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 MnO 2 /Bi 2 O 3 microspheres (MnO 2 /Bi 2 O 3 /GO) for voltammetric detection of cadmium ion (Cd 2+ ) in water samples. The surface morphology and crystal structure of the MnO 2 /Bi 2 O 3 /GO was measured by scanning electron microscopy and powder X-ray diffraction, respectively. The electrochemical properties of the MnO 2 /Bi 2 O 3 /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 MnO 2 /Bi 2 O 3 /GO composites increased the electrochemically active surface area and reduced the charge transfer resistance significantly. As a result, the MnO 2 /Bi 2 O 3 /GO decorated glassy carbon electrode (MnO 2 /Bi 2 O 3 /GO/GCE) significantly enhanced the voltammetric response for Cd 2+ 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 MnO 2 /Bi 2 O 3 /GO demonstrated excellent stripping voltammetric characteristic for Cd 2+ with a wide linear response range (1.12–1120 ​μg ​L −1 ) and a quite low limit of detection (LOD, 0.22 ​μg ​L −1 ), mainly due to the synergistic effect between the bimetallic oxide MnO 2 /Bi 2 O 3 and GO nanosheets . Moreover, the MnO 2 /Bi 2 O 3 /GO/GCE exhibited extraordinary selectivity even in presence of potential interfering substances as well as good repeatability, reproducibility, and stability. The proposed MnO 2 /Bi 2 O 3 /GO/GCE was successfully used for the Cd 2+ detection in actual water samples with satisfactory recoveries (99.4% ​− ​106%).