Effect of active sites poisoning on Fe-N-C ORR platinum group metal-free catalysts operating in neutral media: a rotating disk electrode study

Platinum group metal-free (PGM-free) catalysts are the most promising materials for substituting expensive platinum catalyst for efficient oxygen reduction reaction (ORR), particularly for microbial fuel cells. For these devices contamination due to wastewater is one of the major issues due to the presence of various poisoning anions. The known nitrite contamination effect over PGM-free was studied through rotating disk electrode (RDE) technique in neutral media to understand its patterns. The results were then compared to other contaminants commonly found in wastewater such as chloride (Cl-), perchlorate (ClO4-), and nitrate (NO3-) in the concentration range of 0.05-50 mM. Onset potential (Eonset), half wave potential (E1/2), limiting disk current density (Jlim) and Tafel slopes variations were the parameters exploited to identify specific or unspecific adsorbed contaminants. Chloride and nitrate had no negative effect on ORR performance, while perchlorate slightly reduced the catalyst function with no permanent issues. Durability tests (1000 cycles) were also performed to ensure the stability of the catalyst for relatively long time.