Improved electrode performance in microbial fuel cells and the enhanced visible light-induced photoelectrochemical behaviour of PtOx@M-TiO2 nanocomposites

Visible light active PtOx@M-TiO2 and PtOx@P-TiO2 (x=0, 1 and 2) nanocomposites were fabricated via a simple, green and environmentally benign process using an electrochemically active biofilm. The formation of the PtOx@M-TiO2 and PtOx@P-TiO2 nanocomposites was confirmed by X-ray diffraction, ultraviolet visible near infrared spectrophotometry, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of Pt-0, Pt2+. (PtO) and Pt4+ (PtO2) species on the surface of M-TiO2 and P-TiO2. The presence of mixed valence states of PtOx on the surface of the PtOx@M-TiO2 nanocomposite and defect states in M-TiO2 helps absorb visible light more efficiently compared to the PtOx@P-TiO2 nanocomposite. Cyclic voltammetry, electrochemical impedance spectroscopy and linear scan voltammetry confirmed the enhanced photoelectrochemical performance of the PtOx@M-TiO2 nanocomposite compared to the PtOx@P-TiO2 nanocomposite under visible light irradiation. Furthermore, the PtOx@M-TiO2 nanocomposite was used as a cathode material in microbial fuel cells and showed a higher power density compared to the PtOx@P-TiO2 nanocomposite and plain carbon paper due to the high catalytic activity of platinum and defective M-TiO2. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.