A molecular complex catalyst with low spin Ru and a preparation method and application thereof

Abstract

The application discloses a molecular complex catalyst with low spin Ru, which is composed of a group after deprotonation of a ligand, an active component and a supporting base, the ligand is a compound with an oxime group (-C(=N-OH)-) and capable of forming a Ru-N4 structure with a Ru ion, the active component is a Ru ion, and the active component accounts for 4.8-12.1% of the mass of the catalyst. The catalyst has high electrode stability and selectivity in a chlorine evolution reaction.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically to a molecular complex catalyst with low-spin Ru, its preparation method, and its application. Background Technology

[0002] Chlorine is an indispensable basic chemical in modern industry, widely used in key areas such as water treatment and disinfection, organic synthesis, polyvinyl chloride (PVC) production, pharmaceutical intermediate synthesis, and disinfectant manufacturing. Global annual demand exceeds 70 million tons, supporting the operation of numerous livelihood and industrial supply chains. The chlor-alkali industry, as the core pathway for chlorine production, achieves large-scale production through the electrolysis of saturated chloride water. It is one of the pillar industries of modern chemical industry, and its technological level directly affects the cost and efficiency of downstream industries.

[0003] Ruthenium (Ru)-based catalysts are often used as anodes in the electrolysis of chloride brine to produce chlorine due to their excellent performance in the chlorination reaction. Among them, RuO2-based catalysts, as representative high-efficiency catalysts, are prone to over-oxidation into unstable high-valence Ru species during the chlorination reaction, leading to decreased stability; simultaneously, their selectivity is affected. * OCl and * The similarity scaling relationship between OOH intermediates limits the activity of these catalysts in the competitive oxygen evolution reaction (OER), resulting in low selectivity. Currently, most studies on catalyst design for the chlorine evolution reaction (CER) have not adequately focused on the directional control of reaction intermediates and intrinsic electronic spin states. Research indicates that constructing Ru-N4 low-spin complexes can stabilize the catalytic center and modify its reaction intermediates, thereby improving catalyst stability and selectivity, and developing highly efficient chlorine evolution reaction catalysts. Summary of the Invention

[0004] To address the issues of poor electrode stability and low selectivity of ruthenium-based catalysts in the chlorine evolution reaction, this invention provides a molecular complex catalyst with low-spin Ru.

[0005] The technical solution adopted in this invention is: a molecular complex catalyst with low spin Ru, wherein the catalyst is composed of a deprotonated group of a ligand, an active component and a supported substrate, wherein the ligand is a compound having an oxime group (-C(=N-OH)-) and capable of forming a Ru-N4 structure with Ru ions, and the active component is Ru ions, accounting for 4.8 to 12.1% of the catalyst mass.

[0006] This application employs the aforementioned specific configuration to preferentially adsorb chloride ions rather than oxygen species by the active component, thus avoiding [the problem] at the source. *The formation of OCl intermediates was revealed. In-situ spectroscopic characterization and density functional theory (DFT) calculations uncovered a unique intermediate evolution pattern on the catalyst surface. The study found that in the Ru-N4 coordination environment, the active sites thermodynamically preferentially adsorb Cl. - It forms Ru-Cl species, rather than combining with oxygen-containing species. This characteristic allows the reaction pathway to proceed from the hypochlorite ion on the surface of conventional oxides (…). * The OCl-mediated mechanism was successfully transformed into direct adsorption at metal sites. * Cl-mediated mechanism. This fundamental shift in the pathway disrupts the chlorination intermediate ( * OCl) and oxygen evolution intermediate ( * The linear scaling relationship between OOH and [other components] restricts and effectively lowers the reaction energy barrier of the rate-determining step (Heyrovsky step), thereby significantly improving catalytic activity. Simultaneously, low-spin Ru […]. 3+ center( t 2g 5 e g 0 ) utilize its unoccupied e g The orbital acts as an electron transfer channel, enabling a unique "non-redox" electron transfer process. This mechanism ensures that the Ru center maintains a stable valence state under strong oxidation potentials, avoiding catalyst deactivation caused by over-oxidation.

[0007] Preferably, the ligand is dimethylglyoxime, diphenylglyoxime, or α-difuranoyldioxime.

[0008] Preferably, the supporting substrate is carbon black with a particle size of 10–100 nm and a specific surface area of ​​100–500 m². 2 g -1 .

[0009] This application also provides a method for preparing the above-mentioned catalyst, comprising the following steps: (1) Mix water-soluble ruthenium salt and ligand in deionized water and stir to prepare a mixed solution A of molecular complex with low spin Ru.

[0010] (2) Add the loaded substrate to the mixed solution A from step (1) and continue stirring to obtain mixed solution B.

[0011] (3) The mixed solution B from step (2) is freeze-dried to obtain a molecular complex catalyst with low spin Ru.

[0012] This application mixes the catalyst ligands and active components. Through the interaction between the strong-field ligands and Ru ions, the splitting energy of the 4d orbitals of Ru is increased, leading to a redistribution of electrons in the active component Ru towards a lower spin transition within the 4d orbitals. This results in Ru exhibiting superior Cl... - Adsorption energy and low valence state activity enhance the stability and reaction selectivity of the catalyst.

[0013] Preferably, the water-soluble ruthenium salt in step (1) is a chloride or a sulfate. More preferably, it is ruthenium chloride, potassium ruthenate, or ruthenium sulfate.

[0014] Preferably, in step (1), the molar concentration ratio of water-soluble ruthenium salt to ligand is 1:2 to 1:5, the mass of ruthenium salt accounts for 0.01%-0.06% of the mass of deionized water, and the stirring time is 10 to 60 min.

[0015] Preferably, the mass ratio of the loaded substrate in step (2) to the molecular complex with low spin Ru formed in step (1) is 1:1 to 3:1.

[0016] Preferably, the stirring time in step (2) is 5 to 50 minutes.

[0017] Preferably, the freeze-drying temperature in step (3) is -10 ℃ to -50 ℃, and the time is 24 h to 48 h.

[0018] This application also provides the application of the above-mentioned catalyst in the electrolysis of chlorinated brine to produce chlorine gas.

[0019] The beneficial effects of this invention are: (1) Long-term stability: The catalyst prepared in this application can operate stably for more than 330 h in high-salt and strong acid environments, ensuring the stable operation of the electrolytic chlorine production unit. (2) High-efficiency catalytic performance: The catalyst prepared in this application exhibits excellent chlorine evolution performance in acidic media, with low overpotential, which can significantly reduce the energy consumption of electrochemical chlorine production. (3) High selectivity: Under the same conditions at a high potential of 1.6 V, the catalyst prepared in this application has a selectivity that is about 20% higher than that of commercial DSA and RuO2 electrodes, significantly improving the economic benefits of electrolytic chlorine production. Attached Figure Description

[0020] Figure 1 (a) is the Raman scattering spectrum of the low-spin Ru molecular complex catalyst prepared in Example 1. Figure 1 (b) is the Fourier transform infrared spectrum of the low-spin Ru molecular complex catalyst prepared in Example 1.

[0021] Figure 2(a) Normalized k-edge X-ray absorption near-edge structure (XANES) spectra of the low-spin Ru molecular complex catalyst prepared in Example 1 and its reference samples Ru foil and RuO2. Figure 2 (b) Fourier transform of the low-spin Ru molecular complex catalyst prepared in Example 1 and the Ru K-side extended X-ray absorption fine structure (EXAFS) spectrum of the reference sample Ru foil and RuO2.

[0022] Figure 3 The electron paramagnetic resonance (EPR) spectrum of the low-spin Ru molecular complex catalyst prepared in Example 1 is shown.

[0023] Figure 4 Polarization curves of the low-spin Ru molecular complex catalyst electrode prepared in Example 1, the RuO2 catalyst electrode prepared in Comparative Example 1-1, and the DSA catalyst electrode purchased in Comparative Example 1-2.

[0024] Figure 5 Faraday efficiency test graphs for the low-spin Ru molecular complex catalyst electrode prepared in Example 1, the RuO2 catalyst electrode prepared in Comparative Example 1-1, and the DSA catalyst electrode purchased in Comparative Example 1-2.

[0025] Figure 6 Stability test results for the low-spin Ru molecular complex catalyst electrode prepared in Example 1 and the RuO2 catalyst electrode prepared in Comparative Example 1-1.

[0026] Figure 7 Polarization curves of the low-spin Ru molecular complex catalyst electrodes prepared in Examples 2-7 and the RuO2 catalyst electrode prepared in Example 1-1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and a preferred embodiment.

[0028] The chlorine precipitation activity test conditions used in the examples and comparative examples were as follows: 4.0 mol L -1 NaCl (pH=2) was used as the electrolyte for chlorine evolution. A three-electrode system was used for testing, with a platinum sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and the prepared catalyst electrode as the working electrode. The electrocatalytic performance of the low-spin Ru molecular complex catalyst was tested using a controlled voltage of 1.2–1.6 V vs. RHE. The testing instrument was a Shanghai Chenhua CHI660e electrochemical analyzer. All test voltage values ​​were converted to a reversible hydrogen electrode. Example 1

[0029] (1) Weigh 1 mmol L -1 Ruthenium chloride and 2.5 mmol L -1 Dimethylglyoxime (DMG) was prepared by mixing ruthenium chloride and DMG in 50 ml of deionized water at a molar ratio of 1:2.5, ensuring that the mass ratio of ruthenium chloride in the deionized water was 0.02%, and stirring for 20 min to obtain a mixed solution A of Ru(DMG)2, a molecular complex catalyst with low spin Ru.

[0030] (2) Add particles with a particle size of 30 nm and a specific surface area of ​​254 m² to mixed solution A. 2 g -1 25 mg of carbon black was added, and the mass ratio of the carbon black added to Ru(DMG)2 formed in step (1) was 1.5:1. The mixture was stirred for 10 min to obtain mixed solution B.

[0031] (3) Mixed solution B was freeze-dried at -40 °C for 36 h to obtain a molecular complex catalyst with low spin Ru (in powder form) -Ru(DMG)2, with the active component accounting for 12.1% of the catalyst mass. The final product was characterized by Raman scattering spectroscopy, Fourier transform infrared spectroscopy, X-ray absorption fine structure spectroscopy and electron paramagnetic resonance spectroscopy.

[0032] Catalyst electrode preparation: (1) Weigh 41 mg of catalyst powder and disperse it in 950 μL of anhydrous ethanol, and sonicate for 10 minutes.

[0033] (2) Add 50 μL of Nafion solution and sonicate again for 30 min to obtain catalyst ink.

[0034] (3) The carbon paper was treated in 68 wt.% concentrated nitric acid to remove the surface oxide layer and increase its surface hydrophilicity. Then it was ultrasonically cleaned with deionized water and ethanol for 15 min in sequence to remove the residue. It was then dried at 60 °C for 2 h to obtain the working electrode to be drop-coated.

[0035] (4) Take 120 μL of catalyst ink and drop it onto the working electrode, and then dry it to obtain a catalyst electrode with low spin Ru molecular complex.

[0036] See Figure 1 (a) and Figure 1 (b) Raman scattering and Fourier transform infrared spectroscopy were performed on Ru(DMG)₂ prepared in Example 1 to obtain Raman and FTIR spectra, as shown below. Figure 1 As shown in (a) and (b): the Raman spectra of the Ru(DMG)2 molecular complex prepared in this invention are in the range of 300-1800 cm⁻¹. -1 and infrared spectra in the 500-2000 cm⁻¹ range-1 A series of clear and sharp characteristic vibrational peaks were observed within the range. The characteristic signals attributable to key chemical bonds such as Ru-N and N-OH in the spectrum were clearly defined and completely matched the molecular structure of the target complex, indicating that the material prepared by this invention has a clear structure and high purity, and providing strong evidence for the successful synthesis of the Ru(DMG)2 complex.

[0037] See Figure 2 (a) Normalized k-edge X-ray absorption near-edge structure (XANES) spectral characterization was performed on Ru(DMG)₂ prepared in Example 1. The white line peak intensity of Ru(DMG)₂ was between that of Ru foil and RuO₂, indicating that the valence state of Ru in Ru(DMG)₂ ranges from 0 to +4. See also Figure 2 (b) The catalyst of Example 1 was characterized by X-ray absorption fine structure spectroscopy. The EXAFS Fourier transform spectrum showed a significant Ru-N coordination peak at ~1.6 Å, and no Ru-Ru or Ru-O signal was observed. This indicates that the Ru center forms intramolecular coordination with the nitrogen atom of the ligand, constituting the Ru-N active site, which confirms that the prepared Ru(DMG)2 complex has a clear Ru-N coordination structure.

[0038] See Figure 3 As shown, electron paramagnetic resonance (EPR) spectroscopy characterization of Ru(DMG)2 prepared in Example 1 revealed characteristic signals at g=1.845, 2.010, and 2.285, corresponding to low-spin (LS) ruthenium species with spin quantum number S=1 / 2, confirming that the prepared Ru(DMG)2 complex has a well-defined low-spin electronic structure.

[0039] See Figure 4 Electrolytic chlorine analysis was performed on the catalyst electrode of Example 1. The polarization curve is shown below. Figure 4 As shown, the Ru(DMG)2 electrode is at 4.0 mol / L -1 NaCl (pH=2) chlorine evolution 10 mAcm -2 The overpotential at current density is 80 mV, which outperforms commercial ruthenium oxide catalysts (112 mV) and commercial DSA catalysts (107 mV), and the substrate carbon paper is compatible with 0 mol L⁻¹. -1 The Ru(DMG)2 electrode under NaCl showed almost no OER reaction activity, indicating that the Ru(DMG)2 current density all came from the CER reaction, demonstrating excellent CER activity.

[0040] See Figure 5 For the catalyst electrode of Example 1, at 4.0 mol L... -1Selectivity tests were performed in NaCl (pH=2) electrolyte. At a voltage of 1.6 V vs. RHE, Ru(DMG)₂ showed a selectivity of 94% for CER, significantly higher than RuO₂ (75.2%) and DSA (76.6%). See also Figure 5 At higher voltages (such as 1.65 V, 1.7 V and 1.75 V), the selectivity of Ru(DMG)2 remains above 90%, indicating that the material has excellent CER selectivity.

[0041] See Figure 6 The stability of the catalyst electrode in Example 1 was tested at 4.0 mol L⁻¹. -1 In a NaCl (pH=2) electrolyte, Ru(DMG)₂ catalyst electrode was used as the anode and platinum sheet as the cathode. The electrochemical reaction was conducted at 10 mA cm⁻¹ using a galvanostatic voltammetry method. -2 Stability tests were conducted at current density. The stable operating current-time graph is shown below. Figure 6 As shown, the Ru(DMG)2 electrode exhibits strong durability, with no significant activity decay observed within 330 hours, which is beneficial for long-term commercial applications.

[0042] See Table 1, which shows the EXAFS fitting parameters of the Ru k-edge of the catalyst in Example 1, where ruthenium foil (Rufoil, representing Ru) 0 (state) and ruthenium dioxide powder (RuO2, representing Ru) 4+ The Ru-N4 coordination structure was determined to be 4.2 with a bond length of 2.02 Å, forming the Ru-N4 coordination structure described above. (The sample was used as a standard for energy calibration and as a reference spectrum.)

[0043] EXAFS fitting parameter table for the k-edge of catalyst Ru

[0044] Example 2 (1) Weigh out 2 mmol L -1 Ruthenium chloride and 4 mmol L -1 Diphenylglyoxime was prepared by mixing ruthenium chloride and diphenylglyoxime in 30 ml of deionized water at a molar ratio of 1:2, ensuring that the mass ratio of ruthenium chloride in the deionized water was 0.04%, and stirring for 10 min to obtain a molecular complex catalyst with low-spin Ru – Ru(C 14 H 11 A mixed solution A of N2O2)2.

[0045] (2) Add particles with a particle size of 40 nm and a specific surface area of ​​500 m² to mixed solution A. 2 g-1 35 mg of carbon black was added, and the carbon black added reacted with Ru(C) formed in step (1). 14 H 11 The mass ratio of N2O2 to 2 was 1:1, and the mixture was stirred for 30 min to obtain mixed solution B.

[0046] (3) The mixed solution B was freeze-dried at -10 °C for 30 h to obtain a molecular complex catalyst with low-spin Ru (in powder form) -Ru(C 14 H 11 N2O2)2, the active component accounts for 8.7% of the catalyst mass.

[0047] Catalyst electrode preparation: (1) Weigh 10 mg of catalyst powder and disperse it in 600 μL of anhydrous ethanol, and sonicate for 5 minutes.

[0048] (2) Add 10 μL of Nafion solution and sonicate again for 10 min to obtain catalyst ink.

[0049] (3) The carbon array was treated in 68 wt.% dilute hydrochloric acid to remove the surface oxide layer and increase its surface hydrophilicity. Then it was ultrasonically cleaned with deionized water and ethanol for 15 min in sequence to remove the residue. It was then dried at 60 °C for 2 h to obtain the working electrode to be drop-coated.

[0050] (4) Take 30 μL of catalyst ink and drop it onto the working electrode, and then dry it to obtain a catalyst electrode with low spin Ru molecular complex.

[0051] The catalyst electrode prepared in Example 2 was subjected to electrolytic chlorine testing, and the polarization curve was obtained, as shown in the figure. Figure 7 As shown, the catalyst electrode current density prepared in Example 2 is significantly higher than that of the commercial electrode RuO2 within the operating window, indicating higher commercial value. Example 3

[0052] (1) Weigh out 0.1 mmol L -1 Potassium chlororuthenate and 0.5 mmol L -1 α-Difuryl dioxime was prepared by mixing potassium ruthenium chloride and α-difuryl dioxime at a molar ratio of 1:5 in 60 ml of deionized water, ensuring that the mass ratio of ruthenium chloride in the deionized water was 0.04%, and stirring for 60 min to obtain a molecular complex catalyst with low-spin Ru – Ru(C 10 A mixed solution A of H7N2O4)2.

[0053] (2) Add particles with a particle size of 60 nm and a specific surface area of ​​100 m² to mixed solution A. 2 g-1 6 mg of carbon black was added, and the carbon black added reacted with Ru(C) formed in step (1). 10 The mass ratio of H7N2O4)2 was 2:1, and the mixture was stirred for 15 min to obtain mixed solution B.

[0054] (3) Mixed solution B was freeze-dried at -15 °C for 48 h to obtain a molecular complex catalyst (in powder form) with low-spin Ru -Ru(C 10 H7N2O4)2, the active component accounts for 6.7% of the catalyst mass.

[0055] Catalyst electrode preparation: (1) Weigh 15 mg of catalyst powder and disperse it in 1000 μL of anhydrous ethanol, and sonicate for 20 minutes.

[0056] (2) Add 20 μL of Nafion solution and sonicate again for 20 min to obtain catalyst ink.

[0057] (3) The carbon array was treated in 68 wt.% dilute hydrochloric acid to remove the surface oxide layer and increase its surface hydrophilicity. Then it was ultrasonically cleaned with deionized water and ethanol for 15 min in sequence to remove the residue. It was then dried at 60 °C for 2 h to obtain the working electrode to be drop-coated.

[0058] (4) Take 100 μL of catalyst ink and drop it onto the working electrode, and then dry it to obtain a molecular complex catalyst electrode with low spin Ru.

[0059] The catalyst electrode prepared in Example 3 was subjected to electrolytic chlorine testing, and the polarization curve was obtained, as shown in the figure. Figure 7 As shown, the catalyst electrode current density prepared in Example 3 is significantly higher than that of the commercial electrode RuO2 within the operating window, indicating higher commercial value. Example 4

[0060] (1) Weigh out 0.5 mmol L -1 Potassium chlororuthenate and 2 mmol L -1 Diphenylglyoxime was prepared by mixing potassium ruthenium chloride and diphenylglyoxime in a 1:4 ratio in 100 ml of deionized water, ensuring that the mass ratio of ruthenium chloride in the deionized water was 0.02%, and stirring for 40 min to obtain a molecular complex catalyst with low-spin Ru – Ru(C 14 H 11 A mixed solution A of N2O2)2.

[0061] (2) Add particles with a particle size of 100 nm and a specific surface area of ​​300 m² to mixed solution A. 2 g -172 mg of carbon black was added, and the carbon black added reacted with Ru(C) formed in step (1). 14 H 11 A mixed solution B was prepared by mixing N2O2 in a mass ratio of 2.5:1 and stirring for 5 min.

[0062] (3) Mixed solution B was freeze-dried at -50 °C for 24 h to obtain a molecular complex catalyst (in powder form) with low-spin Ru -Ru(C 14 H 11 N2O2)2, the active component accounts for 5.0% of the catalyst mass.

[0063] Catalyst electrode preparation: (1) Weigh 100 mg of catalyst powder and disperse it in 1200 μL of anhydrous ethanol, and sonicate for 30 minutes.

[0064] (2) Add 60 μL of Nafion solution and sonicate again for 60 min to obtain catalyst ink.

[0065] (3) The nickel foam was treated in 68 wt.% concentrated nitric acid to remove the surface oxide layer and increase its surface hydrophilicity. Then it was ultrasonically cleaned with deionized water and ethanol for 15 min in sequence to remove the residue. It was dried at 60 °C for 2 h to obtain the working electrode to be drop-coated.

[0066] (4) Take 200 μL of catalyst ink and drop it onto the working electrode, and then dry it to obtain a molecular complex catalyst electrode with low spin Ru.

[0067] The catalyst electrode prepared in Example 4 was subjected to electrolytic chlorine testing, and the polarization curve was obtained, as shown in the figure. Figure 7 As shown, the catalyst electrode current density prepared in Example 4 is significantly higher than that of the commercial electrode RuO2 within the operating window, indicating higher commercial value. Example 5

[0068] (1) Weigh out 2 mmol L -1 Potassium chlororuthenate and 7 mmol L -1 α-Difuryl dioxime was prepared by mixing potassium ruthenium chloride and α-difuryl dioxime in a ratio of 1:3.5 in 80 ml of deionized water, ensuring that the mass ratio of ruthenium chloride in the deionized water was 0.04%, and stirring for 55 min to obtain a molecular complex catalyst with low-spin Ru – Ru(C 10 A mixed solution A of H7N2O4)2.

[0069] (2) Add particles with a particle size of 10 nm and a specific surface area of ​​100 m² to mixed solution A. 2 g -1121 mg of carbon black was added, and the carbon black added reacted with Ru(C) formed in step (1). 10 The mass ratio of H7N2O4)2 was 1.4:1, and the mixture was stirred for 30 min to obtain mixed solution B.

[0070] (3) Mixed solution B was freeze-dried at -20 °C for 40 h to obtain a molecular complex catalyst (in powder form) with low-spin Ru -Ru(C 10 H7N2O4)2, the active component accounts for 7.8% of the catalyst mass.

[0071] Catalyst electrode preparation: (1) Weigh 85 mg of catalyst powder and disperse it in 2000 μL of anhydrous ethanol, and sonicate for 70 minutes.

[0072] (2) Add 100 μL of Nafion solution and sonicate again for 50 min to obtain catalyst ink.

[0073] (3) The foamed iron was treated in 68 wt.% hydrofluoric acid to remove the surface oxide layer and increase its surface hydrophilicity. Then it was ultrasonically cleaned with deionized water and ethanol for 15 min in sequence to remove the residue. It was dried at 60 °C for 2 h to obtain the working electrode to be drop-coated.

[0074] (4) Take 150 μL of catalyst ink and drop it onto the working electrode, and then dry it to obtain a molecular complex catalyst electrode with low spin Ru.

[0075] The catalyst electrode prepared in Example 5 was subjected to electrolytic chlorine testing, and the polarization curve was obtained, as shown in the figure. Figure 7 As shown, the catalyst electrode current density prepared in Example 5 is significantly higher than that of the commercial electrode RuO2 within the operating window, indicating higher commercial value. Example 6

[0076] (1) Weigh out 0.4 mmol L -1 Ruthenium sulfate and 1.8 mmol L -1 α-Difuryl dioxime was prepared by mixing ruthenium sulfate and α-difuryl dioxime in a ratio of 1:4.5 in 55 ml of deionized water, ensuring that the mass ratio of ruthenium chloride in the deionized water was 0.01%, and stirring for 45 min to obtain a molecular complex catalyst with low-spin Ru – Ru(C 10 A mixed solution A of H7N2O4)2.

[0077] (2) Add particles with a particle size of 70 nm and a specific surface area of ​​450 m² to mixed solution A. 2 g -135 mg of carbon black was added, and the carbon black added reacted with Ru(C) formed in step (1). 10 The mass ratio of H7N2O4)2 was 3:1, and the mixture was stirred for 40 min to obtain mixed solution B.

[0078] (3) Mixed solution B was freeze-dried at -35 °C for 28 h to obtain a molecular complex catalyst with low spin Ru- (in powder form) -Ru(C 10 H7N2O4)2, the active component accounts for 4.8% of the catalyst mass.

[0079] Catalyst electrode preparation: (1) Weigh 70 mg of catalyst powder and disperse it in 1650 μL of anhydrous ethanol, and sonicate for 15 minutes.

[0080] (2) Add 80 μL of Nafion solution and sonicate again for 40 min to obtain catalyst ink.

[0081] (3) The foamed nickel-iron alloy was treated in 68 wt.% hydrofluoric acid to remove the surface oxide layer and increase its surface hydrophilicity. Then it was ultrasonically cleaned with deionized water and ethanol for 15 min in sequence to remove the residue. It was dried at 60 °C for 2 h to obtain the working electrode to be drop-coated.

[0082] (4) Take 160 μL of catalyst ink and drop it onto the working electrode, and then dry it to obtain a molecular complex catalyst electrode with low spin Ru.

[0083] The catalyst electrode prepared in Example 6 was subjected to electrolytic chlorine testing, and the polarization curve was obtained, as shown in the figure. Figure 7 As shown, the catalyst electrode current density prepared in Example 6 is significantly higher than that of the commercial electrode RuO2 within the operating window, indicating higher commercial value. Example 7

[0084] (1) Weigh out 3 mmol L -1 Ruthenium sulfate and 9 mmol L -1 Diphenylglyoxime was prepared by mixing ruthenium sulfate and diphenylglyoxime in a 1:3 ratio in 65 ml of deionized water, ensuring that the mass ratio of ruthenium chloride in the deionized water was 0.06%, and stirring for 35 min to obtain a molecular complex catalyst with low-spin Ru – Ru(C 14 H 11 A mixed solution A of N2O2)2.

[0085] (2) Add particles with a diameter of 55 nm and a specific surface area of ​​370 m² to mixed solution A. 2 g -1203 mg of carbon black was added, and the carbon black added reacted with Ru(C) formed in step (1). 14 H 11 The mass ratio of N2O2 to N2O2 was 1.8:1, and the mixture was stirred for 50 min to obtain mixed solution B.

[0086] (3) The mixed solution B was freeze-dried at -25 °C for 32 h to obtain a molecular complex catalyst with low-spin Ru (in powder form) -Ru(C 14 H 11 N2O2)2, the active component accounts for 6.2% of the catalyst mass.

[0087] Catalyst electrode preparation: (1) Weigh 60 mg of catalyst powder and disperse it in 1350 μL of anhydrous ethanol, and sonicate for 40 minutes.

[0088] (2) Add 70 μL of Nafion solution and sonicate again for 5 min to obtain catalyst ink.

[0089] (3) The carbon paper was treated in 68 wt.% hydrofluoric acid to remove the surface oxide layer and increase its surface hydrophilicity. Then it was ultrasonically cleaned with deionized water and ethanol for 15 min in sequence to remove the residue. It was dried at 60 °C for 2 h to obtain the working electrode to be drop-coated.

[0090] (4) Take 180 μL of catalyst ink and drop it onto the working electrode, and then dry it to obtain a molecular complex catalyst electrode with low spin Ru.

[0091] The catalyst electrode prepared in Example 7 was subjected to electrolytic chlorine testing, and the polarization curve was obtained, as shown in the figure. Figure 7 As shown, the catalyst electrode current density prepared in Example 7 is significantly higher than that of the commercial electrode RuO2 within the operating window, indicating higher commercial value.

[0092] Comparative Example 1-1 (1) Disperse 2 mg of commercially available RuO2 catalyst powder in 950 μL of anhydrous ethanol and sonicate for 10 minutes.

[0093] (2) Add Nafion solution (50 μL, 0.25 wt%) and sonicate again for 30 min to obtain catalyst ink.

[0094] (3) Take 120 μL of the ink and drop it onto carbon paper (effective contact area is 1 cm). 2 The RuO2 catalyst electrode is obtained by drying the RuO2 catalyst electrode.

[0095] The comparative 1-1 RuO2 catalyst was characterized by X-ray absorption fine structure spectroscopy, such as... Figure 2 As shown, the EXAFS Fourier transform spectrum of the prepared commercial RuO2 catalyst shows significant coordination peaks corresponding to the Ru-O coordination structure, which corresponds to the structural information of RuO2.

[0096] Electrolytic chlorine analysis was performed on the catalyst electrode of Comparative Example 1-1, and the polarization curve is shown in the figure. Figure 4 As shown, commercial ruthenium oxide catalysts at 4.0 mol L -1 NaCl (pH=2) chlorine evolution 10 mA cm -2 The overpotential at current density is 112 mV, which is weaker than the 80 mV of the Ru(DMG)2 electrode, indicating room for improvement.

[0097] The Faraday efficiency of the catalyst electrode in Comparative Example 1-1 was tested. A standard three-electrode system was used: the working electrode was the catalyst electrode from Comparative Example 1-1, the counter electrode was a platinum sheet, the reference electrode was an Ag / AgCl electrode, and the electrolyte was 4.0 mol·L⁻¹. -1 NaCl solution (pH=2), controlled voltage 1.6–1.75 V vs. RHE test, the instrument used was a Shanghai Chenhua CHI660e electrochemical analyzer, and all test voltage values ​​were converted to voltage values ​​against the reversible hydrogen electrode. The specific steps are as follows: Before electrolysis, 40 mL of electrolyte was added to the anode chamber, and argon gas was bubbled through for 10 min to remove dissolved oxygen. Subsequently, a chronoamperometry test was performed at a constant potential for 120 s to ensure the current density stabilized at 10 mA cm⁻¹. -2 That's all. Immediately after electrolysis, transfer 10 mL of the anolyte to a sample vial containing excess NaI. The solution quickly develops a color due to the formation of iodine. Then, use 0.01 mol L... -1 A standard Na₂S₂O₃ solution was titrated, using starch solution as an indicator. The volume of sodium thiosulfate consumed at the titration endpoint was recorded. The experimental chlorine production was calculated based on the titration consumption. Combined with the theoretical production corresponding to the total charge passing through the electrolysis process, the Faraday efficiency of the chlorine evolution reaction was finally calculated. The Faraday efficiency graph is shown below. Figure 5 As shown, the Faraday efficiency of commercial ruthenium oxide catalysts is 75-80% in the range of 1.6-1.75 V, which is significantly lower than that of Ru(DMG)2 electrode (90-95%). The electrode requires more electrical energy to produce chlorine by electrolysis, and there is room for improvement.

[0098] Comparative Examples 1-2 The DSA electrode is a ruthenium-iridium-titanium (10*10 mm) electrode purchased from Suzhou Shuertai Industrial Technology Co., Ltd.

[0099] Electrolytic chlorine analysis was performed on the catalyst electrodes of Comparative Examples 1-2, and the polarization curves are shown below. Figure 4As shown, commercial DSA catalysts at 4.0 mol L -1 NaCl (pH=2) chlorine evolution 10 mA cm -2 The overpotential at current density is 107 mV, which is weaker than the 80 mV of the Ru(DMG)2 electrode, indicating room for improvement.

[0100] The Faraday efficiency of the catalyst electrodes from Comparative Examples 1-2 was tested. A standard three-electrode system was used: the working electrode was the catalyst from Comparative Examples 1-2, the counter electrode was a platinum sheet, the reference electrode was an Ag / AgCl electrode, and the electrolyte was 4.0 mol L⁻¹. -1 NaCl solution (pH=2), controlled voltage 1.6–1.75 V vs. RHE test, the instrument used was a Shanghai Chenhua CHI660e electrochemical analyzer, and all test voltage values ​​were converted to voltage values ​​against the reversible hydrogen electrode. The specific steps are as follows: Before electrolysis, 40 mL of electrolyte was added to the anode chamber, and argon gas was bubbled through for 10 min to remove dissolved oxygen. Subsequently, a chronoamperometry test was performed at a constant potential for 120 s to ensure the current density stabilized at 10 mA cm⁻¹. -2 That's all. Immediately after electrolysis, transfer 10 mL of the anolyte to a sample vial containing excess NaI. The solution quickly develops a color due to the formation of iodine. Then, use 0.01 mol / L... -1 A standard Na₂S₂O₃ solution was titrated, using starch solution as an indicator. The volume of sodium thiosulfate consumed at the titration endpoint was recorded. The experimental chlorine production was calculated based on the titration consumption. Combined with the theoretical production corresponding to the total charge passing through the electrolysis process, the Faraday efficiency of the chlorine evolution reaction was finally calculated. The Faraday efficiency graph is shown below. Figure 5 As shown, the Faraday efficiency of commercial DSA catalysts is 70-80% in the range of 1.6-1.75 V, which is significantly lower than that of Ru(DMG)2 electrode (90-95%). The electrode requires more electrical energy to produce chlorine by electrolysis, and there is room for improvement.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. A molecular complex catalyst with low-spin Ru, characterized in that, The catalyst consists of a deprotonated group of a ligand, an active component, and a supported substrate. The ligand is a compound with an oxime group (-C(=N-OH)-) that can form a Ru-N4 structure with Ru ions. The active component is Ru ions and accounts for 4.8 to 12.1% of the catalyst mass.

2. The catalyst according to claim 1, characterized in that, The ligands are dimethylglyoxime, diphenylglyoxime, or α-difuranoyldioxime.

3. The catalyst according to claim 1, characterized in that, The supporting substrate is carbon black with a particle size of 10–100 nm and a specific surface area of ​​100–500 m². 2 g -1 .

4. A method for preparing the catalyst according to claims 1-3, characterized in that, Includes the following steps: (1) Mix water-soluble ruthenium salt and ligand in deionized water and stir to prepare a mixed solution A of molecular complex with low spin Ru; (2) Add the loaded substrate to the mixed solution A from step (1) and continue stirring to obtain mixed solution B; (3) The mixed solution B from step (2) is freeze-dried to obtain a molecular complex catalyst with low spin Ru.

5. The preparation method according to claim 4, characterized in that, In step (1), the water-soluble ruthenium salt is either chloride or sulfate.

6. The preparation method according to claim 4, characterized in that, In step (1), the molar concentration ratio of water-soluble ruthenium salt to ligand is 1:2 to 1:5, the mass of ruthenium salt accounts for 0.01%-0.06% of the mass of deionized water, and the stirring time is 10 to 60 min.

7. The preparation method according to claim 4, characterized in that, In step (2), the mass ratio of the loaded substrate to the low-spin Ru molecular complex formed in step (1) is 1:1 to 3:

1.

8. The preparation method according to claim 4, characterized in that, The stirring time in step (2) is 5 to 50 minutes.

9. The preparation method according to claim 4, characterized in that, In step (3), the freeze-drying temperature is -10 ℃ to -50 ℃, and the time is 24 h to 48 h.

10. The application of the catalyst as described in claim 1 in the electrolysis of chlorinated brine to produce chlorine gas.

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