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The electrode microstructure and interface stability play an important role during thermal cycles and reversible cycles for protonic reversible solid oxide cells (P-rSOCs). In this work, the effects of microstructural change of air electrodes on the performance and cycling stability are investigated by using tubular cells with large active area (7.5 cm2). The BaCe0.5Zr0.4In0.1O3@ La0.6Sr0.4CoO3 (BCZI@LSC) composite air electrode is prepared through a wet chemical procedure based on infiltration of the LSC precursor solution into the BCZI electrolyte skeleton. The LSC nanoparticles attach to the electrolyte skeleton in a continuous film-forming morphology, affording abundant three-phase reaction boundaries (TPBs) and the continuous conducting phase. Compared to the BCZI + LSC composite air electrode prepared by conventional mechanical mixing, the cell with the BCZI@LSC electrode demonstrates an increased current density of 51%. The cell with the BCZI + LSC electrode shows acceptable stability during 14 reversible FC-EC cycles and 4 thermal cycles (between 650 °C and room temperature) for 360 h in 20% H2O-air atmosphere. The differences in stability for cells prepared by the two processes are compared and discussed.

Abstract Nanofiber-structured La 2 NiO 4+δ (LNO) and LaNi 0.6 Fe 0.4 O 3-δ (LNF) cathodes, which were fabricated by an electrospinning technique, were used for proton-conducting solid oxide fuel cells (H-SOFCs) for the first time, aiming to develop high-performance cobalt-free cathodes for H-SOFCs. High porosity and large specific surface area of LNO, LNF nanofiber-structured cathodes were beneficial for the cathode reactions, resulting in an encouraging peak power density of 508 mWcm−2 and 551 mWcm−2 for LNO and LNF cathode cell at 700 °C, respectively. The nanofiber-structured cathodes showed a higher fuel cell performance and lower polarization resistance compared with that of the cell using corresponding powder cathode, suggesting the construction of nanofiber-structured cathode provided an alternative and promising route to prepare high performance cathodes for H-SOFCs. Graphical abstract Unlabelled Image Highlights • Nanofiber cathodes were used for proton-conducting SOFCs for the first time. • Two different nanofiber cathodes were used and investigated. • Nanofiber structure benefited the cathode reactions. • Cell with nanofiber cathodes showed higher performance than conventional cathodes. [ABSTRACT FROM AUTHOR]

Y-doped BaZrO 3 (BZY) electrolyte films are successfully fabricated by utilizing the driving force from the anode substrate, aiming to circumvent the refractory nature of BZY materials. The BZY electrolyte film on the high shrinkage anode becomes dense after sintering even though no sintering aid is added, while the BZY electrolyte remains porous on the conventional anode substrate after the same treatment. The resulting BZY electrolyte shows a high conductivity of 4.5 × 10 − 3 S cm − 1 at 600 °C, which is 2 to 20 times higher than that for most of BZY electrolyte films in previous reports. In addition, the fuel cell with this BZY electrolyte generates a high power output of 267 mW cm − 2 at 600 °C. These results suggest the strategy presented in this study provides a promising way to prepare BZY electrolyte films for fuel cell applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • First-time achievement of four deep thermal cycles in 7.5 cm2 tubular P-rSOCs. • Preparation of BCZI@LSC air electrodes by a wet chemical method for enhanced TPBs. • An increased current density of 51% is achieved by infiltration. • The cell with BCZI + LSC electrode endures 14 reversible cycles for 360 h. • Investigation of degradation mechanisms of two different electrodes. The electrode microstructure and interface stability play an important role during thermal cycles and reversible cycles for protonic reversible solid oxide cells (P-rSOCs). In this work, the effects of microstructural change of air electrodes on the performance and cycling stability are investigated by using tubular cells with large active area (7.5 cm2). The BaCe 0.5 Zr 0.4 In 0.1 O 3 @ La 0.6 Sr 0.4 CoO 3 (BCZI@LSC) composite air electrode is prepared through a wet chemical procedure based on infiltration of the LSC precursor solution into the BCZI electrolyte skeleton. The LSC nanoparticles attach to the electrolyte skeleton in a continuous film-forming morphology, affording abundant three-phase reaction boundaries (TPBs) and the continuous conducting phase. Compared to the BCZI + LSC composite air electrode prepared by conventional mechanical mixing, the cell with the BCZI@LSC electrode demonstrates an increased current density of 51%. The cell with the BCZI + LSC electrode shows acceptable stability during 14 reversible FC-EC cycles and 4 thermal cycles (between 650 °C and room temperature) for 360 h in 20% H 2 O-air atmosphere. The differences in stability for cells prepared by the two processes are compared and discussed. [ABSTRACT FROM AUTHOR]

A facile strategy was proposed to synthesize Nb-containing BaCeO 3 -based material, which is a potential electrolyte for proton-conducting solid oxide fuel cells (SOFCs), via a wet chemical route while the conventional synthesis of Nb-containing oxides relied on the solid state reaction method due to the unavailability of suitable Nb-precursors such as Nb-nitrates resulting in a less desirable fuel cell performance when used as an electrolyte. The BaCe 0.7 Nb 0.1 Y 0.2 O 3 − δ (BCNY) electrolyte material in this study persisted a good chemical stability against CO 2 and exhibited good performance in the fuel cell application. The fuel cell with BCNY electrolyte film showed a high performance of 533 mW cm − 2 at 700 °C. This cell performance based on BCNY electrolyte was superior to that of many stable modified BaCeO 3 -based proton-conducting SOFCs where the electrolytes were tailored by other strategies. This result indicated that the strategy presented in this study could be an effective way to prepare a stable electrolyte for high performance proton-conducting SOFCs, which could advance the development of proton-conducting SOFCs. [ABSTRACT FROM AUTHOR]

A chemically stable electrolyte structure was developed for proton-conducting SOFCs by using two layers of stable BaZr0.7Pr0.1Y0.2O3−δ to sandwich a highly-conductive but unstable BaCe0.8Y0.2O3−δ electrolyte layer. The sandwiched electrolyte structure showed good chemical stability in both CO2 and H2O atmosphere, indicating that the BZPY layers effectively protect the inner BCY electrolyte, while the BCY electrolyte alone decomposed completely under the same conditions. Fuel cell prototypes fabricated with the sandwiched electrolyte achieved a relatively high performance of 185mWcm−2 at 700°C, with a high electrolyte film conductivity of 4×10−3 Scm−1 at 600°C. [ABSTRACT FROM AUTHOR]

Abstract: BaCeO3 based ceramics have demonstrated high proton conductivity and have been extensively investigated as electrolytes for solid oxide fuel cells (SOFCs). However, these materials are not chemically stable and are prone to reaction with CO2 in air at the typical SOFC operating conditions. This work presents a novel strategy to improve the chemical stability of BaCeO3 based ceramics to CO2 in air while still maintaining high proton conductivity by introducing barium chloride precursor in the powder synthesis process. As an example, BaCe0.8Sm0.2O3−δ with Cl doping has demonstrated significant enhancement in chemical stability in the presence of CO2 in air without compromising its high proton conductivity. [Copyright &y& Elsevier]

Abstract: A BaZr0.4Ce0.4Y0.2O3− δ (BZCY)-NiO anode functional layer was added between the BZCY electrolyte and the BZCY-NiO anode substrate to investigate its effect on the performance of single cells. With BaZr0.4Ce0.4Y0.2O3− δ (BZCY) as the electrolyte and composite BZCY-Ba0.5Sr0.5(Co0.8Fe0.2)0.9Ti0.1O3− δ as the cathode material, anode-supported electrolyte fuel cells were fabricated and tested. The single cell without an anode functional layer generated maximum power densities of 181, 138, 116, 77, and 49mWcm−2 at 700, 650, 600, 550, and 500°C, respectively, whereas those for the single cell with an anode functional layer significantly improved up to 281, 243, 194, 145, and 95mWcm−2 at the same temperatures, almost doubling the power output. Electrochemical impedance spectroscopy (EIS) measurements for these two cells revealed that the addition of the anode functional layer reduced the contact resistance as well as the polarization resistance for the cell, resulting thus in the improved cell performance. [Copyright &y& Elsevier]

Abstract: A novel cathode material BaCe0.4Sm0.2Co0.4O3−δ composed of two phases BaCe1−x (Sm/Co) x O3−δ and BaCo1-x(Sm/Ce) x O3−δ was prepared in situ via the citric–nitrate route and its performance as cathode material for proton conducting solid oxide fuel cell (SOFC-H) was characterized. BaCe0.4Sm0.2Co0.4O3−δ exhibited simultaneous protonic, electronic, and oxygen ionic conduction in air, leading to a good electrode performance. The polarization resistance of the novel cathode material in symmetrical cell was 0.36 Ω cm2 with Pt as the current collector at 700°C in wet air. The electrode performance can be further improved through microstructure optimization. It also showed good thermal expansion compatibility with BaCe0.8Sm0.2O3−δ electrolyte over a 100h duration test. BaCe0.4Sm0.2Co0.4O3−δ is a promising cathode material for SOFC-H. [Copyright &y& Elsevier]

Abstract: We report here that a carbonate can promote the densification and enhance the conductivity of a refractory proton conductor (BaZr0.8Y0.2O3-δ, BZY). Densification of BZY has been successfully demonstrated at as low as 600°C in the presence of carbonate. The ionic conductivities of the carbonate-added BZY reach 0.33 and 0.38S/cm at 600°C in 3%H2O-air and in 3%H2O-H2, respectively. The observation of ionic conductivity increasing with PH2O and PH2 suggests protons as the charge carriers. A new proton transfer and exchange mechanism between oxide and carbonate phases is proposed to interpret the enhanced proton conductivity. A fuel cell based on the composite electrolyte (1mm-thick), a LiNiO2-MPCC (Mixed Proton and Carbonate-ion Conductor) cathode, a BZY-NiO anode blocking layer and a Ni anode yields 114mW/cm2 at 670°C. [Copyright &y& Elsevier]

Abstract: BaZr0.1Ce0.7Y0.2O3−δ (BZCY), an intermediate temperature proton conductor, has been applied as an electronic blocking material for microtubular solid oxide fuel cells (SOFCs) using doped ceria electrolyte. Bi-layer electrolyte consisting of 3μm thick BZCY and 10μm thick Sm0.2Ce0.8O1.9 (SDC) are successfully deposited on anode substrates with 1.0mm diameter using phase inversion, suspension-coating and co-firing techniques. At 700°C, open circuit voltage increases from 0.72V for the cells with single SDC electrolyte to 0.97V for those with bi-layer electrolyte, demonstrating that BZCY can effectively prevent the internal shorting in doped ceria electrolyte. Peak power density of 246mWcm−2 has been achieved at 700°C with the microtubular SOFCs based on the bi-layer electrolyte. [Copyright &y& Elsevier]

Abstract: The ceramic powders of BaCe1− x Y x O3−α (x =0.05, 0.10, 0.15, 0.20) have been prepared via a microemulsion method. Green compacts of the powders were sintered to densities higher than 95% of theoretical at the lower temperature (1500°C). The obtained ceramics showed a single-phase of orthorhombic perovskite. The proton conduction was investigated by employing the techniques of AC impedance and electrochemical hydrogen permeation (hydrogen pumping) at 300–600°C. It was found that the ceramics were almost pure proton conductors in wet hydrogen, and the highest proton conductivity was observed for x =0.15 at 600°C. Ammonia was synthesized successfully from nitrogen and hydrogen at atmospheric pressure in the electrolytic cell using BaCe0.85Y0.15O3−α. The maximum rate of NH3 formation was found to be 2.1×10−9 mols−1 cm−2 at 500°C with an applied current of 0.75mA. [Copyright &y& Elsevier]

Abstract: Choline dihydrogen phosphate ([N1.1.1.2OH]DHP) and 1-butyl-3-methylimidazolium dihydrogen phosphate ([C4mim]DHP) were synthesized as a new class of proton-conducting ionic plastic crystals. Both [N1.1.1.2OH]DHP and [C4mim]DHP showed solid–solid phase transition(s) and showed a final entropy of fusion lower than 20JK−1 mol−1 which is consistent with Timmerman’s criterion for molecular plastic crystals. The ionic conductivity of [N1.1.1.2OH]DHP was in the range of 10−6 Scm−1–10−3 Scm−1 in the plastic crystalline phase. On the other hand, the ionic conductivity of [C4mim]DHP showed about 10−5 Scm−1 in the plastic crystalline phase. [N1.1.1.2OH]DHP showed one order of magnitude higher ionic conductivity than [C4mim]DHP in the temperature range where the plastic phase is stable. [Copyright &y& Elsevier]

Ceria-based composites have been previously developed as functional electrolytes for high performance ITSOFC applications. These composites display hybrid proton and oxygen ion conduction. To meet demands for more functional hybrid proton and oxygen ion conductors we developed further composite electrolyte materials containing a proton conductor, BaCe0.8Y0.2O3 − δ (BCY20), and an oxygen ion conductor, samarium doped ceria (SDC).The BCY20 and SDC composites were prepared based on composite technology using their starting powders produced via sol–gel and co-precipitation processes, respectively. Using the SDC–BCY20 composites as the electrolytes ITSOFCs were constructed using NiO-based composite anodes, silver-based cathodes. Applying hydrogen as the fuel, compressed air as the oxidant, the fuel cells were tested in the temperature region between 300 and 700 °C. The SDC–BCY20 electrolyte ITSOFCs reached a performance of 0.25 W/cm2 at 550 °C. Under a constant discharge water was observed both, on the anode and the cathode side, indicative of hybrid conduction based on proton and oxygen ion transport. Initial experimental results showed that combining a proton with an oxygen ion conductor forming a novel hybrid ion conductor with promising applications for ITSOFCs was successful. [Copyright &y& Elsevier]

Abstract: Proton exchange membrane fuel cell (PEMFC) operation below 100°C causes CO poisoning of the anode catalyst and results in low reaction kinetics of the cathode catalyst. In addition, operation at high relative humidity requires a large-sized humidifier, thereby increasing the complexity of the fuel cell system. These problems can be avoided by operating fuel cells above 100°C and under low relative humidity. We report the performance of a non-humidified hydrogen-air PEMFC using Fe0.4Ta0.5P2O7 as an electrolyte in the temperature range of 100–225°C. The PEMFC with this electrolyte achieves open-circuit voltages of 1000mV or higher at all temperatures tested and demonstrates decreasing voltage drop with increasing temperature. The resultant fuel cell provides a peak power density of 341mWcm−2 at 225°C, exhibiting stable chemical and thermal durability for 100h. [Copyright &y& Elsevier]

Abstract: The thin membrane of BaCe0.8Sm0.2O3−δ (BCS) with high quality was successfully fabricated on porous NiO–BCS anode substrate through a novel in situ reaction method. The key part of this method is to directly spray well-mixed suspension of BaCO3, CeO2 and Sm2O3 instead of pre-synthesized BCS ceramic powder on the anode substrate. After sintering at 1400°C for 5h, the extremely dense electrolyte membrane in the thickness of 10μm is obtained. A single cell was assembled with La0.7Sr0.3FeO3−σ as cathode and tested with humidified hydrogen as fuel at 650°C. The open circuit voltage (OCV) and maximum power density respectively reach 1.04V and 535mW/cm2. Interface resistance of cell under open circuit condition was also investigated. [Copyright &y& Elsevier]

A new proton-conductive electrolyte of (NH4)2TiP4O13 was synthesized for intermediate temperature fuel cells. Structure of the resultant electrolyte was studied by X-ray diffraction and its ionic conductivities was obtained from AC impedance spectroscopy. Partial decomposition of (NH4)2TiP4O13 occurred by annealing at 300 °C under a dry argon atmosphere, resulting in the formation of TiP2O7, and after annealing its proton conductivity was evaluated to be about 5 mS cm−1 at 300 °C under the same dry argon atmosphere. Electrolyte of (NH4)2SiP4O13 was prepared for comparison. In contrast to (NH4)2TiP4O13, it is stable under a dry Ar atmosphere at 300 °C, and its proton conductivity was 0.6 mS cm−1. These results indicate that partial decomposition of (NH4)2TiP4O13 to TiP2O7 should be responsible for high proton conductivity. [Copyright &y& Elsevier]