Carbon-supported Fe/Mn-based perovskite-type oxides boost oxygen reduction in bioelectrochemical systems

Bimetallic Fe-Mn oxides supported on graphene oxide (GO/FeMnO 3 ) and carbon Vulcan (C/FeMnO 3 ) were synthesized via a low-cost and facile chemical/thermal method. As revealed by SEM images, Fe-Mn oxide nanoparticles were homogeneously dispersed on the surface of the carbon nanostructure; the formation of a prevailing bimetallic FeMnO 3 phase with perovskite structure was clearly indicated by X-ray diffraction and confirmed by X-ray photoelectron spectroscopy. Both composites, GO/FeMnO 3 and C/FeMnO 3 , displayed good catalytic activity towards the oxygen reduction reaction (ORR) in neutral environment, as indicated by cyclic voltammetry, hydrodynamic voltammetry with rotating disk electrode experiments, and electrochemical impedance spectroscopy. In particular, higher porosity and more accessible surface area of C/FeMnO 3 lead to a faster ORR as compared to that of GO/FeMnO 3 . When assembled at the cathode side of a single-chamber air-cathode microbial fuel cell (MFC), C/FeMnO 3 showed higher performance than that obtained with a Pt-based MFC, taken as reference, in terms of voltage and power generation, The application of a stability protocol, developed to simulate MFC operating conditions, also demonstrated an excellent temperature-cycling resistance of C/FeMnO 3 , hence indicating its suitability to substitute Pt at MFC cathodes.