Application of Bacterial Biocathodes in Microbial Fuel Cells

This review addresses the development and experimental progress of biocathodes in microbial fuel cells (MFCs). Conventional MFCs consist of biological anodes and abiotic cathodes. The abiotic cathode usually requires a catalyst or an electron mediator to achieve high electron transfer, increasing the cost and lowering the operational sustainability. Such disadvantages can be overcome by biocathodes, which use microorganisms to assist cathodic reactions. Biocathodes are feasible in potentiostat-poised half cells, but only very few studies have investigated them in complete MFCs. The classification of biocathodes is based on which terminal electron acceptor is available. For aerobic biocathodes with oxygen as the terminal electron acceptor, electron mediators, such as iron and manganese, are first reduced by the cathode (abiotically) and then reoxidized by bacteria. Anaerobic biocathodes directly reduce terminal electron acceptors, such as nitrate and sulfate, by accepting electrons from a cathode electrode through microbial metabolism. Biocathodes are promising in MFCs, and we anticipate a successful application after several breakthroughs are made.