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

Abstract

The invention relates to a reversible proton conductor fuel cell air electrode made of a composite high-entropy negative thermal expansion material and a preparation method of the reversible proton conductor fuel cell air electrode, and belongs to the technical field of solid oxide reversible cells. The high-entropy negative thermal expansion material is synthesized through a solid phase method, and the composition molecular formula of the material is BaCoO < 3-delta >-Y < 0.4 > Zr < 0.4 > Er < 0.4 > Sm < 0.4 > Sc < 0.4 > W < 1.5 > Mo < 1.5 > O < 12 >. The high-entropy negative thermal expansion material is introduced into the traditional Co-based electrode material, so that the thermal expansion coefficient of the electrode can be reduced, and meanwhile, a new phase with rapid hydration reaction capability is generated through reactive sintering, so that the air electrode material has excellent electrochemical performance in both battery and electrolysis modes, and the thermal cycling stability is improved.

Description

Technical Field

[0001] The present invention relates to a micro-composite material Y having high entropy negative thermal expansion characteristics. 0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0.4 W 1. 5 M 1.5 O 12 To enhance BaCoO 3-δ Strategies to improve the thermal stability and hydration capacity of solid oxide fuel cells and their applications in the field of reversible proton conductor solid oxide fuel cell air electrodes. Background Art

[0002] Solid oxide fuel cells (SOFCs), as an emerging energy conversion technology, have attracted widespread attention due to their clean and efficient characteristics. The operating temperature of traditional oxygen ion conductor SOFCs is between 700-900℃, which is not conducive to long-term operation of the battery and cost reduction. Therefore, reducing the operating temperature of SOFCs (400-600℃) is the key to its large-scale industrial application. Reversible proton conductor fuel cells (R-PCECs) use proton-conducting electrolytes. Protons have lower activation energy at medium and low temperatures, which is more conducive to material selection, extending battery life and reducing overall costs. However, the reduction in operating temperature will cause the polarization impedance of the cathode to increase sharply, reducing battery performance. Therefore, 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] BCO 3-δ (BC) has been widely studied due to its excellent ionic and electronic conductivity and oxygen reduction reaction (ORR) activity, and has the potential to become an R-PCEC air electrode. However, BC lacks proton conductivity, and when used as an air electrode, the three-phase reaction interface is limited, 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 the spin valence state of cobalt ions and lattice expansion. During operation, it is easy to delaminate with adjacent components of the battery, which poses a challenge to the thermal stability of the battery. Summary of the invention

[0004] The purpose of the present invention is to develop a material Y having high entropy negative thermal expansion properties 0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0. 4 W 1.5 Mo 1.5 O 12 (HE), through the 3-δ(BC) was physically mixed and then reacted and sintered to prepare the R-PCEC composite air electrode BC-HE, which improved 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 a YW / Mo-based high entropy negative thermal expansion material and BaCoO 3-δ , δ represents the oxygen vacancy content, where 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 YW / Mo-based high entropy negative thermal expansion material is BaCoO 3-δ 2-10% of.

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

[0008] BaCoO was milled using ball milling 3-δ It is prepared by mixing with YW / Mo-based high entropy negative thermal expansion material.

[0009] The YW / Mo-based high entropy negative thermal expansion material is prepared by a solid phase method through ball milling and calcination.

[0010] The preparation process of the solid phase method includes the following steps:

[0011] Take Y 2 O 3 、ZrO 2 , Er 2 O 3 、Sm 2 O 3 Sc 2 O 3 , WO 3 、MoO 3 The mixture is mixed and then ball-milled and calcined to obtain the product.

[0012] The calcination conditions are 850-950° C. for 5-20 hours.

[0013] Application of the above-mentioned air electrode material in a reversible proton conductor fuel cell.

[0014] The beneficial effects of the present 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 phase method and has the following effects:

[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.

[0017] (2) Trace amounts of composite high-entropy negative thermal expansion materials can effectively enhance the thermal stability and chemical water adsorption capacity of BC, making it better applicable to the air electrode of reversible proton conductor fuel cells.

[0018] (3) The BC-5% HE air electrode has excellent battery electrolysis performance, with a maximum power density of 1.14 W cm at 650 °C. -2 , electrolysis current density at 1.3 V -1.92 A cm -2 .

[0019] (4) The BC-5% HE air electrode has excellent thermal stability, and the polarization impedance decay rate is less than 5% after 52 thermal cycles in the temperature range of 650-200℃. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Figure 2 Comparison of polarization impedance and activation energy of BC and YW / Mo composite cathodes and composite cathodes with different ratios of HE in humid air;

[0022] Figure 3 It is the H of BC, BC-5%HE and BC-5%YW 2 O programmed temperature desorption test results;

[0023] Figure 4 is the thermal expansion curve of BC composited with YW / Mo and composited with different proportions of HE;

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

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

[0026] Figure 7It is the performance curve of water electrolysis of Ni-BZCYYb|BZCYYb|BC electrolytic cell in the temperature range of 650-500℃;

[0027] Figure 8 It is the performance curve of water electrolysis of Ni-BZCYYb|BZCYYb|BC-5%HE electrolytic cell in the temperature range of 650-500℃;

[0028] Fig. 9 is the hydrogen generation rate and Faraday efficiency of Ni-BZCYYb|BZCYYb|BC-5%HE electrolytic cell at 600℃ for electrolysis of 30% water partial pressure;

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

[0030] Fig.12 Thermal cycling stability of polarization impedance at 650-200℃ for symmetric cells with BC and BC-5%HE as air electrodes. DETAILED DESCRIPTION

[0031] The present invention relates to a micro-composite material Y having high entropy negative thermal expansion characteristics. 0.4 Zr 0.4 Er 0.4 Sm 0.4 Sc 0.4 W 1. 5 M 1.5 O 12 (HE) to enhance BaCoO 3-δ The thermal stability and hydration ability of (BC) are studied. BC has excellent oxygen activation ability, and HE effectively regulates the large thermal expansion coefficient of BC. After reaction sintering, BaMoO is introduced. 4 phase, improving proton conductivity and enhancing hydration reaction ability while regulating the interfacial contact between BC and HE phases.

[0032] After the above beneficial phase reactions, the synergistic effect of each phase enables BC-5%HE to achieve excellent performance as an air electrode in a reversible proton conductor solid oxide fuel cell. In battery mode, the corresponding single cell can obtain 1.14 W cm at 650 °C. -2 Maximum output power; electrolysis of 30% H at 650°C in electrolysis mode 2 O, at 1.3V, can get -1.92A cm -2The maximum current density is 2.5 % and 1.5 % respectively. In addition, in the symmetrical battery impedance test, BC-5% HE showed excellent thermal stability, and the polarization impedance decay rate was less than 5% in 52 thermal cycles in the temperature range of 650-200°C. The present invention develops a high-performance and stable air electrode material and a preparation method thereof, which greatly improves the electrochemical performance of proton ceramic fuel cells and electrolytic cells.

[0033] Example 1

[0034] BaCoO: a reversible proton conductor air electrode material for solid oxide fuel cells 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 The specific steps of the composite method are as follows:

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

[0036] (2) Anhydrous ethanol was added, and the ball mill was operated at 400 rpm for 60 min. The ball mill was then taken out and dried to obtain a BC precursor.

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

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

[0039] (5) Anhydrous ethanol was added, and the ball mill was operated at 400 rpm for 60 min. The ball mill was then taken out and dried to obtain a HE precursor.

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

[0041] (7) Add BC and HE powders (three parallel comparative experiments were conducted, in which the mass of HE in the BC powder was 0 / 5 / 10 wt %, respectively) into a ball mill, add anhydrous ethanol to mix, and ball mill at 400 rpm for 30 min. After taking out and drying, the desired air electrode material was obtained.

[0042] Comparative Example 1

[0043] Adopt YWY 2 W 3O12 was used as a control material to replace HE powder, and the air electrode material was prepared in the same way.

[0044] Test method for polarization impedance of symmetrical battery

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

[0046] Weigh 1 g 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 0.4 W 1. 5 M 1.5 O 12 (HE), 10 ml of isopropanol, 2 ml of ethylene glycol, and 0.8 ml of propylene glycol were poured into a high-energy ball mill. After ball milling at 400 rpm for 30 min, the desired cathode slurry was obtained by transferring the mixture to the culture bottle with a dropper.

[0047] The prepared BZCYYb electrolyte was placed on a heating table and preheated at 150°C. The prepared cathode slurry was evenly sprayed on both sides of the electrolyte using a spray gun under the push of inert gas. After the liquid evaporated completely, the sprayed electrolyte was placed in a high-temperature muffle furnace and calcined at 900°C for 2h to obtain the required symmetrical battery, which was used to test the polarization impedance of the cathode material in the temperature range of 500-700°C. The polarization impedance of the battery at 700°C is 0.05Ωcm 2 .

[0048] Single battery output power test

[0049] Taking BC-HE as an example, the specific steps include the following:

[0050] (1) Weigh 1 g 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. After ball milling at 400 rpm for 30 min, the desired cathode slurry was obtained by transferring it to the culture bottle with a pipette.

[0051] (2) Place the prepared anode support half-cell on a heating table and preheat at 150°C. Use a spray gun to evenly spray the prepared cathode slurry on the electrolyte surface of the dry-pressed sheet under the push of inert gas. After the liquid evaporates completely, place the sprayed dry-pressed battery in a high-temperature muffle furnace and calcine at 900°C for 2 hours to obtain the required single cell, and perform polarization impedance testing in the temperature range of 650-500°C. The output power of the battery at 650°C reaches 1.14Wcm -2 .

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

[0053] Specific steps:

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

[0055] (2) The catalyst tube was heated to 500°C and a solution containing 20% ​​vol. 2 O air for 5 hours.

[0056] (3) Quenching the treated powder.

[0057] (4) Use a flow rate of 20 mL min -1 The air will be purged and passed into the mass spectrometer to detect H 2 O signal.

[0058] 1. XRD characterization analysis

[0059] Figure 1 The XRD patterns of BC, HE and BC-5% HE at room temperature show that BC has a hexagonal structure and HE has an orthorhombic structure. After BC and HE are evenly mixed and calcined at 900℃ for 2h, as shown in the figure, the diffraction pattern does not show a simple superposition of the two, indicating that a phase reaction occurs. After analysis, a new phase is generated after calcination of BC-5% HE, which is BaMoO 4 Mutually.

[0060] 2. Electrochemical impedance spectroscopy

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

[0062] 4.H 2 O temperature programmed desorption (TPD) curve analysis

[0063] Figure 3 The BC-HE composite cathode was treated at 500 °C and 20% water vapor partial pressure for 5 hours and quenched to room temperature. The powder was subjected to temperature-programmed desorption of water (H 2 O-TPD) test was used to study the hydration capacity of the composite air electrode. The composite sample was calcined at 900℃ for 2h in a muffle furnace before being treated with 20% water vapor to ensure the occurrence of phase reaction. As shown in the figure, it can be seen that different materials have obvious water desorption peaks before 400℃, and the water signal intensity of BC is low, indicating its poor water storage capacity. After the introduction of HE, BC-5%HE and BC-5%YW have stronger water desorption signals, indicating that the hydration capacity of the material is significantly enhanced. In addition, above 400℃, BC-5%HE and BC-10%HE materials have weak desorption peak signals, which may correspond to the proton adsorption process in the oxide bulk phase. In contrast, there is no obvious signal peak in BC, which indicates that the proton defect concentration of the material is enhanced.

[0064] 5. Thermal expansion curve analysis

[0065] Figure 4 is the thermal expansion coefficient (TEC) between BC and different materials. It can be found that the thermal expansion curves of HE material and YM have the same trend, showing negative thermal expansion characteristics, and have a lower TEC in the temperature range of 50-900℃, which are 2.22×10 - 6 K -1 and -1.67×10 -6 K -1 The initial TEC of BC is relatively high, and it decreases with the increase of the proportion of composite HE. The TEC of BC-5% HE is 17.71×10 -6 K -1 This shows that although there is a phase reaction between BC and HE, the generated new phase is still beneficial 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 test

[0067] Figure 5The IVP curve of a single cell with a structure of Ni+BZCYYb|BZCYYb|BC-5%HE prepared with Ni-BZCYYb as anode, BZCYYb as electrolyte and BC-5%HE as air electrode was obtained by testing hydrogen as fuel. The power density of the BC-5%HE single cell in the range of 650-500℃ is 1.14, 0.81, 0.59 and 0.46W cm -2 Compared to Figure 6 The performance of the single cells prepared with BC as electrode were 0.79, 0.57, 0.34 and 0.17 W cm -2 , the performance has been significantly improved.

[0068] 7. Electrolytic cell mode performance test

[0069] Figure 7 The IV curves of the electrolytic cell of Ni-BZCYYb|BZCYYb|BC at 650-500 °C are shown in Figure 2. The electrolytic current densities at 1.3 V are -1.03, -0.8, -0.41, and -0.17 A cm, respectively. -2 Thanks to the phase reaction, the high hydration reaction phase was introduced to improve the water storage capacity of BC. BC-5%HE has good performance as air electrode in electrolysis mode, such as Figure 8 The electrolysis currents at 1.3 V in the range of 650–500 °C are −1.92, −1.37, −0.81, and −0.4 A cm, respectively. -2 .

[0070] An important indicator for evaluating the effectiveness of an electrolytic cell is the Faraday efficiency. Fig. 9 The Faraday efficiency and hydrogen generation rate of Ni-BZCYYb|BZCYYb|BC-5%HE electrolytic cell at 600℃ for different water partial pressures. At 600℃ and 30% water partial pressure, the Faraday efficiency increases first and then decreases with the increase of current density. -2 The peak value reached 97.2% at -1000mA cm -2 When the above conditions are met, BC-5% HE maintains a relatively high efficiency, proving its high efficiency in producing hydrogen by electrolyzing water as an air electrode. And with the increase of current density, the hydrogen generation rate continues to increase, and the hydrogen production is close to the theoretical value. The above results show the excellence of the composite electrode material and the overall preparation process of the electrolytic cell of the present invention.

[0071] Fig.10The cross-sectional image shape of a single battery containing a Ni-BZCYYb composite anode, a BZCYYb electrolyte, and a porous BC-5% HE cathode after the performance test is shown. It can be clearly seen from the figure that the layers of the battery are still tightly bonded and no obvious stratification occurs, proving the reliability of the performance test results.

[0072] 8. Symmetrical battery stability characterization

[0073] Fig.11 The symmetrical battery was prepared with BC and BC-5%HE as electrodes and BZCYYb as electrolyte. 2 After running for 200 h under O-Air conditions, as shown in the figure, the polarization impedance growth rate of BC-5% HE after 200 h is 1.5×10 -4 Ωcm 2 h -1 In contrast, the attenuation rate of BC air electrode in high temperature and humid environment is as high as 18.5×10 -4 Ωcm 2 h -1 , demonstrating the excellent electrochemical stability of the composite electrode.

[0074] In order to explore the performance of the composite electrode under harsh working conditions, the thermal stability of the material was tested. Fig.12 The BC and BC-5% HE were subjected to 650-200℃ thermal cycle impedance test under 5% water partial pressure conditions on BZCYYb electrolyte. It can be seen that after more than 200h and 52 thermal cycles, the polarization impedance of BC-5% HE and the polarization impedance decay rate were only 4.9%, while the polarization impedance decay rate of BC was as high as 170%, which further verified the excellent thermal stability of the composite electrode. It shows that high entropy negative thermal expansion materials can effectively improve the poor stability of BC on proton conductor electrolytes.

[0075] The composite air electrode developed in this invention solves the problem 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 has excellent electrochemical performance in both PCFC and PCEC modes. 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 cm -2 , electrolysis mode 1.3V -1.92A cm -2The electrolysis current density is 200h. In addition, the 200h long-term stability and 650-200℃ thermal cycle stability of BC-5%HE applied to symmetrical cells are greatly improved compared with BC. The present invention develops a composite reversible air electrode material with high hydration performance and thermal stability and a preparation method, laying a foundation for the practical application of proton conductor solid oxide fuel cells and electrolytic cells.

Claims

1. A high entropy negative thermal expansion reversible proton conductor fuel cell composite air electrode material, characterized in that: Including YW / Mo-based high entropy negative thermal expansion materials and BaCoO 3-δ , δ represents the oxygen vacancy content, where 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].

2. The high entropy negative thermal expansion reversible proton conductor fuel cell composite air electrode material according to claim 1, characterized in that: The weight of YW / Mo-based high entropy negative thermal expansion material is BaCoO 3-δ 2-10% of.

3. The method for preparing the high entropy negative thermal expansion reversible proton conductor fuel cell composite air electrode material according to claim 1, characterized in that: The steps include: BaCoO was milled using ball milling 3-δ It is prepared by mixing with YW / Mo-based high entropy negative thermal expansion material.

4. The preparation method according to claim 3, characterized in that: It is obtained through ball milling and calcination by solid phase method.

5. The preparation method according to claim 4, characterized in that: The preparation process of the solid phase method includes the following steps: Y2O3, ZrO2, Er2O3, Sm2O3, Sc2O3, WO3, and MoO3 are mixed and then ball-milled and calcined to obtain the mixture.

6. The preparation method according to claim 5, characterized in that: The calcination conditions are 850-950° C. for 5-20 hours.

7. Use of the air electrode material according to claim 1 or 2 in a reversible proton conductor fuel cell.

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