Microbial fuel cell assisted band gap narrowed TiO2 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 2 nanoparticles. Commercial white TiO 2 ( w -TiO 2 ) was treated in the cathode chamber of a Microbial Fuel Cell (MFC), which produced modified light gray TiO 2 ( g -TiO 2 ) nanoparticles. The DRS, PL, XRD, EPR, HR-TEM, and XPS were performed to understand the band gap decline of g -TiO 2 . The optical study revealed a significant decrease in the band gap of the g -TiO 2 (E g = 2.80 eV) compared to the w -TiO 2 (E g = 3.10 eV). The XPS revealed variations in the surface states, composition, Ti 4+ to Ti 3+ ratio, and oxygen vacancies in the g -TiO 2 . The Ti 3+ and oxygen vacancy-induced enhanced visible light photocatalytic activity of g -TiO 2 was confirmed by degrading different model dyes. The enhanced photoelectrochemical response under visible light irradiation further supported the improved performance of the g -TiO 2 owing to a decrease in the electron transfer resistance and an increase in charge transfer rate. During the TiO 2 treatment process, electricity generation in MFC was also observed, which was ~0.3979 V corresponding to a power density of 70.39 mW/m 2 . This study confirms narrow band gap TiO 2 can be easily obtained and used effectively as photocatalysts and photoelectrode material.