Enhancement of microbial fuel cell performance by anodic communities adaptation and cathodic mixed nickel copper oxides (NiO-CuO) on graphene electrocatalyst

Abstract

Mixed transition metal (Ni & Cu) oxides supported on graphene (NiO-CuO/G) electrocatalyst was fabricated and tested as an efficient and cost-effective cathode for oxygen reduction reaction (ORR) in microbial fuel cells (MFCs). The electrocatalytic activity and selectivity of the NiO-CuO/G for ORR were examined using linear sweep voltammetry measurements (LSV) on a rotating disc electrode (RDE) in pH-neutral electrolyte. In comparison with a benchmark platinum cathode, the NiO-CuO/G showed high selectivity towards the ORR. The analysis of Koutecky-Levich relationship suggests that the electrocatalyst follows the four-electron ORR pathway. NiO-CuO/G cathode in an air-cathode MFC exhibited a slightly lower power density 21.25 mWm− 2 compared to 50.4 mW m− 2 for Pt/C. Both scanning and transmission electron microscope analyses of anodic biofilm showed that a thick biofilm was successfully developed with a rod-like shape. Biochemical characterization of the communities showed that four genera named Escherichia coli (E-coli), Shewanella putrefaciens, Bacillus cereus and Bacillus Thuringiensis/mycoides, which belonging to GammaProteobacteria and Firmicutesphylathatwerethe most abundant bacteria in the anodic biofilm. Our results revealed that NiO-CuO/G cathode demonstrates an enhanced electrocatalytic activity toward ORR in a pH-neutral solution; thus, the newly developed mixed transition metal oxides electrocatalyst can replace other expensive Pt-based catalysts for MFC application.