A Ni-doped Co3O4 catalyst material, its preparation method and application

Abstract

This invention discloses a method for preparing and applying a Ni-doped Co3O4 catalyst. The invention employs a pressure co-precipitation method, comprising the following steps: co-current mixing of a cobalt salt solution, a nickel salt solution, and a precipitant solution. Using ultrapure water as a solvent and sodium carbonate as the precipitant solution, nickel nitrate hexahydrate and cobalt nitrate hexahydrate are mixed and calcined to synthesize a magnetic thermocatalytic material. Through nickel ion doping, the Co3+ in Co3O4 undergoes a transition from a low-spin to a high-spin state, enhancing the hybridization of the 3d-2p orbitals, promoting the breaking of O-O bonds, and significantly improving its efficiency in synergistically removing ozone and formaldehyde. This invention is expected to be widely applied in the thermocatalytic treatment of harmful gases.

Description

Technical Field

[0001] This invention relates to photocatalytic environmental remediation technology, specifically to a method of metal doping for removing O3 and VOCs, and more particularly to a Ni-doped Co3O4 catalyst material, its preparation method, and its application. Background Technology

[0002] VOCs pose significant hazards to human health and the environment, primarily manifesting as respiratory irritation, carcinogenic risks, and photochemical pollution. Catalysis is an effective method for VOCs treatment. Among these, thermocatalysis is a highly efficient purification or energy conversion technology that uses catalysts to lower the activation energy of reactions and accelerate chemical reactions. It is widely used in environmental remediation, energy conversion, and other fields.

[0003] Ozone catalytic oxidation technology is highly efficient in removing pollutants; however, due to the spin-forbidden transitions, transitions between certain electronic states are quantum mechanically forbidden, thus ozone catalytic oxidation is influenced by the electronic properties of the catalyst. Recent studies have found that the interfacial atomic metal oxygen species (*O) is a key indicator of ozone catalytic oxidation, determining the derivation of active species and subsequent reaction activity.

[0004] Based on this, it is desirable to obtain a catalyst and a method to improve catalytic efficiency, which can be achieved by adjusting the Co content in Co3O4. 3+ The spin state stabilizes the species on the *O surface, thereby improving catalytic efficiency. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a Ni-doped Co3O4 catalyst material, its preparation method and application, especially addressing the problems of high cost and poor universality of existing VOCs removal methods, and providing a simple, easy-to-implement, low-cost catalyst, preparation method and application.

[0006] To achieve the above objectives, this invention proposes a Ni-doped Co3O4 catalyst, wherein the catalyst is formed by Ni ions being doped into the Co3O4 lattice, causing Co3... + Magnetic thermocatalytic materials that transition from a low-spin state to a high-spin state.

[0007] Preferably, the mass ratio of cobalt salt to nickel salt in the catalyst is 1 to 2.

[0008] Secondly, this invention proposes a method for preparing the above-mentioned Ni-doped Co3O4 catalyst, the method comprising the following steps: dissolving cobalt nitrate hexahydrate and nickel nitrate hexahydrate in ultrapure water to obtain a mixed salt solution; adding a precipitant solution concurrently to carry out a co-precipitation reaction, controlling the reaction pH to be 9-9.5, reacting to a specified particle size to obtain carbonate powder; calcining the carbonate powder in an oxygen-containing atmosphere to obtain the Ni-doped Co3O4 catalyst.

[0009] Preferably, the precipitant solution is a sodium carbonate solution with a concentration of 10 g / L to 20 g / L.

[0010] Preferably, the calcination temperature is 400~500℃ and the calcination time is 2h~3h.

[0011] Preferably, the coprecipitation reaction is continuously stirred for 2 hours, and the reaction product is centrifuged, washed with ultrapure water, and then vacuum dried.

[0012] Thirdly, this invention proposes the application of the above-mentioned Ni-doped Co3O4 catalyst or the Ni-doped Co3O4 catalyst prepared by the above-mentioned method in the synergistic removal of ozone and formaldehyde by thermal catalysis at room temperature.

[0013] Preferably, the specific conditions for the synergistic removal of ozone and formaldehyde are as follows: a glass fiber membrane made of Ni-doped Co3O4 catalyst is packed in a continuous flow reactor; a mixed gas with a formaldehyde concentration of 25~35 ppm and an ozone concentration of 60~80 ppm is introduced, the gas flow rate is 500~1000 SCCM, and the reaction temperature is room temperature.

[0014] The purpose of this invention is to address the shortcomings of existing technologies (limitations of ozone catalysis technology) and market demands (severe air pollution problems) by providing a Ni-doped Co3O4 catalyst material. This material has a simple preparation method, low cost, and promising practical applications. The invention discloses a specific preparation method for Ni-doped Co3O4 material, comprising the following steps: mixing a certain proportion of nickel nitrate hexahydrate and cobalt nitrate hexahydrate in ultrapure water, co-precipitating with sodium carbonate solution, maintaining pH stability during mixing, continuously stirring for 2 hours, centrifuging the resulting solution, and washing with ultrapure water. The washed precipitate is then vacuum dried and calcined at 500 °C for 3 hours in air to obtain the Ni-doped Co3O4 catalyst material.

[0015] The aforementioned Ni-doped Co3O4 catalyst material serves as a thermocatalyst for the synergistic removal of ozone and formaldehyde. The specific steps are as follows: Ozone and formaldehyde are subjected to thermocatalytic oxidation at room temperature in a continuous flow reactor. A glass fiber membrane made of Ni-doped Co3O4 catalyst is placed inside the reactor chamber. A mixture of formaldehyde (25-35 ppm), ozone (60-80 ppm), and high-purity air at a certain concentration is introduced to simulate polluted air. The gas flow rate is 500-1000 SCCM, and room temperature is maintained during the reaction. The product prepared by this invention was tested and characterized by the following methods: X-ray diffraction was performed on the sample using a Rigaku D / Max-RB X-ray diffractometer (Japan); the concentration of NO gas was calibrated using a Thermo 146i gas calibrator (USA); the concentration change of HCHO was analyzed online using a Thermo 42i nitrogen oxide analyzer; and scanning electron microscope images were obtained using a Hitachi S-4800 scanning electron microscope (Japan).

[0016] Compared with the prior art, the present invention has the following advantages and outstanding effects: The materials used in this invention—cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and sodium carbonate—are all commonly used reagents and are inexpensive. Compared with common ozone catalytic oxidation catalysts, this method is simpler to synthesize, easier to operate, more environmentally friendly, and produces a catalyst with good stability, high activity, and good cycle efficiency. The Ni-doped Co3O4 catalyst prepared in this invention can achieve a removal rate of up to 100% for the formaldehyde removal reaction in a flowing gas phase at room temperature, and a removal rate of up to 98% for the ozone removal reaction in a flowing gas phase. Attached Figure Description

[0017] Figure 1 The XRD patterns of the Co3O4 and Ni-doped Co3O4 catalysts prepared in Example 1 are shown. The diffraction peaks in the figure correspond highly to the diffraction peaks of Co3O4 and Ni-Co3O4.

[0018] Figure 2 The figure shows the ozone removal rate reaction process of the Ni-doped Co3O4 catalyst sample prepared in Example 1. The figure shows that the obtained sample has good catalytic activity for oxidizing ozone in the mobile phase. The ozone removal rate is shown at room temperature and at different nickel-cobalt ratios. The highest removal rate is achieved when the nickel-cobalt ratio is 1:1, which can reach up to 99%.

[0019] Figure 3 and Figure 4The figures show the reaction process of ozone and formaldehyde removal rates when the Ni-doped Co3O4 catalyst sample prepared in Example 1 synergistically removes ozone and formaldehyde. The figures show that the obtained sample has good catalytic activity in synergistically removing ozone and formaldehyde, and the removal rate of 30 ppm formaldehyde can reach up to 100%.

[0020] Figure 5 This is a scanning electron microscope image of the Ni-doped Co3O4 catalyst sample prepared in Example 1. Detailed Implementation

[0021] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0022] Experimental methods in the following examples that do not specify specific conditions should be performed according to conventional methods and conditions, or according to the product instructions. All reagents and raw materials used in this invention are commercially available.

[0023] The present invention will be further described below with reference to the embodiments: Nickel nitrate hexahydrate and cobalt nitrate hexahydrate were mixed in ultrapure water at a ratio of 1:2 and co-precipitated with sodium carbonate solution. The pH was kept stable during mixing, and the mixture was stirred continuously for 2 hours. The resulting solution was centrifuged and washed with ultrapure water. The precipitate was then vacuum dried and calcined at 500 °C for 3 hours in air to obtain Ni-doped Co3O4 catalyst material.

[0024] Figure 1 The XRD patterns of the Co3O4 and Ni-doped Co3O4 catalysts prepared in Example 1 are shown. The diffraction peaks in the figure correspond highly to the diffraction peaks of Co3O4 and Ni-Co3O4.

[0025] Figure 2 The figure shows the ozone removal rate reaction process of the Ni-doped Ni-Co3O4 catalyst sample prepared in Example 1. The figure shows that the obtained sample has good catalytic activity for oxidizing ozone in the mobile phase. The ozone removal rate is shown at room temperature and at different nickel-cobalt ratios. The highest removal rate is achieved when the nickel-cobalt ratio is 1:1, which can reach up to 99%.

[0026] Figure 3 and Figure 4The figures show the reaction process of ozone and formaldehyde removal rates when the Ni-doped Co3O4 catalyst sample prepared in Example 1 synergistically removes ozone and formaldehyde. The figures show that the obtained sample has good catalytic activity in synergistically removing ozone and formaldehyde, and the removal rate of 30 ppm formaldehyde can reach up to 100%.

[0027] Figure 5 This is a scanning electron microscope image of the Ni-doped Co3O4 catalyst sample prepared in Example 1.

[0028] Under the conditions of Example 1, formaldehyde and ozone were oxidized at room temperature in a continuous flow reactor. A glass fiber membrane made of Ni-doped Co3O4 catalyst was placed inside the reactor chamber. A mixture of formaldehyde (25-35 ppm), ozone (60-80 ppm), and high-purity air at a certain concentration was introduced to simulate polluted air. The gas flow rate was 500-1000 SCCM, and room temperature was maintained during the reaction. It should be noted that the scope of protection of this invention is not limited to the embodiments given in this application. All prior art that does not contradict the present invention, including but not limited to prior patent documents, prior publications, prior uses, etc., can be included within the scope of protection of this invention.

[0029] Furthermore, the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0030] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A Ni-doped Co304 catalyst, characterized in that, The catalyst is Ni ion doped into Co3O4 lattice, making Co3 + Magnetic heat catalytic material that transforms from low spin state to high spin state.

2. The Ni-doped Co304 catalyst according to claim 1, characterized in that, The mass ratio of cobalt salt to nickel salt in the catalyst is 1 to 2.

3. A method for preparing the Ni-doped Co304 catalyst according to claim 1 or 2, characterized in that, The preparation method includes the following steps: dissolving cobalt nitrate hexahydrate and nickel nitrate hexahydrate in ultrapure water to obtain a mixed salt solution; adding a precipitant solution in parallel to carry out a co-precipitation reaction, controlling the reaction pH to be 9~9.5, and reacting until a specified particle size is obtained to obtain carbonate powder; calcining the carbonate powder in an oxygen-containing atmosphere to obtain a Ni-doped Co3O4 catalyst.

4. The preparation method according to claim 3, characterized in that, The precipitant solution is a sodium carbonate solution with a concentration of 10 g / L to 20 g / L.

5. The preparation method according to claim 3, characterized in that, The calcination temperature is 400~500℃, and the calcination time is 2h~3h.

6. The preparation method according to claim 3, characterized in that, The coprecipitation reaction was continuously stirred for 2 hours. The reaction product was centrifuged, washed with ultrapure water, and then vacuum dried.

7. The application of the Ni-doped Co3O4 catalyst as described in claim 1 or 2, or the Ni-doped Co3O4 catalyst prepared by any one of the preparation methods described in claims 3 to 6, in the synergistic removal of ozone and formaldehyde by thermal catalysis at room temperature.

8. The application according to claim 7, characterized in that, The specific conditions for the synergistic removal of ozone and formaldehyde are as follows: a glass fiber membrane made of Ni-doped Co3O4 catalyst is packed in a continuous flow reactor; a mixed gas with a formaldehyde concentration of 25~35 ppm and an ozone concentration of 60~80 ppm is introduced at a gas flow rate of 500~1000 SCCM and a reaction temperature of room temperature.

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