Oxygen wall before and after composite type transition metal-based porphyrin heterogeneous catalyst and application thereof

Abstract

The application discloses an oxygen wall front-back composite transition metal-based porphyrin heterogeneous catalyst and application thereof. An oxygen wall front-back transition metal-based porphyrin complex is covalently connected to carbon nanomaterial by an amide bond to synthesize a heterogeneous oxygen reduction catalyst. The catalyst combines the advantages of high activity of the oxygen wall back transition metal site and high four-electron oxygen reduction selectivity of the oxygen wall front transition metal site, has excellent oxygen reduction performance, is superior to a physical mixing sample of corresponding two kinds of single unit metal catalysts, and when used as a metal air battery catalyst, the battery has a charge-discharge platform voltage difference of 2 mA / cm 2 or even is superior to a commercial platinum-carbon and iridium-carbon mixed catalyst. The catalyst has simple and easily available raw materials, mild reaction conditions and simple operation, has high reaction performance, low catalyst consumption, easy catalytic conditions and good catalyst stability when catalyzing oxygen reduction and secondary metal air batteries.

Description

Technical Field

[0001] This invention belongs to the field of oxygen reduction reaction catalyst technology, specifically relating to transition metal-based porphyrin catalysts and their applications in oxygen reduction reactions and metal-air batteries. Background Technology

[0002] With the gradual depletion of the traditional energy system based on fossil fuels and the increasing environmental pollution it causes, there is an urgent need to develop renewable and clean energy technologies and corresponding energy storage systems. The development of metal-air batteries based on the oxygen reduction reaction (ORR) has provided new opportunities for the development and storage of clean energy technologies. However, the OCR kinetics are slow, necessitating the development of highly efficient catalysts to promote the reaction.

[0003] Noble metal-based catalysts exhibit excellent activity, but their low reserves and high cost limit their large-scale application. Transition metal catalysts, on the other hand, are abundant, inexpensive, and have easily tunable physicochemical properties, thus attracting widespread attention from the academic community. Group VIII and Group IX transition metals, in their catalytic processes, involve antibonding π-linked oxygen intermediates. * The different numbers of electrons filling the orbitals result in vastly different reaction mechanisms, and the two groups are referred to as the oxygen wall. In the catalytic oxygen reduction reaction, although the transition metal sites behind the oxygen wall are highly active, they have poor selectivity for the four-electron oxygen reduction pathway, tending to reduce oxygen to hydrogen peroxide; while the transition metal sites in front of the oxygen wall have good four-electron pathway selectivity and can directly reduce oxygen to water molecules that are harmless to the energy supply system, their activity is relatively poor.

[0004] Furthermore, porphyrin ligands possess a rigid and stable coordination environment, and can stabilize variable-valence metal ion intermediates, allowing them to coordinate with various metal ions to form diverse metal porphyrin complexes. This enriches the redox properties of metal porphyrin complexes, making them suitable for research on electrocatalytic oxygen reduction reactions (Chem. Rev. 2017, 117, 3717-3797). Moreover, considering the high-speed electron conduction required for electrocatalysis, it is necessary to heterogeneousize the molecular sites, such as immobilizing porphyrin molecules onto carbon nanomaterials to prepare heterogeneous catalytic materials for metal porphyrin complexes (ACS Catal. 2017, 7, 8033-8041). Summary of the Invention

[0005] The purpose of this invention is to provide an oxygen-wall-based transition metal-based porphyrin heterogeneous catalyst with high activity and good stability for use in oxygen reduction reactions and in metal-air batteries based on oxygen reduction reactions.

[0006] To achieve the above objectives, the oxygen-wall-before-and-after composite transition metal-based porphyrin heterogeneous catalyst used in this invention employs 5-(4-aminophenyl)-10,15,20-triphenylporphyrin as a ligand. First, a solvothermal method is used to coordinate the oxygen-wall-before transition metal and the oxygen-wall-after transition metal with the ligand to prepare complexes. Then, the two complexes are covalently immobilized onto carbon nanomaterials to obtain the catalyst.

[0007] The transition metal before the oxygen wall is any one of Mn and Fe, the transition metal after the oxygen wall is any one of Co, Ni, and Cu, and the carbon nanomaterial is any one of carbon nanotubes, graphene, or their derivatives.

[0008] The preparation method of the oxygen wall front and rear composite transition metal-based porphyrin heterogeneous catalyst of the present invention includes the following steps:

[0009] 1. Add 5-(4-aminophenyl)-10,15,20-triphenylporphyrin ligand and a soluble salt of an oxygen-walled transition metal to N,N-dimethylformamide at a molar ratio of 1:2. Reflux at 110–130 °C for 6–10 hours. After cooling to room temperature, separate and purify to obtain the oxygen-walled transition metal-based porphyrin complex.

[0010] 2. 5-(4-aminophenyl)-10,15,20-triphenylporphyrin ligand and a soluble salt of an oxygen-walled transition metal were added to N,N-dimethylformamide at a molar ratio of 1:2. The mixture was refluxed at 100–110 °C for 6–10 hours. After cooling to room temperature, the oxygen-walled transition metal-based porphyrin complex was obtained by separation and purification.

[0011] 3. Carboxylated carbon nanomaterials were added to dichloromethane containing oxygen-walled transition metal-based porphyrin complexes and oxygen-walled transition metal-based porphyrin complexes. Dicyclohexylcarbodiimide, 1-hydroxybenzotriazole, 4-dimethylaminopyridine, and triethylamine were added to the mixture. After ultrasonic treatment to disperse the mixture evenly, it was stirred at room temperature for 4–6 days. Then, it was centrifuged, washed with dichloromethane, and freeze-dried to obtain bimetallic porphyrin covalently linked carbon nanomaterials, namely, oxygen-walled and oxygen-walled composite transition metal-based porphyrin heterogeneous catalysts.

[0012] In the above preparation method, the soluble salt of the transition metal before the oxygen wall is any one of ferrous chloride and manganese acetate, and the soluble salt of the transition metal after the oxygen wall is any one of cobalt acetate, nickel acetate, and copper acetate.

[0013] In step 3 above, the mass ratio of the carboxylated carbon nanomaterial, the oxygen-containing pre-wall transition metal-based porphyrin complex, the post-wall transition metal-based porphyrin complex, dicyclohexylcarbodiimide, 1-hydroxybenzotriazole, 4-dimethylaminopyridine, and triethylamine is 1.5–3:1:1:3–5:3–5:0.15–0.3:0.01–0.02.

[0014] The oxygen-wall-based transition metal-based porphyrin heterogeneous catalyst of this invention can be used to catalyze oxygen reduction reactions and in metal-air batteries.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. This invention is based on a novel relay catalytic mechanism of transition metal sites before and after the oxygen wall, and the stabilizing effect of porphyrin ligands on the transition metal center. Transition metal-based porphyrin complexes before and after the oxygen wall are covalently immobilized on the surface of carbon nanotubes via amide bonds to prepare a multi-component composite transition metal-based porphyrin heterogeneous catalyst. This catalyst achieves molecular-level dispersion of transition metal sites before and after the oxygen wall. The oxygen reduction catalytic reaction is triggered at the transition metal site after the oxygen wall, followed by catalytic relay at the transition metal site before the oxygen wall. The multiple sites cooperate to complete the catalytic reaction, allowing the catalyst to exhibit both the four-electron path selectivity of the transition metal site before the oxygen wall and the high activity of the transition metal after the oxygen wall during the oxygen reduction reaction. Thanks to this catalytic relay, the performance of the catalyst of this invention is far superior to that of mixed materials of corresponding single-metal catalysts.

[0017] 2. This invention constructs a composite transition metal-based porphyrin heterogeneous catalyst with oxygen wall before and after covalent immobilization, which not only realizes heterogeneous catalysis of metal porphyrin complexes, but also possesses the excellent properties of carbon nanomaterials such as high electrical conductivity, large surface area and good chemical stability.

[0018] 3. The oxygen-wall-based transition metal-based porphyrin heterogeneous catalyst prepared in this invention exhibits high activity and good stability in oxygen reduction reactions and metal-air batteries based on oxygen reduction reactions. Furthermore, it outperforms mixed catalysts with multiple corresponding unit catalysts and noble metal-based catalysts. For example, when applied to metal-air batteries, the charge / discharge current density reaches 2 mA / cm². 2 At that time, the voltage difference between the charge and discharge platforms was only 0.75V, which is better than the 0.83V exhibited by commercial platinum-carbon and iridium-carbon mixed catalysts with the same loading.

[0019] 4. The preparation method of the catalyst of the present invention is simple to operate and the reaction conditions are mild. When applied to oxygen reduction reaction and rechargeable metal-air batteries, the catalyst dosage is low and the catalytic conditions are easy to control, which has a good development prospect. Attached Figure Description

[0020] Figure 1 This is the synthetic route diagram for 1-Fe / 1-Co@CNT.

[0021] Figure 2 These are the infrared spectra of porphyrin ligands 1, CNT-COOH, and 1-Fe / 1-Co@CNT.

[0022] Figure 3The following are linear scans of oxygen reduction for 1-Co@CNT, 1-Fe@CNT, and 1-Fe / 1-Co@CNT (a) and a performance comparison (b).

[0023] Figure 4 This is a linear scan of oxygen reduction for a mixed catalyst of 1-Co@CNT and 1-Fe@CNT (mixed at a mass ratio of 1:1) and 1-Fe / 1-Co@CNT.

[0024] Figure 5 The diagram shows a metal-air battery device (a) and a comparison of the constant current charge-discharge performance of a battery based on 1-Fe / 1-Co@CNT and a battery with an equivalent loading of platinum-carbon and iridium-carbon mixed catalyst (b). Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0026] Example 1

[0027] according to Figure 1 The catalyst was synthesized via a specific route, and the detailed synthesis method is as follows:

[0028] 1. 63 mg (0.1 mmol) of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin ligand (denoted as porphyrin ligand 1) and 25 mg (0.2 mmol) of anhydrous ferrous chloride were added to a 50 mL round-bottom flask, followed by 20 mL of N,N-dimethylformamide as solvent. The mixture was refluxed at 120 °C for 8 h. After cooling to room temperature, the solvent was removed by rotary evaporation. The resulting solid was purified by column chromatography using a 20:1 mixture of dichloromethane and methanol as eluent. The product was collected, and the solvent was removed by rotary evaporation under reduced pressure to obtain 61.2 mg of the purple solid product 5-(4-aminophenyl)-10,15,20-triphenylporphyrin iron porphyrin (denoted as 1-Fe), with a yield of 90.8%. The structural characterization data are as follows: HRMS (ESI) m / z:C 44 H 29 FeN5, [M+H] + Theoretical value: 683.1768; Measured value: 683.1759.

[0029] 2. 63 mg (0.1 mmol) of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin ligand and 50 mg (0.2 mmol) of cobalt acetate tetrahydrate were added to a 50 mL round-bottom flask, followed by 20 mL of N,N-dimethylformamide as a solvent. The mixture was refluxed at 100 °C for 8 h. After cooling to room temperature, the solvent was removed by rotary evaporation. The resulting solid was purified by column chromatography using a 1:1 mixture of dichloromethane and petroleum ether as eluent. The product was collected, and the solvent was removed by rotary evaporation under reduced pressure to obtain a red solid product, 5-(4-aminophenyl)-10,15,20-triphenylporphyrin cobalt porphyrin (denoted as 1-Co), at a yield of 90.8%. The structural characterization data were: HRMS (ESI) m / z: C 44 H 29 CoN5, [M+H] + The theoretical value is 686.1749, and the measured value is 686.7164.

[0030] 3. 20 mg of carboxyl-based carbon nanotubes were added to 5 mL of a dichloromethane solution containing 10 mg of 1-Fe and 10 mg of 1-Co. Then, 40 mg of dicyclohexylcarbodiimide, 40 mg of 1-hydroxybenzotriazole, 2 mg of 4-dimethylaminopyridine, and 0.1 g of triethylamine were added to the mixture. The mixture was sonicated for 30 minutes, then stirred at room temperature for 5 days. After centrifugation to obtain a black solid, it was washed three times with dichloromethane and freeze-dried to obtain 30 mg of bimetallic porphyrin covalently linked carbon nanotubes, i.e., an iron-cobalt-based composite porphyrin heterogeneous catalyst (denoted as 1-Fe / 1-Co@CNT), with a yield of 75%. Characterization was performed using infrared spectroscopy; the carboxyl-based carbon nanotubes showed a fluorescence intensity at 1715 cm⁻¹. -1 The characteristic peak of the carboxyl group is present at a certain point. However, when it reacts with aminometal porphyrins 1-Fe and 1-Co, the characteristic peak of the carboxyl group disappears, and a peak at 1643 cm⁻¹ is formed. -1 The new peak, corresponding to the infrared characteristic peak of the amide group, proves that 1-Fe and 1-Co are successfully covalently linked to the carbon nanotube, such as... Figure 2 As shown.

[0031] The 1-Fe / 1-Co@CNT prepared above was used for catalytic oxygen reduction reaction. Specifically, 4 mg of 1-Fe / 1-Co@CNT was dispersed in 950 μL of dimethylamide and 50 μL of Nafion solution, and then sonicated in an ultrasonic bath for 30 minutes to obtain a catalyst dispersion. 10 μL of this dispersion was uniformly drop-coated onto a clean glassy carbon electrode as the working electrode for electrochemical testing. A three-electrode system was formed using a carbon rod as the counter electrode and an Ag / AgCl electrode as the reference electrode. Oxygen reduction reaction performance was tested in 0.1 M KOH electrolyte. Simultaneously, 1-Fe@CNT and 1-Co@CNT (prepared using the same method as 1-Fe / 1-Co@CNT, except that only 1-Fe@CNT or 1-Co@CNT was added in step 3) were also prepared as working electrodes, and their oxygen reduction reaction performance was tested in 0.1 M KOH electrolyte. Figure 3 The results clearly show that 1-Fe / 1-Co@CNT, which has both iron and cobalt bimetallic properties, performs better than either of the two single metals. This is not only because it requires a smaller overpotential to carry out the oxygen reduction reaction, but also because it directly reduces oxygen to water, which is more beneficial for environmental pollution and battery safety.

[0032] In addition, 4 mg of 1-Fe / 1-Co@CNT and a mixture of 4 mg of 1-Fe@CNT and 1-Co@CNT (mixed at a mass ratio of 1:1, denoted as 1-Fe@CNT+1-Co@CNT) were each dispersed in 950 μL of dimethylamide and 50 μL of Nafion solution, and sonicated in an ultrasonic bath for 30 minutes to obtain a catalyst dispersion. 10 μL of this dispersion was uniformly drop-coated onto a clean glassy carbon electrode as the working electrode for electrochemical testing. A three-electrode system was formed using a carbon rod as the counter electrode and an Ag / AgCl electrode as the reference electrode. Oxygen reduction reaction performance was tested in 0.1 M KOH electrolyte. Figure 4 The linear scanning curve of its oxygen reduction is shown in the figure. As can be seen from the figure, compared with the catalyst obtained by physical mixing of 1-Fe@CNT and 1-Co@CNT, the 1-Fe / 1-Co@CNT prepared in this invention exhibits a significantly better potential at the same current density and a larger limiting current, demonstrating significantly higher catalytic activity and four-electron pathway selectivity, which further confirms the rationality of the catalyst design strategy of this invention.

[0033] The 1-Fe / 1-Co@CNTs prepared above were used in a metal-air battery. Specifically, 1-Fe / 1-Co@CNTs were loaded onto a carbon cloth / air diffusion layer as the cathode, and polished zinc metal was used as the anode, forming the galvanic cell system 1-Fe / 1-Co@CNT||6M KOH||Zn. Simultaneously, a metal-air battery with an equivalent loading of platinum-carbon and iridium-carbon mixtures as the cathode, polished zinc metal as the anode, and 6M KOH solution as the electrolyte was used as a comparison for battery performance testing. A schematic diagram of the zinc-air battery is shown below. Figure 5 As shown in Figure a, the battery performance of the two is compared as follows: Figure 5 As shown in b. The results show that the voltage plateau difference required for charging and discharging of the zinc-air battery with 1-Fe / 1-Co@CNT as the cathode catalyst at the same current is smaller than that of the metal-air battery with an equal amount of platinum-carbon and iridium-carbon mixture loaded on the cathode. This indicates that the oxygen reduction performance of the catalyst of the present invention is excellent, even better than that of noble metal-based catalysts, and has broad application prospects.

[0034] In Example 1 above, ferrous chloride can be replaced with an equimolar amount of manganese acetate, cobalt acetate can be replaced with an equimolar amount of nickel acetate or copper acetate, and carbon nanotubes can be replaced with an equal mass of graphene or its derivatives to prepare corresponding bimetallic porphyrin covalently linked carbon nanomaterials, namely, oxygen-wall-front composite transition metal-based porphyrin heterogeneous catalysts. The resulting catalysts can all be used in catalyzing oxygen reduction reactions and metal-air batteries.

Claims

1. A composite transition metal-based porphyrin heterogeneous catalyst with an oxygen wall for catalyzing the oxygen reduction reaction, characterized in that, The catalyst is prepared by first using 5-(4-aminophenyl)-10,15,20-triphenylporphyrin as a ligand, and then using a solvothermal method to coordinate the pre-oxygen wall transition metal and the post-oxygen wall transition metal with the ligand to prepare complexes. The two complexes are then covalently immobilized onto carbon nanomaterials. The transition metal before the oxygen wall is any one of Mn and Fe; the transition metal after the oxygen wall is any one of Co, Ni, and Cu. The catalyst is prepared as follows: (1) 5-(4-aminophenyl)-10,15,20-triphenylporphyrin ligand and soluble salt of oxygen-walled transition metal were added to N,N-dimethylformamide at a molar ratio of 1:

2. The mixture was refluxed at 110-130 °C for 6-10 hours. After cooling to room temperature, the oxygen-walled transition metal-based porphyrin complex was obtained by separation and purification. (2) 5-(4-aminophenyl)-10,15,20-triphenylporphyrin ligand and soluble salt of oxygen-walled transition metal were added to N,N-dimethylformamide in a molar ratio of 1:

2. The mixture was refluxed at 100-110 °C for 6-10 hours. After cooling to room temperature, the oxygen-walled transition metal-based porphyrin complex was obtained by separation and purification. (3) Carboxylated carbon nanomaterials were added to dichloromethane containing oxygen-walled transition metal-based porphyrin complexes and oxygen-walled transition metal-based porphyrin complexes. Dicyclohexylcarbodiimide, 1-hydroxybenzotriazole, 4-dimethylaminopyridine and triethylamine were added to the mixture. After ultrasonic treatment to disperse evenly, the mixture was stirred at room temperature for 4 to 6 days. Then, it was centrifuged, washed with dichloromethane and freeze-dried to obtain bimetallic porphyrin covalently linked carbon nanomaterials, namely oxygen-walled and oxygen-walled composite transition metal-based porphyrin heterogeneous catalysts.

2. The oxygen-wall-before-after composite transition metal-based porphyrin heterogeneous catalyst according to claim 1, characterized in that, The carbon nanomaterial is any one of carbon nanotubes, graphene, or their derivatives.

3. The oxygen-wall-front-and-back composite transition metal-based porphyrin heterogeneous catalyst according to claim 1, characterized in that, The soluble salt of the transition metal before the oxygen wall is any one of ferrous chloride and manganese acetate; the soluble salt of the transition metal after the oxygen wall is any one of cobalt acetate, nickel acetate, and copper acetate.

4. The oxygen-wall-front-and-back composite transition metal-based porphyrin heterogeneous catalyst according to claim 1, characterized in that, In step (3), the mass ratio of the carboxylated carbon nanomaterial, the oxygen-containing pre-transition metal porphyrin complex, the oxygen-containing post-transition metal porphyrin complex, the dicyclohexylcarbodiimide, the 1-hydroxybenzotriazole, the 4-dimethylaminopyridine, and the triethylamine is 1.5-3:1:1:3-5:3-5:0.15-0.3:0.01-0.

02.

5. The application of the oxygen wall-front and rear composite transition metal-based porphyrin heterogeneous catalyst according to claim 1 in the catalytic oxygen reduction reaction.

6. The application of the oxygen wall-front and rear composite transition metal-based porphyrin heterogeneous catalyst according to claim 1 in metal-air batteries.

Images