Strontium hafnate-strontium iridate solid solution catalyst, preparation method and application thereof
By preparing the strontium hafnium-strontium iridium solid solution catalyst SrIrxHf1-xO3 and modifying the Ir-O bond with Hf, the high cost of Ir-based catalysts was solved, and the activity and stability of the oxygen evolution reaction were improved.
Patent Information
- Application Number
- CN202310604568.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-26
- Publication Date
- 2026-02-06
- Estimated Expiration
- 2043-05-26
AI Technical Summary
Existing Ir-based catalysts are expensive and scarce in the oxygen evolution reaction, and there is a need to develop more cost-effective catalysts to replace iridium dioxide.
The strontium hafnium-strontium iridium solid solution catalyst SrIrxHf1-xO3 was used. By modifying the Ir-O bond with Hf, the amount of Ir used was reduced and the charge state of the O site was increased, the Ir-O bond length was shortened, and the electrocatalytic performance was improved.
While reducing the iridium content, the strontium hafnium-strontium iridium solid solution catalyst significantly improved the activity and stability of the oxygen evolution reaction, exhibiting excellent electrocatalytic performance.
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Figure CN116575071B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of electrocatalysis, in particular to a strontium hafnate-strontium iridate solid solution catalyst, a preparation method and application thereof. BACKGROUND
[0002] Electrolysis of water to produce hydrogen refers to the process in which water molecules are dissociated into oxygen and hydrogen under the action of direct current, and the oxygen and hydrogen are respectively discharged from the anode and cathode of an electrolytic cell. According to the different electrolytes, there are three kinds of water electrolysis technologies, namely, alkaline water electrolysis (AWE), proton exchange membrane water electrolysis (PEM) and solid oxide water electrolysis (SOEC). Among them, the PEM water electrolysis technology is considered to have great development prospects because it has the advantages of high operating current density, high purity of hydrogen produced, and the ability to utilize intermittent renewable energy sources.
[0003] In a proton exchange membrane water electrolytic cell (PEM), there are two half-reactions involving the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. Iridium dioxide (IrO2) is the best OER catalyst in terms of activity and stability in acidic media. However, the low natural abundance and high price of iridium (Ir) severely limit the large-scale application of Ir-based catalysts. Therefore, in order to design more cost-effective OER catalysts, it is very necessary to develop perovskite catalyst structures to reduce the loading of Ir-based catalysts. SUMMARY
[0004] The present application aims to provide a strontium hafnate-strontium iridate solid solution catalyst that can improve the electrocatalytic oxygen evolution activity of iridium catalysts while reducing the cost of using the catalyst.
[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:
[0006] A preparation method of a strontium hafnate-strontium iridate solid solution catalyst, the chemical formula of the strontium hafnate-strontium iridate solid solution catalyst is SrIr x Hf 1-x O3, x is 0.1-0.6, and the specific preparation steps are as follows:
[0007] (1) Grind SrCO3, IrO2 and HfO2 uniformly in a mortar; the molar ratio of SrCO3, IrO2 and HfO2 is 1:x:(1-x);
[0008] (2) Sinter the uniformly mixed sample in a low-temperature furnace, control the temperature as follows: increase the temperature from room temperature to 550-650℃ at a rate of (3-5) ℃ / min, then keep it for 4.5-5.5 h, then decrease the temperature from 550-650℃ to 250-350℃ at a rate of (3-5) ℃ / min, and then naturally cool it to room temperature;
[0009] (3) Take out the sample of step (2), put it into a mortar and grind again for 15-40 min;
[0010] (4) Put the sample after regrinding into a high-temperature furnace for sintering, and control the temperature as follows: increase the temperature from room temperature to 1150-1250 DEG C at a rate of (3-5) DEG C / min, and then keep it for 10-15 h, then decrease the temperature from 1150-1250 DEG C to 250-350 DEG C at a rate of (3-5) DEG C / min, and then naturally cool to room temperature.
[0011] Further, x is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6.
[0012] The strontium hafnate-strontium iridate solid solution catalyst prepared by the preparation method.
[0013] Application of the strontium hafnate-strontium iridate solid solution catalyst in preparation of oxygen by electrocatalytic acidic water splitting.
[0014] Further, the strontium hafnate-strontium iridate solid solution catalyst and carbon black are mixed in microliter isopropanol, and a Nafion solution is added to obtain a mixed solution, the mixed solution is dropped on a glassy carbon electrode as a working electrode in an electrolytic cell, and the loading amount of the catalyst on the working electrode is 2.5-3.5 mg / cm 2 ; the reference electrode is a mercury sulfate electrode, the counter electrode is a carbon rod, and the electrolyte is 0.5 M H2SO4.
[0015] Preferably, the mass ratio of the strontium hafnate-strontium iridate solid solution catalyst and carbon black is 2.5:1, 370 microliters of isopropanol and 30 microliters of Nafion solution are needed for every 1 mg of carbon black.
[0016] The present application can obtain higher O site charge state through Hf modification, shorten the Ir-O bond length, reduce the free energy of OER intermediates, and be applied in the field of oxygen evolution electrocatalysts;
[0017] The beneficial effects of the present application are:
[0018] The strontium hafnate-strontium iridate solid solution SrIr 0.4 Hf 0.6 O3 catalyst provided by the present application exhibits significantly improved activity and stability in acidic OER. 0.4 Hf 0.6 O3 catalyst provided by the present application exhibits significantly improved activity and stability in acidic OER. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1Process flow chart for the present application;
[0020] Figure 2 EDS pattern of SrIr 0.4 Hf 0.6 O3 of the present application;
[0021] Figure 3 SEM image of SrIr 0.4 Hf 0.6 O3 of the present application;
[0022] Figure 4 XRD spectrum of SrIrxHf1-xO3 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) catalyst and SrHfO3 of the present application;
[0023] Figure 5 OER polarization curve of SrIr x Hf 1-x O3 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) and SrHfO3 catalyst in 0.5 mol / L H2SO4 solution of the present application;
[0024] Figure 6 Tafel slope of SrIr x Hf 1-x O3 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) catalyst of the present application. DETAILED DESCRIPTION
[0025] The present application will be further described below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.
[0026] The present application provides a strontium hafnate-strontium iridate solid solution catalyst, which has higher O site charge state through modification of Hf, shortens the Ir-O bond length, and reduces the free energy of OER intermediates. The strontium hafnate-strontium iridate solid solution catalyst can be used in the field of oxygen evolution electrocatalysts, and preferably, the strontium hafnate-strontium iridate solid solution catalyst is used for electrocatalytic oxygen evolution reaction in an acidic solution.
[0027] Example 1
[0028] A preparation method of a SrIr 0.4 Hf 0.6 O3 solid solution catalyst is as shown in Figure 1 The process is as follows:
[0029] Step 1: Weigh 0.0235g (0.159mmol) of SrCO3, 0.0143g (0.064mmol) of IrO2, and 0.0201g (0.095mmol) of HfO2, then put them into an agate mortar and mix and grind for 2 hours until the mixture is uniform.
[0030] Step 2: Place the well-mixed sample in a low-temperature furnace for sintering. The temperature is controlled as follows: raise the temperature from room temperature to 600℃ at a rate of 3℃ / min and hold for 5 hours, then lower the temperature to 300℃ at a rate of 3℃ / min and allow it to cool naturally to room temperature.
[0031] Step 3: Take out the sample processed in Step 2 and grind it again in an agate mortar for 30 minutes;
[0032] Step 4: Place the re-ground sample into a high-temperature furnace for sintering. The temperature is controlled as follows: heat up to 1200℃ at a rate of 3℃ / min and hold for 12 hours, then cool down to 300℃ at a rate of 3℃ / min and allow to cool naturally to room temperature.
[0033] Step 5: Place the sample treated in Step 4 into an agate mortar and grind for another 30 minutes to obtain SrIr. 0.4 Hf 0.6 O3 catalyst powder. SrIr 0.4 Hf 0.6 The EDS graph of O3 is as follows Figure 2 As shown, SrIr 0.4 Hf 0.6 SEM images of O3, such as Figure 3 As shown.
[0034] Depend on Figure 2 It can be seen that no other elements were detected except for Sr, Ir, Hf, and O. Although the ratio of hafnium to iridium was not exactly the same as the feed ratio, which may be related to the volatilization of iridium under high temperature conditions, it was generally close to the feed ratio. Figure 3 SrIr was characterized by SEM. 0.4 Hf 0.6 The morphology of O3 indicates that the strontium hafnium-strontium iridium solid solution catalyst is a bulk material with a size between tens and hundreds of nanometers.
[0035] Example 2
[0036] A type of SrIr 0.1 Hf 0.9 The preparation method of O3 solid solution catalyst is as follows:
[0037] Step 1: Preparation of SrIr 0.1 Hf 0.9O3, 0.0235 g (0.159 mmol) of SrCO3, 0.0036 g (0.016 mmol) of IrO2, and 0.0302 g (0.143 mmol) of HfO2 were weighed, then put into an agate mortar to mix and grind for 2 h until mixed uniformly;
[0038] Step 2: The uniformly mixed sample was sintered in a low-temperature furnace, and the temperature was controlled as follows: increased from room temperature to 600°C at a rate of 3°C / min, maintained for 5 h, then decreased to 300°C at a rate of 3°C / min, and naturally cooled to room temperature;
[0039] Step 3: The sample treated in Step 2 was taken out and put into an agate mortar to grind again for 30 min;
[0040] Step 4: The well-grounded sample was sintered in a high-temperature furnace, and the temperature was controlled as follows: increased to 1200°C at a rate of 3°C / min, maintained for 12 h, then decreased to 300°C at a rate of 3°C / min, and naturally cooled to room temperature;
[0041] Step 5: The sample treated in Step 4 was put into an agate mortar to grind again for 30 min, and the catalyst powder prepared in the application was obtained.
[0042] Example 3
[0043] A SrIr 0.2 Hf 0.8 O3 solid solution catalyst was prepared by the following process:
[0044] Step 1: 0.0235 g (0.159 mmol) of SrCO3, 0.0072 g (0.032 mmol) of IrO2, and 0.0268 g (0.127 mmol) of HfO2 were weighed, then put into an agate mortar to mix and grind for 2 h until mixed uniformly;
[0045] Step 2: The uniformly mixed sample was sintered in a low-temperature furnace, and the temperature was controlled as follows: increased from room temperature to 600°C at a rate of 3°C / min, maintained for 5 h, then decreased to 300°C at a rate of 3°C / min, and naturally cooled to room temperature;
[0046] Step 3: The sample treated in Step 2 was taken out and put into an agate mortar to grind again for 30 min;
[0047] Step 4: The well-grounded sample was sintered in a high-temperature furnace, and the temperature was controlled as follows: increased to 1200°C at a rate of 3°C / min, maintained for 12 h, then decreased to 300°C at a rate of 3°C / min, and naturally cooled to room temperature;
[0048] Step 5: Put the sample treated in Step 4 into an agate mortar and regrind for 30 min to obtain a SrIr 0.2 Hf 0.8 O3catalyst powder.
[0049] Example 4
[0050] A SrIr 0.3 Hf 0.7 O3solid solution catalyst was prepared by the following process:
[0051] Step 1: Weigh 0.0235 g (0.159 mmol) of SrCO3, 0.0107 g (0.0477 mmol) of IrO2, and 0.0235 g (0.1116 mmol) of HfO2, and then put them into an agate mortar to mix and grind for 2 h until they are uniformly mixed;
[0052] Step 2: Put the uniformly mixed sample into a low-temperature furnace to sinter, and control the temperature to be raised from room temperature to 600°C at a rate of 3°C / min, then kept for 5 h, and then lowered to 300°C at a rate of 3°C / min, and then naturally cooled to room temperature;
[0053] Step 3: Take out the sample treated in Step 2 and put it into an agate mortar to regrind for 30 min;
[0054] Step 4: Put the regrinded sample into a high-temperature furnace to sinter, and control the temperature to be raised to 1200°C at a rate of 3°C / min, then kept for 12 h, and then lowered to 300°C at a rate of 3°C / min, and then naturally cooled to room temperature;
[0055] Step 5: Put the sample treated in Step 4 into an agate mortar and regrind for 30 min to obtain a SrIr 0.3 Hf 0.7 O3catalyst powder.
[0056] Example 5
[0057] A SrIr 0.5 Hf 0.5 O3solid solution catalyst was prepared by the following process:
[0058] Step 1: Weigh 0.0235 g (0.159 mmol) of SrCO3, 0.0107 g (0.0477 mmol) of IrO2, and 0.0235 g (0.1116 mmol) of HfO2, and then put them into an agate mortar to mix and grind for 2 h until they are uniformly mixed;
[0059] Step 2: Put the well-mixed sample into a low-temperature furnace for sintering, with the temperature controlled as follows: increase the temperature to 600°C at a rate of 3°C / min, keep for 5 h, then decrease the temperature to 300°C at a rate of 3°C / min, and naturally cool to room temperature;
[0060] Step 3: Take out the sample treated in Step 2, and put it into an agate mortar for regrinding for 30 min;
[0061] Step 4: Put the well-regrinded sample into a high-temperature furnace for sintering, with the temperature controlled as follows: increase the temperature to 1200°C at a rate of 3°C / min, keep for 12 h, then decrease the temperature to 300°C at a rate of 3°C / min, and naturally cool to room temperature;
[0062] Step 5: Put the sample treated in Step 4 into an agate mortar for regrinding for 30 min, to obtain SrIr 0.5 Hf 0.5 O3 catalyst powder.
[0063] Example 6
[0064] A method for preparing a SrIr 0.6 Hf 0.4 O3 solid solution catalyst, the process being as follows:
[0065] Step 1: Weigh 0.0235 g (0.159 mmol) of SrCO3, 0.0216 g (0.096 mmol) of IrO2, and 0.0134 g (0.0636 mmol) of HfO2, and then put them into an agate mortar for mixing and grinding for 2 h until well mixed;
[0066] Step 2: Put the well-mixed sample into a low-temperature furnace for sintering, with the temperature controlled as follows: increase the temperature to 600°C at a rate of 3°C / min, keep for 5 h, then decrease the temperature to 300°C at a rate of 3°C / min, and naturally cool to room temperature;
[0067] Step 3: Take out the sample treated in Step 2, and put it into an agate mortar for regrinding for 30 min;
[0068] Step 4: Put the well-regrinded sample into a high-temperature furnace for sintering, with the temperature controlled as follows: increase the temperature to 1200°C at a rate of 3°C / min, keep for 12 h, then decrease the temperature to 300°C at a rate of 3°C / min, and naturally cool to room temperature;
[0069] Step 5: Put the sample treated in Step 4 into an agate mortar for regrinding for 30 min, to obtain SrIr 0.6 Hf 0.4 O3 catalyst powder.
[0070] Comparative Example 1
[0071] Preparation of SrHfO3 catalyst
[0072] Step 1 : Weigh 0.0235 g (0.159 mmol) of SrCO3, 0.0335 g (0.159 mmol) of HfO2, then put them into a marble mortar to mix and grind for 2 h until they are mixed uniformly;
[0073] Step 2: Put the uniformly mixed sample into a low-temperature furnace to sinter, and control the temperature as follows: increase the temperature from room temperature to 600°C at a rate of 3°C / min, keep it for 5 h, then decrease the temperature to 300°C at a rate of 3°C / min, and then naturally cool it to room temperature;
[0074] Step 3: Take out the sample treated in Step 2, and put it into a marble mortar to grind again for 30 min;
[0075] Step 4: Put the well-grounded sample into a high-temperature furnace to sinter, and control the temperature as follows: increase the temperature to 1200°C at a rate of 3°C / min, keep it for 12 h, then decrease the temperature to 300°C at a rate of 3°C / min, and then naturally cool it to room temperature;
[0076] Step 5: Put the sample treated in Step 4 into a marble mortar to grind again for 30 min, and obtain the SrHfO3 catalyst powder.
[0077] The XRD of the products prepared in Examples 1 to 6 and Comparative Example 1 is shown in detail in Figure 4 , and it can be seen from Figure 4 that, as the content of iridium increases, the diffraction peak gradually shifts to the high-angle direction. This is because the ionic radius of Ir 4+ is smaller than that of Hf 4+ . This phenomenon shows that the incorporation of hafnium ions will cause lattice shrinkage.
[0078] The electrocatalytic water splitting (OER) properties of the above-prepared materials and IrO2 were tested in a standard three-electrode electrolytic cell; 2.5 mg of the sample and 1 mg of carbon black were mixed in 370 microliters of isopropanol, and 30 microliters of Nafion solution was added. The solution was dropped on a glassy carbon electrode as the working electrode in the electrolytic cell, to ensure that the loading of the catalyst on the working electrode was 2.92 mg / cm 2 ; the reference electrode was a mercury sulfate electrode, the counter electrode was a carbon rod, and the electrolyte was 0.5 M H2SO4. It should be noted that all the potentials obtained with the mercury sulfate electrode as the reference electrode in the electrocatalytic test were converted to the reversible hydrogen electrode potential in the property graph, and the external power source was the main battery of the electrochemical workstation. The results are shown in Figure 5 and Figure 6 . Figure 5 is SrIr x Hf 1-xOER polarization curves of O3(x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) and IrO2, SrHfO3 catalysts in 0.5 mol / L H2SO4 solution, when the current density is 10 mA / cm 2 0.4 0.6 The overpotential of SrIrHfO3 is the lowest, which is 240 mV. Especially, it is much lower than the overpotential of IrO2, which is 312 mV. Thus, it can be obtained that SrIrHfO3 has excellent oxygen evolution catalytic activity. In addition, the Tafel slope is closely related to the electrocatalytic electron transfer rate, and it is also one of the means for evaluating the electrocatalytic activity. The lower the Tafel slope is, the faster the electron transfer rate is. Figure 6 0.4 0.6 It can be known that the Tafel slope of SrIrHfO3 is the lowest. Considering the content of iridium and the Tafel slope of SrIrHfO3, it is preferred that SrIrHfO3 is used. 0.5 0.5 0.4 0.6 0.4 0.6 0.4 0.6 The Tafel slope of SrIrHfO3 is 66 mV / dec, which is lower than the Tafel slope of IrO2, which is 118 mV / dec.
[0079] The above only describes the preferred embodiments of the present disclosure and is not used to limit the present disclosure. For those skilled in the art, the present disclosure can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.
Claims
1. A method for preparing a strontium hafnium-strontium iridium solid solution catalyst, characterized in that, The chemical formula of the strontium hafnium-strontium iridium solid solution catalyst is SrIr x Hf 1-x O3, with x ranging from 0.1 to 0.6, is prepared using the following steps: (1) Add SrCO3, IrO2 and HfO2 to a mortar and grind them evenly; the molar ratio of SrCO3, IrO2 and HfO2 is 1:x:(1-x); (2) Place the well-mixed sample in a low-temperature furnace for sintering. The temperature is controlled as follows: raise the temperature from room temperature to 550~650℃ and hold it for 4.5~5.5 h, then lower the temperature from 550~650℃ to 250~350℃ and let it cool naturally to room temperature. (3) Take out the sample from step (2) and grind it again in a mortar for 15~40 min; (4) Place the re-ground sample into a high-temperature furnace for sintering. The temperature is controlled as follows: raise the temperature from room temperature to 1150~1250℃ and hold for 10~15 h, then lower the temperature from 1150~1250℃ to 250~350℃ and let it cool naturally to room temperature.
2. The method for preparing the strontium hafnium-strontium iridium solid solution catalyst according to claim 1, characterized in that, In step (2), the heating rate from room temperature to 550~650℃ is (3~5)℃ / min, and the cooling rate from 550~650℃ to 250~350℃ is (3~5)℃ / min.
3. The method for preparing the strontium hafnium-strontium iridium solid solution catalyst according to claim 1, characterized in that, In step (3), the heating rate from room temperature to 1150~1250℃ is (3~5)℃ / min, and the cooling rate from 1150~1250℃ to 250~350℃ is (3~5)℃ / min.
4. The method for preparing the strontium hafnium-strontium iridium solid solution catalyst according to claim 1, characterized in that, x is 0.1, 0.2, 0.3, 0.4, 0.5, 0.
6.
5. The strontium hafnium-strontium iridium solid solution catalyst prepared by the preparation method according to any one of claims 1 to 4.
6. The application of the strontium hafnium-strontium iridium solid solution catalyst according to claim 5 in the electrocatalytic acidic water splitting to produce oxygen.
7. The application according to claim 6, characterized in that, A strontium hafnium-strontium iridium solid solution catalyst and carbon black were mixed in microliters of isopropanol, and Nafion solution was added to obtain a mixed solution. This mixed solution was then dropped onto a glassy carbon electrode as the working electrode in the electrolytic cell. The catalyst loading on the working electrode was 2.5–3.5 mg / cm³. 2 The reference electrode was a mercurous sulfate electrode, the counter electrode was a carbon rod, and the electrolyte was 0.5 M H2SO4.
8. The application according to claim 7, characterized in that, The mass ratio of strontium hafnium-strontium iridium solid solution catalyst to carbon black is 2.5:1, and 370 μL of isopropanol and 30 μL of Nafion solution are required per 1 mg of carbon black.