Tailoring the antifouling agent titanium dioxide in the visible range of solar spectrum for photoelectrochemical activity with hybrid DFT & DFT + U approach

Abstract Titanium dioxide (TiO2) doped with several metal dopants has been studied for photoelectrochemical water splitting and as a shielding agent to overcome the impact of biofouling on marine systems. The n-type TiO2 can be potentially used for water splitting; however, its wide band gap, weak light absorption, and low conductivity limit its applications for water splitting. Hybrid density functional theory (DFT) and DFT + U techniques have been used to investigate the structural parameters, light absorption, optical conductivity, thermodynamic stability, position of conduction, and valence-band edge of TiO2 doped with pristine and metal (Co, Fe, Ag, and Rh). The calculated band gap of pristine was 2.99 eV, and it could absorb photon with a wavelength of 414 nm and generate electron–hole pair, which reacted with water molecule and produced hydroxyl and oxygen ions. The presence of hydroxyl and oxygen ions on the pristine surface increased the antibacterial effect, thereby eliminating the biological toxicants in water. The incorporation of dopants, such as Co, Fe, Ag, and Rh, in TiO2 (2.1 %) significantly altered the properties, including the energy band gap from 2.99 eV to 1.25, 1.51, 1.99, and 2.06 eV, respectively. The narrow band gap and modified band positions were attributed to the new electronic states that appeared due to the dopant cations. The doped material showed significant optical absorption and photoconductivity in the entire visible and ultraviolet regions. Conduction- and valence-band edge locations of Ag-TiO2 facilitated water oxidation–reduction process. Moreover, higher negative free energy of Ag-doped TiO2 made it thermodynamically stable than other compounds. Consequently, the use of metal doping in TiO2 enhanced the optical absorption and photoconductivity owing to a lower band gap energy.