Platinum-based quaternary alloy electrocatalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electrocatalysts, in particular to a platinum-based quaternary alloy electrocatalyst as well as a preparation method and application of the platinum-based quaternary alloy electrocatalyst. Platinum-palladium-ruthenium-iridium quaternary alloy rich in defects is loaded on a hollow carbon nano microsphere carrier with a high specific surface area; wherein the catalytic active sites comprise metal atom species and lattice defects on a (111) crystal face, and the lattice defects can significantly enhance the catalytic performance of adjacent metal atoms, so that the prepared platinum-based quaternary alloy catalyst has the advantages of small density, high stability, acid and alkali corrosion resistance, and porous characteristic, and can be used for preparing a catalyst. According to the present invention, the reaction activation energy can be substantially reduced, the electron / ion transfer and the mass transfer rate of the intermediate product can be substantially reduced, the catalytic activity and the cycle stability of the catalyst can be further improved, the maximum atom utilization rate (100%) can be achieved, and the catalyst material can be used as the catalyst material during the electro-catalytic oxygen reduction (ORR) reaction in the fuel cell and the metal-air cell.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysts, and in particular to a platinum-based quaternary alloy electrocatalyst and a preparation method and application thereof. Background Art

[0002] Fuel cells and metal-air batteries are two important types of electrochemical energy storage and conversion devices that convert chemical energy into electrical energy, characterized by the reduction reaction (ORR) and the evolution reaction (OER) of O2 on the cathode side. The large-scale application of fuel cells and metal-air batteries faces great challenges due to the hysteretic kinetics (high overpotential) and electrode polarization limitations of ORR and OER on the cathode side. Both ORR and OER are multi-electron transfer reactions involving the breaking and rearrangement of chemical bonds, and the reactions are mostly carried out in corrosive or oxidizing environments. In order to promote the rapid electrode reaction, a catalyst is required on the cathode side to overcome the high overpotential (>0.3V, determined by the electrode material) to drive the reaction. Precious metal-based catalysts such as platinum and iridium can significantly reduce the activation energy of the reaction pathway, effectively reduce the electrode reaction overpotential and accelerate the reaction rate. However, the shortcomings of precious metals represented by platinum, such as susceptibility to electrolyte corrosion, high overpotential polarization, and resource scarcity, greatly limit their application prospects in fuel cells and metal-air batteries. The preparation of highly intrinsic platinum-based electrocatalysts with stable crystal faces and enhanced electrocatalytic activity is one of the future development directions of ORR catalysts. In order to reduce the amount of single metals such as platinum and reduce the cost of catalysts, it is particularly necessary to develop efficient platinum-based alloy catalysts.

[0003] In-situ growth of specific crystal planes with defects on a high specific surface area conductive substrate can greatly enhance the reaction activity while maintaining the stability of the catalyst on the surface of the grain, thereby improving the catalytic activity and cycle stability of the catalyst. Studies have shown that when the crystal plane orientation of the platinum-based metal is (111), the stability of the platinum-based metal is higher. However, high stability leads to reduced catalytic activity, which is not conducive to the rapid kinetic reaction of ORR. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings existing in the prior art, and to propose a platinum-based quaternary alloy electrocatalyst and its preparation method and application. By in-situ loading platinum, palladium, ruthenium and iridium according to a certain ratio onto a high specific surface area carbon-based carrier, a defect-dominated intrinsic catalyst with high catalytic activity and high cycle stability is obtained, which can achieve a Faraday efficiency close to 100%; the electrocatalyst prepared can be used to prepare catalyst materials for fuel cells and metal-air batteries.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A platinum-based quaternary alloy electrocatalyst, wherein the platinum-based quaternary alloy electrocatalyst is a hollow carbon nanosphere (HCS) loaded with PtPdRuIr nanoparticles, wherein the catalytic active sites of the platinum-based quaternary alloy electrocatalyst include Pt, Pd, Ru, Ir atoms and lattice defects on the (111) crystal plane; and the metal content in the platinum-based quaternary alloy electrocatalyst is 15-20wt%.

[0007] Preferably, the hollow carbon nanospheres are microporous nanospheres.

[0008] Preferably, the diameter of the hollow carbon nanosphere is 100-300 nm, and the thickness of the carbon shell is 5-30 nm.

[0009] The present invention also provides a method for preparing a platinum-based quaternary alloy electrocatalyst, comprising the following steps:

[0010] Step 1, adding 1-butyl-2-methylimidazolium bromide to a silver chloroplatinate dispersion, adding deionized water, centrifuging, removing the lower layer product and dispersing it in deionized water to obtain a chloroplatinic acid-dimethylimidazolium ionic liquid;

[0011] Step 2: According to the method in step 1, chloropalladic acid-dimethylimidazolium ionic liquid, chlororuthenic acid-dimethylimidazolium ionic liquid, and chloroiridic acid-dimethylimidazolium ionic liquid are prepared in sequence;

[0012] Step 3, the hollow carbon spheres and the chloroplatinic acid-dimethylimidazolium ionic liquids obtained in steps 1 and 2, the chloropalladic acid-dimethylimidazolium ionic liquids, the chlororuthenic acid-dimethylimidazolium ionic liquids, and the chloroiridic acid-dimethylimidazolium ionic liquids are dispersed in deionized water in a certain proportion to obtain a mixed solution, sodium borohydride solution is quickly added, the reaction is carried out for 5-7 hours, and then the reaction product is washed and dried to obtain a hollow carbon-loaded defect-rich PtPdRuIr quaternary alloy electrocatalyst.

[0013] Preferably, in step 1, the molar ratio of 1-butyl-2-methylimidazolium bromide to silver chloroplatinate is 1.5 to 3.0.

[0014] Preferably, in step 3, the concentration of hollow carbon spheres in the mixed solution is 50-100 mg / L, the concentration of chloroplatinic acid-dimethylimidazole is 15-20 g / L, and the concentration of sodium borohydride is 0.9-5.5 g / L.

[0015] Preferably, in step 3, the mass ratio of chloroplatinic acid-dimethylimidazolium ionic liquid, chloropalladic acid-dimethylimidazolium ionic liquid, chlororuthenic acid-dimethylimidazolium ionic liquid and chloroiridic acid-dimethylimidazolium ionic liquid is 50:20:20:10.

[0016] The present invention also provides an application of a platinum-based quaternary alloy electrocatalyst obtained by the above-mentioned preparation method in fuel cells and metal-air battery catalyst materials.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention loads a platinum-based quaternary alloy with rich defects on the (111) crystal surface onto a hollow carbon nanosphere carrier with a high specific surface area, wherein the catalytic active sites include platinum-based noble metal atomic sites and defects, and the defects can enhance the catalytic performance of adjacent metal atoms. The platinum-based quaternary alloy electrocatalyst prepared in this way has low loading, high stability, acid and alkali corrosion resistance, and also exhibits porous properties, which can greatly reduce the reaction activation energy, accelerate electron / ion transfer and the mass transfer rate of intermediate products, thereby improving the catalytic activity and cycle stability of the catalyst, achieving the maximum atomic utilization (100%), and is suitable for use as a catalyst material in fuel cells and metal-air batteries during electrocatalytic oxygen reduction (ORR) and oxygen evolution (OER) reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the Pt / Pd / Ru / Ir electrocatalyst of the present invention;

[0020] Figure 2 The morphology of the platinum-based quaternary alloy active site catalyst in Example 1 of the present invention is shown in Figure 1, wherein (a) is a low-resolution transmission electron microscopy image, and (bd) are high-resolution transmission electron microscopy images;

[0021] Figure 3 is the X-ray diffraction spectrum of the Pt / Pd / Ru / Ir electrocatalyst in Example 1 of the present invention;

[0022] Figure 4 This is a scanning tunneling electron microscope image of the Pt / Pd / Ru / Ir electrocatalyst in Example 1 of the present invention;

[0023] Figure 5 The X-ray photoelectron spectra of the Pt / Pd / Ru / Ir electrocatalyst in Example 1 of the present invention and Comparative Example 1;

[0024] Figure 6 Cyclic voltammetry (a), linear sweep voltammetry (b), constant potential polarization (c) and zinc-air battery cycling performance (d) of the electrocatalytic oxygen reduction (ORR) reaction of the Pt / Pd / Ru / Ir electrocatalyst in Example 1 of the present invention and the commercially available Pt / C catalyst. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0026] Note: All raw materials of the present invention have no particular limitation on their sources and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0027] A platinum-based quaternary alloy electrocatalyst, wherein the platinum-based quaternary alloy electrocatalyst is a hollow carbon nanosphere (HCS) loaded with PtPdRuIr nanoparticles, wherein the catalytic active sites of the platinum-based quaternary alloy electrocatalyst include Pt, Pd, Ru, Ir atoms and lattice defects on the (111) crystal plane; and the metal content in the platinum-based quaternary alloy electrocatalyst is 15-20wt%.

[0028] The hollow carbon nanosphere is a carrier of metal active sites, and the hollow carbon nanosphere is a microporous nanosphere. The diameter of the hollow carbon nanosphere is 100-300 nm, and the thickness of the carbon shell is 5-30 nm.

[0029] A method for preparing a platinum-based quaternary alloy electrocatalyst comprises the following steps:

[0030] Step 1, adding 1-butyl-2-methylimidazolium bromide to a silver chloroplatinate dispersion, adding deionized water, centrifuging, removing the lower layer product and dispersing it in deionized water to obtain a chloroplatinic acid-dimethylimidazolium ionic liquid;

[0031] Step 2: According to the method in step 1, chloropalladic acid-dimethylimidazolium ionic liquid, chlororuthenic acid-dimethylimidazolium ionic liquid, and chloroiridic acid-dimethylimidazolium ionic liquid are prepared in sequence;

[0032] Step 3, the hollow carbon spheres and the chloroplatinic acid-dimethylimidazolium ionic liquids obtained in steps 1 and 2, the chloropalladic acid-dimethylimidazolium ionic liquids, the chlororuthenic acid-dimethylimidazolium ionic liquids, and the chloroiridic acid-dimethylimidazolium ionic liquids are dispersed in deionized water in a certain proportion to obtain a mixed solution, sodium borohydride solution is quickly added, the reaction is carried out for 6 hours, and then the reaction product is washed and dried to obtain a hollow carbon-loaded defect-rich PtPdRuIr quaternary alloy electrocatalyst.

[0033] Figure 1The schematic diagram of the PtPdRuIr quaternary alloy of the present invention is as follows. Specifically, the present invention first adds 1-butyl-2-methylimidazolium bromide to a dispersion of silver chloroplatinate, etc., adds deionized water and centrifuges, removes the lower layer product and disperses it in deionized water to obtain chloroplatinic acid-dimethylimidazolium ionic liquid (Pt-ILs). In the present invention, the molar ratio of 1-butyl-2-methylimidazolium bromide to silver chloroplatinate is preferably 2:1, more preferably 1.8:1.

[0034] After obtaining the chloroplatinic acid-dimethylimidazolium ionic liquid, disperse it and the hollow carbon spheres in deionized water under vigorous stirring, continue stirring to obtain a mixed solution (HCS@Pt-ILs), use the electrostatic and hydrogen bonding between ions to make the HCS nanospheres with negative charges on the surface adsorb the chloroplatinic acid-dimethylimidazolium ionic liquid, add sodium borohydride solution, react for 5 to 7 hours, preferably 6 hours, deposit PtPdRuIr nanoparticles on the surface of the HCS nanospheres, use the difference in the reducibility of the metal precursors, after the addition of sodium borohydride, the atoms preferentially form the (111) crystal plane, and the difference in atomic size leads to defects in the lattice point position. Then, the product obtained by the reaction is washed and dried to obtain a platinum-based quaternary alloy electrocatalyst with rich lattice defects and stable dispersion on the (111) crystal plane. In the present invention, the concentration of HCS nanospheres in the mixed solution is preferably 15-20 mg / L, more preferably 18 mg / L, the concentration of chloroplatinic acid-dimethylimidazole is preferably 15-20 g / L, more preferably 18.8 g / L; the concentration of sodium borohydride is preferably 5 g / L. The metal content in the catalyst prepared by the present invention is mainly affected by the ratio of the metal precursor, and the size of the alloy nanoparticles is affected by the concentration of the sodium borohydride solution.

[0035] An application of the platinum-based quaternary alloy electrocatalyst obtained by the above preparation method in fuel cells and metal-air battery catalyst materials.

[0036] Example 1

[0037] A PtPdRuIr quaternary alloy electrocatalyst, the preparation method of which is as follows:

[0038] (1) Synthesis of chloroplatinic acid ionic liquids: 0.128 g of 1-butyl-2-methylimidazolium bromide (28 mmol) was slowly added to 50 mL of 50 mmol / L chloroplatinic acid dispersion under stirring, centrifuged three times with deionized water, and 0.5 g of the lower layer product was taken and redispersed in 10 mL of deionized water to obtain 0.5 g / mL ferrocyanide dimethylimidazolium ionic liquid (Pt-ILs);

[0039] (2) Construction of a core-shell structure precursor with uniformly dispersed platinum ions: Pt-ILs (4 mL, 0.5 g mL-1) and hollow carbon spheres (50 mg) were dispersed in 100 mL of deionized water under vigorous stirring. The stirring was continued for 10 min to obtain HCS@Pt-ILs. Another three ionic liquids were added according to the precursor ratio. The stirring was continued for 10 min. Sodium borohydride solution (NaBH4, 20 mL, 20 mg) was added and the reaction was carried out for 6 h. The reaction product was washed with deionized water and ethanol, and dried in vacuum at 60 °C for 12 h to obtain the platinum-based quaternary alloy electrocatalyst PtPdRuIr / HCS.

[0040] The metal content of the catalyst of this example was measured by inductively coupled plasma mass spectrometry to be 20 wt %.

[0041] Example 2

[0042] A method for preparing a PtPdRuIr quaternary alloy electrocatalyst (PtPdRuIr / HCS), comprising preparing chloroplatinic acid-dimethylimidazolium ionic liquid (Pt-IL) according to step (1) in Example 1, then replacing chloroplatinic acid in step (2) in Example 1 with chloroplatinic acid, chloropalladic acid and chloroiridic acid, and then preparing PtPdIr / HCS according to step (2) in Example 1.

[0043] The mass content of the iron active sites of the catalyst of this example was measured by inductively coupled plasma mass spectrometry and found to be 16%.

[0044] Example 3

[0045] A method for preparing a PtPdRuIr quaternary alloy electrocatalyst (PtPdRuIr / HCS), comprising preparing chloroplatinic acid-dimethylimidazolium ionic liquid (Pt-IL) according to step (1) in Example 1, then replacing chloroplatinic acid in step (2) in Example 1 with chloroplatinic acid, chloropalladic acid and chlororuthenic acid, and then preparing PtPdRu / HCS according to step (2) in Example 1.

[0046] The mass content of the iron active sites of the catalyst of this example was measured by inductively coupled plasma mass spectrometry and found to be 18%.

[0047] Example 4

[0048] A method for preparing a PtPdRuIr quaternary alloy electrocatalyst (PtPdRuIr / HCS), comprising preparing chloroplatinic acid-dimethylimidazolium ionic liquid (Pt-IL) according to step (1) in Example 1, then replacing chloroplatinic acid in step (2) of Example 1 with chloroplatinic acid and chloropalladic acid, and then preparing PtPd / HCS according to step (2) of Example 1.

[0049] The content of the iron active sites of the catalyst of this example measured by inductively coupled plasma mass spectrometry was 18%.

[0050] Example 5

[0051] A method for preparing a PtPdRuIr quaternary alloy electrocatalyst (PtPdRuIr / HCS), comprising preparing chloroplatinic acid-dimethylimidazolium ionic liquid (Pt-IL) according to step (1) in Example 1, then replacing chloroplatinic acid in step (2) in Example 1 with chloroplatinic acid and chlororuthenic acid, and then preparing PtRu / HCS according to step (2) in Example 1.

[0052] The content of the iron active sites of the catalyst of this example measured by inductively coupled plasma mass spectrometry was 18%.

[0053] Example 6

[0054] A method for preparing a PtPdRuIr quaternary alloy electrocatalyst (PtPdRuIr / HCS), comprising preparing chloroplatinic acid-dimethylimidazolium ionic liquid (Pt-IL) according to step (1) in Example 1, then replacing chloroplatinic acid in step (2) in Example 1 with chloroplatinic acid and chloroiridic acid, and then preparing PtIr / HCS according to step (2) in Example 1.

[0055] The content of the iron active sites of the catalyst of this example measured by inductively coupled plasma mass spectrometry was 16%.

[0056] Comparative Example 1

[0057] The comparative example used in the present invention is commercial platinum carbon (JM, 20 wt%).

[0058] The atomic-level iron active site catalysts obtained in Examples 1-6 and Comparative Example 1 were applied to electrocatalytic ORR and zinc-air batteries: PtPdRuIr (16 mg) and 5 wt% Nafion solution (160 μL) were weighed and dispersed in a water-isopropanol solution with a volume ratio of 3:1, ultrasonicated for 60 min, and 15 μL was taken to prepare a working electrode. Other samples such as PtPdRuIr and commercial platinum carbon were used for electrode preparation and catalytic performance testing under the same conditions.

[0059] The results are shown in Figure 6 ; PtPdRuIr catalyst exhibits the best ORR and zinc-air battery performance, including more positive half-wave potential, limiting diffusion current density and cycling stability.

[0060] The description and practice disclosed in the present invention are easy to think and understand for ordinary technicians in the technical field, and several improvements and modifications can be made without departing from the principles of the present invention. Therefore, modifications or improvements made without departing from the spirit of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A platinum-based quaternary alloy electrocatalyst, It is characterized in that The platinum-based quaternary alloy electrocatalyst is a hollow carbon nanosphere loaded with PtPdRuIr nanoparticles. The catalytic active sites of the platinum-based quaternary alloy electrocatalyst include Pt, Pd, Ru, Ir atoms and lattice defects on the (111) crystal plane. The metal content in the platinum-based quaternary alloy electrocatalyst is 15-20wt%.

2. A platinum-based quaternary alloy electrocatalyst according to claim 1, It is characterized in that The hollow carbon nanospheres are microporous nanospheres.

3. A platinum-based quaternary alloy electrocatalyst according to claim 1, It is characterized in that The diameter of the hollow carbon nanosphere is 100-300 nm, and the thickness of the carbon shell is 5-30 nm.

4. The method for preparing a platinum-based quaternary alloy electrocatalyst according to claim 1, It is characterized in that The following steps are involved: Step 1, adding 1-butyl-2-methylimidazolium bromide to a silver chloroplatinate dispersion, adding deionized water, centrifuging, removing the lower layer product and dispersing it in deionized water to obtain a chloroplatinic acid-dimethylimidazolium ionic liquid; Step 2: According to the method in step 1, chloropalladic acid-dimethylimidazolium ionic liquid, chlororuthenic acid-dimethylimidazolium ionic liquid, and chloroiridic acid-dimethylimidazolium ionic liquid are prepared in sequence; Step 3, the hollow carbon spheres and the chloroplatinic acid-dimethylimidazolium ionic liquids obtained in steps 1 and 2, the chloropalladic acid-dimethylimidazolium ionic liquids, the chlororuthenic acid-dimethylimidazolium ionic liquids, and the chloroiridic acid-dimethylimidazolium ionic liquids are dispersed in deionized water in a certain proportion to obtain a mixed solution, sodium borohydride solution is quickly added, the reaction is carried out for 5-7 hours, and then the reaction product is washed and dried to obtain a hollow carbon-loaded defect-rich PtPdRuIr quaternary alloy electrocatalyst.

5. A method for preparing a platinum-based quaternary alloy electrocatalyst according to claim 4, It is characterized in that In step 1, the molar ratio of 1-butyl-2-methylimidazolium bromide to silver chloroplatinate is 1.5 to 3:

0.

6. A method for preparing a platinum-based quaternary alloy electrocatalyst according to claim 4, It is characterized in that In step 3, the concentration of hollow carbon spheres in the mixed solution is 50-100 mg / L, the concentration of chloroplatinic acid-dimethylimidazole is 15-20 g / L, and the concentration of sodium borohydride is 0.9-5.5 g / L.

7. A method for preparing a platinum-based quaternary alloy electrocatalyst according to claim 4, It is characterized in that In step 3, the mass ratio of chloroplatinic acid-dimethylimidazolium ionic liquid, chloropalladic acid-dimethylimidazolium ionic liquid, chlororuthenic acid-dimethylimidazolium ionic liquid and chloroiridic acid-dimethylimidazolium ionic liquid is 50:20:20:

10.

8. Use of a platinum-based quaternary alloy electrocatalyst obtained by the preparation method according to any one of claims 4 to 7 in fuel cells and metal-air battery catalyst materials.

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