CN113000050A - Perovskite modified by selective dissolution method and modification method and application thereof - Google Patents
Perovskite modified by selective dissolution method and modification method and application thereof Download PDFInfo
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- 238000011978 dissolution method Methods 0.000 title claims abstract description 11
- 238000002715 modification method Methods 0.000 title abstract description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims abstract description 39
- 238000005530 etching Methods 0.000 claims abstract description 33
- 229910019525 La0.6Sr0.4Co0.8Fe0.2O3 Inorganic materials 0.000 claims abstract description 30
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 29
- 239000002243 precursor Substances 0.000 claims abstract description 29
- 239000000243 solution Substances 0.000 claims abstract description 27
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 25
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000001301 oxygen Substances 0.000 claims abstract description 22
- 229910002505 Co0.8Fe0.2 Inorganic materials 0.000 claims abstract description 17
- 229910052751 metal Inorganic materials 0.000 claims abstract description 17
- 239000002184 metal Substances 0.000 claims abstract description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 14
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229960001484 edetic acid Drugs 0.000 claims abstract description 13
- 150000001768 cations Chemical class 0.000 claims abstract description 11
- 229910001960 metal nitrate Inorganic materials 0.000 claims abstract description 10
- 230000007547 defect Effects 0.000 claims abstract description 9
- 239000011259 mixed solution Substances 0.000 claims abstract description 7
- 229910017052 cobalt Inorganic materials 0.000 claims abstract description 4
- 239000010941 cobalt Substances 0.000 claims abstract description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims abstract description 4
- 238000004090 dissolution Methods 0.000 claims abstract description 4
- 229910052742 iron Inorganic materials 0.000 claims abstract description 4
- 229910052746 lanthanum Inorganic materials 0.000 claims abstract description 4
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims abstract description 4
- 229910052712 strontium Inorganic materials 0.000 claims abstract description 4
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims abstract description 4
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 23
- DHEQXMRUPNDRPG-UHFFFAOYSA-N strontium nitrate Chemical compound [Sr+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O DHEQXMRUPNDRPG-UHFFFAOYSA-N 0.000 claims description 21
- 238000010438 heat treatment Methods 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 14
- 239000003054 catalyst Substances 0.000 claims description 12
- -1 salt ions Chemical class 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 9
- 238000005406 washing Methods 0.000 claims description 9
- 229910001981 cobalt nitrate Inorganic materials 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 6
- 238000000227 grinding Methods 0.000 claims description 6
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 claims description 6
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 claims description 6
- 238000002386 leaching Methods 0.000 claims description 6
- 238000002360 preparation method Methods 0.000 claims description 6
- 229910002422 La(NO3)3·6H2O Inorganic materials 0.000 claims description 3
- 238000010000 carbonizing Methods 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 238000010828 elution Methods 0.000 claims 6
- 125000002091 cationic group Chemical group 0.000 claims 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 229910002554 Fe(NO3)3·9H2O Inorganic materials 0.000 description 3
- 235000011114 ammonium hydroxide Nutrition 0.000 description 3
- 238000003763 carbonization Methods 0.000 description 3
- 238000010668 complexation reaction Methods 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- HTXDPTMKBJXEOW-UHFFFAOYSA-N iridium(IV) oxide Inorganic materials O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 230000007935 neutral effect Effects 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 238000007605 air drying Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 239000010411 electrocatalyst Substances 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(IV) oxide Inorganic materials O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical group 0.000 description 1
- 238000004832 voltammetry Methods 0.000 description 1
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/002—Mixed oxides other than spinels, e.g. perovskite
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- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
- B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
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Abstract
The invention provides a perovskite modified by a selective dissolution method and a modification method and application thereof, metal nitrates of lanthanum, strontium, cobalt and iron are placed in a container and added with water for dissolution, citric acid and ethylene diamine tetraacetic acid are added, the PH of the solution is adjusted to 8-9, the mixed solution is heated and stirred at 70-90 ℃ to obtain sol, the sol is dried and carbonized to obtain carbonized dry gel, the carbonized dry gel is combusted and ground, and the ground dry gel is placed in the containerKeeping the temperature at 1000 ℃ for 5-8h under 800-0.6Sr0.4Co0.8Fe0.2O3A perovskite precursor; by nitric acid solution to La0.6Sr0.4Co0.8Fe0.2O3Selectively dissolving out A site cations Sr from the perovskite precursor to generate A site defects, thus obtaining the modified perovskite. The rare nitric acid is used for selectively etching A site metal cation Sr, so that La is added0.6Sr0.4Co0.8Fe0.2O3The specific surface area of the perovskite precursor introduces more oxygen vacancies, exposes more B-site active sites and effectively improves La0.6Sr0.4Co0.8Fe0.2O3Oxygen Evolution (OER) performance of perovskites.
Description
Technical Field
The invention relates to the technical field of perovskite modification catalysis, in particular to perovskite modified by a selective dissolution method and a modification method and application thereof.
Background
Currently, energy problems and environmental problems have become more and more serious. Therefore, much work is being done at home and abroad to develop new clean renewable energy sources to replace the traditional fossil fuels. Oxygen Evolution (OER) reactions are an important link in fuel cells, metal air cells and electrolysis of water. The theoretical electrode potential for Oxygen Evolution (OER) reactions is 1.23V, but Oxygen Evolution (OER) reactions are a four electron reaction process and slow kinetics, often resulting in higher overpotentials, which are detrimental to the reaction. A suitable Oxygen Evolution (OER) catalyst is very important. Commercial noble metal catalyst RuO2And IrO2At present, the catalyst is considered to be the most effective Oxygen Evolution (OER) catalyst at home and abroad, but the catalyst has the defects of rare reserves, high price and unsatisfactory stability, so the catalyst is difficult to popularize.
Perovskite (molecular formula ABO)3A represents an alkali metal or alkaline earth metal element, and B represents a transition metal element) is a member of the family of transition metal oxides. The catalyst has the advantages of low price, relatively mature synthesis process, adjustable electronic structure, good electrocatalytic performance and the like, and thus becomes one of the hot spots of research in recent years. However, perovskites also have some disadvantages themselves: for example, perovskite has a high crystallization temperature, so that it is large in particle size and is liable to occurAgglomeration, resulting in low surface area; and the perovskite itself is less conductive, which also reduces its electrocatalytic activity.
Based on the above points, the current studies on modification of perovskites are roughly three factors, first, increasing the specific surface area of perovskites to increase the number of active sites. The sites where electrocatalysts catalyze Oxygen Evolution (OER) reactions are mainly at the catalyst surface, so a large specific surface area is very important for electrocatalysis. Secondly, the conductivity of the perovskite is increased, and the perovskite is mainly compounded with other materials having a good conductivity, such as a carbon material. Thirdly, the electronic structure of the perovskite is improved. Suntivich et al have reported that perovskites have optimal Oxygen Evolution (OER) performance when the eg orbital occupancy ratio of the B-site transition metal atom is approximately 1.2. The current way of adjusting the eg electron orbit relies mainly on doping of the a-or B-bit element. In addition, there have been many studies focusing on the introduction of oxygen vacancies: the oxygen vacancy can reduce the coordination number of the active site, provide more dangling bonds, increase the bonding strength of free hydroxyl OH of an oxygen intermediate, simultaneously reduce the absorption energy of water molecules adsorbed to the active site, and in addition, localized electrons near the oxygen vacancy are easy to be non-localized, so that the conductivity of the surface of the perovskite can be improved.
La0.6Sr0.4Co0.8Fe0.2O3The catalyst is a perovskite catalyst with good A and B sites doping at present, in recent years, selective etching on the A site of the perovskite, surface area increasing and more oxygen vacancy introducing methods have been reported in some catalytic fields, but no related report exists in the electrocatalysis field.
Disclosure of Invention
The invention overcomes the defects in the prior art, the existing Oxygen Evolution (OER) catalyst has the advantages of rare reserves, high price and unsatisfactory stability, is difficult to popularize, provides a perovskite modified by using a selective dissolution method, a modification method and application thereof, uses dilute nitric acid to selectively etch A-site metal cation Sr, and increases La0.6Sr0.4Co0.8Fe0.2O3Ratio of perovskite precursorsThe surface area is introduced, more oxygen vacancies are introduced, more active sites at B site are exposed, and La is effectively improved0.6Sr0.4Co0.8Fe0.2O3Oxygen Evolution (OER) performance of perovskites.
The purpose of the invention is realized by the following technical scheme.
The perovskite modified by the selective leaching method and the modification method thereof are carried out according to the following steps:
Placing metal nitrates of lanthanum, strontium, cobalt and iron in a container and adding water to dissolve the metal nitrates to obtain an aqueous solution of metal salt ions, adding citric acid and ethylene diamine tetraacetic acid into the aqueous solution of the metal salt ions, adjusting the pH of the solution to 8-9 to obtain a mixed solution, heating and stirring the mixed solution at 70-90 ℃ to obtain a sol, drying the sol at 100-140 ℃ for 20-30h, carbonizing the sol at 140-160 ℃ for 2-4h to obtain a carbonized dry gel, burning the carbonized dry gel at 450-550 ℃ for 80-100min, taking out and grinding the carbonized dry gel, placing the ground dry gel at 800-1000 ℃ for heat preservation for 5-8h, and cooling to room temperature of 20-25 ℃ to obtain La0.6Sr0.4Co0.8Fe0.2O3The perovskite precursor comprises lanthanum nitrate, strontium nitrate, cobalt nitrate and iron nitrate in a molar ratio of (2-4) to (1-3) to (3-5) to (1-2), citric acid in an amount of 0.012-0.018mol, and ethylenediaminetetraacetic acid in an amount of 0.08-0.012 mol;
By nitric acid solution to La0.6Sr0.4Co0.8Fe0.2O3Selective dissolution of a-site cations Sr from the perovskite precursor to produce a-site defects: i.e. La0.6Sr0.4Co0.8Fe0.2O3Dissolving and etching the perovskite precursor in a nitric acid solution for 1-15 hoursAnd then washing and drying to obtain the modified perovskite.
In step 1, La (NO) is used as lanthanum nitrate, strontium nitrate, cobalt nitrate and iron nitrate respectively3)3·6H2O、 Sr(NO3)2、Co(NO3)2·6H2O and Fe (NO)3)3·9H2O，La(NO3)3·6H2O、Sr(NO3)2、Co(NO3)2·6H2O and Fe (NO)3)3·9H2The molar ratio of O is 3:2:4:1, and the concentration of the aqueous solution of metal salt ions is 0.08-0.12 mol/L.
In step 1, the amount of citric acid added was 0.015mol and the amount of ethylenediaminetetraacetic acid added was 0.01 mol.
In the step 1, when the sol is formed, the heating temperature is 75-80 ℃, and the stirring speed is 320-350 r/min.
In the step 1, the carbonized xerogel is placed in a reaction container, firstly, the temperature is raised to 450-.
In the step 2, the concentration of the nitric acid solution is 0.18-0.20mol/L, and the etching time is 1-12 hours.
In step 2, the drying conditions are as follows: drying at 90-100 deg.C for 10-12 hr.
The perovskite after modification is 10mA/cm2The overpotential is 380-460mV, and the modified perovskite is scanned for 1000 circles in CV and then scanned at 10mA/cm2The overpotential difference is 6-8 mV.
The invention has the beneficial effects that: preparing La with good crystallinity by adopting improved sol-gel method0.6Sr0.4Co0.8Fe0.2O3A perovskite precursor; the rare nitric acid is used for selectively etching A site metal cation Sr, so that La is added0.6Sr0.4Co0.8Fe0.2O3The specific surface area of the perovskite precursor is introducedA plurality of oxygen vacancies expose more active sites at the B site, and effectively improve the La0.6Sr0.4Co0.8Fe0.2O3Oxygen Evolution (OER) performance of perovskites; la can be controlled by etching time0.6Sr0.4Co0.8Fe0.2O3The specific surface area of the perovskite and the number of oxygen vacancies introduced.
Drawings
FIG. 1 is La0.6Sr0.4Co0.8Fe0.2O3XRD diffractograms of perovskite before (0h) and after 1 hour (1h), 6 hours (6h) and 12 hours (12h) etching using 0.2mol/L nitric acid;
FIG. 2 is La0.6Sr0.4Co0.8Fe0.2O3Scanning Electron Microscope (SEM) images and EDS energy spectrum results of the perovskite before etching (a) and after etching for 1 hour (b), 6 hours (c) and 12 hours (d) by using 0.2mol/L nitric acid;
FIG. 3 is La0.6Sr0.4Co0.8Fe0.2O3Perovskite before etching (0h) and after etching for 1 hour (1h), 6 hours (6h) and 12 hours (12h) by using 0.2mol/L nitric acid and IrO2Linear voltammetry (LSV) test results;
FIG. 4 is a drawing of a 0.2M nitric acid etch of La0.6Sr0.4Co0.8Fe0.2O3LSV curve of perovskite 6 hours sample 1000 cycles before and after CV, and IrO2Time-current curve over 3 hours with the sample after 6 hours of etching.
Detailed Description
The technical solution of the present invention is further illustrated by the following specific examples.
Example 1
1.La0.6Sr0.4Co0.8Fe0.2O3The preparation of (1): (1) metal nitrate (La (NO) was weighed in a molar ratio of the molecular formula so that the total molar amount was 0.01mol3)3··6H2O,Sr(NO3)2,Co(NO3)2·6H2O,Fe(NO3)3·9H2O) in a 200mL beaker, for example, an ionic water was added to dissolve the metal salt ion to a concentration of 0.1 mol/L. Then 0.015mol of citric acid and 0.01mol of ethylenediamine tetraacetic acid are added for complexation, and the pH of the solution is adjusted to be between 8 and 9 by ammonia water. (2) Heating the solution obtained in the step (1) in a water bath kettle at 80 ℃, and stirring by using magnetic force at the stirring speed of 350r/min until the solution becomes sol. The obtained sol was put into a forced air drying oven, dried at 120 ℃ for 24 hours, and then dried at 150 ℃ for 3 hours for carbonization. (3) And (3) placing the carbonized xerogel obtained in the step (2) into a muffle furnace, heating to 500 ℃ at the speed of 5 ℃/min, burning for 90min, taking out, grinding, placing into the muffle furnace, heating to 500 ℃ at the speed of 5 ℃/min, preserving heat for 120min, heating to 900 ℃ at the speed of 3 ℃/min, preserving heat for 6h, and cooling along with the furnace. La with good crystallinity is obtained0.6Sr0.4Co0.8Fe0.2O3A perovskite precursor.
2. La prepared by the method of 2 by using a selective dissolution method0.6Sr0.4Co0.8Fe0.2O3Modifying the perovskite precursor: adopting 0.2mol/L dilute nitric acid solution to selectively dissolve A site cation Sr to generate A site defects: 0.2g of La0.6Sr0.4Co0.8Fe0.2O3And (3) putting the perovskite precursor into 4mL of 0.2mol/L dilute nitric acid for dissolving and etching for 1 hour. And after the etching is finished, washing the substrate by using deionized water until the washing liquid is neutral. Then placed in an oven and dried at 100 ℃ for 12 hours.
Example 2
1.La0.6Sr0.4Co0.8Fe0.2O3The preparation of (1): (1) metal nitrate (La (NO) was weighed in a molar ratio of the molecular formula so that the total molar amount was 0.01mol3)3··6H2O,Sr(NO3)2,Co(NO3)2·6H2O,Fe(NO3)3·9H2O) in a 200mL beaker, for example, an ionic water was added to dissolve the metal salt ion to a concentration of 0.1 mol/L. Then 0.015mol of citric acid and 0.01mol of ethylenediamine tetraacetic acid are added for complexation, and the pH of the solution is adjusted to be between 8 and 9 by ammonia water. (2) Will (a) to1) The obtained solution is placed in a water bath kettle at 80 ℃ and is heated, and magnetic stirring is carried out, wherein the stirring speed is 350r/min, until the solution becomes sol. The obtained sol was put into a forced air drying oven, dried at 120 ℃ for 24 hours, and then dried at 150 ℃ for 3 hours for carbonization. (3) And (3) placing the carbonized xerogel obtained in the step (2) into a muffle furnace, heating to 500 ℃ at the speed of 5 ℃/min, burning for 90min, taking out, grinding, placing into the muffle furnace, heating to 500 ℃ at the speed of 5 ℃/min, preserving heat for 120min, heating to 900 ℃ at the speed of 3 ℃/min, preserving heat for 6h, and cooling along with the furnace. La with good crystallinity is obtained0.6Sr0.4Co0.8Fe0.2O3A perovskite precursor.
2. La prepared by the method of 2 by using a selective dissolution method0.6Sr0.4Co0.8Fe0.2O3Modifying the perovskite precursor: adopting 0.2mol/L dilute nitric acid solution to selectively dissolve A site cation Sr to generate A site defects: 0.2g of La0.6Sr0.4Co0.8Fe0.2O3And (3) putting the perovskite precursor into 4mL of 0.2mol/L dilute nitric acid for dissolving and etching for 6 hours. And after the etching is finished, washing the substrate by using deionized water until the washing liquid is neutral. Then placed in an oven and dried at 100 ℃ for 12 hours.
Example 3
1.La0.6Sr0.4Co0.8Fe0.2O3The preparation of (1): (1) metal nitrate (La (NO) was weighed in a molar ratio of the molecular formula so that the total molar amount was 0.01mol3)3··6H2O,Sr(NO3)2,Co(NO3)2·6H2O,Fe(NO3)3·9H2O) in a 200mL beaker, for example, an ionic water was added to dissolve the metal salt ion to a concentration of 0.1 mol/L. Then 0.015mol of citric acid and 0.01mol of ethylenediamine tetraacetic acid are added for complexation, and the pH of the solution is adjusted to be between 8 and 9 by ammonia water. (2) Heating the solution obtained in the step (1) in a water bath kettle at 80 ℃, and stirring by using magnetic force at the stirring speed of 350r/min until the solution becomes sol. Drying the obtained sol in a blast drying oven at 120 deg.C for 24 hr, and heating at 150 deg.CThen dried for 3h for carbonization. (3) And (3) placing the carbonized xerogel obtained in the step (2) into a muffle furnace, heating to 500 ℃ at the speed of 5 ℃/min, burning for 90min, taking out, grinding, placing into the muffle furnace, heating to 500 ℃ at the speed of 5 ℃/min, preserving heat for 120min, heating to 900 ℃ at the speed of 3 ℃/min, preserving heat for 6h, and cooling along with the furnace. La with good crystallinity is obtained0.6Sr0.4Co0.8Fe0.2O3A perovskite precursor.
2. La prepared by the method of 2 by using a selective dissolution method0.6Sr0.4Co0.8Fe0.2O3Modifying the perovskite precursor: adopting 0.2mol/L dilute nitric acid solution to selectively dissolve A site cation Sr to generate A site defects: 0.2g of La0.6Sr0.4Co0.8Fe0.2O3And (3) putting the perovskite precursor into 4mL of 0.2mol/L dilute nitric acid for dissolving and etching for 12 hours. And after the etching is finished, washing the substrate by using deionized water until the washing liquid is neutral. Then placed in an oven and dried at 100 ℃ for 12 hours.
La for different etching time0.6Sr0.4Co0.8Fe0.2O3Perovskite relevant characterization and performance test:
as shown in fig. 1, the perovskite structure was not changed within 12 hours of etching, but the diffraction peak was weakened, demonstrating that the surface was changed.
As shown in FIG. 2, after nitric acid etching, the agglomeration effect of perovskite is improved, the surface becomes rough, the specific surface area is proved to be large, and meanwhile, the energy spectrum result shows that Sr is in La0.6Sr0.4Co0.8Fe0.2O3The metal cation content ratio in (1) is decreasing (from 19.99% before etching to 14.79% after 12 hours of etching).
As shown in FIG. 3, La0.6Sr0.4Co0.8Fe0.2O3Under the conditions of non-etching and etching for 1 hour, 6 hours, 12 hours and at 10mA/cm2The corresponding overpotentials are 460mV, 417mV, 385mV and 412mV, respectively. After etching for 6 hours, La0.6Sr0.4Co0.8Fe0.2O3Exhibit optimal Oxygen Evolution (OER) activity.
As shown in FIG. 4, La was formed after 6h of nitric acid etching0.6Sr0.4Co0.8Fe0.2O3The perovskite still maintains better stability: 10mA/cm after 1000 cycles of CV scanning2The corresponding overpotentials are only 7mV different, and the current is constant within 3h (10 mA/cm)2) The corresponding voltage values were substantially unchanged during the test.
The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.
Claims (10)
1. The perovskite modified by the selective leaching method is characterized in that: the method comprises the following steps:
step 1, La0.6Sr0.4Co0.8Fe0.2O3Preparation of perovskite precursors
Placing metal nitrates of lanthanum, strontium, cobalt and iron in a container and adding water to dissolve the metal nitrates to obtain an aqueous solution of metal salt ions, adding citric acid and ethylene diamine tetraacetic acid into the aqueous solution of the metal salt ions, adjusting the pH of the solution to 8-9 to obtain a mixed solution, heating and stirring the mixed solution at 70-90 ℃ to obtain a sol, drying the sol at 140 ℃ under 100-140 ℃ for 20-30h, carbonizing the sol at 160 ℃ under 140-160 ℃ for 2-4h to obtain a carbonized dry gel, burning the carbonized dry gel at 550 ℃ under 450-550 ℃ for 80-100min, taking out and grinding the carbonized dry gel, placing the ground dry gel at 1000 ℃ under 800-800 ℃ for heat preservation for 5-8h, and cooling to room temperature 20-25 ℃ to obtain La0.6Sr0.4Co0.8Fe0.2O3The perovskite precursor comprises lanthanum nitrate, strontium nitrate, cobalt nitrate and iron nitrate in a molar ratio of (2-4) to (1-3) to (3-5) to (1-2), citric acid in an amount of 0.012-0.018mol, and ethylenediaminetetraacetic acid in an amount of 0.08-0.012 mol;
step 2, modifying La by using a selective dissolution method0.6Sr0.4Co0.8Fe0.2O3Perovskite precursors
By nitric acid solution to La0.6Sr0.4Co0.8Fe0.2O3Selective dissolution of a site cation Sr from the perovskite precursor to produce a site defect: i.e. La0.6Sr0.4Co0.8Fe0.2O3And (3) putting the perovskite precursor into a nitric acid solution for dissolving and etching, and washing and drying after etching for 1-15 hours to obtain the modified perovskite.
2. The perovskite modified by the selective leaching method according to claim 1, wherein: in step 1, La (NO) is used as lanthanum nitrate, strontium nitrate, cobalt nitrate and iron nitrate respectively3)3·6H2O、Sr(NO3)2、Co(NO3)2·6H2O and Fe (NO)3)3·9H2O，La(NO3)3·6H2O、Sr(NO3)2、Co(NO3)2·6H2O and Fe (NO)3)3·9H2The molar ratio of O is 3:2:4:1, and the concentration of the aqueous solution of metal salt ions is 0.08-0.12 mol/L; the addition amount of citric acid is 0.015mol, and the addition amount of ethylene diamine tetraacetic acid is 0.01 mol; when the sol is formed, the heating temperature is 75-80 ℃, and the stirring speed is 320-350 r/min.
3. The perovskite modified by the selective leaching method according to claim 1, wherein: in the step 1, the carbonized xerogel is placed in a reaction container, firstly, the temperature is raised to 450-.
4. The perovskite modified by the selective leaching method according to claim 1, wherein: in the step 2, the concentration of the nitric acid solution is 0.18-0.20mol/L, and the etching time is 1-12 hours; drying conditions are as follows: drying at 90-100 deg.C for 10-12 hr.
5. A method for modifying a perovskite by a selective leaching method, comprising: the method comprises the following steps:
step 1, La0.6Sr0.4Co0.8Fe0.2O3Preparation of perovskite precursors
Placing metal nitrates of lanthanum, strontium, cobalt and iron in a container and adding water to dissolve the metal nitrates to obtain an aqueous solution of metal salt ions, adding citric acid and ethylene diamine tetraacetic acid into the aqueous solution of the metal salt ions, adjusting the pH of the solution to 8-9 to obtain a mixed solution, heating and stirring the mixed solution at 70-90 ℃ to obtain a sol, drying the sol at 140 ℃ under 100-140 ℃ for 20-30h, carbonizing the sol at 160 ℃ under 140-160 ℃ for 2-4h to obtain a carbonized dry gel, burning the carbonized dry gel at 550 ℃ under 450-550 ℃ for 80-100min, taking out and grinding the carbonized dry gel, placing the ground dry gel at 1000 ℃ under 800-800 ℃ for heat preservation for 5-8h, and cooling to room temperature 20-25 ℃ to obtain La0.6Sr0.4Co0.8Fe0.2O3The perovskite precursor comprises lanthanum nitrate, strontium nitrate, cobalt nitrate and iron nitrate in a molar ratio of (2-4) to (1-3) to (3-5) to (1-2), citric acid in an amount of 0.012-0.018mol, and ethylenediaminetetraacetic acid in an amount of 0.08-0.012 mol;
step 2, modifying La by using a selective dissolution method0.6Sr0.4Co0.8Fe0.2O3Perovskite precursors
By nitric acid solution to La0.6Sr0.4Co0.8Fe0.2O3Selective dissolution of a site cation Sr from the perovskite precursor to produce a site defect: i.e. La0.6Sr0.4Co0.8Fe0.2O3And (3) putting the perovskite precursor into a nitric acid solution for dissolving and etching, and washing and drying after etching for 1-15 hours to obtain the modified perovskite.
6. The method of modifying a perovskite by a selective elution method according to claim 5, wherein: in step 1, La (NO) is used as lanthanum nitrate, strontium nitrate, cobalt nitrate and iron nitrate respectively3)3·6H2O、Sr(NO3)2、Co(NO3)2·6H2O and Fe (NO)3)3·9H2O，La(NO3)3·6H2O、Sr(NO3)2、Co(NO3)2·6H2O and Fe (NO)3)3·9H2The molar ratio of O is 3:2:4:1, and the concentration of the aqueous solution of metal salt ions is 0.08-0.12 mol/L.
7. The method of modifying a perovskite by a selective elution method according to claim 5, wherein: in the step 1, the addition amount of citric acid is 0.015mol, and the addition amount of ethylene diamine tetraacetic acid is 0.01 mol; when the sol is formed, the heating temperature is 75-80 ℃, and the stirring speed is 320-350 r/min.
8. The method of modifying a perovskite by a selective elution method according to claim 5, wherein: in the step 1, the carbonized xerogel is placed in a reaction container, firstly, the temperature is raised to 450-.
9. The method of modifying a perovskite by a selective elution method according to claim 5, wherein: in the step 2, the concentration of the nitric acid solution is 0.18-0.20mol/L, and the etching time is 1-12 hours; drying conditions are as follows: drying at 90-100 deg.C for 10-12 hr.
10. The modified perovskite obtained by selective elution of cationic Sr in the perovskite by the selective elution method according to any one of claims 1 to 4Use in an Oxygen Evolution (OER) catalyst, characterized in that: the modified perovskite is at 10mA/cm2The overpotential is 380-460mV, and the modified perovskite is scanned for 1000 circles in CV and then scanned at 10mA/cm2The overpotential difference is 6-8 mV.
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