PtRu nanocage as well as preparation method and application thereof

Abstract

The invention discloses a PtRu nanocage and a preparation method and application thereof, and the method comprises the following steps: (1) adsorbing ruthenium chloride and chloroplatinic acid to ZIF-8 to form a PtRu ZIF-8 composite material; (2) performing high-temperature calcination on the PtRu-ZIF-8 composite material in a hydrogen-argon reducing atmosphere to reduce the PtRu-ZIF-8 composite material into metal Ru and Pt, and forming an intermetallic compound by Zn generated by decomposition of ZIF-8, Ru and Pt to obtain a PtRuZn composite material; and (3) selectively etching the PtRuZn composite material by using a hydrochloric acid solution to remove Zn so as to obtain the PtRu nanocage with the cage-shaped structure. The method is easy and convenient to operate, the catalytic activity can be remarkably improved, and the Pt dosage can be greatly reduced. The material is suitable for AEMWE, and a new solution is provided for developing a low-cost and high-stability water electrolysis hydrogen production technology.

Description

Technical Field

[0001] The invention relates to the technical field of alkaline water electrolysis, and in particular to a PtRu nano cage and a preparation method and application thereof. Background Art

[0002] Alkaline anion exchange membrane water electrolysis (AEMWE) technology is a green hydrogen production path with great commercial prospects in the field of energy transformation. However, its industrialization process is limited by two bottlenecks of the cathode catalyst system: one is the high cost of precious metal platinum (Pt), and the other is the relatively low catalytic activity of Pt-based catalysts in alkaline media. Although traditional Pt-based catalysts have ideal hydrogen binding energy, their insufficient water dissociation ability causes the activity of alkaline hydrogen evolution reaction (HER) to be far inferior to that in acidic environments. The scarcity of Pt resources further exacerbates the cost pressure of AEMWE.

[0003] In summary, it is necessary to find a simple and efficient preparation method to synthesize nanomaterial electrocatalysts with low Pt loading and ensure that the material has high activity to meet its application as a Pt-based catalyst material in water electrolysis. Summary of the invention

[0004] The purpose of the present invention is to provide a PtRu nanocage and its preparation method and application, which combines Ru and Pt single atoms with low Pt loading, can effectively improve the alkaline HER catalytic efficiency and reduce the cost of hydrogen production, and provide a new strategy for high-efficiency and low-cost AEMWE cathode catalysts.

[0005] In one aspect of the present invention, the present invention provides a method for preparing a PtRu nanocage. According to an embodiment of the present invention, the method comprises the following steps:

[0006] (1) adsorbing ruthenium chloride and chloroplatinic acid onto ZIF-8 to form PtRu@ZIF-8 composite materials;

[0007] (2) In a hydrogen-argon reducing atmosphere, the PtRu@ZIF-8 composite material is calcined at high temperature to reduce it to metallic Ru and Pt. At the same time, Zn produced by the decomposition of ZIF-8 forms an intermetallic compound with Ru and Pt to obtain a PtRuZn composite material;

[0008] (3) The PtRuZn composite material is selectively etched using a hydrochloric acid solution to remove Zn, thereby obtaining a PtRu nanocage with a cage-like structure.

[0009] In addition, the method for preparing a PtRu nanocage according to the above embodiment of the present invention may also have the following additional technical features:

[0010] In some embodiments of the present invention, step (1) is specifically as follows: adding a mixed solution of ruthenium chloride and chloroplatinic acid to a ZIF-8 suspension, stirring evenly, performing a hydrothermal reaction, and then centrifuging and drying to obtain a PtRu@ZIF-8 composite material.

[0011] In some embodiments of the present invention, the preparation method of the ZIF-8 suspension is as follows: zinc nitrate hexahydrate solution, 2-methylimidazole solution and hexadecyltrimethylammonium bromide solution are stirred and mixed uniformly, and then allowed to stand to obtain a ZIF-8 suspension.

[0012] In some embodiments of the present invention, the mass ratio of zinc nitrate hexahydrate, 2-methylimidazole and hexadecyltrimethylamine bromide is (0.3-0.4):(5-6):(0.016-0.018), the stirring speed is 350-450 rpm, the stirring time is 5-10 min, and the standing time is 2-3 h.

[0013] In some embodiments of the present invention, the mass ratio of ruthenium chloride, chloroplatinic acid, and ZIF-8 is (8-12): (0-10): (16-18); the temperature of the hydrothermal reaction is 50-80°C, and the hydrothermal time is 2-3h; the stirring speed is 350-450rpm; the centrifugal separation speed is 10000-12000rpm; the drying temperature is 60-70°C, and the drying time is 6-7h.

[0014] In some embodiments of the present invention, in step (2), the volume ratio of hydrogen to argon is (5%-10%): (90%-95%), the calcination temperature is 300-350°C, the calcination time is 2-3h, and the heating rate is 5-10°C / min.

[0015] In some embodiments of the present invention, in step (3), the concentration of the hydrochloric acid solution is 0.5-1 mol / L, and the etching time is 20-40 min.

[0016] In another aspect of the present invention, the present invention provides a PtRu nanocage prepared by the preparation method of the PtRu nanocage.

[0017] In another aspect of the present invention, the present invention provides an application of PtRu nanocage in alkaline anion exchange membrane water electrolysis.

[0018] In addition, the application of the PtRu nanocage according to the above embodiment of the present invention in alkaline anion exchange membrane water electrolysis may also have the following additional technical features:

[0019] In some embodiments of the present invention, the PtRu nanocage is used to prepare a cathode material.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention provides a method for preparing PtRu nanocages by simple H 2 / Ar high temperature calcination treatment reduces Ru and Pt to a metallic state, which is beneficial to the improvement of electrocatalytic performance. It has the advantages of simple operation, low cost, good repeatability and uniform product structure. The product obtained by the present invention has a larger specific surface area, excellent stability and outstanding electrochemical performance.

[0022] 2. The present invention removes the non-active site metal Zn by a simple acid etching method, which greatly improves the electrochemical performance of the product.

[0023] 3. The present invention uses ZIF-8 as a template, and by uniformly adsorbing ruthenium chloride and chloroplatinic acid in the pores of ZIF-8, it can give full play to its three-dimensional hollow porous characteristics, provide an efficient channel for the mass transfer and diffusion of substrates and products, thereby accelerating H 2 This not only improves the electrocatalytic performance, but also exhibits excellent reaction kinetics. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 TEM image of ZIF-8 obtained in step (1) of Example 1 of the present invention;

[0025] Figure 2 a, b, and c are transmission electron micrographs of the PtRu@ZIF-8 precursor obtained in step (2) of Example 1-3 of the present invention;

[0026] Figure 3 a, b, and c are transmission electron micrographs of the PtRuZn composite material obtained in step (3) of Example 1-3 of the present invention, respectively;

[0027] Figure 4 In the figure, a, b, and c are transmission electron micrographs of the three nanocages obtained in step (4) of Examples 1-3 of the present invention, respectively, and d is a high-resolution electron micrograph of the PtRu nanocage;

[0028] Figure 5 The EDS element mapping diagram of the PtRu nanocage obtained in step (4) of Example 1 of the present invention, the first diagram is a high-resolution diagram of the PtRu nanocage, and the following three diagrams correspond to the mapping diagrams of the three elements Pt, Ru, and Zn respectively;

[0029] Figure 6 The PtRuZn composite material and PtRu obtained in steps (3) and (4) of Example 1 of the present invention, and the Pt prepared in Examples 2 and 3 1 Ru 20 and Pt2 Ru 5 X-ray diffraction pattern of nanocage (Figure a) and X-ray photoelectron spectrum of PtRu nanocage (Figure b);

[0030] Figure 7 is the PtRu obtained in step (4) of Example 1-3 of the present invention, Pt 1 Ru 20 , Pt 1 Ru 20 Comparison of the electrochemical performance of nanocages (Figure a) and the electrochemical performance of PtRu nanocages compared with commercial platinum carbon (Pt / C) and ruthenium carbon (Ru / C) (Figure b);

[0031] Figure 8 AEMWE performance (Figure a) and mass activity comparison (Figure b) of PtRu nanocages and commercial Pt / C in the application example of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The centrifuge used in the following examples is Anke TGL-10B produced by Shanghai Anting Scientific Instrument Factory, the magnetic stirrer is MS-MS-10 multi-head magnetic stirrer produced by Shanghai Kunquan Biotechnology Co., Ltd., the tube furnace is OTF-1200X produced by Hefei Kejing Material Technology Co., Ltd., and the transmission electron microscope is JEOL-F2010 produced in Japan. The drugs used in the following examples were used directly after purchase without any treatment.

[0034] Example 1

[0035] A method for preparing a PtRu nanocage comprises the following steps:

[0036] (1) Weigh 0.7252 g Zn(NO 3 ) 2 6H 2O, dissolved in 25mL deionized water, and magnetically stirred at 400rpm for 10min at room temperature until the solution is clear and transparent, recorded as solution A. Weigh 11.3504g 2-methylimidazole and 0.035g CTAB, dissolve them in 175mL deionized water, and magnetically stir until completely dissolved under the same conditions (room temperature, 400rpm, 10min), recorded as solution B. Then, solution A was quickly poured into solution B under rapid stirring, and continued to stir at 400rpm for 5min to ensure that the reactants were fully mixed. Finally, the mixed solution was placed in a constant temperature environment of 25℃ for 3h to obtain a ZIF-8 suspension.

[0037] (2) Take 8 mL of the ZIF-8 suspension obtained in step (1), centrifuge at 12000 rpm for 10 min, wash twice with methanol (12000 rpm×4 min), redisperse in 3 mL of deionized water for ultrasonic treatment, and transfer to a 20 mL polytetrafluoroethylene reactor to obtain solution C. 3 With 0.00103g H 2 Cl 6 Pt was dissolved in a mixed solvent of 2 mL deionized water and 1 mL methanol, and dissolved by ultrasound to obtain solution D. Solution C was added to solution D under stirring at 400 rpm, and stirring was continued for 30 min, followed by hydrothermal reaction at 80 °C for 2 h. The product was collected by centrifugation at 12000 rpm for 3 min, and vacuum dried at 60 °C for 7 h to obtain the PtRu@ZIF-8 precursor.

[0038] (3) The PtRu@ZIF-8 composite material obtained in step (2) was placed in a porcelain boat, and then placed in a tube furnace at a volume percentage of 5% H 2 / Ar atmosphere, the temperature was increased to 300 °C at a heating rate of 10 °C / min and calcined for 2 h to obtain a PtRuZn composite material.

[0039] (4) Weigh 5 mg of the PtRuZn composite material obtained in step (3), add 1 mL of 0.5 M HCl solution thereto, soak for 20 min, centrifuge (speed: 12000 rpm, time: 3 min), then wash with deionized water and centrifuge (speed: 12000 rpm, time: 3 min) to obtain PtRu nanocages.

[0040] Depend on Figure 5 As shown, EDS mapping analysis of the PtRu nanocage catalyst shows that Pt and Ru are evenly distributed on the nanocage, and trace amounts of Zn are still present after acid washing.

[0041] 1 mg of PtRu nanocage catalyst was weighed and dissolved in aqua regia, and inductively coupled plasma mass spectrometry (ICP-MS) was performed. As shown in Table 1, the mass fraction of Pt was only 5.4%, and the mass fraction of Ru was 28.4%, indicating that the PtRu nanocage catalyst with low Pt loading was successfully prepared.

[0042] Table 1 Metal mass percentage of Pt and Ru in PtRu nanocages

[0043]

[0044] Example 2

[0045] A Pt 1 Ru 20 The preparation method of the nanocage composite material is different from that of Example 1 only in that: in step (2), RuCl 3 The mass is 0.01035g, H 2 Cl 6 The mass of Pt is 0.000503 g, and the other steps and parameters are the same as those in the embodiment. 1 Ru 20 Nanocage composites.

[0046] Example 3

[0047] A Pt 1 Ru 20 The preparation method of the nanocage composite material is different from that of Example 1 only in that: in step (2), RuCl 3 The mass is 0.01035g, H 2 Cl 6 The mass of Pt is 0.00403 g, and the other steps and parameters are the same as those in the embodiment. 2 Ru 5 Nanocage composites.

[0048] Depend on Figures 1 to 3 As shown, even when different masses of chloroplatinic acid were added, the morphology of the synthesized material did not change significantly after hydrothermal calcination and remained a nanocage structure.

[0049] Depend on Figure 4 As shown in Figures a, c, and d, the three nanocage catalysts still have complete cage structures after acid washing. Figure b shows that single Pt atoms are distributed on the surface of the PtRu nanocage catalyst (the position marked by the red circle).

[0050] Depend on Figure 6 As shown in a, the sample only contains Ru crystal phase, no Pt crystal phase is seen, and the characteristic peak of ZnO disappears after acid washing. Figure 6As shown in b, in the overall spectrum, no characteristic peak of the Zn element was observed at 475.5 eV in the catalyst after etching, further confirming that ZnO had been successfully removed. The above results are highly consistent with the XRD and EDS characterization results.

[0051] Weigh 1 mg of PtRu nanocages and Pt 1 Ru 20 Nanocage, Pt 2 Ru 5 Nanocages, commercial Pt / C and Ru / C, together with 1.5 mg carbon black, were added to 990 μL isopropanol and 10 μL Nafion, and ultrasonicated for more than 30 min to make the catalyst dispersed evenly. Then 10 μL of the dispersion was dropped on the glassy carbon electrode. After the dispersion dried, it was used as the working electrode for HER performance testing. The reference electrode was Hg / HgO and the counter electrode was a carbon rod electrode. 2 The electrochemical tests were carried out in 1 M KOH electrolyte.

[0052] like Figure 7 As shown in Figure 2, the activity of PtRu nanocages is significantly higher than that of Pt 1 Ru 20 Nanocage, Pt 2 Ru 5 Nanocages, commercial Pt / C and Ru / C at a current density of 10 mA / cm 2 When the overpotential is only 37mV.

[0053] Application Examples

[0054] The alkaline anion exchange membrane water electrolysis method comprises the following steps:

[0055] The PtRu nanocage catalyst prepared in Example 1 and commercial Pt / C were sprayed on one side of the anion exchange membrane as the cathode material. The anion membrane is a high-strength and high-alkali-resistant anion exchange membrane based on a polyaromatic backbone, which has the advantages of high strength and high ionic conductivity. The precious metal loading was controlled at 0.06 mg. Pt / cm 2 and 0.5mg Pt / cm 2 The anode is made of NiFe material loaded with nickel foam, and the carbon paper is placed on the cathode side as a gas diffusion layer. The carbon paper, cathode, anode, polytetrafluoroethylene gasket and bipolar plate are assembled to form a membrane electrode assembly. The assembled membrane electrode assembly is subjected to AEMWE performance test under 80°C and 1M KOH electrolyte conditions.

[0056] like Figure 8 As shown, PtRu nanocages at 1A / cm 2At a current density of , the battery voltage is only 1.59V, and the mass activity is significantly higher than that of commercial Pt / C.

[0057] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a PtRu nanocage, characterized in that: The following steps are involved: (1) adsorbing ruthenium chloride and chloroplatinic acid onto ZIF-8 to form PtRu@ZIF-8 composite materials; (2) In a hydrogen-argon reducing atmosphere, the PtRu@ZIF-8 composite material is calcined at high temperature to reduce it to metallic Ru and Pt. At the same time, Zn produced by the decomposition of ZIF-8 forms an intermetallic compound with Ru and Pt to obtain a PtRuZn composite material; (3) The PtRuZn composite material is selectively etched using a hydrochloric acid solution to remove Zn, thereby obtaining a PtRu nanocage with a cage-like structure.

2. The method for preparing a PtRu nanocage according to claim 1, characterized in that: Step (1) is specifically as follows: adding a mixed solution of ruthenium chloride and chloroplatinic acid to a ZIF-8 suspension, stirring evenly, performing a hydrothermal reaction, and then centrifuging and drying to obtain a PtRu@ZIF-8 composite material.

3. The method for preparing a PtRu nanocage according to claim 2, characterized in that: The preparation method of the ZIF-8 suspension is as follows: zinc nitrate hexahydrate solution, 2-methylimidazole solution and hexadecyltrimethylammonium bromide solution are stirred and mixed uniformly, and then allowed to stand to obtain a ZIF-8 suspension.

4. The method for preparing a PtRu nanocage according to claim 3, characterized in that: The mass ratio of zinc nitrate hexahydrate, 2-methylimidazole and hexadecyltrimethylamine bromide is (0.3-0.4):(5-6):(0.016-0.018), the stirring speed is 350-450 rpm, the stirring time is 5-10 min, and the standing time is 2-3 h.

5. The method for preparing a PtRu nanocage according to claim 2, characterized in that: The mass ratio of ruthenium chloride, chloroplatinic acid and ZIF-8 is (8-12): (0-10): (16-18); The temperature of the hydrothermal reaction is 50-80°C, and the hydrothermal time is 2-4h; The stirring speed is 350-450 rpm; The rotation speed of the centrifugal separation is 10000-12000rpm; The drying temperature is 60-70° C., and the drying time is 6-7 hours.

6. The method for preparing a PtRu nanocage according to claim 1, characterized in that: In step (2), the volume ratio of hydrogen to argon is (5%-10%): (90%-95%), the calcination temperature is 300-350°C, the calcination time is 2-3h, and the heating rate is 5-10°C / min.

7. The method for preparing a PtRu nanocage according to claim 1, characterized in that: In step (3), the concentration of the hydrochloric acid solution is 0.5-1 mol / L, and the etching time is 20-40 min.

8. A PtRu nanocage prepared by the method for preparing the PtRu nanocage according to any one of claims 1 to 7.

9. Use of the PtRu nanocage according to claim 8 in alkaline anion exchange membrane water electrolysis.

10. The use of the PtRu nanocage in alkaline anion exchange membrane water electrolysis according to claim 9, characterized in that: The PtRu nanocage is used to prepare cathode materials.

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