Electrochemical engineering of ZIF-7 electrode using ion beam technology for better supercapacitor performance

In the study, ZIF-7 material was exposed to 500 keV copper (Cu++) ions at dosages of 1 x 1014, 1 x 1015, and 5 x 1014 ions/cm2. The ZIF-7 unirradiated reveals a polycrystalline with an intense peak at 16.231 degrees with a crystal plane of (012). The intensity of the peak in the XRD pattern broadens as the radiation of copper ions increases. In the ZIF-7 FTIR, the C--C stretching vibration of the benzene ring is visible at 1469 cm -1, and the hydroxy phenyl benzimidazole (bIm) ligand's C-H bending vibration is visible at 740 cm -1. Irradiated ZIF-7 reveals C-H bending at 758, 759, and 754 cm -1 from the bIm ligand and C--C stretching at 1456, 1460, and 1457 cm -1. The CV plots showed redox peaks, demonstrating faradaic processes. The ZIF-7's unirradiated estimated specific capacitances at scan rates of 50, 40, 30, 20, and 10 mV/s are 156, 195, 260, 390, and 781 F/g. The estimated specific capacitance of the irradiated ZIF-7 material with copper ions of 1 x 1014 ions/cm2 is 185, 308, 462, and 925 F/g. The estimated specific capacitance for ZIF-7 with copper ions of 1 x 1015 and 5 x 1014 ions/cm2 are 187, 234, 468, 937, and 1200 F/g, and 300, 375, 500, 750, and 1200 F/g respectively. The unirradiated (ZIF-7) shows bandgap energy of 3.53 eV which is suitable for applications in gas separation, catalysis, and optoelectronics. The irradiated sample with 1 x 1014 ions/cm2, 1 x 1015 ions/cm2 and 5 x 1014 ions/cm2 revealed bandgap energy of 2.52 to 2.87 eV which is suitable energy storage application.