge transport impedance and reaction energy barrier, provides more active sites, and improves the efficiency and long-term stability of the hydrogen production and oxygen evolution reaction by water electrolysis.
Smart Images
Figure CN121759994A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrocatalysis technology, specifically relating to a catalytic electrode material for hydrogen production by water electrolysis, and particularly to a nickel ferrite catalytic material and its preparation method and application with tunable crystal facets. Background Technology
[0002] Energy crisis and environmental pollution are major challenges facing the world today, making the development of clean and sustainable energy conversion and storage technologies crucial. Hydrogen energy, as a high-energy-density, zero-carbon-emission secondary energy source, is considered one of the ideal alternative energy sources. Electrolysis of water to produce hydrogen is currently the most promising technology for obtaining high-purity hydrogen. This process involves two half-reactions: the hydrogen evolution reaction at the cathode and the oxygen evolution reaction (OER) at the anode. The OER is a complex process involving four electron transfers, and its slow kinetics and high overpotential become bottlenecks restricting the energy conversion efficiency of the entire water electrolyzer. Currently, the most advanced commercially available OER electrocatalysts rely on noble metal-based materials, but their high cost and scarcity severely limit their large-scale industrial application. Therefore, developing efficient, stable, and low-cost non-noble metal OER electrocatalysts has become a research hotspot in this field.
[0003] Among numerous non-precious metal candidate materials, spinel-structured nickel ferrite has attracted widespread attention due to its abundant sources, low cost, high theoretical catalytic activity, and good chemical stability. However, nickel ferrite synthesized by conventional methods still suffers from some inherent defects, severely limiting further improvements in its OER performance. These problems mainly include:
[0004] (1) The intrinsic conductivity is low, resulting in a slow charge transport rate, which limits the current density in the catalytic process; (2) Insufficient exposure of active sites, with most active sites located in the bulk phase of the material, which cannot participate in surface electrochemical reactions; (3) The crystal structure is stable and difficult to control. Traditional synthesis methods have limited ability to precisely control the crystal structure of materials and it is difficult to optimize their electronic structure.
[0005] In existing technologies, strategies such as nanostructuring, constructing porous structures, or compositing with conductive matrices are commonly used to improve the catalytic performance of nickel ferrite. However, these methods mainly focus on the control of microstructure, and effective means to precisely and controllably regulate the most fundamental crystal structure of the material (such as crystal facet control, lattice distortion, oxygen vacancy concentration, coordination environment of metal cations, and valence state distribution) are still lacking. Summary of the Invention
[0006] To address the above-mentioned problems, this invention provides a nickel ferrite catalytic material, its preparation method with tunable crystal facets, and its applications.
[0007] The technical solution of the present invention is as follows: First, this invention provides a method for preparing a nickel ferrite catalyst with tunable crystal facets, comprising the following steps: The conductive substrate is fixed in the cavity of the magnetron sputtering coating machine, ensuring that the substrate and the target surface are parallel, and the target-substrate distance is set to 2~20cm. The cavity of the magnetron sputtering coating machine is pre-evacuated, and after inert gas is introduced, glow discharge cleaning is performed. Nickel ferrite was used as the target material, and a nickel ferrite catalytic layer was deposited in situ on the surface of a conductive substrate by physical vapor deposition to obtain a nickel ferrite catalytic material.
[0008] This invention employs magnetron sputtering technology to successfully control the crystal structure of nickel ferrite by changing the target-substrate distance. Subtle changes in the crystal structure can significantly affect the electronic structure and surface adsorption / desorption energy barrier of the material, thereby simultaneously overcoming the three major bottlenecks faced by nickel ferrite as an OER catalyst: low activity, poor stability, and slow kinetics. This provides key material and technical support for the commercial application of anion-exchange membrane (AEM) electrolyzers.
[0009] Preferably, the conductive substrate is one or more of nickel mesh, nickel foil, nickel foam, copper mesh, copper foil, copper foam, or carbon cloth; more preferably, the conductive substrate is nickel foam.
[0010] Preferably, the target-substrate distance is 5~15cm.
[0011] Preferably, the pre-vacuuming of the magnetron sputtering coating machine cavity includes: pre-vacuuming to a background vacuum level better than 3×10⁻⁶. -3 Pa.
[0012] Preferably, after introducing inert gas, the chamber pressure is adjusted to 0.2~5 Pa; more preferably, the inert gas is argon (Ar).
[0013] Preferably, the glow discharge cleaning time is 5 to 30 minutes.
[0014] Preferably, the sputtering current density for in-situ deposition of the nickel ferrite catalyst layer on the surface of the conductive substrate using physical vapor deposition is 1~10 mA / cm². 2 The sputtering time is 0.5~10h; more preferably, the physical vapor deposition is DC magnetron sputtering.
[0015] In order to remove oil, oxides and adsorbed impurities from the surface of the conductive substrate, expose a clean and active metal surface, provide good adhesion sites for subsequent catalytic layer deposition, and avoid impurities from affecting the film adhesion and electrocatalytic performance, preferably, the conductive substrate is ultrasonically cleaned before fixing it in the cavity of the magnetron sputtering coating machine; more preferably, the ultrasonic cleaning includes: ultrasonically cleaning the conductive substrate with anhydrous ethanol for 10 minutes in sequence.
[0016] Secondly, the present invention provides a nickel ferrite catalyst material obtained by the above-described preparation method with tunable crystal faces.
[0017] Finally, this invention provides an application of the above-mentioned nickel ferrite catalyst in the hydrogen production and oxygen evolution reaction of water electrolysis.
[0018] The beneficial effects of this invention are as follows: (1) Significantly enhanced catalytic activity: By controlling the crystal planes of nickel ferrite, its electronic structure was effectively optimized, reducing charge transport impedance and the OER reaction energy barrier. Experiments show that the nickel ferrite catalytic material prepared in this invention exhibits significantly improved catalytic activity at 10 mA / cm². 2 and 100mA / cm 2 The overpotential at current density can reach 288mV and 325mV, which is superior to most reported non-precious metal catalysts.
[0019] (2) Excellent intrinsic and mechanical stability: Thanks to magnetron sputtering technology, the catalyst film forms a strong bond with the conductive substrate (such as nickel foam), avoiding the problem of catalyst detachment due to bubble erosion in traditional coating methods. At 1 A / cm 2 It can operate stably for more than 12 hours at industrial current densities, and the electrode exhibits extremely low activity decay, demonstrating excellent electrochemical stability. This integrated binder-free electrode structure ensures that the active sites can work continuously and stably under harsh OER reaction conditions. Attached Figure Description
[0020] Figure 1 XRD patterns of NiFe2O4-4 and NiFe2O4-8; Figure 2 The current-voltage characteristic curves and overpotential test results of NF, NiFe2O4-4, NiFe2O4-8, NiFe2O4-12 and NiFe2O4-20 are shown. Figure 3 The fitting results for the double-layer capacitance of NF, NiFe2O4-4, NiFe2O4-8, NiFe2O4-12, and NiFe2O4-20 in the non-Radida region are shown. Figure 4The results show the stability test results of NiFe2O4-4 and NiFe2O4-8 at industrial current densities.
[0021] Figure label: Figure 2 In the figure, (a) is the current-voltage characteristic curve; (b) is the overpotential test result. Detailed Implementation
[0022] The specific embodiments listed in this invention are merely examples, and the invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of this invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of this invention should be covered within its scope. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are commercially available conventional products. To better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.
[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Unless otherwise specified, all units used in this specification are International Standard Units (SI), and all numerical values and ranges appearing in this invention should be understood to include systematic errors unavoidable in industrial production.
[0024] In this invention, the target-to-substrate distance (TS distance) is the vertical straight-line distance between the "target surface" and the "substrate surface".
[0025] All electrochemical data in the examples were measured using a Shanghai Chenhua CHI760E electrochemical workstation. All related tests employed a standard three-electrode system: the working electrode was a prepared nickel ferrite electrode with an effective area of 1 cm × 1 cm; the counter electrode was a carbon rod; and the reference electrode was a Hg / HgO electrode. All electrochemical tests were performed in a 1 mol / L KOH solution at room temperature.
[0026] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0027] I. Examples and Comparative Examples Example 1 This embodiment discloses a method for preparing a nickel ferrite (NiFe2O4) catalytic material with tunable crystal facets, comprising the following steps: S1. Pretreatment of conductive substrate Nickel Foam (NF): The conductive substrate of Nickel Foam is ultrasonically cleaned with anhydrous ethanol for 10 min to obtain clean and fully activated Nickel Foam. S2. Fix the clean and fully activated nickel foam obtained in S1 in the cavity of the magnetron sputtering coating machine, ensuring that the substrate is parallel to the target surface, and set the target-substrate distance to 20cm. S3. Pre-evacuate the magnetron sputtering coating machine cavity to a background vacuum level better than 3×10⁻⁶. -3 After Pa, Ar gas is introduced and the gas pressure is adjusted to 0.5 Pa for glow discharge cleaning for 20 min to further remove adsorbates on the surface of the nickel foam and activate the surface. S4. Using nickel ferrite as the target material, a nickel ferrite catalyst layer was deposited in situ on the surface of nickel foam by DC magnetron sputtering: the sputtering current density was controlled at 10 mA / cm². 2 The sputtering time was 2 hours, and the resulting sample was denoted as NiFe2O4-20.
[0028] Example 2 Except for adjusting the target-substrate distance from 20cm to 12cm, the rest was the same as in Example 1, and the resulting sample was denoted as NiFe2O4-12.
[0029] Example 3 Except for adjusting the target-substrate distance from 20cm to 8cm, the rest was the same as in Example 1, and the resulting sample was denoted as NiFe2O4-8.
[0030] Example 4 Except for adjusting the target-substrate distance from 20cm to 4cm, the rest was the same as in Example 1, and the resulting sample was denoted as NiFe2O4-4.
[0031] II. Performance Testing and Characterization Figure 1 The X-ray diffraction (XRD) patterns of NiFe2O4-4 and NiFe2O4-8 are shown. It can be seen that as the target-substrate distance decreases, the relative intensity of the diffraction peaks on the (400) crystal plane of the sample decreases. The relative intensity of the characteristic diffraction peaks on the (400) crystal plane of NiFe2O4-4 is significantly weaker than that on the (311) crystal plane, indicating a distinct preferred orientation. This is because the small target-substrate distance and the high energy of the magnetron sputtered particles promote the growth of the (311) crystal plane, thus forming a distinct preferred orientation. This also proves that controlling the target-substrate distance to regulate the crystal structure of nickel ferrite is feasible and effective.
[0032] Figure 2The current-voltage characteristic curves and overpotential test results for NF, NiFe2O4-4, NiFe2O4-8, NiFe2O4-12, and NiFe2O4-20 are presented. Figure 2 (b) It can be seen that NiF2O4-20, NiF2O4-12, NiF2O4-8, NiF2O4-4 and NF at 10 mA / cm 2 The overpotentials at current densities were 306 mV, 296 mV, 288 mV, 312 mV, and 371 mV, respectively; at 100 mA / cm², the overpotentials were... 2 The overpotentials at the current densities were 355mV, 345mV, 335mV, 361mV, and 482mV, respectively. Figure 2 (a) It can be seen that the OER performance of the NiF2O4 / NF composite catalytic electrode is far superior to that of pure nickel foam (NF), especially the NiF2O4-8 composite catalytic electrode at 10 mA / cm 2 and 100mA / cm 2 The overpotential at the current density was reduced by 83 mV and 147 mV compared to NF. Furthermore, as the target-substrate distance decreased, the overpotential of the NiFe2O4 / NF composite catalytic electrode showed a trend of first decreasing and then increasing. This may be related to the crystal structure of the material. Combined with XRD results, it was found that when the target-substrate distance was greater than or equal to 8 cm, the crystallinity of the material increased with the increase of the target-substrate distance. At this time, the crystal grew along (400), exposing more active sites and effectively improving the catalytic performance of the material. When the target-substrate distance decreased (4 μm), high-energy particles induced the growth of the (311) crystal plane, forming a significant preferred orientation in the nickel ferrite material, thereby leading to a decrease in catalytic performance.
[0033] Figure 3 The double-layer capacitance (Cdl) of NF, NiFe2O4-4, NiFe2O4-8, NiFe2O4-12, and NiFe2O4-20 in the non-Radidatic region is fitted. Another key parameter for evaluating OER performance—the electrochemical active surface area (ECSA)—is calculated using ECSA = Cdl / Cs, where Cs is the specific capacitance of the material, typically taken as 0.04 mF / cm². 2 .from Figure 3 It can be seen that the double-layer capacitances of the NiF2O4-20, NiF2O4-12, NiF2O4-8, and NiF2O4-4 samples are 4 mF / cm. 2 5.9mF / cm 2 6.8mF / cm 2 and 5.1mF / cm 2 It is far superior to NF's 1.3mF / cm 2Among them, NiF2O4-8 exhibited the best double-layer capacitance, meaning it had the largest electrochemical active area. Overall, the electrochemical active area of the samples showed a trend of first increasing and then decreasing as the target-substrate distance shortened. This is because when the target-substrate distance is shorter, the crystal structure of nickel ferrite changes, the intensity of the (400) crystal facet decreases, and the (311) crystal facet is exposed. The change in the crystal facet structure affects the electrochemical active area of the material. The above results further illustrate that nickel ferrite with the (400) crystal facet can provide a larger electrochemical active area for catalytic reactions and more catalytic active sites for OER reactions, thereby effectively improving catalytic efficiency.
[0034] Figure 4 The stability test results of NiFe2O4-4 and NiFe2O4-8 at industrial current densities are presented. The AEM electrolytic cell device consists of the prepared electrode (anode) and a 40% Pt / C electrode (cathode). Constant current testing was performed in a 1 mol / L electrolyte at 80℃. The results showed that the stability of NiF2O4-8 and NiF2O4-4 samples at 1 A / cm² was [not specified in the original text]. 2 The total water splitting voltages at the current densities were 1.8V and 1.85V, respectively, and after 12 hours of stability testing, the voltages were 1.81V and 1.87V, respectively, with voltage growth rates of approximately 0.8mV / h and 1.7mV / h. These results indicate that NiF₂O₄⁻⁸ with exposed (311) crystal faces not only exhibits higher catalytic activity but also superior long-term stability compared to NiF₂O₄⁻⁴ with exposed (400) crystal faces.
[0035] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.
Claims
1. A method for preparing a nickel ferrite catalyst with tunable crystal facets, characterized in that, Includes the following steps: The conductive substrate is fixed in the cavity of the magnetron sputtering coating machine, ensuring that the substrate and the target surface are parallel, and the target-substrate distance is set to 2~20cm. The cavity of the magnetron sputtering coating machine is pre-evacuated, and after inert gas is introduced, glow discharge cleaning is performed. Using nickel ferrite as the target material, a nickel ferrite catalytic layer is deposited in situ on the surface of the conductive substrate by physical vapor deposition to obtain a nickel ferrite catalytic material.
2. The method for preparing nickel ferrite catalyst with tunable crystal facets according to claim 1, characterized in that, The conductive substrate is one or more of nickel mesh, nickel foil, nickel foam, copper mesh, copper foil, copper foam, or carbon cloth.
3. The method for preparing nickel ferrite catalyst with tunable crystal facets according to claim 1, characterized in that, The target-base distance is 5~15cm.
4. The method for preparing nickel ferrite catalyst with tunable crystal facets according to claim 1, characterized in that, The "pre-vacuuming of the magnetron sputtering coating machine cavity" includes: pre-vacuuming to a background vacuum level better than 3×10⁻⁶. -3 Pa.
5. The method for preparing nickel ferrite catalyst with tunable crystal facets according to claim 1, characterized in that, After introducing inert gas, the chamber pressure is adjusted to 0.2~5 Pa.
6. The method for preparing nickel ferrite catalyst with tunable crystal facets according to claim 1, characterized in that, The glow discharge cleaning time is 5~30 minutes.
7. The method for preparing nickel ferrite catalyst with tunable crystal facets according to claim 1, characterized in that, The sputtering current density for "in-situ deposition of a nickel ferrite catalyst layer on the surface of the conductive substrate using physical vapor deposition" is 1~10 mA / cm². 2 The sputtering time is 0.5~10h.
8. The method for preparing nickel ferrite catalyst with tunable crystal facets according to claim 7, characterized in that, The physical vapor deposition is performed by DC magnetron sputtering.
9. A nickel ferrite catalyst prepared by a method for preparing a nickel ferrite catalyst with tunable crystal facets as described in any one of claims 1-8.
10. The application of the nickel ferrite catalyst as described in claim 9 in the hydrogen production and oxygen evolution reaction by water electrolysis.