Tailoring electrochemically-active biofilm activity grown on binder-free hierarchical core-shell CoFe2O4@NiMoO4 nanocomposite-modified carbon-felt bioanodes for high-efficiency microbial fuel cells

In light of the increasing difficulties posed by the high energy demand and environmental degradation, it becomes evident that there is a pressing need to create economically-feasible and ecologically-acceptable energy solutions to fulfill the requirements of low-carbon development. Microbial fuel cells (MFCs) are one of the recently developed electrochemical-based technologies that use anode-respiring bacteria (ARB) to convert chemical energy stored in various waste streams into renewable electricity. Nevertheless, the extracellular electron transfer (EET) between ARB and the anode surface represents a challenge for the scaling up and commercialization of MFCs. In this study, we aim to enhance the efficiency of carbon felt anodes in MFCs by decorating them with hierarchical cobalt ferrite@nickel molybdate (CoFe 2 O 4 @NiMoO 4 ) nanocomposite. The main goal is to examine whether or not CoFe 2 O 4 @NiMoO 4 nanocomposite could improve the EET rate and the biofilm structure, resulting in higher MFC performance. Our results revealed that MFCs equipped with CoFe 2 O 4 @NiMoO 4 nanocomposite (CF@CoFe 2 O 4 @NiMoO 4 -MFC) exhibited a maximum power density of 1100 ± 50 mW/m 2 , which was much higher than that achieved by MFCs with CoFe 2 O 4 nanoparticles (780 ± 42 mW/m 2 ) and control MFCs (640 ± 22 mW/m 2 ). This high energy recovery is likely due to the enhanced electrochemical catalytic activity, EET rate, and organic matter biodegradation in MFCs having anodes modified with CoFe 2 O 4 @NiMoO 4 nanocomposite. More importantly, we observed that CoFe 2 O 4 @NiMoO 4 stimulated the selective enrichment of ARB, with the relative abundance of Geobacter was approximately 3.6-fold higher than that of control MFCs, implying efficient interfacial electron transfer between ARB and modified anodes with minimal energy loss. Our results provide insights into developing novel MFC anode materials for achieving high-performance resource recovery from wastewater through in-situ decoration of anode electrodes with nanomaterials. This improvement is mainly attributed to enhancing their electrochemical conductivity, active surface area, biocompatibility, and chemical and mechanical stability. • A 3D hierarchical porous free-binder CoFe 2 O 4 @NiMoO 4 anode is developed for MFCs. • Tailoring interfacial property of anode using CoFe 2 O 4 @NiMoO 4 nanocomposites. • Enhanced EET rate, COD removal, and coulombic efficiency after anode modification. • CoFe 2 O 4 @NiMoO 4 stimulated ARB formation and reduced interfacial EET resistance. • Achieved a high power density of 1100 mW/m 2 and a COD removal rate of 94 %.