阅读说明：本技术 一种高效光催化裂解水制氢的磷掺杂超薄空心氮化碳纳米球催化剂 (Phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst for efficient photocatalytic water splitting hydrogen production ) 是由 邓积光 吕思洁 敬林 戴洪兴 刘雨溪 李双 王治伟 于 2020-11-23 设计创作，主要内容包括：一种高效光催化裂解水制氢的磷掺杂超薄空心氮化碳纳米球催化剂,属于催化化学与纳米科学领域。首先,以正硅酸四乙酯和十八烷基三甲氧基硅烷为前驱体,以乙醇、氨水和水为溶剂,利用法制备SiO-2模板；然后以氰胺为前驱体,通过负压超声法制备空心氮化碳纳米球(H-CNS)载体；最后,以红磷为磷源,采用化学气相沉积法,将磷原子沉积在H-CNS载体上,得到磷掺杂的P/UH-CNS复合催化剂；该制备过程中,在H-CNS载体内外表面产生的压力差,会使得原本疏松的H-CNS载体壳层变薄。本发明材料新颖,制备工艺简单,产物形貌规整可控,催化剂表现出良好的光催化产氢活性和稳定性。(A phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst for efficient photocatalytic water splitting hydrogen production belongs to the field of catalytic chemistry and nano science. Firstly, tetraethyl orthosilicate and octadecyl trimethoxy silane are taken as precursors, ethanol, ammonia water and water are taken as solvents, and the precursors are utilized Method for preparing SiO 2 A template; then, preparing a hollow carbon nitride nanosphere (H-CNS) carrier by using cyanamide as a precursor through a negative pressure ultrasonic method; finally, red phosphorus is taken as a phosphorus source, and phosphorus atoms are deposited on the H-CNS carrier by adopting a chemical vapor deposition method to obtain the compoundTo phosphorus doped P/UH-CNS hybrid catalysts; in the preparation process, the pressure difference generated on the inner and outer surfaces of the H-CNS carrier can thin the shell layer of the H-CNS carrier which is originally loose. The invention has novel materials, simple preparation process, regular and controllable product appearance, and good photocatalytic hydrogen production activity and stability of the catalyst.)

1. A phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst for efficient photocatalytic water splitting hydrogen production is characterized by being thin-walled hollow spherical carbon nitride, wherein the spherical wall of the carbon nitride is doped with P, the doping amount of the P is x wt%, and x is 0-10 and is not 0.

2. The phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst for efficient photocatalytic hydrogen production by water splitting as claimed in claim 1, wherein the thickness of the sphere wall is 20-30 nm; the inner diameter of the hollow sphere is 400-600 nm.

3. The phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst for efficient photocatalytic hydrogen production by water splitting as claimed in claim 1, wherein the wall of the nanosphere is provided with holes.

4. The preparation method of the phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst for efficient photocatalytic hydrogen production by water splitting as claimed in any one of claims 1 to 3, characterized by comprising the following steps:

(1) preparing a layer of core-shell spherical SiO with mesoporous surface and solid interior₂A template;

(2) preparing hollow carbon nitride nanospheres (H-CNS) by adopting a negative pressure ultrasonic method, and preparing the core-shell spherical SiO obtained in the step (1)₂Adsorbing and loading cyanamide on a template under the conditions of vacuum pumping and ultrasonic waves, calcining, and then using NH₄HF₂Removal of SiO₂Template to obtain hollow carbon nitride nanosphere (H-CNS);

(3) preparing phosphorus-doped ultrathin hollow carbon nitride nanospheres by adopting a chemical vapor deposition method, adding the hollow carbon nitride nanospheres (H-CNS), iodine and purified red phosphorus into a quartz ampoule bottle, vacuumizing and sealing by using acetylene flame; then heating the quartz tube to 420-; cooling to 260-300 ℃ at the speed of 1 ℃/min, and preserving heat for 3-5 h; then slowly cooling to room temperature at the speed of 0.2 ℃/min; finally, the prepared sample is applied to CS₂Washed with distilled water and ethanol, and dried to obtain x wt% P/UH-CNS catalyst.

5. The method according to claim 4, wherein the mass ratio of H-CNS powder to iodine is 100 (0.5-1.5), and P is adjusted according to the doping amount.

6. The application of the preparation method of the phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst for preparing hydrogen by efficiently photocatalytic splitting of water as claimed in any one of claims 1 to 3 in preparation of hydrogen by photocatalytic splitting of water.

7. The application of the preparation method of the phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst for efficient photocatalytic hydrogen production by water splitting as claimed in claim 6 comprises the following specific steps: mixing the catalyst, water, triethanolamine and Pt under the irradiation of visible light or sunlight to prepare hydrogen.

Technical Field

The invention relates to a phosphorus (P) doped ultrathin hollow carbon nitride nanosphere (UH-CNS) catalyst for efficient photocatalytic water splitting hydrogen production. The invention takes cyanamide and red phosphorus as precursors, respectively prepares hollow carbon nitride nanospheres (H-CNS) and phosphorus-doped ultrathin hollow carbon nitride nanospheres (P/UH-CNS) by using a negative pressure ultrasonic method and a chemical vapor deposition method, and finally realizes efficient hydrogen production by photocatalytic water splitting. Belongs to the field of catalytic chemistry and nano science.

Background

With the rapid development of society and economy since the 21 st century, the excessive dependence of industrial economy on fossil energy causes the fossil fuel stored in the earth to be continuously consumed, and the energy crisis and environmental pollution become global focuses. Solar energy is an inexhaustible renewable energy, and hydrogen energy also has the advantages of cleanness, safety, environmental protection, high energy density and the like, and is considered as a new energy source capable of replacing the traditional ore energy source. Inspired by photosynthesis in the nature, the photocatalyst is used for directly absorbing solar energy to dissociate water, and clean hydrogen energy is prepared, stored and utilized, so that a new way is provided for solving the problems of energy exhaustion and environment. Although the research on the photocatalytic hydrogen production by water splitting has been over 30 years old and has been developed rapidly, the whole process is still in the theoretical exploration and laboratory stage, many practical problems need to be solved, and the process is a certain distance away from industrial application. The main problems that exist at present include: (1) the specific surface area of the catalyst is low; (2) the response to visible light is weak; and (3) the charge recombination rate is higher. Therefore, research and development of semiconductor materials with higher photocatalytic activity in the visible light range are key to realizing solar hydrogen production.

Among the numerous semiconductor photocatalysts, carbon nitride (g-C)₃N₄) Is a more classical non-metallic photocatalyst, and hasExcellent hydrogen production activity. However, the bulk g-C is greatly limited by low specific surface area, low separation efficiency of photogenerated electron-hole pairs, and weak visible light response capability₃N₄Practical application of the material. Researches show that the g-C can be effectively improved by the modes of morphology regulation, doping, photosensitization, heterojunction construction and the like₃N₄The photocatalytic activity of (1). The invention firstly utilizes a negative pressure ultrasonic method to prepare the hollow carbon nitride nanosphere with large specific surface area, wherein the hollow structure can promote electrons and holes to respectively migrate to the reduction center and the oxidation center on the inner surface and the outer surface of the nanosphere, thereby realizing the localization of charges and improving the quantum yield. Then, the non-toxic and low-cost single red phosphorus is selected as a phosphorus source, and the phosphorus-doped ultrathin hollow carbon nitride nanospheres are prepared by a one-step chemical vapor deposition method. In the preparation process, the pressure difference formed by the phosphorus vapor on the inner surface and the outer surface of the hollow carbon nitride nanospheres can thin the shell layers of the originally loose hollow carbon nitride nanospheres. In addition, the doping of the phosphorus element can obviously optimize the electronic structure and the surface property of the hollow carbon nitride nanosphere, and reduce the recombination rate of photo-generated charges, so that the overall hydrogen production activity of the material through photolysis of water is improved.

Meanwhile, the research and research of the literature finds that the preparation of the phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst and the report of the application of the phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst in the photocatalytic water splitting hydrogen production do not exist at present. Therefore, a series of x wt% P/UH-CNS (x ═ 0-10) photocatalysts are prepared by using a modified chemical vapor deposition method for the first time, red phosphorus is used as a phosphorus source, the controllable preparation of the catalyst material is realized, and meanwhile, 2 wt% P/UH-CNS catalyst is found to have the optimal hydrogen production activity by photocatalytic water splitting.

Disclosure of Invention

The invention aims to prepare an x wt% P/UH-CNS (x is 0-10) catalyst by using a chemical vapor deposition method, and the catalyst is used for efficiently preparing hydrogen by photocatalytic water splitting.

The catalyst is characterized by being thin-wall hollow spherical carbon nitride, the spherical wall of the carbon nitride is doped with P, the doping amount of the P is x wt%, and x is 0-10 and is not 0.

Further preferably, the thickness of the spherical wall is 20-30 nm; the inner diameter of the hollow sphere is 400-600 nm. Further, the ball wall is provided with holes.

The preparation method of the phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst is characterized by comprising the following steps of:

(1) preparing a layer of core-shell spherical SiO with mesoporous surface and solid interior₂A template;

(2) preparing hollow carbon nitride nanospheres (H-CNS) by adopting a negative pressure ultrasonic method, and preparing the core-shell spherical SiO obtained in the step (1)₂Adsorbing and loading cyanamide on a template under the conditions of vacuum pumping and ultrasonic processing, calcining, and then using NH₄HF₂Removal of SiO₂Template to obtain hollow carbon nitride nanosphere (H-CNS);

(3) preparing ultrathin hollow carbon nitride nanospheres doped with phosphorus by adopting a chemical vapor deposition method, adding the hollow carbon nitride nanospheres (H-CNS), iodine and purified red phosphorus into a quartz ampoule bottle, vacuumizing and sealing by using acetylene flame; then heating the quartz tube to 420-; cooling to 260-300 ℃ at the speed of 1 ℃/min, and preserving heat for 3-5 h; then slowly cooling to room temperature at the speed of 0.2 ℃/min; finally, the prepared sample is applied to CS₂Washed with distilled water and ethanol, and dried to yield x wt% P/UH-CNS (x ═ 0-10) catalyst.

The mass ratio of the H-CNS powder to the iodine is 100 (0.5-1.5), and the P is adjusted according to the doping amount.

The application of the phosphorus-doped ultrathin hollow carbon nitride nanosphere catalyst is used for preparing hydrogen by photocatalytic water decomposition, and the method comprises the following specific steps: mixing the catalyst, water, triethanolamine and Pt under the irradiation of visible light or sunlight to prepare hydrogen.

The method has the characteristics of simple preparation process, low raw material price, high yield, regular product appearance and the like. The x wt% P/UH-CNS catalyst prepared by the invention has excellent activity and stability for photocatalytic water splitting hydrogen production, wherein the hydrogen production activity of the 2 wt% P/UH-CNS catalyst with the best activity under simulated sunlight and visible light reaches 9653 mu mol h and 2814 mu mol h respectively^-1g^-1(test conditions: 20mg catalyst, 45mL water, 5mL triethanolamine and 2 wt% Pt).

Drawings

FIG. 1 shows the XRD spectrum of the prepared catalyst.

FIG. 2 is a TEM photograph of the resulting catalyst. TEM photographs of (a, b) H-CNS, (c, d)1 wt% P/UH-CNS, (e, f)2 wt% P/UH-CNS, (g, H)5 wt% P/UH-CNS and (l, i)10 wt% P/UH-CNS catalyst are shown in the figure in that order.

Fig. 3 is a diagram showing hydrogen production activity of the catalyst under simulated sunlight (a) and visible light (b). The catalyst in the reaction solution consisted of 20mg catalyst, 45mL water, 5mL triethanolamine and 2 wt% Pt.

Detailed Description

In order to further illustrate the invention, the following examples are given in detail and the accompanying drawings are given to illustrate the various catalyst materials obtained by the present invention.

Example 1: according toMethod for synthesizing SiO₂And (5) template. The specific process is as follows: adding 9mL of ammonia water into a mixed solution of 150mL of ethanol and 20mL of deionized water at 35 ℃, and magnetically stirring for 1h to obtain a transparent precursor solution; quickly adding 11mL of tetraethyl orthosilicate (TEOS) into the precursor solution under vigorous stirring, and standing for 1h to obtain a white suspension; then, 12.5mL tetraethyl orthosilicate (TEOS) and 6mL octadecyltrimethoxysilane (C) were mixed with vigorous stirring₁₈TMOS) is added into the suspension drop by drop, and is kept still for 3 hours at room temperature; centrifuging, drying and roasting the obtained reaction solution, wherein the roasting procedure is as follows: heating from room temperature to 550 ℃ at the speed of 5 ℃/min, preserving heat for 6h, and then cooling to room temperature to obtain a white solid; acidifying the sample with 1M HCl solution at 80 ℃ for 24 h; finally, the core-shell SiO is obtained by centrifugation and drying₂And (5) template.

Example 2: the hollow carbon nitride nanospheres (H-CNS) are prepared by a negative pressure ultrasonic method. The method comprises the following specific steps: 1g of SiO₂The template and 5mL cyanamide were mixed in a pressure bottle connected to a vacuum tube at 60 ℃ in sequencePerforming ultrasonic treatment for 3h, and magnetically stirring for 3h at 80 ℃; the sample was then dried and placed in a tube furnace for calcination, with the following procedure: n is a radical of₂Raising the temperature from room temperature to 550 ℃ at the speed of 5 ℃/min in the atmosphere, preserving the temperature for 2h, and finally cooling to room temperature to obtain a yellow sample; grinding the sample with 4M NH₄HF₂Room temperature treatment for 12h to remove SiO₂A template; centrifuged and washed with distilled water and ethanol and dried at 60 c to give hollow carbon nitride nanospheres (H-CNS).

Example 3: a chemical vapor deposition method is adopted to prepare a phosphorus-doped ultrathin hollow carbon nitride nanosphere (x wt% P/UH-CNS, x is 0-10) catalyst. The method comprises the following specific steps: adding 300mg H-CNS powder, 3mg iodine and a certain amount (1-10 wt%) of purified red phosphorus into a quartz ampoule bottle, vacuumizing and sealing with acetylene flame; then heating the quartz tube to 450 ℃ at the speed of 2 ℃/min, and preserving the heat for 4 h; cooling to 280 ℃ at the speed of 1 ℃/min, and preserving heat for 4 h; then slowly cooling to room temperature at the speed of 0.2 ℃/min; finally, the prepared sample was applied to CS₂Washed with distilled water and ethanol and dried at 60 c to give x wt% P/UH-CNS (x ═ 0-10) catalyst.

The preparation method has the characteristics of simple preparation process, low raw material price, high yield, regular and controllable product morphology and the like, and the 2 wt% P/UH-CNS catalyst prepared by the method shows excellent photocatalytic splitting water hydrogen production activity.