Análisis de materiales catódicos de estructura perovskita para celdas de combustible de óxido sólido, sofc's

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Abstract

Las celdas de combustible convierten directa y eficientemente la energía química de un combustible en energía eléctrica. De los diversos tipos de celdas de combustible, las de óxido solido (SOFC), combinan las ventajas en generación de energía ambientalmente benigna con la flexibilidad del combustible. Sin embargo, la necesidad de elevadas temperaturas de funcionamiento (800-1000°C) se ha traducido en altos costos y grandes retos en relación a la compatibilidad para los materiales catódicos. Como consecuencia, se han realizado importantes esfuerzos en el desarrollo de celdas SOFC de temperatura intermedia (500-700°C). Un obstáculo clave para su funcionamiento en este rango de temperatura, es la limitada actividad de los tradicionales materiales catódicos para la reducción electroquímica de oxígeno. En este artículo, se analiza el progreso de los últimos arios en cátodos para celdas SOFC de estructura perovskita (ABO3), mas eficientes que el tradicionalmente usado La1-xSr xMnO3- δ (LSM) o (La,Sr)CoO3. Tal es el caso de los conductores mixtos (MIEC) de estructura doble perovskita (AA'B2O5+δ) utilizando diversos elementos de dopaje como La, Sr, Fe, Ti, Cr, Sm, Co, Cu, Pr, Nd, Gd, Dy, Mn, entre otros, que puedan mejorar el rendimiento operacional de los materiales catódicos existentes, promoviendo el desarrollo de diseños optimizados de celdas SOFC de temperatura intermedia.

Translated abstract

Fuel cells directly and efficiently convert the chemical energy of a fuel into electrical energy. Of the various types of fuel cells, the solid oxide (SOFC), combine the advantages in environmentally benign energy generation with fuel flexibility. However, the need for high operating temperatures (800 - 1000°C) has resulted in high costs and major challenges in relation to the compatibility the cathode materials. As a result, there have been significant efforts in the development of intermediate temperature SOFC (500 - 700°C). A key obstacle for operation in this temperature range is the limited activity of traditional cathode materials for electrochemical reduction of oxygen. In this article, the progress of recent years is discussed in cathodes for SOFC perovskite structure (ABO3), more efficient than the traditionally used La1-xSr xMnO3- δ (LSM) or (La,Sr)CoO3. Such is the case of mixed conductors (MIEC) double perovskite structure (AA'B2O5+δ) using different doping elements as La, Sr, Fe, Ti, Cr, Sm, Co, Cu, Pr, Nd, Gd, dy, Mn, among others, which could improve the operational performance of existing cathode materials, promoting the development of optimized intermediate temperature SOFC designs.

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A high-performance cathode for the next generation of solid-oxide fuel cells.

Zongping Shao, Sossina M Haile (2004)

Fuel cells directly and efficiently convert chemical energy to electrical energy. Of the various fuel cell types, solid-oxide fuel cells (SOFCs) combine the benefits of environmentally benign power generation with fuel flexibility. However, the necessity for high operating temperatures (800-1,000 degrees C) has resulted in high costs and materials compatibility challenges. As a consequence, significant effort has been devoted to the development of intermediate-temperature (500-700 degrees C) SOFCs. A key obstacle to reduced-temperature operation of SOFCs is the poor activity of traditional cathode materials for electrochemical reduction of oxygen in this temperature regime. Here we present Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-delta)(BSCF) as a new cathode material for reduced-temperature SOFC operation. BSCF, incorporated into a thin-film doped ceria fuel cell, exhibits high power densities (1,010 mW cm(-2) and 402 mW cm(-2) at 600 degrees C and 500 degrees C, respectively) when operated with humidified hydrogen as the fuel and air as the cathode gas. We further demonstrate that BSCF is ideally suited to 'single-chamber' fuel-cell operation, where anode and cathode reactions take place within the same physical chamber. The high power output of BSCF cathodes results from the high rate of oxygen diffusion through the material. By enabling operation at reduced temperatures, BSCF cathodes may result in widespread practical implementation of SOFCs.