The effects of carbon electrode surface properties on bacteria attachment and start up time of microbial fuel cells

Surface roughness, porosity and contact angles of different carbon paper materials (TORAY paper with PTFE from 0% to 60% of and SGL paper with 0% and 20% of PTFE) suitable as electrodes in microbial fuel cells were investigated. The changes of contact angle between dry and clean anode surfaces and the ones after exposure to wastewater were measured using different liquids (pure water and sodium acetate solutions). The results showed that bacterial attachment to the carbon papers caused a significant decrease in the contact angle, shifting the surface property from highly hydrophobic to slightly hydrophobic or even hydrophilic. The quantity of biofilm attached on the anode surface decreased with the increase in PTFE content. Positive correlation between dry biomass content and the amount of pores at the small scale (5-10 μm) was observed. The start up time of MFCs was shortened by using the carbon anodes without PTFE or with low PTFE content (<20 wt%), probably due to the easier biofilm attachment on the surface. On the contrary, the carbon anodes with high PTFE contents had longer start up time. After several cycles of MFC operation, the performances became similar (20-30 mV of differences) regardless of the carbon anode used.