A Bi2O3 / V2C material, its preparation method and application

Abstract

This invention discloses a Bi₂O₃ / V₂C material, its preparation method, and its applications. The Bi₂O₃ / V₂C material is synthesized from Bi salt and V₂C through a hydrothermal reaction and calcination. The elemental molar ratio between Bi salt and V₂C is Bi:V = 14~300:1. By weight, the ratio between Bi salt and V₂C is m(V₂C):m(Bi salt) = 0.1%~2%:1. This invention uses the oxide corresponding to the Bi salt as the main catalyst and introduces V₂C as a co-catalyst. The resulting material exhibits improved catalytic performance, requires a lower V₂C dosage, and can catalytically degrade malachite green at a degradation rate of over 90%.

Description

Technical Field

[0001] This invention relates to a catalyst, and more particularly to a Bi2O3 / V2C material for targeting organic pollutants, as well as a method for preparing and applying this catalyst. Background Technology

[0002] Bismuth-based semiconductors, such as Bi2O3, are metal oxide semiconductors with unique electronic structures and low valence band positions. They are widely used as photocatalysts, for example, in photocatalytic nitrogen fixation, photocatalytic degradation of industrial dyes, and photocatalytic hydrogen production.

[0003] MXene refers to two-dimensional transition metal carbides, nitrides, or carbonitrides. These materials exhibit high conductivity and high carrier mobility, making them highly suitable as co-catalysts in photocatalysis (Bismuth oxide modified V2C MXene as a Schottky catalyst with enhanced photocatalytic oxidation for photo-denitration activities ENVIRONMENTAL TECHNOLOGY 2024, VOL. 45, NO. 9, 1748–1759), improving the separation efficiency of photogenerated carriers. Ti3C2, as the first MXene material, has been extensively studied as a co-catalyst in photocatalysis, for example, CN 111822028 A discloses a bismuth-based photocatalytic composite film based on MXene and its preparation method.

[0004] V2C MXene has a similar morphology to Ti3C2 MXene, but has a higher specific surface area and more active centers, making it a promising co-catalyst that can further enhance the catalytic performance of catalysts. However, there is limited research on V2C MXene as a co-catalyst for the photocatalytic degradation of organic pollutants, and in order to improve catalyst performance, a large amount of V2C is usually required. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a Bi2O3 / V2C material that reduces the amount of V2C used while improving catalytic performance; another purpose of this invention is to provide a method for preparing the material and its application.

[0006] Technical solution: The present invention provides a Bi₂O₃ / V₂C material, which is synthesized from Bi salt and V₂C as raw materials through hydrothermal reaction and calcination. The elemental molar ratio between Bi salt and V₂C raw materials is Bi:V = 14 ~ 300:1. By weight, the ratio between Bi salt and V₂C is m(V₂C): m(Bi salt) = 0.1%~2%:1.

[0007] Preferably, to maintain a catalytic degradation rate >90%, the Bi:V ratio is 25~72:1, and the weight ratio between Bi salt and V2C is m(V2C): m(Bi salt) = 0.35%~1%:1. More preferably, the Bi:V ratio is 33~72:1, and the weight ratio between Bi salt and V2C is m(V2C): m(Bi salt) = 0.35%~0.85%:1. Most preferably, the Bi:V ratio is 35~65:1, and the weight ratio between Bi salt and V2C is m(V2C): m(Bi salt) = 0.45%~0.75%:1.

[0008] Preferably, the bismuth salt is at least one of bismuth nitrate, bismuth sulfate, and bismuth chloride.

[0009] The aforementioned method for preparing Bi2O3 / V2C material includes the following steps: dissolving Bi salt in a mixed solution of acetic acid and water, adding V2C powder, adjusting the mixed solution to neutral with alkali, and carrying out a hydrothermal reaction at a temperature of 120~160℃ for 12~16 hours; after the hydrothermal reaction is completed, taking the solid and calcining it at 280~320℃ for 3~5 hours to obtain Bi2O3 / V2C material.

[0010] Preferably, the hydrothermal method is carried out at a temperature of 130~150℃ and a reaction time of 13~15 hours.

[0011] Preferably, the calcination temperature is 290~310℃ and the calcination duration is 3.5~4.5 hours.

[0012] Preferably, the volume ratio of acetic acid to water is 1:5.8 to 8. More preferably, the volume ratio of acetic acid to water is 1:6.2 to 7.2.

[0013] Preferably, the Bi salt concentration is 0.15~0.2 mol / L, and the alkali is sodium hydroxide and / or potassium hydroxide.

[0014] Preferably, the preparation method of V2C is as follows: prepare an etching solution containing HF using F salt and concentrated hydrochloric acid, add V2AlC to the etching solution, perform a hydrothermal reaction at 85~95℃ for 68~76 hours, take the solid, wash and dry it to obtain V2C.

[0015] Preferably, the F salt is LiF, NaF, or KF, the ratio of F salt to concentrated hydrochloric acid is 1g:18~22mL, and the ratio of V2AlC to etching solution is 1g:18~22mL.

[0016] The aforementioned Bi2O3 / V2C material is used in the catalytic degradation of organic dyes. The dye is at least one of malachite blue (MG), rhodamine B (RhB), methyl orange (MO), and methylene blue (MB).

[0017] Preferably, the medium for the catalytic degradation reaction is an aqueous solution with a pH of 7 to 10.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The present invention uses the oxide corresponding to Bi salt as the main catalyst and V2C as the co-catalyst, and the catalytic performance of the obtained material is significantly improved; 2. The amount of V2C used is only 2% or even less of the mass of Bi salt, which greatly reduces the amount of V2C used, simplifies the catalyst preparation, and reduces the cost of catalyst raw materials; 3. The use of F salt and concentrated hydrochloric acid to form HF in situ avoids the direct use of HF, making the preparation process safer; 4. When the amount of V2C introduced is 0.45%~0.75%, the degradation rate of MG can approach 90% in about 40 minutes, which improves the degradation rate. Attached Figure Description

[0019] Figure 1 Characterization diagrams of the microstructure and elemental distribution of different materials: a, SEM image of V2C, b, SEM image of Bi2O3, c, SEM image of BV-0.50% material, d, TEM image of V2C, e, TEM image of Bi2O3, f, TEM image of BV-0.50% material, g and h, elemental distribution diagrams;

[0020] Figure 2 Figures showing the results of MG degradation catalyzed by different materials;

[0021] Figure 3 The graph shows the results of BV-0.50% catalytic degradation of different dyes. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0023] Example 1: Synthesis and Effect Testing of Bi2O3 / V2C Materials

[0024] 1.1 Preparation of V2C MXene: 1.0 g NaF was gradually added to 20 mL of hydrochloric acid (36-38 wt%) and magnetically stirred in a beaker for 30 min to prepare an etching solution; 1.0 g V2AlC was slowly added under continuous magnetic stirring to obtain a mixture, which was then transferred to a hydrothermal reactor and reacted at 90 °C for 72 h.

[0025] After the reaction was complete, the solid was taken and washed repeatedly with deionized water until the pH of the washing solution was approximately 7. The solid was then dried at 60 °C for 12 h to obtain V2C MXene.

[0026] 1.2 Bi₂O₃ / V₂C The method reported in *Bismuth oxide modified V₂C MXene as a Schottky catalyst with enhanced photocatalytic oxidation for photo-denitration activities*, *ENVIRONMENTAL TECHNOLOGY 2024, VOL. 45, NO. 9, 1748–1759*, was followed by the following steps:

[0027] (1) Add 2.0 g of bismuth nitrate pentahydrate (theoretical molecular weight 485.07) to 20 mL of deionized water containing 3 mL of acetic acid, add a certain amount of V2C powder and stir until homogeneous.

[0028] (2) Add NaOH solid to the mixture in step (1) to adjust the pH value to neutral, stir for 1 h, and then transfer it to a hydrothermal reactor to react at 140 °C for 14 h.

[0029] (3) Take the solid, dry the solid product and transfer it to a tube furnace (no gas protection required) and calcine at 300 °C for 4 h to obtain Bi2O3 / V2C material.

[0030] By changing the amount of V2C added in step (1) to 0, 5 mg, 10 mg, 15 mg, and 40 mg, different samples were prepared. Based on the weight percentage of V2C relative to bismuth nitrate pentahydrate, the samples were labeled according to the format BV-X, and the obtained samples were recorded as Bi2O3, BV-0.25%, BV-0.50%, BV-0.75%, and BV-2%, respectively. The theoretical molecular weight of V2C is 137.88. Excluding the influence of water of crystallization, the elemental molar ratios Bi / V of the samples in BV-0.25%, BV-0.50%, BV-0.75%, and BV-2% were 113.7, 56.8, 37.9, and 14.2, respectively.

[0031] The microstructures of V2C, Bi2O3, and BV-0.50% are as follows: Figure 1 As shown in sections a to f, V₂C has a layered structure, Bi₂O₃ has a plate-like structure, and BV-0.50% is predominantly plate-like, indicating that a small amount of V₂C is introduced into Bi₂O₃. The elemental distribution of BV-0.50% is as follows: Figure 1 As shown in the g to h section, Bi, O, V, and C are evenly distributed.

[0032] The degradation performance of 50 mg V2C, Bi2O3, BV-0.25%, BV-0.50%, and BV-0.75% on 100 mL of 10 ppm MG was determined, and the results are as follows: Figure 2 As shown, the dark reaction stage is from -20 to 0 min. After 100 minutes of introducing a 150W xenon lamp light source, the degradation rates of each material are 67.82%, 56.57%, 77.48%, 90.81%, and 93.15%, respectively, showing a trend of Bi2O3 < V2C < BV-0.25% < BV-0.75% < BV-0.50%. The photocatalytic degradation rate of BV-0.50% is higher than that of BV-0.25% and BV-0.75%, indicating that the introduction of an appropriate amount of V2C can effectively improve the photocatalytic ability of Bi2O3. Under the same conditions, the catalytic degradation performance of BV-2% was tested. In the dark reaction stage from -20 to 0 min, the adsorption effect of BV-2% was greater than that of BV-0.75%. In the light reaction stage, as time increased, especially after 40 min, the MG concentration did not continue to decrease but instead rebounded. After 100 min, the degradation rate of MG by BV-2% was lower than that of BV-0.75%, indicating that excessive introduction of V2C was not conducive to improving the catalytic performance of the material.

[0033] The experimental data were fitted, and the fitted curves conformed to the pseudo-first-order kinetic equation. The reaction rate constants for V₂C, Bi₂O₃, BV⁻⁰.25%, BV⁻⁰.50%, and BV⁻⁰.75% were 0.00928 min⁻¹. -1 0.00556 min -1 0.00537 min -1 0.01367 min -1 0.01136 min -1 The rate constants of BV-0.50% are 1.473 times and 2.459 times that of pure V2C and Bi2O3, respectively, which are consistent with the degradation rate.

[0034] The effects of catalyst content, pollutant concentration, and pH value on photocatalytic degradation performance.

[0035] 30, 40, and 50 mg of BV-0.50% were added to 100 mL of 10 ppm MG, respectively, and the degradation rate was measured within 100 min. The degradation rates were 70.81%, 84.08%, and 93.15%, respectively, indicating that the photocatalytic degradation efficiency is positively correlated with the amount of catalyst used.

[0036] 50 mg of BV-0.50% was added to MG solutions at concentrations of 5 ppm, 10 ppm, 15 ppm, and 20 ppm, respectively, and the degradation rate was measured within 100 min. The degradation rates were 100.00%, 93.15%, 78.87%, and 63.11%, respectively. The photocatalytic degradation rate of MG by BV-0.50% gradually decreased with increasing initial MG concentration. This is mainly because at excessively high concentrations, the active sites of the catalyst are covered by MG, reducing the photocatalytic degradation efficiency.

[0037] The degradation effect of 50 mg BV-0.50% on 100 mL of 10 ppm MG was tested under acidic (pH=3, 5), neutral (pH=7), and alkaline (pH=9) conditions. The degradation efficiencies at pH=7 and pH=9 were 93.15% and 92.33%, respectively, while the degradation rates at pH=3 and pH=5 were 20.39% and 26.01%, respectively. The degradation efficiency decreased, possibly because under acidic conditions, the positively charged surface of BV-0.50% would repel the cationic malachite green, thus hindering the photocatalytic degradation of malachite green by BV-0.50%.

[0038] Effect of light source: Using sunlight as the light source, the degradation rates of 50 mg BV-0.50% and Bi2O3 on 100 mL of 10 ppm MG were tested. After 100 min, the degradation rates were 91.67% and 34.80%, respectively. Using sunlight as the light source, the degradation efficiency of BV-0.50% was close to that of a xenon lamp (93.15%). Without sunlight, the adsorption rate of BV-0.50% on MG was 74.40%.

[0039] Cyclic Performance Test: Under xenon lamp irradiation, the recycling performance of the recovered BV-0.50% was tested. The test method was to wash the recovered BV-0.50% with deionized water and then re-add it to 100 mL of 10 ppm MG to test the photocatalytic degradation rate. After the second, third, fourth, and fifth cycles, the photocatalytic degradation rates were 93.03%, 84.62%, 80.32%, and 79.13%, respectively. After five cycles, BV-0.50% still exhibited good photocatalytic performance.

[0040] Anti-interference test: Cl was added to 100 mL of 10 ppm MG solution. - SO4 2- NO3 - Afterwards, the photocatalytic degradation rate of MG by BV-0.50% decreased, but the decrease was small, indicating that inorganic ions had little effect on the photocatalytic degradation rate of MG.

[0041] Application scope test: The degradation efficiency of 50 mg BV-0.50% on 100 mL of 10 ppm MO, RhB, and MB was measured. Test results are as follows. Figure 3 As shown, BV-0.50% also showed a certain degradation effect on MO, RhB and MB, with degradation rates of 23.03%, 51.00% and 82.76% respectively, but still lower than the degradation rate on MG, indicating that BV-0.50% has better degradation performance on MG.

[0042] Photocatalytic degradation test of MG in actual water samples: 90 mL of tap water and 90 mL of Slender West Lake water sample were taken respectively, and 10 mL of 100 ppm MG solution was added to prepare 100 mL test samples. 50 mg of BV-0.50% was added to each test sample, and photocatalytic degradation was tested. After 100 minutes, the degradation rates of MG were 47.65% and 55.83% respectively, lower than those of the MG sample prepared using deionized water as the dispersion medium. This may be due to the presence of inorganic ions and other interfering substances in the actual water samples, which compete for active free radicals and block reaction sites, thus reducing the degradation rate.

Claims

1. A Bi2O3 / V2C material, characterized in that, The Bi2O3 / V2C material is synthesized from Bi salt and V2C as raw materials through hydrothermal reaction and calcination. The elemental molar ratio between Bi salt and V2C raw materials is Bi:V = 14 ~ 300:

1.

2. The Bi2O3 / V2C material according to claim 1, characterized in that, The molar ratio of elements Bi:V is 25~72:

1.

3. The preparation method according to claim 1, characterized in that, The Bi salt is at least one of bismuth nitrate, bismuth sulfate, and bismuth chloride.

4. The method for preparing the Bi2O3 / V2C material according to any one of claims 1 to 3, characterized in that, The process includes the following steps: dissolving Bi salt in a mixed solution of acetic acid and water, adding V2C powder, adjusting the mixed solution to neutral with alkali, and carrying out a hydrothermal reaction at a temperature of 120~160℃ for 12~16 hours; after the hydrothermal reaction is completed, taking the solid and calcining it at 280~320℃ for 3~5 hours to obtain Bi2O3 / V2C material.

5. The preparation method according to claim 4, characterized in that, The hydrothermal method involves a temperature of 130-150℃, a reaction time of 13-15 hours, a calcination temperature of 290-310℃, and a calcination duration of 3.5-4.5 hours.

6. The preparation method according to claim 4, characterized in that, The volume ratio of acetic acid to water is 1:5.8~8, and the concentration of Bi salt is 0.15~0.2 mol / L.

7. The preparation method according to claim 4, characterized in that, The preparation method of V2C is as follows: prepare an etching solution containing HF using F salt and concentrated hydrochloric acid, add V2AlC to the etching solution, and perform a hydrothermal reaction at 85~95℃ for 68~76 hours. Take the solid, wash and dry it to obtain V2C.

8. The preparation method according to claim 7, characterized in that, The F salt is LiF, NaF, or KF, and the ratio of F salt to concentrated hydrochloric acid is 1g:18~22mL, and the ratio of V2AlC to etching solution is 1g:18~22mL.

9. The application of the Bi2O3 / V2C material according to any one of claims 1 to 3 in the catalytic degradation of organic dyes.

10. The application according to claim 9, characterized in that, The medium for the catalytic degradation reaction is an aqueous solution with a pH of 7 to 10.

Images