Synthesis of hexagonal cobalt hydroxide and cobalt oxide nanorings as promising materials for oxygen evolution and supercapacitive processes

Abstract

Preparing the low-cost nanomaterials for electrocatalytic processes is still a big challenge. Mesoporous cobalt hydroxide and cobalt oxide nanoparticles were prepared through simple soft chemistry as high-performance materials for durable electrocatalyst for OER and supercapacitive applications. The synthesis method is used to prepare nanoring particles in neither emulsion nor template-directed method. The final nanoparticles display mesoporous hexagonal nanoring morphology. The physio-chemical properties of the as-synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption-desorption techniques. The TEM characterizations prove that NPs retain the topotactical relationship in their structure during the conversion process. The BET measurements prove the mesoporous nature of the nanorings, having good specific surface area and pore volume. Finally, the electrochemical performance toward water splitting and supercapacitor applications were investigated by electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and cyclic voltammetry (CV) techniques. The Co3O4 NPs exhibits better catalytic properties than Co(OH)2 NPs when applied as electrocatalyst in an alkaline medium for water splitting and supercapacitor measurements. The enhanced electrocatalytic performance attributed to the mesoporous structure along with high pore volume, which provides more active boundary sites for the electrochemical process, resulted in the enhanced exchange of the intermediates and more efficient electron transfer. This synthetic methodology, with the advantages of inexpensive/non-complicated experimental setup and high electrochemical performance, could shed light on the development of non-expensive electrocatalysts for clean energy production and storage.