Mn-Co-MnO heterojunction oxygen reduction catalyst as well as preparation method and application thereof
By constructing a Mn-Co@MnO heterojunction oxygen reduction catalyst, the problems of electronic conductivity and active sites in the oxygen reduction reaction in microbial fuel cells were solved, achieving efficient oxygen reduction reaction and low-cost catalytic effect, thus promoting the application of microbial electrochemical technology.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-19
- Publication Date
- 2026-04-10
AI Technical Summary
Existing oxygen reduction reaction catalysts in microbial fuel cells suffer from poor electron conductivity, a limited number of active sites, and poor reaction selectivity, resulting in insufficient cathode performance and high cost of precious metal catalysts.
A Mn-Co@MnO heterojunction oxygen reduction catalyst was constructed by forming a heterojunction structure between MnO and Mn-doped Co, and then coating it with a carbon shell to create multiple active sites and electron transfer effects, thereby improving catalytic activity and electron transport efficiency.
It significantly improves the catalytic activity and electron transport efficiency of the oxygen reduction reaction, reduces costs, is suitable for large-scale industrial production, and promotes the commercial development of microbial electrochemical technology.
Smart Images
Figure CN121819863A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of environmental engineering, specifically to a Mn-Co@MnO heterojunction oxygen reduction catalyst and its preparation method and application, and more particularly to the preparation of an oxygen reduction catalyst for the air cathode of a microbial fuel cell, used for the treatment of water bodies polluted by organic matter. Background Technology
[0002] In the treatment of organic wastewater using microbial fuel cells (MFCs), the oxygen reduction reaction (ORR) at the cathode directly determines the performance of the cell. Compared with traditional cathode electron acceptors such as potassium ferricyanide, oxygen as the cathode electron acceptor has many advantages in the reduction process, but its effectiveness still needs improvement. Using an ORR catalyst is the most direct way to improve the efficiency of the cathode ORR reaction. By attaching a highly active catalyst to the cathode, the activation potential of the cathode reaction can be reduced, the rate of reduction reaction can be accelerated, and the performance of the cathode can be improved. Among these catalysts, noble metals such as Pt have good catalytic effects, but their high price leads to a high cost for microbial fuel cells. Transition metal (such as Fe, Co, Ni, Mn, etc.) based catalysts have attracted widespread attention due to their abundant resources, low cost, and high catalytic activity. In addition, single-component transition metal oxides often suffer from poor electron conductivity, a limited number of active sites, and poor reaction selectivity, making it difficult to meet the high-performance requirements of practical applications.
[0003] In view of this, the present invention is hereby proposed. Summary of the Invention
[0004] The purpose of this invention is to provide a Mn-Co@MnO heterojunction oxygen reduction catalyst, its preparation method, and its application. The catalyst of this invention, by constructing a multi-active-site structure and utilizing the interface effect of the heterojunction to regulate the electronic structure and improve charge transport efficiency, thereby enhancing the ORR catalytic activity of the catalyst. This is of great significance for promoting the practical application of non-precious metal catalysts in microbial fuel cells.
[0005] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a Mn-Co@MnO heterojunction oxygen reduction catalyst, wherein the Mn-Co@MnO heterojunction oxygen reduction catalyst comprises a nanomaterial Mn-Co@MnO with a heterostructure and a carbon shell coating the surface of the material Mn-Co@MnO with a heterostructure. The carbon shell has a hollow tubular structure; The heterostructured nanomaterial Mn-Co@MnO is formed by combining Mn-doped Co and MnO; and the Mn-Co@MnO is ellipsoidal and discontinuously coated in the carbon shell.
[0006] Furthermore, the length of the nano-hollow tubular structure is 200~700 nm.
[0007] Furthermore, the particle size of the nanomaterial with the heterostructure is 30~70 nm.
[0008] Furthermore, the thickness of the carbon shell is 5~20 nm.
[0009] In a second aspect, the present invention provides a method for preparing the Mn-Co@MnO heterojunction oxygen reduction catalyst as described in the first aspect, the preparation method comprising: The first cobalt source, manganese source and solvent are mixed to prepare the first solution; The first cobalt source, the second cobalt source, and the solvent are mixed to prepare a second solution; A second solution is added to the first solution to carry out a precipitation reaction, followed by solid-liquid separation and drying to obtain the precursor; The precursor was calcined to obtain the Mn-Co@MnO heterojunction oxygen reduction catalyst.
[0010] Furthermore, the first cobalt source is selected from any one or a combination of at least two of potassium cobalt cyanide, ammonium cobalt cyanide, and sodium cobalt cyanide.
[0011] Furthermore, the second cobalt source is selected from any one or a combination of at least two of cobalt citrate, cobalt nitrate, and cobalt acetate.
[0012] Furthermore, the manganese source is selected from any one or a combination of at least two of manganese nitrate, manganese acetate, and manganese citrate.
[0013] Furthermore, in the preparation of the first solution, the solvent is an aqueous solvent containing sodium citrate, and the content of sodium citrate is 0.1~0.5 g / L; in the preparation of the second solution, the solvent is an aqueous solvent.
[0014] Furthermore, in the process of preparing the first solution, the molar ratio of the first cobalt source to the manganese source is (1~3):1.
[0015] Furthermore, in the process of preparing the second solution, the molar ratio of the first cobalt source and the second cobalt source is 1:(0.9~3).
[0016] Furthermore, the molar ratio of the first cobalt source in the first solution to the first cobalt source in the second solution is (1~2):1.
[0017] Furthermore, the precipitation reaction is carried out at a temperature of 20-40°C for 1-2 hours.
[0018] Furthermore, the solid-liquid separation is carried out by centrifugation; wherein the centrifugation speed is 7000~10000 rpm and the centrifugation time is 10~30 min.
[0019] Furthermore, the drying method is vacuum drying; wherein the drying temperature is 80~100℃ and the drying time is 10~24 h.
[0020] Furthermore, the calcination is carried out under anaerobic conditions.
[0021] Furthermore, the heating rate during calcination is 1~10℃ / min.
[0022] Furthermore, the calcination temperature is 300~500℃, and the calcination time is 1~8 h.
[0023] Furthermore, the pretreatment step before calcination includes grinding the precursor until the particle size of the precursor is <1 μm.
[0024] Thirdly, the present invention provides the application of the Mn-Co@MnO heterojunction oxygen reduction catalyst as described in the first aspect in the preparation of the cathode of a microbial fuel cell.
[0025] Furthermore, the Mn-Co@MnO heterojunction oxygen reduction catalyst is used in the preparation of a cathode for a microbial fuel cell for treating water bodies polluted by organic matter.
[0026] Furthermore, the Mn-Co@MnO heterojunction oxygen reduction catalyst is used in the preparation of a cathode for a microbial fuel cell for removing ethyl xanthate from organic wastewater.
[0027] Fourthly, the present invention provides a microbial fuel cell, the microbial fuel cell comprising an air cathode; wherein the air cathode comprises a Mn-Co@MnO heterojunction oxygen reduction catalyst as described in the first aspect.
[0028] Fifthly, the present invention provides a method for removing ethyl xanthate from organic wastewater, the removal method comprising: The removal of ethyl xanthate from the organic wastewater is achieved by injecting it into the microbial fuel cell described in the fourth aspect.
[0029] Furthermore, the concentration of ethyl xanthate in the organic wastewater is 100~1000 mg / L.
[0030] Compared with the prior art, the present invention has the following beneficial effects: (1) Significant synergistic effect of heterojunction: The Mn-Co@MnO heterojunction oxygen reduction catalyst prepared in this invention constructs a heterojunction structure of Mn-doped Co and MnO and is coated with a carbon shell. There is a significant electron transfer effect at the heterojunction interface. MnO and Mn-doped Co form high electron conductivity and high active sites, which synergistically improve the ORR catalytic activity and electron transport efficiency of the catalyst.
[0031] (2) The preparation method is simple and efficient: The present invention uses a two-step hydrothermal-calcination method to prepare the catalyst. The process is simple and easy to operate. It does not require complex equipment and harsh reaction conditions. Moreover, the raw materials are inexpensive and easy to obtain, making it suitable for large-scale industrial production.
[0032] (3) Broad application prospects: The Mn-Co@MnO heterojunction oxygen reduction catalyst prepared by this invention has excellent ORR performance under neutral conditions, which reduces device cost and promotes the commercial development of microbial electrochemical technology. Attached Figure Description
[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0034] Figure 1 This is a comparison chart of the resistance values of various catalysts provided in Test Example 2 of the present invention.
[0035] Figure 2 This is a comparison chart of the LSVs of the catalysts provided in Test Example 3 of the present invention.
[0036] Figure 3 The image shows the XRD pattern of the Mn-Co@MnO heterojunction oxygen reduction catalyst provided in Example 1.
[0037] Figure 4 The image shows a SEM image of the Mn-Co@MnO heterojunction oxygen reduction catalyst provided in Example 1.
[0038] Figure 5A The image is a TEM image from the TEM test of the Mn-Co@MnO heterojunction oxygen reduction catalyst provided in Example 1.
[0039] Figure 5B The image shows the TEM mapping of the Mn-Co@MnO heterojunction oxygen reduction catalyst provided in Example 1.
[0040] Figure 5C Line scan image from TEM testing of the Mn-Co@MnO heterojunction oxygen reduction catalyst provided in Example 1.
[0041] Figure 5D The image shows the line scan results of the TEM test of the Mn-Co@MnO heterojunction oxygen reduction catalyst provided in Example 1. Detailed Implementation
[0042] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.
[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0044] In a first aspect, the present invention provides a Mn-Co@MnO heterojunction oxygen reduction catalyst, wherein the Mn-Co@MnO heterojunction oxygen reduction catalyst comprises a nanomaterial Mn-Co@MnO with a heterostructure and a carbon shell coating the surface of the material Mn-Co@MnO with a heterostructure. The carbon shell has a hollow tubular structure; the heterostructured nanomaterial Mn-Co@MnO is formed by combining Mn-doped Co and MnO; and the Mn-Co@MnO is ellipsoidal and discontinuously coated in the carbon shell.
[0045] In this invention, the Mn-Co@MnO heterojunction oxygen reduction catalyst is constructed by forming a heterojunction structure of MnO and Mn-doped Co, which is then coated with a carbon shell. This creates multiple active sites and electron transfer effects, synergistically enhancing the catalyst's ORR catalytic activity and electron transport efficiency. The carbon shell layer serves to enhance electron conductivity and optimize the adsorption energy of oxygen reduction reaction intermediates.
[0046] It should be noted that, unlike traditional heterojunction oxygen reduction catalysts, the carbon shell in this invention has a hollow tubular structure, while Mn-Co@MnO is ellipsoidal and discontinuously encapsulated within the carbon shell. The hollow tubular carbon shell facilitates high specific surface area and mass transfer channels, forming a three-dimensional continuous conductive network. That is, the carbon shell is responsible for "macroscopic" electron transport and mass transport, providing a stable and efficient working environment for the core active sites. The ellipsoidal shape of Mn-Co@MnO, discontinuously encapsulated within the carbon shell, maximizes the exposure of the active interface, better ensuring the accessibility of reactants and ions, and guaranteeing multi-point close electrical contact between them and the carbon shell. The specific morphology of these two elements perfectly combines a highly conductive support, optimized mass transfer pathways, stable encapsulation protection, and a highly intrinsically active heterojunction, thereby synergistically and significantly improving the catalyst's ORR catalytic activity and electron transport efficiency.
[0047] As an optional implementation, the length of the nanotube structure is 200~700 nm, for example, it can be 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, etc.
[0048] As an optional implementation, the particle size of the nanomaterial with heterostructure is 30~70 nm, for example, it can be 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, etc.
[0049] As an optional implementation, the thickness of the carbon shell is 5~20 nm, for example, it can be 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, etc.
[0050] In a second aspect, the present invention provides a method for preparing the Mn-Co@MnO heterojunction oxygen reduction catalyst as described in the first aspect, wherein the method for preparing the Mn-Co@MnO heterojunction oxygen reduction catalyst includes: The first cobalt source, manganese source and solvent are mixed to prepare the first solution; The first cobalt source, the second cobalt source, and the solvent are mixed to prepare a second solution; A second solution is added to the first solution to carry out a precipitation reaction, followed by solid-liquid separation and drying to obtain the precursor; The precursor was calcined to obtain the Mn-Co@MnO heterojunction oxygen reduction catalyst.
[0051] As an optional implementation, the first cobalt source is selected from any one or a combination of at least two of potassium cobalt cyanide, ammonium cobalt cyanide, and sodium cobalt cyanide.
[0052] As an optional implementation, the second cobalt source is selected from any one or a combination of at least two of cobalt citrate, cobalt nitrate, and cobalt acetate.
[0053] As an optional implementation, the manganese source is selected from any one or a combination of at least two of manganese nitrate, manganese acetate, and manganese citrate.
[0054] As an optional implementation, in the process of preparing the first solution, the solvent is an aqueous solvent containing sodium citrate, and the content of sodium citrate is 0.1~0.5 g / L, for example, it can be 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.45 g / L, 0.5 g / L, etc.
[0055] As an optional implementation, the solvent used in preparing the second solution is an aqueous solvent.
[0056] As an optional implementation, during the preparation of the first solution, the molar ratio of the first cobalt source to the manganese source is (1~3):1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, etc.
[0057] As an optional implementation, in the process of preparing the second solution, the molar ratio of the first cobalt source and the second cobalt source is 1:(0.9~3), for example, it can be 1:0.9, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc.
[0058] As an optional implementation, the molar ratio of the first cobalt source in the first solution to the first cobalt source in the second solution is (1~2):1, for example, it can be 1:1, 1.2:1, 1.4:1, 1.5:1, 1.6:1, 1.8:1, 2:1, etc.
[0059] As an optional implementation, the precipitation reaction temperature is 20~40℃, for example, 20℃, 25℃, 30℃, 35℃, 40℃, etc., and the precipitation reaction time is 1~2 h, for example, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, etc.
[0060] As an optional implementation, the solid-liquid separation is performed by centrifugation.
[0061] As an optional implementation, the centrifugation speed is 7000~10000 rpm, for example, 7000 rpm, 7500 rpm, 8000 rpm, 8500 rpm, 9000 rpm, 9500 rpm, 10000 rpm, etc., and the centrifugation time is 10~30 min, for example, 10 min, 15 min, 20 min, 25 min, 30 min, etc.
[0062] As an optional implementation, the drying method is vacuum drying.
[0063] As an optional implementation, the drying temperature is 80~100℃, for example, 80℃, 85℃, 90℃, 95℃, 100℃, etc., and the drying time is 10~24 h, for example, 10 h, 12 h, 14 h, 15 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc.
[0064] As an optional implementation, the calcination is carried out under anaerobic conditions.
[0065] As an optional implementation, the heating rate of the calcination is 1~10℃ / min, for example, it can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, etc.
[0066] As an optional implementation, the calcination temperature is 300~500℃, for example, 300℃, 350℃, 400℃, 450℃, 500℃, etc., and the calcination time is 1~8 h, for example, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, etc.
[0067] As an optional implementation, the following pretreatment step is further included before calcination: The precursor is ground to obtain the ground precursor.
[0068] As an optional implementation, the particle size of the milled precursor is <1 μm.
[0069] Thirdly, the present invention provides the application of the Mn-Co@MnO heterojunction oxygen reduction catalyst as described in the first aspect in the preparation of the cathode of a microbial fuel cell.
[0070] As an optional implementation, the Mn-Co@MnO heterojunction oxygen reduction catalyst is used in the preparation of a cathode for a microbial fuel cell for treating water bodies polluted by organic matter.
[0071] As an optional implementation, the Mn-Co@MnO heterojunction oxygen reduction catalyst is used in the preparation of a cathode for a microbial fuel cell for removing ethyl xanthate from organic wastewater.
[0072] Fourthly, the present invention provides a microbial fuel cell, the microbial fuel cell comprising an air cathode; wherein the air cathode comprises the Mn-Co@MnO heterojunction oxygen reduction catalyst as described in the first aspect.
[0073] As an optional implementation, the air cathode is prepared by the following steps: The Mn-Co@MnO heterojunction oxygen reduction catalyst, carbon source, and binder are mixed and then molded to obtain a disc-shaped air cathode.
[0074] As an optional implementation, the mass ratio of the calcined product, carbon source, and binder is 1:(5~15):(0.1~0.2).
[0075] As an optional implementation, the carbon source includes activated carbon powder.
[0076] As an optional implementation, the adhesive includes polytetrafluoroethylene (PTFE adhesive).
[0077] As an optional implementation, the specific steps of the mixing include: The Mn-Co@MnO heterojunction oxygen reduction catalyst, carbon source, and solvent are mixed and subjected to a first ultrasonic dispersion to obtain mixture one; a binder is added to the first dispersion and subjected to a second ultrasonic dispersion to obtain mixture two.
[0078] As an optional implementation, the solvent is ethanol.
[0079] As an optional implementation, the specific steps of the molding process include: The mixture obtained by mixing is rolled and then cultured to obtain the circular air cathode.
[0080] As an optional implementation, the thickness of the roll is less than 1 mm.
[0081] As an optional implementation, the culture temperature is 25~35℃ and the culture time is 5~7 h.
[0082] As an optional implementation, the assembly method of the microbial fuel cell is as follows: the disc-shaped air cathode is loaded onto the cathode of the microbial fuel cell.
[0083] Fifthly, the present invention provides a method for removing ethyl xanthate from organic wastewater, the removal method comprising: The organic wastewater containing ethyl xanthate is injected into the microbial fuel cell described in the fourth aspect to complete the removal of ethyl xanthate from the organic wastewater.
[0084] As an optional implementation, the concentration of ethyl xanthate in the organic wastewater is 100~1000 mg / L, for example, it can be 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, 600 mg / L, 700 mg / L, 800 mg / L, 900 mg / L, 1000 mg / L, etc.
[0085] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.
[0086] Example 1 This embodiment provides a Mn-Co@MnO heterojunction oxygen reduction catalyst, which is prepared by the following steps: (a) Solution preparation: At room temperature, K3[Co(CN)6] (0.46 mmol) and sodium citrate (0.1 g) were dissolved in 200 mL of distilled water, and Mn(NO3)2 (0.40 mmol) was dissolved in 200 mL of distilled water. After stirring evenly, manganese nitrate solution was slowly added to potassium cobalt cyanide solution while stirring continuously for 0.5 h to prepare the first solution, which was then stored for later use. At room temperature, Co(NO3)2·6H2O (0.28 mmol) and K3[Co(CN)6] (0.30 mmol) were dissolved in 50 mL of distilled water, respectively. After stirring evenly, the cobalt nitrate solution was slowly added to the potassium cobalt cyanide solution while stirring continuously for 0.5 h to prepare a second solution, which was then stored for later use.
[0087] (b) Preparation of precursors: At 25°C, the second solution was slowly added to the first solution while stirring continuously for 0.5 h to carry out the precipitation reaction and form a precursor solution. The precursor solution after the above reaction was centrifuged (8000 rpm, 10 min) for solid-liquid separation and washed three times with water to remove unreacted solution, and a solid substance was obtained. The obtained solid substance was placed in a vacuum drying oven for drying (80°C, 5 h) to obtain the precursor.
[0088] (c) Preparation of heterostructured nanomaterials: The precursor was ground to obtain a ground precursor powder (average particle size 600 nm). The ground precursor powder was placed in a tube furnace and heated to 300 °C for 2 h using nitrogen as a protective gas at a heating rate of 5 °C / min, and then naturally cooled to room temperature. The black sample was washed sequentially with ethanol and deionized water. Then it was dried in a vacuum oven at 80 °C for 15 h to obtain the heterostructured nanomaterial g-Co@CoMn.
[0089] Example 2 This embodiment provides a Mn-Co@MnO heterojunction oxygen reduction catalyst, which is prepared by the following steps: (a) Solution preparation: At room temperature, K3[Co(CN)6] (0.10 mmol) and sodium citrate (0.1 g) were dissolved in 200 mL of distilled water, and Mn(NO3)2 (0.40 mmol) was dissolved in 200 mL of distilled water. After stirring evenly, manganese nitrate solution was slowly added to potassium cobalt cyanide solution while stirring continuously for 0.5 h to prepare the first solution, which was then stored for later use. At room temperature, Co(NO3)2·6H2O (0.60 mmol) and K3[Co(CN)6] (0.30 mmol) were dissolved in 50 mL of distilled water and stirred until homogeneous. Then, the cobalt nitrate solution was slowly added to the potassium cobalt cyanide solution while stirring continuously for 0.5 h to prepare a second solution, which was then stored for later use.
[0090] (b) Preparation of precursors: At 25°C, the second solution was slowly added to the first solution while stirring continuously for 0.5 h to carry out the precipitation reaction and form a precursor solution. The precursor solution after the above reaction was centrifuged (9000 rpm, 10 min) for solid-liquid separation and washed three times with water to remove unreacted solution, obtaining a solid substance. The obtained solid substance was placed in a vacuum drying oven for drying (80°C, 5 h) to obtain the precursor.
[0091] (c) Preparation of heterostructured nanomaterials: The precursor was ground to obtain a ground precursor powder (average particle size 600 nm). The ground precursor powder was placed in a tube furnace and heated to 300 °C for 3 h using nitrogen as a protective gas at a heating rate of 5 °C / min, and then naturally cooled to room temperature. The black sample was washed sequentially with ethanol and deionized water. Then it was dried in a vacuum oven at 90 °C for 15 h to obtain the heterostructured nanomaterial g-Co@CoMn.
[0092] Comparative Example 1 This comparative example provides a carbon-coated CoMn catalyst, which is prepared by the following steps: (a) Solution preparation: At room temperature, K3[Co(CN)6] (0.46 mmol) and Mn(NO3)2 (0.40 mmol) were dissolved in 200 mL of distilled water and stirred until homogeneous. Then, manganese nitrate solution was slowly added to potassium cobalt cyanide solution while stirring continuously for 0.5 h to prepare the first solution, which was then stored for later use.
[0093] (b) Preparation of precursors: The first solution was centrifuged (8000 rpm, 10 min) to separate solids and liquids, and washed three times with water to remove unreacted solution, yielding a solid substance. The obtained solid substance was then dried in a vacuum drying oven at 80°C for 10 h to obtain the precursor CoMn-PBA.
[0094] (c) Preparation of nanomaterials: The ground precursor powder was placed in a tube furnace and heated to 300℃ for 2 h using nitrogen as a protective gas at a heating rate of 5℃ / min. The temperature was then maintained at this temperature for 2 h, followed by natural cooling to room temperature. The black sample was then washed sequentially with ethanol and deionized water. Finally, it was dried in a vacuum oven at 80℃ for 15 h to obtain the nanomaterial g-CoMn.
[0095] Comparative Example 2 This comparative example provides a carbon-coated Co catalyst, which is prepared by the following steps: (a) Solution preparation: At room temperature, Co(NO3)2·6H2O (0.28 mmol) and K3[Co(CN)6] (0.30 mmol) were dissolved in 200 mL of distilled water and stirred until homogeneous. Then, the cobalt nitrate solution was slowly added to the potassium cobalt cyanide solution while stirring continuously for 0.5 h to prepare a second solution, which was then stored for later use.
[0096] (b) Preparation of precursors: The second solution was centrifuged (8000 rpm, 10 min) to separate solids and liquids, and washed three times with water to remove unreacted solution, yielding a solid substance. The obtained solid substance was then dried in a vacuum drying oven at 80°C for 10 h to obtain the precursor CoCo-PBA.
[0097] (c) Preparation of nanomaterials: The ground precursor powder was placed in a tube furnace and heated to 300℃ for 2 h using nitrogen as a protective gas at a heating rate of 5℃ / min. The temperature was then maintained at this temperature for 2 h, followed by natural cooling to room temperature. The black sample was then washed sequentially with ethanol and deionized water. Finally, it was dried in a vacuum oven at 80℃ for 15 h to obtain the nanomaterial g-CoCo.
[0098] Comparative Example 3 This comparative example provides a blank control sample of activated carbon without a catalyst.
[0099] Test Example 1 Test samples: catalysts provided in Examples 1-2 and catalysts provided in Comparative Examples 1-3.
[0100] Test method: Cathode sheets loaded with different test samples were assembled into air cathodes for microbial fuel cells, while the anode was a pre-cultured carbon felt loaded with microorganisms. The cell volume was 28 mL, and the effective area of both the cathode and anode was 7 cm². 2 The distance between the cathode and anode is 4 cm. The cathode and anode are connected to a 1000 Ω external resistor via titanium wire, forming a complete circuit for electron transfer. Organic wastewater containing 200 mg / L ethyl xanthate was injected into the microbial fuel cell, water samples were taken to determine COD, and the COD removal rate was calculated.
[0101] The specific test results are shown in Table 1 below. Figure 1 As shown: Table 1
[0102] Table 1 demonstrates the application of the CoMn@Co heterojunction oxygen reduction catalyst of this invention in the preparation of the cathode for a microbial fuel cell used to remove ethyl xanthate from organic wastewater, achieving a removal rate of over 90.53% for ethyl xanthate in the organic wastewater. This fully illustrates that the Mn-Co@MnO heterojunction oxygen reduction catalyst prepared in this invention, by constructing a heterojunction structure and being coated with a carbon shell, forms highly active sites and electron transfer pathways, synergistically enhancing the ORR catalytic activity and electron transport efficiency of the catalyst, thereby significantly improving the removal rate of organic wastewater pollution.
[0103] Test Example 2 Test samples: the catalyst provided in Example 1 and the catalysts provided in Comparative Examples 1 to 3.
[0104] Test Method: Tests were conducted in a three-electrode system. Ag / AgCl (saturated potassium chloride) was used as the reference electrode, a platinum sheet as the auxiliary electrode, and cathodes loaded with different catalysts as the working electrodes. Experiments were performed on an electrochemical workstation in Electrochemical Impedance Spectroscopy mode, with frequencies set from 10 kHz to 0.1 Hz. The obtained data were used to obtain Nernst spectra using Zsimpwin software, and equivalent circuit diagrams were fitted.
[0105] The specific test results are as follows: Figure 1 : like Figure 1 As shown, the total resistance of the Mn-Co@MnO heterojunction oxygen reduction catalyst of the present invention is significantly lower than that of the carbon-coated CoMn or Co in the comparative example. This indicates that the Mn-Co@MnO heterojunction of this embodiment is beneficial to reducing the internal resistance of the catalyst cathode and promoting the transfer of electrons on the cathode surface, thus demonstrating the structural advantages of the Mn-Co@MnO heterojunction.
[0106] Test Example 3 Test samples: the catalyst provided in Example 1 and the catalysts provided in Comparative Examples 1 to 3.
[0107] Test Method: A three-electrode system was used, with Ag / AgCl (saturated potassium chloride) as the reference electrode, a platinum sheet as the auxiliary electrode, and an air cathode loaded with different catalysts as the working electrode. The electrolyte was a 50 mM phosphate buffer solution (pH=7). Experiments were conducted on an electrochemical workstation in Linear Sweep Voltammetry mode. The starting voltage was set to the open-circuit voltage, the ending voltage to -0.3 V, and the scan rate to 0.1 mV s⁻¹.
[0108] The specific test results are as follows: Figure 2 : like Figure 2 As shown, at -0.3 V, the current densities of g-CoMn@Co, g-CoMn, g-Co, and AC are 22.65 mA / cm². -2 20.44 mA cm -2 16.36 mA cm -2 11.03 mA cm -2 The Mn-Co@MnO heterojunction oxygen reduction catalyst of this invention exhibits the highest current density, indicating that it has the best oxygen reduction activity compared with other catalyst materials.
[0109] Test Example 4 Test sample: The catalyst provided in Example 1.
[0110] Test item: XRD test.
[0111] like Figure 3 As shown, the main components of the Mn-Co@MnO heterojunction oxygen reduction catalyst of this invention are MnO and Co elements, and the diffraction peak of Co elements shifts to the left, indicating that larger atoms than Co are embedded in the Co elements. Combined with test example 5, it can be proven that Mn atoms are embedded in Co.
[0112] Test Example 5 Test sample: The catalyst provided in Example 1.
[0113] Test items: SEM test and TEM test (including area scan and line scan).
[0114] like Figure 4 and Figures 5A-5D As shown, the Mn-Co@MnO heterojunction oxygen reduction catalyst comprises a heterostructured nanomaterial Mn-Co@MnO and a carbon shell coating the surface of the heterostructured Mn-Co@MnO; wherein the heterostructured nanomaterial Mn-Co@MnO is formed by combining MnO and Mn-doped Co. Furthermore, the Mn-Co@MnO heterojunction oxygen reduction catalyst exhibits a hollow tubular structure with a length of 200-700 nm; the average particle size of the Mn-Co@MnO is 60 nm; and the average thickness of the carbon shell is 10 nm.
[0115] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A Mn-Co@MnO heterojunction oxygen reduction catalyst, characterized in that, The Mn-Co@MnO heterojunction oxygen reduction catalyst comprises a nanomaterial Mn-Co@MnO with a heterostructure and a carbon shell layer coated on the surface of the material Mn-Co@MnO with the heterostructure; The carbon shell layer has a hollow tubular structure; the nanomaterial Mn-Co@MnO with the heterostructure is formed by combination of Mn-doped Co single element and MnO; and the Mn-Co@MnO has an ellipsoidal shape and is discontinuously coated in the carbon shell layer.
2. The Mn-Co@MnO hetero-nano-catalyst for oxygen reduction according to claim 1, characterized in that, The length of the hollow tubular structure is 200-700 nm; Preferably, the particle size of the nanomaterial with the heterostructure is 30-70 nm; Preferably, the thickness of the carbon shell layer is 5-20 nm.
3. A method for preparing the Mn-Co@MnO heterojunction oxygen reduction catalyst according to claim 1 or 2, characterized in that, The preparation method comprises: mixing a first cobalt source, a manganese source and a solvent to prepare a first solution; mixing a first cobalt source, a second cobalt source and a solvent to prepare a second solution; adding the second solution to the first solution to perform a precipitation reaction, and then performing solid-liquid separation and drying to obtain a precursor; calcining the precursor to obtain the Mn-Co@MnO heterojunction oxygen reduction catalyst.
4. The preparation method of the Mn-Co@MnO heterojunction oxygen reduction catalyst according to claim 3, characterized in that, The first cobalt source is selected from any one or a combination of at least two of potassium cobalt cyanide, ammonium cobalt cyanide and sodium cobalt cyanide; Preferably, the second cobalt source is selected from any one or a combination of at least two of cobalt citrate, cobalt nitrate and cobalt acetate; Preferably, the manganese source is selected from any one or a combination of at least two of manganese nitrate, manganese acetate and manganese citrate; Preferably, in the process of preparing the first solution, the solvent is an aqueous solvent containing sodium citrate, and the content of sodium citrate is 0.1-0.5 g / L; and in the process of preparing the second solution, the solvent is an aqueous solvent; Preferably, in the process of preparing the first solution, the molar ratio of the first cobalt source to the manganese source is (1-3):1; Preferably, in the process of preparing the second solution, the molar ratio of the first cobalt source to the second cobalt source is 1:(0.9-3).
5. The preparation method of the Mn-Co@MnO heterojunction oxygen reduction catalyst according to claim 3, characterized in that, The molar ratio of the first cobalt source in the first solution to the first cobalt source in the second solution is (1-2):1; Preferably, the temperature of the precipitation reaction is 20-40℃, and the time of the precipitation reaction is 1-2 h; Preferably, the solid-liquid separation is performed by centrifugation, wherein the rotation speed of the centrifugation is 7000-10000 rpm, and the time of the centrifugation is 10-30 min; Preferably, the drying is performed by vacuum drying, wherein the temperature of the drying is 80-100℃, and the time of the drying is 10-24 h.
6. The preparation method of the Mn-Co@MnO heterojunction oxygen reduction catalyst according to claim 3, characterized in that, The calcination is performed under an oxygen-free condition; Preferably, the heating rate of the calcination is 1-10℃ / min; Preferably, the temperature of the calcination is 300-500℃, and the time of the calcination is 1-8 h; Preferably, the calcination further comprises the following pretreatment step: grinding the precursor; grinding until the particle size of the precursor is <1 μm.
7. Use of the Mn-Co@MnO heterojunction oxygen reduction catalyst according to claim 1 or 2 in the preparation of a cathode of a microbial fuel cell. And / or, the application of the Mn-Co@MnO heterojunction oxygen reduction catalyst in the preparation of a cathode of a microbial fuel cell for treating water bodies polluted by organic matters. And / or, the application of the Mn-Co@MnO heterojunction oxygen reduction catalyst in the preparation of a cathode of a microbial fuel cell for removing ethyl xanthate in organic wastewater.
8. A microbial fuel cell characterized by, The microbial fuel cell comprises an air cathode; wherein the air cathode comprises the Mn-Co@MnO heterojunction oxygen reduction catalyst according to claim 1 or 2.
9. A method for removing ethyl xanthate from organic wastewater, characterized by, The removal method comprises: The removal of ethyl xanthate in the organic wastewater is completed by injecting the organic wastewater containing ethyl xanthate into the microbial fuel cell according to claim 8.
10. The method for removing ethyl xanthate from organic wastewater according to claim 9, characterized in that, The concentration of ethyl xanthate in the organic wastewater is 100-1000 mg / L.