Carbon paper anodes decorated with TiO2 nanowires and Au nanoparticles for facilitating bacterial extracellular electron transfer.

Abstract

Au nanoparticles-composite TiO₂ nanowires (NWs) modified carbon paper (CP) anode was synthesized via the hydrothermal method. Field emission scanning electron microscopy (FESEM) images demonstrate that the modified nanocomposite electrode features a rough and bumpy surface structure. The electrochemical activities of TiO₂-Au/CP and the control electrodes (TiO₂-NWs/CP, Au/CP, CP) for microbial fuel cell (MFC) are investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). When using TiO₂-Au/CP as a bioanode, the maximum power output density of Shewanella loihica PV-4 inoculated MFC increases by 49.7%, 26.5% and 190.6% compared with that when using TiO₂-NWs/CP, Au/CP and bare CP as bioanodes, respectively. CV analysis indicates that TiO₂-Au mediates direct and indirect electron transfer between the electrode and the bacteria, as evidenced by the appearance of redox peaks with mid-point potentials E_m of - 0.305 V and -0.465 V, respectively. The generation of bioelectricity reveals the formation of a biofilm on the electrode surface. Furthermore, compared with the control electrodes, the MFC assembled with a TiO₂-Au anode exhibits a smaller semicircle in the high-frequency region, representing a lower charge transfer resistance (R_ct). The improvement in MFC performance can be attributed to the fact that the combination of TiO₂ and Au enhances the conductivity and electrochemical activity of the electrode, along with its good biocompatibility and large specific surface area, which are favorable for bacterial colonization. Thus, TiO₂-Au/CP serves as an ideal anode material featuring simple synthesis. Additionally, its surface modifier, TiO₂-Au can be extended for the modification of other base electrodes, enabling the acquisition of high-quality anodes for MFCs.