A hydrogen-oxygen fuel cell anode composite catalyst, its preparation method and application

Abstract

The present invention provides a hydrogen-oxygen fuel cell anode composite catalyst, a preparation method thereof and an application thereof, belonging to the technical fields of catalyst preparation and hydrogen-oxygen fuel cells. In the present invention, a Ni precursor is first loaded on CNT modified by PVP, and then Ir nanoparticles are loaded to obtain the hydrogen-oxygen fuel cell anode composite catalyst. The hydrogen-oxygen fuel cell anode composite catalyst has excellent hydrogen oxidation performance and has potential application prospects in hydrogen-oxygen fuel cells. The preparation process of the present invention is simple and easy to implement, has good repeatability, and is easy to be implemented industrially.

Description

Technical Field

[0001] The present invention relates to the technical fields of catalyst preparation and hydrogen-oxygen fuel cell technology, and particularly relates to an anode composite catalyst for a hydrogen-oxygen fuel cell, a preparation method thereof, and an application thereof. Background Art

[0002] A hydrogen-oxygen fuel cell is a device that converts hydrogen energy into electrical energy. The oxygen reduction reaction and the hydrogen oxidation reaction are respectively carried out at both ends of the cell, and the only product is water. Due to the advantages of pollution-free and high efficiency of the hydrogen-oxygen fuel cell, it has received extensive attention. In the past few decades, proton exchange membrane fuel cells (PEMFCs) have attracted the attention of the scientific community. However, the slow rate of the cathode oxygen reduction reaction (ORR) has led to a high demand for platinum group metals. Non-precious metal-based materials have low activity and poor stability. Developing platinum group metal-free efficient electrocatalysts for proton exchange membrane fuel cells still faces great difficulties and challenges, thus severely limiting the practical application of proton exchange membrane fuel cells.

[0003] In recent years, anion exchange membrane fuel cells (AEMFCs) using alkaline electrolytes have received extensive attention. In alkaline electrolytes, many non-platinum materials can be used as ORR catalysts, and even can achieve almost the same catalytic effect as Pt. However, the hydrogen oxidation reaction (HOR) rate at the anode end in anion exchange membrane fuel cells is slow. Currently, the non-Pt catalysts for catalyzing hydrogen oxidation mainly include various nickel-based materials and alloys and composites formed by non-Pt metals such as Ir and Ru, but they still have deficiencies such as insufficient catalyst activity, poor stability, and cumbersome preparation processes. Therefore, there is an urgent need to provide an efficient and stable Ir-based alkaline HOR electrocatalyst. Summary of the Invention

[0004] Aiming at the problems of insufficient activity, poor stability, and cumbersome preparation process of Ir-based catalysts in the prior art, the present invention provides an anode composite catalyst for a hydrogen-oxygen fuel cell, a preparation method thereof, and an application thereof. In the present invention, a Ni precursor is first loaded on CNT modified by PVP, and then Ir nanoparticles are loaded to obtain an anode composite catalyst for a hydrogen-oxygen fuel cell; the anode composite catalyst for a hydrogen-oxygen fuel cell has excellent hydrogen oxidation performance and has potential application prospects in hydrogen-oxygen fuel cells; the preparation process of the present invention is simple and easy to operate, has good repeatability, and is easy to implement industrially.

[0005] The present invention first provides an anode composite catalyst for a hydrogen-oxygen fuel cell. In the composite catalyst, Ir nanocrystals are uniformly loaded on CNT and NiO-Ni nanoparticles.

[0006] The present invention also provides a preparation method for the above-mentioned anode composite catalyst for a hydrogen-oxygen fuel cell, which specifically includes the following steps:

[0007] (1) Functionalization of carbon support:

[0008] Add carbon nanotubes (CNT) and polyvinylpyrrolidone K30 (PVP) into ethanol, stir and react. After the reaction, filter by suction and dry to obtain PVP-functionalized carbon support (PVP-CNT);

[0009] (2) Preparation of functionalized carbon support loaded with Ni precursor:

[0010] Dissolve PVP-CNT, nickel source and hexamethylenetetramine (HMTA) in a mixed solution of H2O and ethylene glycol. After mixing evenly, carry out hydrothermal reaction. After the reaction, centrifuge, wash and dry, and then calcine the dried product to obtain the functionalized carbon support loaded with Ni precursor, denoted as NiO / CNT;

[0011] (3) Preparation of anode composite catalyst for hydrogen-oxygen fuel cell:

[0012] Dissolve NiO / CNT in ethylene glycol, then add the precursor of Ir, stir evenly and react by oil bath heating. After the reaction, collect the solid product to obtain the anode composite catalyst for hydrogen-oxygen fuel cell, that is, Ir / NiO-Ni / CNT composite catalyst.

[0013] Furthermore, in step (1), the dosage ratio of the carbon nanotubes, polyvinylpyrrolidone K30 and ethanol is 25 - 150 mg: 100 - 600 mg: 10 - 60 mL, preferably 50 mg: 200 mg: 20 mL.

[0014] Furthermore, in step (1), the conditions of the stirring reaction are room temperature and the time is 6 - 24 h, preferably 12 h.

[0015] Furthermore, in step (2), the nickel source is any one of NiCl2, NiSO4, Ni(CH3COO)2, Ni(NO3)2, preferably NiCl2.

[0016] Furthermore, in step (2), the dosage ranges of PVP-CNT, nickel source and HMTA are 25 - 100 mg: 0.5 - 2 mmol: 1 - 4 mmol, preferably 50 mg: 1 mmol: 2 mmol;

[0017] In the mixed solution of H2O and ethylene glycol, the volume ratio of H2O and ethylene glycol is 2:3.

[0018] Furthermore, in step (2), the conditions of the hydrothermal reaction are to react at 100 - 200 °C for 1 - 6 h; preferably, the hydrothermal reaction conditions are to react at 150 °C for 4 h.

[0019] Furthermore, in step (2), the calcination condition is calcining at 400-800° C. for 0.5-5 h;

[0020] Preferably, the calcination condition is calcination at 500° C. for 3 hours.

[0021] Furthermore, in step (3), the ratio of the NiO / CNT, ethylene glycol, and Ir precursors is 24 mg:30 mL:5-50 mg;

[0022] Preferably, the ratio of the NiO / CNT, ethylene glycol and Ir precursors is 24 mg:30 mL:24 mg.

[0023] Furthermore, in step (3), the precursor of Ir is chloroiridic acid.

[0024] Furthermore, in step (3), the oil bath heating condition is 120-200° C. for 1-3 hours.

[0025] The present invention also provides the use of the above hydrogen-oxygen fuel cell anode composite catalyst in a hydrogen-oxygen fuel cell.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] In practical applications, single-component materials are often difficult to meet actual needs, so multiple component materials are often effectively combined to form a composite structure. The composite structure not only has different properties from multiple components, but also often shows enhanced properties or properties that are not possessed by a single component due to the electronic effects between different components. In addition, the difference in electronegativity between different metals in the composite material will lead to the directional movement of charge and can regulate the electronic structure of metal surface sites, prompting it to show the best performance in the HOR catalytic process. There is a synergistic electronic effect between the components of the Ir / NiO-Ni / CNT catalyst constructed in the present invention. The strong Ni-H bond in the Ni-based catalyst leads to its low HOR activity. The introduction of the oxygen-philic element metal Ir is conducive to the adsorption of OH and can accelerate the desorption of H adsorbed on adjacent active sites.

[0028] In this invention, NiO is loaded onto a functionalized carbon support. During heating in an oil bath, elemental Ni is generated, resulting in NiO-Ni nanoparticles. The strong interaction between the Ni and Ir metals and the CNT support enhances reaction activity, modulates catalytic selectivity, and improves catalyst stability, attracting widespread attention. The strong interaction between the metal nanoparticles and the support may also improve the durability of the electrocatalyst.

[0029] Since the alkaline HOR reaction occurs on the surface of catalyst particles, controlling the particle size and particle size distribution of the particles is crucial for improving its activity. In the present invention, the particle size of Ir in the Ir / NiO-Ni / CNT catalyst is controlled to about 2.00 nm by regulating the oil bath time or the oil bath temperature. At this time, the Ir nanoparticles are more evenly loaded on the surfaces of NiO-Ni and CNT. The appropriate heating time and heating temperature avoid the agglomeration of Ir nanoparticles, increase the catalytic reaction active area, and thus enhance the HOR catalytic activity.

[0030] In the present invention, the Ni precursor is first loaded on the PVP-modified CNT, and then the highly catalytically active Ir nanoparticles are loaded to obtain the anode composite catalyst for the hydrogen oxygen fuel cell. The Ir content in the composite catalyst is low, and the reaction temperature and time in the preparation process are low and short. The present invention uses common ethylene glycol in the market as the solvent and reducing agent, the reaction raw materials are easy to obtain, and the prepared Ir / NiO-Ni / CNT catalyst has a uniform particle size and a relatively regular morphology, and its mass activity is 0.77 mA μg -1 PGM , even higher than that of the commercial Pt / C catalyst (0.27 mA μg -1 PGM ). The method described in the invention has a simple and easy preparation process, good repeatability, low cost, and is easy to implement industrially. Description of the Drawings

[0031] Figure 1 It is the X-ray diffraction (XRD) pattern of the Ir / NiO@Ni / CNT composite structure.

[0032] Figure 2 It is the transmission electron microscope (TEM) image of the Ir / NiO@Ni / CNT composite structure.

[0033] Figure 3 It is the comparison diagram of the linear sweep curves of hydrogen oxidation of the Ir / NiO@Ni / CNT composite catalyst and the commercial Pt / C (platinum mass percentage 20%) catalyst, where A is the catalytic LSV curve of the Ir / NiO-Ni / CNT composite catalyst, and B is the catalytic LSV curve of the commercial Pt / C catalyst.

[0034] Figure 4 It is the stability diagram of the Ir / NiO@Ni / CNT composite catalyst. In the figure, curve A is the result of the first linear sweep of hydrogen oxidation, and curve B is the result of the linear sweep of hydrogen oxidation after 2000 cycles of cyclic voltammetry scanning. Detailed Embodiments

[0035] The present invention will be further described below in conjunction with the drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0036] Example 1:

[0037] (1) Functionalization of carbon support:

[0038] Modify CNT by PVP (polyvinylpyrrolidone K30). The specific modification steps are as follows:

[0039] Dissolve 50 mg of CNT and 200 mg of PVP in 20 ml of ethanol, stir magnetically for 12 h, then filter by suction and dry to obtain PVP-CNT.

[0040] (2) Preparation of functionalized carbon support loaded with Ni precursor:

[0041] Accurately weigh 50 mg of the obtained PVP-CNT above, an appropriate amount of NiCl2·6H2O (1 mmol), and HMTA (2 mmol), dissolve them in a mixed solution of 12 mL of H2O and 18 mL of ethylene glycol (EG), after ultrasonic dissolution, place it in a 50 mL autoclave, perform hydrothermal treatment at 120 °C for 4 h. After the solution cools to room temperature, wash it by centrifugation with distilled water and ethanol in sequence, and dry it under vacuum to obtain Ni(OH)2 / CNT powder. Then place the Ni(OH)2 / CNT powder in a porcelain boat, calcine it in an air atmosphere at 500 °C with a heating rate of 2 °C / min for 2 h to obtain NiO / CNT powder.

[0042] (3) Preparation of anode composite catalyst for hydrogen-oxygen fuel cell:

[0043] Dissolve 24 mg of the obtained NiO / CNT powder above in 30 mL of ethylene glycol solution and perform ultrasonic treatment for 0.5 h to obtain a mixed solution. Then add 24 mg of H2IrCl6·xH2O to the above mixed solution, perform ultrasonic treatment for another 10 min, then transfer the ultrasonicated solution to an oil bath device, and carry out a reflux reaction at 120 °C for 3 h. After the reaction ends, after the solution cools, wash it by centrifugation with distilled water and ethanol in sequence, and dry it under vacuum to obtain Ir / NiO@Ni / CNT powder, that is, the anode composite catalyst for hydrogen-oxygen fuel cell.

[0044] Figure 1 is the X-ray diffraction (XRD) pattern of the Ir / NiO@Ni / CNT composite structure. From the figure, the characteristic peaks of metallic Ir, metallic Ni, and the oxide of Ni (NiO) can be seen, indicating that the composite catalyst has been successfully prepared.

[0045] Figure 2 is the transmission electron microscopy (TEM) image of the Ir / NiO@Ni / CNT composite structure. From the figure, it can be seen that Ir nanoparticles are uniformly loaded on NiO-Ni and CNT, with uniform size. By measurement, it can be known that its diameter is about 2.00 nm.

[0046] In this embodiment, the obtained hydrogen-oxygen fuel cell anode composite catalyst is also subjected to an electrochemical performance test in a three-electrode system. The specific test results are as follows:

[0047] Weigh 4 mg of the Ir / NiO-Ni / CNT catalyst prepared in this embodiment and add it to a mixed solution of 980 μL of absolute ethanol and 20 μL of 5 wt% Nafion. After ultrasonic oscillation for 30 minutes to disperse evenly, take 10 μL and coat it evenly on a glassy carbon rotating disk electrode. After drying at room temperature, it is used as the working electrode. Then, a carbon rod and a saturated calomel electrode are used as the counter electrode and the reference electrode respectively. Cyclic voltammetry scanning is carried out for 3 to 6 cycles in a nitrogen-saturated 0.1 mol / L potassium hydroxide aqueous solution to activate the catalyst, and then the polarization curve (LSV) is tested in a hydrogen-saturated 0.1 mol / L potassium hydroxide aqueous solution. An LSV polarization curve with an initial voltage lower than 0 V (vs. RHE) is obtained and shows catalytic performance higher than that of commercial Pt / C. The measurement results are as Figure 3 shown by curve A in Figure 3 It can be seen from

[0048] Example 2:

[0049] In this embodiment, different hydrogen-oxygen fuel cell anode composite catalysts are prepared by adjusting the conditions of the oil bath reaction in step (3) to investigate the influence of the oil bath temperature and time on the activity of the hydrogen-oxygen fuel cell anode composite catalyst. The specific investigation steps are as follows:

[0050] The preparation method of the hydrogen-oxygen fuel cell anode composite catalyst is basically the same as that in Example 1, except that the conditions of the oil bath reaction in step (3) are different. The reaction conditions are shown in Table 1 respectively.

[0051] Table 1. Different conditions for preparing the hydrogen-oxygen fuel cell anode composite catalyst

[0052] Serial number Oil bath temperature / °C Oil bath time / h 1 130 3 2 140 3 3 150 3 4 160 3 5 170 3 6 180 3 7 190 3 8 200 3 9 170 1 10 170 2

[0053] The electrochemical performances of the hydrogen-oxygen fuel cell anode composite catalysts prepared under the conditions described in Table 1 are measured by the method described in Example 1. The catalyst prepared when the oil bath temperature is 170 °C and the oil bath time is 3 h shows more excellent HOR catalytic performance.

[0054] Example 3: Stability test of the Ir / NiO-Ni / CNT catalyst in a three-electrode system

[0055] Weigh 4 mg of the Ir / NiO-Ni / CNT catalyst and add it to a mixed solution of 980 μL of absolute ethanol and 20 μL of 5 wt% Nafion. After ultrasonic oscillation for 30 minutes to disperse evenly, take 10 μL and evenly coat it on a glassy carbon rotating disk electrode. After drying at room temperature, use this as the working electrode, and use a carbon rod and a saturated calomel electrode as the counter electrode and reference electrode respectively.

[0056] First, test the linear sweep voltammetry curve in a 0.1 mol / L potassium hydroxide aqueous solution saturated with hydrogen. The linear sweep result of potassium hydroxide corresponds to Figure 4 Curve A in [reference]. Then, perform cyclic voltammetry scanning for 2000 cycles in a 0.1 mol / L potassium hydroxide aqueous solution saturated with hydrogen. Finally, test the linear sweep voltammetry curve in a 0.1 mol / L potassium hydroxide aqueous solution saturated with hydrogen. The linear sweep result of potassium hydroxide corresponds to Figure 4 Curve B in [reference]. It can be seen from Figure 4 that the Ir / NiO-Ni / CNT catalyst prepared in the present invention has good tolerance. After 2000 cycles of cyclic voltammetry scanning, the catalytic current only decreases slightly.

[0057] Comparative Example 1:

[0058] Weigh 4 mg of commercial Pt / C catalyst and add it to a mixed solution of 980 μL of absolute ethanol and 20 μL of 5 wt% Nafion. After ultrasonic oscillation for 30 minutes to disperse evenly, take 10 μL of the mixed solution and evenly coat it on a glassy carbon rotating disk electrode. After drying at room temperature, use it as the working electrode. Then, use a carbon rod and a saturated calomel electrode as the counter electrode and reference electrode respectively. Perform cyclic voltammetry scanning for 3 - 6 cycles in a 0.1 mol / L potassium hydroxide aqueous solution saturated with nitrogen to activate the catalyst, and then test the linear sweep voltammetry curve in a 0.1 mol / L potassium hydroxide aqueous solution saturated with hydrogen. The measurement result is as shown in Figure 3 Curve B in [reference]. It can be seen from the figure that the catalytic activity of the Ir / NiO-Ni / CNT catalyst prepared by us for HOR is better than that of the commercial Pt / C catalyst.

[0059] In summary, the hydrogen oxygen fuel cell anode composite catalyst prepared in the present invention has excellent hydrogen oxidation performance. By testing its electrochemical performance, the hydrogen oxygen fuel cell anode composite catalyst prepared in the present invention shows higher mass activity, kinetic current density, etc. compared with the commercial Pt / C catalyst. Therefore, this catalyst has potential application prospects in hydrogen oxygen fuel cells, and the preparation process described in the present invention is simple and easy to operate, has good repeatability, and is easy to implement industrially.

[0060] The described embodiments are the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Without departing from the essence of the present invention, any obvious improvements, substitutions or modifications that those skilled in the art can make all fall within the protection scope of the present invention.

Claims

1. A method for preparing an anode composite catalyst of a hydrogen-oxygen fuel cell, characterized in that, It includes the following steps: (1) Functionalization of the carbon support: Carbon nanotubes and polyvinylpyrrolidone K30 are added to ethanol, and stirred for reaction. After the reaction, filtration is carried out, and then drying is carried out to obtain a PVP-functionalized carbon support, denoted as PVP-CNT; (2) Preparation of a functionalized carbon support loaded with a Ni precursor: PVP-CNT, a nickel source, and hexamethylenetetramine HMTA are dissolved in a mixed solution of H2O and ethylene glycol. After being mixed evenly, hydrothermal reaction is carried out. After the reaction, centrifugation, washing, and drying are carried out, and then the dried product is calcined to obtain a functionalized carbon support loaded with a Ni precursor, denoted as NiO / CNT; (3) Preparation of a catalyst for the anode composite of a hydrogen-oxygen fuel cell: NiO / CNT is dissolved in ethylene glycol, and then a precursor of Ir is added and stirred evenly, and then heated by oil bath for reaction. After the reaction, the solid product is collected to obtain a catalyst for the anode composite of a hydrogen-oxygen fuel cell, that is, an Ir / NiO-Ni / CNT composite catalyst.

2. The preparation method of the anode composite catalyst of the hydrogen-oxygen fuel cell according to claim 1, wherein, In step (1), the dosage ratio of the carbon nanotubes, polyvinylpyrrolidone K30, and ethanol is 25 - 150 mg: 100 - 600 mg: 10 - 60 mL; The conditions for the stirring reaction are stirring at room temperature for 6 - 24 h.

3. The preparation method of the anode composite catalyst of the hydrogen-oxygen fuel cell according to claim 2, characterized in that, The dosage ratio of the carbon nanotubes, polyvinylpyrrolidone K30, and ethanol is 50 mg: 200 mg: 20 mL; The time for the stirring reaction is 12 h.

4. The preparation method of the anode composite catalyst of the hydrogen-oxygen fuel cell according to claim 1, characterized in that, In step (2), the nickel source is any one of NiCl2, NiSO4, Ni(CH3COO)2, and Ni(NO3)2; The dosage ranges of PVP-CNT, the nickel source, and hexamethylenetetramine HMTA are 25 - 100 mg: 0.5 - 2 mmol: 1 - 4 mmol; The conditions for the hydrothermal reaction are reacting at 100 - 200 °C for 1 - 6 h; The conditions for the calcination are calcining at 400 - 800 °C for 0.5 - 5 h.

5. The preparation method of the anode composite catalyst for a hydrogen-oxygen fuel cell according to claim 4, characterized in that, The nickel source is NiCl2; The dosage ranges of PVP-CNT, the nickel source, and hexamethylenetetramine HMTA are 50 mg: 1 mmol: 2 mmol; The hydrothermal reaction conditions are reacting at 150 °C for 4 h; The conditions for the calcination are calcining at 500 °C for 3 h.

6. The preparation method of the anode composite catalyst of the hydrogen-oxygen fuel cell according to claim 1, characterized in that, In step (3), the dosage ratio of NiO / CNT, ethylene glycol, and the precursor of Ir is 24 mg: 30 mL: 5 - 50 mg; The precursor of Ir is chloroiridic acid.

7. The preparation method of the anode composite catalyst of the hydrogen-oxygen fuel cell according to claim 6, wherein In step (3), the dosage ratio of NiO / CNT, ethylene glycol, and the precursor of Ir is 24 mg: 30 mL: 24 mg.

8. The preparation method of the anode composite catalyst of the hydrogen-oxygen fuel cell according to claim 1, characterized in that, In step (3), the conditions for the oil bath heating are reacting at 120 - 200 °C for 1 - 3 h.

9. The anode composite catalyst of a hydrogen-oxygen fuel cell prepared by the method according to any one of claims 1 to 8, characterized in that, In the composite catalyst, Ir nanocrystals are uniformly loaded on CNT and NiO-Ni nanoparticles.

10. Application of the catalyst for the anode composite of a hydrogen-oxygen fuel cell according to claim 9 in a hydrogen-oxygen fuel cell.

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