Facile synthesis of graphene oxide coated 3D bimetallic oxide MnO2/Bi2O3 microspheres for voltammetric detection of cadmium ion in water

Herein, we presented a facile synthesis of graphene oxide coated 3D bimetallic oxide MnO2/Bi2O3 microspheres (MnO2/Bi2O3/GO) for voltammetric detection of cadmium ion (Cd2+) in water samples. The surface morphology and crystal structure of the MnO2/Bi2O3/GO was measured by scanning electron microscopy and powder X-ray diffraction, respectively. The electrochemical properties of the MnO2/Bi2O3/GO were also measured by both cyclic voltammetry and electrochemical impedance spectroscopy. The analytical parameters such as deposition time, deposition potential and buffer pH were optimized. The MnO2/Bi2O3/GO composites increased the elec-trochemically active surface area and reduced the charge transfer resistance significantly. As a result, the MnO2/ Bi2O3/GO decorated glassy carbon electrode (MnO2/Bi2O3/GO/GCE) significantly enhanced the voltammetric response for Cd2+ detection. The optimal deposition time, deposition potential and buffer pH were set at 180 s,-1.5 V, and 6.5, respectively. Using the optimal analytical parameters, the MnO2/Bi2O3/GO demonstrated excellent stripping voltammetric characteristic for Cd2+ with a wide linear response range (1.12-1120 mu g L-1) and a quite low limit of detection (LOD, 0.22 mu g L-1), mainly due to the synergistic effect between the bimetallic oxide MnO2/Bi2O3 and GO nanosheets. Moreover, the MnO2/Bi2O3/GO/GCE exhibited extraordinary selectivity even in presence of potential interfering substances as well as good repeatability, reproducibility, and stability. The proposed MnO2/Bi2O3/GO/GCE was successfully used for the Cd2+ detection in actual water samples with satisfactory recoveries (99.4% -106%).