CN115739089A - Preparation and application method of Co-OBC nano catalyst - Google Patents

Abstract

The invention discloses a preparation method of a Co-OBC nano catalyst, which comprises the steps of dispersing carbon black in a nitric acid solution, stirring, washing, filtering, freezing and drying to obtain oxidized carbon black; dispersing oxidized carbon black in ultrapure water, carrying out ultrasonic treatment, then adding a cobalt nitrate solution into a carbon black suspension, stirring, washing cobalt ions absorbed on the surface of the carbon black, centrifuging, and freeze-drying; and then keeping the material prepared in the step B at a high temperature in Ar atmosphere for a period of time to obtain a Co-OBC materialAnd (4) feeding. The Co-OBC nano catalyst of the invention has the advantages of increasing the surface area due to the spherical structure of the material, increasing the content of pyrrole nitrogen and oxygen-containing functional groups, adsorbing and activating O ₂ Enhanced capability and benefit for 2 electron O ₂ Reduction to H ₂ O ₂ . When the catalyst is used for degrading BPS (BPS) by using the electro-Fenton cathode material, higher degradation efficiency can be realized, energy consumption and cost are greatly reduced, and H is generated in situ ₂ O ₂ The safety factor is improved.

Description

A kind of preparation and application method of Co-OBC nano catalyst

technical field

The invention relates to a preparation of a nano catalyst and an application method thereof, in particular to a preparation of a Co-OBC nano catalyst and an application method thereof.

Background technique

Persistent organic pollutants (POPs) refer to long-distance migration through various environmental media (atmosphere, water, organisms, etc.) Natural or synthetic organic pollutants that pose serious hazards to human health and the environment. Humans and other animals are exposed to a range of endocrine-disrupting chemicals (EDCs) throughout their lifetimes through exposure to work, consumer products, pharmaceuticals, natural resources, and other environments, increasing the risk of adverse health outcomes, including cancer, reproductive disorders, cognitive deficits and obesity. Bisphenol S (BPS), as an endocrine disruptor, can replace bisphenol A (BPA) and is widely used in the production of food and beverage plastic containers, adhesives, paints, drinking water pipe linings, and household paper products. Exposure to BPS alters the endocrine function of cells and induces cytotoxicity, resulting in malformed embryos, decreased sperm count, and increased hatching time. Due to the long-term potential harm of BPS to the environment, its removal has become an urgent problem to be solved. Therefore, developing clean, efficient, and economically viable POPs removal methods is an effective way to address potential environmental hazards.

At present, there are many methods for degrading BPS in the environment, such as adsorption, biological, photocatalytic and thermocatalytic methods. But they all have some deficiencies that are difficult to solve. Electro-fenton is a kind of electrocatalytic reaction, which is essentially an oxidation reaction. The principle of the electro-Fenton technology is to reduce oxygen at the cathode to generate H ₂ O ₂ electrochemically, and then decompose it into strongly oxidizing OH under the promotion of Fe ²⁺ , and OH further reacts with persistent organic matter in the solution. Redox reactions and eventual mineralization. According to the addition method of Fe ²⁺ , electro-Fenton can be divided into homogeneous electro-fenton with external iron source and heterogeneous electro-fenton with iron source supported on the catalyst. The reaction equation for the electro-Fenton reaction is as follows:

O ₂ +2e ^- +2H ⁺ →H ₂ O ₂ (1.1)

Fe ²⁺ +H ₂ O ₂ +H ⁺ →Fe ³⁺ +H ₂ O+ OH (1.2)

Fe ³⁺ +e ^- → Fe ²⁺ (1.3)

The crucial step in the electro-Fenton reaction is the occurrence of oxygen reduction reaction, which can be divided into two-electron oxygen reduction reaction (O ₂ +2H+2e ^- →H ₂ O ₂ ) and four-electron oxygen reduction reaction according to the different reaction pathways. Electron oxygen reduction reaction (O ₂ +4H+4e ^- → 2H ₂ O), the four-electron pathway can be used in fuel cells and zinc-air batteries to improve reaction kinetics, the two-electron pathway is usually used in electro-Fenton reactions for pollutants degradation. These two pathways are separated after the reduction of _O2 to form *-O-OH intermediate (where * indicates the active site of the catalyst, - emphasizes the key bond), and the * _-O bond is broken to generate _H2O2 , O-OH bond Fragmentation forms H ₂ O. Therefore, understanding the bond breaking of *-O-OH is of great significance for the selective generation _{of H2O2} . There are many factors that affect the electro-Fenton reaction, such as solution pH, voltage, content of external iron source, and electrode material used, etc., but the electrode material is the decisive factor, which can affect the efficiency and transfer path of the oxygen reduction reaction (ORR) , to improve the selectivity of H ₂ O ₂ .

Among the existing studies, there is "Electrochemical Advanced Oxidation of 4,4′-Sulfonyldiphenol on BDD and Pt Anodes in Aqueous Medium" on the degradation of BPS by electro-fenton. In this study, the effects of different anodes on the degradation performance were compared, but there was no research on cathode catalysts, and the most important factor affecting the electro-Fenton reaction is the selection of cathode catalysts. Most of the cathode catalysts for electro-Fenton degradation of POPs have many problems such as complex preparation methods, high cost, and poor stability.

Contents of the invention

The object of the present invention is to provide a preparation and application method of a Co-OBC nano catalyst. This method has developed a low-cost, simple and efficient cathode catalyst, which is used for electro-Fenton degradation of BPS, showing high-efficiency degradation performance, and provides ideas for solving persistent organic pollutants in environmental water . The content of pyrrole nitrogen and oxygen-containing functional groups of the catalyst is increased, and the ability to absorb and activate O ₂ is enhanced, which is beneficial to the reduction of O ₂ to synthesize H ₂ O ₂ , which in turn is beneficial to the degradation of BPS.

Technical scheme of the present invention: a kind of preparation method of Co-OBC nanometer catalyst comprises the following steps:

A: carbon black is dispersed in nitric acid solution, and stirred, then washed and filtered, freeze-dried to obtain carbon black;

B: Disperse the carbon black oxide in ultrapure water, perform ultrasonic treatment, then add the cobalt nitrate solution into the carbon black suspension and stir, wash the cobalt ions absorbed on the surface of the carbon black, and centrifugally freeze-dry;

C: Then keep the material prepared in step B at a high temperature in an Ar atmosphere for a period of time to obtain a Co-OBC material.

In the preparation method of the aforementioned Co-OBC nano-catalyst, the specific preparation method includes the following steps:

A: Disperse carbon black in 9M nitric acid solution, stir at 90°C for 10 hours, then wash, filter, and freeze-dry to obtain oxidized carbon black. The dosage ratio of carbon black to nitric acid solution is 2g: 100mL;

B: Disperse carbon black in ultra-pure water, perform ultrasonic treatment for 30 minutes, then add 3 mg/mL cobalt nitrate solution into the carbon black suspension and stir for 12 hours, wash and centrifuge the cobalt ions absorbed on the surface of carbon black Freeze-drying, wherein the dosage ratio of carbon black oxide, ultrapure water and cobalt nitrate solution is 1g: 400mL: 60mL;

C: Then, the material prepared in step B was heated up to 900° C. in an Ar atmosphere at 5° C./min and kept for 1 hour to obtain a Co-OBC material.

An application method of a Co-OBC nano-catalyst uses the Co-OBC nano-catalyst as a cathode catalyst for electro-Fenton degradation of BPS.

In the application method of the aforementioned Co-OBC nanocatalyst, the method for electro-Fenton degradation of BPS is: the Co-OBC material, water, isopropanol and Nafion are mixed and ultrasonically dispersed, and the Co-OBC material, water, isopropanol and Nafion The dosage ratio is 10mg: 2.2mL: 0.75mL: 50μL; then drop-coated on the carbon cloth as the working electrode, the loading of drop-coating is 0.4mg/cm ^-2 , and the solution containing BPS is filled in the single-chamber reactor, The electro-Fenton degradation of BPS was carried out with platinum sheet as the counter electrode and calomel as the reference electrode.

In the application method of the aforementioned Co-OBC nanocatalyst, in the process of electro-Fenton degradation of BPS, the concentration of Fe ²⁺ is 0.3mM; the pH value is 1-7; the applied voltage is -0.3-0.7V.

In the application method of the aforementioned Co-OBC nanocatalyst, in the process of electro-Fenton degradation of BPS, the concentration of Fe ²⁺ is 0.3mM; the pH value is 3; and the applied voltage is -0.5V.

Beneficial effects of the present invention: compared with the prior art, the Co-OBC nanocatalyst of the present invention increases its surface area due to the spherical structure of the material, increases the content of pyrrole nitrogen and oxygen-containing functional groups, and enhances the ability to absorb and activate _O2 , It is beneficial to the reduction of 2-electron O ₂ to generate H ₂ O ₂ . When the catalyst prepared by this method is used to degrade BPS by electro-Fenton cathode materials, it can achieve higher degradation efficiency (all degradation within 15 minutes), _which greatly reduces energy consumption and cost, and at the same time produces _H2O2 in situ to improve It improves the safety factor and provides great convenience for the transportation and storage of raw materials.

Description of drawings

Accompanying drawing 1 is the synthesizing schematic diagram of Co-OBC catalyst of the present invention;

Accompanying drawing 2 is the schematic diagram of the morphology characterization result of Co-OBC prepared by the method of the present invention;

(in the figure (a) is the SEM of Co-OBC; (b-d) is the TEM of Co-OBC; (e) is the SAED of Co-OBC, (f) is the C, N, O, Co elements of Co-OBC mapping)

Accompanying drawing 3 is the schematic diagram of the structure characterization result of Co-OBC prepared by the method of the present invention;

(in the figure (a) is the infrared spectrum of Co-OBC, (b) is the XRD spectrum of Co-OBC, (c) is the C 1s fine spectrum, (d) is the N1s fine spectrum, (e) is the O1s fine spectrum, (f) is Co 2p fine spectrum)

Accompanying drawing 4 _is with the Co-OBC prepared by the present invention as the cathode catalyst of electric Fenton when H ₂ O The productive rate schematic diagram;

(In the figure (a) is pH 1, (b) is pH 3, and (c) is pH 5, the yield of H ₂ O ₂ when the applied voltage is -0.3～-0.7V)

Accompanying drawing 5 when using the Co-OBC prepared by the present invention as the cathodic catalyst of electric Fenton, the efficiency schematic diagram of degrading BPS;

(in the figure (a) is Fe ²⁺ concentration (pH is 3 and applied voltage is -0.5V); (b) is pH (voltage is -0.5V, Fe ²⁺ concentration is 0.3mM), (c) is applied The effect of voltage on the degradation of BPS by electro-Fenton; (d) is a repeated experiment, (e) is a comparative experiment, (f) is the degradation effect of BPS in actual water)

Accompanying drawing 6 is the schematic diagram of electro-fenton degrading persistent organic pollutants.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but not as a basis for limiting the present invention.

Embodiment 1 of the present invention: a kind of preparation method of Co-OBC nano-catalyst, as shown in Figure 1, specific preparation method comprises the following steps:

A: Disperse 2g of carbon black in 100mL of 9M nitric acid solution, stir at 90°C for 10h, then wash, filter and freeze-dry to obtain oxidized carbon black.

B: Disperse 1g of carbon black oxide in 400mL of ultrapure water, ultrasonicate for 30min to form a homogeneous solution, then add 60mL of 3mg/mL cobalt nitrate into the carbon black suspension and stir for 12h, and absorb on the surface of carbon black Cobalt ion washing, centrifugal freeze-drying.

C: Then, the material prepared in step B was heated up to 900° C. in an Ar atmosphere at 5° C./min and kept for 1 hour to obtain a Co-OBC material.

An application method of a Co-OBC nano-catalyst uses the Co-OBC nano-catalyst as a cathode catalyst for electro-Fenton degradation of BPS.

The method of electro-Fenton degradation of BPS is: as shown in Figure 6, the Co-OBC material, water, isopropanol and Nafion are mixed and ultrasonically dispersed uniformly, and the dosage ratio of Co-OBC material, water, isopropanol and Nafion is 10mg: 2.2 mL: 0.75mL: 50μL; then drop-coated on the carbon cloth as the working electrode, the drop-coated load was 0.4mg/cm ^-2 , filled the solution containing BPS in the single-chamber reactor, and used the platinum sheet as the counter Electrode, calomel as a reference electrode for electro-Fenton degradation of BPS.

During the electro-Fenton degradation of BPS, the concentration of Fe ²⁺ was 0.3mM; the pH value was 1-7; the applied voltage was -0.3-0.7V.

Accompanying drawing 2 is the scanning electron microscope picture (SEM) and the transmission electron microscope picture (TEM) of Co-OBC, can observe from the figure that Co-OBC presents spherical appearance as a whole, and specific surface area is larger, can provide more The catalytic active sites of the Co(111) crystal plane are measured to be 0.203nm, the lattice fringes of the C(002) crystal plane are 0.34nm, and the diffraction rings of the electron diffraction pattern (SAED) correspond to Co( 111) crystal face and C(002) crystal face, which further confirmed the successful preparation of the catalyst. It can be seen from the element mapping diagram that the four elements of the prepared catalyst, C, N, O, and Co, are distributed very uniformly.

The chemical functional groups of Co-OBC were investigated by FTIR spectroscopic measurements, as shown in Fig. 3(a). The stretching vibration peaks at 3423, 1584, 1204 and 1148 ^cm correspond to -OH, C=O, CN and CO functional groups, respectively. In addition, the crystal structure of the catalyst was characterized by XRD diffraction (Fig. 3(b)), and 2θ≈25° and 43° correspond to the disordered carbon of the (002) crystal plane and the graphitic carbon of the (101) crystal plane, respectively. Diffraction peaks. In addition, the XPS fine-grained spectrum of C1s of Co-OBC showed four main peaks at 284.8, 285.2, 286.7 and 290.8 eV (Fig. 2(c)), corresponding to CC, C=N, CO and C=O functional groups . Four different types of nitrogen, pyridine N (398.9eV), pyridine N (40.1eV), graphite N (401.4eV) and oxide N (404.4eV) appear in the XPS fine spectrum of N1s of Co-OBC in Figure 2(d). , the pyrrole nitrogen contained in Co-OBC is crucial for the selectivity of 2e ^- oxygen reduction. Comparing the XPS fine spectrum of O1s in Figure 2(e), it is found that C-OBC contains C-OH (531.2eV), OC=O (532.3eV), -COOH (533.1eV) and CO (534eV). Oxygen functional groups have good electrocatalytic reaction performance. The fine XPS spectrum of Co 2p (Fig. 2(f)) shows that Co-OBC contains a Co(II) peak at 779.7eV and a Co-Nx peak at 781.8eV, confirming the successful incorporation of Co into carbon black.

In order to verify the performance of the Co-OBC nano-catalyst prepared by the method of the present invention, the following tests were specially done:

H ₂ O ₂ production test

In order to explore the production rate of H ₂ O ₂ , the production rate of H ₂ O ₂ was determined by the titanium potassium oxalate method with Co-OBC as the electro-Fenton cathode catalyst under different pH values and applied voltage conditions.

The specific test method is as follows: 10mg of Co-OBC, 2.2mL of water, 0.75mL of isopropanol and 50μL of Nafion were mixed and dispersed evenly by ultrasonic, each time 120μL was dropped on a 2*2 carbon cloth, dripping 4 times, the loading capacity 0.4mg/cm ^-2 as the working electrode. In the dual-chamber reaction cell with Nafion117 as the diaphragm, the production of H ₂ O ₂ was tested under the conditions of different pH and applied voltage with platinum sheet as the counter electrode and calomel as the reference electrode. Slowly add 272mL of sulfuric acid into 300mL of ultrapure water. After cooling, ultrasonically dissolve 35.4g of potassium titanium oxalate completely, and dilute to 1L with ultrapure water to successfully prepare potassium titanium oxalate solution. During the test, take 5mL potassium titanium oxalate solution and 2mL test water sample, mix and shake well, after standing for 10min, measure the absorbance with a UV spectrophotometer at 387nm, and calculate the concentration of hydrogen peroxide according to the standard curve.

The structure is shown in Figure 4, except that the pH is 1, the more negative the potential, the higher the production of H ₂ O ₂ . H ⁺ can _promote proton-coupled electron transfer during _H2O2 generation. However, lower pH value and higher voltage will also promote the hydrogen evolution competition reaction (HER) of the system, which is not conducive to the formation of H ₂ O ₂ . Considering the impact of energy consumption and HER, it is considered that the optimal reaction conditions for Co-OBC catalyst to generate H ₂ O ₂ are: pH=3, U=-0.5V, and the yield of H ₂ O ₂ can reach 3.53mmol/ L/h.

BPS degradation performance test

The performance of Co-OBC as an electro-Fenton cathode catalyst for the degradation of BPS in a homogeneous system was investigated under _O2 saturated conditions.

The specific test method is as follows: 10mg of Co-OBC, 2.2mL of water, 0.75mL of isopropanol and 50μL of Nafion were mixed and dispersed evenly by ultrasonic, each time 120μL was dropped on a 2*2 carbon cloth, dripping 4 times, the loading capacity 0.4mg/cm ^-2 as the working electrode. In a 150mL single-chamber reactor, in 100mL Na ₂ SO ₄ solution containing 10ppm BPS, the platinum plate was used as the counter electrode, and calomel was used as the reference electrode to test under the conditions of different external Fe ²⁺ concentration, pH and applied voltage Degradation rate of BPS. The degradation device is shown in Figure 6 below.

As shown in Figure 5(a), the effect of 0.1mM～0.7mM Fe ²⁺ was studied, and the results showed that when the Fe ²⁺ concentration was 0.3mM, the degradation rate of BPS was the fastest. As shown in Figure 5(b), when the pH was 1, 3, 5, and 7, BPS could be removed rapidly, and the degradation rate was the fastest when the pH was 3. The influence of the applied voltage during the BPS degradation process is shown in Figure 5(c). As the applied voltage increases from -0.3V to -0.7V, the removal rate of BPS also increases significantly. The applied voltage is -0.3V, At -0.5V and -0.7V, considering the higher energy consumption at -0.7V, it is considered that the best applied voltage is -0.5V. In summary, the optimal reaction conditions for the degradation of BPS are: the concentration of Fe ²⁺ is 0.3mM, the applied voltage is -0.5V and the pH is 3.

In order to evaluate the stability of the catalyst, one electrode was reused 4 times. It can be seen from Figure 5(d) that the degradation efficiency of the electrode loaded with Co-OBC did not decrease significantly after repeated use four times, indicating that the catalyst has good stability. Subsequently, the performance research of using Co-OBC as the electro-Fenton cathode catalyst to degrade BPS was compared under different conditions. As shown in the research results in Figure 5(e), the research results confirmed that Co-OBC was used as the cathode. Electro-fenton degradation properties. Figure 5(f) shows the degradation of BPS in real water samples (Shilitan River water). It can be seen that the degradation efficiency of BPS in real water is higher than that in ultrapure water, which may be due to other organic substances contained in real water samples (such as humic acid) can promote the decomposition of BPS.

Claims (6)

1. A preparation method of Co-OBC nano catalyst is characterized by comprising the following steps: the method comprises the following steps:

a: dispersing carbon black in a nitric acid solution, stirring, washing, filtering, freezing and drying to obtain oxidized carbon black;

b: dispersing oxidized carbon black in ultrapure water, carrying out ultrasonic treatment, then adding a cobalt nitrate solution into a carbon black suspension, stirring, washing cobalt ions absorbed on the surface of the carbon black, centrifuging, and freeze-drying;

c: and C, maintaining the material prepared in the step B at a high temperature in an Ar atmosphere for a period of time to obtain the Co-OBC material.

2. The method of preparing a Co-OBC nanocatalyst of claim 1, wherein: the preparation method comprises the following steps:

a: dispersing carbon black in 9M nitric acid solution, stirring for 10h at 90 ℃, washing, filtering, freezing and drying to obtain the oxidized carbon black, wherein the dosage ratio of the carbon black to the nitric acid solution is 2g:100mL;

b: dispersing oxidized carbon black in ultrapure water, carrying out ultrasonic treatment for 30min, then adding 3mg/mL cobalt nitrate solution into the carbon black suspension, stirring for 12h, washing cobalt ions absorbed on the surface of the carbon black, centrifuging, freezing and drying, wherein the dosage ratio of the oxidized carbon black to the ultrapure water to the cobalt nitrate solution is 1g:400mL:60mL;

c: and C, heating the material prepared in the step B to 900 ℃ at the speed of 5 ℃/min in Ar atmosphere, and keeping for 1h to obtain the Co-OBC material.

3. An application method of a Co-OBC nano catalyst is characterized by comprising the following steps: the Co-OBC nano catalyst is used as a cathode catalyst and applied to the electro-Fenton degradation of BPS.

4. The application method of the Co-OBC nanocatalyst according to claim 3, characterized in that: the method for degrading BPS by electro-Fenton comprises the following steps: mixing Co-OBC material, water, isopropanol and Nafion, and performing ultrasonic dispersion uniformly, wherein the dosage ratio of the Co-OBC material to the water to the isopropanol to the Nafion is 10mg:2.2mL:0.75mL:50 mu L of the solution; then the mixture is dripped on carbon cloth as a working electrode, and the load of the dripping is 0.4mg/cm ^-2 A single-chamber reactor was charged with a solution containing BPS, and electro-Fenton degradation of BPS was performed using a platinum sheet as a counter electrode and calomel as a reference electrode.

5. The application method of the Co-OBC nano catalyst according to claim 4, characterized in that: in the process of degrading BPS by electro-Fenton, fe ²⁺ The concentration is 0.3mM; the pH value is 1-7; the applied voltage is-0.3 to-0.7V.

6. The application method of the Co-OBC nano catalyst according to claim 5, characterized in that: in the process of degrading BPS by electro-Fenton, fe ²⁺ The concentration is 0.3mM; the pH value is 3; the applied voltage was-0.5V.

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