Fabrication of N-doped ZnO for evaluation of photocatalytic degradation of methylene blue, methyl orange and improved supercapacitor efficiency under redox-active electrolyte

Abstract

The fabrication of an N-doped ZnO nanocomposite was described in this study using hydrothermal methods at various temperatures (200–600 °C). The developed N-doped ZnO nanocomposite was also utilized to investigate supercapacitors and photocatalytic degradation of pigments. Improving ZnO supercapacitor and photocatalytic dye decomposition capabilities proved quite difficult. Consequently, it was essential to create an N-doped ZnO at various temperatures. This approach aims to improve photocatalytic dye degradation and energy storage in N-doped ZnO nanocomposites in a synergistic manner. As we evaluated the photocatalytic activity, the N-doped ZnO-600 °C nanocomposite showed better methylene blue (MB) and methyl orange (MO) degradation efficiency. In just 120 min of exposure to visible light, about 99 % and 99.1 % of the MB and MO deterioration was seen; in contrast, only 60.5 %, 70.2 %, 79.6 %, 84 %, and 99 % of the MB degradation and 57.7, 62, 61.6, 70.1, 76.9, 84.2, and 99.1 % was shown on the pure ZnO, TiO₂ (P25), ZnO-200 °C, ZnO-400 °C, ZnO-600 °C, and N-ZnO 600 °C materials, respectively. The increased photocatalytic efficiency was ascribed to the synergistic effect, improved charge separation, and increased visible light absorption by the N-ZnO 600 °C nanocomposite. Using XRD, UV–vis DRS, PL, FE-SEM, and HR-TEM investigations, the structural, optical, and surface morphology of the produced catalyst were examined. Additionally, the produced material was used in potassium hydroxide (KOH) and redox additive electrolytes (RE) electrochemical supercapacitor performance. Comprehensive studies revealed that the N-ZnO electrode enhanced cycle voltammetry (CV), galvanostatic charge-discharge (GCD), rate ability, and reliability under redox additive electrolytes (RE) and potassium hydroxide (KOH). The inclusion of RE increased the efficiency even more, indicating the potential for advanced applications of energy storage. The highest specific capacitance of the ZnO electrode increased significantly from 159 Fg^-1 in KOH to 498 Fg^-1 at 1 Ag^-1. The N-ZnO-600 °C electrode, on the other hand, demonstrated a maximum specific capacitance of 288 Fg^-1 at 1 Ag^-1 in KOH and a significantly higher specific capacitance of 762 Fg^-1 at 1 Ag^-1 in KOH + RE.