A method for preparing a platinum monatomic composite electrode

Abstract

The application discloses a controllable synthesis of Pt single atoms and a preparation method of the Pt single atoms and RuO2-IrO2 composite as an anode electrocatalyst and an electrode thereof. The steps are as follows: H2PtCl6 and tetra-methylammonium ethylborane are mixed and ground in a certain proportion, the mixture is then subjected to a closed heating reaction in a reaction kettle, and then is transferred to a vacuum reaction kettle to be subjected to calcination treatment again, so that PtNCB is obtained. A coating solution containing the prepared PtNCB and RuCl3 and IrCl3 precursor solutions is prepared, is uniformly coated on a substrate, and then the generated electrode is dried, and the electrode containing the coating is sintered in a heating furnace, so that a RuO2-IrO2-PtNCB electrode is finally obtained. By skillfully controlling the amount of the organic diboron compound tetra-methylammonium ethylborane, PtNCB precisely protected by Pt single atoms is successfully synthesized, and RuO2-IrO2 is co-catalyzed as an anode electrocatalyst. The Pt single atom catalyst of the application not only has excellent sintering resistance, but also has excellent electrocatalytic activity.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic redox technology, and in particular to a method for preparing a platinum single-atom composite electrode. Background Technology

[0002] Although RuO2 and IrO2 catalysts have been widely used in electrochemical catalysis, they exhibit poor stability in high-potential acidic media. Platinum or platinum-based catalysts are currently recognized as the most advanced electrocatalysts. Tailoring platinum electrocatalysts to atomically precise ultra-small sizes reveals unique structural and physicochemical properties, ultra-high surface-to-volume ratios, atomically precise structures, and tunable electronic structures, demonstrating superior electrocatalytic performance and stability. Furthermore, atomic-level engineering of Pt is an effective electrocatalytic design strategy for achieving maximum electrocatalytic performance with minimal Pt dosage. Additionally, in existing Pt-doped catalyst electrodes, Pt is easily oxidized to ionic platinum (especially platinum oxide) during preparation, leading to catalyst deactivation. The significant improvement in the performance of the PtNCB catalyst in this invention stems from the downward shift of the d-band center of surface Pt atoms. This not only inhibits the formation of OH and O species at active sites but also prevents the oxidation of surface Pt atoms, thereby significantly improving the activity of the original RuO2–IrO2 composite electrode. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention aims to provide an effective atomic-level engineering strategy to enhance the electrocatalytic properties of Pt-based electrocatalysts. A Pt single-atom catalyst with Pt-B active centers was prepared on an N-doped carbon substrate and then composited with RuO2–IrO2 to prepare a RuO2–IrO2–PtNCB electrode, which has a significant impact on the treatment of industrial wastewater. This method of preparing electrode coatings can enhance the stability and electrocatalytic performance of materials, making it a promising electrode material for the electrocatalytic degradation of organic pollutants in wastewater.

[0004] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0005] A method for preparing a platinum single-atom composite electrode includes the following specific steps:

[0006] Step a. Mix and grind H2PtCl6 and tetramethylaminoborane at a mass ratio of 1:10 to 100. The mixture is then heated in a closed reactor at a temperature of 200 to 400°C for 1 to 10 hours.

[0007] Step b. Then transfer to the vacuum reaction kettle under the condition of 0-100 mbar, 200-800 DEG C, continue to calcine 1-5h to obtain PtNCB, and immerse the obtained PtNCB in 0.05M-5M H2SO4 solution for 6-48h to remove the residual nanoparticles;

[0008] Step c. Mix 0.001-0.1g PtNCB, 0.001-0.1g H2IrCl6 solution with a concentration of 0.01-0.1g / mL and 0.001-0.1g RuCl3 solution with a concentration of 0.01-0.1g / mL, and then add 0.01-100ml ethanol and 0.001-10ml Nafion solution and fully stir;

[0009] Step d. Add lye to the mixed solution prepared in step c until pH=8-14, and then ultrasonic for 1-60min;

[0010] Step e. Gel coat the mixture prepared in step d above on a substrate, dry at 80-120 DEG C for 10-30min, and repeat the coating-drying step 2-50 times, calcine at 300-800 DEG C for 30-150min, and finally obtain a platinum single-atom composite electrode.

[0011] Preferably, the lye in step d is any one or any two or more combinations of ammonia, KOH, NaOH solution.

[0012] Preferably, the substrate in step e is any one of titanium-based, niobium-based, carbon-based, stainless steel-based, copper-based, and carbon steel-based.

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] 1. The compound tetramethylammonium ethylborane is a kind of organic boron reagent with boron-boron bond, which is widely used in the boronation reaction of organic substrates. Due to the boron-boron bond, it has unique Lewis acidity and reducing property, so it can play the role of single electron reducing agent. The present application innovatively introduces the organic dibo ron molecule tetramethylammonium ethylborane into the surface state and band structure regulation of inorganic nanomaterials.

[0015] 2、The platinum monatomic anchored in the boron hole has more d empty orbit above the Fermi level, which effectively adjusts the electronic structure of the catalyst. The platinum monatomic loaded in the boron hole has a larger adsorption energy for alkanes, alkenes and the like than the platinum monatomic loaded in the nitrogen hole and the carbon hole. Different anchoring positions on the carrier can effectively regulate the chemical activity of the loaded platinum monatomic, and the platinum monatomic at the boron hole has better activity. In addition, due to the strong and thermally stable Pt-B bond, the Pt atomic diffusion and nanoparticle migration are inhibited and delayed, and the agglomeration of PtNCB in the high-temperature sintering process is greatly inhibited.

[0016] 3、The presence of PtNCB, especially BB-Pt, can easily change the electronic properties of RuO2-IrO2 and improve the catalytic activity by reducing the energy barrier and increasing the dissociation energy of active oxygen species.

[0017] 4、The key process for controlling the reduction synthesis of platinum monatomic in the application does not require complex and unsafe synthesis operations such as calcination under a hydrogen atmosphere or high-temperature calcination, which is usually used in the previously developed technology and has a safety hazard. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The PtNCB catalyst powder prepared in Example 1 and the electrochemical impedance EIS spectrum of each catalyst; the EIS results show that the Nyquist plot arc radius of NCB and PtNCB is shorter than that of NC and PtNC, indicating that B doping can reduce the electrochemical impedance spectrum and promote electron transfer;

[0019] Figure 2 The physical map of the Ti / RuO2-IrO2-PtNCB electrode prepared in Example 1 and the total nitrogen TN degradation effect; left a: titanium substrate; right a: Ti / RuO2-IrO2-PtNCB-platinum monatomic composite electrode; b: comparison of the effects of Ti / RuO2-IrO2-PtNCB and Ti / RuO2-IrO2 on total N degradation;

[0020] Figure 3 The degradation efficiency of tetracycline degradation under different current densities in Example 2. DETAILED DESCRIPTION

[0021] Example 1

[0022] H2PtCl6 and tetra-methylammonium ethylborane were mixed and ground in a mass ratio of 1:50, and then the mixture was subjected to a closed heating reaction in a reaction kettle at a temperature of 350°C for 3h. Then it was transferred to a vacuum reaction kettle at 100mbar and 350°C for further calcination for 3h to obtain PtNCB. The obtained PtNCB was immersed in a 2M H2SO4 solution for 10h to better remove residual nanoparticles. Then 0.1g of the prepared PtNCB, 0.1g of a H2IrCl6 solution with a concentration of 0.1g / mL, and 0.1g of a RuCl3 solution with a concentration of 0.1g / mL were mixed and stirred well, and then 2ml of ethanol and 0.1ml of a Nafion solution were added. Then NaOH solution was added to the just-prepared mixed solution until pH=12, and ultrasonic treatment was performed for 15min. The ultrasonically prepared mixture gel was coated on a carbon-based graphite felt body, and then dried at 110°C for 30min. The coating-drying step was repeated 15 times, and then calcination was performed at 450°C for 120min to finally obtain a platinum single-atom composite electrode.

[0023] The electrode prepared in Example 1 was used for degradation of total nitrogen TN in wastewater, wherein the TN concentration was 3500mg / L, the electrolyte was 1.5g / L NaCl, the current density was 80mA / cm2, and the operation time was 240min. The TN concentration decreased to 265mg / L, and the removal rate reached 92.43%. 2

[0024] Example 2

[0025] H2PtCl6 and tetra-methylammonium ethylborane were mixed and ground in a mass ratio of 1:60, and then the mixture was subjected to a closed heating reaction in a reaction kettle at a temperature of 250°C for 4h. Then it was transferred to a vacuum reaction kettle at 0mbar and 400°C for further calcination for 3h to obtain PtNCB. The obtained PtNCB was immersed in a 0.5M H2SO4 solution for 24h to better remove residual nanoparticles. Then 0.01g of the prepared PtNCB, 0.1g of a H2IrCl6 solution with a concentration of 0.1g / mL, and 0.1g of a RuCl3 solution with a concentration of 0.1g / mL were mixed and stirred well, and then 2ml of ethanol and 0.1ml of a Nafion solution were added. Then NaOH solution was added to the just-prepared mixed solution until pH=11.5, and ultrasonic treatment was performed for 10min. The ultrasonically prepared mixture gel was coated on a titanium substrate, and then dried at 100°C for 10min. The coating-drying step was repeated 10 times, and then calcination was performed at 400°C for 60min to finally obtain a platinum single-atom composite electrode.

[0026] ​The electrode prepared in Example 2 was used for degradation of tetracycline in wastewater, wherein the tetracycline concentration was 60 mg / L, the electrolyte was 1.0 g / L NaCl, and the current density was 10 mA / cm 2 When the current density was 10 mA / cm

[0027] Example 3

[0028] H2PtCl6and tetramethylammonium borane were mixed and ground in a mass ratio of 1:80. The mixture was then subjected to a closed heating reaction in a reaction kettle at a temperature of 300°C for 3 h. Then, it was transferred to a vacuum reaction kettle at 50 mbar and 300°C for further calcination for 4 h to obtain PtNCB. The obtained PtNCB was immersed in a 1 M H2SO4solution for 12 h to better remove residual nanoparticles. Then, 0.05 g of the obtained PtNCB, 0.05 g of a H2IrCl6solution with a concentration of 0.05 g / mL, and 0.1 g of a RuCl3solution with a concentration of 0.1 g / mL were mixed and stirred well. Then, 5 ml of ethanol and 0.5 ml of a Nafion solution were added to the mixture. Then, a KOH solution was added to the prepared mixture until the pH was 10, and the mixture was ultrasonicated for 30 min. The ultrasonically prepared mixture gel was coated on a titanium substrate, which was then dried at 108°C for 20 min, and the coating-drying step was repeated 20 times. Finally, the titanium substrate was calcined at 500°C for 90 min to obtain a platinum single-atom composite electrode.

[0029] The electrode prepared in Example 3 was used for degradation of ethanol in wastewater, wherein the ethanol concentration was 5000 mg / L, the electrolyte was 1.0 g / L Na2SO4, and the current density was 80 mA / cm 2 When the current density was 80 mA / cm

[0030] Example 4

[0031] H2PtCl6 and tetramethylammonium borane were mixed and ground in a mass ratio of 1:90. The mixture was then subjected to a closed heating reaction in a reaction kettle at a temperature of 400°C for 5h. Then it was transferred to a vacuum reaction kettle at 60mbar and 250°C for further calcination for 5h to obtain PtNCB. The obtained PtNCB was immersed in a 1.5M H2SO4 solution for 20h to better remove residual nanoparticles. Then 0.01g of the prepared PtNCB, 0.1g of a H2IrCl6 solution with a concentration of 0.1g / mL, and 0.05g of a RuCl3 solution with a concentration of 00.5g / mL were mixed and stirred well. Then 5ml of ethanol and 1ml of a Nafion solution were added to the mixture. Then a NaOH solution was added to the prepared mixture until the pH reached 11, and the mixture was ultrasonicated for 45min. The ultrasonically prepared mixture gel was coated on a niobium substrate, which was then dried at 105°C for 30min. The coating-drying step was repeated 10 times, and then the mixture was calcined at 400°C for 90min to obtain a platinum single-atom composite electrode.

[0032] The electrode prepared in Example 4 was used for degradation of dimethylamide wastewater with a dimethylamide concentration of 203mg / L and an electrolyte of 1.5g / L Na2SO4 and a current density of 100mA / cm2. After 60min of treatment, the dimethylamide concentration was reduced to 31.6mg / L, and the removal efficiency reached 84.43%. 2

[0033] Although the present application has been described in detail with reference to the foregoing embodiments, technical solutions recorded in the foregoing embodiments can be modified or some technical features can be replaced by equivalent features by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for preparing a platinum single-atom composite electrode, characterized in that, Includes the following steps: Step a. Mix and grind H2PtCl6 and tetramethylaminoborane in a certain proportion, and then carry out a closed heating reaction in a reaction vessel; Step b. Then transfer to a vacuum reactor for further calcination to obtain PtNCB; Step c. Mix PtNCB, H2IrCl6 solution and RuCl3 solution thoroughly, and then add ethanol and Nafion solution. Step d. Add the alkaline solution to the mixed solution prepared in step c until the pH is 8 to 14, and then sonicate for 1 to 60 minutes; Step e. Coat the mixed gel prepared in step d onto the substrate, dry it at 80–120°C for 10–30 min, and repeat the coating-drying step 2–50 times. Then calcine it at 300–800°C for 30–150 min to finally obtain a platinum single-atom composite electrode.

2. The method for preparing a platinum single-atom composite electrode according to claim 1, characterized in that, In step a, the mass ratio of H2PtCl6 to tetramethylaminoborane is 1:10-100.

3. The method for preparing a platinum single-atom composite electrode according to claim 1, characterized in that, The heating temperature in step a is 200–400°C, and the heating time is 1–10 h.

4. The method for preparing a platinum single-atom composite electrode according to claim 1, characterized in that, The calcination conditions of the vacuum reactor in step b are 0–100 mbar, 200–800 °C, and calcination time of 1–5 h.

5. The method for preparing a platinum single-atom composite electrode according to claim 1, characterized in that, The PtNCB obtained in step b is leached in a 0.05M to 5M H2SO4 solution for 6 to 48 hours to remove residual nanoparticles.

6. The method for preparing a platinum single-atom composite electrode according to claim 1, characterized in that, In step c, the amount of PtNCB is 0.001–0.1 g; the concentration of H2IrCl6 solution is 0.01–0.1 g / mL and the mass is 0.001–0.1 g; the concentration of RuCl3 solution is 0.01–0.1 g / mL and the mass is 0.001–0.1 g; the amount of ethanol added is 0.01–100 ml; and the amount of Nafion solution added is 0.001–10 ml.

7. The method for preparing a platinum single-atom composite electrode according to claim 1, characterized in that, In step d, the alkaline solution is any one or any combination of two or more of the following: ammonia, KOH, and NaOH solution.

8. The method for preparing a platinum single-atom composite electrode according to claim 1, characterized in that, In step e, the substrate can be any one of titanium-based, niobium-based, carbon-based, stainless steel-based, copper-based, or carbon steel-based.

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