Amorphous-crystalline palladium-based catalyst PdCoCu as well as preparation method and application thereof

Abstract

The invention discloses an amorphous-crystalline palladium-based catalyst PdCoCu as well as a preparation method and application of the amorphous-crystalline palladium-based catalyst PdCoCu. The preparation method comprises the following steps: filling Pd (acac) 2, Co (acac) 2, Cu (acac) 2, W (CO) 6 and ascorbic acid into a small bottle, then adding DMF and CH3COOH, and ultrasonically mixing uniformly; and centrifugally washing and collecting the product obtained by reaction in the oil bath pan. Through the synergistic effect of Pd, Co and Cu, the d band center of Pd is reduced, the morphology is adjusted by adding DMF, CH3COOH, ascorbic acid and W (CO) 6, an amorphous-crystalline (a-c) structure is established, unconventional atomic arrangement is shown on an a-c structure interface, and the problem of lattice mismatching in a crystalline-crystalline (c-c) heterostructure can be relieved. Besides, lack of active sites on the interface of the catalyst and limitation of mass transfer become bottlenecks for improving reaction kinetics, more active sites are exposed by the structure, and the bonding strength of the structure with H and OH is optimized, so that adsorption and desorption of reaction intermediates are promoted, the catalytic activity of the HOR is finally improved, and large-scale production can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of proton / anion exchange membrane fuel cells, and in particular relates to an amorphous-crystalline palladium-based catalyst PdCoCu and a preparation method and application thereof. Background Art

[0002] The hydrogen oxidation reaction (HOR) is a key anode reaction in fuel cells. However, in alkaline environments, existing noble metal catalysts (such as platinum-based materials) exhibit high energy barriers in the desorption step due to the high hydrogen binding energy, resulting in sluggish reaction kinetics. Proton / anion exchange membrane fuel cells (PEMFC / AEMFC) are recognized as one of the most promising energy conversion devices, promoting the utilization of clean hydrogen energy and reducing fossil fuel consumption. PEMFC / AEMFC systems involve two electrode reactions: the oxygen reduction reaction (ORR) at the cathode and the hydrogen oxidation reaction (HOR) at the anode. Despite the rapid development of efficient non-noble metal-based cathode ORR catalysts, the sluggish HOR kinetics in alkaline media and the high cost of anode catalysts pose challenges to the widespread application of PEMFC / AEMFC. Against this backdrop, the search for efficient and cost-effective HOR electrocatalysts is underway from various perspectives.

[0003] To date, many studies have been devoted to understanding the effect of HOR on pH. In acidic environments, hydrogen binding energy (HBE) is widely considered to be an indicator of catalyst activity, and a volcanic relationship has been established between current density and hydrogen binding energy of various catalysts. Considering the complex alkaline conditions, a single HBE may not be sufficient to describe the HOR process. Taking into account the role of interfacial H2O, Yan et al. further proposed the apparent hydrogen binding energy (HBE app ) theory, which states that as the pH value of the electrolyte increases, the HBE app The activity changed linearly. They found that HBE app The HOR activity decreases with increasing pH, which is the main reason for the decrease in HOR activity in alkaline media. On the other hand, Markovic et al. demonstrated that HOR performance in alkaline electrolytes can be improved by introducing oxyphilic species that enhance OHBE. However, the interaction between OHBE and HBE on HOR across the entire pH range is complex and rarely discussed. More importantly, it remains challenging to identify the key factors that affect pH-dependent HOR performance in different electrolytes and improve alkaline HOR performance.

[0004] Heterostructured catalysts have attracted considerable attention due to their interfacial electronic controllability. However, crystalline-crystalline (cc) structures suffer from lattice mismatch, resulting in limited interfacial contact and low electron transfer efficiency. Amorphous-crystalline (ac) structures circumvent the lattice mismatch through disordered / ordered interfaces while providing abundant active sites. However, their dynamic electronic behavior and performance optimization mechanisms in HOR remain unclear. Notably, the construction of atomic-scale heterostructures offers an alternative avenue for modulating the electron distribution of metal sites. When two dissimilar components form a heterostructure, interfacial electronic interactions trigger electron transfer, leading to electron redistribution and surface polarization. This, in turn, facilitates charge transfer to reactants on the catalyst surface, thereby enhancing electrocatalytic performance. The construction of amorphous (ac) heterostructures, which exhibit unconventional atomic arrangements at the heterostructure interface, can alleviate the lattice mismatch problem found in cc heterostructures and has shown promising potential in electrocatalytic applications. Summary of the Invention

[0005] To address technical issues such as the slow kinetics of the existing anodic hydrogen oxidation reaction, the most important half-reaction in fuel cells, which seriously affects the performance of the fuel cell, the present invention provides an amorphous-crystalline palladium-based catalyst PdCoCu and a preparation method and application thereof. The method of the present invention is simple, versatile, and low-cost, and the prepared PdCoCu alloy material exhibits excellent activity and stability as a hydrogen oxidation electrocatalyst, making it suitable as a cathode material for proton exchange membrane and anion exchange membrane fuel cells.

[0006] In order to solve the problems of the prior art, the technical solution adopted by the present invention is: A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 2-20 mg of Pd(acac)2, 2-40 mg of Co(acac)2, 2-20 mg of Cu(acac)2, 10-80 mg of W(CO)6, and 5-80 mg of ascorbic acid into a vial, then adding 5-20 mL of DMF and 1-10 mL of CH3COOH, ultrasonically dissolving the mixture, and mixing the mixture uniformly; then placing the vial in an oil bath at 40-80°C and 100-1000 rpm for reaction for 2-15 hours, and then centrifugally washing the mixture with a mixture of ethanol and cyclohexane in a volume ratio of 3:1 to obtain the amorphous-crystalline palladium-based catalyst PdCoCu.

[0007] As an improvement, the added amounts of Pd(acac)2, Co(acac)2, Cu(acac)2, and W(CO)6 were 10 mg, 20 mg, 10 mg, and 60 mg, respectively; the stirring speed of the oil bath reaction was 500 rpm, and the reaction was carried out for 12 h.

[0008] As an improvement, the ultrasonic dissolution time is 10-60 min.

[0009] As an improvement, the heating condition is 80°C.

[0010] The palladium-based catalyst PdCoCu prepared by any of the above preparation methods is a defect-rich two-dimensional nanosheet and exists in an amorphous-crystalline structure; the atomic ratio of Pd, Co, and Cu is 1:1:1, forming a medium-entropy alloy.

[0011] Application of the above-mentioned amorphous-crystalline palladium-based catalyst PdCoCu in acid, alkaline and neutral hydrogen oxidation reaction catalysts.

[0012] The present invention uses palladium acetylacetonate, cobalt acetylacetonate, and copper acetylacetonate as metal sources, ascorbic acid as a reducing agent, and DMF as a solvent. It utilizes the confined growth effect of carbon monoxide produced by the thermal decomposition of tungsten hexacarbonyl to induce the anisotropic growth of palladium nanosheets, thereby constructing a defect-rich porous palladium metalloene material. The pore structure of the porous palladium metalloene can provide abundant hydrogen oxidation active sites. In addition to the morphology of the material, defects in the nanocrystals, such as vacancy defects, dislocations, and grain boundaries, also affect the catalytic performance of the nanomaterial. The defect-rich palladium metalloene is conducive to the adsorption of oxygen molecules, promoting the activation of oxygen molecules, thereby enhancing the oxygen reduction activity of the palladium metalloene. Beneficial effects

[0013] Compared with the prior art, the present invention discloses an amorphous-crystalline palladium-based catalyst PdCoCu, a preparation method thereof, and applications thereof. The method utilizes a one-pot wet chemical process, is simple and easy to implement, has low cost, and is easy to operate. The obtained amorphous-crystalline palladium-based catalyst PdCoCu is a medium-entropy alloy with a strong affinity for H and O, high density, corrosion resistance, and high electrothermal stability. When used as a cathode catalyst in a proton exchange membrane fuel cell, it can exhibit higher power density and stability than commercial 40% Pt / C. Large-scale production is possible, and the specific advantages are as follows: 1. Cobalt metal, due to its transition metal properties, has high activity and variable valence, which enables it to exhibit excellent catalytic performance in electrocatalytic reactions. Co is also abundant in reserves, inexpensive, and has the potential for a tunable microstructure and flexible coupling effects. 2. Metallic Cu has a unique electronic structure with no valence electrons in its 3d orbital, which gives it physical and chemical properties different from other elements. This can lower the d-band center of Pd, thereby preventing the active sites on Pd from being covered by CO, effectively increasing the density of active sites and thus improving the activity and stability of the electrocatalytic reaction. 3. Palladium, as a member of the same family as platinum, has similar intrinsic properties to platinum and is more abundant in reserves. 4. Metalloene has a unique two-dimensional structure with high specific surface area, abundant defect sites, excellent conductivity, and exposes a large number of unsaturated catalytic active sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a SEM image of the amorphous-crystalline palladium-based catalyst PdCoCu prepared in Example 1 of the present invention; Figure 2 TEM spectrum of the amorphous-crystalline palladium-based catalyst PdCoCu prepared in Example 1 of the present invention; Figure 3 This is the HR-TEM spectrum of the amorphous-crystalline palladium-based catalyst PdCoCu prepared in Example 1 of the present invention; Figure 4 is the XRD pattern of the amorphous-crystalline palladium-based catalyst PdCoCu prepared in Example 1 of the present invention; Figure 5 This is the Tafel curve of the amorphous-crystalline palladium-based catalyst PdCoCu prepared in Example 1 of the present invention; Figure 6 Polarization and corresponding power density curve of the amorphous-crystalline palladium-based catalyst PdCoCu prepared in Example 1 of the present invention for use as a cathode material for a proton exchange membrane fuel cell; Figure 7 Comparison of LSV curves of the materials obtained in Example 1 of the present invention and Comparative Examples 1-2;

[0015] Figure 8 The CO dissolution curves obtained in Example 1 of the present invention and Comparative Examples 1 and 2 are shown. DETAILED DESCRIPTION

[0016] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention. Example 1

[0017] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 10 mg Cu(acac)2, 60 mg W(CO)6, and 80 mg ascorbic acid into a 30 mL vial, followed by adding 16 mL DMF and 4 mL CH3COOH, sonicating and dissolving the mixture for 1 h, and mixing the mixture thoroughly. The vial is then placed in an oil bath at 80°C and 500 rpm for 12 h. The solid is separated and then washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected.

[0018] The PdCoCu catalyst material prepared in Example 1 was physically characterized using SEM, TEM, HR-TEM, and XRD. Figure 1 ), it can be seen that the material is composed of metal nanosheet structures. TEM spectrum ( Figure 2 ) shows that the catalyst is an ultra-thin nanosheet structure. Figure 3 ) found that the nanosheet structure is composed of continuous lattice stripes and discontinuous defects, proving its crystalline-amorphous structure from the perspective of spatial structure. Figure 4 , It can be seen from the XRD spectrum that the diffraction peak of the material is completely consistent with the standard card of Pd (JCPDS card, 06-1043), and the intensity of the diffraction peak is relatively small, proving that the structure of the catalyst PdCoCu is amorphous-crystalline. Figure 5 It is the Tafel slope of the material obtained by testing its hydrogen oxidation performance, which is better than most alkaline hydrogen oxidation electrocatalyst materials. Figure 6 The polarization curve and corresponding power density curve of the material as the cathode material of proton exchange membrane fuel cell show that the material has a high power density, and its maximum power density is 360 mW cm -2 .

[0019] The above results all indicate that this material has good application prospects as a hydrogen oxidation electrocatalyst material. Example 2

[0020] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg of Pd(acac)2, 10 mg of Co(acac)2, 10 mg of Cu(acac)2, 60 mg of W(CO)6, and 80 mg of ascorbic acid into a 30 mL vial, followed by adding 16 mL of DMF and 4 mL of CH3COOH, sonicating and dissolving the mixture for 1 h, and mixing the mixture thoroughly. The vial is then placed in an oil bath at 80°C and 500 rpm for 12 h. The solid is separated and then washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected. Example 3

[0021] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 5 mg Cu(acac)2, 60 mg W(CO)6, and 80 mg ascorbic acid into a 30 mL vial, followed by adding 16 mL DMF and 4 mL CH3COOH, sonicating and dissolving the mixture for 1 h, and mixing the mixture thoroughly. The vial is then placed in an oil bath at 80°C and 500 rpm for 12 h. The solid is separated and then washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected. Example 4

[0022] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 10 mg Cu(acac)2, 30 mg W(CO)6, and 80 mg ascorbic acid into a 30 mL vial, followed by adding 16 mL DMF and 4 mL CH3COOH, sonicating and dissolving the mixture for 1 h, and mixing the mixture thoroughly. The vial is then placed in an oil bath at 80°C and 500 rpm for 12 h. The solid is separated and then washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected. Example 5

[0023] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 10 mg Cu(acac)2, 60 mg W(CO)6, and 40 mg ascorbic acid into a 30 mL vial, followed by adding 16 mL DMF and 4 mL CH3COOH, sonicating and dissolving the mixture for 1 h, and mixing the mixture thoroughly. The vial is then placed in an oil bath at 80°C and 500 rpm for 12 h. The solid is separated and then washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected. Example 6

[0024] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 10 mg Cu(acac)2, 60 mg W(CO)6, and 80 mg ascorbic acid into a 30 mL vial, followed by adding 8 mL DMF and 4 mL CH3COOH, sonicating and dissolving the mixture for 1 h, and mixing the mixture thoroughly. The vial is then placed in an oil bath at 80°C and 500 rpm for 12 h. The solid is separated and then washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected. Example 7

[0025] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 10 mg Cu(acac)2, 60 mg W(CO)6, and 80 mg ascorbic acid into a 30 mL vial, followed by adding 16 mL DMF and 8 mL CH3COOH, sonicating and dissolving the mixture for 1 h, and mixing the mixture thoroughly. The vial is then placed in an oil bath at 80°C and 500 rpm for 12 h. The solid is separated and then washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected. Example 8

[0026] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 10 mg Cu(acac)2, 60 mg W(CO)6, and 80 mg ascorbic acid into a 30 mL vial, followed by adding 16 mL DMF and 4 mL CH3COOH, ultrasonically dissolving the mixture for 20 minutes, and mixing thoroughly. Subsequently, the vial is placed in an oil bath at 60°C and 500 rpm for 12 hours. After separation, the solid is washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected. Example 9

[0027] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 10 mg Cu(acac)2, 60 mg W(CO)6, and 80 mg ascorbic acid into a 30 mL vial, followed by adding 16 mL DMF and 4 mL CH3COOH, sonicating and dissolving the mixture for 1 h, and mixing the mixture thoroughly. The vial is then placed in an oil bath at 40°C and 500 rpm for 12 h. The solid is separated and then washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected. Example 10

[0028] A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 10 mg Cu(acac)2, 60 mg W(CO)6, and 80 mg ascorbic acid into a 30 mL vial, followed by adding 16 mL DMF and 4 mL CH3COOH, ultrasonically dissolving the mixture for 1 h, and mixing thoroughly. Subsequently, the vial is placed in an oil bath at 80°C and 500 rpm for 6 h. After separation, the solid is washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected. Example 11

[0029] A method for preparing a palladium-based catalyst PdCoCu comprises the following steps: placing 10 mg Pd(acac)2, 20 mg Co(acac)2, 10 mg Cu(acac)2, 60 mg W(CO)6, and 80 mg ascorbic acid into a 30 mL vial, followed by adding 16 mL DMF and 4 mL CH3COOH, sonicating and dissolving the mixture for 1 h, and mixing the mixture thoroughly. The vial is then placed in an oil bath at 80°C and 1000 rpm for 12 h. The solid is separated and then washed by centrifugation with a mixture of ethanol and cyclohexane (3:1 by volume) and collected.

[0030] Comparative Example 1 The only difference between this comparative example and Example 1 is that Co(acac)2 is not added, and the other implementation conditions remain unchanged.

[0031] Comparative Example 2 The only difference between this comparative example and Example 1 is that Cu(acac)2 is not added, and the other implementation conditions remain unchanged.

[0032] In 0.1M KOH alkaline medium, the LSV test results of the corresponding hydrogen oxidation reaction are as follows: Figure 7 As shown, the overall performance comparison shows the order of PdCoCu>PdCo>PdCu, and the performance of Comparative Example 1 is better than that of Comparative Example 2. At the same time, in alkaline medium, the material shows excellent resistance to CO poisoning, and its performance shows the order of PdCoCu>PdCu, as shown in FIG. Figure 8 shown.

[0033] In summary, the present invention uses palladium acetylacetonate, cobalt acetylacetonate, and copper acetylacetonate as metal sources, ascorbic acid as a reducing agent, and DMF as a solvent. The confined growth effect of carbon monoxide produced by the thermal decomposition of tungsten hexacarbonyl is utilized to induce the anisotropic growth of palladium nanosheets, thereby constructing a defect-rich porous palladium metalloenide material. The resulting amorphous-crystalline palladium-based catalyst, PdCoCu, is a medium-entropy alloy with a strong affinity for H and O, high density, corrosion resistance, and high electrothermal stability. When used as a cathode catalyst in a proton exchange membrane fuel cell, it can exhibit higher power density and stability than commercial 40% Pt / C. In addition, the present invention adopts a one-pot wet chemical method, which is simple, easy to operate, low-cost, and has good industrial prospects.

[0034] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu, characterized in that: 2-20 mg Pd(acac)2, 2-40 mg Co(acac)2, 2-20 mg Cu(acac)2, 10-80 mg W(CO)6 and 5-80 mg ascorbic acid are placed in a vial, followed by the addition of 5-20 mL DMF and 1-10 mL CH3COOH, ultrasonically dissolved and mixed evenly; thereafter, the vial is placed in an oil bath at 40-80 °C and 100-1000 rpm for 2-15 h, and then centrifuged and washed with a mixed liquid of ethanol and cyclohexane in a volume ratio of 3:1 to obtain an amorphous-crystalline palladium-based catalyst PdCoCu.

2. The preparation method according to claim 1, characterized in that The added amounts of Pd(acac)2, Co(acac)2, Cu(acac)2, and W(CO)6 were 10 mg, 20 mg, 10 mg, and 60 mg, respectively; the stirring speed of the oil bath reaction was 500 rpm, and the reaction was carried out for 12 h.

3. The method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu according to claim 1, characterized in that: The ultrasonic dissolution time is 10-60 min.

4. The method for preparing an amorphous-crystalline palladium-based catalyst PdCoCu according to claim 1, characterized in that: The heating condition is 80°C.

5. A palladium-based catalyst PdCoCu prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The palladium-based catalyst PdCoCu is a defect-rich two-dimensional nanosheet and exists in an amorphous-crystalline structure; the atomic ratio of Pd, Co, and Cu is 1:1:1, forming a medium-entropy alloy.

6. Use of the amorphous-crystalline palladium-based catalyst PdCoCu according to claim 5 as a catalyst in acid, alkaline or neutral hydrogen oxidation reactions.

7. A proton exchange membrane fuel cell, characterized in that: Contains the palladium-based catalyst PdCoCu according to claim 5.

8. An anion exchange membrane battery, characterized in that: Contains the palladium-based catalyst PdCoCu according to claim 5.

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