Substantial Enhancement toward the Photocatalytic Activity of CdS Quantum Dots by Photonic Crystal-Supporting Films.

The introduction of photonic crystals (PC) to semiconductors, which usually appear in the form of inverse opal materials, has been proved to be an effective way to enhance the photocatalytic activity, but their enhancement factor is merely two- to fourfold in most previous reports. In this work, a supported thin-film photocatalyst (CdS/SiO2-ETPTA), as a new PC-based catalyst system, is prepared for hydrogen evolution under visible light, which presents an 6.4- to 8.8-fold activity compared to the same CdS quantum dots deposited on a non-PC film. This substantial enhancement originates from the high reflectivity of PCs and absorption of reflected light by CdS, whose absorption edge exactly matches the stopband of PCs. Compared to the traditional inverse opal photocatalysts, the PC-supported photocatalyst possesses many advantages including simplified procedures in synthesis, a substantial enhancement of activity, flexible modification with mature thin-film techniques, good stability, and easy regeneration in reaction.