Abstract
Over the past decade, the doping of nonmetal elements in wide band-gap semiconductors such as TiO2 has been intensively investigated as an effective strategy of expanding the responsive solar spectrum of pristine semiconductors toward visible region. This chapter gives a review of this highly hot research topic. The fundamental principles involved and basic approaches are initially described. A range of nonmetal dopants are subsequently detailed with examples showing their effect on the photocatalytic performance such as pollutant degradation and water splitting under visible light. The problems simultaneously introduced by doping are also discussed.