Fuel heterogeneity in solid oxide carbon fuel cells: according to the internal gasification of carbon

摘要

In solid oxide carbon fuel cell, provided oxygen gas (O2) to a cathode turns into the form of oxide ion (O2-), which later reaches an anode surface through defects within a solid oxide electrode. Basically, the resultant electrochemical reaction with carbon on anode surface happen. In fact, within an anode chamber, various further oxidizable gas molecules could be produced with the aid of internal gasification, and the further oxidizable gas molecules can be employed as fuel in solid oxide carbon fuel cells. The further oxidizable gas molecules could take part in the electrochemical reaction and a gas-state oxidizable material is more readily reachable to triple phase boundary (TPB), and hence rendering higher performance. In this sense, it is crucial and important to know how gaseous molecules are generated and what kind of molecules are produced. According to the origination of the generation of gas molecules, gasification reactions can be classified into two: internal gasification around solid fuel within an anode chamber without the contact to anode surface and internal gasification occurring near TPBs. The former is attributed to various gas molecules within an anode chamber. Apart from the ideal case, having extremely high carbon purity and perfect air-seal, in fact, an anodic atmosphere is not only governed by carbon-oxygen speciation but also with partial pressure of H2, steam, hydrocarbons, etc. This partial pressure could either be utilized as fuel or initiate further internal gasification. The latter occurs due generally to reverse Boudouard reaction (RBR), which substantially fosters the generation of CO at the elevated temperature. This study shows the evidences of two different gasification reactions and demonstrates a mechanism.