Iodine doped anatase TiO2 photocatalyst with ultra-long visible light response: correlation between geometric/electronic structures and mechanisms

Abstract

We report that surface iodine doped TiO₂ with coexisting atomic configurations of iodine dopant, I–O–I and I–O–Ti structures, exhibits an extended absorption edge up to 800 nm. Furthermore, photocatalytic activity investigations confirm the efficient generation of important oxidative species ˙OH radicals in photocatalysis oxidation processes beyond 600 nm. It is theoretically found that iodine atoms prefer to be doped within the surface due to the strong I–O repulsion. I-doping in the surface led to little change in its intrinsic bandgap, but the distribution and occupation of localized states of iodine strongly depend on the surface iodine configurations. The latter is responsible for the wider range visible light response exhibited in anatase TiO₂ with the coexistence of I–O–I and I–O–Ti structures. The coexistence of I–O–I and I–O–Ti structures can distinctly change the surface structure due to the release of local strain energies.