Application of two-dimensional metal phosphorus chalcogenide in production of hydrogen peroxide in seawater

Abstract

The invention discloses an application of a two-dimensional metal phosphorus chalcogenide in production of hydrogen peroxide in seawater. Specifically, the two-dimensional metal phosphorus chalcogenide nanosheet with a specific thickness is prepared through vacuum chemical vapor transport and ultrasonic stripping technologies and is used for producing hydrogen peroxide through efficient electrocatalytic oxygen reduction in seawater. The metal cations comprise magnesium, aluminum, scandium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, palladium, silver, cadmium, indium, tin, mercury and bismuth; the chalcogenide anions comprise sulfur, selenium and tellurium. The nanosheet is good in crystallinity and uniform in thickness. Under the condition of taking seawater as an electrolyte solution, the composite material shows excellent performance of producing hydrogen peroxide through electrocatalytic oxygen reduction, the selectivity of hydrogen peroxide is about 98%, the yield is about 6.0 mol gcat <-1 > h <-1 >, and meanwhile, the composite material shows good stability in a continuous test process for 1000 hours. The compound is simple and universal to prepare and excellent in electrochemical property, and a road is indicated for practical application of production of hydrogen peroxide through electrocatalytic oxygen reduction in seawater.

Description

Technical Field

[0001] The invention relates to the field of nanomaterials and electrocatalysis, and in particular to the application of a two-dimensional metal phosphorus-sulfur compound in producing hydrogen peroxide in seawater. Background Art

[0002] Hydrogen peroxide (H2O2) is a versatile and environmentally friendly oxidant that is widely used in industry, medicine, environmental protection, and chemical synthesis. As one of the 100 most important chemicals, the global demand for H2O2 exceeds 5 million tons per year. Currently, 95% of H2O2 in industry is prepared by anthraquinone oxidation. Although this method is suitable for large-scale production, the production process is complicated, toxic organic reagents are required, and a large amount of hazardous waste is generated. Direct reaction of H2 and O2 to generate H2O2 is a green alternative, but this route requires precious metal catalysts and has low selectivity and yield, and there are huge safety risks. In recent years, the two-electron electrochemical oxygen reduction reaction has attracted much attention as one of the direct routes for the synthesis of H2O2. 2e - ORR uses O2 and H2O as raw materials and electricity as energy source. It does not produce toxic byproducts and is a green, safe and economical H2O2 production route. At present, the research on this process mainly uses fresh water as the electrolyte. Considering that global freshwater resources are limited and seawater resources are significantly abundant (accounting for more than 96% of the total water on Earth), the development of efficient seawater electrocatalytic systems has become one of the most important directions in the field of electrocatalysis. At present, seawater electrocatalytic technology is mainly used for hydrogen and oxygen evolution from water. There are few reports on research in the field of H2O2 synthesis, but it undoubtedly has important theoretical and practical significance. Combining the basic principles of 2e-ORR and the key issues of seawater electrocatalysis, the design of electrocatalysts needs to focus on the following four aspects: (1) rich surface active sites are exposed to provide sufficient reaction centers; (2) directional regulation of electronic structure to optimize the adsorption of reactant O2, the generation and conversion of key intermediates (such as OOH*), and the desorption of the final product (acidic H2O2, alkaline OOH-), thereby improving the selectivity and activity of the reaction; (3) excellent conductivity to ensure rapid electron transfer and high current density during electrocatalysis; (4) the complex composition of seawater, the presence of a large amount of dissolved salts, especially chloride ions, can easily poison the catalyst and reduce the durability of seawater electrosynthesis. Strong salt resistance and corrosion resistance are the basis for maintaining good stability of electrocatalysts, among which how to effectively exclude the adsorption and enrichment of chloride ions on the surface of the electrocatalyst is the key.

[0003] At present, the design and development of seawater 2e-ORR electrocatalysts is in its infancy. In 2021, a research team reported the research work on the catalytic production of H2O2 by 2e-ORR of cobalt atoms under simulated seawater conditions. The H2O2 yield and Faraday efficiency were 3.4 mol g -1h -1 and 80% (Energy Environ. Sci., 2021, 14, 5444-5456). In 2023, a research team reported the research work on nitrogen-doped carbon materials as seawater 2e-ORR electrocatalysts. The yield and Faraday efficiency of H2O2 were 631.2 mmol g -1 h -1 and 79.8% (Adv. Sci., 2023, 10, 2302446). The above work demonstrates the feasibility of electrocatalytic synthesis of H2O2 from seawater. However, the H2O2 yield and Faraday efficiency of the reported electrocatalysts are significantly lower than those of the current electrocatalytic materials in freshwater systems, and there is a lot of room for improvement in catalytic performance. In addition, the above work did not involve research on the catalyst's resistance to chloride ion corrosion and its mechanism, and only tested the stability of the catalyst in a short period of time (≤24 h), making it difficult to evaluate the practical application potential of the catalytic system. Therefore, the development of seawater 2e-ORR electrocatalysts with high activity, selectivity and stability is of great significance, but challenges still exist. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide an application of two-dimensional metal phosphorus sulfide compounds to produce hydrogen peroxide in seawater. Based on vacuum chemical vapor transport and ultrasonic exfoliation technology, two-dimensional metal phosphorus sulfide compound nanosheets with a specific thickness are synthesized. The obtained material can be used as an electrocatalyst for producing hydrogen peroxide in seawater, showing high hydrogen peroxide selectivity (~98%) and yield (6.0 mol g cat -1 h -1 ) and ultra-long term stability (>1000 hours).

[0005] The specific technical scheme for achieving the purpose of the present invention is as follows:

[0006] A use of a two-dimensional metal phosphorus sulfide compound to generate hydrogen peroxide in seawater, wherein the two-dimensional metal phosphorus sulfide compound is a two-dimensional nanosheet having a nanometer-level thickness after exfoliation, and is a two-dimensional nanosheet obtained by vacuum chemical vapor transport and ultrasonic exfoliation technology; a mobile phase gas diffusion electrode device is used to realize the generation of hydrogen peroxide from the two-dimensional metal phosphorus sulfide compound in seawater; the device specifically comprises: a gas diffusion chamber, an anode chamber, an ion exchange membrane, a working electrode, a reference electrode and a counter electrode;

[0007] Carbon paper loaded with two-dimensional metal phosphorus sulfide nanosheets was used as the working electrode, Ag / AgCl as the reference electrode, and platinum sheet as the counter electrode to assemble the mobile phase gas diffusion electrode. The anode and cathode chambers were separated by an ion exchange membrane. Real seawater was used as the electrolyte solution, oxygen as the reactant, and water as the proton. Under constant voltage / constant current conditions, oxygen reduction reaction occurred at the cathode of the electrolytic cell to generate hydrogen peroxide.

[0008] Furthermore, the surface of the two-dimensional nanosheet is relatively flat, with an average thickness of about 5 nanometers. The metal cations include one or more of magnesium, aluminum, scandium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, palladium, silver, cadmium, indium, tin, mercury, and bismuth; the chalcogen anions include one or more of sulfur, selenium, and tellurium.

[0009] Furthermore, the two-dimensional nanosheet has a clear and definite crystal structure and good crystallinity; and has excellent stability under seawater conditions.

[0010] Furthermore, the application requires a two-dimensional metal phosphorus chalcogenide with a specific thickness as a catalyst to ensure that oxygen reduction reacts to generate hydrogen peroxide via a two-electron pathway.

[0011] Furthermore, the generated hydrogen peroxide is quantitatively detected by ultraviolet spectrophotometry, nuclear magnetic resonance hydrogen spectrum and colorimetry.

[0012] The process of preparing the two-dimensional metal phosphorus sulfide compound nanosheets provided by the present invention and applying them to electrosynthesize hydrogen peroxide in seawater comprises the following steps:

[0013] Step 1: weigh the metal element, sulfur powder and red phosphorus in a molar ratio of 1:1:3, with a total mass of 5-10 grams, and mix them thoroughly and evenly by grinding;

[0014] Step 2: Transfer the mixed powder into a quartz tube with a single-side opening and perform vacuum packaging using an oxyhydrogen flame sealing machine;

[0015] Step 3: The obtained quartz tube is heated in a muffle furnace at 650-750° C. for 160-200 hours, and after cooling, a bulk metal phosphorus sulfide compound material is obtained;

[0016] Step 4: taking 100 mg of the obtained bulk metal phosphorus sulfide compound material and dispersing it in 100 ml of ethanol, ultrasonicating it for 24 hours, filtering out the precipitate, and separating the obtained suspension by centrifugation, and washing it to obtain a two-dimensional bulk metal phosphorus sulfide compound nanosheet;

[0017] Step 5: Disperse 10 mg of the obtained two-dimensional metal phosphorus chalcogenide nanosheets in 1 ml of isopropanol and add 40 μl of Nafion membrane solution;

[0018] Step 6: Take 50 μl of the obtained dispersion and evenly apply it on the central area of ​​2 cm×2 cm hydrophobic carbon paper, with a size of 1 square centimeter;

[0019] Step 7: Using carbon paper loaded with two-dimensional metal phosphorus sulfide nanosheet catalyst as working electrode, Ag / AgCl as reference electrode, and platinum sheet as counter electrode, assemble the mobile phase gas diffusion electrode, and separate the anode and cathode chambers with ion exchange membranes. And connect to the electrochemical workstation;

[0020] Step 8: Using the filtered seawater as the electrolyte, the electrolyte is circulated in the reaction chamber by a peristaltic pump to achieve continuous preparation and accumulation of hydrogen peroxide;

[0021] Step 9: Prepare hydrogen peroxide by oxygen reduction reaction using a constant voltage / constant current method, and detect the generated hydrogen peroxide using an ultraviolet spectrophotometer or a nuclear magnetic resonance hydrogen spectrum.

[0022] The advantages of the present invention are:

[0023] Using two-dimensional metal phosphorus chalcogenide nanosheets of specific thickness to produce hydrogen peroxide in seawater;

[0024] The material has a clear structure, high crystallinity and good repeatability;

[0025] It solves the current technical bottleneck of producing hydrogen peroxide in seawater;

[0026] The prepared material has ultra-long-term stability and corrosion resistance in seawater, providing technical support for practical commercial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the application of two-dimensional metal phosphorus sulfide compounds to produce hydrogen peroxide in seawater.

[0028] Figure 2 The SEM and TEM images of the two-dimensional metal phosphorus sulfide nanosheets prepared in the embodiment of the present invention are shown;

[0029] Figure 3 AFM characterization image of two-dimensional metal phosphorus chalcogenide nanosheets;

[0030] Figure 4 Schematic diagram of the test results of electrocatalytic oxygen reduction to produce hydrogen peroxide in seawater. DETAILED DESCRIPTION

[0031] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0032] Example

[0033] The preparation of two-dimensional metal phosphorus chalcogenide nanosheets includes the following steps:

[0034] Step 1: weigh the metal element, sulfur powder and red phosphorus in a molar ratio of 1:1:3, with a total mass of 5 g, and mix them thoroughly and evenly by grinding;

[0035] Step 2: Transfer the mixed powder into a quartz tube with a single-side opening and perform vacuum packaging using an oxyhydrogen flame sealing machine;

[0036] Step 3: The obtained quartz tube is heated at 650° C. in a muffle furnace for 168 hours, and after cooling, a bulk metal phosphorus sulfide compound material is obtained;

[0037] Step 4: taking 100 mg of the obtained bulk metal phosphorus sulfide compound material and dispersing it in 100 ml of ethanol, ultrasonicating it for 24 hours, filtering out the precipitate, and separating the obtained suspension by centrifugation, and washing it to obtain a two-dimensional bulk metal phosphorus sulfide compound nanosheet;

[0038] Step 5: Disperse 10 mg of the obtained two-dimensional metal phosphorus chalcogenide nanosheets in 1 ml of isopropanol and add 40 μl of Nafion membrane solution;

[0039] Step 6: Take 50 μl of the obtained dispersion and evenly apply it on the central area of ​​2 cm×2 cm hydrophobic carbon paper, with a size of 1 square centimeter;

[0040] Step 7: Using carbon paper loaded with two-dimensional metal phosphorus sulfide nanosheet catalyst as working electrode, Ag / AgCl as reference electrode, and platinum sheet as counter electrode, assemble the mobile phase gas diffusion electrode, and separate the anode and cathode chambers with ion exchange membranes. And connect to the electrochemical workstation;

[0041] Step 8: Using the filtered seawater as the electrolyte, the electrolyte is circulated in the reaction chamber by a peristaltic pump to achieve continuous preparation and accumulation of hydrogen peroxide;

[0042] Step 9: Prepare hydrogen peroxide by oxygen reduction reaction using a constant voltage / constant current method, and detect the generated hydrogen peroxide using an ultraviolet spectrophotometer or a nuclear magnetic resonance hydrogen spectrum.

[0043] Characterization of materials:

[0044] The instruments used for characterization are: transmission electron microscope JEOL JEM-2100F; scanning electron microscope Hitachi S-4800; atomic force microscope Dimension 3100; electrochemical workstation CHI600E.

[0045] The characterization results are:

[0046] See also Figure 1 , the application of two-dimensional metal phosphorus chalcogenides to produce hydrogen peroxide in seawater was demonstrated by a mobile phase gas diffusion electrode setup ( Figure 1 a), Actual photo of the installation (( Figure 1 b); seawater is used as the electrolyte, oxygen is used as the reactant, and two-dimensional metal phosphorus sulfide is used as the catalyst. Under the condition of applied voltage, the cathode oxygen reduction reaction occurs to generate hydrogen peroxide (O2 + 2H2O + 2e - → 2OH - + H2O2). The specific components of the device include a gas diffusion chamber, a cathode chamber, an anode chamber, a working electrode, a reference electrode and a counter electrode, wherein the gas diffusion chamber is connected to an oxygen cylinder. The cathode and cathode chambers are separated by an ion exchange membrane. The working electrode is a hydrophobic carbon paper loaded with a two-dimensional metal phosphorus sulfide compound, the reference electrode is an Ag / AgCl electrode, and the counter electrode is a platinum sheet. The circulation of seawater in the reaction chamber is achieved by a peristaltic pump.

[0047] See also Figure 2 , characterized by SEM ( Figure 2 a), we can see the two-dimensional nanosheet structure of the two-dimensional metal phosphorus chalcogenide. Figure 2 b), the lattice fringes of the two-dimensional metal phosphorus chalcogenide can be seen. The results show that the prepared MPS3 nanosheets have a smooth surface and good crystallinity.

[0048] See also Figure 3 , AFM images ( Figure 3 a) and the cross-sectional height of the 2D nanosheet ( Figure 3 b) shows that the thickness of the two-dimensional metal phosphorus chalcogenide nanosheets is uniform, about 5 nanometers.

[0049] See also Figure 4 Electrochemical tests demonstrated the application of two-dimensional metal phosphorus sulfide compounds to produce hydrogen peroxide in seawater. The results showed that the material has high hydrogen peroxide selectivity, with a Faradaic efficiency of about 98% ( Figure 4 a); high hydrogen peroxide yield, about 6.0 mol g cat -1 h -1 ( Figure 4b); and excellent seawater stability, with the current density decaying by only 2% after 1000 hours of continuous testing ( Figure 4 c).

Claims

1. An application of a two-dimensional metal phosphorus sulfide compound to generate hydrogen peroxide in seawater, characterized in that: The two-dimensional metal phosphorus sulfide compound is a two-dimensional nanosheet with a nanometer-level thickness after exfoliation, which is a two-dimensional nanosheet obtained by vacuum chemical vapor transport and ultrasonic exfoliation; a mobile phase gas diffusion electrode device is used to realize the generation of hydrogen peroxide from the two-dimensional metal phosphorus sulfide compound in seawater; the device specifically comprises: a gas diffusion chamber, an anode chamber, an ion exchange membrane, a working electrode, a reference electrode and a counter electrode; Carbon paper loaded with two-dimensional metal phosphorus sulfide nanosheets was used as the working electrode, Ag / AgCl as the reference electrode, and platinum sheet as the counter electrode to assemble the mobile phase gas diffusion electrode. The anode and cathode chambers were separated by an ion exchange membrane. Real seawater was used as the electrolyte solution, oxygen as the reactant, and water as the proton. Under constant voltage / constant current conditions, oxygen reduction reaction occurred at the cathode of the electrolytic cell to generate hydrogen peroxide.

2. The use of the two-dimensional metal phosphorus sulfide compound according to claim 1 to generate hydrogen peroxide in seawater, characterized in that: The two-dimensional nanosheet has a flat surface and a thickness of 3-5 nanometers. The metal cations include one or more of magnesium, aluminum, scandium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, palladium, silver, cadmium, indium, tin, mercury, and bismuth; the chalcogen anions include one or more of sulfur, selenium, and tellurium.

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