Carbon-supported X-manganate (X Ni, Zn, and Cu) nanocomposites for sensitive electrochemical detection of trace heavy metal ions

Heavy metal ion pollution has always been a stringent problem facing the global environment. Therefore, the detection of heavy metal ions has been extremely important and challenging. An efficient and simple method for the preparation of carbon-supported X-manganate (XNi, Zn, and Cu) nanocomposites was explored for the individual and simultaneous electrochemical detection of Pb(II) and Hg(II). The metallic salt solutions were mixed with graphene to form the precursors through a hydrothermal reaction, and calcined in the air to obtain the final products. The structure and morphology of the synthesized NiMn2O4-graphene (NMO-GR), ZnMn2O4-graphene (ZMO-GR), and CuMn2O4-graphene (CMO-GR) nanocomposites were characterized by various methods, and NMO-GR showed more excellent electrochemical performances by square wave anodic stripping voltammetry (SWASV) than ZMO-GR and CMO-GR. NMO-GR provided a large specific surface area, abundant reaction sites, and good electrical conductivity, thereby enhancing its electrochemical performance. The electrochemical sensor based on NMO-GR displayed the widest linear ranges (1.4-7.7 μM for Pb(II) and 0.7-6.7 μM for Hg(II)) and with the lowest detection limits (0.050 μM for Pb(II) and 0.027 μM for Hg(II)) than ZMO-GR and CMO-GR. This study offered a new way to simultaneously detect Pb(II) and Hg(II), and greatly expanded its application in the field of electrochemistry.