Surface-reconstructed oxygen electrode material, preparation method thereof and proton ceramic electrolytic tank

Abstract

The invention relates to a surface-reconstructed oxygen electrode material, a preparation method thereof and a proton ceramic electrolytic tank, and belongs to the technical field of solid oxide fuel. After in-situ treatment, the nano spinel is uniformly distributed on the surface of the parent-phase perovskite type oxide, so that more active sites can be provided for exchange and transmission of oxygen, meanwhile, desorption of oxygen is promoted, and the reaction is accelerated. After in-situ treatment, the polarization impedance of the oxygen electrode is reduced, and the electrochemical activity is obviously improved.

Description

Technical Field

[0001] The present invention relates to an oxygen electrode material with surface reconstruction, a preparation method thereof, and a proton ceramic electrolytic cell, belonging to the technical field of solid oxide fuel. Background Art

[0002] Proton ceramic electrolytic cells (PCECs) have high potential for efficient energy conversion and storage, and excellent chemical stability and mechanical strength, enabling them to operate stably at high temperatures for a long time, avoiding the corrosion and leakage problems common in traditional liquid electrolyte cells. In addition, the low proton migration potential can reduce the operating temperature (400 - 600 °C), and the medium-temperature operation characteristics can further improve the energy utilization efficiency by using waste heat and other heat sources (such as industrial waste heat and solar heat), showing great potential in both comprehensive energy utilization and environmental protection.

[0003] As one of the core components of proton ceramic electrolytic cells, the oxygen electrode mainly undergoes a water oxidation reaction. On the one hand, affected by the low efficiency of the OER reaction, the active oxygen needs a longer diffusion distance to react with protons, resulting in a large polarization impedance and unsatisfactory electrolysis efficiency. On the other hand, most commonly used oxygen electrode materials for PCECs are still traditional mixed ion and electron conducting materials, and their stability and electrochemical activity are severely challenged in a harsh electrochemical environment (high temperature and high humidity conditions). In addition, at a lower operating temperature, its extremely low intrinsic proton conductivity also makes its catalytic activity unsatisfactory. The existence of these problems hinders the reliability and lifespan of PCECs in practical applications and urgently needs to be solved through innovation in material and structure design. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an oxygen electrode material with surface reconstruction, a preparation method thereof, and a proton ceramic electrolytic cell.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows.

[0006] An oxygen electrode material with surface reconstruction, the oxygen electrode material is composed of two phases, cubic perovskite-type oxide and nano-spinel oxide, and the nano-spinel oxide adheres to the surface of the cubic perovskite-type oxide;

[0007] Among them, the chemical formula of the cubic perovskite-type oxide is Sr2Fe 1.5-x M x Mo 0.5 O 6-δ , M is a transition metal element nickel, copper or cobalt, δ is the oxygen vacancy content, x is 0.1 - 0.3; the nano-spinel oxide is NiFe2O4 nanoparticles.

[0008] Preferably, the nano-spinel oxide accounts for 3% to 8% of the total mass of the oxygen electrode material.

[0009] A method for preparing the surface-reconstructed oxygen electrode material of the present invention, the method steps include:

[0010] (1) Weigh soluble salts of strontium, iron, M, and molybdenum according to the stoichiometric ratio, add them to deionized water, and dissolve to obtain a mixed salt solution; add ethylenediaminetetraacetic acid (EDTA) and citric acid (CA), then dropwise add ammonia water until the solution pH is 7 to 8, heat and stir to volatilize the water to obtain a gel-like substance, dry it at 200 - 300 °C for 2 - 3 h to obtain a precursor material;

[0011] (2) Sinter the precursor material in air to obtain a perovskite-type oxide;

[0012] (3) Perform a reduction treatment on the perovskite-type oxide to precipitate Ni-Fe alloy from the perovskite-type oxide structure during the reduction process; then perform a hydration treatment to form stable NiFe2O4 spinel attached to the surface of the perovskite-type oxide to obtain a surface-reconstructed oxygen electrode material.

[0013] Preferably, in step (1), the soluble salt is nitrate or carbonate.

[0014] Preferably, in step (1), the molar ratio of metal elements, EDTA, and CA in the mixed salt is 1:1 - 1.5:1 - 1.5.

[0015] Preferably, in step (1), the heating temperature is 80 - 90 °C.

[0016] Preferably, in step (2), the sintering temperature is 1100 - 1200 °C, and the sintering time is 5 - 10 h.

[0017] Preferably, in step (3), during the reduction treatment, the treatment atmosphere is a mixed gas of hydrogen and argon, and the volume fraction of hydrogen in the mixed gas is 10% - 50%.

[0018] Preferably, in step (3), during the reduction treatment, the treatment temperature is 600 - 700 °C, and the treatment time is 1 - 5 h.

[0019] Preferably, in step (3), during the hydration treatment, the treatment atmosphere is a mixed gas of water vapor and argon, and the volume fraction of water vapor in the mixed gas is 3% - 10%.

[0020] Preferably, in step (3), during the hydration treatment, the treatment temperature is 600 - 700 °C, and the treatment time is 1 - 5 h.

[0021] A proton ceramic electrolyzer, wherein the oxygen electrode material of the electrolyzer is a surface-reconstructed oxygen electrode material as described in the present invention.

[0022] Beneficial effects

[0023] Based on the strategy of surface reconstruction, the present invention provides a surface-reconstructed oxygen electrode material, its preparation method and a proton ceramic electrolyzer. After in-situ treatment, nano-spinel is uniformly distributed on the surface of the parent-phase perovskite-type oxide, which can provide more active sites for the exchange and transport of oxygen, and at the same time promote the desorption of oxygen and accelerate the reaction. After in-situ treatment, the polarization impedance of the oxygen electrode is reduced and the electrochemical activity is significantly improved. Description of the drawings

[0024] Figure 1 XRD patterns of the sample of SFM perovskite calcined in air atmosphere at 1100 °C for 5 h and cooled to room temperature in Example 1; the sample after reduction treatment (R-SFNM); the sample after rehydration treatment (sp-SFNM).

[0025] Figure 2 XRD patterns of the sample of SFM perovskite calcined in air atmosphere at 1100 °C for 5 h and cooled to room temperature in Example 2; the sample after reduction treatment (R-SFCM); the sample after rehydration treatment (sp-SFCM).

[0026] Figure 3 Cross-sectional micrograph of a single electrolyzer with Ni + BZCYYb as the anode, BZCYYb as the electrolyte, and sp-SFNM as the oxygen electrode in Example 1.

[0027] Figure 4 I-V curve of the electrolyzer in Example 1.

[0028] Figure 5 Hydrogen production rate of the electrolyzer described in Example 1.

[0029] Figure 6 Faraday efficiency of the electrolyzer described in Example 1.

[0030] Figure 7 Constant voltage electrolysis test chart of the electrolyzer described in Example 1 at 650 °C and 1.3 V voltage for up to 250 h. Specific embodiments

[0031] The present invention will be further described in detail below with reference to specific embodiments.

[0032] Example 1

[0033] (1) Weigh Sr(NO3)2·6H2O, Fe(NO3)3·9H2O, Ni(NO3)2·6H2O and (NH4)6Mo7O 24 ·4H2O according to the stoichiometric ratio, add deionized water and stir to dissolve, obtaining a clear mixed salt solution; then add ethylenediaminetetraacetic acid (EDTA) and citric acid monohydrate (CA), with the molar ratio of metal elements, EDTA and CA being 1:1.5:1.5, and then dropwise add ammonia water until the pH of the solution is between 7 and 8. Under the condition of heating (80 - 90 °C) and stirring, let the water evaporate to obtain a gel-like substance; place the gel-like substance in an oven at 250 °C and dry it for 2 h to obtain the precursor material (SFM perovskite).

[0034] (2) Sinter the precursor material in air at 1100 °C for 5 h to obtain the perovskite-type oxide Sr2Fe 1.5 Ni 0.1 Mo 0.4 O 6-δ 。

[0035] (3) Conduct a reduction treatment on the perovskite-type oxide to precipitate the Ni-Fe alloy from the perovskite-type oxide structure during the reduction process; then conduct a hydration treatment to form a stable NiFe2O4 spinel of the Ni-Fe alloy attached to the surface of the perovskite-type oxide, obtaining a surface-reconstructed oxygen electrode material;

[0036] Among them, during the reduction treatment, the treatment atmosphere is a mixed gas of hydrogen and argon, the volume fraction of hydrogen in the mixed gas is 50%, the treatment temperature is 600 °C, and the treatment time is 5 h; during the hydration treatment, the treatment atmosphere is a mixed gas of water vapor and argon, the volume fraction of water vapor in the mixed gas is 10%, the treatment temperature is 600 °C, and the treatment time is 5 h.

[0037] Preparation of fuel electrode powder: Add nickel oxide: BZCYYb4411: corn starch to a mortar according to a mass ratio of 3:2:1 by mass fraction, and add an appropriate amount of 5 wt% polyvinyl alcohol (PVA) solution as a binder, and grind thoroughly until obtaining NiO-BZCYYb powder as the fuel electrode.

[0038] Preparation of half-cell: The proton conductor BZCYYb4411 is used as the electrolyte material; the NiO-BZCYYb powder is used as the fuel electrode material. Use a 200-mesh sieve, screen an appropriate amount of electrolyte powder into a tablet die, and then weigh about 0.3 g of fuel electrode powder and spread it evenly on the electrolyte powder. Prepare a half-cell of fuel electrode-supported PCECs by co-pressing method (18 MPa, 3 min). Sinter the pressed half-cell in a muffle furnace at 1400 °C for 8 h.

[0039] Screen printing: The electrode powder, ethyl cellulose, and soluble starch were mixed at a weight ratio of 1:0.12:0.08 and an appropriate amount of terpineol was added, and then they were ground thoroughly to obtain a slurry (where the soluble starch was a pore-forming agent and the ethyl cellulose was a binder). The electrode was printed on the other side of the electrolyte by screen printing, and then sintered in a muffle furnace at 600 °C for 2 h to remove the ethyl cellulose and soluble starch in the slurry, obtaining a complete full cell.

[0040] Connection of the current collector: Silver paste was coated on the surface of the oxygen electrode as the current collector and sintered in a tube furnace at 750 °C for 30 min.

[0041] Testing: In order to measure the electrochemical performance of the prepared oxygen electrode material during the actual working process in the PCEC, an AUTOLAB 302N electrochemical workstation was used to conduct electrolysis tests and long-term stability tests on a single electrolytic cell. During electrolysis, argon-oxygen water vapor (pH2O = 0.1 atm) was introduced into the oxygen electrode side at a flow rate of 100 mL·min -1 ; hydrogen was introduced into the fuel electrode side at a flow rate of 20 mL·min -1 to reduce NiO.

[0042] In this example, the XRD test results of the precursor material, the sample after reduction treatment and hydration treatment are as Figure 1 shown.

[0043] In this example, the microscopic morphology of the single electrolytic cell is as Figure 3 shown. The I-V curve of the electrolytic cell is as Figure 4 shown. The hydrogen production rate of the electrolytic cell is as Figure 5 shown. The Faraday efficiency of the electrolytic cell is as Figure 6 shown. The results of the constant voltage electrolysis test of the electrolytic cell at 650 °C and 1.3 V for up to 250 h are as Figure 7 shown.

[0044] Example 2

[0045] (1) Sr(NO3)2·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, and (NH4)6Mo7O 24 ·4H2O were weighed according to the stoichiometric ratio, deionized water was added and stirred to dissolve, obtaining a clear mixed salt solution; then ethylenediaminetetraacetic acid (EDTA) and citric acid monohydrate (CA) were added, and the molar ratio of metal elements, EDTA, and CA was 1:1.5:1.5. Then ammonia water was added dropwise until the pH of the solution was between 7 and 8, and the water was volatilized under the condition of heating (80 - 90 °C) and stirring to obtain a gel-like substance; the gel-like substance was placed in an oven at 250 °C and dried for 2 h to obtain the precursor material.

[0046] (2) Sinter the precursor material in air at 1100 °C for 5 h to obtain a perovskite-type oxide Sr2Fe 1.5 Ni 0.1 Mo 0.4 O 6-δ .

[0047] (3) Perform a reduction treatment on the perovskite-type oxide to precipitate Co-Fe alloy from the perovskite-type oxide structure during the reduction process; then perform a hydration treatment to form stable CoFe2O4 spinel attached to the surface of the perovskite-type oxide, obtaining a surface-reconstructed oxygen electrode material;

[0048] Among them, during the reduction treatment, the treatment atmosphere is a mixed gas of hydrogen and argon, the volume fraction of hydrogen in the mixed gas is 50%, the treatment temperature is 600 °C, and the treatment time is 5 h; during the hydration treatment, the treatment atmosphere is a mixed gas of water vapor and argon, the volume fraction of water vapor in the mixed gas is 10%, the treatment temperature is 600 °C, and the treatment time is 5 h.

[0049] In this embodiment, the XRD test results of the precursor material, the sample after reduction treatment and hydration treatment are as Figure 2 shown.

[0050] In summary, the invention includes but is not limited to the above embodiments. Any equivalent replacement or partial improvement carried out under the spirit and principle of the present invention will be regarded as within the protection scope of the present invention.

Claims

1. A surface-reconstructed oxygen electrode material, characterized in that: The oxygen electrode material consists of two phases, cubic perovskite-type oxide and nano-spinel oxide, and the nano-spinel oxide adheres to the surface of the cubic perovskite-type oxide; Among them, the chemical formula of the cubic perovskite-type oxide is Sr2Fe 1.5-x M x Mo 0.5 O 6-δ , where M is a transition metal element nickel, copper or cobalt, δ is the oxygen vacancy content, x is 0.1 to 0.3; the nano-spinel oxide is NiFe2O4 nanoparticles.

2. The surface-reconstructed oxygen electrode material according to claim 1, characterized in that: The nano-spinel oxide accounts for 3% - 8% of the total mass of the oxygen electrode material.

3. A method for preparing the surface-reconstructed oxygen electrode material according to claim 1 or 2, characterized in that: The method steps include: (1) Weigh soluble salts of strontium, iron, M, and molybdenum according to the stoichiometric ratio, add them to deionized water, and dissolve to obtain a mixed salt solution; add EDTA and CA, then dropwise add ammonia water until the pH of the solution is 7 - 8, heat and stir to volatilize the water to obtain a gel-like substance, dry it at 200 - 300 °C for 2 - 3 h to obtain a precursor material; (2) Sinter the precursor material in air to obtain a perovskite-type oxide; (3) Perform a reduction treatment on the perovskite-type oxide to precipitate Ni-Fe alloy from the perovskite-type oxide structure during the reduction process; then perform a hydration treatment to form a stable NiFe2O4 spinel of the Ni-Fe alloy adhering to the surface of the perovskite-type oxide to obtain a surface-reconstructed oxygen electrode material.

4. The preparation method of a surface-reconstructed oxygen electrode material according to claim 3, characterized in that: In step (1), the soluble salt is a nitrate or a carbonate; And / or, the molar ratio of the metal elements, EDTA, and CA in the mixed salt is 1:1 - 1.5:1 - 1.5; And / or, the heating temperature is 80 - 90 °C.

5. The preparation method of an oxygen electrode material with surface reconstruction according to claim 3, characterized in that: In step (2), the sintering temperature is 1100 - 1200 °C, and the sintering time is 5 - 10 h.

6. The preparation method of an oxygen electrode material with surface reconstruction according to claim 3, characterized in that: In step (3), during the reduction treatment, the treatment atmosphere is a mixed gas of hydrogen and argon, and the volume fraction of hydrogen in the mixed gas is 10% - 50%.

7. The preparation method of an oxygen electrode material with surface reconstruction according to claim 3 or 6, characterized in that: In step (3), during the reduction treatment, the treatment temperature is 600 - 700 °C, and the treatment time is 1 - 5 h.

8. The preparation method of a surface-reconstructed oxygen electrode material according to claim 3, characterized in that: In step (3), during the hydration treatment, the treatment atmosphere is a mixed gas of water vapor and argon, and the volume fraction of water vapor in the mixed gas is 3% - 10%.

9. The preparation method of an oxygen electrode material with surface reconstruction according to claim 3 or 8, characterized in that: In step (3), during the hydration treatment, the treatment temperature is 600 - 700 °C, and the treatment time is 1 - 5 h.

10. A proton ceramic electrolytic cell, characterized in that: The oxygen electrode material of the electrolytic cell is a surface-reconstructed oxygen electrode material as described in claim 1 or 2.

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