Abstract
Electrodes based on graphite, graphene, and carbon nanomaterials have been used in the anode chamber of microbial fuel cells (MFCs). Carbon quantum dots (C-dots) are a class of versatile nanomaterials hitherto not reported in MFCs. C-dots previously synthesized from coconut husk were reported to possess hydroxyl and carboxyl functional groups on their surface. The presence of these functional groups on a carbon matrix conferred on the C-dots the ability to conduct and transfer electrons. Formation of silver nanoparticles from silver nitrate upon addition of C-dots confirmed their reducing ability. DREAM assay using a mixed microbial culture containing C-dots showed a 172% increase in electron transfer activity and thus confirmed the involvement of C-dots in supplementing redox activity of a microbial culture. Addition of C-dots as a suspension in the anode chamber of an MFC resulted in a 22.5% enhancement in maximum power density. C-dots showed better performance as electron shuttles than methylene blue, a conventional electron shuttle used in MFCs.
Highlights
Microbial fuel cells (MFCs) are microbe-catalyzed electrochemical systems that can breakdown organic compounds in wastewater and harness the electrons produced in the process
Fourier transform infra red (FTIR) spectrum of the Carbon quantum dots (C-dots) revealed the presence of carboxyl and hydroxyl groups
The C-dots synthesized from coconut husk by hydrothermal treatment were monodisperse in nature and no aggregation was observed
Summary
Microbial fuel cells (MFCs) are microbe-catalyzed electrochemical systems that can breakdown organic compounds in wastewater and harness the electrons produced in the process. The anode chamber of an MFC containing microbes and the substrate (typically in the form of wastewater) is maintained under anaerobic conditions to facilitate the uptake of electrons by the electrode. The protons produced in the process move across a selectively permeable membrane to the cathode chamber containing the terminal electron acceptor. Transfer of electrons from microbes to the anode is a critical step in performance of an MFC (Rabaey et al 2004). Inefficient electron transfer has been an impediment to scaling up MFCs for practical real-world applications (Yuan et al 2011). It is essential to understand the mechanism of electron transfer to and from the small, insoluble molecules that function as electron shuttles (Stams et al 2006) and mediate electron transfer in MFCs
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