Local amorphous MnRuOx nanosheet electrocatalyst and preparation method thereof

Abstract

The invention discloses a local amorphous MnRuOx nanosheet electrocatalyst and a preparation method thereof, and belongs to the technical field of electrochemical catalysis. The preparation method comprises the following steps: adding ruthenium chloride hydrate and benzyl alcohol into a reaction kettle, standing in a dark place, sequentially adding a surfactant and a morphology control agent, adding a reducing agent after a certain time, and heating to react to form the manganese-loaded ruthenium nanosheet with triangular morphology; the preparation method comprises the following steps: by taking a manganese-loaded ruthenium nanosheet as a precursor, carrying out annealing reaction through heat preservation and heating under the oxidation action of manganese ions and air, so as to obtain a locally amorphous MnRuOx nanosheet; according to the local amorphous MnRuOx nanosheet, a rich amorphous / crystal interface structure is formed through manganese induction, the number of active sites of the catalyst is remarkably increased, and meanwhile the use amount of precious metal ruthenium can be reduced; and the electrocatalyst can be used as a high-efficiency electrocatalyst in a water electrolysis hydrogen evolution process.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic technology, and specifically relates to a local amorphous MnRuOx nanosheet electrocatalyst and a preparation method thereof. Background Art

[0002] As a renewable energy source with high efficiency, cleanliness, and abundant energy, hydrogen provides an important solution for the decarbonization of the energy system and the realization of sustainable development. Hydrogen production by electrolysis of water is considered one of the most promising clean hydrogen production technologies. Therefore, researching and developing cathode materials with high catalytic performance and reducing the overpotential of the hydrogen evolution reaction (HER) is an effective way to reduce the energy consumption of water electrolysis. Existing research shows that noble metal-based electrocatalysts (such as platinum-based or ruthenium-based oxides) are widely used to reduce the inherent energy barrier due to their excellent hydrogen evolution performance. To further improve the hydrogen evolution performance of ruthenium-based catalysts, researchers have explored the preparation of two-dimensional nanosheets, core-shell structures, single-atom dispersion, and supported ruthenium nanoparticles, etc. Among them, two-dimensional ruthenium-based nanosheets have attracted much attention in electrocatalysis due to their large specific surface area, abundant active sites, and fast electron transfer ability. However, how to achieve the efficient, low-cost, and controllable preparation of two-dimensional metal nanomaterials remains a technical challenge currently faced.

[0003] Compared with platinum-based catalysts, ruthenium-based catalysts not only have lower costs but also exhibit performance comparable to platinum in terms of hydrogen evolution activity. The two-dimensional ruthenium-based nanosheets obtained through structural engineering can expose more active sites, thereby improving the hydrogen evolution performance of ruthenium-based materials. In addition, compared with pure crystalline materials, amorphous catalysts can provide more catalytic active sites due to their rich structural defects and unsaturated coordinated atoms, further enhancing their catalytic activity and stability. In heterogeneous structure materials coexisting with amorphous and crystalline states, the amorphous region can provide abundant active sites, and the crystalline region can achieve rapid charge transfer, thus combining the advantages of both. However, synthesizing local amorphous nanomaterials under mild conditions faces great challenges, and there are uncontrollable defects in the elemental composition, size, and morphology of the synthesized noble metal nanomaterials. Summary of the Invention

[0004] The present invention overcomes the deficiencies of the prior art. The present invention proposes a local amorphous MnRuOx nanosheet electrocatalyst and a preparation method thereof, which solve the defects of uncontrollable elemental composition, size, and morphology of noble metal nanomaterials synthesized by traditional methods, and the purpose is to comprehensively improve the performance of two-dimensional noble metal nanosheet electrocatalysts.

[0005] The present invention is realized through the following technical solutions: A preparation method of a local amorphous MnRuOx nanosheet electrocatalyst, comprising the following steps: S1. Add ruthenium chloride hydrate and benzyl alcohol into a reaction kettle, mix them evenly, and then let them stand still in the dark. S2. Sequentially add a surfactant and manganese acetylacetonate as a morphology control agent into the solution obtained in step S1. After stirring for 5 - 15 min, add a reducing agent. After fully mixing evenly, heat the mixture to 160 - 220 °C and keep reacting for 10 - 16 h to form manganese-loaded ruthenium nanosheets with a triangular morphology; the mass ratio of ruthenium chloride hydrate to manganese acetylacetonate is 0.3 - 1. S3. Using the manganese-loaded ruthenium nanosheets as a precursor, under the oxidation of manganese ions and air, carry out an annealing reaction by holding the temperature and heating to obtain locally amorphous MnRuO x nanosheets.

[0006] Preferably, the mass ratio of ruthenium chloride hydrate to benzyl alcohol is 0.001 - 0.002; the mass ratio of ruthenium chloride hydrate to the reducing agent is 0.01 - 0.03; the mass ratio of ruthenium chloride hydrate to the surfactant is 0.01 - 0.2.

[0007] More preferably, the reducing agent is formaldehyde or ethylene glycol, and the surfactant is polyvinylpyrrolidone.

[0008] Preferably, the time for standing still in the dark is 10 - 30 min.

[0009] Preferably, in step S1, ultrasonic treatment for 20 - 40 min is used to mix ruthenium chloride hydrate and benzyl alcohol.

[0010] Preferably, in step S2, the reaction kettle is placed in a forced-air drying oven for heating reaction.

[0011] More preferably, the product obtained after heating in the forced-air drying oven is centrifuged, washed, and dried to obtain a black powder.

[0012] Preferably, the annealing reaction is carried out in a tube furnace.

[0013] More preferably, the temperature of the tube furnace is 150 - 450 °C, the heat preservation time is 0.5 - 2 h, and the heating rate is 5 °C / min -1 , and the gas in the tube is air.

[0014] A locally amorphous MnRuOx nanosheet electrocatalyst is prepared by using the preparation method of the locally amorphous MnRuOx nanosheet electrocatalyst.

[0015] The beneficial effects of the present invention compared with the prior art are as follows: 1. The present invention controls the formation of triangular nanosheets by controlling the ratio of ruthenium chloride hydrate to the morphology control agent and the interval time between the addition of the morphology control agent and the reducing agent; the annealing temperature is used to regulate the crystallinity of two-dimensional ruthenium-based nanosheets. Compared with the prior art, in the local amorphous MnRuOx nanosheets of the present invention, the pro-oxidizing property of Mn provides additional H 2 O adsorption sites, thus accelerating the alkaline HER in the Volmer step. Moreover, the incorporation of non-precious metals reduces the amount of precious metal Ru used while improving the catalyst activity, thereby reducing the cost of the catalyst. On the other hand, the formation of the amorphous / crystalline interface leads to the redistribution of electrons at the nanointerface, thus optimizing the adsorption energy of reaction intermediates.

[0016] 2. The nanosheets described in the present invention can be used as highly efficient electrocatalysts in the process of hydrogen evolution by electrolyzing water. The catalyst has a triangular micro-morphology with atomic layer thickness and is rich in crystalline / amorphous heterojunctions. The local amorphous MnRuOx nanosheets of the present invention induce the formation of a rich amorphous / crystalline interface structure through manganese (Mn), resulting in the redistribution of electrons in the nanosheets. This not only significantly increases the number of active sites of the catalyst but also reduces the amount of precious metal ruthenium (Ru) used, thereby reducing the cost of the catalyst. This innovation helps to promote the further scientific research and practical popularization and application of two-dimensional noble metal nanomaterials.

[0017] 3. The locally amorphous MnRuOx nanosheets prepared by the present invention have excellent prospects for electrocatalytic applications. The method of the present invention not only reduces the production cost but also improves the activity and durability of the catalyst, which is of great significance for promoting the industrial application and development of the upstream and downstream industries of hydrogen energy. Description of the Drawings

[0018] Figure 1 are the scanning electron microscope image and the corresponding energy spectrum analysis element distribution map of the MnRuOx catalyst prepared in Example 1 of the present invention; Figure 2 is the transmission electron microscope image of the MnRuOx catalyst prepared in Example 1 of the present invention; Figure 3 is the aberration-corrected transmission electron microscope of the MnRuOx catalyst prepared in Example 1 of the present invention; Figure 4 is the X-ray diffraction pattern of the catalyst prepared in Example 1 of the present invention; Figure 5 is the LSV polarization curve of HER of the catalyst prepared in Example 1 of the present invention under alkaline conditions. Detailed Embodiments

[0019] To make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear and understandable, the present invention will be further described in detail in conjunction with embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The technical solutions of the present invention will be described in detail below in conjunction with the embodiments and drawings, but the protection scope is not limited hereby.

[0020] Example 1 A preparation method of a local amorphous MnRuOx nanosheet catalyst includes the following steps: S1. Add 10 mg of ruthenium chloride hydrate and 6 mL of benzyl alcohol solution into a 25-ml reaction kettle. After ultrasonic treatment for 20 min to make it uniform, keep it in the dark and stand still for 20 min.

[0021] S2. Sequentially add 100 mg of the surfactant polyvinylpyrrolidone and 30 mg of the morphology control agent manganese acetylacetonate into the reaction kettle. After stirring for 5 min, add 0.6 ml of the reducing agent formaldehyde and continue to stir for 5 min.

[0022] S3. Place the reaction kettle in a forced-air drying oven and heat it to 180 °C, keep the reaction for 14 h, and then naturally cool it to room temperature.

[0023] S4. Centrifuge the obtained solid-liquid mixture to obtain a black solid product. Wash the product four times with a mixed solution of anhydrous ethanol and acetone, and then dry it in vacuum.

[0024] S5. Grind the obtained powder, place it in a tubular furnace, heat it in air for 1 h, the heating temperature is 250 °C, and the heating rate is 5 °C / min -1 , and then naturally cool it to room temperature to obtain the product local amorphous MnRuOx.

[0025] Example 2 A preparation method of an amorphous MnRuOx nanosheet catalyst includes the following steps: S1. Add 10 mg of ruthenium chloride hydrate and 9 mL of benzyl alcohol solution into a 25-ml reaction kettle. After ultrasonic treatment for 20 min to make it uniform, keep it in the dark and stand still for 30 min.

[0026] S2. Sequentially add 20 mg of polyvinylpyrrolidone and 60 mg of the morphology control agent manganese acetylacetonate into the solution. After stirring for 15 min, add 0.9 ml of the reducing agent formaldehyde and continue to stir for 15 min.

[0027] S3. Place the reaction kettle in a forced-air drying oven and heat it to 220 °C, keep it warm for 16 h, and then naturally cool it to room temperature.

[0028] S4. Centrifuge the obtained solid-liquid mixture to obtain a black solid product. After washing the product four times with a mixed solution of anhydrous ethanol and acetone, dry it under vacuum.

[0029] S5. Grind the above-obtained powder, place it in a tube furnace, heat it in air for 0.5 h at a heating temperature of 150 °C and a heating rate of 5 °C / min -1 , and then naturally cool it to room temperature to obtain the product amorphous MnRuOx.

[0030] Example 3 A preparation method of a crystalline MnRuOx nanosheet catalyst, comprising the following steps: S1. Add 10 mg of ruthenium chloride hydrate and 3 ml of benzyl alcohol solution to a 25-ml reaction kettle. After ultrasonic homogenization, let it stand in the dark for 40 min.

[0031] S2. Add 50 mg of polyvinylpyrrolidone and 10 mg of the morphology control agent manganese acetylacetonate to the solution, stir for 10 min, and then add 0.6 ml of the reducing agent formaldehyde and continue to stir for 10 min.

[0032] S3. Place the reaction kettle in a forced-air drying oven, heat it to 160 °C, keep it warm for 12 h, and then naturally cool it to room temperature.

[0033] S4. Centrifuge the obtained solid-liquid mixture to obtain a black solid product. After washing the product four times with a mixed solution of anhydrous ethanol and acetone, dry it under vacuum.

[0034] S5. Grind the above-obtained powder, place it in a tube furnace, heat it in air for 2 h at a heating temperature of 450 °C and a heating rate of 5 °C / min -1 , and then naturally cool it to room temperature to obtain the product crystalline MnRuOx.

[0035] Example 4 A preparation method of a crystalline RuO 2 catalyst, comprising the following steps: S1. Dissolve 10 mg of ruthenium chloride hydrate in 6 mL of benzyl alcohol solution, mix it evenly, and transfer it to a 25-mL reaction kettle with 100 mg of polyvinylpyrrolidone and stir for 30 min. During stirring, add 0.6 mL of ethylene glycol dropwise.

[0036] S2. Place the reaction kettle in a forced-air drying oven, heat it to 220 °C, keep it warm for 16 h, and then naturally cool it to room temperature.

[0037] S3. Centrifuge the obtained solid-liquid mixture to obtain a black solid product. After washing the product four times with a mixed solution of anhydrous ethanol and acetone, dry it under vacuum.

[0038] S4. Grind the obtained powder above, place it in a tube furnace, heat it in air for 2 h, with the heating temperature being 350 °C and the heating rate being 5 °C / min -1 , and then naturally cool it to room temperature to obtain the product crystalline RuO 2 .

[0039] Figure 1 Figure 8 is the scanning electron microscope image and the corresponding energy spectrum analysis element distribution map of the MnRuOx catalyst prepared in Example 1. It can be seen from the element distribution map that the ruthenium, manganese, and oxygen elements in the nanosheets are evenly distributed.

[0040] Figure 2 Figure 12 is the transmission electron microscope image of the MnRuOx catalyst prepared in Example 1. It can be seen from the figure that the synthesized nanosheets are triangular in morphology. This is because the manganese element promotes the forward growth of ruthenium nanosheets, and the abundant nanosheet edges can expose the most active sites, which is the reason for the high activity of the catalyst.

[0041] Figure 3 Figure 16 is the aberration-corrected transmission electron microscope of the MnRuOx catalyst prepared in Example 1. It can be seen from the figure that both crystalline and amorphous regions coexist in the nanosheets. It is proved that the locally amorphous nanosheets are successfully prepared.

[0042] Figure 4 Figure 20 is the X-ray diffraction pattern of the catalyst prepared in Example 1. The standard card below corresponds to the crystal phase card of RuO 2 (RuO 2 - PDF#43-1027). It can be seen that in MnRuOx, an amorphous phase without prominent characteristic peaks is formed. According to different annealing temperatures, ruthenium oxide nanosheets with different degrees of crystallinity can be prepared, proving that this preparation method has universality and the degree of crystallinity is controllable.

[0043] Figure 5 Figure 28 is the LSV comparison diagram of the MnRuOx catalyst prepared in Example 1 and the commercial platinum-carbon catalyst for HER in 1 M KOH electrolyte solution. It can be seen from the figure that in 1 M KOH electrolyte solution, the overpotential of the MnRuOx catalyst at 10 mA / cm -2 is 31 mV.

[0044] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited to this. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the premise of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the patent protection scope determined by the claims submitted by the present invention.

Claims

1. A method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst, characterized in that: The following steps are involved: S1. Add hydrated ruthenium chloride and benzyl alcohol into a reaction kettle, mix well and keep aside from light; S2, adding a surfactant and manganese acetylacetonate as a morphology control agent to the solution obtained in step S1 in sequence, stirring for 5-15 minutes, then adding a reducing agent, fully mixing, heating to 160-220° C., and keeping the reaction for 10-16 hours to form manganese-supported ruthenium nanosheets with a triangular morphology; the mass ratio of the hydrated ruthenium chloride to the manganese acetylacetonate is 0.3-1; S3, using manganese-loaded ruthenium nanosheets as a precursor, annealing reaction is carried out by heat preservation and heating under the oxidation of manganese ions and air to obtain localized amorphous MnRuO x Nanosheets.

2. The method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst according to claim 1, characterized in that: The mass ratio of the hydrated ruthenium chloride to benzyl alcohol is 0.001-0.002; the mass ratio of the hydrated ruthenium chloride to the reducing agent is 0.01-0.03; the mass ratio of the hydrated ruthenium chloride to the surfactant is 0.01-0.

2.

3. The method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst according to claim 2, characterized in that: The reducing agent is formaldehyde or ethylene glycol, and the surfactant is polyvinyl pyrrolidone.

4. The method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst according to claim 1, characterized in that: The time for standing in dark place is 10-30 minutes.

5. The method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst according to claim 1, characterized in that: In step S1, ruthenium chloride hydrate and benzyl alcohol are mixed by ultrasound for 20-40 min.

6. The method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst according to claim 1, characterized in that: In step S2, the reaction kettle is placed in a forced air drying oven for heating reaction.

7. The method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst according to claim 6, characterized in that: The product obtained after heating in a blast drying oven is centrifuged, washed and dried to obtain a black powder.

8. The method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst according to claim 1, characterized in that: The annealing reaction is carried out in a tube furnace.

9. The method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst according to claim 8, characterized in that: The temperature of the tube furnace is 150-450°C, the holding time is 0.5-2h, and the heating rate is 5°C min -1 , the gas in the tube is air.

10. A localized amorphous MnRuOx nanosheet electrocatalyst, characterized in that: The electrocatalyst is prepared by the method for preparing a localized amorphous MnRuOx nanosheet electrocatalyst as described in any one of claims 1 to 9.

Images