A bimetallic phosphide and its preparation method and application

Abstract

The present invention relates to a bimetallic phosphide and a preparation method and application thereof. The bimetallic phosphide comprises metal Pd and metal Bi, and its chemical formula is Pd 20 Bi3P6, which belongs to the cubic crystal system #imgabs0# space group and has a three-dimensional network structure, is obtained by high-temperature solid-phase reaction using Pd powder, Bi powder and P powder as raw materials, and can be used as an electrocatalyst for hydrogen production reaction. Compared with the prior art, the present invention can reduce the amount of precious metals used, has lower costs, and has a simple preparation method and process steps, which is easy to promote.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic materials, and in particular to a bimetallic phosphide and a preparation method and application thereof. Background Art

[0002] The use of fossil fuels has made a valuable contribution to the improvement of our living standards, but with the consumption of fossil fuels and the accompanying carbon dioxide emissions, global energy and environmental problems have become increasingly serious. In recent years, various clean new energy technologies have developed rapidly. Hydrogen energy, as a new clean energy, has the advantage of zero carbon emissions and is expected to become an effective substitute for fossil fuels. However, the current source of H2 is still fossil fuel reforming, which cannot meet the energy needs of green and sustainable development in the future society. Therefore, low-energy, green and sustainable hydrogen production technology is the key to achieving energy security in the future.

[0003] At present, there are use cases for using renewable energy to provide power, such as solar energy, wind energy, hydropower, tidal power generation, etc. However, the relevant renewable energy faces disadvantages such as timeliness and dispersion, and is difficult to store and use. Electrochemical water decomposition to produce hydrogen refers to the process of passing direct current into an electrolyzer filled with electrolyte, causing water to undergo an electrochemical reaction on the electrodes to decompose into hydrogen and oxygen. The advantages of water electrolysis for hydrogen production, such as high efficiency, environmental friendliness, and high purity of gas production, have attracted widespread attention from researchers.

[0004] Catalysts are usually added to further reduce the overpotential of water decomposition during this process. The activity of the electrocatalyst mainly depends on the conductivity of the electrocatalyst, the number of exposed active sites, and the intrinsic activity of the active sites. The current challenge is that related electrode reactions such as water electrolysis are subject to problems such as complex electron transfer in the solution, slow kinetics, and low conversion efficiency, resulting in their thermodynamic barriers being much higher than the ideal state. Electrocatalysts with ultra-high performance and durability can effectively reduce the overpotential, reduce energy consumption, and reduce electrode cost losses. Precious metals such as Pt, Pd, and their oxides have excellent catalytic activity, but the scarcity and high cost of precious metals prevent them from being widely used. Therefore, the development and exploration of low-cost catalysts has great scientific and application significance. Summary of the invention

[0005] The purpose of the present invention is to provide a bimetallic phosphide and a preparation method and application thereof, so as to reduce the amount of precious metals used.

[0006] The object of the present invention can be achieved by the following technical solution: a bimetallic phosphide, comprising metal Pd and metal Bi, whose chemical formula is Pd 20 Bi3P6 belongs to the cubic crystal system.

[0007] Preferably, the bimetallic phosphide structure belongs to the cubic system Space group.

[0008] Further preferably, the unit cell parameters of the bimetallic phosphide are α=β=γ=90°, Z=4.

[0009] Preferably, the bimetallic phosphide has a three-dimensional network structure with two types of Bi atoms in the structure. The polyhedron centered on Bi1 is a cubic octahedron, which is composed of 12 Pd2s to form 6 squares and 8 regular triangles; the polyhedron centered on Bi2 is composed of 12 Pd2s and 4 Pd1s, with 28 isosceles triangles and 42 bonds.

[0010] Further preferably, there are two kinds of Bi atoms in the bimetallic phosphide structure. The polyhedron centered on Bi1 is a cubic octahedron, which is composed of 12 Pd2s forming 6 squares and 8 equilateral triangles. The 6 phosphorus atoms are all located above the center of the square, and 8 Bi2s are located above the equilateral triangles, connected by coplanar edges. The polyhedron centered on Bi2 is composed of 16 palladium atoms (12 Pd2s and 4 Pd1s), with 28 isosceles triangles and 42 bonds (faces and edges). In the polyhedron, Pd1 is connected to six Pd2s and to 3 Ps; while Pd2 and five Pds (3 Pd2s, two long and one short, and 2 Pd1s are the longest), and the cages are connected by coplanar edges. Bi2 and Pd1 form a regular tetrahedron, and each edge expands outward to a hexagon (4 Pd1s, two Bi2s). The Bi1 and Bi2 polyhedrons are coplanarly connected, and the four Bi1s form a regular tetrahedron with Bi2 at the center.

[0011] A method for preparing the above-mentioned bimetallic phosphide is to place Pd (palladium) powder, Bi (bismuth) powder and P (phosphorus) powder raw materials under vacuum conditions and prepare them by a high-temperature solid-phase reaction method.

[0012] Preferably, the P powder is red phosphorus powder.

[0013] Preferably, the vacuum condition is vacuumed to 0.1-0.3Pa.

[0014] Preferably, the molar ratio of the Pd powder, Bi powder and P powder is 1:0.2-0.5:1-2, so that a product with higher purity can be further obtained.

[0015] Further preferably, the molar ratio of the Pd powder, Bi powder and P powder is 1:0.2:2.

[0016] Preferably, the purity of the Pd powder, Bi powder and P powder is above 90%.

[0017] Preferably, the preparation method comprises the following steps:

[0018] (1) The raw materials Pd powder, Bi powder and P powder are ground evenly according to a certain molar ratio, and the ground raw materials are added into a tablet pressing mold to press into sample tablets;

[0019] (2) Take out the sample piece, put it into a reaction container, evacuate it and seal it;

[0020] (3) placing the sample piece in the reaction container and subjecting it to a high-temperature solid-phase reaction;

[0021] (4) After the reaction is completed, the bimetallic phosphide is obtained.

[0022] Further preferably, the grinding in step (1) is carried out in an agate mortar.

[0023] Further preferably, the reaction container in step (2) is a quartz tube.

[0024] More preferably, in step (2), the sample piece is taken out and placed in a quartz tube with a bottom seal, the quartz tube is evacuated and the top is sealed. Preferably, the quartz tube is evacuated to 0.1 Pa and then melted and sealed.

[0025] Further preferably, in step (3), the sealed reaction container is placed in a muffle furnace or a tubular furnace to perform a high temperature solid phase reaction.

[0026] Further preferably, the high temperature solid phase reaction in step (3) comprises heating to 800-1000° C. and keeping the temperature for 40-60 hours.

[0027] More preferably, the high temperature solid phase reaction in step (3) is heated to 800-1000°C at a rate of 30-60°C / hour, so as to achieve the preparation of high quality and purity crystals. The heating rate is preferably 40°C / hour, the holding temperature is preferably 850-950°C, and the holding time is preferably 45-55 hours.

[0028] Further preferably, after the reaction in step (4) is completed, the mixture is naturally cooled to room temperature, thereby achieving the growth of larger crystals.

[0029] More preferably, after the reaction in step (4) is completed, the sample is taken out and the crystals are picked out.

[0030] An application of the bimetallic phosphide is to use the bimetallic phosphide as an electrocatalyst for hydrogen production reaction.

[0031] In the present invention, transition metal phosphides are used in electrocatalysts due to their exposed surface, high carrier mobility, and short charge transfer distance. Through the synergistic effect of multiple metals, not only the electrocatalytic activity of the catalyst can be improved, but also its electrochemical stability can be enhanced.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The bimetallic phosphide of the present invention has the advantages of reducing the amount of precious metals used, lowering the cost, and having simple preparation process steps, which is easy to promote;

[0034] 2. The present invention uses transition metal phosphides as a matrix, and through the synergistic effect of Pd and Bi, the bimetallic phosphides have both electrocatalytic activity and electrochemical stability when used as an electrocatalyst;

[0035] 3. The crystal structure of the bimetallic phosphide of the present invention is composed of 12 Pd atoms forming a cubic octahedron and 16 palladium atoms forming a polyhedron, respectively forming two Bi-centered cage structures. The exposed noble metal improves the electrocatalytic activity, and the non-noble metal in the cage improves the electrochemical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the bimetallic phosphide crystal of the present invention. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0038] In the following examples, the reagents, materials and instruments used are conventional reagents, conventional materials and conventional instruments unless otherwise specified, and are all commercially available. The reagents involved can also be synthesized by conventional synthesis methods.

[0039] Example 1

[0040] The raw materials Pd powder, Bi powder and P powder are added to an agate mortar in a molar ratio of 1:0.2:1 and fully ground and mixed in the mortar. The ground raw materials are added to a tablet pressing mold and pressed into tablets. The tablets are taken out and transferred to a quartz tube with one end sealed, evacuated and sealed with a hydrogen-oxygen flame. The sealed quartz tube is then placed in a muffle furnace, and the temperature control program of the muffle furnace is set to slowly increase the temperature to 800°C, maintained for 40 hours, and then naturally cooled to room temperature in the furnace. After the reaction is completed, the product is taken out of the quartz tube.

[0041] Example 2

[0042] The raw materials Pd powder, Bi powder and P powder are added to an agate mortar in a molar ratio of 1:0.2:2 and fully ground and mixed in the mortar. The ground raw materials are added to a tablet pressing mold and pressed into tablets. The tablets are taken out and transferred to a quartz tube with one end sealed, evacuated and sealed with a hydrogen-oxygen flame. The sealed quartz tube is then placed in a muffle furnace, and the temperature control program of the muffle furnace is set to slowly increase the temperature to 900°C, maintained for 50 hours, and then naturally cooled to room temperature in the furnace. After the reaction is completed, the product is taken out of the quartz tube.

[0043] Example 3

[0044] The raw materials Pd powder, Bi powder and P powder are added to an agate mortar in a molar ratio of 1:0.5:2 and fully ground and mixed in the mortar. The ground raw materials are added to a tablet pressing mold and pressed into tablets. The tablets are taken out and transferred to a quartz tube with one end sealed, evacuated and sealed with a hydrogen-oxygen flame. Then the sealed quartz tube is placed in a muffle furnace, and the temperature control program of the muffle furnace is set to slowly increase the temperature to 1000℃, maintained for 60 hours, and then naturally cooled to room temperature in the furnace. After the reaction is completed, the product is taken out of the quartz tube.

[0045] The products obtained in Examples 1 to 3 were characterized by single crystal X-ray diffraction.

[0046] Table 1 Pd 20 Crystallographic data of Bi3P6

[0047]

[0048]

[0049] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A bimetallic phosphide, characterized in that: Contains metal Pd and metal Bi, and its chemical formula is Pd 20 Bi3P6 belongs to the cubic crystal system.

2. The bimetallic phosphide according to claim 1, characterized in that The bimetallic phosphide structure belongs to the cubic system Space group.

3. The bimetallic phosphide according to claim 2, characterized in that: The unit cell parameters of the bimetallic phosphide are: α=β=γ=90°.

4. The bimetallic phosphide according to claim 1, characterized in that: The bimetallic phosphide has a three-dimensional network structure, in which there are two types of Bi atoms. The polyhedron centered on Bi1 is a cubic octahedron, which is composed of 12 Pd2s to form 6 squares and 8 regular triangles; the polyhedron centered on Bi2 is composed of 12 Pd2s and 4 Pd1s, and has 28 isosceles triangles and 42 bonds.

5. A method for preparing the bimetallic phosphide according to any one of claims 1 to 4, characterized in that: Pd powder, Bi powder and P powder raw materials are placed under vacuum conditions and prepared by a high temperature solid phase reaction method; The molar ratio of the Pd powder, Bi powder and P powder is 1:0.2-0.5:1-2; The preparation method of the bimetallic phosphide comprises the following steps: (1) Grind the raw materials Pd powder, Bi powder and P powder evenly, add the ground raw materials into a tablet pressing mold, and press them into sample tablets; (2) Take out the sample piece, put it into a reaction container, evacuate it and seal it; (3) placing the sample piece in the reaction container and subjecting it to a high-temperature solid-phase reaction; (4) cooling after the reaction is completed to obtain the bimetallic phosphide; The step (3) high temperature solid phase reaction comprises heating the temperature at a rate of 30 to 60°C / hour to a holding temperature of 800 to 1000°C, and then holding the temperature for 40 to 60 hours after heating to 800 to 1000°C.

6. The method for preparing bimetallic phosphide according to claim 5, characterized in that: The grinding in step (1) is carried out in an agate mortar.

7. Use of the bimetallic phosphide according to any one of claims 1 to 4, characterized in that: The bimetallic phosphide is used as an electrocatalyst for hydrogen production reaction.

Images