Photocatalytic hydrogen production catalyst and preparation method and application thereof
Technical Field
The invention relates to a photocatalytic hydrogen production catalyst, a preparation method and application thereof, which are applied to the field of photocatalytic hydrolysis hydrogen production.
Background
With the development of the times and the progress of the industrial level, the problems of energy shortage and environmental pollution are increasingly highlighted, and the development of clean, green and renewable new energy sources is imperative. At present, solar energy is considered as one of the most promising new energy sources due to its inexhaustible advantages. The utilization efficiency of solar energy is improved, and the method has important strategic significance for changing energy consumption structures. The solar energy is utilized to realize hydrogen production by water photolysis, which is an important way for promoting the economic development of hydrogen energy and solving the environmental and energy crisis. Among numerous methods for producing hydrogen by decomposing water by solar energy, hydrogen production by reducing water through photocatalytic cracking of a semiconductor photocatalytic system has become a focus of attention by virtue of unique advantages.
In recent years, g-C3N4As a novel two-dimensional semiconductor photocatalytic material, the material has great research value and application value in the field of hydrogen production by photocatalytic water splitting due to the advantages of excellent physical characteristics and chemical stability, abundant raw material sources, low price, easy modification, proper energy band structure and the like. However, due to pure g-C3N4Electrons and holes generated under the irradiation of visible light are easy to recombine, and the light absorption efficiency is not high, so that the photocatalytic activity is not high. To increase g-C3N4The photocatalysis performance of the catalyst is improved by adopting the modes of semiconductor compounding, noble metal element doping, specific surface area increasing and the like3N4The photocatalytic performance of the composite material is improved, and some results are obtained. The previous experimental results show that the existing catalyst has limitations in raw material storage and price, production procedures, hydrogen production efficiency and other aspects, and a novel efficient photocatalyst is still yet to be developed.
Disclosure of Invention
In view of the above, the invention aims to provide a photocatalytic hydrogen production catalyst, a preparation method and an application thereof, and the synthesis process is green and simple, easy to operate and low in cost; and synthetic BPOZ/g-C3N4High stability and excellent photocatalytic performance.
The invention provides a BPOZ/g-C3N4Method for preparing material, BPOZ/g-C3N4In the specification, Z is more than or equal to 0 and less than or equal to 0.05; the preparation method comprises the following steps:
(1) mixing red phosphorus powder and boron powder according to a molar ratio of 3:4, fully grinding, heating to 980 ℃ at a heating rate of 8 ℃/min, keeping the temperature for 3 hours, washing with dilute nitric acid, centrifuging, and drying to obtain BPOZ;
(2) BPO (BPO)ZMixing with urea according to the mass ratio of 1:150, grinding, pouring into a crucible, covering with tinfoil, covering, calcining at 550 ℃ for 3h to obtain BPOZ/g-C3N4A composite material.
Further, the heating process in the step (1) is carried out under an argon atmosphere.
Further, the washing process in the step (1) uses dilute nitric acid solution, the volume ratio of nitric acid to deionized water is 1/75, and BPO is poured into the solutionZThe after-stirring washing time was 5 h.
Photocatalytic hydrogen production catalyst BPOZ/g-C3N4Application of catalyst BPO in photocatalytic hydrolysis hydrogen productionZ/g-C3N4Is prepared by the method.
The invention has the beneficial effects that: the recombination of the material provides an effective way for the separation of photon-generated carriers, and the migration efficiency of electrons is improved. The composite material can respond to near infrared light, and the utilization rate of sunlight is improved. The composite material and g-C3N4The research result shows that the hydrogen production efficiency of the composite material is far higher than g-C3N4Has excellent application prospect. And the BPOZ/g-C3N4Low synthesis cost, simple preparation process, strong stability and being beneficial to actual industrial production.
Drawings
FIG. 1 is a BPO of the present inventionZ/g-C3N4Transmission electron micrographs.
FIG. 2 is a BPO of the present inventionZ/g-C3N4, BPOZ And g-C3N4 XRD pattern.
FIG. 3 is a BPO of the present inventionZ/g-C3N4, BPOZ And g-C3N4 The absorption spectrum of (1).
FIG. 4 is a BPO of the present inventionZ/g-C3N4, BPOZ And g-C3N4The hydrogen production efficiency is shown.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments.
BPO in the inventionZ/g-C3N4The composite photocatalyst is synthesized by a solid phase method, and the main process comprises the steps of calcining phosphorus and boron which are used as raw materials to obtain BPOZ;BPOZThermal polymerization with urea to obtain BPOZ/g-C3N4A composite photocatalyst is provided. BPO of the inventionZ/g-C3N4The preparation method of the composite material comprises the following steps: (1) mixing red phosphorus powder and boron powder, fully grinding, heating to 980 ℃ at the temperature rise condition of 8 ℃/min under the argon atmosphere, keeping the temperature for three hours, washing with dilute nitric acid solution, and centrifugally drying to obtain boron phosphide powder. (2) Taking BPOZMixing with urea, grinding, covering with tinfoil, covering with cover, and calcining at 550 deg.C for 3 hr to obtain BPOZ/g-C3N4A composite material.
The molar ratio of the red phosphorus powder to the boron powder is 0.3: 0.4.
The volume ratio of nitric acid to deionized water in the prepared dilute nitric acid solution is 1: 75.
BPOZThe mass ratio of the urea to the urea is 1: 150.
The present invention is further illustrated by the following examples, which are merely illustrative of the process of the present invention and are not intended to limit the scope of the invention.
Example 1 BPOZPreparation of
Mixing and grinding 0.4mol of boron powder and 0.3mol of red phosphorus powder for one hour, pouring the mixture into a crucible, putting the crucible into a tube furnace, introducing argon, heating to 980 ℃ at the heating rate of 8 ℃/min, and keeping the temperature for 3 hours. Grinding to obtain gray black solid, adding 150ml dilute nitric acid solution (nitric acid: water = 1: 75), stirring for 5h, centrifuging, drying, and grinding again to obtain BPOZAnd (3) powder.
Example 2 BPOZ/g-C3N4Preparation of
0.1g of BPOZMixing with 15g urea, grinding for half an hour, pouring into crucible, covering with tinfoil, heating at 550 deg.C for 3 hr, and grindingThen BPO is obtainedZ/g-C3N4(FIG. 1), the product was a grey-green powder.
Example 3 BPOZ/g-C3N4Study of Properties
For BPO prepared in example 2Z/g-C3N4X-ray powder diffraction analysis was performed, and sharp absorption peaks were observed in the XRD spectrum (fig. 2) in the vicinity of 2 θ =27 °, 34 °, 57 °, and 69 °, from which it was judged that the product had a good crystal structure and a high crystallinity. The high crystallinity can improve the catalytic activity of the catalyst, and the compound has better photocatalytic activity.
Example 4 BPOZ/g-C3N4Study of light absorption Properties
For BPO prepared in example 2Z/g-C3N4 Analysis by visible and infrared absorption spectra was performed and the synthesized BPO was seen in the absorption spectra (FIG. 3)Z Compared with the general BP, the red shift shows that the doping of oxygen changes the band gap of the BP, and the utilization of the BP on the spectrum is enhanced. And the pure g-C3N4 is obtained, and the red shift of the compounded material indicates that the band gap of g-C3N4 can be adjusted by compounding the two materials, the band gap of the synthesized material is narrow, the spectrum utilization rate is high, and the hydrogen production performance of the compound by photocatalytic hydrolysis is enhanced.
Example 5 BPOZ/g-C3N4Study of photocatalytic Activity
1.5mgBPOZ/g-C3N4Dispersed in 5mL of methanol-H2O solution (methanol: water = 1: 4) and then added to a 35mL cylindrical reactor and sealed with a rubber septum. The system was degassed by bubbling argon into the dispersion for 30 minutes. The dispersion was sonicated for 5-10 minutes prior to photoreaction. The system was then stirred continuously and irradiated with a filtered wave with a cut-off frequency of 420 nm. Light intensity of about 0.3Wcm-2. The test results show (FIG. 4) that g-C is observed when the lamp is illuminated for 3 hours3N4Has a hydrogen production of about 77.72. mu. mol, BPOZ/g-C3N4Has a hydrogen production of about 120.27. mu. mol, is g-C3N41.55 times of the total weight of the powder. And g-C3N4Compared with the composite materialThe photocatalytic activity of the material is obviously improved.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.