Carbon-supported ruthenium-manganese compound, preparation method and application thereof

Abstract

The present invention discloses a carbon-supported ruthenium-manganese compound, a preparation method, and its application. The preparation method comprises the following steps: (1) dispersing a ruthenium salt, a manganese salt, and a carbon carrier in a solvent, heating and ultrasonicating until the solvent evaporates to dryness, so that the ruthenium salt and the manganese salt are adsorbed on the carbon carrier to obtain an intermediate solid powder; (2) thermally reducing the intermediate solid powder in a reducing atmosphere, so that the ruthenium salt and the manganese salt are decomposed and then reduced to obtain a carbon-supported ruthenium-manganese alloy. By introducing inexpensive manganese metal Mn, this application not only reduces the catalyst cost and the precious metal loading, but also improves the catalytic activity and stability of the Ru-based material. The goal of having both good OER oxygen evolution activity and stability is achieved, overcoming the technical difficulties of traditional acidic oxygen evolution catalysts such as excessive precious metal dosage, poor activity, and poor stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and more specifically, relates to a carbon-supported ruthenium-manganese compound, a preparation method and applications thereof. Background Art

[0002] With the increasing demand for fossil energy, a series of problems such as environmental pollution and energy crisis have been triggered, forcing researchers to seek efficient, clean and sustainable energy compositions to optimize the current energy structure. Among them, hydrogen energy, as a clean energy with high energy density, zero pollution and long-term storage, is considered to be a key link in solving problems such as energy crisis, environmental pollution and greenhouse effect. As an ideal technology for hydrogen production, water electrolysis technology uses electricity to drive the production of high-purity oxygen and hydrogen without producing any by-products, and can be coupled with fuel cell technology to realize hydrogen circulation. At present, acidic proton exchange membrane electrolyzers (PEMWEs) and alkaline electrolyzers (AWEs) have formed a certain scale in practical applications. Compared with traditional AWEs, PEMWEs have a higher working current density (maximum 2-3A cm -2 ), greater energy power density, faster hydrogen production, higher purity hydrogen output, better ionic conductivity, and a wider operating temperature and pressure range make PEMWEs an ideal candidate for coupling with fluctuating input energy. Currently, the main challenges facing the industrialization of water electrolysis technology are the high energy barrier and slow kinetics of the anodic oxygen evolution reaction (OER) and the stability of the anode catalytic materials in strong acid environments. Therefore, the development of efficient and stable anode electrocatalysts is key to the commercialization of PEMWEs.

[0003] For acidic water electrolysis, OER catalysts mainly rely on precious metal-based materials. Although some reports have shown that non-precious metal electrocatalysts have certain OER activity in acid, they still face more severe stability issues compared with precious metal-based materials. To date, acidic oxygen evolution reactions are still dominated by Ru-based and Ir-based precious metal electrocatalysts. Compared with Ir-based materials, Ru-based materials exhibit higher oxygen evolution activity, and Ru-based materials have higher abundance and are much cheaper than Ir-based materials. Therefore, Ru-based materials are considered to be the most promising electrocatalysts in the current acidic medium OER process. However, the stability of Ru-based catalysts remains a very challenging issue. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a carbon-supported ruthenium-manganese compound, a preparation method and its application, the purpose of which is to reduce the precious metal loading, improve the catalytic efficiency and stability of the catalyst, thereby solving the technical problems of acidic water electrolysis.

[0005] To achieve the above object, according to one aspect of the present invention, a method for preparing a carbon-supported ruthenium-manganese compound is provided, comprising the following steps:

[0006] (1) dispersing a ruthenium salt, a manganese salt, and a carbon support in a solvent, heating and ultrasonicating until the solvent is evaporated to dryness, so that the ruthenium salt and the manganese salt are adsorbed on the carbon support to obtain an intermediate solid powder;

[0007] (2) The intermediate solid powder is thermally reduced in a reducing atmosphere, so that the ruthenium salt and the manganese salt are decomposed and then reduced to obtain a carbon-supported ruthenium-manganese alloy.

[0008] Preferably, the thermal reduction includes a pre-burning stage and a thermal reduction stage carried out in sequence, the temperature of the pre-burning stage is 200℃~500℃, the pre-burning time is 0.5~2h, the heating rate of the pre-burning stage is 5~10℃ / min, the temperature of the thermal reduction stage is 900℃~1000℃, the heating time of the thermal reduction stage is 2~10h, and the heating rate of the thermal reduction stage is 5~10℃ / min.

[0009] Preferably, the mass proportion of ruthenium element in the intermediate solid powder is 5% to 45%.

[0010] Preferably, the atomic ratio of ruthenium to manganese in the carbon-supported ruthenium-manganese alloy is 1:(1-9).

[0011] Preferably, the ruthenium salt is at least one of ruthenium chloride, ruthenium acetylacetonate, ruthenium acetate, bismuth ruthenate, potassium ruthenate, ammonium chlororuthenate, sodium chlororuthenate, and potassium chlororuthenate; the manganese salt is at least one of manganese nitrate, manganese chloride, manganese acetate, manganese sulfate, and manganese acetylacetonate.

[0012] Preferably, the carbon support is at least one of carbon black, graphene oxide, reduced graphene oxide, carbon nanotubes, carbon nanofibers and carbon quantum dots.

[0013] Preferably, the reducing atmosphere in step (2) comprises a mixed gas of hydrogen and argon with a hydrogen volume fraction of 2 to 50%, or a mixed gas of hydrogen and nitrogen with a hydrogen volume fraction of 2 to 50%; and the solvent is at least one of water, ethanol, methanol, acetone, acetonitrile or tetrahydrofuran.

[0014] Preferably, the ultrasonic time in step (1) is 0.5 to 3 hours; and the heating temperature in step (1) is 45° C. to 75° C.

[0015] According to another aspect of the present invention, a carbon-supported ruthenium-manganese compound is provided, wherein the ruthenium-manganese compound in the carbon-supported ruthenium-manganese compound is a ruthenium-manganese alloy.

[0016] According to another aspect of the present invention, there is provided an application of a carbon-supported ruthenium manganese compound for use in acidic oxygen evolution electrocatalytic reaction and proton exchange membrane water electrolysis anode catalyst.

[0017] In general, the above technical solutions conceived by the present invention can achieve at least the following beneficial effects compared with the prior art.

[0018] (1) By introducing inexpensive manganese metal (Mn), this application not only reduces catalyst cost and precious metal loading, but also improves the catalytic activity and stability of Ru-based materials. This achieves the goal of simultaneously achieving good OER oxygen evolution activity and stability, overcoming the technical difficulties of traditional acidic oxygen evolution catalysts, such as excessive precious metal usage, poor activity, and poor stability. The preparation method is simple, requires low production equipment, and the raw materials are readily available, which is conducive to the large-scale development of catalytic materials.

[0019] (2) The present application uses two heat treatments to achieve the formation of ruthenium manganese alloy. Specifically, the thermal reduction in the present application includes a pre-sintering stage and a thermal reduction stage carried out in sequence. This is because, on the one hand, the ruthenium salt is easily reduced to nuclei during the low-temperature pre-reduction process, and the self-catalytic effect of its Ru nanoparticles enables better alloying in the subsequent reduction process. On the other hand, Mn is difficult to reduce and is usually in an oxidized state under indoor conditions. The present application found that in the thermal reduction stage, a temperature above 900 degrees Celsius is required to obtain a pure phase of ruthenium manganese alloy. At low temperatures, MnO impurities will appear. The formation of a pure phase of ruthenium manganese alloy is beneficial to improving the stability of the catalyst.

[0020] (3) In this application, when using carbon-loaded ruthenium-manganese alloy, in the process of preparing the electrode, carbon cloth or carbon paper is abandoned as the substrate, and a corrosion-resistant titanium mesh is used as the substrate to prepare a high-efficiency and stable self-supporting electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the X-ray diffraction (XRD) pattern of RuMn3 / C at different temperatures in Example 1;

[0022] Figure 2 : This is the X-ray diffraction (XRD) pattern of the carbon-supported ruthenium-manganese alloy RuMn3 / C and the carbon-supported ruthenium element Ru / C at 900°C in Example 1;

[0023] Figure 3 LSV polarization curves of carbon-supported RuMn3 / C at different temperatures in Example 3;

[0024] Figure 4 This is the test curve of acidic oxygen evolution in Example 3;

[0025] Figure 5This is the acidic oxygen evolution stability test curve of Example 3. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0027] Example 1

[0028] This embodiment provides a carbon-supported ruthenium-manganese alloy, the preparation method of which includes the following steps:

[0029] Step 1: Disperse Vulcan carbon evenly in ruthenium chloride and manganese acetate aqueous solution, ultrasonicate and stir for 30 minutes;

[0030] Step 2: The mixed solution obtained in step 1 is stirred and ultrasonicated at 65°C until the water solvent is evaporated to dryness to obtain an intermediate solid powder (wherein the Ru loading is 20% and the atomic ratio of Ru to Mn is 1:3). The obtained ruthenium manganese precursor is pre-calcined at 300°C for 2h in a 10% Ar / H2 mixed atmosphere, and then thermally reduced at 500°C, 700°C, 900°C and 1000°C, respectively, to obtain a carbon-supported ruthenium manganese alloy, wherein the heating rate is 10°C / min.

[0031] Comparative Example 1

[0032] This comparative example provides a carbon-supported ruthenium-manganese alloy, the preparation method of which comprises the following steps:

[0033] Step 1: Vulcan carbon was uniformly dispersed in a ruthenium chloride aqueous solution, ultrasonicated and stirred for 30 min, wherein the Ru loading was 20%;

[0034] Step 2: The mixed solution obtained in step 1 was heated, stirred, and ultrasonicated until the aqueous solvent evaporated to dryness, obtaining an intermediate solid powder (Ru content of 20% by mass), which was then dried in a vacuum drying oven. The ground precursor was heated at 500°C for 2 hours in a 10% Ar / H2 atmosphere at a heating rate of 10°C / min to obtain carbon-supported ruthenium.

[0035] Example 3

[0036] The carbon-supported ruthenium element and ruthenium-manganese alloy prepared in Example 1 and Comparative Example 1 were subjected to an acidic oxygen precipitation test. 5 mg of ruthenium-manganese alloy catalyst powder was added to 1 mL of an isopropanol / Nafion mixed solution to prepare an ink (wherein the mass fraction of nafion was one thousandth). The ink was ultrasonically mixed for 20 minutes. 5 uL of ink was pipetted using a pipette and evenly coated on a rotating ring disk electrode and allowed to dry naturally. The catalyst-loaded rotating ring disk electrode was used as the working electrode, the carbon rod as the auxiliary electrode, and the reversible hydrogen electrode as the reference electrode. 250 activation cycles were performed at 1.2 to 1.4 V in a 0.1 mol / L perchloric acid solution with a scan rate of 200 mV / s. Subsequently, a polarization curve test was performed in an oxygen-saturated 0.1 mol / L perchloric acid solution at a scan rate of 5 mV / s and a rotation speed of 1600 rpm / min in the range of 1.2 to 1.65 V. In addition, the stability test of the catalyst was carried out in a 0.1 mol / L perchloric acid solution saturated with oxygen using a constant current density method with a current density of 10 mA / cm 2 .

[0037] Figure 1 The X-ray diffraction (XRD) patterns of RuMn3 / C at different temperatures in Example 1 show that as the temperature increases, the easily oxidized manganese is gradually reduced, confirming the synthesis of the carbon-supported ruthenium-manganese alloy. It can be seen that when the temperature is below 900°C, the XRD peak of MnO appears, indicating the formation of impurities, while after 900°C, a pure ruthenium-manganese alloy is obtained.

[0038] Figure 2 The X-ray diffraction (XRD) patterns of the carbon-supported ruthenium-manganese alloy RuMn3 / C and the carbon-supported ruthenium element Ru / C at 900°C in Example 1 show that the introduction of manganese causes the ruthenium lattice to shrink, indicating the successful preparation of carbon-supported ruthenium. This lattice shrinkage demonstrates the successful alloying of ruthenium and manganese. This strong bond helps regulate the electronic structure of Ru, promoting enhanced catalytic activity and improving Ru stability.

[0039] Figure 3 The LSV polarization curves of carbon-supported RuMn3 / C at different temperatures in Example 3 show that the activity of the catalyst increases with increasing temperature, and the activity of the material reaches its peak when the temperature reaches 900°C. As the temperature further increases, over-maturation causes the catalyst activity to decrease.

[0040] Figure 4 This is the test curve of acidic oxygen evolution in Example 3. The results show that the prepared carbon-supported ruthenium-manganese alloy catalyst has acidic oxygen evolution performance. The introduction of manganese promotes the improvement of the catalytic activity of the material, which is even better than the carbon-supported ruthenium metal catalyst Ru / C.

[0041] Figure 5This is the acidic oxygen evolution stability test curve of Example 3. The results show that the introduction of metallic manganese can significantly improve the stability of Ru.

[0042] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-supported ruthenium-manganese compound, characterized in that: The following steps are involved: (1) dispersing a ruthenium salt, a manganese salt, and a carbon support in a solvent, heating and ultrasonicating the solvent until the solvent evaporates to dryness, so that the ruthenium salt and the manganese salt are adsorbed on the carbon support to obtain an intermediate solid powder; the carbon support is at least one of carbon black, graphene oxide, reduced graphene oxide, carbon nanotubes, carbon nanofibers, and carbon quantum dots; (2) thermally reducing the intermediate solid powder in a reducing atmosphere, so that the ruthenium salt and the manganese salt are decomposed and then reduced to obtain a carbon-supported ruthenium-manganese alloy; The thermal reduction includes a pre-burning stage and a thermal reduction stage performed sequentially. The temperature of the pre-burning stage is 200°C to 500°C, and the pre-burning time is 0.5 to 2 hours. The temperature of the thermal reduction stage is 900-1000°C, and the heating time of the thermal reduction stage is 2 to 10 hours.

2. The preparation method according to claim 1, wherein The heating rate of the pre-sintering stage is 5-10°C / min, and the heating rate of the thermal reduction stage is 5-10°C / min.

3. The preparation method according to claim 1 or 2, wherein The mass proportion of ruthenium element in the intermediate solid powder is 5% to 45%.

4. The preparation method according to claim 1, wherein The atomic ratio of ruthenium to manganese in the carbon-supported ruthenium-manganese alloy is 1:(1-9).

5. The preparation method according to claim 1, wherein The ruthenium salt is at least one of ruthenium chloride, ruthenium acetylacetonate, ruthenium acetate, bismuth ruthenate, potassium ruthenate, ammonium chlororuthenate, sodium chlororuthenate, and potassium chlororuthenate; the manganese salt is at least one of manganese nitrate, manganese chloride, manganese acetate, manganese sulfate, and manganese acetylacetonate.

6. The preparation method according to claim 1, wherein The reducing atmosphere in step (2) comprises a mixed gas of hydrogen and argon with a hydrogen volume fraction of 2 to 50% or a mixed gas of hydrogen and nitrogen with a hydrogen volume fraction of 2 to 50%; the solvent is at least one of water, ethanol, methanol, acetone, acetonitrile or tetrahydrofuran.

7. The preparation method according to claim 1, wherein The ultrasonic time in step (1) is 0.5 to 3 h; the heating temperature in step (1) is 45°C to 75°C.

8. A carbon-supported ruthenium-manganese compound prepared according to the preparation method according to any one of claims 1 to 7, characterized in that: The ruthenium-manganese compound in the carbon-supported ruthenium-manganese compound is a pure-phase ruthenium-manganese alloy.

9. Use of the carbon-supported ruthenium-manganese compound according to claim 8, characterized in that: Used for acidic oxygen evolution electrocatalytic reaction and proton exchange membrane water electrolysis anode catalyst.

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