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In this paper, g-Bi 2 O 3 , considered as the best photocatalyst among all Bi 2 O 3 polymorphs, was successfully prepared on the surface of m-BiVO 4 octahedral crystals through an alkaline "etching" process. Extensive XRD, SEM and TEM characterization revealed the formation of a p-n junction in the form of m-BiVO 4 @g-Bi 2 O 3 core-shell heterostructure. In addition, the alkaline concentration and reaction time during the etching process were studied and found to be critical parameters in the formation and yield of the Bi 2 O 3 phase. The visible-light photocatalytic activities of these heterogeneous samples with different g-Bi 2 O 3 /m-BiVO 4 phase ratios were evaluated for the degradation of Rhodamine B (RhB). The results indicated that with an optimum amount of g-Bi 2 O 3 on the m-BiVO 4 surface, the powders showed superior photocatalytic performance over pure m-BiVO 4 octahedral crystals. The enhancement mechanisms were discussed based on the specific surface area and g-Bi 2 O 3 shell thickness, as well as the influences of improved charge carrier transfer on the p-n heterostructure.

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