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Commercial Ni-YSZ anodes of solid oxide fuel cells (SOFCs) are susceptible to carbon deposits using hydrocarbons as fuel. Herein, we explore a simple approach of low fuel partial pressure to investigate the relevant limiting factors for ethanol-fueled SOFCs, providing the evaluation of the electrochemical performance and the carbon tolerance. As the partial pressure of ethanol fuel increases from 30% to 60%, the best cell performance gradually increases from 710.2 mW cm−2 to 856.8 mW cm−2 at 800 °C, which still lower than those of hydrogen-fueled SOFCs (1061.4 mW cm−2 at 800 °C), and the corresponding improvement in concentration polarization can be clearly observed especially in high current discharge area. The corresponding impedance spectra and electrode polarization processes of ethanol-fueled SOFCs are further studied by the equivalent circuit fitting and the distribution function of relaxation time (DRT) analysis, finding that the key improvement of the speed control steps comes from the concentration polarization process with the increase of the fuel partial pressure. Small amount of carbon deposition is observed on the Ni-YSZ anode substrate by SEM-EDS images after short-term discharging testing, and the safety utilization boundaries of ethanol-fueled SOFCs with a certain steam concentration can be predicted by the thermodynamic equilibria calculation. • Ethanol-fueled SOFCs with low fuel partial pressure are evaluated. • Low fuel partial pressure leads to the cell concentration polarization. • Electrode polarization processes are studied by the DRT analysis. • Safety utilization boundaries can be predicted by the thermodynamic equilibria calculation. [ABSTRACT FROM AUTHOR]

A redox-stable perovskite oxide Sm 0.5 Sr 0.5 FeO 3-δ (SSF) at reduced temperatures is investigated as a new promising electrode material for symmetric solid oxide fuel cells (SSOFCs). SSF exhibits well structural stability and catalytic activity in redox atmosphere at intermediate temperatures (≤750 °C), and the electrical conductivity exhibits a semiconductor behavior both in cathode and anode atmosphere. To enhance the electrochemical performance of SSF by adding oxygen-ion conductor Gd 0.1 Ce 0.9 O 2-δ (GDC), the electrode polarization resistances at 750 °C are reduced from 2.86 to 0.67 Ω cm2 in air and from 4.32 to 0.91 Ω cm2 in humidified H 2 , respectively. Accordingly, the cell performance of SSOFCs with SSF-GDC composite electrode is almost twice (201.74 mW cm−2 at 750 °C) of those with the single-phase one. There preliminary experimental results demonstrate SSF-based electrode materials can be new promising candidates for SSOFCs at low temperatures. [ABSTRACT FROM AUTHOR]

Highly active triple-conducting (proton-, oxygen-ion-, and electron-conducting) perovskite oxide BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3- δ need to further optimize the electrochemical performance and chemical stability in carbon dioxide and water containing atmospheres, greatly limiting its widespread use in protonic ceramics fuel cells (PCFCs). Here, Ba-site deficient Ba 0.9 Co 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3- δ (B9CFZY) was synthesized and investigated as a promising candidate concerning the chemical and structural stability, electrical conductivity and electrochemical performance. Anode-supported button cells with the prevalent BaZr 0.1 Ce 0.7 Y 0.2 O 3- δ (BZCY) as electrolyte using B9CFZY and B9CFZY-BZCY cathodes, respectively, were fabricated and then measured at 700-550 °C. The maximum power density of the cells with B9CFZY-based cathodes increase from 452 mW cm−2 to 537 mW cm−2 at 700 °C, however, the corresponding polarization loss decreases from 0.30 to 0.15 Ω cm2 by adding proton-conducting BZCY. Importantly, to better explore the reasons for the improved electrochemical performance, the distribution function of relaxation time (DRT) is used to distinguish different electrode polarization processes of both cells. The results indicate the polarization peaks (P3) of cells with composite cathode resulting from oxygen gas adsorption and dissociation can be greatly accelerated as well as the polarization peaks (P2) resulting from oxygen species diffusion to three phase boundaries or active sites in the cathode. The dramatic improvements demonstrate Ba deficient B9CFZY-BZCY material can be a very competitive cathode material for PCFCs. [ABSTRACT FROM AUTHOR]

In view of the high catalytic activity, enhanced oxygen-ion transport and good stability, the self-assembled hybrid electrocatalyst can be used for symmetrical and reversible solid oxide cells (RSOCs). Herein, a new Ni-free ceramic fuel electrode can be obtained by in situ annealing the orthorhombic perovskite Pr 0.6 Sr 0.4 FeO 3-δ (PSF) in H 2 at 850 °C for 2 h, consisting of orthorhombic perovskite matrix with nano Ruddlesden–Popper oxide (RP/O-PSF). Symmetrical RSOCs consisting of RP/O-PSF fuel electrode, La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ (LSGM) electrolyte and PSF air electrode (PSF|LSGM|PSF) were fabricated and the electrochemical performance was evaluated. The maximum power density of the cell under solid oxide fuel cell (SOFC) mode is 591 mW/cm2 at 800 °C, and the current density of the cell under solid oxide electrolysis cell (SOEC) mode is -1388 mA/cm2 at 800 °C with an applied electrolysis voltage of 1.6 V. The polarization resistances of cell under SOFC mode and SOEC mode are 0.152 Ω cm2 (OCV-0.2 V) and 0.126 Ω cm2 (OCV + 0.2 V), respectively, demonstrating an excellent catalytic activity of RP/O-PSF towards the water electrolysis process compared with hydrogen oxidation reaction (HOR) owing to the accelerated transfer rate of oxygen ions. In addition, the desirable long-term stability indicates the fact that RP/O-PSF hybrid electrode is such a suitable and prospective candidate for symmetrical and reversible solid oxide cells. [ABSTRACT FROM AUTHOR]

Cathode materials containing proton conductivity for protonic ceramics fuel cells (PCFCs) can increase the three phase boundary length of the air/cathode/electrolyte, and thus increase the reaction rate of proton with oxygen-species to form water in cathode side. In this work, a serious of Fe-substituted in BaZr 0.8 Y 0.2 O 3-δ proton conducting oxides, abbreviated as BaZr 0.8-x Fe x Y 0.2 O 3-δ (BZFY-2, BZFY-4, BZFY-6, BZFY-8), were synthesized and investigated as cathode materials for PCFCs, considering the phase structure, mean valence state and electrochemical performance. Accordingly, anode supported button cells using BaZr 0.8-x Fe x Y 0.2 O 3-δ as cathodes are fabricated, and then performed from 700 to 550 °C. The cell performance with BZFY-6 presents optimal electrochemical performance with different Fe doping amount, and the peak power density of 322.23 mW cm−2 and the corresponding polarization resistance of 0.28 Ω cm2 are observed at 700 °C. Moreover, the corresponding electrode polarization processes are further studied by the distribution function of relaxation time (DRT) analysis, and three peaks of P1, P2 and P3 in DRT curves correspond the proton bulk diffusion, electrochemical reaction processes, and adsorption as well as diffusion process of oxygen, respectively. Preliminary results demonstrate that BZFY-6 can be a competitive promising for PCFCs. • Iron is doped to BaZr 0.8 Y 0.2 O 3-δ to produce new proton conducting oxides. • The lattice parameters of BaZr 0.8-x Fe x Y 0.2 O 3-δ decrease after Fe doping. • Electrode polarization processes are studied by DRT analysis. • BZFY-6 can be a competitive promising for protonic ceramics fuel cells. [ABSTRACT FROM AUTHOR]