Method for the production of electrolytes for solid oxide fuel cells and use thereof

Abstract

The present application relates to the field of solid oxide fuel cell, in particular to a preparation method of electrolyte for solid oxide fuel cell, comprising the following steps: sintering CeO2; placing the sintered CeO2 on a sample table in a reaction cavity of a CVD device, introducing hydrogen and argon into the reaction cavity, and then Pd organic metal precursor enters the reaction cavity in the form of gas after evaporation or sublimation, and chemically reacts with the surface of the sintered CeO2 on the sample table, so as to deposit and form a Pd film; thereby obtaining a CeO2 solid state oxide electrolyte covered with the Pd film. The present application also simultaneously provides the use of the electrolyte: for preparing a methane fuel cell. The electrolyte provided by the present application has good ion conductivity and chemical stability, and can maintain stable ion transmission performance under high temperature and polar environment, thereby prolonging the service life of the battery.

Description

Technical Field

[0001] This invention relates to the field of solid oxide fuel cells, and more specifically to an electrolyte for a solid oxide fuel cell, its preparation method, and its applications. Background Technology

[0002] With the continued growth of global energy demand and the increasing severity of environmental problems, the development of efficient and clean energy technologies has become a global focus. Solid oxide fuel cells (SOFCs), as a highly efficient and low-pollution energy conversion device, have attracted much attention due to their high energy conversion efficiency, fuel flexibility, and environmental friendliness. Methane (CH4), as an important hydrocarbon fuel, has become a key choice for SOFC fuel due to its abundant resources, high energy density, and low carbon dioxide emissions. The oxidation reaction of methane in an SOFC mainly involves two steps: first, partial oxidation to syngas (H2 and CO) occurs under the action of an anode catalyst; then, hydrogen and carbon dioxide are further produced at high temperature through a water-gas shift reaction.

[0003] The efficient oxidation of methane in SOFCs depends not only on the performance of the anode catalyst but also on the ionic conductivity and interfacial properties of the electrolyte. To improve the overall performance of SOFCs, the electrolyte material needs to possess high oxygen ion conductivity and excellent chemical stability in the mid-to-low temperature range. To lower the operating temperature of SOFCs, researchers have proposed several novel electrolyte materials, such as scandia-stabilized zirconia (ScSZ) and lanthanum-strontium-magnesium-cobalt oxide (LaSZ). 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ LSGM (La2NiO) and lanthanum nickel oxide (La2NiO) 4+δ Materials such as LNO (Liquid Oxide) exhibit high ionic conductivity in the mid-temperature range, showing potential to reduce the operating temperature of SOFCs. Zhu et al. from Inner Mongolia University (CN202410560404.X) reported a heterostructured solid electrolyte material composed of CeO2 and β-Al2O3, which effectively improves the ionic conductivity of the electrolyte, reducing the minimum operating temperature of the fuel cell to 350℃, while also enhancing the electrocatalytic activity of the electrode material. Based on O... 2-SOFCs with conductive electrolytes have greater fuel flexibility than low-temperature fuel cells based on proton-conductive electrolytes. Bu et al. (CN202410622325.7) reported a Sr / Mg co-doped LaAlO3 electrolyte, which improves the working output efficiency of the cell by introducing a large number of oxygen vacancies, thereby achieving the purpose of applying a wide-bandgap semiconductor to an ion conductor in an advanced fuel cell by appropriate element doping.

[0004] However, these new electrolyte materials still face some challenges in practical applications, such as complex preparation process, insufficient stability, high cost, etc. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of an electrolyte for a solid oxide fuel cell and its use.

[0006] To solve the above technical problems, the present application provides a preparation method of an electrolyte for a solid oxide fuel cell (i.e., for a solid oxide fuel cell using methane as fuel), comprising the following steps:

[0007] 1) CeO2 (powder) is sintered at a set sintering temperature for 2-5 h (to ensure that the CeO2 powder is sintered into a dense solid-state electrolyte), obtaining sintered CeO2;

[0008] The set sintering temperature is 1200-1500℃;

[0009] Note: CeO2 is uniformly spread in a high-temperature crucible, and the crucible is placed in a microwave sintering furnace for sintering;

[0010] 2) The sintered CeO2 is placed on a sample stage in the reaction cavity of a CVD device, hydrogen and argon are introduced into the reaction cavity, and the flow rate ratio of hydrogen to argon is set to 1:(2±0.2); the reaction cavity is heated to 400±20℃, and the Pd organic metal precursor enters the reaction cavity in the form of gas after evaporation or sublimation and chemically reacts with the surface of the sintered CeO2 on the sample stage, thereby depositing a Pd thin film;

[0011] The deposition rate of the Pd thin film is controlled to be (0.1±0.01) nm / s;

[0012] The reaction time is set to (1000±100) seconds to achieve a target thickness of (100±10) nm. That is, a CeO2 solid-state oxide electrolyte with a surface coverage of a Pd thin film of (100±10) nm is obtained.

[0013] Improvements of the preparation method of the electrolyte for a solid oxide fuel cell of the present application:

[0014] The Pd organic metal precursor is Pd(II) acetylacetone, Pd(OAc)2.

[0015] As a further improvement of the method for preparing the electrolyte for solid oxide fuel cells of the present application:

[0016] The flow rates of hydrogen and argon are set to 100 sccm and (200±20) sccm, respectively.

[0017] As a further improvement of the method for preparing the electrolyte for solid oxide fuel cells of the present application:

[0018] In step 1), the heating rate is 10±1℃ / min, and the temperature is raised from room temperature to the set sintering temperature.

[0019] The present application also simultaneously provides the use of the solid electrolyte prepared by any of the above methods: for preparing a methane fuel cell.

[0020] As an improvement of the use of the present application: assembling the anode, electrolyte and cathode components together to form a single cell unit of the fuel cell.

[0021] The steps of applying the electrolyte to the methane fuel cell are as follows:

[0022] 1) Assembling the anode, electrolyte and cathode components together to form a single cell unit of the fuel cell.

[0023] 2) Connecting the methane gas sampling system to the anode side and adjusting the methane flow rate to 50 sccm using a gas flow controller. Connecting the oxygen or air supply system to the cathode side and adjusting the oxygen flow rate to 100 sccm using a gas flow controller.

[0024] 3) Performing cell performance test and analyzing the exhaust gas of the methane fuel cell using a gas chromatograph or mass spectrometer.

[0025] The present application relates to a CeO2 solid state oxide electrolyte using microwave sintering and depositing a Pd thin film on the surface, which is an electrolyte for a solid oxide fuel cell using methane as fuel.

[0026] The electrolyte of the present application has the following advantages:

[0027] 1) CeO2 as an electrolyte has good ionic conductivity and chemical stability, and can maintain stable ion transmission performance at high temperature and in a polar environment, prolonging the service life of the cell.

[0028] The Pd thin film as a catalyst can promote the catalytic oxidation reaction of methane gas on the surface of the electrolyte, and can improve the conversion efficiency of methane and the power density of the cell.

[0029] The present application is to combine the microwave sintered CeO2 with the Pd thin film deposited by CVD method.

[0030] 2) The optimized microwave sintering process and the surface stability of the Pd thin film enhance the thermal mechanical properties of the electrolyte, reducing the damage risk caused by thermal shock and material expansion.

[0031] The present application solves the bottleneck of the existing electrolyte material in performance and cost through reasonable material design and optimized process flow, providing strong technical support for the practical application of SOFC.

[0032] In summary, the present application provides a solid oxide fuel cell electrolyte using methane as fuel. Specifically, a CeO2 solid oxide electrolyte is used by microwave sintering and depositing a Pd thin film on the surface. The electrolyte provided by the present application has good ionic conductivity and chemical stability, can maintain stable ion transport performance in high temperature and polar environment, prolong the service life of the battery, and the deposited Pd thin film can promote the catalytic oxidation reaction of methane gas on the surface of the electrolyte. DETAILED DESCRIPTION

[0033] The present application will be further described below in conjunction with specific embodiments, but the scope of protection of the present application is not limited to this:

[0034] Example 1, a preparation method of a CeO2 solid oxide electrolyte with a Pd thin film deposited on the surface, acetylacetone palladium (II) is set as the Pd organic metal precursor; the following steps are performed in sequence:

[0035] 1) 10g of CeO2 powder is evenly spread in a high-temperature crucible, and the crucible is placed in a microwave sintering furnace; the temperature program of the microwave sintering furnace is set to quickly heat it to 1200℃, that is, the heating rate is set to 10℃ / min, and after heating to 1200℃, it is kept for 2h to ensure that the CeO2 powder is sintered into a dense solid-state electrolyte, obtaining sintered CeO2.

[0036] 2), the sintered CeO2 is placed on the sample table in the reaction cavity of the chemical vapor deposition (CVD) equipment, hydrogen and argon are used as reaction gases and introduced into the reaction cavity, the flow rate ratio of hydrogen and argon is set to 1:2, and the flow rates of hydrogen and argon are set to 100sccm and 200sccm respectively. The reaction cavity is heated to 400℃, and after the evaporation of acetylacetone palladium (II), it enters the reaction cavity in the form of gas and chemically reacts with the surface of the sintered CeO2 on the sample table, thereby depositing a Pd thin film on the surface of the sintered CeO2. The evaporation rate of acetylacetone palladium (II) is controlled (about 0.0344mg / s) to control the deposition rate of the Pd thin film to be 0.1nm / s; the obtained is named as a CeO2 solid oxide electrolyte with a Pd thin film deposited on the surface.

[0037] The reaction time is set to 1000 seconds to achieve a target thickness of 100 nm. That is, a CeO2 solid oxide electrolyte with a surface coverage thickness of 100 nm Pd thin film is obtained.

[0038] The chemical vapor deposition (CVD) equipment is a conventional device. When the reaction chamber is heated to a set temperature, the Pd organometallic precursor enters the reaction chamber by evaporation or sublimation, and chemically reacts with the CeO2 surface on the sample stage to deposit a Pd thin film. The gaseous by-products (such as methane, water vapor) produced by the decomposition of the organic matter, unreacted hydrogen and argon are discharged from the exhaust port.

[0039] The reaction formula is:

[0040] Pd (C5H7O2)2+ H2→ Pd (deposited on the surface of CeO2) + by-products (such as gaseous hydrocarbons, H2O).

[0041] Note: The role of argon in the reaction gas is to maintain a stable atmosphere under inert conditions in the reaction environment, maintain uniform gas composition in the reaction chamber, and promote uniform deposition of the thin film.

[0042] Experiment 1, solid oxide fuel cell using methane as fuel

[0043] The preparation of the solid oxide fuel cell can refer to the embodiment 6 of the published CN118315604A "A composite anode catalytic electrode of a button-type solid oxide fuel cell based on hydrocarbon fuel reforming technology and a preparation method thereof", but without using the catalytic layer, assembling the NiO-GDC anode functional layer, the solid electrolyte of the present application and the LSCF-GDC cathode layer together to form a single cell unit of the fuel cell. Connect the methane gas sampling system to the anode side and use the gas flow controller to adjust the methane flow rate to 50 sccm. Connect the oxygen or air supply system to the cathode side and use the gas flow controller to adjust the oxygen flow rate to 100 sccm. Perform battery performance (power density) test: use an adjustable current source to gradually increase the current, starting from zero current and gradually increasing to the maximum current of the battery (i.e. the voltage drops to near zero). At each current point, measure the corresponding voltage and record the data. Draw the current-voltage (I-V) curve with current density (mA / cm 2 ) as the horizontal coordinate and voltage (V) as the vertical coordinate. The anode exhaust port of the fuel cell is connected to a gas chromatograph or mass spectrometer for exhaust composition analysis, so the exhaust from the anode of the methane fuel cell is analyzed using a gas chromatograph or mass spectrometer to calculate the methane conversion rate.

[0044] Power density calculation formula: power density (W / cm 2 ) = current density (A / cm 2) x voltage (V)

[0045] Find the point with the highest power density from the I-V curve, which is the maximum power density of the cell.

[0046] Methane conversion rate calculation formula: methane conversion rate (%) = (inlet methane flow rate - exhaust methane flow rate) / inlet methane flow rate x 100%

[0047] Apply Example 1 to Experiment 1, and the performance test results are: the maximum power density is 0.25 W / cm 2 , and the methane conversion rate is 95%.

[0048] Experiment 2, stability: use the cell unit assembled in Experiment 1, under the conditions of methane flow rate 50 sccm and oxygen flow rate 100 sccm, let the SOFC cell run continuously for 100 hours, continuously monitor and record the output voltage and current of the cell, and calculate the decay rate of the maximum power density of the cell within 100 hours.

[0049] Power density decay rate (%) = (initial maximum power density - power density after 100 hours) / 100 x 100%

[0050] The performance test results are: the power density decay rate is 0.10%.

[0051] Experiment 3, thermal mechanical performance test: use a thermal mechanical analyzer (TMA) to measure the expansion coefficient of the CeO2 electrolyte at different temperatures, the specific operation conditions are: set the initial temperature to 25℃, set the temperature scanning range from 25℃ to 1000℃, and gradually increase the temperature at a constant rate (10℃ / min). At each temperature point, the TMA device will record the length change ΔL of the sample. After heating to the highest temperature, gradually cool down at the same rate and record the length change of the sample.

[0052] The calculation formula of the thermal expansion coefficient is:

[0053] Where α is the linear thermal expansion coefficient (unit: / ℃), ΔL is the length change of the sample (unit: mm), L0 is the initial length (unit: mm), and ΔT is the temperature change (unit: ℃).

[0054] Apply Example 1 to Experiment 3, and the test results are: the thermal expansion coefficient is 1.1 x 10 -6 / ℃.

[0055] Experiment 4, conductivity test: set the electrochemical workstation to electrochemical impedance spectroscopy (EIS) mode, set the frequency range of EIS measurement to 1 Hz to 1 MHz, and the amplitude to 5 mV, collect impedance spectrum data at room temperature, and obtain the resistance value R of the sample by fitting Nyquist or Bode.

[0056] Ionic conductivity calculation formula:

[0057] Where L is the thickness of the electrolyte membrane (100 μm), R is the resistance of the membrane (obtained from EIS data), A is the contact area of the cathode / anode and the membrane (2 cm 2 ).

[0058] Example 1 was applied to Experiment 4, and the test results were: ionic conductivity of 4.6 x 10 -3 / °C.

[0059] Example 2, relative to Example 1, the following changes were made:

[0060] The heating temperature of Step 1) was changed from "1200°C" to "1500°C", and the rest was the same as Example 1.

[0061] The obtained CeO2 solid oxide electrolyte with a surface covered Pd thin film was subjected to cell performance testing according to the above experiment, and the obtained results were: maximum power density of 0.21 W / cm 2 , methane conversion rate of 94%; power density decay rate of 0.12%, thermal expansion coefficient of 1.1 x 10 -6 / °C, ionic conductivity of 2.5 x 10 -3 / °C.

[0062] Example 3, relative to Example 1, the following changes were made:

[0063] The "holding for 2h" of Step 1) was changed to "holding for 5h", and the rest was the same as Example 1.

[0064] The obtained CeO2 solid oxide electrolyte with a surface covered Pd thin film was subjected to cell performance testing according to the above experiment, and the obtained results were: maximum power density of 0.22 W / cm 2 , methane conversion rate of 95%; power density decay rate of 0.14%, thermal expansion coefficient of 9.0 x 10 -6 / °C, ionic conductivity of 3.1 x 10 -3 / °C.

[0065] Example 4, relative to Example 1, the following changes were made:

[0066] The Pd organic metal precursor was changed from "palladium (II) acetylacetonate" to "Pd(OAc)2", and the deposition rate of the Pd thin film remained unchanged at 0.1 nm / s, and the rest was the same as Example 1.

[0067] The obtained CeO2 solid oxide electrolyte with a Pd thin film on its surface was subjected to battery performance testing according to the above experiments. The results showed that the maximum power density was 0.20 W / cm². 2 The methane conversion rate is 90%; the power density decay rate is 0.16%; and the coefficient of thermal expansion is 1.2 × 10⁻⁶. -5 / ℃, ionic conductivity 2.5×10 -3 / ℃.

[0068] Comparative Example 1, compared to Example 1, the following changes were made:

[0069] Step 2 is cancelled; the rest is the same as in Example 1.

[0070] Using the sintered CeO2 obtained in step 1) directly as the electrolyte, the battery performance was tested according to the above experiment. The results showed that the maximum power density was 0.10 W / cm³. 2 The methane conversion rate was 65%, the power density decay rate was 10.2%, and the ionic conductivity was 3.8 × 10⁻⁶. -4 / ℃.

[0071] Comparative Example 2, compared to Example 1, makes the following changes:

[0072] Change the heating temperature in step 1) from "1200℃" to "1000℃" and change "keep warm for 2 hours" to "keep warm for 3 hours", the rest is the same as in Example 1.

[0073] The obtained CeO2 solid oxide electrolyte with a Pd thin film on its surface was subjected to battery performance testing according to the above experiments. The results showed that the maximum power density was 0.11 W / cm². 2 The methane conversion rate was 58%, the power density decay rate was 11.3%, and the ionic conductivity was 4.6 × 10⁻⁶. -4 / ℃.

[0074] Comparative Example 3-1, compared to Example 1, the following changes were made:

[0075] The reaction time was changed from "1000 seconds" to "600 seconds", so the thickness of the resulting Pd film was 60 nm, and the rest was the same as in Example 1.

[0076] The obtained CeO2 solid oxide electrolyte with a Pd thin film on its surface was subjected to battery performance testing according to the above experiments. The results showed that the maximum power density was 0.15 W / cm². 2 The methane conversion rate was 59%, the power density decay rate was 12.1%, and the ionic conductivity was 4.1 × 10⁻⁶. -4 / ℃.

[0077] Comparative Example 3-2, relative to Example 1, the following changes were made:

[0078] The reaction time was changed from "1000 seconds" to "1500 seconds", and thus the thickness of the Pd film obtained was 150 nm, and the rest was identical to Example 1.

[0079] The Ce02 solid oxide electrolyte with the Pd film obtained was subjected to cell performance testing according to the above experiment, and the results obtained were: maximum power density was 0.14 W / cm 2 , methane conversion rate was 67%, power density decay rate was 9.8%, and ionic conductivity was 3.1 x 10 -4 / °C.

[0080] Comparative Example 4, relative to Example 1, the following changes were made:

[0081] The "heating the reaction chamber to 400°C" in step 2) was changed to "heating the reaction chamber to 100°C", at this time the deposition rate was about 0.025 nm / s, and the reaction time was adjusted accordingly, so that the thickness of the Pd film was kept unchanged at 100 nm; the rest was identical to Example 1.

[0082] The Ce02 solid oxide electrolyte with the Pd film obtained was subjected to cell performance testing according to the above experiment, and the results obtained were: maximum power density was 0.08 W / cm 2 , methane conversion rate was 40%, power density decay rate was 8.7%, and ionic conductivity was 5.5 x 10 -4 / °C.

[0083] Comparative Example 5, relative to Example 1, the following changes were made:

[0084] The "using hydrogen and argon as reaction gases, and setting the flow rates to 100 sccm and 200 sccm, respectively" in step 2) was changed to "using hydrogen and argon as reaction gases, and setting the flow rates to 20 sccm and 200 sccm, respectively", and the rest was identical to Example 1.

[0085] In this case, due to the decrease in hydrogen partial pressure, the deposition rate of the Pd film was about 0.02 nm / s, and the reaction time was adjusted accordingly, so that the thickness of the Pd film was kept unchanged at 100 nm.

[0086] The Ce02 solid oxide electrolyte with the Pd film obtained was subjected to cell performance testing according to the above experiment, and the results obtained were: maximum power density was 0.09 W / cm 2 , methane conversion rate was 41%, power density decay rate was 8.4%, and ionic conductivity was 4.5 x 10 -4 / °C.

[0087] Finally, it should be noted that the above enumeration is only several specific embodiments of the present application. Obviously, the present application is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or inferred from the disclosure of the present application by those of ordinary skill in the art should be considered within the scope of the present application.

Claims

1. A method for the production of an electrolyte for solid oxide fuel cells, characterized in that The method comprises the following steps: 1) sintering CeO2 at a set sintering temperature for 2-5 hours to obtain sintered CeO2; The set sintering temperature is 1200-1500 °C; 2) placing the sintered CeO2 on a sample stage in a reaction cavity of a CVD device, introducing hydrogen and argon into the reaction cavity, setting the flow rate ratio of hydrogen to argon to be 1:(2±0.2), heating the reaction cavity to 400±20 °C, and evaporating or sublimating the Pd organic metal precursor into the reaction cavity in the form of a gas to chemically react with the sintered CeO2 on the sample stage, thereby depositing a Pd thin film; and obtaining an electrolyte for a solid oxide fuel cell; The deposition rate of the Pd thin film is controlled to be (0.1±0.01) nm / s, and the reaction time is set to be (1000±100) seconds.

2. The method for preparing the electrolyte for the solid oxide fuel cell according to claim 1, wherein the Pd organic metal precursor is Pd(II) acetylacetone or Pd(OAc)2.

3. The method for preparing the electrolyte for the solid oxide fuel cell according to claim 2, wherein the flow rates of hydrogen and argon are set to be 100 sccm and (200±20) sccm, respectively.

4. The method for preparing the electrolyte for the solid oxide fuel cell according to any one of claims 1-3, wherein in step 1), the temperature rising rate is 10±1 °C / min, and the temperature is raised from room temperature to the set sintering temperature. The method is used for preparing a methane fuel cell. An anode, an electrolyte and a cathode assembly are assembled together to form a single cell unit of the fuel cell. The method is used for preparing a methane fuel cell.

5. Use of the solid electrolyte prepared according to any one of claims 1 to 4, characterized in that: An anode, an electrolyte and a cathode assembly are assembled together to form a single cell unit of the fuel cell.

6. Use according to claim 5, characterized in that: ​