Ruthenium-based catalyst, preparation method therefor, and use thereof in hydrogen production by water electrolysis

Abstract

The present disclosure relates to a ruthenium-based catalyst, a preparation method therefor, and a use thereof in hydrogen production by water electrolysis. The ruthenium-based catalyst is a porous material, and comprises a ruthenium element having a mass fraction of 70% or above; and a characteristic peak of elemental ruthenium is present in an XRD spectrogram of the ruthenium-based catalyst. When the catalyst of the present disclosure is used as a cathode catalyst or an anode catalyst in hydrogen production by water electrolysis, good mass transfer effect and electrical conductivity, excellent catalytic activity and excellent stability are achieved.

Description

Ruthenium-based catalyst, preparation method thereof, and use in hydrogen production by water electrolysis Technical Field

[0001] The present disclosure relates to a ruthenium-based catalyst, and in particular, to a ruthenium-based catalyst, a preparation method thereof, and use thereof in hydrogen production by water electrolysis. Background Art

[0002] Compared to hydrogen production processes in the chemical industry, water electrolysis offers significant advantages, including abundant raw materials, mild conditions, and higher purity, making it a popular choice within the industry. Compared to traditional alkaline water electrolysis (AWE) technology, proton exchange membrane water electrolysis (PEMWE) offers advantages such as faster response, higher ionic conductivity, a wider operating temperature and pressure range, and higher current density and hydrogen purity. It is currently a highly sought-after advanced water electrolysis hydrogen production technology within the industry. In particular, its integration with green electricity generated from intermittent renewable energy sources such as wind and solar power holds significant developmental significance for the future large-scale production of green hydrogen.

[0003] In PEMWE hydrogen production technology, water oxidation occurs at the anode to produce oxygen. This reaction, involving four electrons coupled to protons, results in a higher overpotential and slower reaction kinetics. Furthermore, under the strongly oxidizing and acidic conditions at the anode, only iridium and ruthenium typically exhibit good stability. Platinum-on-carbon catalysts are currently the primary catalyst used on the cathode side. Due to the high price of platinum, the development of lower-cost catalysts is imperative. Ruthenium is less expensive than platinum, but its catalytic activity and stability still require further improvement.

[0004] Compared with dense catalytic materials, loose and porous catalytic materials have better mass transfer effects when catalyzing chemical reactions, especially mesoporous or macroporous materials, which usually have better mass transfer effects than microporous materials.

[0005] Metals and metal oxides are commonly used catalytic materials. Smaller sizes increase catalytic activity, but correspondingly, larger surface energy increases the susceptibility to aggregation and deactivation. Nanomaterials have high catalytic activity, but they are prone to aggregation during catalytic reactions, resulting in reduced catalytic activity.

[0006] Elemental ruthenium and ruthenium oxide are both commonly used catalytic materials for water electrolysis. Elemental ruthenium has better conductivity and higher catalytic activity, but its stability is not as good as ruthenium oxide. This field still needs to better resolve the contradiction between conductivity, catalytic activity and stability.

[0007] Porous metal materials, especially nanoporous metal materials, have the advantages of high mass transfer efficiency, good electrical conductivity and high catalytic activity. However, to date, there are no reports of porous ruthenium metal materials with mesopores and / or macropores that are mainly composed of a single substance.

[0008] Summary of the Invention

[0009] The purpose of the present disclosure is to provide a ruthenium-based catalyst, a preparation method thereof, and its use in hydrogen production by water electrolysis. The ruthenium-based catalyst is basically composed of elemental ruthenium and optional ruthenium oxide, and has a rich pore structure. When used for hydrogen production by water electrolysis, it has excellent mass transfer effect and conductivity, maintains excellent catalytic activity while having excellent stability, and the catalyst has excellent dispersibility in the slurry for manufacturing membrane electrodes.

[0010] In order to achieve the above-mentioned objectives, the first aspect of the present disclosure provides a ruthenium-based catalyst, which is a porous material and contains ruthenium elements with a mass fraction of more than 70%; the XRD spectrum of the ruthenium-based catalyst contains characteristic peaks of elemental ruthenium.

[0011] Optionally, the ruthenium-based catalyst contains ruthenium element in an amount of 72 to 90% by mass.

[0012] Optionally, the ruthenium-based catalyst contains 10-22% by mass of oxygen.

[0013] Optionally, the porosity of the catalyst is greater than 50%, preferably 52 to 95%, and more preferably 55 to 75%.

[0014] Optionally, the catalyst is a material having mesopores and / or macropores.

[0015] Optionally, the ruthenium-based catalyst has a nanosheet morphology.

[0016] Optionally, the mesoporous and / or macroporous microstructure of the ruthenium-based catalyst is formed by connecting a plurality of nanosheet-like structures in three-dimensional space.

[0017] Optionally, the thickness of the ruthenium-based catalyst nanosheets is 6.6 nm to 17.8 nm, preferably 9.8 nm to 14.6 nm.

[0018] Optionally, the specific surface area of ​​the ruthenium-based catalyst is 60 to 100 cm 2 / g, preferably 70 to 90 cm 2 / g.

[0019] Optionally, the total pore volume of the ruthenium-based catalyst is 0.12 to 0.16 cm 3 / g, preferably 0.13 to 0.15 cm 3 / g.

[0020] Optionally, the apparent mass volume ratio of the ruthenium-based catalyst is 0.15 to 0.45 g / cm 3 .

[0021] Optionally, in the XRD spectrum of the ruthenium-based catalyst, the mass content ratio calculated from the peak area of ​​the characteristic peak of ruthenium oxide to the characteristic peak of elemental ruthenium is 0 to 0.5, preferably 0.05 to 0.35; the mass fraction of ruthenium element in the ruthenium-based catalyst is 77 to 90%.

[0022] Optionally, the XRD spectrum of the ruthenium-based catalyst also contains a characteristic peak of ruthenium oxide, and the mass content ratio calculated by the peak area of ​​the characteristic peak of ruthenium oxide to the characteristic peak of elemental ruthenium is 0.7 to 4.5, preferably 0.8 to 1.2; the mass fraction of ruthenium element in the ruthenium-based catalyst is 73 to 75%.

[0023] Optionally, the XPS Ru 3p In the spectrum, there are characteristic peaks of elemental ruthenium and ruthenium oxide. The characteristic peak of elemental ruthenium moves toward the direction of low electron binding energy relative to the standard position of elemental ruthenium, and the characteristic peak of ruthenium oxide moves toward the direction of high electron binding energy relative to the standard position of ruthenium oxide.

[0024] Optionally, the XPS Ru of the ruthenium-based catalyst 3p In the spectrum, the ratio of the peak area of ​​the characteristic peak of elemental ruthenium to the characteristic peak of ruthenium oxide is (0.1-2.2):1, preferably (0.12-1.5):1, and more preferably (0.4-0.8):1.

[0025] Optionally, the XPS O 1s spectrum of the ruthenium-based catalyst has a characteristic peak at a binding energy of 530.7 eV to 531.1 eV.

[0026] A second aspect of the present disclosure provides a method for preparing a ruthenium-based catalyst, the method comprising:

[0027] (1) mixing a polysaccharide with water to form a first sol; mixing a ruthenium source precursor, a complexing agent, and water, and adjusting the pH of the resulting mixture to 7.5 to 9 to obtain a ruthenium source solution;

[0028] (2) mixing the first sol with the ruthenium source solution to form a second sol; and subjecting the second sol to a first drying to obtain an aerogel;

[0029] (3) calcining the aerogel;

[0030] Wherein, the complexing agent is a polycarboxylate having a hydroxyl group, and the polysaccharide is selected from one or more of sodium alginate, sodium carboxymethyl cellulose and sodium hyaluronate.

[0031] Optionally, in (1), the concentration of the polysaccharide in the first sol is 0.5 to 2 weight %, preferably 0.7 to 1.2 weight %.

[0032] Optionally, in (1), the ruthenium source precursor is a ruthenium precursor commonly used in the art, which is selected from one or more of ruthenium trichloride, ruthenium nitrosyl nitrate, ruthenium acetate, ruthenium acetylacetonate and ruthenium sulfate.

[0033] Optionally, in the preparation of the ruthenium source solution, the complexing agent is one or more selected from sodium citrate, sodium tartrate and sodium malate.

[0034] Optionally, in the preparation of the ruthenium source solution, the molar ratio of the amount of the ruthenium source precursor calculated as ruthenium to the complexing agent is (0.25-4):1, preferably (0.5-2):1.

[0035] Optionally, the first drying can use a drying method known in the art, preferably one or more of supercritical drying and freeze drying, more preferably freeze drying; the freeze drying conditions include: temperature of -30 to -20°C, preferably -25 to -20°C; time of 24 to 48 hours, preferably 36 to 48 hours.

[0036] Optionally, in (3), the calcination conditions include: a temperature of 300-600°C, preferably 300-450°C, and more preferably 310-420°C; a time of 0-3h, preferably 2-3h; and a heating rate of 1-10°C / min, preferably 2-5°C / min.

[0037] Optionally, in (3), the calcination is carried out in an air atmosphere.

[0038] Optionally, the method further comprises washing and second drying the calcined product obtained in (3).

[0039] Alternatively, the washing may be performed by a washing method known in the art, including but not limited to one or more of acid washing, water washing, and alcohol washing. Alternatively, the washing may be performed by acid washing, water washing, and alcohol washing in sequence. The acid used in the acid washing may be an inorganic acid known in the art, for example, one or more selected from hydrochloric acid, sulfuric acid, nitric acid, and acetic acid. The alcohol used in the alcohol washing may be an alcohol known in the art, for example, one or more selected from methanol, ethanol, and isopropanol.

[0040] Optionally, the second drying conditions may be drying conditions known in the art, for example, the second drying conditions include: a temperature of 40 to 60° C., preferably 45 to 55° C.; and a time of 2 to 24 hours, preferably 10 to 20 hours.

[0041] Optionally, the method may further include: annealing the second dried product, wherein the annealing conditions include: heating the second dried product in an air atmosphere to an annealing temperature, and then cooling; the annealing temperature is 200 to 350° C., and the holding time is 0 to 3 hours, preferably 0.5 to 2 hours.

[0042] The third aspect of the present disclosure provides a ruthenium-based catalyst prepared by the preparation method described in the second aspect of the present disclosure.

[0043] The fourth aspect of the present disclosure provides a use of the ruthenium-based catalyst described in the first and third aspects of the present disclosure in hydrogen production by electrolysis of water.

[0044] Technical Effects

[0045] Through the technical solutions of the present disclosure, a ruthenium-based catalyst, a preparation method thereof, and its use in hydrogen production by water electrolysis are provided. The ruthenium-based catalyst is essentially composed of elemental ruthenium and, optionally, ruthenium oxide, and is a loose, porous material with mesopores and / or macropores, thereby exhibiting improved mass transfer performance. Furthermore, the catalyst has a stable porous microstructure, which combines the high catalytic activity of nanomaterials with the ability to suppress the aggregation and deactivation that occurs with nanoparticle-based catalysts, resulting in the catalyst exhibiting both good catalytic activity and excellent stability.

[0046] Furthermore, the ruthenium-based catalyst disclosed herein is primarily composed of metals, exhibiting excellent electrical conductivity when used in water electrolysis. Furthermore, the ruthenium-based catalyst disclosed herein has a low apparent mass-to-volume ratio, high bulkiness, and excellent dispersibility in catalyst film-forming slurries.

[0047] Therefore, the catalyst disclosed herein simultaneously achieves excellent catalytic activity as a nanomaterial and catalyst structural stability. When used in water electrolysis to produce hydrogen, the ruthenium-based catalyst disclosed herein exhibits superior intrinsic activity, a low initial overpotential, a low Tafel slope, and a small increase in the final overpotential after stability testing compared to the initial overpotential, demonstrating promising prospects for industrial application. Furthermore, the preparation method provided herein is simple, convenient, and highly economical.

[0048] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0050] FIG1 is a SEM image of catalyst C1 prepared in Example 1 of the present disclosure;

[0051] FIG2 is an XRD pattern of catalyst C1 prepared in Example 1 of the present disclosure;

[0052] FIG3 is a cyclic voltammogram of catalyst C1 prepared in Example 1 of the present disclosure;

[0053] FIG4 is an XPS spectrum of Ru 3p of catalyst C1 prepared in Example 1 of the present disclosure;

[0054] FIG5 is an XPS spectrum of O1s of catalyst C1 prepared in Example 1 of the present disclosure;

[0055] FIG6 is an XRD pattern of catalyst C3 prepared in Example 3 of the present disclosure;

[0056] FIG7 is an XPS spectrum of Ru 3p of commercial anhydrous ruthenium oxide used in Comparative Example 2 of the present disclosure;

[0057] FIG8 is an XPS spectrum of O1s of commercial anhydrous ruthenium oxide used in Comparative Example 2 of the present disclosure;

[0058] FIG9 is a diagram showing the discharge of bubbles when the catalyst C1 prepared in Example 1 of the present disclosure is coated on carbon paper to prepare an electrode for water electrolysis reaction;

[0059] FIG10 is a diagram showing the bubble discharge when the comparative catalyst D2 of Comparative Example 2 of the present disclosure is coated on carbon paper to prepare an electrode for water electrolysis reaction. DETAILED DESCRIPTION

[0060] The present disclosure is described in detail below in conjunction with specific embodiments. However, it should be noted that the protection scope of the present disclosure is not limited by these specific embodiments and principle explanations, but is determined by the claims.

[0061] In this disclosure, except for the contents explicitly described, any matters or issues not mentioned are directly applicable to the contents known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are considered part of the original disclosure or record of this disclosure and should not be regarded as new content not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0062] All features disclosed in this disclosure may be combined in any combination, and such combinations should be understood as disclosed or described in this disclosure. Unless a person skilled in the art deems such combinations to be obviously unreasonable, such combinations should be considered as specifically disclosed and described in this disclosure. Unless otherwise specified, the numerical values ​​disclosed in this specification include not only the numerical values ​​specifically disclosed in the examples but also the endpoints of the numerical ranges in this specification. Any combination of these numerical values ​​should be considered as the range disclosed or described in this disclosure.

[0063] Technical and scientific terms in this disclosure shall be understood according to their definitions if they are defined, and shall be understood according to their common meanings in the art if they are not defined.

[0064] Terminology Notes:

[0065] The term "mesopore" is defined as pores with a pore diameter in the range of 2 nm to 50 nm; pores with a pore diameter less than 2 nm are defined as micropores, and pores with a pore diameter greater than 50 nm are defined as macropores.

[0066] The term "porous material" is defined as a material with a porosity greater than 15%. The shape, existence form or distribution state of the pores in the porous material is not restricted. For example, the existence form of the pores may include cross-linked pores, through holes or blind holes, and the distribution state may include uniform or irregular distribution on the surface or inside of the material.

[0067] The term "sol" is defined as a dispersed system that has fluidity and a viscosity greater than that of water.

[0068] Ruthenium-based catalysts

[0069] The first aspect of the present disclosure provides a ruthenium-based catalyst, which is a porous material and has a ruthenium element content of more than 70% by mass; the XRD spectrum of the ruthenium-based catalyst contains a characteristic peak of elemental ruthenium.

[0070] In the present disclosure, the characteristic peak of elemental ruthenium refers to the main diffraction peak that appears in the XRD spectrum of elemental ruthenium at 2θ of 43.0 to 45.0°, and the characteristic peak of ruthenium oxide refers to the main diffraction peak that appears in the XRD spectrum of ruthenium oxide at 2θ of 27.0 to 29.0°.

[0071] In the present disclosure, the ruthenium element in the ruthenium-based catalyst is at least partially present in the form of elemental ruthenium, and may also be partially present in the form of ruthenium oxide. Oxygen may be present in the form of an oxide, and its existence form is not limited. The ruthenium content in the ruthenium-based catalyst of the present disclosure is determined by XRF testing.

[0072] The ruthenium-based catalyst disclosed in the present invention may contain unavoidable small amounts or trace amounts of other elements due to the presence of impurities in the synthetic raw materials, but these factors have no obvious effect on the structural properties and catalytic performance of the final catalyst, and these impurities are not considered to be essential components of the present invention. Therefore, the present invention does not need to limit the types and contents of these impurities.

[0073] That is, in the present disclosure, except for possible unavoidable impurities, no other elements, especially other metal elements, are intentionally added / doped into the ruthenium-based catalyst of the present disclosure.

[0074] The ruthenium-based catalyst provided by the present disclosure is essentially composed of elemental ruthenium and, optionally, ruthenium oxide, and has a stable, loose, porous structure. Specifically, the catalyst disclosed herein is a three-dimensional porous material formed by interconnected nanosheets. Therefore, it possesses the high catalytic activity of nanomaterials while suppressing the aggregation and deactivation that occurs with nanoparticle-based catalysts, allowing the catalyst to maintain high catalytic activity while also exhibiting excellent stability. Therefore, the ruthenium-based catalyst of this technology exhibits excellent acidic electrochemical activity and stability.

[0075] In one embodiment of the present disclosure, relative to the total amount of the ruthenium-based catalyst, the content of ruthenium element in the ruthenium-based catalyst expressed as mass fraction can be 70.5%, 71%, 72%, 73%, 74%, 75%, 78%, 80%, 85%, 88%, 90%, 93%, 95% or 98%, or the mass fraction of the content of ruthenium element is a numerical range between any two of them.

[0076] In one embodiment of the present disclosure, the ruthenium content of the ruthenium-based catalyst is 72-90% by mass relative to the total amount of the ruthenium-based catalyst. It should be noted that the ruthenium content of the ruthenium-based catalyst of the present disclosure is obtained by XRF testing. Therefore, the ruthenium content of the ruthenium-based catalyst of the present disclosure includes both elemental ruthenium and ruthenium in ruthenium oxide.

[0077] In the present disclosure, the specific ruthenium element content disclosed in the present disclosure is conducive to further improving the conductivity of the catalyst and thus improving its electrocatalytic activity.

[0078] In one embodiment of the present disclosure, the content of oxygen in the ruthenium-based catalyst is 8 to 25% by mass relative to the total amount of the ruthenium-based catalyst.

[0079] In one embodiment of the present disclosure, the content of oxygen element in the ruthenium-based catalyst is expressed as a mass fraction of 8%, 10%, 12%, 15%, 17%, 18%, 20%, 22%, 25% or 28% relative to the total amount of the ruthenium-based catalyst, or the mass fraction of the content of oxygen element is a numerical range between any two of them; preferably, the mass fraction of the content of oxygen element is 10 to 25%.

[0080] In the present disclosure, by making the ruthenium-based catalyst contain an appropriate amount of oxygen, it is beneficial to reasonably control the ratio of elemental ruthenium and ruthenium oxide in the catalyst.

[0081] In one embodiment of the present disclosure, the porosity of the ruthenium-based catalyst is greater than 30%, preferably greater than 50%, more preferably 52 to 95%, further preferably 55 to 75%, and even more preferably 55 to 65%.

[0082] In one embodiment of the present disclosure, the ruthenium-based catalyst is a material having mesopores and / or macropores.

[0083] In one embodiment of the present disclosure, the pore size of the mesopores and / or macropores of the ruthenium-based catalyst is 2nm~2μm, preferably the mesopore size of the catalyst is 2nm~50nm, preferably the macropore size of the catalyst is 50nm~1000nm, more preferably the macropore size is 50nm~200nm.

[0084] In one embodiment of the present disclosure, the total pore volume of the ruthenium-based catalyst is 0.12 to 0.16 cm 3 / g, preferably 0.13 to 0.15 cm 3 / g.

[0085] In one embodiment of the present disclosure, the specific surface area of ​​the ruthenium-based catalyst is 60 to 100 cm 2 / g, preferably 70 to 90 cm 2 / g.

[0086] In one embodiment of the present disclosure, the apparent mass volume ratio of the ruthenium-based catalyst is 0.15 to 0.45 g / cm 3 .

[0087] In the present disclosure, by making the pore characteristics (total pore volume, specific surface area, apparent mass volume ratio, etc.) of the ruthenium-based catalyst within the scope of the present disclosure, it is beneficial to improve the mass transfer effect of the catalyst and thus improve the electrocatalytic activity of the catalyst.

[0088] In one embodiment of the present disclosure, the mesoporous and / or macroporous microstructure of the ruthenium-based catalyst is formed by connecting a plurality of nanosheet-shaped structures in three-dimensional space. Specifically, the entity part of the mesoporous and / or macroporous microstructure of the ruthenium-based catalyst of the present disclosure is formed by overlapping and connecting a plurality of nanosheets of sheet-like entities. On the one hand, the sheet-like nanosheets extend to form the "walls" of the pore walls of a plurality of holes. On the other hand, the sheet-like nanosheets overlap on other nanosheets to form a "surface" covering the holes. Thus, a plurality of different nanosheets serving as "walls" and "surfaces" overlap with each other, and the holes between the nanosheets are interconnected, thereby forming a porous microstructure.

[0089] As shown in Figure 1, in one embodiment, the ruthenium-based catalyst of the present disclosure is formed by connecting nanosheets less than 100 nm. In a preferred embodiment, the nanosheets of the microstructure substantially do not contain a portion having a thickness exceeding 20 nm, that is, the thickness of the nanosheets does not substantially exceed 20 nm.

[0090] In one embodiment of the present disclosure, the thickness of the nanosheet is preferably 6.6 nm to 17.8 nm, more preferably 9.8 nm to 14.6 nm.

[0091] In the present disclosure, the ruthenium-based catalyst exhibits high catalytic activity in the form of a nanomaterial. Furthermore, because the catalyst is a three-dimensional structure formed by fixed, overlapping nanosheets, it is porous and structurally robust, which helps prevent the aggregation and deactivation of ruthenium-based catalysts in the form of nanoparticles, thereby solving the activity and stability issues of ruthenium-based catalysts. It should be noted that in the present disclosure, the average thickness of the nanosheets was measured using a SEM and statistically analyzed using Nano Measurer 1.2 software. The instrument, method, and conditions for the SEM test were as follows: the scanning electron microscope (SEM) was a Hitachi S-4800, operating at a voltage of 5 kV to 20 kV, and equipped with energy dispersive X-ray spectroscopy (EDS).

[0092] In one embodiment of the present disclosure, the XRD spectrum of the ruthenium-based catalyst basically only has the characteristic peak of elemental ruthenium, that is, the XRD spectrum of the ruthenium-based catalyst shows an obvious main diffraction peak of elemental ruthenium near 2θ=44.0°, but no obvious diffraction peak of ruthenium oxide appears.

[0093] In one embodiment of the present disclosure, the XRD spectrum of the ruthenium-based catalyst contains only characteristic peaks of elemental ruthenium, meaning that the ruthenium element in the ruthenium-based catalyst is substantially present as a single element. In one embodiment of the present disclosure, the ruthenium content, expressed as a mass fraction, may be greater than 80%, preferably greater than 85%, for example, 85-95% or 86-92%.

[0094] In some embodiments of the present technology, the content of elemental ruthenium in the ruthenium-based catalyst is relatively high, and the content of ruthenium oxide is relatively low. In one embodiment of the present disclosure, the mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak area of ​​the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium in the XRD spectrum is 0.5 or less, preferably 0.01 to 0.4, more preferably 0.05 to 0.36, and more preferably 0.1 to 0.35. In one embodiment of the present disclosure, in the XRD spectrum of the ruthenium-based catalyst, the mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak area of ​​the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium is 0 to 0.5, preferably 0.05 to 0.35.

[0095] At this time, the content of ruthenium in the ruthenium-based catalyst can be 76%, 77%, 79%, 80%, 82%, 84%, 88% or 90% by mass, or the mass fraction of the ruthenium content can be a numerical range between any two of them. In one embodiment of the present disclosure, the content of ruthenium in the ruthenium-based catalyst can be 77-90% by mass. In the present disclosure, the presence of elemental ruthenium is beneficial to enhancing the conductivity of the ruthenium-based catalyst, promoting rapid reconstruction, and improving the HER performance.

[0096] In some embodiments of the present technology, the ruthenium-based catalyst has a relatively low content of elemental ruthenium and a relatively high content of ruthenium oxide. In one embodiment of the present disclosure, the XRD spectrum of the ruthenium-based catalyst also includes characteristic peaks of ruthenium oxide.

[0097] In one embodiment of the present disclosure, the mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak areas of the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium in the XRD spectrum can be 0.6 to 5, preferably 0.7 to 4.5.

[0098] In this case, the ruthenium content in the ruthenium-based catalyst can be 71%, 72%, 73%, 74%, 75%, 76%, 77%, 79%, 80%, 82%, 84%, 88% or 90% by mass, or the mass fraction of the ruthenium content is a numerical range between any two of them. In one embodiment of the present disclosure, the ruthenium content in the ruthenium-based catalyst can be 73-80% by mass.

[0099] In one embodiment of the present disclosure, the mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak areas of the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium in the XRD spectrum may be 2 to 4.5.

[0100] In one embodiment of the present disclosure, the mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak areas of the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium in the XRD spectrum can be 0.7 to 1.4, preferably 0.8 to 1.2, and more preferably 0.9 to 1.1.

[0101] In the present disclosure, the ruthenium-based catalyst contains elemental ruthenium and ruthenium oxide, and by making the mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak area of ​​the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium in the XRD spectrum within a specific range, the content ratio of ruthenium oxide to elemental ruthenium is made within a reasonable range, so that the ruthenium element and ruthenium oxide in the ruthenium-based catalyst play a synergistic role at the nanometer level, that is, ensuring the activity of the catalyst and the stability of the catalyst, thereby resolving the contradiction between the activity and stability between the metal and its oxide. On the other hand, ruthenium oxide, as a high-priced ruthenium oxygen evolution active species, can promote the improvement of OER performance.

[0102] In one embodiment of the present disclosure, the XPS Ru 3p In the spectrum, there are characteristic peaks of elemental ruthenium and ruthenium oxide. The characteristic peak of elemental ruthenium moves toward the direction of low electron binding energy relative to the standard position of elemental ruthenium, for example, by 0.35 to 0.45 eV; the characteristic peak of ruthenium oxide moves toward the direction of high electron binding energy relative to the standard position of ruthenium oxide, for example, by 0.55 to 0.65 eV. 3p In the spectrum, the electron binding energy of elemental ruthenium at the standard position is 462.3 eV, and the electron binding energy of ruthenium oxide at the standard position is 462.7 eV.

[0103] In the present disclosure, the XPS Ru 3p In the spectrum, the characteristic peaks of elemental ruthenium and ruthenium oxide produce the above-mentioned movement, which reflects the mutual interaction between ruthenium oxide and elemental ruthenium. This interfacial electronic interaction has a significant effect on improving the hydrogen and oxygen evolution performance.

[0104] In one embodiment of the present disclosure, the XPS Ru 3p In the spectrum, the ratio of the peak area of ​​the characteristic peak of elemental ruthenium to the characteristic peak of ruthenium oxide is (0.1-2.2):1, preferably (0.12-1.5):1, more preferably (0.14-0.8):1, and further preferably (0.35-0.78):1.

[0105] In the present disclosure, the XPS Ru 3p The spectrum shows the distribution of elemental ruthenium and ruthenium oxide in the surface layer of the ruthenium-based catalyst (determined by the detection depth of XPS, generally a region less than 10 nm, mainly a region of about 2 to 5 nm). By ensuring that the peak area ratio of the characteristic peak of elemental ruthenium to the characteristic peak of ruthenium oxide meets the above range, it is beneficial to form a heterojunction between elemental ruthenium and ruthenium oxide. This heterojunction interface is more conducive to improving the intrinsic activity of the catalyst and can further enhance the OER performance of the catalyst.

[0106] In one embodiment of the present disclosure, the XPS O 1s spectrum of the ruthenium-based catalyst has a characteristic peak at a binding energy of 530.7 eV to 531.1 eV.

[0107] In the present disclosure, the XPS O 1s spectrum of the ruthenium-based catalyst shows the above-mentioned characteristic peaks, indicating that the ruthenium-based catalyst of the present disclosure contains a certain amount of oxygen vacancies (O v ), which can synergistically promote the hydrogen and oxygen evolution performance of water electrolysis and further improve the electrochemical catalytic performance of ruthenium-based catalysts.

[0108] A second aspect of the present disclosure provides a method for preparing a ruthenium-based catalyst, the method comprising the following steps:

[0109] (1) using polysaccharide to prepare a first sol;

[0110] (2) preparing a ruthenium source solution using a ruthenium source precursor and a complexing agent;

[0111] (3) mixing the first sol with a ruthenium source solution to prepare a second sol;

[0112] (4) drying the second sol to obtain an aerogel;

[0113] (5) calcining the aerogel to obtain a calcined product;

[0114] The complexing agent is at least one selected from polycarboxylic acids having hydroxyl groups or their salts, and the polysaccharide is at least one selected from alginic acid and its salts, carboxymethyl cellulose and its salts, and hyaluronic acid and its salts.

[0115] In one embodiment of the present disclosure, in step (1), the polysaccharide is at least one selected from alginic acid and its salts, carboxymethyl cellulose and its salts, and hyaluronic acid and its salts. Preferably, the salt of each polysaccharide can be independently an alkali metal salt or an alkaline earth metal salt. More preferably, the salt of each polysaccharide can be independently an alkali metal salt.

[0116] In one embodiment of the present disclosure, the salt of each polysaccharide can be independently a sodium salt, a potassium salt, a calcium salt, or an ammonium salt.

[0117] In one embodiment of the present disclosure, in step (1), the polysaccharide is at least one selected from sodium alginate, sodium carboxymethyl cellulose and sodium hyaluronate.

[0118] In one embodiment of the present disclosure, in step (1), the solvent for preparing the first sol is at least one selected from alcohol solvents, ketone solvents, and water; preferably at least one selected from ethanol, propanol, isopropanol, butanol, acetone, methyl ethyl ketone, butanone, and water; more preferably water.

[0119] In one embodiment of the present disclosure, in step (1), the concentration of the polysaccharide in the first sol is not particularly limited, and those skilled in the art can make an appropriate selection as needed.

[0120] In one embodiment of the present disclosure, in step (2), the ruthenium source precursor can use various types of ruthenium source precursors known to those skilled in the art. Preferably, the ruthenium source precursor is at least one selected from ruthenium trichloride, ruthenium nitrosyl nitrate, ruthenium acetate, ruthenium acetylacetonate and ruthenium sulfate.

[0121] In one embodiment of the present disclosure, in step (2), the complexing agent is at least one selected from polycarboxylic acids having a hydroxyl group or salts thereof.

[0122] In the present disclosure, the polycarboxylic acid having a hydroxyl group may be a carboxylic acid having 1 to 4 hydroxyl groups, 2 to 4 carboxyl groups, and a total carbon number of 3 to 10.

[0123] In one embodiment of the present disclosure, the polycarboxylic acid having a hydroxyl group has 1 to 2 hydroxyl groups. In one embodiment of the present disclosure, the polycarboxylic acid having a hydroxyl group has 2 to 3 carboxyl groups. In one embodiment of the present disclosure, the polycarboxylic acid having a hydroxyl group has a total carbon number of 4 to 8.

[0124] In one embodiment of the present disclosure, the polycarboxylic acid having a hydroxyl group is at least one selected from malic acid, citric acid, isocitric acid, hydroxymalonic acid, tartaric acid, 3-hydroxy-3-methylglutaric acid, and mevalonic acid.

[0125] In one embodiment of the present disclosure, the salts of the polycarboxylic acids having hydroxyl groups may each independently be an alkali metal salt or an alkaline earth metal salt. More preferably, the salts of the polycarboxylic acids having hydroxyl groups may each independently be an alkali metal salt.

[0126] In one embodiment of the present disclosure, the salts of the polycarboxylic acid having a hydroxyl group may each independently be a sodium salt, a potassium salt, a calcium salt, or an ammonium salt.

[0127] In one embodiment of the present disclosure, the complexing agent is at least one selected from sodium citrate, sodium tartrate and sodium malate.

[0128] In one embodiment of the present disclosure, in step (2), the solvent for preparing the ruthenium source solution is at least one selected from alcohol solvents, ketone solvents, and water; preferably at least one selected from ethanol, propanol, isopropanol, butanol, acetone, methyl ethyl ketone, butanone, and water; more preferably water.

[0129] In one embodiment of the present disclosure, when preparing a ruthenium source solution, the pH of the solution is adjusted to 5 to 11, preferably to 6 to 10, for example, it can be adjusted to 7.5 to 9. In the present disclosure, by adjusting the pH of the ruthenium source solution, it is beneficial for the ruthenium source solution to form a uniform and stable state, and the ruthenium element in the ruthenium source solution is evenly distributed. In one embodiment of the present disclosure, the pH of the solution is adjusted using an acidic solution or an alkaline solution conventional in the art. For example, one or more of sodium carbonate solution, sodium hydroxide solution, sodium bicarbonate solution and ammonia solution can be listed.

[0130] In one embodiment of the present disclosure, in step (2), the molar ratio of the ruthenium source precursor to the complexing agent is (0.25-20):1, preferably (0.25-10):1, further preferably (0.25-4):1, and more preferably (0.5-2):1.

[0131] In the above-mentioned embodiments of the present disclosure, the selection of the components and contents disclosed herein is conducive to the final synthesis of a loose and porous ruthenium-based catalyst, thereby increasing the specific surface area and apparent activity of the catalyst.

[0132] In step (3) of the present disclosure, the first sol is mixed with a ruthenium source solution to prepare a second sol.

[0133] In one embodiment of the present disclosure, in the preparation of the second sol, the mass ratio of the polysaccharide in the first sol to the ruthenium source precursor in the ruthenium source solution is (0.1-20):1, preferably (0.2-10):1, and more preferably (0.5-4):1. In the present disclosure, by ensuring that the mass ratio of the polysaccharide in the first sol to the ruthenium source precursor in the ruthenium source solution is specific, it is beneficial to form a suitable three-dimensional aerogel intermediate and accurately control the pyrolysis process.

[0134] In step (4) of the present disclosure, the second sol is dried to obtain an aerogel.

[0135] In one embodiment of the present disclosure, in step (4), the drying method is one or more selected from supercritical drying and freeze drying. In one embodiment of the present disclosure, the drying is freeze drying, and the freeze drying conditions include: a temperature of -30 to -20°C, preferably -25 to -20°C; and a time of 24 to 48 hours, preferably 36 to 48 hours. In one embodiment of the present disclosure, the drying is freeze drying, which is conducive to obtaining an aerogel with a porous structure.

[0136] In step (4) of the present disclosure, the aerogel preparation is different from the existing aerogel preparation method. The aerogel of the present disclosure is directly formed by drying the flowable hydrosol, and no hydrogel is formed before the aerogel is prepared.

[0137] In step (5) of the present disclosure, the aerogel is calcined to prepare a calcined product. In one embodiment of the present disclosure, the calcined product is the ruthenium-based catalyst of the present disclosure.

[0138] In one embodiment of the present disclosure, in step (5), the calcination conditions include: a temperature of 300 to 600°C, preferably 300 to 450°C, and more preferably 310 to 420°C; a time of 0.5 to 3 hours, preferably 2 to 3 hours; a heating rate of 1 to 10°C / min, preferably 2 to 5°C / min. In the present disclosure, specific calcination conditions are more conducive to the conversion of porous aerogel into a ruthenium-based catalyst having a three-dimensional porous structure. In the present disclosure, by controlling the calcination conditions in step (5), the ratio of ruthenium oxide and elemental ruthenium can be regulated. For example, in one embodiment of the present disclosure, the calcination conditions are controlled so that the obtained ruthenium-based catalyst is basically composed of ruthenium. In one embodiment of the present disclosure, the calcination conditions are controlled so that the peaks of ruthenium oxide and elemental ruthenium in the XRD spectrum and XPS spectrum of the obtained ruthenium-based catalyst meet the above-mentioned ranges of the present disclosure.

[0139] In one embodiment of the present disclosure, the method further comprises the following steps:

[0140] (6) The calcined product of step (5) is subjected to a step of washing and a second drying.

[0141] In one embodiment of the present disclosure, the washing comprises: acid washing, water washing and alcohol washing of the calcined product of step (5).

[0142] In one embodiment of the present disclosure, the acid used in the pickling is selected from one or more of dilute hydrochloric acid, sulfuric acid, nitric acid and acetic acid. In one embodiment of the present disclosure, the solvent used in the alcohol washing is one or more selected from methanol, ethanol and isopropanol, or at least one of them.

[0143] In one embodiment of the present disclosure, in the washing in step (6), the order of acid washing, water washing and alcohol washing is not particularly limited, and can be acid washing, water washing and alcohol washing in sequence; can also be acid washing, alcohol washing and water washing in sequence; can also be water washing, acid washing and alcohol washing in sequence. In one embodiment of the present disclosure, in the washing in step (6), it is preferred to carry out acid washing, water washing and alcohol washing in sequence.

[0144] In one embodiment of the present disclosure, in the washing in step (6), the number of times of washing with each washing liquid is not particularly limited, and those skilled in the art can appropriately select as needed, for example, 1 time, 2 times, 3 times, 4 times or 5 times.

[0145] In one embodiment of the present disclosure, the conditions for the second drying include: a temperature of 40 to 60° C., preferably 45 to 55° C.; and a time of 2 to 24 hours, preferably 10 to 20 hours. In the present disclosure, the washing and second drying in step (6) can remove impurity elements remaining on the surface of the catalyst. In one embodiment of the present disclosure, the product obtained after the second drying is the ruthenium-based catalyst of the present disclosure.

[0146] In one embodiment of the present disclosure, the method further comprises the following steps:

[0147] (7) A step of annealing the second dried product obtained in step (6).

[0148] In one embodiment of the present disclosure, the annealing treatment conditions include: heating the second dried product in an air atmosphere to an annealing temperature; the annealing temperature is 200 to 450° C., preferably 220 to 350° C., and the holding time at the annealing temperature can be 0.1 to 3 hours, preferably 0.5 to 2 hours. In the present disclosure, the annealing treatment in step (7) can control the conversion of a portion of the elemental ruthenium in the catalyst into ruthenium oxide without substantially affecting the pore structure of the catalyst.

[0149] In one embodiment of the present disclosure, the product obtained by annealing is the ruthenium-based catalyst of the present disclosure.

[0150] In one embodiment of the present disclosure, the annealing conditions are controlled so that the peaks of ruthenium oxide and elemental ruthenium in the XRD spectrum and XPS spectrum of the obtained ruthenium-based catalyst meet the above-mentioned ranges of the present disclosure.

[0151] The preparation method provided by the present disclosure is simple and convenient, has excellent economic efficiency, and can greatly reduce the cost of current anode ruthenium-based catalysts. The obtained ruthenium-based catalyst has excellent electrochemical catalytic performance and can be used in hydrogen production by electrolysis of water.

[0152] A third aspect of the present disclosure provides a ruthenium-based catalyst prepared by the method described in the second aspect of the present disclosure.

[0153] The fourth aspect of the present disclosure provides a ruthenium-based catalyst according to the first aspect of the present disclosure, and use of the ruthenium-based catalyst prepared by the method described in the second aspect of the present disclosure in hydrogen production by electrolysis of water, wherein the use includes a membrane electrode and / or an electrolyzer.

[0154] The fifth aspect of the present disclosure provides a membrane electrode, characterized in that the membrane electrode includes a proton exchange membrane and a catalyst coated on the proton exchange membrane, and the catalyst is the ruthenium-based catalyst of the first aspect of the present disclosure or the ruthenium-based catalyst prepared by the method described in the second aspect of the present disclosure.

[0155] The sixth aspect of the present disclosure provides a water electrolyzer, characterized in that the water electrolyzer includes a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, and the catalyst is the ruthenium-based catalyst of the first aspect of the present disclosure or the ruthenium-based catalyst prepared by the method described in the second aspect of the present disclosure.

[0156] The ruthenium-based catalyst provided by the present disclosure has excellent electrochemical catalytic performance when used for electrolysis of water to produce hydrogen, with a small initial overpotential, a low Tafel slope, and a small increase in the final overpotential after stability testing compared to the initial overpotential, and has good industrial application prospects.

[0157] Example

[0158] The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereby. Unless otherwise specified, the raw materials used in the examples and comparative examples of the present disclosure were purchased from commercial sources and are pure reagents; the relevant reagents can be prepared into aqueous or alcohol solutions of a certain concentration for subsequent use.

[0159] Instrumental method for BET analysis: The model of the fully automatic BET specific surface area tester is JW-BK200C produced by Jingwei Gaobo. The test conditions include: the test principle is the static capacity method, the adsorption gas is N2, the adsorption temperature is 77K, the N2 adsorption and desorption curve of the catalyst is obtained by test, the multi-point BET specific surface area is obtained by analysis and calculation, the pore volume and pore size distribution are obtained by BJH method analysis, and the micropore analysis adopts the slit pore HK method.

[0160] Calculation of porosity: Porosity = 100% × pore volume / (pore volume + solid volume), where the pore volume is obtained based on the BET test, and the solid volume is calculated based on the mass and density of the catalyst. The solid volume of the catalyst is determined by XRD analysis of the content of elemental ruthenium and ruthenium oxide divided by their respective densities.

[0161] Instrumental method for mass transfer performance testing: A typical three-electrode system was used, and the constant current test was performed using a CHI760E electrochemical workstation. CV activation and stabilization were first performed, and non-wetted bubbles on the electrode surface were removed. Then, a constant current test was performed. A high-speed industrial camera was used to capture the bubbles generated on the electrode surface during the test.

[0162] Instrumental method for testing elemental ruthenium content: A Rigaku Priums IV X-ray fluorescence spectrometer (XRF) was used. The catalyst was pressed into pellets for full elemental analysis. Light elements such as C, H, and O were analyzed using a more precise C, H, and O elemental analyzer. Prior to testing, the catalyst was not pretreated to remove water, oxygen, or other adsorption media in a vacuum.

[0163] The disclosed embodiments and comparative examples employed XRD analysis to analyze the physical phases of elemental ruthenium and ruthenium oxide in the catalysts. The XRD analysis was performed using a Shimadzu XRD-6000 X-ray diffractometer (Japan). The test conditions included a tube voltage of 40 kV, a tube current of 40 mA, Cu target Kα radiation, a 2θ scan range of 5°-70°, and a scan rate of 5° / min. The analysis was performed using the WPF refinement module, diffraction peak fitting, and rapid quantitative calculation methods in Jade 6.5 or Jade 9.0 software.

[0164] The morphology of the catalyst and the thickness of the nanosheets were analyzed by SEM. The instrument, method and conditions for the SEM analysis were as follows: the scanning electron microscope (SEM) was a Hitachi S-4800 scanning electron microscope with an operating voltage of 5 kV-20 kV and equipped with energy dispersive X-ray spectroscopy (EDS).

[0165] XPS was used to analyze the types and contents of elements on the catalyst surface. The instrument, method, and conditions for XPS analysis were as follows: an ESCALab220i-XL X-ray electron spectrometer equipped with Avantage V5.926 software produced by VG Scientific was used as the X-ray photoelectron spectrometer. The X-ray photoelectron spectrometer test conditions were as follows: the excitation source was monochromatic A1 Kα X-ray with a power of 330 W, and the basic vacuum during the analysis was 3×10 -9 In addition, the electron binding energy was calibrated using the C1s peak (284.8 eV) of the internal standard contaminant carbon, using CasaXPS 2.3.25PR1.0 software.

[0166] Example 1

[0167] An appropriate amount of sodium alginate was dissolved in deionized water to prepare a first sol with a concentration of 0.8 wt%.

[0168] Appropriate amounts of RuCl3 and sodium citrate were weighed and dissolved in deionized water so that the molar ratio of RuCl3 to sodium citrate in the mixture was 1.5:1. The pH of the mixture was then adjusted to approximately 7.8 to obtain a uniform and stable ruthenium source solution.

[0169] The ruthenium source solution is added to the first sol and stirred to disperse evenly to obtain a second sol. The mass ratio of polysaccharide to ruthenium source precursor in the second sol is 2.3:1. The second sol is placed in a freeze drying oven for freeze drying at a temperature of -22°C for 38 hours. The second sol becomes an aerogel with a porous structure.

[0170] The resulting aerogel was placed in a muffle furnace in an air atmosphere with a constant flow rate and calcined at 330°C for 2.5 hours at a heating rate of 3°C / min to obtain a calcined product. The calcined product was naturally cooled to room temperature and centrifuged and washed several times in dilute hydrochloric acid, deionized water, and a mixed solution of ethanol and water. The product was then dried in a vacuum drying oven at 45°C for 12 hours. Catalyst 1 was collected and labeled C1. Its composition is shown in Table 1.

[0171] The total pore volume of catalyst C1 prepared in this example is 0.145 cm 3 / g, and a specific surface area of ​​82.025m 2 / g, and the apparent mass volume ratio is 0.28g / cm 3 .

[0172] The SEM image of catalyst C1 prepared in this example is shown in Figure 1, the XRD pattern is shown in Figure 2, the cyclic voltammetry curve is shown in Figure 3, the XPS spectrum of Ru 3p is shown in Figure 4, and the XPS spectrum of O 1s is shown in Figure 5; the bubble discharge diagram when catalyst C1 is coated on carbon paper to prepare an electrode for water electrolysis reaction is shown in Figure 9.

[0173] According to Table 1 and Figure 1, Catalyst C1 has a three-dimensional porous microstructure composed of three-dimensionally connected nanosheets. The "surface" covering the pores and the "wall" of the internal pores in the form of a translucent thin layer are both formed by interconnected nanosheets of multiple sheet-like entities, that is, they are composed of multiple nanosheets connected together, and the thickness of each nanosheet is only 12.2 nm. This shows that Catalyst C1 has a loose three-dimensional porous microstructure and a large specific surface area, which is beneficial to improving the mass transfer effect and apparent electrochemical activity of the catalyst.

[0174] FIG2 shows that the XRD spectrum of catalyst C1 has an obvious main diffraction peak of elemental ruthenium at 2θ=44.0°, while the characteristic diffraction peak of ruthenium oxide is not obvious.

[0175] Figure 3 shows that in the cyclic voltammetry curve, catalyst C1 does not exhibit a clear redox peak in the potential range of 1.06V to 1.41V vs. RHE. The peak shape is similar to that of double-layer capacitance or pseudocapacitance, and the peak area is large, indicating that catalyst C1 has more effective active sites, which is beneficial to improving its apparent activity.

[0176] Figure 4 shows that the high-resolution XPS spectrum of Ru 3p of catalyst C1 shows obvious peaks of elemental ruthenium and ruthenium oxide. Among them, there is a characteristic peak of elemental ruthenium at a binding energy of 461.85eV to 461.95eV, and the characteristic peak of elemental ruthenium shifts by 0.4eV toward the low electron binding energy direction relative to the standard position of elemental ruthenium (462.3eV); there is a characteristic peak of ruthenium oxide at a binding energy of 463.25eV to 463.35eV, and the characteristic peak of ruthenium oxide shifts by 0.63eV toward the high electron binding energy direction relative to the standard position of ruthenium oxide (462.7eV), indicating that the electronic structures of elemental ruthenium and ruthenium oxide on the surface of catalyst C1 are optimized, which is conducive to synergistically promoting the hydrogen / oxygen evolution performance in acidic water electrolysis.

[0177] Figure 5 shows that catalyst C1 has obvious O in the high-resolution XPS spectrum of O1s. v The peak separation indicates that C1 has oxygen vacancies, which is beneficial to promote the adsorption of oxygen-containing intermediates and improve the electrochemical catalytic performance of the catalyst.

[0178] Figure 9 shows that the bubbles on the electrode surface of catalyst C1 during the reaction are very small and easily desorbed from the electrode surface, indicating that catalyst C1 has a good mass transfer effect, which is conducive to maintaining excellent hydrogen / oxygen evolution performance at high current density.

[0179] Example 2

[0180] The same as Example 1, except that in the calcination step, the aerogel was placed in a muffle furnace and calcined at 430°C for 2.5 hours with a heating rate of 3°C / min. The catalyst 2 obtained was finally collected and marked as C2. Its composition is shown in Table 1.

[0181] Example 3

[0182] The same as Example 1, except that: after the second drying step, the second dried result was annealed, and the annealing conditions included: heating the second dried result in an air atmosphere to 260° C. and keeping it warm for 1 hour (i.e., the annealing temperature was 260° C. and the holding time was 1 hour), and then cooled to room temperature to obtain catalyst 3, marked as C3, whose composition is shown in Table 1.

[0183] The XRD pattern of catalyst C3 prepared in this example is shown in FIG6 .

[0184] Figure 6 shows that the XRD spectrum of catalyst C3 contains both characteristic peaks of elemental ruthenium and characteristic peaks of ruthenium oxide, and the content ratio calculated based on the peak area of ​​the characteristic peak of elemental ruthenium and the characteristic peak of ruthenium oxide is 1.0, where the characteristic peak of elemental ruthenium refers to the main diffraction peak of elemental ruthenium appearing at 2θ=44° in the XRD spectrum, and the characteristic peak of ruthenium oxide refers to the main diffraction peak of ruthenium oxide appearing at 2θ=28° in the XRD spectrum, indicating that catalyst C3 contains a certain amount of elemental ruthenium and ruthenium oxide, and the proportion of ruthenium oxide in catalyst C3 is increased after annealing treatment.

[0185] Example 4

[0186] The same as Example 1, the only difference is that in the preparation step of the first sol, sodium alginate is replaced with the same amount of sodium carboxymethyl cellulose, and in the preparation step of the ruthenium source solution, sodium citrate is replaced with the same amount of sodium tartrate. Finally, catalyst 4 is collected and marked as C4. Its composition is shown in Table 1.

[0187] Comparative Example 1

[0188] The process was identical to Example 1, except that, in the ruthenium source solution preparation step, a complexing agent was not used. Instead, a RuCl3 solution was dispersed in an appropriate amount of deionized water, with the same molar amount of RuCl3 as in Example 1, and stirred to obtain a ruthenium source solution. In the calcination step, the aerogel was placed in a muffle furnace in an air atmosphere with a constant flow rate and calcined at 430°C for 2.5 hours at a heating rate of 3°C / min. Comparative catalyst 1 was collected and labeled D1. Its composition is shown in Table 1.

[0189] Comparative Example 2

[0190] Commercial anhydrous ruthenium oxide was used as comparative catalyst 2, marked as D2, which was purchased from Alfa Company with product number A10816. Its composition is shown in Table 1.

[0191] The XPS spectrum of Ru 3p of comparative catalyst D2 is shown in Figure 7, the XPS spectrum of O 1s is shown in Figure 8, and the bubble discharge diagram when D2 is coated on carbon paper to prepare an electrode for water electrolysis reaction is shown in Figure 10.

[0192] FIG7 shows that the high-resolution XPS spectrum of D2 at Ru 3p is a typical characteristic peak of Ru(IV) (ie, ruthenium oxide), with no shift in binding energy and no characteristic peak of elemental ruthenium.

[0193] Figure 8 shows that D2 does not show significant O in the high-resolution XPS spectrum of O1s. v peak.

[0194] Figure 10 shows that the bubbles on the electrode surface of D2 during the reaction are large and not easy to desorb from the electrode surface, indicating that D2 has poor mass transfer effect, which is not conducive to maintaining high hydrogen / oxygen evolution performance at high current density.

[0195] Comparative Example 3

[0196] Commercial iridium black was used as comparative catalyst 3, marked as D3, which was purchased from Alfa Company with product number 010746. Its composition is shown in Table 1.

[0197] Comparative Example 4

[0198] Commercial anhydrous ruthenium powder was used as comparative catalyst 4, marked as D4, which was purchased from Alfa Company with product number 44879. Its composition is shown in Table 1.

[0199] Table 1 Structural characteristics of catalysts prepared in different embodiments and comparative examples

[0200] As can be seen from the data in Table 1 above, the ruthenium-based catalysts prepared in Examples 1-4 have a three-dimensional porous structure formed by multiple nanosheets connected in three dimensions, contain ruthenium by mass fraction of 70% or more, and exhibit distinct characteristic peaks of elemental ruthenium in their XRD spectra, indicating excellent mass transfer performance. In contrast, the comparative catalysts provided in Comparative Examples 1-4 lack a porous structure and exhibit poor mass transfer performance.

[0201] Test cases 1 to 8

[0202] The catalysts prepared in Examples 1 to 4 of the present disclosure and the comparative catalysts prepared in Comparative Examples 1 to 4 were used as oxygen evolution catalysts, and the electrochemical catalytic oxygen evolution performance was evaluated using the following test method. The electrochemical workstation model is PARSTAT3000A-DX, and the rotating disk electrode model is 636A. A three-electrode system was adopted, with a saturated calomel electrode (SCE) protected by a double salt bridge as the reference electrode, a high-purity graphite rod as the counter electrode, and a glassy carbon electrode as the working electrode. The electrolyte used under acidic conditions was a 0.5M H2SO4 solution or a 0.1M HClO4 solution. The catalyst to be tested was ultrasonically uniformly dispersed in a mixed solution of isopropanol, water and Nafion, dropped onto the surface of the glassy carbon electrode, and naturally dried to obtain a working electrode. The catalyst loading was 0.38 mg / cm 2The test temperature was 20-25°C. Oxygen was introduced for at least 30 minutes before the test to saturate the solution with oxygen. The rotation speed was 2500 rpm. The scan range of the cyclic voltammetry curve was 0.80 V to 1.23 V vs. SCE, and the scan rate was 100 mV / s. The scan range of the linear polarization curve was 0.80 V to 1.35 V vs. SCE, and the scan rate was 5 mV / s. The scan range of the stability test was 1.24 V to 1.49 V vs. RHE, the scan rate was 100 mV / s, and the number of scan cycles was 10,000. The test results are shown in Table 2.

[0203] Test Example 9

[0204] The same as test example 1, the only difference is that a three-electrode system is used, and the catalyst prepared in example 1 is used as a hydrogen evolution catalyst to evaluate the electrochemical catalytic hydrogen evolution performance. The test results are: 10mA / cm 2 The overpotential corresponding to the current density is only 33.2mV, 50mA / cm 2 The overpotential corresponding to the current density is 77.2 mV and the Tafel slope is 38.7 mV / dec. 2 Compared with the overpotential of 18 to 20 mV of Pt-based catalysts, the overpotential of the ruthenium-based catalyst disclosed in the present invention is not much different. As a non-Pt-based catalyst, it exhibits excellent acidic HER performance and the cost is greatly reduced.

[0205] Test Example 10

[0206] The same as Test Example 1, the only difference is that a three-electrode system is used, the catalyst prepared in Example 1 is used as the oxygen evolution catalyst, the electrolysis water oxygen evolution performance after the stability test is evaluated, and the measured 10mA / cm 2 The overpotential after stability test under current density conditions is 240mV; 50mA / cm 2 The overpotential after stability test under current density conditions is 274mV.

[0207] Table 2 Electrochemical catalytic properties of catalysts prepared in different examples and comparative examples

[0208] From the data in Table 2 above, it can be seen that compared with the comparative catalysts D1 to D4, when the catalysts C1 to C4 are used for electrolysis of water to produce hydrogen, the battery 2 and 50mA / cm 2The catalysts C1 to C4 prepared in the embodiments of the present invention have excellent catalytic activity, namely, acidic electrochemical oxygen evolution / hydrogen evolution activity and excellent stability, and their preparation costs are greatly reduced compared to iridium-based catalysts, and they have good prospects for industrial application.

[0209] The preferred embodiments of the present disclosure are described in detail above in conjunction with the embodiments. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0210] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0211] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A ruthenium-based catalyst, characterized in that The ruthenium-based catalyst is a porous material, and the content of ruthenium element is more than 70% expressed by mass fraction; the XRD spectrum of the ruthenium-based catalyst has a characteristic peak of single ruthenium.

2. The ruthenium-based catalyst according to claim 1, characterized in that The ruthenium-based catalyst satisfies at least one of the following conditions: 1) The content of ruthenium in the ruthenium-based catalyst is 72 to 90% by mass; 2) The content of oxygen in the ruthenium-based catalyst is 8 to 25% by mass.

3. The catalyst according to claim 1 or 2, characterized in that The ruthenium-based catalyst satisfies at least one of the following conditions: 1) The porosity of the ruthenium-based catalyst is greater than 30%, preferably greater than 50%, more preferably 52 to 95%, further preferably 55 to 75%, and even more preferably 55 to 65%; 2) The specific surface area of ​​the ruthenium-based catalyst is 60 to 100 cm 2 / g, preferably 70 to 90 cm 2 / g; 3) The apparent mass volume ratio of the ruthenium-based catalyst is 0.15 to 0.45 g / cm 3 .

4. The ruthenium-based catalyst according to any one of claims 1 to 3, characterized in that The ruthenium-based catalyst is a material with mesopores and / or macropores. Preferably, the microstructure of the mesopores and / or macropores of the ruthenium-based catalyst is formed by connecting multiple nanosheet-shaped structures in three-dimensional space; the thickness of the nanosheet is 6.6nm to 17.8nm, preferably 9.8nm to 14.6nm.

5. The ruthenium-based catalyst according to any one of claims 1 to 4, characterized in that In the XRD spectrum of the ruthenium-based catalyst, the mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak areas of the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium is 0 to 0.5, preferably 0.01 to 0.4, further preferably 0.05 to 0.36, and more preferably 0.1 to 0.35; the content of ruthenium element in the ruthenium-based catalyst is 77 to 90% expressed as a mass fraction.

6. The ruthenium-based catalyst according to any one of claims 1 to 4, characterized in that The XRD spectrum of the ruthenium-based catalyst also contains a characteristic peak of ruthenium oxide. The mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak areas of the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium is 0.6 to 5, preferably 0.7 to 4.

5. The content of ruthenium element in the ruthenium-based catalyst is 73 to 80% expressed as a mass fraction.

7. The ruthenium-based catalyst according to claim 6, characterized in that The mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak areas of the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium is 2 to 4.5; or The mass content ratio of ruthenium oxide to elemental ruthenium calculated based on the peak areas of the characteristic peak of ruthenium oxide and the characteristic peak of elemental ruthenium is 0.7 to 1.4, preferably 0.8 to 1.2, and more preferably 0.9 to 1.

1.

8. The ruthenium-based catalyst according to any one of claims 1 to 7, characterized in that The XPS Ru 3p In the spectrum, there are characteristic peaks of elemental ruthenium and ruthenium oxide. The characteristic peak of elemental ruthenium moves toward the direction of low electron binding energy relative to the standard position of elemental ruthenium, and the characteristic peak of ruthenium oxide moves toward the direction of high electron binding energy relative to the standard position of ruthenium oxide.

9. The catalyst according to any one of claims 1 to 8, characterized in that In the XPS O 1s spectrum of the ruthenium-based catalyst, there is a characteristic peak at a binding energy of 530.7 eV to 531.1 eV.

10. A method for preparing a ruthenium-based catalyst, characterized in that: The method comprises the following steps: (1) using polysaccharide, preparing a first sol; (2) preparing a ruthenium source solution using a ruthenium source precursor and a complexing agent; (3) mixing the first sol with a ruthenium source solution to prepare a second sol; (4) drying the second sol to obtain an aerogel; (5) calcining the aerogel to obtain a calcined product; The complexing agent is at least one selected from polycarboxylic acids or salts thereof having a hydroxyl group, and the polysaccharide is at least one selected from alginic acid and its salts, carboxymethyl cellulose and its salts, and hyaluronic acid and its salts.

11. The preparation method according to claim 10, characterized in that: In step (1), The polysaccharide is at least one selected from alginic acid and its salts, carboxymethyl cellulose and its salts, and hyaluronic acid and its salts; preferably, at least one selected from sodium alginate, sodium carboxymethyl cellulose and sodium hyaluronic acid; and / or The solvent of the first sol is at least one selected from alcohol solvents, ketone solvents, and water; preferably at least one selected from ethanol, propanol, isopropanol, butanol, acetone, methyl ethyl ketone, butanone, and water; more preferably water.

12. The preparation method according to claim 10 or 11, characterized in that: In step (2), The ruthenium source precursor is at least one selected from ruthenium trichloride, ruthenium nitrosyl nitrate, ruthenium acetate, ruthenium acetylacetonate and ruthenium sulfate; and / or The polycarboxylic acid having a hydroxyl group is a carboxylic acid having 1 to 4 hydroxyl groups, 2 to 4 carboxyl groups and a total carbon number of 3 to 10. Preferably, the polycarboxylic acid having a hydroxyl group is at least one selected from malic acid, citric acid, isocitric acid, hydroxymalonic acid, tartaric acid, 3-hydroxy-3-methylglutaric acid, and mevalonate. The salt of the polycarboxylic acid having a hydroxyl group is a sodium salt, a potassium salt, a calcium salt or an ammonium salt; and / or The molar ratio of the ruthenium source precursor to the complexing agent is (0.25-20):1, preferably (0.25-10):1, more preferably (0.25-4):1, and more preferably (0.5-2):1; and / or The solvent of the ruthenium source solution is at least one selected from alcohol solvents, ketone solvents, and water; preferably at least one selected from ethanol, propanol, isopropanol, butanol, acetone, methyl ethyl ketone, butanone, and water; more preferably water; and / or When preparing the ruthenium source solution, the pH of the solution is adjusted to 5-11, preferably 6-10.

13. The preparation method according to any one of claims 10 to 12, characterized in that: In the mixing of step (3), the mass ratio of the polysaccharide in the first sol to the ruthenium source precursor in the ruthenium source solution is (0.1-20):1, preferably (0.2-10):1, and more preferably (0.5-4):1; and / or In step (4), the drying method is one or more selected from supercritical drying and freeze drying; preferably, the drying is freeze drying, and the freeze drying conditions include: temperature of -30 to -20°C, preferably -25 to -20°C; time of 24 to 48 hours, preferably 36 to 48 hours; and / or In step (5), the calcination conditions include: temperature of 300-600°C, preferably 300-450°C, more preferably 310-420°C; time of 0.5-3h, preferably 2-3h; heating rate of 1-10°C / min, preferably 2-5°C / min.

14. The preparation method according to any one of claims 10 to 13, characterized in that: The method further comprises the following steps: (6) washing and second drying the calcined product of step (5); The washing comprises: acid washing, water washing and alcohol washing the calcined product of step (5); preferably, acid washing, water washing and alcohol washing are carried out in sequence; preferably, the acid used in the acid washing is one or more selected from dilute hydrochloric acid, sulfuric acid, nitric acid and acetic acid, and the solvent used in the alcohol washing is one or more selected from methanol, ethanol and isopropanol, or a mixed solvent of at least one of them and water; The second drying conditions include: a temperature of 40 to 60° C., preferably 45 to 55° C.; and a time of 2 to 24 hours, preferably 10 to 20 hours.

15. The preparation method according to claim 14, characterized in that: The method further comprises the following steps: (7) annealing the second dried product obtained in step (6), The annealing treatment conditions include: heating the second dried product in an air atmosphere to raise its temperature to an annealing temperature; the annealing temperature is 200-450° C., preferably 220-350° C., and the holding time is 0.1-3 hours, preferably 0.5-2 hours.

16. Use of the ruthenium-based catalyst according to any one of claims 1 to 9 or the ruthenium-based catalyst obtained by the preparation method of the ruthenium-based catalyst according to any one of claims 10 to 15 in hydrogen production by electrolysis of water.

17. A membrane electrode, characterized in that The membrane electrode comprises a proton exchange membrane and a catalyst coated on the proton exchange membrane, wherein the catalyst is a ruthenium-based catalyst according to any one of claims 1 to 9 or a ruthenium-based catalyst obtained according to the preparation method of the ruthenium-based catalyst according to any one of claims 10 to 15.

18. A water electrolyzer, characterized in that: The water electrolyzer comprises a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, wherein the catalyst is a ruthenium-based catalyst according to any one of claims 1 to 9 or a ruthenium-based catalyst obtained according to the preparation method of the ruthenium-based catalyst according to any one of claims 10 to 15.

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