CN113398971B - Two-dimensional RuNi/g-C3N4 composite photocatalyst, preparation method and application thereof - Google Patents

Abstract

The invention relates to a two-dimensional RuNi/g-C ₃ N ₄ composite photocatalyst and a preparation method and application thereof. The catalyst is constructed from quasi-hexagonal two-dimensional RuNi nanoparticles and g-C ₃ N ₄ nano-sheets. The composite formed; the catalyst is based on g-C ₃ N ₄ nano-sheets, and is prepared by one-step hydrothermal treatment of a mixed solution containing g-C ₃ N ₄ nano-sheets and ruthenium and nickel ions. The composite photocatalyst has lower recombination efficiency of photogenerated electrons and holes, better photocatalytic water splitting performance for hydrogen production, simple preparation method and required equipment, low cost, short preparation period and easy mass production.

Description

Two-dimensional RuNi/g-C3N4 composite photocatalyst, preparation method and application thereof

technical field

The invention belongs to the composite photocatalyst and the field of preparation and application thereof, in particular to a two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst and a preparation method and application thereof.

Background technique

Hydrogen energy is a non-carbon-based clean energy, and the product of combustion is only water, which is expected to become the "end energy" for human use. In the 21st century, my country and developed countries such as the United States and the European Union have formulated hydrogen energy development plans, and my country has made progress in many aspects in the field of hydrogen energy. At present, how to realize the low-cost and clean production of hydrogen energy is one of the bottlenecks in the development of hydrogen energy. Decomposing water into hydrogen and oxygen under the action of sunlight, that is, using clean and abundant solar energy to produce hydrogen, is an advanced technology to achieve clean hydrogen energy production. The key lies in the development of an efficient photocatalyst. At present, the non _- metallic material _gC3N4 has been widely used as a new type of photocatalyst with visible light response. It has the advantages of simple preparation method, good chemical stability, etc. Catalytic reaction. However, the photogenerated electrons and holes generated by gC ₃ N ₄ under illumination are very easy to recombine, resulting in an unsatisfactory photocatalytic effect.

In order to suppress the recombination of photogenerated electron-hole pairs, it is generally necessary to support the noble metal Pt on its surface as a cocatalyst to improve its photocatalytic water splitting efficiency for hydrogen production. However, the high price of Pt severely restricts the application of photocatalysts in practical production and life. Therefore, it is particularly important to develop inexpensive cocatalysts that can match the structure of photocatalysts.

As a relatively cheap bimetallic material, RuNi alloy has synergistic electronic structure and function. It can be used as a co-catalyst of common photocatalysts and can effectively improve the photocatalyst's photocatalytic water splitting performance. , and RuNi alloys are usually granular and cannot match 2D nanophotocatalysts. Therefore, the development of more efficient 2D _RuNi alloy cocatalysts that can be tightly integrated with 2D _gC3N4 nanophotocatalysts has clear practical significance.

Patent CN111905788A discloses a preparation method and application of NiSe/gC ₃ N ₄ composite photocatalyst material, in situ growth and deposition of ultra-small NiSe nanoparticles on the surface of two-dimensional flake gC ₃ N ₄ , this method makes high dispersion NiSe nanodots are tightly connected on the surface of gC ₃ N ₄ , and the average size of NiSe is 10-12 nm, and the obtained NiSe/gC ₃ N ₄ has good performance. The preparation method of the invention is simple and low in cost. The prepared NiSe/gC ₃ N ₄ composite photocatalyst material has excellent hydrogen production performance under visible light irradiation. However, the cluster structure of NiSe particles in the patent is similar to the two-dimensional gC _The matching of _3N4 photocatalyst is insufficient, and NiSe particles do not form a specific electronic structure, so the catalytic performance of _NiSe is not significantly better than that of commonly used noble metals, but only improves the photocatalytic performance of _gC3N4 .

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst and a preparation method thereof in order to overcome the defects of poor catalytic performance of RuNi alloy and poor matching with two-dimensional photocatalytic materials in the prior art and application, the present invention has simple preparation method, easy control of process parameters, easy large-scale production, low cost of the obtained composite catalyst, and high efficiency and stability of visible light splitting water to produce hydrogen.

The object of the present invention is achieved through the following technical solutions:

A two-dimensional _RuNi / _gC3N4 composite photocatalyst, the composite photocatalyst is a composite constructed by two _- dimensional ruthenium _- nickel nanosheets and _gC3N4 nanosheets, and the _gC3N4 nanosheet is used as a substrate, Loaded ruthenium-nickel nanosheets.

The composite photocatalyst is a composite constructed by quasi-hexagonal two-dimensional _RuNi nanosheets and two-dimensional _gC3N4 materials, the size of the two-dimensional RuNi nanosheets is 10-40 nm, and the composite photocatalyst has a low The recombination efficiency of photogenerated electrons and holes is high, and the photocatalytic water splitting performance is better for hydrogen production; the preparation method and required equipment are simple, the cost is low, the preparation period is short, and the mass production is easy.

Preferably, the mass ratio of the gC ₃ N ₄ nanosheets to the two-dimensional ruthenium-nickel nanosheets is 20:1-1:1. Further preferably, the mass ratio of the gC ₃ N ₄ nanosheets to the ruthenium source nanoparticles is 8:1 to 2:1

Preferably, the molar ratio of ruthenium to nickel is 1:5 to 5:1, and further preferably, the molar ratio of ruthenium to nickel is 1:1.

A preparation method of a two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst is prepared by a one-step hydrothermal method of a mixed solution containing gC ₃ N ₄ nanosheets and ruthenium and nickel ions.

Preferably, the following steps are included:

(1) adding the ruthenium source and the nickel source into the solvent to prepare a RuNi alloy precursor solution;

(2) Mix the gC ₃ N ₄ nanosheets with the precursor solution of step (1), place it in a hydrothermal kettle for a certain period of time, centrifuge, wash with water, and vacuum dry to obtain a two-dimensional RuNi/gC ₃ N ₄ composite catalyst of light.

Preferably, in step (1), the ruthenium source and the nickel source are added to the benzyl alcohol until they are completely dissolved, then polyvinylpyrrolidone (PVP) is added and ultrasonically dispersed, and then the formaldehyde solution is added and stirred to obtain a RuNi alloy precursor solution.

Preferably, the molar ratio of the ruthenium source to the nickel source in step (1) is 1:5 to 5:1; further preferably, the molar ratio of the ruthenium source to the nickel source is 1:1.

Preferably, the volume ratio of the benzyl alcohol to formaldehyde is 100:1 to 10:1; further preferably, the volume ratio of the benzyl alcohol to formaldehyde is 40:1 to 20:1

The ruthenium source is ruthenium chloride hydrate, and the nickel source is nickel acetylacetonate or nickel nitrate hexahydrate.

Preferably, the mass ratio of the gC ₃ N ₄ nanosheets added in step (2) to the ruthenium source in the precursor solution is 20:1 to 1:1

Preferably, the temperature of the hydrothermal in step (2) is 180-250°C, and the reaction time is 8-20h, further preferably, the temperature of the hydrothermal is 200-220°C, and the reaction time is 10-12h

Application of a two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst in photocatalytic water splitting for hydrogen production.

Compared with the prior art, the present invention has the following beneficial effects:

(1) the process and equipment of the present invention are simple, the process parameters are easy to control, the cost is low, and it is easy to produce on a large scale;

(2) The RuNi alloy in the two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst of the present invention has good crystallinity, and the electronic structure between Ru and Ni is relatively stable, so that the synergistic effect between the bimetals can be strengthened, It can be used as an "electron trap" for capturing electrons, and is suitable as an efficient cocatalyst for photocatalysts;

(3) RuNi in the two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst of the present invention acts as a co-catalyst, and it has an ultra-thin two-dimensional nanostructure. _{The gC3N4} nanosheets form a larger area of tight bonding, which is beneficial to the fast and efficient transfer of photogenerated electrons from _gC3N4 to _RuNi alloys, and can reduce the recombination efficiency of _{photogenerated} electron and hole pairs in _gC3N4 , improve the efficiency of photogenerated electrons participating in the hydrogen production process, and can provide a large area of active sites for the photocatalytic decomposition of water production and hydrogen production process;

(4) The hydrogen production performance of the two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst prepared by the present invention is obviously improved compared with the performance of the noble metal Pt supported gC ₃ N ₄ photocatalyst, so the two-dimensional RuNi alloy is an energy An ideal and relatively inexpensive cocatalyst to replace noble metal Pt in the field of photocatalysis.

Description of drawings

1 is a TEM image of the two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst prepared in Example 1;

Figure 2 shows the hydrogen production of the two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst prepared in Example 1, the gC ₃ N ₄ nanophotocatalyst, and the Pt/gC ₃ N ₄ (Pt loading 2wt%) prepared by photodeposition speed comparison chart;

FIG. 3 is a TEM image of the two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst prepared in Example 2. FIG.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example 1

(1) 29.21mg RuCl ₃ xH ₂ O and 36.18mg Ni(acac) ₂ were added to 30ml of benzyl alcohol, stirred until dissolved, then 150mg of PVP was added, sonicated for 30min, then 1ml of aqueous formaldehyde was added, and stirred for 10min;

(2) 150mg gC ₃ N ₄ nanosheets were added to the above mixed solution, sonicated and stirred, placed in a 100 ml hydrothermal kettle at 220°C for 12h, cooled, washed with centrifugal water for 3 times, and vacuum dried at 60°C for 12h to obtain two Dimensional RuNi/gC ₃ N ₄ composite photocatalyst.

The two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst and pure gC ₃ N ₄ nanosheets were used for photocatalytic hydrogen production. The photocatalytic hydrogen production conditions were as follows: 10 mg of the catalyst was placed in an aqueous solution containing 10 vol% triethanolamine, with 300 W A xenon lamp was used as a simulated sunlight source, and samples were taken every hour under the continuous illumination of the light source, and the production of hydrogen was detected by gas chromatography, and the rate was calculated.

Figure 1 shows that the RuNi alloy in the two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst obtained in this example is a composite material formed by loading a quasi-hexagonal two-dimensional nanosheet structure onto the surface of gC ₃ N ₄ nanosheets. The size of the RuNi alloy is around 20 nm.

Figure 2 shows that the two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst obtained in this example has good photocatalytic hydrogen production performance, the yield can reach 35100 μmol/g/h, and its performance is significantly higher than that of gC ₃ N ₄ nanosheets The photocatalytic hydrogen production performance is also significantly higher than that of the Pt/gC ₃ N ₄ prepared by photodeposition method.

Example 2

(1) 38.90mg RuCl ₃ xH ₂ O and 24.12mg Ni(acac) ₂ were added to 30ml of benzyl alcohol, stirred until dissolved, then 150mg of PVP was added, sonicated for 30min, then 1ml of aqueous formaldehyde was added, and stirred for 10min;

(2) 100mg gC ₃ N ₄ nanosheets were added to the above mixed solution, ultrasonicated and stirred, placed in a 100 ml hydrothermal kettle at 220°C for 12h, cooled, washed with centrifugal water for 3 times, and vacuum-dried at 60°C for 12h to obtain two Dimensional RuNi/gC ₃ N ₄ composite photocatalyst.

In this example, the amount of ruthenium source is excessive. It can be seen from the TEM in Figure 3 that the morphology of the RuNi alloy has changed significantly compared with Example 1. The two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst has a Compared with Example 1, the performance also decreased significantly, indicating that the quasi-hexagonal two-dimensional nanostructure of RuNi alloy has better coupling with gC ₃ N ₄ nanosheets, which is beneficial to the transfer of photogenerated electrons.

Example 3

(1) 19.47mg RuCl ₃ xH ₂ O and 24.12mg Ni(acac) ₂ were added to 30ml of benzyl alcohol, stirred until dissolved, then added 200mg of PVP, sonicated for 30min, then added 0.5ml of aqueous formaldehyde solution, stirred for 10min;

(2) 200mg gC ₃ N ₄ nanosheets were added to the above mixed solution, sonicated and stirred, placed in a 100 ml hydrothermal kettle at 200°C for 12h, cooled, washed with centrifugal water for 3 times, and vacuum dried at 60°C for 12h to obtain two Dimensional RuNi/gC ₃ N ₄ composite photocatalyst.

Example 4

(1) Add 29.21 mg RuCl ₃ ·xH ₂ O and 40 mg Ni(NO ₃ ) ₂ ·6H ₂ O to 30 ml of benzyl alcohol, stir until dissolved, then add 150 mg of PVP, sonicate for 30 min, add 1 ml of aqueous formaldehyde solution, and stir 10min;

(2) 100mg gC ₃ N ₄ nanosheets were added to the above mixed solution, ultrasonicated and stirred, placed in a 100 ml hydrothermal kettle at 220°C for 12h, cooled, washed with centrifugal water for 3 times, and vacuum-dried at 60°C for 12h to obtain two Dimensional RuNi/gC ₃ N ₄ composite photocatalyst.

The foregoing description of the embodiments is provided to facilitate understanding and use of the invention by those of ordinary skill in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (8)

1. a two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst, is characterized in that, this composite photocatalyst is the composite that is constructed from two-dimensional ruthenium-nickel nanosheets and gC ₃ N ₄ nano sheets, with gC ₃ N ₄ nanosheets are used as the substrate, and ruthenium-nickel nanosheets are loaded; The mass ratio of the gC ₃ N ₄ nanosheets to the two-dimensional ruthenium-nickel nanosheets is 20:1-1:1; the molar ratio of ruthenium and nickel is 1:1. 2. the preparation method of a kind of two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst as claimed in claim 1, is characterized in that, by containing gC ₃ N ₄ nanosheets and the mixed solution of ruthenium, nickel ion one-step hydrothermal method prepared. 3. the preparation method of a kind of two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst as claimed in claim 2, is characterized in that, comprises the following steps: (1) Add the ruthenium source and the nickel source into the solvent to prepare a RuNi alloy precursor solution; (2) Mix the gC ₃ N ₄ nanosheets with the precursor solution of step (1), place it in a hydrothermal kettle for a certain period of time, centrifuge, wash with water, and vacuum dry to obtain a two-dimensional RuNi/gC ₃ N ₄ composite catalyst of light. 4 . The method for preparing a two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst according to claim 3 , wherein in step (1), the ruthenium source and the nickel source are added to the benzyl alcohol until they are completely dissolved, and then the Polyvinylpyrrolidone is dispersed by ultrasonic, and then formaldehyde solution is added and stirred to obtain a RuNi alloy precursor solution. 5 . The method for preparing a two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst according to claim 4 , wherein the molar ratio of the ruthenium source and the nickel source in step (1) is 1:1; 6 . The volume ratio of the benzyl alcohol to formaldehyde is 100:1 to 10:1; The ruthenium source is ruthenium chloride hydrate, and the nickel source is nickel acetylacetonate or nickel nitrate hexahydrate. 6 . The method for preparing a two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst according to claim 3 , wherein the gC ₃ N ₄ nanosheets added in step (2) and the The mass ratio of the ruthenium source is 20:1~1:1. 7 . The method for preparing a two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst according to claim 3 , wherein the hydrothermal temperature in step (2) is 180-250° C., and the reaction time is 8~20 hours. 8 . The application of the two-dimensional RuNi/gC ₃ N ₄ composite photocatalyst according to claim 1 in photocatalytic water splitting to produce hydrogen. 9 .

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