Application of NbSixTe2 (x= 0.33, 0.40, 0.43, 0.50) crystal as electrocatalytic material

Abstract

The invention discloses an application of an NbSixTe2 (x = 0.33, 0.40, 0.43 or 0.50) crystal as an electro-catalytic material. The crystal is in a sheet shape, has metallic luster and is about millimeter-scale in size. The NbSixTe2 crystal can be regarded as an atomic layer which is formed by alternately arranging and splicing Nb2SiTe4 chains along a b axis and NbTe2 chains containing silicon Si defects along an a axis, and the atomic layer is stacked after rotating along a c axis by 180 degrees, and the chemical formula of the NbSixTe2 crystal can also be written as (Nb2SiTe4) n (NbTe2) (n = 1, 2, 3, infinity). The crystal has a special defect chain structure and a unique topological electronic state and shows excellent electro-catalytic performance, the overpotential can reach eta-10 = 67.38 mV, and the Tafel slope can reach 56.82 mV / dec. The NbSixTe2 electro-catalytic material disclosed by the invention has the advantages of low cost, simplicity in preparation, excellent catalytic performance and the like, has a huge application prospect in the field of catalysis, and is expected to be used for industrial production.

Description

Technical Field

[0001] This invention relates to an electrocatalytic material, and more particularly to a NbSi... x Applications of Te2 (x = 0.33, 0.40, 0.43, 0.50) crystals as electrocatalytic materials. Background Technology

[0002] With the continuous development of society and the economy, the reserves of traditional energy sources, represented by fossil fuels such as oil and coal, are gradually becoming insufficient to meet the energy demands of social production. At the same time, the high pollution and low conversion rate of traditional energy sources also cause environmental pollution and ecological problems. Developing green, clean, and renewable energy sources is an effective means to address the ever-increasing energy demand and environmental issues. Hydrogen energy has advantages such as high calorific value and zero waste during combustion. Electrolysis of water is a common method for hydrogen production; lowering the activation energy of the reaction through catalysts can significantly improve the energy utilization efficiency of the hydrogen production process. Noble metal catalysts such as Ir and Pt have excellent electrocatalytic activity, but their large-scale use is limited by the high cost of raw materials. Therefore, it is necessary to develop a new type of catalyst with high catalytic activity and low cost. Some researchers have attempted to replace noble metal catalysts by synthesizing non-noble metal catalysts, multi-element alloy electrode catalysts, carbide-based composite electrocatalysts, or metal-doped carbon-based catalysts. However, these catalysts still face certain technical bottlenecks in terms of preparation processes, catalytic efficiency, manufacturing costs, and industrial production. In these studies, topological catalysts, due to their unique topological band structure and nontrivial topological surface electronic states, exhibit excellent reaction stability under impurities, environmental interference, and harsh reaction conditions. Furthermore, the high mobility of the topological surface electronic states ensures efficient charge transport during the reaction, effectively promoting the catalytic reaction process and giving them broad application prospects in the field of catalysis. However, the preparation process of topological catalysts is complex, and the preparation cost is difficult to control. Moreover, the catalytic performance of non-noble metal-based topological catalysts still lags behind that of mainstream noble metal catalysts. Therefore, finding a topological material with a simple preparation process, low cost, and excellent catalytic activity is the future direction for the development of topological catalysts. Summary of the Invention

[0003] Purpose of the Invention: The purpose of this invention is to improve the catalytic performance of electrochemical catalysts in water electrolysis for hydrogen production, while reducing the catalyst preparation cost and simplifying the preparation process, by providing an electrocatalytic material NbSi. x Te2 crystals.

[0004] Technical solution: The NbSi described in this invention x The application of Te2 (x = 0.33, 0.40, 0.43, 0.50) crystals as electrocatalytic materials, wherein the crystals are plate-like, have a metallic luster, and are approximately millimeter in size; NbSi xThe Te2 crystal structure is considered as the atomic layers formed by the Nb2SiTe4 chains along the b axis and the NbTe2 chains containing Si defects along the a axis alternately arranged and spliced, and then stacked after rotating 180° along the c axis, and the chemical formula can also be written as (Nb2SiTe4) n (NbTe2)(n = 1, 2,

[0005] 3, ∞), respectively corresponding to x = 0.33, 0.40, 0.43, 0.50.

[0006] Further, the NbSi x The Te2 crystal is grown by a chemical vapor transport method using I2, Br2, TeI4, TeBr4 or TeCl4 as a transport agent, and a vacuum sealed quartz tube as a growth container, in a temperature range of 800-900℃ (growth end) and 900-1000℃ (raw material end).

[0007] Further, the NbSi x The Te2 electrocatalytic material is placed in an electrolyte after being fixed by silver glue, and catalyzes the electrolysis of water to produce hydrogen.

[0008] Further, the NbSi x Catalytic performance of the Te2 crystal in the electrocatalytic production of hydrogen: in a 1M KOH solution, the x = 0.5 (NbSi 0.5 Te2) component, the overpotential is about 87.15mV, and the Tafel slope is about 101.27mV / dec;

[0009] x = 0.43 (NbSi 0.43 Te2) component, the overpotential is about 67.38mV, and the Tafel slope is about 56.82mV / dec;

[0010] x = 0.40 (NbSi 0.40 Te2) component, the overpotential is about 81.55mV, and the Tafel slope is about 65.93mV / dec;

[0011] x = 0.33 (NbSi 0.33 Te2) component, the overpotential is about 132.35mV, and the Tafel slope is about 204.82mV / dec.

[0012] As for the mechanism of the NbSi x Te2 as an electrocatalyst. The NbSi xTe2 (x=0.33, 0.40, 0.43, 0.50) is a typical layered tellurium compound. From the structure, this series of materials can be regarded as the Nb2SiTe4 chain along the b axis and the NbTe2 chain containing silicon Si defects along the a axis alternately arranged and spliced to form the atomic layer along the c axis after rotating 180°. Therefore, their chemical formula can also be written as (Nb2SiTe4)n(NbTe2) (n=1, 2, 3, ∞), corresponding to x=0.33, 0.40, 0.43, 0.50 respectively. These controllable defect chains (NbTe2 metal chains lacking Si), can act as catalytic reaction active centers, making NbSi x Te2 has potential good catalytic performance. At the same time, these defect chains also have special topological electronic states, showing high carrier mobility, which can further improve the catalytic efficiency of NbSi x Te2, making it expected to perform well in the field of electrocatalysis.

[0013] Beneficial effects: compared with the prior art, the present application has the following remarkable advantages: 1, NbSi x Te2 electrochemical catalyst has good catalytic performance for hydrogen evolution reaction in weak alkaline environment, and the catalytic performance is stable; 2, the preparation process is simple, the production cost is low, and the stability is good; 3, after being fixed with silver glue, it can be placed in the electrolyte of the electrochemical workstation as a catalyst, which is low in price, simple in process, good in catalytic stability, easy to use and easy to popularize; 4, the catalyst NbSi x Te2 crystal shows excellent catalytic performance: the overpotential η -2 of the current density is 10 mA cm -10 -2, the overpotential η -1 is 87.15 mV (x=0.50), 67.38 mV (x=0.43), 81.55 mV (x=0.40) and 132.35 mV (x=0.33) respectively; the Tafel slope is 101.27 mV dec -1 (x=0.50), 56.82 mV dec -1 (x=0.43), 65.93 mV dec -1 (x=0.40) and 204.82 mV dec 0.33 (x=0.33) respectively. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The present application is an embodiment 1 NbSi 0.33 Te2 (a) XRD spectrum and crystal photo map, (b) EDS spectrum, (c) electrolytic water hydrogen evolution reaction linear sweep voltammetry curve, (d) Tafel slope curve structure schematic diagram;

[0015] Figure 2 Example 2NbSi of the present invention 0.40 (a) XRD pattern and crystal photograph of Te2, (b) EDS pattern, (c) linear sweep voltammetric curve of hydrogen evolution reaction by water electrolysis, and (d) structural schematic diagram of Tafel slope curve.

[0016] Figure 3 Example 1 of the present invention, NbSi 0.43 (a) XRD pattern and crystal photograph of Te2, (b) EDS pattern, (c) linear sweep voltammetric curve of hydrogen evolution reaction by water electrolysis, and (d) structural schematic diagram of Tafel slope curve.

[0017] Figure 4 Example 1 of the present invention, NbSi 0.50 (a) XRD pattern and crystal photograph of Te2, (b) EDS pattern, (c) linear sweep voltammetric curve of hydrogen evolution reaction by water electrolysis, and (d) schematic diagram of the structure of the Tafel slope curve. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings. The raw materials Nb, Si, and Te used are all commercially available Alfa Aesar elemental powders with purities of 99.99%, 99.999%, and 99.999%, respectively. The transport agent raw materials I2, Br2, TeI4, TeBr4, and TeCl4 are also commercially available Alfa Aesar. The mixing mass ratio of the transport agent to the crystal growth raw materials is 1:10 to 1:20. In a specific embodiment, I2 is used as an example as the transport agent, with a purity of 99.985%. Other transport agents are used in the preparation of NbSi... x The effect is similar in Te2 crystals.

[0019] Example 1

[0020] NbSi 0.33 The preparation method of Te2 crystals specifically includes the following steps:

[0021] (1) Weigh out 4.656g of Nb, 0.477g of Si, and 12.760g of Te in a molar ratio of 3:1:6, mix them, and seal them in a vacuum with a degree of 1×10⁻⁶. -4 Pa is placed in a quartz tube (2 cm in diameter and 20 cm in length), heated to 900°C in a muffle furnace (the temperature can also be selected from 800°C to 900°C), and held at that temperature for seven days (the holding time must be maintained for at least seven days). After cooling, NbSi is obtained. x Te2 polycrystalline powder was used as a raw material for crystal growth.

[0022] (2) Weigh the above crystal growth raw materials and transport agent I2 at a mass ratio of 20:1, mix and grind them, and seal them in another vacuum tube with a vacuum degree of 1×10⁻⁶.-4 The quartz tube of Pa (2 cm in diameter and 20 cm in length) was placed in a double-zone furnace, and the temperature distribution of the growth zone and the raw material zone of the double-zone furnace was set to 850°C (the temperature can also be selected from 800°C to 900°C) and 950°C (the temperature can also be selected from 900°C to 1000°C) for heat preservation for ten days (the heat preservation time is at least maintained for more than seven days) to grow the crystal, and the NbSi x Te2 crystal was obtained after cooling to room temperature.

[0023] As shown in Figure 1 (a) the X-ray diffraction (XRD) spectrum of the crystal and the growth photo of the crystal, the obtained NbSi x Te2 crystal is flaky, has a metallic luster, and the size is in the millimeter level. The NbSi 0.33 Te2 crystal has no impurity peak and good crystallinity. As shown in Figure 1 (b) the energy dispersive spectrometer (EDS) data, the NbSi 0.33 Te2 crystal has a molar ratio of three elements Nb, Si and Te of 1.02:0.33:2.01, which is close to the stoichiometric ratio, indicating that the grown crystal is the target crystal. The NbSi x Te2 crystal was fixed with silver glue and placed in the electrolyte of a three-electrode electrochemical workstation, and can be used as an electrocatalyst for hydrogen evolution reaction of electrolytic water without being ground into powder. The NbSi 0.33 Te2 electrocatalyst catalyzes the electrolysis of water to produce hydrogen, and its HER electrocatalytic performance test is shown in the following Figure 1 (c) and (d). The overpotential η -2 = 132.35 mV at a current density of 10 mAcm -10 -2, and the Tafel slope is 204.82 mVdec -1 .

[0024] Example 2

[0025] Different from example 1, the mass ratio of elemental raw materials Nb, Si and Te is 5:2:10, and the NbSi 0.40 Te2 crystal is prepared, and the mixing mass ratio of the transport agent I2 and the crystal growth raw material is 1:20, and the preparation method is the same as above.

[0026] As shown in Figure 2 (a) the X-ray diffraction (XRD) spectrum of the crystal and the growth photo of the crystal, the NbSi 0.40 Te2 crystal is flaky, has a metallic luster, and the size is in the millimeter level. The NbSi Figure 2 (b) the energy dispersive spectrometer (EDS) data, the NbSi0.40 The molar ratio of the three elements Nb, Si, Te in the Te2crystal is 1.03:0.40:2.01, which is close to the stoichiometric ratio, indicating that the grown crystal is the target crystal. The HER electrocatalytic performance of the crystal in the catalytic electrolysis of water to produce hydrogen was tested in the manner of Example 1, as shown in Figure 2 (c) and (d), the overpotential η of the crystal at a current density of 10 mA cm-2 is 81.55 mV, and the size of the Tafel Slope is 65.93 mV dec-1. -2 -10 -1

[0027] Example 3

[0028] Different from Example 1, the mass ratio of the elemental raw materials Nb, Si, and Te is 7:3:14, and the NbSi 0.43 Te2crystal is prepared, and the mixing mass ratio of the transport agent I2 and the crystal growth raw material is 1:20, and the preparation method is the same as above.

[0029] As shown in Figure 3 (a) the X-ray diffraction (XRD) spectrum of the crystal and the growth photo of the crystal, the NbSi 0.43 Te2crystal is obtained, which is flaky, has a metallic luster, and the size is in the millimeter level. The crystal has no impurity peak and good crystallinity. As shown in Figure 3 (b) the energy dispersive spectrometer (EDS) data, the NbSi 0.43 Te2crystal has a molar ratio of the three elements Nb, Si, Te of 1.03:0.43:2.01, which is close to the stoichiometric ratio, indicating that the grown crystal is the target crystal. The HER electrocatalytic performance of the crystal in the catalytic electrolysis of water to produce hydrogen was tested in the manner of Example 1, as shown in Figure 3 (c) and (d), the overpotential η of the crystal at a current density of 10 mA cm-2 is 67.38 mV, and the size of the Tafel Slope is 56.82 mV dec-1. -2 -10 -1

[0030] Example 4

[0031] Different from Example 1, the mass ratio of the elemental raw materials Nb, Si, and Te is 2:1:4, and the NbSi 0.5 Te2crystal is prepared, and the mixing mass ratio of the transport agent I2 and the crystal growth raw material is 1:20, and the preparation method is the same as above.

[0032] As shown in Figure 4 (a) the X-ray diffraction (XRD) spectrum of the crystal and the growth photo of the crystal, the NbSi 0.5 ​​​​​​Te2 crystals are plate-like, have a metallic luster, and are on the order of millimeters in size. They are free of impurities and exhibit good crystallinity. For example... Figure 4 (b) Energy dispersive spectroscopy (EDS) data shows that NbSi 0.5 The molar ratio of Nb, Si, and Te in the Te2 crystal is 2.02:1.01:3.99, which is close to the stoichiometric ratio, indicating that the grown crystal is the target crystal. The HER electrocatalytic performance of this crystal in catalytic water electrolysis for hydrogen production was tested using the method described in Example 1. Figure 4 As shown in (c) and (d), 10 mAcm -2 overpotential η at current density -10 = 87.55mV, the Tafel slope is 101.27mVdec -1 .

[0033] Comparative Example

[0034] Polycrystalline Co2MnGa, a topological semimetal, is prepared by arc melting. The working electrode for HER performance testing of Co2MnGa is prepared in two ways: 1. grinding the crystal and pressing it into a tablet, this working electrode is denoted as Co2MnGa-TP; 2. cutting the polycrystalline material into blocks using wire, this working electrode is denoted as Co2MnGa-CP.

[0035] Electrodes prepared by the above two methods were tested using the method described in Example 1, and the Co2MnGa-TP electrode was measured at 10 mA / cm². -2 overpotential η at current density -10 =153mV, the Tafel slope is 167.8mVdec -1 Co2MnGa-CP at 10 mA cm⁻¹ -2 overpotential η at current density -10 =294mV, the Tafel slope is 207.7mVdec -1 Its catalytic activity is significantly weaker than that of NbSixTe2 (x=0.40, 0.43, 0.50).

Claims

1. NbSi x The application of Te2 (x = 0.33, 0.40, 0.43, 0.50) crystals as electrocatalytic materials is characterized by, The crystals are plate-like, have a metallic luster, and are approximately millimeter in size; NbSi x The Te2 crystal structure can be viewed as an atomic layer formed by alternating Nb2SiTe4 chains along the b-axis and NbTe2 chains containing silicon defects along the a-axis, stacked together after rotating 180° along the c-axis. The chemical formula can also be written as (Nb2SiTe4). n (NbTe2)(n=1,2,3,∞), corresponding to x=0.33,0.40,0.43,0.50 respectively.

2. The NbSi according to claim 1 x The uses of Te2 crystals are characterized by, The NbSi x Te2 crystals are grown using I2, Br2, TeI4, TeBr4, or TeCl4 as transport agents, in a vacuum-sealed quartz tube as the growth container, and through a chemical vapor transport method in a temperature range of 800–900℃ (growth end) and 900–1000℃ (raw material end).

3. The NbSi according to claim 1 x The uses of Te2 crystals are characterized by, The NbSi x Te2 crystals can be used for catalytic water electrolysis to produce hydrogen.

4. The NbSi according to claim 3 x The uses of Te2 crystals are characterized by, The NbSi x The catalytic performance of Te2 crystals in electrocatalytic hydrogen production is shown to be x = 0.5 (NbSi) in 1M KOH solution. 0.5 The Te2) composition has an overpotential of approximately 87.15 mV and a Tafel slope of approximately 101.27 mV / dec; x = 0.43 (NbSi) 0.43 The Te2) composition has an overpotential of approximately 67.38 mV and a Tafel slope of approximately 56.82 mV / dec; x = 0.40 (NbSi) 0.40 The Te2) composition has an overpotential of approximately 81.55 mV and a Tafel slope of approximately 65.93 mV / dec; x = 0.33 (NbSi) 0.33 The Te2 component has an overpotential of approximately 132.35 mV and a Tafel slope of approximately 204.82 mV / dec.

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