Nitrogen doping of TiO 2 nanosheets greatly enhances bioelectricity generation of S. loihica PV-4

The performance of TiO 2 nanosheets (TiO 2 -NSs) modified carbon paper anode (TiO 2 -NSs/CP) in S. loihica PV-4 inoculated MFCs is greatly improved by intentional N doping of TiO 2 -NSs to modulate its electronic properties. TiO 2 -NSs/CP is calcined in NH 3 atmosphere at different temperatures (T = 400, 500, 600 and 700 °C) to obtain N doped anodes (T-NTiO 2 -NSs/CP, T represents temperature), in which 600-NTiO 2 -NSs/CP electrode show best performance with the maximum output power density increased by 196% and 50% compared to that from the bare CP and TiO 2 -NSs/CP electrodes respectively. The surface morphology, structure and electrochemical activity are characterized by FESEM, XRD, Raman, XPS, CVs and EIS. The results show that heating in NH 3 atmosphere keep surface morphology and bio-affinity of the electrode. The midpoint potential E m (−0.29 V) of outer membrane c-type cytochromes (OMCs) at 600-NTiO 2 -NSs/CP anode is in accordance with that at TiO 2 -NSs/CP. However, 600-NTiO 2 -NSs/CP electrode had smaller charge transfer resistance, more positive flat-band potential and larger transient charge storage capacity than untreated electrode due to modulation of the electronic structure via N doping, which all are favorable to interfacial electron transfer from OMCs to underlying electrode. The method is simply and efficient, and could be extended to other nano-semiconductor modified electrodes for superior MFC anodes.