Air-breathing cathodes for microbial fuel cells based on iron-nitrogen-carbon electrocatalysts

This work reports the development of an iron-nitrogen-carbon electrocatalyst (Fe-N-C) synthesized by functionalization of carbon support using low-cost Fe- and N-based precursors in a wet impregnation procedure followed by a pyrolysis treatment under an inert atmosphere. Structure and surface chemistry were investigated by Raman and X-ray photoelectron spectroscopy (XPS), which indicated an efficient interaction of precursors with the carbon support during the wet-impregnations step, which allows obtaining a carbonized material with a high content of active sites based on Fe-N_x moieties. This led to Fe-N-C materials with high catalytic activity towards oxygen reduction at neutral pH, as demonstrated by cyclic voltammetry (CV) and hydrodynamic linear sweep voltammetry with rotating ring disk electrode (LSV-RRDE). The Fe-N-C electrocatalyst was incorporated in air-breathing cathodes and performance was optimized in terms of oxygen reduction activity and stability. Such cathodes were assembled in single-chamber microbial fuel cell prototypes, and electrical power and voltage generation were evaluated over time.