Effect of fiber diameter on the behavior of biofilm and anodic performance of fiber electrodes in microbial fuel cells

[Display omitted] ► Simple fixation and dehydration method is applied on biofilms and original biofilm morphology in fiber anode is obtained. ► The morphologies of biofilms in anodes are changed from porous to continuous solid with fiber size decreasing to ∼1μm. ► The current density generated by the continuous solid biofilms increases linearly with increase of biofilm thickness. ► Fiber anode with fiber diameter around the size of the dominant microorganisms generates the highest current density. A series of fiber electrodes with fiber diameters ranging from about 10 to 0.1μm were tested as anodes in microbial fuel cells to study the effect of fiber diameter on the behavior of biofilm and anodic performance of fiber electrodes. A simple method of biofilm fixation and dehydration was developed for biofilm morphology characterization. Results showed that the current density of fiber anodes increased until the fiber diameter approached 1μm which was about the length of the dominant microorganisms in biofilm. The highest current density was 3.08mAcm−2, which was obtained from fiber anode with high porosity of over 99% and fiber diameter of 0.87μm. It was believed that the high current density was attributed to the high porosity, as well as proper fiber diameter which ensured formation of thick and continuous solid biofilms.