Nitrogen-doped carbon dots enhanced pollutant degradation and bioelectricity generation in bioelectrochemical systems

Carbon dots (CDs), which enhance extracellular electron transfer, have huge potential for boosting microbial metabolism within bioelectrochemical systems (BESs). Despite this, accelerated metabolic degradation of contaminants via CD-mediated enhancement of electron transfer in BESs has rarely been reported. In this study, a nitrogen-doped carbon dots (N-CDs) with electron-rich and graphite-like carbon core structure was synthesized by simple hydrothermal technology using 5-hydroxymethylfurfural and o-phenylenediamine as raw materials and applied to BESs. By combining N-CDs with bacterial cell components, an efficient electron transfer pathway was constructed to promote extracellular and intracellular electron transfer. In addition, the treatment effect of the system on different types of pollutants (such as sulfamethoxazole, phenolic compounds and papermaking wastewater) was also tested. The experimental results showed that N-CDs could significantly improve the metabolic activity of microorganisms in BESs. The degradation rate of sulfamethoxazole, phenols and organic matter in papermaking wastewater was 4.4, 3.4 and 1.9 times that of the blank group, respectively. Concurrently, N-CDs significantly enhanced the bioelectricity production of the system. This work is the first to explore in detail the mechanism of N-CDs as an electronic medium to accelerate pollutant degradation and promote bioelectricity generation in BESs, providing new ideas for the development of efficient and environmentally friendly wastewater treatment technologies and renewable energy production programs.