Cobalt/Cobalt Oxide Nanorods-Decorated Reduced Graphene\nOxide (Co/Co₃O₄‑rGO) for Enhanced Electrooxidation\nof Glycerol

Abstract

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