Iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrolytic oxygen catalyst and its preparation method

Abstract

This invention belongs to the technical field of seawater electrolytic oxygen evolution catalysts, and relates to an iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrolytic oxygen evolution catalyst and its preparation method. The catalyst comprises a nickel foam substrate and a catalytically active layer supported on the surface of the nickel foam substrate. Fe is introduced into the nickel hydroxyl oxide as a metal dopant, while P and S are introduced as non-metallic modifying elements. The preparation method involves dissolving nickel compounds, iron compounds, thiourea, sodium hypophosphite, ammonium fluoride, and boric acid in deionized water to prepare an electrodeposition electrolyte. Using nickel foam as the working electrode, the catalyst is prepared by electrodeposition. The catalyst of this invention exhibits high oxygen evolution catalytic activity; simultaneously, during seawater electrolysis, the catalyst can form a surface polyanionic layer rich in phosphate and sulfate ions, significantly improving its corrosion resistance and structural stability in chlorinated electrolytes.

Description

Technical Field

[0001] This invention belongs to the field of seawater electrolytic oxygen catalyst technology, specifically relating to an iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrolytic oxygen catalyst and its preparation method. Background Technology

[0002] With the massive consumption of traditional fossil fuels and the resulting environmental pollution and climate change problems becoming increasingly prominent, the development of clean and sustainable energy technologies has become an important direction for the energy sector. Hydrogen energy, due to its high mass energy density and clean combustion products, is considered one of the secondary energy sources with broad application prospects. Water electrolysis for hydrogen production can be coupled with renewable energy sources such as wind and solar power, making it an important pathway to achieve green hydrogen production. Currently, conventional water electrolysis technologies, such as alkaline water electrolysis and proton exchange membrane water electrolysis, typically rely on high-purity freshwater resources. However, global freshwater resources are limited and unevenly distributed, while seawater resources are abundant, accounting for approximately the vast majority of the world's total water volume. Therefore, directly utilizing seawater for hydrogen production through electrolysis is of great significance for alleviating freshwater resource shortages and expanding hydrogen production pathways. Compared to the "seawater desalination followed by electrolysis" approach, direct seawater electrolysis eliminates the need for an additional desalination process, which helps reduce system investment and operating costs, and is easier to couple with clean energy systems such as offshore wind power and photovoltaics, thus attracting widespread attention.

[0003] However, seawater systems are complex in composition, especially containing high concentrations of chloride ions. During electrolysis, competitive chlorination reactions easily occur on the anode side, which not only reduces the selectivity of the oxygen evolution reaction (OER) but also exacerbates the corrosion of electrode materials, affecting the long-term stable operation of the electrolysis system. Meanwhile, the OER itself has slow kinetics and typically requires a high overpotential, leading to increased electrolysis energy consumption and limiting the practical application of direct seawater electrolysis technology. Therefore, developing anode catalysts that combine high OER catalytic activity with excellent stability is crucial for achieving efficient operation of direct seawater electrolysis. Summary of the Invention

[0004] To address the problems of insufficient oxygen evolution catalytic activity, poor chlorine corrosion resistance, and unsatisfactory long-term operational stability in existing seawater electrochemical oxygen evolution catalysts, this invention provides an iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrochemical oxygen evolution catalyst and its preparation method. By introducing iron, phosphorus, and sulfur elements into nickel hydroxyl oxide for doping and regulation, and combining this with an electrodeposition method to construct a catalytic layer in situ on the surface of a nickel foam substrate, the oxygen evolution reaction activity and structural stability of the catalytic material are improved.

[0005] To achieve the above objectives, one of the technical solutions provided by the present invention is to provide an iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrochemical oxygen desorption catalyst, characterized in that the catalyst comprises a nickel foam substrate and a catalytic active layer supported on the surface of the nickel foam substrate; the catalytic active layer is nickel hydroxyl oxide co-modified with iron, phosphorus, and sulfur, and the catalytic active layer contains Ni, Fe, P, S, and O elements; wherein Fe is introduced into the nickel hydroxyl oxide as a metal dopant element, and P and S exist in the catalytic active layer as non-metallic modifying elements.

[0006] Preferably, the Raman spectrum of the catalyst layer is at 200 cm⁻¹. -1 – 400 cm -1 Within the range, located at 290 cm -1 and 330 cm -1 The characteristic peak at 450 cm⁻¹ -1 – 600 cm -1 Within the range, located at 475 cm -1 and 530 cm -1 The characteristic peak at that location.

[0007] Preferably, the catalyst layer is at 450 cm³ relative to the undoped Fe catalyst. -1 – 600 cm -1 The metal-oxygen vibration peaks within the range undergo a blue shift.

[0008] Preferably, the catalyst can form a surface polyanion layer rich in phosphate and sulfate in situ during seawater electrolysis.

[0009] To achieve the above objectives, the second technical solution provided by the present invention is a method for preparing an iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrolytic oxygen desorption catalyst, the method comprising the following steps: S1. Pretreatment of nickel foam substrate: After cutting the nickel foam to the predetermined size, it is ultrasonically treated in 1.0 mol / L sulfuric acid solution to remove the oxide layer on its surface; then it is ultrasonically cleaned in acetone and deionized water in sequence to remove oil and impurities, and then dried for use.

[0010] S2. Preparation of electrodeposition electrolyte: Add nickel salt, iron salt, thiourea, sodium hypophosphite, ammonium fluoride and boric acid to deionized water and mix, stirring until completely dissolved to obtain a homogeneous electrodeposition electrolyte; wherein, the nickel compound and iron compound are metal salt precursors, the thiourea is a sulfur source, and the sodium hypophosphite is a phosphorus source.

[0011] S3. Electrodeposition preparation: A three-electrode system was constructed using pretreated nickel foam as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode. Electrodeposition reaction was carried out under constant current conditions to deposit the iron, phosphorus, and sulfur co-modified nickel hydroxyl oxide catalytic active layer in situ onto the surface of the nickel foam substrate.

[0012] S4. Post-treatment: After electrodeposition, the obtained sample was washed with deionized water and ethanol in sequence and dried to obtain the iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrochemical oxygen desorption catalyst.

[0013] Preferably, the ultrasonic treatment time of the nickel foam in 1.0 mol / L sulfuric acid solution in step S1 is 10 min; the ultrasonic cleaning time in acetone and deionized water is 10 min each.

[0014] Preferably, the electrodeposition electrolyte in step S2 is composed of NiCl2. 6H2O, FeCl3 6H2O, SC(NH2)2, NaH2PO2 It is prepared from H2O, NH4F and H3BO3.

[0015] Preferably, in step S2, the concentration of the metal salt precursor is 0.1 mol / L, the concentration of NH4F is 0.4 mol / L, the concentration of H3BO3 is 0.05 mol / L, and the total concentration of thiourea and sodium hypophosphite is controlled at 1.0 mol / L.

[0016] Preferably, the solvent of the electrodeposition electrolyte in step S2 is 50 mL of deionized water.

[0017] Preferably, the constant current electrodeposition in step S3 is -0.25 A and the deposition time is 900 s.

[0018] Compared with the prior art, the present invention has the following beneficial effects: By introducing iron, phosphorus, and sulfur into nickel hydroxide for doping modification, the electronic structure of the catalyst and the chemical environment around the active sites can be effectively controlled, promoting interfacial charge transport, optimizing the adsorption of oxygen evolution reaction intermediates, and reducing the reaction energy barrier, thereby improving the catalytic activity of oxygen evolution reaction. Simultaneously, the catalyst can form a surface polyanion layer rich in phosphate and sulfate ions in situ during seawater electrolysis. Combined with the regulatory effect of iron doping on chloride ion adsorption behavior, this significantly improves the material's corrosion resistance and structural stability in chloride-containing electrolytes. Furthermore, this invention employs an electrodeposition method to construct the catalytic layer in situ on the surface of a nickel foam substrate. The preparation process is simple, the catalytic layer bonds firmly to the substrate, and it has good application prospects. Attached Figure Description

[0019] Figure 1The image shows the Raman spectrum of the finished material prepared in Example 1. The horizontal axis represents the Raman shift, in centimeters. -1 (cm -1 The vertical axis represents relative intensity.

[0020] Figure 2 The image shows the Raman spectrum of the finished material prepared in Comparative Example 1. The horizontal axis represents the Raman shift, in centimeters. -1 (cm -1 The vertical axis represents relative intensity.

[0021] Figure 3 The image shown is a transmission electron microscope (TEM) image of the finished material prepared in Example 1.

[0022] Figure 4 Linear scan voltammetry curves of samples from Example 1, Example 2, Example 3, and Comparative Example 1 are shown. The test potential range is 1.0–1.9 volts (v vs. RHE), and the scan rate is 5 mV / s. The horizontal axis represents voltage in volts (v vs. RHE), and the vertical axis represents current density in milliamperes per square centimeter (mA / cm²). 2 ).

[0023] Figure 5 The graph shows the electrocatalytic stability test results of the sample from Example 1 and the sample from Comparative Example 1, where the test current density is 100 mA / cm². 2 The horizontal axis represents time, in hours (h); the vertical axis represents voltage, in volts (v vs. RHE). Detailed Implementation

[0024] To further illustrate the technical solution of the present invention, the present invention will be further described in detail below with reference to embodiments. It should be understood that the following embodiments are only used to illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent substitutions or modifications made within the spirit and principles of the present invention should fall within the scope of protection of the present invention. Reagents and instruments not specifically manufactured or modeled are all products that can be obtained through conventional market channels.

[0025] Example 1 (1) Weigh 1.07 g nickel chloride, 0.40 g ferric chloride, 4.24 g sodium hypophosphite, 0.76 g thiourea, 0.16 g boric acid and 0.74 g ammonium fluoride, add them to 50 mL of deionized water, disperse them by ultrasonication and mix them until completely dissolved to obtain the electrodeposition electrolyte.

[0026] (2) The nickel foam substrate is pretreated according to the above method and then used for a three-electrode electrodeposition system with nickel foam as the working electrode, saturated calomel electrode as the reference electrode and platinum sheet as the counter electrode.

[0027] (3) Under the three-electrode system, electrodeposition was performed using a constant current program with a deposition current of -0.25 A and a deposition time of 900 s. After electrodeposition, the electrodes were removed, washed sequentially with deionized water and ethanol, and dried to obtain the iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrochemical oxygen desorption catalyst. For ease of description, the sample obtained in Example 1 is referred to as NiFePSO.

[0028] The Raman spectrum of the obtained sample is as follows Figure 1 As shown, the transmission electron microscope image is as follows: Figure 3 As shown, the linear sweep voltammetry curve is as follows: Figure 4 As shown in the figure. Test results indicate that the prepared material exhibits excellent oxygen evolution catalytic performance: in a 1 mol / L KOH electrolyte, when the current density is 10 mA / cm², the catalytic performance is [missing information]. 2 At that time, its overpotential was only 231 mV; in simulated seawater electrolyte (1 mol / L KOH + 0.5 mol / L NaCl), when the current density was 100 mA / cm², its overpotential was only 231 mV; 2 At that time, its overpotential was only 278 mV.

[0029] Furthermore, the obtained catalytic material also exhibits good electrocatalytic stability. The stability test results are as follows: Figure 5 As shown, the anion exchange membrane water electrolyzer assembled based on this catalyst can operate stably for more than 1400 h in simulated seawater electrolyte (1 mol / L KOH + 0.5 mol / L NaCl). During operation, the cell voltage of the device only showed a slow drift of about 60 mV, and no obvious failure was observed overall, indicating that the catalyst has excellent long-term operational stability.

[0030] Example 2 (1) Weigh 1.07 g nickel chloride, 0.40 g ferric chloride, 5.30 g sodium hypophosphite, 0.16 g boric acid and 0.74 g ammonium fluoride, add them to 50 mL deionized water, disperse them by ultrasonication and mix them until completely dissolved to obtain an electrodeposition electrolyte.

[0031] (2) The nickel foam substrate is pretreated according to the above method and then used for a three-electrode electrodeposition system with nickel foam as the working electrode, saturated calomel electrode as the reference electrode and platinum sheet as the counter electrode.

[0032] (3) Under the three-electrode system, electrodeposition was performed using a constant current program with a deposition current of -0.25 A and a deposition time of 900 s. After electrodeposition, the electrodes were removed, washed sequentially with deionized water and ethanol, and dried to obtain the iron and phosphorus co-modified nickel hydroxyl oxide catalyst. The sample obtained in Example 2 is referred to as NiFePO.

[0033] The obtained linear sweep voltammetric curve of the sample is as follows: Figure 4 As shown in the figure. Test results indicate that the prepared material exhibits excellent oxygen evolution catalytic performance: in a 1 mol / L KOH electrolyte, when the current density is 10 mA / cm², the catalytic performance is [missing information]. 2 At that time, its overpotential was only 240 mV; in simulated seawater electrolyte (1 mol / L KOH + 0.5 mol / L NaCl), when the current density was 100 mA / cm², its overpotential was only 240 mV; 2 At that time, its overpotential was only 304 mV.

[0034] Example 3 (1) Weigh 1.07 g nickel chloride, 0.40 g ferric chloride, 3.81 g thiourea, 0.16 g boric acid and 0.74 g ammonium fluoride, add them to 50 mL of deionized water, disperse them by ultrasonication and mix them until completely dissolved to obtain an electrodeposition electrolyte.

[0035] (2) The nickel foam substrate is pretreated according to the above method and then used for a three-electrode electrodeposition system with nickel foam as the working electrode, saturated calomel electrode as the reference electrode and platinum sheet as the counter electrode.

[0036] (3) Under the three-electrode system, electrodeposition was performed using a constant current program with a deposition current of -0.25 A and a deposition time of 900 s. After electrodeposition, the electrodes were removed, washed sequentially with deionized water and ethanol, and dried to obtain the iron and sulfur co-modified nickel hydroxyl oxide catalyst. The sample obtained in Example 3 is referred to as NiFeSO.

[0037] The linear sweep voltammetry curve of the obtained sample is as follows: Figure 4 As shown in the figure. Test results indicate that the prepared material exhibits excellent oxygen evolution catalytic performance: in a 1 mol / L KOH electrolyte, when the current density is 10 mA / cm², the catalytic performance is [missing information]. 2 At that time, its overpotential was only 260 mV; in simulated seawater electrolyte (1 mol / L KOH + 0.5 mol / L NaCl), when the current density was 100 mA / cm², its overpotential was only 260 mV; 2 At that time, its overpotential was only 335 mV.

[0038] Comparative Example (1) Weigh 1.42 g nickel chloride, 4.24 g sodium hypophosphite, 0.76 g thiourea, 0.16 g boric acid and 0.74 g ammonium fluoride, add them to 50 mL deionized water, disperse and mix them by ultrasonication until completely dissolved to obtain an electrodeposition electrolyte.

[0039] (2) The nickel foam substrate is pretreated according to the above method and then used for a three-electrode electrodeposition system with nickel foam as the working electrode, saturated calomel electrode as the reference electrode and platinum sheet as the counter electrode.

[0040] (3) Under the three-electrode system, electrodeposition was performed using a constant current program with a deposition current of -0.25 A and a deposition time of 900 s. After electrodeposition, the electrodes were removed, washed sequentially with deionized water and ethanol, and dried to obtain phosphorus and sulfur co-modified nickel hydroxyl oxide catalyst. This phosphorus and sulfur co-modified sample is referred to as NiPSO. In this paper, NiFePSO, NiFePO, NiFeSO and NiPSO are only used as sample abbreviations to distinguish samples obtained under different preparation conditions and do not indicate that the corresponding samples have a fixed stoichiometric composition.

[0041] The Raman spectrum of the obtained sample is as follows Figure 2 As shown, the linear sweep voltammetry curve is as follows: Figure 4 As shown in the figure. Test results indicate that the prepared material exhibits excellent oxygen evolution catalytic performance: in a 1 mol / L KOH electrolyte, when the current density is 10 mA / cm², the catalytic performance is [missing information]. 2 At that time, its overpotential was only 289 mV; in simulated seawater electrolyte (1 mol / L KOH + 0.5 mol / L NaCl), when the current density was 100 mA / cm², its overpotential was only 289 mV; 2 At that time, its overpotential was only 381 mV.

[0042] In addition, the stability test results of the obtained catalytic material are as follows: Figure 5 As shown, the anion exchange membrane water electrolyzer assembled based on this catalyst showed significant failure after operating in simulated seawater electrolyte (1 mol / L KOH + 0.5 mol / L NaCl) for more than 300 h, indicating that the stability of the catalyst still needs to be improved.

[0043] Using the finished materials prepared in the embodiments and comparative examples of this invention as the anode for seawater electrolysis, a commercial platinum electrode as the cathode, and a mercury oxide electrode as the reference electrode, a three-electrode system was constructed. The electrolyte was 1 mol / L KOH + 0.5 mol / L NaCl, and the electrochemical performance was tested using a Shanghai Chenhua CHI660E electrochemical workstation. The test results are as follows: Figure 4As shown in Table 1, the potential range for the linear scan voltammetry test is 1.0–1.9 V (vs. RHE), and the scan rate is 5 mV / s.

[0044] Table 1. Electrochemical performance of finished materials prepared in the examples and comparative examples Depend on Figure 4 , Figure 5 As shown in Table 1, compared with the comparative example, the sample prepared in the embodiment of the present invention not only exhibits superior oxygen evolution catalytic activity, but also has better long-term operational stability.

[0045] In summary, the features and advantages of this invention are as follows: by introducing iron, phosphorus, and sulfur co-modification into nickel hydroxyl oxide, the electronic structure of the catalyst and the chemical environment around the active sites can be effectively controlled, promoting interfacial charge transport, optimizing the adsorption of oxygen evolution reaction intermediates, and reducing the reaction energy barrier, thereby improving the oxygen evolution catalytic activity; simultaneously, the catalyst can form a surface polyanion layer rich in phosphate and sulfate ions in situ during seawater electrolysis, and combined with Fe doping, it can enhance the activity of Cl... - The regulation of adsorption behavior significantly improves the corrosion resistance and structural stability of the material in chlorine-containing electrolytes. Furthermore, this invention employs an electrodeposition method to construct a catalytic layer in situ on the surface of a nickel foam substrate. The preparation process is simple, the catalytic layer bonds firmly to the substrate, and it shows promising application prospects.

Claims

1. A co-modified iron-phosphorus-sulfur nickel hydroxyl oxide seawater electrochemical oxygen desorption catalyst, characterized in that, The catalyst comprises a nickel foam substrate and a catalytic active layer supported on the surface of the nickel foam substrate; the catalytic active layer is nickel hydroxy oxide co-modified with iron, phosphorus and sulfur, and the catalytic active layer contains Ni, Fe, P, S and O elements; wherein Fe is introduced into the nickel hydroxy oxide as a metal dopant element, and P and S exist in the catalytic active layer as non-metallic modifying elements.

2. The iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrolytic oxygen catalyst according to claim 1, characterized in that, The Raman spectrum of the catalyst layer is at 200 cm⁻¹ -1 – 400 cm -1 Within the range, located at 290 cm -1 and 330 cm -1 The characteristic peak at 450 cm⁻¹ -1 – 600 cm -1 Within the range, located at 475 cm -1 and 530 cm -1 The characteristic peak at that location.

3. The iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrolytic oxygen catalyst according to claim 1, characterized in that, Compared to the undoped Fe catalyst, the catalyst layer at 450 cm -1 – 600 cm -1 The metal-oxygen vibration peaks within the range undergo a blue shift.

4. The iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrolytic oxygen catalyst according to claim 1, characterized in that, The catalyst can form a surface polyanion layer rich in phosphate and sulfate in situ during seawater electrolysis.

5. A method for preparing the iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrolytic oxygen catalyst according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Pretreatment of the nickel foam substrate; S2. Add nickel salt, iron salt, thiourea, sodium hypophosphite, ammonium fluoride and boric acid to deionized water, mix and dissolve to obtain electrodeposition electrolyte; S3. Using the pretreated nickel foam substrate as the working electrode, the platinum sheet as the counter electrode, and the saturated calomel electrode as the reference electrode, a three-electrode system was constructed. Electrodeposition was carried out under constant current conditions to deposit the nickel-based hydroxyl oxide catalyst layer co-modified by iron, phosphorus, and sulfur on the surface of the nickel foam substrate in situ. S4. Wash and dry the deposited sample to obtain the iron, phosphorus, and sulfur co-modified nickel-based hydroxyl oxide seawater electrochemical oxygen desorption catalyst.

6. The preparation method according to claim 5, characterized in that, The pretreatment described in step S1 includes: ultrasonic treatment of the nickel foam in a 0.5 mol / L - 2.0 mol / L sulfuric acid solution to remove the surface oxide layer; followed by ultrasonic cleaning in acetone and deionized water, and drying for later use.

7. The preparation method according to claim 5, characterized in that, The nickel compound mentioned in step S2 is nickel chloride, and the iron compound is ferric chloride.

8. The preparation method according to claim 5, characterized in that, In step S3, using 50 mL of deionized water as a solvent, nickel compound, iron compound, thiourea, sodium hypophosphite, ammonium fluoride, and boric acid are mixed to prepare an electrodeposition electrolyte. The total concentration of the metal salt precursor composed of nickel compound and iron compound is 0.1 mol / L, and the molar ratio of Ni to Fe is 3:1; the total concentration of thiourea and sodium hypophosphite is 1.0 mol / L; the concentration of ammonium fluoride is 0.4 mol / L; and the concentration of boric acid is 0.05 mol / L.

9. The preparation method according to claim 5, characterized in that, The constant current electrodeposition in step S3 uses a current of -0.25 A and a deposition time of 50 s – 1500 s.

10. A seawater electrolytic oxygen anode, characterized in that, Including the iron-phosphorus-sulfur co-modified nickel hydroxyl oxide seawater electrolytic oxygen catalyst according to any one of claims 1-4.

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