PdCuNi medium-high-entropy alloy catalyst for formic acid oxidation reaction and preparation method of PdCuNi medium-high-entropy alloy catalyst
Through the three-dimensional porous nanowire structure design of the PdCuNi medium-entropy alloy catalyst, the problems of insufficient catalytic activity and poor stability of palladium-based catalysts in the formic acid oxidation reaction were solved, and efficient and low-cost catalytic performance improvement was achieved.
Patent Information
- Application Number
- CN202510570304.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-06
- Publication Date
- 2025-09-05
AI Technical Summary
Existing palladium-based catalysts in direct formic acid fuel cells have problems such as insufficient catalytic activity, poor stability and high cost. In particular, CO poisoning and catalyst agglomeration or dissolution are prone to occur in the formic acid oxidation reaction, and traditional preparation methods make it difficult to achieve a high-entropy alloy structure.
Using PdCuNi medium-entropy alloy catalyst, through the synergistic effect of multiple metals and unique morphology design, a three-dimensional porous nanowire structure is prepared. The average diameter of the nanowires is 5-8nm and the porosity is ≥70%. It is prepared in a one-step method to avoid surfactant contamination and improve catalytic activity and stability.
The catalytic activity and stability of the formic acid oxidation reaction were significantly improved, with MA reaching 2.7A/mg, strong resistance to CO poisoning, low current decay rate, high palladium atom utilization rate, low cost, and simple preparation process.
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Abstract
Description
Technical Field
[0001] The present invention relates to the application field of fuel cell nanomaterials, in particular to a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction and a preparation method thereof. Background Art
[0002] Direct formic acid fuel cells (DFFCs) are considered a promising clean energy device due to their high theoretical equilibrium potential (1.48V), high energy density, environmental friendliness, and safe operation. However, their commercial application is limited by the performance bottleneck of palladium-based catalysts:
[0003] 1. Insufficient catalytic activity: Traditional Pd-based catalysts are prone to CO poisoning in the formic acid oxidation reaction, resulting in deactivation of active sites;
[0004] 2. Poor stability: The catalyst is prone to agglomeration or dissolution during long-term use, resulting in performance degradation;
[0005] 3. High cost: The utilization rate of palladium metal is low, and the palladium loading needs to be reduced through alloying.
[0006] Existing research has shown that by introducing multi-metal doping (such as Cu and Ni) to adjust the electronic structure (such as the d-band center) of palladium-based catalysts, the resistance to CO poisoning and water activation ability can be effectively enhanced. However, traditional preparation methods (such as co-precipitation and sol-gel methods) have difficulty in achieving atomically disordered high-entropy alloy structures and are prone to introducing surfactants to contaminate the active sites.
[0007] Therefore, a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction and a preparation method thereof are proposed. Summary of the Invention
[0008] (1) Technical problems solved
[0009] In response to the shortcomings of the existing technology, the present invention provides a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction and its preparation method. Through the synergistic effect of multiple metals and unique morphology design, the catalytic activity, stability and palladium atom utilization rate of the formic acid oxidation reaction are significantly improved, solving the problems raised by the background technology.
[0010] (2) Technical solution
[0011] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction, the catalyst is composed of Pd, Cu, and Ni with an atomic ratio of 50-55:20-25:20-25, has a three-dimensional porous nanowire structure, the average diameter of the nanowire is 5-8nm, and the specific surface area (ECSA) is ≥50m 2 / g.
[0012] Preferably, in the three-dimensional porous nanowire structure of the catalyst, the nanowires are interwoven to form a network with a porosity of ≥70%, and the pore size distribution is between 2-20 nm.
[0013] Preferably, in the X-ray diffraction (XRD) spectrum of the catalyst, the diffraction peak is located between the standard peaks of Pd, Cu, and Ni elements, and relative to the diffraction peak of Pd element, the (111) crystal plane diffraction angle offset is ≥0.5°.
[0014] The preparation method of the PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction comprises the following steps:
[0015] Step 1: Solution preparation: Add chloropalladium (HPdCl4), copper chloride (CuCl2), and nickel chloride (NiCl2) solutions in a molar ratio of 2:1:1 into a round-bottom flask and stir magnetically (800 rpm) for 30 minutes until uniform;
[0016] Step 2: Reduction reaction: Rapidly inject 2 mL of 1 M NaBH4 aqueous solution, stir continuously for 1 min, and then transfer to a 20°C constant temperature water bath and let stand for 8 h;
[0017] Step 3: washing and drying: the product was washed alternately with water and ethanol three times, frozen in liquid nitrogen for 1 minute, and then vacuum dried to obtain a PdCuNi aerogel nanowire catalyst;
[0018] Step 4: Structure control: Place the dried catalyst in a hydrogen atmosphere (purity ≥ 99.99%) and anneal at 100-300°C for 0.5-2 hours to control the surface oxidation state and lattice defect density of the nanowires;
[0019] Step 5: Loading and molding: Disperse the catalyst in an ethanol-water mixed solution (volume ratio 1:1), ultrasonically homogenize it, and then drop-coat it on the surface of carbon paper (or nickel foam). Vacuum dry it at 60-80°C for 2-4 hours to obtain a self-supporting electrode.
[0020] Preferably, the injection rate of the NaBH4 aqueous solution in step 2 is 1-5 mL / s to ensure rapid reduction to form a uniform nanowire structure.
[0021] Preferably, the vacuum drying temperature in step 3 is 20-50° C. to avoid collapse of the nanowire structure due to high temperature.
[0022] Preferably, the heating rate of the hydrogen annealing treatment in step 4 is 5-10°C / min, and the annealing time is adjusted according to the size of the nanowires. The larger the nanowire diameter, the longer the annealing time.
[0023] Preferably, the loading amount of the catalyst in the electrode in step 5 is 0.2-1.0 mg / cm2 After drop coating, it is processed by roller pressing process (pressure 5-10MPa) to enhance the adhesion between the catalyst and the substrate.
[0024] (3) Beneficial effects
[0025] Compared with the prior art, the present invention provides a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction and a preparation method thereof, which has the following beneficial effects:
[0026] 1. The PdCuNi medium-high entropy alloy catalyst for formic acid oxidation and its preparation method have high catalytic activity: the mass activity (MA) reaches 2.7A / mg, which is 6-9 times that of commercial Pd / C.
[0027] 2. The PdCuNi medium-entropy alloy catalyst for formic acid oxidation and its preparation method have strong stability: the ability to resist CO poisoning is significantly enhanced, and the current decay rate in cyclic voltammetry (CV) and time current method (CA) tests is lower than that of commercial catalysts.
[0028] 3. The PdCuNi medium-high entropy alloy catalyst for formic acid oxidation and its preparation method have high atomic utilization: the three-dimensional porous structure maximizes the exposure of active sites and the specific activity (SA) reaches mA / cm 2 class.
[0029] 4. The PdCuNi medium-high entropy alloy catalyst for formic acid oxidation and its preparation method have the advantages of low cost: the palladium loading is reduced through multi-element alloying, the preparation process is simple (one-step method), and no complex equipment or surfactants are required. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 Macroscopic schematic diagram of PdCuNi aerogel alloy nanowires.
[0031] Figure 2 This is the transmission electron microscope (TEM) image of the PdCuNi aerogel alloy nanowire catalyst.
[0032] Figure 3 Schematic diagram of EDS-Mapping of the ternary PdCuNi aerogel alloy nanowire catalyst area.
[0033] Figure 4 Schematic diagram of the XRD pattern of the ternary PdCuNi aerogel alloy nanowire catalyst.
[0034] Figure 5 Schematic diagram of the test results of the ternary alloy PdCuNi aerogel nanowire catalyst.
[0035] Figure 6This is the test result diagram of the ternary alloy PdCuNi aerogel nanowire catalyst.
[0036] Figure 7 This is a comparison chart of the formic acid electrooxidation performance of PdCuNi aerogel nanowire catalyst, PdCu aerogel nanowire catalyst, PdNi aerogel nanowire catalyst and commercial PtC. DETAILED DESCRIPTION
[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.
[0038] See also Figure 1-7 The PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction is composed of Pd, Cu, and Ni with an atomic ratio of 50-55:20-25:20-25. It has a three-dimensional porous nanowire structure with an average nanowire diameter of 5-8nm and an ECSA of ≥50m 2 / g;
[0039] In the three-dimensional porous nanowire structure of the catalyst, the nanowires are interwoven to form a network with a porosity of ≥70%, and the pore size distribution is between 2-20 nm;
[0040] In the X-ray diffraction (XRD) spectrum of the catalyst, the diffraction peak is located between the standard peaks of Pd, Cu, and Ni, and the crystal plane diffraction angle offset relative to the Pd diffraction peak is ≥0.5°, such as Figure 2 and Figure 4 ,from Figure 2 It can be seen that the PdCuNi aerogel alloy nanowires have a typical three-dimensional porous structure, in which the extended ultrathin nanowires are interconnected. The diameter distribution of the PdCuNi aerogel alloy nanowires is 6nm. Figure 4 It can be seen that the diffraction angle of the ternary PdCuNi aerogel alloy nanowire catalyst is larger than that of the standard card, that is, the lattice shrinks. Figure 5 It can be seen that the ternary alloy PdCuNi is placed in a mixed solution of 0.5MH2SO4+1MHCOOH (under the same test conditions) in the potential range of -0.19-0.96VvSCE and a cyclic scanning test at a scanning speed of 50mV / s. Cyclic voltammetry test is performed. This test is a half-cell reaction. The anode active material is formic acid. Figure 5 、 Figure 6 、 Figure 7It can be seen that the attenuation of the current density of the PdCuNi aerogel nanowire catalyst at a potential of 0.6 V is significantly smaller than that of the commercial Pt / C catalyst, which indicates that the PdCuNi aerogel nanowire catalyst has significantly better resistance to by-products and CO poisoning in the formic acid electrooxidation reaction than the commercial Pt / C catalyst.
[0041] The preparation method of the PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction comprises the following steps:
[0042] Step 1: Solution preparation: Add chloropalladium (HPdCl4), copper chloride (CuCl2), and nickel chloride (NiCl2) solutions in a molar ratio of 2:1:1 into a round-bottom flask and stir magnetically (800 rpm) for 30 minutes until uniform;
[0043] Step 2: Reduction reaction: Rapidly inject 2 mL of 1 M NaBH4 aqueous solution, continue stirring for 1 minute, and then transfer to a 20°C constant temperature water bath and let it stand for 8 hours. The injection rate of NaBH4 aqueous solution is 1-5 mL / s to ensure rapid reduction and formation of uniform nanowire structure.
[0044] Step 3: Washing and drying: The product was washed alternately with water and ethanol three times, frozen in liquid nitrogen for 1 minute, and then vacuum dried to obtain a PdCuNi aerogel nanowire catalyst. The vacuum drying temperature was 20-50°C to avoid high temperature-induced collapse of the nanowire structure.
[0045] Step 4: Structure control: Place the dried catalyst in a hydrogen atmosphere (purity ≥ 99.99%) and anneal it at 100-300°C for 0.5-2h to control the surface oxidation state and lattice defect density of the nanowires. The heating rate of the hydrogen annealing treatment is 5-10°C / min. The annealing time is adjusted according to the size of the nanowires. The larger the nanowire diameter, the longer the annealing time. Introducing lattice defects (such as vacancies and dislocations) can increase the density of active sites and improve the catalytic reaction kinetics.
[0046] Step 5: Loading and forming: The catalyst is dispersed in an ethanol-water mixed solution (volume ratio 1:1), ultrasonically homogenized and then drop-coated on the surface of carbon paper (or nickel foam), and vacuum-dried at 60-80°C for 2-4 hours to obtain a self-supporting electrode. The catalyst loading in the electrode is 0.2-1.0 mg / cm 2 After drop coating, it is processed by roller pressing process (pressure 5-10MPa) to enhance the adhesion between the catalyst and the substrate, clarify the loading amount and roller pressing parameters, ensure that the electrode has good conductivity and mechanical strength, and avoid catalyst shedding.
[0047] Example 1
[0048] The method for preparing the PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction, when implemented:
[0049] Preparation of PdCuNi aerogel nanowire catalyst
[0050] 1. Add 2mmolH2PdCl4, 1mmolCuCl2, and 1mmolNiCl2 to a 50mL round-bottom flask, dissolve in 20mL deionized water, and stir at 800rpm for 30min.
[0051] 2. Rapidly inject 2 mL of 1 M NaBH4 aqueous solution, stir vigorously for 1 min, and then transfer the flask to a 20°C constant temperature water bath and let it stand for 8 h;
[0052] 3. The product was washed three times with deionized water and ethanol, frozen in liquid nitrogen for 1 min, and then dried in a vacuum dryer (-0.1 MPa, room temperature) for 12 h to obtain black PdCuNi aerogel powder.
[0053] Example 2
[0054] Preparation of PdCu aerogel nanowire catalyst
[0055] The addition of NiCl2 in Example 1 was omitted, the molar ratio of Pd:Cu was maintained at 2:1, and the remaining steps were the same as those in Example 1 to prepare a PdCu binary alloy aerogel.
[0056] Example 3
[0057] DFFC performance test
[0058] The PdCuNiAA catalyst was coated on carbon paper (catalyst loading 0.5 mg / cm 2 ) as the anode electrode and Pt / C catalyst as the cathode to assemble the membrane electrode (MEA). The test was carried out in 0.5MHCOOH+0.1MH2SO4 solution at a scanning speed of 50mV / s. The results showed that the maximum power density was 153mW / cm 2 , the performance retention rate after 10h stability test is 82%.
[0059] It should be noted that the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.
[0060] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.
Claims
1. A PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction, characterized by: The catalyst is composed of Pd, Cu and Ni with an atomic ratio of 50-55:20-25:20-25. It has a three-dimensional porous nanowire structure, an average diameter of the nanowires of 5-8nm, and a specific surface area of ≥50m² / g.
2. The PdCuNi medium-high entropy alloy catalyst for formic acid oxidation according to claim 1, characterized in that: In the three-dimensional porous nanowire structure of the catalyst, the nanowires are interwoven to form a network with a porosity of ≥70%, and the pore size distribution is between 2-20 nm.
3. The PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction according to claim 1, characterized in that: In the X-ray diffraction spectrum of the catalyst, the diffraction peak is located between the standard peaks of Pd, Cu and Ni elements, and the crystal plane diffraction angle offset is ≥0.5° relative to the diffraction peak of Pd element.
4. The method for preparing a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation reaction according to any one of claims 1 to 3, characterized in that: The specific steps are as follows: Step 1: Solution preparation: add chloropalladic acid, copper chloride, and nickel chloride solutions in a molar ratio of 2:1:1 into a round-bottom flask and stir magnetically for 30 minutes until uniform; Step 2: Reduction reaction: Rapidly inject 2 mL of 1 M NaBH4 aqueous solution, stir continuously for 1 min, and then transfer to a 20°C constant temperature water bath and let stand for 8 h; Step 3: washing and drying: the product was washed alternately with water and ethanol three times, frozen in liquid nitrogen for 1 minute, and then vacuum dried to obtain a PdCuNi aerogel nanowire catalyst; Step 4: Structural control: placing the dried catalyst in a hydrogen atmosphere and annealing it at 100-300°C for 0.5-2 hours to control the surface oxidation state and lattice defect density of the nanowires; Step 5: Loading and forming: disperse the catalyst in an ethanol-water mixed solution, ultrasonically homogenize it, and then drop-coat it on the surface of the carbon paper. Vacuum dry it at 60-80°C for 2-4 hours to obtain a self-supporting electrode.
5. The method for preparing a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation according to claim 4, wherein: The injection rate of the NaBH4 aqueous solution in step 2 is 1-5 mL / s.
6. The method for preparing a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation according to claim 4, wherein: The vacuum drying temperature in step 3 is 20-50°C.
7. The method for preparing a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation according to claim 4, wherein: The heating rate of the hydrogen annealing treatment in step 4 is 5-10°C / min.
8. The method for preparing a PdCuNi medium-high entropy alloy catalyst for formic acid oxidation according to claim 4, wherein: In step 5, the catalyst loading amount in the electrode is 0.2-1.0 mg / cm², and the electrode is processed by roller pressing after drop coating.