SURFACE REACTION OF NONSTOICHIOMETRIC OXIDE WITH OXYGEN GAS

摘要

The cathode performance in solid oxide fuel cell (SOFC) is getting increased attention, due to higher total efficiency. The direction to lower operation temperature is of essential importance for the next generation SOFC. The cathode reaction is estimated as the slowest step for conventional SOFC using O~(2-) ion conductor as a solid electrolyte, when the operation temperature is reduced. The rate-determining step (RDS) of highly reactive oxide cathodes known today, such as La_(1-x)Sr_xCoO_3 (LSC), La_(1-x)Sr_xCo_(1-y)Fe_yO_3(LSCF), and Ba_(1-x)Sr_xCo_(1-y)Fe_yO_3 (BSCF), is the oxygen reduction reaction (ORR) at surface. Although the overall reaction is expressed as 1/2O_2(g) + Vo → O_o + 2h, its elementary RDS for ORR is still unclear to date. In the present report, the authors summarize our experimental approach using dense oxide cathode films of LC, LSC with very thin surface modification layer with variable La(+Sr)/Co ratios and, and Pr_6O_(11) thin film cathode. In addition, the ab initio molecular dynamics (ai-MD) simulation for the oxygen gas splitting reaction on NiO surface will be discussed, in addition to experimental study using electron spectroscopy.