Studies on photocatalytic performance and supercapacitor applications of undoped and Cu-doped ZnO nanoparticles

Abstract

The structural, morphology and optical properties were characterised using XRD, FTIR, SEM, TEM, and UV-DRS for the undoped and Cu-doped ZnO NPs with varying Cu doping molar concentrations from 0 wt% to 6 wt% through the co-precipitation method. The presence of a ZnO hexagonal wurtzite structure for all samples was confirmed by the structural study of the Cu-doped ZnO NPs, indicating the incorporation of Cu2+ ions into the ZnO lattice by substitution and average crystallite sizes of 25–22 nm. The surface morphology analysis of undoped and Cu-doped ZnO NPs indicated the growth of spherical nanocrystallites with fine particles. Optical studies of Cu-doped ZnO nanostructured particles revealed that increasing the Cu doping agent from 0 wt% to 6 wt% resulted in a blue shift of the absorption band with increasing band gap energy from 3.27 eV to 3.44 eV. The degradation efficiency of MB is 89.2% for Cu-doped ZnO photocatalyst, which performs much better than undoped ZnO under natural sunlight irradiation. The electrochemical analysis determined the specific capacitance of 10 to 100 mV/s scan rate for all the samples. Amongst the various concentrations, 6 wt% Cu-doped ZnO had the most excellent specific capacitance of 539.87 F/g at 10 mV/s. Compared with undoped ZnO NPs, Cu-doped into the ZnO matrix enhanced photocatalytic activities and electrochemical performance for wastewater treatment and supercapacitor applications.