Tuning the electrochemical performance of a hierarchical MoO₃/CdO binary heterostructure for supercapacitor applications

Cadmium oxide (CdO)-incorporating molybdenum trioxide (MoO₃) nanocomposites were synthesized using a facile hydrothermal method by varying the CdO content (1%, 3%, and 5%) to comprehend the influence of CdO concentration on the electrochemical performance of MoO₃. The structural and morphological properties of the synthesized nanomaterials were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). XRD showed that MoO₃ has an orthorhombic structure, and FE-SEM showed that it has a nanobelt shape (0.8-3.2 μm long and 100-228 nm wide) with CdO nanoparticles grown on its surface. Electrochemical properties were analyzed through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The 3%CdO-incorporating MoO₃ electrode exhibited a higher specific capacitance of 671 F g^-1 at a current density of 0.50 A g^-1, while the pristine MoO₃ shows 386 F g^-1. Kinetic analysis of CV data indicates that redox processes in the nanocomposite electrodes involve both capacitive and diffusion-controlled mechanisms. The MoO₃/CdO (3%) electrode showed low charge transfer resistance (2.35 Ω) and series resistance (6.20 Ω), enabling faster faradaic redox reactions and improved electrochemical performance. Moreover, the MoO₃/CdO (3%) electrode demonstrated excellent cycling stability, retaining more than 92% of its initial specific capacitance after 5000 cycles. The incorporation of CdO enhances the diffusion pathways within the nanocomposites, potentially boosting their conductivity and specific capacitance. The symmetric supercapacitor MoO₃/CdO (3%)//MoO₃/CdO (3%) exhibited a notable operating voltage of 1.6 V, achieving an energy density of 124 W h kg^-1 at a power density of 1067 W kg^-1. It also exhibited a capacitance retention of 88.9% after 5000 cycles at a current density of 15 A g^-1, highlighting its potential for energy storage applications.