Green combustion synthesis of multifunctional inorganic ZnO: Co2+ (1–11 mol%) nanoparticles: Electrochemical and photocatalytic applications

Abstract

Aloe Barbadensis Miller (Aloe vera) gel fuel-assisted facile combustion synthesized novel ZnO:Co2+ nanoparticles were analysed for its multifunctional applications such as supercapacitors, sensors, and photocatalytic dye degradation. The PXRD pattern of ZnO was matched with DFT-based computational XRD pattern. The morphology of the prepared nanomaterial was tested using Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) techniques. Band gaps were estimated using the Kubelka-Munk function (K-M function) using diffuse reflectance spectra (DRS). The band gap was found to be a minimum ̴ 1.90 eV for ZnO: Co2+ (7 mol%) nanoparticles. Electrochemical properties of ZnO: Co2+ (1–11 mol%) nanoparticles based modified carbon paste electrodes were studied in KCl electrolyte using cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS) and Galvanostatic charge–discharge (GCD). Enhanced and optimized electrochemical performance in terms of specific capacitance was observed for ZnO: Co2+ (7 mol%) electrodes for supercapacitor application. EIS shows minimum ESR value of 72 Ω and GCD shows ̴ 99 % cyclic stability over 1550 cycles for ZnO: Co2+ (7 mol%) electrode. Effect of low band gap on electrochemical properties were established and found that low band gap leads to high performance in electrochemical activities. Sensitive detection of paracetamol and glucose (1––7 mM concentration) was carried out using the ZnO: Co2+ (7 mol%) electrode, for electrochemical sensor application. Photocatalytic degradation of methylene blue (MB) & acid orange-8 (AO-8) dyes was carried out using ZnO: Co2+ (7 mol%) photocatalyst under sunlight including scavenging examinations. Under sunlight, 92.45 % of MB and 98.29 % of AO-8 dyes were degraded in 120 min. Overall, this paper reports, multifunctional applications (EDLC, Sensor and Photocatalysis) of toxic free green combustion synthesized ZnO: Co2+ (1–11 mol%) nanoparticles.