An adaptive air electrode material, a preparation method and application thereof

Abstract

The application discloses a kind of self-adapting air electrode material and its preparation method and application, belong to solid oxide reversible battery technical field.The electrode material is two-phase composite structure, by perovskite phase PBC and multiple cation oxide MEO composite is formed;The chemical formula of PBC is PrBaCo2O 5+δ1 Wherein δ1 is oxygen non-stoichiometric coefficient, excess oxygen content relative to O5 standard is indicated;The MEO is multiple transition metal cation co-doped CeO2 base fluorite structure oxide, and the transition metal includes Fe, Co, Ni, Cu, Zn, wherein, the molar ratio of transition metal cation and CeO2 carrier is (0.05~0.15):1.The electrode material prepared by the application is driven by multiple cation doping self-regulation of defect chemistry, with oxygen / water self-adapting ability, can quickly establish and maintain favorable reaction state under external atmosphere fluctuation.

Description

Technical Field

[0001] This invention relates to the field of solid oxide reversible battery technology, specifically to an adaptive air electrode material, its preparation method, and its application. Background Technology

[0002] Proton ceramic electrochemical cells have attracted attention due to their ability to achieve high ionic conductivity in the mid-temperature range of approximately 400-700 °C, and are considered an important candidate for cooling operation of traditional solid oxide fuel cells and electrolyzers. Compared to oxygen ion conductor systems, proton conductors typically have lower migration barriers, allowing devices to maintain considerable electrochemical activity at lower temperatures. This reduces thermal stress and material mismatch risks, improves start-stop adaptability and sealing compatibility, and provides a foundation for high efficiency and product purification.

[0003] However, despite significant progress in reversible proton ceramic electrochemical cells over the past decade, their further engineering remains limited by the insufficient performance and stability of air electrodes. Air electrodes perform dual-function catalysis of oxygen reduction and oxygen evolution reactions, while simultaneously coupling with proton-conducting electrolytes to complete complex reaction processes involving multiple charge carriers. Under intermediate temperature conditions, the limitations of air electrodes often stem not only from insufficient intrinsic activity but also from their responsiveness to actual operating environments. Fluctuations in air humidity and changes in oxygen partial pressure can cause continuous adjustments to the near-surface defect states and adsorption states of the electrode, leading to increased polarization impedance, kinetic hysteresis, and slow state recovery. Related studies have shown that even with perovskite-based air electrodes exhibiting higher activity at intermediate temperatures, impedance drift and decreased reversibility may still occur over time under aqueous atmospheres or oxygen partial pressure disturbances.

[0004] To alleviate this problem, previous work has attempted to expand the reaction zone and improve the surface exchange process through composite formation, impregnation modification, or the introduction of surface catalytic phases, which can reduce polarization resistance under certain conditions. However, the effectiveness of these methods often exhibits operating condition dependence, and significant hysteresis and a long steady-state establishment process may still occur after atmosphere switching, indicating that the reequilibrium of the electrode state is not instantaneous. These phenomena suggest that the performance degradation of air electrodes under dynamic operating conditions is closely related to the rate of defect chemical regulation. In typical operating environments with intermediate temperatures, water content, and varying oxygen partial pressures, the generation and annihilation of oxygen vacancies, the adjustment of adsorbed oxygen and hydroxyl coverage, and related charge compensation processes all have characteristic time scales. When the external chemical potential undergoes a step change, the electrode often undergoes an evolution from non-equilibrium to a new steady state, resulting in a high or low impedance at the moment of switching, followed by a slow convergence to the steady state. This time-dependent kinetic response not only affects transient efficiency but may also accumulate as a stability risk over long-term cycling. Therefore, in addition to pursuing lower steady-state polarization impedance, enabling the electrode to recover to a favorable reaction state more quickly after atmospheric changes is a key issue that needs to be addressed in the design of air electrodes for mid-temperature reversible proton ceramic electrochemical cells.

[0005] In the existing technology, some progress has been made in the research and development of triple conductive oxide electrode materials, but it is still difficult to simultaneously achieve high steady-state catalytic activity, rapid dynamic operating condition response capability and excellent long-term humid environment stability, which cannot meet the needs of practical engineering applications of reversible proton ceramic batteries. Summary of the Invention

[0006] This invention addresses the problems of lag in dynamic operating condition response, insufficient stability in humid environments, and limited bifunctional catalytic activity in existing proton ceramic battery air electrodes. It provides an adaptive air electrode material, its preparation method, and its application. This adaptive air electrode material can quickly achieve defect rebalancing under fluctuations in external humidity and oxygen partial pressure, and has the advantages of low polarization loss, high operating condition adaptability, and long-term operational stability.

[0007] In one aspect, the present invention provides an adaptive air electrode material. According to an embodiment of the invention, the electrode material has a dual-phase composite structure, composed of a perovskite phase PBC and a multi-cation oxide MEO; the chemical formula of the PBC is PrBaCo2O. 5+δ1δ1 is the oxygen nonstoichiometry coefficient, representing the excess oxygen content relative to the O5 reference; the MEO is a CeO2-based fluorite structure oxide co-doped with multiple transition metal cations, wherein the transition metals include Fe, Co, Ni, Cu, and Zn, wherein the molar ratio of Fe, Co, Ni, Cu, and Zn is (0.9~1.1):(0.9~1.1):(0.9~1.1):(0.9~1.1), and the molar ratio of the total molar amount of transition metal cations to CeO2 is (0.05~0.15):1.

[0008] Specifically, PBC, as the main phase matrix of the electrode, possesses the typical structural advantages of layered perovskites, exhibiting excellent intrinsic electronic conductivity and oxygen catalytic activity. It can undertake the basic dual-function catalytic tasks of oxygen reduction and oxygen evolution, while providing a continuous loading framework and electron transport network for the MEO functional phase, ensuring the overall conductivity continuity and structural stability of the electrode. MEO, as a functional modification phase, is dispersed on the PBC surface at the nanoscale and is the core component for realizing the electrode's oxygen adaptive characteristics. Through multi-cation co-doping, it regulates the near-surface defect chemistry, enabling rapid defect rebalancing under fluctuations in humidity and oxygen partial pressure, reducing kinetic lag and performance fluctuations caused by atmosphere switching. At the same time, MEO provides abundant surface active sites, enhancing water molecule activation and proton conduction capabilities, widening the electrode's reaction area, effectively alleviating the passivation problem of traditional perovskite electrodes in high-humidity environments, and ultimately improving the electrode's operational robustness under dynamic conditions.

[0009] Secondly, the performance advantage of MEO comes from the synergistic doping of five transition metals: Fe, Co, Ni, Cu, and Zn. Single-element doping can only optimize some performance dimensions and cannot simultaneously take into account activity, stability, and adaptability to operating conditions. However, the combination of five elements can achieve multiple optimizations in structural stability, defect concentration, catalytic activity, ion transport, and water adaptability, breaking through the performance bottleneck of single doping and ultimately endowing the electrode with the core characteristic of oxygen self-adaptation.

[0010] In addition, an adaptive air electrode material according to the above embodiments of the present invention may also have the following additional technical features:

[0011] In some embodiments of the present invention, the MEO maintains a fluorite structure with the Fm-3m space group, and the PBC has a layered perovskite structure with the P4 / mmm space group. The two phases are chemically compatible and no impurity phases are generated. The MEO is dispersed at the nanoscale on the surface of the PBC matrix, constructing high-speed transport channels for protons, oxygen ions, and electrons across the interface and integrating high-concentration active defect sites. The morphology of the MEO nanoscale dispersion is formed by three steps: powder synthesis, two-phase composite, and sintering. The MEO prepared by the precipitation-deposition method is itself a uniform nanoscale particle with good dispersibility; during the ball milling process with PBC, the MEO is uniformly attached to the surface of the PBC particles, achieving uniform mixing at the microscale.

[0012] In some embodiments of the present invention, the mass ratio of MEO to PBC is (0.5~3.5):(6.5~9.5), preferably 2:8.

[0013] In another aspect of the invention, a method for preparing the aforementioned adaptive air electrode material is provided. According to an embodiment of the invention, the method includes the following steps:

[0014] (1) A multi-component transition metal oxide was constructed on the surface of CeO2 by precipitation-deposition method, and MEO powder was obtained by calcination;

[0015] (2) MEO powder and PBC powder are premixed at a preset mass ratio to obtain composite air electrode material.

[0016] In addition, the method for preparing an adaptive air electrode material according to the above embodiments of the present invention may also have the following additional technical features:

[0017] In some embodiments of the present invention, in step (1), CeO2 powder is prepared by precipitation method.

[0018] In some embodiments of the present invention, the preparation method of MEO powder in step (1) is as follows: a mixed solution of transition metal nitrates is prepared, and the mixed solution of nitrates is slowly added to a CeO2 suspension that has been ultrasonically dispersed beforehand, so that the total molar amount of transition metal cations to the molar ratio of CeO2 is (0.05~0.15):1; then urea solution is added for uniform precipitation, and the mixture is stirred at 40~60 ℃ for 4~6 h. After the reaction is completed, the mixture is naturally cooled, filtered, and washed alternately with deionized water and ethanol until the nitrate test is negative. After drying (drying at 60 ℃ for 24 h), the mixture is kept in air at 550~650 ℃ for 2~4 h to obtain MEO powder.

[0019] Specifically, in step (1), the transition metal nitrates include Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cu(NO3)2·3H2O, and Zn(NO3)2·6H2O, which respectively provide Fe, Co, Ni, Cu, and Zn dopants. After deposition and calcination, they enter the CeO2 lattice and, through multi-element synergistic regulation of the defect chemistry, electronic structure, and catalytic activity of the material, are the core functional components for MEO to achieve oxygen adaptive performance. Urea, as a uniform precipitant in the precipitation-deposition stage, slowly hydrolyzes under heating conditions of 40~60℃, continuously and gently releasing OH-. - This process ensures a steady increase in system pH, guaranteeing uniform and synergistic deposition of transition metal hydroxides on the CeO2 surface and preventing particle agglomeration and uneven loading caused by sudden local pH increases. Deionized water and ethanol are used as product washing solvents, and the filter cake is washed alternately to remove residual nitrate and soluble impurities until the nitrate test is negative, ensuring the purity of the final MEO powder.

[0020] In some embodiments of the present invention, the preparation method of PBC powder in step (2) is as follows: metal nitrates of Pr, Ba, and Co are dissolved in deionized water, ethylenediaminetetraacetic acid (EDTA) and citric acid are added, the mixture is heated and stirred until a transparent gel is formed, organic matter is removed by pre-calcination, and then PBC powder is obtained by calcination. The molar ratio of EDTA, citric acid, and metal ions is 1:2:1.

[0021] In some embodiments of the present invention, the pre-calcination temperature is 160~200 ℃ and the time is 10~14 h; the calcination temperature is 950~1050 ℃ and the calcination holding time is 4~6 h.

[0022] Specifically, in step (2), the nitrates corresponding to Pr, Ba, and Co are the metal element precursors of PBC, respectively providing Pr, Ba, and Co cations to form the layered perovskite lattice. The stoichiometric ratio is strictly followed to ensure that the phase composition and crystal structure of the final product meet the design requirements. EDTA is a strong complexing agent that can form stable chelates with various metal ions. Under neutral conditions, it effectively complexes Pr, Ba, and Co cations, avoiding phase segregation due to differences in precipitation characteristics of different metal ions, and ensuring the uniformity of the product element distribution and the accuracy of the stoichiometric ratio. Citric acid, as an auxiliary complexing agent and gel building component, on the one hand, works with EDTA to further enhance the complexing effect of metal ions; on the other hand, it forms a continuous organic gel network during heating and dehydration, anchoring the uniform dispersion of metal ions, inhibiting particle agglomeration, and providing a structural basis for the uniform crystallization of subsequent calcination. Ammonia can be used as a pH adjuster to bring the pH of the reaction system to a neutral range of 6.5-7.5, ensuring that the complexing ability of EDTA and citric acid is at its optimal level. This guarantees that all metal ions fully participate in the complexation reaction and avoids ion precipitation and uneven distribution caused by decreased complexing ability under acidic conditions. Deionized water is used as the reaction solvent to dissolve various metal nitrates and complexing agents, creating a homogeneous liquid-phase reaction environment to ensure that the complexation reaction proceeds uniformly and fully.

[0023] PBC powder is prepared using a citric acid-EDTA complexed sol-gel method. The core principle is to form a stable complex system with Pr, Ba, and Co metal ions through a dual complexing agent system, enabling uniform dispersion of each metal element at the molecular scale and avoiding common problems of element segregation and uneven reaction in solid-state reactions. First, the metal salt and complexing agent are dissolved and the pH is adjusted to 6.5–7.5 to form a homogeneous complex solution. Then, under heating conditions, the solvent gradually evaporates, and the system transforms from a sol into a viscous, transparent gel, with the metal ions fixed in the gel network and maintained in a uniform distribution. Next, pre-calcination at 160–200 °C gradually decomposes and removes the organic matter in the gel, yielding the oxide precursor. Finally, calcination at 950–1050 °C completes the solid-state reaction and crystallization, producing a homogeneous and well-crystallized PrBaCo2O. 5+δ1 Layered perovskite structure PBC powder.

[0024] In another aspect of the invention, an electrode slurry is proposed. According to an embodiment of the invention, the adaptive air electrode material is used for preparation. Specifically, the adaptive air electrode material, isopropanol, ethylene glycol, and glycerol are ball-milled for 30 min at a ratio of 1 g:10 mL:2 mL:1 mL to obtain the electrode slurry. The slurry is sprayed onto the electrolyte surface and kept at 800°C for 2-3 h to obtain the finished battery.

[0025] In another aspect of the invention, a proton ceramic fuel cell is proposed. According to an embodiment of the invention, the electrode is prepared using the aforementioned electrode slurry.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1) Innovation and self-regulation capability of material design

[0028] This invention discloses a material design approach for self-regulating defect chemistry driven by multi-cation doping. By co-doping CeO2 with five transition metals (Fe, Co, Ni, Cu, and Zn) to construct a MEO oxygen buffer phase, the electrode acquires rapid defect rebalancing capability under varying external humidity and oxidation potential, solving the core problems of traditional air electrodes, such as kinetic lag and slow state recovery under dynamic conditions. Unlike conventional air electrodes that rely on fixed defect concentrations or single catalytic sites, the electrode of this invention maintains low polarization resistance within the range of 500–700 °C, 0.10–0.21 atm oxygen partial pressure, and 0–30% (volume fraction) moisture pressure, significantly reducing performance fluctuations caused by atmosphere switching.

[0029] (2) Uniqueness of preparation method and interfacial advantages

[0030] This invention employs a precipitation-deposition method to prepare the MEO phase. Through a "surface deposition-bulk diffusion" mechanism, multiple cations migrate from the CeO2 surface deposition state to the interior of the fluorite framework, achieving atomic-level uniform solid solution. Simultaneously, the MEO phase is dispersed at the nanoscale on the surface of the PBC matrix, constructing a high-speed transport channel for protons, oxygen ions, and electrons across the interface, maximizing the exposure of active sites, and constructing an efficient three-phase reaction interface.

[0031] (3) Excellent electrochemical performance and bifunctional compatibility

[0032] The composite air electrode of this invention exhibits extremely low polarization resistance, with a polarization resistance of only 0.04 Ω cm in dry air at 700 °C. 2 The value is as low as 0.13 Ω cm in humid air at 600 °C. 2 In fuel cell mode, the peak power density at 650 °C reaches 1.690 W / cm³. -2 This represents a 119% improvement over pure PBC electrodes; in electrolytic cell mode, the current density reaches 2.869 A cm⁻¹ at 650 °C and 1.3 V. -2 It improves upon the pure PBC electrode by 168%, exhibiting superior performance and adaptable to the dual-mode operation requirements of reversible proton ceramic batteries.

[0033] (4) Improved adaptability to operating conditions and operational stability

[0034] The electrode material of this invention possesses excellent oxygen / water self-adaptive capability, maintaining highly stable polarization impedance within a wide water vapor partial pressure range of 5%–30%, and avoiding the passivation problem caused by competitive adsorption of water molecules in traditional materials. The symmetric cell exhibits negligible degradation rate after 250 h of operation in humid air at 600 ℃, shows no significant voltage decay after 550 h of constant current operation in full-cell fuel cell mode, and remains stable at high current density for 800 h in electrolysis mode. It also possesses excellent mode-switching cycle reversibility, meeting the long-cycle operation requirements of practical engineering applications.

[0035] (5) Cooperative optimization of multi-carrier transport

[0036] The MEO of this invention simultaneously optimizes the multi-carrier conduction capabilities of oxygen ions, protons, and electrons. At 700 °C, the oxygen permeation flux is increased by more than 55% compared to pure CeO2, and the hydrogen permeation flux is 10.27 times that of pure CeO2. At the same time, it improves the electronic conductivity of the material and significantly accelerates the reaction kinetics of oxygen reduction, oxygen evolution, and water dissociation. Attached Figure Description

[0037] Figure 1 The X-ray diffraction (XRD) pattern and crystal structure model of the multi-cation oxide MEO in Example 1 of this invention;

[0038] Figure 2 The in-situ high-temperature XRD pattern of MEO in Embodiment 1 of the present invention;

[0039] Figure 3 The XRD pattern of the P-20MEO composite air electrode material in Example 1 of this invention;

[0040] Figure 4 The images shown are (a) a high-resolution transmission electron microscope (HR-TEM) image and (b) a fast Fourier transform (FFT) spectrum of MEO in Embodiment 1 of the present invention.

[0041] Figure 5 The images shown in Example 1 of this invention are: (a) High-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of MEO, (b) Energy Dispersive X-ray Spectroscopy (EDX) Fe elemental mapping, (c) EDX Co elemental mapping, (d) EDX Ni elemental mapping, (e) EDX Cu elemental mapping, (f) EDX Zn elemental mapping, (g) EDX Ce elemental mapping, and (h) EDX O elemental mapping.

[0042] Figure 6The images show the microstructure of the P-20MEO composite material in Example 1 of this invention: (a) microstructure, (b) HAADF-STEM image, (c) elemental distribution spectrum of Ba, (d) elemental distribution spectrum of Ce, and (e) superimposed elemental distribution spectrum.

[0043] Figure 7 This is a comparison of the Raman spectra of MEO and pure CeO2 in Example 1 of the present invention;

[0044] Figure 8 The thermogravimetric curves of MEO and pure CeO2 in Example 1 of this invention are used to characterize the lattice oxygen desorption and mass change characteristics of the material at high temperature.

[0045] Figure 9 This is the oxygen temperature-programmed desorption (O2-TPD) spectrum of MEO and pure CeO2 in Example 1 of the present invention;

[0046] Figure 10 The figures are (a) a comparison of oxygen permeation flux of MEO and pure CeO2 under different oxygen partial pressures, and (b) a comparison of normalized oxygen permeation flux of MEO and pure CeO2 under different oxygen partial pressures in Example 1 of the present invention.

[0047] Figure 11 This is a graph showing the changes in oxygen permeation flux of MEO and pure CeO2 after oxygen partial pressure cycling in Example 1 of the present invention.

[0048] Figure 12 This is a comparison chart of hydrogen permeation flux between MEO and pure CeO2 in Example 1 of the present invention. In the chart, p H2 This indicates that the volume percentage of H2 is 10%.

[0049] Figure 13 The above is a temperature-programmed desorption (H2O-TPD) spectrum of MEO and pure CeO2 using steam in Example 1 of this invention.

[0050] Figure 14 The figure shows the Arrhenius curves of the areal resistivity of electrodes with different composite ratios in dry air in Application Example 1 of the present invention. In the figure, Ea refers to the activation energy.

[0051] Figure 15 The following are comparison graphs of (a) the electrochemical impedance of the P-20MEO symmetric cell under a 10% H2O-Ar atmosphere and (b) the areal resistivity (ASR) of the P-20MEO symmetric cell under a 10% H2O-Ar atmosphere in Application Example 1 of the present invention.

[0052] Figure 16 The figure shows the relaxation time distribution (DRT) curves of electrode impedance with different composite ratios under a 10% H2O-Ar atmosphere in Application Example 1 of this invention. In the figure, LFR refers to the low frequency region, IFR refers to the mid frequency region, and HFR refers to the high frequency region.

[0053] Figure 17 The following are examples of the application of this invention: (a) ASR Arrhenius curves of electrodes with different composite ratios under a 10% H2O-air atmosphere, and (b) DRT analysis diagrams of electrodes with different composite ratios under a 10% H2O-air atmosphere.

[0054] Figure 18 The images shown are: (a) ASR comparison of various electrodes under an air atmosphere, (b) ASR comparison of various electrodes under an argon atmosphere containing 10% water, and (c) ASR comparison of various electrodes under an air atmosphere containing 10% water in Application Example 1 of this invention.

[0055] Figure 19 The ASR variation curves of the electrode under different water vapor partial pressures in Application Example 1 of this invention are shown.

[0056] Figure 20 The figures are the current-voltage-power (IVP) curves of the P-20MEO single cell in application example 2 of the present invention in (a) fuel cell mode and (b) current-voltage (IV) curves in electrolysis cell mode.

[0057] Figure 21 The following are performance comparison charts in Application Example 2 of the present invention: (a) P-20MEO and pure PBC (P) in fuel cell mode, and (b) P-20MEO and pure PBC (P) in electrolysis mode.

[0058] Figure 22 The electrochemical impedance spectroscopy of (a) a P-20MEO single cell and (b) a P-20MEO (SG) single cell are shown in Example 2 of the present invention.

[0059] Figure 23 The curves showing the hydrogen production and Faraday efficiency of the P-20MEO battery at different current densities in Application Example 2 of this invention are shown.

[0060] Figure 24 The Faraday efficiency curves of the P-20MEO battery at different temperatures are shown in Application Example 2 of this invention.

[0061] Figure 25 Examples of application of the present invention include (a) the long-term durability test curve of the electrode under humid air at 600 °C and (b) the impedance spectrum at the corresponding time.

[0062] Figure 26 Examples 2 of this invention show the DRT comparison curves of electrode impedance before and after the durability test of P-20MEO (a) and the DRT comparison curves of electrode impedance before and after the durability test of pure PBC (P).

[0063] Figure 27This is the long-term stability test curve of the P-20MEO full cell in application example 2 of the present invention in fuel cell and electrolyzer modes;

[0064] Figure 28 The curves show the cycle performance of the P-20MEO battery in Application Example 2 of this invention under the switching between fuel cell and electrolyzer modes. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0066] Example 1

[0067] A method for preparing an adaptive air electrode material includes the following steps:

[0068] (1) Preparation of multi-cation oxide MEO

[0069] a. Preparation of CeO2 support: Ammonia was slowly added dropwise to Ce(NO3)3·6H2O solution under magnetic stirring at 60 ℃, and the pH was adjusted to 8 in real time. The mixture was stirred continuously and aged for 12 h. After the reaction was completed, the mixture was filtered, washed alternately with deionized water and ethanol, dried in an oven at 60 ℃ for 24 h, and then calcined in a muffle furnace at 600 ℃ for 3 h to obtain CeO2 support powder.

[0070] b. Preparation of MEO powder: Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cu(NO3)2·3H2O, and Zn(NO3)2·6H2O were weighed according to the molar ratio of Fe:Co:Ni:Cu:Zn = 1:1:1:1:1, and 5×10⁻⁶ MEO powders were prepared. -2 molL -1 A nitrate mixture solution was prepared; the above nitrate mixture solution was slowly added to a deionized aqueous solution of CeO2 carrier powder dispersed by ultrasound, and the molar ratio of total transition metal ions to CeO2 carrier was controlled at 0.10:1; then urea solution was added for uniform precipitation, and the reaction was stirred at 50 °C for 5 h, during which the pH of the system was steadily increased to 7.5 by the slow release of urea, which induced the co-deposition of metal hydroxides on the CeO2 surface; after the reaction was completed, the mixture was naturally cooled to room temperature, the product was collected by filtration, and washed alternately with deionized water and ethanol until the nitrate test was negative. After drying at 60 °C for 24 h, the product was placed in a muffle furnace and kept at 600 °C in air for 3 h to obtain MEO powder.

[0071] (2) Preparation of perovskite PBC powder

[0072] PBC was prepared using the citric acid-EDTA complex sol-gel method, and the specific steps are as follows:

[0073] PBC powder preparation: according to PrBaCo2O 5+δ1 (δ1 is the non-stoichiometric coefficient of oxygen, representing the excess oxygen content relative to the O5 standard) stoichiometric ratio, weigh the corresponding metal nitrates of Pr, Ba, and Co and dissolve them in deionized water; add EDTA and citric acid to make the molar ratio of EDTA, citric acid, and total metal ions 1:2:1, stir to dissolve, and then add ammonia water dropwise to adjust the pH of the solution to 7; heat the solution to 120 ℃ and stir thoroughly until the water evaporates to form a transparent gel; place the gel in an oven at 180 ℃ for 12 h to pre-calcine to remove organic matter, then grind and place it in a muffle furnace at 1000 ℃ for 5 h to obtain PBC perovskite precursor powder.

[0074] (3) Preparation of P-20MEO composite air electrode material

[0075] The MEO powder obtained in step (1) and the PBC powder obtained in step (2) are premixed at a mass ratio of 2:8 and then fully ball-milled to obtain P-20MEO composite air electrode material.

[0076] The structure of the prepared MEO and P-20MEO composite air electrode material was characterized and analyzed:

[0077] 1. Crystal structure and phase characterization

[0078] Figure 1 The XRD patterns and corresponding crystal structure models of multi-cation oxide (MEO) are presented. Combined with Rietveld refinement results, MEO maintains the typical Fm-3m space group of CeO2-based fluorite. No characteristic impurity peaks of independent transition metal oxides were detected in the spectra, confirming that five cations (Fe, Co, Ni, Cu, and Zn) were successfully incorporated into the CeO2 framework in a lattice-solution manner. Refinement calculations show that the lattice constant a of MEO is 5.4061 Å, exhibiting significant lattice shrinkage compared to 5.4092 Å for pure CeO2. This further verifies the successful integration of smaller ionic radius transition metal cations into the CeO2 lattice. The goodness of fit of this refinement is [not specified]. The value is 1.02, indicating that the structural model and refinement results are reliable.

[0079] Figure 2The in-situ high-temperature XRD patterns of MEO in the range of 25-800 °C show that the diffraction peak system of MEO is complete within the test temperature range, with no impurity peaks generated, no abrupt peak changes or phase transitions. This confirms that the MEO prepared by this invention has excellent high-temperature thermal stability and can provide a structural basis for the long-term stable operation of air electrodes under medium-temperature conditions.

[0080] Figure 3 The XRD pattern of the P-20MEO composite electrode material, combined with Rietveld refinement results, shows that the composite system consists of a layered perovskite PBC main phase in the P4 / mmm space group and a MEO secondary phase in the Fm-3m space group, with no other impurity phases formed. The proportions of the two phases are basically consistent with the nominal proportions of the experimental design, and the refinement fit is good. The value is only 1.11; this confirms that MEO and PBC retain their independent crystal frameworks after being combined, and that they have excellent chemical compatibility, which can avoid interfacial side reactions during high-temperature sintering and long-term operation.

[0081] 2. Characterization of microstructure and elemental distribution

[0082] Figure 4 The HR-TEM image and corresponding FFT spectrum of MEO are shown. The interplanar spacing of (111) crystal planes of MEO was measured to be 3.11 Å. The FFT lattice is highly consistent with the symmetry of the fluorite structure, which further verifies the crystal structure characteristics of MEO.

[0083] Figure 5 The HAADF-STEM image of MEO and the corresponding EDX elemental mapping diagram show that the five transition metal elements Fe, Co, Ni, Cu, and Zn, along with the matrix elements Ce and O, are continuously and uniformly distributed at the particle scale. This confirms that after precipitation-deposition and calcination treatment, multiple cations successfully entered the same fluorite phase, forming a multi-element solid solution with uniform elemental distribution.

[0084] Figure 6 The HR-TEM image and EDX elemental mapping of the P-20MEO composite material show that in the composite electrode material prepared by this invention, the MEO active phase is uniformly dispersed on the surface of the PBC matrix at the nanoscale. This microstructure can effectively increase the density of active sites at the three-phase interface and provide a structural basis for the construction of high-speed proton, oxygen ion and electron transport channels across the interface.

[0085] 3. Characterization of Defect Chemical and Physicochemical Properties

[0086] (1) Figure 7 The Raman spectra of MEO and pure CeO2 are compared. The results show that, compared to the characteristic peaks of pure CeO2, the F-wavelength of MEO is significantly longer. 2gThe vibrational peaks exhibit a significant redshift and broadening, reflecting the crystal symmetry breaking caused by the co-doping of multiple cations such as Fe, Co, Ni, Cu, and Zn, as well as the weakening of the metal-oxygen bonding strength, which provides a lower thermodynamic energy barrier for the generation of oxygen vacancies.

[0087] (2) Tests were conducted using a NETZSCH STA 449 F3 thermogravimetric analyzer under a nitrogen protective atmosphere. The temperature was programmed to rise at a rate of 3 °C / min, and the change in sample mass with temperature was recorded throughout the process. The adsorption and desorption process of oxygen and the formation mechanism of oxygen defects were analyzed by examining the mass loss characteristics. Figure 8 As shown, the thermogravimetric (TG) curves of MEO and pure CeO2 from room temperature to 1000 °C reveal that MEO experiences a mass loss of approximately 1.43% in the high-temperature range. This change is primarily due to the extraction of lattice oxygen, directly reflecting the oxygen defect formation characteristics of the material.

[0088] (3) Using nitrogen as the carrier gas (flow rate 30 mL / min), the temperature was programmed to increase at a rate of 5 °C / min within the temperature range from room temperature to 1000 °C. The oxygen release signal at a mass-to-charge ratio m / z=32 was monitored using a Hiden HPR-20 online mass spectrometer to characterize the concentration of reactive oxygen species on the sample surface and the oxygen desorption kinetics. Figure 9 As shown, the oxygen temperature-programmed desorption (O2-TPD) spectra of MEO and pure CeO2 show that MEO exhibits a strong oxygen desorption signal at approximately 536 °C, and the desorption peak area is much larger than that of the pure CeO2 control sample, confirming that MEO has a higher concentration of surface active oxygen species and faster oxygen surface exchange reaction kinetics.

[0089] (4) The sample was pressed into a disc under a pressure of 100 MPa and sintered at 1250 °C for 5 h to form a dense oxygen permeable membrane with a thickness of 0.8 mm. The typical test temperature was 700 °C. During the test, the oxygen partial pressure on one side of the membrane was adjusted (covering the oxygen partial pressure range of 10% to 100%), and the oxygen permeation under steady state was measured to obtain the steady state oxygen permeation flux under different oxygen partial pressure conditions.

[0090] Figure 10 The results show the oxygen permeation flux of MEO and pure CeO2 under different oxygen partial pressures. At 700 °C, the steady-state oxygen permeation flux of MEO can reach 0.28 mL / min. -1 cm -2 Compared to 0.18 mL min of pure CeO2 -1 cm -2Significant improvement; when the external oxygen partial pressure is reduced to 10%, MEO can still maintain about 31% of the peak flux, while the normalized flux of pure CeO2 drops sharply to about 6%, confirming that MEO can still maintain efficient oxygen ion bulk phase transport capability under low oxidative potential driving force.

[0091] Figure 11 The results show that after the oxygen partial pressure cycling test, the oxygen permeation flux of MEO and pure CeO2 changed. The results show that when the oxygen partial pressure was switched back to 100% after being treated under low oxygen partial pressure, the oxygen flux of MEO increased by 7.3% compared with the initial state, while the increase of pure CeO2 was only 2.4%. This confirms that low oxygen partial pressure can induce activation effect on MEO lattice and verifies the oxygen adaptive regulation characteristics of the material of the present invention.

[0092] At a test temperature of 700 °C, an atmosphere with a hydrogen volume fraction of 10% was introduced into one side of the membrane, and the hydrogen permeation under steady-state conditions was measured to obtain the hydrogen permeation flux of the sample, which was used to characterize the proton transport capability of the material. Figure 12 The hydrogen permeation flux of MEO and pure CeO2 was measured at 700 °C and 10% H2 atmosphere. The hydrogen permeation flux of MEO was approximately 0.045 mL / min. -1 cm -2 The concentration reached 10.27 times that of pure CeO2, confirming that multi-cation co-doping effectively opened the proton transport pathway of the material, enabling efficient bulk proton transport.

[0093] (5) Pre-treatment of the sample before testing: The sample was placed in a humid air atmosphere and kept at 600 °C for 10 h to allow water molecules to be fully adsorbed on the sample surface and hydroxyl species to be formed. During the formal test, nitrogen was used as the carrier gas (flow rate 30 mL / min), and the temperature was programmed to rise at a rate of 5 °C / min in the temperature range from room temperature to 1000 °C. The water vapor release signal with a mass-to-charge ratio m / z=18 was monitored using a Hiden HPR-20 online mass spectrometer. The activation ability of the sample for water molecules and the water dissociation energy barrier were characterized by the temperature of the water desorption peak and the total amount of desorption.

[0094] Figure 13 The water vapor temperature programmed desorption (H2O-TPD) spectra of MEO and pure CeO2 show that the water desorption peak temperature of MEO decreased from 197 °C to 150 °C, and the amount of desorption increased significantly. This confirms that MEO has a better water molecule activation ability and a lower water dissociation energy barrier, which provides favorable conditions for proton-participated electrochemical reactions.

[0095] Example 2

[0096] The preparation method of P-10MEO composite air electrode material includes the following steps:

[0097] The MEO powder obtained in step (1) of Example 1 and the PBC powder obtained in step (2) were premixed at a mass ratio of 1:9 and then fully ball-milled to obtain P-10MEO composite air electrode material.

[0098] Example 3

[0099] The preparation method of P-30MEO composite air electrode material includes the following steps:

[0100] The MEO powder obtained in step (1) of Example 1 and the PBC powder obtained in step (2) were premixed at a mass ratio of 3:7 and then fully ball-milled to obtain P-30MEO composite air electrode material.

[0101] Comparative Example 1

[0102] The preparation method of P-20CeO2 composite electrode material includes the following steps:

[0103] The pure CeO2 powder prepared in step (1)a of Example 1 and the PBC powder obtained in step (2) were premixed at a mass ratio of 2:8 and then fully ball-milled to obtain P-20CeO2 composite electrode material.

[0104] Comparative Example 2

[0105] The preparation of P-20MEO (SG) composite electrode material by sol-gel method includes the following steps:

[0106] Metal nitrates with a molar ratio of Pr:Ba:Co:Ce:Fe:Ni:Cu:Zn = 1:1:2.0135:0.67:0.0135:0.0135:0.0135:0.0135 were added to deionized water and stirred until completely dissolved to obtain a clear and homogeneous mixed metal salt solution. Then, EDTA and citric acid were added sequentially in a molar ratio of EDTA:citric acid:total metal ions of 1:2:1. After stirring and dissolving, ammonia was slowly added dropwise to adjust the pH of the system to approximately 7, allowing all metal ions to fully complex and form a stable complex solution. The solution was then heated and stirred continuously at 120 °C until the solvent evaporated and the system transformed into a viscous, transparent gel. The gel was transferred to a crucible and kept at 250 °C for 10 hours to allow the organic matter to fully decompose, obtaining a loose oxide precursor powder. Finally, the precursor was ball-milled until homogeneous and kept at 1000 °C for 5 hours in air. After completing the solid-state reaction and crystal growth, P-20MEO(SG) composite powder with PBC and MEO coexisting phases was finally obtained. This yielded the P-20MEO(SG) composite electrode material.

[0107] Comparative Example 3

[0108] Pure PBC electrode material is obtained by directly using the PBC perovskite precursor powder prepared in step (2) of Example 1 as the electrode material.

[0109] Application Example 1

[0110] The method for preparing a symmetric solar cell includes the following steps:

[0111] (1) Preparation of dense BZCYYb electrolyte sheets:

[0112] a. Preparation of BZCYYb powder: according to BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ2 (δ2 is the oxygen non-stoichiometry coefficient, specifically representing the amount of oxygen vacancies relative to an ideal O3 lattice) stoichiometric ratios were used to weigh out the corresponding metal nitrates of Ba, Zr, Ce, Y, and Yb and dissolve them in deionized water; EDTA and citric acid were added to make the molar ratio of EDTA, citric acid, and total metal ions 1:2:1, and after stirring to dissolve, ammonia was added dropwise to adjust the pH of the solution to 7; the solution was heated to 120 °C and stirred thoroughly until the water evaporated to form a transparent gel; the gel was pre-calcined in an oven at 180 °C for 12 h to remove organic matter, then ground and placed in a muffle furnace at 1000 °C for 5 h to finally obtain BZCYYb electrolyte powder;

[0113] b. Add 1 wt% NiO as a sintering aid to the obtained BZCYYb powder, and mix evenly by high-energy ball milling to obtain a mixed powder; weigh 0.4 g of the mixed powder and place it in a stainless steel mold, and dry press it into a disc with a diameter of 15 mm and a thickness of about 1.0 mm under a pressure of 100 MPa, and calcine it in a muffle furnace at 1450 ℃ for 10 h to obtain a dense electrolyte sheet; grind both sides of the dense electrolyte sheet to remove surface carbonates, and control the final thickness to about 0.6 mm.

[0114] (2) Electrode slurry preparation: Weigh the electrode material powders of Examples 1-3 and Comparative Examples 1-3 respectively, mix them according to the ratio of electrode material powder: isopropanol: ethylene glycol: glycerol = 1 g: 10 mL: 2 mL: 1 mL, and ball mill them for 30 min to obtain the electrode slurry.

[0115] (3) Preparation of symmetrical cells: The electrode paste was sprayed on both sides of the dense electrolyte sheet with a thickness of 15 μm, and then placed in a muffle furnace at 800 °C for 3 h to obtain a symmetrical cell with an “electrode / BZCYYb / electrode” structure. Silver paste was used for electrode current collection.

[0116] The prepared symmetrical battery was characterized for electrochemical activity:

[0117] The sintered "electrode / BZCYYb / electrode" symmetrical cell was uniformly coated with silver paste on both sides as a current collector and connected with test leads. It was then placed in a high-temperature test furnace with a sealed gas path, and the gas tightness was checked to ensure independent and controllable atmospheres on both sides. Subsequently, the temperature was increased to the target test temperature range of 500~700 ℃ according to the program, and held until the cell temperature and electrode state stabilized. Finally, an electrochemical workstation (Solartron 1287+1260A) was used to test the cell at a frequency range of 10... 6 ~10 -2 Under the unified test parameters of Hz and AC amplitude of 10 mV, a total flow rate of 100 mL / min was sequentially introduced. -1 Three typical atmospheres were used: dry air, moist argon gas containing 10% water vapor, and moist air. After the atmosphere and electrode state reached steady state, electrochemical impedance spectroscopy (EIS) was collected at different temperatures to evaluate the polarization impedance and reaction kinetics characteristics of the electrode under different operating conditions. Based on this, oxygen partial pressure step perturbation was achieved by rapidly switching the atmosphere under a constant temperature of 600 °C. The evolution of impedance over time was continuously recorded to characterize the electrode's adaptive response to atmospheric fluctuations. Finally, the electrode was continuously operated for 250 hours under a fixed condition of 600 °C and moist air containing 10% water vapor. EIS was collected at fixed intervals. Subsequently, the decay law of each reaction process of the electrode was analyzed by deconvolution of the relaxation time distribution to complete the evaluation of the long-term operating durability of the electrode.

[0118] Figure 14 Arrhenius curves of polarization resistance (ASR) were obtained for air electrodes composed of MEO and PBC with different composite ratios under dry air conditions. The results show that the P-20MEO electrode consistently exhibits the lowest polarization resistance within the test temperature range of 500–700 °C, with an ASR of only 0.04 Ω cm at 700 °C. 2 It is stable at 0.25 Ω cm at 600 ℃ and 500 ℃, respectively. 2 1.49 Ω cm 2 The P-20MEO electrode is significantly superior to the pure PBC electrode. At the same time, the activation energy of the oxygen reduction reaction of P-20MEO is 1.18 eV, which is lower than that of P-10MEO (1.25 eV) and P-30MEO (1.24 eV), confirming that the P-20MEO electrode prepared in Example 1 has achieved the best balance between the construction of the electron-ion conduction network and the enhancement of catalytic activity.

[0119] Figure 15 The Nyquist plot of the P-20MEO symmetric cell under a 10% H2O-Ar atmosphere is compared with the ASR results of different electrodes. The ASR values ​​of P-20MEO at 650 ℃, 600 ℃, 550 ℃, and 500 ℃ are 2.2 Ω cm⁻¹. 2 3.0 Ω cm 24.51 Ω cm 2 8.35 Ω cm 2 Both were significantly lower than the 3.8 Ω cm of the pure PBC electrode. 2 5.5 Ω cm 2 8.9 Ω cm 2 24.0 Ω cm 2 This confirms that the composite electrode of the present invention has excellent water molecule activation and proton generation capabilities.

[0120] Figure 16 The deconvolution curves of the relaxation time distribution (DRT) of the electrochemical impedance spectroscopy (EIS) of the symmetric cell under 600 ℃ and 10% H2O-Ar conditions were analyzed. The results showed that P-20MEO significantly suppressed the low-frequency impedance peaks corresponding to the gas diffusion and surface adsorption processes, confirming that the MEO phase can accelerate the dissociation process of H2O on the electrode surface and maintain efficient proton and hole carrier transport even under anaerobic conditions.

[0121] Figure 17 The ASR Arrhenius curves and DRT analysis results for different air electrodes under a 10% H2O-air atmosphere show that the activation energy of P-20MEO is reduced to 1.07 eV, and the ASR at 600 °C is as low as 0.13 Ω cm⁻¹. 2 Compared with pure PBC electrode, the characteristic peaks of gas adsorption-diffusion and surface exchange processes in P-20MEO showed significant intensity attenuation and frequency redshift, confirming that the MEO phase not only optimizes the oxygen reduction reaction pathway, but also promotes the proton-involved surface charge transfer process through efficient hydration, which can effectively avoid the activity passivation problem caused by water molecule competitive adsorption in traditional perovskite materials under humid environments.

[0122] Figure 18 The ASR (Average Saturation Rate) of P-20MEO, P-20MEO (SG) prepared by the sol-gel method, and P-20CeO2 composite electrode were compared under dry air, 10% H2O-Ar, and 10% H2O-air atmospheres. P-20MEO exhibited the best electrochemical performance under all test conditions; for example, under humid air conditions at 600 °C, the ASR of P-20MEO was 0.13 Ω cm⁻¹. 2 It is significantly lower than the 0.24 Ω cm of P-20MEO(SG) and P-20CeO2. 2 This study confirms that the design of multi-cation co-doped components, combined with the precipitation-deposition method, can maximize the electrochemical performance advantages of the material.

[0123] Figure 19The ASR (Average Saturation Rate) curves of the P-20MEO / P-20CeO2 composite electrode are shown for 600 °C and within a water vapor partial pressure range of 5%–30%. The results show that as the water vapor partial pressure increases from 5% to 30%, the ASR of P-20CeO2 increases from 0.22 Ω cm⁻¹. 2 Increased to 0.25Ω cm 2 The ASR of P-20MEO remained stable at 0.13 Ω cm⁻¹ throughout this process, showing a clear upward trend. 2 The temperature remained around 100°C, with no significant increase or even a slight decrease, confirming that the MEO phase of this invention has extremely strong water self-adaptive ability. It can quickly balance the coverage of surface hydroxyl groups and adsorbed oxygen species within a wide range of water vapor partial pressures, avoiding poisoning and blockage of active sites under high humidity conditions.

[0124] Application Example 2

[0125] A method for preparing an anode-supported reversible proton ceramic single cell includes the following steps:

[0126] (1) Preparation of anode-supported half-cell: Prepare anode composite powder (BZCYYb:NiO:soluble starch (Maclean) = 3.5:6.5:1, mass ratio), mix evenly by high-energy ball milling, weigh 0.35 g of anode composite powder and dry press it into discs at 100 MPa, pre-fire it in air at 1000 ℃ for 2 h to obtain a pretreated anode support layer; prepare electrolyte spin-coating slurry by ball milling for 1 h according to the ratio of BZCYYb:ethyl cellulose:ethanol:ethylene glycol = 1 g:0.1 g:10 mL:2 mL, fix the pretreated anode support layer on the spin coater platform, cover it with electrolyte spin-coating slurry and spin coat at 8000 rpm for 30 s, repeat 4 times to obtain a uniform 10 μm thin layer, and then keep it at 1450 ℃ for 5 h to complete the co-firing densification of the half-cell to obtain NiO-BZCYYb / BZCYYb half-cell.

[0127] (2) Single cell preparation: The electrode slurries prepared in step (2) of Application Example 1 were sprayed to a thickness of about 15 μm onto the electrolyte side of the anode-supported half cell and kept at 800 ℃ for 3 h to obtain a single cell with good interfacial adhesion and an electrode active area of ​​0.28 cm². 2 Silver paste is used for electrode current collection and sealing.

[0128] Electrochemical performance characterization of anode-supported single cells:

[0129] The test subject was an electrode with an active area of ​​0.28 cm². 2The anode-supported reversible proton ceramic single cell was first assembled on a high-temperature test bench before testing. Silver paste / silver sealant was used to complete the current collection and gas path sealing of both electrodes. The temperature was then programmed to the target temperature. Dry hydrogen was introduced into the anode side to complete anode reduction and establish a stable open-circuit voltage. After the temperature and voltage stabilized, various performance tests were conducted sequentially. In fuel cell mode, dry air or humid air containing 10% water vapor was introduced into the air electrode side, with the total flow rate controlled at 100 mL / min. -1 Dry hydrogen gas was continuously introduced into the anode side. Electrochemical impedance spectroscopy (EIS) data were collected using a Solartron 1287+1260A electrochemical workstation within the test temperature range of 500–650 °C to analyze the ohmic resistance and polarization resistance of the battery. IV curves and power density curves at each temperature were recorded using a Keithley 2420 source meter with a four-probe method to obtain core performance parameters such as peak power density. In electrolysis cell mode, humid air containing 10% water vapor was introduced into the air electrode side at a total flow rate of 100 mL / min. -1 Dry hydrogen gas was introduced into the anode side, and the electrolysis IV curves at various temperatures were measured using a Keithley 2420 source meter within the same temperature range. The electrolysis current density corresponding to a thermal neutral voltage of 1.3 V was recorded, and electrochemical impedance spectroscopy (EIS) was acquired at a working voltage of 1.3 V using an electrochemical workstation to analyze the impedance characteristics and kinetic limitations of the electrolysis process. The Faraday efficiency was measured using online gas chromatography with a thermal conductivity detector (TCD) to quantitatively determine the volume fraction of hydrogen products at the fuel electrode side, measuring 500–1000 mA cm⁻ at 550 °C. 2 The hydrogen yield corresponding to different current densities within a certain range was determined and the Faraday efficiency was calculated, while the constant current density was fixed at 800 mA cm⁻. 2 The Faraday efficiency was tested at 500, 550, and 600 °C to analyze the effect of temperature on energy utilization. Stability and reversible cycle tests were conducted at 600 °C. In the long-term steady-state test, the fuel cell mode was tested at 0.4 A cm⁻. 2 Continuous operation under constant current discharge for 550 hours, in electrolytic cell mode at -1.5 A cm⁻ 2 The constant current electrolysis was continuously operated for 800 hours, and the mode switching cycle test controlled the battery at 0.5 A cm⁻. 2 The fuel cell mode with -1.5 A cm⁻ 2 The battery was rapidly switched between different electrolytic cell modes and continuously tested for 1200 minutes, recording voltage evolution patterns to evaluate its reversible operation capability and adaptability to dynamic operating conditions.

[0130] Figure 20For an anode-supported reversible proton ceramic battery employing a P-20MEO composite air electrode, IVP and IV curves were measured in the range of 500–650 °C in both fuel cell and electrolyzer modes. The results show that in fuel cell mode, the peak power density of the battery reaches 1.690 W cm⁻¹ at 650 °C. -2 It reaches 1.360 W cm⁻¹ at 600 °C. -2 It can maintain 0.852 W cm even at 500 ℃. -2 The electrolytic current density reaches a high level; in electrolytic cell mode, at a thermally neutral voltage of 1.3 V, the electrolytic current density at 650 °C can reach 2.869 A cm⁻¹. -2 It reaches 1.987 A cm at 600 ℃. -2 It can still reach 0.956 A cm at 500 ℃. -2 This confirms that the composite electrode of the present invention possesses excellent dual-function catalytic activity for both oxygen reduction and oxygen evolution.

[0131] Figure 21 The results show the performance comparison between P-20MEO cells and pure PBC cells. In fuel cell mode, the peak power density of P-20MEO cells is 119% higher than that of pure PBC cells; in electrolysis cell mode, the current density at 1.3 V is 168% higher than that of pure PBC cells. This confirms that the introduction of the MEO phase can greatly reduce the polarization loss on the cathode side and significantly improve the energy conversion efficiency of the whole cell.

[0132] Figure 22 Electrochemical impedance spectroscopy (EIS) spectra of P-20MEO and P-20MEO (SG) cells measured at open-circuit voltages of 650–500 °C were obtained. The results show that the polarization resistance R of the P-20MEO cell at 650 °C is [missing value]. p Only 0.035 Ω cm 2 It is significantly lower than the 0.050 Ω cm of P-20MEO (SG). 2 Simultaneously test the ohmic resistance R of the battery. o The differences were small, all falling within the range of 0.140–0.150 Ω cm. 2 The results confirm that the improvement in battery performance is mainly due to the enhanced catalytic kinetics of the composite electrode itself, rather than the improvement in interfacial contact.

[0133] Figure 23 The hydrogen yield and corresponding Faraday efficiency of P-20MEO cells at 550 °C and different current densities were calculated. The results show that as the current density increases from 500 mA cm⁻¹, the hydrogen yield increases with the Faraday efficiency. -2 Increased to 1000 mA cm -2 The hydrogen yield showed a good linear growth trend, indicating that the electrode reaction was not limited by gas diffusion and the electrolysis process had excellent kinetic performance.

[0134] Figure 24 800 mA cm -2 Under constant current electrolysis conditions, the Faraday efficiency at different temperatures was measured. The results showed that the Faraday efficiency was as high as 93% at 500℃, 83% at 550℃, and still maintained at 70% at 600℃. The composite electrode of this invention maintained high energy conversion efficiency throughout the entire test temperature range and has excellent potential for medium and low temperature electrolysis hydrogen production.

[0135] Figure 25 The results of long-term durability tests of P-20MEO and unmodified PBC electrodes in symmetric cells under humid air conditions at 600 °C show that the ASR of the P-20MEO symmetric cell remained stable at 0.155~0.168 Ω cm⁻¹ throughout the 250 h test period. 2 Within this range, it hardly changes with time, and the corresponding decay rate is negligible (≤ 5.2 × 10⁻⁶ per 100 h). -3 Ω cm 2 The ASR of the unmodified PBC electrode increased monotonically with operating time, from an initial 0.339 Ω cm⁻¹. 2 Increased to 0.494Ω cm 2 This confirms that the P-20MEO composite electrode of the present invention exhibits excellent intrinsic durability under humid air conditions. During the durability test of the P-20MEO symmetric cell, a Nyquist plot was taken every 50 hours. The curves at each test time point basically overlapped, with only slight fluctuations in the high-frequency intercept and mid-frequency arc, further verifying the long-term stability of the electrode's electrochemical performance.

[0136] Figure 26 The DRT deconvolution curves corresponding to the battery electrochemical impedance spectroscopy at the start and end times of the durability test show that the characteristic peak intensities of the P-20MEO corresponding to the high-frequency charge transport / interface contact process and the mid-to-low frequency surface exchange / gas phase diffusion process remain basically unchanged; while the DRT peaks of the pure PBC electrode in the mid-frequency and low-frequency ranges show a significant increase, confirming that its bulk diffusion and surface exchange impedances continue to deteriorate with operating time.

[0137] Figure 27 The results show the long-term stability of the full cell using the P-20MEO composite air electrode at 600 °C. The results indicate that in fuel cell mode, the stability is 0.4 A cm⁻¹. -2 During constant current operation, the battery voltage remained highly stable over the 800-hour test cycle, with no significant voltage decay; in electrolytic cell mode, -1.5 A cm⁻¹ -2During high current density constant current operation, the battery can operate stably for more than 550 hours. The open circuit voltage of the battery remains consistent before and after the test, ruling out the possibility of electrolyte breakdown and seal failure.

[0138] Figure 28 At 600 °C, the P-20MEO battery in fuel cell mode (0.5 A cm⁻¹) -2 (Constant current) and electrolytic cell mode (-1.5 A cm⁻¹) -2 The performance test results of constant current (Current) cycling showed that after 1200 min of high-intensity mode switching cycle, the battery as a whole still maintained good reversible operation capability, and no performance drop or structural failure occurred. This confirms that the composite electrode of the present invention has excellent mode switching adaptability and operational robustness under dynamic operating conditions, and can meet the frequent start-stop and mode switching requirements in the practical application of reversible proton ceramic batteries.

[0139] In summary, the self-regulating adaptive biphase composite air electrode with multi-cation doping-driven defect chemistry described in this invention, compared with the air electrode of traditional proton ceramic electrochemical cells, possesses not only excellent oxygen ion and electron mixing conductivity, but also superior proton conductivity, rapid hydration activation capability, and unique oxygen / water atmosphere adaptive regulation characteristics. This effectively solves the core pain points of traditional electrodes, such as kinetic hysteresis under dynamic operating conditions and activity decay in high-humidity environments. Therefore, the P-20MEO composite electrode exhibits breakthrough electrochemical performance and operational stability in both proton ceramic fuel cell (PCFC) and proton ceramic electrolyzer (PCEC) modes. In a single cell with proton-conducting electrolyte BZCYYb and NiO-BZCYYb (composed of NiO, BZCYYb, and soluble starch in a mass ratio of 6.5:3.5:1) as the hydrogen electrode, the corresponding single cell can achieve 1690 mW cm⁻¹ in PCFC mode at 650 °C. -2 The maximum output power; when electrolyzing H2O in PCEC mode at the same temperature, 2.869 A cm⁻¹ can be obtained at a thermal neutral voltage of 1.3 V. -2 This invention develops a reversible proton ceramic battery air electrode material and its preparation method that combine high catalytic activity, strong operating condition adaptability, and long-term stability. This significantly improves the electrochemical performance and operational robustness of proton ceramic fuel cells and electrolyzers, providing a widely applicable material design concept and technical solution for the engineering application of such devices.

[0140] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the present invention, and all such modifications or additions should fall within the protection scope of the present invention.

Claims

1. An adaptive air electrode material, characterized in that: The electrode material has a dual-phase composite structure, composed of perovskite phase PBC and multi-cation oxide MEO; the chemical formula of the PBC is PrBaCo2O. 5+δ1 δ1 is the oxygen nonstoichiometry coefficient, representing the excess oxygen content relative to the O5 reference; the MEO is a CeO2-based fluorite structure oxide co-doped with multiple transition metal cations, wherein the transition metals include Fe, Co, Ni, Cu, and Zn, wherein the molar ratio of Fe, Co, Ni, Cu, and Zn is (0.9~1.1):(0.9~1.1):(0.9~1.1):(0.9~1.1), and the molar ratio of the total molar amount of transition metal cations to CeO2 is (0.05~0.15):

1.

2. The adaptive air electrode material according to claim 1, characterized in that: The MEO maintains the fluorite structure of the Fm-3m space group, and the PBC has a layered perovskite structure of the P4 / mmm space group. The two phases are chemically compatible and no impurity phases are generated.

3. The adaptive air electrode material according to claim 1, characterized in that: The mass ratio of MEO to PBC is (0.5~3.5):(6.5~9.5).

4. A method for preparing the adaptive air electrode material according to any one of claims 1-3, characterized in that, Includes the following steps: (1) A multi-component transition metal oxide was constructed on the surface of CeO2 by precipitation-deposition method, and MEO powder was obtained by calcination; (2) MEO powder and PBC powder are premixed at a preset mass ratio to obtain composite air electrode material.

5. The method for preparing an adaptive air electrode material according to claim 4, characterized in that: In step (1), CeO2 powder is prepared by precipitation method.

6. The method for preparing an adaptive air electrode material according to claim 4, characterized in that, In step (1), the specific method for preparing MEO powder is as follows: A mixed solution of transition metal nitrates was prepared and slowly added to a pre-ultrasonically dispersed CeO2 suspension, so that the total molar amount of transition metal cations to the molar ratio of CeO2 was (0.05~0.15):

1. Then, urea solution was added for uniform precipitation, and the reaction was stirred at 40~60 ℃ for 4~6 h. After the reaction was completed, the mixture was naturally cooled, filtered, and washed alternately with deionized water and ethanol until the nitrate test was negative. After drying, the mixture was kept in air at 550~650 ℃ for 2~4 h to obtain MEO powder.

7. The method for preparing an adaptive air electrode material according to claim 4, characterized in that, In step (2), the PBC powder is prepared as follows: Metal nitrates of Pr, Ba, and Co are dissolved in deionized water, ethylenediaminetetraacetic acid and citric acid are added, and the mixture is heated and stirred until a transparent gel is formed. The organic matter is removed by pre-calcination, and then PBC powder is obtained by calcination.

8. The method for preparing an adaptive air electrode material according to claim 7, characterized in that: The pre-firing temperature is 160~200 ℃, and the time is 10~14 h; the calcination temperature is 950~1050 ℃, and the calcination holding time is 4~6 h.

9. An electrode paste, characterized in that: It is prepared using the adaptive air electrode material according to any one of claims 1-3.

10. A proton ceramic fuel cell, characterized in that: Electrodes are prepared using the electrode slurry described in claim 9.

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