阅读说明：本技术 一种rGO@Pd7Se2复合结构纳米材料及其制备方法和应用 (rGO @ Pd7Se2Composite structure nano material and preparation method and application thereof ) 是由 熊杰 郭倚天 杜新川 黄建文 雷天宇 陈伟 晏超贻 邬春阳 王显福 于 2020-12-18 设计创作，主要内容包括：本发明提供一种rGO@Pd-7Se-2复合结构纳米材料及其制备方法和应用,属于纳米材料合成制备技术领域。该复合结构纳米材料为Pd-7Se-2纳米颗粒均匀锚定在还原氧化石墨烯(rGO)上,Pd-7Se-2纳米颗粒粒径～100nm,形状为近立方体形状。制备方法以亚硒酸和四氯钯酸钠为反应物质,去离子水为反应溶剂,通过水热法一步合成rGO@Pd-7Se-2复合结构的纳米材料。且负载rGO@Pd-7Se-2纳米材料的电极在电催化固氮中表现出优秀的催化性能及连续电解稳定性,合成工艺简单、毒性较低、反应条件温和、成本低廉。(The invention provides rGO @ Pd 7 Se 2 A composite structure nano material and a preparation method and application thereof belong to the technical field of nano material synthesis and preparation. The composite structure nano material is Pd 7 Se 2 Nanoparticles homogeneously anchored on reduced graphene oxide (rGO), Pd 7 Se 2 The particle diameter of the nano particles is 100nm, and the shape of the nano particles is a nearly cubic shape. The preparation method takes selenious acid and sodium tetrachloropalladate as reaction substances and deionized water as a reaction solvent, and the rGO @ Pd is synthesized in one step by a hydrothermal method 7 Se 2 A nanomaterial of composite structure. And loaded with rGO @ Pd 7 Se 2 The electrode of the nano material shows excellent catalytic performance and continuous electrolytic stability in electrocatalytic nitrogen fixation, and has the advantages of simple synthesis process, lower toxicity, mild reaction conditions and low cost.)

1. rGO @ Pd₇Se₂Composite structure nano material, characterized in that, the rGO @ Pd₇Se₂The composite structure nano material is Pd₇Se₂The nanoparticles are uniformly anchored on the reduced graphene oxide, wherein Pd₇Se₂The particle size of the nano-particles is 80-150 nm, and the shape of the nano-particles is a nearly cubic shape.

2. rGO @ Pd₇Se₂The preparation method of the composite structure nano material is characterized by comprising the following steps:

step 1: dispersing graphene oxide in deionized water, and uniformly stirring;

step 2: sequentially adding selenious acid, a palladium source, a weak reducing agent, a strong reducing agent and alkali into the solution obtained in the step 1, uniformly mixing and stirring, and stopping stirring when the color of the solution is changed into black;

and step 3: transferring the mixed solution obtained in the step (2) to a reaction kettle for hydrothermal reaction;

and 4, step 4: after the reaction is finished, naturally cooling to room temperature, filtering the solution to obtain a gray black precipitate, washing, and freeze-drying to obtain the rGO @ Pd₇Se₂A nanoparticle composite structure.

3. The rGO @ Pd of claim 2₇Se₂The preparation method of the composite structure nano material is characterized in that the palladium source in the step 2 is sodium tetrachloropalladate or palladium tetraammine dichloride, the weak reducing agent is sodium citrate or ascorbic acid, the strong reducing agent is sodium borohydride, and the alkali is sodium hydroxide or potassium hydroxide.

4. The rGO @ Pd of claim 2₇Se₂The preparation method of the composite structure nano material is characterized in that the molar weight of the weak reducing agent and the strong reducing agent in the step 2 is at least 1 time of that of the palladium source, and the molar weight of the alkali is at least 2 times of that of the palladium source.

5. The rGO @ Pd of claim 2₇Se₂The preparation method of the composite structure nano material is characterized in that the molar ratio of palladium element to selenium element in the step 2 is (1-4): 1.

6. the rGO @ Pd of claim 5₇Se₂The preparation method of the composite structure nano material is characterized in that the molar ratio of palladium element to selenium element in the step 2 is preferably 2: 1.

7. The rGO @ Pd of claim 2₇Se₂The preparation method of the composite structure nano material is characterized in that the hydrothermal reaction temperature in the step 5 is more than or equal to 200 ℃, and the reaction time is more than or equal to 5 hours.

8. The rGO @ Pd of claim 1₇Se₂The composite structure nano material is applied as a cathode catalytic material for electrocatalytic nitrogen fixation.

Technical Field

The invention belongs to the technical field of synthesis and preparation of nano materials, and particularly relates to heptapalladium diselenide-reduced graphene oxide (rGO @ Pd)₇Se₂) A preparation method of the composite structure nano material and application in electrochemical nitrogen fixation reaction.

Background

The current energy consumption mode taking fossil fuels as the leading one is not sustainable due to limited ore reserves and increasingly serious environmental pollution problems, and the search for clean energy sources with abundant reserves is imperative to gradually replace the fossil fuels. As a basic industrial raw material, ammonia also has great potential as a clean energy source due to the characteristics of high energy density, high productivity, green and environment-friendly combustion products and more conformity with the current industrial system. Due to the abundant nitrogen content in the atmosphere and the wide application of clean energy sources such as solar energy, wind energy, geothermal energy and the like in power generation, electrocatalytic nitrogen fixation becomes a new green ammonia production way. In order to overcome the high potential barrier required by the dissociation of nitrogen-nitrogen triple bonds in the electrolytic process, the extensive exploration on the types of high-activity and low-cost nitrogen fixation catalyst materials is urgently needed.

Palladium selenides are one of the potential candidates due to their good electrical conductivity and noble metal-like catalytic mechanisms. At present, Pd is concerned₇Se₂The application of the compound nano material as a catalyst in the field of electrocatalytic nitrogen fixation is still blank. Sampath et al report on partial palladium selenides (Pd)₄Se,Pd₇Se₄,Pd₁₇Se₁₅) The application of the bulk monomer in the electrocatalytic hydrogen evolution reaction (chem.Co mmun.,2016,52,206) and the oxygen reduction reaction (J.Mater.chem.A., 2017,5,4660) has good catalytic activitySex and stability. However, the above-mentioned electrocatalytic performance test for bulk material severely limits the intrinsic activity of the material, and does not help to promote electron transfer in the material and at the interface because an effective composite structure is not introduced, and is not beneficial to further optimization of nitrogen fixation performance.

Pd₇Se₂As between Pd₄Se and Pd₇Se₄Meta-metastable state, similar chemical property to the above compound, and potential hydrogen evolution property of the meta-metastable state to enable Pd to be in a stable state₇Se₂The compounds have the potential to be excellent nitrogen fixation catalysts.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide heptapalladium diselenide-reduced graphene oxide (rGO @ Pd)₇Se₂) A method for preparing a composite structure nano material. The method takes selenious acid and sodium tetrachloropalladate as reaction substances and deionized water as a reaction solvent, and synthesizes rGO @ Pd by one step through a hydrothermal method₇Se₂Nanoparticles of composite structure. The invention provides a load rGO @ Pd₇Se₂The electrode of the nano-particles has excellent catalytic performance and continuous electrolytic stability in electrocatalysis nitrogen fixation, and has the advantages of simple synthesis process, lower toxicity, mild reaction conditions and low cost.

In order to achieve the purpose, the technical scheme of the invention is as follows:

rGO @ Pd₇Se₂Composite structure nano material, characterized in that, the rGO @ Pd₇Se₂The composite structure nano material is Pd₇Se₂Nanoparticles homogeneously anchored on reduced graphene oxide (rGO), Pd₇Se₂The particle size of the nano particles is 80-150 nm, and the shape of the nano particles is a nearly cubic shape.

rGO @ Pd₇Se₂The preparation method of the composite structure nano material comprises the following steps:

step 1: dispersing Graphene Oxide (GO) in deionized water, and uniformly stirring;

step 2: sequentially adding selenious acid, a palladium source, a weak reducing agent, a strong reducing agent and alkali into the solution obtained in the step 1, uniformly mixing and stirring, and stopping stirring when the color of the solution is changed into black; selenious acid, a palladium source, a weak reducing agent, a strong reducing agent and alkali are dissolved in the same solvent, and cannot be dissolved respectively and then mixed;

and step 3: transferring the mixed solution obtained in the step (2) into a reaction kettle, and carrying out hydrothermal reaction;

and 4, step 4: after the reaction is finished, naturally cooling to room temperature, filtering the solution to obtain a gray black precipitate, washing, and freeze-drying to obtain the rGO @ Pd₇Se₂A nanoparticle composite structure.

Further, in the step 2, the palladium source is sodium tetrachloropalladate or tetraamminepalladium dichloride, the weak reducing agent is sodium citrate or ascorbic acid (simultaneously used as a surfactant), the strong reducing agent is sodium borohydride, and the alkali is sodium hydroxide or potassium hydroxide, and is used for adjusting the solution to be an alkaline solution.

Further, in step 2, the molar amount of the weak reducing agent and the strong reducing agent is at least 1 time of the molar amount of the palladium source, and the molar amount of the base is at least 2 times of the molar amount of the palladium source.

Further, the molar ratio of the palladium element to the selenium element in the step 2 is (1-4): 1, preferably 2: 1.

Furthermore, the hydrothermal reaction temperature in the step 5 is more than or equal to 200 ℃, and the reaction time is more than or equal to 5 hours.

The invention also provides the rGO @ Pd₇Se₂The composite structure nano material is applied as a cathode catalytic material for electrocatalytic nitrogen fixation.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the invention provides rGO @ Pd₇Se₂Composite structured nanomaterial, nearly cubic Pd₇Se₂The nanoparticles are uniformly and densely anchored on the reduced graphene oxide. On one hand, the more regular particle shape can expose a specific active crystal face, and the uniform and dense distribution of the particles increases the number of active sites of the material which can participate in the nitrogen fixation reaction; on the other hand, the anchoring of the particles to the reduced graphene oxide can promote Pd₇Se₂The electron transfer between the nano-particle and the reduced graphene oxide interface is beneficial to the adsorption and desorption of the nitrogen fixation reaction substrate and the intermediate on the interface between materials and the solid-liquid interface.

2. The invention provides the loaded Pd₇Se₂The electrode of the nano material with the nano particle-reduced graphene oxide composite structure shows excellent catalytic activity in the electrocatalytic nitrogen fixation reaction, and the water-soluble ammonia yield reaches the optimal value of 22.05 mu g mg at the potential of-0.4V vs RHE according to the water-soluble ammonia yield/Faraday efficiency-overpotential diagram of the material_cat ^-1h^-1The faradaic efficiency of the reaction reaches 11.72 percent, which is superior to most of electrocatalytic nitrogen fixation catalytic materials reported at present; meanwhile, the catalyst has certain continuous electrolytic stability, and the catalytic activity is still maintained to be almost not attenuated after 8h of electrolysis (the time length of a single cycle is 2 h).

Drawings

FIG. 1 shows rGO @ Pd obtained in example 1 of the present invention₇Se₂X-ray diffraction (XRD) pattern of the composite-structured nanomaterial.

FIG. 2 shows rGO @ Pd obtained in example 1 of the present invention₇Se₂Scanning Electron Microscope (SEM) images of the composite structured nanomaterial.

FIG. 3 shows rGO @ Pd obtained in example 1 of the present invention₇Se₂Water-soluble ammonia yield/faradaic efficiency-overpotential diagram for composite structure nanomaterials.

FIG. 4 shows rGO @ Pd obtained in example 1 of the present invention₇Se₂And (3) a cycle performance diagram of the composite structure nano material under-0.4V vs RHE potential.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings.

rGO @ Pd₇Se₂Composite structure nano material, characterized in that, the rGO @ Pd₇Se₂The composite structure nano material is Pd₇Se₂Nanoparticles are uniformly anchored on the reduced graphene oxide, Pd₇Se₂Nanoparticle size hunanThe meter-scale shape is a nearly cubic shape.

Example 1

rGO @ Pd₇Se₂The preparation method of the composite structure nano material comprises the following steps:

step 1: dispersing 10mg of Graphene Oxide (GO) in 15ml of deionized water, and uniformly stirring;

step 2: adding 0.05mmol of selenious acid, 0.1mmol of sodium tetrachloropalladate, 0.1mm of sodium citrate, 0.2mmol of sodium hydroxide and 0.1mmol of sodium borohydride into the solution obtained in the step 1 in sequence, mixing and stirring uniformly, and stopping stirring when the color of the solution becomes black;

and step 3: transferring the mixed solution obtained in the step 2 into a reaction kettle, and carrying out hydrothermal reaction for 5 hours at the temperature of 200 ℃;

and 4, step 4: after the reaction is finished, naturally cooling to room temperature, filtering the solution to obtain a gray black precipitate, washing, and freeze-drying to obtain the rGO @ Pd₇Se₂A nanoparticle composite structure.

rGO @ Pd obtained in example 1₇Se₂The X-ray diffraction (XRD) pattern of the composite structure nano material is shown in figure 1, and the Scanning Electron Microscope (SEM) pattern is shown in figure 2; loaded rGO @ Pd obtained in example 1₇Se₂Carbon paper electrode of composite structure nano material in nitrogen saturated 0.1M Na₂SO₄The performance diagram of electrocatalytic nitrogen fixation reaction in the electrolyte under different potentials is shown in FIG. 3, and the nitrogen is saturated with 0.1M Na₂SO₄The performance stability test curve in the electrolyte is shown in fig. 4.

As can be seen from FIG. 1, Pd is used as the palladium selenide obtained in example 1₇Se₂Phase predominating and containing a small amount of Pd₄Se phase (corresponding to 40.141 DEG diffraction peak position), and hetero-phase possibly derived from Pd₇Se₂A small amount of decomposition of the phases; meanwhile, the major strong diffraction peak intensity ratio is larger than the standard PDF card, which indicates that the crystal may have partial directional growth, is beneficial to exposing a specific active crystal face, increasing active sites and promoting the performance. As can be seen from FIG. 2, this example successfully produced nearly cubic-shaped Pd of 100nm₇Se₂And the nano particles are uniformly and densely anchored on the reduced graphene oxide to form a composite structure. The nearly cubic morphology of the particles illustrates the directional growth of the crystals, consistent with the results of the X-ray diffraction (XRD) pattern of FIG. 1 showing the directional growth of the crystal portions. The directional growth of the crystal is caused by the regulation and control effect of the sodium citrate as the anionic surfactant in the crystal growth process. As can be seen from FIG. 3, the content of Na is 0.1M₂SO₄As an electrolyte (neutral), the rGO @ Pd prepared in this example₇Se₂The composite structure nano material obtains the optimal electrocatalytic nitrogen fixation performance under the RHE potential of-0.4V vs, and the Yield (Yield) of water-soluble ammonia can reach 22.05 mu g mg_cat ^-1h^-1And the faradic Efficiency (Faraday Efficiency) of the reaction reaches 11.72 percent, which indicates that the material has good electrocatalytic nitrogen fixation activity. FIG. 4 shows Pd obtained in this example₇Se₂A cycle performance diagram of the nanoparticle-reduced graphene oxide composite structure nanomaterial at-0.4V vs RHE potential shows that the obtained material still maintains high electrocatalytic nitrogen fixation activity after 8h of electrolysis, which indicates that the material can maintain good performance stability under electrolysis conditions.

Example 2

rGO @ Pd₇Se₂The preparation method of the composite structure nano material comprises the following steps:

step 1: dispersing 10mg of Graphene Oxide (GO) in 15ml of deionized water, uniformly stirring, and stopping stirring when the color of the solution becomes black;

step 2: adding 0.05mmol of selenious acid, 0.1mmol of sodium tetrachloropalladate, 0.1mm of sodium citrate, 0.2mmol of sodium hydroxide and 0.1mmol of sodium borohydride into the solution obtained in the step 1 in sequence, and mixing and stirring uniformly;

and step 3: transferring the mixed solution obtained in the step 2 into a reaction kettle, and carrying out hydrothermal reaction for 6h at the temperature of 300 ℃;

and 4, step 4: after the reaction is finished, naturally cooling to room temperature, filtering the solution to obtain a gray black precipitate, washing, and freeze-drying to obtain the rGO @ Pd₇Se₂A nanoparticle composite structure.

While the invention has been described with reference to specific embodiments, any feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise; all of the disclosed features, or all of the method or process steps, may be combined in any combination, except mutually exclusive features and/or steps.