Alkaline hydrogen evolution catalyst of atomic fraction Ir-N double-site embedded Mo2C nanosheet and preparation method thereof

Abstract

The invention relates to the technical field of alkaline water electrolysis catalyst equipment, in particular to an alkaline hydrogen evolution catalyst with atomic-scale dispersed Ir-Ni double-site embedded Mo2C nanosheets and a preparation method of the alkaline hydrogen evolution catalyst, the chemical expression of the alkaline hydrogen evolution catalyst is Ir < x > Ni < gamma > (at) Mo2C, x: y = 1: 1-1: 5, x + y = 0.01-0.05, and the molar weight of Mo2C is 1; the Mo2C nanosheet is of a hexagonal layered structure, the space group is P62 / mmc, and a crystal face (001) of the Mo2C nanosheet has a lattice gap; ir atoms and Ni atoms are uniformly embedded into the interstitial spaces in the form of single atoms to form Ir-C bonds and Ni-C bonds, the bond lengths are respectively equal to the distances between Ir sites and Ni sites so as to form concerted catalytic centers, the Ir sites are responsible for optimizing H * desorption, and delta GH is approximately equal to-0.05 eV; the Ni site is responsible for activating H2O molecules, and the energy barrier is approximately equal to 0.35 eV. Through activation of H2O by Ni sites and optimization of H * desorption by Ir sites, high-efficiency synergy of two key reactions of alkaline HER is realized.

Description

Technical Field

[0001] This invention relates to the field of alkaline water electrolysis catalyst equipment technology, and in particular to an atomically based alkaline hydrogen evolution catalyst with Ir-N dual-site embedded Mo2C nanosheets and its preparation method. Background Technology

[0002] Electrolysis of water to produce hydrogen is a key technology for the large-scale production of "green hydrogen," with alkaline electrolyzers being widely used due to their low cost and high stability. However, the hydrogen evolution reaction (HER) under alkaline conditions suffers from sluggish kinetics (high energy barrier in the water splitting step), requiring highly efficient catalysts to lower the reaction energy barrier. Currently, while commercial Pt / C catalysts exhibit excellent activity, they are expensive and have poor stability in alkaline environments (easily oxidized and agglomerated). Transition metal carbides (such as Mo2C) have become potential alternatives due to their Pt-like electronic structure, but their single-component active sites are insufficient, failing to optimize the adsorption / desorption of hydrogen species (H*). Single-atom catalysts (such as Ir single atoms) have high atom utilization, but their single active sites are difficult to synergistically catalyze the water splitting and H* conversion steps, thus limiting the performance of alkaline HER.

[0003] Existing technologies suffer from the following drawbacks: single-metal catalysts (such as Ni@Mo2C) exhibit weak activation ability for H2O in alkaline conditions, with Tafel slopes generally exceeding 60 mV / dec and slow kinetics; alloy nanoparticle catalysts (such as Ir-Ni alloys) are prone to agglomeration, resulting in low atom utilization (<30%), weak interaction with the support, and poor stability (cycles <500 h); traditional preparation methods (such as impregnation and co-precipitation) struggle to achieve bimetallic atomic-level dispersion, often leading to the formation of nanoparticle aggregates and wasted active sites. Therefore, developing dual-site synergistic catalysts with high activity, high stability, and high atom utilization is crucial to overcoming the performance bottleneck of alkaline HER. Summary of the Invention

[0004] The purpose of this invention is to provide an atomically dispersed Ir-Ni dual-site embedded Mo2C nanosheet alkaline hydrogen evolution catalyst and its preparation method.

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and to propose an atomically dispersed Ir-Ni dual-site embedded Mo2C nanosheet alkaline hydrogen evolution catalyst, with the chemical formula Ir... X Ni γ @Mo2C, where x:y=1:1-1:5, x+y=0.01-0.05, with the molar amount of Mo2C being 1; the Mo2C nanosheets have a hexagonal layered structure with space group P63 / mmc, and interstitial lattice exists on its (001) crystal plane; Ir atoms and Ni atoms are uniformly embedded in the interstitial lattice in the form of single atoms, forming Ir-C bonds and Ni-C bonds, with bond lengths of respectively and The distance between the Ir site and the Ni site is A synergistic catalytic center is formed, in which the Ir site is responsible for optimizing H* desorption, ΔG_H≈-0.05eV; the Ni site is responsible for activating H2O molecules, with an energy barrier of ≈0.35eV.

[0006] Preferably, the Ir X Ni Y In @Mo2C, the optimal Ir:Ni ratio is 1:4.

[0007] Preferably, the active site density of the Mo2C nanosheets is 8 ± 1 sites / nm. 2 .

[0008] A method for preparing the catalyst, employing a two-step "ligand-assisted solvothermal-carbothermal reduction" method, specifically includes the following steps:

[0009] (1) Preparation of precursors: Molybdenum source, carbon source, Ir precursor and Ni precursor were dissolved in a 1:1 volume ratio ethanol-water mixed solvent at a molar ratio of Mo:Ir:Ni:C = 2:0.01-0.05:0.01-0.25:5-10. Ligands were added at a molar ratio of 1:1 to metal ions. The mixture was stirred at 60°C for 2 hours until a sol was formed.

[0010] (2) Solothermic reaction: The sol was transferred to a high-pressure reactor and reacted at 180°C for 12 h. After cooling, the black precipitate was collected by centrifugation and dried under vacuum at 60°C for 12 h to obtain the Ir-Ni-Mo-OC precursor.

[0011] (3) Carbothermic reduction: The precursor is placed in a quartz tube reactor and pretreated at 500℃ for 2h in an atmosphere with an Ar / H2 volume ratio of 9:1 to remove residual ligands. Then, it is heated to 800-900℃ for 4h and naturally cooled to obtain the target catalyst.

[0012] Preferably, the molybdenum source in step (1) is MoO3, the carbon source is glucose, the Ir precursor is H2IrCl6·6H2O, and the Ni precursor is Ni(NO3)2·6H2O.

[0013] Preferably, the ligand in step (1) is citric acid, which reacts with Ir 3+ Ni 2+ Atomic-level dispersion is achieved by forming stable chelates.

[0014] Preferably, the optimal temperature for carbothermal reduction in step (3) is 850°C.

[0015] Preferably, in step (2), the centrifugation speed is 8000×g and the time is 10min, and the precipitate is washed with ethanol at least 3 times.

[0016] An application of the catalyst in the alkaline hydrogen evolution reaction, in 1 M KOH solution, 10 mA / cm 2 Overpotential at current density ≤25mV, Tafel slope ≤29mV / dec, overpotential increase ≤5mV after 1000h of constant current electrolysis.

[0017] Preferably, the catalyst has an atom utilization rate of ≥92% and a precious metal content that is ≥62% lower than that of commercial Pt / C.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The Ir-Ni dual-site synergistic catalytic center constructed in this invention achieves highly efficient synergistic action in the two key steps of the basic HER reaction by activating H2O at the Ni site (energy barrier ≈ 0.35 eV) and optimizing H* desorption at the Ir site (ΔG_H ≈ -0.05 eV). In 1 M KOH solution, 10 mA / cm² 2 The overpotential at current density is as low as 25 mV, which is superior to commercial Pt / C (30 mV) and single-metal site catalysts (Ir single atom@Mo2C is 42 mV, Ni single atom@Mo2C is 75 mV); the Tafel slope reaches 29 mV / dec, which is close to the efficient kinetic characteristics of Pt / C under acidic conditions (28 mV / dec), thus solving the bottleneck problem of slow HER kinetics in alkaline conditions.

[0020] 2. The hexagonal layered structure of Mo2C nanosheets provides stable intercalation sites for Ir and Ni atoms, and the metal-support interaction energy reaches -5.2 eV (far higher than the -2.1 eV of alloy particles), effectively inhibiting atomic migration and aggregation. At 10 mA / cm²... 2 After 1000 hours of constant current electrolysis, the overpotential only increased by 5mV, which is far superior to commercial Pt / C (30mV increase) and traditional alloy catalysts (such as Ir-Ni alloy@Mo2C, which increases by 40mV), meeting the requirements of long-cycle industrial applications.

[0021] 3. Employing a "ligand-assisted solvothermal-carbothermal reduction" process, and utilizing a citric acid chelation and stepwise heating strategy, atomic-level dispersion of Ir and Ni is achieved (active site density reaches 8±1 sites / nm). 2 With an atom utilization rate of up to 92%, it is more than three times that of Ir-Ni alloy nanoparticles (28%) and 163% higher than commercial Pt / C (35%). The high atom utilization rate can reduce the amount of precious metals (especially Ir) by 62%, significantly reducing catalyst costs.

[0022] 4. For the first time, an "atomic-level dispersed Ir-Ni dual-site embedded Mo2C" structure was constructed, through... The site spacing enables efficient migration of H from Ni sites to Ir sites, forming a "Ni activation-Ir desorption" relay mechanism, solving the problem that a single active site cannot simultaneously activate both H and H2O; the innovative preparation method breaks through the technical bottleneck of atomic-level dispersion of bimetals, achieving an active site density of 8 sites / nm. 2 Far exceeding existing methods (<5 particles / nm) 2 ).

[0023] In summary, this invention comprehensively improves the activity, stability, and atom utilization of the catalyst through dual-site synergy, strong support effect, and atomic-level dispersion design, providing a low-cost and efficient solution for alkaline water electrolysis to produce hydrogen. At the same time, it provides a universal approach for the design of other bifunctional electrocatalysts (such as ORR and OER), demonstrating outstanding creativity and industrial application value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the dual-site synergistic catalytic mechanism of basic HER in this invention;

[0025] Figure 2 This is a flowchart of the ligand-assisted solvothermal-carbothermal reduction preparation process in this invention;

[0026] Figure 3 This is a comparison curve of LSV performance in this invention. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] An atomically dispersed alkaline hydrogen evolution catalyst with dual-site embedded Ir-Ni nanosheets, its chemical formula is Ir X Ni Y @Mo2C (x:y = 1:1 - 1:5, x + y = 0.01 - 0.05, with the molar amount of Mo2C being 1), has the following structural formula as shown in Equation 1:

[0029]

[0030] Mo2C nanosheets have a hexagonal layered structure (space group P63 / mmc) with interstitial lattice on their (001) crystal plane;

[0031] Ir atoms and Ni atoms are uniformly embedded in the aforementioned interstitial spaces in a single-atom form, forming Ir-C bonds and Ni-C bonds with bond lengths of [missing information]. and

[0032] The distance between the Ir site and the Ni site is A synergistic catalytic center is formed, in which the Ir site is responsible for optimizing H desorption (ΔG_H≈-0.05eV), and the Ni site is responsible for activating H2O molecules (energy barrier≈0.35eV).

[0033] Preparation method

[0034] The two-step method of "ligand-assisted solvothermal-carbothermal reduction" is adopted, and the specific steps are as follows:

[0035] Precursor preparation: Molybdenum source (e.g., MoO3), carbon source (e.g., glucose), Ir precursor (e.g., H2IrCl6·6H2O), and Ni precursor (e.g., Ni(NO3)2·6H2O) are dissolved in an ethanol-water mixed solvent (volume ratio 1:1) at a molar ratio of Mo:Ir:Ni:C = 2:0.01-0.05:0.01-0.25:5-10. Citric acid (ligand, molar ratio with metal ions 1:1) is added, and the mixture is stirred at 60°C for 2 hours until a sol is formed.

[0036] Solvent-thermal reaction: The sol was transferred to an autoclave and reacted at 180°C for 12 h. After cooling, the black precipitate was collected by centrifugation and vacuum dried (60°C, 12 h) to obtain the Ir-Ni-Mo-OC precursor.

[0037] Carbothermic reduction: The precursor was placed in a quartz tube reactor and pretreated for 2 hours in an Ar / H2 (volume ratio 9:1) atmosphere by heating to 500℃ at 5℃ / min (to remove residual ligands). Then, the temperature was increased to 800-900℃ for reduction for 4 hours. After natural cooling, the target catalyst Ir was obtained. X Ni γ @Mo2C.

[0038] Example 1: Optimal ratio of catalyst Ir 0.02 N i0.08 Preparation and properties of @Mo2C

[0039] step:

[0040] (1) Weigh MoO3 (2 mmol, 0.240 g), glucose (10 mmol, 1.800 g), H2IrCl6·6H2O (0.02 mmol, 0.012 g), and Ni(NO3)2·6H2O (0.08 mmol, 0.024 g), and dissolve them in 50 mL of ethanol-water mixed solvent (25 mL + 25 mL);

[0041] (2) Add citric acid (0.1 mmol, 0.021 g), stir magnetically at 60°C for 2 h to form a dark green sol;

[0042] (3) Transfer the sol to a 100mL autoclave, react at 180℃ for 12h, cool and centrifuge (8000×g, 10min), wash the precipitate three times with ethanol, and dry it under vacuum at 60℃ for 12h to obtain the precursor powder.

[0043] (4) Place the precursor in a quartz boat, put it in a tube furnace, and introduce an Ar / H2 mixture (flow rate 50 mL / min). Increase the temperature to 500℃ at 5℃ / min and hold for 2 hours. Continue to increase the temperature to 850℃ and hold for 4 hours. After natural cooling, collect the black product, i.e., Ir. 0.02 N i0.08 @Mo2C.

[0044] Characterization results:

[0045] XRD: Mo2C characteristic peaks (JCPDS No. 35-0787) appeared at 34.4°, 38.0°, 39.7°, 52.1°, 61.5°, and 69.7°, with no Ir or Ni elemental or alloy peaks, proving atomic-level dispersion;

[0046] AC-HAADF-STEM: Isolated bright spots (Ir and Ni atoms) were observed to be uniformly distributed on the surface of Mo2C nanosheets, with no aggregated particles and a density of approximately 8 ± 1 particles / nm. 2 ;

[0047] XPS: The binding energy of Ir4f7 / 2 is 61.8 eV (Ir-C bond), and the binding energy of Ni2p3 / 2 is 853.2 eV (Ni-C bond), demonstrating the strong interaction between the metal and the support.

[0048] Performance test (1 M KOH solution):

[0049] LSV curve: 10mA / cm 2 The overpotential at current density is 25 mV, which is better than that of commercial Pt / C (30 mV) and Ir single atom@Mo2C (42 mV);

[0050] Tafel slope: 29 mV / dec, close to Pt / C under acidic conditions (28 mV / dec), indicating extremely fast kinetics;

[0051] Stability: Constant current (10mA / cm) 2 After 1000 hours of electrolysis, the overpotential only increased by 5mV, which is far superior to Pt / C (which increased by 30mV).

[0052] Atom utilization rate: 92% calculated by CO chemisorption, which is more than 3 times that of Ir-Ni alloy nanoparticles (28%).

[0053] Example 2: The effect of Ir / Ni ratio on performance (variable x:y)

[0054] With other conditions kept the same as in Example 1, the molar ratio of Ir to Ni was changed, and the results are shown in Table 1 below:

[0055]

[0056] From Table 1 above, we can conclude that when Ir:Ni = 1:4, the dual-site synergistic effect is the strongest, and the H* desorption capacity of Ir and the water activation capacity of Ni reach equilibrium.

[0057] Example 3: The effect of carbothermic reduction temperature on structure (variable reduction temperature)

[0058] With other conditions fixed as in Example 1, the reduction temperature was changed, and the results are shown in Table 2 below:

[0059]

[0060]

[0061] From Table 2 above, we can conclude that 850℃ is the optimal reduction temperature, at which point Mo2C has high crystallinity and a complete nanosheet structure, and the density of active sites is the highest.

[0062] Example 4: The effect of ligand type on dispersibility (variable ligands)

[0063] With other conditions kept the same as in Example 1, the ligand types were changed, and the results are shown in Table 3 below:

[0064] ligands Dispersed State (STEM) <![CDATA[10mA / cm 2 Overpotential (mV) ligand-free Agglomeration of 5-10nm particles 80 Citric acid Atomic-level dispersion (optimal) 25 ethylenediamine Partially aggregated (2-3nm particles) 45

[0065] From Table 3 above, we can conclude that citric acid reacts with Ir... 3+ Ni 2+ Forming stable chelates to effectively inhibit the aggregation of metal ions during the solvothermal process is the key to achieving atomic-level dispersion.

[0066] Example 5: Comparison with the prior art

[0067]

[0068]

[0069] Conclusion: The Ir-Ni dual-site catalyst of this invention, through synergistic effect (Ir optimizes H* desorption and Ni activates H2O), has comprehensive performance superior to single-metal site and alloy catalysts, and its stability and atom utilization are significantly improved.

[0070] Creative explanation

[0071] Structural Innovation: For the first time, an "atomic-level dispersed Ir-Ni dual-site embedded Mo2C" structure was constructed, through... The site spacing enables synergistic catalysis, solving the problem that a single active site cannot simultaneously activate H* and H2O.

[0072] Methodological Innovation: A "ligand-assisted solvothermal-segmented carbothermal reduction" process was developed, utilizing citric acid chelation and a stepwise heating strategy to overcome the technical bottleneck of atomic-level dispersion of bimetals, achieving an active site density of 8 sites / nm. 2 (Existing methods < 5 per nm) 2 );

[0073] Performance breakthrough: Achieving a low overpotential of 25mV and a fast kinetics of 29mV / dec in alkaline HER, with stability exceeding 1000h, and overall performance surpassing commercial Pt / C, providing a low-cost and efficient solution for alkaline water electrolysis to produce hydrogen.

[0074] Comparative Example 1: Commercial Pt / C catalyst (20 wt% Pt)

[0075] Preparation / Source: Commercially available Pt / C (Sigma-Aldrich, Pt particle size 2-3 nm).

[0076] Performance data:

[0077] 10mA / cm 2 Overpotential: 30mV

[0078] Tafel slope: 35mV / dec

[0079] 1000h constant current electrolysis: overpotential increases by 30mV (poor stability)

[0080] Atom utilization rate: 35% (due to Pt particle agglomeration)

[0081] Comparative Example 2: Ir prepared without ligand 0.02 Ni 0.08 @Mo2C

[0082] Preparation differences: The citric acid ligand in Example 1 was omitted, and the remaining steps were the same.

[0083] Structural characteristics: AC-HAADF-STEM showed that Ir-Ni formed 5-10 nm alloy particles with poor dispersibility and an active site density of only 2 per nm. 2 .

[0084] Performance data:

[0085] 10mA / cm 2 Overpotential: 80mV (55mV higher than in Example 1)

[0086] Tafel slope: 78 mV / dec (kinetic sluggishness)

[0087] 1000h stability: Overpotential increases by 50mV (intensified particle aggregation).

[0088] Comparative Example 3: Single Ir site catalyst (Ir 0.10 @Mo2C)

[0089] Preparation differences: No Ni precursor was included, and the Ir loading was increased to 0.10 (equivalent to the total Ir+Ni in Example 1). The remaining steps were the same.

[0090] Structural characteristics: Only Ir single-atom sites exist, with no synergistic effect.

[0091] Performance data:

[0092] 10mA / cm 2 Overpotential: 42mV (17mV higher than in Example 1)

[0093] Tafel slope: 48 mV / dec (weak water activation ability)

[0094] Reason: The lack of Ni sites results in a high energy barrier of 0.62 eV for the H2O dissociation step (DFT calculation).

[0095] Comparative Example 4: Single Ni-site catalyst (Ni 0.10 @Mo2C)

[0096] Preparation differences: No Ir precursor was included, Ni loading was increased to 0.10, and the remaining steps were the same.

[0097] Structural features: Only Ni single-atom sites exist.

[0098] Performance data:

[0099] 10mA / cm 2 Overpotential: 75mV (50mV higher than in Example 1)

[0100] Tafel slope: 65 mV / dec (H* desorption difficulty)

[0101] Reason: The adsorption of H at the Ni sites is too strong (ΔG_H = -0.38 eV), resulting in a high desorption energy barrier.

[0102] Comparative Example 5: Ir prepared by high-temperature reduction 0.02 N i0.08 @Mo2C

[0103] Preparation differences: The carbothermic reduction temperature was changed to 1000℃ (850℃ in Example 1), and the other steps were the same.

[0104] Structural characteristics: XRD shows that Mo2C grains have grown (particle size > 50 nm), and the density of active sites has decreased to 3 per nm. 2 The Ir-Ni site spacing increased to (The synergistic effect disappears.)

[0105] Performance data:

[0106] 10mA / cm 2 Overpotential: 58mV (33mV higher than in Example 1)

[0107] Conductivity: 40% lower than in Example 1 (grain growth hinders electron transport)

[0108] Comparative Example 6: Ir-Ni alloy@Mo2C prepared by conventional impregnation method

[0109] Preparation differences: The impregnation method was used (Mo2C nanosheets were immersed in Ir and Ni salt solutions and then directly reduced at 850℃), without solvothermal and ligand steps.

[0110] Structural characteristics: Forms 10-20nm Ir-Ni alloy particles with weak interaction with the support (XPS shows that the binding energy of Ir4f7 / 2 is 60.5eV, which is metallic Ir).

[0111] Performance data:

[0112] 10mA / cm 2 Overpotential: 60mV (35mV higher than in Example 1)

[0113] 1000h stability: Overpotential increased by 40mV (severe particle shedding)

[0114] Atom utilization rate: 28% (significantly lower than 92% in Example 1)

[0115] Comparison of the core advantages of Example 1 and the comparative example

[0116]

[0117] Catalyst action principle

[0118] The Ir of the present invention X Ni Y The Mo2C catalyst achieves efficient alkaline hydrogen evolution through atomic-level dual-site synergy and electronic modulation of the support. The specific principle is as follows:

[0119] (1) Two-site division of labor and cooperation to break the bottleneck of basic HER dynamics

[0120] The basic hydrogen evolution reaction involves two key steps:

[0121] Water activation and dissociation: H₂O + e⁻ - →H*+OH- (decisive step, requires low energy barrier)

[0122] Desorption of hydrogen species: H* + H* → H2 or H* + H2O + e - →H2+OH- (Requires appropriate H* adsorption energy)

[0123] Ni site function: Ni forms with C The strong coordination bond (confirmed by XPS) shifts the d-band center of Ni upward through electron transfer, enhancing its adsorption capacity for O atoms in H2O and reducing the water activation barrier from 0.62 eV at a single Ir site to 0.35 eV (DFT calculation), thus accelerating the first step of the reaction.

[0124] Function of Ir sites: Ir-C bond length (Slightly longer than Ni-C), which puts the center of the d-band of Ir in an optimized position, and the H adsorption free energy ΔG_H≈-0.05eV (close to the ideal value of 0eV), thus solving the problem of desorption difficulties caused by excessive adsorption at a single Ni site (ΔG_H*=-0.38eV).

[0125] Synergistic effect: Ir-Ni site spacing (AC-HAADF-STEM determination) precisely allows H* to migrate from Ni site (generation) to Ir site (desorption), forming a highly efficient relay mechanism of "Ni activation-Ir desorption", which increases the overall reaction rate by more than 3 times (compared to single metal sites).

[0126] (2) Dual function of Mo2C carrier

[0127] Electronic regulation: Mo₂C exhibits metallic-like electrical conductivity (conductivity 1.2 × 10⁻⁶). 4 S / m), whose hexagonal layered structure transfers electrons to the metal site through Ir-C / Ni-C bonds, modulates the d-band center position (the d-band center of Ir decreases from -2.5eV to -2.8eV), and optimizes the H* adsorption energy.

[0128] Structural stabilization: The (001) interplane of Mo2C provides stable insertion sites for Ir and Ni atoms. The metal-carrier interaction energy reaches -5.2eV (far higher than -2.1eV of alloy particles), which inhibits atomic migration and agglomeration and ensures stability for 1000h.

[0129] (3) High efficiency of atomic-level dispersion

[0130] Atomic-scale dispersion of Ir and Ni (density 8 atoms / nm) achieved by ligand-assisted solvothermal method2 This design ensures that every metal atom is an active site, achieving an atom utilization rate of 92%. In contrast, the alloy particle catalyst (Comparative Example 6) only involves surface atoms in the reaction, with a utilization rate of less than 30%. This invention can reduce the amount of precious metals used by 62% (significantly reducing Ir costs).

[0131] This invention addresses the three major drawbacks of traditional catalysts—low activity, poor stability, and low atom utilization—by designing a synergistic structure of atomically dispersed Ir-Ni dual sites and Mo2C nanosheets, combined with an innovative preparation method. Compared to comparative examples, its core advantages stem from:

[0132] Two-site synergistic optimization of the energy barrier for water activation and H* desorption;

[0133] Strong metal-support interactions inhibit aggregation;

[0134] Atomic-level dispersion maximizes the utilization of precious metals.

[0135] This principle is not only applicable to alkaline hydrogen evolution, but also provides a universal approach for designing other bifunctional electrocatalysts (such as ORR and OER), demonstrating outstanding creativity and industrial application value.

[0136] (1) Example 1 at 10 mA / cm 2 The overpotential at current density is 25 mV, lower than the 30 mV of commercial Pt / C, indicating higher catalytic activity; the Tafel slope is 29 mV / dec, lower than the 35 mV / dec of Pt / C, indicating that the alkaline hydrogen evolution reaction kinetics are faster and closer to the efficient reaction characteristics of Pt under acidic conditions.

[0137] (2) The overpotential of the single Ir site catalyst was 42 mV, and the overpotential of the single Ni site catalyst was 75 mV, both of which were much higher than the 25 mV in Example 1. The reason is that Example 1, through the synergistic effect of the Ir-Ni dual sites, Ni activates H2O (energy barrier 0.35 eV) and Ir optimizes H* desorption (ΔG_H≈-0.05 eV), which breaks through the bottleneck that a single active site cannot take into account both steps of the reaction, and the overall reaction rate is increased by more than 3 times.

[0138] (3) The overpotential of the ligand-free Ir-Ni particle agglomeration catalyst (Comparative Example 2) was 80 mV, and the overpotential of the Ir-Ni alloy catalyst prepared by the conventional impregnation method (Comparative Example 6) was 60 mV, both significantly higher than that of Example 1. This is because Example 1 achieved atomic-level dispersion (active site density 8 sites / nm). 2 This maximizes the exposure of active sites, while particles / alloys only have surface atoms participating in the reaction, resulting in extremely low utilization of active sites.

[0139] (4) In Example 1, after 1000h of constant current electrolysis, the overpotential increased by only 5mV, while that of Pt / C increased by 30mV, and the stability was improved by 83%. The reason is that the Mo2C support and Ir-Ni inhibit atomic migration and aggregation through strong metal-support interaction (binding energy -5.2eV), while Pt / C has poor stability due to the easy oxidation and aggregation of Pt particles.

[0140] (5) The overpotential of the ligandless particulate catalyst (Comparative Example 2) increased by 50 mV after 1000 h, the stability of the catalyst with grain growth caused by high-temperature reduction (Comparative Example 5) decreased, and the overpotential of the alloy catalyst prepared by the conventional impregnation method (Comparative Example 6) increased by 40 mV, all of which were far lower than the stability of Example 1. This is due to the complete Mo2C nanosheet structure formed by reduction at 850 °C in Example 1, which provides stable intercalation sites for metal atoms and inhibits agglomeration or detachment.

[0141] (6) The atomic utilization rate of Example 1 reaches 92%, which is 2.6 times that of commercial Pt / C (35%) and 3.3 times that of Ir-Ni alloy (28%). Atomic-level dispersion makes each Ir and Ni atom an active site, which can reduce the amount of precious metals (especially Ir) by 62%, significantly reduce the cost of catalyst, and solve the problem of waste of active sites caused by particle agglomeration in traditional catalysts.

[0142] (7) Example 1 first constructed an "atomic-level dispersed Ir-Ni dual-site embedded Mo2C" structure. The site spacing ensures efficient migration of H* from Ni to Ir, forming an "activation-desorption" relay mechanism; while in Comparative Example 5, the site spacing increased due to high-temperature reduction. The synergistic effect disappears, and performance degrades.

[0143] (8) Through the “ligand-assisted solvothermal-segmented carbothermal reduction” process, citric acid chelation inhibits metal ion aggregation (compared to Comparative Example 2 without ligands), and reduction at 850℃ forms a pure Mo2C phase (compared to a mixed phase at 700℃ or grain growth at 950℃ in Comparative Example 3), ultimately achieving a high active site density (8 sites / nm). 2 This is significantly higher than the <5 / nm of existing methods. 2 .

[0144] In summary, Example 1, through dual-site synergy, atomic-level dispersion, and strong support, comprehensively surpasses existing catalysts in terms of activity, kinetics, stability, and atom utilization, providing a low-cost and efficient solution for alkaline water electrolysis to produce hydrogen.

[0145] Figure 1 This is a schematic diagram of the dual-site synergistic catalytic mechanism of basic HER, where the left side shows the activation of H2O molecules by the Ni site, the right side shows the optimization of H desorption by the Ir site, and the middle arrow indicates the migration of H from the Ni site to the Ir site.

[0146] Figure 2 Flowchart of the ligand-assisted solvothermal-carbothermal reduction preparation process.

[0147] Figure 3 The LSV performance comparison curves are shown, with the horizontal axis representing overpotential / mV and the vertical axis representing current density / mA·cm. -2 The curve includes: the Ir of this invention 0.02 Ni 0.08 @Mo2C, Commercial Pt / C, Ir single atom @Mo2C, Ni single atom @Mo2C.

[0148] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only to the claims and their full scope and equivalents.

Claims

1. An atomically dispersed alkaline hydrogen evolution catalyst with dual-site embedded Ir-Ni Mo2C nanosheets, characterized in that, The chemical formula is Ir x Ni γ @Mo2C, where x:y=1:1-1:5, x+y=0.01-0.05, with the molar amount of Mo2C being 1; the Mo2C nanosheets have a hexagonal layered structure with space group P63 / mmc, and interstitial lattice exists on its (001) crystal plane; Ir atoms and Ni atoms are uniformly embedded in the interstitial lattice in the form of single atoms, forming Ir-C bonds and Ni-C bonds, with bond lengths of respectively and The distance between the Ir site and the Ni site is A synergistic catalytic center is formed, in which the Ir site is responsible for optimizing H* desorption, ΔG_H≈-0.05eV; the Ni site is responsible for activating H2O molecules, with an energy barrier of ≈0.35eV.

2. The catalyst according to claim 1, characterized in that, The Ir x Ni Y In @Mo2C, the optimal Ir:Ni ratio is 1:

4.

3. The catalyst according to claim 1, characterized in that, The active site density of the Mo2C nanosheets is 8 ± 1 sites / nm. 2 .

4. A method for preparing the catalyst according to any one of claims 1-3, characterized in that, The two-step method of "ligand-assisted solvothermal-carbothermal reduction" includes the following steps: (1) Preparation of precursors: Molybdenum source, carbon source, Ir precursor and Ni precursor were dissolved in a 1:1 volume ratio ethanol-water mixed solvent at a molar ratio of Mo:Ir:Ni:C = 2:0.01-0.05:0.01-0.25:5-10. Ligands were added at a molar ratio of 1:1 to metal ions. The mixture was stirred at 60°C for 2 hours until a sol was formed. (2) Solothermic reaction: The sol was transferred to a high-pressure reactor and reacted at 180°C for 12 h. After cooling, the black precipitate was collected by centrifugation and dried under vacuum at 60°C for 12 h to obtain the Ir-Ni-Mo-OC precursor. (3) Carbothermic reduction: The precursor is placed in a quartz tube reactor and pretreated at 500℃ for 2h in an atmosphere with an Ar / H2 volume ratio of 9:1 to remove residual ligands. Then, it is heated to 800-900℃ for 4h and naturally cooled to obtain the target catalyst.

5. The preparation method according to claim 4, characterized in that, In step (1), the molybdenum source is MoO3, the carbon source is glucose, the Ir precursor is H2IrCl6·6H2O, and the Ni precursor is Ni(NO3)2·6H2O.

6. The preparation method according to claim 4, characterized in that, The ligand mentioned in step (1) is citric acid, which reacts with Ir 3+ Ni 2+ Atomic-level dispersion is achieved by forming stable chelates.

7. The preparation method according to claim 4, characterized in that, The optimal temperature for carbothermal reduction in step (3) is 850°C.

8. The preparation method according to claim 4, characterized in that, In step (2), the centrifugation speed is 8000×g and the time is 10min. The precipitate is washed with ethanol at least 3 times.

9. The application of a catalyst as described in any one of claims 1-3 in an alkaline hydrogen evolution reaction, characterized in that, In 1 M KOH solution, 10 mA / cm 2 Overpotential at current density ≤25mV, Tafel slope ≤29mV / dec, overpotential increase ≤5mV after 1000h of constant current electrolysis.

10. The application according to claim 9, characterized in that, The catalyst has an atom utilization rate of ≥92% and the amount of precious metals used is reduced by ≥62% compared to commercial Pt / C.

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