The solid oxide fuel cell (SOFC) is a solid oxide material is used as the electrolyte, the anode and cathode of the fuel cell. Conventional solid oxide fuel cells can be divided into three layers in the structure, i.e., a porous cathode layer, a dense electrolyte layer and a porous anode layer. The purpose of the selection of the porous structure of the cathode and the anode electrochemical reaction is to increase the interface and increase the apparent current density. The cathode side of the cell through the O2, the fuel gas into the anode-side passage. Where dense electrolyte from conducting O2- (or H +) and the separation of air (oxygen) and fuel gas effect, while the cathode and anode is a place for the battery reaction. Depending on the ion conductive electrolyte, a solid oxide fuel cell can be divided into two categories: an oxygen ion-conductive electrolyte fuel cell and a hydrogen ion (proton) conductive electrolyte fuel cell.

 

 

For the oxygen ion-conductive electrolyte fuel cell, oxygen is reduced to give electrons to become O2- and into the electrolyte in the cathode (air electrode), the fuel gas (such as H2, CO or CH4, etc.) in the anodic oxidation reaction occurs to generate H2O and O2-, CO2 and release of electrons, etc., since the cation concentration gradient across the anode and cathode, O2- continuously migrate through the electrolyte from the cathode to the anode, the anode to release electrons through the external circuit back to the cathode.