Anna Lashtabeg

Solid oxide fuel cells—a challenge for materials chemists?

Solid oxide fuel cells (SOFCs) are complex electrochemical devices that offer significant advantages over conventional power generation technologies. Many of these advantages surround the environmental impact of energy generation and in particular the efficiency of power production coupled with the potential range of fuel sources that can be foreseen. Despite these advantages there remain a number of challenges that may delay the full commercialisation of the solid oxide fuel cell. Several of these surround the materials selection, function and interactions with other cell components. It is the intention of this article to highlight the contribution that materials chemistry has made to the development of SOFCs and the future progress that is dependent on advances in materials chemistry.

SCOPE: A Scientific Compound Object Publishing and Editing System

This paper presents the SCOPE (Scientific Compound Object Publishing and Editing) system which is designed to enable scientists to easily author, publish and edit scientific compound objects. Scientific compound objects enable scientists to encapsulate the various datasets and resources generated or utilized during a scientific experiment or discovery process, within a single compound object, for publishing and exchange. The adoption of “named graphs” to represent these compound objects enables provenance information to be captured via the typed relationships between the components. This approach is also endorsed by the OAI-ORE initiative and hence ensures that we generate OAI-ORE-compliant Scientific Compound Objects. The SCOPE system is an extension of the Provenance Explorer tool – which enables access-controlled viewing of scientific provenance trails. Provenance Explorer provided dynamic rendering of RDF graphs of scientific discovery processes, showing the lineage from raw data to publication. Views of different granularity can be inferred automatically using SWRL (Semantic Web Rules Language) rules and an inferencing engine. SCOPE extends the Provenance Explorer tool and GUI by: 1) Adding an embedded web browser that can be used for incorporating objects discoverable via the Web; 2) Representing compound objects as Named Graphs, that can be saved in RDF, TriX, TriG or as an Atom syndication feed; 3) Enabling scientists to attach Creative Commons Licenses to the compound objects to specify how they may be re-used; 4) Enabling compound objects to be published as Fedora Object XML (FOXML) files within a Fedora digital library.

Incorporation of molecular species into the vacancies of perovskite oxides

Abstract Complex perovskites from the system Sr 3 Ca 1 (Zr (1− x ) Ta (1+ y ) )O 8.5− x /2 offer a high concentration of oxygen vacancies and show promise as good proton conductors for SOFC and related applications. The oxygen-ion vacancies can be filled by O–H groups, by exposing the sample to a wet 5% H 2 /Ar atmosphere at intermediate temperatures (350–400 °C). However, by using high temperatures (>1000 °C) and/or pressures, we present evidence that molecular species such as carbonate and oxygen may be “forced” into this perovskite structure. Structurally, these would typically exist in a large part as CO 3 2− species, with evidence for a small amount of superoxide (O 2 − ) formation from Electron Paramagnetic Resonance (EPR) results on oxygenated samples. Electron Spin Resonance studies suggest that some of the oxygen species exist as peroxidic groups coordinated to zirconium, giving rise to a sextet. The perovskite structure is retained throughout, although a number of modifications are linked to the loss of molecular species from the lattice.

Thermomechanical and conductivity studies of doped niobium titanates as possible current collector material in the SOFC anode

In the reducing atmosphere of the SOFC anode at operating temperatures of 800 °C and above Nb2TiO7 is reduced to Nb1.33Ti0.67O4. This material displays very high electronic conductivity of >100 Scm−1, suitable for use in such applications as a current collector. It has a low thermal expansion coefficient of 3 × 10−6 K−1, however, which may cause problems due to mismatch with other SOFC components, e.g. YSZ. Doping with Fe2O3 successfully increased the thermal expansion to a maximum of 6 × 10−6 K−1. A conductivity of 140 Scm−1 at 900 °C in dry 5% H2/Ar, with an activation energy of 0.18 eV, was achieved for the Nb1.344Ti0.642Fe0.014O4, making it suitable for the use as a current collector. Conductivity runs in wet 5%H2/Ar showed lower conductivities of 15–18 Scm−1 and lower activation energies of 0.08 − 0.09 eV. Single cell tests of Nb1.33Ti0.67O4 showed power outputs of 5.5 − 7.2 mW·cm−2 at 850 °C, lower than for Ni with 150 − 200 mW·cm−2 at 850 °C, however, this material displayed much better stability at high temperatures than Ni.