Electrochemical Synthesis And Application Research Of Tungstate And Molybdate

The transition metal tungstate and molybdate are two kinds of important inorganic functional materials, which have been widely researched and used in recent years. Application fields include photoluminescence devices, optical fibers, catalysts, microwave components, magnetic devices, supercapacitor materials, lithium batteries, fuel cells, solar energy conversions, corrosion protection, humidity sensors and so forth. Therefore, people studied the preparation methods including microemulsion-based synthesis, sol-gel method, microwave-assisted synthesis method, molten salt method, coprecipitation method, polymerized precursor method, sonochemical method, solid state reaction method, hydrothermal method, and electrochemical synthesis to synthesize metal tungstates and molybdates.In this paper, tungstates and molybdates nano-particles of transition metal Cu, Ni, Zn have been prepared by the cation membrane electrolytic method, their physical properties, especially the optical property have been measured. Prepared nanowire NiMoO₄ on the surface of nickel foam was applied as supercapacitor electrode, and its electrochemical performance was measured.The main research results are as follows:1. The cationic membrane electrolysis method was used in the preparation of tungstate nano-particles ?MWO₄?M=Cu, Ni, Zn??, with 0.1 mol/L Na₂WO₄ as the anolyte,0.1 mol/L diluted hydrochloric acid as the catholyte, Cu films, Ni films and Zn films as the anode respectively and titanium mesh as cathode under the condition of constant current electrolytic. The crystal structures of synthesized particles were determined by XRD, the element compositions and valence bond structures were determined by EDS and FTIR. SEM, TEM, HRTEM were used to characterize the morphology, microstructure and lattice spacing of the products. UV-vis and PL spectra were used to characterize the optical properties. With higher crystallinity and uniform structure, the CuWO₄, NiWO₄ and ZnWO₄ were obtained and emited red, blue violet and red light respectively at the excitation wavelength of 420 nm.2. Adapted the above cation membrane electrolysis method with 0.1 mol/L Na₂MoO₄ as the anolyte, crystallinity and uniform structure of the molybdate nano-particles ?MMoO₄ ?M=Cu, Ni, Zn?? were obtained. The best excitation wavelengths of the three nano-particles are 480 nm,480 nm and 240 nm, respectively, at which these molybdates can separately emit lights of red, red and green.3. Adapted the above cation membrane electrolysis method with 0.1 mol/L Na₂MoO₄ as the anolyte, nickel foam as the anode. Under the conditions:1=0.3 A, T=80 ?, telectrolysis=4 min, NiMoO₄ nanowire was prepared on the surface of nickel foam. XRD, EDS and FTIR were used to characterize the NiMoO₄. The nanowire NiMoO₄ has BET surface area of 27.5890 m²/g and pore size distribution centered at 1 and 5 nm. The electrochemical properity of the electrode was measured through CV and GCD. With 5 mV/s scanning speed, the specific capacity was 875.9 F/g. With 1 A/g current density, the specific capacity was 2130 F/g. The capacity retention rate was 32.7% cycled 200 times at 4 A/g current density.