Perovskite oxide catalyst, preparation method and application

Abstract

The invention discloses a perovskite oxide catalyst, a preparation method and application, and belongs to the field of electro-catalysis. The invention relates to a preparation method of a perovskite oxide catalyst. The preparation method comprises the following steps: dissolving Pr (NO3) 3.4 H2O, Ba (NO3) 2, Sr (NO3) 2, Co (NO3) 2.6 H2O, Fe (NO3) 3.9 H2O and NH4F in deionized water according to a molar ratio of 1.8: 0.9: 0.9: 3: 1: 0.06, heating and stirring to obtain a mixed solution; adding ethylenediaminetetraacetic acid and citric acid into the mixed solution, heating and stirring to generate transparent gel; the transparent gel is preheated and then calcined, and the perovskite oxide catalyst PBSCFF3A95 is obtained. The catalyst has excellent OER catalytic activity and stability.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalysis, and in particular relates to a perovskite oxide catalyst, a preparation method and an application thereof. Background Art

[0002] A large number of research results show that electrochemical catalysis is an effective technical means to achieve large-scale conversion and storage of sustainable energy. Hydrogen energy has attracted widespread attention due to its zero pollution, high energy, and abundant resources. It is regarded as the key to future green energy. In addition, hydrogen (H 2 ) is also an essential raw material for the manufacture of value-added chemicals in the modern chemical industry, including carbon dioxide conversion, hydrocarbon reforming, and nitrogen fixation. Water electrolysis is one of the most important methods for hydrogen production, but its main disadvantage is its high energy and economic costs. Therefore, the use of highly active catalysts for the water splitting half-reaction is key to alleviating these shortcomings. The cathode and anode of water electrolysis undergo hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. The anode OER exhibits slower kinetics and is the bottleneck of water electrolysis. It would be of great significance and challenging to produce a catalytic material that can improve the performance of OER.

[0003] In existing reports, praseodymium barium strontium cobalt iron catalyst (PBSCF) has good OER catalytic performance. Research shows that there is no report on the synergistic improvement of the OER performance of perovskite oxide catalysts by anion doping and A-site defects. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a perovskite oxide catalyst, a preparation method and an application thereof, which solve the problems in the prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a perovskite oxide catalyst comprises the following steps:

[0007] Change Pr(NO 3 ) 3 ·4H 2 O、Ba(NO 3 ) 2 、Sr(NO 3 ) 2 、Co(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O and NH 4F was dissolved in deionized water in a molar ratio of 1.8:0.9:0.9:3:1:0.06, and heated and stirred to obtain a mixed solution;

[0008] Add ethylenediaminetetraacetic acid and citric acid into the mixed solution, heat and stir to produce a transparent gel;

[0009] The transparent gel is preheated and then calcined to obtain the perovskite oxide catalyst PBSCFF 3 A 95 .

[0010] Furthermore, when preparing the mixed solution, the heating temperature is 80° C. and the stirring time is 60 min.

[0011] Furthermore, when preparing the transparent gel, the heating temperature is 100°C.

[0012] Further, the molar ratio of EDTA, citric acid and total metal ions in the mixed solution is 1:1.5:1;

[0013] Furthermore, ethylenediaminetetraacetic acid and citric acid were added to the mixed solution to adjust the pH to 6.5.

[0014] Further, the preheating temperature is 250°C and the heating time is 5h;

[0015] Furthermore, the calcination temperature is 950° C. and the time is 10 h.

[0016] A perovskite oxide catalyst is prepared using the above-mentioned method for preparing a perovskite oxide catalyst.

[0017] Further, the molecular formula of the catalyst is: (PrBa 0.5 Sr 0.5 ) 0.95 Co 1.5 Fe 0.5 O 4.97 +δF 0.03 .

[0018] The above-mentioned perovskite oxide catalyst is used in the electrocatalytic oxygen evolution reaction.

[0019] Beneficial effects of the present invention:

[0020] 1. Additional oxygen active centers in PBSCF are designed through F-doping strategy, which significantly enhances the surface exchange and chemical bulk diffusion properties, improves the lattice oxygen mobility, optimizes the O 2p band center and activates the lattice oxygen, provides a large number of oxygen vacancies as active sites, and enhances the reaction kinetics.

[0021] 2. By constructing A-site defects to coordinately regulate the unit cell parameters and inhibit the dissolution of B-site metals, the starting potential of the catalyst is further reduced.

[0022] 3. After F doping, the catalyst presents a tetragonal phase. After constructing the A-site defect, the catalyst changes from a tetragonal phase to a cubic phase, which improves the chemical stability and electron transfer rate of the catalyst.

[0023] 4. The catalyst prepared by the present invention (PrBa 0.5 Sr 0.5 ) 0.95 Co 1.5 Fe 0.5 O 4.97 +δF 0.03 It has excellent OER catalytic activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 PBSCFF 3 A 95 , PBSCFA 95 , PBSCFF 3 , XRD pattern of PBSCF;

[0026] Figure 2 is the refined XRD pattern of PBSCF;

[0027] Figure 3 PBSCFF 3 Refined XRD pattern of

[0028] Figure 4 PBSCFF 3 A 95 Refined XRD pattern of

[0029] Figure 5 PBSCF and PBSCFF prepared in the examples and comparative examples 3 , PBSCFF 3 A 95 LSV curves in 1M KOH;

[0030] Figure 6 Catalyst PBSCFF 3 A 95 At 10 mA cm -2 Schematic diagram of chronopotentiometry stability at current density;

[0031] Figure 7 PBSCFF 3 A 95 and Pt / C+RuO 2 Long term cycle durability diagram. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] In this embodiment, a perovskite oxide catalyst (PBSCFF) is proposed. 3 A 95 ), comprising the following steps:

[0035] S1, in a beaker, add Pr(NO 3 ) 3 ·4H 2 O、Ba(NO 3 ) 2 、Sr(NO 3 ) 2 、Co(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O and NH 4 F was dissolved in deionized water at a molar ratio of 1.8:0.9:0.9:3:1:0.06 and stirred at 80° C. for 60 min to obtain a mixed solution.

[0036] S2, adding ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) to the mixed solution, adjusting the pH to 6.5, and heating and stirring at 100° C. to produce a transparent gel; wherein the molar ratio of EDTA, CA and the total metal ions in the mixed solution is 1:1.5:1.

[0037] S3, the transparent gel was pretreated at 250 °C for 5 h and then calcined at 950 °C in static air for 10 h to transform into a uniform mixed metal oxide (PrBa 0.5 Sr 0.5 ) 0.95 Co 1.5Fe 0.5 O 4.97 +δF 0.03 , namely the perovskite oxide catalyst PBSCFF 3 A 95 .

[0038] Another form of the perovskite oxide catalyst is: (PrBa 0.5 Sr 0.5 ) y Co 1.5 Fe 0.5 O 5-x +δF x (x=0.03; y=0.95).

[0039] Comparative Example 1

[0040] In this comparative example, a method for preparing a perovskite oxide catalyst (PBSCF) is proposed, comprising the following steps:

[0041] S1, in a beaker, add Pr(NO 3 ) 3 ·4H 2 O、Ba(NO 3 ) 2 、Sr(NO 3 ) 2 、Co(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O was dissolved in deionized water at a molar ratio of 2:1:1:3:1 and stirred at 80° C. for 60 min to obtain a mixed solution.

[0042] S2, adding ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) to the mixed solution, adjusting the pH to 6.5, and heating and stirring at 100° C. to produce a transparent gel; wherein the molar ratio of EDTA, CA and the total metal ions in the mixed solution is 1:1.5:1.

[0043] S3, the transparent gel was pretreated at 250 °C for 5 h and then calcined at 950 °C in static air for 10 h to transform into a uniform mixed metal oxide (PrBa 0.5 Sr 0.5 ) y Co 1.5 Fe 0.5 O 5-x +δF x (x=0; y=1), namely the perovskite oxide catalyst PBSCF.

[0044] Comparative Example 2

[0045] In this comparative example, a perovskite oxide catalyst (PBSCFA 95 ), comprising the following steps:

[0046] S1, in a beaker, add Pr(NO 3 ) 3 ·4H 2 O、Ba(NO 3 ) 2 、Sr(NO 3 ) 2 、Co(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O was dissolved in deionized water at a molar ratio of 1.8:0.9:0.9:3:1 and stirred at 80° C. for 60 min to obtain a mixed solution.

[0047] S2, adding ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) to the mixed solution, adjusting the pH to 6.5, and heating and stirring at 100° C. to produce a transparent gel; wherein the molar ratio of EDTA, CA and the total metal ions in the mixed solution is 1:1.5:1.

[0048] S3, the transparent gel was pretreated at 250 °C for 5 h and then calcined at 950 °C in static air for 10 h to transform into a uniform mixed metal oxide (PrBa 0.5 Sr 0.5 ) y Co 1.5 Fe 0.5 O 5-x +δF x (x=0;y=0.95), namely the perovskite oxide catalyst PBSCFA 95 .

[0049] Comparative Example 3

[0050] In this comparative example, a perovskite oxide catalyst (PBSCFF) is proposed. 3 ), comprising the following steps:

[0051] S1, in a beaker, add Pr(NO 3 ) 3 ·4H 2 O、Ba(NO 3 )2 、Sr(NO 3 ) 2 、Co(NO 3 ) 2 6H 2 O, Fe(NO 3 ) 3 9H 2 O and NH 4 F was dissolved in deionized water at a molar ratio of 2:1:1:3:1:0.06 and stirred at 80° C. for 60 min to obtain a mixed solution.

[0052] S2, adding ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) to the mixed solution, adjusting the pH to 6.5, and heating and stirring at 100° C. to produce a transparent gel; wherein the molar ratio of EDTA, CA and the total metal ions in the mixed solution is 1:1.5:1.

[0053] S3, the transparent gel was pretreated at 250 °C for 5 h and then calcined at 950 °C in static air for 10 h to transform into a uniform mixed metal oxide (PrBa 0.5 Sr 0.5 ) y Co 1.5 Fe 0.5 O 5-x +δF x (x = 0.03; y = 1), namely the perovskite oxide catalyst PBSCFF 3 .

[0054] The experimental tests are as follows:

[0055] 1. Determine the phase composition of the sample in Example 1 and the samples in Comparative Examples 1-3;

[0056] Figure 1 The X-ray diffraction result diagram of the samples provided in Example 1 and Comparative Examples 1-3 of the present application. The phase composition of the samples was tested by X-ray diffraction result diagram (XRD); Figure 1 As shown, the prepared PBSCF and PBSCFF 3 , PBSCFA 95 , PBSCFF 3 A 95 The catalyst exhibits a pure crystalline phase, and all characteristic peaks correspond to the lattice structure of PBSCF, indicating that within this doping range, F can effectively replace O and enter the lattice. The introduction of A-site defects and the doping of F elements will not cause the collapse of the perovskite structure, emphasizing the integrity of the crystal structure in the synthetic material and confirming its perovskite structural characteristics.

[0057] Figure 2is the refined XRD pattern of PBSCF, Figure 2 As shown, the crystal phase of PBSCF is Pm-3m;

[0058] Figure 3 This is the refined XRD pattern after F element doping. It can be seen that PBSCFF after F element doping 3 The crystal phase appears as Pnma; Figure 4 PBSCFF 3 A 95 The refined XRD pattern of Figure 4 It can be seen that after F element doping and A-site defect construction, PBSCFF 3 A 95 The crystal phase changes back to Pm-3m. It can be seen that after constructing the A-site defect and F doping, PBSCFF 3 A 95 It will return to the cubic phase. The cubic perovskite structure has stronger symmetry, and the state density near the Fermi level of the cubic structure is usually at a higher state, which reduces the activation energy of electronic conductivity and improves the chemical stability of the catalyst and the electron transfer rate.

[0059] 2. Determine the OER performance of the catalyst of Example 1 and the catalysts of Comparative Examples 1-3. The test process is as follows:

[0060] Step 1: 7 mg of catalyst and 3 mg of acetylene black were dispersed in a mixture containing 50 μL of 5 wt.% Nafion solution binder to prepare catalyst ink, ethanol was added to the mixed solution, and ultrasonic treatment was performed in a 20° C. water bath for 1 h to fully disperse the catalyst.

[0061] Step 2: 3.5 μL of the prepared catalyst ink was drop cast onto an area of ​​0.1256 cm -2 The working electrode is prepared on a glassy carbon disk electrode;

[0062] Step 3: The test was performed in a three-electrode configuration controlled by an electrochemical workstation (AUT87986, Autolab BV, Metrohm, Switzerland) in 1 M KOH electrolyte, where saturated Hg / HgO and a carbon rod were used as the reference electrode and the counter electrode, respectively.

[0063] The catalysts in step 1 were taken from catalyst samples of Example 1 and Comparative Examples 1-3, and four experiments were conducted.

[0064] The results are as follows Figure 5 As shown in Figure 2, it can be seen that F doping has a positive effect on OER performance and can improve the electrochemical kinetics of the catalyst. Further introduction of A-site defects, such as in PBSCFF 3 A 95A significant decrease in the onset potential was observed in the catalyst samples, further improving the OER performance.

[0065] 3. The constant current method was used to evaluate the catalyst (PBSCFF) in Example 1. 3 A 95 ) stability;

[0066] The specific process is: charge and discharge the electrode under test under constant current conditions, and record the change of its potential over time.

[0067] Step 1: Weigh a certain proportion of catalyst powder and conductive carbon black and put them into a container. Use a pipette to take 900 μL of anhydrous ethanol and 100 μL of Nafion solution and drop them into the container for dissolution. Finally, ultrasonicate for one hour in an ultrasonic machine until the catalyst and conductive carbon black in the slurry are evenly dispersed in the mixed solution of ethanol and Nafion.

[0068] Step 2: Use a pipette to transfer 5uL of slurry and apply it evenly on the GC (glassy carbon) electrode, and let it air dry naturally.

[0069] Step 3: A three-electrode configuration controlled by an electrochemical workstation (AUT87986, Autolab B.V., Metrohm, Switzerland) was used, in which saturated Hg / HgO and a carbon rod were used as the reference electrode and the counter electrode, respectively. -2 Measured at a current density of .

[0070] Evaluation results such as Figure 6 As shown, PBSCFF 3 A 95 The OER potential shows excellent stability at 10 mA cm -2 Its potential remained essentially unchanged during the 150-hour test in 1 M KOH electrolyte at a current density of 2.5 Å, demonstrating its long-lasting catalytic stability.

[0071] 4. Assemble the zinc-air battery and measure the catalyst (PBSCFF) in Example 1. 3 A 95 ) Performance of self-assembled zinc-air batteries;

[0072] Performance test results such as Figure 7 As shown, based on PBSCFF 3 A 95 The OCV (open circuit voltage) of the battery is 1.47V, which exceeds that of Pt / C+RuO 2 OCV obtained in the assembled catalyst, which recorded an OCV of 1.38 V; low-cost PBSCFF 3 A 95The assembled ZAB (zinc-air battery) shows comparable performance to commercial high-cost Pt / C+RuO 2 Catalyst equivalent discharge performance; PBSCFF 3 A 95 It has excellent cycling performance in actual ZAB devices.

[0073] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0074] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a perovskite oxide catalyst, characterized in that: The following steps are involved: Pr(NO3)3·4H2O, Ba(NO3)2, Sr(NO3)2, Co(NO3)2·6H2O, Fe(NO3)3·9H2O and NH4F were dissolved in deionized water at a molar ratio of 1.8:0.9:0.9:3:1:0.06, and heated and stirred to obtain a mixed solution; Add ethylenediaminetetraacetic acid and citric acid into the mixed solution, heat and stir to produce a transparent gel; The transparent gel was preheated and then calcined to obtain the perovskite oxide catalyst PBSCFF3A. 95 ; When preparing the mixed solution, the heating temperature is 80° C. and the stirring time is 60 min; When preparing transparent gel, the heating temperature is 100°C.

2. The method for preparing a perovskite oxide catalyst according to claim 1, characterized in that: The molar ratio of ethylenediaminetetraacetic acid, citric acid and total metal ions in the mixed solution is 1:1.5:

1.

3. The method for preparing a perovskite oxide catalyst according to claim 1, characterized in that: Ethylenediaminetetraacetic acid and citric acid were added to the mixed solution to adjust the pH to 6.

5.

4. The method for preparing a perovskite oxide catalyst according to claim 1, characterized in that: The preheating temperature is 250°C and the heating time is 5h.

5. The method for preparing a perovskite oxide catalyst according to claim 1, characterized in that: The calcination temperature is 950°C and the time is 10 h.

6. A perovskite oxide catalyst, characterized in that The catalyst is prepared by the method for preparing a perovskite oxide catalyst according to any one of claims 1 to 5.

7. A perovskite oxide catalyst according to claim 6, characterized in that: The molecular formula of the catalyst is: (PrBa 0.5 Sr 0.5 ) 0.95 Co 1.5 Fe 0.5 O 4.97 +δF 0.03 .

8. Use of a perovskite oxide catalyst as claimed in claim 6 or 7 in an electrocatalytic oxygen evolution reaction.

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