Perovskite oxide catalyst, preparation method and application thereof

Abstract

The application discloses a perovskite oxide catalyst, a preparation method and application, and belongs to the field of electrocatalysis; a preparation method of a perovskite oxide catalyst comprises the following steps: Pr(NO3)3.4H2O, Ba(NO3)2, Sr(NO3)2, Co(NO3)2.6H2O, Fe(NO3)3.9H2O and NH4F are dissolved in deionized water according to a molar ratio of 1.9:0.95:0.95:3:1:0.06, and a mixed solution is obtained through heating and stirring; ethylenediaminetetraacetic acid and citric acid are added into the mixed solution, and transparent gel is generated through heating and stirring; the transparent gel is preheated first, and then calcined, so that the perovskite oxide catalyst PBSCFF3A is obtained 95 . The catalyst has excellent OER catalytic activity and stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electrocatalysis, and particularly relates to a perovskite oxide catalyst, a preparation method and application thereof. BACKGROUND

[0002] At present, the energy crisis is increasingly serious, and it is urgent to develop and utilize sustainable new energy. A large number of research results show that electrochemical catalysis is an effective technical means that can realize large-scale conversion and storage of sustainable energy. Hydrogen energy is widely concerned due to its zero pollution, high energy, rich resources and other characteristics, and is regarded as the key to future green energy. In addition, hydrogen (H2) is also a basic raw material for the manufacture of value-added chemicals in modern chemical industry, including carbon dioxide conversion, hydrocarbon reforming and nitrogen fixation. Electrolysis of water is one of the most important methods for hydrogen production, but its main drawback is high energy and economic cost. Therefore, using a highly active catalyst for water splitting half-reaction is the key to alleviate these shortcomings. The cathode and anode of water electrolysis undergoes hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, among which the anode OER shows a slower kinetics and is the bottleneck of water electrolysis. It is of great significance and challenge to manufacture a catalytic material that can improve the performance of OER.

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

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

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] A preparation method of a perovskite oxide catalyst, comprising the following steps:

[0007] Pr(NO3)3·4H2O, Ba(NO3)2, Sr(NO3)2, Co(NO3)2·6H2O, Fe(NO3)3·9H2O and NH4F are dissolved in deionized water according to a molar ratio of 1.9:0.95:0.95:3:1:0.06, and heated and stirred to obtain a mixed solution;

[0008] Ethylene diamine tetraacetic acid and citric acid are added to the mixed solution, and heated and stirred to produce a transparent gel;

[0009] The transparent gel is preheated and then calcined to obtain the perovskite oxide catalyst PBSCFF3A 95 .

[0010] Further, the heating temperature is 80 DEG C and the stirring time is 60 min when the mixed solution is prepared.

[0011] Further, the heating temperature is 100 DEG C when the transparent gel is prepared.

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

[0013] Further, ethylenediaminetetraacetic acid and citric acid are added into the mixed solution to adjust the pH to 6.5.

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

[0015] Further, the calcination temperature is 950 DEG C and the time is 10 h.

[0016] A perovskite oxide catalyst is prepared by using the above preparation method of 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+δ F 0.03 .

[0018] The above perovskite oxide catalyst is applied in an electrocatalytic oxygen evolution reaction.

[0019] The beneficial effects of the present application are as follows:

[0020] 1. The additional oxygen active center in PBSCF is designed by F doping strategy, which significantly enhances the surface exchange and chemical species 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 dynamics.

[0021] 2. The A-site defects are constructed to synergistically regulate the cell parameters and inhibit the B-site metal dissolution, which further reduces the starting potential of the catalyst.

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

[0023] 4. The catalyst (PrBa 0.5 Sr 0.5 ) 0.95Co 1.5 Fe 0.5 O 4.97+δ F 0.03 excellent OER catalytic activity and stability. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0025] Figure 1 is the XRD pattern of PBSCFF3A 95 , PBSCF 95 , PBSCFF3, PBSCF;

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

[0027] Figure 3 is the refined XRD pattern of PBSCFF3;

[0028] Figure 4 is the refined XRD pattern of PBSCFF3A 95 ;

[0029] Figure 5 PBSCF, PBSCFF3, PBSCFF3A 95 prepared in the examples and comparative examples are shown in the following table. LSV curves in 1M KOH;

[0030] Figure 6 Catalyst PBSCFF3A 95 Chronoamperometry stability diagram at 10 mA cm -2 current density;

[0031] Figure 7 is the long-term cycle durability diagram of PBSCFF3A 95 and Pt / C+RuO2. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of the present application.

[0033] Example 1

[0034] In this embodiment, a preparation method of a perovskite oxide catalyst (PBSCFF3A 95 ) is provided, comprising the following steps:

[0035] S1, Pr(NO3)3·4H2O, Ba(NO3)2, Sr(NO3)2, Co(NO3)2·6H2O, Fe(NO3)3·9H2O and NH4F are dissolved in deionized water in a beaker according to the molar ratio of 1.9:0.95:0.95:3:1:0.06 according to the accurate stoichiometry, and stirred at 80°C for 60 min to obtain a mixed solution.

[0036] S2, EDTA and CA are added to the mixed solution, the pH is adjusted to 6.5, and the transparent gel is heated and stirred at 100°C; wherein the molar ratio of EDTA, CA and total metal ions in the mixed solution is 1:1.5:1.

[0037] S3, the transparent gel is pretreated at 250°C for 5h, and then calcined at 950°C in static air for 10h to convert into a uniform mixed metal oxide (PrBa 0.5 Sr 0.5 ) 0.95 Co 1.5 Fe 0.5 O 4.97 +δF 0.03 , that is, a perovskite oxide catalyst PBSCFF3A 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+δ F x (x=0.03; y=0.95).

[0039] Comparative Example 1

[0040] In this comparative example, a preparation method of a perovskite oxide catalyst (PBSCF) is provided, comprising the following steps:

[0041] S1, Pr(N03)3-4H20, Ba(N03)2, Sr(N03)2, Co(N03)2-6H20, Fe(N03)3-9H20 were dissolved in deionized water in a beaker according to the precise stoichiometry of 2:1:1:3:1, stirred at 80°C for 60 min, and a mixed solution was obtained.

[0042] S2, EDTA and CA were added to the mixed solution, the pH was adjusted to 6.5, and a transparent gel was produced by heating and stirring at 100°C; wherein the molar ratio of EDTA, CA and total metal ions in the mixed solution was 1:1.5:1.

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

[0044] Comparative Example 2

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

[0046] S1, Pr(N03)3-4H20, Ba(N03)2, Sr(N03)2, Co(N03)2-6H20, Fe(N03)3-9H20 were dissolved in deionized water in a beaker according to the precise stoichiometry of 1.9:0.95:0.95:3:1, stirred at 80°C for 60 min, and a mixed solution was obtained.

[0047] S2, EDTA and CA were added to the mixed solution, the pH was adjusted to 6.5, and a transparent gel was produced by heating and stirring at 100°C; wherein the molar ratio of EDTA, CA and total metal ions in the mixed solution was 1:1.5:1.

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

[0049] Comparative Example 3

[0050] This comparative example presents a method for preparing a perovskite oxide catalyst (PBSCFF3), comprising the following steps:

[0051] S1, Pr(NO3)3·4H2O, Ba(NO3)2, Sr(NO3)2, Co(NO3)2·6H2O, Fe(NO3)3·9H2O and NH4F are dissolved in deionized water in a precise stoichiometric ratio of 2:1:1:3:1:0.06 in a beaker and stirred at 80°C for 60 min to obtain a mixed solution.

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

[0053] S3, the transparent gel was pretreated at 250℃ for 5 h, and then calcined at 950℃ in static air for 10 h to transform it into a homogeneous mixed metal oxide (PrBa) with characteristic perovskite crystals. 0.5 Sr 0.5 ) y Co 1.5 Fe 0.5 O 5-x+δ F x (x = 0.03; y = 1), i.e., perovskite oxide catalyst PBSCFF3.

[0054] The experimental test is as follows:

[0055] 1. The phase composition of the sample from Example 1 and the samples from Comparative Examples 1-3 was determined;

[0056] Figure 1 X-ray diffraction (XRD) patterns of the samples provided in Example 1 and Comparative Examples 1-3 of this application. The phase composition of the samples was determined by XRD patterns; as shown... Figure 1 As shown, the prepared PBSCF, PBSCFF3, and PBSCFA 95 PBSCFF3A 95The catalyst exhibited a pure crystalline phase, with all characteristic peaks corresponding to the lattice structure of PBSCF. This indicates 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 do not cause the perovskite structure to collapse, emphasizing the integrity of the crystal structure in the synthesized material and confirming its perovskite structural characteristics.

[0057] Figure 2 For refined XRD patterns of PBSCF, by Figure 2 As shown, the crystal phase of PBSCF is Pm-3m; Figure 3 The image shows the refined XRD pattern after F element doping. It can be seen that the crystal phase of PBSCFF3 after F element doping is Pnma. Figure 4 PBSCFF3A 95 The refined XRD pattern, by Figure 4 It can be seen that after F element doping and A-site defect construction, PBSCFF3A 95 The crystal phase reverts back to Pm-3m, indicating that after constructing A-site defects and F doping, PBSCFF3A 95 We then return to the cubic phase. The cubic perovskite structure has stronger symmetry, and the density of states near the Fermi level of the cubic structure is usually in a high state. This reduces the activation energy of electronic conductivity and improves the chemical stability and electron transport rate of the catalyst.

[0058] 2. The OER performance of the catalyst in Example 1 and the catalysts in Comparative Examples 1-3 was determined. The test procedure was as follows:

[0059] Step 1: Prepare catalyst ink by dispersing 7 mg of catalyst and 3 mg of acetylene black in a mixture containing 50 μL of 5 wt.% Nafion solution binder. Add ethanol to the mixed solution and sonicate in a water bath at 20 °C for 1 h to ensure thorough dispersion of the catalyst.

[0060] Step 2: Drop 3.5 µL of the prepared catalyst ink onto a surface with an area of ​​0.1256 cm². -2 The working electrode is prepared on a glassy carbon disk electrode;

[0061] Step 3: The test was conducted in a three-electrode configuration controlled by an electrochemical workstation (AUT87986, Metrohm, Autolab BV), in 1 M KOH electrolyte, where saturated Hg / HgO and a carbon rod were used as the reference electrode and counter electrode, respectively.

[0062] In step 1, the catalyst was taken from the catalyst samples of Example 1 and Comparative Examples 1-3, and four experiments were conducted.

[0063] The results are as follows Figure 5As shown, it can be seen that F doping has a positive promoting effect on OER performance, which can improve the electrochemical kinetic performance of the catalyst. Further introduction of A-site defects, such as PBSCFF3A 95 In the catalyst sample, the initial potential is significantly reduced, further improving the OER performance.

[0064] 3. The stability of the catalyst (PBSCFF3A 95 ) in Example 1 was evaluated by using a constant current method;

[0065] The specific process is as follows: under constant current conditions, the measured electrode is charged and discharged, and the change of its potential with time is recorded.

[0066] Step 1: Put a certain proportion of catalyst powder and conductive carbon black into a container, and 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, ultrasonic in the ultrasonic machine for one hour, until the catalyst and conductive carbon black in the slurry are uniformly dispersed in the mixed solution of ethanol and Nafion.

[0067] Step 2: Use a pipette to take 5 uL of slurry and evenly coat it on the GC (glassy carbon) electrode, and air dry naturally.

[0068] Step 3: A three-electrode configuration (AUT87986, Switzerland, Autolab B.V.) controlled by an electrochemical workstation is used, in which a saturated Hg / HgO and a carbon rod are used as a reference electrode and a counter electrode, respectively, and is measured under a current density of 10 mA cm -2 in 1 M KOH electrolyte.

[0069] The evaluation results are shown in Figure 6 , and the OER potential of PBSCFF3A 95 shows excellent stability, and its potential remains basically unchanged during the 150-hour test process in 1 M KOH electrolyte under a current density of 10 mA cm -2 , which shows its long-lasting catalytic stability.

[0070] 4. Assemble a zinc-air battery to determine the performance of the catalyst (PBSCFF3A 95 ) in Example 1 from the self-assembled zinc-air battery;

[0071] The performance test results are shown in Figure 7 , and the OCV (open circuit voltage) of the battery based on PBSCFF3A 95 is 1.47 V, which exceeds the OCV obtained from the Pt / C + RuO2 assembled catalyst, and the recorded OCV of the latter is 1.38 V; the low-cost PBSCFF3A 95Assembled ZAB (zinc-air battery) exhibits discharge performance comparable to commercial high-cost Pt / C + RuO2 catalyst; PBSC FF3A 95 Excellent cycling performance in practical ZAB devices.

[0072] In the description of the present specification, the description referring to the terms "one embodiment", "an example", "a specific example" and the like means that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In the present specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific feature, structure, material or characteristic described can be combined in an appropriate manner in any one or more embodiments or examples.

[0073] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only illustrative of the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for producing a perovskite oxide catalyst, characterized by, The method comprises the following steps: Pr(NO3)3·4H2O, Ba(NO3)2, Sr(NO3)2, Co(NO3)2·6H2O, Fe(NO3)3·9H2O and NH4F are dissolved in deionized water according to a molar ratio of 1.9:0.95:0.95:3:1:0.06, and heated and stirred to obtain a mixed solution; Ethylene diamine tetraacetic acid and citric acid are added to the mixed solution, and heated and stirred to obtain a transparent gel; The transparent gel is preheated and then calcined to obtain a perovskite oxide catalyst PBSCFF3A 95 ; When the mixed solution is prepared, the heating temperature is 80℃, and the stirring time is 60 min; When the transparent gel is prepared, the heating temperature is 100℃.

2. The method for preparing a perovskite oxide catalyst according to claim 1, characterized in that, The molar ratio of ethylene diamine tetraacetic 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, The ethylene diamine tetraacetic acid and citric acid are added to the mixed solution to adjust the pH to 6.

5.

4. The method of claim 1, wherein the perovskite oxide catalyst is prepared by the steps of: preparing a solution of a perovskite oxide precursor; and drying the solution to form a perovskite oxide catalyst. The preheating temperature is 250℃, 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℃, and the time is 10h.

6. A perovskite oxide catalyst characterized by comprising: The method is prepared by using the preparation method of the perovskite oxide catalyst according to any one of claims 1-5.

7. The perovskite oxide catalyst of claim 6 wherein, The molecular formula of the catalyst is: (PrBa 0.5 Sr 0.5 ) 0.95 Co 1.5 Fe 0.5 O 4.97+δ F 0.03 .

8. The perovskite oxide catalyst according to claim 6 or 7 is used in the electrocatalytic oxygen evolution reaction.

Images