Lightweight, conductive hollow fibers from nature as sustainable electrode materials for microbial energy harvesting

Electrode materials with high specific surface area (area per volume or weight) and high conductivity are crucial for high power generation in microbial fuel cells (MFCs). In this paper, a novel hollow natural fiber template (kapok) is introduced to serve as the MFC anode. Advanced microscopy shows that the unique hollow structure doubles the anode active bacterial colonization surface area and for the first time provides double surfaces for microbial colonization through both internal and external surfaces. The high conductivity of hollow kapok fiber was directly achieved via carbonization. The power density of the anode comprised of carbonized hollow fibers (104.1mW g^-1) is orders of magnitude higher than traditional solid fiber electrode (5.5mW g^-1) on weight basis. These results demonstrated that with the same amount of material, generally measured in weights in engineering practice, this sustainable natural kapok fiber provides great advantages in improving MFC system performance and reducing cost.