Preparation method of iridium oxide catalyst

Abstract

The invention belongs to the technical field of catalyst preparation, and particularly relates to a preparation method of an iridium oxide catalyst. The preparation method comprises the following steps: mixing an iridium-based precursor, water and a sulfite compound for ligand exchange at the temperature of 25-40 DEG C for 5-25 minutes to obtain a ligand exchange solution; the ligand exchange solution and an oxidizing agent are mixed for a free radical oxidation reaction, the temperature of the free radical oxidation reaction ranges from 70 DEG C to 140 DEG C, the heat preservation reaction time ranges from 0.5 h to 12 h, and the iridium oxide catalyst is obtained. The iridium oxide catalyst is rapidly prepared on the basis of ligand exchange and free radical oxidation strategies for the first time, preparation conditions are mild, steps are simple, amplification is easy, the iridium oxide catalyst is directly obtained, and the prepared iridium oxide catalyst is excellent in oxygen evolution performance and shows excellent electrocatalytic activity and electrolysis performance in electrolyzed water.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and particularly relates to a method for preparing an iridium oxide catalyst. Background Art

[0002] Due to its high energy density and zero carbon emissions, hydrogen energy is an indispensable energy carrier. Currently, PEM water electrolysis and alkaline water electrolysis coupled with photovoltaic or wind power are very promising ways to prepare green hydrogen. Among them, PEM water electrolysis has the advantages of high current density, high energy conversion efficiency, high hydrogen purity and high responsiveness, and has attracted much attention from scientific researchers. However, in the PEM water electrolysis process, the anode requires a high potential to drive the reaction due to the slow reaction kinetics of the oxygen evolution reaction (OER), which reduces the energy conversion efficiency of the PEM electrolyzer. Under the harsh working conditions of the anode (high potential, pure oxygen environment, high acidity), iridium oxide catalysts have become the mainstream commercial catalysts for PEM water electrolysis due to their excellent stability and catalytic activity.

[0003] At present, the main methods for preparing iridium oxide are the Adams method, hydrothermal method and hydrolysis method. However, these methods are either carried out under high temperature and high pressure conditions (Adams method and hydrothermal method) or generate iridium oxide colloid (hydrolysis method), which requires complicated post-processing. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing an iridium oxide catalyst. The preparation method provided by the present invention has mild conditions and can directly obtain the iridium oxide catalyst.

[0005] In order to achieve the above object, the present invention provides the following technical solutions: The present invention provides a method for preparing an iridium oxide catalyst, comprising the following steps: (1) An iridium-based precursor, water and a sulfite compound are mixed for ligand exchange, wherein the ligand exchange temperature is 25 to 40 °C and the heat preservation exchange time is 5 to 25 min to obtain Ir-SO 3 Ligand exchange solution; (2) The Ir-SO 3 The ligand exchange solution and the oxidant are mixed to carry out a free radical oxidation reaction, wherein the temperature of the free radical oxidation reaction is 70-140° C. and the heat preservation reaction time is 0.5-12 h to obtain the iridium oxide catalyst.

[0006] Preferably, the mass ratio of the iridium-based precursor to water is 1-2.5:200-1500; the mass ratio of the iridium-based precursor to the sulfite compound is 1:4-64.

[0007] Preferably, the iridium-based precursor includes one or more of a trivalent iridium-based precursor and a tetravalent iridium-based precursor.

[0008] Preferably, the trivalent iridium-based precursor includes IrCl 3 , Na 3 IrCl 6 , and NH 3 IrCl 6 or one or more of them; the tetravalent iridium-based precursor includes Na 2 IrCl 6 and H 2 IrCl 6 or one or more of them.

[0009] Preferably, the sulfite compound includes one or more of bisulfites and sulfites.

[0010] Preferably, the oxidant includes one or more of persulfates and peroxymonosulfates.

[0011] Preferably, the persulfate includes one or two of sodium persulfate and potassium persulfate; the peroxymonosulfate includes one or two of sodium peroxymonosulfate and potassium peroxymonosulfate.

[0012] Preferably, the mass ratio of the iridium-based precursor to the oxidant is 1:8 to 256.

[0013] Preferably, the pH value of the system is adjusted to 5 to 11 before the radical oxidation reaction.

[0014] Preferably, the water is ultrapure water.

[0015] The present invention provides a method for preparing an iridium oxide catalyst. The present invention first creates a method for rapidly preparing an iridium oxide catalyst based on a ligand exchange and radical oxidation strategy. The preparation conditions are mild, the steps are simple, it is easy to scale up, and the iridium oxide catalyst is directly obtained. The prepared iridium oxide catalyst has excellent oxygen evolution performance and exhibits excellent electrocatalytic activity and electrolysis performance in water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is the UV-vis test result graph obtained in Test Example 1; Figure 2 It is the EPR test result graph obtained in Test Example 2; Figure 3This is the TEM spectrum obtained for Test Example 3; Figure 4 This is the XRD pattern obtained in Test Example 4; Figure 5 This is the three-electrode performance diagram obtained in Test Example 5; Figure 6 This is the water electrolysis performance diagram obtained in Test Example 6. DETAILED DESCRIPTION

[0018] The present invention provides a method for preparing an iridium oxide catalyst, comprising the following steps: (1) Mixing an iridium-based precursor, water and a sulfite compound for ligand exchange to obtain Ir-SO 3 Ligand exchange solution; (2) The Ir-SO 3 The ligand exchange solution and the oxidant are mixed to carry out a free radical oxidation reaction to obtain the iridium oxide catalyst.

[0019] In the present invention, an iridium-based precursor, water and a sulfite compound are mixed (referred to as the first mixture) to perform ligand exchange to obtain Ir-SO 3 Ligand exchange solution. In the present invention, the iridium-based precursor preferably includes one or more of a trivalent iridium-based precursor and a tetravalent iridium-based precursor; the trivalent iridium-based precursor preferably includes IrCl 3 、Na 3 IrCl 6 and NH 3 IrCl 6 One or more of; the tetravalent iridium-based precursor preferably includes Na 2 IrCl 6 and H 2 IrCl 6 One or more of the .

[0020] In the present invention, the water is preferably ultrapure water.

[0021] In the present invention, the mass ratio of the iridium-based precursor to water is preferably 1-2.5:200-1500, and specifically may be 1.39:45000, 1.48:54000 or 1.53:4.8.

[0022] In the present invention, the sulfite compound preferably includes one or more of bisulfite and sulfite; the bisulfite is preferably sodium bisulfite; and the sulfite is preferably sodium sulfite.

[0023] In the present invention, the mass ratio of the iridium-based precursor to the sulfite compound is preferably 1:4-64, specifically 1:5, 1:8, 1:15, 1:25, 1:35, 1:48, 1:56 or 1:62.

[0024] In the present invention, the first mixing is preferably: dissolving the iridium-based precursor in the water to obtain a precursor solution, and then adding the sulfite compound to the precursor solution.

[0025] In the present invention, the temperature of the ligand exchange is preferably 25-40°C, specifically 27°C, 30°C, 33°C, 36°C or 39°C, and the heat exchange time is preferably 5-25 min, specifically 8 min, 12 min, 16 min, 20 min or 24 min. The present invention converts the Ir-Cl bond into Ir-SO by ligand exchange. 3 .

[0026] Get Ir-SO 3 After the ligand exchange solution, the present invention converts the Ir-SO 3 The ligand exchange solution and the oxidant are mixed (referred to as the second mixing) to carry out a free radical oxidation reaction to obtain the iridium oxide catalyst. In the present invention, the oxidant preferably includes one or more of persulfate and peroxymonosulfate; the persulfate preferably includes one or both of sodium persulfate and potassium persulfate; the peroxymonosulfate preferably includes one or both of sodium peroxymonosulfate and potassium peroxymonosulfate.

[0027] In the present invention, the mass ratio of the iridium-based precursor to the oxidant is preferably 1:8-256, specifically 1:10, 1:20, 1:50, 1:80, 1:120, 1:170, 1:200, 1:220, 1:240 or 1:250.

[0028] In the present invention, the second mixing is preferably: adding the oxidant to the Ir-SO 3 ligand exchange solution.

[0029] In the present invention, before the free radical oxidation reaction, the pH value of the system is preferably adjusted to 5-11, preferably 6-9, and specifically 7; the reagent used to adjust the pH value of the system is preferably an alkali; and the alkali is preferably sodium hydroxide.

[0030] In the present invention, the temperature of the free radical oxidation reaction is preferably 70-140°C, specifically 90°C or 120°C, and the insulation reaction time is preferably 0.5-12 h, specifically 1 h, 3 h, 5 h, 8 h or 11 h. In the free radical oxidation reaction process of the present invention, hydroxyl radicals and sulfate radicals are generated.

[0031] In the present invention, the free radical oxidation reaction preferably further includes solid-liquid separation of the obtained product; the solid-liquid separation is preferably filtration; the pore size of the filter membrane used for the filtration is preferably 200-600 nm, specifically 300 nm, 400 nm or 500 nm.

[0032] In the present invention, after the solid-liquid separation, the obtained solid is preferably dried; the drying temperature is preferably 60-80°C, specifically 65°C, 70°C or 75°C, and the heat preservation and drying time is preferably 6-12 h, specifically 8 h or 10 h.

[0033] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0034] Example 1 (1) 1.39 g of IrCl 3 Dissolve in 4.5 L ultrapure water, add 14.4 g sodium bisulfite, and react at 25 °C for 20 min to exchange ligands, so that the Ir-Cl bond is converted to Ir-SO 3 , Ir-SO 3 Ligand Exchange Solution.

[0035] (2) Add 20.8 g of sodium persulfate to the above Ir-SO 3 The ligand exchange solution was prepared by using NaOH to convert Ir-SO 3 The pH value of the ligand exchange solution was adjusted to 5 to obtain a reaction solution.

[0036] (3) The reaction solution was subjected to free radical oxidation reaction at 90°C for 1 h, filtered through a 200 nm pore size filter membrane, and dried at 60°C for 12 h to obtain an iridium oxide catalyst.

[0037] Example 2 (1) Add 1.48 g of H 2 IrCl 3 Dissolve in 5.4 L ultrapure water, add 12.8 g sodium bisulfite, and react at 25 °C for 20 min to exchange ligands, so that the Ir-Cl bond is converted to Ir-SO 3 , Ir-SO 3 Ligand Exchange Solution.

[0038] (2) Add 18.4 g of sodium persulfate to the above Ir-SO 3 The ligand exchange solution was prepared by using NaOH to convert Ir-SO 3The pH value of the ligand exchange solution was adjusted to 9 to obtain a reaction solution.

[0039] (3) The reaction solution was subjected to free radical oxidation reaction at 90°C for 1 h, filtered through a 400 nm pore size filter membrane, and dried at 70°C for 9 h to obtain an iridium oxide catalyst.

[0040] Example 3 (1) 1.53 g of K 2 IrCl 3 Dissolve in 4.8 L ultrapure water, add 13.2 g sodium bisulfite, and react at 25 °C for 20 min to exchange ligands, so that the Ir-Cl bond is converted to Ir-SO 3 , Ir-SO 3 Ligand Exchange Solution.

[0041] (2) Add 19.2 g of sodium persulfate to the above Ir-SO 3 The ligand exchange solution was prepared by using NaOH to convert Ir-SO 3 The pH value of the ligand exchange solution was adjusted to 9 to obtain a reaction solution.

[0042] (3) The reaction solution was subjected to free radical oxidation reaction at 90°C for 1 h, filtered through a 600 nm pore size filter membrane, and dried at 80°C for 6 h to obtain an iridium oxide catalyst.

[0043] Example 4 The preparation method of this embodiment is the same as that of embodiment 2, the only difference being that the sodium bisulfite in step (1) is replaced by sodium sulfite.

[0044] Example 5 The preparation method of this example is the same as that of Example 2, except that the amount of sodium bisulfite in step (1) is adjusted to 6.0 g.

[0045] Example 6 The preparation method of this example is the same as that of Example 2, except that the amount of sodium bisulfite in step (1) is adjusted to 47.0 g.

[0046] Example 7 The preparation method of this example is the same as that of Example 2, except that the amount of sodium bisulfite in step (1) is adjusted to 94.0 g.

[0047] Example 8 The preparation method of this example is the same as that of Example 2, except that the temperature of the ligand exchange in step (1) is adjusted to 40°C.

[0048] Example 9 The preparation method of this example is the same as that of Example 2, with the only difference being that the ligand exchange time in step (1) is adjusted to 5 min.

[0049] Example 10 The preparation method of this embodiment is the same as that of Embodiment 2, the only difference being that the sodium persulfate in step (2) is replaced by potassium peroxymonosulfate.

[0050] Embodiment 11 The preparation method of this example is the same as that of Example 2, except that the amount of sodium persulfate in step (2) is adjusted to 12 g.

[0051] Example 12 The preparation method of this example is the same as that of Example 2, except that the amount of sodium persulfate in step (2) is adjusted to 50 g.

[0052] Embodiment 13 The preparation method of this example is the same as that of Example 2, except that the amount of sodium persulfate in step (2) is adjusted to 100 g.

[0053] Embodiment 14 The preparation method of this example is the same as that of Example 2, except that the amount of sodium persulfate in step (2) is adjusted to 200 g.

[0054] Embodiment 15 The preparation method of this example is the same as that of Example 2, except that the amount of sodium persulfate in step (2) is adjusted to 300 g.

[0055] Example 16 The preparation method of this embodiment is the same as that of Example 2, with the only difference being that the amount of sodium persulfate in step (2) is adjusted to 378 g.

[0056] Embodiment 17 The preparation method of this embodiment is the same as that of embodiment 2, with the only difference being that in step (2), the pH value of the exchange solution is adjusted to 11 using NaOH.

[0057] Embodiment 18 The preparation method of this embodiment is the same as that of embodiment 2, with the only difference being that the temperature of the free radical oxidation reaction in step (3) is adjusted to 70°C.

[0058] Embodiment 19 The preparation method of this embodiment is the same as that of embodiment 2, with the only difference being that the temperature of the free radical oxidation reaction in step (3) is adjusted to 140°C.

[0059] Embodiment 20 The preparation method of this embodiment is the same as that of embodiment 2, with the only difference being that the heat preservation reaction time of the free radical oxidation reaction in step (3) is adjusted to 0.5 h.

[0060] Embodiment 21 The preparation method of this embodiment is the same as that of embodiment 2, with the only difference being that the insulation reaction time of the free radical oxidation reaction in step (3) is adjusted to 5 h.

[0061] Embodiment 22 The preparation method of this embodiment is the same as that of embodiment 2, except that the heat preservation reaction time of the free radical oxidation reaction in step (3) is adjusted to 12 h.

[0062] Test Example 1 Take 3 mL of H 2 IrCl 6 and H 2 IrCl 6 + NaHSO 3 The mixed solution was tested with UV-vis in the range of 700-300 nm. Figure 1 shown.

[0063] according to Figure 1 It can be seen that H 2 IrCl 6 The UV-vis showed two peaks at 430 nm and 500 nm. 3 After that, the two peaks disappeared, and two peaks were generated at 340 nm and 420 nm, corresponding to Ir-OH and Ir-SO, respectively. 3 The peak.

[0064] Test Example 2 3 mL of the solution of the free radical oxidation reaction in Example 2 was measured and subjected to EPR testing to characterize the free radical changes in the reaction process. The free radicals at different times during the temperature increase reaction were mainly measured. The results are shown in FIG. Figure 2 shown.

[0065] according to Figure 2 It can be seen that in the early stage of the reaction, the reaction process is mainly based on SO 3 ·- and SO 4 ·- Free radicals are dominant (black line); as the reaction proceeds, SO 3 ·- The peaks of ·OH and SO 4 ·-The peak is dominant (red line).

[0066] Test Example 3 The iridium oxide catalyst prepared in Example 2 was characterized by TEM. Figure 3 shown.

[0067] according to Figure 3 It can be seen that the product of Example 2 is a relatively large block structure, and the entire structure appears amorphous.

[0068] Test Example 4 The iridium oxide catalyst prepared in Example 2 was characterized by XRD. Figure 4 shown.

[0069] according to Figure 4 It can be seen that its diffraction peak mainly corresponds to the PDF card (14-5823), indicating that the product has certain crystallinity.

[0070] Test Example 5 The iridium oxide catalyst prepared in Example 2 was subjected to a three-electrode test. In the three-electrode test, 0.1 M HClO 4 The solvent was used and the scan rate was 5 mV / s. The results are shown in Figure 5 As shown. Figure 5 It can be seen that the iridium oxide catalyst of the present invention exhibits better three-electrode performance than the commercial catalyst. 2 The overpotential is 300 mV.

[0071] Test Example 6 The iridium oxide catalyst prepared in Example 2 was subjected to a single cell test. In the single electrode test, the iridium oxide catalyst prepared in Example 2 was ultrasonically sprayed to prepare the anode of the membrane electrode, with a loading of 0.3 mg / cm 2 , Pt / C catalyst is used as cathode, with a loading of 0.1 mg / cm 2 , tested at 80 ℃, the results are as follows Figure 6 As shown. Figure 6 It can be seen that at 2 A / cm 2 At a current density of 1.5 Å, its voltage was 1.72 V, showing excellent water electrolysis performance.

[0072] The test results of other embodiments are similar to those of embodiment 2 and will not be described in detail here.

[0073] It can be seen from the above examples that the preparation method provided by the present invention has mild conditions, simple steps, is easy to scale up, and directly obtains an iridium oxide catalyst. The prepared iridium oxide catalyst has excellent oxygen evolution performance and exhibits excellent electrocatalytic activity and electrolytic performance in electrolyzed water.

[0074] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an iridium oxide catalyst, characterized in that: The following steps are involved: (1) mixing an iridium-based precursor, water and a sulfite compound for ligand exchange, wherein the ligand exchange temperature is 25 to 40 °C and the heat preservation exchange time is 5 to 25 min to obtain an Ir-SO3 ligand exchange solution; (2) The Ir-SO3 ligand exchange solution and an oxidant are mixed to carry out a free radical oxidation reaction, wherein the temperature of the free radical oxidation reaction is 70-140°C and the insulation reaction time is 0.5-12 h to obtain the iridium oxide catalyst.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the iridium-based precursor to water is 1-2.5:200-1500; The mass ratio of the iridium-based precursor to the sulfite compound is 1:4-64.

3. The preparation method according to claim 1 or 2, characterized in that: The iridium-based precursor includes one or more of a trivalent iridium-based precursor and a tetravalent iridium-based precursor.

4. The preparation method according to claim 3, characterized in that: The trivalent iridium-based precursor includes one or more of IrCl3, Na3IrCl6 and NH3IrCl6; The tetravalent iridium-based precursor includes one or more of Na2IrCl6 and H2IrCl6.

5. The preparation method according to claim 1 or 2, characterized in that: The sulfite compound includes one or more of bisulfite and sulfite.

6. The preparation method according to claim 1, characterized in that: The oxidant includes one or more of persulfate and peroxymonosulfate.

7. The preparation method according to claim 6, characterized in that: The persulfate includes one or both of sodium persulfate and potassium persulfate; The peroxymonosulfate includes one or both of sodium peroxymonosulfate and potassium peroxymonosulfate.

8. The preparation method according to claim 1 or 6, characterized in that: The mass ratio of the iridium-based precursor to the oxidant is 1:8-256.

9. The preparation method according to claim 1, characterized in that: Before the free radical oxidation reaction, the pH value of the system is adjusted to 5-11.

10. The preparation method according to claim 1 or 2, characterized in that: The water is ultrapure water.

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