Nitrogen doped titanium dioxide (N-TiO2): Electronic band structure, visible light harvesting and photocatalytic applications

Photocatalysis is considered as a promising technique to mineralize organics from air and water utilizing semiconductor metal oxide under solar energy. Nitrogen doped titanium dioxide (N-TiO2) has attracted researchers' much attention due to its ability to absorb visible spectrum by lowering the band gap of pristine TiO2 as it is accepted as a wide band gap material and has no sufficient ability to absorb visible energy. The N doping methods in TiO2 and the resulting structural characteristics, light absorption behavior, charge-carrier nature etc. of N-TiO2 continue to be extensively researched. N-TiO2 demonstrated extended broad absorption of solar spectrum which is the source of energy leading to photocatalytic mineralizing reactions and showed enhanced photocatalytic activity (PCA) rather than pristine TiO2 under visible light. In depth attention has been given in this review on the synthesis methods of N-TiO2 and its development towards environmental application and characterization techniques including electronic state of N in TiO2 lattice as well as band structure of pristine TiO2 due to doping of N and its consequences in absorbing energy, mode of application techniques in degrading organic pollutants coupled with mechanism. Prospects and future directions are also presented on the N-TiO2 research and its development in the environmental remediation to decompose organic pollutants under visible illumination.