A monolithic three-dimensional macroporous graphene anode with low cost for high performance microbial fuel cells

Abstract

Microbial fuel cells (MFCs), capable of simultaneously degrading substrates and producing bioelectricity, have drawn great attention. However, low power output and high cost have severely hindered their practical application. The present study prepared a monolithic three-dimensional graphene (3D-G) electrode through a self-assembly method. The as-prepared 3D-G electrode featured inflexibility, a crumpled surface, a macroporous structure (with pore spaces of dozens of microns), high specific surface area (188.32 m² g⁻¹), good conductivity and low cost, favoring high bacterial loading capacity and enhancing the extracellular electron transfer (EET) efficiency. Equipped with the prepared 3D-G anode in an air-cathode single chamber MFC reactor, the maximum power density (P_max) increased to 1516 ± 87 mW m⁻² in the 3D-G reactor from 877 ± 57 mW m⁻² in the graphite felt (GF) control and from 584 ± 39 mW m⁻² in the carbon cloth (CC) control after 2 weeks of operation. Moreover, the P_max of the reactor with the 3D-G anode decreased only by 15% after 2 months of operation, which showed durability of the anode due to having macropores which are not easily blocked. Normalized to the cost of the anode, the P_max in the 3D-G reactor was 93 and 133 times those in the GF and CC reactors, respectively. Dynamic analysis results (CV, Tafel and EIS) showed that the 3D-G anode improved the efficiency of EET due to having an appropriate structure and good conductivity. The 3D-G anode, with superior performance and low cost, would powerfully promote the practical and large-scale application of MFCs.