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

Abstract

The present application relates to a kind of ruthenium doped nickel copper-based heterostructure catalyst and its preparation method and application.Wherein, ruthenium doped nickel copper-based heterostructure catalyst includes foam nickel base and in situ growth on foam nickel base on ruthenium doped nickel copper-based heterostructure Cu2O-Ni (OH) 2, Ru is doped in the crystal lattice of Cu2O-Ni (OH) 2 heterostructure.Ruthenium doped nickel copper-based heterostructure catalyst preparation method includes the following steps: surface cleaning is carried out to foam nickel;Oxalic acid, copper salt and ruthenium salt are dissolved in water, to obtain precursor solution;Foam nickel is placed in precursor solution and hydrothermal reaction is carried out, and ruthenium doped nickel copper-based heterostructure catalyst is obtained after washing and drying.The ruthenium doped nickel copper-based heterostructure catalyst disclosed in the present application can be applied to industrial-grade electrocatalytic decomposition of water hydrogen evolution reaction, and has good electrocatalytic hydrogen evolution performance.

Description

TECHNICAL FIELD

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

[0002] Hydrogen energy shows excellent development prospects due to its cleanliness and high efficiency. Water electrolysis hydrogen production technology has been widely studied in recent years due to its high product purity and cleanliness, no greenhouse gas generated in the reaction process, and advantages of renewability, environmental friendliness, simple operation and short cycle. However, developing efficient and stable, low-cost electrocatalysts is still a major challenge for large-scale application of water electrolysis hydrogen production technology.

[0003] So far, transition metals (such as Ni, Cu, Fe) with relatively high content in the earth's crust are often used as non-noble metal materials for water electrolysis due to their low crystal activation energy, excellent synergistic effect and low cost, and become candidate materials for replacing noble metal catalysts. Therefore, by effectively loading a low content of noble metal on the transition metal, not only the cost of the catalyst can be reduced, but also the water electrolysis catalytic performance of the non-noble metal catalyst can be improved. However, these transition metal-based materials generally have poor electrical conductivity, few active center exposures, and low stability, especially at an industrial-grade large current density, the transition metal is easily dissolved / migrated and the particles are easily aggregated, which easily loses the catalytic activity. SUMMARY

[0004] In view of the deficiencies of the prior art, a first aspect of the present application discloses a ruthenium-doped nickel-copper-based heterostructure catalyst, comprising a foam nickel substrate and a ruthenium-doped nickel-copper-based heterostructure grown in situ on the foam nickel substrate; wherein the nickel-copper-based heterostructure is Cu2O-Ni(OH)2, and Ru is doped in the crystal lattice of the Cu2O-Ni(OH)2 heterostructure.

[0005] Further, the nickel-copper-based heterostructure is composed of nanoparticle-shaped Cu2O and nanosheet-shaped Ni(OH)2.

[0006] A second aspect of the present application discloses a preparation method of the aforementioned ruthenium-doped nickel-copper-based heterostructure catalyst, comprising the following steps:

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

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

[0009] Further, the temperature of the hydrothermal reaction is 150-230℃, and the time is 5-16h. Preferably, the temperature of the hydrothermal reaction is 200℃, and the time is 7h.

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

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

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

[0013] The third aspect of the present application discloses an application of the aforementioned ruthenium-doped nickel-copper-based heterostructure catalyst in an electrocatalytic water splitting and hydrogen evolution reaction.

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

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

[0016] (1) In the present application, Ru is doped in the crystal lattice of the Cu2O-Ni(OH)2 heterostructure. The doping of Ru can not only adjust the electronic structure of the electrochemical reaction intermediates, accelerate the electron transfer rate, and optimize the adsorption energy, but also change the microstructure and morphology of the material, exposing more active sites. In addition, the ruthenium atom, as a high-efficiency active site, cooperates with the host material, especially the Cu2O-Ni(OH)2 hetero-interface structure, which 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 application is a super-hydrophilic material that can be in good contact with the electrolyte, thereby accelerating the reaction kinetics. The Cu2O-Ni(OH)2 heterostructure is composed of nanoparticle-like Cu2O and nanosheet-like Ni(OH)2, which has a large electrochemically active surface area and can provide abundant active sites. The unique nanosheet structure of Ni(OH)2 can provide space for the aggregation of Cu2O nanoparticles, effectively stabilize the electron transfer process between Cu and Ru, optimize the surface electronic structure, accelerate the catalytic reaction rate, and improve the catalytic performance for the hydrogen evolution reaction.

[0018] ⑶The Ru-doped nickel copper-based heterostructure catalyst of the present application has good chemical stability and corrosion resistance of Cu2O, which is conducive to the long-term stable operation of the catalyst under industrial-grade large current density. The electrochemical test results show that the Ru@Cu2O-Ni(OH)2 of the embodiment has a lower overpotential (226 mV@1 Acm -2 ) in the HER reaction under industrial-grade large current density, and exhibits good stability. The full water splitting device assembled by the Ru@Cu2O-Ni(OH)2 and the commercial RuO2 has a cell voltage of only 1.945 V under 1 A cm - 2 industrial-grade current density, and has a stability of more than 10 hours, which confirms the excellent practical application feasibility of the Ru@Cu2O-Ni(OH)2.

[0019] In order to more clearly illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described in detail below with reference to the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the XRD pattern of the Ru@Cu2O-Ni(OH)2 catalyst of the embodiment and the comparative example 2 Ru@Ni(OH)2 catalyst;

[0021] Figure 2 In the figure: a is the Ru 3p XPS spectrum of the catalyst of the embodiment, b is the Cu 2p XPS spectrum of the catalysts of the embodiment and the comparative example 1 Cu2O-Ni(OH)2, c is the Ni 2p XPS spectrum of the two, and d is the O1s XPS spectrum of the two;

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

[0023] Figure 4 In the figure: a and b are SEM images of the catalyst of the comparative example 1 Cu2O-Ni(OH)2, c and d are TEM images thereof;

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

[0025] Figure 6 is the double-layer capacitance (C dl ) comparison figure of the embodiment, the comparative example and the commercial Pt / C catalyst, for evaluating the electrochemical surface area (ECSA);

[0026] Figure 7 is the HER chronoamperometry (CP) figure of the catalyst of the embodiment;

[0027] Figure 8 is a full water splitting LSV comparison chart of the example, comparative example 2 and commercial catalysts;

[0028] Figure 9 is a full water splitting chronoamperometry (CP) chart of the example catalysts;

[0029] Figure 10 is a Faraday efficiency (FE) chart of the example Ru@Cu2O-Ni(OH)2 catalysts calculated from the water vapor collection method test;

[0030] Figure 11 is a hydrophilicity contact angle comparison chart of the example catalysts and pure foam nickel. DETAILED DESCRIPTION

[0031] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the application. However, it will be apparent to one skilled in the art that the application can be practiced without the specific details set forth in this application. Therefore, other implementations are contemplated beyond the specific examples described herein to be within the scope of the present application.

[0032] The example of the present application discloses a ruthenium-doped nickel-copper-based heterostructure catalyst, which comprises a foam nickel substrate and a ruthenium-doped nickel-copper-based heterostructure Cu2O-Ni(OH)2 loaded on the foam nickel substrate, and the Ru is doped in the crystal lattice of the Cu2O-Ni(OH)2 heterostructure.

[0033] The ruthenium-doped nickel-copper-based heterostructure catalyst of the example can be obtained by in-situ growth of Ru@Cu2O-Ni(OH)2 heterostructure on the foam nickel substrate through a one-step hydrothermal method, comprising the following steps:

[0034] The foam nickel is subjected to surface cleaning. Specifically, the foam nickel can be sequentially placed in acetone, hydrochloric acid solution and deionized water for ultrasonic cleaning to perform surface cleaning, wherein the acetone can avoid organic impurities remaining on the surface of the foam nickel, and the hydrochloric acid solution can remove the surface oxides.

[0035] Oxalic acid, copper salt and ruthenium salt are dissolved 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 (for example, 0.08M); the molar concentration of the copper salt is 0.01-0.1M, preferably 0.05-0.1M (for example, 0.06M), and the copper salt is preferably copper nitrate; the molar concentration of the ruthenium salt is 0.001-0.01mM, preferably 0.001-0.006mM, and the ruthenium salt is preferably ruthenium chloride.

[0036] The cleaned foam nickel is placed in a precursor solution for hydrothermal reaction, and after washing and drying, a Ru@Cu2O-Ni(OH)2heterostructure catalyst is obtained. 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 will be described in detail in combination with examples and comparative examples.

[0038] Example: Ru@Cu2O-Ni(OH)2catalyst

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

[0040] (2) 300mg of oxalic acid, 580mg of Cu(NO 3)2 ·6H2O and 50mg of RuCl3·xH2O are dispersed in 40mL of deionized water, and stirred at room temperature for 600s, and then the obtained precursor solution is transferred to a Teflon high-pressure reaction kettle. The molar concentration of oxalic acid in the precursor solution is 0.08M, the molar concentration of Cu(NO 3)2 is 0.06M, and the molar concentration of RuCl3 is 0.006mM.

[0041] (3) The cleaned foam nickel is placed horizontally at the bottom of the inner container of the Teflon high-pressure reaction kettle, and then the reaction kettle is placed in a forced air drying oven, set to 200°C, and incubated for 7h.

[0042] (4) The product obtained after the reaction is sequentially washed with deionized water and anhydrous ethanol three times, and placed in a vacuum drying oven at 60°C for 6h to obtain a Ru@Cu2O-Ni(OH)2catalyst.

[0043] Comparative Example 1: Cu2O-Ni(OH)2catalyst

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

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

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

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

[0048] Figure 1X-ray diffraction (XRD) patterns of the catalysts of Example Ru@Cu2O-Ni(OH)2and Comparative Example 2 Ru@Ni(OH)2. The series of strong diffraction peaks at 2Q of 18.6°, 33.1°, 38.3°, 51.6° are assigned to Ni(OH)2(PDF #73-1520), and the series of strong diffraction peaks at 2Q of 38.6°, 52.1°, 59.3° and 62.9° are assigned to Cu2O (PDF #78-2076). No diffraction peaks of Ru were found in the patterns.

[0049] Figure 2 XPS patterns of the catalysts of Example and Comparative Example 1. In which, Figure 2 a shows the Ru 3p XPS spectrum, in which 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 b shows the Cu 2p XPS spectrum, which can indicate that the Cu element is in the form of Cu 0 and Cu 2+ . Figure 2 c shows the Ni 2p XPS spectrum, in which the two peaks correspond to Ni 2+ 2p 3 / 2 and Ni 2+ 2p 1 / 2 , respectively, and the remaining two peaks are satellite peaks. Figure 2 d shows the O 1s XPS spectrum, in which the three peaks are assigned to hydroxyl (OH), unsaturated oxygen and lattice oxygen (M-O). Figure 2 The test results of Figure 1 show that the Ru@Cu2O-Ni(OH)2heterostructure is grown in situ on the surface of the nickel foam by the solvothermal treatment process.

[0050] Figure 3 a and b are field emission scanning electron microscope (FE-SEM) images of the catalyst of Example, which can be seen that the heterostructure of nanoparticulate Cu2O and nanosheet Ni(OH)2is grown in situ on the nickel foam substrate. Figure 3 c and d are its transmission electron microscope (TEM) images, which confirm the nanostructure and size of the catalyst of Example, Figure 3 The high-resolution transmission electron microscope (HRTEM) image in d shows two different lattice fringes with lattice spacings of 0.166 nm and 0.216 nm, which correspond to the (110) crystal plane of Cu2O and the (002) crystal plane of Ni(OH)2, respectively.

[0051] Based on the above analysis, on the one hand, Figure 2 the XPS spectrum of a can prove that Ru is successfully introduced, and Figure 3No obvious phase of Ru was observed in the SEM and TEM images of the catalyst, and Figure 1 No diffraction peak of Ru was observed in the XRD pattern of the catalyst; on the other hand, Figure 1 The XRD pattern of the catalyst showed that the peaks of Cu2O and Ni(OH)2 were negatively shifted relative to the corresponding diffraction peaks of the standard card, which was sufficient to prove that Ru was incorporated into the crystal lattice of the Cu2O-Ni(OH)2 heterostructure.

[0052] Figure 4 a and b are field emission scanning electron microscope (FE-SEM) images of the catalyst of Comparative Example 1. It was observed that Ni(OH)2 in the catalyst of Comparative Example 1 exhibited the same nanosheet shape as the catalyst of the examples, but the morphology of Cu2O changed from the granular shape of the examples to a thin sheet nanoflower shape, which indicated that the introduction of Ru in the examples did not affect the nanosheet structure of Ni(OH)2, but changed the morphology of Cu2O.

[0053] Figure 4 c and d are transmission electron microscope (TEM) images of the catalyst of Comparative Example 1, Figure 4 The high-resolution transmission electron microscope (HRTEM) image in d shows two different lattice fringes with lattice spacings of 0.166 nm and 0.216 nm, which correspond to the (110) crystal plane of Cu2O and the (002) crystal plane of Ni(OH)2, respectively.

[0054] Electrocatalytic performance test of the examples and comparative examples

[0055] Three-electrode system test conditions: tested in 1 mol / L KOH solution saturated with N2; wherein the reference electrode was an Ag / AgCl electrode, and the counter electrode was a Pt sheet electrode.

[0056] Full water splitting test conditions: tested in 1 mol / L KOH solution saturated with N2; wherein the working electrode was a commercial RuO2 electrode, and the reference electrode and the counter electrode were the catalysts of the examples.

[0057] Figure 5 is a linear sweep voltammetry (LSV) comparison chart of the examples, the comparative examples, and the commercial Pt / C catalyst, and it can be seen that Ru@Cu2O-Ni(OH)2 has significantly enhanced HER activity and shows the lowest overpotential. Specifically, the HER overpotential of Ru@Cu2O-Ni(OH)2 is 19 mV at a current density of 10 mAcm-2, and the HER overpotential of Ru@Cu2O-Ni(OH)2 is 226 mV at an industrial current density of 1 Acm-2, which indicates that the catalytic activity of Ru@Cu2O-Ni(OH)2 for the HER reaction is significantly better than that of Ru@Ni(OH)2, Cu2O-Ni(OH)2, and commercial Pt / C. -2 -2 ​​

[0058] Figure 6 is a double-layer capacitor (C dl ) of the Ru@Cu2O-Ni(OH)2 catalyst, which is much higher than that of the commercial Pt / C, Cu2O-Ni(OH)2 and Ru@Ni(OH)2 catalysts, indicating that the Ru@Cu2O-Ni(OH)2 can provide more active sites in the HER process. dl -2 , which is much higher than that of the commercial Pt / C, Cu2O-Ni(OH)2 and Ru@Ni(OH)2 catalysts, indicating that the Ru@Cu2O-Ni(OH)2 can provide more active sites in the HER process.

[0059] Figure 7 is a HER chronoamperogram of the example Ru@Cu2O-Ni(OH)2 catalyst, which shows that the Ru@Cu2O-Ni(OH)2 can work continuously for more than 15 hours at the industrial level of 1 A cm -2 , and the catalytic activity of the Ru@Cu2O-Ni(OH)2 almost does not decay.

[0060] Figure 8 is a full water splitting LSV comparison chart of the example Ru@Cu2O-Ni(OH)2, the comparative example 2 Ru@Ni(OH)2 and the commercial Pt / C catalysts, which shows that the example Ru@Cu2O-Ni(OH)2 catalyst can reach the industrial level of 1 A cm -2 , and the performance of the Ru@Cu2O-Ni(OH)2 is much better than that of the comparative example 2 Ru@Ni(OH)2 and the commercial Pt / C catalysts.

[0061] Figure 9 is a full water splitting chronoamperogram of the example Ru@Cu2O-Ni(OH)2 catalyst, which shows that the Ru@Cu2O-Ni(OH)2 can work continuously for more than 10 hours at the industrial level of 1 A cm -2 , and the catalytic activity of the Ru@Cu2O-Ni(OH)2 almost does not decay, indicating that it has good catalytic stability.

[0062] Figure 10 is a Faraday efficiency (FE) chart of the Ru@Cu2O-Ni(OH)2 calculated by the drainage gas collection method, which compares the theoretical gas production and the actual gas production at different times, and measures that the volume ratio of H2 to O2 is 2:1. The FE of the Ru@Cu2O-Ni(OH)2 for the overall water splitting is close to 100%, which shows its excellent catalytic activity.

[0063] Hydrophilicity test of the examples

[0064] Figure 11 ​In the specific embodiments, by measuring the contact angle of Ru@Cu2O-Ni(OH)2 and pure foam nickel (NF) substrate at the solid-liquid and solid-gas interface, the surface properties of the electrocatalyst are revealed, which is closely related to the improvement of catalytic performance at high current density. Among them, the contact angle of pure foam nickel is 115.63°, indicating that pure foam nickel is a hydrophobic material. The contact angle of Ru@Cu2O-Ni(OH)2 is 0°, indicating that the Ru@Cu2O-Ni(OH)2 electrocatalyst has superhydrophilicity. The strong wettability of Ru@Cu2O-Ni(OH)2 is conducive to the contact of the solution and the surface of the material, thereby accelerating the reaction kinetics and further improving the electrocatalytic efficiency.

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

[0066] Although the present application is described above through specific embodiments, it should be understood that any equivalent changes made in accordance with the present application without departing from the scope of the present application shall be covered by the protection scope of the present application.

Claims

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

2. The ruthenium-doped nickel-copper-based heterostructure catalyst of claim 1, wherein, The nickel-copper-based heterostructure is composed of nanoparticle Cu2O and nanosheet Ni(OH)2.

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

4. The method of claim 3; wherein, The temperature of the hydrothermal reaction is 150-230°C, and the time is 5-16h.

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

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

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

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

9. The Ru-doped nickel-copper-based heterostructure catalyst according to claim 1 or 2 for use in an electrocatalytic water splitting hydrogen evolution reaction.

10. Use according to claim 9; wherein, The electrocatalytic water splitting hydrogen evolution reaction is carried out in an alkaline environment.

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