Method for hydrogen production by catalytic water decomposition by near-infrared laser irradiation of fe3o4 based on plasma phenomena

Abstract

The application discloses a method for preparing hydrogen by catalytic water decomposition of Fe3O4 under near-infrared laser irradiation based on a plasma phenomenon, and is characterized in that Fe3O4 is used as a catalyst, a plasma is generated by irradiating Fe3O4 with near-infrared laser in a water vapor environment, and water vapor is decomposed to generate hydrogen under the action of the plasma. The method can solve the problems of cost and catalyst stability in green hydrogen preparation, and is expected to be applied in the green hydrogen preparation industry on a large scale.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for catalytic water decomposition to produce hydrogen. BACKGROUND

[0002] With the increasing development of industry and technology, the huge energy demand has become an important problem concerning the future development of mankind. Traditional fossil energy represented by oil, coal, natural gas and combustible ice has the shortcomings of being unsustainable and seriously polluting, and the world urgently needs to develop a new energy source to replace fossil energy. Renewable energy such as wind energy, hydro energy, geothermal energy and biomass energy can be produced continuously, but the total amount accounts for only a small proportion of the current energy consumption of mankind, which is not enough to completely solve the future energy problem of mankind. Nuclear energy cannot solve the technical problem of controllable nuclear fusion in the foreseeable future. Hydrogen energy, as an energy being developed, has an inexhaustible source of water, and its oxidation product is only water, without pollution and greenhouse gas carbon dioxide, which can be used as one of the ideal energy carriers in the future. The current hydrogen energy technology route is mainly divided into gray hydrogen, blue hydrogen and green hydrogen. Gray hydrogen refers to hydrogen produced by methane reforming (SMR) or coal gasification, which produces carbon dioxide in the process, and gray hydrogen accounts for about 95% of the global hydrogen production today. Blue hydrogen refers to hydrogen produced by combining carbon capture and storage technology (CCS) based on gray hydrogen. Green hydrogen refers to hydrogen produced by water decomposition reaction using renewable energy, which does not produce carbon dioxide in the hydrogen production process, and is also called "zero-carbon hydrogen", which is the most ideal source of hydrogen energy in the future. However, the current green hydrogen preparation method usually needs to use noble metal-containing electrode materials as electrodes to electrolyze water, which not only has very high cost and cannot be applied on a large scale, but also has problems such as agglomeration, maturation and falling off of special catalysts during use, which seriously hinders the development of green hydrogen technology.

[0003] Fe3O4 is a cheap transition metal oxide with an inverse spinel structure, which is stable in structure and has good light response ability and photothermal effect. The synthesis method is mature, such as coprecipitation method, oxidation precipitation method and reduction precipitation method, etc. Different morphologies and sizes of products can be obtained by controlling the conditions. The intrinsic Fe3O4 (i.e. Fe3O4 without modification such as compounding and doping) has no photocatalytic water decomposition activity and can be used as a catalyst for two-step thermal catalytic water decomposition (Nakamura, T. (1977). "Hydrogen production from water utilizing solar heat at high temperatures." Solar Energy 19(5): 467-475.), the principle of which is that Fe3O4 decomposes oxygen at high temperature (Fe3O4→ Fe3O4-x In the second step, after oxygen release, Fe3O4 reacts with water vapor at a lower temperature to reduce the water vapor and generate hydrogen (Fe3O4 + x / 2O2). 4-x +xH2O→Fe3O4+xH2); Alternatively, solar energy can be used as a heat source to heat Fe3O4 for two-step catalytic water splitting (Steinfeld, A., et al. (1999). "Design aspects of solar thermochamical engineering-A case study: Two-step water-splitting cycle using the Fe3O4 / FeOredox system." Solar Energy 65(1):43-53.), the principle of which is the same as the former. This two-step thermocatalytic water splitting has two problems: first, the heating device is relatively complex and needs to be heated to a very high temperature; second, the two-step method needs to switch between different temperatures, which will cause a large amount of energy waste.

[0004] This invention discovers that the plasma phenomenon of Fe3O4 under laser irradiation can be used for water splitting. Using this inexpensive material as a catalyst to split water and obtain green hydrogen is a direction that needs to be studied now and in the future. Summary of the Invention

[0005] Based on the shortcomings of the existing technologies, this invention proposes a method for producing hydrogen by near-infrared laser irradiation of Fe3O4 catalytic water splitting based on plasma phenomena. This method does not require complex high-temperature heating equipment and is a one-step reaction that does not require switching between two different temperatures. It also solves the problems of cost, catalyst stability, and energy waste in green hydrogen production and is expected to be widely used in the green hydrogen production industry.

[0006] To achieve its objectives, the present invention employs the following technical solution:

[0007] A method for hydrogen production by near-infrared laser irradiation of Fe3O4 catalyzing water splitting based on plasma phenomena is characterized by: using Fe3O4 as a catalyst, in a water vapor environment, near-infrared laser irradiation of Fe3O4 generates plasma. The plasma contains a large number of high-energy positive and negative ions / electrons. These ions / electrons can respectively induce oxidation of oxygen in water molecules and reduction of hydrogen, causing water vapor to decompose under the action of the plasma to produce hydrogen and oxygen. In this invention, water molecules are directly decomposed into hydrogen and oxygen under the action of high-energy positive and negative ions / electrons in the plasma, avoiding the problems existing in the two-step thermocatalytic water splitting method.

[0008] Furthermore, the near-infrared laser includes all wavelengths capable of generating plasma from Fe3O4, preferably in the range of 780-2500 nm.

[0009] Compared with traditional green hydrogen preparation technologies, the beneficial effects of this invention are as follows:

[0010] This invention avoids the use of precious metals, offering a significant cost advantage. It also prevents problems such as agglomeration, aging, and detachment of precious metals from the substrate material, greatly improving the stability of the hydrogen production process. Furthermore, since it eliminates the need for complex electrolysis equipment and high-temperature heating equipment, it is more suitable for large-scale industrial applications. Attached Figure Description

[0011] Figure 1 This is a TEM image of Fe3O4 prepared in Example 1 of the present invention.

[0012] Figure 2 This is a powder X-ray diffraction pattern of Fe3O4 prepared in Example 1 of the present invention.

[0013] Figure 3 This is a diagram of the experimental setup used in Embodiment 1 of the present invention.

[0014] Figure 4 This refers to the plasma phenomenon generated by laser irradiation of Fe3O4 in Embodiment 1 of the present invention.

[0015] Figure 5 This is a graph showing the hydrogen production performance of Example 1 of the present invention. Detailed Implementation

[0016] The present invention will be further illustrated below through specific embodiments, which can provide a more comprehensive understanding of the present invention. However, these embodiments do not represent or limit the scope of protection of the present invention, nor do they limit the content of the present invention in any way.

[0017] Example 1

[0018] This embodiment provides a method for hydrogen production by water splitting under laser catalysis using Fe3O4 as a catalyst. The specific steps are as follows:

[0019] Fe3O4 was prepared by hydrothermal oxidation precipitation: 0.834 g FeSO4·5H2O and 0.292 g KOH were dissolved in 5.2 mL of deionized water, poured into a polytetrafluoroethylene hydrothermal reactor, heated to 50 °C, and kept at that temperature for 0.5 h. Then, 0.21 g KOH was added, heated to 80 °C, and kept at that temperature for 0.5 h. The hydrothermal reactor was then placed in a stainless steel jacket, heated to 110 °C, and kept at that temperature for 4 h. After cooling, the product was washed three times with deionized water and dried under vacuum at 80 °C to obtain Fe3O4.

[0020] 100 mg of Fe3O4 synthesized by the oxidation-precipitation method was first pressed into 1 cm diameter discs using a hydraulic press, then compacted using a cold isostatic press. The discs were then placed in a quartz sample holder (2 cm diameter, 1.5 cm inner diameter, 0.8 cm high) with quartz glass sidewalls and quartz sand bottom to allow water vapor permeation. The quartz sample holder was placed obliquely in the center of a 30 mL quartz bottle, with 5 mL of water added to the bottom, ensuring the water did not contact the sample. The bottle was sealed with a rubber stopper, and the bottom was heated to 110 °C to generate water vapor. Once the temperature was reached, the Fe3O4 sample was vertically irradiated with a 4 W 808 nm near-infrared laser. Obvious plasma phenomena were observed at the laser irradiation site, indicating that water vapor began to react on the catalyst surface at the laser irradiation point. After a period of reaction, 500 μL of product gas was extracted using a syringe and injected into a GC. The hydrogen signal was detected using a TCD detector.

[0021] Figure 1 The TEM image of Fe3O4 prepared in this embodiment shows that the product has a spherical particle morphology with a diameter of about 20-30 nm.

[0022] Figure 2 The X-ray powder diffraction pattern of Fe3O4 obtained in this embodiment is completely consistent with the standard card.

[0023] Figure 3 The diagram shows the experimental setup used in this embodiment. The bottom of the container is filled with deionized water, and the bottom is heated to generate water vapor. The water vapor reacts at the laser irradiation point on the catalyst surface.

[0024] Figure 4 The yellow plasma phenomenon observed when Fe3O4 is irradiated by a near-infrared laser through a filter (which filters out the red light of the laser beam that guides the laser beam) is shown in the demonstration. This invention utilizes this high-energy plasma for water splitting.

[0025] Figure 5 The figure shows a two-cycle diagram of hydrogen production performance. As can be seen from the figure, the hydrogen production rate in the method of the present invention can reach 6 mmol / g·h.

[0026] Although the present invention has been described in detail above with specific implementation schemes, those skilled in the art can make some modifications or improvements based on the present invention. All similar substitutions or improvements made on the basis of the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A method for hydrogen production by near-infrared laser irradiation of Fe3O4 catalyzing water splitting based on plasma phenomena, characterized in that: Using Fe3O4 as a catalyst, plasma is generated by irradiating Fe3O4 with a near-infrared laser in a water vapor environment. The water vapor decomposes under the action of the plasma to produce hydrogen.

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