阅读说明：本技术 一种可见光响应的镍-磷化氮化碳光催化剂的制备方法 (Preparation method of visible light response nickel-phosphorized carbon nitride photocatalyst ) 是由 朱相林 陈金洲 许晖 李华明 于 2020-12-02 设计创作，主要内容包括：本发明属于光催化材料的制备方法技术领域,公开了一种可见光响应的镍-磷化氮化碳光催化剂的制备方法。该方法首先三聚氰胺高温共聚合的方案得到氮化碳,之后通过次亚磷酸钠与氮化碳混合煅烧的方案得到磷化的氮化碳材料,最后通过原位光沉积的方法原位修饰金属镍。镍-磷化氮化碳光催化具有良好的可见光吸收以及不含贵金属的特点,提高了制氢活性并且降低了催化剂成本。(The invention belongs to the technical field of preparation methods of photocatalytic materials, and discloses a preparation method of a nickel-phosphatized carbon nitride photocatalyst with visible light response. According to the method, firstly, carbon nitride is obtained by a scheme of melamine high-temperature copolymerization, then, a phosphated carbon nitride material is obtained by a scheme of mixed calcination of sodium hypophosphite and carbon nitride, and finally, metal nickel is modified in situ by an in-situ light deposition method. The nickel-phosphorized carbon nitride photocatalysis has the characteristics of good visible light absorption and no noble metal, improves the hydrogen production activity and reduces the catalyst cost.)

1. A preparation method of a visible light response nickel-phosphorized carbon nitride photocatalyst is characterized by comprising the following steps:

(1) preparing carbon nitride for later use;

(2) grinding and uniformly mixing carbon nitride and sodium hypophosphite according to a ratio, carrying out programmed heating to a calcination temperature in an argon atmosphere, carrying out heat preservation for a period of time, naturally cooling, washing with deionized water, and finally carrying out vacuum drying to obtain carbon phosphide;

(3) and (3) adding the carbon nitride phosphide and nickel chloride obtained in the step (2) into a triethanolamine solution, ultrasonically dispersing, illuminating for a period of time by using a xenon lamp, finally separating and precipitating, and drying in vacuum to obtain the nickel-carbon nitride phosphide photocatalyst.

2. The method according to claim 1, wherein in the step (1), the carbon nitride is prepared by: 2 g of melamine is put into a crucible, the temperature is raised to 530 ℃ at the heating rate of 7 ℃ per minute, the temperature is kept for 4 hours, and then the melamine is immediately taken out and naturally cooled to obtain powder which is ground for half an hour to obtain the carbon nitride.

3. The method according to claim 1, wherein in the step (2), the mass ratio of the carbon nitride to the sodium hypophosphite is 1: 1-4; the temperature programming rate is 5 ℃/min, the calcining temperature is 400-.

4. The method according to claim 1, wherein in the step (3), the ratio of the amount of the carbon nitride phosphide to the amount of the triethanolamine solution is 50 mg: 50 mL; wherein, the volume percentage concentration of the triethanolamine solution is 10%, the ultrasonic dispersion time is half an hour, the xenon lamp illumination time is 1-5 hours, and the vacuum drying temperature is 60 ℃.

5. The method according to claim 1, wherein in the step (3), the loading amount of nickel is 1 to 10 mass%.

6. Use of the visible-light-responsive nickel-phosphated carbon nitride photocatalyst prepared by the preparation method of any one of claims 1 to 5 in hydrogen production by visible light decomposition of water.

Technical Field

The invention belongs to the technical field of preparation methods of photocatalytic materials, and relates to a preparation method of a nickel-phosphatized carbon nitride photocatalyst with visible light response and application of the nickel-phosphatized carbon nitride photocatalyst in photocatalytic hydrogen production.

Background

The graphite phase carbon nitride is a non-metal semiconductor material, has proper energy band position, can perform visible light catalytic reaction, and has the characteristics of stable physical and chemical properties, simple preparation method and visible light absorption. Therefore, the graphite-phase carbon nitride is widely applied to the fields of hydrogen production by photolysis of water, photocatalytic carbon dioxide reduction and pollutant degradation. However, the activity of ordinary carbon nitride is limited by some disadvantages, such as insufficient light absorption range, high carrier recombination rate, few hydrogen evolution active sites, and the need to load noble metal promoters such as platinum. Researchers have demonstrated that the photocatalytic performance of carbon nitride can be improved by some nano-design methods, such as nano-morphology control, element doping, and the formation of composite photocatalytic materials by constructing a heterojunction with other semiconductor materials. Element doping or modification aiming at carbon nitride is an effective scheme for modifying the photocatalytic activity of the carbon nitride, and mainly comprises metal doping, non-metal doping, co-doping and the like. The method greatly expands the visible light absorption capability of the carbon nitride, provides a large number of Lewis base active sites, and has lower valence band position and lower recombination rate of photo-generated electron hole pairs by carrying out phosphorization modification on common carbon nitride. The main preparation methods of the existing carbon nitride doping comprise a solvothermal method, a solid-phase sintering method and the like. It is necessary to find a simple and high-yield method for preparing carbon nitride by aiming at specific element modification.

The nonmetal-modified carbon nitride is an effective method for preparing the high-activity carbon nitride, and has the following characteristics: the first non-metallic element can be substituted into the nitrogen or carbon atom of the carbon nitride so as not to disrupt the conjugated structure of the carbon nitride, and the incorporated non-metallic element can act as a lewis base site, providing a site for the attachment of the co-catalyst. While metal doping can only be modified at the carbon nitride edge or complexed between triazine rings, such doping elements cannot enter crystal lattices, position uncertainty is caused, and finally a new composite center is possibly formed.

Disclosure of Invention

The invention aims to develop a method for detectingA preparation method of a photoresponse nickel-phosphorization carbon nitride photocatalyst and application of the photocatalytic material in photocatalytic hydrogen production. The improved solid-gas phase interface doping method adopted by the invention can be used for doping into crystal lattices to form the phosphorized carbon nitride material in a carbon nitride polymerization mode in the process of gradually releasing reaction gas molecules. The new carbon nitride conjugate surface is composed of nitrogen, carbon and phosphorus, and phosphorus is taken as a Lewis base site and can anchor Lewis acid Ni²⁺Finally, in-situ photoreduction is carried out to form a metal cluster which is used as a cocatalyst to promote the improvement of hydrogen production activity.

The invention firstly obtains common carbon nitride by a scheme of melamine high-temperature copolymerization, then obtains phosphatized carbon nitride material by a scheme of mixing and calcining sodium hypophosphite and common carbon nitride, and finally modifies metallic nickel in situ by a method of in-situ light deposition. The nickel-phosphorized carbon nitride photocatalysis has the characteristics of good visible light absorption and no noble metal, improves the hydrogen production activity and reduces the catalyst cost.

The technical solution for realizing the purpose of the invention is as follows:

a preparation method of a visible light response nickel-phosphorized carbon nitride photocatalyst comprises the following steps:

(1) preparing carbon nitride for later use;

(2) grinding and uniformly mixing carbon nitride and sodium hypophosphite according to a ratio, carrying out programmed heating to a calcination temperature in an argon atmosphere, carrying out heat preservation for a period of time, naturally cooling, washing with deionized water, and finally carrying out vacuum drying to obtain carbon phosphide;

(3) and (3) adding the carbon nitride phosphide and nickel chloride obtained in the step (2) into a triethanolamine solution, ultrasonically dispersing, illuminating for a period of time by using a xenon lamp, finally separating and precipitating, and drying in vacuum to obtain the nickel-carbon nitride phosphide photocatalyst.

In the step (1), the preparation of the carbon nitride comprises the following steps: 2 g of melamine is put into a crucible, the temperature is raised to 530 ℃ at the heating rate of 7 ℃ per minute, the temperature is kept for 4 hours, and then the melamine is immediately taken out and naturally cooled to obtain powder which is ground for half an hour to obtain the carbon nitride.

In the step (2), the mass ratio of the carbon nitride to the sodium hypophosphite is 1: 1-4; the rate of temperature programming was 5 deg.C/min. The calcination temperature is 400-500 ℃, and the temperature is kept for 2 hours.

In the step (3), the dosage proportion of the phosphated carbon nitride and the triethanolamine solution is 50 mg: 50 mL; wherein, the volume percentage concentration of the triethanolamine solution is 10%, the ultrasonic dispersion time is half an hour, the xenon lamp illumination time is 1-5 hours, and the vacuum drying temperature is 60 ℃.

In the step (3), the loading amount of the nickel is 1-10% by mass.

The visible light response nickel-phosphorized carbon nitride photocatalyst prepared by the invention is used for preparing hydrogen by decomposing water with visible light.

Compared with the prior art, the invention has the following remarkable advantages:

compared with common carbon nitride, the phosphorus carbonitride has a better light absorption range, phosphorus element replaces carbon atoms at specific positions to enter a carbon nitride conjugated skeleton, and the phosphorus atom has lone pair electrons, can influence valence band top positions as Lewis base, and can react with Ni²⁺The catalysis is promoted by Lewis acid-base complexing anchoring. The preparation method is simple, the product yield is high, the operation is simple, the repeatability is good, and the method is suitable for large-scale preparation.

Drawings

FIG. 1 is an X-ray diffraction pattern of a nickel-phosphorous carbon nitride photocatalyst prepared according to an example of the present invention and a general carbon nitride.

FIG. 2 is a scanning electron microscope image of a nickel-phosphorous carbon nitride photocatalyst prepared according to an embodiment of the present invention.

FIG. 3 is a graph comparing the UV-visible diffuse reflection absorption spectra of the Ni-P carbon nitride photocatalyst prepared in this example of the present invention and common carbon nitride.

FIG. 4 is a valence band x-ray photoelectron spectrum of a nickel-phosphorous carbon nitride photocatalyst prepared according to an embodiment of the present invention.

FIG. 5 is a graph showing the activity of a nickel-phosphorous carbon nitride photocatalyst prepared according to an example of the present invention.

Detailed Description

The invention is further illustrated by the following figures and specific examples in conjunction with the description.

Example 1

The preparation method of the nickel-phosphorus carbon nitride photocatalyst specifically comprises the following steps:

(1) 2 g of melamine is put into a crucible, the temperature is raised to 530 ℃ at the heating rate of 7 ℃ per minute, the temperature is kept for 4 hours, and then the melamine is immediately taken out and naturally cooled to obtain powder which is ground for half an hour to obtain carbon nitride;

(2) grinding and uniformly mixing 1 g of carbon nitride and 0.5 g of sodium hypophosphite, heating to 430 ℃ at a heating rate of 5 ℃ per minute in an argon calcination reaction, preserving heat for 2 hours, naturally cooling, washing with ionized water, and finally performing vacuum drying to obtain the carbon phosphide;

(3) adding carbon phosphide nitride and nickel chloride (the load of nickel atoms is 3 percent of mass fraction) into 50ml of 10 percent of triethanolamine solution by volume fraction, ultrasonically dispersing for half an hour, illuminating for 2 hours by a xenon lamp, centrifuging for 5-10 minutes at 6000-8000 rpm, separating and precipitating, and finally vacuum drying at 60 ℃ to obtain the nickel-carbon phosphide photocatalyst.

FIG. 1 shows the X-ray diffraction patterns of the nickel-phosphorous carbon nitride photocatalyst prepared in this example and common carbon nitride. The diffraction peak of ordinary carbon nitride is the (100) crystal face of carbon nitride at 13.1 degrees, and the strong diffraction peak of carbon nitride is the (002) crystal face of carbon nitride at 27.3 degrees, which are respectively caused by the superposition reflection of the repeating units and the interlayer on the planar structure of carbon nitride. Compared with the common carbon nitride, the diffraction peak of the nickel-phosphorus carbon nitride photocatalyst has no obvious change, which shows that the prepared nickel-phosphorus carbon nitride photocatalyst has no change of components and ingredients.

Fig. 2 is a scanning electron microscope picture of the nickel-phosphorous carbon nitride photocatalyst prepared in this example, and it can be seen from fig. 2 that the obtained nickel-phosphorous carbon nitride photocatalyst has a random block structure.

Fig. 3 is a comparison graph of the ultraviolet-visible diffuse reflection absorption spectrum of the nickel-phosphorous carbon nitride photocatalyst prepared in this embodiment and common carbon nitride, and it can be seen from fig. 3 that the nickel-phosphorous carbon nitride photocatalyst has better visible light absorption compared with the common carbon nitride, and the better light absorption capability is beneficial to the photocatalytic hydrogen production performance of the nickel-phosphorous carbon nitride photocatalyst.

FIG. 4 is a valence band x-ray photoelectron spectrum of the nickel-phosphorous carbon nitride photocatalyst prepared in this example. The value of the EVB of the ordinary carbon nitride valence band was determined to be about 1.87eV, while the EVB of the nickel-phosphated carbon nitride photocatalyst was 2.10 eV. The position of the valence band of the nickel-phosphorized carbon nitride photocatalyst catalyst is more positive, which shows that the nickel-phosphorized carbon nitride photocatalyst catalyst has stronger oxidizing capability, and is beneficial to the catalytic reaction.

FIG. 5 is a graph showing the activity of the nickel-phosphorous carbon nitride photocatalyst prepared in this example. As shown in fig. 5, the hydrogen production of 20 mg of nickel-phosphorous carbon nitride photocatalyst was 13.6 micromoles per 2.5 hours under visible light irradiation, while the hydrogen production of ordinary carbon nitride loaded with 1% platinum was 2.1 micromoles, the more the activity was improved by 3.4 times. The superior activity fully represents the advancement of the design of the material.

Example 2

The preparation method of the nickel-phosphorus carbon nitride photocatalyst specifically comprises the following steps:

(1) 2 g of melamine is put into a crucible, the temperature is raised to 550 ℃ at the heating rate of 10 ℃ per minute, the temperature is kept for 4 hours, and then the melamine is immediately taken out and naturally cooled to obtain powder which is ground for half an hour to obtain common carbon nitride;

(2) grinding and uniformly mixing 1 g of common carbon nitride and 0.5 g of sodium hypophosphite, heating to 450 ℃ at a heating rate of 5 ℃ per minute in an argon calcining reaction, preserving heat for 2 hours, naturally cooling, cleaning with ionized water, and finally performing vacuum drying to obtain the carbon phosphide;

(3) adding carbon phosphide nitride and nickel chloride (the load of nickel atoms is 5 percent by mass) into 50ml of 10 percent by volume triethanolamine solution, ultrasonically dispersing for half an hour, illuminating for 2 hours by a xenon lamp, finally centrifuging for 5-10 minutes at 6000-.

Example 3

The preparation method of the nickel-phosphorus carbon nitride photocatalyst specifically comprises the following steps:

(1) 2 g of melamine is put into a crucible, the temperature is raised to 550 ℃ at the heating rate of 10 ℃ per minute, the temperature is kept for 4 hours, and then the melamine is immediately taken out and naturally cooled to obtain powder which is ground for half an hour to obtain common carbon nitride;

(2) grinding and uniformly mixing 1 g of common carbon nitride and 1 g of sodium hypophosphite, heating to 430 ℃ at a heating rate of 5 ℃ per minute in an argon calcining reaction, preserving heat for 2 hours, naturally cooling, cleaning with ionized water, and finally performing vacuum drying to obtain the phosphated carbon nitride;

(3) adding carbon phosphide nitride and nickel chloride (the load of nickel atoms is 1 percent of mass fraction) into 50ml of 10 percent of triethanolamine solution by volume fraction, after ultrasonic dispersion for half an hour, illuminating for 2 hours by a xenon lamp, finally centrifuging for 5-10 minutes at 6000-.