Carbon-supported palladium nanoparticle electrocatalyst capable of inhibiting sintering as well as preparation method and application of carbon-supported palladium nanoparticle electrocatalyst

Abstract

The invention discloses a sintering-inhibiting carbon-supported palladium nanoparticle electrocatalyst and a preparation method and application thereof.The preparation method includes the steps that palladium particles and tri-n-octylphosphorus are dispersed in oleylamine and then react at the temperature of 50-200 DEG C. The average diameter of the obtained palladium nanoparticles subjected to surface phosphating treatment is 6.3 nanometers, and the palladium nanoparticles can be supported on carbon to serve as a catalyst. And the surface phosphorus element plays a bridging role between the palladium nanoparticles and the carbon carrier, so that the metal-carrier interaction is enhanced, and the stability of a catalytic system under an electrochemical condition is improved. The obtained palladium nanoparticles have a surface disordered structure, and show activity superior to that of a conventional palladium catalyst in a catalytic reaction. In addition, the method has good universality, is also suitable for modification treatment of commercial palladium-carbon materials, and provides an effective technical path for performance optimization of the commercial palladium-carbon materials.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, specifically to a carbon-supported palladium nanoparticle electrocatalyst that inhibits sintering, and also to its preparation method and its application in improving the stability of alkaline fuel cells. Background Technology

[0002] Carbon-supported platinum group metal catalysts (such as platinum and palladium) are widely used in energy-related electrocatalysis. However, their durability is often compromised by particle sintering during the catalytic process, a phenomenon that can lead to a several-fold increase in particle size. For example, palladium nanoparticles catalyzing the oxygen reduction reaction can aggregate from 3 nanometers to 10 nanometers within 5000 cycles. This sintering results in a significant loss of active surface area, causing rapid catalyst deactivation and severely limiting the long-term application of oxygen reduction-related devices such as fuel cells and metal-air batteries.

[0003] The sintering of carbon-supported noble metal nanoparticles mainly occurs through two mechanisms: (1) particle migration and aggregation; (2) Ostwald ripening, in which atoms migrate from smaller nanoparticles to larger ones. Aggregation is driven by weak interactions between the metal and the support, while ripening is usually initiated by the high chemical potential of small-sized nanoparticles, leading to metal desorption. Therefore, suppressing sintering requires stabilizing both the interface and surface of the entire catalytic system. A classic design to achieve this goal is to use heteroatoms (X, such as sulfur, selenium, and nitrogen) with strong affinity for platinum group metals to bridge the gap between carbon-supported noble metal nanoparticles and carbon. The resulting MXC coordination structure not only anchors the carbon-supported noble metal nanoparticles to the support but also modulates their surface chemical state through electronic effects, thereby simultaneously suppressing aggregation and ripening.

[0004] Although MXC coordination structures theoretically possess the dual functions of inhibiting sintering and regulating surface properties, the doping density achievable in carbon matrices using traditional heteroatom doping methods is limited, resulting in insufficient anchoring sites for platinum group metal nanoparticles and weak surface chemical state regulation capabilities. Therefore, existing MXC electrocatalysts still commonly undergo significant sintering under cyclic operating conditions, and their durability urgently needs improvement. There is a pressing need to develop novel interface and anchoring strategies to construct high-density, strongly interacting metal-support coordination structures to enhance their resistance to sintering and service life under harsh electrocatalytic environments. Summary of the Invention

[0005] In view of this, one objective of the present invention is to provide palladium-based nanoparticles capable of inhibiting sintering; a second objective of the present invention is to provide a method for preparing the palladium-based nanoparticles capable of inhibiting sintering; a third objective of the present invention is to provide a palladium-carbon catalyst capable of inhibiting sintering; and a fourth objective of the present invention is to provide an application of the palladium-based nanoparticles capable of inhibiting sintering or the palladium-carbon catalyst capable of inhibiting sintering in improving the stability of alkaline fuel cells.

[0006] To achieve the above objectives, the present invention provides the following technical solution: 1. A palladium-based nanoparticle capable of inhibiting sintering, wherein the palladium-based nanoparticle has a core-shell structure, wherein the interior is a crystalline palladium core and the exterior is an amorphous palladium phosphide shell layer with a thickness of about 2 nm.

[0007] Preferably, the molar amount of the phosphorus precursor is 10-100 times the molar amount of the palladium nanoparticles.

[0008] Preferably, the nanoparticles of this invention have an average diameter of 6 nm.

[0009] 2. A method for preparing palladium-based nanoparticles capable of inhibiting sintering, comprising the following steps: Palladium nanoparticles and a phosphorus precursor were dispersed in an organic solvent and reacted in air at a temperature of 180°C to 220°C for 20 seconds to 3 minutes. After centrifugation and washing, the palladium-based nanoparticles capable of inhibiting sintering were obtained.

[0010] Preferably, the phosphorus precursor of the present invention is one of tri-n-octylphosphine, triphenylphosphine, or tri-n-butylphosphine.

[0011] Preferably, the organic solvent of the present invention is one of oleylamine, octadecylamine, or N,N-dimethylformamide.

[0012] 3. A palladium-on-carbon catalyst capable of inhibiting sintering, prepared by loading palladium-based nanoparticles capable of inhibiting sintering onto a carbon matrix, or prepared by surface phosphating of a commercial palladium-on-carbon catalyst, wherein the surface phosphating is performed by dispersing a commercial palladium-on-carbon catalyst and a phosphorus precursor in an organic solvent, reacting them in an air atmosphere at a temperature of 50°C to 100°C for 5 to 10 minutes, and obtaining the palladium-on-carbon catalyst capable of inhibiting sintering after centrifugation and washing; wherein the molar amount of the phosphorus precursor is 1 to 20 times the molar amount of palladium nanoparticles in the commercial palladium-on-carbon catalyst.

[0013] Preferably, the phosphorus precursor is one of tri-n-octylphosphine, triphenylphosphine, or tri-n-butylphosphine; and the organic solvent is one of oleylamine, octadecylamine, or N,N-dimethylformamide.

[0014] 4. The application of the palladium-based nanoparticles capable of inhibiting sintering or the palladium-carbon catalyst capable of inhibiting sintering in improving the stability of alkaline fuel cells.

[0015] The beneficial effects of this invention are as follows: By surface phosphating palladium nanoparticles, palladium phosphide nanoparticles with an average diameter of 6.3 nm are obtained. These nanoparticles possess an amorphous surface structure. When loaded onto carbon as a catalyst, the phosphorus element on the surface acts as a bridge between the palladium nanoparticles and the carbon support, enhancing the metal-support interaction and thus improving the stability of the catalytic system under electrochemical conditions. Even after 10,000 cycles, they maintain good morphology and activity, with almost no attenuation in the polarization curve. Compared with untreated Pd / C, their anti-sintering ability and durability are significantly improved. Furthermore, they exhibit enhanced catalytic performance in catalytic reactions, especially in the electrocatalytic oxygen reduction reaction, demonstrating excellent catalytic performance. In addition, this method has good universality and is also applicable to the modification of commercial palladium-carbon materials, providing an effective technical path for performance optimization.

[0016] The present invention has the following characteristics: the method is simple, fast and easy to repeat; at the same time, the synthesis system used can be widely used; and stable oxygen reduction can be achieved. Attached Figure Description

[0017] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 Transmission electron microscope images of palladium nanoparticles capable of inhibiting sintering prepared in Examples 1-6 of this invention.

[0018] Figure 2 Transmission electron microscope images of commercial palladium on carbon prepared for Examples 7-9 of the invention, capable of suppressing sintering.

[0019] Figure 3 The image shows the X-ray diffraction pattern of the palladium nanoparticle powder prepared in Example 3 of this invention, which is capable of suppressing sintering. The pattern indicates that its phase is consistent with standard metallic palladium, demonstrating that the sintering suppression strategy successfully achieved specific control over the surface of the nanoparticles without affecting their overall crystal structure.

[0020] Figure 4 The images shown are aberration electron microscope images of palladium nanoparticles prepared in Examples 3-6 of this invention, which show that the surface of the palladium nanoparticles is amorphous.

[0021] Figure 5 Transmission electron microscope image of palladium nanoparticles loaded with commercial carbon (PdP / C) prepared in Example 3 of the present invention, which can suppress sintering.

[0022] Figure 6The polarization curves of the palladium nanoparticles capable of inhibiting sintering prepared in Example 3 of the present invention loaded on commercial carbon (PdP / C), the commercial palladium carbon capable of inhibiting sintering prepared in Example 9 of the present invention (C-PdP / C), the palladium nanoparticles loaded on commercial carbon (Pd / C), and the commercial palladium carbon (C-Pd / C) before and after 10,000 cycles show that the palladium nanoparticles capable of inhibiting sintering and the commercial palladium carbon capable of inhibiting sintering have good stability.

[0023] Figure 7 Transmission electron microscopy images of the palladium nanoparticles loaded with commercial carbon (PdP / C) prepared in Example 3 of the present invention and the commercial palladium carbon (C-PdP / C) prepared in Example 9 of the present invention after 10,000 cycles show that the palladium nanoparticles and the commercial palladium carbon that inhibits sintering still maintain good morphology, dispersion and size uniformity after stability testing. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0025] Example 1 (1) In the air, 1.58 × 10 -2 Palladium particles synthesized from sodium chloropalladium and 1.12 mmol of tri-n-octylphosphine were added to 3 mL of oleylamine and stirred until homogeneous.

[0026] (2) In air, the solution from step (1) was placed in an oil bath at 180°C and stirred. After reacting for 3 minutes, it was centrifuged, the supernatant was discarded, and the bottom precipitate was washed three times with ethanol to obtain palladium nanoparticles with a surface phosphating treatment that could inhibit sintering. Its transmission electron microscope image is shown in... Figure 1 middle.

[0027] Example 2 (1) In the air, 1.58 × 10 -2 Palladium particles synthesized from sodium chloropalladium and 1.12 mmol of tri-n-octylphosphine were added to 3 mL of oleylamine and stirred until homogeneous.

[0028] (2) In air, the solution from step (1) was placed in an oil bath at 190°C and stirred. After reacting for 2 minutes, it was centrifuged, the supernatant was discarded, and the bottom precipitate was washed three times with ethanol to obtain palladium nanoparticles that could inhibit sintering. Its transmission electron microscope image is shown in... Figure 1 middle.

[0029] Example 3 (1) In the air, 1.58 × 10 -2Palladium particles synthesized from sodium chloropalladium and 1.12 mmol of tri-n-octylphosphine were added to 3 mL of oleylamine and stirred until homogeneous.

[0030] (2) In air, the solution from step (1) was placed in an oil bath at 200°C and stirred. After reacting for 20 seconds, it was centrifuged, the supernatant was discarded, and the bottom precipitate was washed three times with ethanol to obtain palladium nanoparticles that could inhibit sintering. Its transmission electron microscope image is shown in... Figure 1 middle.

[0031] Example 4 (1) In the air, 1.58 × 10 -2 Palladium particles synthesized from sodium chloropalladium and 1.12 mmol of tri-n-octylphosphine were added to 3 mL of oleylamine and stirred until homogeneous.

[0032] (2) In air, the solution from step (1) was placed in an oil bath at 220°C and stirred. After reacting for 20 seconds, it was centrifuged, the supernatant was discarded, and the bottom precipitate was washed three times with ethanol to obtain palladium nanoparticles that could inhibit sintering. Its transmission electron microscope image is shown in... Figure 1 middle.

[0033] Example 5 (1) In the air, 1.58 × 10 -2 Palladium particles synthesized from sodium chloropalladium and 1.12 mmol of triphenylphosphine were added to 3 mL of oleylamine and stirred until homogeneous.

[0034] (2) In air, the solution from step (1) was placed in an oil bath at 200°C and stirred. After reacting for 20 seconds, it was centrifuged, the supernatant was discarded, and the bottom precipitate was washed three times with ethanol to obtain palladium nanoparticles that could inhibit sintering. Its transmission electron microscope image is shown in... Figure 1 middle.

[0035] Example 6 (1) In the air, 1.58 × 10 -2 Palladium particles synthesized from sodium chloropalladium and 1.12 mmol of tri-n-butylphosphine were added to 3 mL of oleylamine and stirred until homogeneous.

[0036] (2) In air, the solution from step (1) was placed in an oil bath at 200°C and stirred. After reacting for 20 seconds, it was centrifuged, the supernatant was discarded, and the bottom precipitate was washed three times with ethanol to obtain palladium nanoparticles that could inhibit sintering. Its transmission electron microscope image is shown in... Figure 1 middle.

[0037] Example 7 (1) In the air, 3.76 × 10 -3 mmol (molar value of palladium) Commercial palladium on carbon, 4.48 × 10⁻⁶-2 Add mmol of tri-n-octylphosphine to 3 mL of oleylamine and stir until well mixed.

[0038] (2) In air, the solution from step (1) was placed in an oil bath at 100°C and stirred. After reacting for 5 minutes, it was centrifuged, the supernatant was discarded, and the bottom precipitate was washed three times with ethanol to obtain palladium nanoparticles that could inhibit sintering. Its transmission electron microscope image is shown in... Figure 2 middle.

[0039] Example 8 (1) In the air, 3.76 × 10 -3 mmol (molar value of palladium) Commercial palladium on carbon, 4.48 × 10⁻⁶ -2 Add mmol of tri-n-octylphosphine to 3 mL of oleylamine and stir until well mixed.

[0040] (2) In air, the solution from step (1) was placed in an oil bath at 80°C and stirred. After reacting for 7 minutes, it was centrifuged, the supernatant was discarded, and the bottom precipitate was washed three times with ethanol to obtain palladium nanoparticles that could inhibit sintering. Its transmission electron microscope image is shown in... Figure 2 middle.

[0041] Example 9 (1) In the air, 3.76 × 10 -3 mmol (molar value of palladium) Commercial palladium on carbon, 4.48 × 10⁻⁶ -2 Add mmol of tri-n-octylphosphine to 3 mL of oleylamine and stir until well mixed.

[0042] (2) In air, the solution from step (1) was placed in an oil bath at 50°C and stirred. After reacting for 10 minutes, it was centrifuged, the supernatant was discarded, and the bottom precipitate was washed three times with ethanol to obtain palladium nanoparticles that could inhibit sintering. Its transmission electron microscope image is shown in... Figure 2 middle.

[0043] The palladium nanoparticles prepared in Examples 1-6 that can inhibit sintering were observed by transmission electron microscopy, and the results are as follows: Figure 1 As shown, the morphology of nanoparticles is better preserved at higher temperatures and shorter reaction times. The sample obtained at 200℃ for 20 seconds exhibits the best thermal stability and the most intact particle morphology. Compared to tri-n-butylphosphine and triphenylphosphine, tri-n-octylphosphine, with its stronger reducing properties, is more conducive to the synthesis reaction. However, different phosphorus sources did not significantly affect the final morphology of the nanoparticles.

[0044] The commercial palladium-on-carbon (C-PdP / C) samples prepared in Examples 7-9, which are capable of inhibiting sintering, were observed using transmission electron microscopy. The results are as follows: Figure 2As shown, commercial palladium on carbon exhibits better morphology retention and dispersibility at lower temperatures and longer reaction times. The sample obtained by reacting at 50°C for 10 minutes demonstrates the best thermal stability and the most complete morphological retention and dispersion.

[0045] Powder X-ray diffraction was performed on the palladium nanoparticles prepared in Example 3 that were capable of inhibiting sintering (photographs shown in...). Figure 3 Analysis shows that the palladium nanoparticles that can suppress sintering still maintain the crystal structure of metallic palladium, indicating that the sintering suppression treatment only changes its surface structure and does not change its bulk phase.

[0046] Aberration-corrected high-resolution electron microscopy characterization of the palladium nanoparticles from Example 3 that can suppress sintering (images shown in...) Figure 4 (in Chinese) and transmission electron microscopy characterization (photos shown in) Figure 1 In the study, it was discovered that the palladium nanoparticles capable of suppressing sintering are composed of a composite structure with disordered surface atoms and a crystalline internal structure, and contain a 2 nm thick amorphous layer. Aberration-corrected high-resolution electron microscopy characterization of Examples 3-6 (results are shown in...) Figure 4 As can be seen from the image, it has the same structural features as the palladium nanoparticles that can suppress sintering described in Example 3.

[0047] Example 10 The application of characterization of palladium nanoparticles that can inhibit sintering in electrocatalytic oxygen reduction.

[0048] A 10% PdP / C catalyst was prepared by loading the sintering-inhibiting palladium nanoparticles obtained in Example 3 onto commercial carbon. The specific method is as follows: Commercial carbon was uniformly dispersed in a solution of toluene and ethanol at a volume ratio of 9:1, and sonicated. Simultaneously, the sintering-inhibiting palladium nanoparticles described in Example 3 were added at a carbon weight ratio of 10%. After sonication for 1 hour, stirring for 3 hours, and centrifugation, the mixture was stirred in acetic acid solution at 60°C for 12 hours, and then centrifuged and dried for later use. A transmission electron microscope image of the sintering-inhibiting palladium nanoparticles loaded on carbon is shown below. Figure 5 middle.

[0049] Unphosphated palladium nanoparticles were prepared according to Example 3, and Pd / C catalysts were prepared by loading them onto commercial carbon according to the above method.

[0050] The above-mentioned PdP / C catalyst and the commercial palladium on carbon (C-PdP / C) prepared in Example 9, which can inhibit sintering, were applied to the alkaline oxygen oxidation reaction. The catalyst used in the reaction contained 3 μg of palladium. The experimental solvent was 0.1 M KOH. The electrochemical active area (ECSA) was calculated by scanning the CV curve at a rate of 50 mV / s to obtain the charge required for hydrogen desorption. In the ORR polarization curve, the current density was normalized with reference to the ECSA. For the catalyst, the kinetic current was normalized to only the Pd loading to produce a mass activity of 0.90 V relative to RHE. At room temperature, in an O2-saturated 0.1 M KOH solution, cyclic potential scans between 0.7 and 1.1 V were applied to RHE at a scan rate of 50 mV / s for 10,000 cycles. Figure 6 For comparison, Pd / C and commercial Pd / C (i.e., C-Pd / C in Table 1) were used as benchmark catalysts, and electrochemical tests were performed using the same methods described above. Figure 6 The experimental results are shown in Table 1. They indicate that the carbon-supported palladium nanoparticles (PdP / C) prepared in Example 3, which can inhibit sintering, and the commercial palladium on carbon (C-PdP / C) prepared in Example 9, which can inhibit sintering, have enhanced electrochemical oxygen reduction activity and maintain good activity after cyclic potential scanning.

[0051] Table 1 Electrochemical test results of several catalysts <![CDATA[Electrochemically active area (m 2 / g)]]> <![CDATA[Areal activity (mA 2 / cm 2 )]]> <![CDATA[Mass activity (A 2 / mg)]]> Percentage of loss of mass activity (%) C-Pd / C 37.87 0.16 0.06 50.47 C-PdP / C 15.57 0.42 0.09 1.55 Pd / C 23.61 0.55 0.13 45.53 PdP / C 29.4 0.94 0.28 5.28 Figure 7 Transmission electron microscope images of carbon-supported palladium nanoparticles (PdP / C) prepared in Example 3 and commercial palladium on carbon (C-PdP / C) prepared in Example 9, which can inhibit sintering, after 10,000 cycles in an alkaline oxygen reduction reaction, respectively, show that PdP / C and C-PdP / C still maintain good morphology, dispersion and size uniformity after cyclic potential scanning.

[0052] In this invention, we propose a simple and rapid method for synthesizing palladium nanoparticles that suppress sintering. These nanoparticles possess an amorphous surface structure, enabling stable oxygen reduction reactions. Furthermore, this method demonstrates stable oxygen reduction capabilities when applied to commercial palladium on carbon. This invention has the following advantages: the method is simple, rapid, and easily reproducible; the synthesis system used is widely applicable; and stable oxygen reduction can be achieved.

[0053] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A palladium-based nanoparticle capable of inhibiting sintering, characterized in that, The palladium-based nanoparticles have a core-shell structure, with a crystalline palladium core inside and an amorphous palladium phosphide shell layer with a thickness of about 2 nm on the outside.

2. The palladium-based nanoparticles capable of inhibiting sintering according to claim 1, characterized in that, The molar amount of phosphorus precursor is 10-100 times that of palladium nanoparticles.

3. The palladium-based nanoparticles capable of inhibiting sintering according to claim 1, characterized in that, The average diameter of the nanoparticles is 6 nm.

4. A method for preparing palladium-based nanoparticles capable of inhibiting sintering as described in claim 1 or 2, characterized in that, Includes the following steps: Palladium nanoparticles and phosphorus precursors were dispersed in an organic solvent in a certain proportion and reacted in an air atmosphere at a temperature of 180°C to 220°C for 20 seconds to 3 minutes. After centrifugation and washing, the palladium-based nanoparticles that can inhibit sintering were obtained.

5. The preparation method according to claim 3, characterized in that, The phosphorus precursor is one of tri-n-octylphosphine, triphenylphosphine, or tri-n-butylphosphine.

6. The preparation method according to claim 3, characterized in that, The organic solvent is one of oleylamine, octadecylamine, or N,N-dimethylformamide.

7. A palladium-on-carbon catalyst capable of inhibiting sintering, characterized in that, The palladium-based nanoparticles capable of inhibiting sintering as described in claim 1 or 2 are prepared by loading them onto a carbon matrix, or by surface phosphating a commercial palladium-on-carbon catalyst. The surface phosphating process involves dispersing the commercial palladium-on-carbon catalyst and a phosphorus precursor in an organic solvent, reacting them in an air atmosphere at a temperature of 50°C to 100°C for 5 to 10 minutes, and obtaining the palladium-on-carbon catalyst capable of inhibiting sintering after centrifugation and washing. The molar amount of the phosphorus precursor is 1 to 20 times the molar amount of palladium nanoparticles in the commercial palladium-on-carbon catalyst.

8. The palladium-on-carbon catalyst capable of inhibiting sintering according to claim 7, characterized in that, The phosphorus precursor is one of tri-n-octylphosphine, triphenylphosphine, or tri-n-butylphosphine; the organic solvent is one of oleylamine, octadecylamine, or N,N-dimethylformamide.

9. The application of palladium-based nanoparticles capable of inhibiting sintering as described in claim 1 or 2, or palladium-carbon catalyst capable of inhibiting sintering as described in claim 9, in improving the stability of alkaline fuel cells.

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