二硫化钼-硫化镍复合物修饰电极测定河水及饮用水中亚硝酸盐

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

使用一步水热合成法制备了二硫化钼-硫化镍(MoS_(2)-NiS)复合物,然后将此复合物滴涂在玻碳电极(GCE)上制备了MoS_(2)-NiS复合物修饰电极,记为MoS_(2)-NiS/GCE,用于饮用水和河水中亚硝酸盐含量的电化学测定。选择的电化学工作参数如下:(1)以MoS_(2)-NiS/GCE为工作电极,电解液为0.1mol·L^(-1)磷酸盐缓冲溶液(pH 6);(2)采用循环伏安法,扫描速率为50mV·s^(-1),电位范围为0.4~1.4V。透射电子显微镜(TEM)和X射线衍射仪(XRD)表征结果表明:在复合材料中,棒状NiS附着在了片层状MoS_(2)表面,且复合物的XRD图谱中同时出现了NiS和MoS_(2)的衍射峰,说明已成功制备了MoS_(2)-NiS复合物。电化学试验结果表明:MoS_(2)-NiS/GCE的电催化性能明显优于单体制备的MoS_(2)/GCE和NiS/GCE的,且n_(Mo)/n_(Ni)=1∶7的MoS_(2)-NiS/GCE的电催化效果较好;亚硝酸盐在MoS_(2)-NiS/GCE上的氧化受扩散过程控制。安培法检测结果表明,亚硝酸盐的浓度与其对应的氧化峰电流在0.9~1 210.0μmol·L^(-1)内呈线性关系,检出限为0.25μmol·L^(-1)。将该修饰电极在4℃下保存30d后,氧化峰电流仅比初始值下降了7.4%。将该电极连续循环扫描20次,氧化峰电流的相对标准偏差为4.3%。用此修饰电极对饮用水和河水进行加标回收试验,所得回收率为97.4%~101%,测定值的相对标准偏差(n=5)为3.2%~4.5%,且所得测定值比国家标准GB/T 7493-1987的测定值更优异。

MoS_(2)-NiS composite was prepared by one-step hydrothermal synthesis method,and the modified glassy carbon electrode(labeled as MoS_(2)-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) MoS_(2)-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 MoS_(2) surface in the composite,and the diffraction peaks of NiS and MoS_(2) appeared in the XRD pattern of the composite,indicating that the MoS_(2)-NiS composite had been successfully prepared.The results obtained by electrochemical test showed that the electrocatalytic performance of MoS_(2)-NiS/GCE was significantly superior to that of MoS_(2)/GCE and NiS/GCE prepared by monomer,and the electrocatalytic effect of MoS_(2)-NiS/GCE with n_(Mo)/n_(Ni)=1∶7 was better.The oxidation of nitrite on MoS_(2)-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 0.9-1 210.0μmol·L^(-1),with detection limit of 0.25μmol·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.