Cobalt/Cobalt Oxide Nanorods-Decorated Reduced Graphene Oxide (Co/Co₃O₄-rGO) for Enhanced Electrooxidation of Glycerol

Abstract

Reduced graphene oxide with cobalt/cobalt oxide (Co/Co3O4-rGO) nanorod decorations was made by using a chemical synthesis process. The as-synthesized Co/Co3O4-rGO, reduced graphene oxide (rGO), and cobalt/cobalt oxide (Co/Co3O4) nanocomposite were tested for electrocatalytic activity toward the electrooxidation of glycerol in 1 M KOH solution and oxygen evolution reaction simultaneously. The as-synthesized electrocatalytic system was characterized by various techniques, including electrochemical (cyclic voltammetry, electrochemical impedance spectroscopy, and i–t chronoamperometry), spectroscopic (Fourier transform infrared, Raman, and X-ray photoelectron spectroscopy), and morphological (scanning electron spectroscopy and transmission electron microscopy) analyses. Transmission electron microscopy analysis of the Co/Co3O4-rGO nanocomposite showed an average size of ∼36 nm of Co/Co3O4 on rGO. The electrochemical studies exhibited that Co/Co3O4-rGO showed excellent electrocatalytic performance compared to those of rGO and Co3O4 individually. Among these, Co/Co3O4-rGO showed the smallest onset potential (∼1.42 V vs RHE), lowest Tafel slope (56 mV dec–1), lower charge-transfer resistance Rct (600 Ω), and higher stability than Co3O4 and rGO. High-performance liquid chromatography analysis confirmed the formation of formic acid with conversion after 5, 15, and 20 h (∼13.43, 41.93, and 59.44%, respectively) and demonstrated higher Faradaic efficiency (∼63%) toward oxidative product (i.e., formic acid) formation. The improved electrochemical performance of rGO after the decoration of Co/Co3O4 on the GO surface reflected that Co/Co3O4-rGO has good structural and potential stability than Co3O4 nanoparticles and rGO substrate toward glycerol electrooxidation.