Oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure, its preparation and application

Abstract

The present invention belongs to the technical field of reversible proton ceramic electrochemical cells, and discloses an oxygen electrode material with a self-assembled heterostructure for reversible proton ceramic electrochemical cells, and its preparation and application. The oxygen electrode material has a biphasic structure of Ba 0.8 Gd 0.8‑x Pr 0.4 Co 2‑y O 5+δ and Gd x Co y O 3‑δ to form a heterostructure in which Gd x Co y O 3‑δ nanoparticles are coated on the surface of the Ba 0.8 Gd 0.8‑x Pr 0.4 Co 2‑y O 5+δ skeleton; where 0 < x < 0.8, 0 < y < 0.8. The present invention also discloses a preparation method of the oxygen electrode material. The structure of the oxygen electrode material of the present invention provides more reaction sites for the oxygen reduction reaction and the oxygen evolution reaction. When this material is applied to a reversible proton ceramic electrochemical cell, it has a high power density (cell mode) / current density (electrolysis mode) and excellent long-term cyclic operation stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of proton ceramic electrochemical cells, and particularly relates to an oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure, and its preparation and application. Background Art

[0002] With the development of human society and the acceleration of the industrialization process, the consumption of fossil fuels such as coal, oil and natural gas is increasing continuously, exacerbating the global energy crisis and environmental pollution. The traditional energy structure dominated by fossil fuels is accelerating its transformation towards a green and low-carbon one dominated by renewable energy. Solid Oxide Cells (SOCs) have the characteristics of strong fuel adaptability, high energy conversion efficiency, environmental friendliness, etc., and are considered to be one of the energy storage and conversion technologies with great development potential and application prospects. SOCs can operate in two modes: in the Fuel Cell (FC) mode, the chemical energy of various fuels (including hydrogen, hydrocarbons, liquefied petroleum gas, biogas, ammonia, etc.) can be directly converted into electrical energy to provide clean secondary energy; in the Electrolysis Cell (EC) mode, it can effectively utilize intermittent renewable energies such as wind energy, solar energy, tidal energy, etc. to produce hydrogen or high-value carbon-containing fuels, thereby converting the intermittent energy into chemical energy stored temporarily in the fuels for later transportation and further utilization. However, due to the high operating temperature (700 - 900 °C) and the problem of fuel electrode metal oxidation caused by fuel dilution, the traditional SOCs system based on oxygen ion conduction is not suitable for reversible operation. In recent years, Reversible Protonic Ceramic Electrochemical Cells (R-PCECs) based on proton conduction have received great attention. Compared with the conduction of oxygen ions, the conduction of protons has a lower activation energy, which enables R-PCECs to operate in the medium and low temperature range of 500 - 700 °C. In addition, whether in the FC mode or the EC mode, steam only exists on the oxygen electrode side, and there is no risk of oxidation of the metal on the fuel electrode side. When producing hydrogen by electrolyzing water, pure hydrogen is generated on the fuel electrode side without further purification.

[0003] In R-PCECs, the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the oxygen electrode are the main factors limiting their electrochemical performance. An ideal oxygen electrode material not only needs to have high ionic and electronic conductivity but also should have sufficient tolerance to the harsh operating conditions in practical applications (such as air containing pollutants or high-concentration water vapor, etc.). Summary of the Invention

[0004] The object of the present invention is to provide an oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure, as well as its preparation and application. The oxygen electrode material of the present invention has Gd x Co y O 3-δ (GCO) nanoparticles coated on the surface of a Ba 0.8 Gd 0.8- x Pr 0.4 Co 2-y O 5+δ (BGPC) framework, and this structure provides more reaction sites for ORR or OER. The present invention applies this material to the oxygen electrode of a reversible proton ceramic electrochemical cell, achieving a high power density (in battery mode) / current density (in electrolysis mode) and excellent long-term operating stability.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] An oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure, having a biphasic structure of Ba 0.8 Gd 0.8- x Pr 0.4 Co 2-y O 5+δ and Gd x Co y O 3-δ to form a heterostructure (GCO-BGPC) in which Gd x Co y O 3-δ nanoparticles are coated on the surface of the Ba 0.8 Gd 0.8- x Pr 0.4 Co 2-y O 5+δ framework; where 0 < x < 0.8, 0 < y < 0.8; 0 < δ < 1, and δ is the oxygen vacancy content.

[0007] The preparation method of the oxygen electrode material of the reversible proton ceramic electrochemical cell comprises the following steps: Barium nitrate, gadolinium nitrate, praseodymium nitrate, and cobalt nitrate are prepared by the sol-gel method according to the chemical formula Ba 0.8 Gd 0.8 Pr 0.4 Co 2 O 5+δ to obtain the oxygen electrode material.

[0008] Specifically, it comprises the following steps:

[0009] Barium nitrate, gadolinium nitrate, praseodymium nitrate, and cobalt nitrate are dissolved in water according to the chemical formula Ba 0.8 Gd 0.8 Pr 0.4 Co 2 O 5+δ in a stoichiometric ratio, citric acid monohydrate and ethylenediaminetetraacetic acid are added to form a mixed solution; the pH of the solution is adjusted to 7-8; it is continuously heated and stirred evenly, and a gel-like substance is obtained after the water is fully volatilized; then the gel-like substance is heat-treated and calcined to obtain the required oxygen electrode material.

[0010] The molar ratio of the total metal ions of Ba, Gd, Pr, and Co: citric acid monohydrate: ethylenediaminetetraacetic acid is (0.5-1.5): (1.5-2.5): (0.5-1.5).

[0011] The temperature of the continuous heating is 100-150 °C;

[0012] The rotation speed of the uniform stirring is 200-300 r / min;

[0013] Adjusting the pH to 7-8 means dropping ammonia water to adjust the pH value to 7-8;

[0014] The conditions for heat-treating the gel-like substance: keep warm at 250-300 °C for 5-10 h;

[0015] The temperature of the calcination is 900-1000 °C, and the calcination time is 2-5 h.

[0016] The above-mentioned oxygen electrode material is applied to a reversible proton ceramic electrochemical cell. The application refers to the application as the oxygen electrode of a reversible proton ceramic electrochemical cell.

[0017] Specifically, it comprises the following steps: The oxygen electrode material, ethyl cellulose, and terpineol are mixed evenly to obtain the required GCO-BGPC oxygen electrode paste; the paste is evenly coated on the half-cell supported by the fuel electrode, dried, and calcined to obtain a reversible proton ceramic electrochemical cell with a GCO-BGPC porous oxygen electrode.

[0018] The mass ratio of the oxygen electrode powder: ethyl cellulose: terpineol is (0.5 - 1.5):(0.02 - 0.06):(0.38 - 1.14).

[0019] The drying temperature is 60 - 90 °C.

[0020] The calcination temperature is 950 - 1000 °C, and the calcination time is 2 - 4 h.

[0021] The half - cell of the fuel electrode support includes a fuel electrode and an electrolyte; the fuel electrode is disposed on one side of the electrolyte. The oxygen electrode slurry is coated on the other side of the electrolyte.

[0022] The proton - conducting reversible proton ceramic electrochemical cell of the present invention is prepared by the co - casting method, and its structure sequentially includes a fuel electrode, an electrolyte, and an oxygen electrode. The oxygen electrode is the above - mentioned GCO - BGPC oxygen electrode. The electrolyte is BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb). The fuel electrode is a composite electrode composed of NiO and BZCYYb with a mass ratio of (6 - 7):(4 - 3).

[0023] The present invention formulates raw materials according to the stoichiometric ratio of Ba 0.8 Gd 0.8 Pr 0.4 Co 2 O 5+δ Through the sol - gel method, after calcination, they self - assemble into a biphasic structure of Gd x Co y O 3-δ and Ba 0.8 Gd 0.8-x Pr 0.4 Co 2-y O 5+δ to form a heterogeneous structure in which Gd x Co y O 3-δ nanoparticles are coated on the surface of the Ba 0.8 Gd 0.8-x Pr 0.4 Co 2-y O 5+δ skeleton (GCO - BGPC).

[0024] The present invention evaluates the phase structure, chemical compatibility, electrochemical performance, hydrogen production and Faraday efficiency under the electrolysis mode of the oxygen electrode material. The oxygen electrode material of the present invention has a stable phase structure, good chemical compatibility, high power density and electrolysis current, excellent battery stability, and reasonable hydrogen production and Faraday efficiency under the electrolysis mode.

[0025] The present invention has the following beneficial effects:

[0026] The oxygen electrode material GCO-BGPC of the reversible proton ceramic electrochemical cell with self-assembled heterostructure involved in the present invention is prepared by the sol-gel method, and has a stable phase structure, good chemical compatibility, high power density and electrolysis current, excellent battery stability, and reasonable hydrogen production and Faraday efficiency under the electrolysis mode.

[0027] (1) The preparation method is simple

[0028] The double perovskite BGPC coated with GCO nanoparticles of heterostructure is synthesized in one step by a simple sol-gel method, and the synthesis method is simple and efficient.

[0029] (2) Stable structure and good chemical compatibility

[0030] In-situ high-temperature X-ray diffraction (XRD) analysis shows that the prepared GCO-BGPC oxygen electrode material has a stable phase structure. Compatibility analysis shows that the prepared GCO-BGPC oxygen electrode does not undergo obvious chemical reactions with the proton-conducting BZCYYb electrolyte under the actual operating conditions of the electrochemical cell.

[0031] (3) Excellent electrochemical performance

[0032] The maximum output powers of the reversible proton ceramic electrochemical cell Ni-BZCYYb|BZCYYb|GCO-BGPC with GCO-BGPC as the oxygen electrode can reach 1.365, 0.909 and 0.589 W cm at 700, 650 and 600 °C respectively in the fuel cell mode -2 ; the electrolysis current densities reach 3.458, 2.335 and 1.323 A cm at 700, 650 and 600 °C and a voltage of 1.3 V in the electrolysis cell mode -2 . In addition, the single cell has good stability when operating in the fuel cell mode, electrolysis mode and reversible mode. At 600 °C and a water content of 30%, when the current density is +0.5 A cm -2 , the Faraday efficiency of water electrolysis is ~86.69%, and the hydrogen production rate is ~2.810 ml min -1 cm -2 ; when the current density is +0.75 A cm -2At this time, the Faraday efficiency of water electrolysis is ~62.21%, and the hydrogen production rate is ~3.250 ml min -1 cm -2 . Description of the Drawings

[0033] Figure 1 SEM image of the GCO-BGPC powder related to the present invention;

[0034] Figure 2 XRD and its refined pattern of the GCO-BGPC powder related to the present invention;

[0035] Figure 3 TEM image of the GCO-BGPC powder related to the present invention;

[0036] Figure 4 High-temperature XRD pattern of the GCO-BGPC powder related to the present invention from 25°C to 700°C; where (a) is the test pattern in the angular range of 20 - 80°, and (b) is the test pattern in the angular range of 31 - 35°;

[0037] Figure 5 High-temperature in-situ XRD pattern of the GCO-BGPC powder related to the present invention when humidified air containing 3% by volume of water vapor is introduced at 600°C from 0 h to 6 h; where (a) is the test pattern in the angular range of 20 - 80°, and (b) is the test pattern in the angular range of 32 - 34.5°;

[0038] Figure 6 XRD pattern of the GCO-BGPC powder related to the present invention after being mixed evenly with BZCYYb electrolyte powder in a mass ratio of 1:1 and calcined at 950°C for 2 h;

[0039] Figure 7 Polarization impedance spectrum of the symmetrical cell (GCO-BGPC|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode and BZCYYb as the electrolyte related to the present invention at a flow rate of 100 mL min -1 and under humidified air containing 3% by volume of water vapor in the temperature range of 700 - 500°C;

[0040] Figure 8 Activation energy curve obtained by calculating the results of the polarization impedance spectrum of the symmetrical cell (GCO-BGPC|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode and BZCYYb as the electrolyte related to the present invention in the temperature range of 700 - 500°C;

[0041] Figure 9The GCO-BGPC involved in the present invention is an oxygen electrode, and the symmetrical cell (GCO-BGPC|BZCYYb|GCO-BGPC) prepared with BZCYYb as the electrolyte is tested for polarization impedance stability at 600 °C for 100 h under humidified air with a flow rate of 100 mL min -1 and containing 3% volume fraction of water vapor;

[0042] Figure 10 The fuel electrode-supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode involved in the present invention has a battery mode (30 mL min is introduced into the fuel electrode side -1 and humidified hydrogen containing 3% volume fraction of water vapor, and the oxygen electrode side is ambient air) within the temperature range of 700 - 600 °C; the impedance spectrum is tested;

[0043] Figure 11 The fuel electrode-supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode involved in the present invention has an I-V-P curve graph tested in the fuel cell mode (30 mL min is introduced into the fuel electrode side -1 and humidified hydrogen containing 3% volume fraction of water vapor, and the oxygen electrode side is ambient air) within the temperature range of 700 - 600 °C;

[0044] Figure 12 The fuel electrode-supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode involved in the present invention has an 80 h stability test carried out at 650 °C and in the fuel cell mode (30 mL min is introduced into the fuel electrode side -1 and humidified hydrogen containing 3% volume fraction of water vapor, and the oxygen electrode side is ambient air);

[0045] Figure 13 The fuel electrode-supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode involved in the present invention has an electrolytic cell mode (30 mL min is introduced into the fuel electrode side -1 and humidified hydrogen containing 3% volume fraction of water vapor, and 100 mL min is introduced into the oxygen electrode side -1 and humidified air containing 3% volume fraction of water vapor, i.e., 97% Air - 3% H 2I-V curve measured under (O);

[0046] Figure 14 For the fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode in the present invention, at 650 °C and in the electrolytic cell mode (30 mL min of humidified hydrogen containing 3% volume fraction of water vapor is introduced on the fuel electrode side, and 100 mL min of humidified air containing 3% volume fraction of water vapor, i.e., 97% Air - 3% H -1 O, is introduced on the oxygen electrode side) for a 44 h stability test; -1 For the fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode in the present invention, a 100 h stability test under cyclic operation in the fuel cell mode and the electrolytic cell mode at 600 °C; where 97% Air - 3% H 2 O indicates that humidified air containing 3% volume fraction of water vapor is introduced on the oxygen electrode side for a stability test;

[0047] Figure 15 For the fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode in the present invention, the Faraday efficiency and the hydrogen generation rate during water electrolysis at an electrolytic current density of 0.5 A cm 2 and 0.75 A cm at 600 °C; where (a) is the Faraday efficiency during water electrolysis and (b) is the hydrogen generation rate during water electrolysis;

[0048] Figure 16 For the fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode in the present invention, SEM images of the cross-section and the oxygen electrode surface after the stability test; where (a) is the cross-section SEM image after the single cell stability test and (b) is the SEM image of the oxygen electrode surface after the single cell stability test; -2 and 0.75 A cm -2 of the electrolytic current density; where (a) is the Faraday efficiency of water electrolysis and (b) is the rate of hydrogen generation from water electrolysis;

[0049] Figure 17 For the fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) prepared with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode in the present invention, SEM images of the cross-section and the oxygen electrode surface after the stability test; where (a) is the cross-section SEM image after the single cell stability test and (b) is the SEM image of the oxygen electrode surface after the single cell stability test;

[0050] Figure 18The symmetric cell (BGPC44|BZCYYb|BGPC44) prepared with BGPC44 as the oxygen electrode and BZCYYb as the electrolyte has a polarization impedance spectrum in humidified air with a flow rate of 100 mL min -1 and containing 3% by volume of water vapor in the temperature range of 700 - 500 °C;

[0051] Figure 19 It is a comparison diagram of the activation energy curves obtained by fitting the polarization impedance spectra of the symmetric cells prepared from the electrode powders of Example 1 and Example 2 in the temperature range of 700 - 500 °C; GCO - BGPC corresponds to Example 1, and BGPC44 corresponds to Example 2. Detailed implementation manners

[0052] The present invention will be further described in detail below with reference to specific examples, but the implementation manners of the present invention are not limited thereto.

[0053] Example 1

[0054] This example provides a preparation method for an oxygen electrode material of a self - assembled heterostructure reversible proton ceramic electrochemical cell (with a nominal composition of Ba 0.8 Gd 0.8 Pr 0.4 Co 2 O 5+δ ), which specifically includes the following steps:

[0055] 1) According to the stoichiometric ratio of Ba 0.8 Gd 0.8 Pr 0.4 Co 2 O 5+δ , weigh 2.091 g of barium nitrate, 3.611 g of gadolinium nitrate, 1.740 g of praseodymium nitrate, and 5.821 g of cobalt nitrate, and add 200 mL of deionized water to completely dissolve them;

[0056] 2) According to the molar ratio of the total metal ions of Ba, Gd, Pr, and Co: citric acid monohydrate: ethylenediaminetetraacetic acid of 1:2:1, weigh 16.811 g of citric acid monohydrate and 11.690 g of ethylenediaminetetraacetic acid as complexing agents respectively, and add them to 200 mL of deionized water to dissolve; then add the solution containing the complexing agent to the solution containing metal nitrates, and dropwise add an appropriate amount of ammonia water to make the pH of the solution between 7 and 8;

[0057] 2) The mixed solution is heated at a constant temperature of 120 °C and continuously stirred at a speed of 250 r / min until the water is completely evaporated to form a gel - like substance;

[0058] 3) Place the gel - like substance in an oven and heat it to self - ignite at 300 °C, and keep it warm for 5 h to fully dry it to obtain a fluffy precursor powder of the oxygen electrode material;

[0059] 4) Place the oxygen electrode precursor powder in a muffle furnace and calcine it at 1000 °C for 5 h to obtain the required GCO-BGPC oxygen electrode powder. The oxygen electrode material prepared in this example has a heterostructure and a biphasic structure.

[0060] Example 2

[0061] This example provides a skeleton component Ba of the oxygen electrode material described above 0.8 Gd 0.4 Pr 0.4 Co 1.6 O 5+δ (Ba 0.8 Gd 0.8-x Pr 0.4 Co 2-y O 5+δ , when x = y = 0.4), the preparation method specifically includes the following steps:

[0062] 1) Weigh 2.091 g of barium nitrate, 1.805 g of gadolinium nitrate, 1.740 g of praseodymium nitrate, and 4.656 g of cobalt nitrate, and add deionized water to dissolve them completely.

[0063] 2) According to the molar ratio of the total metal ions of Ba, Gd, Pr, and Co: citric acid monohydrate: ethylenediaminetetraacetic acid of 1:2:1, weigh 13.449 g of citric acid monohydrate and 9.352 g of ethylenediaminetetraacetic acid as complexing agents respectively, and add them to deionized water to dissolve; then add the solution containing the complexing agent to the solution containing metal nitrates, and dropwise add an appropriate amount of ammonia water to make the pH of the solution between 7 and 8;

[0064] 2) The mixed solution is heated at a constant temperature of 120 °C and continuously stirred at a speed of 250 r / min until the water is completely evaporated to form a gel-like substance;

[0065] 3) Place the gel-like substance in an oven and heat it to self-ignite at 300 °C, and keep it warm for 5 h to fully dry it to obtain a fluffy oxygen electrode material precursor powder;

[0066] 4) Place the oxygen electrode precursor powder in a muffle furnace and calcine it at 1000 °C for 5 h to obtain a possible skeleton component Ba 0.8 Gd 0.4 Pr 0.4 Co 1.6 O 5+δ oxygen electrode powder.

[0067] Example 3

[0068] This embodiment provides a method for preparing a symmetrical cell with the GCO-BGPC powder in Embodiment 1 as the oxygen electrode. The symmetrical cell adopts a structure of "oxygen electrode|electrolyte|oxygen electrode", that is, "GCO-BGPC|BZCYYb|GCO-BGPC", and specifically includes the following steps:

[0069] 1) Weigh 1 g of the GCO-BGPC oxygen electrode powder prepared in Embodiment 1. According to the mass ratio of powder:ethyl cellulose:terpineol of 1:0.04:0.76, weigh 0.04 g of ethyl cellulose and 0.76 g of terpineol respectively, and place them in a mortar and grind for 1 h to prepare the GCO-BGPC oxygen electrode slurry;

[0070] 2) After pressing the BZCYYb powder into a disc with a diameter of 10 mm under a pressure of 8 MPa, it is calcined at 1450 °C for 5 h;

[0071] 3) Brush the oxygen electrode slurry evenly on both sides of the calcined and dense BZCYYb electrolyte sheet, and sinter it at 950 °C for 2 h in an air atmosphere to form a porous GCO-BGPC oxygen electrode, and the effective active area of the cell is 0.2826 cm 2 , and obtain the prepared symmetrical cell; it is used to test the polarization impedance spectrum in the temperature range of 700 - 500 °C. The polarization impedance of the symmetrical cell at 700 °C is 0.070 Ωcm 2 .

[0072] Embodiment 4

[0073] This embodiment provides a method for preparing a single cell with the GCO-BGPC powder in Embodiment 1 as the oxygen electrode. The single cell adopts a structure of "fuel electrode|electrolyte|oxygen electrode", that is, "Ni-BZCYYb|BZCYYb|GCO-BGPC", and specifically includes the following steps:

[0074] 1) Weigh the GCO-BGPC oxygen electrode powder prepared in Embodiment 1. According to the mass ratio of powder:ethyl cellulose:terpineol of 1:0.04:0.76, weigh 0.04 g of ethyl cellulose and 0.76 g of terpineol respectively, and place them in a mortar and grind for 1 h to prepare the GCO-BGPC oxygen electrode slurry;

[0075] 2) After the fuel electrode-supported half cell Ni-BZCYYb|BZCYYb is prepared into a disc with a diameter of 13 mm by co-casting, it is degreased at 600 °C and then calcined at 1450 °C for 5 h; the mass ratio of NiO to BZCYYb in the fuel electrode of the fuel electrode-supported half cell Ni-BZCYYb|BZCYYb is 6:4;

[0076] 3) The oxygen electrode paste was evenly brush-coated on the surface of the BZCYYb electrolyte and sintered at 950 °C for 2 h in an air atmosphere to form a porous GCO-BGPC oxygen electrode, and the effective active area of the cell was 0.2826 cm 2 , obtaining the prepared single cell; used for testing the output power and electrolysis current in the temperature range of 700 - 600 °C. Among them, the maximum output power of the cell at 700 °C was 1.365 W cm -2 , and the electrolysis current density reached 3.458 A cm -2 when the voltage was 1.3 V.

[0077] Example 5

[0078] This example provides a test method for the symmetric cell in Example 3:

[0079] The symmetric cell prepared in Example 3 was used to test the polarization impedance with a PARSTAT MC200 electrochemical workstation under a flow rate of 100 mL min -1 and humidified air containing 3% volume fraction of water vapor in the temperature range of 700 - 500 °C. Under the condition of open circuit voltage, with a stimulation voltage of 40 mV, it was tested from 1 MHz to 0.01 Hz every 50 °C in the temperature range of 700 - 500 °C. As Figure 7 shown.

[0080] The symmetric cell prepared in Example 3 was used to test the polarization impedance stability with a PARSTAT MC200 electrochemical workstation under a flow rate of 100 mL min -1 and humidified air containing 3% volume fraction of water vapor at 600 °C. Under the condition of open circuit voltage, with a stimulation voltage of 40 mV, it was tested from 1 MHz to 0.01 Hz. As Figure 9 shown.

[0081] Example 6

[0082] This example provides a test method for the single cell in Example 4 in the fuel cell mode:

[0083] The single cell prepared in Example 4 was used to test the impedance spectrum with a PARSTAT MC200 electrochemical workstation in the temperature range of 700 - 600 °C. Humidified hydrogen containing 3% volume fraction of water vapor was introduced on the fuel electrode side at a flow rate of 30 mL min -1 , and ambient air was on the oxygen electrode side. Under the condition of open circuit voltage, with a stimulation voltage of 40 mV, it was tested from 1 MHz to 0.1 Hz every 50 °C in the temperature range of 700 - 600 °C. As Figure 10 shown.

[0084] The single cell prepared in Example 4 was used to test the I-V-P curve diagram within the temperature range of 700 - 600 °C using a PARSTAT MC200 electrochemical workstation. Humidified hydrogen gas containing 3% volume fraction of water vapor was introduced on the fuel electrode side at a rate of 30 mL min -1 and ambient air was used on the oxygen electrode side. As Figure 11 shown.

[0085] The single cell prepared in Example 4 was used to conduct a stability test in fuel cell mode at 650 °C and a current density of -0.5 A cm -2 using a PARSTAT MC200 electrochemical workstation. Humidified hydrogen gas containing 3% volume fraction of water vapor was introduced on the fuel electrode side at a rate of 30 mL min -1 and ambient air was used on the oxygen electrode side. As Figure 12 shown.

[0086] Example 7

[0087] This example provides a method for testing the single cell in Example 4 in electrolytic cell mode:

[0088] The single cell prepared in Example 4 was used to test the I-V curve diagram within the temperature range of 700 - 600 °C using a PARSTAT MC200 electrochemical workstation. Humidified hydrogen gas containing 3% volume fraction of water vapor was introduced on the fuel electrode side at a rate of 30 mL min -1 and humidified air containing 3% volume fraction of water vapor was introduced on the oxygen electrode side at a rate of 100 mL min -1 As Figure 13 shown.

[0089] The prepared single cell was used to conduct a stability test in electrolytic cell mode at 650 °C and a current density of +0.5 A cm -2 using a PARSTAT MC200 electrochemical workstation. Humidified hydrogen gas containing 3% volume fraction of water vapor was introduced on the fuel electrode side at a rate of 30 mL min -1 and humidified air containing 3% volume fraction of water vapor was introduced on the oxygen electrode side at a rate of 100 mL min -1 As Figure 14 shown.

[0090] Example 8

[0091] This example provides a method for testing the single cell in Example 4 in cyclic operation of fuel cell mode and electrolytic cell mode:

[0092] The single cell prepared in Example 4 was used to test at 600 °C with an external ±0.5 A cm -2Under a current density of [current density value], switch every two hours to alternately operate the battery in the fuel cell mode and the electrolytic cell mode, and test the 100h cycle stability. Humidified hydrogen containing 3% volume fraction of water vapor is introduced into the fuel electrode side at 30 mL min -1 and humidified air containing 3% volume fraction of water vapor is introduced into the oxygen electrode side at 100 mL min -1 as shown Figure 15 .

[0093] Characterization results

[0094] (1) SEM characterization

[0095] Figure 1 The SEM image of the oxygen electrode powder prepared in Example 1. It can be seen that the oxygen electrode powder prepared in Example 1 self-assembled into a main phase and a surface-precipitated nanoparticle phase during the powder calcination process.

[0096] (2) XRD characterization

[0097] Figure 2 The XRD pattern of the oxygen electrode powder prepared in Example 1 at room temperature. It can be seen from the XRD refinement that the electrode powder prepared in Example 1 has an orthorhombic perovskite Ba 0.8 Gd 0.8-x Pr 0.4 Co 2-y O 5+δ (BGPC) phase (space group is Pmmm, lattice parameters are ) and ~19.17% of orthorhombic perovskite Gd x Co y O 3-δ (GCO) phase (space group is Pbnm, lattice parameters are ).

[0098] (3) TEM characterization

[0099] Figure 3 The TEM image of the oxygen electrode powder prepared in Example 1. It can be seen from Figure 3 that the oxygen electrode powder prepared in Example 1 has a heterogeneous structure (GCO-BGPC) of a main phase and a surface-precipitated nanoparticle phase. The interplanar spacing of the main phase is 0.277 nm corresponding to the (120) plane of BGPC, and the interplanar spacing of the surface nanoparticles is 0.369 nm corresponding to the (002) plane of GCO.

[0100] (4) High-temperature in-situ XRD characterization

[0101] To investigate the stability of the phase structure of GCO-BGPC powder (i.e., the oxygen electrode powder prepared in Example 1) under actual operating conditions, high-temperature in-situ XRD characterization was carried out on the GCO-BGPC oxygen electrode powder, and the results are as Figure 4 and 5 shown. Figure 4 Figures (a) and (b) in it are the XRD patterns of the GCO-BGPC oxygen electrode powder tested in the angular ranges of 20-80° and 31-35°, respectively. The test temperature range was from 25 °C to 700 °C at intervals of 100 °C. The results show that as the temperature increases, the peak position shows a slight shift towards smaller angles, which is due to the lattice expansion caused by the increase in temperature.

[0102] Figure 5 Figures (a) and (b) in it are the high-temperature in-situ XRD patterns of the GCO-BGPC oxygen electrode powder in a humid air atmosphere (passing humid air containing 3% volume fraction of water vapor) from 0 h to 6 h in the ranges of 20-80° and 32-34.5°, respectively. The results show that the position of the main peak shifts towards smaller angles, especially in the first 1 h, which is due to the lattice expansion caused by the entry of water vapor into the lattice.

[0103] (5) Chemical compatibility characterization

[0104] Figure 6 is the XRD pattern of the GCO-BGPC powder (i.e., the oxygen electrode powder prepared in Example 1) and the BZCYYb electrolyte powder after being mixed evenly at a mass ratio of 1:1 and calcined at 950 °C for 2 h. It can be seen from Figure 6 that after high-temperature calcination, no peaks other than GCO-BGPC and BZCYYb appear in the mixed powder, indicating that the GCO-BGPC oxygen electrode powder and the BZCYYb electrolyte have good chemical compatibility.

[0105] (6) Impedance and activation energy characterization of symmetric cells

[0106] Figure 7 is the polarization impedance spectrum of the symmetric cell (GCO-BGPC|BZCYYb|GCO-BGPC) (the cell prepared in Example 3) with GCO-BGPC as the oxygen electrode and BZCYYb as the electrolyte at a flow rate of 100 mL min -1 and under humid air containing 3% volume fraction of water vapor in the temperature range of 700-500 °C. The polarization impedances at 700, 650, 600, 550, and 500 °C are 0.070, 0.136, 0.270, 0.667, and 1.881 Ω cm 2 , respectively.

[0107] Figure 8The activation energy curve obtained by fitting the polarization impedance spectra of the symmetric cell (GCO-BGPC|BZCYYb|GCO-BGPC) (the cell prepared in Example 3) with GCO-BGPC as the oxygen electrode and BZCYYb as the electrolyte was tested in the temperature range of 700 - 500 °C. The activation energy of the GCO-BGPC oxygen electrode is 1.064 eV.

[0108] Figure 9 For the symmetric cell (GCO-BGPC|BZCYYb|GCO-BGPC) with GCO-BGPC as the oxygen electrode and BZCYYb as the electrolyte, at a flow rate of 100 mL min -1 and humidified air containing 3% volume fraction of water vapor, the polarization impedance stability was tested at 600 °C for 100 h. It can be seen from the figure that the GCO-BGPC oxygen electrode material has good electrochemical stability.

[0109] (7) Electrochemical performance characterization of the single cell in the fuel cell mode

[0110] Figure 10 For the fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) (the single cell prepared in Example 4, which is a reversible proton ceramic electrochemical cell) with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode, in the fuel cell mode (humidified hydrogen containing 3% volume fraction of water vapor is introduced on the fuel electrode side at a flow rate of 30 mL min -1 and ambient air on the oxygen electrode side) in the temperature range of 700 - 600 °C, the impedance spectra were tested. At 700, 650, and 600 °C, the ohmic impedances of the single cell are 0.088, 0.115, and 0.146 Ω cm 2 respectively; the polarization impedances are 0.040, 0.094, and 0.272 Ω cm 2 respectively.

[0111] Figure 11 For the fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) (the single cell prepared in Example 4, which is a reversible proton ceramic electrochemical cell) with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode, in the fuel cell mode (humidified hydrogen containing 3% volume fraction of water vapor is introduced on the fuel electrode side at a flow rate of 30 mL min -1 and ambient air on the oxygen electrode side) in the temperature range of 700 - 600 °C, the I-V-P curve graph was tested. The results show that for the single cell with GCO-BGPC as the oxygen electrode, at 700, 650, and 600 °C, the maximum output powers can reach 1.365, 0.909, and 0.589 W cm-2 .

[0112] Figure 12 The fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) (the single cell prepared in Example 4, that is, the reversible proton ceramic electrochemical cell) with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode was at 650 °C and in the fuel cell mode (humidified hydrogen containing 3% volume fraction of water vapor was introduced on the fuel electrode side at 30 mL min -1 and ambient air was on the oxygen electrode side) with a current density of -0.5 A cm -2 . The 80 h stability test results show that except for performance decay in the initial 15 h, stable operation was maintained in the following 65 h without observing performance decay, indicating the excellent overall preparation process of the single cell and the excellent electrochemical performance of the GCO-BGPC oxygen electrode in the cell mode.

[0113] (8) Electrochemical performance characterization of the single cell in the electrolytic cell mode

[0114] Figure 13 The fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) (the single cell prepared in Example 4, that is, the reversible proton ceramic electrochemical cell) with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode was in the electrolytic cell mode in the temperature range of 700 - 600 °C (humidified hydrogen containing 3% volume fraction of water vapor was introduced on the fuel electrode side at 30 mL min -1 and humidified air containing 3% volume fraction of water vapor, that is, 97% Air - 3% H -1 O, was introduced on the oxygen electrode side at 100 mL min 2 ). The I-V curve test results show that for the single cell with GCO-BGPC as the oxygen electrode, the electrolysis current densities at 700, 650, and 600 °C and a voltage of 1.3 V in the electrolysis mode were 3.458, 2.335, and 1.323 A cm -2 .

[0115] Figure 14 The fuel electrode supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) (the single cell prepared in Example 4, that is, the reversible proton ceramic electrochemical cell) with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode was at 650 °C and in the electrolytic cell mode (humidified hydrogen containing 3% volume fraction of water vapor was introduced on the fuel electrode side at 30 mL min -1And humidified hydrogen containing 3% volume fraction of water vapor, with 100 mL min passed through the oxygen electrode side -1 And humidified air containing 3% volume fraction of water vapor, i.e., 97% Air - 3% H 2 O) at a current density of +0.5 A cm -2 for a 44 - h stability test. The results show that the single cell with the GCO - BGPC oxygen electrode can operate stably in the electrolysis mode, with almost no performance degradation.

[0116] Figure 15 This is the 100 - h stability test of the fuel - electrode - supported single cell (Ni - BZCYYb|BZCYYb|GCO - BGPC) (the single cell prepared in Example 4, which is a reversible proton ceramic electrochemical cell) with GCO - BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni - BZCYYb as the fuel electrode, operating cyclically in the fuel cell mode and the electrolysis cell mode at 600 °C; the results show that the single cell with the GCO - BGPC oxygen electrode can still maintain good stability during cyclic operation in both modes, indicating that GCO - BGPC is an oxygen electrode with high activity and good stability.

[0117] (9) Characterization of the Faraday efficiency of water electrolysis

[0118] Figure 16 For the fuel - electrode - supported single cell (Ni - BZCYYb|BZCYYb|GCO - BGPC) (the single cell prepared in Example 4, which is a reversible proton ceramic electrochemical cell) with GCO - BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni - BZCYYb as the fuel electrode, at 600 °C, the Faraday efficiency of water electrolysis and the hydrogen production rate during water electrolysis at electrolysis current densities of 0.5 A cm -2 and 0.75 A cm -2 respectively; where (a) is the Faraday efficiency of water electrolysis, and (b) is the hydrogen production rate during water electrolysis. Under the condition of 30% water partial pressure, when the electrolysis current densities are +0.5 A cm -2 and +0.75 A cm -2 during water electrolysis, the Faraday efficiencies are ~86.69% and ~62.21% respectively, and the hydrogen production rates are ~2.810 ml min -1 cm -2 and ~3.250 ml min -1 cm -2 respectively.

[0119] (10) SEM characterization

[0120] Figure 17SEM images of the cross-section and the oxygen electrode surface of the fuel electrode-supported single cell (Ni-BZCYYb|BZCYYb|GCO-BGPC) (the single cell prepared in Example 4, i.e., the reversible proton ceramic electrochemical cell) with GCO-BGPC as the oxygen electrode, BZCYYb as the electrolyte, and Ni-BZCYYb as the fuel electrode after the stability test; where (a) is the cross-section SEM image of the single cell after the stability test, and (b) is the SEM image of the oxygen electrode surface of the single cell after the stability test. It can be seen from Figure 17 that after the test, the fuel electrode, the electrolyte, and the oxygen electrode are all tightly bonded, and the GCO nanoparticles stably exist on the surface of the GCO-BGPC oxygen electrode, which is a prerequisite for the excellent electrochemical performance of the single cell and the symmetric cell.

[0121] (11) Compare the performance of the symmetric cell made of the electrode powder prepared in Example 2 and the electrode powder prepared in Example 1

[0122] The electrode powder Ba of Example 2 0.8 Gd 0.4 Pr 0.4 Co 1.6 O 5+δ (x = y = 0.4, denoted as BGPC44) and the electrode powder GCO-BGPC prepared in Example 1 were made into symmetric cells (the preparation method is the same as that in Example 3) for testing, and the results are as Figure 18 shown in Figure 19. The performance of the oxygen electrode material GCO-BGPC with a dual-phase heterostructure prepared in Example 1 is better than that of BGPC44.

[0123] Figure 18 The polarization impedance spectrum of the symmetric cell (BGPC44|BZCYYb|BGPC44) with BGPC44 as the oxygen electrode and BZCYYb as the electrolyte under a flow rate of 100 mL min -1 and humidified air containing 3% volume fraction of water vapor in the temperature range of 700 - 500 °C. The polarization impedances at 700, 650, 600, 550, and 500 °C are 0.096, 0.177, 0.378, 1.022, and 3.224 Ω cm 2 .

[0124] Figure 19 Figure for comparing the activation energy curves obtained by fitting the polarization impedance spectra of the symmetric cells prepared from the electrode powders of Example 1 and Example 2 in the temperature range of 700 - 500 °C. The activation energy (1.064 eV) of the GCO-BGPC oxygen electrode is lower than the activation energy (1.146 eV) of the BGPC44 oxygen electrode.

Claims

1. An oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure, Characterized in that: With Gd x Co y O 3-δ and Ba 0.8 Gd 0.8-x Pr 0.4 Co 2-y O 5+δ The biphasic structure of forms Gd x Co y O 3-δ nanoparticles coated on the surface of the Ba 0.8 Gd 0.8- x Pr 0.4 Co 2-y O 5+δ heterostructure; where 0 < x < 0.8, 0 < y < 0.8; 0 < δ < 1, and δ is the oxygen vacancy content.

2. A preparation method of the oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure according to claim 1, Characterized in that: It includes the following steps: Dissolve barium nitrate, gadolinium nitrate, praseodymium nitrate, and cobalt nitrate in water according to the stoichiometric ratio of Ba 0.8 Gd 0.8 Pr 0.4 Co 2 O 5+δ Add citric acid monohydrate and ethylenediaminetetraacetic acid to form a mixed solution; adjust the pH of the solution to 7-8; continuously heat and stir evenly, and obtain a gel-like substance after sufficient evaporation of water; Then heat-treat and calcine the gel-like substance to obtain the required oxygen electrode material.

3. A preparation method of the oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure according to claim 2, Characterized in that: The molar ratio of the total metal ions of Ba, Gd, Pr, and Co: citric acid monohydrate: ethylenediaminetetraacetic acid is (0.5 - 1.5): (1.5 - 2.5): (0.5 - 1.5).

4. A preparation method of the oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure according to claim 2, Characterized in that: The conditions of the heat treatment: keep warm at 250 - 300 °C for 5 - 10 h; The calcination temperature is 900 - 1000 °C, and the calcination time is 2 - 5 h.

5. A preparation method of the oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure according to claim 2, Characterized in that: Adjusting the pH to 7 - 8 means adding ammonia water dropwise to adjust the pH value to 7 - 8; The continuous heating temperature is 100 - 150 °C; The rotation speed for uniform stirring is 200 - 300 r / min.

6. Application of the oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure according to claim 1 in the preparation of a reversible proton ceramic electrochemical cell.

7. The application according to claim 6, Characterized in that: The oxygen electrode material for a reversible proton ceramic electrochemical cell with a self-assembled heterostructure is used to prepare the oxygen electrode in a reversible proton ceramic electrochemical cell.

8. The application according to claim 7, Characterized in that: The structure of the reversible proton ceramic electrochemical cell successively includes a fuel electrode, an electrolyte, and an oxygen electrode; the fuel electrode and the oxygen electrode are arranged on both sides of the electrolyte.

9. The application according to claim 8, Characterized in that: The electrolyte is BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ ; 0 < δ < 1, where δ is the oxygen vacancy content; The fuel electrode is a composite electrode composed of NiO and BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ in a mass ratio of (6-7):(4-3).

10. The application according to claim 7, Characterized in that: The oxygen electrode is prepared by the following method: mix the oxygen electrode material, ethyl cellulose, and terpineol to obtain a GCO - BGPC oxygen electrode slurry; coat the oxygen electrode slurry on the electrolyte of a half-cell supported by the fuel electrode, dry, and calcine to obtain a reversible proton ceramic electrochemical cell with a GCO - BGPC porous oxygen electrode.

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