A self-supporting, high-efficiency OER Mo / Ru-Ni / NF electrocatalyst and its preparation method

Abstract

This invention discloses a self-supporting, high-efficiency OER Mo / Ru-Ni / NF electrocatalyst and its preparation method, belonging to the field of electrocatalytic materials technology. Addressing the problems of insufficient exposure of active sites, poor conductivity, and high interfacial resistance due to the need for binders in existing catalysts, this invention uses nickel foam as a substrate and employs a two-step electrodeposition method combined with a calcination process to prepare a composite catalyst with a cauliflower-like porous structure. This material optimizes the electronic structure and oxygen intermediate adsorption energy by introducing strongly electron-deficient Mo centers to modify the Ru-Ni heterojunction interface; the unique self-supporting porous structure increases the active area, promoting mass transfer and electron transport. This catalyst requires no binder, exhibits low overpotential, a small Tafel slope, and excellent long-term stability, significantly improving the catalytic performance of the oxygen evolution reaction (OER) and making it suitable for high-efficiency water electrolysis for hydrogen production.

Description

Technical Field

[0001] This invention relates to a self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst and its preparation method, belonging to the field of water electrolysis catalyst preparation technology. Background Technology

[0002] Hydrogen energy, as a clean and renewable energy source, is an important alternative to fossil fuels. Electrolysis of water to produce hydrogen has attracted much attention due to its environmental friendliness and high efficiency; however, its efficiency is severely limited by the kinetics of the oxygen evolution reaction (OER). The OER is a four-electron transfer process with a high energy barrier and slow kinetics, requiring highly efficient electrocatalysts to reduce the overpotential. Currently, while noble metal-based catalysts (such as RuO2) possess excellent OER activity, their high cost and scarcity limit their large-scale application.

[0003] Non-precious metal catalysts, such as transition metal oxides, hydroxides, or sulfides (Ni, Fe, Co, etc.), are relatively inexpensive, but they generally suffer from insufficient exposure of active sites, poor conductivity, and structural instability during the reaction. For example, although Ni-based catalysts exhibit good intrinsic OER activity in alkaline environments, their active sites are prone to reconstruction or dissolution under high voltage currents, leading to performance degradation. Furthermore, traditional powdered catalysts require blending with binders and then coating them onto current collectors (such as nickel foam). This non-in-situ preparation method introduces interfacial contact resistance, hindering electron transport and exacerbating catalyst layer exfoliation, thus affecting mass transfer efficiency and stability.

[0004] In existing technologies, heterojunction interface engineering is an effective strategy for improving catalytic performance. By constructing metal-metal or metal-nonmetal heterojunctions (such as Ru-Ni, Fe-Ni, etc.), the interfacial charge distribution can be adjusted, and the adsorption energy of intermediates can be optimized. However, simple metal coupling has limited ability to regulate electronic structure, and the synergistic effect of heterojunctions is easily affected by the disordered arrangement of interfacial atoms or elemental segregation, leading to uneven distribution of active sites. For example, although Ru-Ni heterojunctions can synergistically improve OER activity through the high valence state of Ru and the d-band center of Ni, its activity improvement is more due to the simple coupling of the two metals, with weak ability to finely regulate the electronic state of active sites, making it difficult to achieve an ideal balance of adsorption free energy.

[0005] In recent years, introducing a third component (such as Mo or W) to modify the heterojunction interface has become a new approach to optimize electronic structure. Mo, due to its strong electron-deficient properties, can serve as an electron control center, optimizing the electronic states of Ru / Ni active sites and enhancing the adsorption energy balance of oxygen intermediates (O, OH, *OOH). However, existing Mo modification methods mostly employ hydrothermal or high-temperature sulfidation methods, which are complex and prone to causing active site coating or aggregation, reducing the active area. Therefore, developing a self-supporting OER electrocatalyst with unique morphology, high active site density, and excellent stability, and achieving precise control of the interface electronic structure through innovative synthesis methods, is of great significance for promoting the development of water electrolysis for hydrogen production technology. Summary of the Invention

[0006] The purpose of this invention is to address the problems of existing OER electrocatalysts by providing a Mo / Ru-Ni / NF self-supporting electrocatalyst with innovative synthesis method, high catalytic activity, and good stability, as well as its preparation method. This catalyst utilizes a two-step electrodeposition method to construct a cauliflower-like porous structure, significantly optimizing the interfacial electronic structure and improving OER performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A self-supporting, high-efficiency OER Mo / Ru-Ni / NF electrocatalyst is disclosed. The electrocatalyst uses nickel foam (NF) as a conductive substrate, and a Ru-Ni heterojunction active layer and a Mo-modified layer are sequentially constructed via stepwise electrodeposition to form a composite catalytic material with a unique cauliflower-like porous structure with a diameter of 3–5 μm. This structure effectively increases the electrochemical active area, optimizes the electronic structure of the active sites, and promotes mass transfer and gas escape during the reaction process.

[0009] Preferably, in the self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst, the Ru-Ni heterojunction precursor is formed by cyclic voltammetry electrochemical deposition of RuCl3 and NiCl2, and the active component Mo is modified at the Ru-Ni heterojunction interface by constant current electrochemical deposition in the form of strongly electron-deficient centers. The molar ratio of Ru to Ni is controlled at 2:5, and the molar ratio of Mo to Ni is controlled at 2:1.

[0010] Preferably, the electrode has a uniformly distributed cauliflower-like porous structure, which is assembled from interwoven nanosheets, providing an ideal channel for electrolyte wetting and bubble desorption.

[0011] This invention also provides a method for preparing the above-mentioned self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst, comprising the following steps:

[0012] (1) Pretreatment of nickel foam substrate: The cut nickel foam is placed in hydrochloric acid, isopropanol / acetone mixed solution and anhydrous ethanol in sequence for acid washing and ultrasonic cleaning to thoroughly remove surface oxides and organic matter. After washing, it is dried for later use.

[0013] (2) Ru-Ni precursor electrodeposition: Prepare 40 ml of 5 mmol / L RuCl3 solution, add 0.0594~0.1782 g NiCl2 to it, mix evenly to obtain a mixed electrolyte containing RuCl3 and NiCl2, use the pretreated nickel foam in step (1) as the working electrode, and perform electrochemical deposition by cyclic voltammetry, set the starting voltage to -0 V, the ending voltage to -1.2 V, the number of deposition cycles to 20~100 cycles, the scan rate to 5 mV / s, and dry the sample after obtaining it;

[0014] (3) Place the dried sample from step (2) into a muffle furnace and control the heating rate to 4~6℃ / min. Calcinate at 250~400℃ for 2-5 hours to obtain the Ru-Ni / NF precursor.

[0015] (4) Electrodeposition of Mo-modified layer: 0.121~0.242g Na2MoO4·2H2O was added to 40 ml of deionized water to obtain Na2MoO4·2H2O electrolyte. The Ru-Ni / NF precursor obtained in step (3) was used as the working electrode, and electrodeposition was performed by constant current method. The deposition time was selected as 1~10 min, and the current density was selected as -2.5~-10 mA / cm. 2 The Mo active component was uniformly modified onto the surface of the precursor to obtain a self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst.

[0016] Preferably, in step (1), the concentration of hydrochloric acid is 2.0-3.0 mol / L, the soaking time is 10-15 min, the volume ratio of isopropanol to acetone is 1:1, the ultrasonic time is 20-40 min, and the ultrasonic time of anhydrous ethanol is 15-25 min.

[0017] Preferably, in step (2), the amount of NiCl2 is 0.1188 g and the number of deposition cycles is 20.

[0018] Preferably, in step (3), the temperature is increased at 5 °C / min and calcined at 300 °C for 4 hours.

[0019] Preferably, in step (4), the amount of Na2MoO4·2H2O is 0.242 g, the constant current electrodeposition time is selected as 2 min, and the current density is selected as -2.5 mA / cm². 2 .

[0020] Compared with the prior art, the main advantages of this invention are:

[0021] 1. This invention employs a two-step electrodeposition method (CV electrodeposition + constant current electrodeposition), which is innovative in synthesis method, simple in process and controllable in parameters.

[0022] 2. The Mo / Ru-Ni / NF self-supporting electrode described in this invention can be directly used as a working electrode for electrocatalytic water splitting without the need for a binder, thus avoiding the interfacial resistance problem of traditional powder catalysts and achieving precise control of active sites.

[0023] 3. The catalyst obtained by this invention has a cauliflower-like porous structure, which significantly increases the electrochemical active area and promotes reaction mass transfer.

[0024] 4. This invention introduces Mo to synergistically optimize the electronic structure of the Ru / Ni interface. The OER overpotential and Tafel slope are lower than those of most reported non-noble metal catalysts, and it has the advantages of high stability and good catalytic performance. Attached Figure Description

[0025] Figure 1 XRD pattern of the catalyst obtained in Example 1

[0026] Figure 2 The SEM-EDS image of the catalyst obtained in Example 1.

[0027] Figure 3 The oxygen evolution catalytic performance of the catalyst obtained in Example 1 under a three-electrode system: (a) linear sweep voltammetry; (b) voltammetry at 300, 600, and 900 mA cm⁻¹. -2 (c) Overpotential; (d) Tafel curve; (e) Double layer capacitance (C dl (e) Electrochemical impedance spectroscopy; (f) Vt curve obtained by the galvanostatic step method.

[0028] Figure 4 The oxygen evolution catalytic performance of the catalyst obtained in Example 1 under a two-electrode system: (a) linear sweep voltammetry; (b) voltammetry at 20, 70, and 140 mA cm⁻¹. -2 (c) The potential below; (d) The Vt curve obtained by the constant current step method. Detailed Implementation

[0029] Example 1: In this example, a self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst and its preparation method are carried out according to the following steps:

[0030] (1) Pretreatment of nickel foam substrate: The cut nickel foam substrate was soaked in 20 ml of 2.4 mol / L hydrochloric acid for 10 min, sonicated in 20 ml of isopropanol / acetone mixed solution (volume ratio of 1:1) for 30 min, and sonicated in 20 ml of anhydrous ethanol for 20 min to thoroughly remove surface oxides and organic matter. After washing, it was dried for later use.

[0031] (2) Ru-Ni precursor electrodeposition: Prepare 40 ml of 5 mmol / L ruthenium chloride solution, add 0.1188 g of nickel chloride to it, mix evenly to obtain a mixed electrolyte containing RuCl3 and NiCl2, use the pretreated nickel foam in step (1) as the working electrode, and perform electrochemical deposition by cyclic voltammetry. Set the starting voltage to -0 V, the ending voltage to -1.2 V, the deposition cycle to 20 cycles, and the scan rate to 5 mv / s. After obtaining the sample, dry it.

[0032] (3) Place the dried sample from step (2) into a muffle furnace and calcine at 300 ℃ for 4 hours with a heating rate of 5 ℃ / min to obtain the Ru-Ni / NF precursor;

[0033] (4) Electrodeposition of the Mo-modified layer: 40 ml of deionized water was added to 0.242 g Na2MoO4·2H2O to obtain the Na2MoO4·2H2O electrolyte. The Ru-Ni / NF precursor obtained in step (3) was used as the working electrode, and electrodeposition was performed by constant current method. The deposition time was 2 min, and the current density was -2.5 mA / cm². 2 The Mo active component was uniformly modified onto the surface of the precursor to obtain a self-supporting high-efficiency OER Mo / Ru-Ni / NF(-2.5) self-supporting electrocatalyst.

[0034] Figure 1 The image shows the XRD pattern of the sample obtained in Example 1. Figure 1 a represents the XRD pattern of the sample directly grown on the Ni mesh, which corresponds to the standard Ni spectrum (JCPDS No: 04-0850) and shows the characteristic diffraction peaks of the Ni substrate. Figure 1 b represents the diffraction peaks at 10-40° and 55-75° after removing the Ni diffraction peaks, which correspond to the standard NiO spectrum (JCPDS No:71-1179) and the (111), (200), and (220) crystal planes of NiO, respectively.

[0035] Figure 2The images show SEM images and EDS spectra of the sample obtained in Example 1 at different magnifications. The SEM images reveal a unique cauliflower-like porous structure with a high specific surface area, ensuring the exposure of numerous active sites. EDS analysis indicates that Ru, Ni, Mo, and O are uniformly distributed across the sample.

[0036] Figure 3 The oxygen evolution catalytic performance of the catalyst obtained in Example 1 is shown in a three-electrode system. In the three-electrode system, Hg / HgO is the reference electrode, graphite carbon rod is the counter electrode, the catalyst electrode in Example 1 is the working electrode, and the electrolyte solution is a 1 mol / L KOH solution. Figure 3 a represents the linear sweep voltammetry curve, showing that the Mo / Ru-Ni / NF, Ni foam, and RuO2-Mo / Ru-Ni / NF(-2.5) electrocatalyst exhibits better electrocatalytic activity compared to these catalysts. Figure 3 As can be seen from b, when the current density is 300 mA cm⁻¹ -2 The overpotential of the Mo / Ru-Ni / NF(-2.5) electrocatalyst is 363 mV, significantly lower than that of Ru-Ni / NF (451 mV) and RuO2 (539 mV). Furthermore, the Mo / Ru-Ni / NF(-2.5) electrocatalyst exhibits a high overpotential at a current density of 600 mA cm⁻¹. -2 and 900mA cm -2 At these times, their overpotentials were 436 mV and 496 mV, respectively, significantly lower than the overpotentials of Ru-Ni / NF and RuO2. From the Tafel curve ( Figure 3 c) The Mo / Ru-Ni / NF(-2.5) electrocatalyst obtained has a lower Tafel slope (58.16 mV / dec), indicating that the driving force required for the reaction is smaller and the catalytic activity is higher. Figure 3 d represents the double-layer capacitance (C) dl The curves show that, compared to Ru-Ni / NF, nickel foam, and RuO2, the Mo / Ru-Ni / NF(-2.5) electrocatalyst has a larger double-layer capacitance of 37.3 mF / cm². 2 According to ECSA=C dl / C s This indicates that the Mo / Ru-Ni / NF(-2.5) electrocatalyst has a larger electrochemical active area, more active sites, and better catalytic activity. Figure 3e represents the electrochemical impedance spectroscopy (EIS) of the catalyst in a three-electrode system. Compared to Ru-Ni / NF, nickel foam, and RuO2, the Mo / Ru-Ni / NF(-2.5) catalyst exhibits a smaller EIS value, indicating that the catalyst in Example 1 undergoes faster electron transfer in the oxygen evolution reaction kinetics. To obtain the catalyst's stability, the Vt curve of the Mo / Ru-Ni / NF(-2.5) catalyst was obtained using a constant current (990 mA) step method. Figure 3 e) As can be seen from the figure, the current density remains relatively stable after 500 h, which indicates that the Mo / Ru-Ni / NF(-2.5) catalyst has high stability under the alkaline environment of 1 M KOH.

[0037] Figure 4 The oxygen evolution catalytic performance of the catalyst obtained in Example 1 is shown in a two-electrode system. In the two-electrode system, the anode is the self-supported Mo / Ru-Ni / NF(-2.5) (NF is nickel foam) electrocatalyst from Example 1, the cathode is Pt-C / NF, and the electrolyte solution is a 1 mol / L KOH solution. In the water electrolysis system, electrons are transferred from the Mo / Ru-Ni / NF(-2.5) anode to the Pt-C / NF cathode, thereby generating O2 at the anode and H2 at the cathode. Figure 4 As shown in a, compared with the NF / / NF and RuO2 / NF / / Pt-C / NF two-electrode catalytic systems, the Mo / Ru-Ni / NF(-2.5) / / Pt-C / NF two-electrode system has a lower overpotential and better electrocatalytic activity. Figure 4 As can be seen in b, at a current density of 20 mA cm⁻¹ -2 At this time, the voltage of the Mo / Ru-Ni / NF(-2.5) / / Pt-C / NF two-electrode system was 1.64 V, significantly lower than that of the RuO2 / NF / / Pt-C / NF (1.69 V) and NF / / NF (1.98 V) two-electrode catalytic systems. Similarly, the stability of the catalyst in the two-electrode system was evaluated using a constant current (180 mA) step method. Figure 4 As shown in c, the current density remained relatively stable after 100 h, indicating that the Mo / Ru-Ni / NF(-2.5) catalyst also has high stability in the two-electrode system under alkaline conditions of 1 M KOH.

[0038] This invention successfully prepared a Mo / Ru-Ni / NF self-supporting electrocatalyst through a two-step electrodeposition method. Its cauliflower-like morphology and interfacial electronic regulation synergistically improved the activity and stability of OER, providing a new solution for efficient and low-cost water electrolysis to produce hydrogen.

[0039] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. The embodiments and descriptions above are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst, characterized in that, The electrode uses nickel foam as a conductive substrate, and a Ru-Ni heterojunction active layer and a Mo modified layer are deposited sequentially to form a cauliflower-like porous structure with a diameter of 3~5 μm. This structure is assembled from interwoven nanosheets.

2. The self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst according to claim 1, characterized in that, The Ru-Ni heterojunction active layer is formed by electrochemical deposition of a mixed electrolyte of RuCl3 and NiCl2 using cyclic voltammetry. The active component Mo in the Mo-modified layer is modified at the interface of the Ru-Ni heterojunction layer by electrochemical deposition of a strongly electron-deficient center using constant current.

3. The self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst according to claim 1, characterized in that, In the Ru-Ni heterojunction active layer, the molar ratio of Ru to Ni is controlled at 2:5, and in the Mo-modified layer, the molar ratio of Mo to Ni in the Ru-Ni heterojunction active layer is controlled at 2:

1.

4. The method for preparing the self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst according to claim 1, characterized in that, The method includes the following steps: (1) Pretreatment of the nickel foam substrate; (2) Ru-Ni precursor electrodeposition: Prepare 40 ml of 5 mmol / L RuCl3 solution, add 0.0594~0.1782 g NiCl2 to it, mix evenly to obtain a mixed electrolyte containing RuCl3 and NiCl2, use the pretreated nickel foam in step (1) as the working electrode, and perform electrochemical deposition by cyclic voltammetry. Set the starting voltage to -0 V, the ending voltage to -1.2 V, the number of deposition cycles to 20~100 cycles, and the scan rate to 5 mV / s. After obtaining the sample, dry it. (3) Place the dried sample from step (2) into a muffle furnace and control the heating rate to 4~6℃ / min. Calcine at 250~400℃ for 2-5 hours to obtain the Ru-Ni / NF precursor. (4) Electrodeposition of Mo-modified layer: 0.121~0.242g Na2MoO4·2H2O was added to 40 ml of deionized water to obtain Na2MoO4·2H2O electrolyte. The Ru-Ni / NF precursor obtained in step (3) was used as the working electrode, and electrodeposition was performed by constant current method. The deposition time was selected as 1~10 min, and the current density was selected as -2.5~-10 mA / cm. 2 The Mo active component was uniformly modified onto the surface of the precursor to obtain a Mo / Ru-Ni / NF self-supporting electrode.

5. The method for preparing the self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst according to claim 4, characterized in that, The pretreatment steps for the nickel foam substrate in step (1) are as follows: After acid washing with 2.0-3.0 mol / L hydrochloric acid, the cut nickel foam is ultrasonically cleaned for 15-25 min in a 1:1 volume ratio isopropanol / acetone mixed solution and anhydrous ethanol to thoroughly remove surface oxides and organic matter. After cleaning, it is dried for later use.

6. The method for preparing the self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst according to claim 4, characterized in that, In step (2), the amount of NiCl2 is 0.1188 g and the number of deposition cycles is 20.

7. The method for preparing the self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst according to claim 4, characterized in that, In step (3), the temperature is increased at 5 °C / min and calcined at 300 °C for 4 hours.

8. The method for preparing the self-supporting high-efficiency OER Mo / Ru-Ni / NF electrocatalyst according to claim 4, characterized in that, In step (4), the amount of Na2MoO4·2H2O is 0.242 g, the constant current electrodeposition time is selected as 2 min, and the current density is selected as -2.5 mA / cm². 2 .

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