Fuel cell composite cathode material, method of making and use

Abstract

The present application relates to a kind of fuel cell composite cathode material, preparation method and use, specifically is related to a kind of strategy for slightly composite to improve the CO2 resistance and proton conductive capacity of material and its application in proton conductor solid oxide fuel cell cathode, composite cathode material composition molecular formula is La 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25‑δ (LWMN)‑Sr2Sc 0.1 Nb 0.1 Co 1.5 Fe 0.3 O 6‑δ (SSNCF).The present application proposes a strategy for improving the CO2 resistance and proton conductive capacity of solid oxide fuel cell cathode, so that the cathode material has excellent proton conductive capacity and CO2 resistance under certain oxygen ion and electronic conductivity, so that the LWMN-SSNCF composite electrode has excellent electrochemical performance on the proton conductor fuel cell, and the maximum output power is up to 1113 mW·cm ‑2 at 650 DEG C.

Description

Technical Field

[0001] This invention relates to a micro-composite hydrogen permeation membrane material La 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ (LWMN) strategies to improve the CO2 resistance and proton conductivity of materials and their application in the field of proton conductor solid oxide fuel cell cathodes. Background Technology

[0002] Due to the urgent need for clean energy, solid oxide fuel cells (SOFCs) have attracted worldwide attention due to their extremely high energy conversion efficiency, diverse fuel selectivity, and clean, zero-pollution operation. However, the extremely high operating temperature (800–1000℃) of traditional SOFCs severely hinders their large-scale industrial development. Therefore, to improve fuel cell stability and reduce material costs, lower operating temperatures (400–700℃) are the trend. As the operating temperature decreases, the advantages of proton conductors become apparent. Compared to oxygen conductors, proton conductor SOFCs offer advantages such as: smaller proton ionic radii, resulting in lower activation energy during transport; increased proton transference number with decreasing temperature; water generation at the cathode, preventing dilution of the fuel gas and concentration polarization; and increased fuel recyclability. Therefore, developing proton conductor fuel cell cathode materials is a breakthrough direction for fuel cell research.

[0003] CN109817997A discloses a Sr2Sc 0.1 Nb 0.1 Co 1.5 Fe 0.3 O 6-δ (SSNCF) cathode material possesses excellent proton conductivity in addition to a certain level of oxygen ion and electronic conductivity. This mixed conductivity of protons, oxygen ions, and electrons gives SSNCF superior electrochemical performance as a proton conductor. However, this material still suffers from limitations in its surface chemical water adsorption capacity and bulk proton adsorption capacity, which have not yet met expectations for its intended use. Summary of the Invention

[0004] The purpose of this invention is to provide a trace amount of composite La 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ (LWMN) employs a strategy to enhance the CO2 resistance and proton conductivity of solid oxide fuel cell cathode materials, and is used to prepare high-performance proton-conducting solid oxide fuel cell composite cathode material La.5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ (LWMN)-Sr2Sc 0.1 Nb 0.1 Co 1.5 Fe 0.3 O 6-δ (SSNCF) and its application in proton conductor solid oxide fuel cells. Composite cathodes possess low polarization resistance, good proton absorption and diffusion capabilities, improved CO2 poisoning resistance compared to single-phase materials, and high power density, making cathode materials suitable for use in medium- and low-temperature proton conductor solid oxide fuel cells.

[0005] A composite cathode material for fuel cells, comprising Sr2Sc 0.05+x Nb 0.05+y Co 1.4+m Fe 0.2+n O 6-δ And perovskite materials containing La and W, wherein the content of perovskite materials containing La and W accounts for a certain percentage of Sr2Sc. 0.05+x Nb 0.05+y Co 1.4+m Fe 0.2+n O 6-δ 1-10wt%, where 0≤x,y≤0.1, 0≤m,n≤0.2, where δ represents the oxygen vacancy content.

[0006] The perovskite material containing La and W is selected from La. 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ .

[0007] x and / or y = 0.05.

[0008] m and / or n = 0.1.

[0009] 0≤δ≤1.

[0010] The above-mentioned method for preparing the composite cathode material for fuel cells includes the following steps:

[0011] According to the content ratio, Sr2Sc 0.05+x Nb 0.05+y Co 1.4+m Fe 0.2+n O 6-δ It was prepared by mixing with perovskite materials containing La and W and then ball milling.

[0012] The ball milling process is carried out in an alcohol solvent at a speed of 200-600 rpm for 10-60 minutes.

[0013] The Sr2Sc 0.05+x Nb 0.05+y Co 1.4+m Fe 0.2+n O 6-δ The preparation method is to obtain it through solid-phase method or sol-gel method.

[0014] The solid-state method includes the following steps:

[0015] According to the stoichiometric ratio, SrCO3, Sc2O3, Nb2O5, Co2O3 and Fe2O3 were mixed, ball-milled and then calcined to obtain the final product.

[0016] The roasting conditions are 1000-1200℃ for 5-25 hours.

[0017] The aforementioned perovskite material containing La and W is La 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ The preparation method is to obtain it through solid-phase method or sol-gel method.

[0018] The solid-state method includes the following steps:

[0019] According to the stoichiometric ratio, La2O3, WO3, (NH4)2MoO4 and Nb2O5 were mixed, ball-milled, and then calcined to obtain the final product.

[0020] The roasting conditions are 1250-1450℃ for 5-25 hours.

[0021] The applications of the above materials in solid oxide fuel cells.

[0022] In one embodiment, the use refers to its use as a proton conductor.

[0023] In one embodiment, the electrolyte used is BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3.

[0024] In one embodiment, the anode material is Ni+BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3(BZCYYb) composite anode.

[0025] In one embodiment, the mass ratio of NiO to electrolyte is 3.5:6.5.

[0026] Beneficial effects

[0027] By using H2O molecule temperature-induced desorption (H2O-TPD) testing, the desorption peak signals of the LWMN-SSNCF cathode at 250℃ and 600℃ were stronger than those of the single-phase perovskite cathode material SSNCF. The composite cathode material's ability to chemically adsorb water on the surface and its ability to adsorb protons in the bulk phase were both stronger than those of SSNCF.

[0028] The composite cathode achieved good results in CO2 poisoning resistance tests, demonstrating superior resistance compared to the SSNCF single-phase cathode. Before and after CO2 introduction, the polarization impedance of the LWMN-SSNCF cathode decreased from 0.53 Ωcm. 2 It becomes 3.40Ωcm 2 The single-phase SSNCF cathode polarization impedance is 0.99 Ωcm 2 It becomes 7.65Ωcm 2 .

[0029] La, a solid oxide fuel cell cathode material prepared by solid-state method 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ (LWMN)-Sr2Sc 0.1 Nb 0.1 Co 1.5 Fe 0.3 O 6-δ (SSNCF). It exhibits high battery output performance; a single cell fabricated using Ni-BZCYYb as the anode support achieves an output power of 1113 mW / cm² at 650℃, 600℃, 550℃, and 500℃. -2 743mWcm -2 514mW cm -2 325mW cm -2 278mW cm -2 . Attached Figure Description

[0030] Figure 1 These are the XRD patterns of LWMN, SSNCF, and LWMN-SSNCF at room temperature.

[0031] Figure 2 shows the comparison of polarization resistance and activation energy of SSNCF and LWMN composite cathodes with different ratios under dry and humid air.

[0032] Figure 3The relaxation time distribution (DRT) of LWMN-SSNCF composite cathode and SSNCF single-phase cathode under humid air is analyzed.

[0033] Figure 4 This is a test of H2O heating desorption of LWMN-SSNCF and SSNCF;

[0034] Figure 5 This is a test of LWMN-SSNCF and SSNCF against CO2 poisoning;

[0035] Figure 6 shows the IVP curves and SEM images of single cells (Ni-BZCYYb||BZCYYb||LWMN-SSNCF) and (Ni-BZCYYb||BZCYYb||SSNCF) prepared with LWMN-SSNCF and SSNCF as cathodes and anode supports, respectively, in the range of 500–650 °C.

[0036] Figure 7 This is a stability test diagram of a symmetric cell prepared using LWMN-SSNCF as an electrode. Detailed Implementation

[0037] Example 1

[0038] La, a cathode material for medium- and low-temperature solid oxide fuel cells 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ (LWMN)-Sr2Sc 0.1 Nb 0.1 Co 1.5 Fe 0.3 O 6-δ The specific steps for preparing the composite of (SSNCF) are as follows:

[0039] (1) Weigh 7.3815g of strontium carbonate, 0.3448g of scandium oxide, 0.3323g of niobium pentoxide, 3.1103g of cobalt trioxide and 0.5988g of ferric oxide and place them in a ball mill jar.

[0040] (2) Add anhydrous ethanol, ball mill at 400 rpm for 60 min, then take it out and dry it to obtain the precursor of SSNCF.

[0041] (3) SSNCF precursor was placed in a high-temperature muffle furnace and calcined at 1100℃ for 10h to obtain SSNCF powder.

[0042] (4) Weigh 8.9597g of lanthanum oxide, 1.0433g of tungsten oxide, 0.7842g of ammonium molybdate and 0.1994g of niobium pentoxide and place them in a ball mill jar.

[0043] (5) Add anhydrous ethanol, ball mill at 400 rpm for 60 min, then take it out and dry it to obtain the precursor of LWMN.

[0044] (6) The precursor was placed in a high-temperature muffle furnace and calcined at 1350°C for 10 hours to obtain the desired LWMN powder.

[0045] (7) Add LWMN and SSNCF powder (LWMN in SSNCF is 1% / 3% / 5% / 10%wt respectively) to 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 cathode material.

[0046] Test method for polarization impedance of symmetrical cells

[0047] Taking LWMN-SSNCF as an example, the specific steps are as follows:

[0048] (1) Weigh 1g of the cathode powder La prepared in Example 1. 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ -Sr2Sc 0.1 Nb 0.1 Co 1.5 Fe 0.3 O 6-δ 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 r / min for 30 min. The resulting slurry was then transferred to a culture bottle using a dropper to obtain the desired cathode slurry.

[0049] (2) The prepared BZCYYb electrolyte was placed on a heating platform and preheated at 150°C. 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 1000°C for 2 hours to obtain the desired symmetrical cell, 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 cell at 700°C was 0.08 Ωcm. 2 .

[0050] Test methods for proton absorption and transport capabilities in the cathode of a solid oxide fuel cell

[0051] Specific steps:

[0052] (1) Weigh 150mg of phase-forming powder LWMN-SSNCF and SSNCF and place them in catalytic tubes respectively.

[0053] (2) Heat the catalytic tube to 500°C, introduce air containing 20% ​​vol. H2O, and treat for 2 hours.

[0054] (3) Quench the processed powder.

[0055] (4) Use air at a flow rate of 20 mL / min to purge and pass it into the mass spectrometer to detect the H2O signal.

[0056] Single-cell output power test

[0057] Taking LWMN-SSNCF as an example, the specific steps are as follows:

[0058] (1) Weigh 1g of the cathode powder La prepared in Example 1. 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ -Sr2Sc 0.1 Nb 0.1 Co 1.5 Fe 0.3 O 6-δ 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.

[0059] (2) The prepared dry-pressed solar cell was placed on a heating table and preheated at 150°C. Using a spray gun under inert gas pressure, the prepared cathode slurry was uniformly sprayed onto the electrolyte surface of the dry-pressed cell. After the liquid had completely evaporated, the sprayed dry-pressed solar cell was placed in a high-temperature muffle furnace and calcined at 1000°C for 2 hours to obtain the required single cell, which was used to test the polarization impedance of the cathode material in the temperature range of 500–650°C. The cell achieved an output power of 1113 W cm⁻¹ at 650°C. -2 .

[0060] Characterization results

[0061] 1. XRD characterization analysis

[0062] Figure 1The XRD pattern of SSNCF at room temperature is shown in the figure. It can be seen that SSNCF exhibits a cubic double perovskite phase, and this phase is pure. LWMN shows sharp diffraction peaks, indicating good crystallinity. After co-firing with SSNCF at 1000℃ for 2 hours, room temperature XRD characterization revealed no formation of other impurity phase peaks, indicating no phase reaction between LWMN and SSNCF and good chemical compatibility. The LWMN-SSNCF cathode performance remains stable during single-cell operation with air as the oxidant.

[0063] 2. Electrochemical impedance analysis

[0064] Figure 2(a) compares the polarization impedance of symmetrical cells prepared by combining LWMN and SSNCF in different proportions with temperature. In a dry air environment, the impedance values ​​of the SSNCF-LWMN series are all lower than those of SSNCF. Among them, the 3wt.% LWMN-SSNCF composite cathode has the lowest polarization impedance. As can be seen from the figure, the 3wt.% LWMN-SSNCF cathode has lower impedance and the lowest activation energy, and the activation energy is lower than that of the SSNCF single-phase cathode. This has a great advantage in electrocatalytic applications. The 3wt.% LWMN-SSNCF composite cathode exhibits the lowest polarization impedance value, and the reduction in polarization impedance becomes more significant as the temperature decreases. This indicates that the addition of a certain amount of LWMN has a significant effect on improving polarization impedance, and the advantage is more obvious at low temperatures. In the following tests, unless otherwise specified, the cathode material was prepared with an addition of 3%. However, excessive recombination of the inactive phase LWMN leads to the covering of the surface active sites of the ORR-active main phase SSNCF, resulting in an increase in the measured polarization impedance when the recombination mass ratio exceeds 3%.

[0065] Figure 2(b) shows the polarization impedance of a symmetric cell supported by a proton conductor electrolyte in a 3 vol.% water vapor-air atmosphere. This study investigates the electrocatalytic performance of single-electrode SSNCF and composite electrodes under an H-SOFC cathode environment. In proton conductor testing mode, the ORR reaction of oxygen and the hydration reaction involving water vapor occur simultaneously, affecting the electrochemical performance of the electrode materials. The impedance values ​​show that the polarization impedance under humid air conditions is similar to that under dry air conditions. Furthermore, the composite cathode exhibits a more significant reduction in SSNCF polarization impedance under humid air conditions compared to dry air. The activation energy of the 3% composite cathode is lower than that of other composite materials, further demonstrating that appropriate LWMN composites can not only improve impedance performance under air conditions and reduce the ORR activation energy of the material, but also optimize electrode impedance and provide active sites for protons under proton absorption conditions. This proves that LWMN is an effective proton conductor additive.

[0066] 3. Relaxation Time Distribution (DRT) Analysis

[0067] Figure 3 The impedance relaxation time distributions (DRTs) of LWMN-SSNCF and the SSNCF single-phase cathode are shown. Impedance information was obtained by integrating a series of frequency-resolved peaks at 500℃ under humid air conditions. Different peak stages in the DRT spectrum correspond to different electrocatalytic processes. Peaks near 1000-10000 Hz are related to charge transfer processes at the electrode-electrolyte interface; peaks near 10-1000 Hz are related to ion diffusion within the cathode bulk phase; and peaks in the 0.01-10 Hz range are related to oxygen adsorption, dissociation, and surface O2 diffusion processes. The DRT spectra show that the peak area in the mid-frequency band significantly decreases after recombination, indicating that the recombination of 3 wt.% LWMN accelerates charge transfer at the electrode-electrolyte interface. This may be due to the increased number of reactive sites in the 3 wt.% LWMN-SSNCF composite electrode compared to the single-phase SSNCF cathode.

[0068] 4. Analysis of H2O heating and desorption curves

[0069] Figure 4 The LWMN-SSNCF composite cathode and SSNCF cathode material were treated at 500℃ and 20 vol.% water vapor partial pressure for 2 hours and then quenched to room temperature to study the water storage capacity of the cathode under actual operating conditions. The TPD curves of both electrode materials showed two desorption peaks, approximately at 250℃ and 600℃, respectively. These two peaks are related to surface chemically adsorbed water and proton absorption in the oxide bulk phase, respectively. The intensity of 3wt.% LWMN-SSNCF at this temperature was higher than that of the SSNCF single-phase cathode, indicating that it has a greater surface water chemical adsorption capacity and better bulk water storage capacity. As shown in the figure, the desorbed water content increases with the addition of LWMN. The proton defect concentration of the 3wt.% LWMN-SSNCF composite material is higher than that of the SSNCF single-phase, further indicating that the addition of 3wt.% LWMN enhances proton absorption.

[0070] 5. Characterization of CO2 resistance performance

[0071] Figure 5 To investigate the change in cathode impedance over time in symmetric cells of SSNCF and 3wt.% LWMN-SSNCF at 600℃ in air containing 10 vol.% CO2. The impedance measured in humid air was recorded as the initial impedance value. Figure 5It can be seen that under the test conditions in the presence of CO2, the SSNCF material shows a significant upward trend, while the polarization impedance of the 3wt.% LWMN-SSNCF composite material increases more gradually, and the polarization impedance value remains basically unchanged after 30 minutes of CO2 introduction. After 1 hour of CO2 introduction, the polarization impedance value of the composite cathode increases to 6.4 times the initial impedance value, and the polarization impedance value of SSNCF increases to 7.3 times the initial impedance value. The change in impedance of the composite cathode is significantly smaller than that of the single-phase SSNCF cathode, indicating that the anti-poisoning function is improved after incorporating 3wt.% LWMN.

[0072] 6. Single-cell output power characterization

[0073] Figure 6(a) shows the IVP test results of a single cell fabricated with a composite cathode of 3 wt.% LWMN-SSNCF and Ni-BZCYYb as the anode support (Ni-BZCYYb||BZCYYb||LWMN-SSNCF) in the range of 500–650 °C. The test results show that the composite cathode achieves output power of 0.325, 0.514, 0.743, and 1.113 Wcm at 500, 550, 600, and 650 °C, respectively. -2 The SSNCF single-phase cathodes shown in Figure 6(b) exhibited W / cm² values ​​of 0.316, 0.487, 0.697, and 997 W / cm² at the same temperature, which are higher than those in Figure 6(b). -2 .

[0074] Figure 6(c) shows a SEM cross-section of a single cell of 3 wt.% LWMN-SSNCF, with a ~13.1 μm thick porous cathode firmly adhered to a ~15.2 μm thick dense BZCYYb electrolyte, which is supported on a porous Ni-BZCYYb anode substrate.

[0075] 7. Characterization of the stability of symmetric cells

[0076] Figure 7 A symmetric cell prepared using 3wt.% LWMN-SSNCF as the electrode and BZCYYb as the electrolyte was operated at 600℃ for 160 h under 3vol.% H2O-Air conditions, and the designed impedance of the electrode remained at approximately 0.33 Ωcm. 2 No significant degradation occurred, indicating that the material has good stability on BZCYYb electrolyte and is expected to become a commercial cathode material.

Claims

1. The use of composite cathode materials for fuel cells in the CO2 resistance performance of solid oxide fuel cells in air containing 10 vol.% CO2, characterized in that, The cathode material contains Sr2Sc 0.05+x Nb 0.05+y Co 1.4+m Fe 0.2+n O 6−δ And perovskite materials containing La and W, wherein the content of perovskite materials containing La and W accounts for a certain percentage of Sr2Sc. 0.05+x Nb 0.05+y Co 1.4+m Fe 0.2+n O 6−δ 3 wt%, where x and / or y = 0.05; m and / or n = 0.1; 0 ≤ δ ≤ 1, where δ represents the oxygen vacancy content; The perovskite material containing La and W is selected from La. 5.5 W 0.45 Mo 0.4 Nb 0.15 O 11.25-δ .

2. The use according to claim 1, characterized in that, The preparation method of fuel cell composite cathode material includes the following steps: Sr2Sc is mixed according to the content ratio... 0.05+x Nb 0.05+y Co 1.4+m Fe 0.2+n O 6−δ It was prepared by mixing with perovskite materials containing La and W and then ball milling.

3. The use according to claim 2, characterized in that, The ball milling process is carried out in an alcohol solvent at a speed of 200-600 rpm for 10-60 min.

4. The use according to claim 2, characterized in that, The Sr2Sc 0.05+x Nb 0.05+y Co 1.4+m Fe 0.2+n O 6−δ The preparation method is to obtain it through solid-phase method or sol-gel method.

5. The use according to claim 4, characterized in that, The solid-state method includes the following steps: according to the stoichiometric ratio, SrCO3, Sc2O3, Nb2O5, CO2O3 and Fe2O3 are mixed, ball-milled and calcined to obtain the final product; the calcination conditions are calcination at 1000-1200℃ for 5-25 h.

6. The use according to claim 4, characterized in that, The preparation method of the perovskite material containing La and W is through solid-state method or sol-gel method.

7. The use according to claim 6, characterized in that, The solid-phase method includes the following steps: La2O3, WO3, (NH4)2MoO4 and Nb2O5 are mixed according to the stoichiometric ratio, ball-milled, and then calcined to obtain the product; the calcination conditions are calcination at 1250-1450℃ for 5-25 h.

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