Carbon-based electrocatalysts have considerable potential for application in renewable and clean energy conversion systems. Although graphitic carbons have the advantages of high conductivity and electrolyte corrosion resistance, their sp2-hybridized skeleton often leads to poor porosity and insufficient intrinsic active sites, resulting in suboptimal catalytic activity for sluggish multi-electron redox reactions. Herein, we demonstrate an efficient strategy for the activation of low-active graphitized carbon nanosheets by a thermal-driven nitrogen atom removal process. The elimination of nitrogen atoms at high temperatures facilitates the rearrangement of neighboring carbon atoms, leading to numerous carbon defects and an increased surface area, while retaining the long-range ordered graphitic structure. As a result, the as-obtained defect-enriched porous graphitized carbon nanosheets (DPGCNSs) simultaneously combine abundant highly active intrinsic defects with a high graphitization degree and numerous micro/mesopores, demonstrating low overpotential and favorable kinetics for oxygen reduction and oxygen evolution reactions. Remarkably, rechargeable Zn–air batteries with DPGCNSs catalysts demonstrate superior cycling performance, exceeding 700 cycles with no obvious voltage fading.