FeS@rGO nanocomposites as electrocatalysts for enhanced chromium removal and clean energy generation by microbial fuel cell

Bioelectrochemical removal of Cr(VI) and consequent renewable energy generation from wastewater is a promising technology. However, slow reaction kinetics, expensive catalysts, and hydrophobic binders remain a significant challenge for the commercialization of this emerging technology. In the present study, for the first time, graphite felt modified with iron sulfide wrapped with reduced graphene oxide (FeS@rGO) nanocomposites were used as a cathode in a dual-chamber microbial fuel cell (MFC) for concurrent Cr(VI) reduction and power generation. The MFC with FeS@rGO nanocomposites (MFC-FeS@rGO) exhibited 100% Cr(VI) removal efficiency for the concentration of 15 mg/L and also acquired a high reduction rate of 1.43 mg/L/h, which was approximately 4.6 times higher than MFC-blank. MFC-FeS@rGO delivered the maximum power density of 154 mW/m(2), and it was 328% high as that of MFC-blank (36 mW/m(2)). High cathodic coulombic efficiency for MFC-FeS@rGO (61 +/- 0.8%) indicated that the substantial amount of charge produced by exoelectrogens was mainly consumed for Cr(VI) reduction. Overall improved electrochemical performance of MFC-FeS@rGO was attributed to the high conductivity, low internal resistance, and better reaction kinetics of FeS@rGO nanocomposites. This study has demonstrated the highest reduction rate and high power production compared with previous studies, which have used very high concentrations of Cr(VI). Hence, it is expected that current findings will help to scale up the simultaneous Cr(VI) reduction and power generation from real wastewater.