Facile template-free synthesis of Bi(2)O(2)CO(3) hierarchical microflowers and their associated photocatalytic activity.

Hierarchical Bi(2)O(2)CO(3) flowerlike microstructures have been synthesized for the first time using a facile, template-free, and low-temperature solution method. With an average diameter of about 3 microm, the as-prepared Bi(2)O(2)CO(3) microflowers are composed of numerous two-dimensional nanosheets with oriented terminal engagement. On the basis of electron microscopy observations, a plausible growth mechanism is proposed as a spatial self-assembly process accompanied by Ostwald ripening. The molar ratio of the initial reagents plays an important role in determining the morphologies of the Bi(2)O(2)CO(3) microstructures. UV/Vis spectroscopy is employed to analyze the band gaps of the products. Both mesopores and macropores are revealed in the Bi(2)O(2)CO(3) microflowers by means of nitrogen sorption and pore-size distribution. Moreover, evaluated by the degradation of methyl orange under UV illumination, the photocatalytic performance of the Bi(2)O(2)CO(3) hierarchical microflowers is almost six times higher than that of commercial Bi(2)O(2)CO(3). The higher specific surface area, the meso/macropores, and the intra-electric field formed between the (Bi(2)O(2))(2+) layer and the slabs comprising CO(3) (2-) in the Bi(2)O(2)CO(3) crystal structure, are believed to facilitate the separation of the photoinduced electrons and holes and thus improve the corresponding photocatalytic activity.