Biofilm evolution and viability during in situ preparation of a graphene/exoelectrogen composite biofilm electrode for a high-performance microbial fuel cell

Abstract

To understand how microbial reduction of graphene oxide (mrGO) influenced the biofilm during the in situ preparation of a graphene/exoelectrogen composite biofilm anode in a microbial fuel cell (MFC), an in situ mrGO-modified anode was fabricated, and the evolution and viability of the anodic biofilm were investigated by sampling the biofilm at different stages of the MFC operation. The total protein, thickness and viability of the anodic biofilm in mrGO-added MFCs were generally lower than that in mrGO-free MFC at the first electricity production cycle (EPC) due to the antibacterial activity of the GO flake. However, the three indicators increased dramatically and were much higher in mrGO-added MFC than in mrGO-free MFC after three EPCs, derived from enhanced bacterial adhesion and accelerated biofilm recovery in the presence of mrGO due to its high specific area for increased biomass attachment and high conductivity for enhanced electron transfer between bacteria and anode. The electricity generation performance of the MFC was found to follow the same trend as biofilm evolution. The power density of the mrGO-modified MFC increased sharply after five electricity production cycles, reaching a maximum value of 1140.63 mW m⁻², which is 65.20% higher than the blank control. This study gives an insight into the interaction between the exoelectrogens and their induced GO reduction which contribute to the understanding of the essence of the process for high-performance MFC application.