CN110854391A

CN110854391A - Pd-Cu nano composite material, preparation method and application method

Info

Publication number: CN110854391A
Application number: CN201910879788.0A
Authority: CN
Inventors: 张钱丽; 李冬宁; 张斌; 刘洁; 魏杰
Original assignee: Suzhou University of Science and Technology
Current assignee: Suzhou University of Science and Technology
Priority date: 2019-06-11
Filing date: 2019-09-16
Publication date: 2020-02-28

Abstract

The application provides a Pd-Cu nano composite material, a preparation method and an application method thereof, wherein the Pd-Cu nano composite material comprises the following components: the composite material comprises chloropalladate, copper nitrate, a structure directing agent and a reducing agent, wherein the molar ratio of the chloropalladate to the copper nitrate is (1-2) to (1-2), the volume ratio of the structure directing agent to the total components is (0.5-1.5) to 5, and the volume ratio of the reducing agent to the total components is (0.5-1.5) to 10. The Pd-Cu nano composite material prepared by the method has the catalytic effect of catalyzing BThe performance of alcohol or ethylene glycol and the electrocatalytic performance are excellent, and the arrangement sequence of the catalyst from high to low according to the catalytic activity is as follows: pd₁Cu₂‑PVP＞Pd₁Cu₂‑(PCA‑Na+PVP)＞Pd₁Cu₂＞Pd₁Cu₁＞Pd₂Cu₁。

Description

Pd-Cu nano composite material, preparation method and application method

Technical Field

The invention belongs to the technical field of electrocatalyst preparation, and relates to a preparation method and an electrocatalysis application method of a Pd-Cu nano composite material.

Background

The chemical formula of the palladium is Pd, and the Pd-based material have excellent catalytic performance; however, since Pd is a precious metal and expensive, it is a hot research focus in recent years to increase the catalytic activity of Pd-based materials and reduce the amount of Pd used.

The alloying of the catalyst material is an effective way to improve the catalytic performance and reduce the use amount of noble metals. The Pd-Cu catalyst is synthesized, the electrocatalytic activity of the catalyst is improved by utilizing the synergistic catalytic effect of Pd and Cu, the cost performance of the catalyst is improved by reducing the using amount of noble metal Pd, and the practical process of the small-molecule fuel cell can be influenced. However, the electrocatalytic performance of the catalyst is closely related to not only the constituent elements, but also the microscopic morphology, the particle size, the element proportion and the like of the catalyst. The micro-morphology, the particle size and the element proportion of the catalyst depend on the synthesis method and the adopted structure directing agent.

The Pd-Cu alloy catalyst disclosed in the prior art has the disadvantages of complex manufacturing process, poor electrocatalysis performance, high energy consumption and high cost, can be synthesized only by high temperature and high pressure, and is not beneficial to industrial application.

Disclosure of Invention

The invention provides a Pd-Cu nano composite material and a preparation method thereof, which aim to solve the problems of high energy consumption and high cost in the Pd-Cu synthetic method in the prior art.

To achieve the above object, in a first aspect, the present application provides a Pd-Cu nanocomposite, comprising the following components: the composite material comprises chloropalladate, copper nitrate, a structure directing agent and a reducing agent, wherein the molar ratio of the chloropalladate to the copper nitrate is (1-2) to (1-2), the volume ratio of the structure directing agent to the total components is (0.5-1.5) to 5, and the volume ratio of the reducing agent to the total components is (0.5-1.5) to 10.

Optionally, in the Pd-Cu nanocomposite described above, the structure directing agent is sodium pyrrolidone carboxylate, or/and polyvinylpyrrolidone.

Optionally, in the Pd-Cu nanocomposite material described above, the reducing agent is hydrazine hydrate.

Optionally, the Pd-Cu nanocomposite material is Pd₁Cu₂、 Pd₁Cu₁、Pd₂Cu₁Is pure of one of the above; or a mixture of two or three.

Alternatively, the Pd-Cu nanocomposite material described above, the Pd₁Cu₂As catalyst for catalyzing ethanol or glycol reaction under alkaline condition, Pd₁Cu₂Has catalytic activity superior to Pd₁Cu₁，Pd₁Cu₁Has catalytic activity superior to Pd₂Cu₁。

In a second aspect, the present application provides a method for preparing a Pd-Cu nanocomposite, the method comprising:

adding a structure directing agent into distilled water by adopting the component proportion of the Pd-Cu nano composite material to prepare a solution;

sequentially adding palladium chloride acid and copper nitrate into the solution while stirring to prepare a blue solution;

slowly adding a reducing agent dropwise and then sealing;

stirring at constant temperature to obtain suspension;

centrifuging and collecting precipitate;

and (4) drying in vacuum to obtain the Pd-Cu nano composite material.

Optionally, in the preparation method of the Pd-Cu nanocomposite, the volume ratio of the total components of the Pd-Cu nanocomposite to the distilled water is 1: 8-10.

Optionally, in the above method for preparing a Pd-Cu nanocomposite, 0.54mL of 0.25 wt% sodium pyrrolidone carboxylate is added into 27mL of distilled water with a pipette to prepare a solution;

to the solution were added, while stirring, 0.6mL of chloropalladate having a concentration of 100mmol/L and 1.56mL of Cu (NO) having a concentration of 38.6mmol/L in that order₃)₂·3H₂O crystal, adding Cu (NO)₃)₂·3H₂The solution is blue after O crystals;

0.3mL of hydrazine hydrate was added dropwise slowly and the solution was sealed after addition of the hydrazine hydrate.

Optionally, in the preparation method of the Pd-Cu nanocomposite, the constant-temperature stirring is: and (3) placing the sealed solution into a constant-temperature magnetic stirrer, stirring at the speed of 800-1000 r/min, and stirring at the temperature of 20-25 ℃ for 1-2 h.

Optionally, in the above method for preparing a Pd-Cu nanocomposite, the vacuum drying to obtain a Pd-Cu nanocomposite includes:

putting the precipitate in a vacuum drying oven, and drying at 80 ℃ in vacuum;

and after drying, cooling the precipitate to room temperature to obtain the Pd-Cu nano composite material.

In a third aspect, the present application provides a method for preparing a Pd-Cu electrocatalytic electrode, comprising:

adding 1mg of the Pd-Cu nano composite material into per milliliter of distilled water, and uniformly dispersing by ultrasonic to prepare a sample solution;

cleaning the glassy carbon electrode;

dropping a sample solution on the glassy carbon electrode;

drying, and dripping perfluorosulfonic acid polymer solution to form a membrane electrode;

sealing and drying to obtain the Pd-Cu electro-catalytic electrode.

In a fourth aspect, the present application provides a method for applying a Pd-Cu nanocomposite to ethanol or ethylene glycol catalytic reaction, comprising:

and inserting the Pd-Cu electro-catalytic electrode into an ethanol or ethylene glycol solution to perform electrochemical catalytic reaction.

Compared with the prior art, the technical scheme provided by the invention has the beneficial effects that at least:

the preparation process of the chain Pd-Cu bimetallic catalyst is simple, convenient and easy to operate, and the chain Pd-Cu bimetallic catalyst has the advantages of good electro-catalytic performance, low energy consumption and low cost, and is beneficial to industrial application.

Compared with the prior art, the synthesis method and the structure directing agent adopted by the electrocatalyst are obviously different, and the micro-morphology, the element proportion and the application object of the electrocatalyst are also obviously different. The catalyst of the invention adopts a simple one-pot method to prepare the chain Pd-Cu catalyst with the particle size of about 30nm, and the synthesis process does not involve high temperature and high pressure. Because the chain Pd-Cu alloy consists of metal clusters with the particle size of 2-3nm, the unique surface characteristics of the material cause the material to show excellent electrocatalytic performance in electrocatalysis of ethanol and glycol. Therefore, the research and development of the novel efficient Pd-Cu series electrocatalyst can save the use of noble metals, and has important practical significance for the practical process of micromolecule fuel electrons.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention without limiting the invention in any way. In the drawings:

FIG. 1 is a flow chart of a method for preparing a Pd-Cu nanocomposite;

FIG. 2 is a flow chart of a method for preparing a Pd-Cu electrocatalytic electrode;

FIG. 3 is a plot of cyclic voltammetric scans of the materials of examples 1, 2, 3 in an electrolyte;

FIG. 4 is a plot of cyclic voltammetric scans catalyzed in ethanol by the materials of examples 1, 2, 3;

FIG. 5 is a plot of cyclic voltammetric scans catalyzed in ethylene glycol for the materials of examples 1, 2, and 3;

FIG. 6 is a plot of chronoamperometry for the materials of examples 1, 2, 3 in ethanol solution;

FIG. 7 is a graph of chronoamperometry plots of the materials of examples 1, 2, and 3 in glycol solution;

FIG. 8 is a plot of cyclic voltammetric scans of the materials of examples 1, 4, 5 in an electrolyte;

FIG. 9 is a plot of cyclic voltammetric scans catalyzed in ethanol of the materials of examples 1, 4, 5;

FIG. 10 is a plot of chronoamperometry for the materials of examples 1, 4, 5 under ethanol solution.

Detailed Description

For further explanation of the objects, technical solutions and advantages of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the detailed description of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

One embodiment of the present application provides a Pd-Cu nanocomposite comprising the following components: the composite material comprises chloropalladate, copper nitrate, a structure directing agent and a reducing agent, wherein the molar ratio of the chloropalladate to the copper nitrate is (1-2) to (1-2), the volume ratio of the structure directing agent to the total components is (0.5-1.5) to 5, and the volume ratio of the reducing agent to the total components is (0.5-1.5) to 10.

In one embodiment of the present application, the palladium chloride acid, the copper nitrate, the structure directing agent and the reducing agent are in a molar ratio of: 1: 2 or 1: 1 or 2: 1, the volume ratio of the structure directing agent to the total components is 1: 5, and the volume ratio of the reducing agent to the total components is 1: 10.

In one embodiment of the present application, the structure directing agent is sodium pyrrolidone carboxylate, or/and polyvinylpyrrolidone.

In one embodiment of the present application, the reducing agent is hydrazine hydrate.

In one embodiment of the present application, the Pd-Cu nanocomposite is Pd₁Cu₂、Pd₁Cu₁、Pd₂Cu₁Is pure of one of the above; or a mixture of two or three.

In one embodiment of the present application, the Pd₁Cu₂As catalyst for catalyzing ethanol or glycol reaction under alkaline condition, Pd₁Cu₂Has catalytic activity superior to Pd₁Cu₁，Pd₁Cu₁Has catalytic activity superior to Pd₂Cu₁。

As shown in fig. 1, the present application provides a method for preparing a Pd-Cu nanocomposite, the method comprising:

s01, adding a structure directing agent into distilled water to prepare a solution according to the component proportion of the Pd-Cu nano composite material;

s02, sequentially adding chloropalladite and copper nitrate into the solution while stirring to prepare a blue solution;

s03, slowly adding a reducing agent drop by drop and then sealing;

s04, stirring at constant temperature to prepare suspension;

s05, centrifuging and collecting precipitates;

and S06, drying in vacuum to obtain the Pd-Cu nano composite material.

In one embodiment of the application, the volume ratio of the total components of the Pd-Cu nano composite material to the distilled water is 1 to (8-10).

In one example of the present application, 0.54mL of 0.25 weight percent sodium pyrrolidone carboxylate was added to 27mL of distilled water using a pipette to make a solution;

to the solution were added, while stirring, 0.6mL of chloropalladate having a concentration of 100mmol/L and 1.56mL of Cu (NO) having a concentration of 38.6mmol/L in that order₃)₂·3H₂O crystal, adding Cu (NO)₃)₂·3H₂The solution is blue, preferably light blue, after O crystals;

0.3mL of hydrazine hydrate is slowly added dropwise, the color is black, and the hydrazine hydrate is sealed after being added dropwise.

In one embodiment of the present application, the constant temperature stirring is: and (3) placing the sealed solution into a constant-temperature magnetic stirrer, stirring at the speed of 800-1000 r/min, and stirring at the temperature of 20-25 ℃ for 1-2 h.

In one embodiment of the present application, the vacuum drying to obtain the Pd-Cu nanocomposite comprises:

As shown in fig. 2, the present application provides a method for preparing a Pd-Cu electrocatalytic electrode, comprising:

s11, adding 1mg of the Pd-Cu nano composite material into per milliliter of distilled water, and ultrasonically dispersing uniformly to prepare a sample solution;

s12, cleaning the glassy carbon electrode;

s13, dropping the sample solution on the glassy carbon electrode;

s14, drying, and dripping into perfluorosulfonic acid polymer solution to form a membrane electrode;

and S15, sealing and drying to obtain the Pd-Cu electro-catalytic electrode.

The application provides a method for applying a Pd-Cu nano composite material to ethanol or ethylene glycol catalytic reaction, which comprises the following steps:

The invention is illustrated below with reference to specific examples:

example 1:

synthesized by a one-pot method, 0.54mL of PCA-Na (0.25 wt%) is accurately transferred to 27mL of distilled water by a liquid transfer gun, and 0.6mL of H is added while stirring₂PdCl₄(100mmol/L) and 1.56mL Cu (NO)₃)₂·3H₂O (38.6mmol/L), and the solution was light blue after addition of copper nitrate. 0.3mL of hydrazine hydrate was added dropwise slowly, and the solution turned black at the moment of the addition of hydrazine hydrate. Sealing the beaker filled with the solution with a sealing film, adjusting the rotating speed to 1000r/min, setting the temperature to 25 ℃, and stirring in a constant-temperature magnetic stirrer for 1 h. Stirring deviceAfter the stirring is finished, taking out the suspension with the obvious black aggregated particles, placing the suspension in a centrifuge for centrifugation, collecting black precipitates, washing the black precipitates with ethanol and water respectively, and centrifuging the black precipitates three times to wash away the residual structure directing agent. The precipitate collected finally was placed in a vacuum drying oven and dried under vacuum at 80 ℃. Drying and cooling to room temperature to obtain Pd₁Cu₁Weighing, storing and using for subsequent test.

Example 2:

compared with the example 1, the Pd is prepared by changing the amount ratio of the precursor Pd/Cu substance and keeping other conditions unchanged₁Cu₂。

Example 3:

compared with the example 1, the Pd is prepared by changing the amount ratio of the precursor Pd/Cu substance and keeping other conditions unchanged₂Cu₁。

Example 4:

compared with example 1, Pd was prepared by adding 1mL of 0.14 wt% polyvinylpyrrolidone PVP instead of 0.54mL of 0.25 wt% PCA-Na under the same conditions₁Cu₂-PVP。

Example 5:

compared with example 1, Pd was prepared by adding 1mL of 0.07 wt% polyvinylpyrrolidone PVP and 0.54mL of 0.13 wt% PCA-Na under otherwise unchanged conditions₁Cu₁-(PCA-Na+PVP)。

Firstly, physical testing:

the structure and the size of the Pd-Cu material are observed by a scanning electron microscope, and specifically comprise the following steps: firstly, respectively marking the samples of the above examples 1-5 as samples 1-5 by using an ultrasonic cleaning machine, and respectively and uniformly dispersing 1mg1-5 samples in 1mL of water by using the ultrasonic cleaning machine; 5 containers were taken, 1mL of distilled water was put in each container, and 10. mu.L of the sample 1-5 solution was pipetted into the 5 containers and ultrasonically dispersed for half an hour using a pipette gun. And (3) putting a 3mm copper net on the surface of the clean filter paper, putting the filter paper into a culture dish, dripping 2 mu L of completely dispersed and diluted solution onto the copper net by using a 10 mu L liquid transfer gun, drying, and covering the culture dish cover to be detected.

Adopts a 200kV transmission electron microscope (the magnification can reach more than 100 ten thousand times, and the energy can be obtainedEnough to distinguish the structure of the substance at the level of 1 nm), samples 1-3 all had different degrees of aggregation, Pd₁Cu₂More particles of smaller aggregate size are present on the material, while Pd₁Cu₁Mostly present a massive aggregate morphology, Pd₂Cu₁More aggregated particles of moderate size are present on the material; therefore, PCA-Na regulates and controls the molecular structure in the system, has a guiding effect on a specific crystal face, promotes the growth along a certain crystal face, and is the main reason for the chain distribution of Pd; and the microscopic aggregation state of the material becomes more dispersed with the increase of the Cu component, and the edges of the structure are more obviously clustered, so that the diffusion capability of the Pd-Cu nano composite material is enhanced and the aggregation capability of the material is reduced with the increase of the Cu component. Therefore, the microstructure of the Pd-Cu nano composite catalyst with high Pd content tends to be more agglomerated, and the edges are smooth and not in cluster shape, so that more surfaces cannot be exposed like the structure of the Pd-Cu nano composite catalyst with low Pd content, and thus the active sites of the Pd-Cu nano composite catalyst with high Pd content are inevitably reduced, and the catalytic activity is influenced.

By using a scanning electron microscope (with a magnification of 5 to 30 ten thousand times), the sample 1 as a whole is in a chain-like structure, has a chain width of about 30nm, and is composed of rice-grain-shaped small particles. At the 20nm scale, it can be seen that the surface roughness of the material is in cluster form, and the surface characteristics determine that the material has larger contact area with reactants in the reaction, so that more active sites are provided, and the catalytic activity of the material is enhanced.

Sample 4 was only small-scale aggregated, in small-scale granular form rather than in bulk form, with sample 4 having more exposed surface than samples 1-3. Under a 20nm transmission electron microscope image, the material is more dispersed and distributed in a cluster shape than the samples 1-3, and has more active sites.

Second, electrochemical test

The catalyst particles of examples 1 to 5 were used to prepare electrocatalytic electrodes by the following method:

the method comprises the following steps: preparing a modified electrode: 1mg of the product prepared in the above examples 1 to 5 was weighed into 1mL of distilled water, and dispersed by ultrasonic to obtain

corresponding sample solutions

1, 2, 3, 4 and 5, respectively.

Step two: polishing a Glassy Carbon Electrode (GCE) on the deer skin, cleaning the electrode in an ultrasonic machine, and performing cyclic voltammetry scanning in a PBS (phosphate buffer solution) with the pH value of 7 by using a three-electrode system to detect the surface cleanliness of the glassy carbon electrode. Accurately transferring 10 mu L of the prepared sample solution by using a 10 mu L liquid transfer gun, dripping the sample solution on a glassy carbon electrode, naturally drying, dripping 8 mu L perfluorosulfonic acid type polymer (Nafion) (0.05 wt%), sealing and drying to obtain the electrocatalytic electrode, and drying to obtain the electrocatalytic electrode for testing.

2.1 testing the electrocatalytic activity of the 5 electrocatalytic electrodes on ethanol or ethylene glycol by adopting a cyclic voltammetry method, and simultaneously testing the electrocatalytic activity of an Ag/AgCl electrode or a platinum (Pt) wire electrode on ethanol or ethylene glycol by adopting the same cyclic voltammetry method, and obtaining the electrochemical activity area (ECSA) and the mass activity by a CV curve.

The method specifically comprises the following steps: background testing: 1.0mol/L NaOH solution; ethanol catalysis test: 1.0mol/L NaOH +1.0mol/L ethanol; ethylene glycol catalysis test: 1.0mol/L NaOH +1.0mol/L glycol; scanning rate: 50 mV. s-1, scanning potential: -0.6V-0.2V.

As shown in FIGS. 3 and 8, in the electrolyte (NaOH solution), a significant reduction peak was observed at a potential of about-0.3V, and it was found that the peak area of the reduction peak was Pd₁Cu₂Approximately equal to Pd₂Cu₁Greater than Pd₁Cu₁. The electrochemical active area can be calculated from the reduction peak area by an integration method.

The electrochemical active area formula is as follows: ECSA is Q/(mC), where Q is the total charge in the reaction (peak area S/sweep velocity v), m is the mass of active metal in the catalyst, C is the capacitance parameter, and the value of C is 420 μ C · cm^-1。

Calculated as Pd₁Cu₂Has an ECSA of 38.24m²/g，Pd₁Cu₁Has an ECSA value of 27.92m²/g， Pd₂Cu₁The ECSA of (b) was 21.57m 2/g. ECSA values indicate Pd₁Cu₂The material of (a) has more active sites and numerically has the strongest electrocatalytic properties. Catalytic activity for ethanol:the peak appearance and peak appearance position of samples 1-3 are approximately similar, and a high oxidation peak appears during the scanning from negative potential to positive potential, and a large reduction peak appears during the retrace. As shown in fig. 4, 5 and 9, the Pd — Cu materials of different compositions all have good peak current values for the oxidation catalysis of ethanol, i.e., each of the component materials has good activity for catalyzing the oxidation of ethanol. Meanwhile, the ethanol catalysis curves of the materials are compared, Pd₁Cu₂Has the best activity on ethanol catalysis, the highest peak current value is generated under the potential of-0.2V and reaches 6.9mA, meanwhile, the reduction peak current is very high, and strong metal poisoning is generated under the potential of-0.3V, which indicates that Pd is poisoned₁Cu₂The material is adsorbed by intermediate products such as CO and the like to be inactivated, and the material has a serious CO poisoning phenomenon; pd₁Cu₁Having a sub-optimal catalytic activity, reaching a peak current of about 3.2 mA for ethanol catalysis at a potential of-0.28V is a rather excellent peak current data, but Pd₁Cu₁The peak current of the material is half of the ethanol catalysis peak current, which indicates that the activity of the material has some difference from the activity of the optimal material. Pd₂Cu₁The ethanol catalytic peak current of the material reaches the highest current density of 2.2mA at the position of-0.2V, and is the lowest catalytic activity of the three materials, but the 2.2mA is a quite good peak current value. Accordingly, the material is also less toxic. Other indices for evaluating catalyst activity: mass activity and area activity, the formula is:

quality activity: MA (MA)_Pd＝I_k/m_Pd

Area activity: SA_Pd＝I_k/(ECSA*m_Pd)

Mass Activity (MA) was calculated based on Pd_Pd) And area activity (SA)_pd)，I_kThe peak current (mA) of the oxidation current of the alcohol in the cyclic voltammogram and the ECSA is the electrochemically active area (m) of Pd²/g)，m_PdIs the mass of Pd (mg).

Therefore, Pd is shown by the above formula₁Cu₂The mass activity of (A) is 1533.3mA/mg, Pd₁Cu₁The mass activity of (A) is 509.7mA/mg, Pd₂Cu₁The mass activity of (A) is 298.7 mA/mg; pd₁Cu₂Has an area activity of 4.38m²/g，Pd₁Cu₁Has an area activity of 1.83m²/g，Pd₂Cu₁Has an area activity of 1.38 m²/g。

As shown in fig. 6, 7 and 10, catalytic activity for ethylene glycol: pd₁Cu₂Is the material with the highest catalytic activity, reaches the maximum peak current of 3.9mA at the position of about-0.07V and is a relatively excellent numerical value, and simultaneously, has the maximum reduction peak current of 5.5mA at the position of-0.2V, and is calculated according to a formula, the mass activity is 904.6mA/mg, and the area activity is 2.36m²(ii) in terms of/g. The second best catalytic activity is Pd₁Cu₁The material shows that the catalytic peak current reaches the maximum value at 0.05V, the current density is 2.9mA, the mass activity reaches 376.6mA/mg, and the area activity is 1.34m²/g。Pd₂Cu₁The catalyst shows the lowest catalytic activity of the three materials, but also reaches 2.6mA, the catalytic efficiency is also excellent, the peak current is about 0.1V, the reduction peak is near-0.1V, the mass activity is 298.7mA/mg, and the area activity is 1.56m²/g。

In summary, the following steps: pd in ethanol and ethylene glycol catalytic tests in sodium hydroxide environment₁Cu₂The material performance is superior to Pd₁Cu₁，Pd₂Cu₁The peak currents of (a) are relatively low.

Sample 4 has the largest reduction peak relative to samples 1-3, i.e., has the largest electrochemically active area. The reduction peak for sample 5 was smaller than samples 1-3. In the catalytic test of ethanol, the highest oxidation peak current of a sample 4 is 7.3mA at the potential of-0.2V, the catalytic oxidation performance of the material is very excellent, and the highest reduction peak appears at the point of-0.3V. Sample 5 exhibited a maximum peak current value of 4.0mA at a potential of about-0.27V, with performance superior to Pd₁Cu₂The peak current value appearing at the same point was 3.6 mA. Thus, samples 4 and 5 are superior to samples 1 to 3 in catalytic activity.

2.2 testing the stability of the catalyst for catalyzing alcohol oxidation and the CO poisoning resistance of the catalyst by adopting a timing current method, specifically comprising the following steps: adding a potential (half-wave potential) on a working electrode, wherein a test solution is 1.0mol/L NaOH +1.0mol/L alcohol (ethanol or ethylene glycol), the half-wave potential is taken as a constant potential, and the test time is 6000 s; the current versus time was recorded.

In ethanol and ethylene glycol solution, Pd₁Cu₂Has good chemical stability. In an ethanol system, Pd₁Cu₂With the highest initial current density, which dropped dramatically over time, the current density was maintained as best in samples 1-3. Pd₂Cu₁Has a certain current density, and the amplitude of the decline along with time is extremely large. Pd₁Cu₁Has a very low current density and is depleted after a short time.

In the ethylene glycol system, all three materials have quite good initial current values, Pd₁Cu₂And Pd₂Cu₁The current drop of (a) is small, indicating that sample 1 and sample 3 have better catalytic stability. Wherein Pd₁Cu₂The initial current value of the material is maximum, the descending amplitude is slowest along with the time, and the material is finally kept at a higher steady-state current value, which indicates that Pd is in the system₁Cu₂The catalytic stability of the material is the most good. Pd₁Cu₁The material has the second highest initial current density, but the descending amplitude along with time is extremely large, the stability is decayed quickly, and the final stable current value is also lower, so that the material is the most unstable material. Pd₂Cu₁It has the lowest initial current density but is very stable, decreases most slowly with time, and finally stays at Pd₁Cu₂Almost out of phase with the steady state current value. By analysis, Pd₁Cu₂The stability of the material is superior to that of Pd₂Cu₁， Pd₁Cu₁The stability of (a) was the worst among samples 1 to 3.

Sample 4 had a higher initial current density than samples 1-3, reached 1.8mA, and decayed very slowly over time, i.e., the material was stable, not prone to decay, and finally remained at a lower steady state current level. Sample 5 had a second highest initial current density of about 1.2mA, but decayed faster, i.e., dropped to a lower steady state current value.

Thus, sample 4 is more stable than samples 1-3.

In conclusion, the Pd-Cu nanocomposite prepared by the method has the performance of catalyzing ethanol or ethylene glycol and excellent catalytic performance, and further, the arrangement sequence of the catalysts from high to low according to the catalytic activity is as follows: pd₁Cu₂-PVP＞Pd₁Cu₂-(PCA-Na+PVP)＞Pd₁Cu₂＞Pd₁Cu₁＞Pd₂Cu₁。

The above-mentioned embodiments of the present invention, which further illustrate the objects, technical solutions and advantages of the present invention, should be understood that the above-mentioned embodiments are only examples of the present invention and should not be construed as limiting the present invention, and any modifications, equivalents, improvements and the like made within the spirit of the present invention should be included in the scope of the present invention.

Claims

1. A Pd-Cu nano composite material is characterized by comprising the following components: the composite material comprises chloropalladate, copper nitrate, a structure directing agent and a reducing agent, wherein the molar ratio of the chloropalladate to the copper nitrate is (1-2) to (1-2), the volume ratio of the structure directing agent to the total components is (0.5-1.5) to 5, and the volume ratio of the reducing agent to the total components is (0.5-1.5) to 10.

2. The Pd-Cu nanocomposite according to claim 1, characterized in that the structure directing agent is sodium pyrrolidone carboxylate, or/and polyvinylpyrrolidone.

3. The Pd-Cu nanocomposite according to claim 1, wherein the reducing agent is hydrazine hydrate.

4. The Pd-Cu nanocomposite as claimed in claim 1, wherein the Pd-Cu nanocompositeThe material is Pd₁Cu₂、Pd₁Cu₁、Pd₂Cu₁Is pure of one of the above; or a mixture of two or three.

5. The Pd-Cu nanocomposite as claimed in claim 4, wherein the Pd₁Cu₂As catalyst for catalyzing ethanol or glycol reaction under alkaline condition, Pd₁Cu₂Has catalytic activity superior to Pd₁Cu₁，Pd₁Cu₁Has catalytic activity superior to Pd₂Cu₁。

6. A method for preparing a Pd-Cu nanocomposite, comprising:

adding a structure directing agent into distilled water according to the component proportion of the Pd-Cu nano composite material as in any one of claims 1 to 5 to prepare a solution;

slowly adding a reducing agent dropwise and then sealing;

stirring at constant temperature to obtain suspension;

centrifuging and collecting precipitate;

and (4) drying in vacuum to obtain the Pd-Cu nano composite material.

7. The method for preparing the Pd-Cu nano composite material according to claim 6, wherein the volume ratio of the total component of the Pd-Cu nano composite material to the distilled water is 1: 8-10.

8. The method for preparing Pd-Cu nanocomposite as claimed in claim 6, wherein 0.54mL of 0.25% by weight sodium pyrrolidone carboxylate is added to 27mL of distilled water with a pipette to prepare a solution;

9. The method for preparing Pd-Cu nanocomposite as claimed in claim 6, wherein the constant-temperature stirring is: and (3) placing the sealed solution into a constant-temperature magnetic stirrer, stirring at the speed of 800-1000 r/min, and stirring at the temperature of 20-25 ℃ for 1-2 h.

10. The method for preparing Pd-Cu nanocomposite as claimed in claim 6, wherein the vacuum drying to obtain the Pd-Cu nanocomposite comprises:

11. A preparation method of a Pd-Cu electro-catalytic electrode is characterized by comprising the following steps:

adding 1mg of the Pd-Cu nanocomposite material as claimed in any one of claims 1 to 5 into per milliliter of distilled water, and ultrasonically dispersing uniformly to prepare a sample solution;

cleaning the glassy carbon electrode;

dropping a sample solution on the glassy carbon electrode;

sealing and drying to obtain the Pd-Cu electro-catalytic electrode.

12. A method for applying a Pd-Cu nano composite material to ethanol or ethylene glycol catalytic reaction is characterized by comprising the following steps:

the Pd-Cu electrocatalytic electrode as set forth in claim 11 inserted into ethanol or ethylene glycol solution for electrochemical catalytic reaction.