Microbial fuel cell assisted band gap narrowed TiO for visible light-induced photocatalytic activities and power generation.

This paper reports a simple, biogenic and green approach to obtain narrow band gap and visible light-active TiO nanoparticles. Commercial white TiO (w-TiO) was treated in the cathode chamber of a Microbial Fuel Cell (MFC), which produced modified light gray TiO (g-TiO) nanoparticles. The DRS, PL, XRD, EPR, HR-TEM, and XPS were performed to understand the band gap decline of g-TiO. The optical study revealed a significant decrease in the band gap of the g-TiO (E  = 2.80 eV) compared to the w-TiO (E  = 3.10 eV). The XPS revealed variations in the surface states, composition, Ti to Ti ratio, and oxygen vacancies in the g-TiO. The Ti and oxygen vacancy-induced enhanced visible light photocatalytic activity of g-TiO was confirmed by degrading different model dyes. The enhanced photoelectrochemical response under visible light irradiation further supported the improved performance of the g-TiO owing to a decrease in the electron transfer resistance and an increase in charge transfer rate. During the TiO treatment process, electricity generation in MFC was also observed, which was ~0.3979 V corresponding to a power density of 70.39 mW/m. This study confirms narrow band gap TiO can be easily obtained and used effectively as photocatalysts and photoelectrode material.