Ruthenium-doped nickel-copper-based heterostructure catalyst as well as preparation method and application thereof

Abstract

The invention relates to a ruthenium-doped nickel-copper-based heterostructure catalyst as well as a preparation method and application thereof. Wherein the ruthenium-doped nickel-copper-based heterostructure catalyst comprises a foamed nickel substrate and a ruthenium-doped nickel-copper-based heterostructure Cu2O-Ni (OH) 2, the ruthenium-doped nickel-copper-based heterostructure Cu2O-Ni (OH) 2 grows on the foamed nickel substrate in situ, and Ru is doped in crystal lattices of the Cu2O-Ni (OH) 2 heterostructure. The preparation method of the ruthenium-doped nickel-copper-based heterostructure catalyst comprises the following steps: cleaning the surface of foamed nickel; the preparation method comprises the following steps: dissolving oxalic acid, copper salt and ruthenium salt in water to obtain a precursor solution; and placing foamed nickel in the precursor solution for hydrothermal reaction, and cleaning and drying to obtain the ruthenium-doped nickel-copper-based heterostructure catalyst. The ruthenium-doped nickel-copper-based heterostructure catalyst disclosed by the invention can be applied to an industrial-grade electro-catalytic water decomposition hydrogen evolution reaction, and has good electro-catalytic hydrogen evolution performance.

Description

Technical Field

[0001] The invention relates to a low-load ruthenium-doped nickel-copper-based heterostructure catalyst, a preparation method thereof and application thereof in an industrial-grade electrocatalytic water decomposition hydrogen evolution reaction. Background Art

[0002] Hydrogen energy has shown great development prospects due to its cleanliness and efficiency. Water electrolysis hydrogen production technology has been widely studied in recent years because of its high purity and clean products, no greenhouse gas production during the reaction, and the advantages of being renewable, environmentally friendly, simple to operate, and short cycle. However, the development of efficient, stable, and low-cost electrocatalysts remains a major challenge for the large-scale application of water electrolysis hydrogen production technology.

[0003] So far, transition metals (such as Ni, Cu, and Fe) that are relatively abundant in the earth's crust are often used as non-precious metal materials for water electrolysis due to their low crystal activation energy, excellent synergistic effects, and low costs, and have become candidate materials to replace precious metal catalysts. Therefore, by effectively loading low-content precious metals on transition metals, it is possible to not only reduce the cost of catalysts, but also improve the catalytic performance of non-precious metal catalysts for water electrolysis. However, these transition metal-based materials generally have problems such as poor conductivity, less exposure of active centers, and low stability. Especially at industrial-grade high current densities, they are easy to lose catalytic activity due to the dissolution / migration of transition metals and particle aggregation. Summary of the invention

[0004] In view of the shortcomings of the prior art, the first aspect of the present invention discloses a ruthenium-doped nickel-copper-based heterostructure catalyst, comprising a nickel foam substrate and a ruthenium-doped nickel-copper-based heterostructure in situ grown on the nickel foam substrate; wherein the nickel-copper-based heterostructure is Cu 2 O-Ni(OH) 2 , Ru doped in Cu 2 O-Ni(OH) 2 within the lattice of heterostructures.

[0005] Furthermore, the nickel-copper based heterostructure is composed of nano-granular Cu 2 O and nanosheet Ni(OH) 2 composition.

[0006] The second aspect of the present invention discloses a method for preparing the aforementioned ruthenium-doped nickel-copper-based heterostructure catalyst, comprising the following steps:

[0007] dissolving oxalic acid, copper salt and ruthenium salt in water to obtain a precursor solution;

[0008] The nickel foam is placed in the precursor solution for hydrothermal reaction, and the ruthenium-doped nickel-copper-based heterostructure catalyst is obtained after washing and drying.

[0009] Furthermore, the temperature of the hydrothermal reaction is 150-230°C, and the time is 5-16 hours. Preferably, the temperature of the hydrothermal reaction is 200°C, and the time is 7 hours.

[0010] Furthermore, the copper salt is copper nitrate, and the ruthenium salt is ruthenium chloride.

[0011] Furthermore, the molar concentration of the ruthenium salt in the precursor solution is 0.001 to 0.01 mM, preferably 0.001 to 0.006 mM.

[0012] Furthermore, the molar concentration of the copper salt in the precursor solution is 0.01 to 0.1 M, preferably 0.05 to 0.1 M; the molar concentration of the oxalic acid in the precursor solution is 0.01 to 0.1 M, preferably 0.05 to 0.1 M.

[0013] The third aspect of the present invention discloses the use of the aforementioned ruthenium-doped nickel-copper-based heterostructure catalyst in the electrocatalytic decomposition of water to generate hydrogen.

[0014] Furthermore, the electrocatalytic water decomposition and hydrogen evolution reaction is carried out in an alkaline environment.

[0015] The technical solution of the present invention has the following beneficial effects:

[0016] (1) The present invention dopes Ru into Cu 2 O-Ni(OH) 2 In the heterostructure lattice, Ru doping can not only adjust the electronic structure of the electrochemical reaction intermediates, accelerate the electron transfer rate, and optimize its adsorption energy, but also change the microstructure and morphology of the material, exposing more active sites; in addition, Ru atoms act as efficient active sites in synergy with the host material, especially Cu 2 O-Ni(OH) 2 The synergistic effect of the heterogeneous interface structure can promote the electronic effect between Ru and Cu, further causing charge transfer between components, thereby affecting the adsorption and desorption between active sites and reactants and intermediates, promoting the dissociation of water, accelerating the reaction rate, and promoting the hydrogen evolution reaction process.

[0017] (2) The ruthenium-doped nickel-copper-based heterostructure catalyst of the present invention is a super-hydrophilic material, which can have good contact with the electrolyte, thereby accelerating the reaction kinetics; Cu 2 O-Ni(OH) 2 The heterostructure consists of nanoparticles of Cu 2 O and nanosheet Ni(OH) 2 composition, has a large electrochemically active surface area, and can provide abundant active sites; Ni(OH) 2 The unique nanosheet structure can be used for Cu 2The aggregation of O nanoparticles provides space, effectively stabilizes the electron transfer process from Cu to Ru, optimizes the surface electronic structure, accelerates the catalytic reaction rate, and improves the catalytic performance of the hydrogen evolution reaction.

[0018] (3) In the ruthenium-doped nickel-copper-based heterostructure catalyst of the present invention, Cu 2 O has good chemical stability and corrosion resistance, which is conducive to the long-term stable operation of the catalyst under industrial-grade high current density. The electrochemical test results show that the Ru@Cu 2 O-Ni(OH) 2 The HER reaction has a low overpotential (226mV@1Acm) at industrial-grade high current density. -2 ) and exhibited good stability. Ru@Cu 2 O-Ni(OH) 2 Compared with commercial RuO 2 The assembled water splitting device, at 1A cm - 2 The cell voltage at industrial-grade current density is only 1.945 V and has a stability of more than 10 hours, confirming that Ru@Cu 2 O-Ni(OH) 2 Excellent practical application feasibility.

[0019] In order to more clearly illustrate the purpose, technical solutions and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Example Ru@Cu 2 O-Ni(OH) 2 And comparative example 2Ru@Ni(OH) 2 XRD pattern of the catalyst;

[0021] Figure 2 In the figure: a is the Ru 3p XPS spectrum of the catalyst of the embodiment, b is the spectrum of the Cu 3p of the catalyst of the embodiment and the comparative example 1. 2 O-Ni(OH) 2 a is the Cu 2p XPS spectrum of the catalyst, c is the Ni 2p XPS spectrum of the two, and d is the O1s XPS spectrum of the two;

[0022] Figure 3 Middle: a and b are SEM images of the catalyst of the embodiment, and c and d are TEM images thereof;

[0023] Figure 4 Middle: a and b are comparative examples 1Cu 2 O-Ni(OH) 2 SEM image of the catalyst, c and d are its TEM images;

[0024] Figure 5 1 is a comparison diagram of the linear sweep voltammetry (LSV) curves of the embodiment, comparative example and commercial Pt / C catalyst;

[0025] Figure 6 is the double layer capacitance (C) of the examples, comparative examples and commercial Pt / C catalysts dl ) comparison chart for evaluating the electrochemical surface area (ECSA);

[0026] Figure 7 is a HER chronovoltage curve (CP) diagram of the catalyst of the embodiment;

[0027] Figure 8 It is a comparison chart of the LSV of complete water splitting of Example, Comparative Example 2 and commercial catalyst;

[0028] Fig. 9 is a graph of the complete water splitting chronopotentiometry (CP) curve of the catalyst of the embodiment;

[0029] Fig.10 The Ru@Cu 2 O-Ni(OH) 2 Faraday efficiency (FE) diagram of the catalyst;

[0030] Fig.11 It is a comparison diagram of the hydrophilic contact angles of the example catalyst and pure nickel foam. DETAILED DESCRIPTION

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other variations or replacements made on this basis. Therefore, other possible implementation methods that may be known to those skilled in the art based on the embodiments described in this application all belong to the protection scope of the present invention.

[0032] The embodiment of the present invention discloses a ruthenium-doped nickel-copper-based heterostructure catalyst, comprising a nickel foam substrate and a ruthenium-doped nickel-copper-based heterostructure Cu supported on the nickel foam substrate. 2 O-Ni(OH) 2 , Ru doped in Cu 2 O-Ni(OH) 2 within the lattice of heterostructures.

[0033] The ruthenium-doped nickel-copper-based heterostructure catalyst of the embodiment can be in situ grown on the nickel foam substrate by a one-step hydrothermal method. 2 O-Ni(OH) 2 The heterostructure is obtained, comprising the following steps:

[0034] The nickel foam is cleaned on the surface. Specifically, the nickel foam can be placed in acetone, hydrochloric acid solution and deionized water for ultrasonic cleaning in sequence to clean the surface, wherein acetone can prevent organic impurities from remaining on the surface of the nickel foam, and the hydrochloric acid solution can remove oxides on the surface.

[0035] Dissolve oxalic acid, copper salt and ruthenium salt in deionized water to obtain a precursor solution. The molar concentration of oxalic acid in the precursor solution is 0.01-0.1M, preferably 0.05-0.1M (e.g. 0.08M); the molar concentration of copper salt is 0.01-0.1M, preferably 0.05-0.1M (e.g. 0.06M), and the copper salt is preferably copper nitrate; the molar concentration of ruthenium salt is 0.001-0.01mM, preferably 0.001-0.006mM, and the ruthenium salt is preferably ruthenium chloride.

[0036] The cleaned nickel foam is placed in the precursor solution for hydrothermal reaction, and Ru@Cu is obtained after washing and drying. 2 O-Ni(OH) 2 Heterogeneous structure catalyst: The temperature of the hydrothermal reaction can be 150-230°C, preferably 200°C; the time can be 5-16h, preferably 7h.

[0037] The following is a detailed description with reference to the embodiments and comparative examples.

[0038] Example: Ru@Cu 2 O-Ni(OH) 2 catalyst

[0039] (1) The nickel foam (2.5 cm*3 cm) was ultrasonically cleaned in acetone, 6.0 M hydrochloric acid solution and deionized water for 30 minutes, and then dried to obtain a clean nickel foam substrate. The thickness of the nickel foam was 1.6 mm and the pore size was 110 ppi.

[0040] ⑵ First, 300 mg oxalic acid, 580 mg Cu(NO 3)2 6H 2 O and 50 mg RuCl 3 ·xH 2 O was dispersed in 40 mL of deionized water and stirred at room temperature for 600 s, and then the obtained precursor solution was transferred to a Teflon autoclave. The precursor solution contained 0.08 M oxalic acid, Cu(NO 3)2 The molar concentration of RuCl is 0.06M. 3 The molar concentration is 0.006mM.

[0041] ⑶ Place the cleaned nickel foam horizontally at the bottom of the Teflon high-pressure reactor liner, then place the reactor in a forced air drying oven, set the temperature to 200°C, and keep it warm for 7 hours.

[0042] (4) The product obtained after the reaction was washed with deionized water and anhydrous ethanol three times in sequence, and then placed in a vacuum drying oven at 60 ° C for 6 h to obtain Ru@Cu 2 O-Ni(OH) 2 catalyst.

[0043] Comparative Example 1: Cu 2 O-Ni(OH) 2 catalyst

[0044] The difference between Comparative Example 1 and the embodiment is that no ruthenium salt is added to the precursor solution.

[0045] Comparative Example 2: Ru@Ni(OH) 2 catalyst

[0046] The difference between Comparative Example 2 and the embodiment is that no copper salt is added to the precursor solution.

[0047] Morphology, size and phase analysis of examples and comparative examples

[0048] Figure 1 Example Ru@Cu 2 O-Ni(OH) 2 And comparative example 2Ru@Ni(OH) 2 X-ray diffraction (XRD) spectrum of the catalyst. In the figure, a series of strong diffraction peaks at 2θ of 18.6°, 33.1°, 38.3°, and 51.6° are attributed to Ni(OH) 2 (PDF#73-1520), a series of strong diffraction peaks at 2θ of 38.6°, 52.1°, 59.3° and 62.9° are attributed to Cu 2 O (PDF#78-2076). No diffraction peak of Ru was found in the spectrum.

[0049] Figure 2 : is the XPS spectrum of the catalyst of Example and Comparative Example 1. Figure 2 a shows the Ru 3p XPS spectrum, where the two peaks at 462.3 and 483.9 eV correspond to Ru 4+ , while the two peaks at 465.4 and 487.8 eV correspond to Ru 3+ . Figure 2 The XPS spectrum of Cu 2p in b shows that the Cu element is Cu 0 and Cu 2+ exists in the form of. Figure 2 c shows the Ni 2p XPS spectrum, where the two peaks correspond to Ni 2+ 2p 3 / 2 and Ni 2+ 2p 1 / 2, and the remaining two peaks are satellite peaks. Figure 2 d shows the O1s XPS spectrum, in which the three peaks are attributed to hydroxyl (OH), unsaturated oxygen, and lattice oxygen (MO). Figure 2 The test results show that the solvent thermal treatment process in situ grows Ru@Cu 2 O-Ni(OH) 2 Heterogeneous structure.

[0050] Figure 3 a and b are field emission scanning electron microscope (FE-SEM) images of the catalyst of the embodiment, and it can be seen that nanoparticles of Cu are grown in situ on the nickel foam substrate. 2 O and nanosheet Ni(OH) 2 heterogeneous structure. Figure 3 c and d are transmission electron microscope (TEM) images, which confirm the nanostructure and size of the catalyst of the embodiment. Figure 3 The high-resolution transmission electron microscopy (HRTEM) image in d shows two different lattice fringes with lattice spacings of 0.166 nm and 0.216 nm, which correspond to Cu 2 O (110) crystal plane and Ni(OH) 2 (002) crystal plane.

[0051] Combined with the above analysis, on the one hand, Figure 2 The XPS spectrum of a can prove that Ru is successfully introduced, and Figure 3 No obvious Ru phase was observed in the SEM and TEM images. Figure 1 There is no diffraction peak of Ru in the XRD spectrum of Figure 1 The XRD pattern of Cu 2 O and Ni(OH) 2 The peak is negatively shifted relative to the corresponding diffraction peak of the standard card, which is sufficient to prove that Ru is doped into Cu 2 O-Ni(OH) 2 Heterostructured lattices.

[0052] Figure 4 a and b are field emission scanning electron microscope (FE-SEM) images of the catalyst in Comparative Example 1. It was observed that Ni(OH) 2 The nanosheet shape is the same as that of the catalyst in Example 1, but Cu 2 The morphology of O changed from the granular form in the embodiment to the flake nanoflower form, which indicates that the introduction of Ru in the embodiment did not affect the Ni(OH) 2 The nanosheet structure changes the Cu 2 The shape of O.

[0053] Figure 4c and d are transmission electron microscope (TEM) images of the catalyst of Comparative Example 1, Figure 4 The high-resolution transmission electron microscopy (HRTEM) image in (d) shows two different lattice fringes with lattice spacings of 0.166 nm and 0.216 nm, which correspond to Cu 2 O (110) crystal plane and Ni(OH) 2 (002) crystal plane.

[0054] Electrocatalytic performance test of examples and comparative examples

[0055] Three-electrode system test conditions: 2 The test was conducted in a saturated 1 mol / L KOH solution; the reference electrode was an Ag / AgCl electrode, and the counter electrode was a Pt sheet electrode.

[0056] Fully decomposed water test conditions: in N 2 The working electrode was commercial RuO 2 The electrode, reference electrode and counter electrode are all catalysts of the examples.

[0057] Figure 5 The linear sweep voltammetry (LSV) curves of the examples, comparative examples and commercial Pt / C catalysts are compared. 2 O-Ni(OH) 2 The HER activity was significantly enhanced and the overpotential was the lowest. -2 At a current density of Ru@Cu 2 O-Ni(OH) 2 The HER overpotential is 19 mV at 1 A cm -2 Ru@Cu 2 O-Ni(OH) 2 The HER overpotential of the catalyst is 226 mV, indicating that its catalytic activity for the HER reaction is significantly better than that of Ru@Ni(OH) 2 , Cu 2 O-Ni(OH) 2 and commercial Pt / C.

[0058] Figure 6 is the double layer capacitance (C) used to evaluate the electrochemical surface area (ECSA) dl ) comparison chart, where Ru@Cu 2 O-Ni(OH) 2 Catalyst C dl 35.70mF cm -2 , much higher than commercial Pt / C and Cu 2 O-Ni(OH)2 and Ru@Ni(OH) 2 catalyst, indicating that Ru@Cu 2 O-Ni(OH) 2 It can provide more active sites in the HER process.

[0059] Figure 7 Example Ru@Cu 2 O-Ni(OH) 2 The HER timing voltage curve of the catalyst shows that at the industrial level of 1Acm -2 The Ru@Cu 2 O-Ni(OH) 2 The catalytic activity was almost unchanged.

[0060] Figure 8 Example Ru@Cu 2 O-Ni(OH) 2 、Comparative Example 2Ru@Ni(OH) 2 Compared with the LSV of commercial Pt / C catalyst for water splitting, it can be seen that the Ru@Cu 2 O-Ni(OH) 2 The catalyst only needs 1.945V to reach the industrial level of 1A cm -2 The current density is much better than that of the comparative example 2Ru@Ni(OH) 2 and commercial Pt / C catalysts.

[0061] Fig. 9 Example Ru@Cu 2 O-Ni(OH) 2 The chronovoltage curve of the catalyst's full water splitting is shown at an industrial level of 1Acm -2 The Ru@Cu 2 O-Ni(OH) 2 The catalytic activity showed little attenuation, indicating that it had good catalytic stability.

[0062] Fig.10 The Ru@Cu 2 O-Ni(OH) 2 The Faraday efficiency (FE) diagram is used to compare the theoretical gas production and the actual gas production at different times. 2 With O 2 The volume ratio of Ru@Cu is 2:1, and the calculated 2 O-Ni(OH) 2 The overall FE of water splitting is close to 100%, demonstrating its excellent catalytic activity.

[0063] Hydrophilicity Test of Examples

[0064] Fig.11 By measuring Ru@Cu 2 O-Ni(OH) 2 The contact angles of the pure nickel foam (NF) substrate at the solid-liquid and solid-gas interfaces reveal the surface properties of the electrocatalyst, which is closely related to the improvement of catalytic performance at high current density. Among them, the contact angle of pure nickel foam is 115.63°, indicating that pure nickel foam is a hydrophobic material. 2 O-Ni(OH) 2 The contact angle of Ru@Cu is 0°, indicating that 2 O-Ni(OH) 2 The electrocatalyst is super hydrophilic. Ru@Cu 2 O-Ni(OH) 2 Stronger wettability is beneficial to the contact between the solution and the material surface, thereby accelerating its reaction kinetics and further improving the electrocatalytic efficiency.

[0065] In summary, the ruthenium-doped nickel-copper-based heterostructure catalyst disclosed in the present invention exhibits relatively excellent hydrogen evolution reaction (HER) catalytic performance in industrial-grade electrocatalytic water decomposition, opening up new ideas for the research and development of industrial-grade water electrolysis hydrogen production catalysts.

[0066] Although the present invention is described above through specific embodiments, it should be understood that any equivalent changes made by ordinary technicians in this field without departing from the scope of the present invention should be covered by the protection scope of the present invention.

Claims

1. A ruthenium-doped nickel-copper-based heterostructure catalyst, comprising a nickel foam substrate and a ruthenium-doped nickel-copper-based heterostructure in-situ grown on the nickel foam substrate; wherein: The nickel-copper based heterostructure is Cu2O-Ni(OH)2, and Ru is doped in the lattice of the Cu2O-Ni(OH)2 heterostructure.

2. The ruthenium-doped nickel-copper-based heterostructure catalyst according to claim 1, wherein: The nickel-copper based heterostructure consists of nano-granular Cu2O and nano-sheet Ni(OH)2.

3. The method for preparing the ruthenium-doped nickel-copper-based heterostructure catalyst according to claim 1 or 2, comprising the following steps: dissolving oxalic acid, copper salt and ruthenium salt in water to obtain a precursor solution; The nickel foam is placed in the precursor solution for hydrothermal reaction, and the ruthenium-doped nickel-copper-based heterostructure catalyst is obtained after washing and drying.

4. The preparation method according to claim 3; wherein The temperature of the hydrothermal reaction is 150-230° C. and the time is 5-16 hours.

5. The preparation method according to claim 3; wherein, The copper salt is copper nitrate, and the ruthenium salt is ruthenium chloride.

6. The preparation method according to claim 3; wherein The molar concentration of the ruthenium salt in the precursor solution is 0.001-0.01 mM.

7. The preparation method according to claim 3; wherein The molar concentration of the copper salt in the precursor solution is 0.01-0.1M.

8. The preparation method according to claim 3; wherein The molar concentration of oxalic acid in the precursor solution is 0.01-0.1M.

9. Use of the ruthenium-doped nickel-copper-based heterostructure catalyst according to claim 1 or 2 in the electrocatalytic decomposition of water for hydrogen evolution reaction.

10. The use according to claim 9; wherein: The electrocatalytic water decomposition and hydrogen evolution reaction is carried out in an alkaline environment.

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