Synthesis of bimetallic tungstates for finding photocatalytic active compounds with a smaller band gap than tungsten oxide

The goal of the project is to find photocatalytic active tungstates which have a smaller band gap than tungsten oxide (WO3). Several bimetallic tungstates (MWO4, M = Cu, Mn, Fe, Ni, Co) have been synthesized by a co-precipitation method and a hydrothermal synthesis method using transition metal salts (CuCl2·2H2O, MnCl2·4H2O, FeSO4·7H2O, Ni(NO3)2·6H2O, CoCl2·6H2O) and sodium tungstate (Na2WO4·2H2O ) as precursors. X-Ray diffraction (XRD) analysis and Raman spectroscopy were used to characterize and understand the crystal structure of the as-prepared compounds. Moreover, Scanning Electron Microscopy (SEM) was applied to study the form of the most photocatalytic active compound, MnWO4. UV–Visible diffuse reflectance spectroscopy is also used to measure the band gap of each material. After the characterization of each compound, several photodegradation experiments were done to observe the photocatalystic activity. Under the UV light, the experiment was followed by changing one parameter per time to attain higher sensitivity of the photocatalyst. Concluding, after the experiment under the visible light, the MnWO4 was found out to be most photocatalytic active with a smaller band gap than tungsten oxide