Solid oxide fuel cells (SOFCs) have received considerable interest nowadays, because they promise greater electrical efficiency than that obtained by a conventional heat engine or other types of low temperature fuel cells. Validated mathematical models provide a very powerful tool for the development of improved SOFC designs and operating conditions. From some literature and numerical simulation results, it could be found that the concentration gradient of fuel and oxidant gas is great on the plane which is normal to the SOFC tri-layer, especially in the porous electrode. But the structures in the previous literature and inventions are always focusing on...