Multi-heteroatom doped vehicle exhaust soot derived nano-onion based economical and efficient electrodes for microbial fuel cell: A waste to wealth strategy

Microbial fuel cell (MFC) is regarded as a clean and renewable source of energy that produces power while also treating wastewater. Vehicle exhaust soot, a known waste and air pollutant, is used as an electrode in MFC and referred to as carbon nanoparticles (CNPs). Microscopy confirmed the presence of concentric nano-onion rings in CNPs. Further, modified heteroatom-doped mesoporous fractal-like CNPs (N-S-CNPs) are used in MFC to treat wastewater and generate electricity as heteroatom-doped carbon has gained recognition as the existence of electron lone pairs which enhance intrinsic and oxygen reduction catalytic activity. The resultant MFC yields an excellent open circuit voltage of 0.8 ± 0.025 V, current density of 9200 ± 100 mA/m² and maximum power density of 2200 ± 50 mW/m², owing to the improved interconnected mass transfer channels, electroactive surface area, hydrophilicity and graphitization of N-S-CNPs with ∼ 70 % COD reduction. The 16 s rRNA sequencing confirmed the existence of five species of bacteria in biofilm; among them, Raoultella ornithinolytica and Serratia marcescens are responsible for forming a thick biofilm. Cytochrome oxidase test confirms Pseudomonas aeruginosa is favourable for quick electron transport. Thus, this study demonstrates that N-S-CNP-based electrodes are inexpensive and efficient and could significantly aid in developing and commercializing MFCs.