Visible light photocatalytic properties of polymorphic brookite titania

Visible light (VL) active titania was prepared via ambient condition sol process. The particles precipitated from titanium tetrachloride solution followed by lattice dehydroxylation using hot $N$-methylpyrrolidone (NMP) yielded a mixed crystal phase of brookite titania with anatase as the minor phase. The mixed phase titania exhibited superior photocatalytic activities for an organic dye and hydrogen evolution from an aqueous solution under $14W$ VL as compared with several other available reference titanias. The superior VL photocatalytic activity may be explained as the effective charge separation by the intercrystalline electron transport from brookite to anatase grains complemented by the strong VL absorption by the nitrogen species in NMP. The probable electron transport mechanism is illustrated.