A carbon skeleton supported platinum monatomic-cobalt nanoparticle catalyst, a preparation method thereof and application thereof in electrocatalytic hydrogen evolution

Abstract

The application belongs to the technical field of electrocatalysis and energy conversion, and provides a carbon skeleton loaded platinum monatomic-cobalt nanoparticle catalyst, a preparation method thereof and application thereof in electrocatalytic hydrogen evolution, wherein a ZIF-67@ZIF-8 precursor is prepared by an epitaxial growth method, and a carbon matrix containing cobalt nanoparticles is constructed by pyrolysis of the precursor; in the preparation process of the ZIF-67@ZIF-8, the length of tannic acid treatment is regulated, and the size of the cobalt nanoparticles is precisely controlled; meanwhile, the uniform N holes generated in the high-temperature pyrolysis process are beneficial to the precise confinement of Pt-N bonds, and finally the carbon skeleton loaded platinum monatomic-cobalt nanoparticle catalyst is constructed. The cobalt enriches the local proton concentration around the platinum sites, thereby significantly promoting the adsorption of protons on the platinum monatomic and the generation of hydrogen. The exhibition of this dual functional catalytic effect effectively improves the overall catalytic efficiency of the alkaline hydrogen evolution reaction. The application shows excellent catalytic performance in the alkaline hydrogen evolution reaction, and is expected to be widely applied in the water electrolysis hydrogen production technology.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrocatalysis and energy conversion, and particularly relates to a carbon skeleton loaded platinum monatomic cobalt nanoparticle catalyst, a preparation method thereof and application thereof in electrocatalytic hydrogen evolution, so as to realize efficient alkaline hydrogen evolution (HER). More specifically, the present application prepares a double-packaged MOF precursor (ZIF-8@ZIF-67 NB) by epitaxial growth, and constructs a carbon matrix containing Co nanoparticles by pyrolysis. In the preparation process of ZIF-67@ZIF-8, tannic acid with multiple phenolic hydroxyl groups can replace dimethyl imidazole and form a stable complex with metal ions to regulate the MOF framework structure. By regulating the tannic acid treatment time (TA x ZIF-67@ZIF-8 NB), the size of Co nanoparticles can be precisely controlled, and platinum monatomic particles can be precisely confined in the carbon skeleton by Pt-N bond to construct a cubic carbon skeleton loaded Pt monatomic-Co nanoparticle catalyst. The catalyst shows excellent catalytic performance in the alkaline hydrogen evolution reaction, and is expected to be widely used in water electrolysis hydrogen production technology. BACKGROUND

[0002] Water electrolysis hydrogen evolution as an effective way to produce and store new energy by renewable energy has attracted widespread attention. Pt-based catalysts are considered to be the best catalysts for catalyzing HER under alkaline conditions. However, the high price and scarcity of Pt have caused people's cost concerns about the large use of Pt catalysts. Pt supported catalysts have become a good substitute. However, Pt monatomic active sites are prone to aggregation to form clusters, resulting in reduced catalytic activity. At the same time, individual active sites have a problem of competing adsorption of OH* and H* in the HER reaction, resulting in slow electrocatalytic kinetics. Therefore, it is necessary to design a dual-site catalyst such as Pt particle-Pt atom to overcome the problem of competing adsorption of OH* and H*.

[0003] Dual-site catalysts include homonuclear (such as Pd particle-Pd atom) and heteronuclear catalysts (Ru particle-Pt atom). Compared with homonuclear, heteronuclear catalysts are beneficial to the identification of active sites. For this particle-monatomic catalyst, the selection of transition metal nanoparticles with moderate OH adsorption capacity is not only beneficial to avoid the use of noble metals, but also can accelerate water splitting by adsorbing OH. Co nanoparticles have strong OH adsorption capacity and become a suitable candidate material. The HER performance of Co nanoparticle material mainly depends on its lattice structure, size and surface properties. By reasonably designing the size of Co nanoparticle material, the adsorption strength of OH can be regulated, and the synergistic effect of Co nanoparticle and Pt can be precisely regulated to improve the HER activity of the catalyst. SUMMARY

[0004] This invention provides a carbon-framework supported platinum single-atom-cobalt nanoparticle catalyst, its preparation method, and its application in electrocatalytic hydrogen evolution. The invention utilizes a method of controlling the Co size in a "Co nanoparticle-Pt single-atom" dual-site catalyst through tannic acid etching, aiming to significantly improve the alkaline HER catalytic performance by controlling the size of the Co particles and achieving a synergistic effect between the two components. Different Co nanoparticles have varying effects on OH... ad Depending on the degree of adsorption, suitable Co nanoparticles require less energy to decompose water. At the same time, they can enrich the local proton concentration around Pt sites by adsorbing OH, thereby significantly promoting the adsorption of protons on Pt single atoms and the generation of hydrogen.

[0005] This invention is achieved using the following technical solution: a method for preparing a carbon-framework-supported platinum single-atom-cobalt nanoparticle catalyst, wherein a ZIF-67@ZIF-8 precursor is prepared by epitaxial growth, and then pyrolyzed to construct a carbon matrix containing Co nanoparticles; during the preparation of ZIF-67@ZIF-8, the tannic acid treatment time is controlled to precisely control the size of the Co nanoparticles; simultaneously, the uniform N vacancies generated during the high-temperature pyrolysis process facilitate the precise confinement of Pt−N bonds, thereby allowing for the experimental analysis of the atomic state distribution of Pt; finally, a carbon-framework-supported platinum single-atom-cobalt nanoparticle catalyst is constructed.

[0006] Further steps include the following:

[0007] (1) Preparation of ZIF-8@ZIF-67 precursor by tannic acid treatment:

[0008] Synthesis of ZIF-8 nanocubes ZIF-8 NB: 5 mL of an aqueous solution containing 300 mg zinc acetate dihydrate Zn(CH2COO)2 was slowly added to 5 mL of an aqueous solution containing 1116 mg dimethylimidazole and 0.8 mg cetyltrimethylammonium bromide CTAB; the mixture was shaken for 10 s and allowed to stand at room temperature for 2 h; the resulting ZIF-8 NC was washed several times with ultrapure water and then dried in a drying oven;

[0009] Synthesis of ZIF-67-coated ZIF-8 nanocubes (ZIF-67@ZIF-8 NB): 360 mg of synthesized ZIF-8 nanocubes were added to 72 mL of ultrapure water and ultrasonically dispersed to obtain solution A; simultaneously, 456.3 mg of cobalt nitrate hexahydrate and 23.67 mg of CTAB were added to 16 mL of ultrapure water, ultrasonically dispersed, and then added to solution A to obtain solution B; 7.134 g of dimethylimidazole was uniformly dispersed in 110 mL of ultrapure water to obtain solution C. Solution C was then slowly added to solution B, stirred for 24 h, centrifuged, and dried to obtain ZIF-67@ZIF-8 NB.

[0010] Synthetic tannic acid-modified ZIF-67-coated ZIF-8 nanocube TA x -ZIF-67@ZIF-8 NB: Under light-protected conditions, 600 mg of tannic acid was dispersed in 133 mL of ultrapure water to prepare a tannic acid solution. 400 mg of ZIF-67@ZIF-8 NB was dispersed in a mixture of 200 mL of ultrapure water and 20 mL of ethanol, and then slowly added to the tannic acid solution. The tannic acid treatment time was adjusted to 0-16 h. The corresponding material was named TA. x -ZIF-67@ZIF-8 NB, where x The processing time for tannic acid;

[0011] (2) Preparation of TA x -ZIF-67@ZIF-8 NB-derived carbon TA x -ZIF-67@ZIF-8 NB-C: TA obtained in step (1) x The ZIF-67@ZIF-8 NB precursor was placed in a ceramic boat and then placed in a tube furnace. The temperature was increased to 920°C at a rate of 2°C / min and held at that temperature for 180 min in an argon atmosphere. After cooling to room temperature, it was removed.

[0012] (3) Preparation of Co nanoparticles of different sizes-Pt single-atom catalysts Co nx -Pt1@C NB: 50 mg of TA obtained in step (2) x -ZIF-67@ZIF-8 NB-C sample was dispersed in 10 mL of ultrapure water and ultrasonically dispersed for 20 min to obtain a homogeneous suspension; 560 μL of chloroplatinic acid hexahydrate aqueous solution (20 mg / mL) was slowly added; after stirring at 10-80℃ for 16 h, the suspension was centrifuged; the precipitate was washed with ultrapure water and then dried overnight under vacuum at 60℃ to obtain Co. nx -Pt1@C NB, where n refers to nanoparticles. x This refers to the treatment time for tannic acid.

[0013] This invention also provides a carbon-framework-supported platinum single-atom-cobalt nanoparticle catalyst Co prepared using the method described above. nx -Pt1@C NB.

[0014] This invention also provides the carbon-framework supported platinum single-atom-cobalt nanoparticle catalyst Co. nx Application of -Pt1@C NB in ​​electrocatalytic hydrogen evolution.

[0015] Furthermore, a carbon framework was used to support platinum single-atom-cobalt nanoparticle catalysts Co. nxA dispersion of -Pt1@C NB was coated on a carbon paper surface as the working electrode, a carbon rod as the counter electrode, and a mercury / mercury oxide electrode as the reference electrode to form a three-electrode system for alkaline HER reaction. The electrocatalytic performance of the catalyst was evaluated by linear sweep voltammetry (LSV), Tafel slope, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) using an electrochemical workstation.

[0016] Furthermore, the specific method is as follows: 2.5 mg of powdered Co nx -Pt1@C NB sample was dispersed in a mixed solution of 100 μL ethanol and 135 μL ultrapure water. After ultrasonic dispersion, 15 μL Nafion reagent was added to the mixed solution and ultrasonic dispersion was continued at ≤20℃ for 1 h to obtain catalyst ink.

[0017] Using a microsyringe, 20 μL of ink was repeatedly dropped onto a 0.5*0.5 cm carbon paper in 10 separate drops, and then dried at room temperature to prepare a working electrode.

[0018] A three-electrode system was formed by selecting a carbon rod as the counter electrode, a mercury / mercury oxide electrode as the reference electrode, and carbon paper coated with catalyst ink as the working electrode. The catalyst was evaluated by linear sweep voltammetry (LSV), Tafel slope, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) using an electrochemical workstation.

[0019] First, the mercury / mercury oxide electrode was reversibly calibrated using a hydrogen electrode (RHE). Calibration was performed in a high-purity H₂-saturated 1 M KOH solution, using two Pt foils as the working and counter electrodes, respectively, with the mercury / mercury oxide electrode as the reference electrode. The calibration was conducted at 2 mV s⁻¹ within a potential range of -0.7 to -1.1 V. -1 Cyclic voltammetry (CV) was performed at a scan rate of [missing value], and the average of the two potentials at which the current was zero was taken as the thermodynamic potential of the hydrogen electrode reaction; the CV results for RHE calibration of mercury / mercury oxide in 1 M KOH can be described as E( [missing value]. vs. RHE) = E ( vs. Mercury / mercury oxide) +0.912 V;

[0020] The three-electrode system was then placed in Ar-saturated 1 M KOH at -0.8 V to -1.25 V. vs. Within the potential range of RHE, linear sweep voltammetry was used at 5 mV s. -1 Perform LSV testing to detect Co nx -Pt1@C NB HER behavior under alkaline conditions; Tafel slope was determined by plotting the current density versus the logarithm of the overpotential (log |j|);

[0021] EIS measurement is in 10 5 Hz to 10 -2 The frequency range is Hz, with an amplitude of 5 mV, at different -0.034 V ( vs. Impedance testing was performed at the RHE potential; the solution resistance R was obtained from the impedance spectrum. s Then use E = E RHE -90%iR s To perform liquid resistance correction on the LSV curve;

[0022] The electrochemically active surface area (ECSA) of this three-electrode system was determined using cyclic voltammetry: from 0.117 to 0.317 V. vs. Within the potential range of RHE, at values ​​of 20, 40, 60, 80, 100, and 120 mV respectively. -1 Perform CV testing on the scan rate; plot Δj / 2 = (j 阳极 -j 阴极 The slope of the graph showing the relationship between ) / 2 and scan rate represents the electrochemical double-layer capacitance (C). dl ), j 阳极 and j 阴极 They represent 0.217 V ( vs. The current density under RHE (Reverse Electrochemical Hypothesis) scans at the anodic and cathode was measured; the ECSA (Electrochemical Double Layer Capacitance) was calculated using the relationship between electrochemical double layer capacitance and capacitance per unit surface area; the formula is: ECSA = C dl / C s , where C s It is the capacitance per unit surface area, which is generally a known constant for a specific electrode material.

[0023] In this invention, the precursor ZIF-67@ZIF-8 is etched with tannic acid and then thermally decomposed to construct a carbon matrix containing Co nanoparticles of different sizes. Simultaneously, Pt single atoms are precisely confined within the carbon framework via Pt−N bonds, thus synthesizing nitrogen-doped carbon hollow nanocubes (Co nanoparticles) loaded with Co nanoparticles of different sizes and Pt single atoms. nx -Pt1@C NB). Co nanoparticles for OH ad Co exhibits stronger adsorption and requires less energy to decompose water. Co enriches the local proton concentration around Pt sites, thereby significantly promoting the adsorption of protons on Pt single atoms and the generation of hydrogen. This bifunctional catalytic effect effectively improves the overall catalytic efficiency of the alkaline hydrogen evolution reaction.

[0024] This invention investigates the effect of tannic acid treatment time in precursors on Co nxThe effect of -Pt1@C on the performance of the NB catalyst is shown. Treatment with tannic acid for an appropriate time yields the best alkaline HER catalytic activity. This structure exhibits uniformly distributed Co nanoparticles with a particle size of approximately 10 nm. This structure not only provides the material with a large specific surface area but also endows it with excellent conductivity and dispersibility, significantly improving the HER performance of the prepared electrode material under alkaline conditions. Compared with existing technologies, the improvement in alkaline HER performance is mainly attributed to its unique structural design. By precisely controlling the synergistic effect of Co nanoparticles and single-atom Pt, the material exhibits higher electrocatalytic activity, better stability, and durability. This innovative design provides a new direction for the development of future high-efficiency electrocatalysts. Attached Figure Description

[0025] Figure 1 Samples treated with tannic acid for 4 h at different resolutions (Co) n4 Transmission electron microscope (TEM) image of Pt1@C NB; the scale bars in the image are: A and B = 10 nm; C = 20 nm; D = 50 nm; E and F = 100 nm.

[0026] Figure 2 Potential calibration of the reference electrode for RHE;

[0027] Figure 3 LSV curves (a) and Tafel curves (b) for samples treated with tannic acid for different durations;

[0028] Figure 4 Impedance plots for samples treated with tannic acid for different durations at a potential of -965 mV (relative to a saturated calomel electrode);

[0029] Figure 5 a represents the untreated sample in 1M KOH at different scan rates (from 20 mV s). -1 up to 20 mV s -1 Cyclic voltammetry curves of the sample at 0.117–0.317 V (relative to a saturated calomel electrode); Figure 5 b represents the tannic acid-treated samples after 4 h of treatment in 1M KOH at different scan rates (from 20 mV / s). -1 up to 20 mV s -1 Cyclic voltammetry curves of the sample at 0.117–0.317 V (relative to a saturated calomel electrode); Figure 5 The double-layer capacitance current as a function of scan rate, calculated at c = 0.217 V (relative to a saturated calomel electrode). Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but 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.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0032] Equivalent technologies of the specific embodiments described herein that are readily apparent to those skilled in the art through routine experimentation are included in this application.

[0033] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the instruments and equipment used in the following examples are all standard laboratory instruments and equipment; unless otherwise specified, the experimental materials used in the following examples were all purchased from regular biochemical reagent stores.

[0034] 1. Carbon-framework supported platinum single-atom-cobalt nanoparticle catalyst Co nx Preparation of -Pt1@C NB

[0035] (1) Preparation of tannic acid-treated ZIF-8@ZIF-67 precursor

[0036] Synthesis of ZIF-8 nanocubes (ZIF-8 NB): 5 mL of an aqueous solution containing 300 mg zinc acetate dihydrate (Zn(CH2COO)2) was slowly added to 5 mL of an aqueous solution containing 1116 mg dimethylimidazole and 0.8 mg hexadecyltrimethylammonium bromide (CTAB). The mixture was shaken for 10 s and allowed to stand at room temperature for 2 h. The resulting ZIF-8 NC was washed several times with ultrapure water and then dried in a drying oven.

[0037] Synthesis of ZIF-67-coated ZIF-8 nanocubes (ZIF-67@ZIF-8 NB): 360 mg of ZIF-8 was added to 72 mL of ultrapure water and ultrasonically dispersed to obtain solution A. Simultaneously, 456.3 mg of cobalt nitrate hexahydrate and 23.67 mg of CTAB were added to 16 mL of ultrapure water, ultrasonically dispersed, and then added to solution A to obtain solution B. 7.134 g of dimethylimidazole was uniformly dispersed in 110 mL of ultrapure water to obtain solution C. Solution C was then slowly added to solution B, stirred for 24 h, centrifuged, and dried to obtain ZIF-67@ZIF-8 NB.

[0038] Synthesis of ZIF-8 nanocubes coated with tannic acid-modified ZIF-67 (TA) x -ZIF-67@ZIF-8 NB): 600 mg of tannic acid was dispersed in 133 mL of ultrapure water to prepare a tannic acid solution (due to the photodegradation of tannic acid, the light was turned off during weighing, and the beaker containing the tannic acid solution was wrapped with aluminum foil or tin foil to protect it from light). 400 mg of ZIF-67@ZIF-8 NB was dispersed in a mixture of 200 mL of ultrapure water and 20 mL of ethanol, and then slowly added to the tannic acid solution. Since the main variable in this experiment was the tannic acid treatment time (0-16 h), the corresponding material was named TA. x -ZIF-67@ZIF-8 NB, where x To determine the treatment time for tannic acid, experiments were conducted with treatment times of 0, 1, 4, 8, and 16 hours. The resulting materials were named TA0-ZIF-67@ZIF-8 NB, TA1-ZIF-67@ZIF-8 NB, TA4-ZIF-67@ZIF-8 NB, TA8-ZIF-67@ZIF-8 NB, and TA4-ZIF-67@ZIF-8 NB, respectively. 16 -ZIF-67@ZIF-8 NB;

[0039] (2) Preparation of TA x -ZIF-67@ZIF-8 NB derived carbon (TA) x -ZIF-67@ZIF-8 NB-C): TA obtained in step (1) x -ZIF-67@ZIF-8 NB was placed in a porcelain boat. The prepared porcelain boats were then placed in a tube furnace and heated to 920°C at a heating rate of 2°C / min, and held at that temperature for 180 min in an argon atmosphere. After cooling to room temperature, it was removed to obtain TA. x -ZIF-67@ZIF-8 NB-C.

[0040] (3) Preparation of Co nanoparticle-Pt single-atom catalyst (Co nx -Pt1@C NB): Take the TA obtained in step (2) x A ZIF-67@ZIF-8 NB-C sample (50 mg) was dispersed in 10 mL of ultrapure water and then ultrasonically dispersed for 20 min to obtain a homogeneous suspension. Next, 560 μL of an aqueous solution of chloroplatinic acid hexahydrate (20 mg / mL) was slowly added. After stirring at 10–80 °C for 16 h, the suspension was centrifuged. The precipitate was washed several times with ultrapure water and then dried overnight under vacuum at 60 °C.

[0041] Figure 1Samples treated with tannic acid for 4 hours (Co) n4 Transmission electron microscopy (TEM) image of -Pt1@C NB, showing Co. n4 -Pt1@C NB has a smooth surface, a regular core-shell structure with a hexahedral structure, and large, uniformly distributed Co nanoparticles with a particle size of approximately 10 nm. The particles are also visibly encapsulated by a thin carbon layer, which helps protect them from corrosion during electrochemical processes, thus improving the Co nanoparticle size distribution. n4 - Corrosion resistance and stability of Pt1@C NB catalyst.

[0042] 2. Electrochemical performance testing of HER under alkaline conditions

[0043] 2.5 mg of powdered sample was dispersed in a mixed solution of 100 μL ethanol and 135 μL ultrapure water. After uniform ultrasonic dispersion, 15 μL of Nafion reagent was added to the mixed solution, and ultrasonic dispersion was continued for 1 h at a temperature below 20 ℃ to obtain catalyst ink. 20 μL of ink was repeatedly added dropwise to 0.5*0.5 cm carbon paper in 10 separate drops using a microsyringe, and then dried at room temperature.

[0044] A three-electrode system was formed by selecting a carbon rod as the counter electrode, a mercury / mercury oxide electrode as the reference electrode, and carbon paper coated with catalyst ink as the working electrode. The catalyst was evaluated by linear sweep voltammetry (LSV), Tafel slope, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) using an electrochemical workstation.

[0045] First, the mercury / mercury oxide electrode was calibrated using a reversible hydrogen electrode (RHE). Calibration was performed in a high-purity H₂-saturated 1 M KOH solution, using two Pt foils as the working and counter electrodes, respectively, with the mercury / mercury oxide electrode as the reference electrode. Calibration was performed at 2 mV s⁻¹ within a potential range of -0.7 to -1.1 V. -1 Cyclic voltammetry (CV) was performed at a scan rate of [missing value], and the average of the two potentials at which the current was zero was taken as the thermodynamic potential of the hydrogen electrode reaction. The CV results for RHE calibration of mercury / mercury oxide in 1 M KOH can be described as E( [missing value]. vs. RHE) = E ( vs. Mercury / mercury oxide) +0.912 V. Figure 2 The potential calibration value of the reference electrode relative to RHE can be obtained.

[0046] The three-electrode system was then placed in Ar-saturated 1 M KOH at -0.8 V to -1.25 V. vs. Within the potential range of RHE, linear sweep voltammetry was used at 5 mV s. -1Perform LSV testing to detect Co nx -Pt1@C NB exhibits HER behavior under alkaline conditions. The Tafel slope was determined by plotting the current density against the logarithm of the overpotential (log |j|).

[0047] EIS measurement is in 10 5 Hz to 10 -2 The frequency range is Hz, with an amplitude of 5 mV, at different -0.034 V ( vs. Impedance testing was performed at the RHE potential. The solution resistance R can be obtained from the impedance spectrum. s Then use E = E RHE -90%iR s To perform liquid resistance correction on the LSV curve.

[0048] The electrochemically active surface area (ECSA) of this three-electrode system was determined using cyclic voltammetry. The ECSA ranged from 0.117 to 0.317 V. vs. Within the potential range of RHE, at values ​​of 20, 40, 60, 80, 100, and 120 mV respectively. -1 The scan rate was used for CV testing. The plot Δj / 2 = (j 阳极 -j 阴极 The slope of the graph showing the relationship between ) / 2 and scan rate represents the electrochemical double-layer capacitance (C). dl ), j 阳极 and j 阴极 They represent 0.217 V ( vs. Current density of the anode and cathode scans under RHE).

[0049] The electrochemical double-layer capacitance (ECSA) is calculated using the relationship between the electrochemical double-layer capacitance and the capacitance per unit surface area. The formula is: ECSA = C dl / C s , where C s It is the capacitance per unit surface area, which is generally a known constant for a specific electrode material.

[0050] 3. Actual Sample Testing: First, following the method shown in step 2, the synthesized carbon framework-supported platinum single-atom-cobalt nanoparticle catalyst Co... nx -Pt1@C NB was uniformly coated onto carbon paper to prepare a working electrode for electrochemical testing. Subsequently, an electrochemical workstation was used to measure the hydrogen evolution reaction (HER) activity of the sample under alkaline conditions in a three-electrode system, performing LSV, EIS, and CV tests sequentially according to the same electrochemical testing method as in step 2. Following the method shown in step 2, the R value obtained from the EIS was... s The LSV curves were corrected for liquid resistance and the electrochemically active surface area of ​​the material was calculated.

[0051] The LSV curve was corrected for liquid resistance to obtain the attached... Figure 3 ,from Figure 3 From a, we can derive the current density as 10 mA cm⁻¹. -2 When treated with tannic acid for 0 h, 1 h, 4 h, 8 h, and 16 h, the overpotentials were 0.058 V, 0.037 V, 0.033 V, 0.037 V, and 0.045 V, respectively. This indicates that a tannic acid treatment duration of 4 h at 10 mA cm⁻¹... -2 It exhibits the lowest overpotential, indicating that it possesses the strongest catalytic activity.

[0052] from Figure 3 From b, we can obtain the Tafel slopes of the samples treated with tannic acid for 0 h, 1 h, 4 h, 8 h, and 16 h as 85.5 mV dec. -1 65.7 mV dec -1 57.1 mV dec -1 58.9 mV dec -1 64.9 mV dec -1 This shows that the tannic acid treatment time of 4 h has the lowest Tafel slope, indicating that it has the fastest catalytic kinetics.

[0053] As the processing time increased, the catalytic activity of the Co nanoparticles first increased and then decreased, indicating that only Co nanoparticles of suitable size can achieve optimal synergistic catalysis with Pt single atoms. If the Co nanoparticles are too small, the adsorption of OH* will be too weak, resulting in limited hydrogen proton coverage on the Pt surface; if they are too large, the adsorption of OH* will be too strong, preventing the dissociation of OH* and thus hindering the continuous supply of hydrogen protons to the Pt surface.

[0054] from Figure 4 The EIS spectra showed that the charge transfer resistance of the sample treated with tannic acid for 4 hours was much lower than that of the samples treated with tannic acid for other durations, thus proving that Co n4 -Pt1@C NB exhibits low charge transfer resistance and fast electron transfer rate, resulting in rapid HER kinetics, particularly in alkaline electrolytes.

[0055] from Figure 5 The results show that the double-layer capacitance of the samples without tannic acid treatment and those treated with tannic acid for 4 hours were 28.3 mF cm⁻¹. -2 and 34.0 mF cm -2 The sample treated with tannic acid for 4 h exhibited a larger double-layer capacitance, indicating that tannic acid treatment improved the Co content. n4 -Pt1@C NB catalyst has an active specific surface area. This is an important factor in improving the activity of electrocatalytic HER.

[0056] Based on the above test results, it can be seen that the Co nanoparticle-Pt single-atom catalyst constructed in this invention exhibits excellent electrocatalytic HER activity under alkaline conditions. This catalyst not only effectively enhances the hydrogen evolution reaction rate through precise control of the synergistic effect of Co nanoparticles and Pt single atoms, but also exhibits a low Tafel slope, further demonstrating its high catalytic efficiency in alkaline media. In summary, this novel catalyst provides an effective approach to improving the efficiency of alkaline electrocatalytic HER and has potential application prospects.

[0057] In this invention, the precursor ZIF-67@ZIF-8 is etched with tannic acid and then thermally decomposed to construct a carbon matrix containing Co nanoparticles. Simultaneously, Pt single atoms are precisely confined within the carbon framework via Pt−N bonds, thus synthesizing nitrogen-doped carbon hollow nanocubes (Co nanoparticles and Pt single atoms supported on the precursor ZIF-67@ZIF-8). nx -Pt1@C NB).

[0058] This invention investigates the effect of tannic acid treatment time in precursors on Co nx The effect of -Pt1@C on the performance of the NB catalyst is shown. Treatment with tannic acid for an appropriate time yields the best alkaline HER catalytic activity. This structure exhibits uniformly distributed Co nanoparticles with a particle size of approximately 10 nm. This structure not only provides the material with a large specific surface area but also endows it with excellent conductivity and dispersibility, significantly improving the HER performance of the prepared electrode material under alkaline conditions. Compared with existing technologies, the improvement in alkaline HER performance is mainly attributed to its unique structural design. By precisely controlling the synergistic effect of Co nanoparticles and single-atom Pt, the material exhibits higher electrocatalytic activity, better stability, and durability. This innovative design provides a new direction for the development of future high-efficiency electrocatalysts.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a carbon-framework supported platinum single-atom-cobalt nanoparticle catalyst, characterized in that: ZIF-67-coated ZIF-8 was prepared by epitaxial growth, and the precursor was designated ZIF-67@ZIF-8. Tannic acid was used to modify the precursor, which was then pyrolyzed to construct a carbon matrix containing Co nanoparticles. During the preparation of ZIF-67@ZIF-8, the tannic acid treatment time was controlled to precisely regulate the size of the Co nanoparticles. The pyrolyzed carbon matrix was ultrasonically dispersed, and an aqueous solution of chloroplatinic acid hexahydrate was added. The reaction was stirred, and the mixture was then centrifuged and dried.

2. The preparation method according to claim 1, characterized in that: Includes the following steps: (1) Preparation of ZIF-8@ZIF-67 precursor by tannic acid treatment: Synthesis of ZIF-8 nanocubes ZIF-8 NB: 5 mL of an aqueous solution containing 300 mg zinc acetate dihydrate Zn(CH2COO)2 was slowly added to 5 mL of an aqueous solution containing 1116 mg dimethylimidazole and 0.8 mg cetyltrimethylammonium bromide CTAB; the mixture was shaken for 10 s and allowed to stand at room temperature for 2 h; the resulting ZIF-8 NC was washed several times with ultrapure water and then dried in a drying oven; Synthesis of ZIF-67-coated ZIF-8 nanocubes (ZIF-67@ZIF-8 NB): 360 mg of synthesized ZIF-8 nanocubes were added to 72 mL of ultrapure water and ultrasonically dispersed to obtain solution A; simultaneously, 456.3 mg of cobalt nitrate hexahydrate and 23.67 mg of CTAB were added to 16 mL of ultrapure water, ultrasonically dispersed, and then added to solution A to obtain solution B; 7.134 g of dimethylimidazole was uniformly dispersed in 110 mL of ultrapure water to obtain solution C. Solution C was then slowly added to solution B, stirred for 24 h, centrifuged, and dried to obtain ZIF-67@ZIF-8 NB. Synthetic tannic acid-modified ZIF-67-coated ZIF-8 nanocube TA x -ZIF-67@ZIF-8 NB: Under light-protected conditions, 600 mg of tannic acid was dispersed in 133 mL of ultrapure water to prepare a tannic acid solution. 400 mg of ZIF-67@ZIF-8 NB was dispersed in a mixed solution of 200 mL of ultrapure water and 20 mL of ethanol, and then slowly added to the tannic acid solution. The treatment time for tannic acid was adjusted to 0-16 h, and the corresponding material was named TA. x -ZIF-67@ZIF-8 NB, where x The processing time for tannic acid; (2) Preparation of TA x -ZIF-67@ZIF-8 NB-derived carbon TA x -ZIF-67@ZIF-8 NB-C: TA obtained in step (1) x The ZIF-67@ZIF-8 NB precursor was placed in a ceramic boat and then placed in a tube furnace. The temperature was increased to 920°C at a rate of 2°C / min and held at that temperature for 180 min in an argon atmosphere. After cooling to room temperature, it was removed. (3) Preparation of Co nanoparticles of different sizes-Pt single-atom catalysts Co nx -Pt1@C NB: 50 mg of TA obtained in step (2) x -ZIF-67@ZIF-8 NB-C sample was dispersed in 10 mL of ultrapure water and ultrasonically dispersed for 20 min to obtain a homogeneous suspension; 560 μL of chloroplatinic acid hexahydrate aqueous solution (20 mg / mL) was slowly added; after stirring at 10-80℃ for 16 h, the suspension was centrifuged; the precipitate was washed with ultrapure water and then dried overnight under vacuum at 60℃ to obtain Co. nx -Pt1@C NB, where: n refers to nanoparticles, x This refers to the treatment time for tannic acid.

3. The preparation method according to claim 2, characterized in that: The tannin treatment time was 4 hours, and the resulting Co nanoparticle-Pt single-atom catalyst was Co. n4 -Pt1@C NB.

4. A carbon-framework-supported platinum single-atom-cobalt nanoparticle catalyst Co prepared by any one of the methods described in claims 1-3. nx -Pt1@C NB.

5. The carbon-framework supported platinum single-atom-cobalt nanoparticle catalyst Co as described in claim 4 nx Application of -Pt1@C NB in ​​electrocatalytic hydrogen evolution.

6. The application according to claim 5, characterized in that: Carbon-framed platinum single-atom-cobalt nanoparticle catalyst Co nx A dispersion of -Pt1@C NB was coated on a carbon paper surface as the working electrode, a carbon rod as the counter electrode, and a mercury / mercury oxide electrode as the reference electrode to form a three-electrode system for alkaline HER reaction. The electrocatalytic performance of the catalyst was evaluated by linear sweep voltammetry (LSV), Tafel slope, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) using an electrochemical workstation.

7. The application according to claim 6, characterized in that: The specific method is as follows: 2.5 mg of powdered Co nx -Pt1@C NB sample was dispersed in a mixed solution of 100 μL ethanol and 135 μL ultrapure water. After ultrasonic dispersion, 15 μL Nafion reagent was added to the mixed solution and ultrasonic dispersion was continued at ≤20℃ for 1 h to obtain catalyst ink. Using a microsyringe, 20 μL of ink was added dropwise 10 times to a final volume of 0.5 μL. The working electrode was prepared by drying on 0.5 cm carbon paper at room temperature. A three-electrode system was formed by selecting a carbon rod as the counter electrode, a mercury / mercury oxide electrode as the reference electrode, and carbon paper coated with catalyst ink as the working electrode. The catalyst was evaluated by linear sweep voltammetry (LSV), Tafel slope, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) using an electrochemical workstation. First, the mercury / mercury oxide electrode was reversibly calibrated using a hydrogen electrode (RHE). Calibration was performed in a high-purity H₂-saturated 1 M KOH solution, using two Pt foils as the working and counter electrodes, respectively, with the mercury / mercury oxide electrode as the reference electrode. The calibration was conducted at 2 mV s⁻¹ within a potential range of -0.7 to -1.1 V. -1 Cyclic voltammetry (CV) was performed at a scan rate of [missing value], and the average of the two potentials at which the current was zero was taken as the thermodynamic potential of the hydrogen electrode reaction; the CV results for RHE calibration of mercury / mercury oxide in 1 M KOH can be described as E( [missing value]. vs. RHE) = E ( vs. Mercury / mercury oxide) +0.912 V; The three-electrode system was then placed in Ar-saturated 1 M KOH at -0.8 V to -1.25 V. vs. Within the potential range of RHE, linear sweep voltammetry was used at 5 mV s. -1 Perform LSV testing to detect Co nx -Pt1@C NB HER behavior under alkaline conditions; Tafel slope was determined by plotting the current density versus the logarithm of the overpotential (log |j|); EIS measurement is in 10 5 Hz to 10 -2 The frequency range is Hz, with an amplitude of 5 mV, at different -0.034 V ( vs. Impedance testing was performed at the RHE potential; the solution resistance R was obtained from the impedance spectrum. s Then use E = E RHE - 90%iR s To perform liquid resistance correction on the LSV curve; The electrochemically active surface area (ECSA) of this three-electrode system was determined using cyclic voltammetry: from 0.117 to 0.317 V. vs. Within the potential range of RHE, at values ​​of 20, 40, 60, 80, 100, and 120 mV respectively. -1 Perform CV testing on the sweep speed; plot Δj / 2 = (j 阳极 -j 阴极 The slope of the graph showing the relationship between ) / 2 and scan rate represents the electrochemical double-layer capacitance (C). dl ), j 阳极 and j 阴极 They represent 0.217 V ( vs. The current density under RHE (Reverse Electrochemical Hypothesis) scans at the anodic and cathode was measured; the ECSA (Electrochemical Double Layer Capacitance) was calculated using the relationship between electrochemical double layer capacitance and capacitance per unit surface area; the formula is: ECSA = C dl / C s ,in, C s It is the capacitance per unit surface area, which is generally a known constant for a specific electrode material.

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