Synthesis and fabrication of palm kernel shell-derived modified electrodes: A practical step towards the industrialization of microbial fuel cells

Bioenergy generation and pollution bioremediation using microbial fuel cells (MFC) are the most eco-friendly and sustainable bioelectrochemical methods. The anode material is a major problem in transferring electrons effectively. This condition has the potential to significantly reduce MFC's performance and economic value. In this study, palm kernel shell-derived graphene oxide derivative materials are used as anode electrode, along with metal oxide modifications. This study hopes to improve electron transport as well as formaldehyde (FA) bioremediation efficiency by modifying the palm kernel shell-derived anodes. The anode was fabricated by incorporating palm kernel shell (PKS) waste rGO with metal oxides (TiO₂ and ZnO) as modifiers. The anodes were identified as PKS-rGO, PKS-rGO/TiO₂, and PKS-rGO/ZnO. PKS-rGO generated a power density of 24.5 mW/m², while the PKS-rGO/TiO₂ composite anode gave a power density of 37.4 mW/m². PKS-rGO/ZnO, on the other hand, had the highest power density of 43.2 mW/m². The current density (CD) followed a comparable trend, with the maximum CD for PKS-rGO/ZnO being 111.1 mA/m². During the anodic biofilm microbial species analysis, the Bacillus siamensis strain and the Brevibacillus parabrevis strain were found to be exoelectrogens. These exoelectrogens are known to transfer electrons to the anode either directly or via their conductive matrix in the form of nanowires or pilli. The maximum bioremediation efficiency in the MFC operation was 87 % for PKS-rGO, 91.70 % for PKS-rGO/TiO₂, and 93 % for PKS-rGO/ZnO. The results of the anode biofilm and SEM analysis clearly demonstrate that the fabricated anodes are highly biocompatible with the microbial biofilms. This study further suggests future research prospects for anodic microbial species mortality and organic substrates in MFC.