Corrosion-resistant Ru dissolution-resistant catalyst and preparation method thereof

Abstract

The invention discloses a corrosion-resistant Ru dissolution-resistant catalyst and a preparation method thereof, and a compact graphene coating layer with the thickness of 3-8 nm is constructed on the surface of a TiO2 nanobelt and is used for isolating synergistic erosion of Cl <-> to Ru active sites in a high-salt system. Controlled nanopores or defects are introduced into the ultrathin graphene layer, it can be guaranteed that H2O2 and substrate molecules can reach ruthenium cluster active sites, Cl <-> migration is blocked, the 50-60 nm micropore structure in the TiO2 nanobelt is combined, the Ru cluster active sites are effectively protected in NaCl aqueous solution high-salt waste water, Ru dissolution caused by chloride ion erosion is remarkably inhibited, and the Ru / TiO2 nanobelt composite material is obtained. The chlorine corrosion resistance and the structural stability of the catalytic material are effectively improved. And the paint has unique corrosion resistance in strong-salt and strong-oxidation environments.

Description

Technical Field

[0001] This technology relates to the field of photocatalysis and noble metal nanocatalytic materials, specifically to a corrosion-resistant and Ru-resistant catalyst and its preparation method. Background Technology

[0002] Nanometals, due to their unique surface electronic structure and quantum size effect, have potential applications in photo-driven chemical conversion, pollutant degradation, and energy catalysis. Among them, noble metals such as Ru exhibit high catalytic activity in H2O2 activation and •OH radical production, but their utilization is limited by insufficient light-energy coupling efficiency and the limited number of available active sites on the metal surface.

[0003] In existing technologies, the following methods are mainly used to improve photocatalytic efficiency: one approach is to control the morphology of noble metal nanoparticles, such as nanospheres, nanorods, nanocages, and hollow structures, to improve their light absorption performance; another approach utilizes metal / semiconductor heterojunctions or plasmon metals to introduce band-matching structures, thereby improving the separation efficiency of photogenerated carriers. Additionally, some technologies enhance H2O2 activation by increasing the noble metal loading or introducing co-catalysts. However, these technological approaches generally suffer from complex processing techniques, high material costs, low utilization of noble metals, uncontrollable hotspot distribution, and limited light-energy coupling efficiency. Furthermore, some structures are prone to noble metal dissolution or deactivation during recycling, affecting their long-term stability.

[0004] Because the traditional photocatalytic structure is disordered and difficult to precisely control, the efficiency of light energy being concentrated on the catalytic active sites is low. The noble metal active centers are not fully excited, and efficient H2O2 directional activation and •OH radical amplification effect cannot be achieved.

[0005] In addition, Ru dissolves in traditional catalysts 3+ Existing as a free hydrated / hydroxyl complex, it exhibits high steric equivalence with Cl-. - It can freely coordinate and is easily excited into a highly active state by 450nm light, undergoing photo-oxidation-Cl with H2O2 at concentrations above 300mg / L. - Synergistic effect: Rapidly oxidized to Ru 6+ Or Ru 7+ and with Cl - An irreversible, inert chlorine-oxygen complex [RuO2Cl4] is formed. 4- Traditional structures cannot simultaneously balance light field intensity and catalytic stability, resulting in problems such as dissolution, poisoning, and activity decay of precious metals during long-term light exposure or reaction. Summary of the Invention

[0006] This invention aims to solve the problem of supported Ru catalysts in high Cl- concentrations. -The problem of catalyst poisoning and deactivation due to dissolution in solution and damage to the effective structure of the catalyst.

[0007] To solve the above problems, this application provides the following technical solution: A method for preparing a catalyst resistant to corrosion and Ru leaching includes the following steps: S1. Add ethanol to the monodisperse PS sphere template and disperse it ultrasonically to obtain a PS sphere alcohol-water dispersion K. S2. Under ice-water bath stirring, titanium reagent is added to ethanol and stirred to obtain solution A; S3. Mix the alcohol solvent, water, and concentrated nitric acid to obtain solution B; S4. Add solution B from step S3 to solution A from step S2, adjust the pH with concentrated nitric acid, and stir to obtain solution C of TiO2 precursor. S5. Add the dispersion K from step S1 to the solution C from step S4, and sonicate and stir to obtain the composite solution L of PS ball-TiO2 precursor; S6. The composite liquid L from step S5 is heated under a sealed environment, kept at a constant temperature, and slowly cooled to room temperature. It is then centrifuged, washed alternately with ethanol and water, and vacuum dried to obtain the powder M of the PS ball@TiO2 nanobelt composite precursor. S7. The powder M from step S6 is laid out in parallel, heated and calcined in an oxygen atmosphere, and cooled to room temperature to obtain TiO2 nanoporous belt substrate. S8. Add HCl to water and RuCl3 to adjust the pH, stir at room temperature to obtain solution N of RuCl3 precursor; S9. Soak the solution N from step S8 in the TiO2 nanoporous tape substrate from step S7 while sonicating; let stand, dry at low temperature and low pressure to obtain the TiO2-loaded RuCl3 precursor substrate Y. S10. The substrate Y from step S9 is purged under Ar gas and heated, and then purged at a constant temperature under an Ar-H2 mixed gas; it is then cooled to room temperature and sealed in an H2 / Ar mixed atmosphere to obtain a Ru-loaded TiO2 nanoporous tape substrate. S11. The TiO2 nanoporous tape substrate loaded with Ru in step S10 is purged with low-pressure Ar gas, heated, reduced at a constant temperature under H2 purging, purged with Ar gas, purged with CH4 gas, deposited at a constant temperature, and then cooled to room temperature in an Ar atmosphere to obtain the graphene / Ru / TiO2 nanoribbon composite catalyst Z. S12. The catalyst Z from step S11 is heated under Ar gas, etched by injecting water vapor, and cooled by high-speed Ar gas purging to obtain a metal nanoporous catalyst.

[0008] In step S1, the mass ratio of monodisperse PS spheres to ethanol is 5%~10%:1.

[0009] The monodisperse PS sphere template material in step S1 is polystyrene with a particle size of 20~100nm, and is ultrasonicated for 30~40min.

[0010] The titanium reagent in step S2 is either tetrabutyl titanate or titanium isopropoxide.

[0011] In step S2, the ratio of titanium reagent to ethanol is 1:5~16 by volume.

[0012] In step S5, the volume ratio of dispersion K to solution C is 1:0.9~1.2.

[0013] In step S6, the heating rate of the composite liquid L is 0.5~2℃ / min, the constant temperature is 170~200℃, and the constant temperature time is 12~24h.

[0014] In step S8, the water:RuCl3 ratio is 3~6:0.103~0.207 by mass.

[0015] In step S11, the CH4 flow rate is 2-5 sccm, the isothermal temperature is 500-700℃, the deposition time is 5-30 min, and the graphene deposition thickness is 3-8 nm; the cooling rate in the Ar atmosphere after deposition is 3-5℃ / min.

[0016] In step S12, the catalyst Z is heated at a rate of 3-5℃ / min under Ar gas, heated to 400-480℃, with an initial water vapor temperature of 98-100℃ and a water vapor content of 100-290 ppm. The etching time is 10-15 s, and the Ar gas flow rate during heating is 50-100 sccm.

[0017] Preferably, in step S2, the stirring speed of the ice-water bath is 300~400 rpm, and the stirring time is 10~20 min.

[0018] Preferably, in step S3, the alcohol solvent is either anhydrous ethanol or ethylene glycol. Preferably, in step S3, the volume ratio of alcohol solvent:water:concentrated nitric acid is 10~20:2~5:0.5~1.

[0019] Preferably, the nitric acid is 68 wt% concentrated nitric acid.

[0020] Preferably, in step S4, the volume ratio of solution A to solution B is 1:1 to 1.2.

[0021] Preferably, in step S4, the mixing rate is 80-100 rpm and the stirring time is 20-35 min.

[0022] Preferably, in step S4, concentrated nitric acid is used to adjust the pH to 2-3.

[0023] Preferably, in step S5, the ultrasonic time is 15-20 min and the stirring time is 10-15 min.

[0024] Preferably, in step S6, the cooling rate is 0.5~1℃ / min, the room temperature is 25℃, the centrifugation rate is 8000~10000r / min, the centrifugation time is 10~15min, the washing is performed 3~4 times with alternating ethanol and water, with a washing volume of 20~30ml / time, and the product is vacuum dried at 75℃~80℃ for 10~12h.

[0025] Preferably, in step S7, the powder M is laid in parallel with a thickness of 20~30μm, the oxygen flow rate is 10~12mL / min, the heating rate is 0.5-1℃ / min, the calcination temperature is 400~500℃, the calcination time is 2~4h, and the TiO2 nanoporous belt substrate is obtained by cooling to room temperature.

[0026] Preferably, in step S8, the HCl concentration is 0.8-1 mol / L, the pH is 1-2, and the stirring time at room temperature is 8-10 min; Preferably, in step S9, the soaking time is 1-2 minutes, the ultrasonic frequency is 20-30 kHz, the standing time is 10-20 minutes, the low temperature is 40-60℃, the low pressure is 0-0.08 MPa, and the drying time is 8-12 hours.

[0027] Preferably, in step S10, the Ar gas flow rate is 50 mL / min to purge for 20 to 30 min, followed by heating to 100 to 200°C at a rate of 0.8 to 1°C / min until the temperature reaches 100 to 200°C. Preferably, in step S10, the flow rate of H2 in the Ar-H2 mixture is 10~25 mL / min, the flow rate of H2 is 25~40 mL / min, and the mixture is purged at a constant temperature for 2~4 hours; then cooled to room temperature of 25℃.

[0028] Preferably, in step S11, the Ru-loaded TiO2 nanoporous substrate is purged for 5 min at 0-10 Pa with an Ar gas flow rate of 100-150 sccm to remove air, then heated to 500-700 °C at 5-8 °C / min with an H2 flow rate of 10-20 sccm, and the isothermal reduction time is 20-30 min, with Ar gas purging for 5-8 min. Preferably, in step S12, after etching, Ar gas is purged at a high speed of 200~300mL / min and the temperature is reduced to room temperature of 25℃.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention constructs a dense graphene coating layer on the surface of TiO2 nanoribbons to isolate Cl in high-salt systems. - Synergistic erosion of Ru cluster active sites. This ultrathin graphene layer introduces controlled nanopores or defects that can simultaneously ensure that H2O2 and substrate molecules can reach the Ru cluster active sites while blocking Cl. - The migration and integration with the microporous structure within the TiO2 nanoribbons effectively protect the Ru cluster active sites in high-salt NaCl aqueous solutions, significantly inhibiting Ru dissolution caused by chloride ion erosion and effectively enhancing the catalytic material's resistance to chloride corrosion and structural stability. This results in unique corrosion resistance under strong salt and strong oxidizing environments. Detailed Implementation

[0030] Unless otherwise specified, the ethanol is anhydrous ethanol. The concentrated nitric acid has a mass fraction of 68 wt%.

[0031] In this application, Ar gas and water vapor can be considered as ideal gases at low pressure (10~30 Pa) and high temperature (400~480 °C).

[0032] Example 1 A method for preparing a catalyst resistant to corrosion and Ru leaching includes the following steps: S1. Monodisperse PS spheres are added to ethanol and ultrasonically dispersed to obtain a PS sphere dispersion K in alcohol and water. In step S1, the mass ratio of monodisperse PS spheres to ethanol is 8%:1.

[0033] In step S1, the monodisperse PS spheres are made of polystyrene with a particle size of 50 nm and are sonicated for 30 min.

[0034] S2. Under ice-water bath stirring, titanium reagent is added to ethanol and stirred to obtain solution A; The titanium reagent in step S2 is tetrabutyl titanate; In step S2, the ratio of titanium reagent to ethanol is 1:10 by volume.

[0035] In step S2, the stirring speed in the ice-water bath is 300 rpm, and the stirring time is 20 min.

[0036] S3. Mix the alcohol solvent, water, and concentrated nitric acid to obtain solution B; In step S3, the alcohol solvent is ethanol; In step S3, the volume ratio of alcohol solvent:water:concentrated nitric acid is 15:2:0.5.

[0037] S4. Add solution B from step S3 to solution A from step S2, then adjust the pH with concentrated nitric acid and stir to obtain solution C of TiO2 precursor. In step S4, the volume ratio of solution A to solution B is 1:1.

[0038] In step S4, the mixing rate is 100 rpm, and the stirring time is 20 min.

[0039] In step S4, the pH is adjusted to 2 with concentrated nitric acid, and stirring continues for 30 minutes. S5. Add the dispersion K from step S1 to the solution C from step S4, and sonicate and stir to obtain the composite solution L of PS ball-TiO2 precursor; In step S5, the dispersion K: solution C ratio is 1:1.1 by volume.

[0040] In step S5, the ultrasonic time is 20 min, the stirring time is 10 min, and the ultrasonic frequency is 20 kHz.

[0041] S6. The composite liquid L from step S5 is heated under a sealed environment, kept at a constant temperature, and slowly cooled to room temperature. It is then centrifuged, washed alternately with ethanol and water, and vacuum dried to obtain the powder M of the PS ball@TiO2 nanobelt composite precursor. In step S6, the heating rate of the composite liquid L is 2℃ / min, the constant temperature is 180℃, and the constant temperature time is 18h.

[0042] In step S6, the cooling rate is 1℃ / min, the room temperature is 25℃, the centrifugation rate is 10000r / min, the centrifugation time is 15min, the washing is performed 3 times with alternating ethanol and water, with each washing volume of ethanol and water being 30ml, the vacuum drying temperature is 80℃, and the drying time is 10h.

[0043] S7. The powder M from step S6 is laid out in parallel, heated and calcined in an oxygen atmosphere, and cooled to room temperature to obtain TiO2 nanoporous belt substrate. In step S7, powder M is laid in parallel with a thickness of 30 μm, oxygen flow rate is 10 mL / min, heating rate is 1 °C / min, calcination temperature is 450 °C, calcination time is 2 h, and TiO2 nanoporous belt substrate is obtained by cooling to room temperature.

[0044] This application employs a conventional scraper for parallel coating. Before scraping, powder M can be uniformly mixed and moistened with approximately 10wt% to 15wt% of its mass in anhydrous ethanol, preferably 15wt%. The distance between the scraper and the base is then set to a coating thickness of 30μm. The scraper's forward speed is 2 to 3 cm / s, preferably 3 cm / s. The anhydrous ethanol is automatically removed during calcination.

[0045] S8. Add HCl to water and RuCl3 to adjust the pH, stir at room temperature to obtain solution N of RuCl3 precursor; In step S8, the water:RuCl3 ratio is 6:0.207 by mass.

[0046] In step S8, the HCl concentration is 1 mol / L, the pH is 2, and the stirring time at room temperature is 10 min. S9. Soak the solution N from step S8 in the TiO2 nanoporous substrate from step S7 while sonicating; let stand, dry at low temperature and low pressure to obtain the TiO2-supported RuCl3 precursor substrate Y. In step S9, the soaking time is 2 minutes, the ultrasonic frequency is 20 kHz, the standing time is 10 minutes, the low temperature is 50°C, the low pressure is 200 Pa, and the drying time is 8 hours.

[0047] S10. The substrate Y from step S9 is purged under Ar gas and heated, and then purged at a constant temperature under an Ar-H2 mixed gas; it is cooled to room temperature in an H2 / Ar mixed atmosphere to obtain a Ru-loaded TiO2 nanoporous belt substrate. In step S10, Ar gas flow rate is 50 mL / min to purge for 30 min, then the temperature is raised to 150℃ at a rate of 1℃ / min until it reaches 150℃. In step S10, the flow rate of H2 in the Ar-H2 mixture is 25 mL / min, the flow rate of Ar is 25 mL / min, and the mixture is purged at a constant temperature for 2 hours; then cooled to room temperature of 25°C.

[0048] The Ru-loaded TiO2 nanoporous tape substrate prepared in step S10 can be sealed and stored in an Ar gas bag.

[0049] S11. The TiO2 nanoporous tape substrate loaded with Ru in step S10 is purged with low-pressure Ar gas, heated, reduced at a constant temperature under H2 purging, purged with Ar gas, purged with CH4 gas, deposited at a constant temperature, and then cooled to room temperature in an Ar atmosphere to obtain the graphene / Ru / TiO2 nanoribbon composite catalyst Z.

[0050] In step S11, the Ru-loaded TiO2 nanoporous tape substrate was purged for 5 min at 10 Pa and an Ar gas flow rate of 100 sccm to remove the air. Then, the temperature was increased to 600 °C at 5 °C / min, the H2 flow rate was 10 sccm, the isothermal reduction time was 20 min, and the Ar gas purge time was 8 min.

[0051] The CH4 flow rate was 2 sccm, the isothermal temperature was 600℃, the CH4 purging time (i.e., deposition time) was 15 min, and the graphene deposition thickness was 3 nm. The cooling rate in the Ar atmosphere after deposition was 3℃ / min.

[0052] S12. The catalyst Z from step S11 is heated under Ar gas, etched by injecting water vapor, and cooled by high-speed Ar gas purging to obtain a metal nanoporous catalyst.

[0053] The catalyst Z was heated at a rate of 3℃ / min under Ar gas to 450℃. The initial water vapor temperature was 100℃ and the water vapor content was 200 ppm. The etching time was 10 s and the Ar gas flow rate was 100 sccm during the heating.

[0054] When etching with water vapor, the injection must be completed within 1 second. After injection, Ar gas purging should be paused, and the water vapor should be kept in a sealed environment.

[0055] After etching, when purging and cooling with high-speed Ar gas, the Ar gas flow rate is increased to 300 mL / min, and purging is carried out at a rate of 5 °C / min until the temperature drops to room temperature. Example 2 All other conditions are the same as in Example 1. The difference from Example 1 is that... In step S11, the CH4 flow rate was 5 sccm, the isothermal temperature was 600℃, the deposition time was 15 min, and the graphene deposition thickness was 5 nm.

[0056] The etching process in step S12 takes 13 seconds.

[0057] Example 3 All other conditions are the same as in Example 1. The difference from Example 1 is that... In step S1, the monodisperse PS spheres are made of polystyrene with a particle size of 60 nm.

[0058] The titanium reagent in step S2 is titanium isopropoxide.

[0059] In step S11, the CH4 flow rate is 4 sccm, the constant temperature is 600℃, the CH4 purging time (i.e., the deposition time) is 20 min, and the graphene deposition thickness is 8 nm.

[0060] The etching process in step S12 takes 15 seconds.

[0061] Comparative Example 1 Compared with Example 2, the difference is that in step S11, the CH4 flow rate is 5 sccm, the isothermal temperature is 600℃, the deposition time is 45 min, and the graphene deposition thickness is 15 nm.

[0062] The etching process in step S12 takes 30 seconds.

[0063] Comparative Example 2 Compared to Example 1, the differences are that the CH4 flow rate was 2 sccm, the isothermal temperature was 600℃, the deposition time was 5 min, and the graphene deposition thickness was 1 nm. The cooling rate in the Ar atmosphere after deposition was 3℃ / min.

[0064] Comparative Example 3 Compared with Example 1, the difference is that no graphene layer is coated, that is, experimental steps S11 and S12 are not included.

[0065] Experiments were conducted on the catalysts from Examples 1-3 and Comparative Examples 1-3: Take 50 mg of each catalyst and place them in a light source at a wavelength of 450 ± 5 nm and a light intensity of 100 mW / cm². 2 The reaction was carried out at room temperature (25℃) with 10L of high-salt organic wastewater containing 7wt% NaCl and 400mg / L H2O2. The reaction was carried out for 120h, and the H2O2 removal rate and Ru dissolution rate were measured. The experimental results of different coating thicknesses on Ru Ru dissolution and H2O2 removal rate are shown in Table 1.

[0066] Table 1

[0067] After the reaction, the solution was filtered, and the liquid sample was centrifuged at 12000 r / min for 10 min. The supernatant was then filtered through a 0.22 μm aqueous filter membrane. Each experiment was repeated 3 times and the average value was taken. The Ru dissolution concentration in the filtrate was determined using ICP-MS (conventional parameters of inductively coupled plasma mass spectrometry: radio frequency power 1500 W, nebulizer gas flow rate 1.0 L / min, sampling depth 8 mm, Ru m / z=101).

[0068] Experimental results show that the Ru-TiO2 composite catalytic material bulk material possesses a dense graphene coating of approximately 3–8 nm and a tunable microporous structure of 50–60 nm. This catalytic material exhibits optimal performance, demonstrating high activity, low Ru dissolution, and long-term stable operation under complex water conditions.

Claims

1. A method for preparing a catalyst resistant to corrosion and Ru leaching, characterized in that, Includes the following steps: S1. Add ethanol to the monodisperse PS sphere template and disperse it ultrasonically to obtain a PS sphere alcohol-water dispersion K. S2. Under ice-water bath stirring, titanium reagent is added to ethanol and stirred to obtain solution A; S3. Mix the alcohol solvent, water, and concentrated nitric acid to obtain solution B; S4. Add solution B from step S3 to solution A from step S2, adjust the pH with concentrated nitric acid, and stir to obtain solution C of TiO2 precursor. S5. Add the dispersion K from step S1 to the solution C from step S4, and sonicate and stir to obtain the composite solution L of PS ball-TiO2 precursor; S6. The composite liquid L from step S5 is heated under a sealed environment, kept at a constant temperature, and slowly cooled to room temperature. It is then centrifuged, washed alternately with ethanol and water, and vacuum dried to obtain the powder M of the PS ball@TiO2 nanobelt composite precursor. S7. The powder M from step S6 is laid out in parallel, heated and calcined in an oxygen atmosphere, and cooled to room temperature to obtain TiO2 nanoporous belt substrate. S8. Add HCl to water and RuCl3 to adjust the pH, stir at room temperature to obtain solution N of RuCl3 precursor; S9. Soak the solution N from step S8 in the TiO2 nanoporous tape substrate from step S7 while sonicating. After standing and drying at low temperature and low pressure, a substrate Y with a TiO2-supported RuCl3 precursor was obtained; S10. The substrate Y from step S9 is purged under Ar gas and heated, and then purged at a constant temperature under an Ar-H2 mixed gas; it is then cooled to room temperature and sealed in an H2 / Ar mixed atmosphere to obtain a Ru-loaded TiO2 nanoporous tape substrate. S11. The TiO2 nanoporous tape substrate loaded with Ru in step S10 is purged with low-pressure Ar gas, heated, reduced at a constant temperature under H2 purging, purged with Ar gas, purged with CH4 gas, deposited at a constant temperature, and then cooled to room temperature in an Ar atmosphere to obtain the graphene / Ru / TiO2 nanoribbon composite catalyst Z. S12. The catalyst Z from step S11 is heated under Ar gas, etched by injecting water vapor, and cooled by high-speed Ar gas purging to obtain a metal nanoporous catalyst.

2. The method for preparing a corrosion-resistant and Ru-resistant catalyst according to claim 1, characterized in that, In step S1, the mass ratio of monodisperse PS spheres to ethanol is 5%~10%:

1.

3. The method for preparing a corrosion-resistant and Ru-resistant catalyst according to claim 1, characterized in that, The monodisperse PS sphere template material in step S1 is polystyrene with a particle size of 20~100nm, and is ultrasonicated for 30~40min.

4. The preparation method of the corrosion-resistant and Ru-resistant catalyst according to claim 1, characterized in that, The titanium reagent in step S2 is either tetrabutyl titanate or titanium isopropoxide.

5. The preparation method of the corrosion-resistant and Ru-resistant catalyst according to claim 1, characterized in that, In step S2, the ratio of titanium reagent to ethanol is 1:5~16 by volume.

6. The method for preparing a corrosion-resistant and Ru-leaching-resistant catalyst according to claim 1, characterized in that, In step S5, the volume ratio of dispersion K to solution C is 1:0.9~1.

2.

7. The method for preparing a corrosion-resistant and Ru-leaching-resistant catalyst according to claim 1, characterized in that, In step S6, the heating rate of the composite liquid L is 0.5~2℃ / min, the constant temperature is 170~200℃, and the constant temperature time is 12~24h.

8. The method for preparing a corrosion-resistant and Ru-resistant catalyst according to claim 1, characterized in that, In step S8, the water:RuCl3 ratio is 3~6:0.103~0.207 by mass.

9. The method for preparing a corrosion-resistant and Ru-resistant catalyst according to claim 1, characterized in that, In step S11, the CH4 flow rate is 2-5 sccm, the isothermal temperature is 500-700℃, the deposition time is 5-30 min, and the graphene deposition thickness is 3-8 nm; the cooling rate in the Ar atmosphere after deposition is 3-5℃ / min.

10. The method for preparing a corrosion-resistant and Ru-resistant catalyst according to claim 1, characterized in that, In step S12, the catalyst Z is heated at a rate of 3-5℃ / min under Ar gas, heated to 400-480℃, with an initial water vapor temperature of 98-100℃ and a water vapor content of 100-290 ppm. The etching time is 10-15s, and the Ar gas flow rate during heating is 50-100 sccm.

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