Oxygen reduction reaction on FeNC catalysts- Identifying the contribution of iron environments to the direct and indirect reaction pathway

FeNC catalysts are promising catalysts for the oxygen reduction reaction (ORR) in fuel cells while their stability need to be improved. Due to their heterogeneous composition, it is difficult to discriminate the contribution of the various iron sites to the activity and degradation. During the ORR, oxygen is either reduced to water or to hydrogen peroxide (H2O2). It is suggested that H2O2 formation is one of the main reasons for the instability. It’s relevance for degradation might decrease, when the catalyst is capable of the further reduction of hydrogen peroxide. In this beam time, we will explore the potential induced changes of iron sites at different conditions to identify which iron sites contribute to which step(s) of the ORR mechanism. Complementary to XAS and XES, the samples will be probed at the same conditions by in situ Mössbauer spectroscopy. Data interpretation is assisted by theoretical calculations.