A ruthenium-doped nanoneedle flake carbon-supported cobalt trioxide self-supporting electrode and a preparation method and application thereof

Abstract

The application discloses a ruthenium-doped nanoneedle flake carbon-supported cobalt trioxide tetroxide self-supporting electrode and a preparation method and application thereof. A mixed solution of cobalt nitrate hexahydrate, ammonium fluoride, ruthenium trichloride and urea is prepared into a ruthenium-cobalt precursor through a hydrothermal method, and the precursor is calcined in air after drying, so as to obtain an RCO catalyst grown on a carbon cloth. The catalyst has a nanoneedle flake structure, can provide a high-quality reactant transmission channel, and exhibits excellent oxygen evolution reaction electrocatalytic activity and stability in alkaline / acid electrolyte. The catalyst can be used as a high-efficiency anode catalyst for an acid / alkaline solution water electrolysis device and has a good market prospect.

Description

Technical Field

[0001] This invention relates to the field of electrocatalyst preparation technology, specifically to a ruthenium-doped nanoneedle-sheet carbon-supported cobalt tetroxide (RCO) self-supporting electrode, its preparation method, and its application. Background Technology

[0002] Climate change has been spreading globally for some time, becoming a major crisis that cannot be ignored in this new era. Developing green and sustainable energy sources to replace traditional fossil fuels has become a focus of attention. One of the most promising alternatives to alleviate fossil fuel-related problems is electrochemical storage and energy conversion devices. Clean energy sources such as wind, solar, and tidal power suffer from intermittent power generation, posing a significant technical challenge to their further development. This involves directly storing the generated electricity through metal-air batteries or using it to produce hydrogen through water electrolysis, converting it into the chemical energy of hydrogen for storage. Hydrogen is considered a renewable secondary energy source to replace fossil fuels due to its zero carbon dioxide emissions and high energy density during production and application. The oxygen evolution reaction at the anode in water electrolysis for hydrogen production is a tetrad process with slow kinetics. Ru / Ir-based catalysts are commonly used to improve reaction efficiency, but precious metals are scarce and expensive, necessitating the development of low-cost, highly active, and stable oxygen evolution reaction (OER) catalysts.

[0003] In recent years, Co-based OER catalysts have become a research hotspot in OER electrocatalysts due to their unique morphology, porous structure, and excellent chemical and mechanical stability. However, problems such as insufficient catalyst conductivity and inadequate exposure of active sites limit further improvement in catalyst performance and hinder the commercialization process of these catalysts. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a ruthenium-doped nanoneedle sheet carbon-supported cobalt tetroxide (RCO) self-supporting electrode, its preparation method, and its application. A trace amount of ruthenium is doped to form a ruthenium-cobalt precursor via a one-pot hydrothermal method, followed by drying and air calcination oxidation to prepare a trace amount of ruthenium-doped cobalt tetroxide nanoneedle sheet self-supporting electrode. The continuous open interface of the catalyst, elemental doping, and carbon cloth support enable the catalyst to exhibit excellent oxygen evolution reaction catalytic activity and stability.

[0005] To address the problems in the existing technology, the technical solution adopted by this invention is as follows:

[0006] A method for preparing a ruthenium-doped nanoneedle sheet carbon-supported cobalt tetroxide (RCO) self-supporting electrode includes the following steps:

[0007] Step 1: Weigh out ammonium fluoride, cobalt nitrate hexahydrate, ruthenium trichloride and urea, dissolve them in deionized water, and stir continuously to obtain a homogeneous mixed solution;

[0008] Step 2: Cut the carbon fiber cloth and pre-treat it;

[0009] Step 3: Place the treated carbon cloth and the mixed solution from Step 1 into a hydrothermal reactor. After hydrothermal reaction at 120-160℃ for 3-5 hours, and after natural cooling, remove the carbon cloth with the ruthenium-cobalt precursor grown on it and wash it with deionized water and ethanol. Then dry it to obtain a semi-finished product for later use.

[0010] Step 4: Place the semi-finished product in a tube furnace and heat it in air for low-temperature oxidation. After natural cooling, a ruthenium-doped nanoneedle thin film carbon-supported cobalt tetroxide (RCO) self-supporting electrode is obtained.

[0011] As an improvement, the molar ratio of ruthenium trichloride, urea, cobalt nitrate hexahydrate and ammonium fluoride in step 1 is 0.0012:5:1:2.

[0012] As an improvement, the pretreatment steps in step 2 are as follows: the cut carbon cloth is ultrasonically cleaned sequentially with acetone, ethanol, and deionized water to remove impurities from the surface of the carbon cloth and to pre-activate the carbon cloth; in order to further activate and enhance the hydrophilicity of the carbon cloth, the cleaned carbon cloth needs to be ultrasonically oxidized again in nitric acid; after the carbon cloth is activated, it needs to be ultrasonically cleaned in distilled water; finally, the pretreated carbon cloth is placed in distilled water for later use.

[0013] Further improvements include a carbon cloth size of 2cm × 4cm; the specific operations for cleaning and activating the carbon cloth surface are as follows: ultrasonically clean the carbon cloth for 30 minutes each with acetone, ethanol, and deionized water, and then rinse it repeatedly with deionized water 3 times, each time for 5 minutes; the concentration of concentrated nitric acid used for soaking is 14M, and ultrasonic oxidation is performed for 30 minutes.

[0014] As an improvement, the heating rate of the tubular furnace in step 4 is 2°C / min. -1 The temperature was raised to 200℃-300℃ for 4 hours for low-temperature oxidation.

[0015] The ruthenium-doped nanoneedle sheets carbon-supported cobalt tetroxide (RCO) self-supporting electrode prepared by the above method has a continuous nanoneedle sheet structure, and the nanosheets composed of cobalt tetroxide on the carbon support are uniformly distributed.

[0016] The application of the ruthenium-doped nanoneedle sheets carbon-supported cobalt tetroxide (RCO) self-supporting electrode prepared by the above method in electrocatalytic water treatment.

[0017] Beneficial effects:

[0018] Compared with existing technologies, the ruthenium-doped nanoneedle-sheet carbon-supported cobalt tetroxide (RCO) self-supporting electrode of the present invention, its preparation method and application, have the following advantages:

[0019] 1. This invention employs a hydrothermal method combined with low-temperature calcination to prepare a self-supporting RCO electrode catalyst. The preparation method is mature and can be mass-produced. Trace ruthenium doping further reduces the use of precious metals and lowers production costs. The prepared RCO catalyst grows on carbon cloth to form a self-supporting electrode, which has an open interface in the form of nanoneedle-like sheets, providing a large number of active sites. Trace ruthenium doping effectively optimizes the electron transport of the catalyst, further enhancing its activity. Air calcination oxidation also greatly improves the stability of the self-supporting electrode.

[0020] 2. The trace amounts of ruthenium-doped nanoneedle sheets of cobalt tetroxide self-supporting electrode material prepared by this invention exhibit OER catalytic performance far exceeding that of commercial RuO2 under alkaline and acidic conditions, and can be widely used in the field of electrocatalytic water splitting. Attached Figure Description

[0021] Figure 1 X-ray diffraction (XRD) patterns of the catalysts prepared in Example 1 and Comparative Example 1;

[0022] Figure 2 Scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) images of the catalyst prepared in Example 1;

[0023] Figure 3 XPS images of the ruthenium-doped nanoneedle sheets prepared in Example 1 and supported by cobalt tetroxide (RCO) on carbon are shown. (a) is the overall spectrum of RCO 140-5250-4, (b) is the oxygen spectrum of RCO 140-5250-4, (c) is the cobalt spectrum of RCO 140-5250-4, and (d) is the ruthenium spectrum of RCO 140-5250-4.

[0024] Figure 4 The OER performance of the catalysts prepared in Examples 1-7, Comparative Example 1, and RuO2 under alkaline conditions is shown in the graph.

[0025] Figure 5 The performance of catalysts prepared in Examples 1-7, Comparative Example 1, and RuO2 under alkaline conditions is shown, where (a) is the Tafel curve and (b) is the ECSA curve.

[0026] Figure 6 The stability characterization results of the catalysts prepared in Example 1 and RuO2 under alkaline conditions;

[0027] Figure 7 The figures show the OER performance of the catalysts prepared in Examples 1-7, Comparative Example 1, and RuO2 under acidic conditions. (a) is the LSV curve, and (b) is the 10 mA cm⁻¹ curve. -2 Overpotential;

[0028] Figure 8 The performance of catalysts prepared in Examples 1-7, Comparative Example 1, and RuO2 under acidic conditions is shown, where (a) is the Tafel curve and (b) is the ECSA curve.

[0029] Figure 9 The stability characterization results of the catalysts prepared in Example 1 and RuO2 under acidic conditions are shown. Detailed Implementation

[0030] The following embodiments are provided to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0031] In this embodiment of the invention, the OER testing method is as follows: a ruthenium-doped nanoneedle-sheet carbon-supported cobalt tetroxide (RCO) self-supporting electrode is used as the working electrode, while an Ag / AgCl electrode and a carbon rod are used as the reference electrode and counter electrode, respectively. Electrochemical activity and stability are characterized in 1 M KOH solution and 0.1 M sulfuric acid solution. The RuO2 used for comparison was purchased from Shanghai Alpha Biotechnology Co., Ltd.

[0032] Example 1

[0033] (1) Weigh 1.2g (4mmol) of Co(NO3)2·6H2O, 0.3g (8mmol) of NH4F, 1.2g (20mmol) of urea and 1mg (0.0048mmol) of ruthenium trichloride and dissolve them in 35mL of deionized water. After continuous stirring, a uniformly dispersed mixed solution is obtained.

[0034] (2) The carbon cloth was cut to a size of 2cm × 4cm. It was then ultrasonically cleaned for 30 minutes each with acetone, ethanol, and deionized water to remove surface impurities and pre-activate the carbon cloth. To further activate and enhance the hydrophilicity of the carbon cloth, it was ultrasonically oxidized again in 14M nitric acid for 30 minutes. After activation, the carbon cloth was ultrasonically cleaned three times in distilled water for 5 minutes each time. Finally, the pre-treated carbon cloth was placed in distilled water for later use.

[0035] (3) The treated carbon cloth and the mixed solution from step 1 were placed in a hydrothermal reactor and hydrothermally reacted at 140°C for 5 hours. After natural cooling, the carbon cloth with the ruthenium-cobalt precursor was removed and washed with deionized water and ethanol until neutral. Then it was placed in an oven and dried at 60°C for 4 hours to obtain a semi-finished product for later use.

[0036] (4) Place the semi-finished product in a tube furnace and heat it at 2°C for 2 minutes. -1After the temperature was increased to 250℃, it was oxidized at low temperature in air for 4 hours. After cooling, a ruthenium-doped nanoneedle sheet carbon-supported cobalt tetroxide (RCO) self-supporting electrode was obtained, denoted as RCO 140-5250-4.

[0037] The ruthenium-doped nanoneedle sheets prepared in Example 1 were characterized as carbon-supported cobalt tetroxide (RCO) self-supporting electrodes. The XRD patterns are shown below. Figure 1 As shown, the Co3O4 precursor obtained during the preparation process corresponds to the standard card PDF#43-1003; the microstructure of the catalyst was characterized by SEM and TEM, as shown in the figure. Figure 2 As shown, the obtained catalyst has a continuous nanoneedle-like structure, and the nanosheets composed of cobalt tetroxide on the carbon support are uniformly distributed, which is beneficial to exposing more active sites, enhancing the material transport in the catalytic reaction and the conductivity of the catalyst.

[0038] Figure 3 The high-resolution XPS spectrum of the ruthenium-doped nanoneedle sheet carbon-supported cobalt tetroxide (RCO) self-supporting electrode is shown in (a). The total spectrum shows that the catalyst mainly contains elements such as O, Co, and Ru.

[0039] Comparative Example 1

[0040] Except that step (1) does not contain ruthenium trichloride, the rest is the same as in Example 1, and CO black carbon cloth is obtained, which is denoted as CO 140-5250-4.

[0041] Example 2

[0042] Except for changing the hydrothermal reaction temperature in step (3) to 120°C, the rest is the same as in Example 1, and RCO black carbon cloth is obtained, which is denoted as RCO 120-5250-4.

[0043] Example 3

[0044] Except for changing the hydrothermal reaction temperature to 160°C in step (3), the rest is the same as in Example 1, and RCO black carbon cloth is obtained, which is denoted as RCO 160-5250-4.

[0045] Example 4

[0046] Except for changing the hydrothermal reaction time to 3 hours, the rest was the same as in Example 1, and RCO black carbon cloth was obtained, denoted as RCO 140-3250-4.

[0047] Example 5

[0048] Except for changing the hydrothermal reaction time to 7 hours, the rest was the same as in Example 1, and RCO black carbon cloth was obtained, denoted as RCO 140-7250-4.

[0049] Example 6

[0050] Except for the low-temperature oxidation temperature of 200℃ in step (4), the rest is the same as in Example 1, and RCO black carbon cloth is obtained, which is denoted as RCO 140-5200-4.

[0051] Example 7

[0052] Except for the low-temperature oxidation temperature of 300℃ in step (4), the rest is the same as in Example 1, and RCO black carbon cloth is obtained, which is denoted as RCO 140-5300-4.

[0053] The OER polarization curves of the catalysts prepared in Examples 1-7 and Comparative Example 1 were tested, and the results are as follows: In 1 M KOH solution, the RCO 140-5250-4 prepared in Example 1 showed a polarization curve at 10 mA / cm². -2 The overpotential at the current density is 186 mV, which is significantly smaller than the overpotential of the RuO2 catalyst (538 mV). Figure 4 The Tafel slope is 184mV dec. -1 Less than RuO2 (300mVdec) -1 ()( Figure 5 This indicates that RCO 140-5250-4 has a relatively fast electrochemical reaction rate. After 26 hours of stability testing under constant voltage, RCO 140-5250-4 still retained 72.5% of its initial current, which is significantly stronger than the 45.3% of commercial RuO2. Figure 6 In 0.1M sulfuric acid solution, RCO 140-5250-4 at 10mA cm⁻¹ -2 The overpotential at the current density is 127 mV, which is significantly smaller than the overpotential of the RuO2 catalyst (397 mV). Figure 7 After a 48-hour stability test under constant voltage, catalyst RCO 140-5250-4 still retained 70% of its initial current, far exceeding the 37% retention of commercial RuO2. Figure 9 ).

[0054] In an alkaline electrolyte, CO 140-5250-4 prepared in Comparative Example 1 was subjected to an electrolysis at 10 mA cm⁻¹. -2 The overpotential at the current density is 225 mV, which is significantly lower than the overpotential of the RuO2 catalyst (538 mV). Figure 4 In acidic electrolyte, CO 140-5250-4 at 10 mA cm⁻¹ -2 The overpotential at the current density is 407 mV, slightly higher than the overpotential of the RuO2 catalyst (397 mV). Figure 7 ).

[0055] In an alkaline electrolyte, RCO 120-5250-4 prepared in Example 2 was reacted at 10 mA / cm².-2 The overpotential at the current density is 354 mV, which is significantly smaller than the overpotential of the RuO2 catalyst (538 mV). Figure 4 In acidic electrolyte, RCO 120-5250-4 at 10 mA cm⁻¹ -2 The overpotential at the current density is 410 mV, slightly higher than the overpotential of the RuO2 catalyst (397 mV). Figure 7 ).

[0056] In an alkaline electrolyte, RCO 160-5250-4 prepared in Example 3 was reacted at 10 mA / cm². -2 The overpotential at the current density is 377 mV, which is significantly smaller than the overpotential of the RuO2 catalyst (538 mV). Figure 4 In acidic electrolyte, RCO 160-5250-4 at 10 mA cm⁻¹ -2 The overpotential at the current density is 398 mV, which matches the overpotential of the RuO2 catalyst (397 mV). Figure 7 ).

[0057] In an alkaline electrolyte, RCO 140-3250-4 prepared in Example 4 was subjected to an electrolysis rate of 10 mA / cm². -2 The overpotential at the current density is 304 mV, which is significantly smaller than the overpotential of the RuO2 catalyst (538 mV). Figure 4 In acidic electrolyte, RCO 140-3250-4 at 10 mA cm⁻¹ -2 The overpotential at the current density is 264 mV, which is significantly lower than the overpotential of the RuO2 catalyst (397 mV). Figure 7 ).

[0058] In an alkaline electrolyte, RCO 140-7250-4 prepared in Example 5 was reacted at 10 mA / cm². -2 The overpotential at the current density is 367 mV, which is significantly smaller than the overpotential of the RuO2 catalyst (538 mV). Figure 4 In acidic electrolyte, RCO 140-7250-4 at 10 mA cm⁻¹ -2 The overpotential at the current density is 299 mV, which is significantly lower than the overpotential of the RuO2 catalyst (397 mV). Figure 7 ).

[0059] In an alkaline electrolyte, RCO 140-5200-4 prepared in Example 6 was reacted at 10 mA / cm². -2 The overpotential at the current density is 336 mV, which is significantly smaller than the overpotential of the RuO2 catalyst (538 mV). Figure 4In acidic electrolyte, RCO 140-5200-4 at 10 mA cm⁻¹ -2 The overpotential at the current density is 436 mV, which is significantly higher than the overpotential of the RuO2 catalyst (397 mV). Figure 7 ).

[0060] In an alkaline electrolyte, RCO 140-5300-4 prepared in Example 7 was reacted at 10 mA / cm². -2 The overpotential at the current density is 228 mV, which is significantly smaller than the overpotential of the RuO2 catalyst (538 mV). Figure 4 In acidic electrolyte, RCO 140-5300-4 at 10 mA cm⁻¹ -2 The overpotential at the current density is 326 mV, which is significantly lower than the overpotential of the RuO2 catalyst (397 mV). Figure 7 ).

[0061] In summary, this invention utilizes a one-pot hydrothermal method to form a ruthenium-cobalt precursor by doping with trace amounts of ruthenium. After drying, the precursor is calcined in air to oxidize, resulting in a self-supporting electrode made of trace amounts of ruthenium-doped cobalt tetroxide nanoneedles. The catalyst's continuous open interface, elemental doping, and carbon cloth support enable the catalyst to exhibit excellent oxygen evolution reaction catalytic activity and stability, demonstrating promising application prospects.

Claims

1. A method for preparing a ruthenium-doped nanoneedle thin sheet carbon supported tri-cobalt tetra-oxide self-supporting electrode, characterized in that, The method comprises the following steps: Step 1, weighing ammonium fluoride, cobalt nitrate hexahydrate, ruthenium trichloride and urea, dissolving them in deionized water, and continuously stirring to obtain a uniform mixed solution; Step 2, cutting and pretreating carbon cloth; Step 3, placing the treated carbon cloth and the mixed solution of step 1 in a hydrothermal reactor, hydrothermally reacting at 120-160 DEG C for 3-5 hours, naturally cooling, taking out the carbon cloth with the grown ruthenium-cobalt precursor, and cleaning it with deionized water and ethanol, and then drying to obtain a semi-finished product for standby; Step 4, the semi-finished product is placed in a tube furnace and is subjected to low-temperature oxidation by being heated in air, and after natural cooling, a ruthenium-doped nanoneedle flake carbon-supported cobalt trioxide tetroxide self-supporting electrode is obtained, wherein the heating speed of the tube furnace in step 4 is 2 ℃ / min -1 , and the temperature is raised to 200-300 ℃ for low-temperature oxidation for 4 h.

2. The method for preparing a ruthenium-doped nanoneedle thin sheet carbon supported cobalt oxide self-supporting electrode according to claim 1, characterized in that, The molar ratio of ruthenium trichloride, urea, cobalt nitrate hexahydrate and ammonium fluoride in step 1 is 0.0012:5:1:

2.

3. The method for preparing a ruthenium-doped nanoneedle thin sheet carbon supported tricobalt tetraoxide self-supporting electrode according to claim 1, characterized in that, The pretreatment in step 2 is: ultrasonic cleaning of the cut carbon cloth with acetone, ethanol and deionized water in sequence to remove impurities on the surface of the carbon cloth and complete pre-activation of the carbon cloth; in order to further activate and enhance the hydrophilicity of the carbon cloth, the cleaned carbon cloth needs to be ultrasonic-oxidized in nitric acid again; after the activation of the carbon cloth is completed, it needs to be ultrasonic-cleaned in distilled water; finally, the pretreated carbon cloth is placed in distilled water for standby.

4. The method for preparing a ruthenium-doped nanoneedle thin sheet carbon supported tricobalt tetraoxide self-supporting electrode according to claim 3, characterized in that, The size of the carbon cloth is 2 cm x 4 cm; the specific operation of cleaning and activating the surface of the carbon cloth is: ultrasonic cleaning of the carbon cloth with acetone, ethanol and deionized water for 30 min respectively, and then repeatedly washing with deionized water for 3 times, each time for 5 min; the concentration of the concentrated nitric acid used for soaking is 14 M, and the ultrasonic oxidation time is 30 min.

5. The production process according to any one of claims 1 to 4, characterized in that The ruthenium-doped nanoneedle flake carbon-supported cobalt trioxide self-supporting electrode has a continuous nanoneedle flake structure, and the nanosheet composed of carbon-supported cobalt trioxide is uniformly distributed.

6. Application of the ruthenium-doped nanoneedle flake carbon-supported cobalt trioxide self-supporting electrode prepared by the preparation method of any one of claims 1-4 in electrocatalytic water.

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