A cobalt single-atom catalyst supported on Mo2TiC2Tx and its preparation method and application

Abstract

The present invention proposes a cobalt single-atom catalyst loaded on Mo2TiC2Tx and its preparation method and application, which belongs to the field of catalyst technology. The method comprises the following steps: adding Mo2TiAlC2 powder to HF solution, stirring for reaction; washing and collecting the supernatant, washing with ethanol, washing with aerated deionized water, centrifuging, freeze-drying, and obtaining a black powder for use; taking the above black powder and adding it to tetrabutylammonium hydroxide solution, stirring at room temperature, washing the obtained suspension with aerated deionized water, adding deionized water for use; taking the above suspension in a beaker, adding Co(NO3)2·6H2O, stirring at room temperature until completely mixed, adding NaBH4 solution, stirring at room temperature, washing with aerated deionized water for several times, and freeze-drying to obtain a black powder. The catalyst of the present invention improves the catalytic activity and can increase the pollutant removal rate to 100% within 10 minutes, which is of great significance for actual sewage treatment.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a cobalt single-atom catalyst supported on Mo2TiC2Tx and a preparation method and application thereof. Background Art

[0002] Persulfate (PMS) catalytic oxidation is an attractive route for the removal of trace pollutants, and an efficient catalyst is required to activate this reaction. Single-atom catalysts are considered to be one of the most promising catalysts because they react kinetically very fast and have efficient ORR catalytic activity, which is beneficial to improving the energy conversion efficiency of electrochemical oxygen reduction reaction.

[0003] Through literature search of the prior art, it was found that the synthesis conditions of previous Co-based catalysts were harsh and the reaction activity was mediocre, while single-atom catalysts have high catalytic activity, low atom loading rate and high utilization rate, making them an ideal catalyst for treating aqueous pollutants.

[0004] 2D MXene has excellent conductivity, hydrophilic surface function and graphene-like laminar structure. Its rich alkaline components, excellent structure and electronic properties have attracted wide attention in environmental remediation and have been applied to lithium-ion batteries, supercapacitors, water purification, photothermal conversion and catalysis such as electrocatalysis, photocatalysis, and thermal catalysis. It is also an ideal carrier for the production of metal single atom catalysts (SACs). Summary of the invention

[0005] The purpose of the present invention is to provide a cobalt single-atom catalyst supported on Mo2TiC2Tx and a preparation method and application thereof, which have good anti-aging effects.

[0006] The technical solution of the present invention is achieved in this way:

[0007] The present invention provides a kind of material loaded on Mo2TiC2T x Cobalt single atom catalyst on Mo2TiC2T x superior.

[0008] The present invention further protects a kind of above-mentioned load on Mo2TiC2T x The method for preparing a cobalt single-atom catalyst comprises the following steps:

[0009] Step 1: Add Mo2TiAlC2 powder into HF solution and stir to react;

[0010] Step 2: rinse and collect the supernatant, wash with ethanol, wash with aerated deionized water, centrifuge, freeze-dry, and obtain a black powder for later use;

[0011] Step 3: Take the above black powder and add it to tetrabutylammonium hydroxide solution, stir it at room temperature, wash the obtained suspension with aerated deionized water, and add deionized water for later use;

[0012] Step 4: Take the above suspension in a beaker, add Co(NO3)2·6H2O, stir at room temperature until completely mixed, then add NaBH4 solution, stir at room temperature, wash several times with aerated deionized water and freeze-dry to obtain a black powder.

[0013] As a further improvement of the present invention, the stirring reaction in step 1 is carried out at a temperature of 50-60° C. and for a time of 45-55 h.

[0014] As a further improvement of the present invention, the step 2 is to wash with ethanol until the pH value is 6-7.

[0015] As a further improvement of the present invention, the stirring at room temperature in step 3 is 45-55 hours.

[0016] As a further improvement of the present invention, the step three is washing to a pH of 6-7.

[0017] As a further improvement of the present invention, the stirring at room temperature in step 4 is 1-3h.

[0018] As a further improvement of the present invention, the freeze-drying temperature is -45 to -50°C.

[0019] The present invention further protects a kind of above-mentioned load on Mo2TiC2T x Application of cobalt single atom catalysts in the degradation of pollutants.

[0020] The present invention has the following beneficial effects:

[0021] First: The present invention adopts a load on Mo2TiC2T x Cobalt single-atom catalyst on Mo2TiC2T x Its own excellent properties and Co to Mo2TiC2T x The change of active sites improves the catalytic activity of the catalyst;

[0022] Second: The Co single-atom catalyst prepared by the present invention has low metal content, simple preparation process, good stability and recyclability, and the Co in it is distributed in the form of single atoms in Mo2TiC2T x On the support material, the Co atomic content is only 1.2wt%, but it has excellent catalytic performance;

[0023] Third: The present invention adopts a normal temperature and pressure reaction system: the catalyst is mixed with the substrate and the solvent, and the reaction can occur under normal temperature and pressure conditions. The pollutant removal rate can be increased to 100% within 10 minutes, which is of great significance for actual sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 Mo2TiC2T prepared in Example 1 of the present invention x TEM image at 300nm size;

[0026] Figure 2 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x Cobalt single atom catalyst (Co-SA / Mo2TiC2T x )TEM image at 1 μm size;

[0027] Figure 3 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x Cobalt single atom catalyst (Co-SA / Mo2TiC2T x ) HAADF image at 5nm size;

[0028] Figure 4 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x Cobalt single atom catalyst (Co-SA / Mo2TiC2T x )'s Co element distribution mapping;

[0029] Figure 5 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x Cobalt single atom catalyst (Co-SA / Mo2TiC2T x )'s O element distribution mapping diagram;

[0030] Figure 6 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x Cobalt single atom catalyst (Co-SA / Mo2TiC2T x )'s Mo element distribution mapping;

[0031] Figure 7 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x Cobalt single atom catalyst (Co-SA / Mo2TiC2T x )’s Ti element distribution mapping;

[0032] Figure 8 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x Cobalt single atom catalyst (Co-SA / Mo2TiC2T x )’s XRD pattern;

[0033] Fig. 9 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x Cobalt single atom catalyst (Co-SA / Mo2TiC2T x )’s EXAFS spectrum;

[0034] Fig.10 This is the degradation diagram of the pollutant CIP after the reaction of Example 3 of the present invention;

[0035] Fig.11 This is a degradation diagram of the organic phase after the reaction of Example 3 of the present invention;

[0036] Fig.12 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x Cobalt single atom catalyst (Co-SA / Mo2TiC2T x )’s EPR diagram.

[0037] Fig.13 The Mo2TiC2T prepared in Example 2 of the present invention is loaded x The synthetic load is adjusted on Mo2TiC2T x Cobalt cluster catalyst (Co-NC / Mo2TiC2T x )’s EPR diagram. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example 1: Catalyst carrier Mo2TiC2T x Preparation

[0040] Step 1: Add 1 g of Mo2TiAlC2 powder weighed into a high-density plastic beaker containing 100 mL of HF solution (45%), and stir at 55°C for 48 h. Prepare 1 L of deionized water and ethanol aerated with N2 for later use.

[0041] Step 2: Rinse and collect the supernatant. The specific requirements are: the speed is 3500r / min, 5min, cycle twice, and wash with ethanol until the pH is 6-7. Wash with N2-aerated deionized water 2-3 times, centrifuge at 3500r / min, and freeze-dry at -49°C to obtain Mo2TiC2T x .

[0042] Example 2: Catalyst Co-SA / Mo2TiC2T x Preparation

[0043] Step 1: Take 0.5 g Mo2TiC2T obtained in Example 1 x Add 10 mL of TBAOH solution (40 wt%) and stir at room temperature for 24 h. The resulting suspension is washed with deionized water aerated with N2 to a pH of 6-7. The specific requirements are a rotation speed of 3500 r / min for 5 min, and then add 40 mL of deionized water for standby use.

[0044] Step 2: Take 20 mL of the above suspension in a beaker, add a certain amount of Co(NO3)2·6H2O solution (10 mg / mL), stir at room temperature until completely mixed, then add 20 mL of NaBH4 solution (0.1 M), stir at room temperature for 2 h, wash several times with N2-aerated deionized water, and freeze-dry at -49 ° C to obtain Co-SA / Mo2TiC2T x .

[0045] Depend on Figure 1-3 It can be seen that Mo2TiC2T x Accordion-shaped, Co-SA / Mo2TiC2T x It is in the form of thin flakes with a large surface area, which provides a basis for excellent catalytic activity and is conducive to the attachment of cobalt in the form of single atoms, thereby ensuring catalytic activity while reducing the loading amount and improving the dispersion of metallic cobalt.

[0046] Depend on Figure 4-7 It can be seen that the Co element is uniformly doped in the catalyst.

[0047] Depend on Figure 8 It can be seen that no diffraction peak of metal Co was found, indicating that the Co element is present in the carrier Mo2TiC2T x The good dispersion further confirms the single-atom structure.

[0048] Depend on Fig. 9It can be seen that the sample did not detect a Co particle signal with sufficient intensity, and the sample only showed a single peak signal similar to Co-O, indicating that the sample was a single-atom structure.

[0049] Example 3: Co-SA / Mo2TiC2T x Activate PMS to degrade pollutants CIP

[0050] In order to ensure the temperature conditions of the reaction, all reactions were carried out in a 100 mL round-bottom flask at room temperature. x The catalyst was added to a round-bottom flask containing 20 mL CIP (20 mg / L), and 1 mM PMS was added to the system, and stirring was started at the same time. 0.2 mL of the sample was taken at 1 min, 3 min, 5 min, 7 min, 10 min, 15 min, and 20 min, and after passing through a 0.22 μm filter membrane, it was added to a previously prepared volumetric tube containing 0.2 mL of methanol. The obtained organic phase was measured by liquid chromatography-mass spectrometry (HPLC).

[0051] Depend on Fig.10 It can be seen that the Co-SA / Mo2TiC2T with loading rates of 1%, 5%, 20%, and 35% x The efficiency of CIP degradation after activated PMS, where the loading rate is 1% Co-SA / Mo2TiC2T x The degradation efficiency of CIP is the highest. Its degradation rate constant k obs The value is 0.105min -1 , which is 1.44-35 times that of other Co-based catalysts in Table 1.

[0052] Depend on Fig.11 It can be seen that the CIP molecule is degraded into seven smaller intermediates mainly through (i) defluorination and (ii) cleavage of the piperazine ring, with m / z values ​​of 305.12 (F1), 242.09 (F2), 287.10 (F3), 217.05 (F4), 344.10 (F5), 302.10 (F6) and 256.30 (F7), respectively. The intermediate F7 eventually generates ethylenediamine.

[0053] Depend on Fig.13 It can be seen that Co-SA / Mo2TiC2T x The reactive species (ROS) that activate PMS to degrade pollutants are singlet oxygen (O2 ·— ), while Co-NC / Mo2TiC2T x The ROS that activates PMS to degrade pollutants are hydroxyl radicals ( · OH) and sulfate radicals (SO4 ·— ).

[0054] Example 4: Repeat the experiment

[0055] The process of Example 3 was repeated three times, and the degradation rates of CIP (2-chloro-1,3-dimethylimidazolium hexafluorophosphate) in the organic phase were determined by HPLC to be 80.1%, 53.8%, 26.4%, 13.9%, 0%, 0%, and 0% at 1 min, 3 min, 5 min, 7 min, 10 min, 15 min, and 20 min, respectively.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A load on Mo2TiC2T x A cobalt single-atom catalyst on a substrate, characterized in that Cobalt is supported in the form of single atoms on Mo2TiC2T x superior; The preparation method of the catalyst comprises the following steps: Step 1: Add Mo2TiAlC2 powder into HF solution and stir to react; Step 2: rinse and collect the supernatant, wash with ethanol, wash with aerated deionized water, centrifuge, freeze-dry, and obtain a black powder for later use; Step 3: Take the above black powder and add it to tetrabutylammonium hydroxide solution, stir at room temperature, wash the obtained suspension with aerated deionized water, and add deionized water for later use; Step 4: Take the above suspension in a beaker, add Co(NO3)2·6H2O, stir at room temperature until completely mixed, then add NaBH4 solution, stir at room temperature, wash several times with aerated deionized water and freeze-dry to obtain a black powder.

2. According to claim 1, the load on Mo2TiC2T x A cobalt single-atom catalyst on a substrate, characterized in that The stirring reaction in step 1 is carried out at a temperature of 50-60° C. and for a time of 45-55 h.

3. According to claim 1, the material loaded on Mo2TiC2T x A cobalt single-atom catalyst on a substrate, characterized in that Wash with ethanol to pH = 6-7 as described in step 2.

4. According to claim 1, the material loaded on Mo2TiC2T x A cobalt single-atom catalyst on a substrate, characterized in that Stir at room temperature for 45-55h as described in step 3.

5. According to claim 1, the material loaded on Mo2TiC2T x A cobalt single-atom catalyst on a substrate, characterized in that Wash as described in step 3 to pH = 6-7.

6. According to claim 1, the material loaded on Mo2TiC2T x A cobalt single-atom catalyst on a substrate, characterized in that Stir at room temperature for 1-3 h as described in step 4.

7. According to claim 1, the material loaded on Mo2TiC2T x A cobalt single-atom catalyst on a substrate, characterized in that The freeze-drying temperature is -45 to -50°C.

8. A method as claimed in any one of claims 1 to 7 loaded on Mo2TiC2T x Application of cobalt single atom catalysts in the degradation of pollutants.

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