Pseudocapacitive behavior of pure and Al-doped NiO/Graphene oxide films on grafoil sheet

Metal oxide nanofilms have drawn interest as essential components for next-generation supercapacitors due to growing demands for effective energy storage devices. Electrodes were fabricated by thermally depositing pure and Al-doped NiO onto graphene oxide (GO), followed by drop-casting the NiO-coated GO onto a grafoil sheet with improved electrochemical properties. The resulting composite electrodes were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and Scanning Electron Microscopy (SEM), confirming the formation of nanoscale NiO coatings and the presence of Ni–O and GO-related vibrational modes. Electrochemical evaluation in 2 M and 3 M KOH electrolytes revealed highly pseudocapacitive behavior. Specific capacitance values obtained from cyclic voltammetry at a scan rate of 10 mV/s were 172, 137.53, and 89.92 F/g for undoped, 2% Al-doped, and 4% Al-doped NiO electrodes, respectively, in 2 M KOH; and 181.25, 157.05, and 93.75 F/g in 3 M KOH. All electrodes demonstrated excellent cycling stability, retaining their performance after 100 charge–discharge cycles at a scan rate of 100 mV/s. These results suggest that NiO/GO-coated grafoil electrodes, particularly undoped NiO, are promising candidates for high-performance supercapacitor applications.