Enhancing the Mechanical Strength of Electrolyte-Supported Solid Oxide Cells with Thin and Dense Doped-Ceria Interlayers.

The penetration of fuel cells and electrolyzers in energy systems calls for their scale-up to the gigawatt (GW) level. High temperature solid oxide cells (SOC) offer unrivaled efficiencies in both electrolysis and fuel cell operation. However, they are made of ceramics and are brittle by nature. Consequently, a high mechanical strength to avoid failure during stacking is essential to achieve a high manufacturing yield. Here, we show that without changing the materials of the state-of-the-art cells, thin and dense ceria interlayers enable comparable power densities and durability in fuel cell operation. The sole tuning of the morphology and processing of the interlayers reduce the residual stress in the cell significantly which increases its mechanical strength by up to 78%. These results promise performance gains of similar magnitude by enabling a substantial decrease of the electrolyte thickness while maintaining robustness. This stress engineering approach presents a way to increase the volumetric power density and material efficiency of SOC systems.

Intercalation of Thin-Film Gd-Doped Ceria Barrier Layers in Electrolyte-Supported Solid Oxide Cells: Physicochemical Aspects.

To minimize alteration of the La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF)/Gd0.2Ce0.8O2-δ(CGO20)/Y0.06Zr0.94O2-δ(3YSZ) interface via strontium zirconate formation in solid oxide cells, electron beam physical vapor deposition was employed to manufacture dense, thin gadolinium-doped ceria (CGO) interlayers. CGO layers with thicknesses of 0.15, 0.3, and 0.5 µm were integrated in state-of-the-art 5 × 5 cm2-large electrolyte-supported cells, and their performance characteristics and degradation behavior were investigated. Electrochemical impedance spectroscopy measurements are correlated with a postmortem scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis to show that 0.15 µm-thick layers lead to the formation of a continuous Sr-containing secondary phase at the CGO/YSZ interface, likely related to the formation of a SrO-ZrO2 phase. Major performance losses were confirmed by an increase in both Ohmic and polarization resistance with an increase in the frequency region ∼103 Hz. Cells with 0.3 µm- and 0.5 µm-thick CGO layers showed similar high performance and low degradation rates over a testing period of ∼800 h. The YSZ/CGO interface of the cells with a 0.3 µm-thick CGO layer showed the formation of a discontinuous Sr-containing secondary phase; however, performance losses were still successfully prevented. Furthermore, it is observed that 0.5 µm-thick CGO layers were sufficient to suppress the formation of the Sr-containing secondary phase.

Performance and Limitations of Nickel-Doped Chromite Anodes in Electrolyte-Supported Solid Oxide Fuel Cells.

Ni-doped chromite anodes were integrated into electrolyte-supported cells (ESC) with 5×5 cm2 size and investigated in fuel cell mode with H2 /H2 O fuel gas. Both a stoichiometric and a nominally A-site deficient chromite anode material showed promising performance at 860 °C approaching the ones of state-of-the-art Ni/Gd-doped ceria (CGO) anodes. While the difference in polarization resistance was small, an increased ohmic resistance of the perovskite anodes was observed, which is related to their limited electronic conductivity. Increasing the chromite electrode thickness was shown to enhance performance and stability considerably. Degradation increased with current density, suggesting its dependency on the electrode potential, and could be reversed by redox cycling. Sulfur poisoning with 20 ppm hydrogen sulfide led to rapid voltage drops for the chromite anodes. It is discussed that Ni nanoparticle exsolution facilitates hydrogen dissociation to the extent that it is not rate-limiting at the investigated temperature unless an insufficiently thick electrode thickness is employed or sulfur impurities are present in the feed gas.

Enhancement of proton transport in an oriented polypeptide thin film.

Proton transport properties of a partially protonated poly(aspartic acid)/sodium polyaspartate (P-Asp) were investigated. A remarkable enhancement of proton conductivity has been achieved in the thin film. Proton conductivity of 60-nm-thick thin film prepared on MgO(100) substrate was 3.4 × 10(-3) S cm(-1) at 298 K. The electrical conductivity of the oriented thin film was 1 order of magnitude higher than the bulk specimen, and the activation energies for the proton conductivity were 0.34 eV for the oriented thin film and 0.65 eV for the pelletized sample, respectively. This enhancement of the proton transport is attributable to the highly oriented structure on MgO(100) substrate. This result proposes great potential for a new strategy to produce a highly proton-conductive material using the concept of an oriented thin film structure without strong acid groups.

Lehualides A-D, metabolites from a Hawaiian sponge of the genus Plakortis.

A collection of an undescribed marine sponge of the genus Plakortis yielded four new "polyketide-derived" metabolites, lehualides A-D (1-4). The structures of compounds 1-4 were elucidated by interpretation of spectral data. Compound 2 demonstrated cytotoxicity against an ovarian cancer cell line, while compound 4 was active against both ovarian cancer and leukemia cell lines.

Poipuol, a new metabolite from a Hawaiian sponge of the genus Hyrtios.

A new metabolite, poipuol (1), was isolated from an undescribed marine sponge Hyrtios sp. collected in Kauai Island, Hawaii. The structure was determined from spectroscopic data.

Identification of palytoxin as a principle which causes morphological changes in rat 3Y1 cells in the zoanthid Palythoa aff. margaritae.

A very potent cell-bursting principle was isolated from the extract of the zoanthid Palythoa aff. margaritae. The compound was identified as palytoxin by comparing the spectral data and HPLC profile with those of an authentic sample.

Albiziahexoside: a potential source of bioactive saponin from the leaves of Albizzia lebbeck.

Albiziahexoside (1), a new hexaglycosylated saponin, was isolated from leaves of Albizzia lebbeck. Saponin 1, which is an analog of cytotoxic albiziatrioside A (2), did not show cytotoxicity. However, 1 is a potential source of 2 and related bioactive saponins for medicinal use because leaves, which can be regenerated after collection, contain 1 in substantial quantity.

Isolation and identification of a potent allelopathic substance in rice root exudates.

A search for growth inhibitors in rice root exudates was undertaken in order to clarify the allelopathic system in rice (Oryza sativa L.). Rice seedlings inhibited the growth of cress (Lepidium sativum L.) and lettuce (Lactuca sativa L.) seedlings when the cress and lettuce were grown with rice seedlings. The putative compound causing the inhibitory effect of rice seedlings was isolated from their culture solution, and the chemical structure of the inhibitor was determined by spectral data as momilactone B. Momilactone B inhibited the growth of cress and lettuce seedlings at concentrations greater than 3 and 30 microM, respectively. The concentration of momilactone B was 3.4 and 1.1 nmol per seedling in the culture solutions of husked and non-husked rice seedlings, respectively. These results suggest that rice seedlings may release momilactone B into the environment and the stress caused by the husk-treatment may increase the amount of momilactone B released. Thus, momilactone B may play an important role in rice allelopathy.

New labdene iterpenes from Eupatorium glutinosum.

The new diterpene glucoside 3,15-dihydroxy-ent-labd-7-en-17-oic acid 3-O-beta-D-glucoside (1) and its aglycone (2) have been isolated from Eupatorium glutinosum. The structures were determined by IR, one- and two-dimensional NMR, high-resolution mass spectrometry, chemical transformations, and comparison of spectroscopic data with closely related diterpenes. Crude extracts showed antimicrobial and cytotoxic activities, but compounds 1 and 2 showed only antimicrobial activity. These results support the vernacular medicinal use of the plant as an antimicrobial.

Degradation of 17beta-estradiol by a gram-negative bacterium isolated from activated sludge in a sewage treatment plant in Tokyo, Japan.

A 17beta-estradiol (E2)-degrading bacterium was isolated from activated sludge in a sewage treatment plant in Tokyo, Japan. The isolate was suggested to be a new Novosphingobium species. Gas chromatography-mass spectrometry and (1)H nuclear magnetic resonance analyses of the metabolites of E2 degradation suggested that no toxic products accumulated in the culture medium.