High-entropy negative thermal expansion reversible proton conductor fuel cell composite air electrode material and preparation method thereof

Abstract

The application relates to a reversible proton conductor fuel cell air electrode of a composite high-entropy negative thermal expansion material and a preparation method thereof, and belongs to the technical field of solid oxide reversible batteries. A high-entropy negative thermal expansion material is synthesized through a solid phase method, the material composition molecular formula is BaCoO 3‑δ -Y 0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0.4 W 1.5 Mo 1.5 O 12 The introduction of the high-entropy negative thermal expansion material in the traditional Co-based electrode material can reduce the thermal expansion coefficient of the electrode, and through reaction sintering, a new phase with a rapid hydration reaction capacity is generated, so that the air electrode material has excellent electrochemical performance in the battery and electrolysis modes and the thermal cycle stability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a micro-composite material Y 0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0.4 W 1. 5M 1.5 O 12 Strategy to improve the thermal stability and hydration ability of BaCoO 3-δ and its application in the field of reversible proton conductor solid oxide fuel cell air electrode. BACKGROUND

[0002] Solid oxide fuel cell (SOFC) as a new energy conversion technology, due to its clean and efficient characteristics, has been widely concerned. The traditional oxygen ion conductor SOFC works at 700-900℃, which is not conducive to the long-term operation of the cell and the reduction of cost. Therefore, reducing the operating temperature of SOFC (400-600℃) is the key to its large-scale industrial application. Reversible proton conductor fuel cell (R-PCEC) uses proton-conducting electrolyte, and protons have lower activation energy at medium and low temperatures, which is more conducive to material selection, prolonging the service life of the cell and reducing the overall cost. However, the reduction of operating temperature will lead to a sharp increase in the polarization resistance of the cathode, reducing the performance of the cell, so the development of air electrode materials with high activity and stability at medium and low temperatures is the key to the commercialization of reversible proton conductor fuel cells.

[0003] BaCoO 3-δ (BC) is widely studied due to its excellent ion and electron conductivity and oxygen reduction reaction (ORR) activity, and has the potential to become an R-PCEC air electrode. However, BC lacks proton conductivity, and the three-phase reaction interface is limited when used as an air electrode, and the hydration reaction activity is not high; in addition, cobalt-based materials generally have a large thermal expansion coefficient due to the reduction of spin valence of cobalt ions and lattice expansion, which is easy to delaminate with adjacent components of the cell during operation, challenging the thermal stability of the cell. SUMMARY

[0004] The purpose of the present application is to develop a material Y 0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0. 4W 1.5 Mo 1.5 O 12 (HE) with high-entropy negative thermal expansion characteristics, which can be combined with BaCoO 3-δ(BC) After physical mixing, reaction sintering is carried out to prepare R-PCEC composite air electrode BC-HE, which improves the hydration performance and thermal stability of the material.

[0005] A high-entropy negative thermal expansion reversible proton conductor fuel cell composite air electrode material, comprising YW / Mo-based high-entropy negative thermal expansion material and BaCoO 3-δ δ represents the oxygen vacancy content, and the chemical formula of the YW / Mo-based high-entropy negative thermal expansion material is: Y 0.4±x Zr 0.4±y Er 0.4±z Sm 0.4±m Sc 0.4±n W 1.5±p Mo 1.5±q O 12 Where x,y,z,m,n∈[0,0.2],p,q∈[0,0.1].

[0006] The weight of the YW / Mo-based high-entropy negative thermal expansion material is BaCoO 3-δ 2-10%.

[0007] The above-mentioned method for preparing air electrode material includes the following steps:

[0008] Using a ball mill to process BaCoO 3-δ It was prepared by mixing with YW / Mo-based high-entropy negative thermal expansion materials.

[0009] The above-mentioned YW / Mo-based high-entropy negative thermal expansion material is obtained by ball milling and calcination using a solid-state method.

[0010] The solid-state preparation process includes the following steps:

[0011] The mixture of Y2O3, ZrO2, Er2O3, Sm2O3, Sc2O3, WO3, and MoO3 was ball-milled and calcined to obtain the final product.

[0012] The roasting conditions are 850-950℃ for 5-20 hours.

[0013] The above-mentioned air electrode materials are used in reversible proton conductor fuel cells.

[0014] The beneficial effects of this invention are:

[0015] The present invention relates to a high-entropy negative thermal expansion reversible proton conductor fuel cell composite air electrode, which is prepared by a solid-state method and has the following advantages:

[0016] (1) The composite electrode is prepared by physical mixing, and the reaction sintering process is included in the battery electrode preparation process, which is simple and easy to implement.

[0017] (2) The trace composite high-entropy negative thermal expansion material can effectively enhance the thermal stability and chemical water adsorption capacity of BC, making it better applied to the air electrode of reversible proton conductor fuel cell.

[0018] (3) The BC-5%HE air electrode exhibits excellent battery electrolysis performance, with a maximum power density of 1.14 W / cm³ at 650℃. -2 Electrolytic current density at 1.3V: -1.92A cm⁻¹ -2 .

[0019] (4) The BC-5%HE air electrode has excellent thermal stability, with a polarization impedance attenuation rate of less than 5% after 52 thermal cycles in the temperature range of 650-200℃. Attached Figure Description

[0020] Figure 1 It is the XRD pattern of BC, BC-5% HE, and HE at room temperature;

[0021] Figure 2 The polarization resistance and activation energy of BC composite cathodes with YW / Mo and composite cathodes with different proportions of HE are compared under humid air.

[0022] Figure 3 These are the H2O temperature-progression desorption test results for BC, BC-5%HE and BC-5%YW;

[0023] Figure 4 These are the thermal expansion curves of BC composites with YW / Mo and composites with different proportions of HE.

[0024] Figure 5 This is an IVP curve of an anode-supported single cell, Ni-BZCYYb|BZCYYb|BC-5%HE, prepared with BC-5%HE as an air electrode, tested in the range of 650-500℃.

[0025] Figure 6 This is an IVP curve of an anode-supported single cell, Ni-BZCYYb|BZCYYb|BC, prepared with BC as an air electrode, tested in the range of 500-650℃.

[0026] Figure 7 These are the electrolysis performance curves of the Ni-BZCYYb|BZCYYb|BC electrolyzer in the temperature range of 650-500℃.

[0027] Figure 8 The electrolysis performance curves of the Ni-BZCYYb|BZCYYb|BC-5%HE electrolyzer in the temperature range of 650-500℃ are shown.

[0028] Figure 9The hydrogen generation rate and Faraday efficiency of a Ni-BZCYYb|BZCYYb|BC-5%HE electrolytic cell at 600℃ with 30% water pressure.

[0029] Figure 10 This is a microstructure image taken by SEM after testing of the Ni-BZCYYb|BZCYYb|BC-5%HE reversible proton conductor battery; Figure 11 The polarization impedance stability of a symmetrical cell with BC and BC-5%HE as air electrodes at 600℃.

[0030] Figure 12 The thermal cycling stability of polarization resistance in symmetrical cells with BC and BC-5%HE as air electrodes at 650-200℃. Detailed Implementation

[0031] This invention relates to a micro-composite material Y with high entropy and negative thermal expansion properties. 0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0.4 W 1. 5M 1.5 O 12 (HE) to enhance BaCoO 3-δ Strategies for improving the thermal stability and hydration capacity of (BC). BC possesses excellent oxygen activation capacity, and HE effectively regulates the large thermal expansion coefficient of BC. After reaction sintering, the BaMoO4 phase is introduced to enhance proton conductivity and hydration capacity, while simultaneously regulating the interfacial contact between the BC and HE phases.

[0032] Following the aforementioned beneficial phase reactions, the synergistic effect of each phase enables BC-5%HE as an air electrode to achieve excellent performance in a reversible proton-conducting solid oxide fuel cell. In cell mode, the corresponding single cell achieves 1.14 W / cm² at 650°C. -2 Maximum output power; Electrolysis of 30% H2O at 650℃ in electrolysis mode yields -1.92A cm⁻¹ at 1.3V. -2 The maximum current density is achieved. Furthermore, BC-5%HE exhibits excellent thermal stability in symmetrical cell impedance testing, with a polarization impedance decay rate of less than 5% after 52 thermal cycles within a temperature range of 650-200℃. This invention develops a high-performance and stable air electrode material and its preparation method, significantly improving the electrochemical performance of proton ceramic fuel cells and electrolyzers.

[0033] Example 1

[0034] BaCoO2 is a reversible proton conductor solid oxide fuel cell air electrode material. 3-δ -Y0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0. 4W 1.5 M 1.5 O 12 The specific steps of the composite method are as follows:

[0035] (1) Weigh 9.867g of barium carbonate and 4.01g of cobalt tetroxide and place them in a ball mill jar.

[0036] (2) Add anhydrous ethanol, ball mill at 400 rpm for 60 min, then take it out and dry it to obtain the precursor of BC.

[0037] (3) The BC precursor was placed in a high-temperature muffle furnace and calcined at 1100℃ for 10h to obtain phased BC powder.

[0038] (4) Weigh 1.25g of yttrium oxide, 0.62g of zirconium oxide, 1.91g of erbium oxide, 1.74g of samarium oxide, 0.66g of scandium oxide, 8.69g of tungsten oxide and 5.39g of molybdenum oxide and place them in a ball mill jar.

[0039] (5) Add anhydrous ethanol, ball mill at 400 rpm for 60 min, then take it out and dry it to obtain the precursor of HE.

[0040] (6) The precursor was placed in a high-temperature muffle furnace and calcined at 900°C for 10 hours to obtain the required HE powder.

[0041] (7) Add BC and HE powder (three parallel comparative experiments were conducted, in which HE accounted for 0 / 5 / 10 wt% of the mass of BC powder respectively) into a ball mill jar, add anhydrous ethanol to mix, ball mill at 400 rpm for 30 min, take out and dry to obtain the required air electrode material.

[0042] Comparative Example 1

[0043] Using YWY2W3O12 as a control material to replace HE powder, air electrode materials were prepared by the same method.

[0044] Test method for polarization impedance of symmetrical cells

[0045] Taking BC-5% HE as an example, the specific steps are as follows:

[0046] Weigh 1g of the air electrode powder BaCoO prepared in Example 1. 3-δ (BC)-Y 0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0.4W 1. 5M 1.5 O 12 (HE), 10ml isopropanol, 2ml ethylene glycol, and 0.8ml glycerol were poured into a high-energy ball mill and milled at 400rpm for 30min. The resulting slurry was then transferred to a culture bottle using a dropper to obtain the desired cathode slurry.

[0047] The prepared BZCYYb electrolyte was preheated at 150°C on a heating stage. Using a spray gun under inert gas, the prepared cathode slurry was evenly sprayed onto both sides of the electrolyte. After the liquid had completely evaporated, the sprayed electrolyte was placed in a high-temperature muffle furnace and calcined at 900°C for 2 hours to obtain the desired symmetrical cell. This cell was used to test the polarization impedance of the cathode material within the temperature range of 500-700°C. The polarization impedance of the cell at 700°C was 0.05 Ωcm. 2 .

[0048] Single-cell output power test

[0049] Taking BC-HE as an example, the specific steps are as follows:

[0050] (1) Weigh 1g of the cathode powder BaCoO prepared in Example 1. 3-δ -Y 0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0.4 W 1.5 M 1.5 O 12 (HE), 10 ml of isopropanol, 2 ml of ethylene glycol, and 0.8 ml of glycerol were poured into a high-energy ball mill and milled at 400 rpm for 30 minutes. The mixture was then transferred to a culture bottle using a pipette to obtain the desired cathode slurry.

[0051] (2) The prepared anode-supported half-cell was placed on a heating table and preheated at 150°C. Using a spray gun and under the influence of inert gas, the prepared cathode paste was uniformly sprayed onto the electrolyte surface of the dry-pressed cell. After the liquid had completely evaporated, the sprayed dry-pressed cell was placed in a high-temperature muffle furnace and calcined at 900°C for 2 hours to obtain the desired single cell. Polarization impedance was then tested within a temperature range of 650-500°C. The cell achieved an output power of 1.14 W / cm² at 650°C. -2 .

[0052] Test method for proton absorption and transport capability of air electrode in reversible proton conductor solid oxide fuel cell

[0053] Specific steps:

[0054] (1) Weigh 150 mg of the phase reaction powder BC-5%HE and place it in a catalytic tube.

[0055] (2) Heat the catalytic tube to 500°C, introduce air containing 20% ​​vol. H2O, and treat for 5 hours.

[0056] (3) Quench the processed powder.

[0057] (4) Use a flow rate of 20 mL / min -1 The air will be blown through and passed into the mass spectrometer to detect the H2O signal.

[0058] 1. XRD characterization analysis

[0059] Figure 1 The figures show the XRD patterns of BC, HE, and BC-5%HE at room temperature. BC exhibits a hexagonal structure, while HE shows an orthorhombic structure. After uniformly mixing BC and HE and calcining at 900℃ for 2 hours, the diffraction patterns do not show a simple superposition of the two, indicating a phase reaction. Analysis revealed that a new phase, BaMoO4, was formed after calcination of BC-5%HE.

[0060] 2. Electrochemical impedance analysis

[0061] Figure 2 The comparison of polarization impedance as a function of temperature for symmetrical cells prepared by BC, its composites with different proportions of HE, and composite negative thermal expansion materials shows that under humid air conditions, BC-5%HE exhibits the lowest polarization impedance at all temperature points. Furthermore, the decrease in polarization impedance is more pronounced as the temperature decreases. BC-5%HE has the lowest activation energy of 0.86 eV at 700-500℃, indicating that the introduction of a small amount of HE is more beneficial to the reaction of BC at medium and low temperatures.

[0062] 4. Analysis of H2O temperature-programmed desorption (TPD) curves

[0063] Figure 3The BC-HE composite cathode was treated at 500℃ and 20% water vapor partial pressure for 5 hours and then quenched to room temperature. Mass spectrometry was used to perform temperature-programmed desorption (H2O-TPD) tests on the powder to study the hydration capacity of the composite air electrode. Before treatment with 20% water vapor, the composite sample was calcined in a muffle furnace at 900℃ for 2 hours to ensure phase reaction. The results are shown in the figure. It can be seen that different materials exhibit obvious water desorption peaks before 400℃, and BC has a lower water signal intensity, indicating its poor water storage capacity. After the introduction of HE, BC-5%HE and BC-5%YW show stronger water desorption signals, indicating a significant enhancement in the hydration capacity of the materials. Furthermore, above 400℃, BC-5%HE and BC-10%HE materials show weak desorption peak signals, possibly corresponding to the proton adsorption process in the oxide bulk phase. In contrast, BC does not show obvious signal peaks, indicating an enhanced proton defect concentration.

[0064] 5. Analysis of thermal expansion curves

[0065] Figure 4 The coefficients of thermal expansion (TEC) for BC and different materials show that HE material exhibits a consistent trend with YM, displaying negative thermal expansion characteristics. It also shows a low TEC of 2.22 × 10⁻⁶ TEC within the temperature range of 50-900℃. - 6 K -1 and -1.67×10 -6 K -1 The initial TEC of BC is relatively high, but it tends to decrease with the increase of the compound HE ratio. The TEC of BC-5% HE is 17.71 × 10⁻⁶. -6 K -1 This indicates that although a phase reaction occurs between BC and HE, the newly formed phase still helps to effectively reduce the TEC of the BC air electrode and enhance the thermomechanical matching between it and the electrolyte.

[0066] 6. Fuel Cell Mode Performance Testing

[0067] Figure 5 The IVP curves of an anode-supported single cell with the structure Ni+BZCYYb|BZCYYb|BC-5%HE, prepared using Ni-BZCYYb as the anode, BZCYYb as the electrolyte, and BC-5%HE as the air electrode, were obtained under hydrogen-fueled conditions. The power densities of the BC-5%HE single cell in the 650-500℃ range were 1.14, 0.81, 0.59, and 0.46 W / cm², respectively. -2 Compared to Figure 6 The single-cell performances prepared using BC as the electrode were 0.79, 0.57, 0.34, and 0.17 W / cm², respectively.-2 The performance has been significantly improved.

[0068] 7. Electrolytic Cell Mode Performance Testing

[0069] Figure 7 The figures show the electrolysis IV curves of Ni-BZCYYb|BZCYYb|BC in electrolytic cells at 650-500℃, with electrolytic current densities of -1.03, -0.8, -0.41, and -0.17 A cm⁻¹ at 1.3V. -2 Benefiting from the introduction of a highly hydrated reactive phase through phase reaction, which enhances the water storage capacity of BC, the BC-5%HE air electrode exhibits excellent performance in electrolysis mode, such as... Figure 8 The electrolytic currents at 1.3V within the temperature range of 650-500℃ shown are -1.92, -1.37, -0.81, and -0.4A cm⁻¹, respectively. -2 .

[0070] An important indicator for evaluating the effectiveness of an electrolytic cell is the Faraday efficiency. Figure 9 This paper presents the Faraday efficiency and hydrogen production rate of a Ni-BZCYYb|BZCYYb|BC-5%HE electrolytic cell at 600℃ under different water pressures. At 600℃ and 30% water pressure, the Faraday efficiency first increases and then decreases with increasing current density, particularly at -1200 mA cm⁻¹. -2 It reaches a peak value of 97.2% at that time, and the overall current density is around -1000 mA cm⁻¹. -2 At the above times, BC-5%HE maintained high efficiency, demonstrating its high efficiency as an air electrode for water electrolysis to produce hydrogen. Furthermore, with increasing current density, the hydrogen generation rate continuously increased, and the hydrogen production approached the theoretical value. These results demonstrate the superiority of the composite electrode material and the overall preparation process of the electrolytic cell of this invention.

[0071] Figure 10 The image shows a cross-sectional view of a single cell containing a Ni-BZCYYb composite anode, BZCYYb electrolyte, and porous BC-5%HE cathode after performance testing. The image clearly shows that the layers of the cell remain tightly bonded, with no obvious delamination, demonstrating the reliability of the performance test results.

[0072] 8. Characterization of the stability of symmetric cells

[0073] Figure 11 Symmetric cells were prepared using BC and BC-5%HE as electrodes and BZCYYb as electrolyte, respectively. After 200 hours of operation at 600℃ under 5% H2O-Air conditions, as shown in the figure, the polarization impedance growth rate of BC-5%HE was 1.5 × 10⁻⁶. -4 Ωcm 2 h-1 In contrast, the attenuation rate of the BC air electrode is as high as 18.5 × 10⁻⁶ under high temperature and humid conditions. -4 Ωcm 2 h -1 This demonstrates the excellent electrochemical stability of the composite electrode.

[0074] To investigate the performance of the composite electrode under harsh operating conditions, the thermal stability of the material was tested. Figure 12 The thermal impedance tests of BC and BC-5%HE on BZCYYb electrolyte under 5% water pressure conditions at 650-200℃ showed that after more than 200 hours and 52 thermal cycles, the polarization impedance of BC-5%HE decreased by only 4.9%, while that of BC reached as high as 170%, further verifying the excellent thermal stability of the composite electrode. This indicates that high-entropy negative thermal expansion materials can effectively improve the poor stability of BC on proton-conducting electrolytes.

[0075] The composite air electrode developed in this invention solves the problems of insufficient hydration reaction activity and thermomechanical mismatch with electrolyte materials when BC is used as a highly active oxygen reduction reaction catalyst in proton conductor solid oxide fuel cells. BC-5%HE exhibits excellent electrochemical performance in both PCFC and PCEC modes, and in NiO-BaZr... 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ The maximum power density of the anode-supported single cell in battery mode at 650°C is 1.14 W / cm². -2 Electrolysis mode at 1.3V -1.92A cm -2 The electrolytic current density is significantly improved. Furthermore, the BC-5%HE applied to symmetric cells exhibits significantly enhanced long-term stability over 200 hours and thermal cycling stability at 650-200℃ compared to BC. This invention develops a composite reversible air electrode material with high hydration performance and thermal stability, as well as its preparation method, laying the foundation for practical applications in proton-conducting solid oxide fuel cells and electrolyzers.

Claims

1. A composite air electrode material for a high-entropy, negatively thermally expanding, reversible proton conductor fuel cell, characterized in that, This includes YW / Mo-based high-entropy negative thermal expansion materials and BaCoO. 3-δ δ represents the oxygen vacancy content, and the chemical formula of the YW / Mo-based high-entropy negative thermal expansion material is: Y 0.4±x Zr 0.4±y Er 0.4±z Sm 0.4±m Sc 0.4±n W 1.5±p Mo 1.5±q O 12 Where x, y, z, m, n ∈ [0, 0.2], p, q ∈ [0, 0.1]; The weight of the YW / Mo-based high-entropy negative thermal expansion material is BaCoO 3-δ 2-10%.

2. The preparation method of the high-entropy negative thermal expansion reversible proton conductor fuel cell composite air electrode material according to claim 1, characterized in that, The process includes the following steps: using a ball mill to process BaCoO 3-δ It was prepared by mixing with YW / Mo-based high-entropy negative thermal expansion materials.

3. The preparation method according to claim 2, characterized in that, The preparation method of YW / Mo-based high-entropy negative thermal expansion material is to obtain it through ball milling and calcination using a solid-state method.

4. The preparation method according to claim 3, characterized in that, The solid-state preparation process includes the following steps: Y2O3, ZrO2, Er2O3, Sm2O3, Sc2O3, WO3, and MoO3 are mixed, ball-milled, and calcined to obtain the final product.

5. The preparation method according to claim 4, characterized in that, The roasting conditions are 850-950 ℃ for 5-20 hours.

6. The application of the air electrode material according to claim 1 in a reversible proton conductor fuel cell.

Images