Cascade electronic band structured zinc oxide/bismuth vanadate/three-dimensional ordered macroporous titanium dioxide ternary nanocomposites for enhanced visible light photocatalysis

Ternary zinc oxide/bismuth vanadate/three-dimensional ordered macroporous titanium dioxide (ZnO/BiVO₄/3DOM TiO₂) heterojuncted nanocomposites with cascade electronic band structures were successfully designed and synthesized for visible light photodegradation of two different molecules: Rhodamine B (RhB) and Tartrazine. The photocatalytic active species have been investigated by using electron scavenger (AgNO₃) and hole scavenger (Triethanolamine: TEOA). The band edge positions of each component in tenary nanocomposites have been measured by using photoelectrochemical Mott-Schottky method and valence band XPS (VB-XPS) spectroscopy. Within the heterojunction, charges are favorably and spatially separated through the gradient potential at the interfaces. This largely suppresses the recombination of photogenerated electrons and holes. Furthermore, 3DOM inverse opal structure is beneficial for high diffusion efficiency and highly accessible surface area of reactants and light and multiple scattering for light harvesting. Consequently, these heterojuncted nanocomposites exhibit highly enhanced photocatalytic performance compared with pure BiVO₄ nanostructure, and binary BiVO₄/3DOM TiO₂, ZnO/BiVO₄ nanocomposites. A detailed mechanism of charge transfer is proposed for these ternary ZnO/BiVO₄/3DOM TiO₂ nanocomposites on the basis of a large series of spectroscopic and photocatalytic results. Our work demonstrates clearly that coupling multicomponent semiconductors with different energy levels of conduction and valence bands can significantly increase the photogenerated charge carriers through the efficient charge separation across their multiple interfaces. This work gives some new ideas on developing new visible light responsive nanocomposites for highly efficient solar energy utilization.