Seawater-corrosion-resistant high-entropy alloy hydrogen catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, and discloses a seawater-corrosion-resistant high-entropy alloy hydrogen catalyst and a preparation method and application thereof.The seawater-corrosion-resistant high-entropy alloy hydrogen catalyst is of a core-shell structure, the core structure is composed of a solid solution prepared from Fe, Co, Ni, Cr and Mo, the shell structure is a Cr2O3 / MoO2 composite passivation layer, and a chemical bonding interface is formed between the core structure and the shell structure. The catalyst obtained by the invention not only has higher corrosion resistance, but also has higher activity, and can well catalyze seawater or industrial wastewater to obtain hydrogen.

Description

Technical Field

[0001] The present invention relates to the field of catalyst technology, and in particular to a seawater corrosion-resistant high-entropy alloy hydrogen catalyst, a preparation method and applications thereof. Background Art

[0002] Among existing technologies, hydrogen energy is one of the cleanest renewable energy sources. Among the many clean energy sources, hydrogen energy is undoubtedly the most promising to replace fossil fuels in the future and then build a new green energy system with hydrogen as the carrier.

[0003] There are many ways to obtain hydrogen energy, among which water electrolysis technology can be driven by renewable energy and is an environmentally friendly technology for producing high-purity hydrogen. However, due to the large overpotential required for the hydrogen evolution reaction, a catalyst needs to be used on the electrode material. Traditional electrocatalytic hydrogen production technology mainly relies on precious metal catalysts (Pt / C) or transition metal sulfides (MoS2), but such catalysts limit traditional electrocatalytic hydrogen production technology to only act in fresh water. Existing catalysts face severe challenges in extreme water conditions such as seawater electrolysis and industrial wastewater hydrogen production. Pt-containing catalysts are prone to anodic dissolution in Cl⁻-containing media. For example, in a 3.5% NaCl solution, the Pt surface will form soluble PtCl4 2- The complex leads to the loss of active sites, and the overpotential increases by more than 40% after 500 hours of operation. MoS2 is easily oxidized to MoO4 under alkaline conditions (pH>9). 2- , and sulfur vacancies are easily occupied by S 2- poison.

[0004] Therefore, the development of hydrogen production catalysts with high activity, strong corrosion resistance and low cost remains a technical bottleneck that needs to be broken through. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a seawater corrosion-resistant high-entropy alloy hydrogen catalyst and its preparation method and application. The catalyst obtained by the present invention not only has high corrosion resistance, but also has high activity, and can well catalyze seawater or industrial wastewater to obtain hydrogen.

[0006] The present invention provides a seawater corrosion-resistant high-entropy alloy hydrogen catalyst. The catalyst has a core-shell structure, wherein the core structure is composed of a solid solution made of Fe, Co, Ni, Cr and Mo, and the shell structure is a Cr2O3 / MoO2 composite passivation layer. A chemically bonded interface is formed between the core structure and the shell structure.

[0007] Furthermore, the atomic percentage of Fe in the catalyst is 25%-35%, the atomic percentage of Co is 15%-25%, the atomic percentage of Ni is 15%-25%, the atomic percentage of Cr is 10%-20%, and the atomic percentage of Mo is 5%-15%.

[0008] Furthermore, the thickness of the composite passivation layer is 2nm-5nm.

[0009] Furthermore, the catalyst has a porous structure with a pore size of 50 nm-200 nm or 1 μm-5 μm.

[0010] Furthermore, the specific surface area of the catalyst is 120m 2 / g-250m 2 / g.

[0011] The present invention also provides a method for preparing the catalyst, which comprises: Step S1: Weighing iron, cobalt, nickel, chromium and molybdenum according to the atomic percentage of the catalyst, and ball milling the mixture of iron, cobalt, nickel, chromium and molybdenum with the assistance of a plasma generator; Step S2: Screening the ball-milled powder, annealing the screened powder in stages, and cooling the powder to obtain a catalyst.

[0012] Furthermore, the atomic percentage of Fe in the catalyst is 25%-35%, the atomic percentage of Co is 15%-25%, the atomic percentage of Ni is 15%-25%, the atomic percentage of Cr is 10%-20%, and the atomic percentage of Mo is 5%-15%.

[0013] Furthermore, during the ball milling, the ball-to-material ratio is 8-10:1.

[0014] Furthermore, during the ball milling, a plasma generator is used to assist, with a pressure of 0.1 MPa-0.3 MPa and a power of 600W-1000W, and argon and hydrogen are introduced, with a volume ratio of argon to hydrogen of 95:5.

[0015] Furthermore, the ball milling time is 6h-12h.

[0016] Furthermore, the ball milling time is 8h-10h.

[0017] During the ball milling process, temperature stability can prevent oxidation, agglomeration, or lattice defects caused by local overheating of the powder, thereby improving the uniformity of the alloy composition. Therefore, during the ball milling process, the rotation direction can be switched every 30 minutes, and the powder temperature is monitored in real time and controlled within the range of 300K-350K to ensure that the alloy powder is fully mechanically alloyed and form a uniform solid solution precursor.

[0018] Furthermore, the powder after sieving has a D50 of 50±5 nm.

[0019] Furthermore, the staged annealing process includes: a first stage, keeping the temperature at 250° C.-350° C. for 0.5 h-2 h; and a second stage, keeping the temperature at 550° C.-650° C. for 1 h-3 h.

[0020] Furthermore, in the first stage, the heating rate to 250°C-350°C is 3°C / min-8°C / min, and in the second stage, the heating rate to 550°C-650°C is 1°C / min-3°C / min.

[0021] Furthermore, during the first stage, a mixed gas of ammonia and hydrogen needs to be introduced, with a volume ratio of ammonia to hydrogen being 1:3 and a flow rate of 30 sccm-100 sccm; during the second stage, argon needs to be introduced.

[0022] Furthermore, the cooling rate of the cooling is not less than 200°C / s.

[0023] Furthermore, the cooling rate is 200°C / s-500°C / s.

[0024] The present invention also provides the use of the catalyst in electrocatalytic hydrogen production in seawater or wastewater.

[0025] The embodiments of the present invention have the following technical effects: 1. The present invention provides a catalyst with a core-shell structure, the shell structure comprising a Cr2O3 / MoO2 composite passivation layer. This composite passivation layer exhibits both corrosion resistance and self-repair capabilities. Furthermore, the atomic radii of Fe, Co, and Ni in the core structure are similar, which reduces lattice distortion when mixed with Cr and Mo, forming a stable solid solution and reducing segregation.

[0026] 2. The catalyst obtained by the present invention can be applied to seawater or wastewater to catalyze the formation of hydrogen from seawater or wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 is a microscopic diagram provided by an embodiment of the present invention, wherein Figure 1 In the middle, a is a layered structure diagram. Figure 1 Figure b is a physical picture of the pores of the catalyst. Figure 1 Figure c is the distribution diagram of Fe elements in the catalyst. Figure 1The d in the middle is the distribution diagram of Co element in the catalyst. Figure 1 In the figure e, it is the distribution diagram of Ni element in the catalyst. Figure 1 Figure f is the distribution diagram of Cr elements in the catalyst. Figure 1 Figure g is the distribution diagram of Mo element in the catalyst.

[0029] Figure 2 This is the XRD pattern during the preparation process of Example 1 of the present invention.

[0030] Figure 3 is the test data of the embodiment and comparative example of the present invention, wherein Figure 3 Where a is the overpotential data, Figure 3 b in the middle is the resistance data.

[0031] Figure 4 is the charge density of the embodiment of the present invention.

[0032] Figure 5 This is test data of an embodiment of the present invention applied to seawater electrolysis to produce hydrogen.

[0033] Figure 6 3. It is a comparison of hydrogen evolution overpotentials of Example and Comparative Example.

[0034] Figure 7 is the corrosion current density of Examples and Comparative Examples.

[0035] Figure 8 It is the overpotential amplification test data of the embodiment and the comparative example. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0037] In a first aspect, some embodiments of the present invention provide a seawater corrosion-resistant high-entropy alloy hydrogen catalyst, wherein the catalyst has a core-shell structure, the core structure is composed of a solid solution of Fe, Co, Ni, Cr and Mo, and the shell structure is a Cr2O3 / MoO2 composite passivation layer, and a chemically bonded interface is formed between the core structure and the shell structure.

[0038] In the present invention, the composite passivation layer (Cr2O3 / MoO2) blocks Cl in seawater or wastewater through a dense oxide network. - and S 2-This significantly improves the catalyst's corrosion resistance by preventing corrosion. Furthermore, the chemically bonded interfaces between the core and shell structures (e.g., Cr-O-Mo bonds) enhance interfacial adhesion. During long-term operation, the composite passivation layer may dissolve trace amounts of Cr / Mo due to localized corrosion. Based on the chemically bonded interfaces formed between the shell structures, Cr and Mo in the core structure migrate to defects in the passivation layer through surface diffusion or oxidation reactions, forming a new Cr2O3 / MoO2 covering layer and enabling dynamic self-repair.

[0039] During the annealing process of the present invention, Cr and Mo preferentially migrate to the alloy surface due to surface energy differences, combining with oxygen to form a Cr2O3 / MoO2 composite passivation layer. By regulating the atomic ratios of the catalyst (Fe: 25-35%, Co: 15-25%, Ni: 15-25%, Cr: 10-20%, Mo: 5-15%), further segregation of chromium and molybdenum is hindered. Furthermore, the atomic radii of Fe, Co, and Ni are similar, and the 3d electrons of Fe (unfilled orbitals) bind to the strong metallic bonds of Co and Ni, forming a uniform electron cloud distribution and reducing surface energy. Consequently, the lattice distortion energy of Fe, Co, and Ni after mixing is reduced, allowing them to form a stable solid solution structure with Cr and Mo while also preventing further segregation of Cr and Mo. Thus, by regulating the atomic ratios of the catalyst as described above, the catalyst of the present invention not only forms a passivation layer, which improves the catalyst's corrosion resistance, but also forms a core structure with high configurational entropy, ensuring the catalyst's catalytic activity.

[0040] In the present invention, a strong chemical bonding interface is formed between the core-shell structure through the Cr-O-Mo bond. This interface not only enhances the strength of the core-shell bond through chemical bonds, but also provides a channel for the migration of Cr / Mo. When the passivation layer is damaged, the Cr / Mo in the core structure diffuses to the defect site through the interface and interacts with the O in the catalytic environment. 2- The reaction forms a new passivation layer.

[0041] In some embodiments, the atomic percentage of Fe in the catalyst is 25%-35%, the atomic percentage of Co is 15%-25%, the atomic percentage of Ni is 15%-25%, the atomic percentage of Cr is 10%-20%, and the atomic percentage of Mo is 5%-15%.

[0042] In the present invention, the percentage of Cr atoms and Mo atoms must not only be sufficient to form a stable solid solution with Fe, Co, and Ni, but also to form a passivation layer of a certain thickness. The control of the ratio of Fe, Co, and Ni is not only to achieve a uniform solid solution, but also to avoid further segregation of Cr atoms and Mo atoms. In addition, the entropy of the catalyst is also increased. The high configurational entropy catalyst obtained by the present invention not only has a long service life, but also has good catalytic activity.

[0043] In some embodiments, the composite passivation layer has a thickness of 2 nm to 5 nm.

[0044] In the present invention, the selection of the thickness of the composite passivation layer can not only ensure the catalytic activity of the catalyst, but also improve the corrosion resistance of the catalyst.

[0045] In some embodiments, the catalyst has a porous structure with a pore size of 50 nm-200 nm or 1 μm-5 μm.

[0046] In the present invention, the porous structure of the catalyst increases the specific surface area of the catalyst, thereby facilitating the improvement of the catalytic efficiency.

[0047] In some embodiments, the specific surface area of the catalyst is 120 m 2 / g-250m 2 / g.

[0048] In a second aspect, some embodiments of the present invention further provide a method for preparing the catalyst, the method comprising: Step S1: iron, cobalt, nickel, chromium and molybdenum are weighed respectively according to the atomic percentage of the catalyst, and the iron, cobalt, nickel, chromium and molybdenum are ball-milled with the assistance of a plasma generator; Step S2: Screening the ball-milled powder, annealing the screened powder in stages, and cooling the powder to obtain a catalyst.

[0049] In this invention, a plasma generator is used for auxiliary processing. First, the plasma generator provides additional energy to accelerate the mixing of metal powders. Second, the high temperature generated promotes atomic diffusion and promotes alloying. Third, it improves efficiency and saves costs. Finally, the impact of plasma on the surface of the material particles can increase the generation of defects and increase the number of catalytically active sites.

[0050] In the method of the present invention, the staged calcination and ball milling process not only forms a composite passivation layer, but also forms a porous structure in the catalyst. The ball milling process promotes uniform dispersion of atoms, which facilitates the formation of a solid solution during the staged annealing process.

[0051] In some embodiments, the atomic percentage of Fe in the catalyst is 25%-35%, the atomic percentage of Co is 15%-25%, the atomic percentage of Ni is 15%-25%, the atomic percentage of Cr is 10%-20%, and the atomic percentage of Mo is 5%-15%.

[0052] In some embodiments, during the ball milling, the ball-to-material ratio is 8-10:1.

[0053] In some embodiments, the ball milling is assisted by a plasma generator with a pressure of 0.1 MPa-0.3 MPa and a power of 600W-1000W, and argon and hydrogen are introduced with a volume ratio of argon to hydrogen of 95:5.

[0054] In some embodiments, the ball milling time is 6 hours to 12 hours.

[0055] In the present invention, ball milling can achieve the target particle size (D50 = 50 ± 5 nm) and compositional uniformity. When the ball milling time is less than 6 hours, the powder is not fully mixed, resulting in an uneven core-shell structure. When the ball milling time is longer than 12 hours, excessive oxidation or lattice defects may occur. Therefore, in the present invention, the ball milling time is controlled between 6 and 12 hours.

[0056] In some embodiments, the ball milling time is 8 hours to 10 hours.

[0057] In the present invention, when the ball milling time is controlled within a range of 8 h to 10 h, the distribution of elements in the catalyst after ball milling is more uniform, and the performance of the catalyst is better.

[0058] In some embodiments, the powder after sieving has a D50 of 50±5 nm.

[0059] In some embodiments, the staged annealing process includes: a first stage, keeping at 250° C.-350° C. for 0.5 h-2 h; a second stage, keeping at 550° C.-650° C. for 1 h-3 h.

[0060] In some embodiments, in the first stage, the heating rate to reach 250°C-350°C is 3°C / min-8°C / min, and in the second stage, the heating rate to reach 550°C-650°C is 1°C / min-3°C / min.

[0061] During the staged annealing process, the catalyst undergoes a transformation from a body-centered cubic (BCC) phase to a face-centered cubic (FCC) phase. The open lattice of the FCC structure facilitates the exposure of active sites and the diffusion of reactants, thereby enhancing catalytic activity. Furthermore, the high symmetry of the FCC phase helps reduce surface energy, minimize element segregation, and enhance the uniformity of the core-shell structure.

[0062] In some embodiments, during the first stage, a mixed gas of ammonia and hydrogen is also introduced, with a volume ratio of ammonia to hydrogen of 1:3 and a flow rate of 30 sccm-100 sccm; during the second stage, argon is also required to be introduced.

[0063] In the present invention, by kinetic control in the staged annealing process (300°C to 600°C), active N atoms in the NH3 / H2 atmosphere are filled in the grain boundaries, limiting further excessive segregation of Cr / Mo, thereby not excessively affecting the formation of solid solution.

[0064] In the present invention, the formation of vacancies in the catalyst and the number of vacancies formed are controlled by controlling the flow rate of ammonia, thereby ensuring the stability of the catalyst structure and improving the catalytic activity of the catalyst.

[0065] In some embodiments, the cooling rate is not less than 200° C. / s.

[0066] In the present invention, the cooling rate is controlled to be not less than 200°C / s, which can inhibit the formation of unfavorable phases and is conducive to maintaining the face-centered cubic phase structure formed at high temperature, which is conducive to the exposure of active sites and the reaction of reactants (protons in water (H + ) or intermediates ) diffusion, preventing reactants from occupying active sites, thereby improving catalytic activity. Rapid cooling also reduces the accumulation of elements at grain boundaries or crystal planes through diffusion, which can lead to uneven segregation. This cooling rate helps maintain a uniform distribution of elements, thereby forming a stable solid solution structure. Rapid cooling helps refine the grains and increase the number of grain boundaries, thereby improving the material's strength and toughness, and ultimately enhancing the hardness and strength of the catalyst. When the catalyst is used in a catalytic environment such as seawater or industrial wastewater, the increased hardness and strength of the catalyst improves its corrosion resistance, chemical stability, and resistance to mechanical wear.

[0067] In some embodiments, the cooling rate is 200° C. / s-500° C. / s.

[0068] In a third aspect, some embodiments of the present invention further provide the use of the catalyst in electrocatalytic hydrogen production from seawater or wastewater.

[0069] The following is described in conjunction with specific examples and comparative examples: Example 1:

[0070] Step S1: Metal powders of iron, cobalt, nickel, chromium, and molybdenum (purity >99.9%, particle size <45 μm) were weighed according to the atomic percentage of the catalyst: 26.8 g of iron, 18.9 g of cobalt, 18.8 g of nickel, 12.5 g of chromium, and 23.0 g of molybdenum, for a total mass of 100 g. After mixing thoroughly in an argon glove box, the mixture was loaded into a carbide ball mill. The mixture of iron, cobalt, nickel, chromium, and molybdenum balls was ball milled under an argon and hydrogen atmosphere. Plasma-assisted ball milling was performed by introducing an Ar / H₂ mixture (volume ratio 95:5, pressure 0.2 MPa). A 20 kHz plasma generator (power 800 W) was activated and the milling process was continued for 8 hours, switching the rotation direction every 30 minutes. The powder temperature was monitored in real time (dynamically fluctuating between 300 K and 350 K). The milling power fluctuation was controlled using a PID controller to ≤±5% to ensure that the powder temperature remained within the target range.

[0071] Step S2: Screening the ball-milled powder and filtering the ball-milled powder through a 200-mesh sieve to obtain an alloy powder with a D50 of 50±5 nm. The screened powder is subjected to staged annealing. The first stage: The powder was placed in a tube furnace, and a NH3 / H2 mixed gas (volume ratio of 1:3, flow rate of 50 sccm) was introduced. The temperature was raised to 300°C at a rate of 5°C / min and kept at this temperature for 1 hour to form a composite passivation layer. The second stage: switch to Ar protective atmosphere, heat up to 600℃ at 2℃ / min, keep warm for 2 hours; quickly cool by liquid nitrogen atomization (cooling rate > 200℃ / s) to obtain catalyst Fe 30 Co 20 Ni 20 Cr 15 Mo 15 The microstructure of the catalyst obtained is as follows Figure 1 As shown, Figure 1 Figure a is a diagram of the catalyst layer structure; Figure 1 b is a physical picture of the pores of the catalyst; Figure 1 Figure c is the distribution diagram of Fe element in the catalyst; Figure 1 Figure d is the distribution diagram of Co element in the catalyst; Figure 1 e in the middle is the distribution diagram of Ni element in the catalyst; Figure 1 Figure f is the distribution diagram of Cr element in the catalyst; Figure 1 Figure g is the distribution diagram of Mo element in the catalyst.

[0072] Comparative Example 1: Step S1: Based on the target catalyst atomic percentage (Fe: 20%, Co: 25%, Ni: 25%, Cr: 20%, Mo: 10%), 21.4g of iron powder, 24.6g of cobalt powder, 24.5g of nickel powder, 16.4g of chromium powder, and 13.1g of molybdenum powder (total mass 100g) were weighed. The mixture was mixed thoroughly in an argon glove box and loaded into a carbide ball mill. The iron, cobalt, nickel, chromium, and molybdenum were ball milled in an argon and hydrogen atmosphere. Plasma-assisted ball milling was performed by introducing an Ar / H2 mixture (95:5 volume ratio, 0.2 MPa pressure). A 20kHz plasma generator (800W power) was activated and the milling was continued for 8 hours, switching the rotation direction every 30 minutes. The powder temperature was monitored in real time (dynamically fluctuating between 300K and 350K). The milling power fluctuation was controlled using a PID controller to ≤±5% to ensure that the powder temperature remained within the target range.

[0073] Step S2: Screening the ball-milled powder and filtering the ball-milled powder through a 200-mesh sieve to obtain an alloy powder with a D50 of 50±5 nm. The screened powder is subjected to staged annealing. The first stage: the powder was placed in a tube furnace, and a mixture of NH3 / H2 (volume ratio of 1:3, flow rate of 50 sccm) was introduced, and the temperature was increased to 300°C at a rate of 5°C / min and kept at this temperature for 1 hour; The second stage: switch to Ar protective atmosphere, heat up to 600℃ at 2℃ / min, keep warm for 2 hours; quickly cool by liquid nitrogen atomization (cooling rate>200℃ / s), and obtain Fe catalyst without Cr2O3 / MoO2 passivation layer. 20 Co 25 Ni 25 Cr 20 Mo 10 .

[0074] Comparative Example 2: Step S1: Metal powders of iron, cobalt, nickel, chromium, and molybdenum (purity >99.9%, particle size <45 μm) were weighed according to the atomic percentage of the catalyst: 26.8 g of iron, 18.9 g of cobalt, 18.8 g of nickel, 12.5 g of chromium, and 23 g of molybdenum, for a total mass of 100 g. After mixing thoroughly in an argon glove box, the powders were loaded into a carbide ball mill. The iron, cobalt, nickel, chromium, and molybdenum were ball milled in an atmosphere of argon and hydrogen. Plasma-assisted ball milling was performed by introducing an Ar / H₂ mixture (95:5 by volume, pressure 0.2 MPa). A 20 kHz plasma generator (800 W) was activated and the milling was continued for 8 hours, switching the rotation direction every 30 minutes. The powder temperature was monitored in real time (dynamically fluctuating between 300 K and 350 K). The milling power fluctuation was controlled using a PID controller to ≤±5% to ensure that the powder temperature remained within the target range.

[0075] Step S2: Screening the ball-milled powder, filtering the ball-milled powder through a 200-mesh sieve to obtain an alloy powder with a D50 of 50±5 nm, and subjecting the screened powder to single annealing; Step S3: After sieving, the powder was directly subjected to single annealing treatment: the temperature was raised to 600°C at 5°C / min, and a NH3 / H2 mixed gas (volume ratio 1:3, flow rate 50 sccm) was introduced. After keeping the temperature for 3 hours, liquid nitrogen atomization cooling (cooling rate > 200°C / s) was performed to finally obtain the catalyst Fe 30 Co 20 Ni 20 Cr 15 Mo 15 .

[0076] Comparative Example 3: Pt / C.

[0077] Comparative Example 4: Step S1: Weigh 40 g of iron, 30 g of cobalt, and 30 g of nickel metal powder (purity > 99.9%, particle size <45 μm) based on the atomic percentage of the catalyst. Mix thoroughly in an argon glove box and place in a carbide ball mill. Mill the iron, cobalt, and nickel in a mixed atmosphere of argon and hydrogen. Plasma-assisted milling: A 95:5 volume ratio of Ar / H₂ gas, 0.2 MPa pressure, is introduced. A 20 kHz plasma generator (800 W power) is activated and milled for 8 hours, switching the rotation direction every 30 minutes. Powder temperature is monitored in real time (dynamically fluctuating between 300 K and 350 K). PID control of milling power fluctuations to ≤±5% ensures the powder temperature remains within the target range.

[0078] Step S2: Screening the ball-milled powder and filtering the ball-milled powder through a 200-mesh sieve to obtain an alloy powder with a D50 of 50±5 nm. The screened powder is subjected to staged annealing. The first stage: the powder was placed in a tube furnace, and a mixture of NH3 / H2 (volume ratio of 1:3, flow rate of 50 sccm) was introduced, and the temperature was increased to 300°C at a rate of 5°C / min and kept at this temperature for 1 hour; The second stage: switch to Ar protective atmosphere, heat up to 600℃ at 2℃ / min, keep warm for 2 hours; quickly cool by liquid nitrogen atomization (cooling rate > 200℃ / s) to obtain catalyst Fe 40 Co 30 Ni 30 .

[0079] Comparative Example 5: Traditional ternary alloy catalysts in existing technology: Fe 50 Co 30 Ni 20 .

[0080] Comparative Example 6: Using physical deposition: Step S1: Metal powders of iron, cobalt, nickel, chromium, and molybdenum (purity >99.9%, particle size <45 μm) were weighed according to the atomic percentage of the catalyst: 26.8 g of iron, 18.9 g of cobalt, 18.8 g of nickel, 12.5 g of chromium, and 23.0 g of molybdenum, for a total mass of 100 g. After mixing thoroughly in an argon glove box, the powders were loaded into a carbide ball mill. The iron, cobalt, nickel, chromium, and molybdenum were ball milled in an argon and hydrogen atmosphere. Plasma-assisted ball milling was performed by introducing an Ar / H₂ mixture (95:5 by volume, pressure 0.2 MPa). A 20 kHz plasma generator (800 W) was activated and the milling was continued for 8 hours, switching the rotation direction every 30 minutes. The powder temperature was monitored in real time (dynamically fluctuating between 300 K and 350 K). The milling power fluctuation was controlled using a PID controller to ≤±5% to ensure that the powder temperature remained within the target range.

[0081] Step S2: The ball-milled powder is sieved and filtered through a 200-mesh sieve to obtain an alloy powder with a D50 of 50 ± 5 nm. The sieved powder is sequentially deposited with Cr2O3 (thickness 2 nm) and MoO2 (thickness 3 nm) on the alloy surface by magnetron sputtering (physical vapor deposition).

[0082] Deposition parameters: substrate temperature 200 °C, sputtering power 150 W, Ar / O2 mixed gas (volume ratio 4:1), vacuum degree 5×10 -3 Pa.

[0083] The catalysts obtained from the examples and comparative examples were tested and applied: (1) The specific surface area of the obtained catalyst was tested, and the pore size of its porous structure was tested.

[0084] (2) XPS analysis: X-ray photoelectron spectrometer was used, with monochromatic Al Kα radiation (1486.6 eV) as the excitation source, and the analysis depth was approximately 5-10 nm. After the sample was sputtered with argon ions (1 keV, 60 s) to remove surface contaminants, charge correction was performed using the C 1s peak (284.8 eV). The high-resolution spectrum was peak-fitted using Avantage software, and the elemental chemical states were analyzed in combination with the NIST XPS database, focusing on the changes in the binding energy of Cr 2p, Mo 3d, Fe 2p, Co 2p, and Ni 2p orbitals. The ratio of Cr2O3 to MoO2 in the passivation layer and the interfacial chemical bonding state were quantitatively analyzed.

[0085] (3) XRD analysis: X-ray diffractometer was used, using Cu Kα radiation, with a scanning range of 10°–90°, a step size of 0.02°, and a scanning rate of 2° / min. The PDF cards were compared using Jade 6.0 software to analyze the phase composition and crystal structure, and to calculate the lattice constant and grain size.

[0086] (4) TEM: Transmission electron microscopy (TEM) was used at an accelerating voltage of 200 kV. The sample was ultrasonically dispersed in ethanol and then drop-coated onto an ultrathin carbon-coated copper mesh. High-resolution TEM (HRTEM) was used to observe the atomic arrangement and chemical bonding characteristics of the core-shell interface, and selected area electron diffraction (SAED) was used to analyze the lattice orientation. The spatial distribution of elements was verified by combined STEM-EDS.

[0087] (5) EDS: Energy dispersive spectroscopic analysis was performed under a scanning electron microscope (SEM) with an accelerating voltage of 15 kV and a beam spot size of 5 nm. Line scan analysis was performed on the catalyst cross section to quantify the atomic percentage gradient of Fe, Co, Ni, Cr, and Mo in the core-shell region and verify the degree of element segregation and the uniformity of the passivation layer thickness.

[0088] (6) The pore distribution of the catalyst was determined using nitrogen adsorption-desorption isotherms.

[0089] (7) Conduct electrochemical performance tests on the obtained catalyst: An electrochemical workstation and a three-electrode system (working electrode: catalyst / nickel foam; reference electrode: Hg / HgO (1MKOH); counter electrode: platinum sheet) were used. Test conditions: Linear sweep voltammetry was performed at a scan rate of 2 mV / s in a 3.5% NaCl solution (pH = 8.5) as the electrolyte at 25°C. The hydrogen evolution overpotential and Tafel slope were calculated using the Tafel equation.

[0090] Electrochemical impedance spectroscopy: frequency range 0.1 Hz-100 kHz, amplitude 10 mV, equivalent circuit fitting to obtain charge transfer resistance and double layer capacitance.

[0091] Cycling stability: constant current density 50mA / cm 2 Run continuously for 1000 h, and record the voltage change and activity decay rate.

[0092] (8) The catalyst obtained in the example is applied to the electrode: Electrode preparation: Catalyst powder was mixed with Nafion solution (5 wt%) at a ratio of 9:1; after ultrasonic dispersion, it was coated on nickel foam (loading capacity 1 mg / cm 2 ); vacuum drying at 80° C. for 12 hours to form a porous electrode.

[0093] Electrolyzer integration: paired with IrO2 / Ti anode (electrode spacing 8mm); using Nafion 117 proton exchange membrane, electrolyte circulation flow rate 50mL / min.

[0094] Working condition verification: In industrial wastewater (COD=4200mg / L, Cl - =3.2mol / L): current density 500mA / cm 2 The voltage is 2.1V; the hydrogen purity is greater than 99.95%, the Faraday efficiency is 97.3%; the activity decay rate is less than 3% after 30 days of continuous operation.

[0095] Results and Analysis: Table 1 Catalyst performance test

[0096] The catalyst of Example 1 was successfully obtained by the method of the present invention. Figure 1 shown. Figure 1 In (a), it can be found that the catalyst of the present invention has obvious stratification, which shows that the catalyst of the present invention has a core-shell structure. Figure 1 In (b), it can be found that the surface of the catalyst has pores, and the pore size distribution is 50nm-200nm. Figure 1 In (c)-(g), it can be seen that the Fe, Co, Ni, Cr and Mo elements in the catalyst are evenly distributed in the catalyst. It can be seen that the method of the present invention achieves a uniform distribution of atoms in the catalyst, which is conducive to the formation of a solid solution.

[0097] The mixture prepared in Example 1 was tested using XRD, and the test results are as follows: Figure 2 It can be seen that a solid solution is successfully formed in Example 1 after annealing.

[0098] Figure 3 The catalytic activity of the catalysts obtained in Example 1, Comparative Example 5 and Comparative Example 3 was tested. Figure 3 As shown. It can be found that the polarization curve of Example 1 shows the smallest overpotential and the smallest Tafel slope, indicating that Example 1 has the highest catalytic activity. At the same time, the radius of the electrochemical impedance curve of Example 1 is the smallest, indicating that the conductivity of the catalyst of Example 1 is better than that of the comparative example. It is speculated that the reason why Example 1 of the present invention is better is that the method of the present invention successfully forms a high configurational entropy solid solution with Fe, Co, Ni and Cr and Mo in the core structure, and the solid solution forms a face-centered cubic phase structure (such as Figure 2As shown, this structure facilitates the exposure of active sites and the diffusion of reactants, and the active sites are evenly dispersed, preventing reactants from occupying the active sites, thereby improving catalytic activity. Furthermore, by regulating the atomic ratios in the catalyst, further segregation of chromium and molybdenum is hindered. Furthermore, Fe, Co, and Ni not only have similar atomic radii, but the 3d electrons of Fe (unfilled orbitals) also form strong metallic bonds with Co and Ni, forming a uniform electron cloud distribution and reducing surface energy. Therefore, the lattice distortion energy of Fe, Co, and Ni is reduced after mixing, allowing them to form a stable solid solution structure with Cr and Mo while also preventing further segregation of Cr and Mo. In contrast, the BCC / FCC mixed phase of Comparative Example 5 and the non-alloy structure of Comparative Example 3 exhibit reduced active site density due to lattice distortion, which is directly reflected in the lowest Tafel slope (32 mV / dec) in Example 1. In addition, the core-shell interface in Example 1 of the present invention forms a strong chemical bond through the Cr-O-Mo bond, which optimizes the electron transfer path from the core to the shell, making the charge transfer resistance (Rct=2.5Ω) significantly lower than that of Comparative Example 5 (12.3Ω). Figure 3 As shown in (b), the multi-level pore structure and high specific surface area provide a fast channel for the diffusion of reactants, reducing concentration polarization, while the comparative example 5 (45m 2 / g) and Pt / C (25m 2 / g) limits the mass transfer efficiency, resulting in its overpotential (η 10 =72mV and 72mV) are much higher than that of Example 1 (38mV). In addition, the Cr2O3 / MoO2 composite passivation layer blocks Cl through a dense oxide network. - and S 2- Corrosion, Cr / Mo in the core dynamically repairs the passivation layer defects through interface diffusion, thereby reducing the loss of catalyst active sites. Therefore, the corrosion current density in Example 1 is as low as 1.2×10 -7 A / cm 2 , whereas Comparative Example 5 lacks a passivation layer, and Comparative Example 3 suffers from continuous loss of active sites due to Pt dissolution, resulting in significantly higher corrosion current densities than Example 1. This indicates that the design of the catalyst in Example 1 of the present invention facilitates the structural advantages of Example 1, enabling Example 1 to achieve high activity, strong corrosion resistance, and a long life under extreme operating conditions.

[0099] On this basis, the charge density of the catalyst obtained in Example 1 was theoretically calculated, and the results are as follows: Figure 4 It can be found that the charge density of the catalyst obtained by the present invention is 0.27e / Å 3 , compared with the traditional ternary alloy (Comparative Example 5, 0.12e / Å 3 ) and Pt / C (Comparative Example 3, 0.18e / Å 3This value indicates that the synergistic effect of Fe, Co, Ni, Cr, and Mo reconstructs the electron cloud distribution through the high entropy solid solution effect, forming a localized high charge density region at the core-shell interface (peak value of 0.35 e / Å). 3 ), the solid solution effectively enhances the H + adsorption capacity and reduce the hydrogen desorption energy barrier (calculated value ), thereby significantly improving the kinetics of the hydrogen evolution reaction. In addition, the spatial uniformity of the charge density (coefficient of variation <5%) further verifies the uniformity of the solid solution structure, avoiding the passivation of active sites due to element segregation, and the charge gradient of the Cr-O-Mo bonding interface (from the core to the shell direction changes to 0.27e / Å 3 -0.15e / Å 3 ) provides a directional channel for electron transfer, reducing the charge transfer resistance. The charge gradient and directional transfer at the core-shell interface, as well as the local high charge density area, can significantly reduce the charge transfer resistance and accelerate the proton (H + ) to the active site, this electronic structure characteristic is consistent with the catalytic activity test results (η 10 =38mV) is highly consistent, theoretically revealing the essential mechanism of multi-element synergistic optimization of active sites. It can be seen that the catalyst of the present invention selects several elements that can jointly achieve a change in the electron cloud distribution. When the electron cloud distribution changes, the atoms of different elements readjust the electron aggregation state through interaction. This adjustment will form some electron "dense areas" or "sparse areas" on the surface of the material. Electron-dense areas are more likely to attract positively charged reactants, allowing them to be quickly adsorbed to the catalyst surface; while electron-sparse areas are conducive to the stability and conversion of reaction intermediates. Therefore, the catalytic activity of the catalyst obtained in Example 1 is significantly improved.

[0100] The catalyst obtained in Example 1 was applied to a seawater electrolysis hydrogen production system. The results are as follows: Figure 5 It can be found that after the catalyst obtained in Example 1 has worked for 1200 hours, its working voltage curve shows a stable trend, which proves that the catalyst obtained in the present invention has excellent stability and can maintain high efficiency and corrosion resistance for a long time under harsh environments.

[0101] In Table 1, the catalysts obtained in Example 1 and Comparative Example 1 were subjected to corrosion resistance tests. In a 3.5% NaCl solution, the corrosion current density of Comparative Example 1 reached 5.8×10 -5 A / cm², while the corrosion current density of Example 1 is 1.2×10 -7 A / cm². On this basis, the activity decay of the catalyst was further tested. The catalysts of Example 1 and Comparative Example 1 were placed in a simulated seawater electrolysis environment (3.5% NaCl solution, pH = 8.5, 25°C) at a constant current density of 50 mA / cm².2 The activity decay was tested after continuous operation for 500 hours. The specific method was as follows: the catalyst was loaded on the nickel foam electrode (loading amount 1 mg / cm 2 ), paired with an IrO2 / Ti anode, using a Nafion 117 proton exchange membrane, and an electrolyte circulation rate of 50 mL / min. The operating voltage was recorded every 24 hours, and the hydrogen evolution overpotential (η) was determined by linear sweep voltammetry (LSV, scan rate 2 mV / s). 10 ) changes, while simultaneously monitoring metal ion concentrations in the electrolyte (ICP-MS) to assess the extent of corrosion. After the run, the catalyst surface morphology was observed by SEM, and the stability of the passivation layer composition was analyzed by XPS. The test results showed that after 20 hours of operation, the overpotential increase in Example 1 was less than 3%, while that in Comparative Example 1, lacking the protection of the Cr / Mo passivation layer, was greater than 30%. Furthermore, the concentrations of Fe, Co, and Ni ions in the electrolyte increased significantly, confirming that the activity decay was due to severe corrosion. In summary, the catalyst obtained in the present invention exhibits excellent corrosion resistance and stability due to the composite passivation layer derived from Cr and Mo. Furthermore, the composite passivation layer of the catalyst obtained in the present invention exhibits corrosion resistance, and its dynamic self-healing ability enhances the catalyst's stability. This can also be verified by Comparative Example 6. As shown in Table 1, the corrosion potential of Comparative Example 6 is significantly higher than that of Example 1. This indicates that the physically deposited Cr2O3 / MoO2 layer is only physically adsorbed to the core structure, lacking Cr-O-Mo chemical bonding, resulting in weak interfacial bonding and easy flaking in the electrolyte. After the passivation layer is damaged, the Cr / Mo in the core structure cannot repair defects through interfacial diffusion, resulting in increased corrosion current density and continuous loss of active sites. Physical deposition methods can only form a mechanically bonded passivation layer and cannot achieve interface-driven element migration and dynamic protection, demonstrating the necessity of the staged annealing process in this invention.

[0102] The hydrogen evolution overpotential of the catalysts obtained in Example 1, Comparative Examples 1 to 3 and Comparative Example 5 was compared. The results are as follows: Figure 6 As shown. Example 1 has the lowest hydrogen evolution overpotential (38 mV), significantly better than all comparative examples (58 mV-85 mV), indicating that Example 1 has the highest catalytic activity. Comparison of Example 1 and Comparative Example 1 reveals that during the ball milling and step annealing processes of Example 1, interfacial bonding is formed on the surface of Example 1, while Comparative Example 1 has no interfacial bonding. The overpotentials are 38 mV and 85 mV, respectively, indicating that the Cr / Mo composite passivation layer and the chemically bonded interface are the key to improving activity.

[0103] Comparison of Example 1 and Comparative Example 2 shows that Example 1 adopts step-wise annealing. During the step-wise annealing process, the catalyst is induced to transform from a body-centered cubic phase (BCC) to a face-centered cubic phase (FCC). The open lattice of the FCC structure is conducive to the exposure of active sites and the diffusion of reactants, thereby improving the catalytic activity. In addition, the high symmetry of the FCC phase helps to reduce surface energy, reduce element segregation, and enhance the uniformity of the core-shell structure. It can be seen that in the method of the present invention, the first stage of the step-wise annealing stabilizes the passivation layer, the high-temperature phase transition (second stage) optimizes the crystal structure, and the step-wise annealing process is conducive to improving the activity of the catalyst. This can be verified by comparing Example 1 and Comparative Example 2. The catalytic activity of the catalysts obtained in Example 1 and Comparative Example 2 was tested. The results show that the hydrogen evolution overpotential η of Comparative Example 2 in Table 1 is 10 =58mV (38mV in Example 1), and charge transfer resistance Rct =5.2Ω (2.5Ω in Example 1). It can be seen that the staged annealing in the present invention is beneficial for the transformation of the catalyst structure to a face-centered cubic phase structure, which is beneficial for improving the catalytic activity of the catalyst.

[0104] exist Figure 7 The corrosion current density of Example 1 is always stable at 1.2×10 -7 A / cm 2 , which hardly changes with time, indicating that the passivation layer has long-term protection capability. The corrosion current density of comparative example 1 (without Cr / Mo) increases from 5.8×10 -5 A / cm 2 Rapidly increased to 8×10 -4 A / cm 2 (1000 hours), it can be seen that the corrosion is out of control when there is no Cr2O3 / MoO2 passivation layer. The corrosion current density of comparative example 3 (Pt / C) (5.1×10 -6 A / cm 2 ) is lower than that of Comparative Example 1, but still 2 orders of magnitude higher than that of Example 1, further verifying the corrosion resistance advantage of the high entropy alloy core-shell structure.

[0105] exist Figure 8 The overpotential increase in Example 1 was only 3%, well below the threshold (10%), demonstrating excellent long-term stability. Comparative Examples 1 and 5 showed increases of 30% and 25%, respectively, indicating rapid performance degradation due to the lack of a passivation layer and self-repair mechanisms. Comparative Example 3 (Pt / C) showed a 40% increase, further demonstrating the unsuitability of traditional precious metal catalysts under extreme operating conditions.

[0106] In summary, the catalyst obtained by the present invention can be applied to seawater or wastewater, and has good catalytic activity and corrosion resistance.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A seawater corrosion-resistant high-entropy alloy hydrogen catalyst, characterized in that: The catalyst has a core-shell structure, wherein the core structure is composed of a solid solution of Fe, Co, Ni, Cr and Mo, and the shell structure is a Cr2O3 / MoO2 composite passivation layer, and a chemical bonding interface is formed between the core structure and the shell structure.

2. The catalyst according to claim 1, characterized in that The catalyst contains 25%-35% Fe atomic percentage, 15%-25% Co atomic percentage, 15%-25% Ni atomic percentage, 10%-20% Cr atomic percentage, and 5%-15% Mo atomic percentage.

3. The catalyst according to claim 1, characterized in that The thickness of the composite passivation layer is 2nm-5nm.

4. The catalyst according to claim 1, characterized in that The catalyst has a porous structure with a pore size of 50nm-200nm or 1μm-5μm; the specific surface area of the catalyst is 120m 2 / g-250m 2 / g.

5. The method for preparing the catalyst according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Step S1: Weighing iron, cobalt, nickel, chromium, and molybdenum according to the atomic percentage of the catalyst, and ball-milling the mixture of iron, cobalt, nickel, chromium, and molybdenum in a mixed atmosphere of argon and hydrogen; Step S2: Screening the ball-milled powder, annealing the screened powder in stages, and cooling the powder to obtain a catalyst.

6. The preparation method according to claim 5, characterized in that The catalyst contains 25%-35% Fe atomic percentage, 15%-25% Co atomic percentage, 15%-25% Ni atomic percentage, 10%-20% Cr atomic percentage, and 5%-15% Mo atomic percentage.

7. The preparation method according to claim 5, characterized in that During the ball milling, the ball-to-material ratio is 8-10:1; the volume ratio of argon gas to hydrogen gas is 95:5; During the ball milling, plasma is used for assistance, with a pressure of 0.1-0.3 MPa and a power of 600-1000W.

8. The preparation method according to claim 5, characterized in that The staged annealing process includes: a first stage, keeping the temperature at 250° C.-350° C. for 0.5 h-2 h; and a second stage, keeping the temperature at 550° C.-650° C. for 1 h-3 h.

9. The preparation method according to claim 8, characterized in that In the first stage, the heating rate to 250°C-350°C is 3-8°C / min, and in the second stage, the heating rate to 550°C-650°C is 1-3°C / min; During the first stage, a mixed gas of ammonia and hydrogen needs to be introduced, with a volume ratio of ammonia to hydrogen of 1:3 and a flow rate of 30-100 sccm; during the second stage, argon needs to be introduced.

10. Use of the catalyst according to any one of claims 1 to 4 in electrocatalytic hydrogen production from seawater or wastewater.

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