The roles of density-tunable surface oxygen vacancy over bouquet-like Bi2O3 in enhancing photocatalytic activity.

Bouquet-like hierarchical Bi2O3 photocatalyst materials with high-density surface oxygen vacancy are synthesized via a hydrothermal method by the synergetic control of NaOH and a polyvinyl alcohol (PVA) stabilizer. The OH(-) ion addition led to the formation of more relaxed PVA macromolecular clusters, as a result, a thinner PVA film was formed, the species adsorbed on the surface of the produced Bi2O3 crystal nucleus could tune both the surface microstructure size and oxygen vacancy density via controlling the velocity, transfer and reaction of the OH(-) ions. The significant enhancement of photocatalytic performances could be attributed to the high density of the surface oxygen vacancy which was propitious to the charge separation efficiencies, distribution characteristic, and its role in a photo-redox reaction. A turnable-bending self-assembly mechanism was proposed to clarify the formation process of the bouquet-like hierarchical structure.