علی اکبر آشکاران

We prepared a binary transition metal oxide material of nickel tungstate nanoparticles (NiWO4-NPs) through a simple co-precipitation method. The synthesized NPs were characterized using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) techniques. NiWO4-NPs represent nearly spherical morphologies with an average size of ~97 nm and tungstate as a dominant phase. Carbon paste electrode (CPE) modified with NiWO4-NPs (NiWO4-NPs/CPE) was used for electrooxidation of formaldehyde in alkaline solution. Cyclic voltammetry demonstrated that NiWO4-NPs/CPE electrode can decrease the overpotential for formaldehyde oxidation while increasing the current density in comparison to CPE. The results revealed that the CPE modified with calcined NiWO4-NPs (NiWO4-cal-NPs/CPE) shows less current response to formaldehyde oxidation compared with the amorphous sample. Moreover, the variation of scan rate and concentration of formaldehyde were investigated on the electrooxidation of formaldehyde and the results indicated that the electrooxidation on the NiWO4-NPs/CPE electrode is a diffusion-controlled mechanism. The diffusion coefficient and catalytic rate constant of formaldehyde, evaluated by chronoamperometry, were 40.4 × 10−4 cm2 s−1 and 1.37 × 104 cm 3 mol−1 s−1, respectively. Furthermore, we show that the prepared sensor has a wide linear range of 8 μM to 1 mM and low detection limit of 3.6 μM.