High-entropy bismuth oxide-based solid oxide fuel cell electrolyte as well as preparation method and application thereof
By employing multi-element doping and preparation processes for high-entropy bismuth oxide-based solid oxide fuel cell electrolytes, the problems of thermodynamic instability and insufficient reduction resistance of electrolytes at low temperatures have been solved, thereby improving the stability and performance of the electrolytes and making them suitable for the field of solid oxide fuel cells.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-03-10
AI Technical Summary
Existing high-entropy bismuth oxide-based solid oxide fuel cell electrolytes are thermodynamically unstable at low temperatures, prone to phase transitions, and lack sufficient resistance to reduction, leading to performance degradation. Traditional doping methods have limited effectiveness and are complex and costly to prepare.
A high-entropy bismuth oxide-based solid oxide fuel cell electrolyte was prepared by using equimolar or near-equimolar ratio doping of rare earth elements such as La, Pr, Sm, Gd, Dy, and Yb, combined with co-precipitation and high-temperature solid-state sintering processes to ensure uniform mixing and densification of the multi-component structure, thus producing an electrolyte with a stable fluorite phase structure.
It significantly broadens the stable operating temperature range of the electrolyte, improves its resistance to reduction and thermal stability, has good material composition uniformity, is easy to mass-produce, and reduces costs.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of solid oxide fuel cell materials, and particularly relates to a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte as well as a preparation method and application thereof. BACKGROUND
[0002] As a kind of full solid energy conversion device, the solid oxide fuel cell (SOFC) has the outstanding advantages of wide fuel adaptability, high energy conversion efficiency and zero emission, and shows broad prospects in the field of distributed power generation and clean energy utilization. However, the high operating temperature of the traditional SOFC leads to severe material challenges and high system cost, so reducing the operating temperature to the medium-low temperature range (300-600℃) has become the core path to promote its commercialization. The key to achieving this goal lies in the development of electrolyte materials that can maintain excellent oxygen ion conductivity at low temperatures.
[0003] Among the many electrolyte candidate materials, δ-Bi2O3 with a cubic fluorite structure exhibits excellent oxygen ion conductivity at medium temperatures, which is 1-2 orders of magnitude higher than that of traditional yttrium-stabilized zirconia (YSZ), and is considered as an ideal medium-low temperature electrolyte. However, the δ-Bi2O3 phase is thermodynamically unstable at low temperatures, prone to phase transition and accompanied by volume change, leading to structural damage; at the same time, it is easily reduced to metallic bismuth in a reducing atmosphere, producing harmful electronic conductivity and destroying the electrolyte density, which seriously restricts its practical application.
[0004] Therefore, how to effectively widen the stable working temperature range of δ-Bi2O3 and significantly improve its reduction resistance has become a core problem that must be solved to promote the large-scale commercial application of bismuth oxide-based electrolytes. To stabilize the δ-Bi2O3 phase and improve its performance, researchers generally use element doping strategies. The existing technology is mostly focused on single or double rare earth element doping, which can stabilize the phase structure to some extent, but the effect is limited, and it is difficult to simultaneously consider ion conductivity and structural / chemical stability. These traditional doping systems cannot effectively suppress element segregation and oxygen vacancy ordering due to their simple composition and low entropy, leading to performance degradation during long-term operation.
[0005] In addition, the existing preparation methods of bismuth oxide-based electrolytes, such as solid phase method, sol-gel method, etc., have problems such as complex process, high cost, or difficulty in accurately controlling the uniformity of multi-component composition. SUMMARY
[0006] The technical problem to be solved by the present application is to provide a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte as well as a preparation method and application thereof, which overcomes the defects of narrow working temperature range and poor thermal stability of δ-Bi2O3 in the prior art.
[0007] To solve the above technical problems, according to one aspect of the present application, there is provided a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte with a general chemical formula of (Bi2O3)x(RE2O3)1-x, wherein x = 0.25, 0.33 or 0.50; RE is a combination of any four of La, Pr, Sm, Gd, Dy, Er and Yb, and the molar ratio of the selected four elements is 0.99-1.01. 1-x (RE2O3) x wherein x = 0.25, 0.33 or 0.50; RE is a combination of any four of La, Pr, Sm, Gd, Dy, Er and Yb, and the molar ratio of the selected four elements is 0.99-1.01.
[0008] As a preferred embodiment, the selected four elements in RE are in equimolar ratio.
[0009] According to another aspect of the present application, there is provided a preparation method of the high-entropy bismuth oxide-based solid oxide fuel cell electrolyte described above, comprising: Step one, mixing bismuth nitrate and nitrate salts corresponding to the selected four elements in a dilute nitric acid solution to prepare a nitrate salt mixed solution; Step two, adding ammonia water to the nitrate salt mixed solution under stirring, controlling the end-point pH value of the system to be maintained at 8.0-10.0, and obtaining a precipitate after the reaction is completed, and the precipitate is washed and dried to obtain a high-entropy bismuth oxide precursor powder; Step three, performing first heat treatment on the high-entropy bismuth oxide precursor powder, and the first heat treatment process is: heating at a rate of 4-6 ℃ / min to 550-650 ℃, maintaining for 50-70 min, and then naturally cooling; Step four, pressing the high-entropy bismuth oxide precursor powder after the first heat treatment into a shape, and obtaining a product after pre-sintering and second heat treatment; the pre-sintering process is: heating at a rate of 4-6 ℃ / min to 350-450 ℃, maintaining for 50-70 min; and the second heat treatment process is: heating at a rate of 4-6 ℃ / min to 950-1050 ℃, maintaining for 20-28 hours.
[0010] As a preferred embodiment, in step one, the total metal ion concentration of the nitrate salt mixed solution is 0.15-0.25 mol / L.
[0011] As a preferred embodiment, in step two, the precipitate is repeatedly washed with deionized water until it is neutral, and then dried at a temperature of 75-85 ℃.
[0012] As a preferred embodiment, in step three, the first heat treatment process is: heating at a rate of 5 ℃ / min to 600 ℃, maintaining for 60 min, and then naturally cooling.
[0013] As a preferred embodiment, in step four, the pre-sintering process is: heating at a rate of 5 ℃ / min to 400 ℃ for pre-sintering for 60 min.
[0014] As a preferred embodiment, in step four, the second heat treatment process is: heating to 1000℃ at a rate of 5℃ / min, and holding for 24 hours to obtain the product.
[0015] According to another aspect of the present application, there is provided a use of the high-entropy bismuth oxide-based solid oxide fuel cell electrolyte as described above in the preparation of a solid oxide fuel cell.
[0016] According to another aspect of the present application, there is provided a solid oxide fuel cell comprising the high-entropy bismuth oxide-based solid oxide fuel cell electrolyte as described above.
[0017] The present application adopts any four rare earth elements of La, Pr, Sm, Gd, Dy, Er and Yb to construct an equimolar or near-equimolar high-entropy system, and stabilizes the cubic fluorite phase structure of δ-Bi2O3 through the synergistic effect of multiple elements, thereby breaking the limitations of traditional single / dual-element doping and achieving the purpose of stable wide temperature range.
[0018] The preparation process of the present application adopts a co-precipitation process combined with a high-temperature solid-phase sintering process, to ensure uniform mixing of multiple elements and formation of a densified structure. (1) Optimized co-precipitation reaction process: the co-precipitation method is simplified by directly adding ammonia water to a nitrate solution, the pH value and reaction time are accurately controlled, to ensure uniform mixing of multiple elements at the atomic level and obtain a precursor with uniform composition. (2) Precise segmented heat treatment system: the first heat treatment realizes complete conversion of hydroxide to oxide, impurities are removed and the crystal structure is preliminarily formed, and long-time holding after the second heat treatment promotes grain growth and densification. DRAWINGS
[0019] Figure 1 X-ray diffraction results of the high-entropy bismuth oxide-based solid oxide fuel cell electrolytes obtained in Examples 1-3; Figure 2 Ion conductivity results of the high-entropy bismuth oxide-based solid oxide fuel cell electrolytes obtained in Examples 1-3; Figure 3 Ion conductivity results of the high-entropy bismuth oxide-based solid oxide fuel cell electrolytes obtained in Examples 4-5; Figure 4 Thermogravimetric-differential scanning calorimetry results of commercial Bi2O3; Figure 5 Thermogravimetric-differential scanning calorimetry results of the high-entropy bismuth oxide-based solid oxide fuel cell electrolyte obtained in Example 2; Figure 6 X-ray diffraction results of the high-entropy bismuth oxide-based solid oxide fuel cell electrolytes obtained in Comparative Examples 1 and 2; Figure 7X-ray diffraction results of the high-entropy bismuth oxide-based solid oxide fuel cell electrolyte obtained in Comparative Examples 1 and 2 after 800℃ holding for 150h. DETAILED DESCRIPTION
[0020] The basic concept of the present application is to introduce the high-entropy material design concept, to effectively inhibit element diffusion and adverse phase transition by doping with multiple cations in equimolar or near-equimolar ratio, to utilize the significant high-configuration entropy effect, to stabilize the fluorite phase structure in a wide temperature range, and to simultaneously enhance the electrolyte thermodynamic stability.
[0021] Based on the above concept, a typical embodiment of the present application provides a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte, which has a chemical formula of (Bi2O3) 1-x (RE2O3) x wherein x=0.25, 0.33 or 0.50.
[0022] RE is an equimolar or near-equimolar high-entropy system composed of any four trivalent rare earth elements selected from La, Pr, Sm, Gd, Dy, Er and Yb.
[0023] Taking Pr, Sm, Gd and Yb as examples, the molar ratio of Pr, Sm, Gd and Yb is (0.99-1.01):(0.99-1.01):(0.99-1.01):(0.99-1.01), for example, 0.99:1:1.01:1, 1:1.01:1:0.99; the preferred molar ratio is 1:1:1:1.
[0024] Through the synergistic doping of four rare earth elements, the high-entropy effect is utilized to stabilize the cubic fluorite phase structure, effectively broaden the stable working temperature range, effectively inhibit the harmful low-temperature phase transition, thereby significantly improving the thermal stability of the material. At the same time, the prepared high-entropy electrolyte material has the characteristics of uniform composition, controllable particle size and high sintering activity, and is easy to obtain a dense electrolyte layer.
[0025] Another typical embodiment of the present application provides a preparation method of the above-mentioned high-entropy bismuth oxide-based solid oxide fuel cell electrolyte, which adopts a co-precipitation combined with high-temperature solid-phase sintering process route to ensure uniform mixing of multiple components and formation of a dense structure, comprising the following steps one to four.
[0026] Step one, preparation of a mixed nitrate solution.
[0027] Bi(NO3)3 and the selected four kinds of element corresponding nitrate are mixed in dilute nitric acid solution to prepare a mixed nitrate solution.
[0028] Bismuth nitrate and nitrate salts of the selected four elements are weighed according to the stoichiometric ratio, and the bismuth nitrate is dissolved in a dilute nitric acid solution, and then the nitrate salts of the remaining four elements are sequentially added.
[0029] The concentration of the dilute nitric acid solution is 0.7-1.00 mol / L, and the total metal ion concentration of the nitrate salt mixed solution is 0.15-0.25 mol / L, preferably 0.2 mol / L.
[0030] Step two, co-precipitation reaction.
[0031] Under stirring conditions, ammonia water is directly added to the nitrate salt mixed solution, the end point pH value of the system is controlled to be maintained at 8.0-10.0 by adjusting the ammonia water addition amount, and the precipitation reaction time is controlled to be about 30 minutes. After the reaction is completed, the precipitate is obtained by standing and filtering, and the precipitate is washed and dried for several times to obtain a high-entropy bismuth oxide precursor powder with uniform composition.
[0032] Exemplarily, the precipitate is repeatedly washed to neutral with deionized water, and then dried at a temperature of 75-85°C, preferably at a drying temperature of 80°C.
[0033] Step three, first heat treatment.
[0034] The high-entropy bismuth oxide precursor powder is transferred to an alumina crucible and placed in a muffle furnace for first heat treatment to realize the conversion from the precursor to the metal oxide phase.
[0035] The first heat treatment process is: heated to 550-650°C at a rate of 4-6°C / min, and naturally cooled after holding for 50-70 min.
[0036] The preferred first heat treatment process is: heated to 600°C at a rate of 5°C / min, and naturally cooled after holding for 60 min.
[0037] Step four, pre-sintering and second heat treatment.
[0038] The high-entropy bismuth oxide precursor powder after the first heat treatment is pressed into a product by a manual press, and the product is obtained after pre-sintering and second heat treatment.
[0039] The pre-sintering process is: heated to 350-450°C at a rate of 4-6°C / min, and held for 50-70 min to realize the decomposition of water and impurities in the precursor and the preliminary formation of the crystal structure.
[0040] The preferred pre-sintering process is: heated to 400°C at a rate of 5°C / min, and held for 60 min.
[0041] The second heat treatment process is: heating to 950-1050℃ at a rate of 4-6℃ / min, and holding for 20-28 hours to realize grain growth and densification, and ensure obtaining high-quality electrolyte sheets with stable fluorite structure.
[0042] The preferred second heat treatment process is: heating to 1000℃ at a rate of 5℃ / min, and holding for 24 hours.
[0043] The present application adopts a co-precipitation method to prepare high-entropy bismuth oxide-based electrolyte, which can ensure uniform mixing and synchronous precipitation of multiple metal precursors at the atomic scale of the solution, thereby directly obtaining a powder with highly uniform components and high material purity. The prepared powder has the characteristics of narrow particle size distribution, controllable particle size and morphology, and the product is a superfine powder with high activity, which is helpful for subsequent sintering into a dense electrolyte film. In addition, this technology also has a series of advantages such as short cycle, low cost, safe and reliable operation, simple process flow, etc., and is very suitable for large-scale batch production, laying a solid process foundation for the industrial application of high-performance high-entropy electrolyte materials.
[0044] The technical solutions claimed in the present application will be further described below through some examples. However, the examples and comparative examples are used to explain the embodiments of the present application and do not exceed the scope of the subject matter of the present application, and the protection scope of the present application is not limited by the examples. Unless otherwise specified, the materials and reagents used in the present application can be obtained from commercial products in the art. Example 1
[0045] Preparation of high-entropy bismuth oxide-based solid oxide fuel cell electrolyte with chemical formula (Bi 3 / 4 Pr 1 / 16 Sm 1 / 16 Gd 1 / 16 Yb 1 / 16 ).
[0046] Accurately weigh Bi(NO3)3·5H2O, Pr(NO3)3·6H2O, Sm(NO3)3·6H2O, Gd(NO3)3·6H2O and Yb(NO3)3·5H2O raw materials according to the stoichiometric ratio of 12:1:1:1:1. First, dissolve Bi(NO3)3·5H2O in a 1.00 mol / L dilute nitric acid solution, and then add the remaining four rare earth nitrate salts in turn, dissolve them together and configure into a mixed nitrate solution with a total metal ion concentration of 0.2 mol / L.
[0047] Under the condition of continuous stirring, ammonia solution was added into the above nitrate mixed solution at a constant rate, the end point pH value of the system was controlled at 9.0, and uniform precipitate was generated after 30 minutes of continuous reaction. After the reaction was completed, the precipitate was filtered and washed with deionized water until it was neutral, and then dried at 80°C for 12 hours to obtain high-entropy bismuth oxide precursor powder.
[0048] The high-entropy bismuth oxide precursor powder was transferred to an alumina crucible and placed in a muffle furnace for heat treatment. The temperature was raised to 600°C at a rate of 5°C / min, and the temperature was kept for 60 minutes to complete the conversion of hydroxide to oxide.
[0049] Then, 0.4 g of the heat-treated powder was weighed and pressed into a shape under a pressure of 10 T for 3 minutes.
[0050] The shaped piece was placed in a muffle furnace and heated from room temperature to 400°C at a rate of 5°C / min, and the temperature was kept for 60 minutes to remove moisture and impurities and to form a preliminary crystal structure. The temperature was then continuously raised to 1000°C at the same rate, and the temperature was kept for 24 hours to promote the growth of crystal grains and the densification of the structure, thereby obtaining a high-quality electrolyte sheet with a stable fluorite structure. Example 2
[0051] A high-entropy bismuth oxide-based solid oxide fuel cell electrolyte with the chemical formula (Bi 2 / 3 Pr 1 / 12 Sm 1 / 12 Gd 1 / 12 Yb 1 / 12 )2O3 was prepared. Bi (NO3)3·5H2O, Pr (NO3)3·6H2O, Sm (NO3)3·6H2O, Gd (NO3)3·6H2O, and Yb (NO3)3·5H2O raw materials were accurately weighed according to the stoichiometric ratio of 8:1:1:1:1. First, Bi (NO3)3·5H2O was dissolved in a 1.00 mol / L dilute nitric acid solution, and then the remaining four rare earth nitrate salts were added in sequence, dissolved together, and diluted to a total metal ion concentration of 0.2 mol / L to prepare a nitrate mixed solution.
[0052] Under the condition of continuous stirring, ammonia solution was added into the above nitrate mixed solution at a constant rate, the end point pH value of the system was controlled at 9.0, and uniform precipitate was generated after 30 minutes of continuous reaction. After the reaction was completed, the precipitate was filtered and washed with deionized water until it was neutral, and then dried at 80°C for 12 hours to obtain high-entropy precursor powder.
[0053] The high-entropy bismuth oxide precursor powder was transferred to an alumina crucible and placed in a muffle furnace for heat treatment. The temperature was raised to 600°C at a rate of 5°C / min, and the temperature was kept for 60 minutes to complete the conversion of hydroxide to oxide.
[0054] Subsequently, 0.4 g of the heat-treated powder was weighed and molded under a pressure of 10 T for 3 minutes.
[0055] The molded piece was placed in a muffle furnace and heated at a rate of 5°C / min from room temperature to 400°C and held for 60 minutes to remove moisture and impurities and to form a crystal structure. The temperature was then increased at the same rate to 1000°C and held for 24 hours to promote grain growth and densification of the structure, thereby obtaining a high-quality electrolyte piece with a stable fluorite structure. To test the thermal stability, the prepared electrolyte piece was placed in a muffle furnace and heated at a rate of 5°C / min to 800°C and held for 150 hours. Example 3
[0056] A high-entropy bismuth oxide-based solid oxide fuel cell electrolyte with a chemical formula of (Bi 1 / 2 Pr 1 / 8 Sm 1 / 8 Gd 1 / 8 Yb 1 / 8 )2O3 was prepared. Bi(NO3)3·5H2O, Pr(NO3)3·6H2O, Sm(NO3)3·6H2O, Gd(NO3)3·6H2O, and Yb(NO3)3·5H2O were accurately weighed according to the stoichiometric ratio of 4:1:1:1:1. First, Bi(NO3)3·5H2O was dissolved in a 1.00 mol / L dilute nitric acid solution, and then the remaining four rare earth nitrate salts were added in sequence, dissolved together, and diluted to a total metal ion concentration of 0.2 mol / L to prepare a nitrate mixed solution.
[0057] Under continuous stirring, an ammonia solution was added to the above-mentioned nitrate mixed solution at a constant rate, and the final pH value of the system was controlled at 9.0. The reaction was allowed to proceed for 30 minutes to generate a uniform precipitate. After the reaction was completed, the precipitate was allowed to stand, filtered, and washed repeatedly with deionized water until it was neutral. The precipitate was then dried at 80°C for 12 hours to obtain a high-entropy precursor powder.
[0058] The high-entropy bismuth oxide precursor powder was transferred to an alumina crucible and placed in a muffle furnace for heat treatment. The temperature was increased at a rate of 5°C / min to 600°C and held for 60 minutes to complete the conversion of the hydroxide to the oxide.
[0059] Subsequently, 0.4 g of the heat-treated powder was weighed and molded under a pressure of 10 T for 3 minutes.
[0060] The shaped piece is placed in a muffle furnace to be heated at a rate of 5°C / min from room temperature to 400°C, and kept for 60 minutes to remove moisture and impurities and to form a crystal structure; the temperature is continued to be raised at the same rate to 1000°C, and kept for 24 hours to promote full grain growth and structure densification, and a high-quality electrolyte piece with a stable fluorite structure is obtained. Example 4
[0061] A high-entropy bismuth oxide-based solid oxide fuel cell electrolyte with a chemical formula of (Bi 2 / 3 Pr 1 / 12 Sm 1 / 12 Gd 1 / 12 Er 1 / 12 )2O3 is prepared. Bi (NO3)3·5H2O, Pr (NO3)3·6H2O, Sm (NO3)3·6H2O, Gd (NO3)3·6H2O and Er (NO3)3·5H2O raw materials are accurately weighed according to the stoichiometric ratio of 8:1:1:1:1. Bi (NO3)3·5H2O is first dissolved in a 1.00 mol / L dilute nitric acid solution, and then the remaining four rare earth nitrate salts are sequentially added and dissolved to prepare a mixed nitrate solution with a total metal ion concentration of 0.2 mol / L.
[0062] Under continuous stirring, ammonia solution is added to the above-mentioned mixed nitrate solution at a constant rate, and the final pH value of the system is controlled at 8.0. The reaction is continued for 30 minutes to generate a uniform precipitate. After the reaction is completed, the precipitate is filtered and washed with deionized water until it is neutral. Then, the precipitate is dried at 80°C for 12 hours to obtain a high-entropy precursor powder.
[0063] The high-entropy bismuth oxide precursor powder is transferred to an alumina crucible and placed in a muffle furnace for heat treatment. The temperature is raised to 550°C at a rate of 4°C / min, and kept for 70 minutes to complete the conversion of hydroxide to oxide.
[0064] Then, 0.4 g of the heat-treated powder is weighed and pressed into a shaped piece under a pressure of 10 T for 3 minutes.
[0065] The shaped piece is placed in a muffle furnace to be heated at a rate of 4°C / min from room temperature to 350°C, and kept for 70 minutes to remove moisture and impurities and to form a crystal structure; the temperature is continued to be raised at the same rate to 950°C, and kept for 28 hours to promote full grain growth and structure densification, and a high-quality electrolyte piece with a stable fluorite structure is obtained. Example 5
[0066] A high-entropy bismuth oxide-based solid oxide fuel cell electrolyte with a chemical formula of (Bi 2 / 3 Pr 1 / 12 Sm 1 / 12 Gd 1 / 12 Dy1 / 12 High-entropy bismuth oxide-based solid oxide fuel cell electrolyte of Bi2O3 Bi(NO3)3·5H2O, Pr(NO3)3·6H2O, Sm(NO3)3·6H2O, Gd(NO3)3·6H2O and Dy(NO3)3·6H2O raw materials were accurately weighed according to the stoichiometric ratio of 8:1:1:1:1. Bi(NO3)3·5H2O was first dissolved in a dilute nitric acid solution of 1.00 mol / L, and then the other four rare earth nitrate salts were sequentially added, dissolved together and constant volume to prepare a mixed nitrate solution with a total metal ion concentration of 0.2 mol / L.
[0067] Under continuous stirring, ammonia solution was added to the above mixed nitrate solution at a constant rate, and the final pH value of the system was controlled at 10.0. The reaction was continued for 30 minutes to generate a uniform precipitate. After the reaction was completed, the precipitate was allowed to stand, filtered, washed repeatedly with deionized water until neutral, and then dried at 80°C for 12 hours to obtain a high-entropy precursor powder.
[0068] The high-entropy bismuth oxide precursor powder was transferred to an alumina crucible and placed in a muffle furnace for heat treatment. The temperature was raised to 650°C at a rate of 6°C / min, and the temperature was maintained for 70 min to complete the conversion of hydroxide to oxide.
[0069] Then, 0.4 g of the heat-treated powder was weighed and pressed into a pellet under a pressure of 10 T for 3 minutes.
[0070] The formed pellet was placed in a muffle furnace and heated from room temperature to 450°C at a rate of 6°C / min, and the temperature was maintained for 50 min to remove moisture and impurities and to form a preliminary crystal structure. The temperature was then continuously raised to 1050°C at the same rate, and the temperature was maintained for 20 hours to promote the growth of crystal grains and densification of the structure, thereby obtaining a high-quality electrolyte pellet with a stable fluorite structure.
[0071] Comparative Example 1 Based on the results of literature research, among the single-element doped bismuth oxide systems, Er-doped showed the best performance to prepare a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte of the chemical formula (Bi 2 / 3 Er 1 / 3 )2O3 Bi(NO3)3·5H2O and Er(NO3)3·5H2O were accurately weighed according to the stoichiometric ratio of 2:1. Bi(NO3)3·5H2O was first dissolved in a dilute nitric acid solution of 1.00 mol / L, and then Pr(NO3)3·6H2O was added, dissolved together and constant volume to prepare a mixed nitrate solution with a total metal ion concentration of 0.2 mol / L.
[0072] Under continuous stirring, ammonia solution was added into the above nitrate mixed solution at a constant rate, and the end point pH value of the system was controlled at pH = 9.0, respectively, and uniform precipitate was generated after 30 minutes of reaction. After the reaction was completed, the precipitate was placed and filtered, and the obtained precipitate was repeatedly washed with deionized water until it was neutral, and then dried at 80°C for 12 hours, to obtain a precursor powder.
[0073] The precursor powder was transferred to an alumina crucible and placed in a muffle furnace for heat treatment, and the temperature was increased to 600°C at a rate of 5°C / min, and the temperature was kept for 60 min to complete the conversion of hydroxide to oxide.
[0074] Subsequently, 0.4 g of the heat-treated powder was weighed and pressed into a shape under a pressure of 10 T for 3 minutes.
[0075] The shaped piece was placed in a muffle furnace and heated from room temperature to 400°C at a rate of 5°C / min, and the temperature was kept for 60 min to remove moisture and impurities and to form a preliminary crystal structure; the temperature was then increased to 850°C at the same rate, and the temperature was kept for 24 hours to promote the full growth of the crystal grains and the densification of the structure, to obtain a high-quality electrolyte sheet with a stable fluorite structure. To test its thermal stability, the prepared electrolyte sheet was placed in a muffle furnace and heated to 800°C at a rate of 5°C / min and kept for 150 hours.
[0076] Comparative Example 2 A high-entropy bismuth oxide-based solid oxide fuel cell electrolyte with a chemical formula of (Bi 2 / 3 Er 1 / 6 Sm 1 / 6 )2O3 Bi (NO3)3·5H2O, Er (NO3)3·5H2O and Sm (NO3)3·6H2O raw materials were accurately weighed according to the stoichiometric ratio of 2:1. First, Bi (NO3)3·5H2O was dissolved in a 1.00 mol / L dilute nitric acid solution, and then Pr (NO3)3·6H2O and Sm (NO3)3·6H2O were added and dissolved together, and the volume was adjusted to prepare a nitrate mixed solution with a total metal ion concentration of 0.2 mol / L.
[0077] Under continuous stirring, ammonia solution was added into the above nitrate mixed solution at a constant rate, and the end point pH value of the system was controlled at pH = 9.0, respectively, and uniform precipitate was generated after 30 minutes of reaction. After the reaction was completed, the precipitate was placed and filtered, and the obtained precipitate was repeatedly washed with deionized water until it was neutral, and then dried at 80°C for 12 hours, to obtain a precursor powder.
[0078] The precursor powder was transferred to an alumina crucible and placed in a muffle furnace for heat treatment, and the temperature was increased to 600°C at a rate of 5°C / min, and the temperature was kept for 60 min to complete the conversion of hydroxide to oxide.
[0079] Subsequently, 0.4 g of the heat-treated powder was weighed and pressed into shape under a pressure of 10 T for 3 minutes.
[0080] The shaped electrolyte sheet was placed in a muffle furnace and heated from room temperature to 400°C at a rate of 5°C / min, and held at that temperature for 60 minutes to remove moisture and impurities and to initially form a crystal structure. The temperature was then increased to 850°C at the same rate and held for 24 hours to promote sufficient grain growth and structural densification, resulting in a high-quality electrolyte sheet with a stable fluorite structure. To test its thermal stability, the prepared electrolyte sheet was placed in a muffle furnace and heated to 800°C at a rate of 5°C / min, and held at that temperature for 150 hours.
[0081] X-ray diffraction analysis (XRD, test range 10–90°) was performed on the electrolyte sheets obtained in Examples 1-3 above, and the results are as follows: Figure 1 As shown, the material has a high degree of crystallinity and strong diffraction peaks. Comparing the spectrum with the standard XRD spectrum, the three strong peaks have a high degree of overlap, confirming that the prepared electrolyte has a stable fluorite-type crystal structure at room temperature.
[0082] The electrochemical performance of the electrolyte sheets obtained in Examples 1-3 was evaluated using AC impedance spectroscopy. The test conditions were: temperature range 500–700 °C, with tests conducted at 50 °C intervals, amplitude 50 mV, and frequency range 0.1–10 MHz. An equivalent circuit was constructed based on the test results for fitting, and the ionic conductivity was calculated using the formula σ = L / (R·S), where L is the electrolyte sheet thickness (measured using vernier calipers), R is the charge transfer impedance obtained from the equivalent circuit fitting, and S is the effective conductive area. The ionic conductivity at 500–700 °C calculated from the test results is shown below. Figure 2 As shown, the optimal doping level is around 66%, and excessive element doping will lead to a significant decrease in ionic conductivity.
[0083] The electrochemical performance of the electrolyte sheets obtained in Examples 4-5 was evaluated using AC impedance spectroscopy. The ionic conductivity in the temperature range of 500–700 °C was as follows: Figure 3 As shown, at 500℃, the ionic conductivity of each component is relatively close; as the temperature increases, the high-entropy bismuth oxide system co-doped with Pr, Sm, Gd, and Yb exhibits the highest ionic conductivity.
[0084] Thermogravimetric-differential scanning calorimetry (TG-DSC) was used to evaluate commercial Bi2O3 and the (Bi2O3) obtained in Example 2. 2 / 3 Pr 1 / 12 Sm 1 / 12 Gd 1 / 12 Yb 1 / 12Thermal stability of O₂ was tested under the following conditions: temperature range 100-800℃, heating rate 10℃ / min, air atmosphere, and gas flow rate 250 ml / min. Test data are as follows: Figures 4-5 As shown, the thermogravimetric (TG) curves of both groups of samples did not show significant mass changes, indicating that under these thermal analysis conditions, the samples did not undergo decomposition, oxidation, or the removal of volatile components. Differential scanning calorimetry (DSC) curves showed that commercial Bi₂O₃ exhibited a distinct endothermic peak near 730°C, corresponding to its transition from the α phase to the δ phase, indicating that the δ phase Bi₂O₃ exists only at high temperatures; while (Bi… 2 / 3 Pr 1 / 12 Sm 1 / 12 Gd 1 / 12 Yb 1 / 12 The 2O3 sample did not exhibit any characteristic peaks within this temperature range, indicating that the low-temperature phase transition of the material was effectively suppressed through high-entropy design, and it showed excellent thermal stability throughout the entire test temperature range.
[0085] X-ray diffraction analysis (XRD, test range 10–90°) was performed on the electrolyte sheets obtained by sintering for 24 h in Comparative Examples 1 and 2. The results are as follows: Figure 6 As shown in the figure, its XRD pattern exhibits clear diffraction peaks with high intensity, indicating good crystallinity of the material. Comparison of this pattern with the standard XRD card of fluorite-structured bismuth oxide-based electrolytes shows good agreement between the main diffraction peak positions, confirming that the prepared electrolyte possesses a stable fluorite-type crystal structure at room temperature.
[0086] To investigate long-term thermal stability, X-ray diffraction analysis (XRD, scanning range 10–90°) was performed on the electrolyte sheets of Comparative Examples 1–3 after incubation at 800℃ for 150 h. The results are as follows: Figure 7 As shown, the bismuth oxide samples doped with single and dual elements exhibited characteristic peaks in their spectra that did not belong to the fluorite structure, indicating poor thermal stability. In contrast, the high-entropy bismuth oxide sample doped with four elements did not show significant changes in its XRD pattern and maintained a stable fluorite crystal structure, indicating that high-entropy doping helps improve the thermal stability of the material.
[0087] The scope of protection claimed by this invention is not limited to the specific embodiments described above. For those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.
Claims
1. A high-entropy bismuth oxide-based solid oxide fuel cell electrolyte, characterized in that, Chemical formula: (Bi2O3) 1-x (RE2O3) x wherein x = 0.25, 0.33 or 0.50; RE is a combination of any four of La, Pr, Sm, Gd, Dy, Er and Yb, and the molar ratio of the selected four elements is 0.99-1.
01.
2. The high-entropy bismuth oxide-based solid oxide fuel cell electrolyte of claim 1, wherein: The four selected elements in the RE are in an equimolar ratio.
3. The method of producing a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte according to claim 1, characterized by, The application also provides a preparation method of the high-entropy bismuth oxide-based solid oxide fuel cell electrolyte. Step one: mix bismuth nitrate and nitrate salts of the four selected elements in a dilute nitric acid solution to prepare a nitrate salt mixed solution; Step two: add ammonia water to the nitrate salt mixed solution under stirring, control the final pH value of the system to be 8.0-10.0, and obtain a precipitate after the reaction is completed, which is washed and dried to obtain a high-entropy bismuth oxide precursor powder; Step three: perform first heat treatment on the high-entropy bismuth oxide precursor powder, the first heat treatment process is: heating at 4-6 ℃ / min to 550-650 ℃, maintaining for 50-70 min, and then naturally cooling; Step four: press the high-entropy bismuth oxide precursor powder after the first heat treatment into a shape, and obtain a product after pre-sintering and second heat treatment; the pre-sintering process is: heating at 4-6 ℃ / min to 350-450 ℃, maintaining for 50-70 min; the second heat treatment process is: heating at 4-6 ℃ / min to 950-1050 ℃, maintaining for 20-28 hours.
4. The method of producing a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte according to claim 3, characterized by: In step one, the total metal ion concentration of the nitrate salt mixed solution is 0.15-0.25 mol / L.
5. The method for producing a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte according to claim 3 or 4, characterized by: In step two, the precipitate is repeatedly washed with deionized water until it is neutral, and then dried at a temperature of 75-85 ℃.
6. The method of producing a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte according to claim 5, characterized by: In step three, the first heat treatment process is: heating at 5 ℃ / min to 600 ℃, maintaining for 60 min, and then naturally cooling.
7. The method of producing a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte according to claim 1 or 6, characterized by: In step four, the pre-sintering process is: heating at 5 ℃ / min to 400 ℃ for pre-sintering for 60 min.
8. The method of producing a high-entropy bismuth oxide-based solid oxide fuel cell electrolyte according to claim 7, characterized by: In step four, the second heat treatment process is: heating at 5 ℃ / min to 1000 ℃, maintaining for 24 hours, and obtaining a product.
9. Use of the high-entropy bismuth oxide-based solid oxide fuel cell electrolyte in claim 1 or 2 in the preparation of a solid oxide fuel cell.
10. A solid oxide fuel cell, characterized by: The application also provides a solid oxide fuel cell comprising the high-entropy bismuth oxide-based solid oxide fuel cell electrolyte in claim 1 or 2.