A zirconium-iron bimetallic doped tricobalt tetraoxide material and a preparation method thereof

Abstract

This invention discloses a zirconium-iron bimetallic doped cobalt tetroxide material and its preparation method, wherein the atomic ratio of zirconium to iron in the material is 1~5:1, and Zr 4+ Co is occupied in spinel Co3O4 through lattice substitution. 3+ Dominant octahedral sites (Oh sites), Fe 3+ Occupy Co 2+ The dominant tetrahedral sites (Td sites) are present. The preparation method of the zirconium-iron bimetallic doped cobalt tetroxide electrocatalytic material includes: adding a cobalt source, a zirconium source, and an iron source to an organic solvent, mixing them uniformly, and then performing a molding process to obtain a precursor; the molding process is one of the following: hydrothermal method, solvothermal method, sol-gel method, coprecipitation method, spray drying granulation method, electrospinning method, freeze-drying method, or ball milling method; finally, the material is obtained after drying and calcination. This invention features a simple and streamlined preparation process with low equipment requirements, making it easy for industrial-scale production. The obtained transition metal oxide material does not require the addition of an additional conductive agent and can be directly used as a catalyst for electrocatalytic oxygen reduction reactions, exhibiting excellent electrochemical performance and demonstrating high selectivity and high yield in two-electron oxygen reduction tests.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, and more specifically, to highly efficient two-electron oxygen reduction (2e... - A zirconium-iron bimetallic doped cobalt tetroxide material for preparing hydrogen peroxide (H2O2) and its preparation method. Background Technology

[0002] Hydrogen peroxide (H2O2) is a green and environmentally friendly oxidant widely used in industrial bleaching, wastewater purification, medical disinfection, and many other fields. Currently, the mainstream industrial production process for H2O2 is the anthraquinone process, but this process has drawbacks such as high energy consumption, cumbersome procedures, and potential environmental pollution. The electrochemical two-electron oxygen reduction reaction (2e...) - -ORR can directly convert O2 and H2O into H2O2, and has outstanding advantages such as good environmental compatibility, simple operation and mild reaction conditions. It has become the preferred technical route for the sustainable preparation of H2O2.

[0003] Cobalt tetroxide (Co3O4), as a typical transition metal oxide, possesses significant advantages such as abundant reserves, low cost, and tunable electronic structure, showing broad application prospects in the field of electrocatalysis. This material has an inverse spinel crystal structure, where Co²⁺ occupies tetrahedral interstitial sites, and Co... 3+ Located at octahedral interstitial sites, the catalytic performance of these sites is directly related to their electronic structure and coordination environment. However, pure-phase Co3O4 is less effective in the two-electron oxygen reduction reaction (2e...). - When performing ORR (or similar reaction), it generally suffers from poor selectivity, insufficient catalytic activity, and weak stability. The root cause lies in the mismatch in adsorption strength for the key reaction intermediate *OOH, which easily induces the breaking of the OO bond, causing the reaction pathway to deviate from the 2e group. - The path then shifts to a four-electron path and generates H2O.

[0004] Elemental doping is a core strategy for regulating the catalytic performance of Co3O4, and bimetallic synergistic doping can overcome the limitations of single doping through "site regulation + electronic state reshaping". Zirconium (Zr) is advantageous due to its high ionic potential, stable electronic configuration, and affinity for Co. 3+ Matched ionic radii can precisely replace Co3O4 octahedral sites, regulating OOH adsorption strength and stabilizing active centers; the multivalent state characteristics of iron (Fe) (Fe²⁺↔Fe) 3+ It can optimize charge distribution and electron transport, forming a functional complement to Zr. The synergy between the two can precisely regulate the OOH adsorption-desorption balance and simultaneously enhance 2e... - ORR activity and selectivity.

[0005] Currently, research on Zr-Fe bimetallic co-doping modification of Co3O4 remains lacking, and key issues such as site occupancy and electronic coupling mechanisms remain unclear. Developing catalysts of this type that combine high selectivity, high activity, and stability could not only enrich the 2e- electron pool... - The ORR catalytic material system can further reduce the equipment cost of electrosynthesis of hydrogen peroxide, simplify the process, save energy, provide core support for the industrialization of the technology, and meet the needs of green chemical development. Summary of the Invention

[0006] The purpose of this invention is to provide a zirconium-iron bimetallic doped cobalt tetroxide material and its preparation method. Through synergistic modification with zirconium-iron bimetals, the electronic structure and surface properties of cobalt tetroxide are optimized, achieving high efficiency in 2e⁻ production. - -ORR catalytic performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing zirconium-iron bimetallic doped cobalt tetroxide material, the method comprising the following steps: Step S1: Dissolve the cobalt source, zirconium source and iron source in an organic solvent, mix them evenly to obtain a mixed solution; Step S2: The mixed solution obtained in step S1 is subjected to molding treatment to obtain the precursor; Step S3: After drying the precursor obtained in step S2, calcine it in a tube furnace to obtain zirconium iron bimetallic doped cobalt tetroxide material.

[0008] Furthermore, the stirring in step S1 is mechanical stirring, magnetic stirring, or ultrasonic stirring.

[0009] Further, the organic solvent in step S1 is ethylene glycol or dimethyl sulfoxide; the cobalt source is selected from at least one of cobalt nitrate and cobalt chloride; the zirconium source is selected from at least one of zirconium sulfate and zirconium nitrate; and the iron source is selected from at least one of ferric nitrate and ferric chloride.

[0010] Furthermore, the molding process described in step S2 is one of the following: hydrothermal method, solvothermal method, sol-gel method, coprecipitation method, spray drying granulation method, electrospinning method, freeze drying method, or ball milling method.

[0011] Furthermore, the molding process described in step S2 is a hydrothermal method, with the reaction conditions being a treatment at 160~200 ℃ for 6~10 h.

[0012] Further, the drying in step S3 is heating drying, vacuum drying or adsorption drying; the calcination temperature is 500~800 ℃, the calcination time is 3~6 h, the calcination atmosphere is air, nitrogen or argon, and the heating rate is 2~5 ℃ / min.

[0013] This invention discloses a zirconium-iron bimetallic doped cobalt tetroxide material, its preparation method, and its application, which have the following advantages and beneficial effects:

[0014] (1) Zr 4+ Fixed-site occupation of Co3O4 octahedral Co 3+ At the site, Fe element synergistically optimizes the d-band center of Co through valence state regulation. The synergistic effect of these two elements precisely regulates the adsorption strength of the *OOH intermediate, effectively inhibits the breaking of the OO bond, and significantly enhances the 2e- group. - -ORR selectivity; Zirconium-iron co-doping exposes more active sites and accelerates charge transfer, significantly improving catalytic activity.

[0015] (2) Zirconium and iron are abundant and cost-controllable. Compared with precious metal doping systems, they significantly reduce the preparation cost of catalysts, combining economy and practicality, and better meeting the cost requirements of industrial applications.

[0016] (3) The stable defect structure on the material surface and the synergistic interaction sites of zirconium and iron can suppress the loss of active components and valence distortion during the reaction process, improve the catalyst’s anti-interference ability in complex reaction environment, and further ensure long-term service stability.

[0017] (4) The raw materials used in the preparation process are green and low in toxicity, the reaction conditions are mild, and no harmful gases or difficult-to-treat wastes are generated, which is in line with the concept of green chemistry development and reduces the environmental governance costs in the industrial production process. Attached Figure Description

[0018] Figure 1 The image shows the XRD characterization results of the zirconium-iron bimetallic doped cobalt tetroxide material in Example 1 of the invention.

[0019] Figure 2 The image shows the Raman characterization results of the zirconium-iron bimetallic doped cobalt tetroxide material in Example 1 of the invention.

[0020] Figure 3 The current density curve of the ring disk of the zirconium-iron bimetallic doped cobalt tetroxide material in Embodiment 1 of the invention.

[0021] Figure 4 The electrochemical 2e-ORR selectivity curve of the zirconium-iron bimetallic doped cobalt tetroxide material in Example 1 of the invention.

[0022] Figure 5 The graph shows the H2O2 yield and Faraday efficiency in the zirconium-iron bimetallic doped cobalt tetroxide material of Example 1 of the invention.

[0023] Figure 6 The image shows the XRD characterization results of the iron-doped cobalt tetroxide material in Example 2 of the invention.

[0024] Figure 7 The image shows the Raman characterization results of the iron-doped cobalt tetroxide material in Example 2 of the invention.

[0025] Figure 8 The current density curve of the iron-doped cobalt tetroxide ring disk in Embodiment 2 of the invention.

[0026] Figure 9 The saturated current density curve of the iron-doped cobalt tetroxide material in the flow cell in Example 2 of the invention. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail and completely below with reference to specific embodiments. It should be understood that the embodiments described herein are only some exemplary implementations of the present invention and do not cover all embodiments of the present invention. All other corresponding embodiments obtained by those skilled in the art based on the embodiments disclosed in this invention without creative effort fall within the protection scope of this invention.

[0028] Example 1: This example describes a method for preparing a zirconium-iron bimetallic doped cobalt tetroxide material. The preparation steps include the following: Step 1: Cobalt nitrate hexahydrate, zirconium nitrate pentahydrate, and ferric nitrate nonahydrate are added to the organic solvent ethylene glycol and magnetically stirred for 0.5 h to form a homogeneous mixed solution; Step 2: The mixed solution from Step 1 is transferred to a hydrothermal reactor and kept at 180°C for 6 h. After cooling, it is filtered to obtain a precursor; Step 3: The precursor prepared above is vacuum dried at 80°C for 12 h and then calcined in a tube furnace at 800°C for 2 h in an air atmosphere to obtain the final product, zirconium-iron bimetallic doped cobalt tetroxide material.

[0029] The zirconium-iron bimetallic doped cobalt tetroxide material obtained in the embodiments of the present invention is characterized as follows: The XRD characterization results of the zirconium-iron bimetallic doped cobalt tetroxide material prepared in Example 1 of the present invention are as follows: Figure 1 As shown, it can be determined that the synthesized material is cobalt tetroxide doped with zirconium iron bimetallic, without any impurity peaks of zirconium oxide or iron oxide.

[0030] The Raman characterization results of the zirconium-iron bimetallic doped cobalt tetroxide material prepared in Example 1 of this invention are as follows: Figure 2 As shown, it can be determined that zirconium-iron bimetallic doping enters the cobalt tetroxide spinel lattice through cation substitution, introducing lattice defects.

[0031] The 2e-ORR performance test of the efficient production of zirconium iron bimetallic doped cobalt tetroxide material obtained in the embodiments of the present invention was performed as follows: 5 mg of the active material was placed in a mixture of anhydrous ethanol and Nafion solution, and sonicated for one hour. 5 μL of the mixture was then uniformly dropped onto a polished rotating ring electrode to obtain the working electrode. Using an Hg / HgO electrode as the reference electrode, a platinum sheet as the counter electrode, and 0.1 MkOH solution as the electrolyte, a three-electrode system was assembled under oxygen saturation conditions, and the test was performed using an electrochemical workstation.

[0032] The 2e-ORR performance was systematically tested using a flow cell system in 1.0 M KOH solution.

[0033] The test results are attached. Figure 3-5 As shown: Appendix Figure 3 The LSV curve of the zirconium-iron bimetallic doped cobalt tetroxide material in 0.1KOH alkaline electrolyte is shown below. Figure 4 The LSV current density curve of zirconium-iron bimetallic doped cobalt tetroxide material in a flow cell is shown. The highest current reaches 137 mA cm-2, showing its potential for large-scale electrosynthesis of H2O2. Figure 5 The graph shows the H2O2 yield and Faraday efficiency of zirconium-doped acid-etched cobalt tetroxide material. At the optimal potential, the H2O2 yield can reach about 11 mol gcat-1h-1, and the Faraday efficiency is close to 99% at 0V (vs. RHE).

[0034] Example 2 The preparation method of iron-doped cobalt tetroxide material in Example 2 includes the following steps: Step 1: Cobalt nitrate hexahydrate and ferric nitrate nonahydrate are added to the organic solvent ethylene glycol and stirred at a stirring speed of 1000 r / min to obtain a homogeneous mixed solution; Step 2: The solution is hydrothermally heated at 180℃ for 6 h, and the hydrothermal product solution is filtered to separate the precipitate; the precipitate is washed 6 times alternately with deionized water and anhydrous ethanol until the filtrate becomes colorless, thus obtaining iron-doped cobalt-based precursor powder.

[0035] Step 3: Take the iron-doped cobalt-based precursor obtained by filtration, dry it in an oven at 80℃ for 12 hours, and then place the dried sample into a tube furnace for calcination. Select air as the calcination atmosphere, and control the calcination temperature at 500-800℃, the calcination time at 3-6 hours, and the heating rate at 2-5℃ / min to finally obtain iron-doped cobalt tetroxide material.

[0036] The iron-doped cobalt tetroxide material obtained in Example 2 of the present invention is characterized as follows: The XRD characterization results of the iron-doped cobalt tetroxide material prepared in Example 2 of the present invention are as follows: Figure 6 As shown, it can be determined that the synthesized material is iron-doped cobalt tetroxide, without any zirconium oxide impurity peaks.

[0037] The Raman characterization results of the iron-doped cobalt tetroxide material prepared in Example 2 of this invention are as follows: Figure 7 As shown, it can be determined that iron bimetallic doping enters the tetrahedral sites of cobalt tetroxide spinel through cation substitution, introducing lattice defects.

[0038] The iron-doped cobalt tetroxide prepared above was used as an electrocatalyst for oxygen reduction performance testing. 5 mg of catalyst was weighed and added sequentially to 950 μL of anhydrous ethanol and 50 μL of 5% Nafion solution, then ultrasonically dispersed for 30 min to obtain a homogeneous and stable catalyst ink. Oxygen reduction performance testing was performed using a three-electrode system in an oxygen-saturated 0.1 mol / L KOH electrolyte. The LSV current density was measured in a flow cell.

[0039] Figure 8 This is the current density curve of the ring disk in the ring disk electrode system. Figure 9 It exhibits a current density of 56 mA cm⁻² in an oxygen-saturated 1 mol / L KOH electrolyte within a potential range of 0–0.8 V.

Claims

1. A zirconium-iron bimetallic doped cobalt tetroxide material, characterized in that: Zr 4+ Co is acquired in spinel cobalt tetroxide through lattice substitution. 3+ Dominant octahedral sites (Oh sites), Fe 3+ Occupy Co 2+ The dominant tetrahedral sites (Td sites) have an atomic ratio of zirconium to iron of 1 to 5:

1.

2. The method for preparing a zirconium-iron bimetallic doped cobalt tetroxide material according to claim 1, characterized in that... The preparation process includes the following steps: Step S1: Dissolve the cobalt source, zirconium source and iron source in an organic solvent and stir continuously to obtain a homogeneous mixed solution; Step S2: Transfer the mixed solution from step S1 to a molding process to obtain the precursor; Step S3: After drying the precursor obtained in step S2, calcine it in a tube furnace to obtain the final product, zirconium iron bimetallic doped cobalt tetroxide material.

3. The preparation method according to claim 2, characterized in that, The stirring in step S1 is mechanical stirring, magnetic stirring or ultrasonic stirring.

4. The preparation method according to claim 2, characterized in that, The organic solvent in step S1 is ethylene glycol or dimethyl sulfoxide; the cobalt source is selected from at least one of cobalt nitrate and cobalt chloride; the zirconium source is selected from at least one of zirconium sulfate and zirconium nitrate; and the iron source is selected from at least one of ferric nitrate and ferric chloride.

5. The preparation method according to claim 2, characterized in that, The molding process described in step S2 is one of the following: hydrothermal method, solvothermal method, sol-gel method, coprecipitation method, spray drying granulation method, electrospinning method, freeze drying method, or ball milling method.

6. The preparation method according to claim 5, characterized in that, The molding process described in step S2 is a hydrothermal method, and the reaction conditions are hydrothermal treatment at 160-200℃ for 6-10 hours.

7. The preparation method according to claim 2, characterized in that, The drying in step S3 is heating drying, vacuum drying or adsorption drying; the calcination temperature is 500~800 ℃, the calcination time is 3~6 h, the calcination atmosphere is air, nitrogen or argon, and the heating rate is 2~5 ℃ / min.

8. The application of the zirconium-iron bimetallic doped cobalt tetroxide material according to claim 1 as a catalyst for the two-electron oxygen reduction reaction in the preparation of hydrogen peroxide.

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