Mesoporous 3D network Ce-doped NiO nanoflakes as high performance electrodes for supercapacitor applications

Abstract

In the present study, pristine NiO- and Ce (0.5, 1.0, 1.5, and 2%)-doped NiO nanoflakes were synthesised using the sol–gel method for supercapacitor applications. All the samples were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman analysis. The in situ chemical species and oxidation state of the elements present on the surface of the compounds were revealed by X-ray photoelectron spectroscopy. The field emission scanning electron microscopic analysis (FESEM) explored the transformation in the morphology from pristine NiO nanosheets to 3D flower-like nanostructure of Ce-doped NiO nanoflakes. Further, BET analysis revealed that the surface area of the NiO nanoflakes increased with the Ce dopant concentration. Ce-1% flower-like nanostructure showed a large surface area of 226.6 m² g⁻¹ with an average pore volume of 1.41 cm³ g⁻¹. As expected, among the five electrodes, Ce-1% exhibited the maximum surface redox activity and offered a high specific capacitance of 2444 F g⁻¹ at 5 mV s⁻¹ scan rate, which is three times that of the pure NiO nanosheets. The charge–discharge analysis results revealed a maximum specific capacitance of 1725 F g⁻¹ at 1 A g⁻¹ current density for the Ce-1% doped NiO nanoflakes. The electrochemical impedance spectra showed a very low resistance of 1.5 Ω for Ce-1% doped NiO nanoflakes.