Recent worldwide interest in building a decentralized, hydrogen-based energy economy has refocused attention on the solid oxide fuel cell (SOFC) as a potential source of efficient, environmentally friendly, fuel-versatile electric power. Due to its high operating temperature, the SOFC offers several potential advantages over polymer-based fuel cells, including reversible electrode reactions, low internal resistance, high tolerance to typical catalyst poisons, production of high-quality waste heat for (among other uses) reformation of hydrocarbon fuels, as well as the possibility of burning hydrocarbon fuels directly. Today, SOFCs are much closer to commercial reality than they were 20 years ago, due largely to technological advances in electrode material composition, microstructure control, thin-film ceramic fabrication, and stack and system design. These advances have led to dozens of active SOFC development programs in both stationary and mobile power and contributed to commercialization or development in a number of related technologies, including gas sensors,1 solid-state electrolysis devices,2 and iontransport membranes for gas separation and partial oxidation.3 Many reviews are available which summarize the technological advances made in SOFCs over the last 15-35 yearssreaders who are primarily interested in knowing the state-of-the art in materials, design, and fabrication (including the electrodes) are encouraged to consult these reviews.4-12 This review focuses on the factors governing SOFC cathode performancesadvances we have made over † Dedicated to Brian Steele, 1929-2003. Researcher, Entrepreneur, Consensus Seeker. 4791 Chem. Rev. 2004, 104, 4791−4843

Factors Governing Oxygen Reduction in Solid Oxide Fuel Cell Cathodes

In the past few years, spiropyran has emerged as the molecule-of-choice for the construction of novel dynamic materials. This unique molecular switch undergoes structural isomerisation in response to a variety of orthogonal stimuli, e.g. light, temperature, metal ions, redox potential, and mechanical stress. Incorporation of this switch onto macromolecular supports or inorganic scaffolds allows for the creation of robust dynamic materials. This review discusses the synthesis, switching conditions, and use of dynamic materials in which spiropyran has been attached to the surfaces of polymers, biomacromolecules, inorganic nanoparticles, as well as solid surfaces. The resulting materials show fascinating properties whereby the state of the switch intimately affects a multitude of useful properties of the support. The utility of the spiropyran switch will undoubtedly endow these materials with far-reaching applications in the near future.

/pdf/spiropyran-based-dynamic-materials-4c1onvrhup.pdf

Spiropyran-based dynamic materials

Solid oxide fuel cells (SOFCs) have the promise to improve energy efficiency and to provide society with a clean energy producing technology. The high temperature of operation (500−1000 °C) enables the solid oxide fuel cell to operate with existing fossil fuels and to be efficiently coupled with turbines to give very high efficiency conversion of fuels to electricity. Solid oxide fuel cells are complex electrochemical devices that contain three basic components, a porous anode, an electrolyte membrane, and a porous cathode. In this short review, a survey of the types and properties of materials that have been considered for each of these components is presented with an emphasis on the requirements for operation at intermediate temperature (500−800 °C). Some directions for future research are discussed.

Materials for Solid Oxide Fuel Cells

Progress in material selection for solid oxide fuel cell technology: A review

Recent advances and challenges in designing stimuli-responsive polymers

The search for an ideal magnetic semiconductor with tunable ferromagnetic behaviour over a wide range of doping or by electrical gating is being actively pursued as a major step towards realizing spin electronics. A magnetic semiconductor having a high Curie temperature, capable of independently controlled carrier density and magnetic doping, is crucial for developing spin-based multifunctional devices. Cr-doped In2O3 is such a unique system, where the electrical and magnetic behaviour—from ferromagnetic metal-like to ferromagnetic semiconducting to paramagnetic insulator—can be controllably tuned by the defect concentration. An explicit dependence of magnetic interaction leading to ferromagnetism on the carrier density is shown. A carrier-density-dependent high Curie temperature of 850–930 K has been measured, in addition to the observation of clear magnetic domain structures in these films. Being optically transparent with the above optimal properties, Cr-doped In2O3 emerges as a viable candidate for the development of spin electronics.

Carrier-controlled ferromagnetism in transparent oxide semiconductors

Electrical conductivity relaxation studies of an epitaxial La0.5Sr0.5CoO3−δ thin film

The interfacial force microscope has been used to establish the changes in the surface chemistry that accompany photoactivated opening and closing of rings in tethered spiropyran monolayers. Contact potential measurements show that ring opening via ultraviolet light creates a more polar surface, while exposure to visible light closes the rings and resets the surface. Normal force measurements show that open ring structures are protonated in electrolyte solutions, amplifying the switching of electrical double-layer forces.

/pdf/direct-observation-of-photo-switching-in-tethered-2p20xsb62q.pdf

Direct Observation of Photo Switching in Tethered Spiropyrans Using the Interfacial Force Microscope

Ferroelectric Bi4Ti3O12 thin films have been grown on MgO (100) and MgO(110) substrates by the pulsed laser deposition. X‐ray diffraction studies show that the films on both substrates have preferential crystallographic orientation such that most of their c axes are close to the substrate normal direction. The film on MgO(110) shows quadratic and hysteretic electro‐optic characteristics with the effective coefficient of about 3.8×10−15 m2/V2.

https://www.uh.edu/~kbyung/paperpdf/Apl_afm.pdf

Structural and electro‐optic properties of pulsed laser deposited Bi4Ti3O12 thin films on MgO

An apparatus may comprise an optical detector configured to detect an optical beam reflected from a cantilever. The apparatus may further comprise an optical fiber probe suspended from the cantilever and a piezotube configured to move a sample substance in proximity to the optical fiber probe. The cantilever may be configured to deflect in response to an interfacial force between the sample substance and the optical fiber probe. The apparatus may further comprise a feedback controller communicatively coupled to the optical detector and a semiconductive circuit element abutting the cantilever. In response to detecting movement of the optical beam reflected from the cantilever, the feedback controller may apply a voltage to the semiconductive circuit element, which may reduce deflection of the cantilever. The voltage applied by the feedback controller may indicate a strength of the interfacial force between the sample substance and the optical fiber probe.

/pdf/cantilever-based-optical-interfacial-force-microscope-1h2x2tsna4.pdf

Byung I. Kim

Papers

Carrier-controlled ferromagnetism in transparent oxide semiconductors

Electrical conductivity relaxation studies of an epitaxial La0.5Sr0.5CoO3−δ thin film

Direct Observation of Photo Switching in Tethered Spiropyrans Using the Interfacial Force Microscope

Structural and electro‐optic properties of pulsed laser deposited Bi4Ti3O12 thin films on MgO

Cantilever-based optical interfacial force microscope