A method for preparing a sponge-like porous Pd-based nanocatalyst

Abstract

This invention provides a method for preparing a sponge-like porous Pd-based nanocatalyst, relating to the field of catalyst preparation technology. The method includes the following steps: preparing a reaction solution; preparing a precursor solution; preparing a reduction solution; preparing a sponge-like Pd-based nanocrystal precursor; and electrochemical activation treatment. The sponge-like porous Pd-based nanocatalyst prepared by this method, through the prior synthesis of Pd-based nanoparticles followed by surface modification, overcomes the structural stability defects of traditional composite materials. It allows for control over the size, morphology, distribution, and bonding degree of the composite material, improving the synergistic effect between the Pd-based nanomaterials and hydroxides, thereby inhibiting CO poisoning and enhancing the activity and stability of the material in catalyzing EOR.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of catalyst preparation processes, in particular to a preparation method of a Pd-based nanometer catalyst with a sponge-like porous structure. BACKGROUND

[0002] With the further aggravation of global environmental problems and energy crisis, in order to realize sustainable development and reduce the use of fossil fuels, fuel cells, as a new type of energy conversion device, have the advantages of high energy density and no pollution, and are considered as one of the best energy sources to replace traditional fossil energy. Among many fuel cells, direct ethanol fuel cells (DEFCs) use liquid ethanol / water mixture as fuel and do not need additional equipment to handle waste heat of the cell, so they are one of the preferred small power sources. DEFCs have the advantages of high energy density, low toxicity, renewability and low cost, which make fuel cells become a potential energy source for realizing low pollution and sustainable development.

[0003] At present, Pt material is the best anode electrocatalyst for fuel cells due to its excellent physical and chemical properties. However, the global reserves of Pt are rare, which greatly increases the cost of the catalyst, thereby limiting the commercial development of Pt in fuel cells. In addition, Pt has strong binding to adsorbed carbon monoxide (CO ads ) in the catalytic process, which poisons the Pt active sites and causes the original catalytic performance to be lost. Therefore, we choose to add some other metals to reduce the poisoning of Pt and improve the utilization of Pt, that is, to reduce the cost and improve the performance, or to use Pd with similar crystal structure and relatively low price as a substitute for Pt.

[0004] Pd-based catalysts also face similar problems in fuel cell catalysis, namely relatively low catalytic activity and poor stability. A large amount of intermediate CO is produced in the reaction process and is easily adsorbed on the surface, thereby occupying the surface active sites and causing the catalyst to be poisoned and lose catalytic activity. The EOR reaction mechanism on the surface of the nanometer catalyst is unclear, and the intermediate catalyst poisoning reason is not clear, which restricts the optimization design of the catalyst. Many researchers have designed and developed three effective strategies:

[0005] 1) Some pure Pd materials with high specific surface area, such as Pd nanospheres and nanoflowers, are designed and synthesized. These materials have high specific surface area and can expose more active sites, so they have high catalytic performance.

[0006] 2) Pd is prepared into an alloy material with other non-noble metal components through alloying method. The use of non-noble metal reduces the use amount of Pd to a certain extent, and also adjusts the electronic structure of Pd, weakens the adsorption of CO and enhances the adsorption of oxygen-containing species, so it has high catalytic performance.

[0007] 3) Design and synthesis of some Pd-based composite materials, such as Pd hydroxide, which can adsorb a large amount of oxygen-containing species to achieve the effect of removing CO by oxidation, thereby having higher catalytic performance, designing new Pd-based composite catalysts, how to overcome the structural stability defects of traditional composite materials in structure, and reduce the cost, improve the utilization rate of Pd and other metals is the key challenge of catalyst development. ads SUMMARY

[0008] TECHNICAL PROBLEMS SOLVED

[0009] In view of the deficiencies of the prior art, the present application provides a preparation method of a sponge-like porous Pd-based nanocatalyst, which is rapidly synthesized by one-pot method, and the preparation process is relatively simple and has low requirements on production conditions. The sponge-like porous Pd-based nanocatalyst prepared by the method can overcome the structural stability defects of traditional composite materials in structure, can make the combination between materials more compact and not easy to be damaged, and can realize the control of the size, morphology structure, mutual distribution and combination degree of the composite material, adjust the synergistic effect between the sponge-like Pd-based nanoparticles and the surface amorphous hydroxide, and then realize the inhibition of CO poisoning, improve the activity and stability of the material in catalytic EOR, and based on the changes of the electrode surface structure and components, reveal the structure-activity relationship between the Pd-based composite material and EOR, and further guide the optimization of the synthesis conditions and process of new efficient Pd-based composite material.

[0010] TECHNICAL SCHEME

[0011] In order to achieve the above purpose, the present application is implemented by the following technical scheme: a preparation method of a sponge-like porous Pd-based nanocatalyst, the preparation method comprising the following steps:

[0012] Sp1, preparing a reaction solution, dissolving a certain amount of surfactant in deionized water as a reaction solvent;

[0013] Sp2, preparing a precursor solution, dissolving a predetermined proportion of a precursor palladium salt and a precursor nickel salt in a certain amount of a reaction solvent to obtain a precursor solution;

[0014] Sp3, preparing a reducing solution, dissolving a certain amount of a reducing agent in the reaction solvent prepared in Sp1 to obtain a reducing solution;

[0015] ​Sp4, the sponge-like Pd-based nanocrystal primary product is prepared by stirring the precursor solution prepared in Sp2 at room temperature, the stirring speed is controlled to be 500-1000 r / min, the stirring time is 2-4 h, and the sponge-like Pd-based nanocrystal is obtained after cleaning by standing at an environment of 10-30 DEG C for 3-5 days, and freeze-drying at an environment of-80 DEG C for 24 h;

[0016] Sp5, electrochemical activation treatment: the Pd-based nanocrystal primary product is surface-modified to obtain a sponge-like porous Pd-based nanocatalyst.

[0017] Preferably, the surfactant in Sp1 is cyclodextrin, and the concentration of cyclodextrin in the reaction solvent is greater than or equal to 0.01 mol / L.

[0018] Preferably, in the precursor solution of Sp2, the concentration of palladium ions is 0.02-0.06 mol / L, the concentration of nickel ions is 0.02-0.06 mol / L, and the molar ratio of palladium ions to nickel ions in the precursor solution is 1:(0.5-3).

[0019] Preferably, the palladium salt in the precursor is any combination of one or more of potassium platinous chloride and palladium acetylacetonate, and the nickel salt in the precursor is any combination of one or more of nickel acetate tetrahydrate and nickel chloride hexahydrate.

[0020] Preferably, the reducing agent in Sp3 is sodium borohydride, and the concentration of the reducing agent in the reducing solution in Sp3 is greater than or equal to 0.04 mol / L.

[0021] Preferably, the electrochemical activation treatment includes electrochemical cyclic voltammetry activation or chronoamperometry activation, the electrolyte is a 0.5-2 mol / L NaOH or KOH solution, the potential range is-0.95-0.2 V, and the scan speed is 50-500 mV / s.

[0022] Beneficial effects

[0023] The application provides a preparation method of a sponge-like porous Pd-based nanocatalyst.

[0024] 1. The Pd-based nanocatalyst with a sponge-like porous structure prepared by the method can overcome the structural stability defects of traditional composite materials, realize the control of the size, morphology structure, mutual distribution and combination degree of the composite material, improve the synergistic effect between the Pd-based nanomaterial and the hydroxide, and then realize the inhibition of CO poisoning, improve the activity and stability of the material in the catalytic EOR, and simultaneously through the precise analysis of the catalytic activity and stability, the change of the reaction condition and the electrode surface structure and component, the key factors of the Pd-based composite material with a sponge-like porous structure and the performance improvement of the EOR are explored, and a series of novel and efficient Pd-based composite materials are further synthesized.

[0025] 2. In the catalyst after the electrochemical activation treatment, the Pd nanocrystals form an amorphous Ni(OH)2 layer, and in the actual reaction process, the Ni(OH)2 can accelerate the dissociation of water, and is beneficial to the generation of adsorbed hydroxyl (OH ads ), and the OH ads has a good oxidation effect on the CO adsorbed on the Pd site in the Pd nanocrystals, and plays a rapid activation and removal effect, so that more active sites can act on the EOR, and the prepared Pd-Ni(OH)2 nanocrystal catalyst with a sponge-like porous structure has excellent catalytic EOR reaction activity and stability. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a preparation method flow chart of the Pd-based nanocatalyst with a sponge-like porous structure of the embodiment of the application;

[0027] Figure 2 It is a scanning electron microscope and transmission electron microscope graph of the Pd-based nanocatalyst with a sponge-like porous structure prepared by the preparation method of the Pd-based nanocatalyst with a sponge-like porous structure of the embodiment of the application;

[0028] Figure 3 It is a scanning electron microscope and transmission electron microscope graph of the Pd-based nanocatalyst with a sponge-like porous structure prepared by the preparation method of the Pd-based nanocatalyst with a sponge-like porous structure of the embodiment of the application;

[0029] Figure 4 It is a scanning electron microscope and transmission electron microscope graph of the Pd-based nanocatalyst with a sponge-like porous structure prepared by the preparation method of the Pd-based nanocatalyst with a sponge-like porous structure of the embodiment of the application;

[0030] Figure 5A transmission electron microscope diffraction pattern of the sponge-like Pd-Ni(OH)2 nanocrystal catalyst according to an embodiment of the present application;

[0031] Figure 6 An X-ray diffraction pattern of the sponge-like Pd-Ni(OH)2 nanocrystal catalyst according to an embodiment of the present application;

[0032] Figure 7 An X-ray photoelectron spectroscopy pattern of the sponge-like Pd-Ni(OH)2 nanocrystal catalyst according to an embodiment of the present application;

[0033] Figure 8 Cyclic voltammograms of the sponge-like Pd-Ni(OH)2 nanocrystal catalyst according to an embodiment of the present application and a commercial Pd / C catalyst in an ethanol oxidation reaction;

[0034] Figure 9 Chronoamperograms of the sponge-like Pd-Ni(OH)2 nanocrystal catalyst according to an embodiment of the present application and a commercial Pd / C catalyst in an ethanol oxidation reaction. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without any creative effort belong to the scope of protection of the present application. Embodiment one:

[0037] A Pd-based nanocatalyst with a sponge-like porous structure, as shown in FIG. 1, comprises a sponge-like porous structure and a Pd-Ni(OH)2 nanocrystal. Figure 1 The method specifically comprises the following steps:

[0038] (1) 5.675 g of β-cyclodextrin is mixed with 500 mL of deionized water, and ultrasonic treatment is performed for 1 h, so that the β-cyclodextrin is fully dissolved in the aqueous solution to obtain a β-cyclodextrin reaction solvent.

[0039] (2) Potassium chloropalladate and nickel acetate tetrahydrate solids with a molar ratio of 1:2 are weighed, and are dissolved in 4 mL of the β-cyclodextrin reaction solvent, and ultrasonic treatment is performed for 20 min to obtain a mixed precursor solution.

[0040] In the precursor solution, the concentration of palladium ions is 0.02 mol / L, and the concentration of nickel ions is 0.02 mol / L.

[0041] (3) Sodium borohydride is added to 4 mL of the reaction solvent for mixing, and ultrasonic treatment is performed for 30 min to obtain a reduction solution.

[0042] In the reducing solution, the concentration of sodium borohydride is 0.04 mol / L.

[0043] (4) Measure 192 mL of the reaction solvent obtained in step (1) and add it to the precursor solution obtained in step (2) above to obtain 196 mL of mixed precursor solution.

[0044] (5) The mixed precursor solution obtained in step (4) is stirred at a high speed for 15 minutes, with the rotation speed controlled at 800 r / min.

[0045] (6) Quickly add the newly prepared reduction solution obtained in step (3) to the precursor solution obtained in step (5) to obtain 200 mL of reaction solution.

[0046] (7) Stir the reaction solution obtained in step (6) at a speed of 800 r / min for 2 h. After stirring, let it stand at 25 °C for 3 days. After standing, sonicate for 5 min to remove the black solid catalyst attached to the bottle wall and rotor. Centrifuge the reaction solution at 9500 r for 8 min. Wash it three times with deionized water and ethanol, disperse it in an aqueous solution, and freeze dry it to obtain a black solid powder. The black solid powder is a primary product of Pd nanocrystals.

[0047] (8) Prepare the black solid powder obtained in step (7) into catalyst ink, then drop it onto the surface of glassy carbon electrode and let it air dry. Activate it by electrochemical cyclic voltammetry with 1 mol / L NaOH solution as electrolyte, potential range of -0.95 to 0.2 V (relative to saturated calomel electrode, SCE) and scan rate of 50 mV / s. After electrochemical activation, Pd-Ni(OH)2 sponge-like porous nanocrystal catalyst can be obtained.

[0048] The obtained Pd-Ni(OH)2 sponge-like porous nanocrystalline catalyst was observed using a scanning electron microscope (SEM), as follows: Figure 2 As shown, the obtained Pd-Ni(OH)2 sponge-like porous nanocrystals exhibit a sponge-like bulk morphology with a loosely distributed porous structure on the surface. Observation using a transmission electron microscope (TEM) reveals... Figure 3 As shown, the sponge-like porous nanocrystal structure of Pd-Ni(OH)2 is fluffy and can provide a large specific surface area, further as... Figure 4 As shown, the nanocrystal has distinct lattice fringes with a lattice spacing of 0.23 nm, corresponding to the (111) plane of the Pd material. Meanwhile, as... Figure 5 The sponge-like porous nanocrystals of Pd-Ni(OH)2 observed by transmission electron microscopy in diffraction mode (SEAD) show that they have a polycrystalline structure.

[0049] The Pd-Ni(OH)2sponge-like porous nanocrystalline catalyst was scanned by X-ray diffractometer, and the results are shown in FIG. 2, which shows that all the XRD spectrum peaks correspond to the face-centered cubic phase of Pd (JCPDF, 46-1043), wherein the diffraction peaks of 2θ = 40.1°, 46.0°, 67.8° and 81.9° can be indexed as the (111), (200), (220) and (311) crystal planes of Pd. Figure 6

[0050] Further, the valence state of Ni in the Pd-Ni(OH)2sponge-like porous nanocrystalline catalyst was detected by X-ray photoelectron spectroscopy, and the results are shown in FIG. 3, which shows that for the element Ni, a pair of peak patterns appears at 855.1 eV and 872.9 eV, which correspond to Ni 2p3 / 2 and Ni 2p1 / 2, respectively, and a group of satellite peaks of Ni2+ appear at 860.3 eV and 879.7 eV. The spin energy separation of 17.8 eV has the characteristics of Ni(OH)2phase, which can prove the existence of the Ni(OH)2phase on the surface of the porous material, and thus it can be proved that the above-prepared Ni(OH)2modified Pd nanocrystalline is the Pd-Ni(OH)2sponge-like porous nanocrystalline catalyst. Figure 7

[0051] Ethanol oxidation reaction (EOR) catalytic activity test:

[0052] (1) Preparation of catalytic electrode

[0053] The above-prepared Pd-Ni(OH)2sponge-like porous nanocrystalline catalyst and Vulcan XC-72 carbon (25% of the Pd catalyst) were dispersed in 0.5 mL of water, 0.5 mL of anhydrous ethanol and a Nafion solution (Vwater+ethanol / VNafion solution = 1:0.03), and then ultrasonic treatment was performed for 30 min to form a uniform ink. The catalyst was prevented from excessive aggregation during the ultrasonic treatment by shaking multiple times. The amount of Pd in the catalyst was controlled based on the ICP test data, and the Pd loading was maintained at 28 μg / cm2. 2 4 μL of the ink was dropped onto a glassy carbon electrode with an area of 3 mm, and then the electrode was dried at room temperature for use.

[0054] (2) EOR test

[0055] ​​Before the test, the solution was saturated with Ar gas for 30 min to remove the dissolved oxygen, and then cyclic voltammetry was performed in Ar-saturated 1 mol / L NaOH solution at a scan rate of 50 mV / s to remove the excess impurities and modify the surface of the Ni(OH)2species, and then the EOR performance test was performed in 1 mol / L NaOH solution containing 1 mol / L C2H5OH at a scan rate of 50 mV / s, and finally the long-term stability of the prepared sample was determined by chronoamperometry in 1 mol / L NaOH solution containing 1 mol / L C2H5OH at a potential of -0.27 V (vs. saturated calomel electrode, SCE). For comparison, a commercial Pd / C (10 wt% Pd nanoparticles supported on Vulcan XC-72 carbon, Aladdin) was prepared and tested by the same method.

[0056] The EOR performance of the Pd-Ni(OH)2sponge-like porous nanocrystal catalyst obtained in Example 1 was tested in a three-electrode cell system by using a CHI660e workstation, with a saturated calomel electrode and a Pt mesh as the reference electrode and the counter electrode, respectively.

[0057] Figure 8 The cyclic voltammogram of the Pd-Ni(OH)2sponge-like porous nanocrystal catalyst of Example 1 in 1 mol / L NaOH solution containing 1 mol / L C2H5OH at a potential range of -0.95 V to 0.2 V (vs. saturated calomel electrode, SCE) and a scan rate of 50 mV / s was obtained from Figure 8 It can be seen that the EOR activity of the Pd-Ni(OH)2sponge-like porous nanocrystal catalyst is 3.73 A mg －1 Pd In comparison, the activity of the commercial Pd / C is only 1.23 A mg －1 .

[0058] Figure 9 The potential change of the Pd-Ni(OH)2sponge-like porous nanocrystal catalyst of Example 1 in 1 mol / L NaOH solution containing 1 mol / L C2H5OH at a potential of -0.27 V (vs. saturated calomel electrode, SCE) after 10,000 s was obtained from Figure 9 It can be seen that the activity of the Pd-Ni(OH)2sponge-like porous nanocrystal catalyst decreases by 80% after the 10,000 s stability test, and in comparison, the activity of the commercial Pd / C decreases by 98.4% after the 10,000 s stability test, and the activity is almost close to 0, i.e., the activity is lost. Specific embodiment two:

[0060] A method for preparing a Pd-based nanocatalyst with a sponge-like porous structure, as shown in Figure 1 The method specifically comprises the following steps:

[0061] (1) Mix 5.675 g of β-cyclodextrin with 500 mL of deionized water, and ultrasonicate for 1 h to fully dissolve the β-cyclodextrin in the aqueous solution to obtain a β-cyclodextrin reaction solvent.

[0062] (2) Weigh potassium chloropalladate and nickel acetate tetrahydrate with a molar ratio of 1:1, and dissolve them in 4 mL of the β-cyclodextrin reaction solvent obtained in step (1) to obtain a mixed precursor solution.

[0063] In the precursor solution, the concentration of palladium ions is 0.02 mol / L, and the concentration of nickel ions is 0.02 mol / L.

[0064] (3) Add sodium borohydride to the 4 mL reaction solvent and mix, and ultrasonicate for 30 min to obtain a reduction solution.

[0065] In the reduction solution, the concentration of sodium borohydride is 0.04 mol / L.

[0066] (4) Measure 192 mL of the reaction solvent obtained in step (1), and add it to the precursor solution obtained in step (2) to obtain 196 mL of a mixed precursor solution.

[0067] (5) Highly stir the mixed precursor solution obtained in step (4), and control the stirring speed to be 800 r / min for 15 min.

[0068] (6) Quickly add the freshly prepared reduction solution obtained in step (3) to the precursor solution obtained in step (5) to obtain 200 mL of a reaction solution.

[0069] (7) Stir the reaction solution obtained in step (6), and control the stirring speed to be 800 r / min for 2 h. After stirring, place it at 25°C for 3 days. After standing, ultrasonicate for 5 min to remove the black solid catalyst attached to the bottle wall and the rotor. Centrifuge the reaction solution, and wash it with deionized water and ethanol for 3 times. Disperse it in an aqueous solution, and freeze-dry to obtain a black solid powder, which is a Pd nanocrystal primary product.

[0070] (8) The black solid powder obtained in step (7) is prepared into a catalyst ink, which is then dropped onto the surface of a glassy carbon electrode and naturally dried, and then activated by electrochemical cyclic voltammetry, with a 1 mol / L NaOH solution as the electrolyte, a potential range of -0.95-0.2 V (relative to a saturated calomel electrode, SCE), and a scan rate of 50 mV / s. After the electrochemical activation treatment, the Pd-Ni(OH)2sponge-like porous nanocrystal catalyst is obtained. Embodiment Three

[0072] A method for preparing a Pd-based nanocatalyst with a sponge-like porous structure, as shown in Figure 1 The method specifically comprises the following steps:

[0073] (1) 5.675 g of β-cyclodextrin is mixed with 500 mL of deionized water, and ultrasonic treatment is performed for 1 h, so that the β-cyclodextrin is fully dissolved in the aqueous solution to obtain a β-cyclodextrin reaction solvent.

[0074] (2) Potassium chloropalladate and nickel acetate tetrahydrate with a molar ratio of 1:3 are weighed, and then dissolved in 4 mL of the β-cyclodextrin reaction solvent, and ultrasonic treatment is performed for 20 min to obtain a mixed precursor solution.

[0075] In the precursor solution, the concentration of palladium ions is 0.02 mol / L, and the concentration of nickel ions is 0.02 mol / L.

[0076] (3) Sodium borohydride is added to 4 mL of the reaction solvent and mixed, and ultrasonic treatment is performed for 30 min to obtain a reduction solution.

[0077] In the reduction solution, the concentration of sodium borohydride is 0.04 mol / L.

[0078] (4) 192 mL of the reaction solvent obtained in step (1) is measured and added to the precursor solution obtained in step (2) to obtain 196 mL of a mixed precursor solution.

[0079] (5) The mixed precursor solution obtained in step (4) is subjected to high-speed stirring, and the stirring speed is controlled at 800 r / min for 15 min.

[0080] (6) The freshly prepared reduction solution obtained in step (3) is quickly added to the precursor solution obtained in step (5) to obtain 200 mL of a reaction solution.

[0081] (7) Stir the reaction solution obtained in step (6) at a speed of 800 r / min for 2 h. After stirring, let it stand at 25 °C for 3 days. After standing, sonicate for 5 min to remove the black solid catalyst attached to the bottle wall and rotor. Centrifuge the reaction solution at 9500 r for 8 min. Wash it three times with deionized water and ethanol, disperse it in an aqueous solution, and freeze dry it to obtain a black solid powder. The black solid powder is a primary product of Pd nanocrystals.

[0082] (8) Prepare the black solid powder obtained in step (7) into catalyst ink, then drop it onto the surface of glassy carbon electrode and let it air dry. Activate it by electrochemical cyclic voltammetry with 1 mol / L NaOH solution as electrolyte, potential range of -0.95 to 0.2 V (relative to saturated calomel electrode, SCE) and scan rate of 50 mV / s. After electrochemical activation, Pd-Ni(OH)2 sponge-like porous nanocrystal catalyst can be obtained. Specific Implementation Example 4:

[0084] A method for preparing a Pd-based nanocatalyst with a sponge-like porous structure, such as... Figure 1 As shown, the method specifically includes the following steps:

[0085] (1) Mix 5.675g of β-cyclodextrin with 500mL of deionized water and sonicate for 1h to fully dissolve the β-cyclodextrin in the aqueous solution to obtain the β-cyclodextrin reaction solvent.

[0086] (2) Weigh potassium palladium chloride and nickel acetate tetrahydrate solids in a molar ratio of 2:1, dissolve them in 4 mL of β-cyclodextrin reaction solvent, and sonicate for 20 min to obtain a mixed precursor solution.

[0087] In the precursor solution, the concentration of palladium ions was 0.02 mol / L, and the concentration of nickel ions was 0.02 mol / L.

[0088] (3) Add sodium borohydride to 4 mL of reaction solvent and mix. Sonicate for 30 min to obtain a reduced solution.

[0089] In the reducing solution, the concentration of sodium borohydride is 0.04 mol / L.

[0090] (4) Measure 192 mL of the reaction solvent obtained in step (1) and add it to the precursor solution obtained in step (2) above to obtain 196 mL of mixed precursor solution.

[0091] (5) The mixed precursor solution obtained in step (4) is stirred at a high speed for 15 minutes, with the rotation speed controlled at 800 r / min.

[0092] (6) Quickly add the newly prepared reduction solution obtained in step (3) to the precursor solution obtained in step (5) to obtain 200 mL of reaction solution.

[0093] (7) Stir the reaction solution obtained in step (6) at a speed of 800 r / min for 2 h. After stirring, let it stand at 25 °C for 3 days. After standing, sonicate for 5 min to remove the black solid catalyst attached to the bottle wall and rotor. Centrifuge the reaction solution at 9500 r for 8 min. Wash it three times with deionized water and ethanol, disperse it in an aqueous solution, and freeze dry it to obtain a black solid powder. The black solid powder is a primary product of Pd nanocrystals.

[0094] (8) Prepare the black solid powder obtained in step (7) into catalyst ink, then drop it onto the surface of glassy carbon electrode and let it air dry. Activate it by electrochemical cyclic voltammetry with 1 mol / L NaOH solution as electrolyte, potential range of -0.95 to 0.2 V (relative to saturated calomel electrode, SCE) and scan rate of 50 mV / s. After electrochemical activation, Pd-Ni(OH)2 sponge-like porous nanocrystal catalyst can be obtained.

[0095] In summary, the Pd-Ni(OH)2 sponge-like porous nanocrystal catalyst prepared by the method of the present invention has excellent catalytic activity for ethanol oxidation reaction, i.e., good EOR activity, and excellent stability. The preparation process is simple, low-cost, and easy to scale up for industrial production.

[0096] The foregoing description has fully disclosed the specific embodiments of the present invention. Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Pd-based nanocatalyst with a sponge-like porous structure, characterized by: The preparation method comprises the following steps: Sp1, preparing a reaction solution, a certain amount of surfactant is dissolved in deionized water as a reaction solvent; the surfactant in Sp1 is cyclodextrin, and the concentration of cyclodextrin in the reaction solvent is greater than or equal to 0.01 mol / L; Sp2, preparing a precursor solution, a predetermined proportion of precursor palladium salt and precursor nickel salt are dissolved in a certain amount of reaction solvent to obtain a precursor solution; in the precursor solution of Sp2, the concentration of palladium ions is 0.02-0.06 mol / L, the concentration of nickel ions is 0.02-0.06 mol / L, and the molar ratio of palladium ions to nickel ions in the precursor solution is 1:(0.5-3); Sp3, preparing a reducing solution, a certain amount of reducing agent is dissolved in the reaction solvent prepared in Sp1 to obtain a reducing solution; Sp4, preparing a sponge-like Pd-based nanocrystal primary product: the reaction solvent obtained in Sp1 is added to the precursor solution obtained in Sp2 to obtain a mixed precursor solution, the mixed precursor solution is highly stirred, then the newly prepared reducing solution obtained in Sp3 is quickly added to the precursor solution, a reaction solution is obtained, and stirring is performed, after stirring is completed, it is placed at 25°C, after standing is completed, the black solid catalyst attached to the bottle wall and the rotor is removed by ultrasonic, the reaction solution is centrifuged, washed with deionized water and ethanol, dispersed in an aqueous solution, and freeze-dried to obtain a black solid powder, which is a Pd nanocrystal primary product; Sp5, electrochemical activation treatment: after surface modification of the Pd-based nanocrystal primary product, a sponge-like porous Pd-based nanocatalyst is obtained, the electrochemical activation treatment comprises: electrochemical cyclic voltammetry activation or chronoamperometry activation, the electrolyte is 0.5-2 mol / L NaOH or KOH solution, the potential range is-0.95-0.2 V, and the scan rate is 50-500 mV / s.

2. The method of claim 1, wherein the method of preparing a Pd-based nano-catalyst with a sponge-like porous structure is characterized by: The palladium salt in the precursor is any combination of one or more of potassium chloropalladite and palladium acetylacetonate, and the precursor nickel salt is any combination of one or more of nickel acetate tetrahydrate and nickel chloride hexahydrate.

3. The method of claim 1, wherein the method of preparing a Pd-based nano-catalyst with a sponge-like porous structure is characterized by: The reducing agent in Sp3 is sodium borohydride, and the concentration of the reducing agent in the reducing solution in Sp3 is greater than or equal to 0.04 mol / L.

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