Highly monodisperse Cu3Mo2O9 micropompons with excellent performance in photocatalysis, photocurrent response and lithium storage

We developed a simple and facile method for preparing two types of transition metal molybdates: AMoO(4) (A = Ni and Zn) and B3Mo2O9 (B = Cu and Zn). Initially, a hydrothermal reaction at 383 K for 10 h in an aqueous solution of ammonium molybdate tetrahydrate (AMT) and metal acetates (MAc2, M = Ni, Cu and Zn) was carried out to synthesize their precursors: NiMoO4 center dot xH(2)O, ZnMoO4 center dot 0.8H(2)O, Cu-3(OH)(2)(MoO4)(2) and Zn-3(OH)(2)(MoO4)(2). Subsequently, AMoO(4) with a 1D structure and B3Mo2O9 with a 3D structure were successfully constructed by sintering the precursors at 873 K for 3 h in air. Our result presented the first evidence that the generation of alpha-ZnMoO4 and Zn3Mo2O9 is dependent on the initial concentration of AMT or Zn(Ac)(2). More importantly, a highly monodisperse Cu3Mo2O9 micropompon structure was successfully created by an ethylenediaminetetraacetic acid (H4Y)-mediated hydrothermal route and a subsequent sintering process. We considered that H4Y, a strong competitive chelating ligand, played a significant role in prohibiting the formation of the intermediate (NH4)(2)Cu(MoO4)(2), thereby not only producing a monodisperse structure of Cu-3(OH)(2)(MoO4)(2) but also reducing the size of the structure by forming a stable complex: CuY. Three independent experiments: photocatalysis, photocurrent response and lithium storage were performed to discuss several possible applications of the as-obtained Cu3Mo2O9 micropompons. Our data demonstrated that the Cu3Mo2O9 material exhibited excellent photocatalytic efficiency for the degradation of Congo red under visible light irradiation. Also, the time-dependent photoresponse of the Cu3Mo2O9 gave a very high ratio (about 171) of light current to dark current and a stable photocurrent density, which were a reflection of a high concentration of photogenerated electron-hole pairs. Further, the material indicated good charge-discharge stability and high coulombic efficiency in lithium-ion batteries even during the 100 cycles. We believe that the present study represents a significant step in the development of transition metal molybdates.