Macro-quantity preparation method of phase change reversible nickel-iron-sulfur catalyst capable of resisting reverse current
By using an ultrasound-assisted liquid-phase reaction method to grow nickel-iron-sulfur catalysts in situ on metal substrates, the problems of uniformity and phase transition reversibility of non-precious metal-based catalysts in large-scale water electrolysis devices were solved. This method enabled low-cost and high-efficiency catalyst preparation, improving the stability and energy efficiency of the water electrolysis device.
Patent Information
- Application Number
- CN202511850227.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-02-27
AI Technical Summary
Existing non-precious metal-based catalysts cannot achieve large size, high uniformity, excellent catalytic activity and high phase change reversibility in large-scale water electrolysis hydrogen production devices. Furthermore, traditional preparation methods suffer from problems such as complex processes, high costs and high energy consumption.
An ultrasonic-assisted liquid-phase reaction method was used to grow a phase change reversible nickel-iron-sulfur catalyst resistant to reverse current in situ on a metal substrate. The ultrasonic ice bath synthesis technology enabled uniform and rapid growth of the catalyst in a short time, reducing equipment investment and energy consumption.
The catalyst maintains the integrity of the electrode structure under reverse current impact, significantly slows down performance degradation, reduces energy consumption, and improves the stability and efficiency of the electrolyzer, making it suitable for low-cost production of large-size electrodes.
Smart Images
Figure CN121575433A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of hydrogen production technology through water electrolysis. Background Technology
[0002] As the global energy structure shifts towards cleaner and lower-carbon energy, hydrogen energy, as a high-energy-density, green, and zero-carbon secondary energy source, is increasingly strategically important. Utilizing renewable energy sources such as wind and solar power to drive water electrolysis for hydrogen production is a key pathway to achieving large-scale "green hydrogen" supply and is of great significance for building a sustainable energy system. However, in actual operation, due to the inherent intermittency and volatility of renewable energy, water electrolysis devices frequently face complex operating conditions such as start-up and shutdown, and rapid load changes, which can induce reverse current problems. The mechanism is as follows: when the device suddenly loses power or experiences a sharp load reduction, the external driving voltage disappears, and the generated oxygen and hydrogen remain attached to the electrode surfaces, causing the electrolyzer to spontaneously transform from an "electrolysis cell" into a "fuel cell." At this time, oxygen on the anode (formerly the oxygen evolution electrode) undergoes a reduction reaction, while hydrogen on the cathode (formerly the hydrogen evolution electrode) undergoes an oxidation reaction. Electrons flow in the reverse direction along the external circuit, forming a reverse current. This process causes a sharp negative shift in the anode potential, posing a serious threat to the anode catalyst. High-valence reactive species (such as γ-NiOOH) formed in the high-potential oxygen evolution reaction are easily forced to reduce under this strong reducing environment. For most conventional catalysts, this reduction process is irreversible, leading to the loss of the active phase, collapse of the microstructure, and permanent degradation of catalyst performance. This not only results in energy loss and reduced system efficiency but also seriously affects the durability and operational safety of the electrolyzer.
[0003] Existing technologies (such as sacrificial anodes and surface modification) have failed to fundamentally solve the problem of intrinsic phase transition irreversibility in catalysts. Therefore, developing novel catalysts with intrinsic phase transition reversibility, enabling them to recover smoothly like a spring during "operation-shutdown-restart" cycles, is a fundamental solution to overcome the reverse current bottleneck at the materials level. Currently, some noble metal-based catalysts (such as Ir, Ru, and their oxides) exhibit certain phase transition reversibility characteristics in the laboratory due to their unique electronic structure and stability. However, their high cost and scarce reserves severely restrict their application in large-scale water electrolysis hydrogen production devices. Therefore, researchers have turned their attention to abundant and inexpensive non-noble metal-based materials, striving to endow them with reversible phase transition capabilities similar to noble metal materials through rational composition and structural design. Although some existing catalysts have shown good catalytic activity and structural tunability in laboratory studies, their large-scale preparation methods still face significant challenges. Existing synthesis strategies, such as hydrothermal / solvothermal methods, high-temperature solid-state reactions, or vapor deposition, typically suffer from complex processes, harsh reaction conditions, high energy consumption, and long production cycles. Furthermore, these methods generally exhibit a "scale-up effect" during mass and heat transfer unevenness, making it difficult to achieve highly uniform and dense loading of active components on large-size electrodes, as well as robust bonding with the precursor substrate. This results in a significant degradation of the catalyst's structural stability and overall performance on a macroscopic scale.
[0004] Based on the aforementioned technological bottlenecks, in the context of renewable energy-driven fluctuating water electrolysis, there is an urgent need to develop a large-scale preparation method for non-precious metal-based catalysts that achieve large size, high uniformity, and both excellent catalytic activity and high phase transition reversibility. This method must overcome the limitations of existing preparation technologies to achieve low-cost, high-efficiency large-scale production under mild conditions, thereby meeting the pressing needs of industrial water electrolysis hydrogen production devices for high-performance, long-life, and highly safe electrode materials. Summary of the Invention
[0005] This invention aims to address the problem that existing methods for preparing non-precious metal-based catalysts cannot simultaneously achieve large size, high uniformity, excellent catalytic activity, and high phase change reversibility resistant to reverse current. Therefore, it provides a method for the large-scale preparation of a phase change reversible nickel-iron-sulfur catalyst resistant to reverse current.
[0006] A method for the large-scale preparation of a phase-change reversible nickel-iron-sulfur catalyst resistant to reverse current, comprising the following steps:
[0007] I. Preparation of iron salt mixture:
[0008] Iron salts and conductive salts are dissolved in deionized water to obtain a mixed solution of iron salts;
[0009] II. Preparation of sulfur-containing mixed solution:
[0010] The sulfur source and the polymeric dispersant were mixed in a vacuum environment and then ultrasonically dispersed to obtain a sulfur-containing mixture.
[0011] III. Ultrasonic Ice Bath Synthesis:
[0012] A composite solution is obtained by mixing an iron salt mixture with a sulfur-containing mixture. A metal substrate is then immersed in the composite solution and reacted under the influence of an ice bath and an ultrasonic energy field. The metal substrate is then removed, cleaned, and dried, thus completing the large-scale preparation method of a phase-change reversible nickel-iron-sulfur catalyst resistant to reverse current.
[0013] The beneficial effects of this invention are:
[0014] The purpose of this invention is to provide a method for the large-scale preparation of a phase-change reversible nickel-iron-sulfur catalyst resistant to reverse current. This method utilizes an ultrasound-assisted liquid-phase reaction to directly grow a catalytic active layer in situ on a macroscopic metal substrate. While preparing a nickel-iron-sulfur catalyst with excellent phase-change reversibility, this method successfully solves the problems of uniformity, stability, and cost faced by traditional methods in large-scale preparation.
[0015] 1. The nickel-iron-sulfur catalyst prepared in this invention forms active high-valence species (such as Ni) during the oxygen evolution reaction. 3+ This catalyst system can achieve rapid and reversible reduction and structural recovery when the system is powered off or the voltage reverses, thus maintaining the integrity of the electrode structure under reverse current impact and significantly slowing down performance degradation. Tests show that under simulated shutdown conditions, the peak reverse voltage (0.4V) of the catalyst system of this invention is significantly reduced by 60% compared with the traditional NiFe-LDH (1.0V), and the voltage rapidly decays to 0V within 70 seconds, demonstrating excellent reverse current suppression and self-protection capabilities.
[0016] 2. This invention employs an ultrasound-assisted liquid-phase synthesis route, eliminating the reliance on high-pressure reactors, high-temperature heat treatment, or inert atmosphere protection required by traditional hydrothermal methods and high-temperature deposition processes, thus significantly reducing equipment investment and energy consumption costs. This method enables in-situ, uniform, and rapid growth of catalysts on large-scale metal substrates (with reaction times of only 3-10 minutes), effectively overcoming the "scale-up effect" in traditional synthesis routes and ensuring the consistency of catalyst layer structure and performance at the macroscopic scale. It provides a practical and feasible technical path for the continuous and low-cost production of large-size non-precious metal catalytic electrodes.
[0017] 3. This invention employs an ice-water method during the ultrasonic synthesis step to increase heat dissipation, precisely controlling the local temperature and nucleation kinetics of the reaction system, and successfully constructing a catalytic layer with rich interfacial structures. This unique structure not only optimizes charge transport and the adsorption / desorption behavior of reaction intermediates, but also significantly shortens the solid-phase diffusion path of ions / electrons during the phase transition and enhances the material's tolerance to volumetric stress caused by the phase transition. This allows the catalyst to operate at 10 mA / cm². 2 It requires only a low overpotential of 180mV at current density and exhibits voltage fluctuations of less than 0.01V during 500 hours of continuous testing, combining high catalytic activity with long-term operational stability.
[0018] 4. The catalyst electrode prepared by this invention exhibits excellent reaction kinetics and low energy consumption characteristics. At 0.6 A / cm 2 At the specified current density, the electrolyzer operates at only 2.22V, corresponding to a hydrogen production energy consumption of 5.32kWh / Nm³. 3 Compared to traditional NiFe-LDH catalysts, energy consumption is reduced by more than 14.8%. This energy efficiency advantage becomes increasingly significant with increasing current density, making it of considerable economic value under high current density conditions in actual industrial operation. Attached Figure Description
[0019] Figure 1 The images show the microstructure of the nickel-iron-sulfur electrolytic water catalysts prepared in Examples 1 to 4.
[0020] Figure 2 The nickel-iron-sulfur water electrolysis catalyst prepared in Example 1 was tested at 10 mA / cm². 2 Results of long-term stable test timing potential under current density;
[0021] Figure 3 The oxygen evolution reaction polarization curves of the nickel-iron-sulfur electrolytic water catalysts prepared in Example 1 and Control Group 2, and the NiFe-LDH catalyst in Control Group 1;
[0022] Figure 4 The shutdown voltage decay curves of the ALK electrolyzer for the nickel-iron-sulfur electrolyzer catalysts prepared in Example 1 and Control Group 2, and the NiFe-LDH catalyst in Control Group 1 are shown.
[0023] Figure 5 Electrode lifetime curves of the ALK electrolyzer for the nickel-iron-sulfur electrolytic water catalysts prepared in Example 1 and Control Group 2, and the NiFe-LDH catalyst in Control Group 1.
[0024] Figure 6 The voltage and energy consumption curves of the ALK electrolyzer polarization curves of the nickel-iron-sulfur electrolyzing catalysts prepared in Example 1 and Control Group 2, and the NiFe-LDH catalyst in Control Group 1 are shown.
[0025] Figure 7 The images show the Ni 2p X-ray photoelectron spectroscopy (XPS) spectra of the nickel-iron-sulfur electrolytic water catalyst prepared in Example 1 under different states. 1 is the initial state in step a, 2 is the working state in step b, 3 is the shutdown and reduction state in step c, and 4 is the reworking state in step d.
[0026] Figure 8 The Fe 2p spectrum of the nickel-iron-sulfur electrolytic water catalyst prepared in Example 1 during step d is shown.
[0027] Figure 9 The S 2p spectrum of the nickel-iron-sulfur electrolytic water catalyst prepared in Example 1 during step d is shown.
[0028] Figure 10 The image shows the O 1s spectrum of the nickel-iron-sulfur electrolytic water catalyst prepared in step d of Example 1 during its reworking state. Detailed Implementation
[0029] Specific Implementation Method 1: This implementation method provides a large-scale preparation method for a phase change reversible nickel-iron-sulfur catalyst resistant to reverse current, which is carried out according to the following steps:
[0030] I. Preparation of iron salt mixture:
[0031] Iron salts and conductive salts are dissolved in deionized water to obtain a mixed solution of iron salts;
[0032] II. Preparation of sulfur-containing mixed solution:
[0033] The sulfur source and the polymeric dispersant were mixed in a vacuum environment and then ultrasonically dispersed to obtain a sulfur-containing mixture.
[0034] III. Ultrasonic Ice Bath Synthesis:
[0035] A composite solution is obtained by mixing an iron salt mixture with a sulfur-containing mixture. A metal substrate is then immersed in the composite solution and reacted under the influence of an ice bath and an ultrasonic energy field. The metal substrate is then removed, cleaned, and dried, thus completing the large-scale preparation method of a phase-change reversible nickel-iron-sulfur catalyst resistant to reverse current.
[0036] In step three of this specific embodiment, the polymeric dispersant and the sulfur source work together to help form uniform active species under ultrasonic conditions and promote their firm adhesion to the substrate.
[0037] The beneficial effects of this embodiment are:
[0038] The purpose of this embodiment is to provide a method for the large-scale preparation of a phase-change reversible nickel-iron-sulfur catalyst resistant to reverse current. This method utilizes an ultrasound-assisted liquid-phase reaction to directly grow a catalytic active layer in situ on a macroscopic metal substrate. While preparing a nickel-iron-sulfur catalyst with excellent phase-change reversibility, this method successfully solves the uniformity, stability, and cost problems faced by traditional methods in large-scale preparation.
[0039] 1. The nickel-iron-sulfur catalyst prepared in this embodiment forms active high-valence species (such as Ni) during the oxygen evolution reaction. 3+ This catalyst system can achieve rapid and reversible reduction and structural recovery when the system is powered off or the voltage reverses, thus maintaining the integrity of the electrode structure under reverse current impact and significantly slowing down performance degradation. Tests show that under simulated shutdown conditions, the peak reverse voltage (0.4V) of the catalyst system in this embodiment is significantly reduced by 60% compared to the traditional NiFe-LDH (1.0V), and the voltage rapidly decays to 0V within 70 seconds, demonstrating excellent reverse current suppression and self-protection capabilities.
[0040] 2. This invention employs an ultrasound-assisted liquid-phase synthesis route, eliminating the reliance on high-pressure reactors, high-temperature heat treatment, or inert atmosphere protection required by traditional hydrothermal methods and high-temperature deposition processes, thus significantly reducing equipment investment and energy consumption costs. This method enables in-situ, uniform, and rapid growth of catalysts on large-scale metal substrates (with reaction times of only 3-10 minutes), effectively overcoming the "scale-up effect" in traditional synthesis routes and ensuring the consistency of catalyst layer structure and performance at the macroscopic scale. It provides a practical and feasible technical path for the continuous and low-cost production of large-size non-precious metal catalytic electrodes.
[0041] 3. This invention employs an ice-water method during the ultrasonic synthesis step to increase heat dissipation, precisely controlling the local temperature and nucleation kinetics of the reaction system, and successfully constructing a catalytic layer with rich interfacial structures. This unique structure not only optimizes charge transport and the adsorption / desorption behavior of reaction intermediates, but also significantly shortens the solid-phase diffusion path of ions / electrons during the phase transition and enhances the material's tolerance to volumetric stress caused by the phase transition. This allows the catalyst to operate at 10 mA / cm². 2 It requires only a low overpotential of 180mV at current density and exhibits voltage fluctuations of less than 0.01V during 500 hours of continuous testing, combining high catalytic activity with long-term operational stability.
[0042] 4. The catalyst electrode prepared by this invention exhibits excellent reaction kinetics and low energy consumption characteristics. At 0.6 A / cm 2 At the specified current density, the electrolyzer operates at only 2.22V, corresponding to a hydrogen production energy consumption of 5.32kWh / Nm³. 3Compared to traditional NiFe-LDH catalysts, energy consumption is reduced by more than 14.8%. This energy efficiency advantage becomes increasingly significant with increasing current density, making it of considerable economic value under high current density conditions in actual industrial operation.
[0043] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the iron salt mentioned in step one is ferric chloride, ferric nitrate, or ferric oxalate; and the conductive salt mentioned in step one is sodium chloride. Everything else is the same as in Specific Implementation Method One.
[0044] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the concentration of iron salts in the iron salt mixture described in step one is 1 mol / L to 4 mol / L, and the concentration of conductive salts is 1 mol / L to 4 mol / L. Everything else is the same as in Specific Implementation Method One or Two.
[0045] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the sulfur source mentioned in step two is sodium sulfide, ferrous sulfide, or sodium sulfite; and the polymeric dispersant mentioned in step two is polyethylene glycol. Everything else is the same as in Specific Implementation Methods One to Three.
[0046] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the concentration of the sulfur source in the sulfur-containing mixed solution described in step two is 2 mol / L to 6 mol / L. Everything else is the same as in Specific Implementation Methods One to Four.
[0047] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the ultrasonic dispersion described in step two is performed under conditions of ultrasonic power of 100W to 300W for 3 to 10 minutes. Everything else is the same as in Specific Implementation Methods One to Five.
[0048] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: the metal substrate mentioned in step three is nickel foam, nickel felt, twill nickel mesh, or plain nickel mesh, and the size of the metal substrate is not less than 10 μm. 2 ×10cm 2 The rest is the same as in specific implementation methods one through six.
[0049] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the metal substrate mentioned in step three is a pretreated metal substrate, and the pretreatment is specifically carried out according to the following steps: immersing the metal substrate in an acid solution for 1-2 hours, removing it, rinsing it with deionized water, and drying it, then using it within 5 minutes; the acid solution is a dilute hydrochloric acid with a concentration of 1 mol / L to 3 mol / L or a dilute sulfuric acid with a concentration of 1 mol / L to 2 mol / L. Everything else is the same as in Specific Implementation Methods One to Seven.
[0050] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the molar ratio of Fe to S in the composite solution described in step three is 1:(2~4). Everything else is the same as in Specific Implementation Methods One to Eight.
[0051] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: in step three, the iron salt mixture and the sulfur-containing mixture are mixed within 1 to 2 minutes after preparation to obtain a composite solution; the reaction described in step three under the influence of an ice bath environment and an ultrasonic energy field is specifically performed under the conditions of an ice bath temperature of -5℃ to 5℃ and an ultrasonic power of 100W to 300W for 3 to 10 minutes of ultrasonic treatment. Everything else is the same as in Specific Implementation Methods One to Nine.
[0052] The beneficial effects of the present invention are verified using the following embodiments:
[0053] Example 1:
[0054] A method for the large-scale preparation of a phase-change reversible nickel-iron-sulfur catalyst resistant to reverse current, comprising the following steps:
[0055] I. Preparation of iron salt mixture:
[0056] Iron salts and conductive salts are dissolved in deionized water to obtain a mixed solution of iron salts;
[0057] The iron salt is ferric chloride; the conductive salt is sodium chloride.
[0058] The concentration of iron salt in the iron salt mixture is 1 mol / L, and the concentration of conductive salt is 1 mol / L.
[0059] II. Preparation of sulfur-containing mixed solution:
[0060] In a vacuum environment, the sulfur source and the polymeric dispersant were mixed, and then ultrasonically dispersed for 3 minutes under an ultrasonic power of 100W to obtain a sulfur-containing mixture.
[0061] The sulfur source is sodium sulfite; the polymeric dispersant is polyethylene glycol.
[0062] The concentration of the sulfur source in the sulfur-containing mixture is 2 mol / L;
[0063] III. Ultrasonic Ice Bath Synthesis:
[0064] The iron salt mixture and the sulfur-containing mixture were mixed within 1 to 2 minutes after preparation to obtain a composite solution. The metal substrate was immersed in the composite solution and ultrasonically treated for 5 minutes at an ice bath temperature of 0°C and an ultrasonic power of 200W. Then the metal substrate was removed, rinsed with deionized water, and finally air-dried at room temperature to obtain the nickel-iron-sulfur water electrolysis catalyst.
[0065] The molar ratio of Fe to S in the composite solution is 1:2;
[0066] The metal substrate is a plain-weave nickel mesh, and the metal substrate has a size of 10 μm. 2 ×10cm 2 ;
[0067] The metal substrate is a pretreated metal substrate, and the pretreatment is carried out according to the following steps: the metal substrate is immersed in an acid solution for 2 hours, then taken out, rinsed with deionized water and dried, and immersed in a composite solution within 2 minutes; the acid solution is dilute hydrochloric acid with a concentration of 1 mol / L.
[0068] Example 2: This example differs from Example 1 in that the metal substrate described in step three is a twill nickel mesh. Everything else is the same as in Example 1.
[0069] Example 3: This example differs from Example 1 in that the metal substrate mentioned in step three is nickel felt. Everything else is the same as in Example 1.
[0070] Example 4: This example differs from Example 1 in that the metal substrate described in step three is nickel foam. Everything else is the same as in Example 1.
[0071] Control group 1: This control group consists of commercially available NiFe-LDH catalysts.
[0072] Control Group 2: This control group differs from Example 1 in that, in step three, the ultrasonic treatment was performed for 5 minutes at room temperature and an ultrasonic power of 200W. Everything else was the same as in Example 1.
[0073] Figure 1 The images show the microstructure of the nickel-iron-sulfur water electrolysis catalysts prepared in Examples 1 to 4. It can be seen that the products obtained by impregnation and loading on different metal substrates are all distributed in a dense and uniform lamellar structure. This morphological characteristic significantly enhances the bonding force between the catalyst and the substrate, ensuring that the electrode maintains excellent structural stability and long catalytic lifetime even under high current density operating conditions.
[0074] Figure 2 The nickel-iron-sulfur water electrolysis catalyst prepared in Example 1 was tested at 10 mA / cm². 2The results of the long-term stability test at current density were obtained using a potentiostatic chronometry method. During a 500-hour oxygen evolution reaction (OER) test, the material maintained stable performance with voltage fluctuations less than 0.01V, and the catalytic activity degradation was negligible, indicating that the prepared electrocatalyst material possesses excellent stability.
[0075] Figure 3 The oxygen evolution reaction polarization curves are shown for the nickel-iron-sulfur water electrolysis catalysts prepared in Example 1 and Control Group 2, as well as the NiFe-LDH catalyst in Control Group 1. A three-electrode system was tested using the catalysts as the working electrode and a 1 mol / L KOH solution as the electrolyte. The nickel-iron-sulfur water electrolysis catalyst prepared in Example 1 showed the best performance at a current density of 10 mA / cm². 2 Under the specified conditions, the OER reaction requires only an overpotential of 180.7 mV, and the overpotential is as low as 225 mV at a current density of 100 mA / cm², significantly reducing energy loss. The overpotential is relatively low compared to similar catalysts, indicating good catalytic performance. Furthermore, the forward and reverse scan curves highly overlap at higher current densities, while the polarization curves of the other two materials show significant separation. This suggests that the nickel-iron-sulfur water electrolysis catalyst prepared in Example 1 possesses a certain degree of phase transition reversibility, which can mitigate the influence of reverse current to some extent.
[0076] The anode materials in the ALK electrolyzer were the nickel-iron-sulfur electrolytic water catalysts prepared in Example 1 and Control Group 2, as well as the NiFe-LDH catalyst in Control Group 1. The cathode materials for all three groups were graphite electrodes. The ALK electrolyzer (5cm²) was set up as follows: the electrolyzer was connected to a power source, a water pipe was inserted to connect to a water pump, and voltage probes were placed at the two electrode plates. 2L of a 1mol / L KOH solution was prepared and poured into the water tank. The heating device was started, and once the electrolyte reached 60°C, the water pump was turned on, with a flow rate set to 120mL / min to ensure a stable and leak-free water flow. The power was then turned on, and the voltage and current were adjusted to a suitable level to begin the test.
[0077] Figure 4 The shutdown voltage decay curves of the ALK electrolyzers for the nickel-iron-sulfur electrolytic water catalysts prepared in Example 1 and Control Group 2, as well as the NiFe-LDH catalyst in Control Group 1, are shown. The reverse current intensity was characterized by monitoring the voltage decay behavior after shutdown of the ALK electrolyzers. After stable operation at a current density of 0.1 A / cm², the peristaltic pump was kept constant and the power supply was disconnected. Transient voltage changes were recorded at a sampling frequency of 1 s / time. The voltage decay behavior after shutdown was compared with that at a current density of 0.1 A / cm². 2The shutdown voltage decay curves of the three sets of experiments at different current densities show that the shutdown peak voltage (0.4V) of the nickel-iron-sulfur water electrolysis catalyst prepared in Example 1 is significantly lower than that of control group 1 (1.0V) and control group 2 (0.65V), decreasing by 60% and 38.5% respectively. Furthermore, the voltage decay rate is much faster (reducing to 0V within 70s), while control groups 1 and 2 require more than 300s to reach 0V. This phenomenon indicates that the nickel-iron-sulfur water electrolysis catalyst prepared in Example 1 has a significant effect on suppressing reverse current and exhibits excellent electrochemical stability.
[0078] Figure 5 Electrode lifetime curves of the nickel-iron-sulfur water electrolysis catalysts prepared in Example 1 and Control Group 2, as well as the NiFe-LDH catalyst in Control Group 1, are shown in the ALK electrolyzer electrode lifetime curves. Lifetime is a key indicator for evaluating the stability and practicality of materials. At 0.1 A / cm... 2 The electrolyzer was operated continuously for 48 hours at a constant current density, and voltage time-series changes were monitored at a sampling frequency of 1 second. It can be seen that the nickel-iron-sulfur electrolytic water catalyst prepared in Example 1 has significantly better stability than control groups 1 and 2. During the 48-hour test, its operating voltage fluctuation range was strictly controlled within 0.02V, fully verifying the excellent long-term operational stability and reliability of this material.
[0079] Figure 6 The graphs show the voltage and energy consumption of the ALK electrolyzer polarization curves for the nickel-iron-sulfur water electrolysis catalysts prepared in Example 1 and Control Group 2, as well as the NiFe-LDH catalyst in Control Group 1. It can be seen that the voltage and energy consumption of the nickel-iron-sulfur water electrolysis catalyst prepared in Example 1 are significantly lower than those of the control group. The current density is 0.2 A / cm². 2 0.6A / cm 2 At that time, the voltages in Example 1 were 1.71V and 2.22V, respectively, which were 0.27V and 0.39V lower than those in Control Group 1, and 0.68V and 1.09V lower than those in Control Group 2, respectively; the energy consumption of Example 1 was 4.10kWh / Nm³. 3 5.32 kWh / Nm 3 Compared with control group 1, the energy consumption was reduced by 13.4% and 14.8%, and compared with control group 2, the energy consumption was reduced by 28.0% and 32.8%. The comparative experiment fully demonstrated the advantages of the nickel-iron-sulfur electrolytic water catalyst prepared in Example 1 in terms of electrode reaction overpotential (voltage) and energy consumption. Moreover, its energy consumption advantage increases with the increase of current density, which has significant application value.
[0080] To further verify the phase transition reversibility of the nickel-iron-sulfur water electrolysis catalyst prepared in the examples, the nickel-iron-sulfur water electrolysis catalyst prepared in Example 1 was used as the base material. Materials in different states were obtained through a four-step method, and the chemical state changes were analyzed to verify the phase transition reversibility. The specific process is as follows:
[0081] Step a: The nickel-iron-sulfur electrolytic water catalyst prepared in Example 1 was directly subjected to XPS analysis without any electrochemical treatment to obtain the Ni 2p spectrum of the "initial state";
[0082] Step b: Using the nickel-iron-sulfur water electrolysis catalyst prepared in Example 1 as the anode, the catalyst was operated under standard oxygen evolution reaction conditions. Specifically, the voltage scan range was 0–1 V, the scan rate was 0.02 V / s, and a total of 50 scans were performed. After the scan, the material was immediately removed, quickly washed with deionized water, dried, and tested using XPS equipment to obtain the Ni 2p spectrum in the "working state."
[0083] Step c: For the catalyst material that has undergone the oxygen evolution reaction in step two, a shutdown process simulation is performed. That is, the catalyst after operation is placed in an environment simulating reverse current, and after 10,000 start-stop cycles, it is taken out for XPS testing to obtain the Ni 2p spectrum of the "shutdown reduced state".
[0084] In step d, the catalyst that had undergone the simulated shutdown process was placed back into the standard oxygen evolution reaction conditions, with the same reaction conditions as in step b. After the scan was completed, it was immediately removed, quickly washed with deionized water, dried, and tested using an XPS device to obtain the Ni 2p spectrum of the "reworking state".
[0085] Figure 7 The images show the Ni 2p X-ray photoelectron spectroscopy (XPS) spectra of the nickel-iron-sulfur electrolytic water catalyst prepared in Example 1 under different states. 1 represents the initial state in step a, 2 represents the working state in step b, 3 represents the shutdown and reduction state in step c, and 4 represents the restart state in step d.
[0086] The comparison of the spectra shows that the Ni 2p spectrum of the "initial state" sample without any electrochemical treatment exhibits a Ni 2p distribution. 2+ and Ni 0 The dominant characteristic peak reflects the original chemical state of the catalyst and serves as the basis for subsequent state comparisons; while the "working state" sample, which has undergone oxygen evolution reaction conditions, shows Ni as the dominant characteristic peak in curve 2. 2+ and Ni 3+ Mainly, Ni 0 The characteristic peaks disappear, and Ni with a larger peak area ratio appears. 3+ Characteristic peak, Ni 3+ The signal was significantly enhanced, indicating the successful generation of the high-valence active species required for OER during anodic operation, which is direct evidence of the catalyst's high catalytic activity. For the "shutdown reduced state" sample after simulating electrolyzer shutdown and experiencing a reverse current impact, compared to the operating state, Ni... 3+ The signal is significantly weakened or disappears, and the Ni spectrum recovers to Ni2+ and Ni 0 The predominant characteristic indicates that when the catalyst is subjected to a reverse current impact, high-valence active species can be reduced, and the overall chemical state reversibly returns to a near-initial state; analysis of the Ni 2p spectrum of the "reworking state" sample shows that Ni... 3+ The signal was significantly enhanced again, with intensity and related peak area ratios comparable to the working state. This result confirms that the catalyst can be oxidized again to generate high-valence Ni after undergoing a complete oxidation-reduction cycle. 3+ The presence of active species thus completed the verification of the reversibility of the phase transition.
[0087] Combination Figure 7 The Ni 2p XPS spectra of the samples in four states were analyzed. By analyzing the evolution of the chemical valence state of the catalyst in four key states, it was concluded that the catalyst prepared in Example 1 can achieve Ni valence state transformation in the "operation-shutdown-reoperation" cycle. 2+ with Ni 3+ The phase transition is reversible, and after undergoing a reduction process, it can still recover to its initial chemical state and re-enter a highly active state. This result directly confirms that the catalyst possesses excellent intrinsic phase transition reversibility, and can maintain the regeneration ability of active species under reverse current impact, thereby effectively ensuring its long-term stability under fluctuating operating conditions.
[0088] Figure 7 Curve 4 shows the X-ray photoelectron spectroscopy (XPS) results of the nickel-iron-sulfur electrolytic water catalyst prepared in Example 1 after undergoing 10,000 start-stop cycles in an ALK electrolyzer and then undergoing electrolysis again (the reworking state in step d). The spectrum shows that the Ni 2p spectrum can be fitted into three sets of double peaks with binding energies of ~853.25 V and ~870.60 eV, corresponding to Ni... 2+ 2p 3 / 2 and Ni 2+ 2p 1 / 2 The main peak has binding energies of ~856.20 eV and ~874.30 eV, corresponding to Ni, respectively. 3+ 2p 3 / 2 and Ni 3+ 2p 1 / 2 The main peak represents a key reactive species in the oxygen evolution reaction (OER); with binding energies of ~862.40 eV and ~878.75 eV, it belongs to Ni. 2+ The satellite peak. The binding energy is 881.75 eV, corresponding to Ni. 3+ The satellite peaks. This result clearly confirms the simultaneous presence of Ni in the catalyst. 2+ and Ni 3+ .
[0089] Figure 8The image shows the Fe 2p spectrum of the nickel-iron-sulfur electrolytic water catalyst prepared in step d of Example 1 during its reworking state. It can be seen that the Fe 2p spectrum can be fitted to four peaks with binding energies of ~712.0 eV and ~725.5 eV, corresponding to Fe... 3+ 2p 3 / 2 and Fe 3 + 2p 1 / 2 The main peak has binding energies of ~718.5 eV and ~731.2 eV, corresponding to Fe, respectively. 3+ The satellite peak.
[0090] Figure 9 The image shows the S 2p spectrum of the nickel-iron-sulfur electrolytic water catalyst prepared in step d of Example 1 during its reworking state. It can be seen that the S 2p spectrum can be fitted into three sets of bimodal peaks, with binding energies of ~161.92 eV and ~163.91 eV, corresponding to S... 2- 2p 3 / 2 and S 2- 2p 1 / 2 It belongs to metal sulfides (MS); the binding energies are ~168.73 eV and ~170.40 eV, respectively, corresponding to S 6+ 2p 3 / 2 and S 6+ 2p 1 / 2 This indicates the presence of sulfates (SO4) produced due to surface oxidation. 2- ) species; with binding energies of ~163.46 eV and ~164.97 eV, they can be classified as polysulfides (S n 2- ) or thiosulfate.
[0091] Figure 10 The image shows the O 1s spectrum of the nickel-iron-sulfur electrolytic water catalyst prepared in step d of Example 1 during its reworking state. It can be seen that the O 1s spectrum of Example 1 can be fitted with three peaks: a binding energy of ~529.81 eV, corresponding to lattice oxygen (MO); a binding energy of ~531.5 eV, corresponding to surface hydroxyl groups, oxygen vacancies, or adsorbed oxygen species; and a binding energy of ~533.0 eV, which is generally attributed to chemisorbed water molecules. The strong peak at 531.5 eV indicates abundant oxygen vacancies in the material, which helps optimize the adsorption behavior of reaction intermediates and improve charge transport efficiency.
[0092] comprehensive Figure 7-10 The results show that the prepared catalyst has a reversible phase transition process, and therefore can stably exist in the high-valence state Ni. 3+The active phase is a key catalytic center for the oxygen evolution reaction (OER). The introduction of Fe and S promotes the formation of this active phase and optimizes the reaction pathway through a synergistic effect. The strong interfacial electronic interactions among Ni, Fe, S, and O elements collectively reconstruct the electronic environment of the active sites, placing them in an optimal state for catalytic reaction, thereby significantly improving catalytic activity and stability.
Claims
1. A method for the large-scale preparation of a phase-change reversible nickel-iron-sulfur catalyst resistant to reverse current, characterized in that... It is done in the following steps: I. Preparation of iron salt mixture: Iron salts and conductive salts are dissolved in deionized water to obtain a mixed solution of iron salts; II. Preparation of sulfur-containing mixed solution: The sulfur source and the polymeric dispersant were mixed in a vacuum environment and then ultrasonically dispersed to obtain a sulfur-containing mixture. III. Ultrasonic Ice Bath Synthesis: A composite solution is obtained by mixing an iron salt mixture with a sulfur-containing mixture. A metal substrate is then immersed in the composite solution and reacted under the influence of an ice bath and an ultrasonic energy field. The metal substrate is then removed, cleaned, and dried, thus completing the large-scale preparation method of a phase-change reversible nickel-iron-sulfur catalyst resistant to reverse current.
2. The method for large-scale preparation of a reverse current-resistant phase change reversible nickel-iron-sulfur catalyst according to claim 1, characterized in that... The iron salt mentioned in step one is ferric chloride, ferric nitrate, or ferric oxalate; the conductive salt mentioned in step one is sodium chloride.
3. The method for large-scale preparation of a reverse current-resistant phase change reversible nickel-iron-sulfur catalyst according to claim 1, characterized in that... The concentration of iron salt in the iron salt mixture mentioned in step one is 1 mol / L to 4 mol / L, and the concentration of conductive salt is 1 mol / L to 4 mol / L.
4. The method for large-scale preparation of a reverse current-resistant phase change reversible nickel-iron-sulfur catalyst according to claim 1, characterized in that... The sulfur source mentioned in step two is sodium sulfide, ferrous sulfide, or sodium sulfite; the polymeric dispersant mentioned in step two is polyethylene glycol.
5. The method for large-scale preparation of a reverse current-resistant phase change reversible nickel-iron-sulfur catalyst according to claim 1, characterized in that... The concentration of the sulfur source in the sulfur-containing mixture mentioned in step two is 2 mol / L to 6 mol / L.
6. The method for large-scale preparation of a reverse current-resistant phase change reversible nickel-iron-sulfur catalyst according to claim 1, characterized in that... The ultrasonic dispersion described in step two is carried out under the condition of ultrasonic power of 100W~300W for 3min~10min.
7. The method for large-scale preparation of a reverse current-resistant phase change reversible nickel-iron-sulfur catalyst according to claim 1, characterized in that... The metal substrate mentioned in step three is nickel foam, nickel felt, twill nickel mesh, or plain nickel mesh, and the size of the metal substrate is not less than 10 μm. 2 ×10cm 2 .
8. The method for large-scale preparation of a reverse current-resistant phase change reversible nickel-iron-sulfur catalyst according to claim 1, characterized in that... The metal substrate mentioned in step three is a pretreated metal substrate, and the pretreatment is specifically carried out according to the following steps: immerse the metal substrate in an acid solution for 1 to 2 hours, take it out, wash it with deionized water and dry it, and then use it within 5 minutes; the acid solution is a dilute hydrochloric acid with a concentration of 1 mol / L to 3 mol / L or a dilute sulfuric acid with a concentration of 1 mol / L to 2 mol / L.
9. The method for large-scale preparation of a reverse current-resistant phase change reversible nickel-iron-sulfur catalyst according to claim 1, characterized in that... The molar ratio of Fe to S in the composite solution described in step three is 1:(2~4).
10. The method for large-scale preparation of a reverse current-resistant phase change reversible nickel-iron-sulfur catalyst according to claim 1, characterized in that... In step three, the iron salt mixture and the sulfur-containing mixture are mixed within 1 to 2 minutes after preparation to obtain a composite solution. The reaction described in step three under the action of an ice bath environment and an ultrasonic energy field is specifically performed under the conditions of an ice bath temperature of -5℃ to 5℃ and an ultrasonic power of 100W to 300W for 3 to 10 minutes of ultrasonic treatment.