A fuel cell / electrolyzer oxygen electrode material, preparation method and application thereof

Abstract

The present invention relates to a fuel cell / electrolyzer oxygen electrode material, a preparation method and its application, the chemical formula of which is A 1‑x A ′ x B n O 3‑δ , wherein A is one of Pr, Nd, Gd, Ce, Sm, A′ is one or any two of Ba, Sr, Ca, B contains Co and other metals, and the other metals are one or more of Ni, Fe, Nb, wherein 0<x<1, 0.75≤n≤1, 0≤δ≤1. The oxygen electrode material is obtained by dissolving the metal oxide or metal salt in dilute nitric acid, adding a reaction reagent to prepare a precursor solution, and then heating, drying, grinding, and high-temperature sintering. The oxygen electrode material involved in the present invention can be a layered perovskite structure oxide or a composite oxygen electrode material. Alkaline earth metal doping at the A position reduces its cost and enhances its redox activity. At the same time, the introduction of other metals at the B position to reduce the proportion of Co helps to improve thermal expansion matching. It is an excellent low-temperature proton ceramic fuel cell / electrolyzer oxygen electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells / electrolyzers, and in particular to a fuel cell / electrolyzer oxygen electrode material, a preparation method and applications thereof. Background Art

[0002] Reversible solid oxide cells (RSOCs) can use hydrogen energy to generate electricity efficiently and also use abandoned electricity to produce hydrogen efficiently by electrolysis, playing the role of peak shaving and valley filling. Compared with high-temperature RSOCs, medium- and low-temperature RSOCs (<700°C) have obvious advantages in sealing, startup speed, cost (construction, operation, maintenance), and supporting materials. The oxygen electrode is a key component of RSOC. As the temperature decreases, it faces the following challenges: (1) As the temperature decreases, the polarization loss caused by the slow redox reaction at the oxygen electrode accounts for the majority of the entire battery; (2) The materials currently developed are mainly for RSOCs with oxygen ion conductor electrolytes (O-RSOCs). Although RSOCs with proton conductor electrolytes (H-RSOCs) have a lower operating temperature, the oxygen electrode materials that match them are still under study, especially electrode materials that can conduct protons, oxygen ions, and electrons at the same time; (3) In the process of reverse water electrolysis, the oxygen electrode faces the problems of catalysis and stability under high concentrations of water vapor. Common oxygen electrode materials such as Pr x Ba 1-x Co2O3 (PBC, x = 0.1, 0.3, 0.5, 0.7, 0.9) has high redox activity at low temperatures, but its Co content is high and its thermal expansion coefficient is large; oxygen electrode material PrNi 0.5 Co 0.5 O 3-δ (PNC) has been widely used in low-temperature H-RSOC in recent years, but the proportion of Pr element is high and the price is relatively high. Summary of the Invention

[0003] In view of the problems existing in the existing oxygen electrode materials, the present invention has developed a fuel cell / electrolyzer oxygen electrode material, the chemical formula of which is A 1-x A′ x B n O 3-δ , wherein A is one of Pr, Gd, Ce, Sm, and Nd, A′ is one or any two of Ba, Sr, and Ca, B contains Co and other metals, and the other metals are one or more of Ni, Fe, and Nb, wherein 0<x<1, 0.75≤n≤1, and 0≤δ≤1.

[0004] Preferably, a method for preparing a fuel cell / electrolyzer oxygen electrode material is characterized by comprising the following steps:

[0005] Step 1: dissolving different metal oxides or metal salts in dilute nitric acid in a certain proportion, mixing and stirring to form a metal nitrate solution, wherein the metal ion components of the metal oxides or metal salts are four or more of Pr, Gd, Ce, Sm, Nd, Ba, Sr, Ca, Co, Ni, Fe, and Nb;

[0006] Step 2, preparation of a precursor, adding a reaction reagent to the metal nitrate solution formed in the above step 1 to prepare a stable precursor solution, wherein the reaction reagent is any two of citric acid, glycine, urea, ethylene glycol, glycerol, and ammonium ethylenediaminetetraacetate;

[0007] Step 3: Evaporate the precursor solution obtained in step 2 to remove water, and control the heating temperature to 100° C. to 150° C.;

[0008] Step 4: Rapidly heating the components after evaporation and removal of water in step 3 to 350-500° C. to obtain primary powder;

[0009] Step 5: Add the primary powder obtained in step 4 to an equal mass of ethanol and grind it on a ball mill to fully mix the powder, and sinter it at high temperature for 2 to 5 hours. By adjusting the sintering temperature, a perovskite phase oxygen electrode material or a composite oxygen electrode material can be prepared.

[0010] Preferably, the reaction reagents in step 2 are citric acid and ethylene glycol, and the total molar number of the citric acid and ethylene glycol is 2 to 4 times the total number of metal ions.

[0011] Preferably, in step 5, for component A 1-x A′ x B n O 3-δ Wherein 0.75≤n≤1,0≤δ≤1, 0.5≤x<1, when the molar ratio of Co and other metal components in the B position is 1:1, the primary powder sintering temperature is less than or equal to 1050°C, and a composite oxygen electrode material is obtained.

[0012] Preferably, the high temperature sintering process in step 5 is that the powder is sintered at a low temperature of 950° C. for 4 hours, the slurry is prepared and then sintered at 1050° C. for 2 hours.

[0013] Preferably, in step 5, for component A 1-x A′ x B n O 3-δ Among them, 0.75≤n≤1,0≤δ≤1, 0<x<0.5, the molar ratio of Co in the B position is not less than 50%, and a composite oxygen electrode material is obtained when the sintering temperature is 950-1000°C. A perovskite phase oxygen electrode material can be obtained when the sintering temperature is greater than or equal to 1050°C.

[0014] Preferably, an application of a fuel cell / electrolyzer oxygen electrode material is provided, wherein the oxygen electrode material is applied to an oxygen ion conductor fuel cell / electrolyzer and a proton ceramic fuel cell / electrolyzer.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1) The present invention develops a new type of oxygen electrode material with a relatively low material price, a lower Co content and a lower thermal expansion coefficient than PBC. At the same time, it has high catalytic activity and stability in medium and low temperature proton ceramic fuel cells, making it an ideal RSOC oxygen electrode material.

[0017] 2) The oxygen electrode material involved in the present invention can be a layered perovskite oxide or a perovskite mixture. The technical solution provided by the present invention, through chemical composition design, introduces alkaline earth metal elements at the A position to reduce its cost, and introduces other metals at the B position to reduce the proportion of the Co element and maintain a small chemical expansion.

[0018] 3) The oxygen electrode material provided by the present invention can be a single-phase material or a composite material. The one-step preparation of the composite material can simultaneously maintain the proton conduction, oxygen ion conduction and electron conduction properties, further improving the catalytic activity of the electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The XRD results of the starting components with a molar ratio of Pr:Ba:Ni:Co of 3:1:2:2 (PBNC3122) sintered at different temperatures are shown in the figure.

[0020] Figure 2 This is the morphology of the elements Pr:Ba:Ni:Co with a molar ratio of 3:1:2:2 (PBNC3122) sintered at 1050℃.

[0021] Figure 3 These are the XRD characterization diagrams of the starting components with a molar ratio of Pr:Ba:Ni:Co of 1:1:1:1 sintered at different temperatures.

[0022] Figure 4 This is a morphology diagram of the sintered sample at 1050°C with a molar ratio of Pr:Ba:Ni:Co of 1:1:1:1 (PBNC1111) in the embodiment.

[0023] Figure 5 The AC impedance spectrum of a symmetrical battery with proton conductor BZCYYb as the electrolyte. (b) is an enlarged view of (a).

[0024] Figure 6This is the AC impedance spectrum of a symmetrical battery with oxygen ion conductor GDC as electrolyte.

[0025] Figure 7 This is the AC impedance spectrum of a symmetrical battery with proton conductor BZCYYb as electrolyte.

[0026] Figure 8 This study tested the water vapor stability of a symmetrical battery with PBNC1111 as electrode and BZCYYb as electrolyte within 100 hours. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] Example 1

[0029] In this embodiment, component A 1-x A′ x B n O 3-δ , wherein 0.75≤n≤1, 0≤δ≤1, 0≤x<0.5, and the molar ratio of Co in the B position is not less than 50%, the preparation method of the oxygen electrode material is as follows:

[0030] Praseodymium oxide, barium nitrate, cobalt oxide, and nickel oxide are added to dilute nitric acid at a molar ratio of 3:1:2:2, and heated and stirred until the solution is clear. Then, ethylene glycol and glycine are weighed and added according to a molar ratio of 1:1:2 between the metals and ethylene glycol and glycine. After stirring and heating to evaporate the water, the temperature is quickly raised to about 450°C in an electric furnace, and self-propagating combustion is used to obtain a primary powder. Ethanol and zirconium oxide balls of equal mass are added to the primary powder and ground on a ball mill. After drying the ground powder, calcination for 4 to 6 hours can obtain the desired oxygen electrode material. Figure 1 The XRD results of sintering at different temperatures with a molar ratio of Pr:Ba:Ni:Co of 3:1:2:2 in the embodiment are shown; it can be seen from the figure that a composite oxygen electrode material is obtained at 1000°C or below, and the generated composite oxygen electrode material is a composite material, and a perovskite phase powder can be obtained at 1050°C or above. Figure 2 The morphology of the sintered material at 1050° C. with a molar ratio of Pr:Ba:Ni:Co of 3:1:2:2 in the embodiment is shown. It can be seen from the figure that the particle size distribution of the prepared material is relatively uniform.

[0031] Example 2

[0032] In this embodiment, component A 1-x A′ x B n O 3-δ , wherein 0.75≤n≤1, 0≤δ≤1, 0.5≤x<1, and the molar ratio of Co in the B position is not less than 50%, the preparation method of the oxygen electrode material is as follows:

[0033] Praseodymium oxide, barium nitrate, cobalt oxide, and nickel oxide are added to dilute nitric acid at a metal molar ratio of 1:1:1:1. Heat and stir until the solution is clear. Ethylene glycol and glycine are then weighed and added at a metal to ethylene glycol to glycine molar ratio of 1:1:2. After stirring and heating to evaporate the water, the mixture is quickly heated to approximately 450°C in an electric furnace and subjected to self-propagating combustion to obtain a primary powder.

[0034] The primary powder is added with equal amounts of ethanol and zirconium oxide balls and ground on a ball mill. After the ground powder is dried, it is calcined at 1050°C for 4 hours to obtain the required oxygen electrode material. Figure 3 The XRD results of sintering at different temperatures for an embodiment in which the molar ratio of elements Pr:Ba:Ni:Co is 1:1:1:1 are shown. As can be seen from the figure, within the entire temperature range, the composite oxygen electrode material is a composite material. Figure 4 This is an SEM image of the oxygen electrode material sintered at 1050°C. The image shows that the surface of the composite material is composed of several nanoparticles. To further enhance the performance of the oxygen electrode material for RSOCs based on proton conductor / oxygen ion conductor electrolytes, the electrode powder prepared above was prepared into a slurry. This slurry was then applied to both sides of a dense electrolyte using conventional screen printing or tape casting methods. Sintering at 1000°C for 2 hours removed organic matter and achieved a mechanically strong electrode / electrolyte interface. Using the same preparation method, symmetric cells with PBC, PNC, and PBNC1111 electrodes were fabricated. Figure 5 The embodiment shows that PBNC1111 is based on BaZr O.1 Ce 0.7 Y O.1 Yb 0.1 0 3-δ (BZCYYb) The AC impedance spectrum in a symmetrical battery with an electrolyte of PBNC1111 and PBC shows that under the test condition of 600 ° C, PBNC1111 and PBC have comparable catalytic activity, indicating that the partial replacement of Co by Ni reduces the cost and thermal expansion coefficient while not affecting its catalytic performance in proton ceramic fuel cells. According to the type of electrolyte, SOC can be divided into SOC based on proton conductors and SOC based on oxygen ion conductors. In order to study its performance in oxygen ion conductor-based SOC, its performance in a symmetrical battery composed of an oxygen ion conductor electrolyte (GDC) was tested, and the AC impedance spectrum is shown in FIG. Figure 6 . Figure 6 The test conditions were dry air at 550°C. Comparison showed that PBNC1111 had higher catalytic activity than PNC under dry air, indicating that Ba doping improves its catalytic activity and that it can also be used in fuel cells with oxygen ion conductor electrolytes.

[0035] Example 3

[0036] In this embodiment, component A 1-x A′ x B n O 3-δ , wherein 0.75≤n≤1, 0≤δ≤1, 0.5≤x<1, and the molar ratio of Co in the B position is not less than 50%, the preparation method of the oxygen electrode material is as follows:

[0037] Praseodymium oxide, barium nitrate, cobalt oxide, and nickel oxide are added to dilute nitric acid at a molar ratio of 1:1:1:1 of metals, and heated with stirring until the solution is clear. Then, ethylene glycol and glycine are weighed and added according to a molar ratio of 1:1:2 between metals, ethylene glycol, and glycine. After stirring and heating to evaporate the water, the temperature is quickly raised to about 400°C in an electric furnace, and a primary powder is obtained by self-propagating combustion. Equal amounts of ethanol and zirconium oxide balls are added to the primary powder and ground on a ball mill. After drying, the ground powder is calcined at 950°C for 4 hours to obtain the desired oxygen electrode material. XRD characterization is shown in FIG. Figure 3 , indicating that the oxygen electrode material is a composite oxygen electrode material, and the generated composite oxygen electrode material is a composite material.

[0038] To further enhance the performance of oxygen electrode materials for RSOCs based on proton-conducting electrolytes, the electrode powder prepared above was prepared into a slurry and applied to both sides of a dense BZCYYb electrolyte via conventional screen printing. Sintering then removed organic matter and achieved a mechanically strong electrode / electrolyte interface. After sintering at 1050°C for 2 hours in a symmetrical cell mode with 3 v.% water vapor, AC impedance measurements were conducted from 450°C to 700°C. The polarization impedance of PBNC1111 was found to be lower than that of PNC prepared under the same conditions across the test range. Figure 7 The impedance spectrum at 600 ° C is shown. By comparison, it can be concluded that PBNC1111 has higher catalytic activity than PNC, indicating that Ba doping significantly improves its catalytic activity as a cathode for proton ceramic fuel cells. In order to verify its stability under water vapor, as shown in Figure 8 As shown, the sample was subjected to a stability test for approximately 100 hours at 600°C in 3% H2O humidified air. The AC impedance spectrum showed no attenuation over 95 hours, indicating a certain degree of stability in the presence of 3% water vapor.

[0039] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. Persons skilled in the art will appreciate that improvements and modifications may be made without departing from the spirit and scope of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fuel cell / electrolyzer oxygen electrode material, characterized in that: The chemical formula of the oxygen electrode material is A 1-x A′ x BnO 3-δ , wherein A is one of Pr, Nd, Gd, Ce, and Sm, A′ is one or any two of Ba, Sr, and Ca, B contains Co and other metals, and the other metals are one or more of Ni and Nb, wherein 0<x<1, 0.75≤n≤1, and 0≤δ≤1; A method for preparing a fuel cell / electrolyzer oxygen electrode material comprises the following steps: Step 1: dissolving different metal oxides or metal salts in dilute nitric acid in a certain proportion, mixing and stirring to form a metal nitrate solution, wherein the metal ion components of the metal oxides or metal salts are four or more of Pr, Gd, Ce, Nd, Sm, Ba, Sr, Ca, Co, Ni, and Nb; Step 2, preparation of a precursor, adding a reaction reagent to the metal nitrate solution formed in the above step 1 to prepare a stable precursor solution, wherein the reaction reagent is any two of citric acid, glycine, urea, ethylene glycol, glycerol, and ammonium ethylenediaminetetraacetate; Step 3: Evaporate the precursor solution obtained in step 2 to remove water, and control the heating temperature to 100° C. to 150° C.; Step 4: Rapidly heating the components after evaporation and removal of water in step 3 to 350°C to 500°C to obtain a primary powder; Step 5: Add the primary powder obtained in step 4 to an equal amount of ethanol and grind it on a ball mill to fully mix the powder, and sinter it at high temperature for 2 to 5 hours. By adjusting the sintering temperature, a perovskite-phase oxygen electrode material or a composite oxygen electrode material can be prepared; In step 5, for component A 1-x A′ x BnO 3-δ Wherein 0.75≤n≤1, 0≤δ≤1, 0.5≤x<1, when the molar ratio of Co and other metal components in the B position is 1:1, and when the primary powder sintering temperature is less than or equal to 1050°C, a composite oxygen electrode material is obtained; In step 5, for component A 1-x A′ x BnO 3-δ , where 0.75≤n≤1, 0≤δ≤1, 0<x<0.5, the Co molar ratio in the B position is not less than 50%, and a composite oxygen electrode material is obtained when the sintering temperature is 950-1000°C, and a perovskite phase oxygen electrode material is obtained when the sintering temperature is greater than or equal to 1050°C.

2. A fuel cell / electrolyzer oxygen electrode material according to claim 1, characterized in that: The reaction reagents in step 2 are citric acid and ethylene glycol, and the total molar number of the citric acid and ethylene glycol is 2 to 4 times the total number of metal ions.

3. The fuel cell / electrolyzer oxygen electrode material according to claim 1, characterized in that: The oxygen electrode material is applied to oxygen ion conductor fuel cells / electrolyzers and proton ceramic fuel cells / electrolyzers.

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