Ru x Cr 1-x O2 bimetallic electrocatalytic materials, their preparation, and their application in acidic OER and PEM water electrolysis for hydrogen production.

Abstract

This invention belongs to the field of electrocatalytic materials, specifically relating to Ru x Cr 1‑x The method for preparing O2 bimetallic electrocatalytic materials involves subjecting a raw material solution containing a Ru source, a Cr source, a structure modifier of Formula 1, and a base to a solvothermal reaction, followed by calcination of the solvothermal product at 300–500°C. The Ru / Cr molar ratio in the Ru and Cr sources is x / 1–x, where x is 0.5–0.7, and the pH of the raw material solution is above 10. This invention also includes the material prepared by the above method and its application in OER catalysis. The preparation method of this invention is simple, and the use of transition metals reduces the amount of noble metals required, effectively lowering the production cost of the electrocatalyst. The catalytic material exhibits lower reaction overpotential and higher stability in electrochemical tests.

Description

Technical Field

[0001] This invention relates to the field of electrocatalyst technology, and more specifically to the field of OER electrocatalytic materials. Background Technology

[0002] In recent years, proton exchange membrane (PEM) water electrolysis for hydrogen production has attracted widespread attention due to its advantages such as high energy efficiency, small gas cross-section, and compact structure. In PEM water electrolyzers, the OER catalyst must withstand harsh acidic environments, thus placing stricter requirements on the catalyst. Noble metals iridium (Ir), ruthenium (Ru), and their derivatives remain the best candidates for acidic OERs due to their suitable electronic structures and high resistance to corrosion and oxidation.

[0003] For example, Chinese patent document CN118026300A discloses a method for preparing rhodium-ruthenium binary metal oxides for PEM electrolytic cells. Specifically, rhodium-ruthenium binary metal oxide nanoparticles are constructed from bottom to top by an impregnation reduction method; the element precursors are kept in uniform particle size during the high-temperature reduction step by the binding of the structural aid carbon black; and the electronic aid Rh is introduced to form a binary metal oxide with the main element Ru, thereby optimizing the electronic structure of Ru species and stabilizing the lattice of the nanoparticles.

[0004] For example, Chinese patent document CN118127561A discloses a rare earth element-doped RuO2 material, its preparation method and application. The rare earth element-doped RuO2 material has a rutile crystal structure, wherein rare earth atoms occupy the Ru atom lattice points of the rutile RuO2 and are distributed in the crystal structure of the material.

[0005] Chinese patent document CN116356361A discloses a method for preparing an amorphous IrOx / Ru catalyst for PEM water electrolysis to produce hydrogen, comprising: ultrasonically treating and stirring ruthenium powder, iridium salt, and isopropanol to form a solid suspension, adding sodium nitrate powder and mixing evenly; heating and stirring in a water bath at a constant temperature until the liquid evaporates to dryness to obtain a brownish-yellow powder; calcining at 350-450℃, naturally cooling, adding perchloric acid solution and ultrasonically treating, centrifuging to obtain a black solid; and obtaining an amorphous IrOx / Ru catalyst after centrifugation, washing, and drying.

[0006] In summary, although existing technologies provide some Ru-based OER materials that can achieve good OER performance under acidic conditions, these materials still have a high noble metal content, resulting in high material costs. Furthermore, the OER performance of existing materials under high current and acidic conditions still needs to be improved. Summary of the Invention

[0007] To address the problems of high cost, high current requirements, and unsatisfactory OER catalytic activity under acidic conditions associated with existing Ru-based noble metal catalysts, the first objective of this invention is to provide a Ru-based catalyst. x Cr 1-x The method for preparing O2 bimetallic electrocatalytic materials aims to prepare OER materials with low Ru content that can still exhibit excellent catalytic activity under high current and acidic systems.

[0008] The second objective of this invention is to provide Ru prepared by the aforementioned method. x Cr 1-x O2 bimetallic electrocatalytic material.

[0009] A third objective of this invention is to provide the aforementioned Ru x Cr 1-x O2 bimetallic electrocatalytic materials are used as OER catalysts.

[0010] Existing Ru-based OER materials mostly require multi-metal bonding to achieve ideal results. The OER performance of bimetallic and low Ru content materials is unsatisfactory. Furthermore, the performance of existing materials under acidic high current conditions is also unsatisfactory. To address these problems, this invention, after in-depth research, provides the following technical solution:

[0011] Ru x Cr 1-x The preparation method of O2 bimetallic electrocatalytic material involves subjecting a raw material solution containing Ru source, Cr source, structure modifier of formula 1, and base to a solvothermal reaction, followed by calcination of the solvothermal product at 300-500℃ to obtain the product.

[0012] Wherein, the Ru / Cr molar ratio in the Ru source and Cr source is x / 1-x; and x is 0.5 to 0.7; the pH of the raw material solution is above 10;

[0013]

[0014] In Formula 1, M is H, Na, K or NH4; R1 and R2 are individually H, amino, hydroxyl, alkoxy, alkylamino or carboxyl.

[0015] This invention innovatively involves solvothermal treatment of the Ru and Cr sources in the specified proportions with the assistance of a structure modifier of Formula 1 and at the specified pH, followed by calcination. This allows for the construction of a physicochemical structure suitable for high-current, acidic applications. Thus, even with a reduced Ru content and a bimetallic precursor, a catalytic material exhibiting excellent OER activity under high current and acidic conditions can be achieved.

[0016] In this invention, the solvothermal treatment of the Ru and Cr sources under Formula 1 and the specified pH is crucial for constructing the physicochemical structure required for OER catalysis under high current and acidic conditions. Based on this, further optimization of the material's physicochemical structure can be achieved by jointly controlling the Ru / Cr molar ratio, the structure modifier in Formula 1, and the pH, thereby further enhancing the material's OER performance under high current and acidic conditions.

[0017] In this invention, the Ru source is Ru. 3+ Water-soluble salts of ions.

[0018] In this invention, the Cr source is Cr 3+ Water-soluble salts of ions.

[0019] In this invention, the water-soluble salt can be, for example, at least one of the chloride, nitrate, sulfate, or organic acid salt of the metal element.

[0020] Preferably, x is 0.55 to 0.65. Studies have shown that at this preferred ratio, it can be combined with other processes to help further enhance the OER activity of the prepared material under high current and acidic conditions.

[0021] There are no special requirements for the molar concentration of Ru source in the raw material solution; for example, it can be 0.01–0.1 M.

[0022] In this invention, in Formula 1, R1 is H, and R2 is an amino, hydroxyl, or carboxyl group. Research in this invention indicates that the preferred material of Formula 1 facilitates synergistic effects with other processes, further enhancing the OER activity of the prepared material under high current and acidic conditions.

[0023] In this invention, there are no special requirements for the substitution positions of R1 and R2.

[0024] In this invention, the molar ratio of the structure modifier of Formula 1 to the total molar ratio of Ru+Cr metal elements in the raw material solution is 0.1 to 1:1, and can be further 0.3 to 0.5:1.

[0025] In this invention, the physicochemical structure of the solvothermal products can be optimized under Formula 1 and pH conditions, thereby facilitating the calcination of OER catalysts that meet the requirements of high current and acidic applications.

[0026] In this invention, the alkali can be an alkali metal hydroxide; preferably, it is at least one of sodium hydroxide and potassium hydroxide.

[0027] Preferably, the pH of the raw material solution is 10 to 13.5, and more preferably 10 to 11.

[0028] Preferably, the solvent in the raw material solution is an aqueous solvent, preferably water, or a mixture of water and a water-soluble organic solvent.

[0029] In this invention, the solvothermal temperature is above 100°C, preferably 130–180°C;

[0030] Preferably, the solvothermal time is 10 hours or more, and more preferably 10 to 15 hours.

[0031] In this invention, the calcination stage is carried out in an oxygen-containing atmosphere.

[0032] Preferably, the oxygen-containing atmosphere is air.

[0033] Preferably, the calcination temperature is 350–450°C.

[0034] Preferably, the calcination time is 1 to 6 hours, and more preferably 3 to 5 hours.

[0035] The present invention also provides Ru prepared by the above-described preparation method. x Cr 1-x O2 bimetallic electrocatalytic material.

[0036] The preparation method described in this invention can endow the prepared material with special structure and active exposure characteristics, and the material prepared by the method can be adapted to the requirements of high current and acidic catalysis, and can still obtain excellent OER catalytic performance under such conditions.

[0037] The present invention also provides Ru prepared by the above-described preparation method. x Cr 1-x The application of O2 bimetallic electrocatalytic materials is to use them as OER catalytic materials.

[0038] Preferably, it is used as an OER catalyst in an acidic system.

[0039] Preferably, it is used to prepare proton exchange membrane water electrolysis for hydrogen production.

[0040] This invention also provides a PEM water electrolysis hydrogen production device, which comprises Ru obtained by the preparation method described in this invention. x Cr 1-x O2 bimetallic electrocatalytic materials, or through the Ru x Cr 1-x O2 bimetallic electrocatalytic materials were prepared.

[0041] In this invention, the Ru described herein can be based on conventional ideas and methods. x Cr 1-x The desired OER catalytic device was fabricated using O2 bimetallic electrocatalytic materials.

[0042] Beneficial effects

[0043] This invention innovatively involves solvothermal treatment of the Ru and Cr sources in the specified proportions with the assistance of a structure modifier of Formula 1 and at the specified pH, followed by calcination. This process enables the preparation of a bimetallic OER catalyst with low Ru content. Furthermore, the catalyst is unexpectedly adaptable to high current and acidic catalytic requirements, and can still achieve excellent OER catalytic activity under high current and acidic systems.

[0044] This invention also shows that further optimization of the structure of Formula 1, calcination mechanism and other processes can further improve the OER catalytic performance of the prepared material under high current and acid conditions. Attached Figure Description

[0045] 【 Figure 1 [Ru prepared in Example 1] x Cr 1-x TEM image of the O2 catalyst.

[0046] 【 Figure 2 [Ref] Ru prepared in Example 1 x Cr 1-x HRTEM image of O2 catalyst.

[0047] 【 Figure 3 [Ru prepared in Example 1] x Cr 1-x Comparison of LSV polarization curves of O2 catalyst and commercial RuO2 in OER electrochemical tests.

[0048] 【 Figure 4 [Ru prepared in Example 1] x Cr 1-x O2 catalyst and Comparative Example 4 showed performance at 100 mA / cm² in OER electrochemical testing. 2 Stability test curves at current density.

[0049] 【 Figure 5 [Ru prepared in Example 1] x Cr 1-x Polarization curves of O2 catalyst on PEM device. Detailed Implementation

[0050] The following specific embodiments are intended to further illustrate the content of the present invention, rather than to further limit the scope of protection of the claims of the present invention.

[0051] Unless otherwise specified, the reagents used in the following examples are commercially available reagents purchased directly from the market.

[0052] An optional Ru of the present invention x Cr1-x A method for preparing O2 catalytic materials, comprising the following steps:

[0053] S1: Mix ruthenium source, chromium source, structure modifier of Formula 1, base and solvent (aqueous solvent, such as water) to obtain a solution, and sonicate the mixed solution;

[0054] S2: Perform a hydrothermal reaction on the ultrasonically mixed solution;

[0055] S3: Centrifuge the mixed solution after the reaction and collect the precipitate;

[0056] S4: Dry the precipitate;

[0057] S5: Anneal the dried precipitate to obtain Ru. x Cr 1-x O2 catalyst. (The desired product is obtained.)

[0058] As a preferred embodiment, the Ru x Cr 1-x In the O2 catalyst, the molar ratio of ruthenium to chromium, x:1-x, is 1-2:1-2. The Ru of this invention... x Cr 1-x The O2 catalyst exhibits the best oxygen evolution catalytic performance at a ruthenium to chromium ratio of 1.5:1, and the amount of ruthenium required is significantly reduced compared to existing noble metal-based catalysts.

[0059] As a preferred technical solution, the ruthenium source is either hydrated ruthenium chloride or chlororuthenic acid; the chromium source is either chromium nitrate or chromium chloride.

[0060] The structure modifier of Formula 1 may be further defined as at least one of Formula 1A and Formula 1B.

[0061]

[0062] As a preferred technical solution, the hydrothermal reaction time is 12-15 hours, and the hydrothermal reaction temperature is 130-180°C.

[0063] As a preferred technical solution, the annealing process is as follows: under an air atmosphere, the temperature is increased to 300℃ to 500℃ at a heating rate of 2℃ / min to 5℃ / min, and held for 1 to 6 hours.

[0064] The following is the specific implementation plan:

[0065] Example 1

[0066] Step 1, Preparation of the mixed solution:

[0067] Preparation of mixed solution: Weigh 3 mmol of hydrated ruthenium chloride, 2 mmol of chromium nitrate, and 2 mmol of structure modifier (Formula 1B) according to the molar ratio of Ru:Cr = 1.5:1. Then add them to 150 mL of deionized water and mix well. Add 5 mmol of sodium hydroxide to adjust the pH to 10. Sonicate the solution for 10 min to obtain mixed solution A.

[0068] Step 2, hydrothermal treatment:

[0069] The obtained mixture A was placed in a reaction vessel and heated at a rate of 5℃ / min until it reached 150℃. The temperature was then maintained for 12 hours and allowed to cool naturally to room temperature.

[0070] Step 3: Centrifugal drying process:

[0071] After hydrothermal treatment, the material was washed twice with N,N-dimethylformamide (DMF) and ethanol, respectively, and then centrifuged twice before being placed in an 80°C oven to dry for 8 hours.

[0072] Step 4, Annealing:

[0073] The material obtained in step three was ground and placed in a muffle furnace. Under air atmosphere, the temperature was increased to 400°C (denoted as T) at a heating rate of 5°C / min. After holding at this temperature for 4 hours, it was naturally cooled to room temperature to complete the annealing. The catalytic material obtained in this embodiment was named Ru. 0.6 Cr 0.4 O2.

[0074] Electrochemical detection

[0075] Take 2mg of the prepared Ru x Cr 1-x O2 catalyst (Ru in this case) 0.6 Cr 0.4 O2) was dispersed in a mixture of 280 μL ethanol, 200 μL distilled water, and 20 μL 5 wt% Nafion solution. After sonication for half an hour, 50 μL of the mixture was dropped onto carbon paper and allowed to dry naturally. The Ru content was then tested using an electrochemical workstation. x Cr 1-x The electrochemical performance of the O2 catalyst was assessed using a saturated calomel electrode as the reference electrode, a platinum sheet as the counter electrode, and 0.5 M H2SO4 as the electrolyte. The catalyst activity under acidic conditions was tested at a scan rate of 5 mV / s. Stability was tested using a chronopotentiometric method at 100 mA / cm². 2 The test was conducted at a current density of [value missing].

[0076] PEM polarization test: First, 20mg Ru... x Cr 1-xThe O2 catalyst material was dispersed in 3 mL of deionized water and ultrasonically dispersed for 30 min. Then, it was ball-milled for 25 min, followed by the addition of 100 μL of naphthol (5 wt.%) and 1 mL of isopropanol, and ultrasonically dispersed for another 30 min. Subsequently, it was uniformly sprayed onto a single-cathode (platinum-carbon) electrolytic electrode (purchased from Shengerno) as the anolyte membrane electrode. The prepared membrane electrode was assembled into a PEM water electrolyzer for performance evaluation. Note: The gas diffusion layer was titanium felt, the test temperature was 80℃, and the active area was 1 cm². 2 .

[0077] Example 2

[0078] Compared with Example 1, the only difference is that the molar ratio of Ru to Cr is controlled as Ru:Cr = 2:1, and the total molar amount of Ru and Cr, as well as other operations and parameters, are the same as in Example 1.

[0079] Example 3

[0080] Compared with Example 1, the only difference is that the molar ratio of Ru to Cr is controlled as Ru:Cr = 1:1, and the total molar amount of Ru and Cr, as well as other operations and parameters, are the same as in Example 1.

[0081] Example 4

[0082] Compared to Example 1, the only difference is that the conditions in steps 1 and 2 are changed, and the experimental groups are as follows:

[0083] Group A: Change the structural modifier to Formula 1A;

[0084] Group B: In step 1, the pH is 11, the dosage of Formula 1B is 2.5 mmol, the hydrothermal temperature is changed to 160℃, and the hydrothermal time is 10 h.

[0085] All other operations and parameters are the same as in Example 1.

[0086] Example 5

[0087] Compared with Example 1, the only difference is that the process of step 4 is changed, specifically:

[0088] Group A: Annealing temperature T is 300℃;

[0089] Group B: Annealing temperature T is 500℃, time is 3h;

[0090] All other operations and parameters are the same as in Example 1.

[0091] Comparative Example 1

[0092] Compared with Example 1, the only difference is that chromium nitrate is not added, and the remaining molar amount of Ru is the same as the total molar amount of Ru+Cr in Example 1, while all other operations and parameters are the same as in Example 1.

[0093] Comparative Example 2

[0094] Compared with Example 1, the only difference is that ruthenium chloride is not added, and the remaining molar amount of Cr is the same as the total molar amount of Ru+Cr in Example 1, while other operations and parameters are the same as in Example 1.

[0095] Comparative Example 3

[0096] Compared with Example 1, the only difference is that in step 1, the pH of the raw material solution is 9, and all other operations and parameters are the same as in Example 1.

[0097] Comparative Example 4

[0098] Compared with Example 1, the only difference is that in step 1, an equimolar amount of sodium ethylenediaminetetraacetate is used to replace the structure modifier, while other operations and parameters are the same as in Example 1.

[0099] Comparative Example 5

[0100] Compared with Example 1, the only difference is that Ru is not added in step 1, but in step 3. That is, the Ru source is missing in step 1, and the product of step 1 without the Ru source is processed in step 2. Then, in step 3, the hydrothermal product containing only Cr and ruthenium are mixed in step 3 and then processed in step 4. All other operations and parameters are the same as in Example 1.

[0101] Table 1 shows the current density as 100 mA / cm². 2 Oxygen evolution potential test results at time

[0102] <![CDATA[Overpotential (100 mA / cm 2 )]]> Example 1 298mV Example 2 338mV Example 3 364mV Example 4-A 325mV Example 4-B 304mV Example 5-A 372mV Example 5-B 351mV Comparative Example 1 437mV Comparative Example 2 / Comparative Example 3 395mV Comparative Example 4 379mV Comparative Example 5 421mV

[0103] Table 1 Electrochemical performance of each catalyst

[0104] As shown in Table 1, the catalyst exhibits the lowest overpotential at a molar ratio of 1.5:1 for hydrated ruthenium chloride and chromium nitrate, at a current density of 100 mA / cm². 2 The overpotential at that time was 298mV, which indicates that 1.5:1 is the optimal molar ratio of hydrated ruthenium chloride to chromium nitrate.

[0105] As shown in Table 1, compared with Comparative Examples 1-5, the catalyst prepared in Example 1 has a performance of 100 mA / cm². 2 The lowest overpotential at the given current density is only 298mV, indicating that the catalyst material provided by this invention has good electrocatalytic OER performance.

[0106] like Figure 4 As shown, compared with the catalyst prepared in Comparative Example 4, where the structural modifier of Formula 1 was replaced with sodium ethylenediaminetetraacetate, the catalyst prepared in Example 1 exhibits better performance at 100 mA / cm². 2 Even at a current density of [value missing], it can still maintain stable catalysis for more than 6 hours, thus demonstrating that Ru [missing information]. 0.6 Cr 0.4 O2 exhibits good catalytic stability.

[0107] like Figure 5 As shown, in the PEM electrolytic cell, the current density is 1.0 A cm⁻¹. -2 At this point, the required voltage is only 1.85V, indicating that the catalyst has excellent catalytic performance.

[0108] The specific embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Ru x Cr 1-x The method for preparing O2 bimetallic electrocatalytic materials is characterized by... The raw material solution containing Ru source, Cr source, structure modifier of formula 1 and base is subjected to solvothermal reaction, and then the solvothermal product is calcined at 350~450 °C to obtain the product. Wherein, the Ru / Cr molar ratio in the Ru source and Cr source is 1.5:1; the pH of the raw material solution is 10~11; Formula 1 In Formula 1, M is H, Na, K or NH4; R1 is H and R2 is an amino group; The molar ratio of the structure modifier of Formula 1 to the total molar ratio of Ru+Cr metal elements in the raw material solution is 0.3~0.5:

1.

2. The Ru as described in claim 1 x Cr 1-x The method for preparing O2 bimetallic electrocatalytic materials is characterized by... The Ru source mentioned is Ru 3+ Water-soluble salts of ions; Cr source is Cr 3+ Water-soluble salts of ions; The molar concentration of Ru source in the raw material solution is 0.01~0.1M.

3. The Ru as described in claim 1 x Cr 1-x The method for preparing O2 bimetallic electrocatalytic materials is characterized by... The alkali mentioned is an alkali metal hydroxide; The solvent in the raw material solution is water, or a mixture of water and water-soluble organic solvents.

4. The Ru as described in claim 1 x Cr 1-x The method for preparing O2 bimetallic electrocatalytic materials is characterized by... The solvothermal temperature is above 100 ℃; The solvothermal time is more than 10 hours.

5. The Ru as described in claim 4 x Cr 1-x The method for preparing O2 bimetallic electrocatalytic materials is characterized by... The solvothermal temperature is 130~180 ℃; The solvothermal time is 10-15 h.

6. The Ru as described in claim 1 x Cr 1-x The method for preparing O2 bimetallic electrocatalytic materials is characterized by... The calcination stage is carried out in an oxygen-containing atmosphere.

7. The Ru as described in claim 6 x Cr 1-x The method for preparing O2 bimetallic electrocatalytic materials is characterized by... The oxygen-containing atmosphere is air.

8. Ru as described in claim 1 x Cr 1-x The method for preparing O2 bimetallic electrocatalytic materials is characterized by... The calcination time is 1 to 6 hours.

9. Ru prepared by the method according to any one of claims 1 to 8 x Cr 1-x O2 bimetallic electrocatalytic material.

10. Ru prepared by the method according to any one of claims 1 to 8 x Cr 1-x The application of O2 bimetallic electrocatalytic materials is characterized by... It is used as an OER catalyst in acidic systems.

11. The application as described in claim 10, characterized in that, It was used to prepare proton exchange membranes for water electrolysis to produce hydrogen.

12. A PEM water electrolysis hydrogen production device, characterized in that, Ru containing the preparation method according to any one of claims 1 to 8 x Cr 1-x O2 bimetallic electrocatalytic material, or Ru as described in claim 9 x Cr 1-x O2 bimetallic electrocatalytic materials were prepared.

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