Multi-metal Ru-based electrocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a multi-metal Ru-based electrocatalyst as well as a preparation method and application thereof, and belongs to the field of electrocatalysis. Carbon black is used as a carrier, Ni, Co and Ru are loaded on the carbon black, and the stability of RuO2 is greatly improved through simultaneous introduction of Ni and Co. Carbon black is removed through H2 / Ar atmosphere reduction and air heat treatment, so that the catalyst is granulated, the catalytic performance of the catalyst is improved, unstable Ni and Co are removed through acid treatment, and the final NiCo-RuO2 catalyst is obtained. The performance of the acidic OER is greatly improved through heat treatment and acid pickling in the air. The NiCo-RuO2 catalyst shows remarkable performance in the aspect of promoting oxygen evolution reaction (OER) under the acidic condition, has high activity and high stability, and becomes an electrocatalyst which has a promising prospect and can replace iridium to be used in acidic electrolyte.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalysis technology, and specifically relates to a multi-metal Ru-based electrocatalyst and a preparation method and application thereof. Background Art

[0002] The development of clean and renewable energy has become a very promising way to reduce dependence on fossil fuels. Currently, hydrogen energy is a clean and renewable energy source that can replace traditional fuels such as coal and oil to reduce air pollution and greenhouse effect. Hydrogen has a high energy density and can be used as an effective way to store energy. Electrocatalytic water oxidation can efficiently produce hydrogen, providing an important way to produce hydrogen energy. Electrocatalytic water oxidation is a clean method that does not produce harmful emissions and helps protect the environment. Therefore, using hydrogen as an energy source can reduce air pollution and greenhouse gas emissions, thereby protecting the environment. Water electrolysis technology uses water resources to produce hydrogen and is an effective way to sustainably produce hydrogen.

[0003] Ruthenium-based electrocatalysts play a crucial role in acidic electrolytes, demonstrating great potential in a variety of electrochemical reactions, including the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and hydrogen oxidation reaction (HOR). The primary advantage of ruthenium-based electrocatalysts is their high catalytic activity and stability in acidic electrolytes. Their exceptional performance in promoting electrochemical reactions makes them a valuable asset in fuel cells, electrolyzers, and other electrochemical devices. Furthermore, ruthenium-based electrocatalysts can be easily synthesized and modified to enhance their catalytic performance, leading to the development of electrocatalysts with enhanced activity, selectivity, and durability. The OER in acidic electrolytes is of great significance because it exhibits a low energy threshold and high reaction rate. However, OER in acidic electrolytes also presents several challenges. Conventional acidic OER requires the use of precious metal catalysts, such as platinum (Pt) and iridium (Ir), which increases catalyst cost. Furthermore, OER is a high-energy reaction, placing high demands on catalyst stability. In acidic electrolytes, catalysts are susceptible to corrosion and oxidation, resulting in reduced activity. At present, people can improve the catalytic activity and stability of Ru-based catalysts by designing new Ru catalyst materials and regulating the surface structure of Ru catalysts. Ruthenium oxides and mixed metal oxides have good catalytic activity and stability in OER reactions. The most common of them is ruthenium dioxide (RuO2), and their high activity is attributed to the ruthenium ions (Ru 4+ ) can effectively catalyze the dissociation of oxygen molecules and the reaction of generating oxygen.

[0004] In general, the challenges of Ru-based electrocatalysts in acidic electrolytes are catalytic activity and stability, as the acidic environment may lead to deactivation or corrosion of the catalyst, thus affecting its catalytic activity and stability. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of a multi-metal Ru-based electrocatalyst, so as to achieve good OER catalytic activity and stability of the catalyst in an acidic electrolyte.

[0006] The present invention first provides a multi-metallic Ru-based electrocatalyst, denoted as NiCo-RuO2, wherein the ratio of the total molar amount of Ni and Co to the molar amount of Ru is 1:1; wherein the molar ratio of Ni to Co is 0.25~4:1, preferably 0.67~1.5:1, more preferably 1~1.5:1, and most preferably 1.5:1.

[0007] The present invention's multi-metallic Ru-based electrocatalyst is prepared through a three-step process, incorporating Ni and Co into the RuO2 lattice to produce a NiCo-RuO2 catalyst. First, using carbon black as a support, Ni, Co, and Ru are loaded onto the carbon black by wet impregnation of metal precursors. Subsequently, the carbon black is annealed and reduced in an H2 / Ar atmosphere to obtain Ru5Ni3Co2 / C supported on the carbon black. The carbon support is crucial in preventing particle aggregation during this process. The resulting Ru5Ni3Co2 / C is then heat-treated in air to convert it to Ru5Ni3Co2Ox while simultaneously removing the carbon black, resulting in catalyst granulation and improving its catalytic performance. Finally, the resulting Ru5Ni3Co2Ox is acid-treated to remove unstable Ni and Co, yielding the final NiCo-RuO2 catalyst. This catalyst exhibits excellent OER performance in acidic electrolytes. Its high activity and stability make it a promising electrocatalyst to replace iridium for the oxygen evolution reaction in acidic electrolytes.

[0008] Specifically, the present invention provides a method for preparing the above-mentioned multi-metal Ru-based electrocatalyst, comprising the following steps: (1) After drying the carbon black, uniformly disperse it in anhydrous ethanol to obtain a carbon black dispersion; (2) adding ruthenium salt, nickel salt and cobalt salt to the carbon black dispersion in sequence, stirring thoroughly to load the metal precursor on the carbon black carrier, and obtaining a catalyst precursor; (3) annealing and reducing the catalyst precursor in a H2 / Ar atmosphere to prepare RuNiCo / C; (4) heat-treating the obtained RuNiCo / C in air to prepare RuNiCoOx; (5) The obtained RuNiCoOx is acid-washed to obtain the final catalyst, namely NiCo-RuO2.

[0009] Furthermore, in the carbon black treatment method described in step (1), the carbon black is dried in an oven at 60°C for 3 hours. The concentration of the carbon black dispersion is 20-30 mg / mL.

[0010] Furthermore, in step (2), the molar ratio of Ru, Ni and Co is (0.5:0:0, 0.5:0.5:0, 0.5:0.4:0.1, 0.5:0.3:0.2, 0.5:0.25:0.25, 0.5:0.2:0.3, 0.5:0.1:0.4, 0.5:0:0.5) (mmol). The optimal ratio of Ru:Ni:Co is 0.5:0.3:0.2. The ruthenium salt is RuCl3·xH2O, the nickel salt is Ni(NO3)2·6H2O, and the cobalt salt is Co(NO3)2·6H2O. The ratio of carbon black to metal salt is 250mg:1mmol.

[0011] Furthermore, in step (3), the H2 / Ar (5% H2) atmosphere treatment is performed by heating the temperature from room temperature to 200°C at a heating rate of 10°C / min, annealing and holding for 1 hour, and then cooling the temperature back to room temperature.

[0012] Furthermore, in step (4), the heat treatment in air is performed by heating the temperature from room temperature to 450°C at a heating rate of 5°C / min, annealing and keeping the temperature for 1 hour, and then cooling the temperature to room temperature.

[0013] Furthermore, in step (5), the acid treatment is to acid-wash the RuNiCoOx obtained in step (4) in 1 M HCl for 2 h.

[0014] Application of the multi-metal Ru-based electrocatalyst prepared by the above method in acidic oxygen evolution reaction.

[0015] Compared with the prior art, the present invention has the following advantages and benefits: The present invention uses a three-step method to synthesize a multi-metal Ru-based electrocatalyst with simple preparation method and low cost, and its activity and stability in acidic electrolyte are higher than those of single RuO2 electrocatalyst. The multi-metallic Ru-based electrocatalyst of the present invention has an adjustable metal ratio and can form granular oxide nanoparticles, achieving a highly efficient acidic oxygen evolution reaction with a low noble metal content. Furthermore, the synthesis method involves only calcination in an oven, tube furnace, and muffle furnace, making it simple to operate, highly universal, and with low production costs, allowing for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1(a, b) Field emission images of RuO2 prepared in Example 1 of the present invention; (c, d) Field emission images of Ni-RuO2; (e, f) Field emission images of NiCo-RuO2; (g, h) Field emission images of Co-RuO2; Figure 2 XRD patterns of RuO2, Ni-RuO2, NiCo-RuO2 and Co-RuO2 electrocatalysts; Figure 3 Linear sweep voltammetry (LSV) curves of RuO2, Ni-RuO2, NiCo-RuO2, and Co-RuO2 electrocatalysts in OER under 0.5 M H2SO4; Figure 4 Tafel plots of RuO2, Ni-RuO2, NiCo-RuO2 and Co-RuO2 electrocatalysts in OER under 0.5 M H2SO4 Figure 5 EIS graphs of RuO2, Ni-RuO2, NiCo-RuO2 and Co-RuO2 electrocatalysts in OER under 0.5 M H2SO4; Figure 6 10 mA cm for RuO2, Ni-RuO2, NiCo-RuO2, and Co-RuO2 electrocatalysts in OER under 0.5 M H2SO4 -2 CP stability curve under current density; Figure 7 The linear sweep voltammetry (LSV) curves of RuO2, Ni-RuO2, NiCo-RuO2 and Co-RuO2 electrocatalysts after 5000 cycles in 0.5 M H2SO4 are shown; Figure 8 Linear sweep voltammetry (LSV) curves of Ru:Ni:Co (0.5:0:0, 0.5:0.5:0, 0.5:0.4:0.1, 0.5:0.3:0.2, 0.5:0.25:0.25, 0.5:0.2:0.3, 0.5:0.1:0.4, 0.5:0:0.5) electrocatalysts in OER under 0.5 M H2SO4; Figure 9 Tafel plots of Ru:Ni:Co (0.5:0:0, 0.5:0.5:0, 0.5:0.4:0.1, 0.5:0.3:0.2, 0.5:0.25:0.25, 0.5:0.2:0.3, 0.5:0.1:0.4, 0.5:0:0.5) electrocatalysts in OER under 0.5 M H2SO4. DETAILED DESCRIPTION

[0017] The present invention is described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0018] Example 1

[0019] The preparation method of the multi-metal Ru-based electrocatalyst comprises the following steps: (1) Dry the carbon black in an oven at 60 °C for 3 h. Disperse 250 mg of carbon black in 10 mL of anhydrous ethanol to obtain a carbon black dispersion. (2) RuCl3·xH2O (0.5 mmol), Ni(NO3)2·6H2O (0.3 mmol), and Co(NO3)2·6H2O (0.2 mmol) were sequentially added to the carbon black dispersion at a molar ratio of Ru, Ni, and Co of 0.5:0.3:0.2. The mixture was stirred thoroughly to load the metal precursors onto the carbon black support to obtain a catalyst precursor. (3) The catalyst precursor was heated from room temperature to 200 °C at a rate of 10 °C / min in a H2 / Ar (5% H2) atmosphere, annealed and kept at this temperature for 1 h, and then cooled to room temperature to obtain RuNiCo / C; (4) The obtained RuNiCo / C was heated from room temperature to 450°C in air at a heating rate of 5°C / min, annealed and kept at this temperature for 1 hour, and then cooled to room temperature to obtain Ru5Ni3Co2Ox; (5) The obtained Ru5Ni3Co2Ox was acid-washed in 1 M HCl for 2 h to obtain the final catalyst, namely NiCo-RuO2.

[0020] Example 2

[0021] The difference between this embodiment and embodiment 1 is that the molar ratio of Ru:Ni:Co is 0.5:0.4:0.1.

[0022] Example 3

[0023] The difference between this embodiment and embodiment 1 is that the molar ratio of Ru:Ni:Co is 0.5:0.25:0.25.

[0024] Example 4

[0025] The difference between this embodiment and embodiment 1 is that the molar ratio of Ru:Ni:Co is 0.5:0.2:0.3.

[0026] Example 5

[0027] The difference between this embodiment and embodiment 1 is that the molar ratio of Ru:Ni:Co is 0.5:0.1:0.4.

[0028] Example 6

[0029] The difference between this embodiment and embodiment 1 is that the metal precursor salt contains only Ru salt (Ru:Ni:Co molar ratio is 0.5:0:0), and the prepared catalyst is recorded as RuO2.

[0030] Example 7

[0031] The difference between this embodiment and embodiment 1 is that no Co salt is contained, the molar ratio of Ru:Ni:Co is 0.5:0.5:0, and the prepared catalyst is recorded as Ni-RuO2.

[0032] Example 8

[0033] The difference between this embodiment and embodiment 1 is that no Ni salt is contained, the molar ratio of Ru:Ni:Co is 0.5:0:0.5, and the prepared catalyst is recorded as Co-RuO2.

[0034] Characterization and performance testing: All electrochemical tests for acidic oxygen evolution were performed using a three-electrode system. An Ag / AgCl electrode served as the reference electrode, a carbon rod served as the counter electrode, and a 0.5 M H₂SO₄ solution served as the electrolyte. The electrode potentials were normalized by applying the Nernst equation and converted to potential differences relative to the reversible hydrogen electrode (RHE). The calculation formula under acidic conditions is: E(vs. RHE) = E(vs. Ag / AgCl) + 0.059 pH + 0.21.

[0035] Linear Sweep Voltammetry (LSV): The polarization curve of hydrogen evolution reaction (OER) was tested in 0.5 M H2SO4 medium with a scan rate of 5 mV / s. -2 Under these conditions, the electrochemical performance of the catalyst was quantitatively evaluated through overpotential measurement and comparative analysis.

[0036] Tafel curve: Through further analysis of the LSV curve, the Tafel curve (η=b log j+a) can be constructed, where a and b represent the Tafel coefficients, and j refers to the injection current density.

[0037] AC impedance test: Electrochemical impedance spectroscopy (EIS) was performed using a PARSTAT 3000 instrument by applying 5 mV AC in the 100K to 0.1 Hz frequency range, and then the circuit parameters were matched.

[0038] Stability test: The electrochemical performance degradation of the catalyst was analyzed by long-term chronopotentiometry (CP) and comparison of electrode polarization curves before and after 5000 cyclic voltammetry tests.

[0039] Figure 1 (a, b) are field emission images of RuO2. Figure 1 (c, d) are field emission images of Ni-RuO2. Figure 1 (e, f) are field emission images of NiCo-RuO2. Figure 1 (g, h). Field emission images of Co-RuO2; Figure 1 The microstructure of the sample was observed and found to be granular.

[0040] Figure 2 The XRD patterns of RuO2, Ni-RuO2, NiCo-RuO2 and Co-RuO2 electrocatalysts of Example 1 prove the successful synthesis of the samples.

[0041] Figure 3 The linear sweep voltammetry (LSV) curves of RuO2, Ni-RuO2, NiCo-RuO2 of Example 1 and Co-RuO2 electrocatalysts in OER under 0.5 M H2SO4 are shown in FIG. Figure 3 It can be seen that when Ni and Co are introduced into RuO2 at the same time, when the current density reaches 10 mA cm -2 When , its overpotential is reduced to 236 mV, which significantly improves the OER activity of RuO2.

[0042] Figure 4 The Tafel curves of RuO2, Ni-RuO2, NiCo-RuO2 and Co-RuO2 electrocatalysts in OER under 0.5 M H2SO4 are shown in FIG. Figure 4 It can be seen that NiCo-RuO2 has the smallest Tafel slope, indicating that its reaction kinetics is the fastest in the acidic oxygen evolution process.

[0043] Figure 5 The EIS diagrams of RuO2, Ni-RuO2, NiCo-RuO2 and Co-RuO2 electrocatalysts in OER under 0.5 M H2SO4 are shown in Figure 2. Figure 5 It can be seen that NiCo-RuO2 has the lowest charge transfer resistance and the best oxygen reduction reaction kinetics.

[0044] Figure 6 10 mA cm for RuO2, Ni-RuO2, NiCo-RuO2 of Example 1, and Co-RuO2 electrocatalysts in OER under 0.5 M H2SO4 -2 CP stability curve under current density, from Figure 6 It can be seen that when Ni and Co are introduced at the same time, the stability of RuO2 is greatly improved.

[0045] Figure 7 The linear sweep voltammetry (LSV) curves of RuO2, Ni-RuO2, NiCo-RuO2 and Co-RuO2 electrocatalysts of Example 1 after 5000 cycles in 0.5 M H2SO4 are shown in FIG. Figure 7 It can be seen that after cycling, the overpotential of NiCo-RuO2 is reduced from 236 mV@10 mA cm -2 Increased to 273 mV@10 cm -2 , maintaining 84% stability.

[0046] Figure 8 Linear sweep voltammetry (LSV) curves of Ru:Ni:Co electrocatalysts (0.5:0:0, 0.5:0.5:0, 0.5:0.4:0.1, 0.5:0.3:0.2, 0.5:0.25:0.25, 0.5:0.2:0.3, 0.5:0.1:0.4, 0.5:0:0.5) in OER under 0.5 M H2SO4. Figure 9 Tafel curves of Ru:Ni:Co (0.5:0:0, 0.5:0.5:0, 0.5:0.4:0.1, 0.5:0.3:0.2, 0.5:0.25:0.25, 0.5:0.2:0.3, 0.5:0.1:0.4, 0.5:0:0.5) electrocatalysts in OER under 0.5 M H2SO4. Figure 8 and Figure 9 In this paper, representative RuO2 (Ru:Ni:Co=0.5:0:0), Ni-RuO2 (Ru:Ni:Co=0.5:0.5:0), NiCo-RuO2 (Ru:Ni:Co=0.5:0.3:0.2) and Co-RuO2 (Ru:Ni:Co=0.5:0:0.5) were selected for analysis. Figure 8 Linear sweep voltammetry (LSV) curves of Ru:Ni:Co (0.5:0:0, 0.5:0.5:0, 0.5:0.4:0.1, 0.5:0.3:0.2, 0.5:0.25:0.25, 0.5:0.2:0.3, 0.5:0.1:0.4, 0.5:0:0.5) in OER under 0.5 M H2SO4. Figure 9The Tafel curves of Ru:Ni:Co (0.5:0:0, 0.5:0.5:0, 0.5:0.4:0.1, 0.5:0.3:0.2, 0.5:0.25:0.25, 0.5:0.2:0.3, 0.5:0.1:0.4, 0.5:0:0.5) in OER under 0.5 M H2SO4 are shown. Figure 8 and Figure 9 Representative RuO2 (Ru:Ni:Co=0.5:0:0), Ni-RuO2 (Ru:Ni:Co=0.5:0.5:0), NiCo-RuO2 (Ru:Ni:Co=0.5:0.3:0.2) and Co-RuO2 (Ru:Ni:Co=0.5:0:0.5) were selected for analysis. Figure 8 As shown in the figure, the introduction of Ni and Co alone can slightly improve the OER performance of RuO2 at 10 mA cm −2 Under the current density condition, Ni-RuO2 and Co-RuO2 showed overpotentials of 303 mV and 316 mV respectively, which were significantly lower than the 340 mV overpotential required for RuO2. When Ni and Co were introduced into RuO2 at the same time, the overpotential of Ni-RuO2 was 303 mV and 316 mV respectively, which were significantly lower than the 340 mV overpotential required for RuO2. −2 When the overpotential is reduced to 236mV, the OER activity of RuO2 is significantly improved. Compared with Ni-RuO2 and Co-RuO2, the overpotential required for the catalyst is much lower. As the current density increases further, the overpotential difference increases rapidly. This is because the Tafel slope (67 mV dec-1) of NiCo-RuO2 material shows significant superiority, which is better than Ni-RuO2 (89 mV dec-1), Co-RuO2 (113 mV dec-1) and RuO2 (157 mV dec-1) ( Figure 9 ). This shows that NiCo-RuO2 has the fastest reaction kinetics in the acidic oxygen evolution process.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A multi-metal Ru-based electrocatalyst, characterized in that: The metals include Ni and Co, and the Ni and Co are combined in a RuO2 lattice; the ratio of the total molar amount of Ni and Co to the molar amount of Ru is 1:1, and the molar ratio of Ni to Co is 0.25-4:

1.

2. The method for preparing the multi-metal Ru-based electrocatalyst according to claim 1, characterized in that: The steps include: (1) uniformly dispersing carbon black in anhydrous ethanol to obtain a carbon black dispersion; (2) adding ruthenium salt, nickel salt and cobalt salt to the carbon black dispersion in sequence, stirring thoroughly to load the metal precursor on the carbon black carrier, and obtaining a catalyst precursor; (3) annealing and reducing the catalyst precursor in a H2 / Ar atmosphere to prepare RuNiCo / C; (4) heat-treating the obtained RuNiCo / C in air to prepare RuNiCoOx; (5) The obtained RuNiCoOx is subjected to acid washing treatment to obtain the multi-metallic Ru-based electrocatalyst, which is denoted as NiCo-RuO2.

3. The method for preparing a multi-metal Ru-based electrocatalyst according to claim 2, characterized in that: The concentration of the carbon black dispersion is 20-30 mg / mL.

4. The method for preparing a multi-metal Ru-based electrocatalyst according to claim 2, characterized in that: The ratio of the total molar amount of the nickel salt and the cobalt salt to the molar amount of the ruthenium salt is 1:1, and the ratio of the total amount of the ruthenium salt, the nickel salt and the cobalt salt to the carbon black is 1 mmol:250 mg.

5. The method for preparing a multi-metal Ru-based electrocatalyst according to claim 2, characterized in that: The molar ratio of nickel salt to cobalt salt is 0.25~4:

1.

6. The method for preparing a multi-metal Ru-based electrocatalyst according to claim 2, characterized in that: The annealing reduction in step (3) is as follows: heating from room temperature to 200°C at a heating rate of 10°C / min, annealing and keeping the temperature for 1 hour, and then cooling to room temperature.

7. The method for preparing a multi-metal Ru-based electrocatalyst according to claim 2, characterized in that: The heat treatment in step (4) is to increase the temperature from room temperature to 450°C at a heating rate of 5°C / min, anneal and keep the temperature for 1 hour, and then cool it down to room temperature.

8. The method for preparing a multi-metal Ru-based electrocatalyst according to claim 2, characterized in that: In step (5), the acid treatment is to acid-wash the RuNiCoOx obtained in step (4) in a 1 mol / L HCl solution for 2 h.

9. Use of the multi-metallic Ru-based electrocatalyst according to claim 1 or the multi-metallic Ru-based electrocatalyst prepared by the method according to any one of claims 2 to 8 in oxygen evolution reaction in acidic medium.

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