Supported Ru6 cluster catalyst for hydrogen evolution of alkaline electrolyzed water as well as preparation method and application of supported Ru6 cluster catalyst

Abstract

The invention relates to a supported Ru6 cluster catalyst for hydrogen evolution from alkaline electrolyzed water as well as a preparation method and application of the supported Ru6 cluster catalyst. The invention relates to a supported Ru6 cluster catalyst for hydrogen evolution by alkaline electrolysis of water, in the catalyst, six accurate Ru atoms are used as a cluster to be supported on an oxidized Ketjen black carrier, the coordination number of Ru-Ru is 2.5-2.7, the Ru-Ru is of a plane-like structure, and the loading amount of Ru is 0.5-2.4 wt%. The catalyst is expressed as Ru6 / KBO, and Ru6 nanoclusters with accurate atom number are calcined by a Joule furnace, reduced and loaded on oxyketjen black. The Ru6 cluster loaded on KBO is prepared and has good hydrogen evolution catalytic activity under the alkaline condition, the utilization efficiency of Ru atoms is high, the catalyst structure is stable, the electro-catalysis HER performance is remarkably improved, and the catalytic effect is lasting.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst materials, and in particular relates to a supported Ru6 cluster catalyst for hydrogen evolution in alkaline water electrolysis, and a preparation method and use thereof. Background Art

[0002] As the global demand for clean energy continues to increase to address issues such as climate change and energy security, hydrogen has attracted widespread attention as a clean and efficient energy carrier. Hydrogen production by water electrolysis is a sustainable method of hydrogen production that uses electricity generated by renewable energy sources (such as solar energy, wind energy, etc.) to decompose water into hydrogen and oxygen. Among the many water electrolysis hydrogen production technologies, alkaline water electrolysis (AWE) technology is a relatively mature water electrolysis system. Its working principle is to achieve water decomposition through electrode reactions in an alkaline electrolyte (usually potassium hydroxide or sodium hydroxide solution). Compared with other water electrolysis technologies (such as proton exchange membrane water electrolysis and solid oxide water electrolysis), alkaline water electrolysis technology has the advantages of low cost and simple equipment. In the alkaline water electrolysis process, the hydrogen evolution reaction (HER) is a key half-reaction, and its reaction efficiency directly affects the overall efficiency of water electrolysis hydrogen production. However, the hydrogen evolution reaction has the problem of sluggish kinetics in an alkaline environment. This is because in an alkaline medium, water molecules need to first dissociate into hydrogen ions (H + ) and hydroxide ions (OH - ), and then the hydrogen ions accept electrons to generate hydrogen. Compared with the hydrogen evolution reaction in acidic media, the hydrogen evolution reaction in alkaline media has an additional slow step of water molecule dissociation, resulting in a higher reaction overpotential. The existence of overpotential will increase the energy consumption in the electrolysis process and reduce the efficiency of hydrogen production. Precious metal catalysts are usually used to reduce the overpotential of hydrogen evolution reaction.

[0003] In the field of hydrogen evolution by alkaline water electrolysis, an ideal catalyst should have the characteristics of high catalytic activity, good stability and low cost. Platinum-based catalysts are recognized as efficient HER catalysts, but their scarce resources and high cost have hindered their widespread application, thus triggering the development of efficient non-Pt-based catalysts. Ru has a much lower cost than Pt, but has similar hydrogen adsorption strength and lower water dissociation energy barrier as Pt, as well as good durability, and is considered to be an ideal alternative catalyst to Pt-based catalysts. In the past few years, Ru has been widely studied as a catalytic active center for alkaline HER, but as a noble metal, if the utilization rate of Ru is not high, the cost of the catalyst will remain high. Therefore, reducing the noble metal loading while maintaining high activity and stability is crucial for the design of high-performance catalysts. An obvious choice is to reduce the size to nanoclusters or single atoms to greatly improve the atomic utilization efficiency. Single-atom catalysts have discrete metal centers and can theoretically achieve 100% metal utilization, but they cannot provide multiple metal atomic sites, and the adsorption of active intermediates is relatively single, which is not suitable for the regulation of multiple adsorptions of H* and OH* at the same time. Clusters with precise atomic numbers have clear composition, size and structure, and can accurately determine active sites, thereby establishing a clear catalyst structure-activity relationship, which provides a basis for in-depth understanding of the mechanism of hydrogen evolution reaction and further optimization of catalyst performance. On the other hand, selecting a support material with a high specific surface area is the key to reducing the load of precious metals. Ketjen black oxide has a rich pore structure and a large specific surface area, which can not only provide a large number of attachment sites for loading active substances, but also fully expose the active centers of the catalyst in the catalytic reaction, thereby improving the catalytic activity. In addition, due to its high surface energy, ruthenium-based catalysts face the problems of relatively strong H adsorption and severe aggregation of Ru atoms, which not only makes the Tafel step challenging, but also leads to the loss of active sites. The metal-support interaction can adjust the surface electronic structure so that the active site has the best hydrogen adsorption energy, thereby enhancing the catalytic activity for HER. Therefore, the active component can select a metal cluster catalyst with a precise atomic number, and the carrier can select a carbon carrier.

[0004] CN115584536A discloses a ruthenium nanocluster catalyst for alkaline hydrogen evolution reaction, wherein the ruthenium nanocluster catalyst is a composite material of ruthenium oxide in the form of nanoclusters supported on a carbon carrier; the preparation method thereof comprises the following steps: S1. crushing dried agricultural waste, mixing with an active agent, and calcining to obtain biochar; S2. stirring, filtering, and washing the biochar obtained in S1 in a hydrochloric acid aqueous solution to obtain a carbon carrier; S3. dispersing a ruthenium salt in a solvent, adding the carbon carrier obtained in S2, mixing and dispersing evenly, and then drying by rotary evaporation to obtain a precursor material; S4. heat-treating the precursor material obtained in S3 to obtain a ruthenium nanocluster catalyst.

[0005] CN118403074A discloses a graphite phase carbon nitride loaded with Ru single atoms and Ru atomic cluster nanomaterials, and the preparation method includes the following steps: S1. Weigh 1,10-phenanthroline and put it into a round-bottom flask containing anhydrous ethanol, then drip ruthenium chloride solution into the round-bottom beaker, add a magnetic stirrer, stir vigorously at room temperature, then add carbon nitride, and ultrasonically dissolve for a period of time. S2. Stir the solution of step S1 magnetically, evaporate the solvent after reflux, and then put the powder into a vacuum drying oven to dry, grind it evenly after drying, and then put it into a crucible, put the crucible into the furnace of a tubular furnace, and pyrolyze it under an argon atmosphere, and wait for it to cool naturally to room temperature to obtain a black final product Ru SA+AC .

[0006] CN115584536A discloses a ruthenium nanocluster catalyst for alkaline electrolytic hydrogen evolution reaction, and its preparation method includes the following steps: S1. crushing dried agricultural waste and mixing with an active agent to obtain biochar; S2. stirring, filtering and washing the biochar obtained in S1 in a hydrochloric acid aqueous solution to obtain a carbon carrier; S3. dispersing a ruthenium salt in a solvent, adding the carbon carrier obtained in S2, mixing and dispersing evenly, and then drying by rotary evaporation to obtain a precursor material; S4. heat-treating the precursor material obtained in S3 to obtain a ruthenium nanocluster catalyst. In this patent, ruthenium exists in the form of oxide nanoclusters. It is not a cluster of metallic ruthenium, and its HER catalytic activity is not good.

[0007] CN114318362A discloses a method for preparing a ruthenium nanocluster hydrogen evolution electrocatalyst, comprising the following steps: step 1, placing a zinc zeolite imidazole framework in a tubular furnace and performing high-temperature carbonization in a hydrogen-argon mixed gas to obtain a nitrogen-doped carbon nanoframe; step 2, soaking the nitrogen-doped carbon nanoframe in a phytic acid solution, stirring and transferring it to an evaporation container, evaporating and inducing self-assembly to obtain a phytic acid-modified nitrogen-doped carbon nanoframe; step 3, soaking the phytic acid-modified nitrogen-doped carbon nanoframe in a hydrated ruthenium trichloride solution, stirring and obtaining a ruthenium nanocluster hydrogen evolution electrocatalyst.

[0008] CN111906327A discloses a method for synthesizing a ruthenium nanocluster electrocatalyst for producing hydrogen by electrolyzing water. The method comprises the following steps: placing carbon nanotubes and N,N-dimethylformamide in a round-bottom flask and subjecting the flask to ultrasonic treatment. Ruthenium trichloride is then added dropwise to the flask and the mixture is stirred in an oil bath at 140°C for reaction for 6 hours. Finally, the reacted material is centrifuged and washed three times and dried. 20 mg of the dried material is added to 12 mL of a 3 wt% hydrogen peroxide solution and the mixture is reacted at 180°C for 3 hours using a hydrothermal method to finally obtain a composite material of ruthenium nanoclusters and carbon nanotubes.

[0009] The above-mentioned Ru clusters reported in the prior art are used for HER reaction catalysis, but the Ru6 clusters of the present invention have a precise number of atoms, a low loading of the precious metal Ru, a high atomic utilization rate, and a cost advantage; in addition, under high current density, the activity and stability of the Ru6 clusters are relatively excellent.

[0010] The inventor previously disclosed in patent CN119082792A a Ru3 cluster catalyst with a precise number of atoms for hydrogen evolution by alkaline electrolysis. However, the activity and stability of the Ru3 cluster catalyst at high current density are not as good as those of the Ru6 cluster catalyst. (At 250 mA cm -2 The overpotential of Ru3 cluster is 144.3mV under the current density, while that of Ru6 cluster is 128.9mV)

[0011] Prior art Inorg.Chem.1982,21,3816-3820, Journal of OrganometallicChemistry 669(2003)44-47, Organometallics 1997,16,4531-453 reported the synthesis of Ru6 clusters, but they were not applied to HER reaction. It has not been reported before that Ru6 clusters are loaded on oxidized Ketjen black as catalytic active centers for electrocatalytic alkaline HER. Summary of the invention

[0012] In order to solve the defects of low atomic utilization rate, low catalytic activity or short catalytic life of supported Ru catalysts in alkaline hydrogen evolution reaction, the present invention proposes a supported catalyst using Ru6 clusters as catalytic active centers, and obtains a composite material with high catalytic activity, stable structure and long service life, which is used for HER reaction under alkaline conditions. Due to its ultra-low loading and good stability, it is a new type of alkaline HER electrocatalytic material.

[0013] The present invention achieves the above object through the following technical solutions:

[0014] The first object of the present invention is to provide a supported Ru6 cluster catalyst for hydrogen evolution in alkaline water electrolysis, in which exactly 6 Ru atoms are supported as a cluster on an oxidized Ketjen black carrier, the coordination number of Ru-Ru is 2.5-2.7, it is a quasi-planar structure, and the loading amount of Ru is 0.5-2.4wt%.

[0015] Further, the loading amount of Ru is 0.5-2.4 wt %; preferably, the loading amount of Ru is 1.4-2.1 wt %.

[0016] The inventors found that the Ru6 cluster supported catalyst synthesized by the present invention has excellent alkaline hydrogen evolution catalytic activity and catalytic stability. And there is no report on alkaline hydrogen evolution activity of Ru6 clusters with accurate numbers of other related atoms, and the stability of the catalyst reported at present is not satisfactory under high current density. Generally, when preparing supported catalysts, due to the slow heating speed of ordinary tubular furnaces, the restriction that the material has a long residence time at high temperature can cause the problem of noble metal agglomeration to form nanoparticles. The present invention adopts a Joule furnace that can reach extremely high temperatures within a few seconds to carry out the calcination process, and the heating process can be accurately controlled. Targeted heat treatment can be achieved at a specific temperature, avoiding the rapid aggregation of materials at high temperatures, while minimizing the interference with the original structure of the precursor. It is generally believed that catalysis is a surface reaction, and cluster aggregation into particles can reduce the utilization rate of surface atoms, and performance can be slightly increased, but the atomic utilization rate is not high, resulting in an increase in cost. The present invention regulates the size and dispersion of Ru6 clusters loaded on the oxidized Ketjen black carrier by rapid temperature rise and fall calcination in a Joule furnace and the amount of precursor loaded, and characterizes the catalyst by means of XRD crystal diffraction, electron microscopy technology characterization and the like.

[0017] The present invention also provides a method for preparing the above-mentioned supported Ru6 cluster catalyst, comprising the following steps:

[0018] (S1) weighing Ketjen black, treating it with nitric acid, washing it, and drying it to obtain oxidized Ketjen black;

[0019] (S2) Take the Ru source precursor [NBu4]2[Ru6C(CO) 16 ]Ultrasonic dispersion in a solvent, slowly added to a solution uniformly dispersed with oxidized Ketjen black, stirred, centrifugally washed, and dried to obtain a precursor, which was rapidly heated and calcined in a Joule furnace under an inert gas atmosphere at a temperature of 350-500°C for 100-120s, and then naturally cooled to obtain a Ru6 catalyst with a precise atomic number loaded on oxidized Ketjen black.

[0020] Furthermore, in step (S1), the concentration of nitric acid is 5-6 mol L -1 The mass volume ratio of Ketjen black and nitric acid is 1g:100-150mL. The nitric acid treatment is carried out at 60-80℃ for 20-30h. There is no special limitation on washing and drying, such as water washing and oven drying.

[0021] Furthermore, in step (S2), the organic solvent is one of dichloromethane and tetrahydrofuran; the amount of Ru source and solvent used is that the concentration of Ru source precursor in the solvent is 0.1-0.5 mg / mL; the corresponding solvent in which oxidized Ketjen black is uniformly dispersed, the amount of oxidized Ketjen black and the corresponding solvent used is that the concentration of oxidized Ketjen black in the solvent is 1-5 mg / ml; the magnetic stirring for a period of time is stirring at room temperature for 9-12 hours; the stirring time should not be too short, otherwise the loading may be incomplete. Here, it can be judged according to the color of the solution after stirring and centrifugation. If the solution is clear and transparent, it proves that the loading is complete. If the solution color is darker, it proves that the loading is incomplete. This step will directly determine the electrochemical HER performance of the synthesized Ru6 clusters; the washing solution is the corresponding organic solution.

[0022] Furthermore, in step (S2), the inert gas is nitrogen atmosphere, the calcination temperature is 400-500°C, and the ligands in the precursor are burned off, the purpose is to expose the active sites after removing the ligands, so that the clusters are more firmly bound to the carrier, which is beneficial to enhance the activity of the Ru6 clusters while ensuring good stability. The calcination temperature should not be higher, and the calcination time should not be longer, otherwise the Ru6 clusters will further agglomerate to form large particles.

[0023] Furthermore, in step (S2), the rapid heating is performed using a Joule furnace, which can quickly heat the temperature to the target temperature within 1-2 seconds.

[0024] The third object of the present invention is to provide the use of the above-mentioned alkaline water electrolysis hydrogen evolution supported Ru6 cluster catalyst for electrocatalytic HER under alkaline conditions. The supported catalyst based on Ru6 cluster provided by the present invention has high atomic utilization, high catalytic activity and the catalyst can remain stable for a long time, can catalyze the reduction of hydrogen at room temperature, and the product is non-toxic and harmless.

[0025] The fourth object of the present invention is to provide a method for electrolyzing water, wherein the hydrogen electrode uses the above-mentioned alkaline water electrolysis hydrogen evolution supported Ru-based catalyst Ru6 / KBO as a catalyst for HER. Compared with the prior art, the present invention has the following beneficial effects:

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention prepares Ru6 clusters with precise atomic numbers loaded on oxidized Ketjen black, which have excellent alkaline HER electrocatalytic activity, high Ru utilization efficiency, and stable catalyst structure. The present invention uses Ru6 clusters as catalytic active centers, significantly improves electrocatalytic HER performance, and has a long-lasting catalytic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a transmission electron microscope (TEM) photograph of the oxidized Ketjen black catalyst prepared in Preparation Example 1.

[0029] Figure 2 This is a transmission electron microscope (TEM) photograph of the Ru6 / KBO catalyst prepared in Example 1.

[0030] Figure 3 This is the spherical aberration transmission electron microscopy (AC-TEM) photograph of the Ru6 / KBO catalyst prepared in Example 1.

[0031] Figure 4 This is the X-ray powder diffraction pattern (XRD) of the catalyst prepared in Example 1.

[0032] Figure 5 Schematic diagram of the structure of the Ru6 / KBO catalyst prepared in this example

[0033] Figure 6 This is a transmission electron microscope (TEM) photograph of the catalyst prepared in Comparative Example 1.

[0034] Figure 7 This is a transmission electron microscope (TEM) photograph of the catalyst prepared in Comparative Example 2.

[0035] Figure 8 This is a transmission electron microscope (TEM) photograph of the catalyst prepared in Comparative Example 4.

[0036] Fig. 9 This is the spherical aberration transmission electron microscopy (AC-TEM) photograph of the catalyst prepared in Comparative Example 7.

[0037] Fig.10 LSV diagrams of hydrogen evolution reactions of catalysts prepared in Example 1 and Comparative Examples 6, 7, 8, 9 and 10 in 1M KOH solution.

[0038] Fig.11 It is a stability diagram of the catalysts prepared in Example 1 and Comparative Examples 7, 8 and 9 in 1M KOH solution. DETAILED DESCRIPTION

[0039] To make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be described in detail below. The following examples are convenient for better understanding of the present invention, but are not intended to limit the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified.

[0040] In the embodiments of the present invention, "parts" are parts by mass unless otherwise specified, and "%" are percentages by mass unless otherwise specified.

[0041] Preparation Example 1

[0042] Pretreatment of the carrier: weigh 200 mg of Ketjen black and add 30 ml of 6 mol L -1Ultrasonic vibration was performed in an ultrasonic cleaner for 5 minutes. After uniform dispersion, magnetic stirring was performed in a 70°C oil bath for 24 hours. After stirring, the mixture was cooled to room temperature, then centrifuged and washed with deionized water until neutral, dried in an 80°C oven, and ground for later use.

[0043] Figure 1 This is a transmission electron microscope (TEM) image of the oxidized Ketjen black carrier prepared in Preparation Example 1. As can be seen from the image, the carrier is a relatively uniform loose and porous structure formed by stacking nanoparticles.

[0044] Example 1

[0045] A method for preparing Ru6 clusters supported by alkaline water electrolysis for hydrogen evolution comprises the following steps:

[0046] Take 5 mg of the synthesized precursor cluster [NBu4]2[Ru6C(CO) 16 ] was dissolved in 10 ml of dichloromethane by ultrasonication, and then added dropwise to 100 ml of dichloromethane in which 100 mg of oxidized Ketjen black carrier was uniformly dispersed, with stirring while dropping. After magnetic stirring for 12 h, the mixture was centrifuged and washed twice at 10,000 rpm. The black product obtained was [NBu4]2[Ru6C(CO) 16 ] / KBO, put it into a vacuum drying oven and dry it for later use. Take part of the above black product and place it on a carbon cloth, quickly heat it to 400°C in a Joule furnace, calcine it in a N2 atmosphere for 120s, and then quickly cool it naturally to obtain Ru6 / KBO. Naturally cool it to room temperature to obtain an alkaline water electrolysis hydrogen evolution supported Ru6 cluster catalyst. By inductively coupled plasma emission spectrometry (ICP) testing, the Ru loading in the composite catalyst obtained in Example 1 is 1.487wt%.

[0047] Figure 2 This is a transmission electron microscope (TEM) photograph of the Ru6 / KBO catalyst prepared in this example. No visible black spots attributable to Ru nanoparticles are observed in the figure.

[0048] Figure 3 This is a spherical aberration transmission electron microscopy (AC-TEM) photograph of the supported Ru6 cluster catalyst for hydrogen evolution in alkaline water electrolysis prepared in Example 1. It can be seen from the figure that the cluster is composed of 6 Ru atoms, with a size of about 1 nm, uniformly dispersed on the carrier without agglomeration.

[0049] Figure 4 This is the X-ray diffraction pattern (XRD) of the Ru6 cluster catalyst supported for hydrogen evolution in alkaline water electrolysis prepared in Example 1. Compared with the standard card, no characteristic peak of Ru was observed, indicating that there were no Ru particles in the catalyst, that is, the Ru6 clusters did not agglomerate.

[0050] Table 1 shows the EXAFS curve fitting analysis results of the Ru6 / KBO catalyst prepared in this example. It can be seen that the coordination number of Ru-Ru in the prepared catalyst Ru6 / KBO is 2.7, which is a quasi-planar structure.

[0051] Table 1 EXAFS curve fitting analysis results of Ru6 / KBO catalyst

[0052]

[0053] Path: coordination element, indicating the type of coordination atoms in the sample that are combined with the central element; CN: coordination number, indicating the type of coordination atoms in the sample that are combined with the central element; R: bond length, indicating the average distance between coordination atoms; σ 2 : Debye-Waller factor, which indicates the degree of disorder of atomic arrangement in the sample; ΔE: internal potential correction value, which indicates the magnitude of energy change during the fitting process. R factor: goodness of fit, which is used to evaluate the accuracy of the fitting results.

[0054] Figure 5 Schematic diagram of the structure of the Ru6 / KBO catalyst prepared in this example.

[0055] Example 2

[0056] Other conditions and operations were the same as those in Example 1, except that in the rapid temperature rise and fall calcination reduction step, the calcination temperature was changed to 350° C. and the time was changed to 100 s.

[0057] Example 3

[0058] Other conditions and operations were the same as those in Example 1, except that in the rapid temperature rise and fall calcination reduction step, the calcination temperature was changed to 500° C. and the time was changed to 120 s.

[0059] Example 4

[0060] Other conditions and operations were the same as those in Example 1, except that the precursor cluster [NBu4]2[Ru6C(CO) 16 ] was added in an amount of 2 mg. Through inductively coupled plasma emission spectrometer (ICP) testing, the Ru loading in the composite catalyst prepared in this embodiment was 0.594 wt%.

[0061] Example 5

[0062] Other conditions and operations were the same as those in Example 1, except that the precursor cluster [NBu4]2[Ru6C(CO) 16 ] was added in an amount of 7 mg. Through inductively coupled plasma emission spectrometer (ICP) testing, the Ru loading in the composite catalyst prepared in this embodiment was 2.074 wt%.

[0063] Comparative Example 1

[0064] Other conditions and operations were the same as those in Example 1, except that in the rapid temperature rise and fall calcination reduction step, the calcination temperature was changed to 300° C. The ligand was not completely removed, and the catalytic performance was poor.

[0065] Comparative Example 2

[0066] Other conditions and operations are the same as those in Example 1, except that in the rapid temperature rise and fall calcination reduction step, the calcination temperature is changed to 550°C.

[0067] Figure 7 This is the TEM image of the catalyst obtained in Example 2. It can be seen that black spots are distributed on the carrier, indicating that the calcination temperature is too high, resulting in the aggregation of Ru6 clusters.

[0068] Comparative Example 3

[0069] Other conditions and operations were the same as those in Example 1, except that in the rapid temperature rise and fall calcination reduction, the calcination holding time was changed from 120 s to 60 s.

[0070] Comparative Example 4

[0071] Other conditions and operations were the same as those in Example 1, except that in the rapid temperature rise and fall calcination reduction, the calcination holding time was changed from 120 s to 150 s. Figure 8 This is the TEM image of the catalyst obtained in Example 4. It can be seen that there are also many black spots distributed on the carrier, indicating that too long calcination time will also cause the Ru6 clusters to agglomerate.

[0072] Comparative Example 5

[0073] Other conditions and operations were the same as those in Example 1, except that the precursor cluster [NBu4]2[Ru6C(CO) 16 ] was added in an amount of 1 mg, and tested by inductively coupled plasma emission spectrometer (ICP), the loading amount of Ru in the composite catalyst prepared in this embodiment was 0.295 wt%.

[0074] Comparative Example 6

[0075] Other conditions and operations were the same as those in Example 1, except that a black product [NBu4]2[Ru6C(CO) 16 ] / KBO without subsequent calcination.

[0076] Comparative Example 7

[0077] 50 mg OCNT was dispersed in 20 mL methanol and ultrasonically treated for 60 min. Using RuCl3·3H2O as the Ru source, 250 uL aqueous solution containing 0.2 mg RuCl3·3H2O (the pH of the solution was adjusted to 1 with hydrochloric acid) was added dropwise to the OCNT dispersion with stirring. After magnetic stirring at room temperature for 24 h, the solid product was collected by centrifugation, washed twice with methanol solution, and then dried in a vacuum freeze-drying method at 30°C. After drying, the powder was heated at 400°C for 120 s in a Joule furnace under a flowing Ar atmosphere to obtain a Ru SAs / OCNT catalyst as a comparison catalyst. Fig. 9 This is a spherical aberration transmission electron microscopy (AC-TEM) photograph of the single-atom catalyst prepared in Comparative Example 7. From the figure, it can be seen that the Ru single atoms are uniformly dispersed on the carrier and no agglomeration occurs.

[0078] Comparative Example 8

[0079] Commercial Pt / C with a mass fraction of 20 wt% was used as a comparative catalyst for the catalyst.

[0080] Comparative Example 9

[0081] Commercial Ru / C with a mass fraction of 5 wt% was used as a comparative catalyst for the catalyst.

[0082] Comparative Example 10

[0083] The same as Example 1, except that step S1 is not performed, and the mass of oxidized Ketjen black in step S2 is replaced by Ketjen black (KB). It is found that the color of the solution after loading is darker, and the amount of Ru that can be loaded is extremely low.

[0084] Comparative Example 11

[0085] The above black product was placed on a carbon cloth and heated in a tube furnace at 5 °C min -1 The temperature was raised to 400°C at a heating rate of 100 °C, calcined in a N2 atmosphere for 120 s, and naturally cooled to room temperature to obtain an alkaline water electrolysis hydrogen evolution supported Ru6 cluster catalyst.

[0086] Application Examples

[0087] The catalyst performance of the above-mentioned embodiments and comparative examples was tested, specifically: the test was carried out in a standard three-electrode system, with a carbon rod as the counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and the prepared Ru6 / KBO (dropped on hydrophilic carbon paper) as the working electrode. All data were calibrated to the potential relative to the standard hydrogen electrode (RHE), and the electrolyte test results were 95% IR corrected to reduce the impedance of the solution during the test.

[0088] The calibration formula is:

[0089] E (RHE) =E (SCE) +0.0591*pH+0.24-0.95*I*R

[0090] Among them, E (RHE) : potential of the standard hydrogen electrode;

[0091] E (SCE) : potential of saturated calomel electrode;

[0092] I: current density generated during the test;

[0093] R: Impedance during the test.

[0094] Overpotential η 10 At a current density of 10 mA cm -2 When , the magnitude of the overpotential.

[0095] Table 2 Catalyst performance indicators

[0096]

[0097] As can be seen from Table 2, the catalyst prepared by the method of Example 1 has excellent HER performance and stability at room temperature under alkaline conditions; although Example 5 also has excellent performance under the same environment, the addition amount of precious metal Ru is large and the cost is slightly high; Comparative Examples 1 and 2 verify the effect of calcination temperature on the activity of the catalyst. If the temperature is too low (Comparative Example 1), the ligand is not completely removed and the HER activity is poor; if the temperature is too high (Comparative Example 2), the clusters are prone to agglomeration; Comparative Examples 3 and 4 are the effects of calcination time. If the calcination time of Comparative Example 3 is too short, the ligand is not completely removed and the HER activity is poor. If the calcination time of Comparative Example 4 is too long, the clusters are prone to agglomeration; If Comparative Example 5 adds The amount of Ru is too small, there are few reactive sites, and the activity of HER reaction is poor; Comparative Example 6 has poor activity due to the lack of ligand removal; Comparative Example 7 is a single atom comparison with poor activity; Comparative Examples 8 and 9 are both commercial catalysts, and the activity and stability of the catalyst prepared in this experiment are better than those of commercial catalysts; Comparative Example 10 is the effect of the carrier on the activity of the catalyst. When Ketjen black is used directly as a carrier without acid treatment, the loading of Ru is incomplete and the activity is extremely poor; Comparative Example 11 is the effect of the heating device. When an ordinary tubular furnace device is used, the nature of the device itself will cause the catalyst to be at high temperature for a long time, resulting in agglomeration of Ru6 clusters.

[0098] Fig.10 LSV diagram of hydrogen evolution reaction of catalysts prepared in Example 1, Comparative Examples 7, 8, 9, and 10 in 1M KOH solution; Fig.10 It can be seen that at 10mAcm -2At a current density of 2.5 wt%, the overpotential of Ru6 / OCNT is 25.6 mV, which is close to that of Pt / C catalyst (26.1 mV), and better than that of Ru / C catalyst (50.6 mV) and Ru SAs / OCNT catalyst (171.9 mV). However, the Pt loading in Pt / C catalyst is 20 wt%, which is costly. This patent achieves an effect close to that of commercial 20 wt% Pt / C catalyst at an extremely low Ru loading, and the catalyst of the present invention is more stable at high current density, and has the potential for commercial application.

[0099] Fig.11 The stability diagram of the catalysts prepared in Example 1, Comparative Examples 8 and 9 in 1M KOH solution is shown in FIG. Fig.11 It can be seen that the Ru6 / KBO catalyst has a -2 The voltage hardly changed after 24 h of electrolysis at a current density of , which is better than that of the commercial Ru / C catalyst and similar to that of the commercial Pt / C catalyst.

[0100] The present invention has innovatively discovered that the catalyst made of Ru6 clusters with precise atomic numbers has significantly improved catalytic activity and excellent catalytic effect on HER, while single atoms do not achieve the same excellent catalytic activity. This may be because the unique structure of Ru6 clusters can optimize the free energy of the hydrogen adsorption step at the active site to achieve the best, which can promote the HER kinetics under alkaline conditions, making it have catalytic activity and catalyst life similar to those of commercial electrodes. However, due to its single active site, ruthenium single atom catalysts are difficult to adjust the binding mode of adsorbed intermediates during the reaction and lack synergy. In some reactions, such as alkaline hydrogen evolution reaction, the catalytic activity is not as good as that of Ru6 clusters.

Claims

1. A supported Ru6 cluster catalyst for hydrogen evolution in alkaline water electrolysis, characterized in that: In the catalyst, exactly 6 Ru atoms are loaded as a cluster on the oxidized Ketjen black carrier, the coordination number of Ru-Ru is 2.5-2.7, it is a quasi-planar structure, and the loading amount of Ru is 0.5-2.4wt%.

2. The supported Ru6 cluster catalyst according to claim 1, characterized in that The loading amount of Ru is 0.5-2.4 wt %; preferably, the loading amount of Ru is 1.4-2.1 wt %.

3. The method for preparing the supported Ru6 cluster catalyst according to claim 1 or 2, characterized in that: The following steps are involved: (S1) weighing Ketjen black, treating it with nitric acid, washing it, and drying it to obtain oxidized Ketjen black; (S2) Take the Ru source precursor [NBu4]2[Ru6C(CO) 16 ]Ultrasonic dispersion in a solvent, slowly added to a solution uniformly dispersed with oxidized Ketjen black, stirred, centrifugally washed, and dried to obtain a precursor, which was rapidly heated and calcined in a Joule furnace under an inert gas atmosphere at a temperature of 350-500°C for 100-120s, and then naturally cooled to obtain a Ru6 catalyst with a precise atomic number loaded on oxidized Ketjen black.

4. The preparation method according to claim 3, characterized in that: In step (S1), the concentration of nitric acid is 5-6 mol·L -1 The mass volume ratio of Ketjen black and nitric acid is 1g:100-150mL, and the nitric acid treatment is carried out at 60-80℃ for 20-30h.

5. The preparation method according to claim 3, characterized in that: In step (S2), the organic solvent is one of dichloromethane and tetrahydrofuran; the amount of Ru source and solvent used is such that the concentration of Ru source precursor in the solvent is 0.1-0.5 mg / mL.

6. The preparation method according to claim 3, characterized in that: In step (S2), the corresponding solvent in which Ketjen black oxide is uniformly dispersed is used in an amount such that the concentration of Ketjen black oxide in the solvent is 1-5 mg / ml.

7. The preparation method according to claim 3, characterized in that: In step (S2), the magnetic stirring is performed for a period of time, which is 9-12 hours at room temperature.

8. The preparation method according to claim 3, characterized in that: In step (S2), the inert gas is nitrogen atmosphere, and the calcination temperature is 400-500°C.

9. The preparation method according to claim 3, characterized in that: In step (S2), the rapid heating is performed using a Joule furnace to rapidly heat the temperature to the target temperature within 1-2 seconds.

10. Use of the supported Ru6 cluster catalyst according to claim 1 or 2 for electrocatalytic HER under alkaline conditions.

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