Enhanced photocatalytic activity of hexagonal flake-like Bi₂S₃ / ZnS composites with a large percentage of reactive facets

Selectively exposing surfaces with high reactivity is an effective strategy to enhance the photocatalytic activity of semiconductor photocatalysts. We report the facile synthesis of hexagonal flake-like Bi₂S₃/ZnS composites with a large percentage of reactive exposed {2 2 1} facets by tuning only the molar ratios of Bi to Zn. The samples exhibit enhanced optical absorption and red shift of absorption edge. The Bi₂S₃/ZnS composites with hexagon morphology display superior photocatalytic degradation of methylene blue (MB), faster than that with pure Bi₂S₃ and pure ZnS by a factor of 7.1 and 3.6, respectively. The enhanced photocatalytic activity can be attributed to the highly reactive {2 2 1} exposed facets and the more efficient separation of photogenerated electron–hole pairs is due to the interface of the hetero-junction. Furthermore, a tentative mechanism for photodegradation of MB over Bi₂S₃/ZnS composites has been proposed involving the photogenerated holes and ⋅OH radicals as the main active species, which is confirmed by using different scavengers. The novel constructed Bi₂S₃/ZnS composite is expected to be an attractive candidate as a photocatalyst for environmental purification and energy conversion. (paper)