A high-efficiency and stable bifunctional catalytic electrode applied to seawater full-electrolysis hydrogen production, preparation and application

Abstract

The application belongs to the field of green hydrogen energy, and provides a high-efficiency and stable bifunctional catalytic electrode applied to seawater full-electrolysis hydrogen production, preparation and application. The bifunctional catalytic electrode has three-dimensional metal foam as a self-supporting carrier, and has in-situ growth of iron-phosphorus co-doped cobalt sulfide nanowire arrays on the surface of the carrier. The co-doping strategy can effectively regulate the electronic structure of the catalyst and thus improve the multifunction, especially the oxygen evolution and hydrogen evolution bifunctional activity. Among them, phosphorus is an electronic structure regulator for regulating hydrogen evolution, and iron is an electronic structure regulator for oxygen evolution. The application is directly used for the bifunctional electrode of the cathode and anode of seawater full-electrolysis hydrogen production, which has an industrial-level current density (1000 mA cm ‑2 ) at a low driving potential (2.0 V) in alkaline seawater, and a stability of more than 1000 hours, and can be used as a low-cost bifunctional catalytic electrode for future promising seawater full-electrolysis hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of green hydrogen energy, and specifically relates to a highly efficient and stable bifunctional catalytic electrode for hydrogen production by full electrolysis of seawater, its preparation and application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Hydrogen, as a secondary energy source, is the most abundant substance in the universe, constituting 75% of its mass. Hydrogen has a high calorific value, three times that of gasoline, 3.9 times that of alcohol, and 4.5 times that of coke. The product of hydrogen combustion is water, making it the cleanest energy source in the world. With the continued decline in the price of renewable electricity, sustainable hydrogen production through water electrolysis is progressing globally. However, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water electrolysis have high overpotentials and energy consumption, requiring highly efficient catalysts. Platinum and iridium-ruthenium oxides are currently the best-performing catalysts for these reactions, but their high cost limits their large-scale application. Furthermore, current research mainly focuses on developing monofunctional catalysts for either HER or OER, requiring the design of two different types of catalysts in practical applications, which undoubtedly increases the complexity of water electrolysis equipment. Therefore, developing novel, highly active, and low-cost bifunctional catalysts is key to achieving efficient hydrogen production through water electrolysis.

[0004] Furthermore, current research largely focuses on freshwater splitting with added electrolytes, but using freshwater as the electrolyte for hydrogen production through water electrolysis would place a heavy burden on vital freshwater resources. In contrast, seawater accounts for 96.5% of the Earth's total water volume and is spatially evenly distributed. Seawater electrolysis can produce chlorine via chlorination or oxygen via water oxidation. Although chlorine is a valuable chemical, the ever-growing hydrogen market will produce far more than the global demand for Cl2. Therefore, developing catalysts for highly selective seawater electrolysis for hydrogen and oxygen evolution is a major challenge. Moreover, even though carbonate and borate ions are present in seawater, their average concentrations are too low to sustain high current densities. Furthermore, because seawater is inherently a non-buffered electrolyte, the pH near the electrode surface changes during electrolysis (by as much as 5-9 pH units), leading to salt precipitation, catalyst and electrode degradation of other ions, bacteria, microorganisms, and small particles, which limits the long-term stability of the catalyst and membrane. Despite significant resources and efforts invested in seawater electrolysis technology, it remains in its early stages and is far from commercialization. Therefore, developing efficient bifunctional catalysts for anodic oxygen evolution and cathodic hydrogen evolution and improving catalyst stability have very broad application prospects, but have always been a very important and arduous task. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a highly efficient and stable bifunctional catalytic electrode for seawater electrolysis hydrogen production, enabling operation at industrial-grade current densities (greater than 500 mA cm⁻¹). -2 ) Continuous and stable bifunctional hydrolysis of seawater for hydrogen production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides a highly efficient and stable bifunctional catalytic electrode for seawater electrolysis hydrogen production, comprising:

[0008] Three-dimensional metal foam;

[0009] An array of cobalt sulfide nanowires co-doped with iron and phosphorus is grown in situ on the surface of the three-dimensional metal foam.

[0010] A second aspect of the present invention provides a method for preparing a highly efficient and stable bifunctional catalytic electrode for seawater electrolysis hydrogen production, comprising:

[0011] Cobalt salt, iron salt, and urea are dissolved in water to form a solution;

[0012] The three-dimensional metal foam was placed in the solution and reacted by heating and pressurizing to obtain an iron-doped cobalt-iron bimetallic hydroxide precursor electrode.

[0013] The cobalt-iron bimetallic hydroxide precursor electrode described in step 1 is placed downstream of a ceramic boat. Sulfate and phosphorus salts are weighed, mixed, and placed upstream of the ceramic boat. The mixture is then transferred to an inert atmosphere for calcination. After the calcination is completed, a cobalt sulfide nanowire array electrode co-doped with iron and phosphorus is obtained.

[0014] The molar ratio of cobalt salt to iron salt is 1:10 to 10:1, the total molar concentration of metal salt is 10 to 100 mM, and the molar ratio of urea to total metal salt is 5:1 to 1:5.

[0015] A third aspect of the present invention provides the application of the above-described bifunctional catalytic electrode in the full electrolysis of seawater to produce hydrogen, wherein the catalytic reactions include oxygen evolution reaction, hydrogen evolution reaction and full hydrolysis reaction in alkaline freshwater, alkaline simulated seawater and alkaline seawater.

[0016] Beneficial effects of the present invention

[0017] (1) The present invention adopts a co-doping strategy to enable the electrode to simultaneously have the cathode hydrogen evolution and anolyl oxygen evolution reaction activities of dual-function seawater electrolysis, thus avoiding the pollution and waste caused by using different catalysts.

[0018] (2) The three-dimensional nanoarray structure in this invention helps to expose more active sites and improve the proton and gas mass transfer rate.

[0019] (3) Based on the excellent structural characteristics of the electrode of the present invention, it exhibits an industrial-grade current density (1000 mA cm⁻¹) in alkaline seawater at a relatively low driving potential (2.0 V). -2 It also boasts stability for over 1000 hours.

[0020] (4) The precursors used in the preparation of the electrodes of the present invention are inexpensive, abundant, easy to scale up and apply to future industrial applications. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is a schematic diagram of the synthesis route for preparing the iron-phosphorus co-doped cobalt sulfide nanowire array of the present invention.

[0023] Figure 2 These are field emission scanning electron microscope images (a, b) and elemental distribution (c) of the iron-phosphorus co-doped cobalt sulfide nanowire array prepared in Example 1 of this invention.

[0024] Figure 3 These are field emission scanning electron microscope (SEM) images (a, b) of the iron-doped cobalt sulfide nanowire array prepared in Example 2 of this invention.

[0025] Figure 4 These are field emission scanning electron microscope (SEM) images (a, b) of the phosphorus-doped cobalt sulfide nanowire array prepared in Example 3 of this invention.

[0026] Figure 5 These are field emission scanning electron microscope (SEM) images (a, b) of the cobalt sulfide nanowire array prepared in Example 4 of this invention.

[0027] Figure 6 These are X-ray diffraction patterns of cobalt sulfide (co-doped with iron and phosphorus), cobalt sulfide (co-doped with iron and cobalt sulfide), cobalt sulfide (co-doped with phosphorus and cobalt sulfide) nanowire arrays prepared in Examples 1-4 of this invention.

[0028] Figure 7 The X-ray photoelectron spectra of the iron-phosphorus co-doped cobalt sulfide nanowire array prepared in Example 1 of this invention are shown, where (a) is Fe 2p, (b) is P 2p, (c) is Co 2p, and (d) is S 2p.

[0029] Figure 8 The results are the electrochemical test results of the iron-phosphorus co-doped cobalt sulfide, iron-doped cobalt sulfide, phosphorus-doped cobalt sulfide and cobalt sulfide nanowire arrays prepared in Examples 1-4 of this invention. Among them, (a) is the linear sweep voltammetric curve of oxygen evolution reaction in 1M KOH (alkaline fresh water) electrolyte; (b) is the Tafel curve of oxygen evolution in 1M KOH (alkaline fresh water) electrolyte.

[0030] Figure 9 The results are the electrochemical test results of the iron-phosphorus co-doped cobalt sulfide, iron-doped cobalt sulfide, phosphorus-doped cobalt sulfide and cobalt sulfide nanowire arrays prepared in Examples 1-4 of this invention. Among them, (a) is the linear sweep voltammetric curve of oxygen evolution reaction in 1M KOH + 0.5M NaCl (simulated seawater) electrolyte; (b) is the Tafel curve of oxygen evolution in 1M KOH + 0.5M NaCl (simulated seawater) electrolyte.

[0031] Figure 10 The results are the electrochemical test results of the iron-phosphorus co-doped cobalt sulfide, iron-doped cobalt sulfide, phosphorus-doped cobalt sulfide and cobalt sulfide nanowire arrays prepared in Examples 1-4 of this invention. Among them, (a) is the linear sweep voltammetric curve of oxygen evolution reaction in 1M KOH + seawater (alkaline seawater) electrolyte; (b) is the Tafel curve of oxygen evolution in 1M KOH + seawater (alkaline seawater) electrolyte.

[0032] Figure 11The linear sweep voltammetric curves are those of the iron-phosphorus co-doped cobalt sulfide nanowire array prepared in Example 1 of this invention for the oxygen evolution reaction in 1M KOH (alkaline fresh water), 1M KOH + 0.5M NaCl (simulated seawater), and 1M KOH + seawater (alkaline seawater).

[0033] Figure 12 This is the stability curve of the iron-phosphorus co-doped cobalt sulfide nanowire array prepared in Example 1 of the present invention, showing the change of oxygen evolution reaction current density over time in alkaline seawater.

[0034] Figure 13 The results are the electrochemical test results of the iron-phosphorus co-doped cobalt sulfide, iron-doped cobalt sulfide, phosphorus-doped cobalt sulfide and cobalt sulfide nanowire arrays prepared in Examples 1-4 of this invention. Among them, (a) is the linear sweep voltammetric curve of hydrogen evolution reaction in 1M KOH (alkaline fresh water) electrolyte; (b) is the Tafel curve of hydrogen evolution in 1M KOH (alkaline fresh water) electrolyte.

[0035] Figure 14 The results are electrochemical test results of the iron-phosphorus co-doped cobalt sulfide, iron-doped cobalt sulfide, phosphorus-doped cobalt sulfide, and cobalt sulfide nanowire arrays prepared in Examples 1-4 of this invention. Among them, (a) is the linear sweep voltammetric curve of hydrogen evolution reaction in 1M KOH + 0.5M NaCl (simulated seawater) electrolyte; (b) is the Tafel curve of hydrogen evolution in 1M KOH + 0.5M NaCl (simulated seawater) electrolyte.

[0036] Figure 15 The results are electrochemical test results of the iron-phosphorus co-doped cobalt sulfide, iron-doped cobalt sulfide, phosphorus-doped cobalt sulfide, and cobalt sulfide nanowire arrays prepared in Examples 1-4 of this invention. Among them, (a) is the linear sweep voltammetric curve of hydrogen evolution reaction in 1M KOH + seawater (alkaline seawater) electrolyte; (b) is the Tafel curve of hydrogen evolution in 1M KOH + seawater (alkaline seawater) electrolyte.

[0037] Figure 16 The linear sweep voltammetric curves are those of the iron-phosphorus co-doped cobalt sulfide nanowire array prepared in Example 1 of this invention for hydrogen evolution reactions in 1M KOH (alkaline fresh water), 1M KOH + 0.5M NaCl (simulated seawater), and 1M KOH + seawater (alkaline seawater).

[0038] Figure 17 This is the stability curve of the co-doped cobalt sulfide nanowire array prepared in Example 1 of the present invention, showing the change of hydrogen evolution reaction current density over time in alkaline seawater.

[0039] Figure 18The results are as follows: the electrochemical test results of water splitting using iron-phosphorus co-doped cobalt sulfide, iron-doped cobalt sulfide, phosphorus-doped cobalt sulfide, and cobalt sulfide nanowire arrays prepared in Examples 1-4 of this invention as anodic oxygen evolution reaction and cathodic hydrogen evolution reaction, respectively. Among them, (a) is the linear sweep voltammetric curve of water splitting in 1M KOH (alkaline fresh water) electrolyte; (b) is the linear sweep voltammetric curve of water splitting in alkaline seawater.

[0040] Figure 19 This is the stability curve of the iron-phosphorus-doped cobalt sulfide nanowire array prepared in Example 1 of the present invention, showing the change of current density over time in the total water splitting reaction in alkaline seawater. Detailed Implementation

[0041] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] A highly efficient and stable bifunctional catalytic electrode for hydrogen production by full electrolysis of seawater is characterized in that the catalytic electrode uses a three-dimensional metal foam as a catalyst support, and an iron-phosphorus co-doped cobalt sulfide nanowire array is grown in situ on the surface of the support as a catalyst.

[0043] In some embodiments, the three-dimensional self-supporting foam includes: nickel foam, nickel-iron foam, cobalt foam, copper foam, and titanium foam.

[0044] In some embodiments, the catalytic electrode is a bifunctional electrode for both cathode hydrogen evolution and anodic oxygen evolution.

[0045] Combination Figure 1 The present invention prepares a bifunctional catalytic electrode according to the following steps:

[0046] Step 1: Weigh 10-100mM cobalt salt, 0-100mM iron salt, and 10-100mM urea and add them to a certain amount of deionized water, stirring until a mixed solution is formed;

[0047] Step 2: Place the three-dimensional metal foam in the solution prepared in Step 1 and react it in a closed container at 20-200℃ for 2-72 hours to obtain an iron-doped cobalt-iron bimetallic hydroxide precursor electrode.

[0048] Step 3: Place the cobalt-iron bimetallic hydroxide precursor electrode obtained in Step 2 downstream of a ceramic boat, mix 0.05-1M sulfur source and 0.05-1M phosphorus source, place the mixture in the ceramic boat and place it upstream of a tube furnace, and react at 50-500℃ for 2-12 hours under argon atmosphere protection. After the reaction is completed, iron-phosphorus co-doped cobalt sulfide nanowire array electrode is obtained.

[0049] In some embodiments, the cobalt salt and iron salt are selected from any soluble metal salt.

[0050] In some embodiments, the molar ratio of cobalt salt to iron salt is 1:10 to 10:1.

[0051] In some embodiments, the total molar concentration of the metal salt is 10–100 mM.

[0052] In some embodiments, the molar ratio of urea to total metal salt is 5:1 to 1:5.

[0053] In some embodiments, the reaction temperature in step 2 is 20–200°C, the reaction time is 2–72 h, and the container is a sealed container.

[0054] In some embodiments, the sulfur source used in step 3 may be: sodium sulfide, thioacetamide, thiourea, and sulfur powder;

[0055] In some embodiments, the phosphorus source may be: sodium metaphosphate, potassium metaphosphate (but not limited to these).

[0056] In some embodiments, the molar ratio of sulfur source to phosphate salt is 10:1 to 1:10.

[0057] In some embodiments, the inert gas may be nitrogen or argon, and the container may be an inert gas furnace.

[0058] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0059] Example 1

[0060] Step 1: Weigh out 6mM cobalt salt, 0.6mM iron salt, and 36mM urea, add them to a certain amount of deionized water, and stir until a mixed solution is formed;

[0061] Step 2: Place the nickel foam (2*3cm) 2 The solution prepared in step one is placed in a sealed container at 120°C and reacted for 6 hours to obtain an iron-doped cobalt-iron bimetallic hydroxide precursor electrode.

[0062] Step 3: Place the cobalt-iron bimetallic hydroxide precursor electrode obtained in Step 2 downstream of a ceramic boat, mix 500 mg of thioacetamide and 100 mg of sodium metaphosphate, place the mixture in a ceramic boat upstream of a tube furnace, and react at 350 °C for 2 h under an argon atmosphere. After the reaction is complete, an iron-phosphorus co-doped cobalt sulfide nanowire (Fe,P-Co3S4 / NF) array electrode is obtained.

[0063] The field emission scanning electron microscope image of the obtained Fe,P-Co3S4 / NF electrode is shown below. Figure 2As shown, the Fe,P-Co3S4 / NF electrode is an ordered nanowire array uniformly grown on the NF surface. The nanowires have a relatively large specific surface area, exposing more catalytic active sites. The intrinsic porosity of the nanowires and the NF substrate facilitates electrolyte diffusion, desorption, and transfer of gaseous products. Simultaneously, the nanowire array deposited in situ on the NF surface exhibits strong adhesion and is not easily detached. The absence of a binder prevents the active sites from being covered and increases the rapid transfer of protons and electrons. The elemental distribution of the Fe,P-Co3S4 / NF electrode is shown in the figure. Figure 2 As shown in Figure c, Co, Fe, P, and S elements are uniformly distributed on the nanowires. Co and Fe can produce a bimetallic synergistic effect, enhancing the intrinsic catalytic activity. The X-ray diffraction (XRD) pattern is shown below. Figure 6 As shown, the strongest peak, when compared with the PDF card, is identified as a diffraction peak of Co3S4, indicating its good crystallinity. Although no obvious Fe or P peaks were observed in the X-ray diffraction pattern (XRD), in the X-ray photoelectron spectroscopy (XPS) of the Fe,P-Co3S4 / NF electrode, as shown... Figure 7 The images show high-resolution energy dispersive spectroscopy (EDS) spectra for (a) Fe 2p, (b) P 2p, (c) Co 2p, and (d) S 2p. In summary, this demonstrates the successful synthesis of iron-phosphorus co-doped cobalt sulfide nanowire arrays (Fe,P-Co3S4 / NF) electrodes.

[0064] The linear sweep voltammetric curve of oxygen evolution in 1M KOH (alkaline freshwater) electrolyte is shown below. Figure 8 As shown in Figure a, at 500 and 1000 mA cm -2 The overpotentials were 320 mV and 340 mV, respectively, which were 200 mV and 310 mV lower than those of commercial RuO2. The Tafel curves for oxygen evolution in 1 M KOH (alkaline freshwater) electrolyte are shown below. Figure 8 As shown in Figure b, the Tafel slope of Fe,P-Co3S4 / NF is only 81.6 mVdec. -1 It is far lower than that of commercial RuO2 (130.9 mV dec). -1 This indicates that Fe,P-Co3S4 / NF exhibits excellent oxygen evolution kinetics.

[0065] Linear sweep voltammetric curves of oxygen evolution reactions in 1M KOH (alkaline freshwater), 1M KOH + 0.5M NaCl (simulated seawater), and 1M KOH + seawater (alkaline seawater) are compared. Figure 11 As shown, in alkaline seawater, 500 mA cm -2 The overpotential was only 360 mV, only 40 mV higher than that of 1 M KOH (alkaline freshwater) and simulated seawater, respectively. Meanwhile, at 500 mA cm⁻¹... -2The overpotential at this time is less than the onset potential of the chlorine evolution reaction, avoiding the occurrence of chlorine evolution side reactions. Therefore, Fe,P-Co3S4 / NF exhibits excellent seawater electrochemical oxygen evolution performance. The stability curve of the oxygen evolution reaction current density over time in alkaline seawater is shown in the figure below. Figure 12 As shown, at 500mAcm -2 The electrode remained stable after 1000 hours of operation, showing no performance degradation, indicating that the Fe,P-Co3S4 / NF electrode exhibits good stability in alkaline seawater electrolytic oxygen evolution. In conclusion, the Fe,P-Co3S4 / NF electrode can be used as the anolyte catalytic electrode for rapid seawater electrolysis to produce hydrogen.

[0066] The linear sweep voltammetric curve for hydrogen evolution in a 1M KOH (alkaline desalinated water) electrolyte is shown below. Figure 13 As shown in Figure a, at 500 and 1000 mA / cm -2 The overpotentials were 350 mV and 405 mV, respectively. The Tafel curves for hydrogen evolution in 1 M KOH (alkaline desalinated water) electrolyte are shown below. Figure 13 As shown in Figure b, the Tafel slope of Fe,P-Co3S4 / NF is only 78.5 mV dec. -1 It is much lower than that of the NF substrate (122.7 mVdec). -1 This indicates that Fe,P-Co3S4 / NF exhibits excellent hydrogen evolution kinetics.

[0067] Linear sweep voltammetric curves of hydrogen evolution reactions in 1M KOH (alkaline freshwater), 1M KOH + 0.5M NaCl (simulated seawater), and 1M KOH + seawater (alkaline seawater) are compared. Figure 16 As shown, in alkaline seawater, 500 mA cm -2 The overpotential is only 360 mV, which is only 10 mV higher than that of 1 M KOH (alkaline freshwater) and 5 mV higher than that of simulated seawater. Therefore, Fe,P-Co3S4 / NF exhibits excellent hydrogen electrolysis performance in seawater. Especially in alkaline seawater at 500 mA / cm², the overpotential is significantly higher. -2 The hydrogen evolution remained stable even after 1000 hours of continuous hydrogen evolution. Figure 17 The absence of a significant voltage increase indicates that the Fe,P-Co3S4 / NF electrode also exhibits good stability in alkaline seawater electrolysis for hydrogen evolution. In conclusion, the Fe,P-Co3S4 / NF electrode can be used as the cathode catalytic electrode for rapid seawater electrolysis hydrogen production.

[0068] The linear sweep voltammetric curve for the complete hydrolysis of water in 1M KOH (alkaline desalinated water) electrolyte is shown below. Figure 18 As shown in Figure a, Fe,P-Co3S4 / NF is used as the cathode and anode, respectively, and only 1.98V is required to achieve 1000mA cm⁻¹. -2The current density is such that only 2.0V is needed to reach 1000mA / cm² in alkaline seawater. -2 current density ( Figure 18 Figure b) shows that Fe,P-Co3S4 / NF can resist interference from other ions in seawater and has excellent seawater decomposition performance. The stability curve of the reaction current density versus time in alkaline seawater decomposition is shown in Figure b). Figure 19 As shown, at 500mAcm -2 The electrode remained stable after 1000 hours of operation, showing no performance degradation, indicating that the Fe,P-Co3S4 / NF electrode exhibits good stability in alkaline seawater electrolysis. In conclusion, the Fe,P-Co3S4 / NF electrode can serve as a bifunctional catalytic electrode for rapid seawater electrolysis to produce hydrogen.

[0069] Example 2

[0070] Step 1: Weigh out 6mM cobalt nitrate, 0.6mM ferric nitrate, and 36mM urea, add them to 40mL of deionized water, and stir until a mixed solution is formed;

[0071] Step 2: Cut the 2*3cm 2 The nickel foam was placed in the solution prepared in step one and reacted in a sealed container at 120°C for 6 hours to obtain a cobalt-iron bimetallic hydroxide precursor electrode (CoFe-LDH / NF) with a Co:Fe ratio of 10:1.

[0072] Step 3: Place the cobalt-iron bimetallic hydroxide precursor electrode obtained in Step 2 in a ceramic boat and place it downstream of a tube furnace. Weigh 500 mg of thioacetamide, place it in the ceramic boat, and place it upstream of the tube furnace. Under the protection of argon atmosphere, set the temperature to 350℃ and react for 2 hours. After the reaction is completed, the iron-doped cobalt sulfide electrode (Fe-Co3S4 / NF) is obtained.

[0073] The field emission scanning electron microscope image of the obtained Fe-Co3S4 / NF catalytic electrode is shown below. Figure 3 As shown, the morphology of the catalytic electrode is a nanowire arrangement structure.

[0074] As an anode electrode catalyst for oxygen evolution, the linear sweep voltammetric curve for oxygen evolution in 1M KOH (alkaline fresh water) electrolyte is shown below. Figure 8 As shown in Figure a, at 500 and 1000 mA / cm -2 The overpotentials were 340 mV and 360 mV, respectively. The Tafel curves for oxygen evolution in 1 M KOH (alkaline freshwater) electrolyte are shown below. Figure 8 As shown in Figure b, the Tafel slope of Fe-Co3S4 / NF is 83.5 mV dec. -1 This is lower than that of commercial RuO2 (130.9 mV dec). -1The linear sweep voltammetric curve of oxygen evolution in a 1M KOH + 0.5M NaCl (simulated seawater) electrolyte is shown below. Figure 8 As shown in Figure a, at 500 and 1000 mA / cm -2 The overpotentials were 360 ​​mV and 380 mV, respectively. The Tafel curves for oxygen evolution in a 1 M KOH + 0.5 M NaCl (simulated seawater) electrolyte are shown below. Figure 8 As shown in Figure b, the Tafel slope of Fe-Co3S4 / NF is only 88.2 mV dec. -1 It is far lower than that of commercial RuO2 (135.9 mV dec). -1 The linear sweep voltammetric curve of oxygen evolution in a 1M KOH + seawater (alkaline seawater) electrolyte is shown below. Figure 8 As shown in Figure a, at 500 and 1000 mA cm -2 The overpotentials were 370 mV and 400 mV, respectively. The Tafel curves for oxygen evolution in a 1 M KOH + seawater (alkaline seawater) electrolyte are shown below. Figure 8 As shown in Figure b, the Tafel slope of Fe-Co3S4 / NF is only 97.2 mV dec. -1 The concentration of RuO2 (142.6 mV dec) is significantly lower than that of commercial RuO2. -1 )

[0075] As a cathode electrode catalyst for hydrogen evolution, the linear sweep voltammetric curve for hydrogen evolution in 1M KOH (alkaline fresh water) electrolyte is shown below. Figure 13 As shown in Figure a, at 500mA cm -2 The overpotential is 405 mV. The Tafel curve for oxygen evolution in a 1 M KOH (alkaline freshwater) electrolyte is shown below. Figure 13 As shown in Figure b, the Tafel slope of Fe-Co3S4 / NF is 90.7 mV dec. -1 The linear sweep voltammetric curve for oxygen evolution in a 1M KOH + 0.5M NaCl (simulated seawater) electrolyte is shown below. Figure 13 As shown in Figure a, at 500 mA cm -2 The overpotential is 420 mV. The Tafel curve for oxygen evolution in a 1 M KOH + 0.5 M NaCl (simulated seawater) electrolyte is shown below. Figure 13 As shown in Figure b, the Tafel slope of Fe-Co3S4 / NF is only 126.7 mV dec. -1 The linear sweep voltammetric curve for oxygen evolution in a 1M KOH + seawater (alkaline seawater) electrolyte is shown below. Figure 13 As shown in Figure a, at 500mA cm -2 The overpotential is 435 mV. The Tafel curve for oxygen evolution in a 1 M KOH + seawater (alkaline seawater) electrolyte is shown below. Figure 13As shown in Figure b, the Tafel slope of Fe-Co3S4 / NF is only 129.7 mV dec. -1 .

[0076] The linear sweep voltammetric curve for the complete hydrolysis of water in 1M KOH (alkaline desalinated water) electrolyte is shown below. Figure 18 As shown in Figure a, Fe-Co3S4 / NF is used as both the cathode and anode, requiring 2.08V to achieve 1000mA cm⁻¹. -2 The current density. In alkaline seawater, 2.12V is required to reach 1000mA cm⁻¹. -2 current density ( Figure 18 b).

[0077] Example 3

[0078] Step 1: Weigh 6 mM cobalt nitrate and 36 mM urea and add them to 40 mL of deionized water. Stir well to form a mixed solution.

[0079] Step 2: Cut the 2*3cm 2 The nickel foam was placed in the solution prepared in step one and reacted in a sealed container at 120°C for 6 hours to obtain the cobalt precursor electrode.

[0080] Step 3: Place the cobalt precursor electrode obtained in Step 2 in a ceramic boat and place it downstream of a tube furnace. Weigh out 500 mg of thioacetamide and 100 mg of sodium metaphosphate, mix them, place them in a ceramic boat, place it upstream of the tube furnace, and under the protection of argon atmosphere, set the temperature to 350℃ and react for 2 hours. After the reaction is completed, a phosphorus-doped cobalt sulfide electrode (P-Co3S4 / NF) is obtained.

[0081] The field emission scanning electron microscope image of the obtained P-Co3S4 / NF catalytic electrode is shown below. Figure 4 As shown, the morphology of the catalytic electrode is a nanowire array structure.

[0082] As an anode electrode catalyst for oxygen evolution, the linear sweep voltammetric curve for oxygen evolution in 1M KOH (alkaline fresh water) electrolyte is shown below. Figure 8 As shown in Figure a, at 500 and 1000 mA / cm -2 The overpotentials were 390 mV and 490 mV, respectively. The Tafel curves for oxygen evolution in a 1 M KOH (alkaline freshwater) electrolyte are shown below. Figure 8 As shown in Figure b, the Tafel slope of P-Co3S4 / NF is 103.3 mV dec. -1 This is lower than that of commercial RuO2 (130.9 mV dec). -1 The linear sweep voltammetric curve of oxygen evolution in a 1M KOH + 0.5M NaCl (simulated seawater) electrolyte is shown below. Figure 8 As shown in Figure a, at 500 and 1000 mA / cm-2 The overpotentials were 410 mV and 520 mV, respectively. The Tafel curves for oxygen evolution in a 1 M KOH + 0.5 M NaCl (simulated seawater) electrolyte are shown below. Figure 8 As shown in Figure b, the Tafel slope of P-Co3S4 / NF is only 112.7 mV dec. -1 It is far lower than that of commercial RuO2 (135.9 mV dec). -1 The linear sweep voltammetric curve of oxygen evolution in a 1M KOH + seawater (alkaline seawater) electrolyte is shown below. Figure 8 As shown in Figure a, at 500 and 1000 mA / cm -2 The overpotentials were 420 mV and 570 mV, respectively. The Tafel curves for oxygen evolution in a 1 M KOH + seawater (alkaline seawater) electrolyte are shown below. Figure 8 As shown in Figure b, the Tafel slope of P-Co3S4 / NF is only 120.3 mV dec. -1 .

[0083] As a cathode electrode catalyst for hydrogen evolution, the linear sweep voltammetric curve for hydrogen evolution in 1M KOH (alkaline fresh water) electrolyte is shown below. Figure 13 As shown in Figure a, at 500 and 1000 mA cm -2 The overpotentials were 355 mV and 407 mV, respectively. The Tafel curves for oxygen evolution in 1 M KOH (alkaline freshwater) electrolyte are shown below. Figure 13 As shown in Figure b, the Tafel slope of P-Co3S4 / NF is 78.8 mV dec. -1 The linear sweep voltammetric curve for oxygen evolution in a 1M KOH + 0.5M NaCl (simulated seawater) electrolyte is shown below. Figure 13 As shown in Figure a, at 500 and 1000 mA / cm -2 The overpotentials were 360 ​​mV and 417 mV, respectively. The Tafel curves for oxygen evolution in a 1 M KOH + 0.5 M NaCl (simulated seawater) electrolyte are shown below. Figure 13 As shown in Figure b, the Tafel slope of P-Co3S4 / NF is only 80.1 mV dec. -1 The linear sweep voltammetric curve for oxygen evolution in a 1M KOH + seawater (alkaline seawater) electrolyte is shown below. Figure 13 As shown in Figure a, at 500 and 1000 mA cm -2 The overpotentials were 362 mV and 426 mV, respectively. The Tafel curves for oxygen evolution in a 1 M KOH + seawater (alkaline seawater) electrolyte are shown below. Figure 13 As shown in Figure b, the Tafel slope of P-Co3S4 / NF is only 85.7 mV dec. -1 .

[0084] The linear sweep voltammetric curve for the complete hydrolysis of water in 1M KOH (alkaline desalinated water) electrolyte is shown below. Figure 18 As shown in Figure a, P-Co3S4 / NF is used as the cathode and anode, respectively, requiring 2.12V to achieve 1000mA cm⁻¹. -2 The current density. In alkaline seawater, 2.15V is required to reach 1000mA cm⁻¹. -2 current density ( Figure 18 (b)

[0085] Example 4

[0086] Step 1: Weigh 6 mM cobalt nitrate and 36 mM urea and add them to 40 mL of deionized water. Stir well to form a mixed solution.

[0087] Step 2: Cut the 2*3cm 2 The nickel foam was placed in the solution prepared in step one and reacted in a sealed container at 120°C for 6 hours to obtain the cobalt precursor electrode.

[0088] Step 3: Place the cobalt precursor electrode obtained in Step 2 in a ceramic boat and place it downstream of a tube furnace. Weigh 500 mg of thioacetamide and place it in the ceramic boat, which is then placed upstream of the tube furnace. Under an argon atmosphere, set the temperature to 350 °C and react for 2 hours. After the reaction is complete, a cobalt sulfide electrode (Co3S4 / NF) is obtained.

[0089] The field emission scanning electron microscope image of the obtained Co3S4 / NF catalytic electrode is shown below. Figure 4 As shown, the morphology of the catalytic electrode is a nanowire array structure.

[0090] As an anode electrode catalyst for oxygen evolution, the linear sweep voltammetric curve for oxygen evolution in 1M KOH (alkaline fresh water) electrolyte is shown below. Figure 8 As shown in Figure a, at 500mA cm -2 The overpotential is 450 mV. The Tafel curve for oxygen evolution in a 1 MkOH (alkaline freshwater) electrolyte is shown below. Figure 8 As shown in Figure b, the Tafel slope of Co3S4 / NF is 116.4 mV dec. -1 Lower than commercial RuO2 (130.9 mVdec) -1 The linear sweep voltammetric curve of oxygen evolution in a 1M KOH + 0.5M NaCl (simulated seawater) electrolyte is shown below. Figure 8 As shown in Figure a, at 500mA cm -2 The overpotential is 510 mV. The Tafel curve for oxygen evolution in a 1 M KOH + 0.5 M NaCl (simulated seawater) electrolyte is shown below. Figure 8 As shown in Figure b, the Tafel slope of Co3S4 / NF is only 182.3 mV dec. -1The linear sweep voltammetric curve for oxygen evolution in a 1M KOH + seawater (alkaline seawater) electrolyte is shown below. Figure 8 As shown in Figure a, at 500mA cm -2 The overpotential is 550 mV. The Tafel curve for oxygen evolution in a 1 M KOH + seawater (alkaline seawater) electrolyte is shown below. Figure 8 As shown in Figure b, the Tafel slope of Co3S4 / NF is only 198.7 mV dec. -1 .

[0091] As a cathode electrode catalyst for hydrogen evolution, the linear sweep voltammetric curve for hydrogen evolution in 1M KOH (alkaline fresh water) electrolyte is shown below. Figure 13 As shown in Figure a, at 500 mA / cm -2 The overpotential is 415 mV. The Tafel curve for oxygen evolution in 1 MkOH (alkaline fresh water) electrolyte is shown below. Figure 13 As shown in Figure b, the Tafel slope of Co3S4 / NF is 109.6 mV dec. -1 The linear sweep voltammetric curve for oxygen evolution in a 1M KOH + 0.5M NaCl (simulated seawater) electrolyte is shown below. Figure 13 As shown in Figure a, at 500mA cm -2 The overpotential is 450 mV. The Tafel curve for oxygen evolution in a 1 M KOH + 0.5 M NaCl (simulated seawater) electrolyte is shown below. Figure 13 As shown in Figure b, the Tafel slope of Co3S4 / NF is only 135.9 mV dec. -1 The linear sweep voltammetric curve for oxygen evolution in a 1M KOH + seawater (alkaline seawater) electrolyte is shown below. Figure 13 As shown in Figure a, at 500mA cm -2 The overpotential is 480 mV. The Tafel curve for oxygen evolution in a 1 M KOH + seawater (alkaline seawater) electrolyte is shown below. Figure 13 As shown in Figure b, the Tafel slope of Co3S4 / NF is only 145.6 mV dec. -1 .

[0092] The linear sweep voltammetric curve for the complete water hydrolysis in 1M KOH (alkaline desalinated water) electrolyte is shown below. Figure 18 As shown in Figure a, Co3S4 / NF is used as the cathode and anode, respectively, requiring 2.4V to achieve 1000mA cm⁻¹. -2 The current density. In alkaline seawater, 2.55V is required to reach 1000mA cm⁻¹. -2 current density ( Figure 18 (b)

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A bifunctional catalytic electrode for hydrogen production via seawater electrolysis, characterized in that, include: Three-dimensional metal foam; An iron-phosphorus co-doped cobalt sulfide nanowire array is grown in situ on the surface of the three-dimensional metal foam, wherein the cobalt sulfide is Co3S4.

2. The bifunctional catalytic electrode for seawater electrolysis hydrogen production as described in claim 1, characterized in that, The three-dimensional metal foam includes: nickel foam, nickel-iron foam, cobalt foam, copper foam, and titanium foam.

3. The bifunctional catalytic electrode for seawater electrolysis hydrogen production as described in claim 1, characterized in that, The bifunctional catalytic electrode is for hydrogen evolution at the cathode and oxygen evolution at the anode.

4. A method for preparing a bifunctional catalytic electrode for hydrogen production by full electrolysis of seawater, characterized in that, include: Cobalt salt, iron salt, and urea are dissolved in water to form a solution; The three-dimensional metal foam was placed in the solution and reacted by heating and pressurizing to obtain an iron-doped cobalt-iron bimetallic hydroxide precursor electrode. The cobalt-iron bimetallic hydroxide precursor electrode was placed downstream of a ceramic boat. A sulfur source and a phosphorus source were weighed, mixed, and placed upstream of the ceramic boat. The mixture was then transferred to an inert atmosphere for calcination. After the calcination, a cobalt sulfide nanowire array electrode co-doped with iron and phosphorus was obtained. The cobalt sulfide was Co3S4. The molar ratio of cobalt salt to iron salt is 1:10 to 10:1, the total molar concentration of metal salt is 10 to 100 mM, and the molar ratio of urea to total metal salt is 5:1 to 1:

5.

5. The method for preparing a bifunctional catalytic electrode for seawater electrolysis hydrogen production as described in claim 4, characterized in that, The reaction conditions are as follows: in a closed container, at 20~200 °C, for 2~72 h.

6. The method for preparing a bifunctional catalytic electrode for seawater electrolysis hydrogen production as described in claim 4, characterized in that, The sulfur source is at least one of sodium sulfide, thioacetamide, thiourea, and sulfur powder.

7. The method for preparing a bifunctional catalytic electrode for seawater electrolysis hydrogen production as described in claim 4, characterized in that, The phosphorus source is sodium metaphosphate or potassium metaphosphate.

8. The method for preparing a bifunctional catalytic electrode for seawater electrolysis hydrogen production as described in claim 4, characterized in that, The molar ratio of the sulfur source to the phosphorus source is 10:1 to 1:

10.

9. The method for preparing a bifunctional catalytic electrode for seawater electrolysis hydrogen production as described in claim 4, characterized in that, The inert atmosphere is nitrogen or argon.

10. The application of the bifunctional catalytic electrode according to any one of claims 1-3 in the full electrolysis of seawater for hydrogen production, characterized in that, Catalytic reactions include oxygen evolution reaction, hydrogen evolution reaction and total hydrolysis reaction in alkaline fresh water, alkaline simulated seawater and alkaline seawater.

Images