Purple phosphorus antimony single crystal, preparation method thereof and photocatalytic hydrogen production application thereof

Abstract

The application discloses purple phosphorus antimony single crystal and a preparation method and photocatalytic hydrogen production application thereof, and belongs to the inorganic nanomaterial field.The purple phosphorus antimony single crystal is a monoclinic lattice structure, the lattice constant of which is beta=97.776 degrees; two positions P9 and P21 of phosphorus atoms are partially occupied by antimony atoms. The application first prepares the purple phosphorus antimony single crystal through a gas phase transmission method and first calibrates the crystal structure of the purple phosphorus antimony single crystal through single crystal XRD, and can realize efficient, high-yield and controllable preparation of high-quality purple phosphorus antimony, the method is simple in process and is conducive to large-scale production. The application first discloses the application of the prepared purple phosphorus antimony single crystal as a photocatalytic hydrogen production catalyst, fully utilizes the high crystalline quality and excellent electron band structure of the purple phosphorus antimony, effectively improves the migration efficiency of photoinduced carriers, and promotes the photocatalytic hydrogen production performance and cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of inorganic nanomaterials, specifically relating to a purple phosphorus antimony single crystal, its preparation method, and its application in photocatalytic hydrogen production. Background Technology

[0002] With the continuous consumption of fossil fuels and increasingly severe environmental pollution, finding a new energy source to replace fossil fuels is becoming increasingly important. Hydrogen energy, as a clean, efficient, and sustainable new energy source, has received widespread attention. Hydrogen can be produced through a simple photocatalytic hydrogen evolution reaction, which requires a catalyst to promote the decomposition of water under sunlight. Platinum is an excellent photocatalytic hydrogen production catalyst, but its low abundance and high price make large-scale application difficult. Therefore, developing a highly efficient and sustainable catalyst is a key technology for photocatalytic hydrogen production.

[0003] Phosphorus is one of the most abundant elements on Earth, existing in various allotropes (white phosphorus, red phosphorus, black phosphorus, and purple phosphorus). Amorphous red phosphorus was first demonstrated to possess visible-light photocatalytic hydrogen evolution activity in 2012. Subsequently, black phosphorus was shown to have high visible-light photocatalytic hydrogen evolution activity; however, its instability limits its applications. The novel semiconductor purple phosphorus has been proven to be the most stable phosphorus allotrope, exhibiting excellent performance in anisotropy, mechanical, electrical, and optical properties. Purple phosphorus also demonstrates excellent photocatalytic activity in the hydrogen evolution process. In 2022, Gu and his collaborators first demonstrated that purple phosphorus is an effective photocatalyst for the UV-Vis light-catalyzed hydrogen evolution reaction, exhibiting excellent photocatalytic hydrogen evolution activity under visible light, although its photocatalytic hydrogen production rate and cycling performance are unsatisfactory. Furthermore, purple phosphorus possesses a layer-dependent tunable bandgap, theoretically predicted to have a hole mobility of up to 7000 cm⁻¹. 2 V -1 s -1 The tunability of the optoelectronic properties of semiconductor materials is often achieved through alloying or doping. Substituting antimony atoms into purple phosphorus can further improve its performance in these areas and unlock its potential applications in optoelectronics and nanoelectronics.

[0004] Therefore, by partially replacing phosphorus atoms in purple phosphorus with antimony atoms to overcome the aforementioned shortcomings, it is hoped that the photocatalytic hydrogen production performance of purple phosphorus can be further improved. Currently, due to the lack of methods for preparing single crystals of purple phosphorus and the uncertainty of its structure, there is no experimental research on it or data on its use as a photocatalyst. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a purple phosphorus antimony single crystal, its preparation method and photocatalytic hydrogen production application. For the first time, purple phosphorus antimony single crystal is prepared by gas phase transport method, thereby effectively solving the technical problem that the existing technology cannot produce purple phosphorus antimony single crystal on an industrial scale.

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

[0007] This invention discloses a purple phosphorus antimony single crystal, the elemental composition of which, by mass percentage, consists of 88.8% to 94.4% phosphorus and 5.6% to 11.2% antimony;

[0008] This purple phosphorus antimony single crystal has a monoclinic lattice structure and its lattice constant is . β = 97.776°; two positions of the phosphorus atom, P9 and P21, are partially occupied by antimony atoms.

[0009] Preferably, the structure of the purple phosphorus antimony single crystal is a layered semiconductor, and the microstructure is a rectangular shape with regular edges and a flat surface.

[0010] This invention also discloses a method for preparing the above-mentioned purple phosphorus antimony single crystal, characterized by comprising the following steps:

[0011] 1) Amorphous red phosphorus, metallic antimony and gas phase transport agent are placed in a sealed cavity, and then the sealed cavity is evacuated and sealed to obtain a vacuum-sealed raw material mixture.

[0012] 2) The sealed cavity is placed horizontally in a dual-temperature zone heating device, and the corresponding heating, heat preservation and cooling procedures are performed on the sealed cavity to obtain purple phosphorus antimony single crystal.

[0013] Preferably, in step 1), the molar ratio of the amorphous red phosphorus to metallic antimony is 30:1 to 3:1.

[0014] Preferably, in step 1), the gas-phase transport agent is at least one of SnI4, BiI3, I2, PbI2, Sn, NaI, KI and LiI.

[0015] Preferably, in step 1), the gas-phase transport agent is a mixture of Sn and SnI4, and the molar ratio of Sn to SnI4 is 3:1 to 1:2.

[0016] Preferably, in step 1), the material of the sealing cavity is stainless steel, quartz or corundum; the temperature difference between the high temperature zone and the low temperature zone in the dual temperature zone is 4 to 15°C.

[0017] Preferably, in step 2), the heating and heat preservation treatment of the sealing cavity involves heating the high-temperature area of ​​the sealing cavity to 600-900°C and keeping it warm for 5-30 hours.

[0018] Preferably, in step 2), the cooling adopts a gradient cooling method: in the high temperature zone, the first stage of cooling is carried out at 5-70℃ / hour; when the temperature in the high temperature zone drops to 530-550℃, the second stage of cooling is carried out at 0.27-3.0℃ / hour to 250-450℃; and then the third stage of cooling is carried out at 38-56℃ / hour to room temperature.

[0019] This invention also discloses the application of the above-mentioned purple phosphorus antimony single crystal as a photocatalyst.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention discloses for the first time a purple phosphorus antimony single crystal with a monoclinic lattice structure and a lattice constant of . β = 97.776°, two positions (P9 and P21) of the phosphorus atom are partially occupied by antimony atoms, and the Sb content in the purple phosphorus antimony single crystal is about 5.6 wt%. The microstructure of this single crystal is a layered crystal with regular edges and flat surface.

[0022] This invention is the first to prepare purple antimony phosphorus single crystals by vapor phase transport method and the crystal structure of purple antimony phosphorus single crystals was determined by single crystal XRD for the first time. Furthermore, this method can achieve high-efficiency, high-yield and controllable preparation of high-quality purple antimony phosphorus by systematically controlling the vapor phase transport growth of purple antimony phosphorus single crystals. The method is simple and conducive to large-scale production.

[0023] This invention discloses for the first time the application of the prepared purple phosphorus antimony single crystal as a photocatalytic hydrogen production catalyst. It makes full use of the high crystallinity and excellent electronic band structure of purple phosphorus antimony, effectively improving the migration efficiency of photoinduced charge carriers and promoting the photocatalytic hydrogen production performance and cycle performance. Attached Figure Description

[0024] Figure 1 Images of the obtained antimony phosphorus single crystals; wherein, (a) is an optical image of the antimony phosphorus single crystal in a sealed quartz tube; (b) is an optical image of the antimony phosphorus polycrystal; (c) and (d) are optical images of the antimony phosphorus single crystal;

[0025] Figure 2 SEM images of the three types of black arsenic phosphate single crystals obtained;

[0026] Figure 3 EDS images of the three types of black arsenic phosphorus single crystals obtained;

[0027] Figure 4 A bar chart comparing the hydrogen production rates of purple phosphorus antimony and purple phosphorus as photocatalysts;

[0028] Figure 5 Cyclic curves of hydrogen production rate for purple phosphorus antimony and purple phosphorus as photocatalysts. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings:

[0032] Example 1

[0033] The method for preparing the purple phosphorus antimony single crystal is as follows:

[0034] 470 mg of amorphous red phosphorus, 121 mg of antimony, 10 mg of tin, and 18 mg of tin iodide were placed into quartz tubes (inner diameter 6–8 mm, wall thickness 2 mm, length 12–15 cm). The quartz tubes were then evacuated (vacuum degree below 10 Pa) and sealed. Subsequently, they were placed horizontally in a dual-temperature zone furnace. The high-temperature zone and low-temperature zone of the quartz tube were heated to 650 °C and 640 °C respectively, with a heating time of 8 hours and a holding time of 5 hours. Then, a gradient cooling process was performed, specifically: in the high-temperature zone, the first stage of cooling was carried out at 60 °C / hour; when the temperature in the high-temperature zone dropped to 550 °C, the second stage of cooling was carried out at 1.0 °C / hour to 450 °C; finally, the third stage of cooling was carried out at 56 °C / hour to room temperature, thus obtaining purple phosphorus-antimony single crystals. The single crystal data analysis results are shown in Table 1 below.

[0035] Table 1. Analysis data of purple phosphorus antimony single crystals

[0036]

[0037] The photocatalytic hydrogen evolution reaction was carried out in a quartz cell under UV-Vis irradiation (350 nm–780 nm). A suspension of antimony phosphorus was prepared by ultrasonically exfoliating 10 mg of antimony phosphorus crystals in 50 mL of deionized water for 2 hours. 50 mL of this suspension was mixed with a sacrificial reagent, including 0.2 M ascorbic acid and Pt (1.5 wt%), as a co-catalyst for photocatalytic hydrogen production. The quartz cell used in the reaction was connected to a glass-sealed gas circulation and exhaust system (Labsolar-6a, PERFECTLIGHT, Beijing). A 300 W Xelamp (CEL-PF300-T8) light source was used. Hydrogen generation was detected in real time using an online gas chromatograph with a TCD detector (GC-9720). High-purity argon was used as the carrier gas. The system was evacuated to remove air before the suspension was irradiated. The hydrogen production rate of antimony phosphorus was measured to be 1473 μmol / h. -1 g -1 It maintains similar performance after 4 cycles, exhibiting excellent hydrogen production rate and cycle stability.

[0038] See Figures 1 to 3 The image shows the single-crystal structure of the purple phosphorus antimony obtained in this embodiment. The layered structure and good crystal quality of the purple phosphorus antimony are easily observed from optical and SEM images. The uniform substitution of antimony atoms in the purple phosphorus antimony... Figure 3 As can be seen from the corresponding elemental mapping analysis, phosphorus and antimony are uniformly distributed.

[0039] See Figures 4 to 5 The results show the photocatalytic hydrogen evolution performance of antimony phosphorus. It can be seen that the photocatalyst prepared in this invention has significantly better catalytic performance than the antimony crystal before antimony atom substitution, indicating that the single crystal structure of antimony phosphorus has significantly improved photocatalytic activity and photocatalytic cycle stability.

[0040] Example 2

[0041] 350 mg of amorphous red phosphorus, 590 mg of antimony, 13 mg of tin, and 21 mg of tin iodide were placed into a quartz tube (8 mm inner diameter, 2 mm wall thickness, 15 cm length). The quartz tube was then evacuated (vacuum degree below 10 Pa) and sealed. It was then placed horizontally in a dual-temperature zone furnace. The high-temperature zone and low-temperature zone of the quartz tube were heated to 680 °C and 700 °C respectively, with a heating time of 8 hours and a holding time of 5 hours. A gradient cooling process was then performed, specifically: in the high-temperature zone, the first stage of cooling was carried out at 60 °C / hour; when the temperature in the high-temperature zone dropped to 550 °C, it was held for 30 hours, followed by a second stage of cooling at 7.0 °C / hour to room temperature, thus obtaining purple phosphorus-antimony single crystals.

[0042] The photocatalytic hydrogen evolution reaction was carried out in a quartz cell under UV-Vis irradiation (350nm–780nm). A suspension of antimony phosphorus was prepared by ultrasonically exfoliating 10mg of antimony phosphorus crystals in 50mL of deionized water for 2 hours. 50mL of this suspension was mixed with a sacrificial reagent, including 0.1M ascorbic acid and Pt (1wt%) as a co-catalyst, for photocatalytic hydrogen production. The quartz cell used in the reaction was connected to a glass-sealed gas circulation and exhaust system (Labsolar-6a, PERFECTLIGHT, Beijing). A 300W Xelamp (CEL-PF300-T8) light source was used. Hydrogen generation was detected in real time using an online gas chromatograph with a TCD detector (GC-9720). High-purity argon was used as the carrier gas. The system was evacuated to remove air before the suspension was irradiated. The hydrogen production rate of antimony phosphorus was measured to be 1320 μmol / h. -1 g -1 It maintains similar performance after 4 cycles, exhibiting excellent hydrogen production rate and cycle stability.

[0043] Example 3

[0044] 500 mg of amorphous red phosphorus, 60 mg of antimony, 11 mg of tin, and 20 mg of tin iodide were placed into quartz tubes (8 mm inner diameter, 2 mm wall thickness, 15 cm length). The quartz tubes were then evacuated (vacuum degree below 10 Pa) and sealed. They were then placed horizontally in a dual-temperature zone furnace. The high-temperature zone and low-temperature zone of the quartz tube were heated to 800 °C and 780 °C respectively, with a heating time of 8 hours and a holding time of 5 hours. A gradient cooling process was then performed, specifically: in the high-temperature zone, the first stage of cooling was carried out at 60 °C / hour; when the temperature in the high-temperature zone dropped to 550 °C, it was held for 30 hours, followed by a second stage of cooling at 2.0 °C / hour to 250 °C, and finally cooling to room temperature at 20.0 °C / hour, thus obtaining purple phosphorus-antimony single crystals.

[0045] The photocatalytic hydrogen evolution reaction was carried out in a quartz cell under UV-Vis irradiation (350nm–780nm). A suspension of antimony phosphorus was prepared by ultrasonically exfoliating 10mg of antimony phosphorus crystals in 50mL of deionized water for 2 hours. 50mL of this suspension was mixed with a sacrificial reagent, including 0.2M ascorbic acid and Pt (2wt%) as a co-catalyst, for photocatalytic hydrogen production. The quartz cell used in the reaction was connected to a glass-sealed gas circulation and exhaust system (Labsolar-6a, PERFECTLIGHT, Beijing). A 300W Xelamp (CEL-PF300-T8) light source was used. Hydrogen generation was detected in real time using an online gas chromatograph with a TCD detector (GC-9720). High-purity argon was used as the carrier gas. The system was evacuated to remove air before the suspension was irradiated. The hydrogen production rate of antimony phosphorus was measured to be 1522 μmol / h. -1 g -1 It maintains similar performance after 4 cycles, exhibiting excellent hydrogen production rate and cycle stability.

[0046] Example 4

[0047] 450 mg of amorphous red phosphorus, 121 mg of antimony, 12 mg of tin, and 21 mg of tin iodide were placed into quartz tubes (8 mm inner diameter, 2 mm wall thickness, 15 cm length). The quartz tubes were then evacuated (vacuum degree below 10 Pa) and sealed. They were then placed horizontally in a dual-temperature zone furnace. The high-temperature zone and low-temperature zone of the quartz tube were heated to 650 °C and 640 °C respectively, with a heating time of 6 hours and a holding time of 5 hours. A gradient cooling process was then performed, specifically: in the high-temperature zone, the first stage of cooling was carried out at 60 °C / hour; when the temperature in the high-temperature zone dropped to 550 °C, the second stage of cooling was carried out at 0.5 °C / hour to 450 °C; finally, the temperature was lowered to room temperature at 50.0 °C / hour, thus obtaining purple phosphorus-antimony single crystals.

[0048] The photocatalytic hydrogen evolution reaction was carried out in a quartz cell under UV-Vis irradiation (350 nm–780 nm). A suspension of antimony phosphorus was prepared by ultrasonically exfoliating 10 mg of antimony phosphorus crystals in 50 mL of deionized water for 2 hours. 50 mL of this suspension was mixed with a sacrificial reagent, including 0.2 M ascorbic acid and Pt (3 wt%) as a co-catalyst, for photocatalytic hydrogen production. The quartz cell used in the reaction was connected to a glass-sealed gas circulation and exhaust system (Labsolar-6a, PERFECTLIGHT, Beijing). A 300 W Xelamp (CEL-PF300-T8) light source was used. Hydrogen generation was detected in real time using an online gas chromatograph with a TCD detector (GC-9720). High-purity argon was used as the carrier gas. The system was evacuated to remove air before the suspension was irradiated. The hydrogen production rate of antimony phosphorus was measured to be 1302 μmol / h. -1 g -1 .

[0049] In summary, the purple phosphorus-antimony single crystal prepared by this invention successfully altered the band structure of purple phosphorus by partially substituting antimony atoms, effectively improving its photocatalytic hydrogen production performance. The photocatalytic hydrogen production performance of the purple phosphorus-antimony single crystal is superior to that of purple phosphorus. The hydrogen evolution rate of the purple phosphorus-antimony single crystal is 1473 μmol / h. -1 g -1 Under the same conditions, purple phosphorus (299 μmol h) -1 g -1 Nearly five times that of the original, purple phosphorus antimony single crystal significantly improves the suppression of photogenerated carrier recombination, reduces transfer resistance, and increases the adsorption free energy of hydrogen atoms, thus exhibiting excellent photocatalytic hydrogen production performance.

[0050] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing purple phosphorus antimony single crystals, characterized in that, Includes the following steps: 1) Amorphous red phosphorus, metallic antimony, and a gas-phase transport agent are placed in a sealed cavity, and then the sealed cavity is evacuated to a vacuum degree below 10 Pa and sealed to obtain a vacuum-sealed raw material mixture; the molar ratio of amorphous red phosphorus to metallic antimony is 30:1 to 3:1; the gas-phase transport agent is a mixture of Sn and SnI4, and the molar ratio of Sn to SnI4 is 3:1 to 1:2; 2) The sealed cavity is placed horizontally in a dual-temperature zone heating device, and the corresponding heating, heat preservation and cooling procedures are performed on the sealed cavity to obtain purple phosphorus antimony single crystals; The temperature difference between the high-temperature zone and the low-temperature zone in the dual-temperature zone is 4~15℃; the heating and heat preservation treatment of the sealed cavity involves heating the high-temperature zone of the sealed cavity to 600~900℃ and holding it for 5~30 hours; the cooling adopts a gradient cooling method: in the high-temperature zone, the first stage of cooling is carried out at 5~70℃ / hour, when the temperature of the high-temperature zone drops to 530~550℃, the second stage of cooling is carried out at 0.27~3.0℃ / hour to 250~450℃, and then the third stage of cooling is carried out at 38~56℃ / hour to room temperature.

2. The method for preparing purple phosphorus antimony single crystals according to claim 1, characterized in that, In step 1), the material of the sealing cavity is stainless steel, quartz or corundum.

3. The purple phosphorus-antimony single crystal prepared by the method described in claim 1 or 2, characterized in that, The elemental composition of this purple phosphorus antimony single crystal, by mass percentage, consists of 88.8%~94.4% phosphorus and 5.6%~11.2% antimony; The purple phosphorus antimony single crystal has a monoclinic lattice structure with lattice constants a=9.210 Å, b=9.128 Å, c=21.893 Å, and β=97.776°; two positions of phosphorus atom, P9 and P21, are partially occupied by antimony atoms.

4. The purple phosphorus antimony single crystal according to claim 3, characterized in that, The structure of this purple phosphorus antimony single crystal is a layered semiconductor, with a microstructure consisting of rectangular shapes with regular edges and a flat surface.

5. The application of the purple phosphorus antimony single crystal as a photocatalyst as described in claim 3 or 4.

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