Design of Ni-modified ZnSe nanostructures embedded in rGO for efficient supercapacitor electrodes

Abstract

Energy crises have prompted researchers to develop new electrode materials for efficient energy storage, leading to the creation of effective energy storage devices. Therefore, this study introduces Ni-doped ZnSe/rGO-based materials fabricated through a hydrothermal synthesis method, which demonstrated enhanced electrical and electrochemical performance. X-ray diffraction (XRD) analysis revealed an increase in the crystallite size from 49.72 nm to 96.74 nm, accompanied by a corresponding growth in the particle size, which can be attributed to the incorporation of Ni and rGO as substituents. The electrochemical characterization of all fabricated electrodes indicated that the best-performing Zn_0.90Ni_0.10Se/rGO composite achieved a high specific capacitance of 1920.20 F g⁻¹ at 5 mV s⁻¹, significantly surpassing that of pure ZnSe (346.8 F g⁻¹), as determined from CV measurements. Additionally, the Zn_0.90Ni_0.10Se/rGO electrode demonstrated excellent cycling stability (90.85% capacitance retention after 10 000 cycles), a high power density of 3500 W kg⁻¹ at a current density of 7 A g⁻¹, and an energy density of 83.81 Wh kg⁻¹ at a current density of 1 A g⁻¹, with a storage capability of 1058.75 F g⁻¹. The combined effect of Ni and rGO doping in the composites resulted in a notable reduction in series and charge transfer resistances. Under optimal conditions, it exhibited excellent electrochemical performance, as indicated by good ionic conductivity (0.037 S cm⁻¹), the highest transference number for cations (0.90), and a rate constant of 1.42 × 10⁻⁸ cm s⁻¹ at an exchange current density of 0.00137 A g⁻¹, as well as a diffusion coefficient of 8.03 × 10⁻¹³ m² s⁻¹, suggesting enhanced ion transport characteristics. These promising attributes of Zn_0.90Ni_0.10Se/rGO strongly demonstrate it as an ideal electrode material for advanced energy storage applications.