Carbon nanodots chelated with metal ions as efficient electrocatalysts for enhancing performance of microbial fuel cell based on sulfate reducing bacteria

We report the electrocatalytic activity of a graphite electrode chemically coated with ultra-small nitrogen-doped carbon nanodots (N-doped C-dots), which formed an intermediate diazo-metal chelate phase. Its performance as cathode for enhanced current production was demonstrated in a dual-chamber microbial fuel cell (MFC) through synergistic cooperation with electroactive biofilm of sulfate-reducing bacteria (SRB) on the anode. For that purpose, the immobilized SRB biofilm on the anode facilitated direct transfer of electrons to the graphite surface by filaments network, known as nano-pili, which provided cell-to-cell link. A significantly improved acceleration of the electrons was measured on the cathode in the presence of chemically conjugated N-doped C-dots chelated with metal ions, because they acted as efficient electrocatalysts for oxygen reduction reaction (ORR) in a neutral phosphate buffer solution. As a result, the power density obtained from the occurred synergistic effect in MFC increased almost double higher than the initial value in the control experiment. The chemical resistance, exploitation life and the easy protocol for fabrication of the reported cathode coated with electrocatalytic nanolayer open up the possibility for new class cheap electrocatalytic electrodes with a wide practical applications in fuel cell engineering and technology.