Symmetrical Solid Oxide Fuel Cells Research Articles

A High-Performance and Durable Direct-Ammonia Symmetrical Solid Oxide Fuel Cell with Nano La0.6Sr0.4Fe0.7Ni0.2Mo0.1O3-δ-Decorated Doped Ceria Electrode.

Solid oxide fuel cells (SOFCs) offer a significant advantage over other fuel cells in terms of flexibility in the choice of fuel. Ammonia stands out as an excellent fuel choice for SOFCs due to its easy transportation and storage, carbon-free nature and mature synthesis technology. For direct-ammonia SOFCs (DA-SOFCs), the development of anode catalysts that have efficient catalytic activity for both NH3 decomposition and H2 oxidation reactions is of great significance. Herein, we develop a Mo-doped La0.6Sr0.4Fe0.8Ni0.2O3-δ (La0.6Sr0.4Fe0.7Ni0.2Mo0.1O3-δ, LSFNM) material, and explore its potential as a symmetrical electrode for DA-SOFCs. After reduction, the main cubic perovskite phase of LSFNM remained unchanged, but some FeNi3 alloy nanoparticles and a small amount of SrLaFeO4 oxide phase were generated. Such reduced LSFNM exhibits excellent catalytic activity for ammonia decomposition due to the presence of FeNi3 alloy nanoparticles, ensuring that it can be used as an anode for DA-SOFCs. In addition, LSFNM shows high oxygen reduction reactivity, indicating that it can also be a cathode for DA-SOFCs. Consequently, a direct-ammonia symmetrical SOFC (DA-SSOFC) with the LSFNM-infiltrated doped ceria (LSFNM-SDCi) electrode delivers a superior peak power density (PPD) of 487 mW cm-2 at 800 °C when NH3 fuel is utilised. More importantly, because Mo doping greatly enhances the reduction stability of the material, the DA-SSOFC with the LSFN-MSDCi electrode exhibits strong operational stability without significant degradation for over 400 h at 700 °C.

Novel sr-doped NdMn0.5Cr0.5O3-δ electrodes for symmetrical solid oxide fuel cell

Solid oxide fuel cells (SOFCs) have emerged as promising energy conversion devices, offering high efficiency and environmental sustainability. Efficient electrode materials are crucial for the overall cell performance of SOFCs. Perovskite type Nd1-xSrxMn0.5Cr0.5O3-δ (x = 0.25, 0.5) (NSCM25, NSCM50) was synthesized via conventional solid-state reaction technique. Structural, thermal and electrochemical characterizations were performed using X-ray diffraction, thermogravimetric analysis, conductivity measurements, scanning electron microscope, thermal expansion coefficient analysis and impedance spectroscopy. Structural analysis revealed that both compositions exhibit orthorhombic symmetry in the Pbnm space group. Thermogravimetric analysis (TGA) indicated minimal weight changes in both pre-reduced and as-prepared samples. The electrical conductivities in air at 600 ℃ were found to be 1.69 S/cm for NSCM25 and 4.91 S/cm for NSCM50, with a decrease observed under reduced oxygen partial pressure. Polarization resistance (Rp) analysis was conducted on symmetrical cells composed of NSCM25|GDC|NSCM25, NSCM50|GDC|NSCM50, NSCM25|YSZ|NSCM25, and NSCM50|YSZ|NSCM50. At 900 ℃, the polarization resistances were 0.12 Ωcm2, 0.21 Ωcm2, 0.11 Ωcm2, and 0.67 Ωcm2, respectively. The results suggest that NSCM25 and NSCM50 hold promise as electrode materials for symmetrical solid oxide fuel cells (SSOFC) employing YSZ or GDC electrolyte.

Enhanced electrochemical performance of (PrBa)xFe1.9Nb0.1O5+δ symmetrical electrodes with A-site deficient for symmetrical solid oxide fuel cells

Symmetrical solid oxide fuel cells (SSOFCs) with symmetrical electrodes have many desirable characteristics compared with conventional SOFCs. However, the lack of electrode materials simultaneously satisfied the high electrocatalytic activity in oxidizing and reducing atmospheres. Herein, a novel perovskite oxide electrode (PrBa)xFe1.9Nb0.1O5+δ ((PB)xFN, x = 1, 0.97, 0.95 and 0.93) was reported as a promising symmetrical electrode material for SSOFCs. XRD results reveal that the (PB)0.95FN sample has a tetragonal structure and good chemical compatibility with Gd0.1Ce0.9O2-δ electrolyte. Among all the samples, (PB)0.95FN has the lowest polarization resistance (Rp). At 800 °C, compared with primary PBFN, the cathode Rp of (PB)0.95FN is reduced from 0.109 Ω cm2 to 0.063 Ω cm2 in air, whereas the anode Rp is decreased from 0.3808 Ω cm2 to 0.3109 Ω cm2 in H2. In addition, an electrolyte-supported single cell with (PB)0.95FN symmetrical electrodes achieves a maximum peak power density at 800 °C, which is enhanced by 14.67% compared with that of PBFN. A-site deficiency on PBFN perovskite shows better electrochemical performance, which is attributed to an increase in oxygen vacancy concentration. The results indicate that (PB)0.95FN is a potential electrode material for SSOFCs.

In situ self-reconstructed nanoparticle-coated cathode and anode by nitric acid etching for symmetric solid oxide fuel cells

In this study, we developed an innovative strategy to fabricate highly active cathode and anode materials by acid etching perovskite oxide (ABO3) powder. (CoxFe1-x)3O4 nanoparticles were exsoluted in situ on an etched Pr0.2Sr0.8Co0.2Fe0.8O3-δ (P0.2SCF) catalyst to reconstruct heterojunctions in air. As a result, the exsolution of (CoxFe1-x)3O4 nanoparticles on the P0.2SCF surface led to the formation of perovskite-spinel interfaces in the cathode, and the generation of CoFe alloy and CoO nanoparticles embedded on the surface of the anode in 5 % H2. Two new composite catalysts modified with nanoparticles on the P0.2SCF skeleton were simultaneously prepared through the in situ exsolution of perovskite. At 850 °C, the polarization resistance values of the anode and cathode decreased by 37 % and 57 %, respectively. Furthermore, in a single cell with LSGM electrolyte and P0.2SCF-30-GDC symmetrical electrodes, we achieved a maximum power density of 692 mW/cm2 at 850 °C under wet H2 conditions, demonstrating good electrochemical output performance. The proposed catalyst design, which employed acid etching, was not only suitable for the optimization of symmetrical solid oxide fuel cell (SSOFC) electrodes, but also for the application in other types of catalysis, providing the potential for improving the electro-catalytic activity of perovskite electrodes.

RuOx modified PrBaFe1.8Hf0.2O5+δ surface for boosting the performance of symmetrical solid oxide fuel cells

The development of symmetrical solid oxide fuel cells (SSOFCs) faces a significant challenge in designing electrode materials that exhibit both high activity and stability. In this work, a novel layered perovskite oxide symmetric electrode material PrBaFe1.8Hf0.2O5+δ (PBFH) for SSOFCs is proposed and synthesized. Doping Hf at the B-site of PrBaFe2O5+δ (PBF) improves the stability in reducing atmosphere and increases the concentration of oxygen vacancies. Furthermore, a small amount of RuOx is deposited by atomic layer deposition (ALD) onto PrBaFe1.8Hf0.2O5+δ scaffold as symmetric electrodes. The surface modification of ALD-RuOx significantly boosts the catalytic activity for both fuel oxidation and oxygen reduction, simultaneously. Compared to PBF electrodes, the interfacial polarization resistances of RuOx-PBFH decrease to 0.77 Ω cm2 under H2/Ar and 0.021 Ω cm2 under air atmosphere at 800 °C, respectively. At 800 °C, SSOFCs equipped with RuOx-PBFH symmetric electrodes exhibit a high peak power density of 0.85 W cm−2 and 0.41 W cm−2 using humidified hydrogen and propane as fuels, respectively. Moreover, the RuOx-PBFH electrode demonstrates long-lasting performance, displaying high resistance against coking. These findings reveal a facile ALD approach for tailoring symmetric perovskite electrodes, offering robust and efficient electrocatalysis with efficient noble metal utilization.

A kinetic study of La0.75Sr0.25Cr0.5Mn0.5O3-δ nano-structured electrodes for intermediate temperature symmetric solid oxide fuel cells

La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) mixed conducting has been studied as nanostructured air and fuel electrode, for intermediate temperature symmetric Solid Oxide Fuel cell (S–SOFC). The possible mechanisms involved in the oxygen reduction and hydrogen oxidation reactions of these LSCM nanostructures porous electrodes deposited on La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte, were analyzed by electrochemical impedance spectroscopy (EIS) at 700 °C varying the oxygen partial pressure (pO2) and the hydrogen partial pressure (pH2). This analysis was complemented by the study of the electrical conductivity by the four-probe DC technique in the range between 300 and 800 °C in flowing dry atmospheres of air or H2. Results suggested that the O2 reduction reaction mechanism involves the O2- dissociative adsorption and O- ion migration near the surface region, while the H2-oxidation reaction limiting-step is controlled by a slow charge transfer process, and H2- dissociative adsorption on the ultimate O-layer.

(Digital Presentation) Ni-Doped PrBaFe2O5+ δ As Symmetrical Electrode for Solid Oxide Cells

The development of new redox stable electrode materials for Solid Oxide Cells (SOFs) have attracted great attention in recent years, since finding suitable compositions to operate efficiently in both fuel cell and electrolyzer modes is crucial for their wide commercialization [1]. For this reason, research on new doping strategies [2] and advanced deposition techniques [3] for symmetrical electrode materials have significantly increased with the aim of simplifying cell fabrication and extending cell durability. In this sense, double perovskites are gaining great interest due to their excellent electrical properties and high redox and long-term stability in different atmospheres [4].In this study, the double-perovskite (PrBa)0.95Fe2O5+δ (PBF) is proposed as symmetrical electrode for SOCs [5]. Two different strategies are implemented: on the one hand, Ni-doping in order to improve the electrical properties under reducing atmosphere and, on the other hand, the preparation of nanostructured electrodes in one-step by spray-pyrolysis deposition. A thorough characterization of the material is performed regarding its crystal structure, microstructure and electrochemical properties in both oxidizing and reducing atmospheres.With that purpose, PBF and (PrBa)0.95Fe2-xNixO5+ δ (PBFNx) powders are prepared by the freeze-drying precursor method. XRD patterns show the formation of a single perovskite-type phase in both air and H2 atmospheres, without the presence of any secondary phases. As for conductivity tests, they reveal increased values for the Ni-doped material over the pristine PBF material in air and 5% H2 at 600 ºC. These materials were thereafter screen-printed onto La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) electrolyte and calcined at 1100 ºC for 1h to ensure adequate adhesion to the electrolyte.Alternatively, spray-pyrolysis deposition method is employed to infiltrate PBFNx, with a 0.02 M precursor solution of the corresponding nitrate salts, into a porous Ce0.9Gd0.1O1.95 (CGO) layer previously fixed onto LSGM electrolyte (PBFNx-CGO). SEM images reveal that the screen-printed PBFNx has a thickness of 30 µm and a particle size of around 1 µm, while the same composition deposited by spray-pyrolysis shows a nanometric particle size and it is well-infiltrated in the 10 µm-thick CGO layer (Figure 1a). These electrode microstructures are maintained after ongoing a reduction process, where exsolved Ni particles are observed on the surface.The impedance spectra show lower polarization resistance (Rp) values for PBFNx with respect to PBF, i.e. 0.47 and 0.62 Ω cm2 at 650 ºC in air, respectively. But most significantly, further Rp reduction is observed for PBFNx-CGO prepared by spray-pyrolysis, values as low as 0.17 Ω cm2 at 650 ºC in air (Figure 1b). In reducing atmosphere, the PBFNx-CGO electrode also has lower Rp values (0.23 Ω cm2 at 650 ºC) when compared to the pristine PBF (0.52 Ω cm2 at 650 ºC).All in all, the nanostructured Ni-doped PBF electrodes exhibit high redox stability and low polarization resistance values under both oxidizing and reducing atmospheres, demonstrating their potential application as symmetrical electrodes for SOCs. These findings show that the optimization of the electrode composition but mostly its microstructure is key when developing new electrode materials for solid oxide cells.This research is supported by Ministerio de Ciencia, Innovación y Universidades through the RTI2018-093735-B-I00 and UMA18-FEDERJA-033 projects (Spain), and the University of Malaga through the B1-2021_03 project.[1] J. Zamudio-García, L. Caizán-Juanarena, J.M. Porras-Vázquez, E.R. Losilla, D. Marrero-López, A review on recent advances and trends in symmetrical electrodes for solid oxide cells, J. Power Sources. 520 (2022). https://doi.org/10.1016/j.jpowsour.2021.230852.[2] T. Su, Y. Li, Y. Yang, Z. Xu, N. Shi, Y. Wan, Y. Xie, D. Huan, S. Xue, C. Xia, Effect of tungsten doping on strontium ferrite electrode for symmetrical solid oxide electrochemical cell, Int. J. Hydrogen Energy. 45 (2020) 23401–23410.[3] Y. Kwon, S. Kang, J. Bae, Development of a PrBaMn2O5+δ-La0.8Sr0.2Ga0.85Mg0.15O3-δ composite electrode by scaffold infiltration for reversible solid oxide fuel cell applications, Int. J. Hydrogen Energy. 45 (2019) 1748–1758.[4] B. Zhang, Y. Wan, Z. Hua, K. Tang, C. Xia, Tungsten-Doped PrBaFe2O5+δ Double Perovskite as a High-Performance Electrode Material for Symmetrical Solid Oxide Fuel Cells, ACS Appl. Energy Mater. 4 (2021) 8401–8409.[5] D. Kim, S.J. Son, M. Kim, H.J. Park, J.H. Joo, PrBaFe2O5+δ promising electrode for redox-stable symmetrical proton-conducting solid oxide fuel cells, J. Eur. Ceram. Soc. 41 (2021) 5939–5946. Figure 1. a) PBFNx-CGO electrode deposited by spray-pyrolysis onto LSGM electrolyte: (i) Low magnification image of the electrode and electrolyte; (ii) Zoomed image of the pure PBFN top layer and the PBFNx layer infiltrated in CGO; and (iii) Zoomed image of PBFNx particles infiltrated on CGO scaffold. b) Polarization resistance (Rp) in air of PBF, PBFNx and PBFNx-CGO electrodes as a function of temperature (450-800 ºC). Figure 1

A review on new cobalt-free cathode materials for reversible solid oxide fuel cells

The exponential growth in the requirement of fuel cells and batteries leads to increased demand for cobalt due to its common use in high-performance Li-ion batteries and high-temperature fuel cells/electrolyzers. This sharp increment in demand raises concern about the availability of limited reserves of cobalt which can impact the price of cobalt. Moreover, the geographic limitations of cobalt resources may endanger the whole supply chain. In addition to all those, huge moral issues of cobalt mining are also another problem. Hence, leading battery, fuel cells and electrolyzer manufacturers are looking for sustainable alternatives to reduce cobalt dependency. A more specific limitation is shown in Solid Oxide Fuel Cells (SOFCs) cathode materials that contain cobalt. Incompatibilities have already been observed between the cathode materials containing cobalt and the electrolytes in terms of the thermal expansion coefficient mismatch during the transition of the operating temperature from high to low. An advantage of low operating temperatures is the reduction of material costs compared to high temperature. Increasing the electrochemical performance of the cell and eliminating thermal expansion coefficient difference problems are in concert aimed at the development of cobalt-free cathode materials. Therefore, cobalt-free cathode materials are vital for the sustainability of SOFCs and green transition of the energy sector since they can be used as cathode and anode material in symmetrical SOFCs which is also known as reversible SOFC (RSOFC). In this review, we comprehensively summarize the recent advances of cobalt-free perovskite cathode materials for intermediate temperature RSOFCs.

Nb-doped double perovskite Sr2CoFeO6−δ as an efficient and prospective electrode for quasi-symmetrical solid oxide fuel cells

The utilization of identical anode and cathode materials in symmetrical solid oxide fuel cells (SSOFCs) can efficiently reduce their fabrication costs and prolong their operational life. Herein, Nb-doped double perovskite Sr2CoFeO6-δ of a traditional cathode was employed as the electrode material for SSOFCs. Notably, the electrochemical performance and reversibility were improved due to Nb doping. The Nb-doped sample Sr2CoFe0.7Nb0.3O6−δ.5 (SCFN3) was synthesized in air, which decomposed into Co–Fe alloy, SrCoO2.25, and Sr3FeNbO6−δ in H2. Following calcination in air, the sample reverted to the original perovskite structure. The SCFN3 sample exhibited good chemical compatibility with SOFC electrolytes such as La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM), Sm0.2Ce0.8O2−δ, and BaZr0.1Ce0.7Y0.1Yb0.1O3−δ. A single cell consisting of 300-μm LSGM electrolyte exhibited maximum power densities of 951, 510, 563, and 397 mW/cm2 at 850℃ when using H2, C3H8, liquid C2H5OH, and solid C as fuels, respectively. These findings adequately demonstrate the fuel-flexible characteristics of SOFCs.

Composite electrolyte used for low temperature SOFCs to work at 390°C

A combination of yttria stabilized zirconia (YSZ) and Ba(NO3)2 commercial powders was used as electrolytes in the construction of symmetrical SOFC. As X-ray diffraction pattern and Raman spectra revealed, the YSZ-Ba(NO3)2 electrolyte in situ converted into YSZ and yttrium-doped barium zirconate (BZY) composite at 450°C in hydrogen atmosphere. The power maximum (Pmax) of YSZ-BZY based fuel cell can reach 634.06 mW cm-2 at 450°C. Notly, the Pmax can evenly maintain at 300 mW cm-2 as the operational temperature reduced to 390°C. The outstanding cell performance at low temperature indicate the excellent ion conductivity of the composite electrolyte. The promising ion conductivity is originated from the proton conduction of BZY, the oxygen conductivity of YSZ, and the enhanced ion conduction through interface transport. Our work demonstrates that the developed YSZ-BZY electrolyte holds enormous potential for LT-SOFCs.

Dual electrode functioning lithiated nickel based for solid oxide fuel cell

Research into producing electrode materials has increasingly focused on addressing the issues of durability experienced by electrode materials. There is a new configuration developing for the growing SOFC market. Symmetrical solid oxide fuel cells (S-SOFC) are a very new and innovative kind of fuel cell. S-SOFCs may be made practical by integrating lithiated nickel oxide-based materials, which are often used for lithium-ion battery applications. Accordingly, the focus of these studies will be on fundamental research, in particular the characterisation and chemical performance of lithiated nickel doped ruthenium (abbreviated as LN1-xRxO2 (x = 0.1,0.2, and 0.3). The LNRO-based powder was analysed in both oxidising and reducing environments to replicate the operating conditions of a dual-functioning electrode. The screen-printed LNRO/SDC/LNRO symmetrical cell was then subjected to 2 h of heat treatment at 800 °C. Additionally, the electrode's electrical conductivity and EIS analysis were performed on the samples. In a oxidised environment (H2:N2 gas mixture), LNR1, LNR2, and LNR3 have activation energies of 0.08, 0.07, and 0.09 eV, respectively; in a reduced environment (humidified air), these values are 0.22, 0.13, and 0.18 eV. Meanwhile, the best sample LNR2′s ASR value, determined by EIS analysis, is 6.123 Ω cm2 in air and 2.250 Ω cm2 in a reduced environment at 800 °C. This result proved that the dopant used in LNR2 has great promise as an electrode for the S-SOFC application, which is more than merely a means to enhance SOFC performance.

Evaluation of La1−xSrxNi0.4Fe0.6O3-δ as Electrode Materials for Direct Methane Symmetrical Solid Oxide Fuel Cells

In this work, La1−xSrxNi0.4Fe0.6O3-δ (0 ≤ x ≤ 0.2) oxides were synthesized and employed as the identical electrode of direct methane symmetrical solid oxide fuel cell (SSOFC). In addition, the phase structure, redox stability, electrical conductivity, chemical compatibility, and thermal expansion of La1−xSrxNi0.4Fe0.6O3-δ oxides were evaluated. The La2NiO4 phase occurs when the amount of doped Sr rises to 0.2. The composition of La0.9Sr0.1Ni0.4Fe0.6O3-δ (LSNF9146) boasts the highest conductivity of 463 S cm−1 with lowest activation energy of 0.066 eV as well as a relatively large thermal expansion coefficient. After treatment in methane for 10 h, the LSNF9146 oxide exhibits 33% lower carbon deposition than the LaNi0.4Fe0.6O3-δ (LNF46) oxide. Moreover, the impregnated LSNF9146 electrode demonstrates lower polarization resistance in both air and methane atmospheres. SSOFCs with impregnated LSNF9146 and LNF46 identical composite electrodes have the maximum power densities of 233 and 170 mW cm−2 at 850 °C in methane, respectively. These results prove that LSNF9146 is a promising symmetrical electrode with high catalytic activity, good redox stability, and coking resistance to direct methane SSOFCs.

Pr-Doped SrTi0.5Mn0.5O3-δ as an Electrode Material for a Quasi-Symmetrical Solid Oxide Fuel Cell Using Methane and Propane Fuel.

The use of identical electrodes for both the cathode and the anode in a symmetrical solid oxide fuel cell (SSOFC) can simplify the preparation process and increase the durability of the cell, but it is also demanding on the properties of the electrode including stability, electric conductivity, and electrocatalysis. The doping of variable-valence Mn4+/3+2+ on the B site of stable SrTiO3 is explored in this study as both the cathode and the anode for an SSOFC. Though the limit of Mn doping in SrTiO3 is generally low, the additional Pr3+/4+ donor on the Sr site of SrTi0.5Mn0.5O3 was found to enhance the structure stability, electric conductivity, and electrocatalysis. The cell with Pr0.5Sr0.5Ti0.5Mn0.5O3 electrodes excels under H2, propane, or CH4/H2 fuel, providing the cocatalyst was infiltrated on the anode side. The polarization resistance value of Pr0.5Sr0.5Ti0.5Mn0.5O3 was 0.27 Ω·cm2 as the cathode and 0.33 Ω·cm2 for the SSOFC using H2 fuel. The performance under CH4/H2 fuel can be boosted to above 0.9 W cm-2 if Ni/ceria was loaded onto the anode to enhance the methane reforming. This work contributes to a perovskite anode with high Mn doping in SrTiO3 for application in SSOFC for natural gas with renewable H2 injection.

Bifunctional electrocatalysts Pr0.5Sr0.5Cr0.1Fe0.9−xNixO3−δ (x = 0.1, 0.2) for the HOR and ORR of a symmetric solid oxide fuel cell

Pr0.5Sr0.5Cr0.1Fe0.9−xNixO3−δ (PSCFNx, x = 0.1, 0.2) catalysts are prepared and utilized as electrodes in symmetric solid oxide fuel cells (SOFCs) for the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR).

Redox Stable Electrode Material of Symmetrical Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) technologies are considered the most efficient and environmentally-friendly option for both stationary and distributed power generation due to their advantages of low pollution, low noise and strong building blocks. Despite the potential, widespread adoption of SOFC technology has not yet been achieved. The main reason is that the high cost of manufacturing and maintenance and the insufficient operating life make SOFC technology less competitive economically. More and more people begin to pay attention to symmetrical solid oxide fuel cells (SSOFCs) because SSOFCs have many potential advantages, such as improving the thermal mechanical compatibility between electrolyte and electrode, reducing manufacturing costs, and improving the ability to resist coking and sulfur poisoning. This article reviews the development of SSOFCs redox stable electrodes in recent years, summarizes the current research hotspots, and looks forward to the future development of redox stable electrode materials.

A novel yttrium stabilized zirconia and ceria composite electrolyte lowering solid oxide fuel cells working temperature to 400 °C.

Reducing the working temperature and improving the ionic conductivity of electrolytes have been the critical challenges for the gradual development of solid oxide fuel cells (SOFCs) in practical applications. The researchers all over the world attempt to develop alternative electrolyte materials with sufficient ionic conductivity. In this work, YSZ-CeO2 composite material was used as electrolytes in the construction of symmetrical SOFCs. The maximum power densities (Pmax) of YSZ-CeO2 based fuel cell can reach 680 mW cm-2 at 450 °C, 510 mW cm-2 at 430 °C, 330 mW cm-2 at 410 °C and even 200 mW cm-2 as the operational temperature was reduced to 390 °C. A series of characterizations indicates that the activation energy of the YSZ-CeO2 composite is significantly decreased, and the enhancement effect for ion conduction comes from interface transport. Our findings indicate the YSZ-CeO2 composite material can be a highly promising candidate for advanced low-temperature SOFC.

Boosting the Electrode Reaction Kinetics of SSOFCs by the Synergistic Effect of Nanoparticle Codecoration on Both the Cathode and Anode

A novel (SmBa)0.9Mn1.8Co0.2O5+δ (SBMCo) electrode is elaborately designed for symmetrical solid oxide fuel cells (SSOFCs). In operating conditions, the SBMCo material is codecorated with exsolved metallic cobalt for the anode and cobalt oxide for the cathode. The electrochemical impedance spectroscopy (EIS) results combined with distribution of relaxation times (DRT) analysis reveal that the rate-limiting step for hydrogen oxidation at the anode is the adsorbed hydrogen dissociation process, while for the oxygen reduction at the cathode, it is the charge transfer process. The exsolved nanoparticles on the SBMCo backbone of Co and Co3O4 significantly promote the corresponding rate-limiting steps and enable the decorated electrodes to exhibit remarkable catalytic activity toward hydrogen oxidation and oxygen reduction, respectively. When fueled with humidified hydrogen, the constructed symmetrical cell based on the designed SBMCo electrodes with the 300 μm La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolyte-supported configuration delivers an attractive maximum power density of 712 mW cm–2 at 900 °C. The results demonstrate that the elaborate design of the codecorated anode and cathode from a single parent compound is a promising route for the development of candidate electrodes for SSOFCs.

La0.3Sr0.7Ti0.3Fe0.7O3-δ-Based Electrodes for Symmetrical Solid Oxide Fuel Cells by A-Site Deficiency Manipulation

Solid oxide fuel cells (SOFC) with symmetric configuration have received widespread attention for their potential immunity toward resisting coking and sulfur poisoning. A key requirement for electrodes in the development of symmetric solid oxide fuel cells is the high electrocatalytic activity in both oxidizing and reducing atmospheres. Herein we report a facile method to improve the electrochemical performance of La0.3Sr0.7Ti0.3Fe0.7O3-δ- (LSTF-) based perovskite electrode material by introducing the deficiency in the A-site. X-ray diffraction (XRD) results demonstrated that A-site deficient LSTF exsolves a small amount of Fe0 metallic particles and layer perovskite Sr2TiO4, which exhibits high electrical conductivity in H2 atmosphere, while at the same time the exsolution is reversible. The polarization resistances (Rp) of (La0.3Sr0.7)0.95Ti0.3Fe0.7O3-δ (LSTF-5%) are 0.032 and 0.110 Ω cm2 in air and wet H2 (containing 3% H2O), respectively, at 800 °C. The power density of the electrolyte-supported SSOFCs with LSTF-5% as symmetrical electrode reaches up to 431.8 mW cm–2 at 800 °C in wet H2/air. And the LSTF-5% symmetrical cell also exhibits excellent electrochemical performance and high stability for electrochemically reducing pure CO2. Therefore, LSTF-5% perovskite can act as an excellent electrode material in a symmetrical SOFC. The results in this paper also indicate that an appropriate amount of A-site deficiency on LSTF perovskite can lead to an increase in oxygen vacancy concentration and better electrochemical performance.

Ta-doped PrBaFe2O5+δ double perovskite as a high-performance electrode material for symmetrical solid oxide fuel cells

Symmetrical solid oxide fuel cells (S-SOFCs) have received considerable attention due to fewer preparation steps in recent years. The PrBaFe2O5+δ (PBF) is a candidate material due to good catalytic activity and electrochemical stability. In this work, Ta-substituted PBF materials (PrBaFe2-xTaxO5+δ, denoted as PBFTx, x = 0, 0.1, 0.2, 0.3) are prepared and evaluated as symmetrical electrodes on GDC(Gd0.1Ce0.9O2-δ)-YSZ(yttria-stabilized zirconia)-GDC three-layer electrolyte. The PrBaFe1.8Ta0.2O5+δ (PBFT0.2) symmetrical cell presents the lowest polarization resistance, and the value is 0.171 Ω cm2 and 0.503 Ω cm2 in air and hydrogen atmosphere at 800 °C, respectively. In addition, the PBFT0.2 cell shows a peak power density of 234 mW/cm2 using humidified hydrogen as fuel gas and air as oxidant at 800 °C, which is enhanced by 68% compared with that of PBF (138 mW/cm2). The results indicate that the strategy of Ta doping can improve the electrochemical performance of PBF and PBFT0.2 is a potential electrode for S-SOFCs.

A New Electroactive and Stable Electrode Based on Praseodymium Molybdate for Symmetrical SOFCs

A New Electroactive and Stable Electrode Based on Praseodymium Molybdate for Symmetrical SOFCs