Y and S co-doped RuO2 electrocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a Y and S co-doped RuO2 electrocatalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: adding anhydrous ruthenium trichloride, anhydrous yttrium chloride and powdered sulfur into absolute ethyl alcohol, uniformly stirring and dispersing, transferring the obtained mixture into a muffle furnace, heating to 550-650 DEG C, calcining for 1.5-3.5 hours, cooling to room temperature, and grinding the product into powder, thereby obtaining the Y and S co-doped RuO2 electrocatalyst. The Y and S co-doped RuO2 electrocatalyst has excellent oxygen evolution activity and stability in a strong acid medium, the preparation process is simple, the energy consumption is low, and a new thought is provided for reasonably constructing a high-stability ruthenium-based oxygen evolution electrocatalyst.

Description

Technical Field

[0001] This invention relates to a Y, S co-doped RuO2 electrocatalyst, its preparation method and application, belonging to the field of electrocatalysis technology. Background Technology

[0002] my country's energy structure has long relied on fossil fuels, but their non-renewable nature and the environmental problems caused by global warming and the greenhouse effect, such as CO2 produced after combustion, are becoming increasingly serious. Therefore, finding sustainable and clean energy sources is urgent. With the advancement of the "dual carbon" goal, hydrogen energy, due to its wide availability, high calorific value, and clean, pollution-free nature, is gradually becoming an important component of the future energy system. Research shows that water electrolysis is a highly efficient and environmentally friendly method for hydrogen production. Currently, this technology mainly includes alkaline water electrolysis (AWE), proton exchange membrane water electrolysis (PEMWE), solid oxide water electrolysis (SOEC), and anion exchange membrane water electrolysis (AEMWE). Among them, acidic water electrolysis technology based on proton exchange membranes (PEMWE) is particularly advantageous because it can achieve high current densities (>2 A / cm³). 2 It has attracted much attention due to its advantages such as high energy conversion efficiency (80-90%), high hydrogen purity (>99.99%), and high compatibility with fluctuating renewable energy sources.

[0003] The water electrolysis process consists of two half-reactions: the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. HER is a simple two-electron transfer process with relatively fast reaction kinetics; however, OER involves a complex four-electron transfer process with slow reaction kinetics, often requiring high overpotentials. Furthermore, the catalyst is prone to dissolution or deactivation under strongly acidic conditions, making stability difficult to guarantee. This severely restricts the large-scale commercial application of PEMWE technology. Therefore, developing highly active and stable OER catalysts under acidic conditions is a crucial issue that urgently needs to be addressed to promote the commercialization of PEMWE.

[0004] Noble metal oxides IrO2 and RuO2 are considered benchmark electrocatalysts for acidic OERs. RuO2 is relatively inexpensive and exhibits higher catalytic activity; however, in acidic environments with potentials above 1.39 V, its lattice oxygen may participate in oxidation, forming soluble RuO4, leading to the dissolution of the active component and a decrease in catalyst stability. Element doping strategies, by introducing foreign atoms to modulate the electronic structure and surface properties of the catalyst, can significantly improve catalytic activity, lower the reaction energy barrier, and optimize reactant adsorption and activation capabilities. Simultaneously, doping also helps to achieve multifunctional regulation of the catalyst and optimization of the reaction pathway, thus demonstrating excellent overall performance in electrocatalytic reactions such as acidic OERs. Therefore, improving the activity and stability of RuO2 in acidic OERs through rational element doping has become one of the research hotspots in this field. Summary of the Invention

[0005] The present invention aims to provide a Y, S co-doped RuO2 electrocatalyst, its preparation method, and its application. This invention uses a one-step calcination method to dope Y and S elements into RuO2, which has the advantages of simple process and equipment, and low energy consumption. The resulting electrocatalyst can effectively improve the electrochemical water splitting activity and stability of RuO2 in acidic media.

[0006] The technical solution of the present invention is as follows: A Y, S co-doped RuO2 electrocatalyst was prepared by the following method: Anhydrous ruthenium trichloride (RuCl3), anhydrous yttrium chloride (YCl3), and sulfur powder (S) were added to anhydrous ethanol and stirred until uniformly dispersed. The resulting mixture was transferred to a muffle furnace and calcined at 550–650 °C for 1.5–3.5 h. After cooling to room temperature, the product was ground into powder to obtain the Y, S co-doped RuO2 electrocatalyst, denoted as: YS-RuO X The incorporation of Y and S induces the generation of more oxygen vacancies. Figure 4 The stoichiometric ratio of O must be less than 2; in, All reactants used are anhydrous; The preferred molar ratio of anhydrous yttrium chloride, sulfur powder, and anhydrous ruthenium trichloride is 1:1:50; typically, the combined molar percentage of Y and S relative to Ru is no higher than 10%. The preferred volume molar ratio of anhydrous ethanol to anhydrous ruthenium trichloride is 6~10:1, mL / mmol; Preferably, the temperature is increased to 550~650℃ at a rate of 5℃ / min and calcined for 1.5~3.5 h, and then cooled to room temperature at a rate of 5℃ / min.

[0007] The Y, S co-doped RuO2 electrocatalyst described in this invention can be used in acidic electrocatalytic oxygen evolution reaction. Specifically: Y, S co-doped RuO2 electrocatalyst was formulated into a catalyst ink and loaded onto carbon paper as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode to carry out the electrocatalytic oxygen evolution reaction in the electrolyte. The catalyst ink is prepared by mixing Y, S co-doped RuO2 electrocatalyst, deionized water, ethanol, and Nafion (5wt%) in a ratio of 5 mg: 485 μL: 485 μL: 30 μL. The preferred loading of the Y, S co-doped RuO2 electrocatalyst on carbon paper is 0.4 mg / cm³. 2 ; The electrolyte is an aqueous sulfuric acid solution, preferably a 0.5 M aqueous sulfuric acid solution; The preferred amount of sulfuric acid used, based on the area of ​​the Y, S co-doped RuO2 electrocatalyst supported on the carbon paper, is 0.03 mol / cm². 2 .

[0008] Compared with the prior art, the present invention has the following beneficial effects: (1) The raw materials are readily available, and the preparation process is simple and reproducible, which is conducive to the large-scale production of yttrium (Y) and sulfur (S) co-doped RuO2 electrocatalysts. The obtained catalyst can be effectively used for the electrocatalytic oxygen evolution reaction under acidic conditions.

[0009] (2) By simultaneously introducing metal element Y and non-metal element S through one-step calcination, the electronic structure and surface chemical properties of the catalyst can be synergistically controlled, the distribution of active sites can be optimized, the oxidation and dissolution of lattice oxygen during the reaction can be suppressed, thereby stabilizing the surface Ru sites, preventing the collapse of the crystal structure, and significantly improving the overall stability of the catalyst.

[0010] (3) The Y, S co-doped RuO2 electrocatalyst of the present invention was applied to a water electrolysis system, at 10 mA / cm 2 It exhibits excellent electrocatalytic activity with an overpotential of only 215 mV at a given current density. Chronopotentiometric (CP) measurements show that this catalyst exhibits excellent electrocatalytic activity at 10 mA / cm². 2 It can operate stably for over 400 hours at a constant current density, demonstrating significantly enhanced long-term operational stability. This invention effectively solves the problem of insufficient stability of RuO2 in acidic electrolytes. Attached Figure Description

[0011] Figure 1 XRD patterns of the electrocatalysts prepared in Examples 1-4 of this invention.

[0012] Figure 2 SEM images of the electrocatalysts prepared in Examples 1-4 of this invention.

[0013] Figure 3 TEM image of the electrocatalyst prepared in Example 1 of this invention.

[0014] Figure 4 EPR diagrams of the electrocatalysts prepared in Examples 1-4 of this invention.

[0015] Figure 5 Polarization curves of the electrocatalysts prepared in Examples 1-4 of this invention and the commercial anhydrous ruthenium oxide RuO2 of Comparative Example 1 in 0.5 MH2SO4 solution.

[0016] Figure 6Tafel slope comparison of the electrocatalysts prepared in Examples 1-4 of this invention with those of commercial anhydrous ruthenium oxide RuO2 in 0.5 MH2SO4 solution in Comparative Example 1.

[0017] Figure 7 Comparison of the double-layer capacitance of the electrocatalysts prepared in Examples 1-4 of this invention with that of commercial anhydrous ruthenium oxide RuO2 in 0.5 MH2SO4 solution in Comparative Example 1.

[0018] Figure 8 Electrochemical impedance comparison diagram of the electrocatalysts prepared in Examples 1-4 of this invention and commercial anhydrous ruthenium oxide RuO2 in Comparative Example 1 in 0.5 MH2SO4 solution.

[0019] Figure 9 Electrochemical stability tests of the electrocatalysts prepared in Examples 1-4 of this invention and the commercial anhydrous ruthenium oxide RuO2 of Comparative Example 1 in 0.5 MH2SO4 solution. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0021] Example 1: Preparation of Y and S co-doped RuO2 electrocatalyst (denoted as YS-RuO) X )

[0022] Anhydrous ruthenium trichloride (RuCl3, 103.72 mg, 0.5 mmol), anhydrous yttrium chloride (YCl3, 1.95 mg, 0.01 mmol), and sulfur powder (S, 0.32 mg, 0.01 mmol) were dissolved in 4 mL of anhydrous ethanol and stirred to ensure thorough mixing. The mixture was then placed in a muffle furnace and heated to 600 °C at a heating rate of 5 °C / min and held for 120 min. It was then cooled to room temperature at a rate of 5 °C / min. The resulting product was collected as a Y and S-doped RuO2 electrocatalyst, denoted as YS-RuO2. X .

[0023] Example 2: Preparation and application of Y-doped RuO2 electrocatalyst (denoted as Y-RuO2) X )

[0024] Anhydrous ruthenium trichloride (RuCl3, 103.72 mg, 0.5 mmol) and anhydrous yttrium chloride (YCl3, 3.90 mg, 0.02 mmol) were dissolved in 4 mL of anhydrous ethanol and stirred to ensure thorough mixing. The mixture was then placed in a muffle furnace and heated to 600 °C at a heating rate of 5 °C / min and held for 120 min. It was then cooled to room temperature at a rate of 5 °C / min. The resulting Y-doped RuO2 electrocatalyst was collected and designated as Y-RuO2. X .

[0025] Example 3: Preparation and application of S-doped RuO2 electrocatalyst (denoted as S-RuO2) X )

[0026] Anhydrous ruthenium trichloride (RuCl3, 103.72 mg, 0.5 mmol) and sulfur powder (S, 0.64 mg, 0.02 mmol) were dissolved in 4 mL of anhydrous ethanol and stirred to ensure thorough mixing. The mixture was then placed in a muffle furnace and heated to 600 °C at a heating rate of 5 °C / min and held for 120 min. It was then cooled to room temperature at a rate of 5 °C / min. The resulting S-doped RuO2 electrocatalyst was collected and denoted as S-RuO2. X .

[0027] Example 4: Preparation and application of undoped RuO2 electrocatalyst (denoted as HM-RuO2)

[0028] Anhydrous ruthenium trichloride (RuCl3, 103.72 mg, 0.5 mmol) was dissolved in 4 mL of anhydrous ethanol, and the solution was thoroughly mixed by stirring. The mixture was then placed in a muffle furnace and heated to 600 °C at a heating rate of 5 °C / min and held for 120 min, followed by cooling to room temperature at a rate of 5 °C / min. The resulting product was collected to prepare a RuO2 electrocatalyst, denoted as HM-RuO2.

[0029] Comparative Example 1: Application of commercial anhydrous ruthenium oxide RuO2 (denoted as C-RuO2)

[0030] Take 5 mg of commercial anhydrous ruthenium oxide (RuO2) (purchased from Suzhou Shengernuo Technology Co., Ltd., model: SRu75, CAS No. 12036-10-1, ruthenium content: >75%, denoted as C-RuO2), 485 μL of ethanol, and 30 μL of 5% Nafion solution (DuPont D520) and add them to 485 μL of deionized water. Sonicate for 30 minutes to disperse evenly, obtaining 1000 μL of catalyst ink. Take 80 μL of catalyst ink (containing 0.4 mg C-RuO2) and drop it onto a 1×1 cm⁻¹ plate. 2Using carbon paper as the working electrode, a carbon rod as the counter electrode, and silver / silver chloride as the reference electrode, the oxygen evolution performance of Comparative Example 1 C-RuO2 was tested in a 0.5 M H2SO4 electrolyte system.

[0031] The electrocatalysts of Examples 1-4 of this application were analyzed.

[0032] The crystal phases of the electrocatalysts in Examples 1-4 were analyzed using X-ray powder diffraction (XRD), and the results are as follows: Figure 1 As shown. The prepared YS-RuO X Y-RuO X S-RuO X HM-RuO2 has the same crystal phase and matches the standard card for RuO2 (JCPDS No. 40-1290) with no impurity peaks found. However, a careful comparison with YS-RuO... X Y-RuO X S-RuO X Compared with HM-RuO2, it is easy to see that the diffraction peaks of all samples are broadened after doping with Y and S elements, indicating that the grain size is smaller and the crystallinity is reduced after doping.

[0033] The surface morphology of the electrocatalyst materials in Examples 1-4 was observed using a scanning electron microscope (SEM), and the results are as follows: Figure 2 As shown in the figure, nanoparticle aggregation can be observed in HM-RuO2. When Y and S are doped as single elements, as in Example 2, Y-RuO2... X Example 3 S-RuO X Compared with HM-RuO2, the surface morphology of the sample did not change significantly. When Y and S are simultaneously incorporated, i.e., Example 1 YS-RuO2, the surface morphology of the sample did not change significantly. X The surface morphology of the material undergoes significant changes, transforming from nanoparticles to a structure where nanosheets and particles coexist. This structure indirectly explains the changes in YS-RuO in Example 1. X It exhibits the largest electrochemical active area in subsequent electrochemical tests.

[0034] Example 1 YS-RuO was examined using a transmission electron microscope (TEM). X The materials were observed; the results were as follows Figure 3 As shown. This illustrates Example 1, YS-RuO. XY and S elements were successfully incorporated into the electrocatalyst, at amounts of 0.33 wt% and 0.11 wt%, respectively, and were uniformly distributed throughout the material. The vacancy defects in the electrocatalyst materials of Examples 1-4 were analyzed using electron paramagnetic resonance (EPR), and the results are as follows: Figure 4 As shown. YS-RuO can be found. X Y-RuO X S-RuO X Both YS-RuO2 and HM-RuO2 showed electron paramagnetic resonance (EPR) signals at g = 2.003, proving that all materials contain oxygen vacancies. By comparing the signal intensities of each material at g = 2.003, the following trend can be observed: YS-RuO2... X >S-RuO X Y-RuO X > HM-RuO2; Example 1 YS-RuO X It exhibits the strongest electron paramagnetic resonance signal, proving that it contains the most oxygen vacancies.

[0035] Electrochemical performance testing: The electrocatalysts of Examples 1-4 were each dispersed at a rate of 5 mg in 485 μL of deionized water, 485 μL of ethanol, and 30 μL of Nafion (5 wt%) to form catalyst inks. These catalyst inks were then dropped onto 1 cm × 1 cm carbon paper, dried, and used as the working electrode. A carbon rod was used as the counter electrode, and Ag / AgCl as the reference electrode. Oxygen evolution performance was tested using a 0.5 M H₂SO₄ electrolyte system. The amount of sulfuric acid added was 0.03 mol / cm², calculated based on the area of ​​the Y,S-doped RuO₂ electrocatalyst supported on the working electrode carbon paper. 2 The catalyst loading was 0.4 mg / cm³. 2 .

[0036] In 0.5 M H2SO4 electrolyte, at a scan rate of 5 mV / s, within a voltage window of 1.1 to 1.8 V (V vs. RHE), the YS-RuO of Example 1 was subjected to [further testing]. X Example 2 Y-RuO X Example 3 S-RuO X Example 4 HM-RuO2 and Comparative Example 1C-RuO2 were subjected to linear sweep voltammetry (LSV) testing. The results are as follows: Figure 5 As shown, the horizontal axis represents the potential relative to the reversible hydrogen electrode (V vs. RHE), and the vertical axis represents the current density (mA / cm²).2 ), at 10 mA / cm 2 At current densities, YS-RuO in Example 1 X Y-RuO in Example 2 X S-RuO in Example 3 X The oxygen evolution reaction (OER) overpotentials of the HM-RuO2 electrocatalyst in Example 4 were 215 mV, 234 mV, 226 mV, and 237 mV, respectively, all lower than the 300 mV of commercial anhydrous ruthenium oxide RuO2 catalyst. This invention significantly reduces the overpotential by co-doping RuO2 with Y and S, resulting in YS-RuO2... X Compared to commercially available anhydrous ruthenium oxide (RuO2), the overpotential was reduced by 73 mV, demonstrating its significant advantage in efficient oxygen evolution.

[0037] The corresponding Tafel slope was calculated, and the result is as follows: Figure 6 The horizontal axis represents the logarithm of the current density j (log|j|, unit log(mA / cm²)). 2 The vertical axis represents overpotential (in V). A smaller slope means that a smaller increase in overpotential yields a larger increase in current density, indicating faster reaction kinetics and higher intrinsic catalyst activity. It is evident that the Tafel slopes of all examples are smaller than those of Comparative Example 1 C-RuO2 (111.52 mV / dec), indicating that their kinetic performance is superior to Comparative Example 1 C-RuO2, and also superior to that of Example 2 Y-RuO2. X Example 3 S-RuO X Example 4: HM-RuO2, Example 1: YS-RuO X The electrocatalyst exhibits the smallest Tafel slope (68.77 mV / dec), indicating that it possesses optimal kinetic performance.

[0038] Cyclic voltammetry (CV) curves were recorded at different scan rates (scan rate gradients of 10, 20, 30, 40, and 50 mV / s) within the non-Radial range of 1.2 to 1.3 V (relative to the reversible hydrogen electrode, vs. RHE). The electrochemical double-layer capacitance (C0) was calculated from the CV curves. dl ), the result is as follows Figure 7 The horizontal axis represents the scan rate (mV / s), and the vertical axis represents half of the current density ((ja - jc) / 2, mA / cm²). 2 The steeper the slope, the larger the double-layer capacitance. Using the equation ECSA = C dl / C S (C) S= 0.040 mF / cm 2 The ECSA (electrochemical active area) was derived from the calculations in Example 1, YS-RuO. X The double-layer capacitance is 41.95 mF / cm. 2 Example 2 Y-RuO X The double-layer capacitance is 26.95 mF / cm. 2 Example 3 S-RuO X The double-layer capacitance is 27.30 mF / cm. 2 In Example 4, the double-layer capacitance of HM-RuO2 was 19.35 mF / cm. 2 All of these values ​​are greater than the 13.85 mF / cm² double-layer capacitance of Comparative Example 1 C-RuO₂. 2 Then, the formula was used to calculate YS-RuO in Example 1. X It has the largest electrochemical active area.

[0039] Electrochemical impedance spectroscopy (EIS) was performed in the spectrum from 100 kHz to 0.01 Hz with an applied voltage of 1.3 V. The results are as follows: Figure 8 As shown: YS-RuO of Example 1 X Compared to Example 2 Y-RuO X Example 3 S-RuO X Example 4 HM-RuO2 and Comparative Example 1 C-RuO2 have the lowest impedance, indicating that they have the lowest solution resistance.

[0040] At 10 mA / cm 2 The timing potential (CP) test was performed, and the test results are as follows: Figure 9 As shown, the longer the potential remains relatively stable, the better the catalyst's stability. Example 4: HM-RuO2 only maintained stability for 60 hours, while single-element doped catalysts showed significant improvement. Example 2: Y-RuO X and Example 3 S-RuO X The stability of the electrocatalyst was improved to 120 h; Y, S co-doped -S-RuO X The electrocatalyst can maintain high stability for over 400 h, significantly improving the stability of RuO2-based catalysts in acidic oxygen evolution reactions. Its stability is more than 30 times higher than that of the comparative example 1 C-RuO2, demonstrating its significant advantage in efficient oxygen evolution.

[0041] Comparative Example 2: Existing technologies utilize RuO2 electrocatalysts obtained by doping with different elements, and their application in the acidic oxygen evolution reaction (OER) was tested at 10 mA cm⁻¹. -2Overpotential and stability analyses are shown in Table 1.

[0042] Table 1

[0043] In summary, the Y,S-doped RuO2 electrocatalyst prepared by the method of this invention can effectively regulate the electronic structure, promote the electron transfer rate, and reduce the energy barrier required for the formation of active substances, thus significantly improving the activity and stability of the catalyst. Furthermore, the catalyst preparation process is simple, efficient, and easily reproducible. The prepared catalyst has significant application potential in the field of electrocatalysis and is of important research value for promoting the industrialization of catalysts in water electrolysis.

[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications or equivalent variations made using the above technical content without departing from the scope of the present invention shall still fall within the scope of the present invention and shall be included within the protection scope of the present invention.

Claims

1. A Y, S co-doped RuO2 electrocatalyst, characterized in that, It is prepared by the following method: Anhydrous ruthenium trichloride, anhydrous yttrium chloride, and sulfur powder were added to anhydrous ethanol and stirred until evenly dispersed. The resulting mixture was transferred to a muffle furnace and calcined at 550-650 °C for 1.5-3.5 h. After cooling to room temperature, the product was ground into powder to obtain the Y,S co-doped RuO2 electrocatalyst.

2. The Y, S co-doped RuO2 electrocatalyst as described in claim 1, characterized in that, The molar ratio of anhydrous yttrium chloride, sulfur powder, and anhydrous ruthenium trichloride is 1:1:

50.

3. The Y, S co-doped RuO2 electrocatalyst as described in claim 1, characterized in that, The volume molar ratio of anhydrous ethanol to anhydrous ruthenium trichloride is 6~10:1, mL / mmol.

4. The Y, S co-doped RuO2 electrocatalyst as described in claim 1, characterized in that, The temperature is increased to 550~650℃ at a rate of 5℃ / min and calcined for 1.5~3.5 h, then cooled to room temperature at a rate of 5℃ / min.

5. The application of the Y, S co-doped RuO2 electrocatalyst as described in claim 1 in the acidic electrocatalytic oxygen evolution reaction.

6. The application as described in claim 5, characterized in that, The application method is as follows: Y, S co-doped RuO2 electrocatalyst was formulated into a catalyst ink and loaded onto carbon paper as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode to carry out the electrocatalytic oxygen evolution reaction in the electrolyte. The electrolyte is an aqueous solution of sulfuric acid.

7. The application as described in claim 6, characterized in that, The catalyst ink is prepared by mixing Y, S co-doped RuO2 electrocatalyst, deionized water, ethanol, and 5 wt% Nafion in a ratio of 5 mg: 485 μL: 485 μL: 30 μL.

8. The application as described in claim 6, characterized in that, The loading of Y, S co-doped RuO2 electrocatalyst on carbon paper was 0.4 mg / cm³. 2 .

9. The application as described in claim 6, characterized in that, The electrolyte is a 0.5 M sulfuric acid aqueous solution.

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