II. Structure of Perovskites 1982 A. Crystal Structure 1982 B. Nonstoichiometry in Perovskites 1983 1. Oxygen Nonstoichiometry 1983 2. Cation Nonstoichiometry 1984 C. Physical Properties 1985 D. Adsorption Properties 1986 1. CO and NO Adsorption 1986 2. Oxygen Adsorption 1987 E. Specific Surface and Porosity 1987 F. Thermal Stability in a Reducing Atmosphere 1989 III. Acid−Base and Redox Properties 1990 A. Acidity and Basicity 1990 B. Redox Processes 1991 1. Kinetics and Mechanisms 1992 2. Reduction−Oxidation Cycles 1993 C. Ion Mobility 1993 1. Oxygen Transport 1993 2. Cation Transport 1994 IV. Heterogeneous Catalysis 1995 A. Oxidation Reactions 1995 1. CO Oxidation 1995 2. Oxidation of Hydrocarbons 1996 B. Pollution Abatement 2001 1. NOx Decomposition 2001 2. Exhaust Treatment 2002 3. Stability 2004 C. Hydrogenation and Hydrogenolysis Reactions 2004 1. Hydrogenation of Carbon Oxides 2004 2. Hydrogenation and Hydrogenolysis Reactions 2006

Chemical structures and performance of perovskite oxides.

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

This article provides a perspective on solid oxide fuel cells operating at low temperature, defined here to be the range from ∼400 °C to 650 °C. These low-temperature solid oxide fuel cells (LT-SOFCs) have seen considerable research and development and are widely viewed as the “next generation” technology, following the 650–850 °C SOFCs that are currently undergoing commercialization. LT-SOFCs have potential advantages for conventional SOFC applications such as stationary power generation, and may be viable for new portable and transportation power applications, along with electrolytic fuel production and energy storage. The characteristics of electrolyte and electrode materials are reviewed, with a focus on materials that have demonstrated good properties and cell performance at low temperature. Only oxygen-ion-conducting electrolytes are considered here. Anode materials are discussed, primarily the various Ni–cermet anode compositions that yield good low-temperature performance. Mixed ionically and electronically conducting cathode materials are described in detail, reflecting the extensive research activity that has aimed at providing useful oxygen reduction kinetics at low operating temperature. Cell design, materials compatibility, processing methods, and resulting microstructures are discussed, along with their role in determining cell performance. Results from state of the art LT-SOFCs are presented, and future prospects are discussed.

A perspective on low-temperature solid oxide fuel cells

Solid oxide fuel cells (SOFCs) have the potential to be one of the cleanest and most efficient energy technologies for direct conversion of chemical fuels to electricity. Economically competitive SOFC systems appear poised for commercialization, but widespread market penetration will require continuous innovation of materials and fabrication processes to enhance system lifetime and reduce cost. One early technical opportunity is minimization of resistance to the oxygen reduction reaction (ORR) at the cathode, which contributes the most to performance degradation and efficiency loss in the existing SOFCs, especially at temperatures <700 °C. Detailed study over the past 15 years has revealed the positive impact of catalyst infiltration on SOFC cathode performance, both in power density and durability metrics. However, realizable performance improvements rely upon strongly-coupled relationships in materials and morphology between the infiltrate and the backbone, and therefore efficacious systems cannot be simply generated with a set of simple heuristics. This article reviews recent progress in enhancing SOFC cathode performance by surface modification through a solution-based infiltration process, focusing on two backbone architectures – inherently functional and skeletal – infiltrated using wet-chemistry processes. An efficient cathode consists of a porous mixed-conducting backbone and an active coating catalyst; the porous backbone provides excellent ionic and electronic conductivity, while the infiltrated surface coating possesses high catalytic activity and stability. As available, performance comparisons are emphasized and reaction schematics for specific infiltrate/backbone systems are summarized. While significant progress has been achieved in enhancing surface catalytic activity and durability, the detailed mechanisms of performance enhancement are insufficiently understood to obtain critical insights and a scientific basis for rational design of more efficient catalysts and novel electrode architectures. Recent progress in characterization of surfaces and interfaces is briefly discussed with challenges and perspectives in surface modification of SOFC electrodes. Surface modification through infiltration is expected to play an increasingly important role in current and next-generation commercial SOFC development, and this review illustrates the sophisticated technical considerations required to inform judicious selection of an infiltrate for a given SOFC system.

Enhancing SOFC cathode performance by surface modification through infiltration

The high-temperature solid oxide fuel cell (SOFC) is the most efficient and environmentally friendly energy conversion technology to generate electricity from fuels such as hydrogen and natural gas as compared to the traditional thermal power generation plants. In the last 20–30 years, there has been significant progress in the materials development and stack technologies in SOFC. Among the electrode materials, lanthanum strontium manganite (LSM) perovskites, till today, are the most investigated and probably the most important electrode materials in SOFCs. The objective of this article is to review and update the development, understanding, and achievements of the LSM-based materials in SOFC. The structure, nonstoichiometry, defect model, and in particular the relation between the microstructure, their properties (electrical, thermal, mechanical, chemical, and interfacial), and electrochemical performance and performance stability are critically reviewed. Finally, challenges and prospects of LSM-based materials as cathodes for intermediate and low-temperature SOFCs are discussed.

Development of lanthanum strontium manganite perovskite cathode materials of solid oxide fuel cells: a review

Oxygen transport in selected nonstoichiometric perovskite-structure oxides

Development of a novel SIMS technique for oxygen self-diffusion and surface exchange coefficient measurements in oxides of high diffusivity

The oxygen self-diffusion coefficient in YBa 2 Cu 3 O 7−δ single crystals has been measured along different crystallographic directions at two temperatures. The role of different crystallographic positions of oxygen has been established. A mechanism has been proposed explaining the strong anisotropy of the oxygen diffusion.

S. Carter

Papers

Oxygen transport in selected nonstoichiometric perovskite-structure oxides

Development of a novel SIMS technique for oxygen self-diffusion and surface exchange coefficient measurements in oxides of high diffusivity

Anisotropy of oxygen self-diffusion in YBa2Cu3O7−δ single crystals