Carbon black nanoparticles embedded in anodic biofilm to facilitate electron transfer in bio-electrochemical systems

Bioelectrochemical systems (BES), particularly microbial fuel cells (MFC) and microbial electrolysis cells (MECs), are emerging technologies that can clean wastewater and generate currents or biohydrogen. The anode material, often carbon-based, significantly impacts BES performance. Carbon black (CB) improves electron transfer and current generation by reducing the biofilm resistance. On day 46, MEC with integrated CB (MEC-CB) exhibited significantly higher currents compared to MEC-control (without CB). Linear Sweep Voltammetry (LSV) oxidation currents at 0.8 V were 46.38 ± 7.14 mA for MEC-CB and 9.76 ± 2.95 mA for MEC-control. LSV reduction currents at −0.8 V in MEC-CB were −23.23 ± 2.46 mA, while in MEC-control, it was −5.80 ± 0.96. The highest hydrogen evolution rate was obtained by MEC-CB 1.29 m³m⁻³d⁻¹, compared to MEC-control, which was 0.32 m³m⁻³d⁻¹. The R_BF and Rct, in MEC-CB systems, were 5.75 Ω cm² and 32.58 Ω cm², while in MEC-control systems, it was 16.59 Ω cm² and 41.38 Ω cm², respectively. Chemical oxygen demand (COD) removal and biofilm viability assay results did not show significant differences between the MEC-CB and MEC-control systems. The results of this study demonstrate that MEC-CB, which is biofilm-integrated with CB nanoparticles, exhibits the least biofilm and charge transfer resistance, as well as a stable biofilm as seen by SEM analysis. Based on the electrochemical data, CB improved the conductivity of the biofilm and helped in electron transfer efficiency to the electrode.