Molybdenum Disulfide-Nickel Sulfide Composites Modified Eletrode for Determination of Nitrite in River Water and Drinking Water

MoS₂-NiS composite was prepared by one-step hydrothermal synthesis method, and the modified glassy carbon electrode (labeled as MoS₂-NiS/GCE) was obtained by dropping the composite on GCE for electrochemical determination of nitrite content in drinking water and river water. The selected electrochemical working parameters were as follows: ① MoS₂-NiS/GCE was used as the working electrode, 0.1 mol·L^-1 phosphate buffer solution (pH 6) was used as the electrolyte; ② cyclic voltammetry was used as the analytical method under conditions of the scanning rate of 50 mV·s^-1 and the potential in the range of 0.4-1.4 V. The characterization results obtained by TEM and XRD showed that rod NiS adhered to the lamellar MoS₂ surface in the composite, and the diffraction peaks of NiS and MoS₂ appeared in the XRD pattern of the composite, indicating that the MoS₂-NiS composite had been successfully prepared. The results obtained by electrochemical test showed that the electrocatalytic performance of MoS₂-NiS/GCE was significantly superior to that of MoS₂/GCE and NiS/GCE prepared by monomer, and the electrocatalytic effect of MoS₂-NiS/GCE with n_Mo/n_Ni=1:7 was better. The oxidation of nitrite on MoS₂-NiS/GCE was controlled by diffusion process. Results of amperometric test showed that linearity relationship between concentration of nitrite and corresponding peak oxidation current was kept in the range of 0.9-1 210.0 μmol·L^-1, with detection limit of 0.25 μmol·L^-1. After placing the modified electrode at 4 ℃ for 30 d, the oxidation peak current decreased by 7.4% of the initial value. The modified electrode was scanned 20 times continuously, and RSD of oxidation peak currents was 4.3%. The modified electrode was used to analyze drinking water and river water in the spiked recovery test, giving recoveries in the range of 97.4%-101%, and RSDs (n=5) of determined values were ranged from 3.2% to 4.5%, with the determined values better than those of national standard GB/T 7493-1987.