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In this study, ZnO/BiOI heterostructures were synthesized by a facile chemical bath method at low temperature. Control of the morphology and constituents of the ZnO/BiOI heterostructures was realized by simply tuning the Bi/Zn molar ratios. The resulting ZnO/BiOI heterostructures exhibited high photocatalytic activity in the degradation of methyl orange under visible-light irradiation. The high photocatalytic activity of the ZnO/BiOI heterostructures was first attributed to their high surface area. Surface photovoltage spectroscopy and transient photovoltage measurements revealed that the photoinduced charge-transfer property of p-type BiOI could be improved greatly by coupling with n-type ZnO. The heterojunction at the interface between the BiOI and ZnO could efficiently reduce the recombination of photoinduced electron–hole pairs to increase the lifetime of charge carriers by 15 times and thus enhance the photocatalytic activity of the ZnO/BiOI heterostructures, in addition to the high surface area. This study reveals that the heterostructure construction between two different semiconductors plays a very important role in determining the dynamic properties of their photogenerated charge carriers and their photocatalytic properties.
Jiang et al. (2011) studied this question.