Rietveld Refinement, Morphology Analysis, Electronic, Magnetic, Optical and Photocatalytic Performance of AMoO 4 (A= Co 2+ and Mn 2+) Nanopowders Synthesized by Sol-Gel Method

Abstract

Molybdenum-based binary oxides AMoO4 (A= Co2+ and Mn2+) have been successfully synthesized using the sol-gel method. The prepared nanopowders were characterized by means of thermal analysis (TGA/DTA), X-ray diffraction (XRD) and Rietveld refinement data. Scanning electron microscope (SEM) of the powders obtained from cobalt nitrate (G1 gel) showed porous agglomerate that formed cages, which came from the degassing in several stages. Meanwhile, pre-sintering was observed in the powders obtained from cobalt chloride (G2 gel). The transmission electron microscopy (TEM) of CoMoO4 molybdate showed quasi-spherical particles with nanometric size range of 10-60 nm. Raman spectroscopy revealed the presence of the vibrational modes O-Metal, Metal-O-Metal, and O-Metal-O, which confirm the formation of the desired phase. Based on the optical band-gap energy (Eg=1.98 eV), the monoclinic b-MnMoO4 is a semiconductor material. The theoretical magnetic moment of the b-MnMoO4 sample is approximately μtheorical = 5.00049 μB. The photocatalytic degradation process of Indigo dye was investigated using cobalt molybdate (CoMoO4) as a photocatalyst, this process was followed by UV–vis absorption spectroscopy analyzes. The photocatalytic activity tests under UV light irradiation show a 45% of discoloration efficiency after 125 min. The addition of H2O2 increases this rate to 74 %.