Effect of addition of surfactant on physicochemical properties of cobalt oxide nanoparticles synthesised using a domestic microwave: Applications as photocatalyst and supercapacitor

The present work highlights the comparison of the physicochemical properties of the metal oxide nanoparticles of cobalt synthesised using a domestic microwave in the presence and absence of surfactant. XRD analysis revealed that the addition of the surfactant was responsible for the reduction in the crystallite size of the metal oxide nanoparticles. SEM images showed more agglomeration in the case of surfactant-capped nanoparticles than the bare ones. The elemental composition obtained using EDAX of both nanoparticles showed a higher percentage of oxygen in the bare nanoparticles and better elemental stoichiometry in the surfactant-capped nano -materials. The energy band gap calculated from the optical studies was higher in the case of surfactant-loaded nanoparticles than the bare ones. The photocatalytic studies of nanoparticles without and with surfactant showed 48 % and 40 % degradation of Methylene blue, respectively, in the presence of UV light with 1 g L-1 catalyst dose and 50 mg L-1 dye concentration at 300 min of irradiation time. Langmuir-Hinshelwood kinetic plots showed a marginally higher apparent rate constant value (2.22 x 10-3 min-1) for nanoparticles without surfactant than for nano -particles with surfactant (2.11 x 10-3 min-1). The cyclic voltammograms of both the nano -particles at a scan rate of 5 mV s-1 were faradic in nature and showed pseudo capacitance. The capacitance of nanoparticles with surfactant (166 F g-1) was found to be higher than that ob-tained for bare nanoparticles (111 F g-1). A comparison of the properties indicated that the addition of surfactant plays a vital role in tuning the properties of cobalt oxide nanoparticles for their specific application.