Preparation and application of b-doped pdcu metalloalkene catalysts

Abstract

The application discloses a B-doped PdCu bimetallic olefin catalyst and a preparation method thereof. The preparation method comprises the following steps: mixing a palladium source, a copper source, potassium hydroxide, dimethylformamide, ethylene glycol and diethylene triamine to obtain a mixed solution; placing the mixed solution into a reaction kettle to react to obtain a sample; washing and drying the sample to obtain a precursor; and immersing the precursor into a dimethylformamide solution containing a boron source to react in an ice water bath to obtain the B-doped PdCu bimetallic olefin catalyst. The catalyst obtained by the application has the characteristics of high activity. The application further discloses an application of the B-doped PdCu bimetallic olefin catalyst.

Description

[Technical Field]

[0001] This application relates to the field of water electrolysis technology, and in particular to the preparation method and application of boron-doped metal olefin catalysts. [Background Technology]

[0002] Hydrogen energy, due to its high calorific value, good combustion performance, and clean, pollution-free nature, has the potential to replace traditional fossil fuels. Among current hydrogen production methods, water electrolysis is particularly noteworthy for its simplicity, wide availability of raw materials, and high product purity. However, the anodic oxygen evolution oxidation (OER) faces significant challenges (1.23V vs. RHE), prompting the search for alternative reactions with lower oxidation potentials to reduce the electricity consumption for H2 production. Due to the low theoretical oxidation potential of formic acid (-0.25V vs. RHE), the formic acid oxidation reaction (FAOR) has become the most promising alternative to OER. Therefore, the formic acid-assisted hydrogen evolution reaction (HER) has attracted considerable attention. The key to this system lies in highly efficient catalysts, especially those with dual HER and FAOR functions. Pt-based materials are traditionally excellent catalysts for hydrogen evolution, but their activity for formic acid oxidation is not high, and they are prone to intermediate poisoning under acidic conditions, leading to poor stability. High cost and scarcity also hinder their widespread application. Therefore, there is an urgent need to develop highly active, highly stable, and economically feasible catalysts that can simultaneously catalyze HER and FAOR. [Summary of the Invention]

[0003] The purpose of this application is to provide a B-doped PdCu metal olefin catalyst and its preparation method.

[0004] A boron-doped PdCu metalloalkene catalyst, comprising nanosheet catalysts, wherein the nanosheets are 1–2 nm thick or 4–8 atomic layers thick. This atomically thin sheet structure possesses an ultra-large specific surface area, increasing the number of reactive sites and the contact area between reactants and the catalyst, thus enhancing catalytic activity. Furthermore, irregular wrinkles and pores on the nanosheets further increase the specific surface area. The incorporation of boron atoms into the interstitial spaces of the PdCu octahedron causes lattice expansion, leading to an increase in the interatomic spacing within the PdCu crystal. This results in partial collapse and amorphization of the crystal structure, forming both boron-doped PdCu crystalline and amorphous regions, thereby creating a crystalline / amorphous interface. This heterogeneous interface between the crystalline and amorphous regions introduces numerous defects, which further enhance the specific surface area of ​​the catalyst and optimize the electronic structure of the PdCu atoms. Furthermore, the 2s or 2p orbitals of B atoms can form d-sp orbital hybridization with the 3d orbitals of Pd or Cu, optimizing the outer electronic structure of PdCu atoms, thereby increasing the central position of its d band and enhancing its adsorption of intermediates in the electrocatalytic reaction process, thus achieving higher electrocatalytic activity.

[0005] A method for preparing a B-doped PdCu metal olefin catalyst includes the following steps:

[0006] Step 1: Mix the palladium source, copper source, potassium hydroxide and solvent to obtain a mixture;

[0007] In step 1, the molar ratio of palladium source:copper source:potassium hydroxide is 4:1:2400.

[0008] In step 1, the solvents are dimethylformamide, ethylene glycol, and diethylenetriamine.

[0009] In step 1, the palladium source is either palladium acetylacetonate or sodium tetrachloropalladate, and the copper source is copper acetylacetonate.

[0010] In step 1, the ratio of the molar fractions of palladium in the palladium source, the molar fractions of copper in the copper source, to the volume fractions of the solvent in step 1 is 4:1:2000. The molar fractions are in mmol and the volume fractions are in mL.

[0011] Step 2: The mixture from Step 1 is hydrothermally heated at 200°C for 8 hours to obtain a sample. The sample is then washed and dried to obtain the precursor.

[0012] In step 2, anhydrous ethanol and water are used alternately for washing.

[0013] In step 2, the drying temperature is room temperature to 60°C, and the drying time is 3 to 15 hours.

[0014] Step 3: Immerse the precursor obtained above in a solution containing a boron source and react in an ice-water bath for 1 to 4 hours.

[0015] In step 3, the boron source is sodium borohydride, and the solution is dimethylformamide.

[0016] In step 3, the ratio of the molar amount of the precursor, the molar amount of sodium borohydride, and the volume fraction of the solvent in step 3 is 2:1:667. The molar amount is in mmol and the volume fraction is in mL.

[0017] The B-doped PdCu metal olefin catalyst obtained above can be used for at least one of the following electrocatalytic reactions: cathode hydrogen evolution reaction, formic acid oxidation reaction, anodic oxygen evolution reaction, and methanol oxidation reaction.

[0018] The B-doped PdCu metal olefin catalyst obtained above possesses abundant crystalline / amorphous heterointerfaces and d-sp orbital hybridization, modifying the electronic structure of Pd, increasing the d-band center of Pd, and enhancing the local electric field strength, thereby improving electron transfer efficiency and improving the adsorption of reaction intermediates. Therefore, it can simultaneously catalyze FAOR and HER. At 10 mA cm⁻¹ -2Under these conditions, the potentials for HER and FAOR are only 52 mV and 83 mV, respectively. The coupled B2-PdCu dual electrodes at 10 mA cm⁻¹ -2 Under certain conditions, only an electrolysis voltage of 0.19V is required to efficiently produce hydrogen from fully formic acid. [Attached Image Description]

[0019] Figure 1 This is the XRD pattern of the B-doped PdCu metal olefin catalyst obtained in this application;

[0020] Figure 2 This is the AFM diagram of the B-doped PdCu metal olefin catalyst obtained in this application;

[0021] Figure 3 These are TEM and HRTEM images of the B-doped PdCu metal olefin catalyst obtained in this application;

[0022] Figure 4 This is a linear sweep voltammetry (LSV) curve of B2-PdCu obtained in Example 1 of this application, PdCu obtained in Comparative Example 1, and B4-PdCu obtained in Comparative Example 2 in 0.5M H2SO4 electrolyte.

[0023] Figure 5 These are Tafel diagrams of B2-PdCu obtained in Example 1, PdCu obtained in Comparative Example 1, and B4-PdCu obtained in Comparative Example 2 of this application.

[0024] Figure 6 These are EIS diagrams of B2-PdCu obtained in Example 1 of this application, PdCu obtained in Comparative Example 1, and B4-PdCu obtained in Comparative Example 2.

[0025] Figure 7 This is a graph showing the electrochemical active area (ECSA) of B2-PdCu obtained in Example 1 of this application, PdCu obtained in Comparative Example 1, and B4-PdCu obtained in Comparative Example 2.

[0026] Figure 8 This is a comparison of the cathode LSV of the B-doped PdCu metal olefin catalyst obtained in this application before and after 1000 CV cycles;

[0027] Figure 9 This is a cathode stability test diagram of the B-doped PdCu metal olefin catalyst obtained in this application;

[0028] Figure 10 This is an anodic polarization curve of the B-doped PdCu metal olefin catalyst obtained in this application before and after the addition of 0.5 M HCOOH;

[0029] Figure 11This is a cyclic voltammetry (CV) diagram of B2-PdCu obtained in Example 1 of this application, PdCu obtained in Comparative Example 1, and B4-PdCu obtained in Comparative Example 2 in 0.5M H2SO4 and 0.5M HCOOH.

[0030] Figure 12 This is a cyclic voltammetry (CV) diagram of B2-PdCu obtained in Example 1 of this application, PdCu obtained in Comparative Example 1, and B4-PdCu obtained in Comparative Example 2 in 0.5M H2SO4 and 0.5M HCOOH.

[0031] Figure 13 This is a graph showing the anodic stability of the B-doped PdCu metal olefin catalyst obtained in this application at a voltage of 0.25V.

[0032] Figure 14 This is a graph showing the total water-splitting performance of B2-PdCu obtained in Example 1 of this application;

Detailed Implementation Methods

[0033] The present application will be further described below with reference to the accompanying drawings and specific embodiments:

[0034] To enable those skilled in the art to better understand the technical solutions of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the drawings described below are merely some embodiments of this application. Those skilled in the art can obtain other drawings based on these drawings without creative effort. The directional terms such as "upper" and "lower" used herein are defined by the relative positions of the components shown in the drawings, and are only used for clarity and convenience in expressing the technical solutions. It should be understood that the directional terms used herein should not limit the scope of protection claimed in this application.

[0035] The raw material information involved in the following examples is as follows:

[0036] name Chemical formula Specification Manufacturer Sodium tetrachloropalladium <![CDATA[Na2PdCl4]]> 98％ Shanghai Aladdin Biochemical Technology Co., Ltd. Copper acetylacetonate <![CDATA[Cu(acac)2]]> 97％ Shanghai Aladdin Biochemical Technology Co., Ltd. potassium hydroxide KOH AR Shanghai McLean Biochemical Technology Co., Ltd. Sodium borohydride <![CDATA[NaBH4]]> AR Shanghai McLean Biochemical Technology Co., Ltd. dimethylformamide DMF AR Shanghai McLean Biochemical Technology Co., Ltd. Ethylene glycol EG Shanghai Aladdin Biochemical Technology Co., Ltd. Diethylenetriamine DETA AR Shanghai Aladdin Biochemical Technology Co., Ltd. sulfuric acid <![CDATA[H2SO4]]> AR Hangzhou Gaojing Chemical Reagent Co., Ltd. Formic acid HCOOH AR Hangzhou Gaojing Chemical Reagent Co., Ltd. ethanol <![CDATA[CH3CH2OH]]> AR Hangzhou Gaojing Chemical Reagent Co., Ltd.

[0037] Example 1

[0038] 0.04 mmol Na2PdCl4, 0.01 mmol Cu(acac)2, 23.24 mmol potassium hydroxide KOH, 6 mL DMF, 5 mL DETA, and 4 mL EG were mixed and stirred until homogeneous. The mixture was placed in a reaction vessel and heated hydrothermally at 200 °C for 8 h to obtain the sample PdCu. The sample was cooled to room temperature, washed three times alternately with ethanol and water, and dried in an oven at 60 °C for 4 h to obtain PdCu.

[0039] The obtained PdCu was added to 9.5 mL of DMF solution, and then 500 μL of 0.1 mol / L NaBH4 solution (dissolved in DMF) was added to the mixed solution. The mixed solution was then placed in an ice-water bath for 2 h to obtain B2-PdCu.

[0040] Comparative Example 1

[0041] 0.04 mmol Na2PdCl4, 0.01 mmol Cu(acac)2, 24 mmol KOH, 6 mL DMF, 5 mL DETA and 4 mL EG were mixed and stirred until homogeneous to obtain a mixture. The mixture was placed in a reaction vessel and heated hydrothermally at 200 °C for 8 h to obtain the sample PdCu. The sample was cooled to room temperature, washed three times alternately with ethanol and water, and dried in an oven at 60 °C for 4 h to obtain PdCu.

[0042] Comparative Example 2

[0043] 0.04 mmol Na2PdCl4, 0.01 mmol Cu(acac)2, 23.24 mmol KOH, 6 mL DMF, 5 mL DETA and 4 mL EG were mixed and stirred until homogeneous to obtain a mixture. The mixture was placed in a reaction vessel and heated hydrothermally at 200 °C for 8 h to obtain the sample PdCu. The sample was cooled to room temperature, washed three times alternately with ethanol and water, and dried in an oven at 60 °C for 4 h to obtain PdCu.

[0044] The obtained PdCu was added to 9.5 mL of DMF solution, and then 500 μL of 0.1 mol / L NaBH4 solution (dissolved in DMF) was added to the mixed solution. The mixed solution was then placed in an ice-water bath for 4 h to obtain B4-PdCu.

[0045] To verify the successful synthesis of the B-doped PdCu metal olefin catalyst of this invention, its structure was characterized.

[0046] The phase composition of the samples was characterized by X-ray powder diffraction (XRD, Bruker D8 Discover Cu target). The morphology and lattice information of the samples were analyzed by transmission electron microscopy (TEM, JEM-2100). The HER and FAOR performance of the catalysts in solutions containing 0.5 M sulfuric acid and 0.5 M formic acid were tested using an electrochemical workstation (CHI760E). Linear sweep voltammetry (LSV) was performed at a rate of 5 mV·s. -1 All potentials are corrected using the following formula:

[0047] E RHE =E Ag / AgCl +0.0592×pH+0.197-IR

[0048] Overpotential was further compensated by incorporating I (current in LSV) and solution internal resistance (R). Electrochemical impedance spectroscopy (EIS) measurements were performed at -0.053 V vs. RHE at frequencies ranging from 100,000 to 0.1 Hz. Double-layer capacitance (C... dl The current density (CV) curves are derived from the cyclic voltammograms (CV) between -0.097V vs. RHE and 0.197V vs. RHE. The current density difference at the intermediate potential is plotted against the sweep rate, and half of the linear slope is taken as C. dl value.

[0049] Figure 1 The X-ray diffraction (XRD) patterns of B2-PdCu and PdCu obtained in Embodiment 1 and Comparative Example 1 of this invention are shown. Figure 1 In the diagram, the horizontal axis represents the X-ray diffraction angle, and the vertical axis represents the X-ray diffraction intensity. For example... Figure 1 As shown, the XRD pattern reveals that the PdCu metallene exhibits five characteristic XRD peaks at 40.07°, 46.49°, 68.05°, 81.98°, and 86.54°, slightly lower than those of pure Pd crystals, pointing to the (111), (200), (220), (311), and (222) crystal planes of a typical face-centered cubic Pd structure (JCPDS No. 461043). Furthermore, after ice-water bath treatment with sodium borohydride solution, the peak values ​​of the product and PdCu showed a negative shift, and the peak intensity was slightly weaker than that of PdCu. This indicates that lattice expansion occurred after alloying, causing a leftward shift of the peak values. The further leftward shift and weakening of the peak intensity after the ice-water bath treatment indicate that the incorporation of B atoms led to further lattice expansion and induced an amorphous transformation. This confirms the successful preparation of B2-PdCu.

[0050] Figures 2 to 3 These are, respectively, atomic force microscopy (AFM) and transmission electron microscopy (HRTEM) images of B2-PdCu obtained in Embodiment 1 of the present invention. Figure 2 As can be seen, B2-PdCu exhibits a sheet-like structure with nanosheets approximately 1.8 nanometers in diameter, about 8 atomic layers thick. This atomically thin sheet-like structure provides an extremely large specific surface area, increasing the number of reactive sites and expanding the contact area between reactants and catalyst, thus enhancing catalytic activity. Furthermore, the irregular wrinkles and pores on the nanosheets further increase the specific surface area. Figure 3 Clear crystalline and amorphous regions are visible. The heterogeneous interface between crystalline and amorphous materials leads to numerous defects, which further increase the specific surface area of ​​the catalyst and optimize the electronic structure of PdCu atoms.

[0051] from Figure 4It can be seen that the overpotential of PdCu obtained in Comparative Example 1 is 70 mV. When B doping is introduced simultaneously in Example 1, the overpotential is 52 mV. This indicates that the crystal and amorphous caused by B atom doping have a positive effect on improving the HER performance.

[0052] It can be seen from Figure 5 that the Tafel slope of B2-PdCu obtained in Example 1 is 53.21 mV dec -1 , which is lower than 109.12 mV dec of PdCu obtained in Comparative Example 1 -1 . This shows that the reaction kinetics of B-doped PdCu metalene is higher, and the introduction of B atoms is beneficial to improving the HER kinetics.

[0053] In addition, in order to understand its catalytic ability more deeply, electrochemical impedance spectroscopy (EIS) studies were also carried out on it. As Figure 6 shown, the sequence of charge transfer resistance (R ct ) is as follows: B2-PdCu (1.183 Ω) < PdCu (2.55 Ω). This indicates that B2-PdCu has a higher electron transfer ability than the PdCu material without B doping. In addition, the double-layer capacitance (C dl ) was also detected, which proves the relatively large electrochemical active area of Example 1. It can be seen from Figure 7 that the C dl value of B2-PdCu is 54.07 mF cm -2 , exceeding 48.61 mF cm of PdCu -2 , thus highlighting the richness of its active sites. In addition, stability tests were carried out on B2-PdCu. As Figure 8 shown, after 1000 CV cycles, the LSV curves almost coincide, indicating its good stability. At the same time, as Figure 9 shown, B2-PdCu can also maintain a stable potential for 10 hours at 10 mA cm -2 .

[0054] As Figure 10 shown, the FAOR of B2-PdCu is better than OER, which indicates that after formic acid is introduced into the electrolyte, the anodic oxidation potential decreases significantly.

[0055] In addition, as Figure 11 shown, the cyclic voltammetry (CV) diagrams of B2-PdCu obtained in Example 1, PdCu obtained in Comparative Example 1, and B4-PdCu obtained in Comparative Example 2 in 0.5 M H2SO4 and 0.5 M HCOOH. According to the reduction peak of PdO at 0.4 - 0.6 V and based on the formula ECSA = Q / m × 420 (m is the Pd loading on the electrode surface, 420 μC cm -2Let Q be the reduction charge of the Pd oxide monolayer on the Pd surface (where Q is the reduction charge obtained by integrating the reduction charge of the Pd oxide layer). The electrochemically active surface area of ​​the catalyst can then be calculated. The calculated active area of ​​B2-PdCu is 475 cm². -2 The active surface area of ​​PdCu is 227.2 cm². -2 In addition, such as Figure 12 As shown, the peak current density of B2-PdCu is Much higher than PdCu This indicates that the crystal / amorphous interface and d-sp orbital hybridization generated after boron doping enhance the activity of formic acid oxidation. Figure 13 As shown, B2-PdCu maintained a stable current for 4000s at 0.25V, indicating that B2-PdCu has good formic acid oxidation stability.

[0056] Using B2-PdCu as both cathode and anode, such as Figure 14 As shown. Compared with total water splitting (OWS), formic acid oxidation (FAOR)-assisted total water splitting has better thermodynamic and kinetic advantages, reaching 10 mA cm⁻¹. -2 The voltage was 0.18V, which is 1.46V less than that of a traditional OWS system. This indicates that formic acid-assisted hydrolysis of water to produce hydrogen is a feasible and energy-saving method for hydrogen production.

[0057] It should be noted that the above embodiments are only used to illustrate this application and are not intended to limit the technical solutions described in this application. Although this specification has described this application in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions to this application. All technical solutions and improvements that do not depart from the spirit and scope of this application should be covered within the scope of the claims of this application.

Claims

1. A B-doped PdCu bimetallic olefin catalyst characterized in that, The catalyst is a nanosheet catalyst with a thickness of 1 nm to 2 nm. The nanosheet catalyst has a crystalline phase of B-doped PdCu and an amorphous phase of B-doped PdCu.

2. A method for preparing a B-doped PdCu bimetallic olefin catalyst, the method comprising the following steps: Step 1: Mix the palladium source, copper source, potassium hydroxide and solvent to obtain a mixture with a molar ratio of palladium source: copper source: potassium hydroxide = 4 : 1 : 2400; Step 2: The mixture obtained in Step 1 is hydrothermally heated at 200 °C for 8 hours to obtain a sample. The sample is then washed and dried to obtain the precursor. Step 3: Immerse the precursor obtained above in a solution containing a boron source and bathe it in an ice-water bath for 1 to 4 hours.

3. The preparation method of the B-doped PdCu bimetallic olefin catalyst according to claim 2, characterized in that, The solvent in step 1 is dimethylformamide, ethylene glycol, and diethylenetriamine; the solvent in step 3 is dimethylformamide; the palladium source is sodium tetrachloropalladium or palladium acetylacetonate, and the copper source is copper acetylacetonate.

4. The method of claim 2 or 3, wherein the B-doped PdCu bimetallic olefin catalyst is prepared by the steps of: The ratio of the mass fraction of palladium in the palladium source, the mass fraction of copper in the copper source, to the volume fraction of the solvent is 4:1:2000, where the mass fraction is in mmol and the volume fraction is in mL.

5. The method for preparing the B-doped PdCu bimetallic olefin catalyst according to claim 2, characterized in that, In step 2, anhydrous ethanol and water are used for washing alternately, and the drying temperature is room temperature to 60 ℃, and the drying time is 3 to 15 h.

6. The method for preparing the B-doped PdCu bimetallic olefin catalyst according to claim 2, characterized in that, The boron source is sodium borohydride, and the molar ratio is precursor:sodium borohydride = 2:

1.

7. The method for preparing the B-doped PdCu bimetallic olefin catalyst according to claim 6, characterized in that, In step 3, the ratio of the molar amount of the precursor, the molar amount of sodium borohydride, and the volume fraction of the solvent is 2:1:667, where the molar amount is measured in mmol and the volume fraction is measured in mL.

8. An application characterized in that, The B-doped PdCu bimetallic olefin catalyst of claim 1 or the B-doped PdCu bimetallic olefin catalyst prepared according to any one of claims 2 to 6 is applied to an electrocatalytic reaction, wherein the electrocatalytic reaction is at least one of the following: cathode hydrogen evolution reaction, formic acid oxidation reaction, anodic oxygen evolution reaction, and methanol oxidation reaction.

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