Bimetallic catalysts are appealing for electrochemical CO reduction reaction (ECO2RR), yet the introduction of bimetallic sites leads to an incomprehensive understanding of the metal atom interaction and catalytic mechanism. In this study, a series of bimetallic NiCu@NC catalysts with varied Ni to Cu weight ratios are prepared. The as-prepared NiCu@NC catalyst shows high carbon monoxide (CO) Faradaic efficiencies (FE) over 90% in a broad potential range of -0.7 to -1.1 V (vs reversible hydrogen electrode (RHE)) with an exceptional durability of CO selectivity over 80% and a high partial current density of -44 mA cm at an extremely high potential of -1.3 V (vs RHE). The distinguished CO selectivity and activity are primarily attributed to the integration of Ni and Cu, which lowers the d-band center position and reconstructs the electronic structure according to the valence band spectra. More specifically, the downshifted d-band center position weakens the interaction strength with the *CO intermediate on the NiCu@NC catalyst's surface during the ECO2RR process, resulting in fast *CO desorption and high CO selectivity. This study provides researchers with a new insight for designing and optimizing the electrocatalysts for ECO2RR.