A single-material strategy: graphene sponge bioanode and cathode for Shewanella oneidensis MR-1 microbial fuel cells

Abstract

Microbial fuel cells (MFCs) enable conversion of organic matter chemical energy to electricity and provide a great opportunity to upscale green energy production. However, fabricating MFCs with high power output demands strong electrode surface modification with metal nanostructures, for both the anode and cathode. Here, we propose a rational strategy to use different functionalities of graphene sponge in Shewanella oneidensis MR-1 MFCs. In such a fuel cell, a graphene sponge functions as a bioanode and an oxygen reduction reaction (ORR) catalyst. The ORR activity of the graphene reaches 98 mV dec⁻¹, which is comparable to that of bare Pt electrodes. The maximum power density is 184 μW cm⁻², and the current density is 753 μA cm⁻², which is comparable with MFCs based on a Pt/C cathode (50 μW cm⁻² and 280 μA cm⁻²). Furthermore, the MFC equipped with the free-standing graphene electrodes has a coulombic efficiency of 70%.