A fluctuation-resistant start-stop alkaline electrolytic water cathode palladium-ruthenium catalyst and a preparation method thereof

Abstract

This invention discloses a palladium-ruthenium catalyst for alkaline water electrolysis with resistance to start-stop and fluctuation conditions, and its preparation method. The method includes: pretreating carbon black to obtain a support; adding the support to a palladium-ruthenium precursor mixed solution; ultrasonically mixing and stirring for aging; drying and grinding to obtain a crude catalyst; and finally annealing under a mixed gas atmosphere to obtain the target catalyst. The catalyst prepared by this invention exhibits excellent resistance to fluctuations and high catalytic activity under alkaline water electrolysis start-stop and fluctuation conditions, with low cost; the preparation process is short, convenient, requires no complex and expensive equipment, has mild reaction conditions, low energy consumption, adjustable production capacity, and is easy to scale up industrially, demonstrating significant industrial compatibility and application potential.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and catalysis technology, specifically relating to a palladium-ruthenium catalyst for an alkaline water electrolysis cathode that is resistant to fluctuations and its preparation method. Background Technology

[0002] With the rapid development of renewable energy sources (such as wind and solar power), using intermittent electricity for water electrolysis to produce hydrogen has become a key technological approach to solving energy storage and conversion problems. However, renewable energy power generation is typically characterized by fluctuations and intermittency, leading to frequent start-ups and shutdowns or operation under high current fluctuations in water electrolysis hydrogen production units. This operating condition poses a severe challenge to the stability of cathode catalytic materials: traditional cathode catalysts are prone to dissolution, agglomeration of active components or corrosion of the support under frequent potential cycling and reverse current impacts, resulting in a sharp decline in catalytic activity and severely limiting the efficiency and lifespan of water electrolysis hydrogen production systems.

[0003] Currently, alkaline water electrolysis cathode catalysts are mainly based on platinum group metals (such as Pt and Pd) or non-precious metals (such as Ni and Co-based materials). Although precious metal catalysts (such as Pt / C) have high hydrogen evolution catalytic activity, they are expensive, and under start-up and shutdown fluctuations, carbon support corrosion and metal particle shedding are prominent problems, resulting in insufficient resistance to fluctuations. While non-precious metal catalysts are cheaper, their activity and stability are often difficult to balance under strongly alkaline media and fluctuating potential conditions, especially since the reverse current generated during start-up and shutdown can easily lead to their oxidative deactivation.

[0004] Ruthenium (Ru)-based materials have attracted widespread attention in recent years due to their high intrinsic hydrogen evolution activity and relatively lower cost compared to platinum. However, the long-term stability of single ruthenium catalysts in alkaline media remains unsatisfactory, and their interaction with the support is weak. Palladium (Pd) possesses excellent electronic modulation capabilities and corrosion resistance; alloying palladium with ruthenium or forming composite structures holds promise for synergistically improving the activity and stability of catalysts. While there are reports on palladium-ruthenium catalysts in existing technologies, most focus on steady-state electrolysis conditions and lack specific designs for fluctuating start-stop conditions. Furthermore, existing preparation methods generally suffer from complex processes, harsh conditions, and poor batch repeatability, making it difficult to meet the needs of large-scale production. Therefore, developing a cathode palladium-ruthenium catalyst with high activity and stability under fluctuating start-stop conditions in alkaline water electrolysis, with a simple and mild preparation process that is easy to scale up, has significant technological value and industrialization implications. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical defects of existing alkaline water electrolysis cathode catalysts, such as poor anti-suspension and start-up performance, uneven dispersion of active components, weak bonding between the support and active components, and the difficulty of adapting traditional preparation processes to industrial production. This invention provides a method for preparing a palladium-ruthenium catalyst for alkaline water electrolysis with anti-suspension and start-up conditions. The palladium-ruthenium catalyst prepared by this method achieves small particle size and uniform size distribution of the palladium-ruthenium active components, which are uniformly dispersed on the carbon support surface. Through the synergistic electronic effect between palladium and ruthenium and the strong interaction between the support and the active components, the catalytic activity and long-term operational stability of the catalyst under fluctuating start-up and stop-up conditions in alkaline water electrolysis are significantly improved. This results in superior anti-suspension performance compared to traditional ruthenium-based catalysts. Simultaneously, the preparation process is simplified, and production costs are reduced. Ultimately, this provides a high-performance cathode catalyst preparation scheme suitable for industrial applications and meeting the needs of intermittent water electrolysis for hydrogen production from renewable energy sources, demonstrating promising prospects for industrial application.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: This invention first provides a method for preparing a palladium-ruthenium catalyst for an alkaline water electrolysis cathode that is resistant to fluctuations and start / stop, comprising the following steps: (1) Disperse the carbon source in a mixture of concentrated nitric acid and water, heat and reflux for acid treatment, and after the reaction is complete, wash and dry to obtain the carbon support. (2) Add the palladium source, ruthenium source, and carbon support obtained in step (1) into the solvent and disperse them evenly by ultrasonication in an ice bath to obtain a precursor mixed solution; (3) Continue stirring and aging the precursor mixture solution, then transfer it to an evaporating dish and place it in an oven for drying; (4) After the dried powder is ground evenly, it is annealed to obtain palladium-ruthenium catalyst for anti-fluctuation start-stop alkaline water electrolysis cathode.

[0007] As a preferred embodiment of the present invention, in step (1): the carbon source is conductive carbon black (specifically, one or more of XC72, KJ300, and KJ600 can be selected); the volume ratio of concentrated nitric acid to water is 1~3:1; the temperature of the heating reflux is 60~80℃; and the acid treatment time is 1~3 h.

[0008] As a preferred embodiment of the present invention, in step (2), the ultrasonic dispersion power is 30~80 W and the ultrasonic time is 15~60 min.

[0009] As a preferred embodiment of the present invention, in step (2), the palladium source is selected from one or more of palladium nitrate, palladium chloride, and palladium acetylacetonate, the ruthenium source is selected from one or more of ruthenium chloride, potassium pentachlororuthenate, and ruthenium acetylacetonate, and the solvent is one or more of methanol, ethanol, acetone, and ultrapure water.

[0010] As a preferred embodiment of the present invention, in step (2), the total molar amount of palladium source and ruthenium source to the molar ratio of carbon support is 1.5~2.5:100, and the molar ratio of palladium source to ruthenium source is 1~3:1~3.

[0011] As a preferred embodiment of the present invention, in step (3), the aging time is 18~24 h, the drying temperature is 60~100℃, and the drying time is 5~12 h.

[0012] As a preferred embodiment of the present invention, in step (4), the atmosphere selected for the annealing treatment is one or more of Ar, N2 and H2, the annealing temperature is 100~500℃, the heating rate is 5~10℃ / min, and the treatment time is 6~10 h.

[0013] This invention also provides the application of the palladium-ruthenium catalyst prepared by the above preparation method. The catalyst can be used for the hydrogen evolution reaction at the cathode of alkaline water electrolysis under fluctuating operating conditions, and can also be applied to industrial anion exchange membrane (AEM) water electrolysis devices.

[0014] Compared with the prior art, the beneficial effects of the present invention are reflected in: 1. The overall preparation process of this invention is simple and compact, the reaction conditions are mild and controllable, no precision and expensive preparation equipment is required throughout the process, the production energy consumption is low, it is green and pollution-free, the process compatibility is strong, the production capacity is flexible and adjustable, and the process scale-up from laboratory pilot to industrial mass production can be successfully realized, and the difficulty of industrialization is low.

[0015] 2. This invention, through carbon support acidification modification combined with liquid phase loading and atmosphere annealing reduction process, can effectively control the metal nucleation and growth process. The resulting palladium-ruthenium catalyst active component particles are small in size and uniform in size distribution, and can be highly uniformly dispersed on the surface of the modified carbon support, which greatly increases the number of effective catalytic active sites, and at the same time effectively strengthens the interfacial interaction between the metal active component and the carbon support.

[0016] 3. Relying on the unique electronic synergistic regulation effect between palladium and ruthenium bimetals, the catalyst of this invention can precisely optimize the energy barrier of hydrogen adsorption and desorption reactions, and has excellent intrinsic hydrogen evolution catalytic activity in alkaline water electrolysis systems. Under harsh operating conditions such as frequent start-stop and large current fluctuations caused by intermittent energy sources such as wind and solar power generation, it can effectively suppress problems such as active metal dissolution and loss, particle agglomeration and growth, and carbon support corrosion failure. After accelerated aging stability testing, the catalytic activity decay is minimal, and its resistance to fluctuation shocks and long-term service stability are far superior to single ruthenium-based catalyst materials.

[0017] 4. Under the premise of ensuring excellent electrochemical catalytic performance and stability under operating conditions, this invention rationally controls the ratio of precious metals, effectively reduces the raw material preparation cost, and takes into account both catalytic performance and economic practicality. It can provide a new cathode hydrogen evolution catalyst material with high performance, high stability, low cost and easy mass production for the large-scale alkaline water electrolysis hydrogen production industry driven by fluctuating renewable energy. Its market application prospects and industrial promotion value are very prominent. Attached Figure Description

[0018] Figure 1 This is a transmission electron microscope (TEM) image of the catalyst obtained in Example 3 of the present invention; Figure 2 The X-ray diffraction (XRD) patterns of the palladium-ruthenium catalysts obtained in Examples 1-5 of this invention are shown below. Figure 3 The above are the electrochemical performance curves of the catalysts obtained in Examples 1-5 of this invention under alkaline hydrogen evolution (HER) conditions. Figure 4 These are performance test diagrams of the catalysts obtained in Examples 1-5 of this invention applied to anion exchange membrane (AEM) water electrolysis devices. Figure 5 This is a comparison chart of the operational stability of the catalyst obtained in Example 3 and the catalyst obtained in Example 5 under repeated start-stop conditions. Figure 6 This is a test diagram of the long-term stability of the catalyst obtained in Example 3 of the present invention under simulated wind and solar power fluctuation conditions. Detailed Implementation

[0019] To further understand the present invention, the preparation of the palladium-ruthenium catalyst provided by the present invention and its application as a catalyst for the alkaline water electrolysis hydrogen evolution reaction under fluctuating operating conditions are described in detail below with reference to the embodiments.

[0020] Example 1 This embodiment describes the palladium-ruthenium catalyst nanomaterial according to the following steps: (1) Add 300 mg KJ 300 to 100 mL of a mixture of concentrated nitric acid (mass fraction of about 68%) and water in a volume ratio of 2:1, heat under reflux for acid treatment, control the reaction temperature at 70℃ and the acid treatment time at 2h; after the reaction is complete, wash with deionized water and ethanol alternately until the filtrate is neutral, place the washed solid in a vacuum oven at 60℃ overnight to dry, and obtain carbon support.

[0021] (2) Add 0.3 mmol of palladium acetylacetonate (Pd:Ru molar ratio of 1:0) and 15 mmol of the carbon support prepared in step (1) to 15 mL of acetone, and sonicate for 30 min under ice bath conditions. The ultrasonic power is controlled at 50W. After uniform dispersion, a precursor mixed solution is obtained.

[0022] (3) Continue stirring and aging the precursor mixture for 20 hours. After aging, transfer it to a 9cm evaporating dish and dry it in an oven at 80°C for 8 hours.

[0023] (4) The dried solid powder was ground for 30 min (using a 9 cm mortar), then placed in a ceramic boat and placed in a tube furnace for annealing. A 3% H2 / 97% Ar mixed gas was first introduced for 20 min to remove air from the tube, and then the mixed gas was continued to be introduced. The heating rate was controlled at 5 °C / min. After heating to 450 °C, the mixture was annealed at this temperature for 8 h to fully reduce the metal ions into metal nanoparticles. After annealing, the mixture was allowed to cool naturally to room temperature, and the product was collected. The resulting catalyst was denoted as Pd / C.

[0024] Example 2 In Example 1, the molar ratio of palladium to ruthenium was adjusted to Pd:Ru = 3:1, while the total molar amount of both remained unchanged. All other methods and conditions were completely consistent with those in Example 1, and the resulting catalyst was denoted as Pd3Ru1 / C.

[0025] Example 3 In Example 1, the molar ratio of palladium to ruthenium was adjusted to Pd:Ru = 1:1, while the total molar amount of both remained unchanged. All other methods and conditions were completely consistent with those in Example 1, and the resulting catalyst was denoted as Pd2Ru2 / C.

[0026] Figure 1 This is a transmission electron micrograph of the palladium-ruthenium catalyst prepared in this embodiment. The high degree of dispersion of PdRu particles can be determined by the TEM image.

[0027] Example 4 In Example 1, the molar ratio of palladium to ruthenium was adjusted to Pd:Ru = 1:3, while the total molar amount of both remained unchanged. All other methods and conditions were completely consistent with those in Example 1, and the resulting catalyst was denoted as Pd1Ru3 / C.

[0028] Example 5 In Example 1, the molar ratio of palladium to ruthenium was adjusted to Pd:Ru = 0:1, while the total molar amount of both remained unchanged. All other methods and conditions were completely consistent with those in Example 1, and the resulting catalyst was denoted as Ru / C.

[0029] Figure 2 The XRD characterization spectra of the palladium-ruthenium catalysts prepared in Examples 1-5 show that the series of catalysts prepared in this invention all exhibit an amorphous phase structure.

[0030] Membrane electrode preparation and device assembly: A two-electrode system was used to construct an anion exchange membrane (AEM) water electrolysis test device. 30 mg of catalyst active material was weighed, ball-milled for 20 min, and then dispersed in a mixture of 1 mL deionized water, 3 mL isopropanol, and 18 mL polytetrafluoroethylene (PTFE). The mixture was ultrasonically dispersed for 30 min to obtain a uniformly dispersed catalyst slurry. The slurry was then uniformly sprayed onto the surface of the anion exchange membrane using an ultrasonic spraying process. The effective spraying area was 2 cm × 2 cm, and the catalyst loading was controlled at 1 mg / cm². 2 NiFe-LDH prepared by hydrothermal method was selected as the anode catalyst (preparation method reference: Zhao J, Zhang Y, Ye Y, et al. Remote Iron dynamics of NiFe (oxy) hydroxides toward robust active sites in water oxidation[J]. Nature Communications, 2025, 16(1): 5601.). The anode used nickel foam as a porous transport layer, and the cathode used hydrophilic carbon paper as a porous transport layer. A 50 μm thick anion exchange membrane was selected, and a serpentine flow channel was arranged inside the device. The overall assembly completed the AEM water electrolysis test device A. Commercial nickel felt was selected as the anode catalyst. The anode used nickel foam as a porous transport layer, and the cathode used hydrophilic carbon paper as a porous transport layer. An 80 μm thick anion exchange membrane was selected, and a serpentine flow channel was arranged inside the device. The overall assembly completed the AEM water electrolysis test device B. Device A was used for activity testing, and device B was used for stability testing.

[0031] Figure 3 The graphs show the alkaline hydrogen evolution (HER) electrochemical performance of the catalysts obtained in Examples 1-5 of this invention. The test results show that the HER catalytic performance of the palladium-ruthenium bimetallic composite catalyst is between that of the pure palladium-carbon catalyst and the pure ruthenium-carbon catalyst.

[0032] Figure 4 The polarization curves of the AEM water electrolysis test device A assembled with the catalysts obtained in Examples 1-5 of this invention were compared. The test electrolyte was 1M KOH, and the test temperature was 60℃. The results show that Pd2Ru2 / C (Example 3, Pd:Ru=1:1) has the lowest cell voltage across the entire current density range, exhibiting the best performance of the AEM water electrolysis device.

[0033] Figure 5The test curves show the long-term stability of the AEM water electrolysis test device B assembled from the catalysts obtained in Example 3 (Pd2Ru2 / C) and Example 5 (pure Ru / C) under repeated start-stop conditions. The test conditions were: electrolyte 1 MkOH, test temperature 60°C; start-stop cycle condition 1 A cm⁻¹. -2 The circuit was run at constant current for 5 minutes, followed by a 5-minute power-off rest period, with each cycle lasting 10 minutes. A total of approximately 4530 cycles were completed (total duration approximately 755 hours). The results show that the pure Ru / C catalyst exhibits significant performance degradation within approximately 100 hours, while the Pd₂Ru₂ / C catalyst maintained stable cell pressure throughout the 755-hour test, demonstrating significantly superior start-stop stability and long-term operational reliability compared to the pure Ru / C catalyst.

[0034] Figure 6 The image shows the operational stability test curve of the AEM water electrolysis test device B assembled from the Pd2Ru2 / C catalyst obtained in Example 3 of this invention under simulated wind and solar power generation fluctuation conditions. The test conditions were: power range of 0~5 W / cm². -2 The current fluctuations were periodically varied to simulate the intermittent output of renewable energy, with a protection voltage of 2.5V set, and the total test duration was approximately 65 days. The results show that during the approximately 65-day current fluctuation test, the electrolyzer assembled with the Pd2Ru2 / C catalyst responded quickly to wind and solar power fluctuations, maintained stable operation under fluctuating power input, and kept the cell voltage consistently below the protection voltage without significant increases or abnormal fluctuations. This demonstrates excellent resistance to current fluctuations and long-term operational reliability, showing potential for industrial applications in renewable energy water electrolysis scenarios.

[0035] In summary, the palladium-ruthenium catalyst prepared by this invention, when applied to the AEM water electrolysis system, exhibits both excellent electrocatalytic activity and stability under various operating conditions, making it suitable for practical applications of intermittent renewable energy electrolysis for hydrogen production.

[0036] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications still fall within the protection scope of the technical solution and claims of the present invention.

Claims

1. A method for preparing a palladium-ruthenium catalyst for an alkaline water electrolysis cathode with anti-fluctuation start-stop capability, characterized in that, Includes the following steps: (1) Disperse the carbon source in a mixture of concentrated nitric acid and water, heat and reflux for acid treatment, and after the reaction is complete, wash and dry to obtain the carbon support. (2) Add the palladium source, ruthenium source, and carbon support obtained in step (1) into the solvent and disperse them evenly by ultrasonication in an ice bath to obtain a precursor mixed solution; (3) Continue stirring and aging the precursor mixture solution, then transfer it to an evaporating dish and place it in an oven for drying; (4) After the powder obtained by drying is ground evenly, it is annealed to obtain palladium-ruthenium catalyst for water electrolysis with anti-fluctuation start-stop.

2. The preparation method according to claim 1, characterized in that, In step (1): the carbon source is conductive carbon black; the volume ratio of concentrated nitric acid to water is 1~3:1; the temperature of the heating reflux is 60~80℃; and the acid treatment time is 1~3h.

3. The preparation method according to claim 1, characterized in that, In step (2), the ultrasonic dispersion power is 30~80 W and the ultrasonic time is 15~60 min.

4. The preparation method according to claim 1, characterized in that, In step (2), the palladium source is selected from one or more of palladium nitrate, palladium chloride, and palladium acetylacetonate; the ruthenium source is selected from one or more of ruthenium chloride, potassium pentachlororuthenate, and ruthenium acetylacetonate; and the solvent is one or more of methanol, ethanol, acetone, and ultrapure water.

5. The preparation method according to claim 1, characterized in that, In step (2), the total molar amount of palladium source and ruthenium source is 1.5~2.5:100 to the molar ratio of carbon support, and the molar ratio of palladium source to ruthenium source is 1~3:1~3.

6. The preparation method according to claim 1, characterized in that, In step (3), the aging time is 18~24h, the drying temperature is 60~100℃, and the drying time is 5~12h.

7. The preparation method according to claim 1, characterized in that, In step (4), the annealing treatment uses one or more of Ar, N2 and H2 atmospheres, the annealing temperature is 100~500℃, the heating rate is 5~10℃ / min, and the treatment time is 6~10 h.

8. A palladium-ruthenium catalyst for an alkaline water electrolysis cathode with anti-fluctuation start-stop capability, prepared by the method described in any one of claims 1 to 7.

9. The application of the alkaline water electrolysis cathode palladium-ruthenium catalyst of claim 8 in the hydrogen evolution reaction of water electrolysis under fluctuating operating conditions.

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