Doped perovskite catalyst and preparation method and application thereof

Abstract

The invention relates to a doped perovskite catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts. The doped perovskite catalyst provided by the invention comprises a catalytic substrate and SrMoO4 dispersed in the catalytic substrate, the chemical formula of the catalytic substrate is AaSr (1-a) CobB (1-b) O3, a is greater than or equal to 0.6 and less than 1, b is greater than or equal to 0.1 and less than 1, A is selected from Pr, La or Nd, and B is selected from Fe, Ni or Cu. SrMoO4 is introduced and is partially converted into conductive SrMoO3 under a CO2 reduction condition, and SMO4 and SMO3 derived from SMO4 form a conductive Sr < 2 + > cation trap. By means of a conductive Sr < 2 + > cation trap, segregation of Sr < 2 + > to an electrochemical inert phase can be effectively prevented, and the conductivity of the electrode and the CO2 reduction activity are synchronously improved.

Description

Technical Field

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

[0002] High temperature CO based on solid oxide electrolysis cell (SOEC) 2 Reduction reaction (HT-CO 2 RR) is a feasible path to achieve net-zero emission chemical synthesis. 3 Perovskite oxides are widely used as HT-CO due to their high ionic / electronic conductivity, redox cycle stability and abundant active sites. 2 RR catalysts. However, the current mainstream catalysts (such as La x Sr 1-x MnO 3 ,La 0.8 Sr 0.2 CoO 3 ,La 1-x Sr x Co 0.2 Fe 0.8 O 3 ) After the initial high activity, the A-site Sr 2+ Cations segregate on the surface of the material to form SrCO 3 These electrochemically inert products will block the contact between the active center and the reactants, causing serious attenuation of the ion-oxygen surface exchange coefficient, electronic conductivity and catalytic stability, which will lead to the solid oxide CO 2 The electrolysis device has poor stability and low efficiency.

[0003] Sr 2+ The driving force of segregation mainly comes from two aspects: one is the cation redistribution caused by the free energy difference between the surface and the bulk phase (the phase separation barrier can be overcome at high temperature); the other is the electrostatic interaction between the A-site cations and the oxygen vacancies (Ov). Studies have shown that segregation can be suppressed by reducing the surface Ov concentration by doping with difficult-to-reduce cations (Ti, Nb, Zr, Hf, Al, etc.), or by using the "reverse cation capture" method to prepare Sr 2+ Deplete the surface to avoid precipitation. But HT-CO 2 The more negative potential required for RR (about 1 V lower than the ORR anode of SOEC) will generate additional Ov through the B-site cation desolvation pathway, exacerbating the Sr 2+ In addition, when HT-CO 2 When RR operates beyond the thermoneutral potential (~1.47 V), the exothermic mode is initiated, and the cathode temperature rise further deteriorates the segregation process.

[0004] Therefore, it is necessary to develop a catalytic material with excellent performance to improve its performance in HT-CO 2 Stability in RR, etc., is still extremely challenging. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a doped perovskite catalyst and a preparation method and application thereof, by introducing SrMoO 4 , in CO 2 Partially converted into conductive SrMoO under reducing conditions 3 , SMO 4 and SMO 4 Derivative SMO 3 Composed of "conductive Sr 2+ In this trap, SMO 4 For capturing desolvated Sr 2+ , while SMO 4 SMO formed by (electro)chemical reduction 3 Provides high electronic conductivity. 2+ Cation trap”, which can effectively prevent Sr 2+ Segregation into an electrochemically inert phase simultaneously improves electrode conductivity and CO 2 Reduction activity.

[0006] The first object of the present invention is to provide a doped perovskite catalyst, comprising a catalytic substrate and SrMoO dispersed in the catalytic substrate. 4 ; The chemical formula of the catalytic substrate is A a Sr (1-a) Co b B (1-b) O 3 , 0.6≤a<1, 0.1≤b<1, A is selected from Pr, La or Nd, and B is selected from Fe, Ni or Cu.

[0007] In one embodiment of the present invention, the SrMoO 4 The mass percentage is 10%-50%.

[0008] The second object of the present invention is to provide a method for preparing the doped perovskite catalyst, comprising the following steps: adding a complexing agent and an auxiliary complexing agent to an aqueous solution containing A salt, Sr salt, Co salt, B salt and Mo salt, adjusting the pH to 5-9, and obtaining the doped perovskite catalyst by stirring, heating, drying and calcining.

[0009] In one embodiment of the present invention, the A salt is selected from Pr(NO 3 ) 2 、La(NO 3) 3 and C 4 H 4 nnJC 9 One or more of; And / or, the Sr salt is selected from Sr(NO 3 ) 2 、SrO、SrCO 3 and Sr(OH) 2 One or more of; And / or, the Co salt is selected from Co(NO 3 ) 2 and / or (CH 3 COO 2 Co; And / or, the B salt is selected from Cu(NO 3 ) 2 , (CH 3 COO 2 Cu, Fe(NO 3 ) 3 and Ni(NO 3 ) 2 One or more of; And / or, the Mo salt is selected from H 24 Mo 7 N 6 O 24 and / or (NH 4 ) 3 [PMo 12 O 40 ].

[0010] In one embodiment of the present invention, the complexing agent is citric acid; And / or, auxiliary complexing agent ethylenediaminetetraacetic acid.

[0011] In one embodiment of the present invention, the molar ratio of the total metal ions, the complexing agent and the auxiliary complexing agent is 1:(1-2):(1-2).

[0012] In one embodiment of the present invention, the stirring and heating temperature is 190°C-210°C.

[0013] In one embodiment of the present invention, the calcination temperature is 940° C.-960° C., and the calcination time is 5 h-7 h.

[0014] The third object of the present invention is to provide a solid oxide electrolytic cell, which comprises the doped perovskite catalyst.

[0015] The fourth object of the present invention is to provide a solid oxide electrolytic cell for reducing CO 2Application in the production of CO.

[0016] The technical solution of the present invention has the following advantages over the prior art: (1) The doped perovskite catalyst of the present invention utilizes “conductive Sr 2+ The cation trap strategy introduces SrCO 3 With higher Sr 2+ Chemically stable substances that block Sr through thermodynamic mechanisms 2+ Migration to the inert phase. The trap can continuously capture Sr 2+ The Sr-poor perovskite surface is stably formed, solving the contradiction between high performance and long-term stability. The specific method is to chemically fix Sr 2+ In SrMoO 4 (SMO 4 ), which can be converted in situ into highly conductive SrMoO 3 (SMO 3 ).

[0017] (2) The doped perovskite catalyst described in the present invention improves the stability by an order of magnitude while doubling the current density. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 The structure and morphology of the material before catalytic reaction in the test example of the present invention; wherein a is the X-ray diffraction structure diagram of SPG-19, SPG-3 and PG, and bd is PSCC, 3wt% SMO 4 / PSCC and 19wt% SMO 4 / SEM energy spectrum analysis results of PSCC; Figure 2 The HT-CO of SPG-19, SPG-3 and PG in the test example of the present invention at 1.3V and 0.1atm intake CO partial pressure 2 RR stability comparison results; Figure 3 The morphology of the material after the catalytic reaction in the test example of the present invention; wherein a is the scanning electron microscope image of PG, and b is the scanning electron microscope image of SPG-19; Figure 4 is the photoelectron spectrum of the material after the catalytic reaction in the test example of the present invention; wherein a is the deconvoluted Sr 3d X-ray photoelectron spectrum result of the untested material, b is the deconvoluted Sr 3d X-ray photoelectron spectrum result of the tested material, and c is the ratio of the corresponding Sr species in a and b; Figure 5 The SMO in the test example of the present invention 4 Phase changes of the electrolytic cell after electrolysis test; where a is the phase change of SMO at 0.1atm and 0.3atm CO partial pressures. 4 Electrolyte conductivity of the electrolytic cell at different potentials relative to the open circuit voltage (OCV), b is SMO 4 Comparison of X-ray structure spectra of the electrolytic cell before and after the test in a, and SMO after the test in b in c 4 Transmission electron microscope image of the sample after the sample was cut by focused ion beam; Figure 6 Compared with the original SrO in the test example of the present invention, the molar ratio of SrO and SMO is 1:1 4 X-ray structures after calcination at 400, 600, 800, and 1000 °C for 3 h; Figure 7 In the test example of the present invention, pure CO 2 PSCC and 19wt% SMO in the atmosphere 4 / Results of in situ Raman studies conducted by PSCC; Figure 8 The SrMoO 4 and SrCO 3 Comparison of thermodynamic stability with temperature and CO partial pressure; Fig. 9 The single electrolytic cell with SPG-19 cathode in the test example of the present invention is at 1.3A / cm 2 Stability test results under constant current. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0020] In the present invention, unless otherwise specified, the raw materials used in the preparation of the doped perovskite catalyst were purchased from Aladdin Reagent.

[0021] In the present invention, unless otherwise specified, LSCF and GDC powders were purchased from Ningbo SOFCMAN Energy Technology Co., Ltd. Example 1

[0022] The doped perovskite catalyst and the preparation method thereof of the present invention specifically comprise the following steps: Put 6g Pr(NO 3 ) 2 6H 2 O, 1.458 g Sr(NO 3 )2 、4.51g Co(NO 3 ) 2 6H 2 O, 0.32 g Cu(NO 3 ) 2 ·xH 2 O and 2.13 g H 24 Mo 7 N 6 O 24 ·4H 2 O was dissolved in deionized water, and 14.41 g of citric acid and 14.61 g of ethylenediaminetetraacetic acid (EDTA) were added in sequence, with the molar ratio of total metal ions, citric acid and EDTA being about 1:1.5:1; then the pH was adjusted to 7 with ammonia water, and the mixture was heated to 200 °C with continuous stirring to form a gel and then dried; finally, the doped perovskite catalyst was calcined at 950 °C in an air atmosphere for 6 h to obtain the catalyst; wherein the chemical formula of the catalytic substrate is Pr 0.8 Sr 0.2 Co 0.9 Cu 0.1 O 3 (PSCC), SrMoO 4 (SMO 4 ) is 19% by mass, recorded as 19wt% SMO 4 / PSCC. Comparative Example 1

[0023] The same as Example 1, except that: Sr(NO 3 ) 2 The dosage is 0.911g, H 24 Mo 7 N 6 O 24 ·4H 2 The amount of O used was 0.532 g, and SrMoO 4 The mass percentage of 3% doped perovskite catalyst is denoted as 3wt% SMO 4 / PSCC. Comparative Example 2

[0024] The same as Example 1, except that: Sr(NO 3 ) 2 The dosage is 0.729 g, and H 24 Mo 7 N 6 O 24 ·4H 2 The amount of O is 0, and SrMoO-free 4 The perovskite catalyst is denoted as PSCC. Test Case

[0025] Preparation of solid oxide electrolytic cell: S1, a SSZ substrate with a thickness of about 0.2 mm and a diameter of about 40 mm was prepared by tape casting and sintered at 1500 °C for 5 h; S2, screen printing a GDC barrier layer on both sides of the SSZ substrate, and calcining at 1350°C for 3h to obtain a GDC|SSZ|GDC component; S2, ball-milling LSCF powder and GDC powder at a mass ratio of 60:40 for 12 h, then adding 20 wt % pineol and 10 wt % PMMA binder, and stirring to obtain anode slurry; The materials prepared in Example 1 and Comparative Examples 1-2 were respectively ball-milled with gadolinium-doped ceria (GDC) at a mass ratio of 60:40 for 12 hours to obtain mixed materials (respectively marked as SPG-19, SPG-3 and PG); then 20wt% of pineol and 10wt% of PMMA binder were added and stirred evenly to obtain a cathode slurry.

[0026] S3. Screen print the anode slurry on the GDC|SSZ|GDC component to form the anode layer (effective area 0.2cm 2 ) and calcined at 1150 °C for 2 h; the cathode slurry was screen-printed on the other side of the GDC|SSZ|GDC component to form a cathode layer (effective area 0.5 cm 2 ), calcined at 1050 °C for 2 h, and used silver paste as the current collector to obtain a solid oxide electrolytic cell (SOEC).

[0027] Performance Test: Before the catalytic reaction, XRD characterization of SPG-19, SPG-3 and PG was performed using a PANalytical Empyrean diffractometer (Cu Kα radiation, λ = 1.54Å). Figure 1 As shown in a. Figure 1 As can be seen in a, PSCC adopts the orthorhombic Pnma phase, while SMO 4 It presents tetragonal I41 / a phase with obvious reflection peaks at (112), (004) and (204).

[0028] Before the catalytic reaction, TALOS 200X and JEOL JEM-2100F were used with Oxford X-Max 80T spectrometer to analyze PSCC and 3wt% SMO. 4 / PSCC and 19wt% SMO 4 / PSCC was characterized by SEM and EDS. The results are as follows Figure 1 As shown in bd. Figure 1 As can be seen from the bd, SMO is evenly distributed on the PSCC surface.4 Coverage increases from 0% PSCC to 19wt% SMO 4 / About 50% of PSCC.

[0029] The degradation rates of SPG-19, SPG-3 and PG were tested by constant current timing method. 2 The flow rate of the reactants is 50 sccm / min, the operating temperature is 800°C, and the operating potential is 1.3V. The results are as follows Figure 2 As shown. Figure 2 It can be seen that the decay rate of SPG-19 is 0.1% h -1 , compared with PG's 1.17% h -1 and 1.63% h of SPG-3 -1 One order of magnitude lower, indicating that SPG-19 has excellent stability.

[0030] After the catalytic reaction, SPG-19 and PG were characterized using a Zeiss G500 scanning electron microscope. Figure 3 As shown. Figure 3 It can be seen that there are precipitated cobalt-copper nanoparticles and lamellar strontium element aggregation layers on the surface of PG, while there is no strontium enrichment phenomenon on the surface of SPG-19 except for the precipitated cobalt-copper nanoparticles, which shows that SMO 4 Inhibition of Sr segregation.

[0031] The surface composition of SPG-19, SPG-3 and PG before and after catalytic reaction was analyzed by photoelectron spectroscopy (XPS, ULTRA DLD). Figure 4 As shown. Figure 4 It can be seen that with the SMO 4 The increase of Sr content 2+ In the case of pristine PG, due to surface redistribution, there is Sr 2+ In CO 2 In SPG-3 before electrolysis, Sr 2+ Surface redistribution and SMO 4 The formation of Sr 2+ Spectrum. 2 After RR test, PG's Sr 2+ The proportion increased from 76.2% to 86.6% in SPG-3 and from 88.5% to 94.3% in SPG-19. No Sr species agglomeration appeared in SPG-19. 2+ SrCO 3 Form segregation.

[0032] In order to explore the 4 Improved HT-CO 2Other possibilities of RR, preparation using only SMO 4 Batteries as catalysts (i.e. SMO 4 Electrolytic cell) for HT-CO 2 RR; Electrochemical impedance spectroscopy was used to test the SMO 4 The structural analysis was performed by PANalytical Empyrean diffractometer and TALOS 200X. Figure 5 As shown. Figure 5 As can be seen in a, when the applied voltage is swept from 0 to 900mV vs OCV, SMO 4 The conductivity of the electrolytic cell increased by about two orders of magnitude. Specifically, the conductivity at OCV was ~3.1×10 -6 Scm -1 , 4.5×10 at 0.3atm PCO - 6 Scm -1 , and then increased to 5.1±1.4×10 at 900mV -4 Scm -1 .from Figure 5 As can be seen in b, SrMoO 3 (SMO 3 ) does exist, and the perovskite oxide has 10 4 Scm -1 The high electronic conductivity of the material is indicated by the cubic phase diffraction peaks at (110), (200), and (211). Figure 5 As can be seen in Figure c, the combination of focused ion beam (FIB) and TEM has enabled the bulk SMO 4 SMO was identified within about 3nm of the surface 3 In summary, SMO 4 Under applied potential, the conductivity increases significantly, and the surface is covered with in-situ generated SMO 3 Nanoshell, demonstrating that SMO 3 The conductivity of the catalyst is improved and the SMO 3 Easily oxidized to SMO 4 , confirm the conductivity of Sr 2+ Traps by SMO 4 and SMO 4 Derived SMO 3 composition.

[0033] PANalytical Empyrean diffractometer was used to analyze the molar ratio of SrO and SMO in 1:1 ratio. 4 The crystal structures of the samples calcined at 400℃, 600℃, 800℃ and 1000℃ for 3h were analyzed. Figure 6 As shown. Figure 6 It can be seen that the disappearance of the SrO (100) reflection peak during the sintering process indicates that SrO and SMO 4 Solid phase reaction occurs, SMO 4 It can react the surface-enriched Sr element. When SrO and SMO are calcined in a 1:1 molar ratio 4 When the product is Sr 11 Mo 4 O 23 and Sr 2 MoO 4 This further confirms that SMO 4 In a wide range of Sr 2+ Capability to capture continuously at segregation levels.

[0034] In-situ Raman spectroscopy was used to characterize the surface state of PG and SPG-19 under working conditions. Figure 7 As shown. Figure 7 It can be seen that during the reaction of PG, Sr element segregated, with SrCO 3 The morphology exists on the PG surface, while SPG-19 has no Sr segregation during the reaction.

[0035] Density functional theory was used to calculate the SrMoO 4 and SrCO 3 The relationship between formation energy and CO partial pressure is as follows: Figure 8 As shown. Figure 8 It can be seen that at 800 °C and 0.3 atm CO atmosphere, SrCO 3 and SrMoO 4 The energy difference between atoms is 0.46 eV -1 Description SrMoO 4 The formation of SrCO 3 The formation of SrMoO 4 The preference of reacting free Sr ions.

[0036] The 0.2 cm2 SPG-19 cathode was tested by constant current timing method. 2 Button battery, at high current density (1.3A / cm 2 The stability of the constant current) is shown in the following figure. Fig. 9 As shown. Fig. 9 It can be seen that SPG-19 runs smoothly without obvious decline, proving that SMO 4 It has a positive effect on improving the stability of catalysts.

[0037] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A doped perovskite catalyst, characterized in that: It includes a catalytic substrate, and SrMoO4 ​​dispersed in the catalytic substrate; The chemical formula of the catalytic substrate is A a Sr (1-a) Co b B (1-b) O3, 0.6≤a<1, 0.1≤b<1, A is selected from Pr, La or Nd, and B is selected from Fe, Ni or Cu.

2. The doped perovskite catalyst according to claim 1, characterized in that The mass percentage of SrMoO4 ​​is 10%-50%.

3. The method for preparing the doped perovskite catalyst according to any one of claims 1 or 2, characterized in that: The following steps are involved: Add a complexing agent and an auxiliary complexing agent to an aqueous solution containing A salt, Sr salt, Co salt, B salt and Mo salt, adjust the pH to 5-9, and obtain the doped perovskite catalyst by stirring, heating, drying and calcining.

4. The method for preparing a doped perovskite catalyst according to claim 3, characterized in that: The A salt is selected from one or more of Pr(NO3)2, La(NO3)3 and C4H4NNbO9; and / or, the Sr salt is selected from one or more of Sr(NO3)2, SrO, SrCO3 and Sr(OH)2; and / or, the Co salt is selected from Co(NO3)2 and / or (CH3COO)2Co; and / or, the B salt is selected from one or more of Cu(NO3)2, (CH3COO)2Cu, Fe(NO3)3 and Ni(NO3)2; And / or, the Mo salt is selected from H 24 Mo7N6O 24 and / or (NH4)3[PMo 12 O 40 ].

5. The method for preparing a doped perovskite catalyst according to claim 3, characterized in that: The complexing agent is citric acid; And / or, auxiliary complexing agent ethylenediaminetetraacetic acid.

6. The method for preparing a doped perovskite catalyst according to claim 3, characterized in that: The molar ratio of the total metal ions, the complexing agent and the auxiliary complexing agent is 1:(1-2):(1-2).

7. The method for preparing a doped perovskite catalyst according to claim 3, characterized in that: The stirring and heating temperature is 190°C-210°C.

8. The method for preparing a doped perovskite catalyst according to claim 3, characterized in that: The calcination temperature is 940° C.-960° C., and the calcination time is 5 h-7 h.

9. A solid oxide electrolytic cell, characterized in that: The solid oxide electrolytic cell comprises the doped perovskite catalyst according to any one of claims 1 or 2.

10. Use of the solid oxide electrolytic cell according to claim 9 in reducing CO2 to produce CO.

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