Visible-light photocatalysis in CdTe nanoflakes with exposed {111} facets and charge separation between polar CdTe {111}surfaces

Abstract

The search for active semiconductor photocatalysts that can utilize adequately solar-energy remains to be an open issue. CdTe nanoflakes and nanowires with a range of texture coefficients of (111) have been synthesized. Photocatalytic activities of the CdTe nanocrystals in degradation of malachite green, methyl orange, acid red 88 and ciprofloxacin can be enhanced by increasing the texture coefficients of (111) and reducing texture coefficient of (220). The exposed polar {111} facets were found to be the active facets, and a charge separation model between polar Cd-CdTe (111) and Te-CdTe (1¯1¯1¯) surfaces is proposed. An internal electric field is created between polar Cd-CdTe (111) and Te-CdTe (1¯1¯1¯) surfaces by the spontaneous polarization, and the internal electric field drives separation of the photoinduced electrons and holes. Therefore, the CdTe nanoflakes with exposed polar {111} facets synthesized by using oleylamine as a morphology controlling agent show superior photocatalytic activity, compared with CdTe nanowires, nanocrystals with irregular shapes and commercial powders as well as CdS branched nanostructures. The charge separation model provides a clear opinion into charge transfer in the semiconductor nanocrystals with exposed active facets, and affords guidance to design more effective photocatalysts, solar cells and other photoelectronic devices.