Dual gradient design of bioanode for significant bioelectrochemical improvement of microbial fuel cells

Bioelectricity generation by microbial fuel cells (MFCs) has become particularly appealing due to its vast potential in energy production, pollution treatment, and resource utilization. However, developing high-performance bioanodes for bioelectricity generation remains a significant challenge. Herein, taking carbon felt (CF) as the model electrode, we first improved the conductivity of CF by modification with copper sulfide (CuS@CF), and the electron shuttle pair of S 0 /S 2− enhanced extracellular electron transfer process. Then, combining the modification of CF by dopamine (PDA@CF) for hydrophilicity, a novel dual gradient bioanode was designed with the three-layer structure of CF-PDA@CF-CuS@PDA@CF, effectively modulating electroactive biofilm growth. The innovative gradient design optimized bacterial cell adhesion, promoting a controlled bottom-up biofilm growth and circumventing the top growth issue. This approach had led to an MFC with the dual gradient bioanode that achieved a high power density of 18.25 ± 2.67 W/m 3 , ranking among the highest reported to date for MFCs with three-dimensional structured bioanodes. Our findings contribute to a deeper understanding of biofilm-anode interactions and offer insights for the rational design and modification of electrode materials in bioenergy recovery and storage.