Efficient and stable alkaline hydrogen evolution electrocatalyst mediated by combining carbon nano tube and boride as well as preparation method and application of efficient and stable alkaline hydrogen evolution electrocatalyst

Abstract

The invention discloses a carbon nanotube and boride mediated efficient and stable alkaline hydrogen evolution electrocatalyst as well as a preparation method and application thereof. The electrocatalyst comprises a metal active phase, a metal oxide active phase, a boron oxide matrix phase, a carbon nanotube support and a carrier, the carbon nanotube support grows on the carrier, the metal active phase is dispersed and distributed on the surfaces of the metal oxide active phase and the boron oxide matrix phase in a nano-particle form, and the metal oxide active phase and the boron oxide matrix phase are distributed in a mixed manner and are loaded on the carrier on which the carbon nanotube support grows. Based on simultaneous optimization of intrinsic activity, density and accessibility of active sites and charge and substance transmission characteristics, the catalytic performance of the high-activity alkaline hydrogen evolution electrocatalyst taking the boride and the carbon nanotubes as media is superior to that of a noble metal Pt catalyst, and the high-activity alkaline hydrogen evolution electrocatalyst has excellent stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen evolution electrocatalysts, and in particular relates to a highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride, and a preparation method and application thereof. Background Art

[0002] As an important material basis of modern human civilization, fossil energy has now become one of the main issues restricting the sustainable development of society. The combination of water electrolysis technology and renewable energy not only provides a clean way to produce hydrogen, but also promotes advanced energy conversion technology, and is expected to play a key role in the future clean energy economy. However, the key to realizing this vision lies in the development of highly active and low-cost hydrogen evolution electrocatalytic materials. Although the precious metal platinum (Pt) is recognized as an efficient hydrogen evolution reaction (HER) catalyst, its high cost and scarcity severely limit its widespread application. In recent years, the development of non-precious metal catalysts to reduce costs and improve catalytic performance has become a mainstream trend in the field of water electrolysis technology. Thanks to the progress of material preparation and characterization technology and the improvement of computing power, non-precious metal catalysts have made significant progress in material composition design, nanostructure regulation and reaction mechanism analysis. At present, a variety of nickel-based (Ni) and cobalt-based (Co) alloys or compounds have shown hydrogen evolution catalytic activity close to that of precious metal Pt, which preliminarily proves the feasibility of developing high-performance and low-cost catalysts. However, the activity of existing non-precious metal electrocatalysts still cannot meet the needs of practical applications, especially in terms of simultaneously optimizing the catalytic intrinsic activity, active site density and electronic conductivity, which still faces major challenges, especially in alkaline hydrogen evolution reactions that require multi-site synergy.

[0003] Transition metal borides are considered an important class of electrocatalytic materials due to their excellent metallic conductivity, good chemical inertness and unique electronic properties. However, the hydrogen evolution activity of most reported transition metal boride catalysts is mediocre. For example, typical cobalt-based or nickel-based boride catalysts require an overpotential of 60 to 80 mV under alkaline conditions to drive a hydrogen evolution reaction of 10 mA cm-2. The complex catalyst phase composition and the difficult-to-finely control microstructure have caused the development of transition metal borides in the field of water electrolysis to stagnate. Specifically, most researchers use a simple chemical reduction method to prepare transition metal boride catalysts, but the catalysts prepared by this method are usually amorphous and often mixed with by-products such as boron oxides and metal oxides, making the phase characterization and interface regulation of the catalyst extremely difficult. In addition, the reaction kinetics of the traditional chemical reduction method are too fast, making it difficult to precisely control the morphology and microstructure of the catalyst, further affecting its hydrogen evolution reaction activity.

[0004] To address these challenges, researchers have developed a series of surface engineering strategies in recent years, such as nanostructure regulation, heterogeneous atom doping, defect introduction, crystal plane control, and heterogeneous interface construction, to optimize the surface chemical and physical properties of catalysts. These strategies are often used in combination to produce synergistic effects and significantly improve catalytic performance. For example, by combining transition metals with related oxides, the intrinsic activity of the catalyst can be effectively enhanced. Studies have shown that the alkaline hydrogen evolution reaction of metal / metal oxide composite catalysts is achieved through a synergistic catalytic process, in which the metal oxide promotes the dissociation of water molecules, while the adjacent metal sites promote the composite desorption of hydrogen atoms. In addition, the interface between the conductive transition metal and the semiconductor metal oxide forms a built-in electric field, thereby enhancing the charge transfer kinetics. Although these strategies have made significant progress in improving catalyst performance, existing catalysts still find it difficult to meet the needs of industrial applications, especially in terms of stability and efficiency at high current density. To this end, there is an urgent need to find a simple and controllable preparation method that can achieve high activity and high stability of the catalyst. Summary of the invention

[0005] In view of the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide an efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and borides. The catalyst of the present invention has high intrinsic activity, abundant active sites and good conductivity, and can efficiently catalyze the hydrogen evolution reaction of water electrolysis under alkaline conditions, and its comprehensive catalytic performance is better than that of commercial Pt / C catalysts.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride. The method has readily available raw materials, simple operation, controllable reaction, and is convenient for mass production.

[0007] Another object of the present invention is to provide the use of the above-mentioned highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and borides in hydrogen production by electrolysis of water.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride, the electrocatalyst comprising a metal active phase, a metal oxide active phase, a boron oxide matrix phase, a carbon nanotube support and a carrier; the carbon nanotube support is grown on the carrier, the metal active phase is dispersed and distributed on the surface of the metal oxide active phase and the boron oxide matrix phase in the form of nanoparticles, the metal oxide active phase and the boron oxide matrix phase are mixed and distributed, and are both loaded on the carrier grown with the carbon nanotube support.

[0010] Preferably, the metal active phase is a transition metal, and the metal oxide active phase is a transition metal oxide; the transition metal is at least one of Fe, Co, and Ni.

[0011] Preferably, the carrier is selected from foamed metal, metal mesh, ion exchange resin, molecular sieve or porous carbon material; more preferably, foamed cobalt.

[0012] Preferably, the carbon nanotube support is in the form of a carbon nanotube layer, and the thickness of the nanotube layer is 2-3 μm.

[0013] Preferably, the particle size of the metal active phase is 2-5 nm.

[0014] Preferably, the metal oxide active phase and the boron oxide matrix phase exist in an amorphous form; the metal oxide active phase and the boron oxide matrix phase have a nanoporous structure, the nanopore size is 2 to 10 nm, the nanosheet thickness is 1 to 10 nm, and the nanosheet length is 50 to 500000 nm.

[0015] The above-mentioned method for preparing a highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride comprises the following steps:

[0016] (1) adding the carrier to an ethanol solution containing acetylacetonate, and growing carbon nanotube supports on the surface of the carrier by an immersion combustion method;

[0017] (2) adding the support supported by carbon nanotubes obtained in step (1) to an aqueous solution containing a transition metal salt, a boron reducing agent and a complexing agent, and growing a metal boride derivative precursor having a nanostructure on the surface of the support supported by carbon nanotubes by a chemical reduction method;

[0018] (3) After washing and drying the metal boride derivative precursor obtained in step (2), the precursor is subjected to high-temperature heat treatment in an inert atmosphere to obtain a highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride.

[0019] Preferably, the acetylacetonate in step (1) is cobalt acetylacetonate, and the concentration of the acetylacetonate is 0.1 to 0.5 mol / L;

[0020] Preferably, the immersion time in step (1) is 10 to 20 seconds.

[0021] Preferably, the transition metal salt in step (2) refers to at least one of the halides, nitrates, sulfates, aminosulfonates and acetates of transition metals; the transition metal refers to at least one of Fe, Co and Ni;

[0022] Preferably, the complexing agent in step (2) is C 4 H4 Na 2 O 4 (disodium succinate); the boron reducing agent is C 2 H 10 BN (dimethylaminoborane);

[0023] Preferably, in step (2), the concentration of the transition metal salt is 0.001 to 1 M, the concentration of the boron reducing agent is 0.001 to 1 M; the concentration of the complexing agent is 0.001 to 1 M;

[0024] Further preferably, the concentration of the transition metal salt is 0.01 to 0.02 M, the concentration of the boron reducing agent is 0.01 to 0.1 M; the concentration of the complexing agent is 0.01 to 0.02 M;

[0025] Preferably, the reaction temperature of the chemical reduction method in step (2) is 35 to 65° C.; the reaction time of the chemical reduction method is 20 to 100 min;

[0026] Preferably, the inert atmosphere in step (3) is argon; the temperature of the high-temperature heat treatment is 200-400° C.; and the time of the high-temperature heat treatment is 1-3 hours.

[0027] The above-mentioned high-efficiency and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and borides is applied in hydrogen production by electrolysis of water.

[0028] Preferably, the solution used to produce hydrogen by electrolyzing water is an alkaline solution.

[0029] The design principle of the present invention is:

[0030] For electrocatalysts, the key factors affecting their alkaline hydrogen evolution reaction (HER) performance include intrinsic activity, density and accessibility of active sites, and charge and material transport properties. Traditional electrocatalyst preparation methods are often difficult to optimize these factors at the same time. The catalyst provided by the present invention takes these key factors into consideration in design and provides a simple and controllable preparation method. First, carbon nanotube support is grown on the surface of the support material by an impregnation combustion method, providing a high specific surface area and a good electrical conductivity basis for the catalyst. Subsequently, a metal boride derivative precursor containing catalytic active components and having a high specific surface area is grown on the surface of the support material by a chemical reduction method, laying the material composition and structural foundation for the synthesis of high-performance catalysts. Among them, the metal boride derivative precursor is a composite material containing metal boride, metal oxide and boric acid. Finally, the precursor is subjected to high-temperature heat treatment in an inert atmosphere. Since metal boride has a certain reducibility, metal boride and metal oxide undergo redox reaction under high-temperature heat treatment in an inert atmosphere to generate metal and boron oxide. On the one hand, the metal precipitated in situ is combined with the original oxide matrix to construct a synergistic catalytic active site, in which the oxide promotes the dissociation of water molecules, and the metal provides a composite desorption active site for hydrogen atoms, and the two work together to improve the efficiency of the hydrogen evolution reaction in alkaline water electrolysis. On the other hand, the in situ precipitation of metal particles ensures the close combination between the metal and the oxide, which is conducive to the transfer of electrons in the electrocatalytic process. At the same time, the conversion of metal oxides with poor conductivity into metals with better conductivity also improves the conductivity of the catalyst material. In addition, the pre-grown carbon nanotubes support the construction of a hierarchical mesoporous-macroporous structure, which not only increases the accessibility of active sites, but also improves the transmission of water and the release of gas, and further optimizes the mass transfer characteristics of the catalyst. In summary, the hydrogen evolution electrocatalyst provided by the present invention has excellent intrinsic activity, richness and accessibility of active sites, and charge and mass transfer characteristics.

[0031] The advantages and beneficial effects of the present invention are:

[0032] (1) The method and material provided by the present invention have the characteristics of optimizing intrinsic activity, active site richness and accessibility, and charge and mass transfer characteristics at the same time. On the one hand, the metal generated by the reduction reaction during the high-temperature heat treatment combines with the original metal oxide to construct synergistic catalytic active sites; on the other hand, the in-situ generation of more highly conductive metals after the high-temperature heat treatment ensures the high conductivity of the catalyst material; in addition, the hierarchical pore structure constructed by the pre-grown carbon nanotube support provides more active sites while further improving the mass transfer performance of the catalyst.

[0033] (2) The preparation method of the present invention has readily available raw materials, simple process, controllable reaction, and is convenient for mass production.

[0034] (3) The alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride obtained in the present invention can efficiently and stably catalyze the hydrogen evolution reaction by electrolysis of water under alkaline conditions, and its catalytic performance is better than that of the precious metal Pt catalyst and has excellent stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 (a) SEM image and (b) TEM image of the combustion sample in Example 1.

[0036] Figure 2 (a) X-ray diffraction patterns and (b) Raman patterns of the burned sample, reduced sample and heat-treated sample in Example 1.

[0037] Figure 3 Scanning electron microscope images of (a) the reduced sample and (b) the heat-treated sample in Example 1.

[0038] Figure 4 High-resolution transmission electron microscopy images of (a) the reduced sample and (b) the heat-treated sample in Example 1.

[0039] Figure 5 The X-ray photoelectron spectra of the reduced sample and the heat-treated sample in Example 1.

[0040] Figure 6 The heat-treated sample Co / CoO / CNT / CF and the reference sample Co / CoO / CF and the reduced sample Co 2 Comparison of (a) hydrogen evolution reaction polarization curves and (b) Tafel curves of B / CoO / CNT / CF and reference sample Pt / C.

[0041] Figure 7 The heat-treated sample Co / CoO / CNT / CF and the reference sample Co / CoO / CF and the reduced sample Co 2 (a) Relationship between current density and potential scan rate of B / CoO / CNT / CF and (b) impedance spectrum test results at open circuit potential.

[0042] Figure 8 This is a diagram showing the durability test results of the heat-treated sample Co / CoO / CNT / CF in Example 1.

[0043] Fig. 9 This is a scanning electron microscope morphology image of the heat-treated sample Co / CoO / CNT / CF in Example 1 after 100 hours of durability test.

[0044] Fig.10(a) hydrogen evolution reaction polarization curve and (b) durability test result diagram of high concentration Co / CoO / CNT / CF and Co / CoO / CF in Example 1.

[0045] Fig.11 The reference sample high concentration Co / CoO / CNT / CF in Example 1 is 100 mA cm -2 Scanning electron microscope morphology after 100 hours of durability test at a current density of .

[0046] Fig.12 (a) The polarization curve of the hydrogen evolution reaction, (b) The polarization curve of the complete water electrolysis, (c) The durability test result of the complete water electrolysis cell, and (d) The photo of the seawater electrolysis in the solar-driven complete water electrolysis cell, of the heat-treated sample Co / CoO / CNT / CF in Example 1 under alkaline seawater.

[0047] Fig.13 (a) Comparison of hydrogen evolution reaction polarization curves and (b) durability test results of the heat-treated sample Co / CoO / CNT / NF and the reference sample in Example 2.

[0048] Fig.14 (a) Comparison diagram of hydrogen evolution reaction polarization curves and (b) durability test result diagram of the heat-treated sample Co / CoO / CNT / Ti and the reference sample in Example 3.

[0049] Fig.15 (a) Comparison diagram of hydrogen evolution reaction polarization curves and (b) durability test results of the heat-treated sample Ni / NiO / CNT / NF and the reference sample in Example 4.

[0050] Fig.16 (a) Comparison diagram of hydrogen evolution reaction polarization curves and (b) durability test result diagram of the heat-treated sample Ni-Co / NiO / CoO / CNT / NF and the reference sample in Example 5. DETAILED DESCRIPTION

[0051] The present invention is described in detail below in conjunction with examples, but the implementation manner and protection scope of the present invention are not limited to the following examples.

[0052] The present invention is described in detail below through specific examples.

[0053] Example 1

[0054] Synthesis, Structure and Catalytic Performance of Co / CoO / CNT / CF Catalyst

[0055] Catalyst preparation:

[0056] (1) Using cobalt foam (CF) as a carrier, CF (2 mm, 1 × 2 cm2 ) was washed with ethanol, hydrochloric acid and deionized water in turn to completely remove surface impurities. The cleaned CF was immersed in 30 mL of 0.1 M Co(acac) 2 The mixture was placed in an ethanol solution for about 10 seconds, then taken out and ignited to allow carbon nanotubes (CNTs) to grow on the CF surface, obtaining a CNT-modified CF carrier (combustion state sample).

[0057] (2) The Co / CoO composite catalyst was synthesized on the CNT-modified CF support using a boride-mediated method. 4 7H 2 O, 2.0mmol C 2 H 10 BN and 0.4 mmol C 4 H 4 Na 2 O 4 Dissolve in 25 ml of deionized water, stir vigorously and keep the temperature at 45°C. Then immerse the CNT-modified CF support in the solution for 80 minutes for chemical reduction reaction. The obtained sample (reduced state sample) is fully cleaned and vacuum dried, and then annealed at 300°C for 2 hours in an argon atmosphere to obtain the target catalyst Co / CoO / CNT / CF (heat-treated state sample).

[0058] Catalyst phase / structure / element chemical state characterization:

[0059] Scanning electron microscope (SEM) image of the combustion sample obtained in this example ( Figure 1 a) and transmission electron microscopy (TEM) images ( Figure 1 b) shows that the CNT network grows uniformly on the CF surface, with a layer thickness of 2-3 μm and a single CNT diameter ranging from a few nanometers to more than ten nanometers. According to X-ray diffraction (XRD) analysis ( Figure 2 a) The combustion-synthesized sample does not show the diffraction peak corresponding to the target CNT, but has crystalline Co 3 O 4 (JCPDS#43-1003) and CoO(JCPDS#43-1004). Raman spectroscopy analysis ( Figure 2 b) at 1342.2 and 1586.3 cm -1 The characteristic D and G bands of carbon materials appeared at , and the ID / IG ratio was 0.96, confirming the successful growth of CNT support on the CF surface.

[0060] The scanning electron microscopy images of the reduced sample and the heat-treated sample are shown in Figure 3 Scanning electron microscopy revealed that the reduced sample formed a wrinkled nanosheet that intertwined with CNTs to form a three-dimensional network covering the CF surface ( Figure 3 a in the figure). After high temperature heat treatment, the three-dimensional network structure did not change significantly ( Figure 3 b). Further transmission images ( Figure 4 a) in the figure shows that the reduced sample exists in an amorphous form, and the corresponding XRD analysis ( Figure 2 In addition, it was observed that the broad bulge of the diffraction peak in the XRD diffraction pattern was related to the Co 2 The strongest diffraction peak of B corresponds to that of amorphous Co. 2 B. According to X-ray photoelectron spectroscopy (XPS) analysis ( Figure 5 ), the reduced sample showed Co 0 、Co 2+ , B 0 and BO x Signal. Among them, Co 0 The signal shifted negatively relative to the standard sample, and B 0 The signal shifted positively relative to the standard sample, which proved that the amorphous Co 2 In addition, according to the chemical reduction reaction principle and the large amount of Co in the reduced sample 2+ with BO x The presence of the signal finally confirmed that the reduced sample actually contained Co 2 B, CoO, H 3 BO 3 amorphous mixture.

[0061] After the reduced sample was subjected to high temperature heat treatment, the phase composition of the sample changed significantly. According to XRD analysis ( Figure 2 In a), the heat-treated sample shows a weak diffraction peak corresponding to metal Co. In addition, the TEM image ( Figure 4 b) in Figure 2 also confirms the presence of metal Co nanoparticles. Figure 5 ) shows that B 0 The signal disappears completely, and Co 0 The signal offset relative to the standard sample also completely disappeared. In addition, Co 0 Signal relative to Co 2+ The signal intensity increased. Comprehensive analysis showed that Co 2 During the high temperature heat treatment, B and CoO underwent a redox reaction to generate Co and B. 2 O 3 In addition, Raman spectroscopy ( Figure 2The characteristic peaks of carbon materials in b) still exist, indicating that CNTs are retained during the entire material synthesis process. Based on the above analysis, the heat-treated samples were determined to be metal nanoparticles Co, amorphous CoO / B 2 O 3 and CNT-supported mixture. Therefore, the target catalyst is named Co / CoO / CNT / CF. The dispersion of Co metal nanoparticles on the CoO surface, coupled with the hierarchical porous structure of CNT support, can simultaneously enhance the density of active sites while promoting efficient mass transport through interconnected channels.

[0062] Electrocatalytic performance test of catalyst:

[0063] The reference catalysts involved in the following tests were prepared as follows:

[0064] High concentration Co / CoO / CNT / CF: In the synthesis method of this catalyst, 0.3 mmol CoSO 4 7H 2 O, 2.0mmolC 2 H 10 BN and 0.4 mmol C 4 H 4 Na 2 O 4 Replaced with 3mmol CoSO 4 7H 2 O, 4mmol C 2 H 10 BN and 4mmol C 4 H 4 Na 2 O 4 The other preparation conditions are consistent with Co / CoO / CNT / CF.

[0065] Co / CoO / CF: In the synthesis method of this catalyst, only the CNT-modified CF carrier is replaced with a CF carrier, and the other preparation conditions are consistent with Co / CoO / CNT / CF.

[0066] Co 2 B / CoO / CNT / CF: the above reduced sample.

[0067] Pt / C: Commercial Pt / C.

[0068] The catalytic performance of Co / CoO / CNT / CF catalyst for alkaline HER was tested using a three-electrode system in 1.0 M potassium hydroxide aqueous solution ( Figure 6 The catalyst reaches 10 mA cm at an overpotential of 17 mV. -2 The current density reaches 500mA·cm at 185mV.-2 The current density is significantly better than that of high concentration Co / CoO / CNT / CF( Fig.10 a), Co / CoO / CF, Co 2 The overpotentials of B / CoO / CNT / CF and Pt / C reference catalysts were 22mV, 29mV, 73mV, and 32mV, respectively, to reach 10mA·cm -2 The current density reaches 500 mA cm at overpotentials of 205 mV, 236 mV, and 309 mV respectively. -2 The current density is 31mV dec. -1 , which is lower than that of other reference catalysts, indicating that it is more efficient in promoting the Volmer step ( Figure 6 b) in the above.

[0069] Figure 7 The electrochemically active surface areas (ECSA) of the catalysts are given respectively ( Figure 7 a) and charge transfer resistance (Rct) ( Figure 7 b), the results show that Co / CoO / CNT / CF has the largest ECSA and the lowest Rct. Compared with Co / CoO / CF, the introduction of CNT improves the alkaline HER activity in three aspects: enhancing the electron transfer kinetics, reducing Rct, and promoting electron transfer in the HER process; increasing the density of accessible active sites, and constructing a three-dimensional porous catalyst layer with a large surface area, which enhances the exposure of the Co / CoO heterogeneous interface boundary; improving mass transfer characteristics, and forming a hierarchical mesoporous-macroporous structure, combined with superhydrophilicity and gas repellency, promotes electrolyte penetration and gas diffusion.

[0070] Figure 8 The stability test results of the target catalyst are given. The stability of the Co / CoO / CNT / CF catalyst was tested by chronopotentiometry at 100, 500 and 1000 mA cm -2 During the 100-hour constant current operation, the potential fluctuations were only 10, 15, and 28 mV, respectively. At 100 hours, the voltage values ​​were only -2 mV, -4 mV, and +3 mV compared to 0 hours. Scanning electron microscope image ( Fig. 9 ) shows that the catalyst morphology and microstructure did not change significantly before and after 100 hours of operation, indicating that it has good stability. -2 After 100 hours of constant current operation, a large potential decay occurred, which was 21mV and 26mV ( Fig.10 b); SEM image of the reference sample after stability test of high concentration Co / CoO / CNT / CF ( Fig.11), the catalyst coating had obvious cracking and peeling problems ( Fig.11 a), and the nanosheets under the microscopic view have undergone some aggregation ( Fig.11 Therefore, the introduction of CNT support and the optimization of the concentration of the target catalyst significantly improved the stability of the catalyst.

[0071] Fig.12 The results show that Co / CoO / CNT / CF exhibits good HER activity in alkaline natural seawater, and overpotentials of 19 and 191 mV are required to reach current densities of 10 and 500 mA cm-2, respectively. Fig.12 a). As the cathode, Ni 1-x Fe x O(OH) 1-y F y A two-electrode electrolytic cell was constructed with / NiO / NF as the anode. The electrolytic cell was subjected to the conditions of 100 and 500 mA cm -2 At current densities of only 1.64 and 1.76 V ( Fig.12 b) and at 500 mA cm -2 The voltage fluctuation during the 100-hour constant current test was only 25mV ( Fig.12 c), in addition, the assembled solar-driven seawater electrolysis system can achieve continuous and stable hydrogen production under sunlight ( Fig.12 d) in.

[0072] The catalyst of the present embodiment is composed of a cobalt / cobalt oxide active phase, a carbon nanotube support and a foamed cobalt carrier. Through a boride-mediated synthesis method, a cobalt / cobalt oxide heterogeneous interface is grown on a carbon nanotube support to form a rich active site. The introduction of the carbon nanotube support not only improves the conductivity of the catalyst, but also constructs a hierarchical porous structure and enhances the mass transfer performance. During the high-temperature heat treatment process, metal cobalt and boron oxide are generated by the solid-phase redox reaction of the boride and cobalt oxide, a cobalt / cobalt oxide heterogeneous interface is constructed, and a synergistic catalytic active site is formed. After high-temperature heat treatment, the metal cobalt nanoparticles generated in situ are closely combined with cobalt oxide to ensure the high conductivity of the catalyst. At the same time, the three-dimensional porous structure of the carbon nanotube support and the large number of nanopores formed by boric acid dehydration during the calcination process further improve the mass transfer and electronic conductivity of the catalyst and provide more active sites; therefore, excellent hydrogen evolution reaction activity and stability are exhibited under alkaline conditions.

[0073] Example 2

[0074] Synthesis, Structure and Catalytic Performance of Co / CoO / CNT / NF Catalyst

[0075] Catalyst preparation:

[0076] In the synthesis method of this embodiment, only the cobalt foam (CF) is replaced by nickel foam (NF), and the other preparation conditions are the same as those in Example 1.

[0077] Electrocatalytic performance test of catalyst:

[0078] Hydrogen evolution reaction polarization curve test results ( Fig.13 The results in a) show that the Co / CoO / CNT / NF catalyst has excellent electrocatalytic activity for hydrogen evolution reaction, and it can reach 10 mA / cm in 1.0 M potassium hydroxide solution with only 18 mV hydrogen evolution overpotential. 2 Current density; 100 hours constant current durability test results ( Fig.13 b) in the figure shows that the activity of the catalyst has not declined significantly, indicating that the catalyst has excellent stability.

[0079] Example 3

[0080] Synthesis, Structure and Catalytic Performance of Co / CoO / CNT / Ti Catalyst

[0081] Catalyst preparation:

[0082] In the synthesis method of this embodiment, only the foamed cobalt (CF) is replaced with the Ti mesh, and the other preparation conditions are the same as those in Embodiment 1.

[0083] Electrocatalytic performance test of catalyst:

[0084] Hydrogen evolution reaction polarization curve test results ( Fig.14 The results in a) show that the Co / CoO / CNT / Ti catalyst has excellent electrocatalytic activity for hydrogen evolution reaction, and it can reach 10 mA / cm in 1.0 M potassium hydroxide solution with only 36 mV hydrogen evolution overpotential. 2 Current density; 100 hours constant current durability test results ( Fig.14 b) in the figure shows that the activity of the catalyst has not declined significantly, indicating that the catalyst has excellent stability.

[0085] Example 4

[0086] Synthesis, Structure and Catalytic Performance of Ni / NiO / CNT / NF Catalyst

[0087] Catalyst preparation:

[0088] In the synthesis method of this embodiment, only CoSO 4 7H 2 O replaced by NiSO 4 7H 2 O, and the other preparation conditions are consistent with those in Example 1.

[0089] Electrocatalytic performance test of catalyst:

[0090] Hydrogen evolution reaction polarization curve test results ( Fig.15 The figure (a) shows that the Ni / NiO / CNT / NF catalyst has excellent electrocatalytic activity for hydrogen evolution reaction, and it can reach 10 mA / cm in 1.0 M potassium hydroxide solution with only 26 mV hydrogen evolution overpotential. 2 Current density; 100 hours constant current durability test results ( Fig.15 b) in the figure shows that the activity of the catalyst has not declined significantly, indicating that the catalyst has excellent stability.

[0091] Example 5

[0092] Synthesis, Structure and Catalytic Performance of Ni-Co / NiO / CoO / CNT / NF Catalyst

[0093] Catalyst preparation:

[0094] In the synthesis method of this embodiment, only 0.3 mmol CoSO 4 7H 2 The amount of O added was changed to 0.15 mmol NiSO 4 7H 2 O and 0.15 mmol CoSO 4 7H 2 The remaining preparation conditions were the same as those in Example 1.

[0095] Electrocatalytic performance test of catalyst:

[0096] Hydrogen evolution reaction polarization curve test results ( Fig.16 The figure (a) shows that the Ni-Co / NiO / CoO / CNT / NF catalyst has excellent electrocatalytic activity for hydrogen evolution reaction, and its hydrogen evolution overpotential can reach 10 mA / cm in 1.0 M potassium hydroxide solution with only 20 mV. 2 Current density; 100 hours constant current durability test results ( Fig.16 b) in the figure shows that the activity of the catalyst has not declined significantly, indicating that the catalyst has excellent stability.

[0097] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. Combining carbon nanotubes and boride-mediated efficient and stable alkaline hydrogen evolution electrocatalysts, characterized by: The electrocatalyst comprises a metal active phase, a metal oxide active phase, a boron oxide matrix phase, a carbon nanotube support and a carrier; the carbon nanotube support is grown on the carrier, the metal active phase is dispersed in the form of nanoparticles on the surface of the metal oxide active phase and the boron oxide matrix phase, the metal oxide active phase and the boron oxide matrix phase are mixed and distributed, and are both loaded on the carrier grown with the carbon nanotube support.

2. The highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride according to claim 1, characterized in that: The metal active phase is a transition metal, and the metal oxide active phase is a transition metal oxide; the carrier is selected from foam metal, metal mesh, ion exchange resin, molecular sieve or porous carbon material; the transition metal refers to at least one of Fe, Co and Ni.

3. The highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride according to claim 1, characterized in that: The carbon nanotube support is in the form of a carbon nanotube layer, and the thickness of the nanotube layer is 2 to 3 μm; The particle size of the metal active phase is 2-5 nm.

4. The highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride according to claim 1, characterized in that: The metal oxide active phase and the boron oxide matrix phase exist in amorphous form; the metal oxide active phase and the boron oxide matrix phase have a nanoporous structure, the nanopore size is 2-10nm, the nanosheet thickness is 1-10nm, and the nanosheet length is 50-500000nm.

5. The method for preparing a highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) adding the carrier to an ethanol solution containing acetylacetonate, and growing carbon nanotube supports on the surface of the carrier by an immersion combustion method; (2) adding the support supported by carbon nanotubes obtained in step (1) to an aqueous solution containing a transition metal salt, a boron reducing agent and a complexing agent, and growing a metal boride derivative precursor having a nanostructure on the surface of the support supported by carbon nanotubes by a chemical reduction method; (3) After washing and drying the metal boride derivative precursor obtained in step (2), the precursor is subjected to high-temperature heat treatment in an inert atmosphere to obtain a highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and boride.

6. The preparation method according to claim 5, characterized in that: The acetylacetonate in step (1) is cobalt acetylacetonate, and the concentration of the acetylacetonate is 0.1-0.5 mol / L; the immersion time is 10-20 s.

7. The preparation method according to claim 5, characterized in that: In step (2), the transition metal salt is at least one of the halides, nitrates, sulfates, aminosulfonates and acetates of transition metals; the transition metal is at least one of Fe, Co and Ni; the complexing agent is C4H4Na2O4; the boron reducing agent is C2H 10 BN; In step (2), the concentration of the transition metal salt is 0.001 to 1 M, the concentration of the boron reducing agent is 0.001 to 1 M; the concentration of the complexing agent is 0.001 to 1 M; The reaction temperature of the chemical reduction method in step (2) is 35 to 65° C.; the reaction time of the chemical reduction method is 20 to 100 min.

8. The preparation method according to claim 7, characterized in that: The concentration of the transition metal salt is 0.01-0.02M, the concentration of the boron reducing agent is 0.01-0.1M; and the concentration of the complexing agent is 0.01-0.02M.

9. The preparation method according to claim 5, characterized in that: The inert atmosphere in step (3) is argon; the temperature of the high-temperature heat treatment is 200-400° C.; and the time of the high-temperature heat treatment is 1-3 hours.

10. Use of the highly efficient and stable alkaline hydrogen evolution electrocatalyst mediated by carbon nanotubes and borides as claimed in any one of claims 1 to 4 in hydrogen production by electrolysis of water.

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