Nitrogen doping of TiO2 nanosheets greatly enhances bioelectricity generation of S. loihica PV-4

Abstract The performance of TiO2 nanosheets (TiO2-NSs) modified carbon paper anode (TiO2-NSs/CP) in S. loihica PV-4 inoculated MFCs is greatly improved by intentional N doping of TiO2-NSs to modulate its electronic properties. TiO2-NSs/CP is calcined in NH3 atmosphere at different temperatures (T = 400, 500, 600 and 700 °C) to obtain N doped anodes (T-NTiO2-NSs/CP, T represents temperature), in which 600-NTiO2-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 TiO2-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 NH3 atmosphere keep surface morphology and bio-affinity of the electrode. The midpoint potential Em (−0.29 V) of outer membrane c-type cytochromes (OMCs) at 600-NTiO2-NSs/CP anode is in accordance with that at TiO2-NSs/CP. However, 600-NTiO2-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.