<p>Alkali metal modification of cobalt-based Fischer-Tropsch synthesis catalysts suffers from poor stability. Exploring new strategies to enhance olefin selectivity and catalyst stability is of significant importance. In this work, a nitrogen-doped carbon layer-modified Co/NC-Al₂O₃ catalyst was prepared using oleylamine as the nitrogen source and glucose as the carbon source. Under conditions of 230 ℃, 1&#xa0;MPa, and 6 SL·g^− 1·h^− 1, the Co/NC-Al₂O₃ catalyst achieved an activity of 4.2 × 10^− 5 molCO·gCo^− 1 s^− 1 with an olefin selectivity of 34.4%, while exhibiting high stability. Characterization and performance results demonstrate that: the electron-donating effect of pyrrolic nitrogen enriches electrons in adjacent metallic Co, enhancing CO adsorption and activation while inhibiting secondary hydrogenation of α-olefins, thereby increasing olefin selectivity; The improved stability originates from the confinement effect of the carbon layer and the stabilizing role of graphitic nitrogen on Co nanoparticles.</p> Graphical Abstract <p></p>