阅读说明：本技术 一种负载型高分散金属单原子催化剂的光还原合成方法 (Photoreduction synthesis method of supported high-dispersion metal monatomic catalyst ) 是由 李越湘 纪孟菲 孟鲁慧 何榕昌 彭绍琴 于 2021-07-02 设计创作，主要内容包括：本发明公开了一种负载型高分散金属单原子催化剂的光还原合成方法,该方法采用过量的高浓度金属盐溶液为反应物,使用高光强照射,在短时间内、在光催化剂作用下将金属离子还原为原子高分散负载在光催化剂表面。本发明提供一种简单、快速的光还原负载高分散金属单原子催化剂的方法,克服了传统单原子催化剂制备方法能耗高,制备周期长的弊端。(The invention discloses a photoreduction synthesis method of a supported high-dispersion metal monatomic catalyst, which adopts excessive high-concentration metal salt solution as a reactant, uses high-light intensity irradiation to reduce metal ions into atoms which are loaded on the surface of the photocatalyst in a high-dispersion manner under the action of the photocatalyst in a short time. The invention provides a simple and rapid method for preparing a high-dispersion metal monatomic catalyst by photoreduction, which overcomes the defects of high energy consumption and long preparation period of the traditional monatomic catalyst preparation method.)

1. A photoreduction synthesis method of a supported high-dispersion metal monatomic catalyst is characterized in that: according to the method, excessive high-concentration metal salt solution is used as a reactant, high-light-intensity irradiation is used, and metal ions are reduced into atoms which are loaded on the surface of a photocatalyst in a high-dispersion manner under the action of the photocatalyst in a short time.

2. The photoreduction synthesis method of the supported high-dispersion metal monatomic catalyst according to claim 1, characterized in that: the metal salt is a transition metal salt, and comprises one or more of Pt salt and Au salt.

3. The photoreduction synthesis method of the supported high-dispersion metal monatomic catalyst according to claim 1 or 2, characterized in that: the excessive high-concentration metal salt solution means that the amount of the metal salt is greatly higher than the amount required by the actual loading amount, so that the metal ions approach or reach a saturated adsorption state on the photocatalyst.

4. The photoreduction synthesis method of the supported high-dispersion metal monatomic catalyst according to claim 1, characterized in that: the high light intensity is not less than 100mW cm^-2。

5. The photoreduction synthesis method of the supported high-dispersion metal monatomic catalyst according to claim 1, characterized in that: the short time means the irradiation time is not more than 30 s.

Technical Field

The invention belongs to the technical field of catalyst preparation, and particularly relates to a photoreduction synthesis method of a supported high-dispersion metal monatomic catalyst.

Background

Semiconductor material (e.g. TiO)₂、PCN、ZnIn₂S₄Etc.) are widely used in the field of catalysis as catalysts or carriers. For example, TiO₂、PCN、ZnIn₂S₄Can be used for photocatalytic hydrogen production, pollutant degradation and CO degradation₂Reduction, nitrogen fixation reaction and the like, and has very good application prospect due to mild reaction conditions and no secondary pollution. In order to improve the reaction efficiency of the photocatalyst, it is generally necessary to support a small amount of transition metal as a promoter in order to promote charge separation and interfacial catalyst reaction.

The traditional supported metal catalyst has poor metal dispersibility and larger particles, and only a small amount of surface active components have catalytic action. Generally, metal ions are reduced to elemental metals by a photo-reduction method or by an impregnation-hydrogen reduction method, resulting in larger metal nanoparticles. The utilization of the metal catalyst component is still low. Loading highly dispersed monoatomic metals can fundamentally solve this problem.

The preparation methods of the prior monatomic catalysts mainly include a coprecipitation method (a metal salt and a water solution of a substrate substance are mixed under a proper condition and then the acid-base of the solution is adjusted to generate coprecipitation, a precipitate is filtered, washed and roasted), an impregnation method (a carrier substance is added into a solution containing an active component, and after the active component is adsorbed to the surface of a carrier, drying, roasting and activation are carried out), a solid-phase fusion method (the carrier substance and a metal load are ball-milled under a specific atmosphere, then high-temperature calcination is carried out under a proper atmosphere, and drying is carried out after acid washing or alkali washing), an atomic layer deposition method (metal is plated on the surface of the carrier layer by layer through physical evaporation), a reverse Ostwald curing method (nano particles loaded on a special carrier are automatically dispersed into monatomic after programmed temperature rise), and the like, although the performance of the prepared monatomic catalysts is excellent, however, these methods are generally high in energy consumption and long in preparation period. Researchers are constantly working on improving the reaction conditions to achieve the purposes of reducing energy consumption and improving efficiency. Particularly, a universal method is found under mild environmental conditions to prepare the monatomic catalyst with good performance.

Disclosure of Invention

Aiming at the defects and problems in the prior art, the invention aims to provide a photoreduction synthesis method of a supported high-dispersion metal monatomic catalyst.

The invention is realized by the following technical scheme:

a photoreduction synthesis method for the supported high-dispersity metal monatomic catalyst features that the solution of high-concentration metal salt is used as reactant, and the high-light-intensity radiation is used to reduce the metal ions to atoms which are loaded on the surface of photocatalyst in high-dispersity mode in short time under the action of photocatalyst.

Further, the metal salt is a transition metal salt, which comprises one or more of Pt salt and Au salt.

Further, an excess of a high concentration metal salt solution means that the amount of the metal salt is much higher than the amount required for the actual loading amount, so that the metal ions approach or reach a saturated adsorption state on the photocatalyst.

Further, high light intensity means light intensity of not less than 100mW cm^-2。

Further, the short time means that the irradiation time is not more than 30 s.

After the illumination is finished, the supported high-dispersion metal monatomic catalyst is filtered out from the solution, and the solution containing the metal salt obtained by solid-liquid separation can be recycled after the corresponding metal salt is supplemented.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention provides a simple and rapid method for preparing a high-dispersion metal monatomic catalyst by photoreduction, which overcomes the defects of high energy consumption and long preparation period of the traditional monatomic catalyst preparation method.

Drawings

FIG. 1 is a high-power transmission electron micrograph of the Pt/U-PCN-480 monatomic catalyst obtained in example 1.

Detailed Description

The invention will be further described with reference to the accompanying drawings.

The preparation method of the monatomic catalyst comprises the following steps: (1) dispersing a semiconductor photocatalyst in an excessive metal salt solution, wherein the reaction system is N₂Or Ar atmosphere; (2) high light intensity (greater than 100mW cm)^-2) Irradiating the load metal for a short time (not more than 30 s); (3) the metal monatomic catalyst is separated from the reaction solution.

EXAMPLE 1 monatomic catalyst Pt/U-PCN-480

The preparation method of the monatomic catalyst Pt/U-PCN-480 comprises the following steps:

(1) preparation of an oligomerization grade pore U-PCN-480 photocatalyst: adding 10g of needle-like urea into a 100mL alumina crucible with a cover, placing the mixture in a muffle furnace, and preserving the heat for 2h at 480 ℃ (the heating rate is 10 ℃ for min^-1) And naturally cooling to room temperature, taking out the sample, and grinding into powder.

(2) Preparation of U-PCN-480-RF: 1.0g U-PCN-T and 200mL of 1.0mol L^-1Continuously stirring the mixture of the formic acid for 12 hours to achieve adsorption equilibrium, wherein the formic acid is inserted into a U-PCN-T phase in the process, and meanwhile, a small amount of impurity molecules such as melem and the like in the U-PCN-T are dissolved by the formic acid solution; then filtered, the product was washed 3 times with distilled water and dried at 170 ℃ for 10 h.

(3) Preparation of a monatomic catalyst Pt/U-PCN-480: 0.065gU-PCN-480-RF and 96.6mL of 1mo 1L were added to a Pyrex reaction flask with a flat light window^-1The solution was ultrasonically dispersed for 5min, and 3.4mL of 1.93X 10 solution was added^-3mol L^-1The chloroplatinic acid solution is placed on a magnetic stirrer, high-purity nitrogen is introduced, and bubbling is carried out for 20min to remove air in the system (the above operation process needs to be carried out in a dark state); then placing the reaction bottle between two xenon lamps, and simultaneously illuminating with light intensity of 370mW cm^-2(the light intensity of each lamp is 180-190mW cm^-2The same as the above), and irradiating for 5s, wherein the catalyst is always kept in a suspension state through magnetic stirring in the process; and then immediately carrying out suction filtration in a dark state environment, washing with water for 3 times, washing with ethanol for 3 times, and then drying in a vacuum drying oven at 60 ℃ for 5 hours.

After the illumination in the step (3) is finished, the solution containing the metal salt obtained by solid-liquid separation can be illuminated according to the step (3) again to prepare the monatomic catalyst Pt/U-PCN-480-1, and after the corresponding metal salt (500 mu L) is supplemented, the illumination is performed according to the step (3) again to obtain the Pt/U-PCN-480-2.

ICP test is carried out on the prepared Pt/U-PCN-480 monatomic catalyst, and the result shows that the Pt loading amounts of Pt/U-PCN-480-1 and Pt/U-PCN-480-2 are 0.16 wt%, 0.17 wt% and 0.14 wt%, respectively.

FIG. 1 is a transmission electron micrograph of the Pt/U-PCN-480 monatomic catalyst obtained in this example, illustrating that Pt is uniformly and highly dispersed.

Comparative example: a Nano-catalyst Pt/U-PCN-480 is prepared as a contrast, under the same conditions as other reaction conditions of example 1, a chloroplatinic acid solution with the loading of 2.0 wt% is reduced by light reduction for 1h, the loaded metal is (with the size of 2.3-6.4nm) Nano-particles, and a sample is marked as Nano-Pt/U-PCN-480. ICP test shows that the Pt loading amount of Nano-Pt/U-PCN-480 is 1.52 wt%

The Pt/U-PCN-480-1 monatomic catalyst and the Nano-Pt/U-PCN-480100mg prepared in the examples and 100mL of 1mol L are taken respectively^-1Adding the formic acid solution into a Pyrex reaction bottle with a plane light window, performing ultrasonic treatment for 5min to disperse uniformly, introducing high-purity nitrogen for 20min to remove system air, and performing xenon lamp (full spectrum, 100mW cm)^-2) The hydrogen production amounts of Pt/U-PCN-480, Pt/U-PCN-480-1, Pt/U-PCN-480-2 and Nano-Pt/U-PCN-480 are 369.0 mu mol h respectively under the condition of 1h illumination^-1，366.6μmol h^-1，369.4μmol h^-1And 379.0. mu. mol h^-1。

EXAMPLE 2 monatomic catalyst Pt/U-PCN-480

(1) U-PCN-480 was prepared as in example 1.

(2) U-PCN-480-RF was prepared as in example 1.

(3) Preparation of a monatomic catalyst Pt/U-PCN-480: 0.065gU-PCN-480-RF and 98.3mL of 1mol L were added to a Pyrex reaction flask with a flat light window^-1The solution was ultrasonically dispersed for 5min, and 1.7mL of 1.93X 10 solution was added^-3mol L^-1The chloroplatinic acid solution is placed on a magnetic stirrer, high-purity nitrogen is introduced, and bubbling is carried out for 20min to remove air in the system (the above operation process needs to be carried out in a dark state); then the reaction flask is placed in twoThe middle of a xenon lamp is illuminated at the same time, and the light intensity is 370mW cm^-2Irradiating for 5s, and enabling the catalyst to be always kept in a suspension state through magnetic stirring in the process; and then immediately carrying out suction filtration in a dark state environment, washing with water for 3 times, washing with ethanol for 3 times, and then drying in a vacuum drying oven at 60 ℃ for 5 hours.

The prepared Pt/U-PCN-480 monatomic catalyst is subjected to ICP test, and the result shows that the Pt loading amount is 0.10 wt%.

Hydrogen production Performance test conditions As in example 1, the Pt/U-PCN-480 monatomic catalyst prepared in this example had a hydrogen production of 265.2. mu. mol h^-1。

EXAMPLE 3 monoatomic catalyst Pt/U-PCN-480

(1) U-PCN-480 was prepared as in example 1.

(2) U-PCN-480-RF was prepared as in example 1.

(3) Preparation of a monatomic catalyst Pt/U-PCN-480: 0.065gU-PCN-480-RF and 94.9mL of 1mol L were placed in a Pyrex reaction flask with a flat light window^-1The methanol solution is added with 5.1mL of 1.93X 10 after being evenly dispersed by ultrasonic for 5min^-3mol L^-1The chloroplatinic acid solution is placed on a magnetic stirrer, high-purity nitrogen is introduced, and bubbling is carried out for 20min to remove air in the system (the above operation process needs to be carried out in a dark state); then placing the reaction bottle between two xenon lamps, and simultaneously illuminating with light intensity of 370mW cm^-2Irradiating for 5s, and enabling the catalyst to be always kept in a suspension state through magnetic stirring in the process; and then immediately carrying out suction filtration in a dark state environment, washing with water for 3 times, washing with ethanol for 3 times, and then drying in a vacuum drying oven at 60 ℃ for 5 hours.

The Pt/U-PCN-480 monatomic catalyst prepared in example 3 was subjected to an ICP test, and the result showed that the supported Pt amount was 0.19% by weight.

Hydrogen production Performance test conditions As in example 1, the Pt/U-PCN-480 monatomic catalyst prepared in this example had a hydrogen production of 366.6. mu. mol h^-1。

Comparing examples 1, 2 and 3, it can be seen that the addition of chloroplatinic acid to achieve supersaturated adsorption (examples 1 and 3) produces a high efficiency monatomic catalyst in this manner, whereas example 2 produces a lower amount of chloroplatinic acid and produces a monatomic catalyst with insufficient hydrogen production performance.

EXAMPLE 4 monatomic catalyst Pt/ZIS

(1) Preparation of ZnIn₂S₄: 1.0mmol of ZnCl₂，1.0mmol In₂(SO₄)₃·6H₂Dissolving O and 4.8mmol thioacetamide in a mixed solution of 30mL distilled water and 30mL ethanol in turn, stirring until the mixture is clear, transferring the mixture into a high-pressure reaction kettle with the volume of 100mL, heating the mixture for 2 hours at 160 ℃, cooling the mixture naturally, washing the mixture by using distilled water and absolute ethanol in a centrifugal mode, and drying the mixture for 4 hours at 80 ℃ to obtain a product marked as ZIS.

(2) Preparation of the monatomic catalyst Pt/ZIS: 0.065g ZIS and 96.6mL of 1mol L were added to a Pyrex reaction flask with a flat light window^-1The solution was ultrasonically dispersed for 5min, and 3.4mL of 1.93X 10 solution was added^-3 mol L^-1The chloroplatinic acid solution is placed on a magnetic stirrer, high-purity nitrogen is introduced, and bubbling is carried out for 20min to remove air in the system (the above operation process needs to be carried out in a dark state); then placing the reaction bottle between two xenon lamps, and simultaneously illuminating with light intensity of 370mW cm^-2The catalyst is kept in a suspension state all the time by magnetic stirring in the process of illumination for 5 s; and then immediately carrying out suction filtration in a dark state environment, washing with water for 3 times, washing with ethanol for 3 times, and then drying in a vacuum drying oven at 60 ℃ for 5 hours.

The prepared Pt/ZIS monatomic catalyst was subjected to an ICP test, and the result showed that the supported Pt amount was 0.27 wt%.

Comparative example: the nanocatalyst Pt/ZIS was prepared according to the conditions of example 4, the illumination time was changed to 1h only, the conditions were the same, and the sample was labeled Nano-Pt/ZIS.

Respectively taking 100mg of Pt/ZIS monatomic catalyst in example 4 and 100mL of 10 vol% triethanolamine solution of Nano-Pt/ZIS catalyst in comparative example, adding the Pt/ZIS monatomic catalyst and the 100mL of 10 vol% triethanolamine solution into a Pyrex reaction flask with a plane light window, ultrasonically dispersing the solutions uniformly for 5min, introducing high-purity nitrogen for 20min to remove system air, illuminating the solutions for 1h under a xenon lamp (full spectrum), wherein the hydrogen yield of the Pt/ZIS monatomic catalyst is 288.8 mu molh^-1The hydrogen production amount of Nano-Pt/ZIS was 291.4. mu. mol h^-1。

EXAMPLE 5 monoatomic catalyst Pt/TiO₂

Preparation of a monoatomic catalyst Pt/TiO₂: 0.065g TiO was added to a Pyrex reaction flask with a flat light window₂And 96.6mL of 1mol L^-1The solution was ultrasonically dispersed for 5min, and 3.4mL of 1.93X 10 solution was added^-3mol L^-1The chloroplatinic acid solution was placed on a magnetic stirrer and bubbled with high-purity nitrogen for 20min to remove air in the system (the above operation process needs to be carried out in a dark state). Then placing the reaction bottle between two xenon lamps, and simultaneously illuminating with light intensity of 370mW cm^-2And (5) illuminating for 5s, and keeping the catalyst in a suspended state all the time through magnetic stirring. And then immediately carrying out suction filtration in a dark state environment, washing with water for 3 times, washing with ethanol for 3 times, and then drying in a vacuum drying oven at 60 ℃ for 5 hours.

Pt/TiO prepared in example 5₂The single atom catalyst was subjected to ICP test, and the result showed that the amount of supported Pt was 0.36 wt%.

Comparative example: preparation of the Nanocatalyst Pt/TiO according to the conditions of example 5₂Changing the illumination time to 1h only, and marking the sample as Nano-Pt/TiO under the same conditions₂。

Hydrogen production performance test conditions were the same as those of example 4, Pt/TiO prepared in this example₂Monatomic catalyst and Nano-Pt/TiO₂Respectively, the hydrogen production amounts of (1) and (7) are 157.1 mu mol h^-1And 157.8. mu. mol h^-1。

Example 6Au/U-PCN-480

(1) U-PCN-480 and U-PCN-480-RF were prepared as in (1) and (2) of example 1.

(2) Preparation of a monatomic catalyst Au/U-PCN-480: 0.065gU-PCN-480-RF and 96.6mL of 1mol L were added to a Pyrex reaction flask with a flat light window^-1After the methanol solution is dispersed uniformly by ultrasonic for 5min, 3.4mL of 0.01 mol L-1 chloroauric acid solution is added, and the mixture is placed on a magnetic stirrer, high-purity nitrogen is introduced, and the mixture is bubbled for 20min to remove air in the system (the above operation process needs to be carried out in a dark state). Then placing the reaction bottle between two xenon lamps, and simultaneously illuminating with light intensity of 370mW cm^-25s of illumination, this process is generalThe catalyst is kept in suspension state all the time by magnetic stirring. And then immediately carrying out suction filtration in a dark state environment, washing with water for 3 times, washing with ethanol for 3 times, and then drying in a vacuum drying oven at 60 ℃ for 5 hours.

The Au/U-PCN-480 monatomic catalyst prepared in example 6 was subjected to the ICP test, and the result showed that the supported Au amount was 0.13% by weight.

Comparative example: the nanocatalyst Au/U-PCN-480 was prepared according to the conditions of example 6, the illumination time was changed to 1h only, the conditions were the same, and the sample was labeled Nano-Au/U-PCN-480.

Hydrogen production Performance test conditions As in example 1, the Au/U-PCN-480 monatomic catalyst and the Nano-Au/U-PCN-480 prepared in this example had hydrogen production amounts of 170.9. mu. mol h^-1And 170.6. mu. mol h^-1。

The embodiments show that the invention can prepare the monatomic catalyst with good performance under mild environmental conditions, and has the advantages of low energy consumption, short preparation period, high efficiency and excellent performance of the monatomic catalyst.

The foregoing merely represents preferred embodiments of the invention, which are described in some detail and detail, and therefore should not be construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, various changes, modifications and substitutions can be made without departing from the spirit of the present invention, and these are all within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.