Oxygen reduction reaction catalysts used in microbial fuel cells for energy-efficient wastewater treatment: a review

Microbial fuel cells (MFCs) as an energy-efficient wastewater treatment technology have attracted increasing interest in the past decade. Cathode catalysts for the oxygen reduction reaction (ORR) present a major challenge for the practical applications of MFCs. An ideal cathode catalyst should be scalable, durable, and cost-effective. A variety of non-precious metal catalysts have been developed for MFC applications, including carbon-based catalysts, metal-based catalysts, metal-carbon hybrids, metal-nitrogen-carbon complexes, and biocatalysts. This paper comprehensively reviews these materials with emphasis on their synthesis, performance, durability, and cost. It is anticipated that insights offered in this review could facilitate the development of ORR catalysts for MFC applications towards energy-efficient wastewater treatment.