Carbon Quantum Dot-Enabled Microcrystalline Domain Engineering for Selective Four-Electron Oxygen Reduction

Engineering carbon-based electrocatalysts with well-defined microcrystalline domains remain a central challenge for achieving efficient and durable oxygen reduction reaction (ORR) without relying on noble metals. Here, a carbon quantum dot (CQD)-enabled microcrystalline domain engineering strategy that regulates graphitic ordering, electronic structure, and active-site distribution in carbon catalysts is reported. The incorporation of CQDs during carbonization promotes the formation of spatially distributed microcrystalline domains, together with enriched B-N coordination and optimized charge density. This structural configuration enhances O₂ activation and *O adsorption while suppressing peroxide pathways, thereby favoring a selective four-electron ORR process. As a result, the optimized catalyst delivers a half-wave potential approaching that of commercial Pt/C, together with a near four-electron transfer pathway. When applied as the air cathode in zinc-air batteries, it exhibits high power densities of 153 mW cm^-2 in liquid cells and 123.8 mW cm^-2 in flexible devices, along with stable operation over 1200 h. This work establishes CQD-enabled microcrystalline domain engineering as an effective strategy for regulating structure-property relationships in carbon electrocatalysts and provides design insights for high-performance energy conversion devices.