阅读说明：本技术 一种硒化钴石墨氮化碳复合材料及其制备方法和应用 (Cobalt selenide graphite carbon nitride composite material and preparation method and application thereof ) 是由 沈锦妮 夏种类 刘旭 徐慧慧 于 2021-10-16 设计创作，主要内容包括：本发明属于光催化材料技术领域,具体涉及一种硒化钴石墨氮化碳复合材料及其制备方法和应用。通过水热形成Co-(0.85)Se,煅烧形成石墨氮化碳(g-C-(3)N-(4))；将Co-(0.85)Se和g-C-(3)N-(4)分散到去离子水中,然后做超声处理,洗涤、干燥,最后通过煅烧得到Co-(0.85)Se/g-C-(3)N-(4)复合材料。本发明通过简单水热超声煅烧合成了硒化钴石墨氮化碳复合光催化材料,制备原材料价格低廉,不含贵金属和污染环境的重金属,用于可见光下高效光催化分解水制氢气,而氢气是高热能、无污染、可再生的能源。(The invention belongs to the technical field of photocatalytic materials, and particularly relates to a cobalt selenide graphite carbon nitride composite material as well as a preparation method and application thereof. Formation of Co by hydrothermal reaction 0.85 Se, calcination to form graphitic carbon nitride (g-C) 3 N 4 ) (ii) a Mixing Co 0.85 Se and g-C 3 N 4 Dispersing in deionized water, ultrasonic treating, washing, drying, and calcining to obtain Co 0.85 Se/g‑C 3 N 4 A composite material. The cobalt selenide graphite carbon nitride composite photocatalytic material is synthesized by simple hydrothermal ultrasonic calcination, the prepared raw materials are low in price, and the material does not contain noble metals and heavy metals polluting the environment, and is used for preparing hydrogen by efficiently decomposing water under visible light through photocatalysis, wherein the hydrogen is high-heat energy, pollution-free and renewable energy.)

1. The preparation method of the cobalt selenide graphite carbon nitride composite material is characterized in that cobalt selenide Co_0.85Se and graphitic carbon nitride g-C₃N₄Dispersing the mixture into deionized water for ultrasonic treatment, washing, drying and finally calcining to obtain Co_0.85Se/g-C₃N₄A composite material.

2. The method for preparing a cobalt selenide graphite carbon nitride composite material as claimed in claim 1, wherein the graphite carbon nitride g-C₃N₄The preparation method comprises the following steps:

(1) putting urea into a ceramic crucible, and then putting the crucible into a muffle furnace for calcining to obtain g-C₃N₄。

3. The method for preparing a cobalt selenide graphite carbon nitride composite material as claimed in claim 2, wherein the graphite carbon nitride g-C₃N₄In the preparation process, the calcining temperature is 550 ℃, the calcining time is 4 h, and the heating rate is 5 ℃/min.

4. The method for preparing cobalt selenide graphite carbon nitride composite material according to claim 1, wherein the cobalt selenide Co_0.85The specific preparation of Se comprises the following steps:

(1) adding a certain amount of cobalt acetate tetrahydrate and sodium selenite into an ethylene glycol solvent, and stirring for 5 minutes;

(2) and carrying out hydrothermal reaction on the solution, cooling, washing, drying and grinding to obtain a sample.

5. The method for preparing the cobalt selenide graphite carbon nitride composite material according to claim 4, wherein the molar ratio of cobalt to selenium elements in the cobalt acetate tetrahydrate and the sodium selenite in the step (1) is 1: 2.

6. The preparation method of the cobalt selenide graphite carbon nitride composite material according to claim 4, wherein the hydrothermal temperature in the step (2) is 200 ℃, the reaction time is 24 hours, and the drying treatment temperature is 60 ℃.

7. The method for preparing a cobalt selenide graphite carbon nitride composite material as claimed in claim 1, wherein the added Co_0.85The mass of Se is g-C₃N₄5-15% of the mass, 8h of ultrasonic time and 400W of ultrasonic power.

8. The method for preparing a cobalt selenide graphite carbon nitride composite material according to claim 1, wherein the calcination time is 2 hours, the temperature rise rate is 3 ℃/min, and the calcination temperature is 320 ℃.

9. A cobalt selenide graphite carbon nitride composite material obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the cobalt selenide graphite carbon nitride composite material of claim 9 in the production of hydrogen by visible light catalyzed decomposition of water.

Technical Field

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a cobalt selenide graphite carbon nitride composite material, a preparation method thereof and an effect of photocatalytic decomposition of water under visible light to produce hydrogen.

Background

In the world, the energy shortage and the environmental problem are becoming more severe, and the development of clean energy is urgently needed. Hydrogen energy is a very good clean energy source, does not produce any pollutant in the consumption process, has high energy density, and is an ideal choice. However, the current situation is that the industrial hydrogen production technology is far from the ideal requirement, and not only the energy consumption is high, but also the efficiency is low. The development of a photocatalytic technology for decomposing water to generate hydrogen by using solar energy is an important way for clean and sustainable hydrogen production, so that the exploration and preparation of a photocatalyst for efficient hydrogen production are particularly important.

In the process of photocatalytic water decomposition by using a semiconductor, when light with energy larger than the forbidden bandwidth is irradiated, photoproduction electron hole pairs are generated, the photoproduction electrons have reducibility, and the photoproduction holes have oxidability. When the conduction band potential of a certain material is respectively higher than H⁺/H₂(0V vs. NHE) minus, ratio H₂O/O₂Oxidation potential of (1.23V) positive, H₂O molecules are reduced to H by electrons₂Is oxidized to O by the cavity₂. However, the single-component photocatalytic material is actually inefficient in producing hydrogen because of the low efficiency of separating electrons and holes. The use of noble metal loading is considered to be one of the effective methods to improve the efficiency of photogenerated electron-hole separation.

But inIn the actual synthesis and preparation, problems such as rare and expensive noble metals used as raw materials, strict and complicated synthesis process conditions, and the generation of substances polluting the environment exist. Chinese patent CN106268874A discloses an Ag/g-C₃N₄The composite film, the preparation method and the application thereof have high raw material cost. Similar studies have been made to improve photocatalytic performance by using noble metals such as Au, Pt and Pd as promoters. There has of course been much research directed to the modification of non-noble metal promoters. Chinese patent CN107715859A discloses a preparation method of a graphene perovskite composite photocatalytic hydrogen production catalyst, nitrate, tetrabutyl titanate and a complexing agent are weighed and dissolved in ethanol, graphene is added and stirred until the mixture becomes dry gel, then organic matter is removed by roasting, and the dried gel is obtained by vacuum calcination, wherein the preparation process is complex, for example, the preparation condition of the graphene is difficult; chinese patent CN108927222A discloses a preparation method of CdS-PAN/graphene composite nano-fibers, which is complex in preparation and harsh in reaction conditions, and relates to heavy metal sulfide CdS, so that the environment is polluted. In addition, most of the existing semiconductor catalysts are only active under ultraviolet light, visible light does not respond, and the main part of sunlight is visible light, so the sunlight utilization efficiency is low.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a cobalt selenide graphite carbon nitride composite material, a preparation method thereof and an effect on photocatalytic decomposition of water to produce hydrogen. The preparation method has simple experimental conditions, mainly adopts a hydrothermal ultrasonic calcination method, does not contain substances such as heavy metals and the like which pollute the environment in the preparation process, and has low price and easy obtainment of the used raw materials.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a cobalt selenide graphite carbon nitride composite material for photocatalytic hydrogen production under visible light comprises the following steps:

(1) adding a certain amount of cobalt acetate tetrahydrate and sodium selenite into an ethylene glycol solvent, and stirring for 5 minutes;

(2) the solution is put into hydrothermal reaction and then cooledWashing and drying to obtain Co_0.85A Se sample;

(3) putting urea into a ceramic crucible and putting the ceramic crucible into a muffle furnace to calcine under the air condition to prepare the graphite carbon nitride g-C₃N₄；

(4) Respectively weighing a certain amount of samples prepared in the step (2) and the step (3), dispersing the samples into deionized water for ultrasonic treatment, and then washing and drying;

(5) calcining the sample obtained in the step (4) in a muffle furnace to prepare Co_0.85Se/g-C₃N₄A composite material.

The molar ratio of cobalt to selenium elements in the cobalt acetate tetrahydrate and the sodium selenite in the step (1) is 1:2, and the selenium element is excessive.

And (3) performing hydrothermal reaction at 200 ℃ for 24 h, and drying in an oven at 60 ℃.

And (3) the calcining temperature is 550 ℃, the heat preservation time is 4 h, and the heating rate is 5 ℃/min.

Co used in the process of the step (4)_0.85The mass of Se is g-C₃N₄5-15% of the mass, 8h of ultrasonic dispersion time and 400W of ultrasonic power.

The calcining temperature in the step (5) is 320 ℃, the heat preservation time is 2 h, and the heating rate is 3 ℃/min.

The application comprises the following steps: the cobalt selenide graphite carbon nitride composite material is applied to preparing hydrogen by decomposing water under the catalysis of visible light.

The invention provides a method for preparing a composite material, which comprises the steps of firstly forming cobalt selenide through hydrothermal treatment, calcining and synthesizing graphite carbon nitride, then dispersing a certain amount of two materials into water, performing ultrasonic treatment, washing, drying, and finally calcining in a muffle furnace to form a composite sample.

The photocatalytic activity of the cobalt selenide graphite carbon nitride composite photocatalytic material is tested by irradiating visible light through a xenon lamp and a 420nm cut-off filter and using triethanolamine as a sacrificial agent to carry out photocatalytic decomposition on water.

The characterization method of the performance of the cobalt selenide graphite carbon nitride composite photocatalytic material comprises the following steps: the product material composition and structure were analyzed by X-ray diffraction (XRD) spectroscopy. The maximum light absorption wavelength of the composite was analyzed with an ultraviolet-visible diffuse reflectance (UV-Vis-DRS) spectrometer.

The invention has the advantages that: the preparation conditions of the composite material are simple, the hydrothermal calcination ultrasonic method is mainly adopted, the cost price of the used raw materials is low, and substances polluting the environment can not be generated in the preparation process.

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

the cobalt selenide graphite carbon nitride composite photocatalytic material is synthesized by a simple hydrothermal calcination and ultrasonic method, and the raw materials for preparing the cobalt selenide graphite carbon nitride composite photocatalytic material are low in price and do not contain precious metals and heavy metals polluting the environment. In the aspect of performance, the light response range is wide, the catalyst can be used for preparing hydrogen by photocatalytic efficient water decomposition under visible light, has high solar energy utilization efficiency compared with most catalysts which can only respond under ultraviolet light, and fully utilizes visible light accounting for a high proportion in solar energy. The prepared hydrogen is a high-heat energy, pollution-free and renewable energy source.

Co_0.85Se/g-C₃N₄The action principle of the composite material for high hydrogen production activity is as follows: g-C₃N₄And Co_0.85Se has a work function of 5.60eV and 5.70eV, respectively, the Fermi level of the former being higher than that of the latter. g-C when both are formed close to the formation interface₃N₄The electrons on the surface will be transferred to Co_0.85Se until the Fermi levels of the Se and the Se are equal to each other to form a Schottky junction, namely Co_0.85Se acts like the noble metal Pt. g-C under illumination₃N₄Excited, a large number of photogenerated electrons will pass from g-C₃N₄Migration to upper Co_0.85Se participates in hydrogen production reaction, so that the effective separation of photo-generated electrons and holes is realized, and the photocatalytic activity is improved. And a single component g-C₃N₄And Co_0.85Se is easy to recombine photoproduction electrons and holes generated during light irradiation, and electrons cannot participate in reaction, so that the hydrogen production activity is very low.

Drawings

FIG. 1 shows the Co obtained by the synthesis method of example 1_0.85XRD spectrum of Se product.

FIG. 2 shows 12% Co obtained by the synthesis method of example 1_0.85Se/g-C₃N₄And g-C₃N₄XRD spectrum of the product.

FIG. 3 shows 12% Co obtained by the synthesis method of example 1_0.85Se/g-C₃N₄UV-Vis-DRS spectrum of the product.

FIG. 4 is a graph showing the hydrogen production effect of the catalyst obtained in example 1.

FIG. 5 shows the Co obtained by the synthesis method of example 1_0.85Se and g-C₃N₄Work function plot of the product.

FIG. 6 is a schematic view of a reactor for photocatalytic water splitting by visible light in example 1.

FIG. 7 is a diagram of a photolytic reaction apparatus according to example 1.

Detailed Description

The invention is further illustrated by the following examples, which are intended to be illustrative only and not limiting.

Example one

Dissolving 152mg of cobalt acetate tetrahydrate and 210mg of sodium selenite in 30ml of ethylene glycol solvent, stirring for 5 minutes, transferring the mixture to a stainless steel autoclave, sealing and maintaining at 200 ℃ for 24 hours, cooling to room temperature, washing the resultant and drying in an oven at 60 ℃ to obtain Co_0.85And (5) Se. Graphitic carbon nitride (g-C)₃N₄) The urea is prepared by putting 10 g of urea into a 30ml crucible and calcining the urea for 4 hours at 550 ℃ in a muffle furnace, wherein the heating rate in the calcining process is 5 ℃/min. Then 6 mg of Co_0.85Se and 50 mg g-C₃N₄Dissolving in 5 ml deionized water, performing ultrasonic treatment for 8h with the ultrasonic power of 400W, washing, drying, calcining in a muffle furnace at 320 ℃ for 2 h under the air condition, wherein the heating rate in the calcining process is 3 ℃/min to obtain 12% Co_0.85Se/g-C₃N₄The target product of (1). Using the same method, a range of composite materials with different proportional contents were obtained.

From Co_0.85The XRD pattern of Se (as shown in figure 1) shows that Co synthesized by the method_0.85Se is consistent with the peak of the standard card and does not contain other impurities. From 12% Co_0.85Se/g-C₃N₄XRD pattern of composite material (FIG. 2), it can be seen that Co synthesized by the method of the above scheme_0.85Se/g-C₃N₄Co in composite materials_0.85The peak of Se also matched that of the standard card, with two peaks at 2 θ =13 ° and 27 ° assigned to g-C₃N₄Higher peak, pure phase g-C₃N₄The peaks of (a) substantially coincide. 12% Co_0.85Se/g-C₃N₄The ultraviolet-visible diffuse reflection spectrogram of the composite material is shown in fig. 3, the maximum absorption wavelength of the composite material is about 435nm according to the spectrogram, and the visible light response proves that the material has hydrogen production activity under visible light. As can be seen from the hydrogen production effect diagram (figure 4) of the obtained photocatalyst, Co_0.85Se and g-C₃N₄Compounding with pure g-C₃N₄Compared with the activity of hydrogen production by photocatalytic water decomposition, the activity of the catalyst is greatly improved when being Co_0.85The activity is highest when the mass ratio of Se is 12%, and the hydrogen production activity under visible light is 226 mu mol g^-1h^-1Much higher than the single component g-C₃N₄Hydrogen production activity (8 mu mol. g)^-1h^-1). Calvin Probe test (FIG. 5) shows g-C₃N₄And Co_0.85Se has a work function of 5.60eV and 5.70eV, respectively, the Fermi level of the former being higher than that of the latter. g-C when both are formed close to the formation interface₃N₄The electrons on the surface will be transferred to Co_0.85Se until the Fermi levels of the Se and the Se are equal to each other to form a Schottky junction, namely Co_0.85Se acts like the noble metal Pt. g-C under illumination₃N₄Excited, a large number of photogenerated electrons will pass from g-C₃N₄Migration to upper Co_0.85Se participates in hydrogen production reaction, so that the effective separation of photo-generated electrons and holes is realized, and the photocatalytic activity is improved. And a single component g-C₃N₄And Co_0.85Se is easy to recombine photoproduction electrons and holes generated during light irradiation, and electrons cannot participate in reaction, so that the hydrogen production activity is very low.

Application example 1

The experiment of photocatalytic water decomposition comprises the following specific steps:

the reaction device for testing the photocatalytic water splitting activity of a series of prepared binary composite material samples is shown in FIG. 6, and the specific operation steps are as follows: 20 mg of catalyst was placed in the reactor (see FIG. 6) followed by 90 ml of deionized water and 10 ml of triethanolamine (triethanolamine as sacrificial agent).

And then connecting the reactor into a photolysis water reaction system by vacuum grease sealing, externally connecting circulating condensate water with the temperature of 5 ℃, and vacuumizing the system by using a vacuum pump of a reaction device shown in figure 7 to ensure that the system does not contain nitrogen and oxygen. And finally, irradiating by using a 300W xenon lamp light source, feeding samples every 1 h, and sending the gas obtained by the reaction to GC-2014C gas chromatography by using argon as a carrier gas to detect the amount of generated hydrogen.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.