Facet-, composition- and wavelength-dependent photocatalysis of Ag₂MoO₄

Faceted β-Ag₂MoO₄ microcrystals are prepared by controlled nucleation and growth in diethylene glycol (DEG) or dimethylsulfoxide (DMSO). Both serve as solvents for the liquid-phase synthesis and surface-active agents for the formation of faceted microcrystals. Due to its reducing properties, truncated β-Ag₂MoO₄@Ag octahedra are obtained in DEG. The synthesis in DMSO allows avoiding the formation of elemental silver and results in β-Ag₂MoO₄ cubes and cuboctahedra. Due to its band gap of 3.2 eV, photocatalytic activation of β-Ag₂MoO₄ is only possible under UV-light. To enable β-Ag₂MoO₄ for absorption of visible light, silver-coated β-Ag₂MoO₄@Ag and Ag₂(Mo_0.95Cr_0.05)O₄ with partial substitution of [MoO₄]^2- by [CrO₄]^2- were prepared, too. The photocatalytic activity of all the faceted microcrystals (truncated octahedra, cubes, cuboctahedra) and compositions (β-Ag₂MoO₄, β-Ag₂MoO₄@Ag, β-Ag₂(Mo_0.95Cr_0.05)O₄) is compared with regard to the photocatalytic decomposition of rhodamine B and the influence of the respective faceting, composition and wavelength.