Angela Kruth

Water incorporation studies on doped barium cerate perovskites

BaCeO3-based perovskites exhibit high proton conductivities and are attractive candidates for application in electrocatalysis and fuel cells. In BaCe1 � xYxO3 � x/2 ,0 VxV0.15, the degree of hydration is directly related to the oxygen vacancy concentration and increases linearly with dopant content, x. The water content of the material depends predominantly on the number of oxygen vacancies. At maximum hydration, ca. 80% of oxygen vacancies are filled. The loss of water is primarily dependent upon temperature, with water loss occurring over a range of f200 jC. Samples with higher oxygen vacancy contents retain more water at high temperatures, and hence probably also have higher proton transport numbers at high temperatures. Under reducing conditions, water loss is accompanied by oxygen loss. D 2003 Elsevier B.V. All rights reserved.

Photocatalytic Hydrogen Production with Copper Photosensitizer–Titanium Dioxide Composites

A series of heteroleptic copper photosensitizers [(

Plasma Synthesis of Polymer‐Capped Dye‐Sensitised Anatase Nanopowders for Visible‐Light‐Driven Hydrogen Evolution

\widehat{PP}

Vanadia–titania multilayer nanodecoration of carbon onions via atomic layer deposition for high performance electrochemical energy storage

)Cu(

Scandia-Zirconia Electrolytes and Electrodes for SOFCS

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New oxygen-deficient perovskite series, Ca2Mn2–xNbxOγ: 0<x<1.2

(SO3Na)2)]+ containing sulfonate anchor groups is described. In the presence of titanium dioxide they form composites, which are active photosensitizers in the light driven reduction of protons. Further stabilization of these systems is achieved by encapsulation within a plasma‐polymerized allylamine (PPAAm) layer. The resulting PPAAm‐CuPS‐TiO2‐composites exhibit a strong absorption in the visible region of the light. Photocatalytic hydrogen production is performed by using only non‐noble metals. In the presence of an iron reduction catalyst a maximum turnover number of 2452 is obtained.

Synthesis, structure, electrical and magnetic properties of the new non-stoichiometric perovskite phase, Ca2MnNbOγ

Visible-light-driven photocatalysis is currently attracting a great deal of attention because of its potential application in solar water splitting. However, the development of efficient and durable catalyst systems is still a challenging problem. In Ru dye-sensitised TiO(2) nanopowders, catalyst performances are found to decline as a result of poor bonding of the dye molecule to the TiO(2) surface and subsequent detachment and self-aggregation of the dye. Our strategy to improve the stability of the dye-TiO(2) interface is the encapsulation of the dye/TiO(2) assembly in an amino-group-containing polyallylamine layer anchored to TiO(2). A low-pressure pulsed microwave discharge plasma polymerization process was employed to coat a commercial anatase nanopowder with a thin polyallylamine layer to nanoconfine the adsorbed dye molecules. Electron microscopy and UV/Vis spectroscopy was carried out to characterise the resulting encapsulated nanostructures. The long-term stability of the new nanomaterial as the photoactive component of a water reduction catalyst system for H(2) evolution investigated in a slurry reactor under visible-light irradiation showed stable evolution rates over a period of several days.

Morphology, Optical Properties and Photocatalytic Activity of Photo- and Plasma-Deposited Au and Au/Ag Core/Shell Nanoparticles on Titania Layers

Atomic layer deposition has proven to be a particularly attractive approach for decorating mesoporous carbon substrates with redox active metal oxides for electrochemical energy storage. This study, for the first time, capitalizes on the cyclic character of atomic layer deposition to obtain highly conformal and atomically controlled decoration of carbon onions with alternating stacks of vanadia and titania. The addition of 25 mass% TiO2 leads to expansion of the VO2 unit cell, thus greatly enhancing lithium intercalation capacity and kinetics. Electrochemical characterization revealed an ultrahigh discharge capacity of up to 382 mA h g−1 of the composite electrode (554 mA h g−1 per metal oxide) with an impressive capacity retention of 82 mA h g−1 (120 mA h g−1 per metal oxide) at a high discharge rate of 20 A g−1 or 52C. Stability benchmarking showed stability over 3000 cycles when discharging to a reduced potential of −1.8 V vs. carbon. These capacity values are among the highest reported for any metal oxide system, while in addition, supercapacitor-like power performance and longevity are achieved. At a device level, high specific energy and power of up to 110 W h kg−1 and 6 kW kg−1, respectively, were achieved when employing the hybrid material as anode versus activated carbon cathode.

Atomic Layer-Deposited Molybdenum Oxide/Carbon Nanotube Hybrid Electrodes: The Influence of Crystal Structure on Lithium-Ion Capacitor Performance

The aim of this study was to assess the potential of scandia stabilised zirconias for use in high temperature fuel cells. Such materials offer much better performance than the conventional yttria stabilised materials and now it seems that availability and cost may not be hugely problematic. This offers a very important way forward to fuel cell manufacturing. It has been shown that a small addition of 2 mol% yttria to scandia stabilised zirconia results in formation of cubic phase and so avoids major phase changes which we believe to be detrimental to long term electrolyte stability. This addition of yttria can be achieved without significant impairment of the electrical conductivity of the scandia-stabilised zirconia. We have shown that the mechanical properties of these scandia-stabilised zirconias are inferior to the yttria-stabilised zirconias, but the difference is not that great. Thus we have identified a new range of composition for use in solid oxide fuel cell electrolytes, which exhibits good compromise between phase stability and electrical properties. Some experiments were also performed to investigate the properties of titania doped scandia stabilised zirconia as a possible fuel cell electrode material. This has shown that the scandia containing titania zirconias were better than those of the yttria analogue. However, electronic conductivity was still not high enough to use such materials as electrodes without appropriate current collection.

Formation, structure, and stability of titanate nanotubes and their proton conductivity.

An extensive range of orthorhombic perovskites with the GdFeO 3 structure, variable B-cation content and variable oxygen content form according to the formula Ca 2 Mn 2–x Nb x O γ : 0<x<1.2. A second, closely-related, oxygen-deficient solid solution with a simple cubic perovskite structure forms over the range 0.3<x<0.8. Oxygen contents range from 5.0<γ<6.0 for x=0 to 5.8 <γ<6.0 for x=1.2 and are obtained by post-reaction heat treatment, either in air at different temperatures or in H 2 -N 2 . The orthorhombic solid solutions are either oxygen-stoichiometric or lightly reduced and transform to the cubic structure on more extensive reduction. A phase diagram is presented showing the equilibrium γ values in air over the temperature range 1000-1350°C. The variable composition of the solid solutions is accommodated by vacancies in up to 20% of the oxygen positions and variations in the oxidation state of Mn, between +2 and +4.