Manganese-polypyrrole-carbon nanotube, a new oxygen reduction catalyst for air-cathode microbial fuel cells

► We synthesized cost-effective manganese-polypyrrole-carbon nanotube composite successfully. ► We characterized the manganese-polypyrrole-carbon nanotube composite comprehensively. ► Manganese-polypyrrole-carbon nanotube composite catalyzed oxygen reduction effectively. ► Manganese-polypyrrole-nanotube composite showed good activity as cathode catalyst in air-cathode microbial fuel cells. ► Stability of manganese-polypyrrole-carbon nanotube composite was found to be remarkably good.