Tailoring Iron-Ion Release of Cellulose-Based Aerogel-Coated Iron Foam for Long-Term High-Power Microbial Fuel Cells

The presence of iron (Fe) has been found to favor power generation in microbial fuel cells (MFCs). To achieve long-term power production in MFCs, it is crucial to effectively tailor the release of Fe ions over extended operating periods. In this study, we developed a composite anode (A/IF) by coating iron foam with cellulose-based aerogel. The concentration of Fe ions in the anode solution of A/IF anode reaches 0.280 μg/mL (Fe²⁺ vs. Fe³⁺  = 61%:39%) after 720 h of aseptic primary cell operation. This value was significantly higher than that (0.198 μg/mL, Fe²⁺ vs. Fe³⁺  = 92%:8%) on uncoated iron foam (IF), indicating a continuous release of Fe ions over long-term operation. Notably, the resulting MFCs hybrid cell exhibited a 23% reduction in Fe ion concentration (compared to a 47% reduction for the IF anode) during the sixth testing cycle (600–720 h). It achieved a high-power density of 301 ± 55 mW/m² at 720 h, which was 2.62 times higher than that of the IF anode during the same period. Furthermore, a sedimentary microbial fuel cell (SMFCs) was constructed in a marine environment, and the A/IF anode demonstrated a power density of 103 ± 3 mW/m² at 3240 h, representing a 75% improvement over the IF anode. These findings elucidate the significant enhancement in long-term power production performance of MFCs achieved through effective tailoring of Fe ions release during operation.