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A simple phase-inversion method is employed to achieve anode-supported micro-tubular solid oxide fuel cells based on BaZr0.1Ce0.7Y0.1Yb0.1O3-δ proton conducting electrolyte. The whole-cell configuration is Ni-BaZr0.1Ce0.7Y0.1Yb0.1O3-δ|BaZr0.1Ce0.7Y0.1Yb0.1O3-δ | La0.75Sr0.25MnO3-δ-Sm0.2Ce0.8O2-δ. The novel asymmetric structure of “sponge-like micro-pores electrode | homogeneous porous functional layer” is obtained. The results achieved in the present work include: i) the electrodes reveal the single phase collected by the powder X-Ray Diffractometer analysis; ii) the single cell exhibits uniform distribution of micro sponge-like pores electrodes are well-adhered to the dense, crack-free 12 μm thick electrolyte layer observed by Scanning Electron Microscope; iii) the cells show excellent electrochemical performance with the maximum power densities of 1.01, 0.89, 0.75 and 0.58 W·cm−2 at 750, 700, 650 and 600 °C, respectively, characterized by Electrochemical Impedance Spectroscopy; iv) the cell design especially reveal very low concentration polarization values (0.014–0.019 Ω·cm2 at 750–600 °C).

This study employed a simple phase-inversion method to achieve anode-supported micro-tubular solid oxide fuel cells on the basis of the BaZr0.1Ce0.7Y0.1Yb0.1O3−δ proton conducting electrolyte. The typical cell with configuration of Ni–BaZr0.1Ce0.7Y0.1Yb0.1O3−δ|BaZr0.1Ce0.7Y0.1Yb0.1O3−δ|La0.6Sr0.4Co0.2Fe0.8O3-δ-Sm0.2Ce0.8O2-δ. The novel “sponge-like micro-pores electrode | homogeneous porous functional layer” asymmetric pore structure is obtained. Achieved results include: i) the electrodes revealed the single phase collected by the powder X-Ray Diffractometer analysis; ii) observed by Scanning Electron Microscope, the single cell presenting uniform distribution of micro sponge-like pores electrode was well-adhered to the dense and crack-free 12 μm thick electrolyte layer; iii) the cells showed excellent electrochemical performance with the maximum power densities of 1.070, 0.976, 0.815, and 0.700 W cm−2 at 750, 700, 650 and 600 °C, respectively, characterized by Electrochemical Impedance Spectroscopy; iv) the designed cell clearly indicated a very low concentration polarization value (0.01 and 0.02 Ω cm2 at 750 and 700 °C). Our findings provide a promising approach to improve intermediate temperature solid oxide fuel cells performance by optimizing the electrode-electrolyte interface microstructure, based on proton and oxide ion mixed conductor electrolytes.

Thermally robust and chemically inert Ag@SiO2 nanoprobes are employed to provide the surface enhanced Raman scattering (SERS) effect for an in situ/operando study of the early stage of carbon deposition on nickel-based solid oxide fuel cell (SOFC) anodes. The enhanced sensitivity to carbon enables the detection of different stages of coking, offering insights into intrinsic coking tolerance of material surfaces. Application of a thin coating of gadolinium doped ceria (GDC) enhances the resistance to coking of nickel surfaces. The electrochemically active Ni-YSZ interface appears to be more active for hydrocarbon reforming, resulting in the accumulation of different hydrocarbon molecules, which can be readily removed upon the application of an anodic current. Operando SERS is a powerful tool for the mechanistic study of coking in SOFC systems. It is also applicable to the study of other catalytic and electrochemical processes in a wide range of conditions.

Cermet membranes composited of Ni and doped barium cerate have been widely studied for hydrogen separation; however, their practical application is limited primarily by the relatively low permeation rate and instability of doped barium cerate in H2O and CO2 containing gases. Here we report our findings on the development of a thin-film cermet membrane consisting of Ni and BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb), supported on a porous Ni–BZCYYb substrate. High fluxes of 1.12 and 0.49 ml min−1 cm−2 have been demonstrated at 900 °C and 700 °C, respectively, when hydrogen was used as the feed gas on one side and N2 as the sweep gas on the other side. Most importantly, the high-performance membrane can be easily fabricated by a cost-effective particle-suspension coating/co-firing process, offering great promise for large scale hydrogen separation applications.

To reduce the fabrication cost and avoid unfavorable reactions between components of solid oxide fuel cells, it is necessary to improve the sinterability of the electrolyte materials, especially doped ceria for intermediate-temperature operation. Here we report a unique process for fabrication of single cells at a co-sintering temperature as low as 1150 °C using highly active SDC powders derived from a glycine-nitrate process, demonstrating higher cell performance than those co-sintered at higher temperatures while maintaining adequate long-term stability. In particular, it is found that the electrode polarization at high current densities is significantly suppressed when operated at 650 °C.

To develop next generation solid oxide fuel cells operated at reduced temperatures with a wide variety of hydrocarbon fuels, surface modification of electrodes is an effective approach to enhancing the performance of both the state-of-the-art Ni-YSZ anode and La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathodes. For example,, BaO nano-islands on the surfaces of Ni grains greatly improved the coking-tolerance of Ni-YSZ anode through a water mediated carbon removal process. Similarly, an efficient catalyst layer was created in Ni-YSZ anodes when proper amount of BaCO3 was added to the NiO-YSZ anode support in the early stage of processing. For SOFC cathodes, a solution infiltration process has been used to coat various active catalysts on the surface of LSCF cathodes to enhance the catalytic activity and stability. The surface coatings include discrete particles of doped ceria and samarium doped strontium cobaltite (SSC), and dense, continuous thin films of La1-xSrxMnO3−δ (LSM), Pr0.75Sr0.2MnO3−δ (PSM), and PrSrCoMnO6-δ (PSCM).

The future commercialization and application of solid oxide fuel cell (SOFC) technologies requires the development of novel anode materials with excellent performance and stability at intermediate-temperatures with various fuels including hydrogen, syngas and particularly hydrocarbons. Whether by modifying the state-of-the-art Ni based anodes, or through exploring alternative metal cermet or ceramic based materials, wet impregnation/infiltration is shown to be one of the most effective approaches for both cell fabrication and performance optimization. This paper reviews most of the progress reported in the literature committed to the fabrication and optimization of SOFC anodes by wet impregnation for low temperature and/or hydrocarbon operation. The optimization of traditional nickel based anodes by adding excellent catalyst, the replacement of nickel by other inert metal or ceramic species, and some metal supported designs with impregnated catalyst are all presented and discussed, mainly focusing on the cell performance, redox and thermal stability, long-term reliability, carbon and sulfur tolerance of the anodes.

Mixed ionic-electronic conductors in the family of La x Sr 1– x Co y Fe 1– y O 3–δ have been widely studied as cathode materials for solid oxide fuel cells (SOFCs). However, the long-term stability was a concern. Here we report our findings on the effect of a thin film coating of La 0. 85 Sr 0. 15 MnO 3–δ (LSM) on the performance of a porous La 0. 6 Sr 0.4 Co 0.2 Fe 0.8 O 3–δ (LSCF) cathode. When the thicknesses of the LSM coatings are appropriate, an LSM-coated LSCF electrode showed better stability and lower polarization (or higher activity) than the blank LSCF cathode without LSM infiltration. An anode-supported cell with an LSM-infiltrated LSCF cathode demonstrated at 825 °C a peak power density of ∼1.07 W/cm 2 , about 24% higher than that of the same cell without LSM infiltration (∼0.86 W/cm 2 ). Further, the LSM coating enhanced the stability of the electrode; there was little degradation in performance for the cell with an LSM-infiltrated LSCF cathode during 100 h operation.

Low apparent density Sm0.2Ce0.8O1.9 (SDC) powders of different morphology and microstructure are derived from a glycine–nitrate process using Ce(NO3)3 and Ce(NH4)2(NO3)6 as the cerium sources. When the molar ratio of the two cerium precursors is around 1:1, the derived SDC powders can be readily sintered to high density, exhibiting the highest conductivities (∼0.084 and ∼0.020 S cm−1 at 800 and 600 °C, respectively) with an activation energy of ∼0.70 eV. When the molar ratio of Ce(NO3)3 to Ce(NH4)2(NO3)6 was adjusted to 3:1, the derived SDC powders have the lowest apparent density (36.0 ± 0.5 mg cm−3), best suited for preparation of dense, thin-film SDC electrolyte membranes on porous anode substrates, a critical step toward low-cost fabrication of high-performance SOFCs.

BaZr0.7Sn0.1Y0.2O3–δ (BZSY) is developed as a novel chemically stable proton conductor for solid oxide fuel cells (SOFCs). BZSY possesses the same cubic symmetry of space group Pm-3m with BaZr0.8Y0.2O3-δ (BZY). Thermogravimetric analysis (TGA) and X-ray photoelectron spectra (XPS) results reveal that BZSY exhibits remarkably enhanced hydration ability compared to BZY. Correspondingly, BZSY shows significantly improved electrical conductivity. The chemical stability test shows that BZSY is quite stable under atmospheres containing CO2 or H2O. Fully dense BZSY electrolyte films are successfully fabricated on NiO–BZSY anode substrates followed by co-firing at 1400 °C for 5 h and the film exhibits excellent electrical conductivity under fuel cell conditions. The single cell with a 12-μm-thick BZSY electrolyte film outputs by far the best performance for acceptor-doped BaZrO3-based SOFCs. With wet hydrogen (3% H2O) as the fuel and static air as the oxidant, the peak power density of the cell achieves as high as 360 mWcm−2 at 700 °C, an increase of 42% compared to the reported highest performance of BaZrO3-based cells. The encouraging results demonstrate that BZSY is a good candidate as the electrolyte material for next generation high performance proton-conducting SOFCs.

While the desired microstructure of the state-of-the-art Ni-YSZ anode for a solid oxide fuel cell (SOFC) based on YSZ is well known, the anode microstructure for a SOFC based on a proton conductor is yet to be optimized. In this study, we examined the effect of anode porosity on the performance of a SOFC based on BaZr0.1Ce0.7Y0.1Yb0.1O3� d (BZCYYb), a mixed ion (proton and oxygen anion) conductor with high ionic conductivity at intermediate temperatures. Three cells with Ni-BZCYYb cermet anodes of different porosities (37%, 42%, and 50%) and identical electrolytes and cathode components were fabricated and tested. Under typical fuel cell operating conditions, the cell with anode of the lowest porosity (37%), prepared without pore former, achieved the highest performance, demonstrating a peak power density of 1.2 W/cm 2 at 750

The demand for electric vehicles has inspired extensive efforts to develop solid oxide fuel cells (SOFCs) for transportation. However, the high cost of hydrogen fueled SOFC systems and the deactivation of Ni-YSZ anodes in hydrocarbon fuels hinder the progress of SOFCs' development and commercialization. Here, we report a unique multi-functional anode for SOFCs that allows direct utilization of transportation fuels (iso-octane) without co-feeding O 2 and CO 2 , demonstrating a peak power density of ∼0.6 W/cm 2 at 750 °C. The multi-functional anode is derived from a conventional NiO-YSZ anode with BaCO 3 modification in the anode support, creating a catalytically active conformal coating of BaZr 1− x Y x O 3− δ (BZY) on YSZ and nano-islands of BaO on Ni surface, which greatly promote reforming of octane and oxidation of the reformed fuels. Further, the simple and cost-effective modification process can be readily adopted in the fabrication of the state-of-the-art NiO-YSZ supported cells.

Mixed ionic-electronic conductors in the family of LaxSr1−xCoyFe1−yO3−δ (LSCF) have been widely studied as cathode materials for solid oxide fuel cells (SOFCs). However, the long-term stability and the limited surface catalytic activity are still a concern. Here we report a new catalyst La0.4875Ca0.0125Ce0.5O2−δ (LCC), which can significantly enhance the performance and stability of LSCF cathodes when applied as a thin-film coating on LSCF surface. For example, with 5 μL 0.25 mol L−1 LCC solution infiltrated into LSCF cathode, the cathodic polarization resistance was reduced by ∼60% (to ∼0.076 Ω cm2) at 750 °C, leading to a peak power density of ∼1.25 W/cm2, which is ∼18% higher than that for the unmodified LSCF cathode in an anode-supported cell. In addition, stable power output was observed for over 500 h operation at 750 °C under a constant voltage of 0.7 V.

The effect of nickel oxide addition on the sintering behavior and electrical properties of BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) as an electrolyte for solid oxide fuel cells was systematically studied. Results suggest that the addition of a small amount (∼1 wt%) of NiO to BZCYYb greatly promoted densification, achieving ∼96% of the theoretical density after sintering at 1350 °C in air for 3 h (reducing the sintering temperature by ∼200 °C). Further, a sample sintered at 1450 °C for 3 h showed high open circuit voltages (OCVs) when used as the electrolyte membrane to separate the two electrodes under typical SOFC operating conditions, indicating that the electrical conductivity of the electrical conductivity of the BZCYYb was not adversely affected by the addition of ∼1 wt% NiO.

BaZr0.1Ce0.7Y0.2O3−δ (BZCY) electrolyte has been extensively studied as novel electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). In this short communication, we report our progress on the fabrication and characterization of the high performance anode supported BZCY cell. Maximum power density of 650 mW/cm2 at 700 °C is obtained for the single cell with configuration of Ni-BZCY/BZCY (20 um)/SSC-BZCY. Further, significant performance enhancement is observed during long-term stability test at 600 °C under constant voltage of 0.5 V, indicating excellent stability of BZCY under fuel cell operating condition. Those results indicate that BZCY based cell is very promising for practical applications.

Anode-supported tubular solid oxide fuel cells (SOFCs) based on a proton and oxide ion mixed conductor, BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb), have been fabricated using a dip coating and co-firing process. This new fabrication technique effectively reduced the Ohmic resistances of tubular cells to ~0.1 and ~0.3 Ω cm2 at 750 and 600 °C, respectively. Typical tubular cells with Ni-BZCYYb anode, BZCYYb electrolyte, and La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)-BZCYYb composite cathode demonstrated much-improved performance, achieving peak power densities of 1.13, 0.81, 0.63, and 0.53 W cm−2 at 750, 700, 650, and 600 °C, respectively, when humidified (3 v% water vapor) hydrogen was used as fuel and ambient air as oxidant. Keywords: Tubular SOFCs, BZCYYb, Dip coating, Ohmic resistance

Uniform, dense, and conformal coatings of (La,Sr)MnO3−δ (LSM) have been successfully deposited on a silicon wafer and a dense (La,Sr)(Co,Fe)O3−δ (LSCF) substrate using a stable LSM sol consisting of metal acetate and nitrate precursors dissolved in a mixed organic solvent of 2-methoxyethanol and acetic acid with enhanced wettability. The processing conditions are optimized for precise control of composition, morphology, microstructure, and thickness of the LSM films to examine the microstructure and chemical stability of an LSM film as a catalytic coating for an LSCF cathode. The thicknesses of the LSM films are controlled within the range of 5–60 nm by spin-coating of LSM sol with different concentrations. The LSM films grow epitaxially on the LSCF substrate grains after annealing at 800°C for 1 h due to their structural similarity. The LSM coatings show good stability on LSCF substrates and may suppress strontium oxide segregation on LSCF surface during annealing at 850°C for 900 h, implying that LSM-coated LSCF surfaces have better structural and chemical stability under typical fuel cell operating conditions.

Porous La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathodes are coated with a thin film of Sm0.2Ce0.8O1.95−δ (SDC) using a one-step infiltration process. Examination of the microstructures reveals that small SDC particles are formed on the surface of LSCF grains with a relatively narrow size distribution. Impedance analysis indicates that the SDC infiltration has dramatically reduced the polarization of LSCF cathode, reaching interfacial resistances of 0.074 and 0.44 Ω cm2 at 750 °C and 650 °C, respectively, which are about half of those for LSCF cathode without infiltration of SDC. The activation energies of the SDC infiltrated LSCF cathodes are in the range of 1.42–1.55 eV, slightly lower than those for a blank LSCF cathode. The SDC infiltrated LSCF cathodes have also shown improved stability under typical SOFC operating conditions, suggesting that SDC infiltration improves not only power output but also performance stability and operational life.

A porous NiO/yttria-stabilized zirconia (YSZ) anode substrate for zirconia-based tubular solid oxide fuel cells (SOFCs) was prepared by the gelcasting. The effect of the impregnation of SDC in the substrate was studied. Electrochemical impedance spectroscopy and I–V and I–P curves of the cells were measured. Scanning electron microscopy (SEM) was used to observe the microstructures. The results indicate that the performance of the cell can be significantly improved by incorporating the nano-structured SDC particles in the substrate. The peak power density of the cell is increased by about 60% and the area specific resistance (ASR) decreased by about 47% at 700 °C, compared with the unmodified cells. It is explained as the extended triple-phase boundary (TPB) in the anode substrate and the excellent electrocatalytic property of SDC. It is also found that the nano-scale SDC particles change a lot during the reduction of the anode substrate, and the morphology of the resultant SDC particles on the metal Ni is significantly different from that on the YSZ. After the long-term operation, the morphology of the SDC particles on the Ni changes again, but that on the YSZ keeps almost unchanged.

The SrCo0.9Sb0.1O3–δ (SCS) composite oxide with cubic perovskite structure was synthesized by a modified Pechini method, and examined as a novel cathode for intermediate-to-low temperature solid oxide fuel cells (ILT-SOFCs). At 700°C and under open-circuit condition, a symmetrical SCS cathode on Sm0.2Ce0.8O1.9 (SDC) electrolyte showed a low polarization resistance (Rp) of 0.09 Ωcm2 in air. A porous layer of SCS was deposited on an anode-supported fuel cell, consisting of a ∼30 μm thick dense electrolyte of SDC prepared by a cost-effective dip coating process, and an NiO-SDC cermet as an anode (Ni-SDC/SDC/SCS). The single cells obtained were tested with humidified (∼3% H2O) hydrogen as fuel and static air as oxidant. A high open-circuit voltage of 0.86 V, a maximum power density of 354 mW/cm2, and a low polarization resistance of the electrodes of 0.13 Ωcm2 was achieved at 650°C.

A novel nano-network of Sm 0.5 Sr 0.5 CoO 3− δ (SSC) is successfully fabricated as the cathodes for intermediate-temperature solid oxide fuel cells (SOFCs) operated at 500–600 °C. The cathode is composed of SSC nanowires formed from nanobeads of less than 50 nm thus exhibiting high surface area and porosity, forming straight path for oxygen ion and electron transportation, resulting in high three-phase boundaries, and consequently showing remarkably high electrode performance. An anode-supported cell with the nano-network cathode demonstrates a peak power density of 0.44 W cm −2 at 500 °C and displays exceptional performance with cell operating time. The result suggests a new direction to significantly improve the SOFC performance.

Anode coking problem of solid oxide fuel cell (SOFC) when using hydrocarbon fuels has been the major barrier for the practice and commercialization of well-developed high performance SOFC. In this work, based on fuels consideration, we chose liquid methanol as the candidate fuel for SOFC with the configuration of NiO/SDC–SDC–SSC/SDC. For comparison, traditional fuels, hydrogen and ammonia, were tested. With methanol as fuel, the maximum power densities were 698, 430 and 223 mW cm −2 at 650, 600 and 550 °C, respectively, which were higher than that with ammonia and lower than that of hydrogen. The electrochemical properties of the cells with the three fuels were investigated by AC impedance spectroscopy. The long-term stability of the cell with methanol, methane and ethanol were also studied at a constant output voltage of 0.5 V.

(Pr–Nd)1−ySryMnO3−δ (P-NSM, y = 0.2, 0.25, 0.3, 0.35) powders made from commercial Pr–Nd mixed oxide, as well as (Pr1−xNdx)0.7Sr0.3MnO3−δ (PN3SM, x = 0, 0.5, 0.7, 1) were synthesized by a glycine-nitrate process and characterized as cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC). XRD patterns showed the powders had formed pure perovskite phase after being calcined at 800 °C for 2 h. (Pr–Nd)0.7Sr0.3MnO3−δ (P-N3SM) achieved a high conductivity of 194 S cm−1 at 500 °C and showed a good chemical stability against YSZ at 1150 °C. And the thermal expansion coefficient of P-N3SM/YSZ cathode was 11.1 × 10−6 K−1, which well matched YSZ electrolyte film. The tubular SOFC with P-N3SM/YSZ cathode exhibited the maximum power densities of 415, 367, 327 and 282 mW cm−2 at 850, 800, 750 and 700 °C, respectively, which indicated P-N3SM was potentially applied in SOFC for low cost.

A microwave-induced monomer gelation and gel combustion synthesis process was successfully developed to synthesize well-dispersed Pr 0.35 Nd 0.35 Sr 0.3 MnO 3− δ (PNSM)/YSZ composite cathode powders for tubular solid oxide fuel cells (SOFCs). The thermo-gravimetric (TG) analysis of as-prepared ash indicated the decomposition process of most of metal nitrates during gel combustion. The X-ray diffraction (XRD) pattern of the powders calcined at 1000 °C showed only pure PNSM and YSZ phase. Transmission electron microscopy (TEM) revealed that the morphology of powders was characterized with the YSZ particles enwrapped by fine PNSM particles so that PNSM/YSZ composite powders were much better-dispersed compared with the powders made simply by mechanical mixing process. The cell made from PNSM/YSZ composite powder showed lower cathode ohmic resistance and polarization resistance, and produced higher power density subsequently.

To improve cathode–electrolyte interfaces of solid oxide fuel cells (SOFCs), dense YSZ electrolyte membranes with indented surfaces were fabricated on tubular NiO/YSZ anode supports by two comparable methods. Electrochemistry impedance spectroscopy (EIS) and current–voltage tests of the cells were carried out to characterize the cathode–electrolyte interfaces. Results showed that the electrode polarization resistances of the modified cells were reduced by 52% and 35% at 700 °C, and the maximum power densities of cells were remarkably increased, even by 146.6% and 117.8% at lower temperature (700 °C), respectively. The indented surfaces extended the active zone of cathode and enhanced interfacial adhesion, which led to the major improvement in the cell performance.

The effects of co-sintering temperature on anode microstructure, electrolyte film microstructure, and final cell performance of tubular solid oxide fuel cells (SOFCs) were fully studied. The co-sintering of the NiO/YSZ anode-YSZ electrolyte double layers at temperature ranging from 1350 to 1400 °C for 5 h was carried out. Porosity and electrical conductivity were measured to examine the anodes microstructure, and the electrolyte films microstructure were characterized by scanning electronic microscope (SEM). A higher open current voltage (OCV) value of 0.99 V was achieved by co-sintering the cell at 1400 °C indicating denser electrolyte film, while the maximum power density of the cell co-sintered at 1380 °C was achieved with 322 mW cm−2 at 800 °C, which was higher than that (241.3 mW cm−2) of the cell co-sintered at 1400 °C because of better anode microstructure.

A mixed ionic and electronic conductor, BaPr0.8In0.2O3−δ (BPI), was synthesized and examined as a cathode material for proton-conducting solid oxide fuel cells (H-SOFCs). X-ray diffraction analysis revealed that BPI had a perovskite structure and showed satisfactory tolerance to CO2 and H2O and good chemical compatibility with BaZr0.1Ce0.7Y0.1 Yb0.1O3−δ (BZCYYb) electrolyte. Test cells with a single-phase BPI cathode exhibited excellent electrochemical performances, demonstrating a peak power density of ~688 mW cm−2 at 750 °C. Furthermore, the cells with a BPI cathode showed very stable power output at a cell voltage of 0.7 V at 600 °C over 100 h, suggesting that BPI is a promising alternative cathode for H-SOFCs. Keywords: SOFC, In-doped BaPrO3, Mixed conductor, Cathode, Stability

The SrCo0.9Sb0.1O3−δ (SCS) composite oxide with cubic perovskite structure was synthesized by a modified Pechini method and examined as a novel cathode for intermediate-to-low temperature solid oxide fuel cells (ILT-SOFCs). At 700 °C and under open-circuit condition, symmetrical SCS cathode on Sm0.2Ce0.8O1.9 (SDC) electrolyte showed low polarization resistances (Rp) of 0.09 Ω cm2 in air. A porous layer of SCS was deposited on an anode-supported fuel cell consisting of a ∼30-μm thick dense electrolyte of SDC prepared by a cost-effective dip coating process and a NiO-SDC cermet as an anode (Ni-SDC/SDC/SCS). The obtained single cells were tested with humidified (∼3% H2O) hydrogen as fuel and the static air as oxidant. A high open-circuit potential of 0.86 V, a maximum power density of 354 mW cm−2, and a low polarization resistance of the electrodes of 0.13 Ω cm2 was achieved at 650 °C.

Following exposure to ppm-level hydrogen sulfide at elevated temperatures, a section of a solid oxide fuel cell (SOFC) Ni-YSZ anode was examined using a combination of synchrotron-based x-ray nanotomography and x-ray fluorescence techniques. While fluorescence measurements provided elemental identification and coarse spatial mapping, x-ray nanotomography was used to map the detailed 3-D spatial distribution of Ni, YSZ and a nickel-sulfur poisoning phase. The nickel-sulfur layer was found to form a scale covering most of the exposed nickel surface, blocking most fuel reformation and hydrogen oxidation reaction sites. Although the exposure conditions precluded the ability to develop a detailed kinetic description of the nickel-sulfur phase formation, the results provide strong evidence of the detrimental effects of 100 ppm hydrogen sulfide on typical Ni-YSZ anode materials.

Sulfur poisoning can deactivate nickel catalysts in solid oxide fuel cells (SOFCs), resulting in a significant drop in fuel cell performance. In this paper, a Ni/YSZ SOFC anode exposed to 100 ppm H2S was examined using x-ray absorption contrast imaging for its microstructure and x-ray fluorescence (XRF) spectroscopy to probe and map Ni, S, and YSZ phases. It was observed that S was frequently found to be collocated with Ni, with higher concentrations being located on or near the surface of the Ni particles exposed to gas, while little S was found near the YSZ phase.Copyright © 2012 by ASME

The existing Ni-yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) perform poorly in carbon-containing fuels because of coking and deactivation at desired operating temperatures. Here we report a new anode with nanostructured barium oxide/nickel (BaO/Ni) interfaces for low-cost SOFCs, demonstrating high power density and stability in C3H8, CO and gasified carbon fuels at 750°C. Synchrotron-based X-ray analyses and microscopy reveal that nanosized BaO islands grow on the Ni surface, creating numerous nanostructured BaO/Ni interfaces that readily adsorb water and facilitate water-mediated carbon removal reactions. Density functional theory calculations predict that the dissociated OH from H2O on BaO reacts with C on Ni near the BaO/Ni interface to produce CO and H species, which are then electrochemically oxidized at the triple-phase boundaries of the anode. This anode offers potential for ushering in a new generation of SOFCs for efficient, low-emission conversion of readily available fuels to electricity., Anodes composed of nickel/yttria-stabilized zirconia in solid oxide fuel cells are known to suffer from coking, which reduces their performance. Here, Yang and colleagues report a new barium oxide/nickel anode, which efficiently oxidizes fuel with minimum carbon buildup.

A carefully designed test cell platform with a new electrode structure is utilized to determine the intrinsic surface catalytic properties of an electrode. With this design, the electrocatalytic activity and stability of an La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode is enhanced by a dense thin La0.85Sr0.15MnO3±δ (LSM) coating, suggesting that an efficient electrode architecture has been demonstrated that can make effective use of desirable properties of two different materials: fast ionic and electronic transport in the backbone (LSCF) and facile surface kinetics on the thin-film coating (LSM). Theoretical analyses suggest that the enhanced electrocatalytic activity of LSM-coated LSCF is attributed possibly to surface activation under cathodic polarization due to the promotion of oxygen adsorption and/or dissociation by the surface layer and the dramatically increased oxygen vacancy population in the surface film. Further, the observed time-dependent activation over a few hundreds of hours and durability are likely associated with the formation of a favorable hybrid surface phase intermediate between LSM and LSCF. This efficient electrode architecture was successfully applied to the state-of-the-art LSCF-based cathodes by a simple solution infiltration process, achieving reduced interfacial resistance and improved stability under fuel cell operating conditions.