General synthesis and phase control of metal molybdate hydrates MMoO4.nH2O (M = Co, Ni, Mn, n = 0, 3/4, 1) nano/microcrystals by a hydrothermal approach: magnetic, photocatalytic, and electrochemical properties.

Different phases and morphologies of molybdate hydrates MMoO 4. nH 2O (M = Co, Ni, Mn, n = 0, 3/4, 1) nano/microcrystals, which include NiMoO 4.H 2O microflowers, MnMoO 4.H 2O microparallelogram plates, and CoMoO 4.3/4H 2O microrods, can be selectively synthesized by a hydrothermal process. The pH and reaction temperature have a crucial influence on the synthesis and shape evolution of the final products. Uniform CoMoO 4.3/4H 2O and NiMoO 4.H 2O nanorod bundles can be produced by a hydrothermal process with the assistance of PEG-400. The calcination of CoMoO 4.3/4H 2O and NiMoO 4.H 2O at 500 and 550 degrees C, respectively, allows the formation of monoclinic beta-CoMoO 4 and alpha-NiMoO 4. The antiferromagnetic property of MnMoO 4.H 2O, MnMoO 4, and CoMoO 4.3/4H 2O has been studied for the first time. The photocatalytic activity of metal molybdate particles with different morphologies has been tested by degradation of acid fuchsine under visible light. Electrochemical performances of MMoO 4 (M = Ni, Co) nanorod bundles and MnMoO 4 microrods have been evaluated.