Chemical Etching of TiO<sub>2</sub> Nanorods Greatly Improves Current Generation of <i>S. loihica</i> PV-4 on a Carbon Paper Electrode

Abstract

Anode surface plays important role for extracellular electron transfer (EET) of exoelectrogenic microbes in microbial fuel cell (MFC). In this report, the electrochemical performance of a TiO2nanorod array modified carbon paper electrode (TiO2NRs/CP) is greatly improved by controlled chemical etching process. The etching process keeps the array morphology but yields obvious hollows on tops of TiO2nanorods. The etched electrode (TiO2NRs-HOT/CP) exhibits better hydrophilicity than carbon paper (CP) and TiO2NRs/CP electrode as seen from smaller contact angle (CA) and more attached microbes S.loihica PV-4. Meanwhile, the hollows allow higher local concentration of microbial self-secreted flavins that can act as electron mediators for interfacial electron transfer of PV-4 through in-direct pathway. Accordingly, PV-4 produces larger current density at TiO2NRs-HOT/CP electrode with maximum current density of 0.038 mA cm–2, which was much higher than that at CP electrode, and almost five times higher than that at un-etched TiO2NRs/CP electrode.