Search

Manganate cathodes have good stability, but their performance at intermediate temperatures is not satisfactory, restricting the application for proton-conducting solid oxide fuel cells (H–SOFCs). A new composition, Pr 0.25 Nd 0.25 Sr 0. 5 MnO 3-δ (PNSM), is proposed to solve this problem. First-principles calculations indicate PNSM should have better performance than the classical Sr-doped LaMnO 3 (LSM) cathode by favoring the formation of oxygen vacancies and proton defects. Experimental studies indicate that the PNSM material can be successfully synthesized and show good chemical stability. The H–SOFC using the single-phase PNSM cathode shows improved performance than that using the traditional LSM cathode, demonstrating the prediction from the theoretical calculations. Further optimizing the cell structure, an encouraging performance of 1266 mW cm−2 at 700 °C is obtained, which is larger than many other manganates cathode-based H–SOFCs. The performance is even comparable to many high-performing cathodes for H–SOFCs, indicating PNSM is an efficient cathode material for H–SOFCs. [ABSTRACT FROM AUTHOR]

This study proposes a new Pr 0.25 Nd 0.25 Ca 0.5 MnO 3-δ (PNCM) cathode material for protonic ceramic fuel cells (PCFCs). As demonstrated by first-principles calculations, the Ca-doping strategy can promote oxygen vacancy formation and accelerate the oxygen reduction reaction (ORR) compared to the conventional Sr-doping method. Additional experiments reveal the doping of Ca can enhance the proton and oxygen diffusion abilities compared with the traditional Sr-doped material. Consequently, the PCFC with single-phase PNCM cathode produces a high peak power density of 1232 mW cm-2 at 700 °C, which is significantly greater than the cell with Sr-doped cathode, which only produces 749 mW cm-2 under the same testing conditions. The PNCM cathode inherits the excellent stability of manganate cathodes, allowing the fuel cell to exhibit good stability under operational conditions. PNCM is a new and promising cathode material for PCFCs due to its excellent fuel cell performance and stability. [ABSTRACT FROM AUTHOR]

Sintering aids are commonly used to improve the sinterability of proton-conducting oxides, whereas the sintering aid elements are being used alone in previous research. In this study, a high-entropy design method for the BaCe 0.4 Zr 0.4 Y 0.2 O 3 (BCZY) proton-conducting oxides sintering aid is proposed. In contrast to the use of sintering aids such as Ni, Fe, Cu, Co, and Zn alone, the high-entropy design allows for the simultaneous use of all five elements, resulting in the new composition BaCe 0.4 Zr 0.4 Y 0.15 Ni 0.01 Cu 0.01 Co 0.01 Fe 0.01 Zn 0.01 O 3 (HE-BCZY). Compared to conventional BaCe 0.4 Zr 0.4 Y 0.15 M 0.05 O 3 (BCZYM, M = Ni, Cu, Co, Fe, Zn) materials, the sinterability of the new HE-BCZY material is significantly greater than that of BCZYM, despite the fact that the concentration of sintering aids is the same. Following sintering at 1300 °C, the HE-BCZY electrolyte membrane is completely dense. In addition, the HE-BCZY electrolyte has a higher conductivity than BCZYM. The low sintering temperature allows the successful preparation of proton ceramic fuel cells (PCFCs) with the HE-BCZY electrolyte, and the fuel cell reaches a high peak power density of 1218 mW cm−2 at 700 °C, which is much higher than that of PCFCs using BCZY-based electrolytes. In addition, the excellent chemical stability of HE-BCZY is maintained under both H 2 O and CO 2 conditions. Consequently, a fuel cell employing the HE-BCZY electrolyte operates without detectable degradation for 200 h. This study demonstrates that although the high-entropy design is seldom used for sintering aids of proton-conducting oxides, it is an intriguing and promising strategy for creating high-performance electrolyte materials with good sinterability, high conductivity, and excellent stability. [ABSTRACT FROM AUTHOR]

By screening a series of La 0.5 Sr 0.5 MnO 3-δ (LSM)-La 0.5 Sr 0.5 FeO 3-δ (LSF) solid solutions using first-principles calculations, an optimal solid solution of LSM and LSF was chosen as the cathode for proton-conducting solid oxide fuel cells (H–SOFCs). In terms of oxygen vacancy formation energy, O 2 adsorption energy, bond length of adsorbed O 2 , and O p-band center, La 0.5 Sr 0.5 Mn 0.875 Fe 0.125 O 3 (LSMF125) and La 0.5 Sr 0.5 Mn 25 Fe 0.75 O 3 (LSMF75) exhibited superior properties. Subsequent experimental investigations revealed that the H–SOFC with the LSMF75 cathode performed better than the cell with the LSMF125 cathode. The structure analysis revealed that LSMF75 has both Mn and Fe cations on its surface, similar to the designs of several naturally occurring enzymes, hence the increased cathode activity. By improving the LSMF75 cathode further, the cell utilizing the LSMF75 cathode attained a peak power density of 1238 mW cm-2 at 700 °C, which was much greater than that of the cells using the LSM or LSF cathodes, illustrating the benefits of using the LSM-LSF solid solution. Additionally, the good chemical stability of the LSMF75 cathode was maintained, allowing for 150 h of stable operation under operational conditions. [ABSTRACT FROM AUTHOR]

In this study, both cathode powder preparations and fuel cell fabrications for proton-conducting solid oxide fuel cells (H–SOFCs) were performed using the microwave sintering technique. The microwave sintering approach produced Sr 2 Fe 1.5 Mo 0.25 Sc 0.25 O 6-δ (SFMS) cathode particles with a lower phase formation temperature and smaller grain size than the standard muffle furnace sintering method. The advantages of microwave sintering were also recognized during the fuel cell manufacturing process. Using the same electrolyte and anode, conventional sintering and microwave sintering were used to produce SFMS cathodes, resulting in varied fuel cell performance. The fuel cell output of the conventionally sintered cell was 1312 mW cm−2 at 700 °C, whereas the power density of the microwave-prepared cell achieved 1452 mW cm−2 under the same testing conditions, which was also higher than the performance of a number of recently reported H–SOFCs. Surface chemistry research revealed that microwave sintering generated more oxygen vacancies (Vo). Calculations based on first-principles indicated that the greater surface abundance of Vo increased the oxygen reduction reaction (ORR) activity. The benefits of microwave sintering can be discovered in both the powder preparation and cell construction stages, making it an intriguing and simple way to enhance the performance of H–SOFCs. [ABSTRACT FROM AUTHOR]

The BaCe 0 · 4 Zr 0 · 4 Y 0 · 2 O 3 (BCZY) was modified with the NiO sintering aid and prepared by a microwave sintering (MVS) method as the electrolyte for proton-conducting solid oxide fuel cells (H–SOFCs). The incorporation of NiO into the BCZY lattice improves the sinterability of the material, leading to the increase of the shrinkage from 3% to 26% after the high-temperature sintering. The dense BaCe 0 · 4 Zr 0 · 4 Y 0 · 15 Ni 0 · 05 O 3 (BCZYN) pellet can be obtained after sintering at 1500 °C, whereas the Ni-free BCZY is porous after sintering at the same condition. By further using the MVS method, the BCZYN can be densified at 1300 °C, which is 200 °C lower than conventional sintering. Furthermore, the microwave-sintered BCZYN has a higher conductivity than the conventionally sintered one due to the larger grain size. Using the MVS method in the H–SOFCs fabrication, the high porosity of the anode substrate can be retained. In contrast, the cell prepared by the conventional sintering (CS) method has a relatively dense anode, which is detrimental to gas fuel transportation. As a result, the microwave sintered cell exhibits an output of 1010 mW cm−2 at 700 °C, which is significantly larger than that for the conventionally sintered cell, being 535 mW cm−2 at the same testing condition, suggesting the advantage of using the MVS method for the fuel cell fabrication. [ABSTRACT FROM AUTHOR]

A new spinel oxide CoFe 1.9 Li 0.1 O 4 (CFLO) has been synthesized as a cathode material for proton-conducting solid oxide fuel cells. CFLO has good structure stability up to 900 °C. In addition, the material can survive in both CO 2 and steam-containing atmospheres. Compared with the Li-free sample, the Li-doping strategy significantly regulates the material's electronic structure. The low valence of Li leads to the increased amount of Fe and Co cations with higher valences. Furthermore, doping Li creates more oxygen vacancies at the material surface, which benefits the oxygen reduction reaction (ORR). The improved cathode performance for CFLO has been demonstrated that a cell using CFLO cathode reaches a peak power density of 1052 mW cm−2 at 700 °C. The cell performance is 60% larger than the Li-free cell, and similar results can be detected at other testing temperatures. In addition, the CFLO cell shows good long-term stability in the working condition. This study proposes the Li-doping strategy to modify spinel oxides and also provides a new spinel oxide as a high-performing cathode for H–SOFCs. [ABSTRACT FROM AUTHOR]

U cations were immobilized in the traditional Sr 2 Fe 2 O 6-δ (SFO) oxide, which was subsequently evaluated as a cathode for proton-conducting solid oxide fuel cells (H–SOFCs). Experimental studies indicated that the U cations could be incorporated into the SFO lattice, forming the new Sr 2 Fe 1.5 U 0.5 O 6-δ (SFUO) oxide material. The SFUO material exhibited improved chemical stability than the SFO material, preventing the formation of carbonates after treatment in a CO 2 atmosphere. Although the total electrical conductivity was decreased with the U-doping, the surface catalytic activity of SFUO was improved compared with SFO, which was demonstrated by first-principles calculations. The subsequent electrochemical studies indicated that an H–SOFC using the SFUO cathode showed higher fuel cell output and smaller polarization resistance than the SFO cathode. The present study demonstrated that SFO could locate U cations in the lattice, and the produced SFUO oxide exhibited improved performance, suggesting the utilization of SFO cathode in the harsh environment (such as U-containing conditions) would be possible, and the electrochemical performance of the fuel cell is not reduced. [ABSTRACT FROM AUTHOR]

The electrospinning technique was employed to prepare the La 0.5 Sr 0.5 Mn 0.875 Zn 0.125 O 3-δ (LSMZn) cathode for proton-conducting solid oxide fuel cells (H–SOFCs). Although the fiber structure can be obtained with the electrospinning technique for the LSMZn precursor, the fiber structure disappeared after the calcination procedure, leading to the formation of fine LSMZn nano-powders. It was found that the electrospun LSMZn can reach a pure phase after firing at 1100 °C, whereas the traditional sol-gel prepared LSMZn required a calcination temperature of 1150 °C. Furthermore, the electrospun LSMZn had a smaller particle size and richer oxygen vacancy than the traditional sol-gel LSMZn. First-principles calculations indicated that the oxygen vacancy-rich surface promoted the cathode reaction. The H–SOFC using the single-phase electrospun LSMZn generated a power density of 1122 mW cm−2 at 700 °C. The performance was not only larger than the sol-gel LSMZn cell reported in this study but also larger than previous H–SOFCs using the single-phase Mn-based cathodes, suggesting the electrospinning technique was an effective method to produce high-performing cathodes for H–SOFCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The new Pr 0.5 Sr 0.5 Fe 0.9 Mn 0.1 O 3 cathode was prepared. • The Mn-doping method mitigated the high thermal expansion of Pr 0.5 Sr 0.5 FeO 3. • The oxygen vacancy formation and proton diffusion were improved with Mn-doping. • Better fuel cell performance was obtained with the cathode using Mn-doping. The traditional Pr 0.5 Sr 0.5 FeO 3 (PSF) cathode is customized with Mn cations to generate the new Pr 0.5 Sr 0.5 Fe 0.9 Mn 0.1 O 3 (PSFMn) cathode for proton-conducting solid oxide fuel cells (H-SOFCs). Compared to the PSF oxide, the new PSFMn has a reduced thermal expansion, making it more compatible with electrolytes. Furthermore, Mn-doping enhances oxygen vacancy production in PSF, as revealed by experimental and first-principle calculations. More crucially, doping Mn into PSF improves proton diffusion kinetics, resulting in quicker proton diffusion and surface exchange. As a result, the H-SOFC with the PSFMn cathode achieves an output of 1446 mW cm−2 at 700 °C, but the PSF cell only achieves fuel cell performance of 1009 mW cm−2. The fundamental cause of the increased cell performance is the significantly reduced polarization resistance, implying that using the Mn-doping strategy enhances the cathode kinetics of conventional PSF cathodes for H-SOFC. [ABSTRACT FROM AUTHOR]

A single-step co-firing process is employed to fabricate solid oxide fuel cells (SOFCs) with an Sm-doped CeO 2 (SDC) electrolyte, aiming to simplify the SOFC fabrication procedure. Complete tri layer green cells are co-fired in a single step at different fabrication temperatures, and the co-firing temperature significantly influences the cell microstructure and thus influences its performance. Electrochemical investigations indicate that the cell resistance, including the ohmic and polarization resistance, varies with the co-firing temperatures used and leads to a different cell power output. Although the cell polarization resistance follows the rule that higher firing temperatures lead to higher polarization resistance values, the cell ohmic resistance does not follow the expectation that the cell fired at 1200 °C gives the largest ohmic resistance. The morphology analysis reveals the mechanism behind this phenomenon. The best cell performance is obtained by co-firing the cell at 1000 °C, reaching 401 mW cm−2 at 700 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • The diffusion of Ni from the anode to the electrolyte is revealded for H-SOFC. • The diffused Ni has significnalty influeced the performance of fuel cells. • Microwave sintering can mitigate the Ni diffusion at the interface. • Better performance is obtained with the microwave sintered fuel cell. Although Ni-based anodes are commonly employed in proton-conducting solid oxide fuel cells (H-SOFCs), interfacial diffusion of Ni from the anode to the electrolyte is difficult to avoid, resulting in lower electrolyte and fuel cell performance. In this study, the electrolyte/anode half-cells are co-sintered using a microwave sintering process, providing a lower co-sintering temperature than the standard sintering approach. The lower co-sintering temperature minimizes Ba-evaporation at the electrolyte and mitigates anode/electrolyte interfacial Ni diffusion, resulting in decreased electrolyte and interfacial polarization resistance. The microwave-sintered cell outperforms the traditionally sintered cell in electrochemical performance, with higher fuel cell performance and lower cell resistances. Furthermore, the improved interfacial condition improves the fuel cell's long-term durability, allowing the cell to operate for 200 h without detectable degradation. This study presents an intriguing and simple way to reduce anode/electrolyte interfacial Ni diffusion, which improves fuel cell output and operational stability. [ABSTRACT FROM AUTHOR]