1. Introduction to Gas Transport in Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) produce electricity by oxidizing fuel gases. The biggest characteristic of SOFCs is their high energy conversion efficiency, up to 60–80 % in theory, since the conversion efficiency is not limited by the Carnot cycle due to the absence of combustion in SOFC devices. Other advantages of SOFCs include fuel flexibility, low emission, long-term stability, and relatively low cost. The major challenge associated with SOFCs is their high operating temperatures, typically above 500 °C. For SOFCs to find a large range of applications for electricity generation in the twenty-first century, numerous efforts are needed to lower the operating temperatures and to enhance the practical conversion efficiency at moderate operating temperatures. The key is to improve mass transfer involved in SOFCs. Since SOFCs operate with gaseous fuels and oxidants, gas transport in the porous electrodes largely influences their performance. In this chapter, a brief introduction to SOFCs will be first given. The main issues to be solved, gas transport phenomenon, as well as the scientific problems in this field will then be depicted in later chapters.