A bifunctional electrocatalyst and its preparation method and application
By using a bifunctional electrocatalyst composed of niobium-doped titanium dioxide composites loaded with iridium nanoparticles in a proton exchange membrane electrolyzer, the problems of unstable anode catalysts and high costs were solved, and efficient water electrolysis catalysis in an acidic environment was achieved.
Patent Information
- Application Number
- CN202411561154.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-04
- Publication Date
- 2025-10-03
- Estimated Expiration
- 2044-11-04
AI Technical Summary
In existing proton exchange membrane electrolyzers, the noble metal Ru, the oxygen evolution reaction catalyst at the anode, is unstable, and the bifunctional electrocatalyst is missing in the acidic solution, resulting in low catalytic efficiency and high cost, which limits the application of water electrolysis.
Niobium-doped titanium dioxide composite is used as a carrier to load iridium nanoparticles. The specific surface area and conductive properties of the carrier are improved by taking advantage of the oriented self-assembly characteristics of polyethyleneimine to prepare a bifunctional electrocatalyst.
The catalytic activity and stability of OER and HER are improved in an acidic environment, the utilization rate of precious metals is reduced, and the cost of the fuel cell stack is reduced.
Smart Images
Figure CN119506945B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of electrocatalysis technology, and in particular to a bifunctional electrocatalyst and a preparation method and application thereof. Background Art
[0002] Hydrogen energy is a promising alternative energy source, offering advantages such as high energy density, clean and environmentally friendly properties, and widespread application. Water electrolysis is an effective and sustainable method for producing green hydrogen. Compared to alkaline electrolyzers, proton exchange membrane electrolysis (PEMWE) offers advantages such as low resistance loss, high electrolyzer efficiency, high current density, and rapid response, making it considered the most promising hydrogen production technology. However, the high cost of PEM limits its further application. Therefore, optimizing catalyst design to reduce stack costs and improve catalyst efficiency is urgently needed to promote large-scale application.
[0003] Currently, the anode, due to its relatively slow kinetics and high overpotential, has become the main factor affecting the application of water electrolysis. Among them, in PEM electrolyzers, the oxygen evolution reaction (OER) catalyst is composed of the precious metal Ru with a low overpotential. However, due to Ru's instability, it is easy to dissolve in acidic electrolytes. In addition, the amount of precious metal used is high, the utilization rate is low, the catalytic efficiency is low, and the activity is unstable. Secondly, OER and HER electrocatalysts synthesized separately for different equipment and processes are relatively expensive. Related technologies have developed bifunctional electrocatalysts with high OER and HER activities, such as NiSe, Ni2P, CoMnO, etc., but these bifunctional catalysts are all used for alkaline overall water splitting. There is still a lack of bifunctional electrocatalysts in acidic solutions.
[0004] Therefore, it is necessary to provide a bifunctional electrocatalyst to improve its catalytic efficiency and stability in water electrolysis in an acidic environment. Summary of the Invention
[0005] In view of this, the present application provides a bifunctional electrocatalyst and its preparation method and application, which are used to solve the problem of how to improve the catalytic efficiency and stability of bifunctional electrocatalysts in water electrolysis in an acidic environment.
[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions:
[0007] In a first aspect, the present application provides a bifunctional electrocatalyst comprising a carrier and iridium nanoparticles supported on the carrier, wherein the carrier is a niobium-doped titanium dioxide composite.
[0008] In a second aspect, the present application provides a method for preparing a bifunctional electrocatalyst, comprising the following steps:
[0009] S1. The titanium-containing organic compound and the niobium-containing compound are added to an acidic solution containing polyethyleneimine and stirred, heated to react, and then dried to obtain a niobium-doped titanium dioxide composite;
[0010] S2. A solution containing an iridium compound is added dropwise to a dispersion of the niobium-doped titanium dioxide composite, and the mixture is heated in a gradient manner for reaction. After washing and drying, a bifunctional electrocatalyst is obtained.
[0011] Preferably, in step S1, the stirring temperature is 20-40°C, and the stirring time is 3-5 hours; the heating reaction temperature is 95-105°C, and the heating reaction time is 24-28 hours.
[0012] Preferably, in step S2, the gradient heating reaction process is: stirring at 70-90° C. for 4-6 hours, and stirring at 140-160° C. for 4-6 hours.
[0013] Preferably, in step S1, the titanium-containing organic compound includes one or more of isopropyl titanate and titanium tetrachloride; the niobium-containing compound includes one or more of niobium pentachloride and niobium ethoxide; and the acidic solution containing polyethyleneimine includes a mixture of polyethyleneimine, glacial acetic acid, and water.
[0014] Preferably, in step S2, the iridium-containing compound includes one or more of chloroiridic acid and iridium trichloride; the solvent of the dispersion of the niobium-doped titanium dioxide composite includes one or more of ionized water, ethanol, and isopropanol; and the solvent of the solution of the iridium compound includes isopropanol.
[0015] Preferably, the molar ratio of the titanium-containing organic compound to the niobium-containing compound is 19:1-3, calculated as metal ions; and the amount of polyethyleneimine used is 1.5 g.
[0016] Preferably, the molar ratio of the iridium-containing compound to the niobium-doped titanium dioxide composite is 0.214-2.136:1, calculated as metal ions.
[0017] In a third aspect, the present application provides an application of a bifunctional electrocatalyst in the field of water electrolysis.
[0018] Preferably, the hydrolysis system for water electrolysis is an acidic system.
[0019] The beneficial effects of the present application are as follows: the present application uses niobium-doped titanium dioxide as a carrier to prevent electrochemical oxidative corrosion and improve catalytic stability; at the same time, doping niobium into the carrier improves the conductive properties of the carrier, which is conducive to better dispersion and anchoring of iridium precious metal, thereby improving the catalytic activity and stability of OER and HER in an acidic environment, and the utilization rate of iridium precious metal is high.
[0020] In this application, the characteristic of polymer polyethyleneimine that it can be oriented and self-assembled is utilized to successfully prepare a niobium-doped titanium dioxide support. At the same time, the specific surface area of the niobium-doped titanium dioxide support is increased, and more binding sites for iridium precious metal to bind to the niobium-doped titanium dioxide support are provided, thereby improving the catalytic activity of OER and HER and the utilization rate of iridium precious metal. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is the XRD pattern of the niobium-doped titanium dioxide-supported iridium nanoparticle catalyst prepared in Example 1 of the present invention;
[0022] Figure 2 and Figure 3 This is a TEM image of the niobium-doped titanium dioxide-supported iridium nanoparticle catalyst prepared in Example 4 of the present invention;
[0023] Figure 4 Polarization curves of the catalysts obtained in Example 2, Comparative Example 1 and Comparative Example 2 of the present invention under OER;
[0024] Figure 5 Polarization curves of the catalysts obtained in Example 4, Comparative Example 1, and Comparative Example 3 under HER conditions are shown;
[0025] Figure 6 The chronoamperometry diagrams of the catalysts obtained in Example 4 of the present invention and Comparative Example 1 under OER conditions are shown;
[0026] Figure 7 The chronoamperographs of the catalysts obtained in Example 1 of the present invention and Comparative Example 3 under HER are shown. DETAILED DESCRIPTION
[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0028] The present application provides a bifunctional electrocatalyst, which includes a carrier and iridium nanoparticles loaded on the carrier, wherein the carrier is a niobium-doped titanium dioxide composite.
[0029] The bifunctional electrocatalyst of this application is a niobium-doped titanium dioxide-supported iridium nanoparticle catalyst, which exhibits high OER and HER catalytic activity and high catalytic stability in acidic systems. This is because, on the one hand, the niobium-doped titanium dioxide as a support can prevent electrochemical oxidative corrosion, thereby improving catalytic stability; on the other hand, the niobium doping of the support can enhance the support's conductivity, facilitate better dispersion and anchoring of the iridium noble metal, and improve the catalytic activity and stability of the OER and HER. The high utilization rate of the iridium noble metal reduces the cost of the catalyst.
[0030] The present application provides a method for preparing a bifunctional electrocatalyst, comprising the following steps:
[0031] S1. The titanium-containing organic compound and the niobium-containing compound are added to an acidic solution containing polyethyleneimine and stirred, heated to react, and then dried to obtain a niobium-doped titanium dioxide composite;
[0032] S2. A solution containing an iridium compound is added dropwise to a dispersion of the niobium-doped titanium dioxide composite, and the mixture is heated in a gradient manner for reaction. After washing and drying, a bifunctional electrocatalyst is obtained.
[0033] In this application, the characteristic of polymer polyethyleneimine that it can be oriented and self-assembled is utilized to successfully prepare a niobium-doped titanium dioxide support. At the same time, the specific surface area of the niobium-doped titanium dioxide support is increased, providing more binding sites for iridium precious metal to bind to the niobium-doped titanium dioxide support, thereby improving the catalytic activity of OER and HER and the utilization rate of iridium precious metal.
[0034] In some embodiments, in step S1, the stirring temperature is 20-40°C, and the stirring time is 3-5 hours; the heating reaction temperature is 95-105°C, and the heating reaction time is 24-28 hours, and the heating reaction vessel is a high-pressure reactor.
[0035] In some embodiments, in step S2, the gradient heating reaction process is: stirring at 70-90° C. for 4-6 hours, stirring at 140-160° C. for 4-6 hours, and the vessel for the gradient heating reaction is a high-pressure reactor.
[0036] In some embodiments, in step S1, the titanium-containing organic compound includes one or more of isopropyl titanate and titanium tetrachloride; the niobium-containing compound includes one or more of niobium pentachloride and niobium ethoxide; and the acidic solution containing polyethyleneimine includes a mixture of polyethyleneimine, glacial acetic acid, and water.
[0037] In some embodiments, in step S2, the iridium-containing compound includes one or more of chloroiridic acid and iridium trichloride; the solvent of the dispersion of the niobium-doped titanium dioxide composite includes one or more of ionized water, ethanol, and isopropanol; and the solvent of the solution of the iridium compound includes isopropanol.
[0038] In some embodiments, the molar ratio of the titanium-containing organic compound to the niobium-containing compound is 19:1-3, calculated as metal ions; and the amount of polyethyleneimine used is 1.5 g.
[0039] In some embodiments, the molar ratio of the iridium-containing compound to the niobium-doped titanium dioxide composite, calculated as metal ions, is 0.214-2.136:1. Under these conditions, the iridium loading (ratio of the mass of Ir in the iridium compound to the mass of the support) in the resulting niobium-doped titanium dioxide-supported iridium nanoparticle catalyst (Ir / NTO) is 0.5:1-5:1.
[0040] This application provides a bifunctional electrocatalyst for use in water electrolysis, including but not limited to use as an anode catalyst, a cathode catalyst, and in full-cell water electrolysis. In the full-cell water electrolysis process, the anode and cathode catalyst layers comprise niobium-doped titanium dioxide-supported iridium nanoparticle catalysts.
[0041] In the present application, the hydrolysis system for water electrolysis is an acidic system.
[0042] The present invention is further described below through specific examples.
[0043] Example 1
[0044] A method for preparing a bifunctional electrocatalyst comprises the following steps:
[0045] S1. Add 1.5 g of polyethyleneimine dropwise to a mixed solution consisting of 30 ml of deionized water and 1.5 ml of glacial acetic acid and stir at room temperature for 30 minutes to prepare Solution A. Then, add 3 ml of isopropyl titanate and 1.256 g of niobium pentachloride to Solution A and continue stirring for 3 hours. Transfer the resulting colloidal suspension to a 100 ml autoclave and react at 100°C for 24 hours. Wash the resulting powder three times with deionized water by centrifugation. Then, dry the powder in a vacuum drying oven at 80°C for 12 hours to obtain a niobium-doped titanium dioxide composite, which serves as a niobium-doped titanium dioxide support.
[0046] S2. Weigh 0.2 g of a chloroiridic acid compound (Ir = 39 wt%) and dropwise add it to isopropanol (Ir concentration: 15.6 mg / mL). Stir at room temperature to obtain a uniform solution, i.e., the iridium-containing solution. Disperse 50 mg of a niobium-doped titania support in 50 ml of a solvent (deionized water: ethanol: isopropanol = 1:8:1) to obtain a dispersion of the niobium-doped titania composite. Add 3.205 ml of the iridium-containing solution dropwise to the dispersion of the niobium-doped titania composite. Heat to 80°C in a water bath with continuous stirring for 6 h. Then, transfer the mixture to an autoclave and react at 150°C for 5 h. Wash the mixture four times with alternating centrifugation using ethanol and deionized water. Place the resulting sample in a vacuum drying oven and dry it at 90°C for 12 h to obtain the product, Ir / NTO. The mass ratio of iridium nanoparticles to niobium-doped titania support is 1:1.
[0047] Example 2
[0048] A method for preparing a bifunctional electrocatalyst comprises the following steps:
[0049] S1. Add 1.5 g of polyethyleneimine dropwise to a mixed solution consisting of 30 ml of deionized water and 1.5 ml of glacial acetic acid and stir at room temperature for 30 minutes to prepare Solution A. Then, add 1.802 g of titanium tetrachloride and 1.256 g of niobium pentachloride to Solution A and continue stirring for 2 hours. Transfer the resulting colloidal suspension to a 100 ml autoclave and react at 100°C for 24 hours. Wash the resulting powder three times with deionized water by centrifugation. Then, dry the powder in a vacuum drying oven at 80°C for 12 hours to obtain a niobium-doped titanium dioxide composite, which serves as a niobium-doped titanium dioxide support.
[0050] S2. Weigh 0.2 g of a chloroiridic acid compound (Ir = 39 wt%) and dropwise add it to isopropanol (Ir concentration: 15.6 mg / mL). Stir at room temperature to obtain a uniform solution, i.e., the iridium-containing solution. Disperse 50 mg of a niobium-doped titanium dioxide support in 50 ml of a solvent (deionized water: ethanol: isopropanol = 1:8:1) to obtain a dispersion of the niobium-doped titanium dioxide composite. Add 3.205 ml of the iridium-containing solution dropwise to the dispersion of the niobium-doped titanium dioxide composite. Heat the mixture to 80°C in a water bath with continuous stirring for 5 h. The mixture is then transferred to an autoclave and reacted at 150°C for 5 h. The mixture is then washed four times by alternating centrifugation with ethanol and deionized water. The resulting sample is then dried in a vacuum oven at 90°C for 12 h to obtain the product, Ir / NTO. The mass ratio of iridium nanoparticles to niobium-doped titanium dioxide support in the product, Ir / NTO, is 1:1.
[0051] Example 3
[0052] A method for preparing a bifunctional electrocatalyst comprises the following steps:
[0053] S1. Add 1.5 g of polyethyleneimine dropwise to a mixed solution consisting of 30 ml of deionized water and 1.5 ml of glacial acetic acid and stir at room temperature for 30 minutes to prepare solution A. Then, add 3 ml of isopropyl titanate and 1.478 g of niobium ethanol to solution A and continue stirring for 3 hours. Transfer the resulting colloidal suspension to a 100 ml autoclave and react at 100°C for 24 hours. Wash the resulting powder three times with deionized water by centrifugation. Then, dry the powder in a vacuum drying oven at 80°C for 12 hours to obtain a niobium-doped titanium dioxide composite, which serves as a niobium-doped titanium dioxide support.
[0054] S2. Weigh 0.1g of a chloroiridic acid compound (Ir = 39wt%) and dropwise add it to isopropanol (Ir concentration: 15.6mg / mL). Stir at room temperature to obtain a uniform solution, i.e., the iridium-containing solution. Disperse 50mg of a niobium-doped titanium dioxide support in 50ml of a solvent (deionized water: ethanol: isopropanol = 1:9:0) to obtain a dispersion of the niobium-doped titanium dioxide composite. Add 1.603ml of the iridium-containing solution dropwise to the dispersion of the niobium-doped titanium dioxide composite. Heat to 80°C in a water bath with continuous stirring for 6h. Then, transfer the mixture to an autoclave and react at 150°C for 5h. Wash the mixture four times by alternating centrifugation with ethanol and deionized water. Place the resulting sample in a vacuum drying oven and dry it at 90°C for 12h to obtain the product, Ir / NTO. The mass ratio of iridium nanoparticles to niobium-doped titanium dioxide support in the product, Ir / NTO, is 0.5:1.
[0055] Example 4
[0056] A method for preparing a bifunctional electrocatalyst comprises the following steps:
[0057] S1. Add 1.5 g of polyethyleneimine dropwise to a mixed solution consisting of 30 ml of deionized water and 1.5 ml of glacial acetic acid and stir at room temperature for 30 minutes to prepare Solution A. Then, add 3 ml of isopropyl titanate and 1.256 g of niobium pentachloride to Solution A and continue stirring for 3 hours. Transfer the resulting colloidal suspension to a 100 ml autoclave and react at 100°C for 24 hours. Wash the resulting powder three times with deionized water by centrifugation. Then, dry the powder in a vacuum drying oven at 80°C for 12 hours to obtain a niobium-doped titanium dioxide composite, which serves as a niobium-doped titanium dioxide support.
[0058] S2. Weigh 0.4 g of a chloroiridic acid compound (Ir = 39 wt%) and dropwise add it to isopropanol (Ir concentration: 31.2 mg / mL). Stir at room temperature to obtain a uniform solution, i.e., the iridium-containing solution. Disperse 50 mg of a niobium-doped titanium dioxide support in 50 ml of a solvent (deionized water: ethanol: isopropanol = 1:8:1) to obtain a dispersion of the niobium-doped titanium dioxide composite. Add 3.205 ml of the iridium-containing solution dropwise to the dispersion of the niobium-doped titanium dioxide composite. Heat the mixture to 80°C in a water bath and stir continuously for 6 h. Then, transfer the mixture to an autoclave and react at 150°C for 5 h. Wash the mixture by centrifugation four times with alternating ethanol and deionized water. Place the resulting sample in a vacuum drying oven and dry it at 90°C for 12 h to obtain the product, Ir / NTO. The mass ratio of iridium nanoparticles to niobium-doped titanium dioxide support in the product, Ir / NTO, is 2:1.
[0059] Example 5
[0060] A method for preparing a bifunctional electrocatalyst comprises the following steps:
[0061] S1. Add 1.5 g of polyethyleneimine dropwise to a mixed solution consisting of 30 ml of deionized water and 1.5 ml of glacial acetic acid, and stir at room temperature for 30 minutes to prepare Solution A. Then, add 3 ml of titanium tetrachloride and 1.478 g of niobium ethanol to Solution A and continue stirring for 3 hours. Transfer the resulting colloidal suspension to a 100 ml autoclave and react at 100°C for 24 hours. Wash the resulting powder three times with deionized water by centrifugation. Then, dry the powder in a vacuum drying oven at 80°C for 12 hours to obtain a niobium-doped titanium dioxide composite, which serves as the niobium-doped titanium dioxide support.
[0062] S2. Weigh 0.5 g of a chloroiridic acid compound (Ir = 39 wt%) and dropwise add it to isopropanol (Ir concentration: 31.2 mg / mL). Stir at room temperature to obtain a uniform solution, i.e., the iridium-containing solution. Disperse 50 mg of a niobium-doped titanium dioxide support in 50 ml of a solvent (deionized water: ethanol: isopropanol = 1:8:1) to obtain a dispersion of the niobium-doped titanium dioxide composite. Add 4.808 ml of the iridium-containing solution dropwise to the dispersion of the niobium-doped titanium dioxide composite. Heat the mixture to 80°C in a water bath and stir continuously for 6 h. The mixture is then transferred to an autoclave and reacted at 150°C for 5 h. The mixture is then washed four times by alternating centrifugation with ethanol and deionized water. The resulting sample is then dried in a vacuum oven at 90°C for 12 h to obtain the product, Ir / NTO. The mass ratio of iridium nanoparticles to niobium-doped titanium dioxide support in the product, Ir / NTO, is 3:1.
[0063] Example 6
[0064] A method for preparing a bifunctional electrocatalyst comprises the following steps:
[0065] S1. Add 1.5 g of polyethyleneimine dropwise to a mixed solution consisting of 30 ml of deionized water and 1.5 ml of glacial acetic acid and stir at room temperature for 30 minutes to prepare Solution A. Then, add 3 ml of titanium tetrachloride and 1.256 g of niobium pentachloride to Solution A and continue stirring for 3 hours. Transfer the resulting colloidal suspension to a 100 ml autoclave and react at 100°C for 24 hours. Wash the resulting powder three times with deionized water by centrifugation. Then, dry the powder in a vacuum drying oven at 80°C for 12 hours to obtain a niobium-doped titanium dioxide composite, which serves as a niobium-doped titanium dioxide support.
[0066] S2. Weigh 0.6 g of a chloroiridic acid compound (Ir = 39 wt%) and dropwise add it to isopropanol (Ir concentration: 46.8 mg / mL). Stir at room temperature to obtain a uniform solution, i.e., the iridium-containing solution. Disperse 50 mg of a niobium-doped titanium dioxide support in 50 ml of a solvent (deionized water: ethanol: isopropanol = 1:8:1) to obtain a dispersion of the niobium-doped titanium dioxide composite. Add 4.274 ml of the iridium-containing solution dropwise to the dispersion of the niobium-doped titanium dioxide composite. Heat to 80°C in a water bath with continuous stirring for 6 h. Then, transfer the mixture to an autoclave and react at 150°C for 5 h. Wash the mixture four times by alternating centrifugation with ethanol and deionized water. Place the resulting sample in a vacuum drying oven and dry it at 90°C for 12 h to obtain the product, Ir / NTO. The mass ratio of iridium nanoparticles to niobium-doped titanium dioxide support in the product, Ir / NTO, is 4:1.
[0067] Example 7
[0068] A method for preparing a bifunctional electrocatalyst comprises the following steps:
[0069] S1. Add 1.5 g of polyethyleneimine dropwise to a mixed solution consisting of 30 ml of deionized water and 1.5 ml of glacial acetic acid, and stir at room temperature for 30 minutes to prepare Solution A. Then, add 3 ml of titanium tetrachloride and 1.478 g of niobium ethanol to Solution A and continue stirring for 3 hours. Transfer the resulting colloidal suspension to a 100 ml autoclave and react at 100°C for 24 hours. Wash the resulting powder three times with deionized water by centrifugation. Then, dry the powder in a vacuum drying oven at 80°C for 12 hours to obtain a niobium-doped titanium dioxide composite, which serves as the niobium-doped titanium dioxide support.
[0070] S2. Weigh 0.7 g of a chloroiridic acid compound (Ir = 39 wt%) and dropwise add it to isopropanol (Ir concentration: 46.8 mg / mL). Stir at room temperature to obtain a uniform solution, i.e., the iridium-containing solution. Disperse 50 mg of a niobium-doped titanium dioxide support in 50 ml of a solvent (deionized water: ethanol: isopropanol = 1:8:1) to obtain a dispersion of the niobium-doped titanium dioxide composite. Add 5.342 ml of the iridium-containing solution dropwise to the dispersion of the niobium-doped titanium dioxide composite. Heat to 80°C in a water bath with continuous stirring for 6 h. Then, transfer the mixture to an autoclave and react at 150°C for 5 h. Wash the mixture by centrifugation four times with alternating ethanol and deionized water. Place the resulting sample in a vacuum drying oven and dry it at 90°C for 12 h to obtain the product, Ir / NTO. The mass ratio of iridium nanoparticles to niobium-doped titanium dioxide support in the product, Ir / NTO, is 5:1.
[0071] Comparative Example 1
[0072] A method for preparing an electrocatalyst comprises the following steps:
[0073] Weigh 0.3 g of iridium chloride (Ir = 39 wt%) and drop it into isopropanol (Ir concentration is 15.6 mg / mL). Stir at room temperature to obtain a uniform solution. Prepare 50 ml of solvent (deionized water: ethanol: isopropanol = 1:8:1) and record it as solution B. Take 5.342 ml of the iridium chloride solution prepared in step (1) and add it to solution B. Heat it to 80 ° C in a water bath and stir it continuously for 6 h. Then transfer it to a high-pressure reactor and react it at 150 ° C for 5 h. Then, wash it with ethanol and deionized water alternately by centrifugation 4 times. The obtained sample is placed in a vacuum drying oven and dried at 90 ° C for 12 h to obtain the product self-prepared Ir nanoparticles (SP Ir NP).
[0074] Comparative Example 2
[0075] Commercial iridium oxide catalyst, manufactured by MacLean Company.
[0076] Comparative Example 3
[0077] Commercial platinum-carbon catalyst, manufactured by Aladdin.
[0078] Comparative Example 4
[0079] A method for preparing an electrocatalyst is the same as Example 1 in other aspects, except that the chloroiridic acid compound is replaced by an equal mass of water.
[0080] Comparative Example 5
[0081] A method for preparing an electrocatalyst is the same as Example 1 except that niobium pentachloride is replaced by isopropyl titanate of equal mass.
[0082] Testing and Evaluation
[0083] The polarity properties of the resulting electrocatalysts were tested using a CHI660e electrochemical workstation. A three-electrode system was employed, with a saturated calomel electrode as the reference electrode, a high-purity graphite carbon electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The electrolyte used was a 0.5M H₂SO₄ solution. 5 mg of each catalyst was weighed into a centrifuge tube, and 100 μL of deionized water, 375 μL of ethanol, and 25 μL of a 5 wt% Nafion solution (a perfluorosulfonic acid polymer solution) were added sequentially. The mixed solution was placed in an ultrasonicator and sonicated in an ice bath for 30 minutes to obtain an ink. A 1.8 μL droplet of the ink was applied to a 3 mm diameter glassy carbon electrode and allowed to dry naturally to obtain the working electrode.
[0084] (1) For oxygen evolution reaction, before testing, the electrode was activated in the range of 1.1-1.5 V (vs. RHE) until the curve reached a plateau. The scanning range of the CV curve was 0-1.4 V (vs. RHE) with a scan rate of 50 mV s -1 The scanning range of the linear polarization curve is 1.1~1.7V (vs.RHE) and the scanning rate is 5mV s -1 ; 0~1.4V (vs.RHE), scan rate 50mV s -1 The electrochemical impedance spectroscopy (EIS) test was conducted at a constant voltage of 1.55 V (vs. RHE) with a frequency range of 0.1 Hz to 106 Hz. The stability test was conducted using the chronopotentiometry (CP) test at a constant current density of 10 mA cm -2 The stability of the material was tested and the results are shown in Table 1.
[0085] Table 1 Oxygen evolution reaction test results
[0086]
[0087] (2) For hydrogen evolution reaction, before testing, the electrode was activated in the range of 0.2 to -0.3 V (vs. RHE) until the curve reached a plateau. The scanning range of the linear polarization curve was 0.2 to -0.3 V (vs. RHE) with a scanning rate of 5 mV s -1 The electrochemical impedance spectroscopy (EIS) test was carried out at a constant voltage of -0.29 V (vs. RHE) and a frequency range of 0.1 Hz to 106 Hz. The stability test was carried out using the chronopotentiometry (CP) test at a constant current density of -10 mA cm -2 The stability of the material was tested and the results are shown in Table 2.
[0088] Table 2 Hydrogen evolution reaction test results
[0089]
[0090] Tables 1 and 2 show the performance of the embodiments and comparative examples under OER and HER tests. It can be seen that the oxygen evolution overpotential of the embodiment is significantly less than that of the comparative example, indicating that a higher current density can be achieved at a lower voltage. The smaller the Tafel slope and Rct, the better the catalytic performance. And in terms of mass activity, it can be seen that the embodiment has a higher mass activity, indicating that the precious metal utilization rate in the embodiment is higher.
[0091] X-ray diffraction (XRD) testing involves taking a small amount of powder and testing it within an angle range of 10-80° at a scanning speed of 3° / min. High-resolution transmission electron microscopy (HRTEM) testing involves dispersing a small amount of powder in an ethanol solvent, placing a drop of the liquid on an ultra-thin carbon film grid, and then performing the HRTEM test after the liquid evaporates. Figure 1 This is the XRD pattern of the niobium-doped titanium dioxide-supported iridium nanoparticle catalyst prepared in Example 1; Figure 1 It can be seen that the niobium-doped titanium dioxide-supported iridium nanoparticle catalyst synthesized by the present invention exhibits obvious diffraction peaks at 2θ=25.26°, 37.73°, 48.11°, 53.78°, 55.11°, and 62.43°. These diffraction peaks are attributed to the anatase structure, and no obvious diffraction peaks of niobium compounds are observed. There are obvious diffraction peaks at 2θ=41.09° and 47.37°, which are attributed to the iridium metal structure.
[0092] Figure 2 and Figure 3 TEM image of niobium-doped titanium dioxide-supported iridium nanoparticle catalyst prepared in Example 4 of the present invention; Figure 2-3 It can be seen that the iridium metal nanoparticles are uniformly dispersed on the niobium-doped titanium dioxide support, and the lattice fringes of the niobium-doped titanium dioxide support and the metal iridium nanoparticles can be clearly seen, and the values are consistent with XRD.
[0093] Figure 4 Polarization curves of the catalysts obtained in Example 2, Comparative Example 1 and Comparative Example 2 of the present invention under OER; Figure 5 Polarization curves of the catalysts obtained in Example 4, Comparative Example 1, and Comparative Example 3 under HER conditions are shown; Figure 6 The chronoamperometry diagrams of the catalysts obtained in Example 4 of the present invention and Comparative Example 1 under OER conditions are shown; Figure 7 The chronoamperometry diagrams of the catalysts obtained in Example 1 and Comparative Example 3 under HER conditions are shown in FIG. Figure 4-7 It can be seen that Example 1 and Example 4 prepared using the present invention have excellent catalytic efficiency in both oxygen evolution reaction and hydrogen evolution reaction, which are better than the catalyst of the comparative example; in terms of stability, it can also be seen that the stability performance of the niobium-doped titanium dioxide-supported iridium nanoparticle catalyst synthesized by the present invention is better than that of the catalyst of the comparative example.
[0094] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.
Claims
1. A bifunctional electrocatalyst, characterized in that The invention comprises a carrier and iridium nanoparticles loaded on the carrier, wherein the carrier is a niobium-doped titanium dioxide composite. The preparation method of the bifunctional electrocatalyst comprises the following steps: S1. The titanium-containing organic compound and the niobium-containing compound are added to an acidic solution containing polyethyleneimine and stirred, heated to react, and then dried to obtain a niobium-doped titanium dioxide composite; the acidic solution containing polyethyleneimine comprises a mixture of polyethyleneimine, glacial acetic acid, and water; S2. A solution containing an iridium compound is added dropwise to a dispersion of a niobium-doped titanium dioxide composite, and the mixture is subjected to a gradient heating reaction. The mixture is washed and dried to obtain a bifunctional electrocatalyst. The gradient heating reaction process is as follows: stirring at 70-90°C for 4-6 hours, and then stirring at 140-160°C for 4-6 hours.
2. The bifunctional electrocatalyst according to claim 1, characterized in that In step S1, the stirring temperature is 20-40° C., and the stirring time is 3-5 h; the heating reaction temperature is 95-105° C., and the heating reaction time is 24-28 h.
3. The bifunctional electrocatalyst according to claim 1, characterized in that In step S1, the titanium-containing organic compound includes one or more of isopropyl titanate and titanium tetrachloride; the niobium-containing compound includes one or more of niobium pentachloride and niobium ethoxide.
4. The bifunctional electrocatalyst according to claim 1, characterized in that In step S2, the iridium-containing compound includes one or more of chloroiridic acid and iridium trichloride; the solvent of the dispersion of the niobium-doped titanium dioxide composite includes one or more of deionized water, ethanol, and isopropanol; and the solvent of the solution of the iridium compound includes isopropanol.
5. The bifunctional electrocatalyst according to claim 1, characterized in that Calculated on the basis of metal ions, the molar ratio of the titanium-containing organic matter to the niobium-containing compound is 19:1-3.
6. The bifunctional electrocatalyst according to claim 1, wherein Calculated on the basis of metal ions, the molar ratio of the iridium-containing compound to the niobium-doped titanium dioxide composite is 0.214-2.136:
1.
7. Use of the bifunctional electrocatalyst according to any one of claims 1 to 6 in the field of water electrolysis.
8. The use according to claim 7, characterized in that The hydrolysis system for water electrolysis is an acidic system.