阅读说明：本技术 一种类珊瑚状Pd4Se化合物的制备方法 (Coral-like Pd4Method for producing Se compound ) 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：本发明提供一种类珊瑚状Pd-4Se化合物的制备方法,属于纳米材料合成制备技术领域。该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类珊瑚状的Pd-4Se化合物纳米材料,合成工艺简单、毒性较低、反应条件温和、成本低廉,且合成的Pd-4Se纯度高,适合工业化生产。(The invention provides coral-like Pd 4 A preparation method of Se compound, belonging to the technical field of nano material synthesis and preparation. The method takes selenious acid and sodium tetrachloropalladate as reaction substances and deionized water as a reaction solvent, and synthesizes coralliform Pd in one step by a hydrothermal method 4 The Se compound nano material has the advantages of simple synthesis process, lower toxicity, mild reaction condition and low cost, and the synthesized Pd 4 The Se has high purity and is suitable for industrial production.)

1. Coral-like Pd₄A method for producing a Se compound, comprising the steps of:

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

step 2: sequentially adding a palladium source, a weak reducing agent, a strong reducing agent and alkali into the solution obtained in the step 1, and mixing and stirring;

and step 3: dissolving selenious acid in deionized water, and uniformly stirring;

and 4, step 4: mixing the solutions obtained in the step 2 and the step 3, and uniformly stirring;

and 5: transferring the mixed solution obtained in the step (4) to a reaction kettle for hydrothermal reaction;

step 6: after the reaction is finished, naturally cooling to room temperature, then filtering the solution to obtain black precipitate, washing, and freeze-drying to obtain the Pd₄A Se compound.

2. The coral-like Pd as set forth in claim 1₄The preparation method of the Se compound 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.

3. The coral-like Pd as set forth in claim 1₄The method for preparing Se compound is characterized in that the molar amount of the weak reducing agent and the strong reducing agent in the step 2 is at least 1 time of the molar amount of the palladium source, and the molar amount of the alkali is at least 2 times of the molar amount of the palladium source.

4. The coral-like Pd as set forth in claim 1₄A method for producing a Se compound, wherein the stirring time in step 2 is more than 20 minutes.

5. The coral-like Pd as set forth in claim 1₄The preparation method of the Se compound is characterized in that the molar ratio of the palladium element to the selenium element in the step 4 is (1-4): 1.

6. The coral-like Pd as set forth in claim 1₄The preparation method of the Se compound is characterized in that the hydrothermal reaction temperature in the step 5 is 200-250 ℃, and the reaction time is more than or equal to 5 hours.

7. The coral-like Pd as set forth in any one of claims 1 to 6₄A method for producing a Se compound, characterized in that Pd obtained by the production method₄Purity of Se compoundReaching 93.2 percent.

8. The coral-like Pd as set forth in any one of claims 1 to 6₄A method for producing a Se compound, characterized in that Pd obtained by the production method₄The Se compound has a coral-like structure.

9. The coral-like Pd as set forth in any one of claims 1 to 6₄Pd obtained by preparation method of Se compound₄The application of Se compound in the field of catalysis.

Technical Field

The invention belongs to the technical field of synthesis and preparation of nano materials, and particularly relates to coral-like palladium (Pd) selenide₄Se) compound.

Background

The palladium metal and the compound thereof are used as an important noble metal catalyst, and have excellent catalytic performance and wide application in the directions of organic cross coupling reaction, hydrogen evolution reaction, oxygen reduction reaction, magnesium-air battery and the like. However, palladium is rare on earth, as low as 0.0006PPM, and also presents similar problems of volatile activity as catalysts for other noble metal catalysts. Therefore, the preparation of corresponding compounds and the design of nanostructures to improve the catalytic efficiency of palladium catalysts are important for the continuous development of the related industries.

Tetrapalladium (Pd) selenide₄Se) is a main phase in the chalcogenide of the noble metal palladium, and has good electrical conductivity and thermal stability. The palladium selenide belongs to a phase rich in palladium, the palladium element of the palladium selenide is in a low oxidation state, and the tetragonal phase structure is similar to the face-centered cubic structure of a palladium simple substance, so that the catalytic mechanism of the palladium selenide is close to that of a noble metal simple substance catalyst, and the palladium selenide has good catalytic performance; the palladium selenide is equivalent to light selenization of noble metal palladium, so that the catalytic stability of the catalyst is enhanced, and the noble metal can be effectively prevented from being oxidized and inactivated; compared with the palladium simple substance and the sulfide, the selenized catalyst weakens the adsorption effect on the reaction substrate and the intermediate molecule to a certain extent, and is balanced in the steps of adsorption and desorption of the reaction substrate and the intermediate molecule, thereby being beneficial to the catalytic reaction. In summary, palladium selenide represented by tetrapalladium selenide is a catalytic functional material with high development potential which can be used for improving the catalytic efficiency of a palladium catalyst; while the successful preparation of pure phase is helpful to the deep exploration of the catalytic mechanism of palladium selenide.

At present, the preparation method of palladium tetraselenide is mainly a complex thermal decomposition method. S.sampath et al (chem.commu., 2016,52,206) reported a method for preparing a thin film of tetrapalladium selenide, comprising the steps of: mixing the synthesized organic selenide decadiselenide (DDSe) with organic palladium source palladium acetate at normal temperature, continuously stirring, uniformly coating the obtained slurry on the surface of a substrate, naturally evaporating the solvent at normal temperature, and sintering at 250 ℃ for 1 hour in a tubular furnace under the protection of nitrogen atmosphere to obtain the black tetrapalladium selenide film. The method has the disadvantages of complicated synthesis steps of the related organic selenide, long preparation period, high toxicity of the required medicine and no contribution to green production; the subsequent synthesis of the tetrapalladium selenide needs to be carried out in a tubular furnace under the protection of nitrogen, so that the preparation cost is high; ajai k.singh et al (Dalton Trans,2012,41,1142) report a preparation method of tetrapalladium selenide nanoparticles, in which a prepared palladium-selenium coexisting organic compound [ PdCl2(PhSe-CH2C H2CH2-NH2) ] is used as a palladium-selenium shared precursor, and the palladium-selenium shared precursor is mixed with tri-n-octylphosphine (TOC), and pyrolyzed at the temperature of 280-300 ℃ to obtain a majority of tetrapalladium selenide bulk and a small portion of nanoparticles with the diameter of about 38-43 nm. The method has simple pyrolysis steps, but the prefabrication preparation of the organic precursor also involves the problems of complicated steps, high toxicity and the like, and is not beneficial to rapid production in a comprehensive way.

In summary, Pd is currently available₄The preparation of Se compounds has the disadvantages of complicated preparation process steps, long preparation period, high process toxicity, high preparation cost and no contribution to batch preparation; in addition, the tetrapalladium selenide compound prepared by the prior art is mostly composed of bulk materials with uncontrollable structures, and a definite preparation method of the tetrapalladium selenide nano-material is not related at present.

Disclosure of Invention

In view of the problems of the background art, the present invention is to provide a coral-like Pd₄A method for preparing Se compound. The method takes selenious acid as a selenium source, sodium tetrachloropalladate or palladium dichlorotetraammine as a palladium source and deionized water as a reaction solvent, and synthesizes coral-like Pd by one step through a hydrothermal method₄The Se compound nano material has the advantages of simple synthesis process, lower toxicity, mild reaction condition and low cost, and the synthesized Pd₄The Se has high purity and is suitable for industrial production.

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

coral-like Pd₄A method for preparing a Se compound, comprising the steps of:

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

step 2: sequentially adding a palladium source, a weak reducing agent, a strong reducing agent and alkali into the solution obtained in the step 1, and mixing and stirring;

and step 3: adding selenious acid into deionized water, and uniformly stirring;

and 4, step 4: mixing the solutions obtained in the step 2 and the step 3, and uniformly stirring, wherein the palladium source and the selenium source are separately dissolved and then mixed so as to ensure that the reaction ratio of the palladium source and the selenium source in the first contact time is close to the molar ratio of palladium and selenium elements in the added medicine to the maximum extent, and if selenious acid is directly dissolved in the mixed solution obtained in the step 2, the ratio of selenium at the beginning is locally too high/too low, and exceeds the range of the molar ratio Pd: Se ═ 1 (1-4): 1, so that the impure phase is increased;

and 5: transferring the mixed solution obtained in the step (4) into a reaction kettle, and carrying out hydrothermal reaction;

step 6: after the reaction is finished, naturally cooling to room temperature, then filtering the solution to obtain black precipitate, washing, and freeze-drying to obtain the Pd₄A Se compound.

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 stirring time in the step 2 is more than 20 minutes;

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

Furthermore, the hydrothermal reaction temperature range in the step 5 is 200-250 ℃, and the reaction time is more than or equal to 5 hours.

Further, the invention discloses Pd prepared by the technical scheme of protection₄The purity of the Se compound can reach 93.2 percent.

The invention also claims Pd prepared by the method₄Se compound, and the Pd₄The Se compound has a coral-like structure.

The invention also claims Pd prepared by the method₄The application of Se compound in the field of catalysis.

The mechanism of the invention is as follows: according to the invention, graphene oxide is added into reactants, and the graphene oxide has the functions of providing nucleation sites and participating in the reaction as a weak oxidant. In the initial stage of the reaction, the precursor forms Pd on the nucleation sites provided by the graphene oxide₄Se core forms nano particles along with the prolonging of reaction time, and residual weak reducing agent in the solution acts on the formed nano particles as an anionic surfactant, so that the particles are self-assembled at the orientation positions of similar crystal faces, and are continuously and alternately grown and assembled along with the reaction to finally form a coral-like structure.

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

1. the invention adopts a one-step synthesis method, uses deionized water as a reaction solvent, and synthesizes Pd by a hydrothermal method in one step₄The Se compound has the advantages of simple synthesis and preparation process, lower toxicity, mild reaction conditions and low cost.

2. Pd prepared by the invention₄The Se compound has high purity and good crystallinity, and is beneficial to the improvement of intrinsic conductivity; the obtained high-purity phase can be directly used for further researching the catalytic mechanism of the palladium-selenium compound in each catalytic reaction to avoid the interference of heterogeneous phase, and can be expected to have better application prospect in the catalytic field.

3. Pd prepared by the invention₄The Se compound has a coral-like structure, the conductivity of the material is further improved by the staggered and criss-cross structure composition, the specific surface area of the material is obviously increased compared with that of a block material, and more active sites are obtainedSo as to expose the catalyst, and further improve the catalytic activity of the material.

Drawings

FIG. 1 shows Pd prepared in example 1 of the present invention₄X-ray diffraction (XRD) pattern of Se compound.

FIG. 2 shows Pd prepared in example 1 of the present invention₄Scanning Electron Microscope (SEM) images of Se compounds.

FIG. 3 shows Pd obtained in example 1 of the present invention₄Water-soluble ammonia yield/faradaic efficiency vs. overpotential diagram for Se compounds.

FIG. 4 shows Pd obtained in example 1 of the present invention₄Cycling performance profile of Se compounds at-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.

Example 1

Coral-like Pd₄A method for preparing a Se compound, comprising the steps of:

step 1: dispersing 10mg of Graphene Oxide (GO) in 7.5ml of deionized water, and uniformly stirring;

step 2: adding 0.1mmol of sodium tetrachloropalladate, 0.1mmol 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 then mixing and stirring for 20 minutes;

and step 3: preparing 7.5ml of deionized water, adding 0.1mmol of selenious acid into the deionized water, and uniformly stirring;

and 4, step 4: mixing the solutions obtained in the step 2 and the step 3, and uniformly stirring;

and 5: transferring the mixed solution obtained in the step (4) into a reaction kettle, and carrying out hydrothermal reaction for 5 hours at the temperature of 200 ℃;

step 6: after the reaction is finished, naturally cooling to room temperature, filtering the solution to obtain black precipitate, repeatedly washing with deionized water, ethanol and deionized water in sequence, and freeze-drying to obtain Pd₄A Se compound.

This examplePrepared Pd₄The X-ray diffraction (XRD) pattern of the Se compound is shown in figure 1. from figure 1, the product is Pd which is better crystallized₄Se compound, by preliminary calculation, Pd₄Se accounts for about 93.2% of the total composition. The rest components are palladium simple substance which is not selenized, and the diffraction peak corresponds to the position near about 45 degrees; the multiple crystal faces all have stronger diffraction peak signals, the intensity ratio is close to that of a standard PDF card, the side surface shows that the crystal faces are assembled into a coral-like structure by particles instead of being in a directional growth nano-line form, and all the crystal faces tend to grow uniformly.

Pd prepared in this example₄The Scanning Electron Microscope (SEM) image of the Se compound is shown in figure 2, and the product is a coral-like structure of tetrapalladium selenide which can be seen from figure 2. Wherein the coral-like structure takes graphene oxide (converted into reduced graphene oxide in reaction) as a growth substrate and consists of infinite Pd₄Se nano particles are mutually fused, crosslinked and self-assembled.

Pd prepared in this example₄The electrolyte of Se compound is 0.1M Na₂SO₄The application of the electrocatalytic nitrogen fixation direction is carried out under the neutral environment. Coral-like Pd₄The water-soluble ammonia yield/Faraday efficiency vs. overpotential graph for Se compounds is shown in FIG. 3, and it can be seen from FIG. 3 that at 0.1M Na₂SO₄As an electrolyte (neutral), the coral-like Pd prepared in this example₄The Se compound obtains the optimal Yield (Yield) of water-soluble ammonia under the RHE potential of-0.4V vs, and can reach 17.41 mu g mg_cat ^-1h^-1The optimal faradic Efficiency (faradic Efficiency) of the reaction is obtained under-0.3V vs RHE potential and reaches 5.29 percent, which shows that the material has good electrocatalytic nitrogen fixation activity. Coral-like Pd₄The cycle performance diagram of the Se compound under-0.4V vs RHE potential is shown in FIG. 4, and it can be obtained from FIG. 4 that the obtained material still maintains higher electrocatalytic nitrogen fixation activity after 8h electrolysis (2 h for single cycle and 4 cycles), the Faraday efficiency is improved after the material is fully soaked and activated, and is stable at about 6%, which indicates that the material can maintain good performance stability under electrolysis conditions.

Example 2

Coral-like Pd₄A method for preparing a Se compound, comprising the steps of:

step 1: dispersing 5mg of Graphene Oxide (GO) in 15ml of deionized water, and uniformly stirring;

step 2: adding 0.1mmol of sodium tetrachloropalladate, 0.1mmol 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 then mixing and stirring for 20 minutes;

and step 3: preparing 15ml of deionized water, adding 0.025mmol of selenious acid into the deionized water, and uniformly stirring;

and 4, step 4: mixing the solutions obtained in the step 2 and the step 3, and uniformly stirring;

and 5: transferring the mixed solution obtained in the step (4) into a reaction kettle, and carrying out hydrothermal reaction for 10 hours at the temperature of 250 ℃;

step 6: after the reaction is finished, naturally cooling to room temperature, filtering the solution to obtain black precipitate, repeatedly washing with deionized water, ethanol and deionized water in sequence, and freeze-drying to obtain Pd₄A Se compound.

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.