Pt-co bimetallic site self-supported integrated electrode and preparation method and application thereof

Abstract

The application belongs to the technical field of electrode materials, and particularly relates to a Pt-Co bimetallic site self-supporting integrated electrode and a preparation method and application thereof. The electrode takes carbon cloth as a substrate, and through in-situ growth of CoZn-MOFs, high-temperature annealing, acid washing etching and platinum impregnation anchoring, a nano-onion carbon loaded Pt-Co bimetallic site structure with carbon vacancy defects is prepared. By using a three-effect coupling mechanism of "confined catalysis-electric field enhancement-hydrogen overflow", at an ultra-low platinum loading (6.16 mu g / cm 2 ), in 0.5 M H2SO4, a 10 mA / cm² overpotential is only 14.1 mV; as a PEM electrolytic cell cathode, a 1.74 V cell voltage can drive 1000 mA / cm 2 for more than 1400 hours, solving the problems of high noble metal consumption, slow acid hydrogen evolution kinetics and poor stability of existing electrodes, and being suitable for industrial current density green hydrogen production.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, particularly to Pt-Co dual-atom-site self-supporting integrated electrodes, their preparation methods, and applications. Background Technology

[0002] Hydrogen production through water electrolysis has garnered significant attention in the field of green energy conversion and storage due to its environmental friendliness and high product purity. Among these technologies, proton exchange membrane (PEM) water electrolysis for hydrogen production boasts unique advantages such as high current density and rapid start-up and shutdown, making it a research hotspot. Currently, the hydrogen evolution reaction (HER) cathode in PEM electrolyzers typically employs a platinum (Pt)-based catalyst, with a Pt loading generally greater than 0.3 mg cm⁻¹. -2 However, the high cost and scarcity of Pt severely restrict its large-scale commercial application.

[0003] In recent years, shrinking platinum nanoparticles to the single-atom level to construct single-atom catalysts (SACs) has become a research hotspot in this field. This strategy, by exposing every platinum atom as an active site, theoretically enables extremely high platinum mass activity, providing a promising pathway for significantly reducing platinum loading. However, as research progresses, especially when evaluating industrial-scale high current density applications, the inherent limitations of single-atom catalysts are becoming increasingly apparent. These catalysts possess only a single, isolated active site, making it difficult to break the inherent linear scaling relationship between the adsorption and desorption of complex multi-intermediate reactions. This limitation severely restricts further improvements in the hydrogen evolution reaction (HER) kinetics, making it difficult to meet the demands of practical applications for high current density catalytic performance.

[0004] To overcome the aforementioned bottlenecks, constructing atomic-level catalysts with bimetallic or multimetallic sites has become a promising strategy. By introducing adjacent dissimilar metal atoms, not only can the electronic structure of the active sites be modulated, but it is also expected to achieve the synergistic adsorption and transfer of reaction intermediates between different sites, thereby decoupling linear scaling relationships. In recent years, "confined catalysis" has provided a new perspective for the precise construction of such bimetallic sites. That is, by utilizing the nanoscale space of the support (such as channels, interlayers, or defect vacancies) to spatially confine and electronically modulate metal atoms, metal migration can be effectively suppressed and synergistic catalytic effects can be induced.

[0005] However, existing finite-domain systems (such as MOFs and interlayer structures in two-dimensional materials) generally suffer from insufficient structural stability or limited functionality in strongly acidic environments, making it difficult to simultaneously achieve stable anchoring of two atomic sites and the transport and separation of reactive species. Therefore, it is crucial to construct support materials that combine excellent acid corrosion resistance with precise confinement effects, and to precisely control the adsorption of hydrogen species (H2O) on the surface at the atomic scale. *Synergistic adsorption and controllable transfer between heteronuclear active sites are key to constructing highly active, highly stable low-platinum-load catalysts. Summary of the Invention

[0006] One objective of this invention is to develop a Pt-Co dual-atom-site integrated electrode material, PtCo-DAS@OLC, with strong electron interactions. v This electrode fully leverages the advantages of bimetallic synergistic catalysis by constructing a Pt-Co dual-atom site proximity-cooperative configuration; simultaneously, the hierarchical porous structure and high-curvature surface of the nano-onion carbon provide an efficient channel for hydrogen spillover, promoting the adsorption of hydrogen (H2O). * From strongly adsorbed Pt-Co sites to weakly adsorbed Co sites SA@OLC v Surface migration accelerates the coupling and desorption process along the Tafel path. Combined with Co SA@OLC v PtCo-DAS@OLC exhibits high stability and high specific surface area characteristics. v It exhibits high electrocatalytic activity and excellent long-term stability at high current densities, providing a reliable strategy for the design, preparation and widespread application of efficient electrocatalytic hydrogen evolution electrodes.

[0007] To achieve the above objectives, the present invention employs the following technical solution: a Pt-Co diatomic site self-supporting integrated electrode, the electrode comprising a carbon cloth as a conductive substrate and a catalytic layer supported on the surface of the carbon cloth; the catalytic layer comprising a nano-onion carbon support doped with cobalt single atoms and rich in carbon vacancy defects, and platinum single atoms confined and anchored on the surface of the support; the platinum single atoms and cobalt single atoms form Pt-Co diatomic sites with strong electronic interactions, the diatomic sites being highly dispersed in the form of adjacent heteronuclear diatomic pairs, without obvious metal clusters or grains; wherein, both Pt atoms and Co atoms are anchored in the support through C, O coordination bonds, the two atoms are in a near-neighbor coordination state, and the interatomic distance is 2.0–3.0 Å.

[0008] Further improvements to the Pt-Co dual-atom-site self-supporting integrated electrode: Preferably, the cobalt single-atom doping amount in the integrated electrode is 0.1-0.8 μg / cm³. 2 The loading of platinum single atoms was 3.6–9.7 μg / cm³. 2 .

[0009] A second objective of this invention is to provide a method for preparing the Pt-Co dual-atom-site self-supporting integrated electrode as described in any one of the above claims, comprising the following steps: S1. Using carbon cloth as a conductive substrate, a cobalt-zinc-based metal-organic framework nanosheet array precursor is grown in situ on its surface. The product is denoted as CoZn-MOFs. S2. CoZn-MOFs were annealed at high temperature in an inert atmosphere to synthesize a core-shell structure intermediate with onion-like carbon layers encapsulating cobalt nanoparticles and carbon vacancy defects, denoted as Co NPs@OLC. v ; S3. Using acid solution to treat Co NPs@OLC v Acid etching was performed to remove the cobalt nanoparticles (which were resistant to acid etching because some Co atoms were stably anchored by carbon vacancies or defects in the graphene layer). Cobalt single-atom doped nano-onion carbon support rich in carbon vacancies was then constructed in situ, denoted as Co SA@OLC. v ; S4. Will Co SA@OLC v The platinum single atom is confined and anchored on the support by immersion in an aqueous solution of chloroplatinic acid to obtain a Pt-Co two-atom site self-supporting integrated electrode.

[0010] Further improvements to the fabrication method of Pt-Co dual-atom-site self-supporting integrated electrode: Preferably, the preparation method of the cobalt-zinc based metal-organic framework nanosheet array precursor in step S1 is as follows: Co(NO3)2·6H2O and Zn(NO3)2·6H2O are dissolved in deionized water to obtain a mixed metal salt solution, which is then rapidly mixed with a 2-methylimidazole aqueous solution and stirred vigorously. The solution is then immersed in pretreated carbon cloth and reacted at room temperature to obtain the cobalt-zinc based metal-organic framework nanosheet array precursor.

[0011] Preferably, the molar ratio of Co(NO3)2·6H2O to Zn(NO3)2·6H2O is (1-4):1, wherein the concentration of Zn(NO3)2·6H2O is 0.016-0.048 mol / L; the mixed metal salt solution is rapidly mixed with an equal volume of 0.4-0.8 M 2-methylimidazole aqueous solution, stirred vigorously for 15-40 seconds, and the cleaned carbon cloth is immersed in it, and the reaction is carried out at room temperature for 3-20 hours.

[0012] Preferably, the conditions for the high-temperature annealing treatment in step S2 are as follows: under a high-purity argon atmosphere and a flow rate of 30-60 sccm, the temperature is raised to 700-1050 ℃ at a heating rate of 2-10 ℃ / min, and held at that temperature for 1-12 hours.

[0013] Preferably, the acid etching conditions in step S3 are as follows: acid etching is performed using a 3-6 M HNO3 solution at 80-100 °C.

[0014] Preferably, the conditions for the impregnation treatment in step S4 are as follows: using an aqueous solution of chloroplatinic acid with a concentration of 0.05-0.2 mg / mL, and hydrothermally reacting at 45-60 °C for 4 hours.

[0015] The third objective of this invention is to provide an application of the Pt-Co dual-atom-site self-supporting integrated electrode described in any one of the above-mentioned claims in water electrolysis for hydrogen production.

[0016] Further improvements to the application of the aforementioned Pt-Co dual-atom-site self-supporting integrated electrode in water electrolysis for hydrogen production: Preferably, the Pt-Co dual-atom-site self-supporting integrated electrode is used as a cathode for acidic water electrolysis to produce hydrogen, or as a cathode in a proton exchange membrane electrolyzer for water electrolysis to produce hydrogen.

[0017] The advantages of this invention compared to the prior art are as follows: (1) This invention provides a method for preparing a Pt-Co dual-atom site self-supporting integrated electrode. This method is an organic technical whole, with each step working together and none of them being dispensable. Together, they solve the technical problems of insufficient stability and single function of HER catalyst in acidic media.

[0018] First, using carbon cloth as a conductive substrate, a CoZn-MOF nanosheet array precursor is grown in situ on its surface. The introduction of zinc ions is crucial in this step: zinc volatilizes at high temperatures, contributing to the formation of a rich porous structure during subsequent carbonization, while effectively inhibiting excessive aggregation of cobalt nanoparticles. Subsequently, high-temperature annealing is performed under an inert atmosphere, carbonizing the organic ligands in the CoZn-MOFs to form an onion-like carbon layer. Simultaneously, cobalt ions are reduced to cobalt nanoparticles, which are then in situ encapsulated by the onion-like carbon layer, forming Co NPs@OLC with carbon vacancy defects. v Core-shell intermediate.

[0019] Next, an acid solution was used to treat Co NPs@OLC. v Acid etching is then performed. This step demonstrates the originality of this invention: existing technologies generally believe that acid etching completely removes the metal components, but this invention utilizes acid etching to selectively remove cobalt nanoparticles, unexpectedly achieving two key effects: in-situ construction of atomically dispersed cobalt single active sites and the introduction of abundant carbon vacancy defects into the onion carbon support. These two effects provide an ideal coordination environment and electronic structure regulation basis for the subsequent anchoring of platinum single atoms.

[0020] Finally, through immersion treatment with chloroplatinic acid aqueous solution, using Co SA@OLC vThe strong interaction between carbon vacancy defects and Co single-atom sites on the support and the platinum precursor confines and anchors platinum single atoms on the support, forming Pt-Co diatomic sites. The overall design of this method enables synergistic effects between the steps, ultimately achieving a balance of low noble metal usage, high catalytic activity, and excellent stability. Furthermore, the process conditions are mild and highly reproducible, making it suitable for large-scale preparation.

[0021] (2) This invention provides a Pt-Co dual-atom site self-supporting integrated electrode (PtCo-DAS@OLC) with strong electronic interactions. v The electrode uses carbon cloth as a conductive substrate, on which a cobalt single-atom doped nano-onion carbon support (CoSA@OLC) rich in carbon vacancy defects is constructed in situ. v The platinum single atoms are stably loaded onto the support through confined anchoring, forming a well-defined Pt-Co diatomic site catalytic system. Its core advantage lies in its unique three-effect coupling mechanism of "confined catalysis - electric field enhancement - hydrogen spillover": First, the cage-like structure of the nano-onion carbon provides physical and electronic confinement effects for the Pt-Co diatomic sites. Second, the introduction of Pt induces charge redistribution at the Co sites, which, combined with carbon vacancy defects, forms a strong local electric field enhancement effect, significantly reducing the reaction energy barrier of the Volmer step. Finally, the hierarchical porous structure and high-curvature surface of the nano-onion carbon provide an efficient channel for hydrogen spillover, promoting the adsorption of hydrogen (H₂O). * From strongly adsorbed Pt-Co sites to weakly adsorbed Co sites SA@OLC v Surface migration accelerates the coupling-desorption process along the Tafel path. DFT calculations show that PtCo-DAS@OLC v The system's electron transfer rate reaches 0.91 e. - Significantly higher than Co SA@OLC v 0.62 e - Its H * Adsorption Gibbs free energy (ΔG) H * The voltage is only -0.03 eV, close to the ideal value of zero. Under the above-mentioned synergistic mechanism, excellent hydrogen evolution reaction kinetics are exhibited.

[0022] (3) The PtCo-DAS@OLC prepared in this invention v The integrated electrode has demonstrated groundbreaking performance in proton exchange membrane (PEM) water electrolysis for hydrogen production.

[0023] This electrode operates at an ultra-low platinum loading (only 6.16 μg / cm³). 2 Under these conditions, only a 14.1 mV overpotential is required to drive a 10 mA cm⁻¹ electrolyte in 0.5 M H₂SO₄. -2With a low current density and a small Tafel slope, it exhibits excellent hydrogen evolution reaction kinetics.

[0024] When this electrode is used as the cathode in a proton exchange membrane electrolyzer for hydrogen production via water electrolysis, it requires only an ultra-low cell voltage of 1.74 V to drive a 1000 mA cm⁻¹ electrolyzer. -2 It exhibits industrial-grade high current density and has maintained stable operation for over 1400 hours without significant performance degradation. This stability data is significantly superior to similar catalysts reported in existing technologies, solving the key technical bottlenecks of traditional precious metal catalysts being prone to deactivation and support corrosion under high current densities.

[0025] Meanwhile, mass activity tests showed that PtCo-DAS@OLC v The mass activities of the electrode at overpotentials of 50 mV, 100 mV, and 150 mV reached 20.36, 82.60, and 161.70 A mg, respectively. -1 Pt The efficiency is 23.56–35.38 times that of commercial Pt / C catalysts; its conversion frequency (TOF) is 32.63 times that of Pt / C. This indicates that the present invention achieves a significant improvement in the utilization efficiency of precious metals with extremely low platinum loading.

[0026] In summary, this invention forms a complete technical solution from product structure and preparation method to application performance, and has the comprehensive advantages of low cost, high activity and ultra-high stability. It provides a practical new electrode solution for industrial-grade current density green hydrogen production, and has important value for promoting the commercialization of PEM water electrolysis hydrogen production technology. Attached Figure Description

[0027] Figure 1 PtCo-DAS@OLC was prepared for this invention. v Process flow diagram of integrated electrode.

[0028] Figure 2 PtCo-DAS@OLC as described in Example 1 v The morphological structure characterization diagrams of the integrated electrode are shown below; (a) is a macroscopic optical image of the large-size electrode; (b) is a low-magnification SEM image; (c) is a high-magnification SEM image; and (d) is a low-magnification TEM image.

[0029] Figure 3 PtCo-DAS@OLC as described in Example 1 v The morphological structure characterization diagrams of the integrated electrode are shown below; (a) is an HRTEM image; (b) is a HAADF-STEM image; (c) and (d) are magnified views of part of (b); (e) is a contrast enhancement image of (c); (f) is a contrast enhancement image of (d); (g) is a spherical aberration diagram; and (h) is the elemental distribution diagram corresponding to (g).

[0030] Figure 4 PtCo-DAS@OLC as described in Example 1 v The structure and surface electronic state characterization; (a) EPR characterization; (b) XRD characterization; (c) XPS characterization.

[0031] Figure 5 PtCo-DAS@OLC as described in Example 1 v The structure and surface electronic state characterization of Pt foil and PtO2 as standard samples; (a) Pt L3 edge XANES characterization; (b) EXAFS characterization; (c) Co K edge XANES characterization; (d) EXAFS characterization; (e) Pt L3 edge wavelet transform image.

[0032] Figure 6 PtCo-DAS@OLC prepared in Example 1 v Comparison sample Co SA@OLC v HER performance characterization; where (a) is the LSV curve; (b) is the Tafel curve; and (c) is the curve at 10, 100, and 500 mA cm⁻¹. -2 Overpotential comparison diagrams under current density; (d) and (e) are PtCo-DAS@OLC v Comparison of Pt mass activity with commercial Pt / C; (f) is the TOF curve; (g) is the constant current stability curve.

[0033] Figure 7 PtCo-DAS@OLC prepared in Example 1 v Performance characterization of PEM electrolytic cell devices; where (a) is a schematic diagram of PEM electrolytic cell; (b) is a PtCo-DAS@OLC device. v (c) Steady-state polarization curves of commercial Pt / C; PtCo-DAS@OLC v Stability test curves under constant current conditions.

[0034] Figure 8 In the figures (a), (b), and (c), Co SA@OLC is presented as a comparative example. v Example 1: PtCo-DAS@OLC v The atomic structure model of PtCo-DAS@OLC, where (d) is the corresponding migration barrier.

[0035] Figure 9 (a) is a pair Figure 8 (b) shows the electronic localization function (ELF) calculations performed on the three constructed atomic structure models, and (c) shows the proton distribution concentration calculation and the Gibbs free energy ΔG for adsorbed H atoms.H * .

[0036] Figure 10 To Figure 8 The differential charge density calculations were performed using three atomic structure models constructed in the model. (a) is a comparative example of Co SA@OLC. v (b) is PtCo-DAS@OLC of Example 1. v (c) is PtCo-DAS@OLC. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Example 1 This embodiment provides a method for fabricating a Pt-Co dual-atom-site self-supporting integrated electrode. A schematic diagram of the fabrication process is shown below. Figure 1 As shown, the specific steps include the following: S1. Cut the carbon cloth into small pieces (2×2 cm). 2 The carbon cloth is then placed in acetone, ethanol, and deionized water in sequence for ultrasonic cleaning to remove surface impurities and obtain clean carbon cloth. Weigh out Co(NO3)2·6H2O and Zn(NO3)2·6H2O in a molar ratio of 2:1, dissolve them in 45 mL of deionized water to obtain a mixed metal salt solution, wherein the concentration of Zn(NO3)2·6H2O is 0.016 mol / L; then rapidly mix the mixed metal salt solution with 45 mL of 0.4 M 2-methylimidazole aqueous solution and stir vigorously for 20 seconds to obtain a mixed solution. Cleaned and activated carbon cloth was added to the mixed solution and reacted at room temperature for 4 hours. The carbon cloth was then removed and washed with deionized water. A CoZn-MOF nanosheet array precursor was grown on the surface of the carbon cloth and dried in air for later use. This precursor was denoted as CoZn-MOF.

[0039] S2. Place the above CoZn-MOF in a tube furnace and heat it to 1050 °C at a rate of 10 °C / min under a high-purity argon atmosphere (flow rate 60 sccm). Hold the temperature at this point for 2 hours and allow it to cool naturally to room temperature. This yields a core-shell structure intermediate with onion-shaped carbon layers containing carbon vacancy defects and encapsulating cobalt nanoparticles, denoted as Co NPs@OLC. v .

[0040] S3. Using a 6 M HNO3 solution, incubate Co NPs@OLC at 100 °C.v Acid etching was performed to remove cobalt nanoparticles, and a cobalt single-atom-doped nano-onion carbon support rich in carbon vacancies was constructed in situ, denoted as Co SA@OLC. v .

[0041] S4. The above Co SA@OLC v The sample was immersed in a 0.1 mg / mL aqueous solution of chloroplatinic acid and subjected to hydrothermal reaction in a 60 °C oven for 4 h. After cooling to room temperature, the sample was removed, washed several times with ultrapure water, and air-dried at room temperature to obtain PtCo-DAS@OLC grown in situ on carbon cloth. v , denoted as PtCo-DAS@OLC v .

[0042] The PtCo-DAS@OLC prepared in this embodiment was measured using inductively coupled plasma mass spectrometry (ICP-MS). v The surface density of the metal in -5 is: cobalt single-atom doping amount 0.16 μg / cm³. 2 Platinum single-atom loading: 6.16 μg / cm³ 2 .

[0043] Example 2 This embodiment provides a method for fabricating a Pt-Co dual-atom-site self-supporting integrated electrode. The fabrication process is as follows: Figure 1 As shown, the specific steps are the same as in Example 1, except that the carbon cloth in step S1 is cut into 5×4 cm pieces. 2 Size. Finally, PtCo-DAS@OLC was produced through in-situ growth on large-size carbon cloth. v , denoted as PtCo-DAS@OLC v -1, cut into 2×2 cm pieces when using. 2 size.

[0044] The PtCo-DAS@OLC prepared in this embodiment was measured using inductively coupled plasma mass spectrometry (ICP-MS). v The surface density of the metal in -5 is: cobalt single-atom doping amount 0.18 μg / cm³. 2 Platinum single-atom loading: 6.16 μg / cm³ 2 .

[0045] Example 3 This embodiment provides a method for fabricating a Pt-Co dual-atom-site self-supporting integrated electrode. The fabrication process is as follows: Figure 1 As shown, the specific steps are the same as in Example 1, except that in step S4, the concentration of the chloroplatinic acid aqueous solution is 0.05 mg / mL. Finally, PtCo-DAS@OLC grown in situ on carbon cloth was obtained. v, denoted as PtCo-DAS@OLC v -2.

[0046] The PtCo-DAS@OLC prepared in this embodiment was measured using inductively coupled plasma mass spectrometry (ICP-MS). v The surface density of the metal in -5 is: cobalt single-atom doping amount 0.22 μg / cm³. 2 Platinum single-atom loading: 4.62 μg / cm³ 2 .

[0047] Example 4 This embodiment provides a method for fabricating a Pt-Co dual-atom-site self-supporting integrated electrode. The fabrication process is as follows: Figure 1 As shown, the specific steps are the same as in Example 1, except that in step S4, the concentration of the chloroplatinic acid aqueous solution is 0.2 mg / mL. Finally, PtCo-DAS@OLC grown in situ on carbon cloth was obtained. v , denoted as PtCo-DAS@OLC v -3.

[0048] The PtCo-DAS@OLC prepared in this embodiment was measured using inductively coupled plasma mass spectrometry (ICP-MS). v The surface density of the metal in -5 is: cobalt single-atom doping amount 0.19 μg / cm³. 2 Platinum single-atom loading: 9.23 μg / cm³ 2 .

[0049] Example 5 This embodiment provides a method for fabricating a Pt-Co dual-atom-site self-supporting integrated electrode. The fabrication process is as follows: Figure 1 As shown, the specific steps include the following: S1. Cut the carbon cloth into small pieces (2×2 cm). 2 The carbon cloth is then placed in acetone, ethanol and deionized water in sequence for ultrasonic cleaning to remove surface impurities and obtain clean carbon cloth. Weigh out Co(NO3)2·6H2O and Zn(NO3)2·6H2O in a molar ratio of 1:1, dissolve them in 45 mL of deionized water to obtain a mixed metal salt solution, wherein the concentration of Zn(NO3)2·6H2O is 0.048 mol / L; then rapidly mix the mixed metal salt solution with 45 mL of 0.8 M 2-methylimidazole aqueous solution and stir vigorously for 15 seconds to obtain a mixed solution. Cleaned and activated carbon cloth was added to the mixed solution and reacted at room temperature for 20 hours. The carbon cloth was then removed and washed with deionized water. A CoZn-MOF nanosheet array precursor was grown on the surface of the carbon cloth and dried in air for later use. This precursor was denoted as CoZn-MOF.

[0050] S2. The above CoZn-MOF was placed in a tube furnace and heated to 700 °C at a heating rate of 2 °C / min under a high-purity argon atmosphere (flow rate 30 sccm). The temperature was held constant for 12 hours and then naturally cooled to room temperature to obtain a core-shell structure intermediate with onion-shaped carbon layers containing carbon vacancy defects, denoted as Co NPs@OLC. v .

[0051] S3. Using a 3 M HNO3 solution, incubate Co NPs@OLC at 80 °C. v Acid etching was performed to remove cobalt nanoparticles, and a cobalt single-atom-doped nano-onion carbon support rich in carbon vacancies was constructed in situ, denoted as Co SA@OLC. v .

[0052] S4. The above Co SA@OLC v The sample was immersed in a 0.1 mg / mL aqueous solution of chloroplatinic acid and subjected to hydrothermal reaction in a 45 °C oven for 4 h. After cooling to room temperature, the sample was removed, washed several times with ultrapure water, and air-dried at room temperature to obtain PtCo-DAS@OLC grown in situ on carbon cloth. v , denoted as PtCo-DAS@OLC v -4.

[0053] The PtCo-DAS@OLC prepared in this embodiment was measured using inductively coupled plasma mass spectrometry (ICP-MS). v The surface density of the metal in -4 is: cobalt single-atom doping amount 0.17 μg / cm³. 2 Platinum single-atom loading: 3.6 μg / cm³ 2 .

[0054] Example 6 This embodiment provides a method for fabricating a Pt-Co dual-atom-site self-supporting integrated electrode. The fabrication process is as follows: Figure 1 As shown, the specific steps include the following: S1. Cut the carbon cloth into small pieces (2×2 cm). 2 The carbon cloth is then placed in acetone, ethanol and deionized water in sequence for ultrasonic cleaning to remove surface impurities and obtain clean carbon cloth. Weigh out Co(NO3)2·6H2O and Zn(NO3)2·6H2O in a molar ratio of 4:1, dissolve them in 45 mL of deionized water to obtain a mixed metal salt solution, wherein the concentration of Zn(NO3)2·6H2O is 0.048 mol / L; then rapidly mix the mixed metal salt solution with 45 mL of 0.8 M 2-methylimidazole aqueous solution and stir vigorously for 40 seconds to obtain a mixed solution. Cleaned and activated carbon cloth was added to the mixed solution and reacted at room temperature for 3 hours. The carbon cloth was then removed and washed with deionized water. A CoZn-MOF nanosheet array precursor was grown on the surface of the carbon cloth and dried in air for later use. This precursor was denoted as CoZn-MOF.

[0055] S2. Place the above CoZn-MOF in a tube furnace and heat it to 1050 °C at a rate of 10 °C / min under a high-purity argon atmosphere (flow rate 60 sccm). Hold the temperature at this point for 1 hour and allow it to cool naturally to room temperature. This yields a core-shell structure intermediate with onion-shaped carbon layers containing carbon vacancy defects and encapsulating cobalt nanoparticles, denoted as Co NPs@OLC. v .

[0056] S3. Using a 6 M HNO3 solution, incubate Co NPs@OLC at 100 °C. v Acid etching was performed to remove cobalt nanoparticles, and a cobalt single-atom-doped nano-onion carbon support rich in carbon vacancies was constructed in situ, denoted as Co SA@OLC. v .

[0057] S4. The above Co SA@OLC v The sample was immersed in a 0.2 mg / mL aqueous solution of chloroplatinic acid and subjected to hydrothermal reaction in a 60 °C oven for 4 h. After cooling to room temperature, the sample was removed, washed several times with ultrapure water, and air-dried at room temperature to obtain PtCo-DAS@OLC grown in situ on carbon cloth. v , denoted as PtCo-DAS@OLC v -5.

[0058] The PtCo-DAS@OLC prepared in this embodiment was measured using inductively coupled plasma mass spectrometry (ICP-MS). v The surface density of the metal in -5 is: cobalt single-atom doping amount 0.37 μg / cm³. 2 Platinum single-atom loading: 8.3 μg / cm³ 2 .

[0059] Comparative Example This embodiment provides a method for preparing a Co single-atom site self-supporting integrated electrode, the preparation process of which is as follows: Figure 1 As shown, the specific steps are the same as in Example 1, except that step S4 is omitted. Finally, a cobalt single-atom doped nano-onion carbon support (CoSA@OLC) rich in carbon vacancies was obtained. v ), denoted as Co SA@OLC v .

[0060] Performance testing: The prepared Pt-Co@OLC was studied using field emission scanning electron microscopy (FE-SEM), high-resolution scanning transmission electron microscopy (HR-STEM), and aberration-corrected scanning transmission electron microscopy (AC-STEM). v The morphology of the electrode was characterized. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray absorption fine structure analysis (XAFS) were used to characterize the electrode structure. Pt-Co@OLC was measured by inductively coupled plasma mass spectrometry (ICP-MS). v The Pt content in the sample was determined. Electrochemical tests were performed in 0.5 M H₂SO₄ using a standard three-electrode testing system. An Ag / AgCl electrode was used as the reference electrode, and a graphite rod as the counter electrode. The HER performance of the catalytic electrodes was tested sequentially, including linear sweep voltammetry (LSV), Tafel slope, electrochemical impedance spectroscopy (EIS), and constant current stability testing (CP). The HER performance of the catalyst was evaluated by analyzing the overpotential, Tafel slope, electrochemical impedance, and stability data obtained at different current densities and scan rates. In a proton exchange membrane (PEM) water electrolysis testing system, a pre-prepared integrated electrode was used as the cathode, commercial IrO₂ as the anode, and a membrane electrode assembly (MEA) was formed by hot-pressing with a Nafion 115 membrane. Pure water was used as the electrolyte, and the water electrolysis performance was tested at 80 °C.

[0061] (1) Morphology and structural characterization of the catalyst This invention provides a PtCo-DAS@OLC integrated electrode material with strong electron-electron interactions and dual atomic sites. v The preparation method of the integrated electrode is shown in the schematic diagram below. Figure 1 As shown: This invention first uses a room-temperature liquid-phase method to directly grow a CoZn-MOF nanosheet array on a carbon cloth electrode, and then anneals the CoZn-MOF nanosheets at high temperature in a tube furnace to form Co NPs@OLC with carbon vacancy defects. v Core-shell structure intermediates were then subjected to acidic solutions to Co NPs@OLC. v Acid etching was performed to construct a CoSA@OLC nano-onion carbon support with cobalt single-atom doping and rich carbon vacancies. v Finally, the platinum single atoms are confined and anchored on the support by immersion in chloroplatinic acid aqueous solution to form Pt-Co diatomic sites.

[0062] Figure 2 PtCo-DAS@OLC as described in Example 1 vThe morphological structure characterization images of the integrated electrode are shown, where (a) is a macroscopic optical image of the large-size electrode; (b) is a low-magnification SEM image; (c) is a high-magnification SEM image; and (d) is a low-magnification TEM image. Figure 2 As shown in (a), (b), and (c), the nano-onion carbon material in the product is still uniformly and stably grown on the carbon cloth; (d) transmission electron microscopy (TEM) image shows that the Co nanoparticles have been washed away.

[0063] Figure 3 PtCo-DAS@OLC as described in Example 1 v Morphological structure characterization diagram of the integrated electrode; Figure 3 (a) A large number of nano-onion carbon structures were observed in the high-resolution transmission electron microscopy (HRTEM) image. Figure 3 (b) The high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image shows the distribution of the metal at the atomic scale, with Co single atoms and Pt single atoms coexisting. Figure 3 (c) Figure 3 (d) is Figure 3 (b) is a magnified view of a portion of the image. Figure 3 (e) Figure 3 (f) is a contrast diagram corresponding to the magnified view, which more clearly shows that several Pt atoms are closely dispersed around the Co single atom. Such close spacing is conducive to enhancing the synergistic effect between atoms, electron transfer and interfacial adsorption capacity, thereby improving catalytic activity. Figure 3 (g) and Figure 3 (h) The PtCo-DAS@OLC was further confirmed by scanning transmission electron microscopy combined with energy dispersive spectroscopy (STEM-EDS). v Distribution of Pt and Co elements in PtCo was determined using inductively coupled plasma mass spectrometry (ICP-MS). v The loading of metallic Pt in the medium was 6.16 μg / cm³. 2 .

[0064] Figure 4 PtCo-DAS@OLC as described in Example 1 v The structure and surface electronic states were characterized. Figure 4 (a) Demonstrates PtCo-DAS@OLC v Electron paramagnetic resonance (EPR) spectrum of PtCo-DAS@OLC. v A distinct unpaired electron signal is observed at g=2.002, indicating that in PtCo-DAS@OLC... v A large number of carbon vacancies exist. The presence of these vacancies facilitates the trapping of Pt single atoms and the modulation of their electronic structure, thereby controlling their activity. X-ray diffraction (XRD) was used to investigate the presence of carbon vacancies in Co SA@OLC.v and PtCo-DAS@OLC v To characterize, such as Figure 4 As shown in (b), two broad peaks were observed at 26.04° and 43.71°, corresponding to the (002) and (101) crystal planes of C. No diffraction peaks corresponding to Pt particles were observed, indicating that Pt may be modified in Co SA@OLC in the form of single atoms. v Above. The surface chemical states of PtCo-DAS@OLCv were further analyzed using X-ray photoelectron spectroscopy (XPS). Figure 4 (c) In the Pt 4f spectrum, PtCo-DAS@OLC v The 4f doublet (72.7, 76.1 eV) of Pt in medium oxidation state is shifted to a lower binding energy by 0.9 eV compared to the doublet (73.6, 77.0 eV) of +2 valence Pt in commercial 20 wt% Pt / C, indicating a significantly lower valence state. This weak oxidation state is attributed to the significant electron enrichment at the Pt single atom.

[0065] The local coordination environments of Pt and Co atoms were further investigated using extended X-ray absorption fine structure (EXAFS) and its wavelet transform (WT-EXAFS). Due to the phase shift in EXAFS, the distances in R space do not correspond to the actual bond lengths. Figure 5 Images (a) and (b) show PtCo-DAS@OLC v X-ray near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra of platinum L3 edge Pt foil and PtO2. From normalized platinum L3 edge XANES spectra... Figure 5 (a) It can be seen that PtCo-DAS@OLC v The intensity of the white line peak is between that of Pt foil and PtO2, indicating that PtCo-DAS@OLC v The platinum price in XANES is slightly above zero. Furthermore, in XANES ( Figure 5 (c)), PtCo-DAS@OLC v The Co K-side absorption curve tends to shift towards higher energies, suggesting that electrons may have transferred from Co to Pt. The Fourier transform (R-space) of the EXAFS spectrum of Pt shows that PtCo-DAS@OLC... v A strong scattering signal is observed near 1.6 Å, which can be attributed to the first coordination shell of Pt-O, while a weak scattering signal at 2.75 Å can be attributed to the second coordination shell of Pt-Co. Figure 5(b)). A strong scattering signal can be observed near 1.55 Å in the Co-O / C R-space, which can be attributed to the first coordination shell of Co-O / C, while the weak scattering signal at 2.32 Å can be attributed to the second coordination shell of Co-Pt. Figure 5 (d)). Further analysis using WT-EXAFS revealed PtCo-DAS@OLC v Two higher oscillation signals appeared, at 5.8 Å. -1 9.5 Å -1 Left and right, corresponding to Pt-O and Pt-Co scattering ( Figure 5 (e)). These results indicate that Pt single atoms modify Co SA@OLC through Pt-O and Pt-Co bond interactions. v superior.

[0066] (2) Hydrogen evolution performance testing and analysis Using 0.5 M H₂SO₄ solution as the electrolyte, a typical three-electrode testing system was employed to study the CoSA@OLC. v PtCo-DAS@OLC v The HER activity of a commercial Pt / C catalyst (20% wt) was investigated. Linear sweep voltammetry (LSV) curves were used. Figure 6 (a) indicates that, compared to the Pt-loaded electrode, the unmodified Pt Co SA@OLC v The HER performance is negligible, indicating that it is anchored to Co SA@OLC. v Pt species play a crucial role in the HER process. Figure 6 (b) shows the Tafel slope corresponding to the polarization curve, PtCo-DAS@OLC v The electrode exhibits a minimal Tafel slope, indicating a rapid electrocatalytic rate and excellent HER reaction kinetics. Figure 6 As shown in (c), at a current density of 10 mA cm⁻¹ -2 At that time, the overpotential of PtCo-DAS@OLCv was only 14.1 mV, slightly lower than that of commercial 20% Pt / C (27.24 mV, manufacturer: Shengnuo, model: SPT20X). With increasing current density, the overpotential of PtCo-DAS@OLCv... v It gradually exhibited HER activity significantly superior to Pt / C. At 500 mA cm⁻¹ -2 At high current densities, the overpotential is approximately 97.96 mV, significantly better than Pt / C (243.3 mV) and Co. SA@OLC. v (402.2 mV). This result indicates that PtCo-DAS@OLC vDue to its unique Co single-atom doped nano-onion carbon structure and efficient active sites, the electrode is conducive to electrolyte transport and desorption of generated gas, which significantly improves the mass transfer rate. Therefore, its catalytic activity is significantly better than that of Pt / C powder-coated catalyst.

[0067] To objectively compare catalytic activity, PtCo-DAS@OLC was used. v The current density of the electrode and the Pt / C catalyst was normalized with respect to the Pt loading to investigate the mass activity of the catalyst. Figure 6 As shown in (d) and 6(e), PtCo-DAS@OLC v The electrode's quality activity is far superior to that of commercially available Pt / C (manufacturer: Shengnuo, model: SPT20X). Specifically, Pt-Co@OLC v It exhibited 20.36 A mg at overpotentials of 50 mV, 100 mV, and 150 mV, respectively. -1 Pt 82.60 A mg -1 Pt 161.70 Amg -1 Pt The mass activity of PtCo-DAS@OLC was 23.56, 32.39, and 35.38 times that of commercial Pt / C, respectively. Meanwhile, at an overpotential of 100 mV, PtCo-DAS@OLC... v The reaction transition frequency (TOF) is 32.63 times that of Pt / C. Figure 6 (f)).

[0068] The effect was evaluated using the chronopotentiometric method at a current density of 500 mA cm⁻¹. -2 Pt-Co@OLC v The acidic HER stability. For example... Figure 6 As shown in (g), this catalyst can be applied at 500 mA cm⁻¹. -2 It operated stably for 125 hours at the current density. Based on the above tests and analyses, it can be concluded that PtCo-DAS@OLC... v Not only does it possess excellent electrocatalytic HER activity, but it also exhibits excellent stability, making it a promising candidate for further application as a cathode in industrial hydrogen production. Under the same testing conditions, the integrated electrodes prepared in Examples 2, 3, 4, 5, and 6 were subjected to high current density acidic HER stability tests. At a current density of 500 mA cm⁻¹... -2 At current densities, the series PtCo-DAS@OLC v The electrodes all exhibited excellent long-term stability, and the samples in each embodiment could operate stably for more than 100 hours without significant attenuation of catalytic performance.

[0069] Based on actual working conditions, the constructed PtCo-DAS@OLC v Commercial IrO2 was used as the cathode, and a proton exchange membrane (PEM) electrolyzer was assembled as the anode. Figure 7 (a)). Tests revealed that Pt-Co@OLC v The assembled PEM electrolyzer requires only an ultra-low cell voltage of 1.74 V to drive a 1000 mA cm⁻¹ electrolyzer. -2 High current density ( Figure 7 (b) In particular, PtCo-DAS@OLC v The assembled PEM electrolyzer can operate at 1000 mA cm⁻¹ -2 It operated stably for over 1400 hours at high current density without any significant performance degradation. Figure 7 (c) thus confirming its practical application potential at industrial current densities. Under the same test conditions, proton exchange membrane (PEM) electrolyzers were assembled using the integrated electrodes prepared in Examples 2, 3, 4, 5, and 6, respectively, and tests revealed a series of PtCo-DAS@OLC... v The electrodes all exhibited excellent long-term stability, and the samples in each embodiment could operate stably for more than 1200 hours without significant attenuation of catalytic performance.

[0070] (3) DFT theoretical calculation and analysis Based on the local structure information of Pt atoms obtained from the above characterization, we used the C240 ​​fullerene-encapsulated C60 model to represent the onion carbon model, and constructed CoSA@OLC respectively. v ( Figure 8 (a) 、 PtCo-DAS@OLC v ( Figure 8 (b) PtCo-DAS@OLC ( Figure 8 (c) Atomic structure model of Pt / Co atoms in Co SA@OLC v PtCo-DAS@OLC v The lowest diffusion barrier on PtCo-DAS@OLC was calculated. Figure 8 (d) where Pt Co-DAS@OLC is a theoretically calculated model, the purpose of which is to compare Pt Co-DAS@OLC with Pt Co-DAS@OLC. v The contrast reflects C v The impact on related performance. The corresponding lowest diffusion barriers are 3.09 eV, 4.86 eV, and 4.12 eV, respectively, indicating that PtCo-DAS@OLC v The diffusion of active sites requires overcoming obstacles compared to Co SA@OLC. vThe higher energy barrier of PtCo-DAS@OLC indicates that this arrangement has excellent structural stability.

[0071] To Co SA@OLC v PtCo-DAS@OLC v Electronic locality functions were calculated using PtCo-DAS@OLC. Figure 9 (a) Calculation of proton distribution concentration Figure 9 (b) and Gibbs free energy ΔG H * ( Figure 9 (c) Calculation. With Co SA@OLC v Compared to PtCo-DAS@OLC, PtCo-DAS@OLC v It exhibits a stronger local electric field and a higher proton concentration. This is because most of the electrons are concentrated at the metal active sites, PtCo-DAS@OLC v The active site has the highest concentration of electrons, resulting in the strongest electric field at that location. This maximizes proton aggregation and accelerates the HER reaction rate. (This is related to the Gibbs free energy ΔG). H * ( Figure 9 The calculation results of (c) show that PtCo-DAS@OLC v H * The adsorption Gibbs free energy is only -0.03 eV, almost close to the ideal value of zero. Meanwhile, Co SA@OLC... v H and PtCo-DAS@OLC * The adsorption Gibbs free energies were 0.86 eV and 0.27 eV, respectively, indicating that PtCo-DAS@OLC v An ideal balance between hydrogen adsorption and desorption was achieved, thus improving catalytic efficiency.

[0072] Finally, we calculated the density of states for the three structures. Figure 10 Calculations show that when Co and Pt atoms work together to form active sites, their d-orbital electrons undergo redistribution. This redistribution alters the overall d-band energy position of the active site. Pt atoms have a higher atomic number and more d electrons; compared to Co atoms, Pt's d-band is closer to the Fermi level. When Co and Pt work together, the d-electron energy level of Co is pulled up by the d-electron energy level of Pt, causing the center of the overall d-band at the active site to shift towards the Fermi level. The presence of carbon vacancies introduces defect states into the material. These defect states localize electrons and provide additional electronic states that can couple with the d-band, leading to an upward shift of the d-band center. Therefore, PtCo-DAS@OLC... vCompared to Co SA@OLC v The d-band center of the PtCo-DAS@OLC density of states is closer to the Fermi level, which means stronger interaction with the intermediates and can promote the reaction.

[0073] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A Pt-Co dual-atom-site self-supporting integrated electrode, characterized in that, The electrode comprises a carbon cloth serving as a conductive substrate and a catalytic layer supported on the surface of the carbon cloth. The catalytic layer comprises a nano-onion carbon support doped with cobalt single atoms and rich in carbon vacancy defects, and platinum single atoms confined and anchored on the surface of the support. The platinum single atoms and cobalt single atoms form Pt-Co diatomic sites with strong electronic interactions. These diatomic sites are highly dispersed in the form of adjacent heteronuclear diatomic pairs, without obvious metal clusters or grains. Pt atoms and Co atoms are both anchored in the support through C and O coordination bonds, and the two atoms are in a near-neighbor coordination state with an interatomic distance of 2.0–3.0 Å. The preparation method of this electrode includes the following steps: S1. Using carbon cloth as a conductive substrate, a cobalt-zinc based metal-organic framework nanosheet array precursor is grown in situ on its surface. The product is denoted as CoZn-MOFs. S2. CoZn-MOFs were annealed at high temperature in an inert atmosphere to synthesize a core-shell structure intermediate with onion-like carbon layers encapsulating cobalt nanoparticles and carbon vacancy defects, denoted as Co NPs@OLC. v ; S3. Using acid solution to treat Co NPs@OLC v Acid etching was performed to remove cobalt nanoparticles, and a cobalt single-atom-doped nano-onion carbon support rich in carbon vacancies was constructed in situ, denoted as Co SA@OLC. v ; S4. Will Co SA@OLC v The platinum single atoms are confined and anchored on the support by immersion in an aqueous solution of chloroplatinic acid to obtain a Pt-Co two-atom site self-supporting integrated electrode.

2. The Pt-Co dual-atom-site self-supporting integrated electrode according to claim 1, characterized in that, The cobalt single-atom doping level in the integrated electrode is 0.1-0.8 μg / cm³. 2 The loading of platinum single atoms was 3.6–9.7 μg / cm³. 2 .

3. The Pt-Co dual-atom-site self-supporting integrated electrode according to claim 1, characterized in that, The preparation method of the cobalt-zinc based metal-organic framework nanosheet array precursor in step S1 is as follows: Co(NO3)2·6H2O and Zn(NO3)2·6H2O are dissolved in deionized water to obtain a mixed metal salt solution, which is then rapidly mixed with a 2-methylimidazole aqueous solution and stirred vigorously. The solution is then immersed in pretreated carbon cloth and reacted at room temperature to obtain the cobalt-zinc based metal-organic framework nanosheet array precursor.

4. The Pt-Co dual-atom-site self-supporting integrated electrode according to claim 3, characterized in that, The molar ratio of Co(NO3)2·6H2O to Zn(NO3)2·6H2O is (1-4):1, wherein the concentration of Zn(NO3)2·6H2O is 0.016-0.048 mol / L. The mixed metal salt solution is rapidly mixed with an equal volume of 0.4-0.8 M 2-methylimidazole aqueous solution and stirred vigorously for 15-40 seconds. The cleaned carbon cloth is then immersed in the mixture and reacted at room temperature for 3-20 hours.

5. The Pt-Co dual-atom-site self-supporting integrated electrode according to claim 1, characterized in that, The conditions for the high-temperature annealing treatment in step S2 are as follows: under a high-purity argon atmosphere and a flow rate of 30-60 sccm, the temperature is increased to 700-1050 ℃ at a heating rate of 2-10 ℃ / min, and held at this temperature for 1-12 hours.

6. The Pt-Co dual-atom-site self-supporting integrated electrode according to claim 1, characterized in that, The acid etching conditions described in step S3 are as follows: acid etching is performed using a 3-6 M HNO3 solution at 80-100 °C.

7. The Pt-Co dual-atom-site self-supporting integrated electrode according to claim 1, characterized in that, The conditions for the impregnation treatment in step S4 are as follows: using an aqueous solution of chloroplatinic acid with a concentration of 0.05-0.2 mg / mL, and hydrothermally reacting at 45-60 °C for 4 hours.

8. The application of a Pt-Co dual-atom-site self-supporting integrated electrode according to any one of claims 1-7 in water electrolysis for hydrogen production.

9. The application of the Pt-Co dual-atom-site self-supporting integrated electrode according to claim 8 in water electrolysis for hydrogen production, characterized in that, The Pt-Co dual-atom-site self-supporting integrated electrode can be used as a cathode for acidic water electrolysis to produce hydrogen, or as a cathode to assemble a proton exchange membrane electrolyzer for water electrolysis to produce hydrogen.

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