Abstract
This paper reports a simple, biogenic and green approach to obtain narrow band gap and visible light-active TiO2 nanoparticles. Commercial white TiO2 (w-TiO2) was treated in the cathode chamber of a Microbial Fuel Cell (MFC), which produced modified light gray TiO2 (g-TiO2) nanoparticles. The DRS, PL, XRD, EPR, HR-TEM, and XPS were performed to understand the band gap decline of g-TiO2. The optical study revealed a significant decrease in the band gap of the g-TiO2 (Eg = 2.80 eV) compared to the w-TiO2 (Eg = 3.10 eV). The XPS revealed variations in the surface states, composition, Ti4+ to Ti3+ ratio, and oxygen vacancies in the g-TiO2. The Ti3+ and oxygen vacancy-induced enhanced visible light photocatalytic activity of g-TiO2 was confirmed by degrading different model dyes. The enhanced photoelectrochemical response under visible light irradiation further supported the improved performance of the g-TiO2 owing to a decrease in the electron transfer resistance and an increase in charge transfer rate. During the TiO2 treatment process, electricity generation in MFC was also observed, which was ~0.3979 V corresponding to a power density of 70.39 mW/m2. This study confirms narrow band gap TiO2 can be easily obtained and used effectively as photocatalysts and photoelectrode material.
Highlights
Since 1972, titanium dioxide (TiO2) has been recognized as a potential photocatalyst by researcher’s worldwide[1]
The modification process was achieved in Microbial Fuel Cell (MFC), which can produce an array of defects or disorder in the TiO2 nanoparticles, by this means, imparting novel characteristics, such as a reduced band gap, rapid charge carrier movements, and visible light-induced photocatalytic activities
The k value for the degradation of brilliant blue G (BB) was 0.0028/h and 0.02284/h for white TiO2 (w-TiO2) and gray TiO2 (g-TiO2) respectively, whereas it was 0.0003/h and 0.0048/h for degradation of Methyl orange (MO) by w-TiO2 and g-TiO2, respectively. These results clearly show that g-TiO2 has higher k values for the degradation of Congo red (CR), methylene blue (MB), BB, and MO compared to w-TiO2
Summary
Since 1972, titanium dioxide (TiO2) has been recognized as a potential photocatalyst by researcher’s worldwide[1]. Researchers used hydrogenation and other techniques to produce a black, red, blue form of TiO2 by introducing disorder, which absorbs light in the UV, visible and near infrared regions of the spectrum[6,7,8,9] This increases the amount of solar light absorption of the black, red, and blue TiO2, which can be used to generate hydrogen gas and be applied in other visible light-induced applications, such as environmental remediation[6,7,8,9,23,24]. Researchers have found that the hydrogenation process produces disorder in the surface layer of the TiO2 nanocrystals Based on these studies, researchers have suggested that the hydrogen ‘mops up’ broken titanium and oxygen bonds, forming new bonds that lower the band gap to the near infrared region[23,24,25,26,27,28]. Compared to conventional TiO2 and other metal oxide materials, it exhibits significantly higher efficiency under the same conditions[6]
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