The design of cost-effective, highly active catalysts for hydrogen energy production is a vital element in the societal pursuit of sustainable energy. Water electrolysis is one of the most convenient processes to produce high purity hydrogen. Cobalt-based catalysts are well-known electrocatalysts for oxygen evolution reaction(OER). In this article, all these merits indicate that the present cobalt nanocomposite is a promising electrocatalyst for OER. C–Co_3O_4-nanorods catalyst with nanorod structure was synthesized by hydrothermal treatment of CoCl_2·6H_2O/dextrose/urea mixture at 180 °C for 18 h and then calcined at400 °C for 3.5 h. The role of dextrose percentage in solution to achieve the uniform coating of carbon on the surface of Co_3O_4-nanorods has been demonstrated. The prepared materials were characterized by X-ray diffraction(XRD), X-ray photoelectron spectrum(XPS), field emission scanning electron microscopy(FE-SEM), high-resolution transmission electron microscopy(HR-TEM), and Brunauer–Emmett–Teller instrument(BET). Due to its unique morphology, the C–Co_3O_4-nanorods catalyst exhibited better activity than Co_3O_4-microplates catalyst for OER in 1 M KOH aqueous solution. The results showed a highly efficient, scalable, and low-cost method for developing highly active and stable OER electrocatalysts in alkaline solution. The design of cost-effective, highly active catalysts for hydrogen energy production is a vital element in the societal pursuit of sustainable energy. Water electrolysis is one of the most convenient processes to produce high purity hydrogen. Cobalt-based catalysts are well-known electrocatalysts for oxygen evolution reaction (OER). In this article, all these merits indicate that the present cobalt nanocomposite is a promising electrocatalyst for OER. C-Co_3O_4-nanorods catalyst with nanorod structure was synthesized by hydrothermal treatment of CoCl_2 · 6H_2O / dextrose / urea mixture at 180 ° C for 18 h and then calcined at 400 ° C for 3.5 h. The role of dextrose percentage in solution to achieve the uniform coating of carbon on the surface of Co_3O_4-nanorods has been demonstrated. The prepared materials were characterized by X ray diffraction (XRD), X-ray photoelectron spectrum (XPS), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR- TEM), and Brunauer-Emmett-Teller instrument (BET). Due to its unique morphology, the C-Co_3O_4-nanorods catalyst catalysts better activity than Co_3O_4-microplates catalyst for OER in 1 M KOH aqueous solution. , scalable, and low-cost method for developing highly active and stable OER electrocatalysts in alkaline solution.