Two-dimensional transition metal hydroxides with abundant reserves and low prices have played an indispensable role in energy catalytic applications. Recent reports indicated that the incorporation of Fe species into Co-based catalysts can synergistically enhance oxygen evolution reaction (OER) activity. Constructing a heterointerface on the surface of Co-based catalysts can provide a platform to investigate the role of heterointerface in reaction kinetics. Herein, we constructed a Fe-O-Co heterointerface without electronic effect by depositing FeO_x clusters on the oxygen vacancies of CoOOH surface. FeO_x/CoOOH exhibited excellent OER intrinsic activity, which can deliver the turnover frequency (TOF) of 4.56 s⁻¹ at the overpotentials of 300 mV and the Tafel slope of 33 mV·dec⁻¹. In-situ electrochemical impedance spectroscopy (EIS) and density functional theory (DFT) calculations demonstrated that the synergistic effect between Fe sites and Co sites confined at the Fe-O-Co heterointerface accelerated the charge transfer during OER and optimized the adsorption of oxygen intermediates, consequently enhancing OER.