Porous perovskite type cobalt iron titanate alkaline hydrogen evolution electrocatalyst, preparation method and application

Abstract

The invention relates to the technical field of electro-catalytic materials, in particular to a porous perovskite type cobalt iron titanate alkaline hydrogen evolution electro-catalyst and a preparation method and application thereof.The composite catalyst is composed of layered double hydroxide (LDH) and polyarylpiperidine (PAP), the layered double hydroxide is NiFe-LDH or CoMn-LDH or CuNiFe-LDH, and the polyarylpiperidine (PAP) is a porous perovskite type cobalt iron titanate alkaline hydrogen evolution electro-catalyst and / or a porous perovskite type cobalt iron titanate alkaline hydrogen evolution electro-catalyst and / or a porous perovskite type cobalt iron titanate alkaline hydrogen evolution electro-catalyst and / or a porous perovskite type cobalt iron titanate alkaline hydrogen evolution electro-catalyst. The quaternization degree of the polyaryl piperidine is 70%-90%, and the mass ratio of the layered double hydroxide to the polyaryl piperidine is (1: 0.1)-(1: 0.5). Through the collaborative design of a porous structure, fluorine doping and MXene heterojunction, the alkaline hydrogen evolution reaction (HER) performance is greatly optimized. In a 1M KOH electrolyte, under the current density of 10mA / cm < 2 >, the overpotential is as low as 85mV (embodiment 1), the Tafel slope is only 45mV / dec, the electrochemical impedance is reduced to 0.5 omega, the performance is close to that of a commercial Pt / C catalyst (the overpotential is 60mV) and is far superior to that of a traditional perovskite catalyst (the overpotential is greater than 200mV) and an unoptimized control group (the overpotential is 180-220mV), and the reaction kinetics is remarkably accelerated.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic materials, and in particular to a porous perovskite-type cobalt iron titanate alkaline hydrogen evolution electrocatalyst, a preparation method and applications thereof. Background Art

[0002] The hydrogen evolution reaction (HER) under alkaline conditions is one of the core reactions for hydrogen production by water electrolysis. Its kinetics are limited by the water dissociation step and the hydrogen atom adsorption / desorption equilibrium. Although commercial Pt / C catalysts have excellent HER activity (overpotential ≤ 60mV@10mA / cm 2 ), but scarcity and high cost limit large-scale application. Transition metal perovskite oxides (ABO3) have become an important candidate to replace precious metal catalysts due to their structural tunability, thermal stability and elemental abundance.

[0003] In the prior art, perovskite-type catalysts have low specific surface area (usually <30m 2 / g), poor electrical conductivity (conductivity < 1S / cm), and hydrogen adsorption energy deviating from the optimal value (ΔG_H* ≠ 0eV). For example, the overpotential of unmodified CoFeTiO3 perovskite in 1MKOH often exceeds 200mV@10mA / cm 2 , and the Tafel slope is greater than 100mV / dec, which cannot meet the actual application requirements.

[0004] The present invention solves the technical bottlenecks of insufficient active sites, hindered electron transfer and slow reaction kinetics of traditional perovskite catalysts through a synergistic strategy of porous structure design, fluorine doping regulation and MXene heterostructure construction. Summary of the Invention

[0005] The present invention aims to provide a porous perovskite-type cobalt iron titanate alkaline hydrogen evolution electrocatalyst, a preparation method and an application thereof.

[0006] A fluorine-doped porous perovskite-MXene heterojunction electrocatalyst, characterized in that the chemical formula is CoxFeyTi(O1-zFz)3, wherein 0.4≤x≤0.6, 0.4≤y≤0.6, x+y=1, 0.05≤z≤0.15; forms a heterojunction with Ti3C2Tx-MXene, and the MXene mass accounts for 20%-30%; has a three-dimensional through-hole channel of 30-100nm, and a specific surface area of ​​80-92m 2 / g, porosity 50%-70%.

[0007] In some embodiments, fluorine atoms are interstitially doped in the perovskite lattice, with a fluorine substitution degree z=0.08-0.12, and an F1s peak measured by XPS is located at 684.5±0.3 eV.

[0008] In some embodiments, the MXene is a single layer of Ti3C2Tx with a thickness of 1-2 nm, and the surface functional groups include -OH, -O and -F. The Raman spectroscopy is performed at 200-300 cm -1 The Ti-C characteristic peak is shown at .

[0009] In some embodiments, a Schottky barrier of 0.2-0.3 eV is formed at the heterojunction interface, and the interface potential difference measured by Kelvin probe force microscopy is 0.25±0.03 eV.

[0010] A method for preparing the catalyst comprises:

[0011] (1) Using polystyrene microspheres with a particle size of 50 nm as templates, porous CoFeTiO3 was prepared by a sol-gel method, where the molar ratio of tetrabutyl titanate to Co / Fe nitrate was 2:1 and the sol pH was controlled at 6.0 ± 0.2;

[0012] (2) Porous CoFeTiO3 was impregnated with 0.1M NH4F solution for 24 h, and the secondary calcination temperature was 500-700 °C, and the temperature was kept for 1-2 h;

[0013] (3) Fluorine-doped perovskite and MXene were ultrasonically compounded in a mass ratio of 5:2, with an ultrasonic power of 300 W and a time of 30 min.

[0014] In some embodiments, 0.15 mol of citric acid is added as a chelating agent in the sol-gel process in step (1), and the formed gel is dried at 80° C. in vacuum for 12 h, and then heated to 600° C. at a rate of 5° C. / min and calcined for 3 h.

[0015] In some embodiments, the fluorine-doped perovskite in step (2) shows a lattice constant shrinkage of 0.2%-0.5% as shown by XRD characterization, and Rietveld refinement confirms that fluorine atoms enter the lattice gaps.

[0016] In some embodiments, in 1M KOH electrolyte, the current density is 10 mA / cm 2 The overpotential is ≤105mV, the Tafel slope is ≤60mV / dec, the electrochemical impedance is ≤1.0Ω, and the potential fluctuation is <10mV after 200h stability test.

[0017] In some embodiments, the active site density of the catalyst is ≥2.8×10 19 sites / g, and the hydrogen adsorption free energy ΔG_H* is -0.1±0.05eV.

[0018] In some embodiments, the porous structure shows a pore size distribution concentrated in the range of 30-80 nm by nitrogen adsorption-desorption test, an average pore size of 55±5 nm and a total pore volume of 0.4-0.6 cm 3 / g.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention significantly optimizes the performance of alkaline hydrogen evolution reaction (HER) through the collaborative design of "porous structure + fluorine doping + MXene heterojunction". In 1MKOH electrolyte, 10mA / cm 2 The overpotential at the current density was as low as 85 mV (Example 1), the Tafel slope was only 45 mV / dec, and the electrochemical impedance dropped to 0.5 Ω. The performance was close to that of commercial Pt / C catalysts (overpotential 60 mV), far superior to traditional perovskite catalysts (overpotential > 200 mV) and the non-optimized control group (overpotential 180-220 mV), significantly accelerating the reaction kinetics.

[0021] 2. The catalyst exhibited a potential fluctuation of <10mV during a 200-hour constant current test, an activity retention rate of 93%-98%, and a mass loss of <2%. In comparison, the activity retention rate of conventional perovskite catalysts after 200 hours was only 60% (Comparative Example 1), and even as low as 30% for single metal oxides (Comparative Example 2). The stress buffering effect of the porous framework and the structural protection effect of MXene effectively suppressed catalyst pulverization and loss of active sites, addressing the pain point of poor stability of traditional materials.

[0022] 3. Fluorine doping increases the carrier concentration from 1.5×10 19 cm -3 Increased to 4.8×10 19 cm -3 The electrical conductivity is increased to 40-58S / cm, which is 33-48 times that of unoptimized perovskite (1.2S / cm); the three-dimensional conductive network constructed by MXene further reduces the charge transfer resistance, and combined with 30-100nm through-hole channels (porosity 50%-70%), the electrolyte penetration depth is increased by 3 times, the hydrogen bubble desorption resistance is reduced by 40%, and the mass transfer efficiency is significantly improved.

[0023] 4. The three-dimensional porous structure makes the specific surface area reach 80-92m 2 / g, and the active site density increased to 2.8×10 19 sites / g, which is a typical non-porous perovskite (15m 2 / g). Oxygen vacancies introduced by fluorine doping (1.2×10 19 cm -3) provides abundant active centers for the water splitting reaction, and the hydrogen adsorption free energy (ΔG_H*) is optimized to -0.1±0.05eV, close to the ideal value of Pt (0eV), which greatly improves the intrinsic catalytic efficiency of the active sites.

[0024] 5. The raw materials used are transition metals (Co, Fe, Ti) and MXene, and the cost is only 1 / 20 of commercial Pt / C. The preparation process is based on mature processes such as the sol-gel method and the template method, and does not require complex equipment. The performance can be precisely controlled by adjusting parameters such as the Co / Fe ratio and the calcination temperature (for example, the overpotential is adjustable from 85 to 105 mV), which can adapt to the needs of different scenarios and is easy to industrialize and mass-produce.

[0025] 6. The catalyst is stable in the strong alkaline environment of 1MKOH. The -OH groups on the MXene surface reduce the contact angle from 85° to 42°, solving the problems of poor wettability and rapid activity decay of traditional catalysts in alkaline electrolytes. It is suitable for large-scale alkaline electrolyzer systems and provides an efficient and low-cost non-precious metal solution for green hydrogen production. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] Catalyst composition

[0028] The catalyst provided by the present invention is a fluorine-doped porous perovskite-MXene heterojunction material with the following characteristics:

[0029] Chemical composition: general formula is Co x Fe y Ti(O 1-z F z )3(0.4≤x≤0.6, 0.4≤y≤0.6, x+y=1, 0.05≤z≤0.15), forming a heterojunction with Ti3C2Tx-MXene, with the mass proportion of MXene being 20%-30%.

[0030] Microstructure: three-dimensional porous structure, pore size distribution 30-100nm, porosity 50%-70%, specific surface area 80-92m 2 / g.

[0031] Surface properties: Fluorine atoms replace oxygen sites to form surface defects, and a Schottky barrier (0.2-0.3 eV) is formed at the interface between MXene and perovskite.

[0032] The preparation method is as follows:

[0033] Preparation of porous CoFeTiO3 precursor by template method

[0034] (1) Pretreatment of raw materials: polystyrene microspheres (PS, particle size 50 nm) were washed with ethanol three times and vacuum dried (60 ° C, 2 h); tetrabutyl titanate (C 16 H 36 O4Ti) was dehydrated with molecular sieves; Co(NO3)2·6H2O and Fe(NO3)3·9H2O were of analytical grade and used directly.

[0035] (2) Add 50 mL of anhydrous ethanol to a 500 mL three-necked flask, introduce nitrogen protection, and add 0.05 mol of Co(NO3)2·6H2O and 0.05 mol of Fe(NO3)3·9H2O in sequence under mechanical stirring (300 rpm). After dissolution, slowly add 0.1 mol of tetrabutyl titanate (drop rate 1 mL / min) and continue stirring for 30 min.

[0036] (3) Then, 0.15 mol of citric acid (C6H8O7) was added as a chelating agent, and the pH was adjusted to 6.0±0.2 with 1 M nitric acid. The temperature was raised to 60°C and the reaction was carried out for 2 h to form a light red sol.

[0037] (4) Disperse 1 g of PS microspheres in 10 mL of ethanol, ultrasonicate (200 W) for 10 min until homogeneous, pour into the above sol, and stir at 50 °C for 12 h until gel is formed.

[0038] (5) Calcination: The gel was vacuum dried at 80°C for 12 h to obtain a dry gel block. The block was placed in a muffle furnace and heated to 600°C at a rate of 5°C / min and kept at this temperature for 3 h (in air atmosphere) to complete the template decomposition and oxide crystallization:

[0039]

[0040] After natural cooling, the mixture was ground to obtain porous CoFeTiO3 powder (particle size 2-5 μm).

[0041] Fluorine doping modification

[0042] Impregnation treatment: Take 1g of porous CoFeTiO3 powder, add 50mL of 0.1MNH4F solution, stir at room temperature for 24h, and ultrasonicate (100W) for 5min every 2h to promote the diffusion of fluoride ions.

[0043] Secondary calcination: After filtering, wash with deionized water until the filtrate pH = 7, vacuum dry at 60 ° C for 6 hours, place in a muffle furnace and heat at 5 ° C / min to 500 ° C, and keep warm for 1 hour (nitrogen atmosphere):

[0044]

[0045] (x = 0.1, i.e. fluorine substitution degree 10%)

[0046] MXene heterojunction composite

[0047] MXene preparation: Ti3C2Tx-MXene was prepared by HF etching: 1 g Ti3AlC2 powder was added to 20 mL 40% HF solution, stirred at 35 ° C for 24 h, washed to pH = 6, and vacuum dried to obtain multilayer MXene, which was then peeled off into single-layer sheets (diameter 1-5 μm) by ultrasonication (300 W) for 30 min.

[0048] Composite process: Take 0.5g fluorine-doped porous CoFeTiO3 (F-CoFeTiO3) and 0.2g MXene, add 30mL ethanol, ultrasonicate (300W) for 30min to form a uniform dispersion, and vacuum dry at 60℃ (vacuum degree -0.09MPa) for 8h to obtain F-CoFeTiO3 / MXene heterojunction catalyst.

[0049] The catalyst mechanism of action is supplemented as follows:

[0050] 1. Fluorine doping regulates the electronic structure. After fluorine atoms (electronegativity 3.98) replace oxygen atoms in the perovskite lattice, the catalytic activity is optimized through the following mechanisms:

[0051] The d-band center shifts upward: The strong electronegativity of fluorine shifts the d-band center of Co / Fe from -1.5 eV to -1.2 eV, enhancing the adsorption capacity of hydrogen intermediates (H*), and ΔG_H* is optimized from -0.3 eV to -0.1 eV (close to 0 eV of Pt).

[0052] Surface defect formation: Fluorine substitution generates oxygen vacancies (V_O··), and EPR characterization shows that the defect concentration reaches 1.2×10 19 cm -3 , becoming the active site for the water splitting reaction (Volmer step).

[0053] Increased carrier concentration: Fluorine doping introduces holes (h + ), the carrier concentration was measured from 1.5×10 19 cm -3 Increased to 4.8×10 19 cm -3 , significantly improving the conductivity.

[0054] 2. The three-dimensional porous structure effect, the through-hole channels (30-100nm) constructed by the template method, improve performance through three mechanisms:

[0055] Active site exposure: Specific surface area from 15m2 / g (non-porous) increased to 92m 2 / g, and the active site density reaches 2.8×10 19 sites / g, which is 6 times that of traditional perovskites.

[0056] Mass transfer channel optimization: A porosity of 65% increases the electrolyte penetration depth by 3 times and reduces the hydrogen bubble desorption resistance by 40% (verified by bubble dynamics simulation).

[0057] Stress buffering effect: The porous skeleton can release lattice stress during the reaction and inhibit catalyst pulverization. The mass loss after 200h testing is less than 2%.

[0058] 3. MXene heterojunction synergistic effect

[0059] The interfacial interactions between Ti3C2Tx-MXene and perovskite include:

[0060] Schottky barrier regulation: The interface barrier measured by XPS was 0.25eV, which promoted the transfer of electrons from MXene (work function 4.3eV) to perovskite (work function 4.55eV), and the charge transfer resistance was reduced from 2.1Ω to 0.5Ω.

[0061] Conductive network construction: MXene sheets (conductivity 2×10 4 S / cm) to form a three-dimensional conductive skeleton, which increases the overall conductivity from 1.2S / cm to 58S / cm.

[0062] Optimization of surface hydrophilicity: The -OH groups on the MXene surface reduce the contact angle from 85° to 42°, promoting electrolyte infiltration and bubble discharge.

[0063] Example 1: F-CoFeTiO3 / MXene (Co:Fe:Ti=1:1:2)

[0064] Raw materials and process: Co(NO3)2·6H2O, Fe(NO3)3·9H2O, and tetrabutyl titanate were used as raw materials with a molar ratio of 1:1:2; 50nm polystyrene microspheres were used as templates and porous CoFeTiO3 was prepared by calcining at 600℃ for 3h; it was impregnated with 0.1MNH4F solution for 24h and calcined at 500℃ for 1h (fluorine substitution degree 10%); it was compounded with Ti3C2Tx-MXene in a mass ratio of 5:2, treated with ultrasound at 300W for 30min, and vacuum dried at 60℃ for 8h.

[0065] Structural characterization: three-dimensional porous structure, pore size 30-80nm, porosity 65%, specific surface area 92m 2 / g; fluorine element is evenly distributed in the perovskite lattice, and MXene sheets are tightly combined with perovskite particles; the electrical conductivity is 58S / cm, and the interface potential barrier is 0.25eV.

[0066] Performance test: in 1MKOH electrolyte, 10mA / cm 2 The overpotential at the current density is 85mV, the Tafel slope is 45mV / dec, and the electrochemical impedance is 0.5Ω; after 200h constant current test, the potential fluctuation is <5mV, and the activity retention rate is 98%.

[0067] Example 2: F-Co 0.6 Fe 0.4 TiO3 / MXene (Co:Fe:Ti=3:2:5)

[0068] Raw materials and process: The molar ratio of Co(NO3)2·6H2O and Fe(NO3)3·9H2O was adjusted to 3:2, and the other raw materials were the same as in Example 1; the calcination temperature was increased to 700°C (keeping temperature for 2.5 hours), the secondary calcination temperature was 600°C (keeping temperature for 1.5 hours), and the fluorine substitution degree was 8%; the MXene composite ratio was the same as in Example 1.

[0069] Structural characterization: pore size 40-90nm, specific surface area 85m 2 / g, porosity 60%; the increase of Co element content makes the lattice constant slightly increase to Conductivity 45S / cm.

[0070] Performance test: 10mA / cm 2 The lower overpotential is 98mV, the Tafel slope is 52mV / dec, and the impedance is 0.8Ω; the stability fluctuation after 200h is less than 8mV, and the activity retention rate is 95%.

[0071] Example 3: High-temperature calcination of F-CoFeTiO3 / MXene

[0072] Raw materials and process: The raw material ratio is the same as in Example 1, the template calcination temperature is increased to 800°C (keeping temperature for 2 hours), the secondary calcination temperature is 700°C (keeping temperature for 1 hour), and the fluorine substitution degree is 6%; the MXene composite process remains unchanged.

[0073] Structural characterization: High temperature promotes grain growth, pore size increases to 50-100nm, specific surface area 80m 2 / g, porosity 55%; crystallinity increased to 92%, conductivity 40S / cm.

[0074] Performance test: 10mA / cm 2 The lower overpotential is 105mV, the Tafel slope is 58mV / dec, and the impedance is 1.0Ω; the stability fluctuation after 200h is less than 10mV, and the activity retention rate is 93%.

[0075] Example 4: Fluorine substitution gradient experiment

[0076] Raw materials and process: Maintain Co:Fe:Ti=1:1:2, adjust the NH4F concentration to 0.05M (z=0.05), 0.1M (z=0.10), and 0.15M (z=0.15), and the remaining steps are the same as in Example 1.

[0077] Performance comparison:

[0078] When z = 0.05, the overpotential is 102 mV, the Tafel slope is 50 mV / dec, and ΔG_H* = -0.15 eV;

[0079] When z = 0.10, the overpotential is 85 mV, the Tafel slope is 45 mV / dec, and ΔG_H* = -0.10 eV;

[0080] When z = 0.15, the overpotential is 98 mV, the Tafel slope is 52 mV / dec, and ΔG_H* = -0.08 eV.

[0081] Example 5: MXene composite ratio optimization

[0082] Raw materials and processes: Keeping other conditions unchanged, adjust the MXene mass proportion to 10%, 20%, 30%, and 40%.

[0083] Performance comparison:

[0084] At 10%, the conductivity is 32S / cm and the overpotential is 120mV;

[0085] At 20%, the conductivity is 48S / cm and the overpotential is 95mV;

[0086] At 30%, the conductivity is 58S / cm and the overpotential is 85mV;

[0087] At 40%, the conductivity is 62S / cm, but the active sites are covered and the overpotential rises to 92mV. Comparative Example 1: Non-porous CoFeTiO3 (no template / doping / composite)

[0088] Raw materials and process: The raw material ratio is the same as that in Example 1, but without adding the polystyrene microsphere template, CoFeTiO3 is directly prepared by the sol-gel method and calcined at 600°C for 3h; there is no fluorine doping and MXene composite step.

[0089] Structural characterization: dense block structure, no obvious pores, specific surface area of ​​only 15m 2 / g, conductivity 1.2S / cm, no interface barrier.

[0090] Performance test: 10mA / cm 2The lower overpotential is 180mV, the Tafel slope is 120mV / dec, and the impedance is 5.2Ω; after 200h, the potential drops by 40% and the activity retention rate is 60%.

[0091] Comparative Example 2: Single Metal CoTiO3 (without Fe element)

[0092] Raw materials and process: Only Co(NO3)2·6H2O and tetrabutyl titanate (molar ratio 1:1) were used, without Fe source; no template, fluorine dopant or MXene was added, and the product was calcined at 600℃ for 3h.

[0093] Structural characterization: pure phase CoTiO3, dense structure, specific surface area 10m 2 / g, conductivity 0.8S / cm.

[0094] Performance test: 10mA / cm 2 The lower overpotential was 220 mV, the Tafel slope was 150 mV / dec, and the impedance was 8.5 Ω. After 200 h, the activity was only 30% of the initial value.

[0095] Comparative Example 3: Commercial 20% Pt / C catalyst

[0096] Raw materials and process: Commercially available AlfaAesar 20% Pt / C catalyst (carbon-supported Pt particles, particle size 2-5 nm) was directly used for performance testing.

[0097] Structural characterization: Pt particles are evenly dispersed on the surface of the carbon support with a specific surface area of ​​60m 2 / g, conductivity 120S / cm.

[0098] Performance test: 10mA / cm 2 The lower overpotential is 60mV, the Tafel slope is 30mV / dec, and the impedance is 0.38Ω; the stability fluctuation after 200h is less than 3mV, and the activity retention rate is 99%.

[0099] Comparative Example 4: Fluorine-free control group

[0100] Raw materials and process: The NH4F impregnation step was omitted, and the rest was the same as in Example 1.

[0101] Structure and performance:

[0102] Specific surface area 88m 2 / g, but ΔG_H*=-0.30eV, overpotential 180mV, Tafel slope 120mV / dec, and activity decreased by 40% after 200h.

[0103] Comparative Example 5: Control group without MXene

[0104] Raw materials and process: The MXene compounding step was omitted, and the rest was the same as in Example 1.

[0105] Structure and performance: conductivity 1.2S / cm, charge transfer resistance 5.2Ω, overpotential 180mV, Tafel slope 120mV / dec.

[0106] The summary is as follows: In the example, a 30-100 nm three-dimensional porous structure with a specific surface area of ​​80-92 m was constructed by polystyrene template method. 2 / g, is comparative example 1 (15m 2 / g) by 5-6 times, and the active site density was increased to 2.8×10 19 The porous structure not only increases the contact area between the catalyst and the electrolyte, but also optimizes the hydrogen bubble desorption path through the through-hole channels, solving the core pain point of "insufficient active sites" of traditional perovskite catalysts; after the fluorine atom (electronegativity 3.98) replaces the oxygen site, the d-band center of Co / Fe is shifted up by 0.3eV, and the hydrogen adsorption free energy (ΔG_H*) is optimized from -0.3eV in comparative example 1 to -0.1eV (close to 0eV of Pt), significantly improving the hydrogen intermediate adsorption / desorption equilibrium ability: Compared with MX The heterojunction interface barrier (0.25 eV) formed by ene promotes electron transfer, and the conductivity is improved from 1.2 S / cm in comparative example 1 to 40-58 S / cm, and the charge transfer resistance is as low as 0.5-1.0 Ω, which solves the problem of "poor conductivity and slow reaction kinetics" of perovskite: in the 200h constant current test, the potential fluctuation of the embodiment is less than 10mV, and the activity retention rate is 93%-98%, which is far higher than comparative example 1 (60%) and comparative example 2 (30%), and is close to the stability of commercial Pt / C. At the same time, the raw material cost is only 1 / 20 of that of Pt / C, and it can be prepared through scalable processes such as template method and sol-gel method, which is suitable for industrial mass production: by adjusting the Co / Fe ratio (Example 1 vs. Example 2) and calcination temperature (Example 1 vs. Example 3), the pore size distribution (30-100nm) and fluorine substitution degree (6%-10%) of the catalyst can be precisely controlled to achieve performance adjustment of overpotential 85-105mV, meeting the needs of water electrolysis and hydrogen production in different scenarios (such as Example 1 for low power consumption scenario and Example 3 for high stability scenario): The example shows stable performance in a 1MKOH strong alkaline environment, and optimizes the hydrophilicity (contact angle 42°) by the -OH group on the MXene surface, which solves the problem of "poor wettability and rapid activity decay" of traditional catalysts in alkaline electrolytes, and is suitable for large-scale alkaline electrolyzer systems.

[0107] In summary, the embodiments of the present invention achieve breakthroughs in traditional perovskite catalysts in terms of activity, stability, and cost through the coordinated design of "porous structure + fluorine doping + heterojunction". At the same time, the performance is close to that of commercial Pt / C, providing an efficient and economical solution for alkaline hydrogen evolution.

[0108] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A fluorine-doped porous perovskite-MXene heterojunction electrocatalyst, characterized in that: The general chemical formula is CoxFeyTi(O1-zFz)3, where 0.4≤x≤0.6, 0.4≤y≤0.6, x+y=1, 0.05≤z≤0.15; it forms a heterojunction with Ti3C2Tx-MXene, with MXene accounting for 20%-30% of the mass; it has three-dimensional through-holes of 30-100nm and a specific surface area of ​​80-92m 2 / g, porosity 50%-70%.

2. The catalyst according to claim 1, characterized in that Fluorine atoms exist in the perovskite lattice as interstitial doping, with a fluorine substitution degree z=0.08-0.12, and an F1s peak measured by XPS is located at 684.5±0.3 eV.

3. The catalyst according to claim 1, characterized in that The MXene is a single-layer Ti3C2Tx layer with a thickness of 1-2 nm and surface functional groups including -OH, -O and -F. The Raman spectroscopy can detect the presence of -1 The Ti-C characteristic peak is shown at .

4. The catalyst according to claim 1, characterized in that The heterojunction interface forms a Schottky barrier of 0.2-0.3 eV, and the interface potential difference measured by Kelvin probe force microscopy is 0.25±0.03 eV.

5. A method for preparing the catalyst according to claim 1, characterized in that include: (1) Using polystyrene microspheres with a particle size of 50 nm as templates, porous CoFeTiO3 was prepared by a sol-gel method, where the molar ratio of tetrabutyl titanate to Co / Fe nitrate was 2:1 and the sol pH was controlled at 6.0 ± 0.2; (2) Porous CoFeTiO3 was impregnated with 0.1M NH4F solution for 24 h, and the secondary calcination temperature was 500-700 °C, and the temperature was kept for 1-2 h; (3) Fluorine-doped perovskite and MXene were ultrasonically compounded in a mass ratio of 5:2, with an ultrasonic power of 300 W and a time of 30 min.

6. The preparation method according to claim 5, characterized in that In step (1), 0.15 mol of citric acid was added as a chelating agent during the sol-gel process. The formed gel was dried at 80° C. in vacuum for 12 h, and then heated to 600° C. at a rate of 5° C. / min and calcined for 3 h.

7. The preparation method according to claim 5, characterized in that The XRD characterization of the fluorine-doped perovskite in step (2) showed that the lattice constant shrank by 0.2%-0.5%, and Rietveld refinement confirmed that fluorine atoms entered the lattice gap.

8. Use of the catalyst according to claim 1 in alkaline hydrogen evolution, characterized in that: In 1M KOH electrolyte, current density 10mA / cm 2 The overpotential is ≤105mV, the Tafel slope is ≤60mV / dec, the electrochemical impedance is ≤1.0Ω, and the potential fluctuation is <10mV after 200h stability test.

9. The use according to claim 8, characterized in that The active site density of the catalyst is ≥2.8×10 19 sites / g, and the hydrogen adsorption free energy ΔG_H* is -0.1±0.05eV.

10. The catalyst according to claim 1, characterized in that The porous structure was tested by nitrogen adsorption and desorption, and the pore size distribution was concentrated in the range of 30-80 nm. The average pore size calculated by the BJH model was 55±5 nm, and the total pore volume was 0.4-0.6 cm 3 / g.

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