Advances in carbon-based anode materials for microbial fuel cells

Abstract

The overuse of resources and the frequent occurrence of environmental problems have necessitated the use of sustainable energy technologies. The microbial fuel cell (MFC) is a kind of green energy-generation technology that metabolizes the organic compounds in wastewater by the catalytic oxidation of microorganisms. This new technology provides the dual advantages of cleaning the environment and generating electricity. As MFCs can potentially convert biodegradable and recyclable wastes into clean energy, they are a promising application prospect in environmental treatment and energy utilization. However, the practical applicability of present-day MFCs is limited by their low power-generation efficiency. Anode electrodes can enrich the power generation and electron transfer of microorganisms, but require high polarization, electronic conductivity, and biological compatibility with the fuel cell. Broadly speaking, the anode electrode affects the performance and operating costs of an MFC. Commonly used carbon-based materials include graphite sheets, carbon cloths, carbon paper, and carbon felt. However, most of these materials are two-dimensional structures providing few attachment sites for microorganisms; other materials have few reactive sites, which limits their electrochemical reactive surface areas and slows the initiation of the MFC. Carbon nanomaterials have been extensively researched for their high electrical conductivity, large specific surface area, high porosity, and low cost. All of these properties are demanded in the anode materials of MFCs. This paper summarized and analyzed methods for improving the biological compatibility of electrodes, increasing the adhesion of electrically-producing microorganisms, and improving the reactive activation sites. To this end, it discussed various types of anode electrodes, electrode structure designs, and electrode material modifications. A mechanism that improved the electricity generation performance was also discussed. Finally, carbon-based electrode materials might provide theoretical guidance for preparing anode materials with high electrochemical activity.