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

A comprehensive review of recent advances in the field of oxygen reduction electrocatalysis utilizing nonprecious metal (NPM) catalysts is presented Progress in the synthesis and characterization of pyrolyzed catalysts, based primarily on the transition metals Fe and Co with sources of N and C, is summarized Several synthetic strategies to improve the catalytic activity for the oxygen reduction reaction (ORR) are highlighted Recent work to explain the active-site structures and the ORR mechanism on pyrolyzed NPM catalysts is discussed Additionally, the recent application of Cu-based catalysts for the ORR is reviewed Suggestions and direction for future research to develop and understand NPM catalysts with enhanced ORR activity are provided

Nonprecious Metal Catalysts for Oxygen Reduction in Heterogeneous Aqueous Systems

The roles of oxygen vacancies in electrocatalytic oxygen evolution reaction

Chemical looping offers a versatile platform to convert fuels and oxidizers in a clean and efficient manner. Central to this technology are metal oxide materials that can oxidize fuels, affording a reduced material that can be reoxidized to close the loop. Recent years have seen substantial advances in the design, formulation and manufacture of these oxygen carrier materials and their incorporation into chemical looping reactors for the production of various chemicals. This Review describes the mechanisms by which oxygen carriers undergo redox reactions and how these carriers can be incorporated into robust chemical looping reactors. One promising technology for modern energy and chemical conversions is chemical looping, central to which are redox cycles of metal oxides. This Review describes chemical looping schemes and the mechanisms by which metal oxide particles enable these technologies.

Metal oxide redox chemistry for chemical looping processes

Nanomaterials and technologies for low temperature solid oxide fuel cells : Recent advances, challenges and opportunities

Zirconia and ceria possess fluorite-type structure and conduct electricity by means of oxide ion transport through the lattice. On doping, vacancies created at the oxygen site make way for the neighbouring oxygen atoms to ‘hop’ in the direction of electric field. Among doped zirconia, 8 mol% yttria-stabilized zirconia and 9–11 mol% scandia-stabilized zirconia exhibit the highest conductivity. Ceria electrolytes require lower operational temperature (~600–800°C) compared to that of zirconia electrolytes (800–1000°C). With improvement in the processing and fabrication techniques, researchers have developed thinner electrolytes to minimize ohmic polarization and enhance the ionic conductivity enabling operation at lower temperatures (~400–600°C). But such electrolytes are required to be supported on electrodes (anode or cathode) and in later times heterostructured bi-, tri- and multi-layered electrolyte films have been constructed. Since the last decade, development of submicron grain size electrolytes and u...

Doped zirconia and ceria-based electrolytes for solid oxide fuel cells: a review

Effect of sintering on mechanical properties of ceria reinforced yttria stabilized zirconia

Introduction: Primary central nervous system lymphoma (PCNSL) is rare and accounts for 1-2% of all primary intracranial tumors (ICT). There are conflicting reports regarding the increased incidence of PCNSL over the last two decades in both immunocompromised and immunocompetent patients. Aim: This study was designed to study the clinicopathological characteristics of PCNSL and to access the trend of PCNSL at our institute. Materials and Methods: All the histopathologically proven cases of PCNSL were reviewed from January 1997 to December 2009 (13 years). Immunophenotyping was performed on available paraffin-embedded tissue blocks. Immune status was evaluated and human immunodeficiency virus (HIV) serology was performed in all cases. Cerebrospinal fluid (CSF) findings were recorded whenever available. Possibility of secondary involvement by a systemic lymphoma was excluded in every case. Statistical analysis was done using χ2 -test. Results: During the study period (13 years), a total of 4715 cases of ICT were diagnosed, out of which 66 cases were PCNSL, which accounted for 1.4%. The age ranged from 10 to 75 years with a median age of 46 years. All the patients were immunocompetent. Frontal lobe was the most common site of involvement. Diffuse large B-cell lymphoma was the histological pattern in all the cases. CSF involvement was seen in only one case. Conclusions: In this study, no significant increase in the incidence of PCNSL was found at our institute. Association of PCNSL cases with HIV or acquired immunodeficiency syndrome was not found in our study.

Primary central nervous system lymphoma: a study of clinicopathological features and trend in western India.

Solid oxide fuel cells (SOFC) have emerged as energy conversion devices in achieving high efficiency of over 70% with regeneration. The critical components of SOFC include anode, electrolyte, and cathode. However, for a stack of individual SOFCs, the evaluation of sealants and interconnects are also essential. In this review article, material selection, fundamentals of operation and underlying mechanisms, processing, microstructural and phase characterization, and the functionality and performance of individual SOFC components are presented in detail. The major challenges and complexity in functional section of SOFC include: (i) poisoning via sulfur and coke deposition, surface diffusion of adsorbate, and charge transfer at triple-phase boundary (TPB) in anode, (ii) hindered O2− migration that converts chemical energy into electrical energy in the solid electrolyte (thus, the creation of ion transfer channels, ease of O2− migration, dissociation of vacancy around dopants, straining of lattice, and other factors such as control of phase and its distribution, grain and grain boundary conductivity, become critical in designing the electrolytes for SOFCs), (iii) multiple rate determining factors such as geometry of active surfaces, and existence of overpotential, in cathode (thereby, comprehensive electrochemical impedance spectroscopy is required for the analysis of solid cathodes in SOFC), (iv) chemical incompatibility and instability in both oxidizing and reducing environments while matching the coefficient of thermal expansion (CTE) in the interconnects in order to sustain large number of thermal cycling during the operation of SOFC, and (v) isolation of the fuel and oxidizing gases while matching the CTE of the anode, cathode and interconnects, using sealant. Moreover, the glass-transition of sealant dictates the maximum allowable working temperature of SOFC. Thus, the necessitated temporal progress in material selection along with a detailed insight into the conceptual role of thermodynamics and kinetics of surface/cell reactions, effect of phases and microstructure on conductivity, fuel flexibility and deterioration in performance of individual fuel cell components, and evolution of new materials are coherently presented. This article provides a comprehensive review with respect to the structure, chemistry, design and selection of materials, underlying mechanisms, and performance of each SOFC component, and it opens up the future directions towards pursuing SOFC research.

Alka Gupta

Papers

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

Doped zirconia and ceria-based electrolytes for solid oxide fuel cells: a review

Effect of sintering on mechanical properties of ceria reinforced yttria stabilized zirconia

Primary central nervous system lymphoma: a study of clinicopathological features and trend in western India.

Progress in Material Selection for Solid Oxide Fuel Cell Technology: A Review