A modified siloxane and its preparation method and loaded noble metal-based electrocatalyst

Abstract

The present invention discloses a modified siloxene, a preparation method thereof, and a loaded noble metal-based electrocatalyst. The preparation method comprises two steps: preparing siloxene by a hydrochloric acid etching CaSi2 method and preparing modified siloxene by a NaBH4 treatment method. The process is simple, convenient, and controllable. The prepared modified siloxene presents a loose, porous flake structure with more abundant defects, which is beneficial to the anchoring and highly dispersed nucleation growth of noble metal particles, and its specific surface area, electrical conductivity, and light absorption capacity are significantly improved. It is suitable for use as a carrier material to develop high-performance noble metal-based electrocatalysts, and has good application prospects in the fields of materials science and electrocatalysis. When the prepared modified siloxene is used as a carrier raw material to prepare the noble metal-based electrocatalyst, no reducing agent or surfactant of the noble metal precursor is added, which simplifies the preparation conditions, reduces pollution, and helps to avoid the problem of active sites being masked due to the use of reducing agents or surfactants, thereby improving the utilization rate of the noble metal.

Description

Technical Field

[0001] The present invention relates to the fields of material science and electrocatalysis, and in particular to a modified siloxane and a preparation method thereof, and a loaded noble metal-based electrocatalyst. Background Art

[0002] With the increasing energy crisis and environmental pollution caused by the use of traditional fossil fuels such as coal and oil, the development of sustainable energy conversion technologies has become urgent for human survival and social development. Hydrogen energy has the advantages of high energy density and zero pollution emissions, making it a promising new clean energy source. Water electrolysis powered by renewable electricity is considered to be an important electrochemical energy conversion technology that is effective, safe, and carbon-free. In order to improve the electrochemical energy conversion efficiency of water electrolysis hydrogen production technology, it is crucial to explore and develop efficient and low-cost hydrogen evolution reaction (HER) electrocatalysts.

[0003] Although significant progress has been made in the research of non-precious metal-based electrocatalysts, precious metal-based materials, represented by platinum, are still considered the most advanced HER electrocatalysts, especially with excellent electrocatalytic activity in acidic media. However, the scarcity and high cost of precious metals seriously restrict their widespread application. Therefore, improving the electrocatalytic utilization of precious metals and developing high-performance precious metal-based electrocatalysts with low precious metal loading remain urgent needs and challenges in the fields of materials science and electrocatalysis, and are of great practical significance for promoting the widespread application of water electrolysis hydrogen production technology.

[0004] Supported noble metal-based catalytic materials have become an important class of heterogeneous catalysts. The noble metals on the support surface can expose more surface atoms, which helps improve the utilization rate of the noble metal and reduce the amount of noble metal used. Therefore, the design and development of effective noble metal support materials is a key research direction in this field, and they offer outstanding advantages in improving the catalytic activity and stability of noble metal-based catalysts. Recently, silicene, as a new type of two-dimensional material, has attracted increasing attention in energy storage materials and other fields due to its unique electronic structure and hydrophilicity. It is expected to be developed as an effective support material for noble metal-based electrocatalysts. However, related research still faces problems such as agglomeration and uneven distribution of noble metal particles, especially platinum particles, which to some extent limit the catalytic activity and stability of silicene-supported noble metal-based electrocatalysts. Modifying the properties of the support plays a key role in regulating the dispersion and stability of the noble metal. Therefore, the modification of silicene materials has great potential for the design and development of high-performance noble metal-based electrocatalysts. Summary of the Invention

[0005] The present invention aims to provide a modified siloxene, a preparation method thereof, and a loaded noble metal-based electrocatalyst. The modified siloxene preparation method provided is simple and can increase the specific surface area and conductivity of the siloxene and enhance its light absorption properties. At the same time, the siloxene can produce more defects, thereby facilitating the anchoring and highly dispersed nucleation growth of noble metal particles on its surface. The noble metal-based electrocatalyst prepared using the modified siloxene as a carrier raw material has good noble metal dispersion, low loading, and excellent hydrogen evolution electrocatalytic activity and stability.

[0006] To achieve the above purpose, the present invention mainly adopts the following technical solutions:

[0007] A modified siloxene having a loose, porous sheet structure and a specific surface area greater than 100 m 2 / g, with abundant oxygen vacancy defects.

[0008] A method for preparing the modified siloxane comprises the following steps:

[0009] 1) Preparation of siloxane: 2 g of calcium silicide (CaSi2) powder was added to 50-1000 mL of concentrated hydrochloric acid under vigorous stirring, and an etching reaction was carried out at -10-30°C for 24-120 hours. The product after the reaction was purified by repeated washing with acetone and water, and then centrifuged and dried to obtain the original siloxane.

[0010] 2) Modification of siloxene: The original siloxene obtained in step 1) is added to 20 to 1000 mL of deionized water and ultrasonically treated for 10 to 60 minutes to form a uniform siloxene dispersion. Subsequently, 1.5 to 75 mL of sodium borohydride (NaBH4) solution is added to the siloxene dispersion, and the mixture is stirred at -10 to 45°C for 1 to 10 hours. The product after the reaction is centrifuged, washed, and dried to obtain modified siloxene.

[0011] Preferably, in step 2), the concentration of the silicone dispersion is 0.1 to 10 mg / mL.

[0012] Preferably, in step 2), the concentration of the sodium borohydride (NaBH4) solution is 0.05 to 2 mol / L.

[0013] A modified siloxene-supported noble metal-based electrocatalyst is prepared by using the modified siloxene obtained by the above preparation method as a carrier raw material.

[0014] Preferably, the noble metal is one or more of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), and rhodium (Rh).

[0015] Preferably, no reducing agent or surfactant of the noble metal precursor is added during the preparation of the noble metal-based electrocatalyst.

[0016] Preferably, the electrocatalyst is a hydrogen evolution reaction electrocatalyst.

[0017] Preferably, the modified siloxane-supported noble metal-based electrocatalyst is prepared by a photochemical method, a room temperature method, or a hydrothermal method.

[0018] Further preferably, the specific process of the photochemical method is: 10 to 100 mg of the modified siloxane obtained by the above preparation method is added to 40 mL of deionized water, ultrasonically treated for 10 to 60 min, and then slowly added with 0.1 to 3 mL of a noble metal precursor solution (10 to 50 mmol / L), and continued ultrasonic treatment for 1 to 20 min, and then stirred under xenon lamp irradiation and a temperature of -10 to 50 ° C for 1 to 12 h. The product after the reaction is centrifuged, washed, and dried to finally obtain a modified siloxane-supported noble metal-based electrocatalyst.

[0019] Further preferably, the specific process of the room temperature method is: adding 10 to 100 mg of the modified siloxane obtained by the above preparation method to 10 mL of a noble metal precursor solution (1 to 20 mmol / L), and then stirring the reaction at room temperature for 1 to 72 hours. After the reaction, the product is centrifuged, washed, and dried to obtain a modified siloxane-supported noble metal-based electrocatalyst.

[0020] Further preferably, the specific process of the hydrothermal method is: 10 to 100 mg of the modified siloxene obtained by the above preparation method is added to 40 mL of deionized water, ultrasonically treated for 10 to 60 minutes, and then slowly added with 0.1 to 5 mL of a noble metal precursor solution (10 to 50 mmol / L), and continued ultrasonic treatment for 1 to 20 minutes. The mixture is then transferred to a high-pressure reactor and reacted at a temperature of 140 to 200 ° C for 2 to 48 hours. The product after the reaction is centrifuged, washed, and dried to obtain a modified siloxene-supported noble metal-based electrocatalyst.

[0021] More preferably, the noble metal precursor is one or more of chloroplatinic acid, potassium chloroplatinate, ammonium chloroplatinate, sodium chloropalladate, potassium chloropalladate, ruthenium trichloride, iridium trichloride, chloroiridic acid, ammonium chlororhodate, or rhodium chloride.

[0022] When the noble metal precursor is chloroplatinic acid, potassium chloroplatinate, or ammonium chloroplatinate, the obtained material is a modified siloxane-supported platinum-based electrocatalyst;

[0023] When the noble metal precursor is sodium chloropalladate or potassium chloropalladate, the obtained material is a modified siloxane-supported palladium-based electrocatalyst;

[0024] When the noble metal precursor is ruthenium trichloride, the obtained material is a modified siloxene-supported ruthenium-based electrocatalyst;

[0025] When the noble metal precursor is iridium trichloride or chloroiridic acid, the obtained material is a modified siloxane-supported iridium-based electrocatalyst;

[0026] When the noble metal precursor is ammonium chlororhodiumate or rhodium chloride, the obtained material is a modified siloxane-supported rhodium-based electrocatalyst.

[0027] The present invention discloses a modified siloxene, its preparation method, and a supported noble metal-based electrocatalyst. The modified siloxene exhibits a loose, porous, thin-sheet structure with a high specific surface area and abundant oxygen vacancy defects. The preparation method involves two steps: preparing the siloxene by hydrochloric acid etching with CaSi2 and then treating it with NaBH4. The process is simple, convenient, and controllable. The prepared modified siloxene can be used as a carrier material to prepare noble metal-based electrocatalysts and exhibits excellent electrocatalytic performance.

[0028] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0029] (1) The preparation process of the modified siloxane material successfully prepared by the present invention is simple, convenient and controllable, and easy to synthesize in batches;

[0030] (2) The modified siloxane material successfully prepared by the present invention has more defects, which is conducive to the anchoring and highly dispersed nucleation growth of precious metal particles. Its specific surface area, conductivity and light absorption capacity are significantly improved. It is suitable for use as a carrier material to develop high-performance precious metal-based electrocatalysts and has good application prospects in the fields of materials science and electrocatalysis.

[0031] (3) When the prepared modified siloxane material is used as a carrier raw material to prepare a noble metal-based electrocatalyst, there is no need to add a reducing agent or surfactant to the noble metal precursor, which can simplify the catalyst preparation reaction conditions, reduce pollution, and help avoid the problem of active sites being masked by the use of reducing agents or surfactants in traditional noble metal synthesis methods, thereby improving the electrocatalytic utilization rate of the noble metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a transmission electron microscopy image of the original siloxane obtained in step 1) of Example 1;

[0033] Figure 2 is a transmission electron microscopy image of the modified siloxane prepared in Example 1;

[0034] Figure 3 is a transmission electron microscopy image of the modified siloxane-supported platinum-based electrocatalyst prepared in Example 2;

[0035] Figure 4 1 and 2 are the LSV polarization curves of the catalysts prepared in Example 2 and the comparative example and the commercial Pt / C catalyst. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below with reference to the embodiments, but the protection scope of the present invention is not limited thereto.

[0037] Example 1

[0038] A method for preparing modified siloxane comprises the following steps:

[0039] 1) Preparation of siloxane: 2 g of CaSi2 powder was added to 200 mL of concentrated hydrochloric acid with vigorous stirring at 0°C for 96 h. The product was washed and purified repeatedly with acetone and water, then centrifuged and dried to obtain the original siloxane.

[0040] 2) Modification of siloxene: 25 mg of the original siloxene obtained in step 1) was added to 40 mL of deionized water and ultrasonically treated for 30 min to form a uniform siloxene dispersion. Subsequently, 3 mL of NaBH4 solution (0.88 mol / L) was added to the siloxene dispersion, and the mixture was stirred at 25°C for 4 h. After the reaction, the product was centrifuged, washed, and dried to obtain modified siloxene. Figure 1 is a transmission electron microscope image of the original siloxane obtained in step 1); Figure 2 Transmission electron microscopy image of the prepared modified siloxane.

[0041] Example 2

[0042] A modified siloxene-supported platinum-based electrocatalyst is prepared using the obtained modified siloxene as a carrier raw material. No reducing agent or surfactant is added in the preparation of the platinum-based electrocatalyst. The modified siloxene-supported platinum-based electrocatalyst is prepared by a photochemical method. The specific process is as follows: 25 mg of the modified siloxene obtained by the above preparation method is added to 40 mL of deionized water, ultrasonically treated for 20 minutes, then slowly added with 0.5 mL of chloroplatinic acid solution (19.3 mmol / L), ultrasonically treated for 10 minutes, and then stirred under xenon lamp irradiation at 0°C for 5 hours. The product after the reaction is centrifuged, washed, and dried to obtain the modified siloxene-supported platinum-based electrocatalyst. Figure 3 Transmission electron microscopy image of the prepared modified siloxane-supported platinum-based electrocatalyst.

[0043] Example 3

[0044] A modified siloxene-supported platinum-based electrocatalyst is prepared using the obtained modified siloxene as a carrier raw material. No reducing agent or surfactant is added in the preparation of the platinum-based electrocatalyst. The modified siloxene-supported platinum-based electrocatalyst is prepared by a room temperature method. The specific process is as follows: 25 mg of the modified siloxene obtained by the above preparation method is added to 10 mL of chloroplatinic acid solution (5 mmol / L), and then stirred at room temperature for 3 hours. After the reaction, the product is centrifuged, washed, and dried to obtain the modified siloxene-supported platinum-based electrocatalyst.

[0045] Example 4

[0046] A modified siloxene-supported platinum-based electrocatalyst is prepared using the obtained modified siloxene as a carrier raw material. No reducing agent or surfactant is added in the preparation of the platinum-based electrocatalyst. The modified siloxene-supported platinum-based electrocatalyst is prepared by a hydrothermal method. The specific process is as follows: 25 mg of the modified siloxene obtained by the above preparation method is added to 40 mL of deionized water, ultrasonically treated for 20 minutes, then slowly added 1.5 mL of chloroplatinic acid solution (19.3 mmol / L), and ultrasonically treated for 10 minutes. The mixed solution is then transferred to a high-pressure reactor, reacted at 180°C for 12 hours, and the product after the reaction is centrifuged, washed, and dried to obtain the modified siloxene-supported platinum-based electrocatalyst.

[0047] Comparative Example

[0048] Preparation of pristine siloxane-supported platinum-based electrocatalyst: 25 mg of unmodified pristine siloxane was added to 40 mL of deionized water and ultrasonically treated for 20 min. Subsequently, 0.5 mL of chloroplatinic acid solution (19.3 mmol / L) was slowly added and ultrasonicated for 10 min. The mixture was then stirred under xenon lamp irradiation and 0°C for 5 h. The product after the reaction was centrifuged, washed, and dried to obtain the pristine siloxane-supported platinum-based electrocatalyst.

[0049] Example 5

[0050] Experiment on the electrocatalytic effect of modified siloxene-supported platinum-based electrocatalyst on hydrogen evolution reaction: The modified siloxene-supported platinum-based electrocatalyst prepared in Example 2 was tested for HER electrocatalytic performance with the original siloxene-supported platinum-based electrocatalyst prepared in the comparative example and the commercial Pt / C catalyst. The test conditions were as follows: a standard three-electrode system was used on a CHI 660D electrochemical workstation (Shanghai Chenhua), with a graphite rod as the auxiliary electrode, a saturated calomel electrode (SCE) as the reference electrode, and a glassy carbon electrode (GCE, 3 mm in diameter) as the working electrode. The glassy carbon electrode was quenched with 7 μL of 5 mg mL -1The catalyst dispersion was modified and the hydrogen evolution electrocatalytic performance was tested in 0.5 M H2SO4 solution saturated with argon. The linear sweep voltammetry (LSV) curve was tested at a sweep rate of 5 mV s -1 . Figure 4 The LSV polarization curves of the catalysts prepared in Example 2 and the comparative example and the commercial Pt / C catalyst are shown.

[0051] The test results show that the modified siloxane-supported platinum-based electrocatalyst has excellent HER electrocatalytic activity at low platinum loading, and can drive 10 mA cm-1 with a low overpotential of only 36 mV. -2 The current density of 10 mA cm-2 is comparable to that of commercial Pt / C catalysts. -2 Compared to the modified siloxene-supported platinum electrocatalyst (with an overpotential of 43 mV at a current density of 1.5 GHz), the electrocatalytic activity and stability of the modified siloxene-supported platinum electrocatalyst were significantly improved. Furthermore, the mass activity of the modified siloxene-supported platinum electrocatalyst was far higher than that of a commercial Pt / C catalyst. Therefore, the modified siloxene obtained by the preparation method proposed in this invention can be used as a support material to effectively improve the utilization rate of precious metals in electrocatalytic reactions, thereby achieving high catalytic performance while reducing the amount of precious metals used.

[0052] The above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Any changes, modifications, combinations, additions, or substitutions made by a person skilled in the art within the spirit and scope of the present invention shall also fall within the scope of protection of the present invention.

Claims

1. A method for preparing modified siloxane, characterized in that: The following steps are involved: 1) Preparation of siloxane: 2 g of calcium silicide (CaSi2) powder was added to 50-1000 mL of concentrated hydrochloric acid under vigorous stirring, and an etching reaction was carried out at -10-30°C for 24-120 hours. The product after the reaction was purified by repeated washing with acetone and water, and then centrifuged and dried to obtain the original siloxane. 2) Modification of siloxene: The original siloxene obtained in step 1) is added to 20 to 1000 mL of deionized water, and ultrasonically treated for 10 to 60 minutes to form a uniform siloxene dispersion. Subsequently, 1.5 to 75 mL of sodium borohydride (NaBH4) solution is added to the siloxene dispersion, and the mixture is stirred at -10 to 45°C for 1 to 10 hours. After the reaction, the product is centrifuged, washed, and dried to obtain a modified siloxene. In the step 2), the concentration of the siloxane dispersion is 0.1 to 10 mg / mL; In the step 2), the concentration of the sodium borohydride (NaBH4) solution is 0.05 to 2 mol / L.

2. A modified siloxane prepared by the preparation method according to claim 1, characterized in that: The modified siloxane presents a loose, porous flake structure with a specific surface area of ​​more than 100 m 2 / g, with abundant oxygen vacancy defects.

3. A modified siloxane-supported noble metal-based electrocatalyst according to claim 2, characterized in that: The noble metal-based electrocatalyst is prepared by using modified siloxane as a carrier raw material.

4. A modified siloxane-supported noble metal-based electrocatalyst according to claim 3, characterized in that: The noble metal is one or more of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), and rhodium (Rh).

5. A modified siloxane-supported noble metal-based electrocatalyst according to claim 4, characterized in that: No additional reducing agent or surfactant of the noble metal precursor is added during the preparation of the noble metal-based electrocatalyst.

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