Comparative Study of the Dissolution Behavior of CoO Nanoparticles and Bulk CoO in Deep Eutectic Solvents

ABSTRACT This study investigates the comparative dissolution behavior, electrochemical performance, and dispersion characteristics of cobalt(II) oxide nanoparticles (CoO NPs) and bulk CoO in ethaline, a deep eutectic solvent (DES) composed of choline chloride and ethylene glycol. Nanoparticles offer unique physicochemical advantages—such as increased surface area and reactivity—making them promising candidates for catalytic and electrochemical applications. To explore these advantages in green solvent systems, both CoO NPs and bulk CoO were subjected to thermal treatment (95°C–110°C) in ethaline, followed by analysis using UV–vis spectroscopy, inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), dynamic light scattering (DLS), and cyclic voltammetry. CoO NPs exhibited significantly enhanced dissolution rates, greater cobalt‐ion release (1694 mg/L vs 634 mg/L for bulk CoO), smaller hydrodynamic diameters under thermal agitation, and higher redox activity. The findings demonstrate that nanoparticle structuring, combined with DES media, facilitates efficient ion transport and improved electrochemical response. This work supports the strategic utilization of metal oxide nanoparticles in green chemistry contexts, such as energy storage, catalysis, and recyclable solvent systems.