Sr‐ and Ni‐Doped LaCoO3 and LaFeO3 Perovskites: New Cathode Materials for Solid‐Oxide Fuel Cells

Abstract

An improved cathode material f or a solid-oxide fuel cell would be a mixed electronic and oxide-ion conductor with a good catalytic activity for oxygen reduction at an operating temperature 7', 700°C and a thermal expansion matched to that of the electrolyte and interconnect. We report on the properties of r-and Ni-doped LaCoO3 and LaFeO3 perovskites that meet these criteria. Single-phase regions were determined by X-ray diffraction, and thermogravimetric analysis measurements were used to obtain the temperatures above which oxygen loss, and hence oxide-ion conductivity, occurs. The conductivity and Seebeck measurements indicate the coexistence of both p-type and n-type ,polaronic charge carriers resulting from an overlap of the Ni'17Ni2 redox couple with the low-spin/intermediate-spin Co' /Co1° and hiqh-spin Fe47Fe2' redox couples. Motional enthalpies Hm = 0.03, 0.02, and 0.08 eV, respectively, were estimated for Ni , Co"', and Fe4 polarons. Optimal compositions have percolation pathways between dopants. Comparisons with transport data for the conventional cathode materials La1SrCoO,_8 and La1Sr MnO, indicate superior cathode performance can be expected.

Mesoporous Silica Particles as Templates for Preparing Enzyme‐Loaded Biocompatible Microcapsules

“…[7,8] The second entails loading target materials into preformed LbL-assembled polyelectrolyte microcapsules by altering the shell permeability with, for example, pH. [9] A key limitation of the first method is the restricted number of materials that can be crystallized for encapsulation, while low degrees of loading (particularly for larger biomacromolecules) and poorly reproducible data limit the microcapsule postloading method. [10] In this study, we report an alternative, facile process for encapsulating biomacromolecules within polyelectrolyte microcapsules using mesoporous silica (MS) spheres as sacrificial templates for both enzyme immobilization and polyelectrolyte multilayer capsule formation.…”

Thermal evolution of the crystal structure of the orthorhombic perovskite LaFeO3

“…The series of lanthanide orthoferrites LnFeO 3 have been widely studied for a variety of physical and chemical properties, for example magnetism 1 , multiferroicity 2 , catalysis 3 and application in solid-oxide fuel cells 4 . This family also represents a very rich source of information for understanding trends in fundamental perovskite crystallography as a function of A-cation size 5,6 .…”

Fabrication and performance of LaGaO3-Based tubular SOFC’s

“…On the anode side, Ni was similar or slightly better than Co, observed from celll and cell 5. However, Ni-SDC anode (cell 3 in Table 2) did not show the expected advantages, in terms of electrical performance, compared with the Ni anode (cell 2 in Table 2), as described by Huang et al [15].…”