Controlled synthesis of Ag2O microcrystals with facet-dependent photocatalytic activities

Abstract

Ag₂O microcrystals with different morphologies have been successfully synthesized by using various complexing agents. To achieve kinetic control of the growth of the Ag₂O microcrystals, [Ag(NH₃)₂]⁺ complexing ions are required to restrict the release rate of silver ions before adding NaOH solution. The complexing anions play an important role in the growth process of the Ag₂O microcrystals. This kinetic control leads to five morphologies of Ag₂O microcrystals (cubic, octahedral, rhombic dodecahedra, polyhedra with 18 faces and rhombicuboctahedral), which exhibit facet-dependent photocatalytic activity for the degradation of methyl orange (MO) under visible light irradiation. The cubic Ag@Ag₂O photocatalyst with exposed {100} facets showed the greatest activity of all the other morphologies of the photocatalysts. The mechanism of dramatic enhancement of the photocatalytic activity of Ag@Ag₂O with exposed {100} facets was discussed in detail from three aspects, including the highest surface energy of the {100} facet, the larger difference value between the weighted average of the effective mass of holes and electrons along the [100] direction, and the suitable redox potentials of the (100) surface.